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The resonance Raman spectrum of 45( + - 3) Å diameter CdSe clusters was measured. The incident photons were resonant with the HOMO-LUMO transition in the clusters. At low temperature, one mode at 205 cm-1 is observed, as well as two overtones, with the integrated areas under these peaks in the ratio of 9:3:1. This mode is assigned as the longest wavelength longitudinal optical vibration of the cluster. The strength of the coupling between the lowest electronic excited state and the LO vibration is found to be 20 times weaker in these clusters than in the bulk solid. The CdSe cluster resonance Raman spectrum is shown to be consistent with the recently measured homogeneous cluster absorption spectrum. © 1989 American Institute of Physics.

To evaluate bifunctional ligand reactivity involving NH acidic sites in the secondary coordination sphere, complexes where the proton has been substituted with a methyl group (NMe) are often investigated. An alternative strategy involves substitution of the NH group for an O. This contribution considers and compares the merits of these approaches; the synthesis and characterization of cationic square-planar Rh carbonyl complexes bearing diprotic bispyrazole pyridine ligand L1, and the bis-methylated pyrazole pyridine ligand L1Me are described. The syntheses and characterization of the novel monoprotic pyrazole isoxazole pyridine ligand L2 and aprotic bisisoxazole pyridine ligand L3, and their corresponding Rh carbonyl complexes are also described. Comparison of the CO stretching frequencies of the four Rh complexes suggest that substitutions of NH with NMe, as well as with O, lead to significant electronic differences. These electronic differences result in different reactivities with respect to ligand addition/substitution of the Rh carbonyl complexes. Overall, the data suggest that electronic differences arising due to the NH substitutions can be significant and should be considered when the NH group is substituted in investigations of the participation of the NH proton in a reaction., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Objectives/aims: The primary aim of this study was to assess the current standard of shoulder radiographs in Ireland. The secondary aim of this study was to determine whether orthopaedic surgeons in Ireland are of the opinion that a national protocol is required, and what this protocol should consist of., Methods: A national audit of shoulder trauma series x-rays performed in emergency departments was conducted. The number and type of views performed was recorded. The anteroposterior (AP) and axillary or Velpeau views were assessed to determine if they met pre-defined audit criteria. Consultant orthopaedic surgeons working in public trauma hospitals were invited to participate in an online survey by email., Results: The number of shoulder trauma series included in this audit was 789. The majority of patients had two views performed (75.92%, n ​= ​599) and 21.17% (n ​= ​167) had an axillary or Velpeau view. The AP view met the audit criteria in 23.09% (n ​= ​181) of cases. The survey response rate was 70.8% (n ​= ​17). 88.2% (n ​= ​15) of surgeons agreed that three views should be performed for a shoulder trauma series and 94.12% (n ​= ​16) agreed that an axillary or Velpeau view should be included. The majority of surgeons surveyed (94%, n ​= ​16) are in favour of establishing a national protocol., Conclusion: The current standard shoulder trauma series in Irish hospitals consists of two views, most frequently a thoracic AP and a scapular Y view. We propose the introduction of a national protocol consisting of three views: Grashey AP, Scapular Y, and an axillary or Velpeau view., Competing Interests: Declaration of competing interest The authors have no conflict of interest to declare., (Copyright © 2024 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.)

Quaternary ammonium compounds have served as a first line of protection for human health as surface disinfectants and sanitizers for nearly a century. However, increasing levels of bacterial resistance have spurred the development of novel QAC architectures. In light of the observed reduction in eukaryotic cell toxicity when the alkyl chains on QACs are shorter in nature (≤10 C), we prepared 47 QAC architectures that bear multiple short alkyl chains appended to up to three cationic groups, thus rendering them "bushy-tailed" multiQACs. Antibacterial activity was strong (often ~1-4 μM) in a varied set of bushy-tailed architectures, though observed therapeutic indices were not significantly improved over QAC structures bearing fewer and longer alkyl chains., (© 2024 Wiley-VCH GmbH.)

The use of a nonrigid, pyridyldialdimine-derived macrocyclic ligand ( 3 PDAI 2 ) enabled the synthesis of well-defined mono-, di-, tri-, and tetra-nuclear Cu(I) complexes in good yields through rational synthetic means. Starting from mono- and diargentous 3 PDAI 2 complexes, transmetalation to Cu(I) proceeded smoothly with formation of AgX (X = Cl, I) salts to generate mono-, di-, and trinuclear copper complexes. Monodentate supporting ligands (MeCN, xylNC, PMe 3 , PPh 3 ) were found to either transmetallate with or bind various di- and trinuclear clusters. The solution-phase dynamic behaviors of these species were studied through NMR spectroscopic investigations, and an in-depth study of the trinuclear systems revealed a rate dependence on the identity of the supporting ligand, indicating that ligand dissociation reactions were involved in the dynamic exchange processes. Synthetic investigations further found methods for the purposeful interconversion between the di- and trinuclear systems as well as the synthesis of a pseudotetrahedral tetracopper complex with two μ-Ph supporting ligands.

Examples of stable 3d transition metal methylidene complexes are extremely rare. Here we report an isolable and stable vanadium methylidene complex, [(PNP)V(=NAr)(=CH 2 )] (PNP = N[2-P i Pr 2 -4-methylphenyl] - , Ar = 2,6- i Pr 2 C 6 H 3 ), via H atom transfer (HAT) from [(PNP)V(NHAr)(CH 3 )] or [(PNP)V(=NAr)(CH 3 )] using two or one equivalents of the TEMPO radical (TEMPO = (2,2,6,6-tetramethylpiperidin-1-yl)oxyl), respectively. Alternatively, the vanadium methylidene moiety can also be formed via the treatment of transient [(PNP)V=NAr] with the Wittig reagent, H 2 CPPh 3 . Structural and spectroscopic analysis, including 13 C enriched labeling of the methylidene ligand, unequivocally confirmed the terminal nature of a rare 3d methylidene complex, featuring a V=CH 2 bond distance of 1.908(2) Å and a highly downfield 13 C NMR spectral shift at 298 ppm. In the absence of the ylide, intermediate [(PNP)V=NAr] activates dinitrogen to form an end-on bridging N 2 complex, [(PNP)V(=NAr)] 2 (μ 2 -η 1 :η 1 -N 2 ), having a singlet ground state. Complex [(PNP)V(=NAr)(=CH 2 )] reacts with H 3 COTf to form [(PNP)V(=NAr)(OTf)], accompanied by the release of ethylene as evidenced by 1 H NMR spectroscopy, and reactivity studies suggest a β-hydride elimination pathway.

The synthesis and characterization of two cerium complexes of redox-active amine/amido-phenolate-type ligands are reported. A tripodal framework comprising the tris(2-(3',5'-di- tert -butyl-2'-hydroxyphenyl)amino-phenyl) amine (H 6 Clamp) proligand was synthesized for comparison of its cerium complex with a potassium-cerium heterobimetallic complex of the 4,6-di- tert -butyl-2-[(2,6-diisopropylphenyl)imino]quinone ( dipp ap) proligand. Structural studies indicate differences in the cerium(III) cation coordination spheres, where Ce III (CH 3 CN) 1.5 (H 3 Clamp) ( 1-Ce(H 3 Clamp) ) exhibits shorter Ce-O distances and longer Ce-N bond distances compared to the analogous distances in K 3 (THF) 3 Ce III ( dipp ap) 3 ( 2-Ce(ap) ), due to the gross structural differences between the systems. Differences are also evident in the temperature-dependent magnetic properties, where smaller χT products were observed for 2-Ce(ap) compared to 1-Ce(H 3 Clamp) . Solution electrochemical studies for the complexes were interpreted based on ligand- and metal-based oxidation events, and the cerium(III) oxidation of 2-Ce(ap) was observed to be more facile than that of 1-Ce(H 3 Clamp) , behavior that was cautiously attributed to the rigidity of the encrypted 1-Ce(H 3 Clamp) complex compared to the heterobimetallic framework of 2-Ce(ap) . These results contribute to the understanding of how ligand designs can promote facile redox cycling for cerium complexes of redox-active ligands, given the large contraction of cerium-ligand bonds upon oxidation.

Electron-rich organocerium complexes (C 5 Me 4 H) 3 Ce and [(C 5 Me 5 ) 2 Ce( ortho -oxa)], with redox potentials E 1/2 = -0.82 V and E 1/2 = -0.86 V versus Fc/Fc + , respectively, were reacted with fullerene (C 60 ) in different stoichiometries to obtain molecular materials. Structurally characterized cocrystals: [(C 5 Me 4 H) 3 Ce] 2 ·C 60 ( 1 ) and [(C 5 Me 5 ) 2 Ce( ortho -oxa)] 3 ·C 60 ( 2 ) of C 60 with cerium-based, molecular rare earth precursors are reported for the first time. The extent of charge transfer in 1 and 2 was evaluated using a series of physical measurements: FT-IR, Raman, solid-state UV-vis-NIR spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and magnetic susceptibility measurements. The physical measurements indicate that 1 and 2 comprise the cerium(III) oxidation state, with formally neutral C 60 as a cocrystal in both cases. Pressure-dependent periodic density functional theory calculations were performed to study the electronic structure of 1 . Inclusion of a Hubbard-U parameter removes Ce f states from the Fermi level, opens up a band gap, and stabilizes FM/AFM magnetic solutions that are isoenergetic because of the large distances between the Ce(III) cations. The electronic structure of this strongly correlated Mott insulator-type system is reminiscent of the well-studied Ce 2 O 3 .

Described here is a direct entry to two examples of 3d transition metal catalysts that are active for the cyclic polymerization of phenylacetylene, namely, [(BDI)M{κ 2 -C,C-(Me 3 SiC 3 SiMe 3 )}] (2-M) (BDI=[ArNC(CH 3 )] 2 CH - , Ar=2,6- i Pr 2 C 6 H 3 ; M=Ti, V). Catalysts are prepared in one step by the treatment of [(BDI)MCl 2 ] (1-M, M=Ti, V) with 1,3-dilithioallene [Li 2 (Me 3 SiC 3 SiMe 3 )]. Complexes 2-M have been spectroscopically and structurally characterized and the polymers that are catalytically formed from phenylacetylene were verified to have a cyclic topology based on a combination of size-exclusion chromatography (SEC) and intrinsic viscosity studies. Two-electron oxidation of 2-V with nitrous oxide (N 2 O) cleanly yields a [V V ] alkylidene-alkynyl oxo complex [(BDI)V(=O){κ 1 -C-(=C(SiMe 3 )CC(SiMe 3 ))}] (3), which lends support for how this scaffold in 2-M might be operating in the polymerization of the terminal alkyne. This work demonstrates how alkylidynes can be circumvented using 1,3-dianionic allene as a segue into M-C multiple bonds., (© 2023 Wiley-VCH GmbH.)

Reported is the catalytic cyclic polymer synthesis by a 3d transition metal complex: a V(V) alkylidyne, [(dBDI)V≡C t Bu(OEt 2 )] ( 1-OEt 2 ), supported by the deprotonated β-diketiminate dBDI 2- (dBDI 2- = ArNC(CH 3 )CHC(CH 2 )NAr, Ar = 2,6- i Pr 2 C 6 H 3 ). Complex 1-OEt 2 is a precatalyst for the polymerization of phenylacetylene (PhCCH) to give cyclic poly(phenylacetylene) ( c -PPA), whereas its precursor, complex [(BDI)V≡C t Bu(OTf)] ( 2-OTf ; BDI - = [ArNC(CH 3 )] 2 CH, Ar = 2,6- i Pr 2 C 6 H 3 , OTf = OSO 2 CF 3 ), and the zwitterion [((C 6 F 5 ) 3 B-dBDI)V≡C t Bu(OEt 2 )] ( 3-OEt 2 ) exhibit low catalytic activity despite having a neopentylidyne ligand. Cyclic polymer topologies were verified by size-exclusion chromatography (SEC) and intrinsic viscosity studies. A component of the mechanism of the cyclic polymerization reaction was probed by isolation and full characterization of 4- and 6-membered metallacycles as model intermediates. Metallacyclobutadiene (MCBD) and deprotiometallacyclobutadiene (dMCBD) complexes (dBDI)V[C( t Bu)C(H)C( t Bu)] ( 4- t Bu ) and (BDI)V[C( t Bu)CC(Mes)] ( 5-Mes ), respectively, were synthesized upon reaction with bulkier alkynes, t Bu- ( t BuCCH) and Mes-acetylene (MesCCH), with 1-OEt 2 . Furthermore, the reaction of the conjugate acid of 1-OEt 2 , [(BDI)V≡C t Bu(OTf)] ( 2-OTf ), with the conjugated base of phenylacetylene, lithium phenylacetylide (LiCCPh), yields the doubly deprotio-metallacycle complex, [Li(THF) 4 ]{(BDI)V[C(Ph)CC( t Bu)CC(Ph)]} ( 6 ). Protonation of the doubly deprotio-metallacycle complex 6 yields 6-H + , a catalytically active species toward the polymerization of PhCCH, for which the polymers were also confirmed to be cyclic by SEC studies. Computational mechanistic studies complement the experimental observations and provide insight into the mechanism of cyclic polymer growth. The noninnocence of the supporting dBDI 2- ligand and its role in proton shuttling to generate deprotiometallacyclobutadiene (dMCBD) complexes that proposedly culminate in the formation of catalytically active V(III) species are also discussed. This work demonstrates how a dMCBD moiety can react with terminal alkynes to form cyclic polyalkynes.

Here we report the use of a base metal complex [( tBu pyrpyrr 2 )Fe(OEt 2 )] (1-OEt 2 ) ( tBu pyrpyrr 2 2- =3,5-tBu 2 -bis(pyrrolyl)pyridine) as a catalyst for intermolecular amination of C sp3 -H bonds of 9,10-dihydroanthracene (2 a) using 2,4,6-trimethyl phenyl azide (3 a) as the nitrene source. The reaction is complete within one hour at 80 °C using as low as 2 mol % 1-OEt 2 with control in selectivity for single C-H amination versus double C-H amination. Catalytic C-H amination reactions can be extended to other substrates such as cyclohexadiene and xanthene derivatives and can tolerate a variety of aryl azides having methyl groups in both ortho positions. Under stoichiometric conditions the imido radical species [( tBu pyrpyrr 2 )Fe{=N(2,6-Me 2 -4-tBu-C 6 H 2 )] (1-imido) can be isolated in 56 % yield, and spectroscopic, magnetometric, and computational studies confirmed it to be an S = 1 Fe IV complex. Complex 1-imido reacts with 2 a to produce the ferrous aniline adduct [( tBu pyrpyrr 2 )Fe{NH(2,6-Me 2 -4-tBu-C 6 H 2 )(C 14 H 11 )}] (1-aniline) in 45 % yield. Lastly, it was found that complexes 1-imido and 1-aniline are both competent intermediates in catalytic intermolecular C-H amination., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

While niobium and tantalum are found together in their mineral ores, their respective applications in technology require chemical separation. Nb/Ta separations are challenging due to the similar reactivities displayed by these metals in the solution phase. Coordination complexes of these metals have been studied in the contexts of catalysis, small-molecule activation, and functional group insertion reactivity; relatively few studies exist directly comparing the properties of isostructural Nb/Ta complexes. Such comparisons advance the development of Nb/Ta separation chemistry through the potential for differential reactivity. Here, we explore fundamental physicochemical properties in extensively characterized Nb/Ta coordination complexes [Na(DME) 3 ][MClamp], (Clamp 6- = tris -(2-(3',5'-di- tert- butyl-2'-oxyphenyl)amidophenyl)amine; M = Nb, Ta) to advance the understanding of the different electronic, optical, and excited-state properties that these metals exhibit in pi-loaded coordination complexes.

Introduction: A recent study based on a large osteological collection reported an association between clavicle fractures and osteoarthritis of the glenohumeral joint. No clinical study has yet addressed this potential association. Other radiographic parameters such as the critical shoulder angle have been associated with the risk of glenohumeral joint osteoarthritis. The primary outcome of this study was to determine if there is an association between glenohumeral joint arthritis and clavicle fractures. The secondary outcome was to determine the association between critical shoulder angle and glenohumeral joint arthritis in our patient cohort., Methods: We retrospectively analysed 572 consecutive shoulder arthroplasty surgeries. Osteoarthritis was the indication for 343 shoulder arthroplasties. 229 shoulder arthroplasties were performed due to another diagnosis such as trauma or fracture, cuff arthropathy, or revision surgery. Three fellowship trained consultant shoulder surgeons assessed the pre- and post-operative radiographs of all patients., Results: A clavicle fracture was suspected in 5/343 (1.5 %) shoulder arthroplasties performed due to osteoarthritis and 5/229 (2.1 %) shoulder arthroplasties performed for another diagnosis. Interobserver variability was assessed using a Fisher Exact test and showed no significant relationship between osteoarthritis and a fracture of the clavicle (p = 0.531). Critical shoulder angle results correlated with the previously published literature regarding critical shoulder angle and osteoarthritis and rotator cuff arthropathy., Conclusion: Clavicle fractures were not associated with glenohumeral osteoarthritis in our patient cohort of shoulder arthroplasty patients. Critical shoulder angle results were consistent with published literature. Further research in the form of prospective long term studies are needed to establish if any association exists between clavicle fractures and osteoarthritis of the glenohumeral joint., Level of Evidence: Level III. Retrospective analysis., Competing Interests: We have no conflict of interest., (© 2023 The Authors.)

We show in this work how lithium tellurolate Li(X) n TeCH 2 SiMe 3 (X = THF, n = 1, 1; X = 12- crown -4, n = 2, 2), can serve as an effective Te-atom transfer reagent to all group 5 transition metal halide precursors irrespective of the oxidation state. Mononuclear and bis(telluride) complexes, namely (PNP)M(Te) 2 (M = V; Nb, 3; Ta, 4; PNP - = N[2-P i Pr 2 -4-methylphenyl] 2 ), are reported herein including structural and spectroscopic data. Whereas the known complex (PNP)V(Te) 2 can be readily prepared from the trivalent precursor (PNP)VCl 2 , two equiv. of tellurolate, and elemental Te partially solubilized with PMe 3 , complex 3 can also be similarly obtained following the same procedure but with or without a reductant, Na/NaCl. Complex 4 on the other hand is formed from the addition of four equiv. of tellurolate to (PNP)TaF 4 . Having access to a triad of (PNP)M(Te) 2 systems for group 5 metals has allowed us to compare them using a combination of theory and spectroscopy including Te-L 1 edge XANES data., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report the first mononuclear Ti III complex possessing a terminal imido ligand. Complex [Tp t Bu,Me Ti{NSi(CH 3 ) 3 }(THF)] (2) (Tp t Bu,Me = hydridotris(3- tert -butyl-5-methylpyrazol-1-yl)borate) is prepared by reduction of [Tp t Bu,Me Ti{NSi(CH 3 ) 3 }(Cl)] (1) with KC 8 in high yield. The connectivity and metalloradical nature of 2 were confirmed by single crystal X-ray diffraction studies, Q- and X-band EPR, UV-Vis and 1 H NMR spectroscopies. The d 1 complex [(Tp t Bu,Me )TiCl(OEt 2 )][B(C 6 F 5 ) 4 ] (3), was prepared to spectroscopically compare it to 2. Electrochemical studies of 1 and 2 reveal a reversible 1e - process, and chemical oxidants ClCPh 3 or 1/2 eq. XeF 2 react cleanly with 2 yielding 1 or the fluoride derivative [Tp t Bu,Me Ti{NSi(CH 3 ) 3 }(F)] (4), respectively.

Manifesting chemical differences in individual rare earth (RE) element complexes is challenging due to the similar sizes of the tripositive cations and the corelike 4f shell. We disclose a new strategy for differentiating between similarly sized Dy 3+ and Y 3+ ions through a tailored photochemical reaction of their isostructural complexes in which the f-electron states of Dy 3+ act as an energy sink. Complexes RE(hfac) 3 (NMMO) 2 (RE = Dy ( 2-Dy ) and Y ( 2-Y ), hfac = hexafluoroacetylacetonate, and NMMO = N -methylmorpholine- N -oxide) showed variable rates of oxygen atom transfer (OAT) to triphenylphosphine under ultraviolet (UV) irradiation, as monitored by 1 H and 19 F NMR spectroscopies. Ultrafast transient absorption spectroscopy (TAS) identified the excited state(s) responsible for the photochemical OAT reaction or lack thereof. Competing sensitization pathways leading to excited-state deactivation in 2-Dy through energy transfer to the 4f electron manifold ultimately slows the OAT reaction at this metal cation. The measured rate differences between the open-shell Dy 3+ and closed-shell Y 3+ complexes demonstrate that using established principles of 4f ion sensitization may deliver new, selective modalities for differentiating the RE elements that do not depend on cation size.

This article describes the synthesis, characterization, and S-atom transfer reactivity of a series of C 3 v -symmetric diiron complexes. The iron centers in each complex are coordinated in distinct ligand environments, with one (Fe N ) bound in a pseudo-trigonal bipyramidal geometry by three phosphinimine nitrogens in the equatorial plane, a tertiary amine, and the second metal center (Fe C ). Fe C is coordinated, in turn, by Fe N , three ylidic carbons in a trigonal plane, and, in certain cases, by an axial oxygen donor. The three alkyl donors at Fe C form through the reduction of the appended N═PMe 3 arms of the monometallic parent complex. The complexes were studied crystallographically, spectroscopically (NMR, UV-vis, and Mössbauer), and computationally (DFT, CASSCF) and found to be high-spin throughout, with short Fe-Fe distances that belie weak orbital overlap between the two metals. Further, the redox nature of this series allowed for the determination that oxidation is localized to the Fe C . S-atom transfer chemistry resulted in the formal insertion of a S atom into the Fe-Fe bond of the reduced diiron complex to form a mixture of Fe 4 S and Fe 4 S 2 products.

Two structurally diverse cyclic β-hydroxy-α-nitrosulfones have been prepared and their isomerisation reactions studied. These cyclic β-hydroxy-α-nitrosulfones undergo isomer equilibration via open-chain aldehyde forms under a variety of mild conditions. Michael condensation of 1,1'-[(1,3-dinitro-1,3-propanediyl)bis(sulfonyl)]bis(benzene) with propenal and subsequent cyclisation afforded 2,4-dinitro-2,4-bis(phenylsulfonyl)cyclohexanol in 98% yield as a mixture of four diastereomers. Sequential chromatography and recrystallization afford pure (1 R ,2 R ,4 S )-rel-2,4-dinitro-2,4-bis(phenylsulfonyl)cyclohexanol based on spectroscopic and X-ray crystallographic data. This diastereomer equilibrates with the other three possible diastereomers under a variety of mild conditions: during silica gel chromatography, when dissolved in basic solution, and when dissolved in neutral polar solvents. Open-chain aldehyde forms are implicated as intermediates in isomer interconversion. Condensation of 1-methyl-4-[(nitromethyl)sulfonyl]benzene and pentanedial gives 2-(4-methylphenylsulfonyl)-2-nitrocyclohexane-1,3-diol as predominantly two diastereomers. Purification affords pure racemic diastereomer in 55% yield. This racemic diastereomer interconverts with several other isomers during silica gel chromatography. These isomers were identified as one, likely two, diastereomeric meso 2-(4-methylphenylsulfonyl)-2-nitrocyclohexane-1,3-diol isomers and four cyclic hemiacetal constitutional isomers. When dissolved in neutral polar solvents, the racemic diastereomer also interconverts with meso diastereomers and cyclic hemiacetals showing a marked solvent dependence. Reaction of the racemic diastereomer with triethylamine in dichloromethane results in isomerisation as well as substantial reversion to 1-methyl-4-[(nitromethyl)sulfonyl]benzene and pentanedial. Reaction with triethylamine in DMSO as well as simply warming in DMSO results in ring opening and concomitant dehydration to afford ( E )-6-(4-methylphenylsulfonyl)-6-nitrohex-4-enal.

Iron compounds containing a bridging oxo or sulfido moiety are ubiquitous in biological systems, but substitution with the heavier chalcogenides selenium and tellurium, however, is much rarer, with only a few examples reported to date. Here we show that treatment of the ferrous starting material [( t Bu pyrpyrr 2 )Fe(OEt 2 )] (1-OEt 2 ) ( t Bu pyrpyrr 2 = 3,5- t Bu 2 -bis(pyrrolyl)pyridine) with phosphine chalcogenide reagents E = PR 3 results in the neutral phosphine chalcogenide adduct series [( t Bu pyrpyrr 2 )Fe(EPR 3 )] (E = O, S, Se; R = Ph; E = Te; R = t Bu) (1-E) without any electron transfer, whereas treatment of the anionic starting material [K] 2 [( t Bu pyrpyrr 2 )Fe 2 (μ-N 2 )] (2-N 2 ) with the appropriate chalcogenide transfer source yields cleanly the isostructural ferrous bridging mono-chalcogenide ate complexes [K] 2 [( t Bu pyrpyrr 2 )Fe 2 (μ-E)] (2-E) (E = O, S, Se, and Te) having significant deviation in the Fe-E-Fe bridge from linear in the case of E = O to more acute for the heaviest chalcogenide. All bridging chalcogenide complexes were analyzed using a variety of spectroscopic techniques, including 1 H NMR, UV-Vis electronic absorbtion, and 57 Fe Mössbauer. The spin-state and degree of communication between the two ferrous ions were probed via SQUID magnetometry, where it was found that all iron centers were high-spin ( S = 2) Fe II , with magnetic exchange coupling between the Fe II ions. Magnetic studies established that antiferromagnetic coupling between the ferrous ions decreases as the identity of the chalcogen is tuned from O to the heaviest congener Te., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A series of thorium anilide compounds [ThNHAr R (TriNOx)] (R = para -OCH 3 ( 1-Ar OMe ), para -H ( 1-Ar H ), para -Cl ( 1-Ar Cl ), para -CF 3 ( 1-Ar 4-CF3 ), TriNOx 3- = tris (2- tert -butylhydroxylaminato)benzylamine), and their corresponding imido compounds [Li(DME)][Th═NAr R (TriNOx)] ( 2-Ar R ) as well as the alkyl congeners [ThNHAd(TriNOx)] ( 1-Ad ) and [Li(DME)][Th═NAd(TriNOx)] ( 2-Ad ), have been prepared. The para -substituents on the arylimido moiety were introduced for systematic variation of their electron-donating and withdrawing abilities, changes that were evident in measurements of the 13 C{ 1 H} NMR chemical shifts of the ipso -C atom of the Ar R moiety. Room temperature, solution-state luminescence of the four new thorium imido compounds, along with the previously reported [Li(THF) 2 ][Th═NAr 3,5-CF3 (TriNOx)] ( 2-Ar 3,5-CF3 ) and [Li(THF)(Et 2 O)][Ce═NAr 3,5-CF3 (TriNOx)] ( 3-Ar 3,5-CF3 ) have been described. Among these complexes, 2-Ar 3,5-CF3 demonstrated the most intense luminescence feature with excitation at 398 nm and emission at 453 nm. The luminescence measurements, together with a time-dependent density functional theory (TD-DFT) study, helped uncover an intra-ligand n → π* transition that was assigned as the origin of the bright blue luminescence; 3-Ar 3,5-CF3 has an 1.2 eV redshift in excitation energy compared with its proligand. The weak luminescence of other derivatives ( 2-Ar R and 3-Ar 3,5-CF3 ) was attributed to non-radiative decay from low-lying excited states originating from inter-ligand transitions ( 2-Ar R ) or ligand-to-metal charge transfer bands ( 3-Ar 3,5-CF3 ). Overall, the results expand the range of the thorium imido organometallic compounds and demonstrate that thorium(IV) complexes can support strong ligand luminescence. The results also demonstrate the utility of applying a Th(IV) center for tuning the n → π* luminescence energy and intensity of an associated imido moiety.

Catalytic C-H borylation is an attractive method for the conversion of the most abundant hydrocarbon, methane (CH 4 ), to a mild nucleophilic building block. However, existing CH 4 borylation catalysts often suffer from low turnover numbers and conversions, which is hypothesized to result from inactive metal hydride agglomerates. Herein we report that the heterogenization of a bisphosphine molecular precatalyst, [(dmpe)Ir(cod)CH 3 ], onto amorphous silica dramatically enhances its performance, yielding a catalyst that is 12-times more efficient than the current standard for CH 4 borylation. The catalyst affords over 2000 turnovers at 150 °C in 16 h with a selectivity of 91.5% for mono- vs diborylation. Higher catalyst loadings improve yield and selectivity for the monoborylated product (H 3 CBpin) with 82.8% yield and >99% selectivity being achieved with 1255 turnovers. X-ray absorption and dynamic nuclear polarization-enhanced solid-state NMR spectroscopic studies identify the supported precatalyst as an Ir I species, and indicate that upon completion of catalysis, multinuclear Ir polyhydrides are not formed. This is consistent with the hypothesis that immobilization of the organometallic Ir species on a surface prevents bimolecular decomposition pathways. Immobilization of the homogeneous Ir I fragment onto amorphous silica represents a unique and simple strategy to improve the TON and longevity of a CH 4 borylation catalyst.

Background: Parkinson's disease is a degenerative neurological disorder that can cause both motor and nonmotor symptoms. Motor symptoms are associated with increasing the patient's falls risk. Shoulder arthroplasty surgery in this patient cohort is associated with more complications than non-Parkinsonian patients. We sought to identify any increase in complications associated with this patient cohort and any surgical considerations that ought to be taken in light of their disease process., Methods: We performed a systematic review of articles using PubMed, MEDLINE, Cochrane Central, and Google Scholar. All studies which included any shoulder arthroplasty surgery for patients with Parkinson's disease were included., Results: Complication rates were higher in patients with Parkinson's disease than in the normal arthroplasty cohort in all studies. There was significant heterogeneity between all 8 studies included in the systematic review. Complication rates ranged from 26% to 100%. Complications included subluxation, loosening, malunion, nonunion, scapular notching, stiffness, fracture, baseplate failure, dislocation, and infection. Reoperation rates ranged from 5% to 29%., Conclusion: Compared to patients without Parkinson's disease undergoing shoulder arthroplasty, patients with Parkinson's disease achieved similar reductions in pain but inferior clinical function. The range of movement was less predictable, and complication rates were significantly higher in Parkinson's disease patients. This study will aid the surgeon and patient regarding surgical intervention, informed consent, and allow the surgeon to anticipate potential complications of shoulder arthroplasty in this patient cohort., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)

Purpose: To study the literature to evaluate the functional outcomes, radiologic outcomes, and revision rates following arthroscopic rotator cuff repair (ARCR) at a minimum of 10-years follow-up., Methods: Two independent reviewers performed a literature search of PubMed, Embase, and Scopus using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Only studies reporting on outcomes of ARCR with a minimum 10-year follow-up were considered for inclusion. Patient demographics, satisfaction, and clinical, radiologic, and surgical outcomes were evaluated., Results: Our search found 9 studies including 455 shoulders in 448 patients (51.6% male patients), with age at time of surgery ranging from 45 to 90 years met our inclusion criteria. Overall follow-up ranged from 10 to 18 years. At final follow-up, the ranges of American Shoulder & Elbow Surgeons, age- and sex-adjusted Constant-Morley, and University of California Los Angeles scores were reported in 5, 6, and 3 studies, respectively, as 79.4 to 93.2, 73.2 to 94, and 26.5 to 33, respectively. Of the included studies, satisfaction rates varied in 6 studies from 85.7% to 100% in the long-term. Additionally, the overall radiologic retear rate ranged from 9.5% to 63.2%. The overall surgical revision rates ranged in 6 studies from 3.8% to 15.4%, with from 0% to 6.7% requiring revision ARCR and from 1.0% to 3.6% requiring revision subacromial decompression in 6 and 2 studies, respectively, at minimum 10-years' follow-up., Conclusions: In this study, we found that ARCR results in high rates of patient satisfaction, satisfactory clinical outcomes with respect to patient-reported functional outcomes and range of motion, and low revision rates at minimum 10-years' follow-up. However, an overall 30% retear rate was observed in asymptomatic patients., Level of Evidence: Level IV, systematic review of Level II-IV studies., (Copyright © 2022 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Complexes featuring lanthanide-ligand multiple bonds are rare and highly reactive. They are important synthetic targets to understand 4f/5d-bonding in comparison to d-block and actinide congeners. Herein, the isolation and characterization of a bridging cerium(IV)-nitride complex: [(TriNOx)Ce(Li 2 μ-N)Ce(TriNOx)][BAr F 4 ] is reported, the first example of a molecular cerium-nitride. The compound was isolated by deprotonating a monometallic cerium(IV)-ammonia complex: [Ce IV (NH 3 )(TriNOx)][BAr F 4 ]. The average Ce═N bond length of [(TriNOx)Ce(Li 2 μ-N)Ce(TriNOx)][BAr F 4 ] was 2.117(3) Å. Vibrational studies of the 15 N-isotopomer exhibited a shift of the Ce═N═Ce asymmetric stretch from ν = 644 cm -1 to 640 cm -1 , and X-ray spectroscopic studies confirm the +4 oxidation state of cerium. Computational analyses showed strong involvement of the cerium 4f shell in bonding with overall 16% and 11% cerium weight in the σ- and π-bonds of the Ce═N═Ce fragment, respectively.

5-Methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) is considered to be the most crystalline polymorphic organic molecule discovered to date with 12 fully characterized crystal structures present in the Cambridge Structural Database (CSD). However, metal complexes of ROY have not previously been described. Here, we explore the synthetic chemistry of ROY (denoted as H-ROY hereafter for the purpose of our study) and demonstrate that it can be deprotonated using either NaH or KH and that the resulting sodium and potassium salts of H-ROY can be cleanly isolated. Furthermore, we introduce two new metal complexes of the ROY anion (ROY - ) with Co(II) and Ni(II) cations, formed by the reaction of the sodium salt of ROY, Na(ROY) , with the respective transition-metal chloride salts. Solid-state X-ray diffraction studies confirm the presence of Co(II) or Ni(II) centers, with the ROY - ligand in a 1:2 ratio forming neutral trinuclear clusters of the forms [Co 3 ROY 6 ] ( Co-ROY) and [Ni 3 ROY 6 ] ( Ni-ROY) in both cases. Here, the ROY - moiety interacts with the metal center through the anionic N atom, an O atom of the -NO 2 group, and the N atom of the -CN group. IR and electronic absorption spectroscopies reveal the influence of the Co(II) and Ni(II) centers on the properties of the complexes. Taken together, our results show that the metal complexes of the H-ROY proligand can be prepared with late 3d transition metals. The results of these structural chemistry studies may contribute to resolving polymorphism in H-ROY and related compounds.

Decarbonylation along with P-atom transfer from the phosphaethynolate anion, PCO - , to the Nb IV complex [(PNP)NbCl 2 (N t BuAr)] (1) (PNP=N[2-P i Pr 2 -4-methylphenyl] 2 - ; Ar=3,5-Me 2 C 6 H 3 ) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(N t BuAr)] (2). Reduction of 2 with CoCp* 2 cleaves the P-P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(N t BuAr)] (3). Theoretical studies have been used to understand both the coupling of the P-atom and the reductive cleavage of the P-P bond. Reaction of 3 with a two-electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P-P coupled ligand, namely [(PNPP)Nb=S(N t BuAr)] (4)., (© 2022 Wiley-VCH GmbH.)

Thermolysis of [ H (BPI)Pt(CH 3 )][OTf] (BPI = 1,3-bis(2-(4- tert -butyl)pyridylimino)isoindole) to release methane and form (BPI)Pt(OTf) is reported. Kinetic, mechanistic, and computational studies point to an unusual anion-assisted pathway that obviates the need for a higher oxidation state intermediate to couple the metal-bound methyl group with the ligand-bound hydrogen. Leveraging this insight, a triflimide derivative of the (BPI)Pt complex was shown to activate benzene, highlighting the role of the counteranion in controlling the activity of these complexes.

This report describes the first examples of unassisted C(sp)-C(sp 2 ) and C(sp)-C(sp 3 ) bond oxidative addition reactions to give thermodynamically favorable products. Treatment of a diiron complex supported by a geometrically and electronically flexible macrocyclic ligand, ( 3 PDI 2 )Fe 2 (μ-N 2 )(PPh 3 ) 2 ( [Fe 2 N 2 ] 0 ), with stoichiometric amounts of various 4,4'-disubstituted diphenylacetylenes (Ar X -C≡C-Ar X ; X = OMe, H, F, CF 3 ) yielded C(sp)-C(sp 2 ) bond oxidative addition products. When Ph-C≡C-R substrates were used as substrates (R = Me, Et, i Pr, t Bu), products of either C(sp)-C(sp 2 ) or C(sp)-C(sp 3 ) bond activation were obtained, with the less sterically encumbering alkynes exclusively undergoing C(sp)-C(sp 3 ) bond activation. Treatment of the C-C activation species with either H 2 or HBpin was found to form products of C-C σ-bond hydrofunctionalization. In both the hydrogenation and hydroboration schemes, the diiron species was observed to return to [Fe 2 N 2 ] 0 , thereby completing synthetic cycles for C-C σ-bond functionalization.

Highly modular and rational syntheses of titanium compounds containing ditelluride, terminal telluride, and bis(telluride) structural motifs are disclosed in this study. Titanate anions bearing two cis and terminal telluride functionalities bound to the same metal center represent a unique example of a group 4 transition metal bis(chalcogenide) ion and are accessed in a simple, single-step procedure from Ti(III) bis(alkyl) complexes in the presence of an outer-sphere reductant and at least 3 equiv of Te 0 powder. These compounds have been characterized crystallographically and spectroscopically with some preliminary reactivity reported for the anionic Ti(═Te) 2 motif. We also report solution 125 Te NMR spectral data in addition to theoretical studies addressing the bonding and structure for these titanate bis(tellurido) systems.

Syntheses of Vaska-type complexes [IrP 2 X(CO)] (P = phosphine, X = halide) with all four common halides (fluoride, chloride, bromide, and iodide) was attempted using a protic and hemilabile imidazolyl di- tert -butyl phosphine ligand. In the solid-state, all four complexes were found to be ionic with the halides in the outer-sphere, and the fourth coordination site of the square plane occupied by the imidazole arm of the ligand. In solution, however, the chloride complex was found to be in equilibrium with an octahedral Ir III -H species at room temperature. For the bromide and iodide analogs, the corresponding Ir III -H species were also observed but only after heating the solutions. The neutral Ir I Vaska's analogs for X = Cl, Br, and I were obtained upon addition of excess halide salt, albeit heating was required for X = Br and I. The Ir III -H species are proposed to originate from tautomerization of minor amounts of the electron rich neutral Vaska analog (halide inner-sphere and phosphines monodentate) that are in equilibrium with the ionic species. Heating is required for the larger anions of bromide and iodide to overcome a kinetic barrier associated with their movement to an inner-sphere position prior to tautormerization. For the fluoride analog, the Ir III -H was not observed, attributable to strong hydrogen bonding interactions of the imidazolyl proton with the fluoride anion., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Transmetallation of [VCl 3 (THF) 3 ] and [TlTp t Bu,Me ] afforded [(Tp t Bu,Me )VCl 2 ] ( 1 , Tp t Bu,Me = hydro-tris(3- tert- butyl-5-methylpyrazol-1-yl)borate), which was reduced with KC 8 to form a C 3v symmetric V II complex, [(Tp t Bu,Me )VCl] ( 2 ). Complex 1 has a high-spin ( S = 1) ground state and displays rhombic high-frequency and -field electron paramagnetic resonance (HFEPR) spectra, while complex 2 has an S = 3/2 4 A 2 ground state observable by conventional EPR spectroscopy. Complex 1 reacts with NaN 3 to form the V V nitride-azide complex [(Tp t Bu,Me )V≡N(N 3 )] ( 3 ). A likely V III azide intermediate en route to 3 , [(Tp t Bu,Me )VCl(N 3 )] ( 4 ), was isolated by reacting 1 with N 3 SiMe 3 . Complex 4 is thermally stable but reacts with NaN 3 to form 3 , implying a bis-azide intermediate, [(Tp t Bu,Me )V(N 3 ) 2 ] ( A ), leading to 3 . Reduction of 3 with KC 8 furnishes a trinuclear and mixed-valent nitride, [{(Tp t Bu,Me )V} 2 (μ 4 -VN 4 )] ( 5 ), conforming to a Robin-Day class I description. Complex 5 features a central vanadium ion supported only by bridging nitride ligands. Contrary to 1 , complex 2 reacts with NaN 3 to produce an azide-bridged dimer, [{(Tp t Bu,Me )V} 2 (1,3-μ 2 -N 3 ) 2 ] ( 6 ), with two antiferromagnetically coupled high-spin V II ions. Complex 5 could be independently produced along with [(κ 2 -Tp t Bu,Me ) 2 V] upon photolysis of 6 in arene solvents. The putative {V IV ≡N} intermediate, [(Tp t Bu,Me )V≡N] ( B ), was intercepted by photolyzing 6 in a coordinating solvent, such as tetrahydrofuran (THF), yielding [(Tp t Bu,Me )V≡N(THF)] ( B - THF ). In arene solvents, B-THF expels THF to afford 5 and [(κ 2 -Tp t Bu,Me ) 2 V]. A more stable adduct ( B-OPPh 3 ) was prepared by reacting B-THF with OPPh 3 . These adducts of B are the first neutral and mononuclear V IV nitride complexes to be isolated.

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb mixtures uses an energy-intensive process with caustic and toxic conditions. It is of interest to develop alternative, fundamental methodologies for the purification of these technologically important metals that improve upon their environmental impact. Herein, we introduce new Ta/Nb imido compounds: M( t BuN)(TriNOx) (1-M) bound by the TriNOx 3- ligand and demonstrate a fundamental, proof-of-concept Ta/Nb separation based on differences in the imido reactivities. Despite the nearly identical structures of 1-M, density functional theory (DFT)-computed electronic structures of 1-M indicate enhanced basic character of the imido group in 1-Ta as compared to 1-Nb. Accordingly, the rate of CO 2 insertion into the M[double bond, length as m-dash]N imido bond of 1-Ta to form a carbamate complex (2-Ta) was selective compared to the analogous, unobserved reaction with 1-Nb. Differences in solubility between the imido and carbamate complexes allowed for separation of the carbamate complex, and led to an efficient Ta/Nb separation ( S Ta/Nb = 404 ± 150) dependent on the kinetic differences in nucleophilicities between the imido moieties in 1-Ta and 1-Nb., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A synthetic route has been developed for a series of 3d homobimetallic complexes of Mn, Fe, Co, Ni, and Cu using three different pyridyldiimine and pyridyldialdimine macrocyclic ligands with ring sizes of 18, 20, and 22 atoms. Crystallographic analyses indicate that while the distances between the metals can be modulated by the size of the macrocycle pocket, the flexibility in the alkyl linkers used to construct the macrocycles enables the ligand to adjust the orientation of the PD(A)I fragments in response to the geometry of the [M 2 (μ-Cl) 2 ] 2+ core, particularly with respect to Jahn-Teller distortions. Analyses by UV-vis spectroscopy and SQUID magnetometry revealed deviations in the properties [M 2 (μ-Cl) 2 ] 2+ -containing complexes bound by standard mononucleating ligands, highlighting the ability of macrocycles to use ring size to control the magnetic interactions of pseudo -octahedral, high-spin metal centers.

The affinity of small molecules for biomolecular cavities is tuned through a combination of primary and secondary interactions. It has been challenging to mimic these features in organic synthetic host molecules, however, where the cavities tend to be highly symmetric and nonpolar, and less amenable to chemical manipulation. Here, a host molecule composed of a TREN ligand and cyclotriveratrylene moiety was investigated. Size-matched polar guests were encapsulated within the cavity via triple protonation of the TREN moiety with various sulfonic acids. X-ray crystallography confirmed guest encapsulation and identified three methanesulfonates, p -toluenesulfonates, or 2-naphthalenesulfonates hydrogen-bonded with H 3 TREN at the periphery of the cavity. These structurally diverse counteranions were shown by 1 H NMR spectroscopy to differentially regulate guest access at the three portals, and to undergo competitive displacement in solution. This work reveals "counteranion tuning" to be a simple and powerful strategy for modulating host-guest affinity, as applied here in a TREN-hemicryptophane.

This study presents the role of 5d orbitals in the bonding, and electronic and magnetic structure of Ce imido and oxo complexes synthesized with a tris(hydroxylaminato) [((2- t BuNO)C 6 H 4 CH 2 ) 3 N] 3- (TriNO x 3- ) ligand framework, including the reported synthesis and characterization of two new alkali metal-capped Ce oxo species. X-ray spectroscopy measurements reveal that the imido and oxo materials exhibit an intermediate valent ground state of the Ce, displaying hallmark features in the Ce L III absorption of partial f-orbital occupancy that are relatively constant for all measured compounds. These spectra feature a double peak consistent with other formal Ce(iv) compounds. Magnetic susceptibility measurements reveal enhanced levels of temperature-independent paramagnetism (TIP). In contrast to systems with direct bonding to an aromatic ligand, no clear correlation between the level of TIP and f-orbital occupancy is observed. CASSCF calculations defy a conventional van Vleck explanation of the TIP, indicating a single-reference ground state with no low-lying triplet excited state, despite accurately predicting the measured values of f-orbital occupancy. The calculations do, however, predict strong 4f/5d hybridization. In fact, within these complexes, despite having similar f-orbital occupancies and therefore levels of 4f/5d hybridization, the d-state distributions vary depending on the bonding motif (Ce[double bond, length as m-dash]O vs. Ce[double bond, length as m-dash]N) of the complex, and can also be fine-tuned based on varying alkali metal cation capping species. This system therefore provides a platform for understanding the characteristic nature of Ce multiple bonds and potential impact that the associated d-state distribution may have on resulting reactivity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The mono -benzaldimine (HN═CHPh) complex [( t Bu pyrpyrr 2 )Fe(HN═CHPh)] ( 1 -HN═CHPh) has been prepared by reaction of [( t Bu pyrpyrr 2 )Fe(OEt 2 )] ( 1 -OEt 2 ) ( t Bu pyrpyrr 2 = 2,6-bis(3,5-di- tert -butyl-pyrrolyl)pyridine) with one equivalent of benzyl azide. Compound 1 -HN═CHPh retains the cis -divacant octahedral coordination geometry akin to 1 , as established by single crystal X-ray diffraction study. A bis -HN═CHPh complex [( t Bu pyrpyrr 2 )Fe(HN═CHPh) 2 ] ( 2 ) was also prepared by the addition of two equivalents of benzyl azide to 1 , and its molecular structure exhibits the two HN═CHPh ligands coordinated trans to each other, thereby forming a square pyramidal coordination geometry at the Fe II center. Reaction of 1 with excess benzyl azide yields [( t Bu pyrpyrr 2 )Fe(HN═CHPh) 2 ·PhCHNCH(NH 2 )Ph] ( 2 -PhCHNCH(NH 2 )Ph), which contains an unstable benzylideneamino phenyl methanamine fragment, effectively hydrogen bonded to 2 . Thermolysis of 2 or 2 -PhCHNCH(NH 2 )Ph releases the HN═CHPh self-coupling products hydrobenzamide ( A ), N -benzylidine benzylamine ( B ), and benzonitrile ( C ). Under catalytic conditions, free HN═CHPh ( cis/trans -HN═CHPh mixture) is produced using 2.5 mol % of 1 in 90% spectroscopic yield. These studies provide a clearer understanding for the conversion of the HN═CHPh in 2 or 2 -PhCHNCH(NH 2 )Ph to the C-C and C-N coupled products. Reduction of 1 -HN═CHPh with KC 8 yields the reductively coupled benzylamide complex [K(OEt 2 )] 2 [( t Bu pyrpyrr 2 ) 2 Fe 2 (μ 2 -NHCHPhCHPhNH)] ( 3 ) as the result of a new C-C bond formed between two radical benzylamide fragments.

The critical metals niobium (Nb) and tantalum (Ta) coexist in mineral sources, requiring a separation step to purify the elements from one another. The industrial separation process by solvent extraction uses stoichiometric hydrofluoric acid to manifest differences in the speciation of these otherwise chemically similar elements. The identification of alternative methods to separate Nb/Ta is desirable for fluoride waste reduction. In pursuit of this goal, the novel complexes [Na(CH 3 CN) 3 (Et 2 O)][M(( S )-BINOLate) 3 ] [M = Nb ( 1-Nb ), Ta ( 1-Ta )] were synthesized and characterized. In electrochemical studies, a reduction event at the potential -2.04 V versus ferrocene/ferrocenium was observed for 1-Nb , whereas 1-Ta exhibited no metal-based waves in the electrochemical window. In addition to the inherent 4d/5d orbital energy differences between Nb/Ta, density functional theory calculations suggest a larger degree of π donation from the ligands to the metal cation in 1-Ta compared to 1-Nb , destabilizing the lowest unoccupied molecular orbital. This phenomenon contributes to a calculated reduction potential difference of ca. 0.75 V, allowing for the selective reduction of 1-Nb and separation of the reduction product through leaching with diethyl ether for a separation factor of 6 ± 2.

Background: A 'terrible triad injury of the elbow' (TTIE) refers to an injury pattern involving posterior dislocation of the ulnohumeral joint, fracture of the radial head, and fracture of the coronoid process of the ulna. It is a complex injury to the elbow joint and can result in long-term elbow instability, pain, stiffness, and arthritis. In specific cases, it may be treated conservatively, but in most circumstances, surgical stabilization is advised.The 'drop sign' is an objective static radiographically measured ulnohumeral distance of ≥4 mm seen intraoperatively and postoperatively. Although controversial, it may portend postoperative instability and arthritis. The senior author repairs these injuries in a standardized fashion through a modified Boyd rather than a lateral approach. Our aim was to assess the number of cases demonstrating an intraoperative drop sign after surgical treatment of a TTIE with this approach., Methods: We retrospectively analyzed 22 consecutive patients with 23 acute TTIEs. These injuries were treated by a single surgeon using a modified Boyd (posterior) approach to the elbow. Intraoperative image intensifier x-rays were analyzed by the two authors to assess for a 'drop sign'., Results: None of the 23 cases had 'drop signs' on intraoperative imaging after stabilization. No patient has redislocated, underwent reoperation, or had symptoms of instability at follow-up., Conclusion: None of our patient cohort had an intraoperative 'drop sign' after standardized stabilization for a TTIE injury using a modified Boyd approach., (© 2022 The Authors.)

A low-spin and mononuclear vanadium complex, ( Me nacnac)V(CO)(η 2 -P≡C t Bu) (2) ( Me nacnac - =[ArNC(CH 3 )] 2 CH, Ar=2,6- i Pr 2 C 6 H 3 ), was prepared upon treatment of the vanadium neopentylidyne complex ( Me nacnac)V≡C t Bu(OTf) (1) with Na(OCP)(diox) 2.5 (diox=1,4-dioxane), while the isoelectronic ate-complex [Na(15-crown-5)]{([ArNC(CH 2 )]CH[C(CH 3 )NAr])V(CO)(η 2 -P≡C t Bu)} (4), was obtained via the reaction of Na(OCP)(diox) 2.5 and ([ArNC(CH 2 )]CH[C(CH 3 )NAr])V≡C t Bu(OEt 2 ) (3) in the presence of crown-ether. Computational studies suggest that the P-atom transfer proceeds by [2+2]-cycloaddition of the P≡C bond across the V≡C t Bu moiety, followed by a reductive decarbonylation to form the V-C≡O linkage. The nature of the electronic ground state in diamagnetic complexes, 2 and 4, was further investigated both theoretically and experimentally, using a combination of density functional theory (DFT) calculations, UV/Vis and NMR spectroscopies, cyclic voltammetry, X-ray absorption spectroscopy (XAS) measurements, and comparison of salient bond metrics derived from X-ray single-crystal structural characterization. In combination, these data are consistent with a low-valent vanadium ion in complexes 2 and 4. This study represents the first example of a metathesis reaction between the P-atom of [PCO] - and an alkylidyne ligand., (© 2021 Wiley-VCH GmbH.)

Oxidation of the low-spin Fe IV imido complex [{( t Bu pyrr) 2 py}Fe═NAd] ( 1 ) (( t Bu pyrr) 2 py 2- = 2,6-bis(3,5-di- tert -butyl-pyrrolyl)pyridine, Ad = 1-adamantyl) with AgOAc or AgNO 3 promotes reductive N-N bond coupling of the former imido nitrogen with a pyrrole nitrogen to form the respective ferric hydrazido-like pincer complexes [{( t Bu pyrrNAd)( t Bu pyrr)py}Fe(κ 2 -X)] (X = OAc - , 2 OAc ; NO 3 - , 2 NO 3 ). Reduction of 2 OAc with KC 8 cleaves the N-N bond to reform the Fe IV imido ligand in 1 , whereas acid-mediated demetalation of 2 OAc or 2 NO 3 yields the free hydrazine ligand [( t Bu pyrrNHAd)( t Bu pyrrH)py] ( 3 ), the latter of which can be used as a direct entry to the iron imido complex when treated with [Fe{N(SiMe 3 ) 2 } 2 ]. In addition to characterizing these Fe systems, we show how this nitrene transfer strategy can be expanded to Co for the one-step synthesis of Co{( t Bu-NHAd pyrr)( t Bu pyrr)py}] ( 4 ) (( t Bu-NHAd pyrr)( t Bu pyrr)py 2- = 2-(3- t Bu-5-(1-adamantylmethyl-2-methylpropane-2-yl)-pyrrol-2-yl)-6-(3,5- t Bu 2 -pyrrol-2-yl)-pyridine).

The functionalization of methane, ethane, and other alkanes derived from fossil fuels is a central goal in the chemical enterprise. Recently, a photocatalytic system comprising [Ce IV Cl 5 (OR)] 2- [Ce IV , cerium(IV); OR, -OCH 3 or -OCCl 2 CH 3 ] was disclosed. The system was reportedly capable of alkane activation by alkoxy radicals (RO•) formed by Ce IV -OR bond photolysis. In this work, we present evidence that the reported carbon-hydrogen (C-H) activation of alkanes is instead mediated by the photocatalyst [NEt 4 ] 2 [CeCl 6 ] (NEt 4 + , tetraethylammonium), and RO• are not intermediates. Spectroscopic analyses and kinetics were investigated for C-H activation to identify chlorine radical (Cl•) generation as the rate-limiting step. Density functional theory calculations support the formation of [Cl•][alcohol] adducts when alcohols are present, which can manifest a masked RO• character. This result serves as an important cautionary note for interpretation of radical trapping experiments., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The nitride salt [(PN) 2 Ti≡N{μ 2 -K(OEt 2 )}] 2 ( 1 ) (PN - = ( N -(2-P i Pr 2 -4-methylphenyl)-2,4,6-Me 3 C 6 H 2 ) can be oxidized with two equiv of I 2 or four equiv of ClCPh 3 to produce the phosphinimide-halide complexes (NPN')(PN)Ti(X) (X - = I ( 2 ), Cl ( 3 ); NPN' = N-(2-NP i Pr 2 -4-methylphenyl)-2,4,6-Me 3 C 6 H 2 2- ), respectively. In the case of 2 , H 2 was found to be one of the other products; whereas, HCPh 3 and Gomberg's dimer were observed upon the formation of 3 . Independent studies suggest that the oxidation of 1 could imply the formation of the transient nitridyl species [(PN) 2 Ti(≡N•)] ( A ), which can either oxidize the proximal phosphine atom to produce the Ti(III) intermediate [(NPN')(PN)Ti] ( B ) or, alternatively, engage in H atom abstraction to form the parent imido (PN) 2 Ti≡NH ( 4 ). The latter was independently prepared and was found to photochemically convert to the titanium-hydride, (NPN')(PN)Ti(H) ( 5 ). Isotopic labeling studies using (PN) 2 Ti≡ND ( 4 - d 1 ) as well as reactivity studies of 5 with a hydride abstractor demonstrate the presence of the hydride ligand in 5 . An alternative route to putative A was observed via a photochemically promoted incomplete reduction of the azide ligand in (PN) 2 Ti(N 3 ) ( 6 ) to 4 . This process was accompanied by some formation of 5 . Frozen matrix X-band EPR studies of 6 , performed under photolytic conditions, were consistent with species B being formed under these reaction conditions, originating from a low barrier N-insertion into the phosphine group in the putative nitridyl species A . Computational studies were also undertaken to discover the mechanism and plausibility of the divergent pathways (via intermediates A and B ) in the formation of 2 and 3 , and to characterize the bonding and electronic structure of the elusive nitrogen-centered radical in A .

A series of 2,6-diiminopyridine-derived macrocyclic ligands have been synthesized via [2+2] condensation around alkaline earth metal triflate salts. The inclusion of a tert -butyl group at the 4-position of the pyridine ring of the macrocyclic synthons results in macrocyclic complexes that are soluble in common organic solvents, thereby enabling a systematic comparison of the physical properties of the complexes by NMR spectroscopy, mass spectrometry, solution-phase UV-Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Solid-state structures determined crystallographically demonstrate increased twisting in the ligand, concurrent with either a decrease in ion size or an increase in macrocycle ring size (18, 20, or 22 membered rings). The degree of folding and twisting within the macrocycle can be quantified using parameters derived from the N pyr -M-N pyr bond angle and the relative orientation of the pyridinediimine (PDI) and pyridinedialdimine (PDAI) fragments to each other within the solid state structures. Cyclic voltammetry and UV-Vis spectroscopy were used to compare the relative energies of the imine π* orbital of the redox active PDI and PDAI components in the macrocycle when coordinated to redox inactive metals. Both methods indicate the change from a methyl to hydrogen substitution on the imine carbon lowers the energy of the ligand π* system., Competing Interests: Declaration of Interest. The authors have no known competing interests to declare.

The synthesis of bona fide organometallic Ce IV complexes is a formidable challenge given the typically oxidizing properties of the Ce IV cation and reducing tendencies of carbanions. Herein, we report a pair of compounds comprising a Ce IV  - C aryl bond [Li(THF) 4 ][Ce IV (κ 2 -ortho-oxa)(MBP) 2 ] (3-THF) and [Li(DME) 3 ][Ce IV (κ 2 -ortho-oxa)(MBP) 2 ] (3-DME), ortho-oxa = dihydro-dimethyl-2-[4-(trifluoromethyl)phenyl]-oxazolide, MBP 2-  = 2,2'-methylenebis(6-tert-butyl-4-methylphenolate), which exhibit Ce IV  - C aryl bond lengths of 2.571(7) - 2.5806(19) Å and strongly-deshielded, Ce IV  - C ipso 13 C{ 1 H} NMR resonances at 255.6 ppm. Computational analyses reveal the Ce contribution to the Ce IV  - C aryl bond of 3-THF is ~12%, indicating appreciable metal-ligand covalency. Computations also reproduce the characteristic 13 C{ 1 H} resonance, and show a strong influence from spin-orbit coupling (SOC) effects on the chemical shift. The results demonstrate that SOC-driven deshielding is present for Ce IV  - C ipso 13 C{ 1 H} resonances and not just for diamagnetic actinide compounds.

The super electron donor (SED) ability of 2-azaallyl anions has recently been discovered and applied to diverse reactivity, including transition metal-free cross-coupling and dehydrogenative cross-coupling processes. Surprisingly, the redox properties of 2-azaallyl anions and radicals have been rarely studied. Understanding the chemistry of elusive species is the key to further development. Electrochemical analysis of phenyl substituted 2-azaallyl anions revealed an oxidation wave at E 1/2 or E pa = -1.6 V versus Fc/Fc + , which is ∼800 mV less than the reduction potential predicted ( E pa = -2.4 V vs. Fc/Fc + ) based on reactivity studies. Investigation of the kinetics of electron transfer revealed reorganization energies an order of magnitude lower than commonly employed SEDs. The electrochemical study enabled the synthetic design of the first stable, acyclic 2-azaallyl radical. These results indicate that the reorganization energy should be an important design consideration for the development of more potent organic reductants., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

A series of tetradentate tris(phosphinimine) ligands ( R3 P 3 tren) was developed and bound to Cu I to form the trigonal pyramidal, C 3v -symmetric cuprous complexes [ R3 P 3 tren-Cu][BAr F 4 ] ( 1PR3 ) (PR 3 = PMe 3 , PMe 2 Ph, PMePh 2 , PPh 3 , PMe 2 (NEt 2 ), BAr F 4 = B(C 6 F 5 ) 4 ). Electrochemical studies on the Cu I complexes were undertaken, and the permethylated analog, 1PMe3 , was found to display an unprecedentedly cathodic Cu I /Cu II redox potential (-780 mV vs. Fc/Fc + in isobutyronitrile). Elucidation of the electronic structures of 1PR3 via density functional theory (DFT) studies revealed atypical valence manifold configurations, resulting from strongly σ-donating phosphinimine moieties in the xy -plane that destabilize 2 e (d xy /d x 2 - y 2 ) orbital sets and uniquely stabilized a 1 (d z 2 ) orbitals. Support is provided that the a 1 stabilizations result from intramolecular electrostatic fields (ESFs) generated from cationic character on the phosphinimine moieties in R3 P 3 tren. This view is corroborated via 1-dimensional electrostatic potential maps along the z -axes of 1PR3 and their isostructural analogues. Experimental validation of this computational model is provided upon oxidation of 1PMe3 to the cupric complex [ Me3 P 3 tren-Cu][OTf] 2 ( 2PMe3 ), which displays a characteristic Jahn-Teller distortion in the form of a see-saw, pseudo- C s -symmetric geometry. A systematic anodic shift in the potential of the Cu I /Cu II redox couple as the steric bulk in the secondary coordination sphere increases is explained through the complexes' diminishing ability to access the ideal C s -symmetric geometry upon oxidation. The observations and calculations discussed in this work support the presence of internal electrostatic fields within the copper complexes, which subsequently influence the complexes' properties via a method orthogonal to classic ligand field tuning., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A high-spin, mononuclear Ti II complex, [(Tp t Bu,Me )TiCl] [Tp t Bu,Me- = hydridotris(3- tert -butyl-5-methylpyrazol-1-yl)borate], confined to a tetrahedral ligand-field environment, has been prepared by reduction of the precursor [(Tp t Bu,Me )TiCl 2 ] with KC 8 . Complex [(Tp t Bu,Me )TiCl] has a 3 A 2 ground state (assuming C 3 v symmetry based on structural studies), established via a combination of high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy, solution and solid-state magnetic studies, Ti K-edge X-ray absorption spectroscopy (XAS), and both density functional theory and ab initio (complete-active-space self-consistent-field, CASSCF) calculations. The formally and physically defined Ti II complex readily binds tetrahydrofuran (THF) to form the paramagnetic adduct [(Tp t Bu,Me )TiCl(THF)], which is impervious to N 2 binding. However, in the absence of THF, the Ti II complex captures N 2 to produce the diamagnetic complex [(Tp t Bu,Me )TiCl] 2 (η 1 ,η 1 ;μ 2 -N 2 ), with a linear Ti═N═N═Ti topology, established by single-crystal X-ray diffraction. The N 2 complex was characterized using XAS as well as IR and Raman spectroscopies, thus establishing this complex to possess two Ti III centers covalently bridged by an N 2 2- unit. A π acid such as CNAd (Ad = 1-adamantyl) coordinates to [(Tp t Bu,Me )TiCl] without inducing spin pairing of the d electrons, thereby forming a unique high-spin and five-coordinate Ti II complex, namely, [(Tp t Bu,Me )TiCl(CNAd)]. The reducing power of the coordinatively unsaturated Ti II -containing [(Τp t Bu,Me )TiCl] species, quantified by electrochemistry, provides access to a family of mononuclear Ti IV complexes of the type [(Tp t Bu,Me )Ti═E(Cl)] (with E 2- = NSiMe 3 , N 2 CPh 2 , O, and NH) by virtue of atom- or group-transfer reactions using various small molecules such as N 3 SiMe 3 , N 2 CPh 2 , N 2 O, and the bicyclic amine 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene.

A series of cerium(iv) mixed-ligand guanidinate-amide complexes, {[(Me 3 Si) 2 NC(N i Pr) 2 ] x Ce IV [N(SiMe 3 ) 2 ] 3- x } + ( x = 0-3), was prepared by chemical oxidation of the corresponding cerium(iii) complexes, where x = 1 and 2 represent novel complexes. The Ce(iv) complexes exhibited a range of intense colors, including red, black, cyan, and green. Notably, increasing the number of the guanidinate ligands from zero to three resulted in significant redshift of the absorption bands from 503 nm (2.48 eV) to 785 nm (1.58 eV) in THF. X-ray absorption near edge structure (XANES) spectra indicated increasing f occupancy ( n f ) with more guanidinate ligands, and revealed the multiconfigurational ground states for all Ce(iv) complexes. Cyclic voltammetry experiments demonstrated less stabilization of the Ce(iv) oxidation state with more guanidinate ligands. Moreover, the Ce(iv) tris(guanidinate) complex exhibited temperature independent paramagnetism (TIP) arising from the small energy gap between the ground- and excited states with considerable magnetic moments. Computational analysis suggested that the origin of the low energy absorption bands was a charge transfer between guanidinate π orbitals that were close in energy to the unoccupied Ce 4f orbitals. However, the incorporation of sterically hindered guanidinate ligands inhibited optimal overlaps between Ce 5d and ligand N 2p orbitals. As a result, there was an overall decrease of ligand-to-metal donation and a less stabilized Ce(iv) oxidation state, while at the same time, more of the donated electron density ended up in the 4f shell. The results indicate that incorporating guanidinate ligands into Ce(iv) complexes gives rise to intense charge transfer bands and noteworthy electronic structures, providing insights into the stabilization of tetravalent lanthanide oxidation states., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)