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Multidentate Schiff base ligands derived from a selection of biphenyl- and terphenyl polyamines were synthesized, and their reactivity towards divalent (Ni, Cu, Zn, Cd) and trivalent (Co, Y, Lu) metals was studied by single-crystal X-ray diffraction analysis, NMR spectroscopy, and UV/Vis spectroscopy for the Cu(II) complexes. Large variations in the resulting complexes were observed based on the relative position of the amine substituents in the parent triamines, as well as the electronic properties of the Schiff base ligand itself. Most notably, Schiff base ligands derived from a m-terphenyl-2,2’,2’’-triamine were found to coordinate in a tetradentate, pentadentate or hexadentate fashion, depending on the size and the valency of the corresponding metal center.

Zn complexes of Schiff base ligands derived from 2,2'‐diaminobiphenyls and salicylaldehyde derivatives were synthesized and characterized by NMR and single‐crystal X‐ray diffraction analysis. The detailed NMR studies suggest that the Zn complexes have a complicated behavior in solution, which is strongly dependent on the donating ability of the solvent, the steric properties of the ligand, as well as the concentration of the complex in the solvent. All these factors are decisive for the determination of the coordination number of the complex in solution. Furthermore, pentacoordinated Zn complexes of the aforementioned type, ligated by a series of nitrogen bases, were synthesized. NMR studies of the different complexes at different concentrations and temperatures, revealed information about their conformational stability. The differences were further examined by single‐crystal X‐ray diffraction analysis. In addition to the studies conducted on Zn complexes, comparative studies were conducted on a series of Cd complexes.

2‐Nitrophenylboronic acids serve as interesting starting materials for the construction of biphenyl‐ and terphenyl‐based amines if subjected to the Suzuki–Miyaura reaction. Unfortunately, these boronic acids suffer from low reactivity in Suzuki reactions, alongside their low stability in the presence of Pd. Herein, a general method for the construction of 2‐nitro‐substituted bi‐ and terphenyls is presented, with special emphasis on the synthesis of 2‐amino‐2'‐nitrobi‐ and terphenyls. Comparisons are made with other boronic acids that have some of the aforementioned issues. Finally, the application of the obtained 2‐amino‐2'‐nitrobi‐ and terphenyls as starting materials for the synthesis of bi‐ and terphenyl based di‐ and triamines is encountered for, with emphasis on the use of these amines as precursors for Schiff base ligands. In addition, the synthesis of some Zn complexes of these ligands is presented.

Cyclometalated Au(III) complexes are of interest due to their catalytic, medicinal, and photophysical properties. Herein, we describe the synthesis of derivatives of the type (N,C)Au(OAcF)2 (OAcF = trifluoroacetate) and (N,C,C)AuOAcF by a cyclometalation route, where (N,C) and (N,C,C) are chelating 2-arylpyridine ligands. The scope of the synthesis is explored by substituting the 2-arylpyridine core with electron donor or acceptor substituents at one or both rings. Notably, a variety of functionalized Au(III) complexes can be obtained in one step from the corresponding ligand and Au(OAc)3, eliminating the need for organomercury intermediates, which is commonly reported for similar syntheses. The influence of substituents in the ligand backbone on the resulting complexes was assessed using DFT calculations, 15N NMR spectroscopy and single-crystal X-ray diffraction analysis. A correlation between the electronic properties of the (N,C) ligands and their ability to undergo cyclometalation was found from experimental studies combined with natural charge analysis, suggesting the cyclometalation at Au(III) to take place via an electrophilic aromatic substitution-type mechanism. The formation of Au(III) pincer complexes from tridentate (N,C,C) ligands was investigated by synthesis and DFT calculations, in order to assess the feasibility of C(sp3)–H bond activation as a synthetic pathway to (N,C,C) cyclometalated Au(III) complexes. It was found that C(sp3)–H bond activation is feasible for ligands containing different alkyl groups (isopropyl and ethyl), although the C–H activation is less energetically favored compared to a ligand containing tert-butyl groups.

A gold(III) complex with the hitherto most electron poor mesoionic carbene ligand is presented. Aqua regia was the oxidizing agent of choice for the synthesis of this unusual organometallic compound. The AuIII complex is redox-rich, and also acts as a catalyst for oxazole formation, delivering selectively a completely different isomer compared to its AuI congener.

A modular one-pot synthesis yielding tetracoordinated-N,N,N,N-copper(I) complexes bearing imine and diimine ligands was developed. Copper aids the condensation of a pyridine or imidazole carbaldehyde with a biphenyl amine and even stabilizes labile ligands. Tetradentate and bidentate ligands were formed, the latter forming homoleptic CuL2 complexes. The identity and purity of the compounds were assessed by NMR, elemental analysis and mass spectrometry. The interconversion of different species in solution was studied by variable temperature NMR. The complexes aim to mimic the histidine copper brace of lytic polysaccharide monooxygenases (LPMOs) and bond lengths obtained from XAS and single crystal XRD for the complexes were compared to reported photoreduced LPMOs.

Seven gold(I) N-heterocyclic carbene (NHC) complexes were synthesized, characterized, and identified as suitable precursors for focused electron beam-induced deposition (FEBID). Several variations on the core Au(NHC)X moiety were introduced, that is, variations of the NHC ring (imidazole or triazole), of the alkyl N-substituents (Me, Et, or iPr), and of the ancillary ligand X (Cl, Br, I, or CF3). The seven complexes were tested as FEBID precursors in an on-substrate custom setup. The effect of the substitutions on deposit composition and growth rate indicates that the most suitable organic ligand for the gold precursor is triazole-based, with the best deposit composition of 15 atom % gold, while the most suitable anionic ligand is the trifluoromethyl group, leading to a growth rate of 1 × 10−2 nm3/e−.

A comparative study of vacuum versus ambient pressure inert gas thermogravimetry was performed on silver carboxylates compounds. Some of the complexes from this group have been previously successfully applied as precursors for both chemical vapour deposition and electron beam-induced deposition. Considerable differences were found between the thermogravimetry methods, which we associate with changes in evaporation dynamics. Vacuum thermogravimetry sublimation onsets consistently occurred at lower temperatures than ambient pressure N2-flow thermogravimetry, where the differences reached up to 120 °C. Furthermore, compound sublimation during N2-TGA was suppressed to such an extent that significant thermal decomposition of the compounds into metal and volatile organic fragments was observed while at vacuum the same complexes sublimed as intact molecules. Moreover, thermal stability of silver complexes was investigated using isothermal thermogravimetry. These findings are interesting for the field of thin film synthesis and nanomanufacturing via chemical vapour deposition, atomic layer deposition and focused electron beam induced deposition. In all three methods, delivery of functional precursor over the substrate is crucial. The presented results prove that vacuum thermogravimetry can be used as fast method of pre-screening for novel, especially low-volatility precursors. Graphic abstract

The title compound, an (N^C)-cyclo­metalated gold(III) diazide, namely, di­azido­[5-eth­oxy­carbonyl-2-(5-eth­oxy­carbonyl­pyridin-2-yl)phenyl-κ2 C 1,N]gold(III), [Au(C17H16NO4)(N3)2] or Au(ppyEt)(N3)2, was synthesized by reacting Au(ppyEt)Cl2 with NaN3 in water for 24 h. The complex features a gold center with a square-planar environment., The title compound, an (N^C)-cyclo­metalated gold(III) diazide, namely, di­azido­[5-eth­oxy­carbonyl-2-(5-eth­oxy­carbonyl­pyridin-2-yl)phenyl-κ2 C 1,N]gold(III), [Au(C17H16NO4)(N3)2] or Au(ppyEt)(N3)2, was synthesized by reacting Au(ppyEt)Cl2 with NaN3 in water for 24 h. The complex has been structurally characterized and features a gold center with a square-planar environment. The Au—N(azide) bond lengths are significantly different depending on the influence of the atom trans to the azide group [Au—N(trans to C) of 2.067 (2) Å versus Au—N(trans to N) of 2.042 (2) Å]. The azide groups are twisted in-and-out of plane by 56.2 (2)°.

Cyclometalated gold(III) complexes Au(L)(OAcF)2 (L = phenylpyridine dicarboxylic diester (ppyde) or phenylpyridine dicarboxylic acid (ppydc)) have been prepared reacting Au(OAc)3 with corresponding phenyl pyridines (ppyde or ppydc) in trifluoroacetic acid (HOAcF) under microwave heating. Further treatment of Au(L)(OAcF)2 with aqua regia resulted in dichloro complexes Au(L)Cl2. Au-functionalized UiO-67 MOF has been synthesized by exchanging linkers of UiO-67 with Au(ppydc)Cl2, furnishing the MOF with (N^C)-cyclometalated Au(III) centers. The catalytic activities of the molecular cyclometalated complexes and the Au-incorporated MOF were studied in gold-catalyzed propargyl ester cyclopropanations. Almost all complexes and the MOF showed catalytic activity to the cyclopropanation product (up to 97% conversion), with a preference for the trans diastereoisomer (up to 14:86 d.r.). The recyclability of the most active molecular complex has also been investigated. © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).

Four different ruthenium(II) complexes were incorporated into the metal–organic framework (MOF) UiO-67 using three different synthetic strategies: premade linker synthesis, postsynthetic functionalization, and postsynthetic linker exchange. One of these complexes was of the type (N–N)3Ru2+, and three of the complexes were of the type (N–N)2(N–C)Ru+, where N–N is a bipyridine-type ligand and N–C is a cyclometalated phenylpyridine-type ligand. The resulting materials were characterized by PXRD, SC-XRD (the postsynthetic functionalization MOFs), N2 sorption, TGA-DSC, SEM, EDS, and UV-Vis spectroscopy, and were digested in base for subsequent 1H NMR analysis. The absorption profiles of the MOFs that were functionalized with cyclometalated Ru(II) complexes extend significantly further into the visible region of the spectrum compared to the absorption profiles of the MOFs that were functionalized with the non-cyclometalated reference, (N–N)3Ru2+.

International audience; Amides functionalities are among the most widely found groups in biologically active molecules, and their selective catalytic reduction is an important target for synthetic methods. Recent advances in base metal catalysis have identified efficient systems for selective hydrogenolysis of the amide C–N linkage. This study examines in detail the mechanism for deaminative hydrogenation of formanilide and dimethylformamide (DMF) to the corresponding amines (aniline and dimethylamine, respectively) and methanol catalyzed by (iPrPNHP)Fe(H)2(CO) (iPrPNHP = HN{CH2CH2(PiPr2)}2) using density functional theory (DFT) calculations and microkinetic modeling. Following an initial hydrogenation of the amide carbonyl group, protonolysis of the C–N bond of the hemiaminal intermediate produces amine and formaldehyde, which is further hydrogenated to methanol. Remarkably, protonolysis of the C–N bond of the hemiaminal intermediate follows different pathways, depending on the nature of the substrate and the experimental conditions (presence or absence of cocatalyst) to yield the same products. In particular, cleavage of the C–N bond can be facilitated by either the metal catalyst or one of the organic species present (the amide substrate itself or an amide cocatalyst), with interesting consequences on the kinetics as evidenced by simulations using DFT calculated energy profiles for the entire pathway. This study reveals the subtle interplay between the nature of the substrate and the need for additives and changes the long-established principle that the hydrogenation of electron rich carbonyl substrates is governed by their carbonyl hydrogenation step and, therefore, only metal-hydride hydricity is relevant for catalyst design.

A highly asymmetric AuIII η3‐allyl complex has been generated by treating Au(η1‐allyl)Br(tpy) (tpy=2‐(p‐tolyl)pyridine) with AgNTf2. The resulting η3‐allyl complex has been characterized by NMR spectroscopy and X‐ray crystallography. DFT calculations and variable temperature 1H NMR suggest that the allyl ligand is highly fluxional., Gold and dynamic: The π coordination of an allyl group at the cyclometalated (N,C coordinated) AuIII moiety induces high asymmetry in the allyl group. DFT calculations and variable temperature 1H NMR spectroscopy suggest that the allyl ligand is highly fluxional.

We describe here the application of the well-defined bench-stable cationic aminoborane complex as highly efficient pre-catalysts for the semi-hydrogenation of internal alkynes, 1,3-diynes and 1,3-enynes with molecular hydrogen under mild conditions.

A highly asymmetric AuIII η3‐allyl complex has been generated by treating Au(η1‐allyl)Br(tpy) (tpy=2‐(p‐tolyl)pyridine) with AgNTf2. The resulting η3‐allyl complex has been characterized by NMR spectroscopy and X‐ray crystallography. DFT calculations and variable temperature 1H NMR suggest that the allyl ligand is highly fluxional.

The reactivity of Au(OAcF)2(tpy) (1, OAcF = OCOCF3; tpy = 2-(p-tolyl)pyridine) toward a wide variety of different alkenes with various substitution patterns and different oxygen-based nucleophiles has been investigated. These reactions are two-step processes where a ligand substitution is followed by a nucleophilic addition furnishing Au(III) complexes with C(sp3) ligands. In this work we have found that the reactions always occur trans to tpy-N while the OAcF ligand remains in place trans to tpy-C. The nucleophilic addition takes place exclusively at the most substituted side of the double bond, in a Markovnikov manner, and the nucleophilic addition occurs in an anti fashion as can be seen from the reaction with the 2,3-disubstituted alkene trans-2-hexene. This study has provided valuable insight into the scope and regiochemistry of Au(III) mediated nucleophilic additions, which is of great importance for further development of Au(III) catalysis and alkene functionalization.

Aryl sulfamates are valuable electrophiles for cross-coupling reactions because they can easily be synthesized from phenols and can act as directing groups for C–H bond functionalization prior to cross-coupling. Recently, it was demonstrated that (1-tBu-Indenyl)Pd(XPhos)Cl (XPhos = 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) is a highly active precatalyst for room-temperature Suzuki–Miyaura couplings of a variety of aryl sulfamates. Herein, we report an in-depth computational investigation into the mechanism of Suzuki–Miyaura reactions with aryl sulfamates using an XPhos-ligated palladium catalyst. Particular emphasis is placed on the turnover-limiting oxidative addition of the aryl sulfamate C–O bond, which has not been studied in detail previously. We show that bidentate coordination of the XPhos ligand via an additional interaction between the biaryl ring and palladium plays a key role in lowering the barrier to oxidative addition. This result is supported by NBO and NCI-Plot analysis on the transition states for oxidative addition. After oxidative addition, the catalytic cycle is completed by transmetalation and reductive elimination, which are both calculated to be facile processes. Our computational findings explain a number of experimental results, including why elevated temperatures are required for the coupling of phenyl sulfamates without electron-withdrawing groups and why aryl carbamate electrophiles are not reactive with this catalyst.

A new one-dimensional coordination polymer formed unexpectedly during the synthesis of a Pt-functionalized bi­pyridine linker for metal–organic frameworks. We report here the synthesis, structure determination and energy-dispersive X-ray spectroscopy analysis of this new coordination polymer., The title compound, {[MgPtCl2(C12H6N2O4)(C3H7NO)2(H2O)]·C3H7NO}n, is a one-dimensional coordination polymer. The structure consists of Pt-functionalized bi­pyridine ligands connected by MgII cations, as well as coordinating and non-coordinating solvent mol­ecules. The PtII cation is coordinated by the two N atoms of the bi­pyridine moiety and two Cl atoms in a square-planar fashion. This coordination induces an in-plane bend along the bi­pyridine backbone of approximately 10° from the linear ideal of a conjugated π-system. Likewise, the coordination to the MgII cation induces a significant bowing of the plane of the bi­pyridine of about 12°, giving it a distinct curved appearance. The carboxyl­ate groups of the bi­pyridine ligand exhibit moderate rotations relative to their parent pyridine rings. The MgII cation has a fairly regular octa­hedral coordination polyhedron, in which three vertices are occupied by O atoms from the carboxyl­ate groups of three different bi­pyridine ligands. The remaining three vertices are occupied by the O atoms of two di­methyl­formamide (DMF) mol­ecules and one water mol­ecule. The one-dimensional chains are oriented in the [01-1] direction, and non-coordinating DMF mol­ecules can be found in the space between the chains. The shortest inter­molecular O⋯H contacts are 2.844 (4) and 2.659 (4) Å, suggesting moderate hydrogen-bonding inter­actions. In addition, there is a short inter­molecular Pt⋯Pt contact of 3.491 (1) Å, indicating a Pt stacking inter­action. Some structure-directing contribution from the hydrogen bonding and Pt⋯Pt inter­action is probable. However, the crystal packing seems to be directed primarily by van der Waals inter­actions.

The Au(III) complex Au(tpy)(OAcF)2 (OAcF = OCOCF3; tpy = 2-(p-tolyl)pyridine) catalyzes the anti addition of trifluoroacetic acid (HOAcF) to acetylene to furnish vinyl trifluoroacetate. The Au(III) vinyl complex Au(tpy)(OAcF)(CH═CHOAcF) (vinyl group bonded trans to tpy-N) is formed during the early stage of the reaction. The vinyl complex, which has been isolated and structurally characterized, resists protolytic cleavage of the vinyl group, and therefore catalysis does not proceed by a simple formal insertion (i.e., coordination-nucleophilic attack-protolysis at the site trans to tpy-N) mechanism. Experimental evidence, including isotopic labeling, rather suggests that a double-insertion process is operative. The unobserved Au(III) divinyl complex Au(tpy)(CH═CHOAcF)2 is a crucial intermediate for which the true catalytic activity, comprising a coordination-nucleophilic attack-protolysis sequence, occurs at the site trans to tpy-C. The overall mechanism is in full agreement with DFT calculations and is a result of the considerable differences in the kinetic and thermodynamic trans effects of tpy-N versus tpy-C on each reaction step. The computational data provide a rationale for the catalytic functionalization of acetylene trans to tpy-C, whereas ethylene (previously reported) only undergoes a stoichiometric insertion, and then comes to a full stop, trans to tpy-N. © 2017 American Chemical Society

The title compound, {[MgPtCl2(C12H6N2O4)(C3H7NO)2(H2O)]·C3H7NO}n, is a one-dimensional coordination polymer. The structure consists of Pt-functionalized bipyridine ligands connected by MgII cations, as well as coordinating and non-coordinating solvent molecules. The PtII cation is coordinated by the two N atoms of the bipyridine moiety and two Cl atoms in a square-planar fashion. This coordination induces an in-plane bend along the bipyridine backbone of approximately 10° from the linear ideal of a conjugated π-system. Likewise, the coordination to the MgII cation induces a significant bowing of the plane of the bipyridine of about 12°, giving it a distinct curved appearance. The carboxylate groups of the bipyridine ligand exhibit moderate rotations relative to their parent pyridine rings. The MgII cation has a fairly regular octahedral coordination polyhedron, in which three vertices are occupied by O atoms from the carboxylate groups of three different bipyridine ligands. The remaining three vertices are occupied by the O atoms of two dimethylformamide (DMF) molecules and one water molecule. The one-dimensional chains are oriented in the [01-1] direction, and non-coordinating DMF molecules can be found in the space between the chains. The shortest intermolecular O...H contacts are 2.844 (4) and 2.659 (4) Å, suggesting moderate hydrogen-bonding interactions. In addition, there is a short intermolecular Pt...Pt contact of 3.491 (1) Å, indicating a Pt stacking interaction. Some structure-directing contribution from the hydrogen bonding and Pt...Pt interaction is probable. However, the crystal packing seems to be directed primarily by van der Waals interactions.

Incorporation of the simple, readily available, building blocks ethylene, water and acetonitrile into Au(tpy)(OCOCF3)2 (tpy = 2-(p-tolyl)pyridine) in a one-step reaction leads to high yields of a new 6-membered ring gold(III) metallacycle complex. The metallacycle has been characterized spectroscopically and crystallographically, and the mechanism of its formation has been investigated with the aid of DFT calculations.

The contribution of Au(III) species to catalysis is still debated due to the limited number of characterized intermediates with this oxidation state. In particular, the coordination of alkenes and alkynes to Au(III) followed by insertion into Au(III)-X bonds has been suggested but rarely proven experimentally. Here, these reactions are explored by means of DFT and CCSD(T) calculations considering [AuX3(L)] and [AuX2(L)2](+) complexes. In these complexes, L = ethylene and acetylene have been chosen as substrates of high interest and representative of any unsaturated organic substrate, whereas X is Cl, Me or H, as found in metal salts and as model for intermediates involved in catalysis. Isoelectronic Pt(II) complexes are also considered for comparison. Ethylene coordination occurs preferentially perpendicular for all X except H, whereas for acetylene, coordination takes place in-plane for all X except Cl. These coordination isomers can represent either minima (intermediates) or saddle points (transition states) on the potential energy surface, depending on X. NBO analysis shows how this variety of structures results from the combination of electronic (M-L donation and back-donation) and steric (cis L-X repulsion) effects. With the sole exception of [AuMe2(ethylene)2](+), rotation of the unsaturated ligand and insertion into a cis Au-X bond involve low to moderate energy barriers, ΔG(‡) = 2.5 to 23.5 kcal mol(-1), and are thermodynamically feasible, ΔG = 4.3 to -47.2 kcal mol(-1). The paucity of experimental observations for such reactions should thus be caused by other factors, like the participation of the intermediates and products in competitive side reactions including the reductive elimination of XCHnCHnX (n = 1 or 2).

The equilibrium solid-state structure, electronic structure, formation enthalpy, chemical bonding, and optical properties of IRMOF-10 and its alkaline earth metal analogues M-IRMOF-10 (M = Cd, Be, Mg, Ca, Sr, Ba) have been investigated with density functional calculations. The unit cell volume and atomic positions were fully optimized with the GGA functional. This supplements the incomplete experimental structural parameters available for Zn-IRMOF-10. The calculated bulk moduli decrease monotonically from Zn to Cd, and from Be to Ba, and indicate that Zn-IRMOF-10 and its analogues are relatively soft materials. The estimated bandgap values are in the range 2.9 to 3.0 eV, indicating nonmetallic character. Importantly, the bandgaps within the M-IRMOF-10 series (containing a rather long 4,4′-biphenyldicarboxylate linker) are smaller than those within the M-IRMOF-1 series (shorter benzene dicarboxylate linker). The optical properties (dielectric function e(ω), refractive index n(ω), absorption coefficient α(ω), optical conductivity σ(ω), reflectivity R(ω), and electron energy-loss spectrum L(ω)) of the M-IRMOF-10 series were computed. The observation of very small reflectivities over a wide energy range suggests possible uses in hybrid solar cell applications. The main characteristics of the optical properties are similar for the whole series although differences are seen in the details. An analysis of chemical bonding in the M-IRMOF-10 series reveals as might be anticipated that M–O bonds are largely ionic whereas C–O, C–H and C–C exhibit mainly covalent interactions. The BOP values of M–O decrease through the series when going from Zn to Cd, and from Be to Ba, i.e. the ionicity increases and the covalency decreases for the M–O bonds.

A DFT computational investigation predicts that the Au(III) complex (bpy)Au(C(6)H(5))(2+) reacts with benzene to furnish square planar (bpy)Au(C(6)H(5))(eta(1)-C(6)H(6))(2+). Intramolecular processes that occur within this species have been located, and the energetics of all processes have been quantified. The dynamic processes that have been identified are (1) benzene ring rotation with respect to Au, (2) direct hydrogen transfer from the benzene to the phenyl ligand, (3) hydrogen transfer from the ipso to the ortho positions in the coordinated benzene ligand, and (4) hydrogen transfer from the benzenium ligand formed by the ipso/ortho isomerization to the phenyl ligand. Similarities and differences are seen between the behavior of (bpy)Au(C(6)H(5))(eta(1)-C(6)H(6))(2+) and previously reported isoelectronic Pt(II) complexes. Preliminary experimental results related to this chemistry are reported, and possible consequences for C-H bond activation mediated by gold are discussed.

Two new Pd(II) N -heterocyclic iminocarbene complexes (C–N)PdCl 2 that contain 5-membered chelate rings have been prepared by carbene transfer from a silver iminocarbene precursor to (COD)PdCl 2 . The new Pd imonocarbene complexes, as well as two that have been previously reported (altogether three 5-membered and one 6-membered chelate ring complexes) have been evaluated as catalysts for the Suzuki–Miyaura coupling reaction. The complexes were found to be active in the reaction, but without exceptional catalytic performances. The 5-membered chelate ring complexes appeared to be more robust and remained active for a longer time than the 6-membered ring congener. The catalytic performance of the 5-membered chelate ring complexes appeared to be rather insensitive to the steric demands of the imine-N-aryl group. The X-ray structure of one of the Ag iminocarbene complexes reveals the κ 1 (C) bonding of the iminocarbene moiety in a nearly linear Ag(I) complex; two monomeric units are associated through a weak Ag–Ag interaction. The X-ray structures of two new Pd iminocarbene complexes (C–N)PdCl 2 confirm the chelating κ 2 (C,N) nature of the iminocarbene moiety; in both complexes, the Pd–Cl distances trans to carbene-C are slightly longer than those trans to imine-N.

The oxidation of the Pt(IV) tetramethyl complex [Ar N CH CH N Ar]PtMe 4 (Ar = 2,6-Me 2 C 6 H 3 ) has been investigated in acetonitrile and dichloromethane. Cyclic voltammetry demonstrates that the irreversible oxidation of [Ar N CH CH N Ar]PtMe 4 occurs at a slightly less positive oxidation potential than the irreversible oxidation of the analogous Pt(II) species [Ar N CH CH N Ar]PtMe 2 . The product distribution arising from the oxidation depends strongly on the reaction conditions and includes cationic Pt(IV) species (acetonitrile, dichloromethane solvents) and Pt(II) species (dichloromethane only). Evidence is presented that suggests that homolytic cleavage of a weakened Pt C bond in [ ArN CH CH NAr ] PtMe 4 + is involved in the oxidatively induced reactions.

A novel N-iminoylimidazolium salt serves as a precursor to an iminoyl-substituted N-heterocyclic carbene ligand system with the potential to form 5-ring chelates. Reaction of 3 - Me - 1 - [ C ( C 6 H 5 ) N ( 2 , 6 - i Pr 2 C 6 H 3 ) ] C 3 H 3 N 2 + Cl - (3; (C–N)H+Cl−) with Ag2O leads to the silver carbene complex (C–N)AgCl 4. A crystallographic analysis of 4 reveals a monomeric (carbene)AgCl moiety with a κ1-(C) bonded iminoylcarbene ligand, in accord with NMR and IR spectroscopic data. Carbene transfer from Ag to Pd occurs upon reaction of 4 with (COD)PdCl2, resulting in the κ2-(C,N) iminoylcarbene complex (C–N)PdCl2 (5). Carbene transfer from 4 to Pt takes place with Pt2Me4(μ-SMe2)2 yielding (C–N)PtMe2 (6), which was characterized by X-ray crystallography. The monomeric Pt complex contains a 5-ring chelate with a κ2-(C,N)-bonded iminoylcarbene ligand. The Pt–Me bond distances in 6 are nearly identical (2.071(5) A trans to carbene-C; 2.051(4) A cis) but the 2J(195Pt–H) coupling constants are significantly different (63.1 Hz trans; 92.0 Hz cis), as are the 1J(195Pt–C) coupling constants (618 Hz trans; 799 Hz cis).

The one-step synthesis of the known acetyl complex κ 3 -TpFe(CO)(PMe 3 )(COMe) ( 1 , 78% yield) is achieved by reaction of cis , trans -Fe(CO) 2 (PMe 3 ) 2 MeI with potassium hydrotris(pyrazolyl)borate (KTp), in CH 2 Cl 2 at room temperature. This reaction is specific to the parent Tp ligand. Visible light irradiation of 1 in toluene for 1 h afforded the first octahedral methyl–iron complex featuring the hydrotris(pyrazolyl)borate ligand TpFe(CO)(PMe 3 )Me ( 2 ) in 80% yield. Compound 2 has been fully characterized by elemental analysis, IR, NMR spectroscopies, cyclic voltammetry and by an X-ray diffraction analysis. A comparison of steric and electronic properties is made with those of related cyclopentadienyl (Cp, Cp*, C 5 Ph 5 ) complexes, and suggests that relative donating abilities follow the trend Cp, Cp*, C 5 Ph 5 >Tp, and structural comparisons indicate that Tp is the most sterically demanding ligand.

Reactions between [Cp∗IrCl2]2 and diaryl-substituted diazabutadienes (dab) ArNCR′CR′NAr (R′=H: Ar=4-MeC6H4, 2,6-Me2C6H3, 2,6- i Pr 2 C 6 H 3 ; R′=Me: Ar=4-MeC6H4) proceed straightforwardly to give the dab complexes Cp∗Ir(dab)Cl+Cl−. Sterically more encumbered dab ligands (R′=Me: Ar=2,6-Me2C6H3, 2,6- i Pr 2 C 6 H 3 , 2,4,6-Me2C6H3) instead give products Cp ∗ IrClCH 2 C ( NHAr ) CMe  N ( Ar ) + Cl − in which the dab ligand has undergone CH activation at one of methyl groups of the dab bridge. The CH cleavage reaction is reversible in the sense that thermally, the cyclometalated Ir complex decomposes to regenerate the free ligand.

High-resolution synchrotron radiation x-ray powder diffraction (HR-XRPD) combined with Hf $L$3-edge extended x-ray absorption fine structure allowed us to determine the structure of a Hf-UiO-66 metal-organic framework (MOF) showing that it is isoreticular to Zr-UiO-66 MOF [Cavka et al., J. Am. Chem. Soc. 130, 13850 (2008).]. Thermal gravimetric measurements (coupled with mass spectroscopy) and temperature-dependent synchrotron radiation XRPD proved the high thermal stability of the Hf-UiO-66 MOF. The Langmuir surface area (849 m${}^{2}/$g) combined with the high stability of the UiO-66 framework and with the high neutron absorption cross section of Hf suggest that among all microporous crystalline materials the Hf-UiO-66 MOF possesses the physical and chemical requirements for the interim storage of radioactive waste in a much safer way than is currently available. The first results proving the synthesis of a MOF material with UiO-66 topology realized by a B-containing linker are also reported, allowing a further improvement of the neutron shielding power of this class of materials.

The asymmetric unit of the title structure, C14H30N2O42+·2PF6−, contains the anion and half of the cation, the latter being completed by a crystallographic twofold axis. The cation has a cage structure with the ammonium H atoms pointing into the cage. These H atoms are shielded from intermolecular interactions and form only intramolecular contacts. There are short intermolecular C—H...F interactions in the structure, but no conventional intermolecular hydrogen bonds.

The performance of recently reported highly cis-diastereoselective Rh(I) cyclopropanation catalysts has been significantly improved by a systematic study of different reaction parameters (catalyst activation, solvent, temperature, stoichiometry). The catalyst efficiency and diastereoselectivity were enhanced by changing the activating agent from AgOTf to NaBArf. With this new system, the Rh(I) catalyst was shown to be a highly efficient and cis-diastereoselective cyclopropanation catalyst in reactions between α-diazoacetates and a range of different alkenes and substituted derivatives. Particularly noteworthy is the remarkable reactivity and cis-diastereoselectivity displayed in the reactions between ethyl diazoacetate and cyclopentene, 2,5-dihydrofuran, and benzofuran, with yields up to 99% and cis-selectivities greater than 99%.

The oxidation chemistry of CpMo(CO) 2 (PPh 3 )H ( 1 ) has been investigated by electrochemical and other methods. The molybdenum hydride 1 undergoes oxidation at +0.26 V vs. the ferrocene/ferricinium couple in acetonitrile solution, forming cis -CpMo(CO) 2 (PPh 3 )(NCMe) + ( cis - 2 ). Hydride abstraction from 1 by the substituted trityl reagent ( p -MeOC 6 H 4 )Ph 2 C + BF 4 − generates trans - 2 . The stereochemical outcome of this reaction implies a non-electron-transfer pathway for the hydride abstraction. The thermal isomerization of trans - 2 to the more stable cis - 2 in acetonitrile- d 3 proceeds without concomitant ligand exchange with the solvent. The kinetics of the isomerization have been investigated, and give the activation parameters Δ H # = 24.2±0.4 kcal/mol and Δ S # = −3.4±1.4 cal/K mol. The near-zero entropy of activation is in accord with an intramolecular non-dissociative isomerization process. In contrast, treatment of trans - 2 with a catalytic amount of cobaltocene results in fast partial isomerization to cis - 2 accompanied by ligand exchange with the solvent. This behavior is compared with the non-dissociative nature of the previously reported electrocatalytic isomerization of cis -CpW(CO) 2 (PMe 3 )(NCMe) + , and suggests that the intermediate 19-electron radicals are more loosely bound for molybdenum than for tungsten.

A detailed kinetic study of the protonation and subsequent benzene elimination reactions of a (diimine)Pt(II) diphenyl complex (denoted as (N-N)PtPh(2)) has been undertaken in dichloromethane solution with and without acetonitrile as a cosolvent. Spectroscopic monitoring of the reactions by UV-vis stopped-flow and NMR techniques over the temperature range -80 to +27 degrees C allowed the assessment of the effects of acid concentration, coordinating solvent (MeCN) concentration, temperature, and pressure. Protonation of (N-N)PtPh(2) with HBF(4) x Et(2)O in CH(2)Cl(2)/MeCN occurs with a kinetic preference for protonation at the metal, rather than at a phenyl ligand, and rapidly produces (N-N)PtPh(2)H(NCMe)(+) (DeltaH(double dagger) = 29 +/- 1 kJ mol(-1), DeltaS(double dagger) = -47 +/- 4 J K(-1) mol(-1)). At higher temperatures, (N-N)PtPh(2)H(NCMe)(+) eliminates benzene to furnish (N-N)PtPh(NCMe)(+). This reaction proceeds by rate-limiting MeCN dissociation (DeltaH(double dagger) = 88 +/- 2 kJ mol(-1), DeltaS(double dagger) = +62 +/- 6 J K(-1) mol(-1), DeltaV(double dagger) = +16 +/- 2 cm(3) mol(-1)). Protonation of (N-N)PtPh(2) in dichloromethane in the absence of MeCN cleanly produces the Pt(II) pi-benzene complex (N-N)PtPh(eta(2)-C(6)H(6))(+) at low temperatures. Addition of MeCN to a solution of the pi-benzene complex causes an associative substitution of benzene by acetonitrile, the kinetics of which were monitored by (1)H NMR (DeltaH(double dagger) = 39 +/- 2 kJ mol(-1), DeltaS(double dagger) = -126 +/- 11 J K(-1) mol(-1)). When the stronger triflic acid is employed in dichloromethane/acetonitrile, a second protonation-induced reaction also occurs. Thus, (N-N)PtPh(NCMe)(+) produces (N-N)Pt(NCMe)(2)(2+) and benzene with no detectable intermediates (DeltaH(double dagger) = 69 +/- 1 kJ mol(-1), DeltaS(double dagger) = -43 +/- 3 J K(-1) mol(-1)). The mechanisms for all steps are discussed in view of the accumulated data. Interestingly, the data allow a reinterpretation of a previous report on proton exchange between the phenyl and benzene ligands in (N-N)PtPh(eta(2)-C(6)H(6))(+). It appears that the exchange occurs by a direct sigma-bond metathesis pathway, rather than by the oxidative cleavage/reductive coupling sequence that was proposed.

Treatment of CpRu(PPh 3 ) 2 H ( 1 ) with 1 equivalent of the substituted trityl reagent Tol 3 C + PF 6 − (Tol = p -Mec 6 H 4 )in 9/1 dichloromethane- d 2 /acetonitrile- d 3 at − 80° C led to attachment of the trityl cation to the Cp ring and generation of the ring-substituted dihydride complex trans -[η 5 -C 5 H 4 (Tol 3 C)]Ru(PPh 3 ) 2 + ( 5 ). At ambient temperature the reaction yielded a mixture of 5 , CpRu(PPh 3 ) 2 H 2 + ( 2 ), and CpRu(PPh 3 ) 2 (NCCD 3 ) + ( 3 - d 3 ). Oxidation of 1 with 1 equivalent of Cp 2 Fe + PF 6 − yielded a 1:1 mixture of 2 and 3 - d 3 . The mechanism of the generation of the products is discussed in the light of the experimental evidence that suggests that 5 is formed by electrophilic attack by the trityl cation at the Cp ring of 1 via initial electron transfer.

A general one-pot synthetic route for mixed methyl−aryl Pt(II) diimine complexes is described. Performing the alkylation in neat Me_2S instead of ether or THF greatly reduces the amount of comproportionation products otherwise formed, diminishes separation problems, and improves yields. Treatment of the intermediate methyl−aryl complexes (Me_2S)_2Pt(Me)(Ar) with diimines (N−N) furnishes the methyl−aryl Pt(II) diimine complexes (N−N)Pt(Me)(Ar) in 76−84% yields. The Pt methyl−phenyl complex [p-Tol-N ═ VC(Me)C(Me) ═ N-p-Tol]Pt(Me)(Ph) has been characterized by X-ray diffraction.

The asymmetric unit of the title coordination polymer, [Y(2)(C(8)H(5)NO(4))(3)(C(3)H(7)NO)(4)](n), contains one Y(3+) ion, three half-mol-ecules of the 2-amino-benzene-1,4-dicarboxyl-ate (abz) dianion and two O-bonded N,N-dimethyl-formamide (DMF) mol-ecules. Each abz half-mol-ecule is completed by crystallographic inversion symmetry and its -NH(2) group is disordered in each case [relative occupancies within the asymmetric unit = 0.462 (18):0.538 (18), 0.93 (2):0.07 (2) and 0.828 (16):0.172 (16)]. The combination of disorder and crystal symmetry means that each of the four C-H atoms of the benzene ring of each of the dianions bears a statistical fraction of an -NH(2) group. The coordination geometry of the yttrium ion is a fairly regular YO(8) square anti-prism arising from its coordination by two DMF mol-ecules, four monodentate abz dianions and one O,O-bidentate abz dianion. The polymeric building unit is a dimeric paddle-wheel with two metal ions linked by four bridging abz dianions. Further bridging linkages connect the dimers into a three-dimensional framework containing voids in which highly disordered DMF mol-ecules are presumed to reside.

Reduction of the metal - metal-bonded complex FvW[sub 2](CO)[sub 6] generated the dianion FvW[sub 2](CO)[sub 6][sup 2[minus]]. An X-ray crystallographic analysis of [Et[sub 4]N[sup +]][sub 2]FvW[sub 2](CO)[sub 6][sup 2[minus]] (monoclinic space group P2[sub 1]/c, a = 7.687(2) [angstrom], b = 13.752(4) [angstrom], c = 16.297(5) [angstrom], [beta] = 94.80(2)[degree], V = 1716.8(8) A[sup 3], Z = 4) showed the dianion to contain a planar Fv ring system bonded to the two metal centers in an anti fashion. The dianion reacted with a number of electrophiles to yield the neutral species FvW[sub 2](CO)[sub 6]E[sub 2] E = H, Me, Et, [sigma]-C[sub 3]H[sub 6], CH[sub 2]Ph. The pK[sub a] values for the two consecutive deprotonations of FvW[sub 2](CO)[sub 6]H[sub 2] were determined as 14.0 and 16.6 by equilibrium measurements in acetonitrile. Thermolysis and photolysis of FvW[sub 2](CO)[sub 6]H[sub 2] yielded FvW[sub 2]-(CO)[sub 6] and H[sub 2]. Unlike Cp[sub 2]W[sub 2](CO)[sub 6], FvW[sub 2](CO)[sub 6] underwent protonation at the W-W bond by HBF[sub 4][center dot]Et[sub 2]O in acetonitrile. Reactions of FvW[sub 2](CO)[sub 6] and FvMo[sub 2](CO)[sub 6] with PMe[sub 3] and Me[sub 2]-PCH[sub 2]PMe[sub 2] (dmpm) resulted in generation of the dinuclear zwitterions FvM[sub 2](CO)[sub 5](PMe[sub 3])[sub 2] and FvM[sub 2](CO)[sub 5](dmpm), respectively.more » 62 refs., 5 figs., 7 tabs.« less