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The behavior of the potassium alumanyl, [{SiN Dipp }AlK] 2 ({SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6- i -Pr 2 C 6 H 3 ), toward organic nitriles has been investigated. In common with earlier studies of the reactivity of charge neutral Al(I) species with multiply bonded small molecules, it is suggested that the initial step in all the reactions involves [2 + 1] cycloaddition and the generation of an [η 2 -C=N-Al] alumina azacyclopropane unit. In the cases of o - and m -tolyl-substituted aryl nitriles, this species is too kinetically labile to allow its isolation and undergoes C-C coupling via immediate Al-C/C≡N insertion to yield the alumina diazabutadiene derivatives. In contrast, the increased steric profile of alkyl nitriles imposes a marked influence on the nature of the products formed. Consistent with the proposed sequential pathway, reaction of [{SiN Dipp }AlK] 2 with t -BuCN provides an isolable alumina cyclopropane species that is kinetically resistant to onward reaction with a further nitrile equivalent. While reduction in the alkyl nitrile steric demands by use of i -PrCN again facilitates C-C bond formation, the crowding of the Al center by the resultant alumina-diazabutadienediide moiety appears to be beyond the limit of kinetic viability, resulting in an unusual 2-fold C-H to N-H isomerization from one of the C- iso-propyl substituents and the isolation of a 1-alumina-2,5-diazabutadiene structure., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

[{SiN Dipp }BeClM] 2 ({SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; M = Li, Na, K, Rb) are converted to ionic species by treatment with a crown ether. Whereas the lithium derivative reacts with Na or K to provide [{SiN Dipp }BeCl] - [M(12-cr-4) 2 ] + (M = Na, K), the resultant sodium species is resistant to reduction by potassium. These observations are rationalised by a hybrid experimental/theoretical analysis.

The dimeric β-diketiminato calcium hydride, [(BDI)CaH] 2 (BDI = HC{(Me)CN-2,6- i Pr 2 C 6 H 3 } 2 ), reacts with ZnMe 2 to afford the bimetallic calcium zincate complex, [(BDI)Ca(μ-CH 3 ) 2 Zn(μ-H)] 2 , which subsequently undergoes an intramolecular reaction to effect the formation of [(BDI)CaMe] 2 , a notable omission from the homologous series of β-diketiminato alkylcalcium derivatives.

Reactions of β-diketiminato alkaline earth alkyldiboranate derivatives [(BDI)Ae{pinBB(R)pin}] (BDI = HC{(Me)CNDipp} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 ; Ae = Mg, R = n -Bu or Ae = Ca, R = n -hexyl) with t -BuNC provide access to the respective group 2 derivatives of unprecedented diborata-allyl, {(pinB) 2 CNBpin( t -Bu)} - , anions. Although the necessary mode of B-C bond cleavage implicated in these transformations could not be elucidated, further studies of the reactivity of magnesium triboranates toward isonitriles delivered a more general and rational synthetic access to analogous anionic moieties. Extending this latter reactivity to a less symmetric triboranate variant also provided an isomeric Mg-C-bonded dibora-alkyl species and sufficient experimental insight to prompt theoretical evaluation of this reactivity. DFT calculations, thus, support a reaction pathway predicated on initial RNC attack at a peripheral boron centre and the intermediacy of such dibora-alkyl intermediates., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The β-diketiminato calcium and magnesium complexes, [(BDI)Mg n Bu] and [(BDI)CaH] 2 (BDI = HC{C(Me)NDipp} 2 ; Dipp = 2,6-di-isopropylphenyl), react with ortho -carborane ( o -C 2 B 10 H 12 ) to provide the respective [(BDI)Ae( o -C 2 B 10 H 11 )] (Ae = Mg or Ca) complexes. While the lighter group 2 species is a monomer with magnesium in a distorted trigonal planar environment, the heavier analogue displays a puckered geometry at calcium in the solid state due to Ca⋯H-B intermolecular interactions. These secondary contacts are, however, readily disrupted upon addition of THF to provide the 4-coordinate monomer, [(BDI)Ca(THF)( o -C 2 B 10 H 11 )]. [(BDI)Mg( o -C 2 B 10 H 11 )] was reacted with [NHC IPr MCl] (NHC IPr = 1,3-bis(isopropyl)imidazol-2-ylidene; M = Cu, Ag, Au) to provide [NHC IPr M( o -C 2 B 10 H 11 )], rare C -bonded examples of coinage metal derivatives of unsubstituted ( o -C 2 B 10 H 11 ) - and confirming the alkaline earth compounds as viable reagents for the transmetalation of the carboranyl anion.

Reported is the reaction of a series of iron(II) bisphosphine complexes with PH 3 in the presence of NaBAr F 4 [where BAr F 4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate]. The iron(II) bisphosphine reagents bear two chlorides or a hydride and a chloride motif. We have isolated six different cationic terminal-bound PH 3 complexes and undertaken rigorous characterization by NMR spectroscopy, single crystal X-ray diffraction, and mass spectrometry, where the PH 3 often remains intact during the ionization process. Unusual bis- and tris-PH 3 complexes are among the compounds isolated. Changing the monophosphine from PH 3 to PMe 3 results in the formation of an unusual Fe 7 cluster, but with no PMe 3 being ligated. Finally, by using an iron(0) source, we have provided a rare example of a terminally bound iron-PH 2 complex.

The bimetallic species, [{SiN Dipp }MgNa] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; (Dipp = 2,6- i -Pr 2 C 6 H 3 )], is shown to be a potent reducing agent, able to effect one- or two-electron reduction of either dioxygen, TEMPO, anthracene, benzophenone, or diphenylacetylene. In most cases, the bimetallic reaction products imply that the dissimilar alkaline metal centers react with a level of cooperativity. EPR analysis of the benzophenone-derived reaction and the concurrent isolation of [{SiN Dipp }Mg(OCPh 2 ) 2 ], however, illustrate that treatment with such reducible, but O -basic, species can also result in reactivity in which the metals provide independent reaction products. The notable E -stereochemistry of the diphenylacetylene reduction product prompted a computational investigation of the PhC≡CPh addition. This analysis invokes a series of elementary steps that necessitate ring-opening via Mg + → Na + amido group migration of the SiN Dipp ligand, providing insight into the previously observed lability of the bidentate dianion and its consequent proclivity toward macrocyclization., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Liquid assisted ball milling of [NHC]HBr (NHC = N-heterocyclic carbene) salts with copper(I) chloride, and a range of alkali metal complexes was shown to efficiently produce (NHC)CuX (NHC = normal or RE-NHC, X = halide, alkoxide, amide, alkyl, aryl; RE-NHC = ring-expanded NHC).

Room temperature reaction of elemental cesium with the dimeric lithium chloroberyllate [{SiN Dipp }BeClLi] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 , where Dipp = 2,6-di-isopropylphenyl, in C 6 D 6 results in activation of the arene solvent. Although, in contrast to earlier observations of lithium and sodium metal reduction, the generation of a mooted cesium phenylberyllate could not be confirmed, this process corroborates a previous hypothesis that such beryllium-centered solvent activation also necessitates the formation of hydridoberyllium species. These observations are further borne out by the study of an analogous reaction performed in toluene, in which case the proposed generation of formally low oxidation state beryllium radical anion intermediates induces activation of a toluene sp 3 C-H bond and the isolation of the polymeric cesium benzylberyllate, [Cs({SiN Dipp }BeCH 2 C 6 H 5 )] ∞ ., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Reaction of (6-Dipp)CuOtBu (6-Dipp=C{NDippCH 2 } 2 CH 2 , Dipp=2,6-iPr 2 C 6 H 3 ) with B 2 (OMe) 4 provided access to (6-Dipp)CuB(OMe) 2 via σ-bond metathesis. (6-Dipp)CuB(OMe) 2 was characterised by NMR spectroscopy and X-ray crystallography and shown to be a monomeric acyclic boryl of copper. (6-Dipp)CuB(OMe) 2 reacted with ethylene and diphenylacetylene to provide insertion compounds into the Cu-B bond which were characterised by NMR spectroscopy in both cases and X-ray crystallography in the latter. It was also competent in the rapid catalytic deoxygenation of CO 2 in the presence of excess B 2 (OMe) 4 . Alongside π-insertion, (6-Dipp)CuB(OMe) 2 reacted with LiNMe 2 to provide a salt metathesis reaction at boron, giving (6-Dipp)CuB(OMe)NMe 2 , a second monomeric acyclic boryl, which also cuproborated diphenylacetylene. Computational interrogation validated these acyclic boryl species to be electronically similar to (6-Dipp)CuBpin., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Counter to synthetic convention and expectation provided by the relevant standard reduction potentials, the chloroberyllate, [{SiN Dipp }BeClLi] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 )], reacts with the group 1 elements (M = Na, K, Rb, Cs) to provide the respective heavier alkali metal analogues, [{SiN Dipp }BeClM] 2 , through selective reduction of the Li + cation. Whereas only [{SiN Dipp }BeClRb] 2 is amenable to reduction by potassium to its nearest lighter congener, these species may also be sequentially interconverted by treatment of [{SiN Dipp }BeClM] 2 by the successively heavier group 1 metal. A theoretical analysis combining density functional theory (DFT) with elemental thermochemistry is used to rationalise these observations, where consideration of the relevant enthalpies of atomisation of each alkali metal in its bulk metallic form proved crucial in accounting for experimental observations., (© 2023. The Author(s).)

Deprotonation of triphenyl germane with NHC-supported copper alkoxides afforded four novel (NHC)CuGePh 3 complexes. Of these, (IPr)CuGePh 3 (IPr = :C{N(2,6-iPr 2 C 6 H 3 )CH} 2 ) was selected for further investigation. Analysis by EDA-NOCV indicates it to be a germyl nucleophile and its σ-bond metathesis reaction with a range of p-block halides confirmed it to be a convenient source of [Ph 3 Ge] - . The Cu-Ge bond of (IPr)CuGePh 3 underwent π-bond insertions with t BuNCS, CS 2 , and PhNCO to furnish a series of germyl substituted carboxylate derivatives, (IPr)CuXC(Y)GePh 3 (X = S, NPh; Y = S, N t Bu, O), which were structurally characterised. (IPr)CuGePh 3 inserted phenyl acetylene, providing both the Markovnikov and anti-Markovnikov products. The (NHC)CuGePh 3 compounds were validated as catalytic intermediates; addition of 10 mol% of NHC-copper(i) alkoxide to a mixture of triphenyl germane and a tin(iv) alkoxide resulted in a tin/germanium cross coupling with concomitant formation of alcohol. Moreover, a catalytic hydrogermylation of Michael acceptors was developed with Ph 3 GeH adding to 7 activated alkenes in good conversions and yields in the presence of 10 mol% of NHC-copper(i) alkoxide. In all cases, this reaction provided the β-germylated substrate implicating nucleophilicity at germanium., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The dimeric β-diketiminato calcium hydride, [( Dipp BDI)CaH] 2 ( Dipp BDI = HC{(Me)CN-2,6-i-Pr 2 C 6 H 3 } 2 ), reacts with ortho-, meta- or para-tolyl mercuric compounds to afford hydridoarylcalcium compounds, [( Dipp BDI) 2 Ca 2 (μ-H)(μ-o-,m-,p-tolyl)], in which dimer propagation occurs either via μ 2 -η 1 -η 1 or μ 2 -η 1 -η 6 bridging between the calcium centers. In each case, the orientation and hapticity of the aryl units is dependent upon the position of the methyl substituent. While wholly organometallic meta- and para-tolyl dimers, [( Dipp BDI)Ca(m-tolyl)] 2 and [( Dipp BDI)Ca(p-tolyl)] 2 , can be prepared and are stable, the ortho-tolyl isomer is prone to isomerization to a calcium benzyl analog. Computational analysis of this latter process with density functional theory (DFT) highlights an unusual mechanism invoking the generation of an intermediate dicalcium species in which the group 2 centers are bridged by a toluene dianion formed by the formal attachment of the original hydride anion to the initially generated ortho-tolyl substituent. Use of a more sterically encumbered aryl substituent, {3,5-t-Bu 2 C 6 H 3 }, facilitates the selective formation of [( Dipp BDI)Ca(μ-H)(μ-3,5-t-Bu 2 C 6 H 3 )Ca( Dipp BDI)], which can be converted into the unsymmetrically-substituted σ-aryl calcium complexes, [( Dipp BDI)Ca(μ-Ph)(μ-3,5-t-Bu 2 C 6 H 3 )Ca( Dipp BDI)] and [( Dipp BDI)Ca(μ-p-tolyl)(μ-3,5-t-Bu 2 C 6 H 3 )Ca( Dipp BDI)] by reaction with the appropriate mercuric diaryl. Conversion of [( Dipp BDI)Ca(H)(Ph)Ca( Dipp BDI)] to afford [{{( Dipp BDI)Ca} 2 (μ 2 -Cl)} 2 (C 6 H 5 -C 6 H 5 )], comprising a biphenyl dianion, is also reported. Although this latter transformation is serendipitous, AIM analysis highlights that, in a related manner to the ortho-tolyl to benzyl isomerization, the requisite C-C coupling may be facilitated in an "across dimer" fashion by the experimentally-observed polyhapto engagement of the aryl substituents with each calcium., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

We report the activation and functionalization of Si-N bonds with pinacol borane catalyzed by a three-coordinate iron(II) β-diketiminate complex. The reactions proceed via the mild activation of silazanes to yield useful hydrosilanes and aminoboranes. The reaction is studied by kinetic analysis, along with a detailed investigation of decomposition pathways using catecholborane as an analogue of the pinacol borane used in catalysis. We have extended the methodology to develop a polycarbosilazane depolymerization strategy, which generates hydrosilane quantitatively along with complete conversion to the Bpin-protected diamine. The analogous Si-O bond cleavage can also be achieved with heating, using silyl ether starting materials to generate hydrosilane and alkoxyborane products. Depolymerization of poly(silyl ether)s using our strategy successfully converts the polymer to 90% Bpin-protected alcohols., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The potassium diamidoalumanyl, [K{Al(SiN Dipp )}] 2 (SiN Dipp = {CH 2 SiMe 2 NDipp} 2 ), reacts with the terminal B-O bonds of pinacolato boron esters, ROBpin (R = Me, i -Pr), and B(OMe) 3 to provide potsassium (alkoxy)borylaluminate derivatives, [K{Al(SiN Dipp )(OR)(Bpin)}] n (R = Me, n = 2; R = i -Pr, n = ∞) and [K{Al(SiN Dipp )(OMe)(B(OMe) 2 )}] ∞ , comprising Al-B σ bonds. An initial assay of the reactivity of these species with the heteroallene molecules, N , N '-diisopropylcarbodiimide and CO 2 , highlights the kinetic inaccessibility of their Al-B bonds; only decomposition at high temperature is observed with the carbodiimide, whereas CO 2 preferentially inserts into the Al-O bond of [K{Al(SiN Dipp )(OMe)(Bpin)}] 2 to provide a dimeric methyl carbonate species. Treatment of the acyclic dimethoxyboryl species, however, successfully liberates a terminal alumaboronic ester featuring trigonal N 2 Al-BO 2 coordination environments at both boron and aluminum.

Like the previously reported potassium-based system, rubidium and cesium reduction of [{SiN Dipp }AlI] ({SiN Dipp } = {CH 2 SiMe 2 NDipp} 2 ) with the heavier alkali metals [M = Rb and Cs] provides dimeric group 1 alumanyl derivatives, [{SiN Dipp }AlM] 2 . In contrast, similar treatment with sodium results in over-reduction and incorporation of a formal equivalent of [{SiN Dipp }Na 2 ] into the resultant sodium alumanyl species. The dimeric K, Rb, and Cs compounds display a variable efficacy toward the C-H oxidative addition of arene C-H bonds at elevated temperatures (Cs > Rb > K, 110 °C) to yield (hydrido)(organo)aluminate species. Consistent with the synthetic experimental observations, computational (DFT) assessment of the benzene C-H activation indicates that rate-determining attack of the Al(I) nucleophile within the dimeric species is facilitated by π-engagement of the arene with the electrophilic M + cation, which becomes increasingly favorable as group 1 is descended., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The potassium aluminyl complex K 2 [Al{N(Dipp)SiMe 3 } 2 ] 2 was synthesised via reduction of [AlI{N(Dipp)SiMe 3 } 2 ] (Dipp = 2,6-i-Pr 2 C 6 H 3 ). This represents the first example of an aluminyl anion supported by an acyclic ligand framework. Attempts to yield the same structure with a larger ligand framework, {N(Dipp)Si(i-Pr) 3 }, led to C-H cleavage. K 2 [Al{N(Dipp)SiMe 3 } 2 ] 2 behaves as a nucleophilic source of aluminium; reaction with an electrophilic β-diketiminate supported magnesium(II) iodide forms a monomeric, acyclic magnesium aluminyl complex.

[{SiN Dipp }MgNa] 2 ({SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 ) reacts directly with H 2 to provide a heterobimetallic hydride. Although the transformation is complicated by the simultaneous disproportionation of magnesium, computational density functional theory (DFT) studies suggest that this reactivity is initiated by orbitally-constrained and interactions between the frontier MOs of both H 2 and the tetrametallic core of [{SiN Dipp }MgNa] 2 .

The copper(i) alumanyl derivative, [{SiN Dipp }Al-Cu(NHC iPr )] (SiN Dipp = {CH 2 SiMe 2 NDipp} 2 ; Dipp = 2,6-di-isopropylphenyl; NHC iPr = N , N '-di-isopropyl-4,5-dimethyl-2-ylidene), reacts in a stepwise fashion with up to three equivalents of various terminal alkynes. This reactivity results in the sequential formation of cuprous (hydrido)(alkynyl)aluminate, (alkenyl)(alkynyl)aluminate and bis(alkynyl)aluminate derivatives, examples of which have been fully characterised. The process of alkene liberation resulting from the latter reaction step constitutes a unique case of alkyne transfer semi-hydrogenation in which the C-H acidic alkyne itself acts as a source of proton, with the Cu-Al bond providing the requisite electrons to effect reduction. This reaction sequence is validated by DFT calculations, which rationalise the variable stability of the initially formed heterobimetallic hydrides., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Reaction of BeCl 2 with the dilithium diamide, [{SiN Dipp }Li 2 ] ({SiN Dipp } = {CH 2 SiMe 2 NDipp} 2 ), provides the dimeric chloroberyllate, [{SiN Dipp BeCl}Li] 2 , en route to the 2-coordinate beryllium amide, [SiN Dipp Be]. Lithium or sodium reduction of [SiN Dipp Be] in benzene, provides the relevant organoberyllate products, [{SiN Dipp BePh}M] (M = Li or Na), via the presumed intermediacy of transient Be(I) radicals.

The (IPr)CuO t Bu catalysed reduction of 11 aryl and alkyl isocyanates with pinacolborane gave only the boraformamides, pinBN(R)C(O)H, in most cases. Overreduction, which hampers almost all isocyanate hydroborations, was restricted to electron poor aryl isocyanates (4-NC-C 6 H 4 NCO, 4-F 3 C-C 6 H 4 NCO, 3-O 2 N-C 6 H 4 NCO). Computational analysis showed stability of [(IPr)CuH]2, which was proposed to be the catalyst resting state, drives selectivity, suggesting an approach to prevent overreduction in future work. In the case of iPrNCO, formation of this species renders overreduction kinetically inaccessible. For 4-NC-C 6 H 4 NCO, however, the barrier height for the first step of over-reduction is much lower, even relative to [(IPr)CuH]2, resulting in unselective reduction.

Ionic compounds containing sodium cations are notable for their stability and resistance to redox reactivity unless highly reducing electrical potentials are applied. Here we report that treatment of a low oxidation state {Mg 2 Na 2 } species with non-reducible organic bases induces the spontaneous and completely selective extrusion of sodium metal and oxidation of the Mg I centers to the more conventional Mg II state. Although these processes are also characterized by a structural reorganisation of the initially chelated diamide spectator ligand, computational quantum chemical studies indicate that intramolecular electron transfer is abetted by the frontier molecular orbitals (HOMO/LUMO) of the {Mg 2 Na 2 } ensemble, which arise exclusively from the 3s valence atomic orbitals of the constituent sodium and magnesium atoms., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Reaction of [Ru(C 6 H 4 PPh 2 ) 2 (Ph 2 PC 6 H 4 AlMe(THF))H] with CO results in clean conversion to the Ru-Al heterobimetallic complex [Ru(AlMePhos)(CO) 3 ] ( 1 ), where AlMePhos is the novel P-Al(Me)-P pincer ligand ( o -Ph 2 PC 6 H 4 ) 2 AlMe. Under photolytic conditions, 1 reacts with H 2 to give [Ru(AlMePhos)(CO) 2 (μ-H)H] ( 2 ) that is characterized by multinuclear NMR and IR spectroscopies. DFT calculations indicate that 2 features one terminal and one bridging hydride that are respectively anti and syn to the Al Me group. Calculations also define a mechanism for H 2 addition to 1 and predict facile hydride exchange in 2 that is also observed experimentally. Reaction of 1 with B(C 6 F 5 ) 3 results in Me abstraction to form the ion pair [Ru(AlPhos)(CO) 3 ][MeB(C 6 F 5 ) 3 ] ( 4 ) featuring a cationic [( o -Ph 2 PC 6 H 4 ) 2 Al] + ligand, [AlPhos] + . The Ru-Al distance in 4 (2.5334(16) Å) is significantly shorter than that in 1 (2.6578(6) Å), consistent with an enhanced Lewis acidity of the [AlPhos] + ligand. This is corroborated by a blue shift in both the observed and computed ν CO stretching frequencies upon Me abstraction. Electronic structure analyses (QTAIM and EDA-ETS) comparing 1 , 4 , and the previously reported [Ru(ZnPhos)(CO) 3 ] analogue (ZnPhos = ( o -Ph 2 PC 6 H 4 ) 2 Zn) indicate that the Lewis acidity of these pincer ligands increases along the series ZnPhos < AlMePhos < [AlPhos] + .

The reactivity of a molecular magnesium silanide toward ketones displays a significant variability of outcome, resulting in adduct formation, deprotonation, dearomatisation or deoxygenation, that is dependent on the structure and electronic character of the carbonyl-containing reagent.

The application of an alkyne cyclotrimerization regime with an [Fe(salen)] 2 -μ-oxo (1) catalyst to triphenylmethylphosphaalkyne (2) yields gram-scale quantities of 2,4,6-tris(triphenylmethyl)-Dewar-1,3,5-triphosphabenzene (3). Bulky lithium salt LiHMDS facilitates a rearrangement of 3 to the 1,3,5-triphosphabenzene valence isomer (3'), which subsequently undergoes an intriguing phosphorus migration reaction to form the ring-contracted species (3''). Density functional theory calculations provide a plausible mechanism for this rearrangement. Given the stability of 3, a diverse array of unprecedented transformations was investigated. We report novel crystallographically characterized products of successful nucleophilic/electrophilic addition and protonation/oxidation reactions., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The reactivity of a seven-membered cyclic potassium diamidoalumanyl toward a variety of ketone small molecules has been assessed. Whilst acetophenone generates an aluminium pinacolate derivative, reductive C-C coupling is induced between the ketyl and ortho -carbon centres of two equivalents of benzophenone. In contrast, whereas oxidative addition of an enolisable proton is observed with 2,4-dimethyl-3-pentanone, 2,2,4,4-tetramethyl-3-pentanone undergoes an unprecedented hydroalumination process, where the reducing hydride may be traced to intramolecular oxidative addition of a (sp 3 )C-H bond.

Thermolysis of a 1,3-dioxa-2-phospholane supported by the terphenyl ligand Ar iPr4 (Ar iPr4 =[C 6 H 3 -2,6-(C 6 H 3 -2,6-iPr 2 )]) at 150 °C gives [Ar iPr4 PO 2 ] 2 via loss of ethene. [Ar iPr4 PO 2 ] 2 was characterised by X-ray crystallography and NMR spectroscopy; it contains a 4-membered P-O-P-O ring and is the isostructural oxygen analogue of Lawesson's and Woollins' reagents. The dimeric structure of [Ar iPr4 PO 2 ] 2 was found to persist in solution through VT NMR spectroscopy and DOSY, supported by DFT calculations. The addition of DMAP to the 1,3-dioxa-2-phospholane facilitates the loss of ethene to give Ar iPr4 (DMAP)PO 2 after days at room temperature, with this product also characterised by X-ray crystallography and NMR spectroscopy. Replacement of the DMAP with pyridine induces ethene loss from the 1,3-dioxa-2-phospholane to provide gram-scale samples of [Ar iPr4 PO 2 ] 2 in 75 % yield in 2 days at only 100 °C., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The syntheses, reactivity and electronic structure analyses of [Ru(PPh 3 ) 2 (ZnMe) 4 H 2 ], 1 a, and [Ru(PPh 3 ) 2 (ZnPh) 4 H 2 ], 2 b, are reported. 1 a exhibits an 8-coordinate Ru centre with axial phosphines and a symmetrical (2 : 2) arrangement of ZnMe ligands in the equatorial plane. The ZnMe ligands in 1 a undergo facile, sequential exchange with ZnPh 2 to give 2 b, which shows a 3 : 1 arrangement of ZnPh ligands. Both 1 a and 2 b exist in equilibrium with their respective 3 : 1 and 2 : 2 isomers. Mechanisms for ZnMe/ZnPh exchange and isomerisation are proposed using DFT calculations. The relationships of these {Ru(ZnR) 4 H 2 } species to isoelectronic Group 8 transition metal polyhydrides and related Schlenk equilibria in the Negishi reaction are discussed., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Hydrocarbon-soluble β-diketiminato phenylcalcium derivatives, which display various modes of Ca-μ 2 -Ph-Ca bridging, are accessible from reactions of Ph 2 Hg and [(BDI)CaH] 2 . Although the resultant compounds are inert toward the C-H bonds of benzene, they yield selective and uncatalyzed biaryl formation when reacted with readily available aryl bromides., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Reactions of the seven-membered heterocyclic potassium diamidoalumanyl, [K{Al(SiN Dipp )}] 2 (SiN Dipp = {CH 2 SiMe 2 NDipp} 2 ; Dipp = 2,6-di-isopropylphenyl), with a variety of Cu(I), Ag(I) and Au(I) chloride N-heterocyclic carbene (NHC) adducts are described. The resultant group 11-Al bonded derivatives have been characterised in solution by NMR spectroscopy and, in the case of [{SiN Dipp }Al-Au(NHC iPr )] (NHC iPr = N , N '-di-isopropyl-4,5-dimethyl-2-ylidene), by single crystal X-ray diffraction. Although similar reactions of LAgCl and LAuCl, where L is a more basic cyclic alkyl amino carbene (CAAC), generally resulted in reduction of the group 11 cations to the base metals, X-ray analysis of [( Cy CAAC)AgAl(SiN Dipp )] ( Cy CAAC = 2-[2,6-bis(1-methylethyl)phenyl]-3,3-dimethyl-2-azaspiro[4.5]dec-1-ylidene) provides the first solid-state authentication of an Ag-Al σ bond. The reactivity of the NHC-supported Cu, Ag and Au alumanyl derivatives was assayed with the isoelectronic unsaturated small molecules, N , N '-di-isopropylcarbodiimide and CO 2 . While these reactions generally provided products consistent with nucleophilic attack of the group 11 atom at the electrophilic heteroallene carbon centre, treatment of the NHC-supported copper and silver alumanyls with N , N '-di-isopropylcarbodiimide yielded less symmetric Cu- C and Ag- C -bonded isomers. In contrast to the previously described copper and silver alumanyl derivatives, [(NON)Al(O 2 C)M(P t -Bu 3 )] (M = Cu or Ag; NON = 4,5-bis(2,6-di-isopropylanilido)-2,7-di- tert -butyl-9,9-dimethylxanthene), which were prone to facile CO extrusion and formation of carbonate derivatives, the NHC-supported dioxocarbene species, [(NHC iPr )M(CO 2 )Al(SiN Dipp )] (M = Cu, Ag, Au), are all stable at room and moderately elevated temperatures. The stabilising role of the NHC co-ligand was, thus, assessed by preparation of the t -Bu 3 P adducted copper-alumanyl, [( t -Bu 3 P)CuAl(SiN Dipp )]. Treatment of this latter compound, which was also structurally characterised by X-ray analysis, with both N , N '-di-isopropylcarbodiimide and CO 2 again provided smooth heteroallene insertion and formation of the relevant Cu- C -bonded products. Although both compounds were quite stable at room temperature, heating of [( t -Bu 3 P)Cu(CO 2 )Al(SiN Dipp )] at 60 °C induced elimination of CO and formation of the analogous carbonate, [( t -Bu 3 P)Cu(OCO 2 )Al(SiN Dipp )], which was identified by 13 C and 31 P NMR spectroscopy. Reflective of the more reliable nucleophilic behaviour of the gold centres in these group 11 alumanyls, computational (QTAIM and NBO) analysis highlighted a lower level of covalency of the Al-Au linkage in comparison to the analogous Al-Cu and Al-Ag interactions. Although substitution of the co-ligand significantly perturbs the charge distribution across the Cu-Al bond of [LCuAl(SiN Dipp )] (L = NHC iPr or t -Bu 3 P), only a negligible difference is observed between the phosphine-coordinated copper systems derived from either the [SiN Dipp ]- or (NON)-based alumanyl ligands. Computational mapping of the reaction profiles arising from treatment of the various group 11 alumanyls with N , N '-di-isopropylcarbodiimide indicates that the observed formation of the Cu-N and Ag-N bound isomers do not provide the thermodynamic reaction outcome. In contrast, examination of the CO 2 -derived reactions, and their potential toward CO extrusion and subsequent carbonate formation, implies that the identity of the co-ligand exerts a greater influence on this aspect of reactivity than the architecture of the diamidoalumanyl anion.

A synthetic study into the catalytic hydrogen/deuterium (H/D) exchange of 1° silanes, 2° silanes, and 3° siloxanes is presented, facilitated by iron-β-diketiminato complexes ( 1a and 1b ). Near-complete H/D exchange is observed for a variety of aryl- and alkyl-containing hydrosilanes and hydrosiloxanes. The reaction tolerates alternative hydride source pinacolborane (HBpin), with quantitative H/D exchange. A synthetic and density functional theory (DFT) investigation suggests that a monomeric iron-deuteride is responsible for the H/D exchange., Competing Interests: The authors declare no competing financial interest., (© 2022 American Chemical Society.)

We report a new series of homoleptic Ni(I) bis-N-heterocyclic carbene complexes with a range of torsion angles between the two ligands from 68° to 90°. Electron paramagnetic resonance measurements revealed a strongly anisotropic g -tensor in all complexes with a small variation in g ∥ ∼ 5.7-5.9 and g ⊥ ∼ 0.6. The energy of the first excited state identified by variable-field far-infrared magnetic spectroscopy and SOC-CASSCF/NEVPT2 calculations is in the range 270-650 cm -1 . Magnetic relaxation measured by alternating current susceptibility up to 10 K is dominated by Raman and direct processes. Ab initio ligand-field analysis reveals that a torsion angle of <90° causes the splitting between doubly occupied d xz and d yz orbitals, which has little effect on the magnetic properties, while the temperature dependence of the magnetic relaxation appears to have no correlation with the torsion angle.

Three ring-expanded N-heterocyclic carbene-supported copper(I) triphenylstannyls have been synthesised by the reaction of (RE-NHC)CuO t Bu with triphenylstannane (RE-NHC = 6-Mes, 6-Dipp, 7-Dipp). The compounds were characterised by NMR spectroscopy and X-ray crystallography. Reaction of (6-Mes)CuSnPh 3 with di- p -tolyl carbodiimide, phenyl isocyanate and phenylisothiocyanate gives access to a copper(I) benzamidinate, benzamide and benzothiamide respectively via phenyl transfer from the triphenylstannyl anion with concomitant formation of (Ph 2 Sn) n . Attempts to exploit this reactivity under a catalytic regime were hindered by rapid copper(I)-catalysed dismutation of Ph 3 SnH to Ph 4 Sn, various perphenylated tin oligomers, H 2 and a metallic material thought to be Sn(0). Mechanistic insight was provided by reaction monitoring via NMR spectroscopy and mass spectrometry.

Herein, we report coupling in situ high temperature postsynthetic modifications (PSMs) in metal-organic frameworks (MOFs). Thermo-reactive propargyloxy-functionalized zinc IRMOFs (isoreticular metal-organic frameworks) prepared from 2-(prop-2-yn-1-yloxy)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (H 2 bpdcOCH 2 CCH) were investigated for their high-temperature postsynthetic rearrangement (PSR) chemistry to heterocyclic chromenes and benzofurans and then coupled to solid-gas reactions with molecular oxygen. The selectivity for the initial molecular rearrangements was found to be inverted in the porous MOF environment compared to conventional melt reactions of the ester compound Me 2 bpdcOCH 2 CCH and proceeded far more easily than the solid-state transformation from H 2 bpdcOCH 2 CCH, showing the potential of MOFs to give rise to different chemistry. The major oxidative process was thermolysis of the chromene ring with a minor pathway of allylic-type oxidation to give heterocyclic chromenone functionality. The sequence was also successful on a series of two-component multivariate IRMOF frameworks prepared from thermo-reactive H 2 bpdcOCH 2 CCH and thermo-resistant H 2 bpdcOMe linkers, demonstrating that these reactions can be used with known crystal engineering strategies. All transformations were fully compatible with the requirements to maintain MOF crystallinity and porosity as evidenced by surface area analysis and X-ray powder diffraction measurements. This work contributes to establishing the feasibility of high-temperature solid-gas manifolds for MOF PSM.

The stoichiometric reactivity of a β-diketiminato (BDI) magnesium silanide towards a variety of organic isocyanates has been assessed. While the primary outcome of reactions of t -BuNCO, DippNCO and CyNCO was the production of β-diketiminato magnesium siloxide adducts of the isonitrile resulting from isocyanate deoxygenation, analogous treatment with i -PrNCO led to multiple products, four of which have been positively identified. Although the specificity of this latter reaction was hampered by competitive isocycanate addition at the γ-methine carbon of the BDI supporting ligand, the identification of [{ i -PrNCO}CH{(Me)CNDipp}Mg{Me 2 PhSi}C(O)N i -Pr] 6 provided corroborative evidence for the likely generation of sila-amidate intermediates in all four reactions under study. The formation of [{Me 2 PhSi}C(O)NR] - anions as the most likely initial species formed en route to isonitrile and siloxide formation was, therefore, validated by a computational density functional theory (DFT) study.

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) is expressed at high levels in testes and seminal vesicles; it is also present in prostate tissue and involved in gonadal and non-gonadal testosterone biosynthesis. The enzyme is membrane-bound, and a crystal structure is not yet available. Selective aryl benzylamine-based inhibitors were designed and synthesised as potential agents for prostate cancer therapeutics through structure-based design, using a previously built homology model with docking studies. Potent, selective, low nanomolar IC 50 17β-HSD3 inhibitors were discovered using N -(2-([2-(4-chlorophenoxy)phenylamino]methyl)phenyl)acetamide ( 1 ). The most potent compounds have IC 50 values of approximately 75 nM. Compound 29 , N -[2-(1-Acetylpiperidin-4-ylamino)benzyl]- N -[2-(4-chlorophenoxy)phenyl]acetamide, has an IC 50 of 76 nM, while compound 30 , N -(2-(1-[2-(4-chlorophenoxy)-phenylamino]ethyl)phenyl)acetamide, has an IC 50 of 74 nM. Racemic C -allyl derivative 26 (IC 50 of 520 nM) was easily formed from 1 in good yield and, to determine binding directionality, its enantiomers were separated by chiral chromatography. Absolute configuration was determined using single crystal X-ray crystallography. Only the S -(+)-enantiomer ( 32 ) was active with an IC 50 of 370 nM. Binding directionality was predictable through our in silico docking studies, giving confidence to our model. Importantly, all novel inhibitors are selective over the type 2 isozyme of 17β-HSD2 and show <20% inhibition when tested at 10 µM. Lead compounds from this series are worthy of further optimisation and development as inhibitors of testosterone production by 17β-HSD3 and as inhibitors of prostate cancer cell growth.

Reaction of bis(pinacolato)diboron with (6-Dipp)CuO t Bu generates a ring-expanded N-heterocyclic carbene supported copper(I) boryl, (6-Dipp)CuBpin. This compound showed remarkable stability and was characterised by NMR spectroscopy and X-ray crystallography. (6-Dipp)CuBpin readily dechalcogenated a range of heterocumulenes such as CO 2 , isocyanates and isothiocyanates to yield (6-Dipp)CuXBpin (X = O, S). In the case of CO 2 catalytic reduction to CO is viable in the presence of excess bis(pinacolato)diboron. In contrast, in the case of iso(thio)cyanates, the isocyanide byproduct of dechalcogenation reacted with (6-Dipp)CuBpin to generate a copper(I) borylimidinate, (6-Dipp)CuC(NR)Bpin, which went on to react with heterocumulenes. This off-cycle reactivity gives selective access to a range of novel boron-containing heterocycles bonded to copper, but precludes catalytic reactivity.

A combined experimental and computational study of the structure and reactivity of two [RuZn 2 Me 2 ] complexes, neutral [Ru(PPh 3 )(Ph 2 PC 6 H 4 ) 2 (ZnMe) 2 ] ( 2 ) and cationic [Ru(PPh 3 ) 2 (Ph 2 PC 6 H 4 )(ZnMe) 2 ][BAr F 4 ] ([BAr F 4 ] = [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ]) ( 3 ), is presented. Structural and computational analyses indicate these complexes are best formulated as containing discrete ZnMe ligands in which direct Ru-Zn bonding is complemented by weaker Zn···Zn interactions. The latter are stronger in 2 , and both complexes exhibit an additional Zn···C aryl interaction with a cyclometalated phosphine ligand, this being stronger in 3 . Both 2 and 3 show diverse reactivity under thermolysis and with Lewis bases (P n Bu 3 , PCy 3 , and IMes). With 3 , all three Lewis bases result in the loss of [ZnMe] + . In contrast, 2 undergoes PPh 3 substitution with P n Bu 3 , but with IMes, loss of ZnMe 2 occurs to form [Ru(PPh 3 )(C 6 H 4 PPh 2 )(C 6 H 4 PPhC 6 H 4 Zn(IMes))H] ( 7 ). The reaction of 3 with H 2 affords the cationic trihydride complex [Ru(PPh 3 ) 2 (ZnMe) 2 (H) 3 ][BAr F 4 ] ( 12 ). Computational analyses indicate that both 12 and 7 feature bridging hydrides that are biased toward Ru over Zn.

The hydrogen/halogen exchange of phosphines has been exploited to establish a truly useable substrate scope and straightforward methodology for the formation of cyclopolyphosphines. Starting from a single dichlorophosphine, a sacrificial proton "donor phosphine" makes the rapid, mild synthesis of cyclopolyphosphines possible: reactions are complete within 10 min at room temperature. Novel (aryl)cyclopentaphosphines (ArP) 5 have been formed in good conversion, with the crystal structures presented. The use of catalytic quantities of iron(III) acetylacetonate provides significant improvements in conversion in the context of diphosphine (Ar 2 P) 2 and alkyl-substituted cyclotetra- or cyclopentaphosphine ((AlkylP) n , where n = 4 or 5) formation. Both iron-free and iron-mediated reactions show high levels of selectivity for one specific ring size. Finally, investigations into the reactivity of Fe(acac) 3 suggest that the iron species is acting as a sink for the hydrochloric acid byproduct of the reaction.

Sodium reduction of [{SiN Dipp }Mg] [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6- i- Pr 2 C 6 H 3 ] provides the Mg(I) species, [{SiN Dipp }MgNa] 2 , in which the long Mg-Mg bond (>3.2 Å) is augmented by persistent Na-aryl interactions. Computational assessment indicates that this molecule is best considered to comprise a contiguous tetrametallic core, a viewpoint borne out by its reaction with CO, which results in ethynediolate formation mediated by the dissimilar metal centers.

The seven-membered cyclic potassium alumanyl species, [{SiN Mes }AlK] 2 [{SiN Mes }={CH 2 SiMe 2 N(Mes)} 2 ; Mes=2,4,6-Me 3 C 6 H 2 ], which adopts a dimeric structure supported by flanking K-aryl interactions, has been isolated either by direct reduction of the iodide precursor, [{SiN Mes }AlI], or in a stepwise manner via the intermediate dialumane, [{SiN Mes }Al] 2 . Although the intermediate dialumane has not been observed by reduction of a Dipp-substituted analogue (Dipp=2,6-i-Pr 2 C 6 H 3 ), partial oxidation of the potassium alumanyl species, [{SiN Dipp }AlK] 2 , where {SiN Dipp }={CH 2 SiMe 2 N(Dipp)} 2 , provided the extremely encumbered dialumane [{SiN Dipp }Al] 2 . [{SiN Dipp }AlK] 2 reacts with toluene by reductive activation of a methyl C(sp 3 )-H bond to provide the benzyl hydridoaluminate, [{SiN Dipp }AlH(CH 2 Ph)]K, and as a nucleophile with BPh 3 and RN=C=NR (R=i-Pr, Cy) to yield the respective Al-B- and Al-C-bonded potassium aluminaborate and alumina-amidinate products. The dimeric structure of [{SiN Dipp }AlK] 2 can be disrupted by partial or complete sequestration of potassium. Equimolar reactions with 18-crown-6 result in the corresponding monomeric potassium alumanyl, [{SiN Dipp }Al-K(18-cr-6)], which provides a rare example of a direct Al-K contact. In contrast, complete encapsulation of the potassium cation of [{SiN Dipp }AlK] 2 , either by an excess of 18-cr-6 or 2,2,2-cryptand, allows the respective isolation of bright orange charge-separated species comprising the 'free' [{SiN Dipp }Al] - alumanyl anion. Density functional theory (DFT) calculations performed on this moiety indicate HOMO-LUMO energy gaps in the of order 200-250 kJ mol -1 ., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The addition of PPh 2 H, PPhMeH, PPhH 2 , P(para-Tol)H 2 , PMesH 2 and PH 3 to the two-coordinate Ni 0 N-heterocyclic carbene species [Ni(NHC) 2 ] (NHC=IiPr 2 , IMe 4 , IEt 2 Me 2 ) affords a series of mononuclear, terminal phosphido nickel complexes. Structural characterisation of nine of these compounds shows that they have unusual trans [H-Ni-PR 2 ] or novel trans [R 2 P-Ni-PR 2 ] geometries. The bis-phosphido complexes are more accessible when smaller NHCs (IMe 4 >IEt 2 Me 2 >IiPr 2 ) and phosphines are employed. P-P activation of the diphosphines R 2 P-PR 2 (R 2 =Ph 2 , PhMe) provides an alternative route to some of the [Ni(NHC) 2 (PR 2 ) 2 ] complexes. DFT calculations capture these trends with P-H bond activation proceeding from unconventional phosphine adducts in which the H substituent bridges the Ni-P bond. P-P bond activation from [Ni(NHC) 2 (Ph 2 P-PPh 2 )] adducts proceeds with computed barriers below 10 kcal mol -1 . The ability of the [Ni(NHC) 2 ] moiety to afford isolable terminal phosphido products reflects the stability of the Ni-NHC bond that prevents ligand dissociation and onward reaction., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Copper-alumanyl complexes, [LCu-Al(SiN Dipp )], where L=carbene=NHC iPr (N,N'-diisopropyl-4,5-dimethyl-2-ylidene) and Me2 CAAC (1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) and featuring unsupported Al-Cu bonds, have been prepared. Divergent reactivity observed with carbodiimides and CO 2 implies an ambiphilicity in the Cu-Al interaction that is dependent on the identity of the carbene co-ligand., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The utilization of phosphirenium ions is presented; optimized and broadened three-membered ring construction is described together with the use of these ions as efficient pre-catalysts for metal-free carbonyl reduction with silanes. Full characterization of the phosphirenium ions is presented, and initial experimental and computational mechanistic studies indicate that these act as a "masked phosphenium" source that is accessed via ring opening. Catalysis proceeds via associative transfer of {Ph 2 P + } to a carbonyl nucleophile, H-SiR 3 bond addition over the C=O group, and associative displacement of the product by a further equivalent of the carbonyl substrate, which completes the catalytic cycle. A competing off-cycle process leading to vinyl phosphine formation is detailed for the hydrosilylation of benzophenone for which an inverse order in [silane] is observed. Experimentally, the formation of side products, including off-cycle vinyl phosphine, is favored by electron-donating substituents on the phosphirenium cation, while catalytic hydrosilylation is promoted by electron-withdrawing substituents. These observations are rationalized in parallel computational studies., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

A series of complexes generated through reactions of the β-diketiminato magnesium diboranate species, [(BDI)Mg{(n-Bu)pinB-Bpin}] (BDI = HC{(Me)CNDipp}2; Dipp = 2,6-di-iso-propylphenyl), and a variety of organic nitriles are reported. Although, in every case, the diboranate anion acts as a surrogate source of the {Bpin} nucleophile, resulting in B-C bond formation at the electrophilic sp-hydridised nitrile carbon, the resultant compounds display a variable propensity to undergo subsequent reaction with additional nitrile equivalents. This behaviour is rationalised to be a consequence of substituent-dependent modulation in the basicity and resultant electrophilicity of magnesium-coordinated nitrile intermediates.