Hydrido Ligand Research Articles

Reactivity of Diruthenium Bisborylene Complexes: Formation of B-C and B-H Bonds via Borylene Ligand Coupling.

Thermal or photoinduced isomerization of diruthenium bridging bisborylene complexes [{Cp*(H)2Ru}2(μ-BAr)2] (1a, Ar = Ph; 1b, Ar = 3,4,5-F3C6H2) led to nido-ruthenacarboranes 2a and 2b with newly formed B-C and B-H bonds. The reaction mechanism was analyzed by deuterium-labeling experiments and density functional theory calculations. Additionally, 2-fold B-H coupling between borylene and two hydrido ligands of 1a can be achieved, assisted by Lewis base IPr2Me2 to generate a dinuclear bridging borylene complex [(Cp*Ru)2(μ-H)2(μ-BPh)] (3). Our results provide new reactivity patterns for borylene-based functionalizations.

Terminal Hydride Complex of High-Spin Mn.

The iron-molybdenum cofactor of nitrogenase (FeMoco) catalyzes fixation of N2 via Fe hydride intermediates. Our understanding of these species has relied heavily on the characterization of well-defined 3d metal hydride complexes, which serve as putative spectroscopic models. Although the Fe ions in FeMoco, a weak-field cluster, are expected to adopt locally high-spin Fe2+/3+ configurations, synthetically accessible hydride complexes featuring d5 or d6 electron counts are almost exclusively low-spin. We report herein the isolation of a terminal hydride complex of four-coordinate, high-spin (d5; S = 5/2) Mn2+. Electron paramagnetic resonance and electron-nuclear double resonance studies reveal an unusually large degree of spin density on the hydrido ligand. In light of the isoelectronic relationship between Mn2+ and Fe3+, our results are expected to inform our understanding of the valence electronic structures of reactive hydride intermediates derived from FeMoco.

Stoichiometric and Catalytic Reduction of Carbon Dioxide by a Sterically Encumbered Amidinato Magnesium Hydride

AbstractA sterically encumbered dinuclear amidinato magnesium hydride 3 with bridging hydrido ligands was synthesized from the metalation of the corresponding amidine 1 with dibutylmagnesium and subsequent treatment with phenylsilane. This complex reacts stoichiometrically with 1 atm of carbon dioxide at room temperature in tetrahydrofuran (THF) to the corresponding bis(thf) adduct of the dinuclear formate complex 4‐2 thf with bridging formate anions. This complex is stable in THF at 60 °C for more than 16 hours but decomposes into the amidine 1 upon removal of ligated thf ligands. Complex 3 efficiently catalyzes the reduction of carbon dioxide with 9‐BBN, yielding bis(boryl)acetal (R2BO)2CH2, and with silanes H4‐nSiPhn (n=1, 2, and 3). The bis(silyl)acetal is quantitatively accessible for Ph3SiH (n=3) whereas during the reduction of CO2 with hydrogen‐richer silanes (n=1, 2) siloxanes form and methane evolves.

Electrophilic Si-H Activation by Acetonitrilo Benzo[h]quinoline Iridacycles: Influence of Electronic Effects in Catalysis.

The performance of six newly synthesized benzo[h]quinoline-derived acetonitrilo pentamethylcyclopentadienyl iridium(III) tetrakis(3,5-bis-trifluoromethylphenyl)borate salts bearing different substituents -X (-OMe, -H, -Cl, -Br, -NO2 and -(NO2 )2 ) on the heterochelating ligand were evaluated in the dehydro-O-silylation of benzyl alcohol and the monohydrosilylation of 4-methoxybenzonitrile by Et3 SiH, two reactions involving the electrophilic activation of the Si-H bond. The benchmark shows a direct dependence of the catalytic efficiency with the electronic effect of -X, which is confirmed by theoretical assessment of the intrinsic silylicities Π of hydridoiridium(III)-silylium adducts and by the theoretical evaluation of the propensity of hydridospecies to transfer the hydrido ligand to the activated substrate. The revisited analysis of the Ir-Si-H interactions shows that the most cohesive bond in hydridoiridium(III)-silylium adducts is the Ir-H one, while the Ir-Si is a weak donor-acceptor dative bond. The Si…H interaction in all the cases is noncovalent in nature and dominated by electrostatics confirming the heterolytic cleavage of the hydrosilane's Si-H bond in this key catalytically relevant species.

Catalytic Nitrous Oxide Reduction with H2 Mediated by Pincer Ir Complexes.

Reduction of nitrous oxide (N2O) with H2 to N2 and water is an attractive process for the decomposition of this greenhouse gas to environmentally benign species. Herein, a series of iridium complexes based on proton-responsive pincer ligands (1-4) are shown to catalyze the hydrogenation of N2O under mild conditions (2 bar H2/N2O (1:1), 30 °C). Among the tested catalysts, the Ir complex 4, based on a lutidine-derived CNP pincer ligand having nonequivalent phosphine and N-heterocyclic carbene (NHC) side donors, gave rise to the highest catalytic activity (turnover frequency (TOF) = 11.9 h-1 at 30 °C, and 16.4 h-1 at 55 °C). Insights into the reaction mechanism with 4 have been obtained through NMR spectroscopy. Thus, reaction of 4 with N2O in tetrahydrofuran-d8 (THF-d8) initially produces deprotonated (at the NHC arm) species 5NHC, which readily reacts with H2 to regenerate the trihydride complex 4. However, prolonged exposure of 4 to N2O for 6 h yields the dinitrogen Ir(I) complex 7P, having a deprotonated (at the P-arm) pincer ligand. Complex 7P is a poor catalytic precursor in the N2O hydrogenation, pointing out to the formation of 7P as a catalyst deactivation pathway. Moreover, when the reaction of 4 with N2O is carried out in wet THF-d8, formation of a new species, which has been assigned to the hydroxo species 8, is observed. Finally, taking into account the experimental results, density functional theory (DFT) calculations were performed to get information on the catalytic cycle steps. Calculations are in agreement with 4 as the TOF-determining intermediate (TDI) and the transfer of an apical hydrido ligand to the terminal nitrogen atom of N2O as the TOF-determining transition state (TDTS), with very similar reaction rates for the mechanisms involving either the NHC- or the P-CH2 pincer methylene linkers.

Alkyne Coupling and Cyclization on Metal Cluster Complexes. Additions and Couplings of Dimethyl acetylenedicarboxylate to Ru6(μ6-C)(CO)14(μ3-η4-C4H4)

Reactions of the hexaruthenium cluster complex Ru6(μ6-C)(CO)14(μ3−η4−C4H4), 2 with dimethyl acetylenedicarboxylate (DMAD) at 25 °C yielded five new compounds: Ru6(μ5-C)(CO)16(μ−η4−C4H4), 3; Ru6(μ6-C)(CO)14[η6-1,2-C6H4(CO2Me)2], 4; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 5; Ru6(μ5-C)(CO)14(μ−η4−C4H4)[μ3−C2(CO2Me)2], 6 and Ru6(μ6-C)(CO)14[μ3−η6−1,2−C6H4(CO2Me)2], 7. Compounds 4 and 7 are isomers that contain the six-membered arene, dimethyl phthalate, 1,2−C6H4(CO2Me)2, as a ligand. Compound 3 was formed as a side product in low yield (6%) by the simple addition of CO to 2. The addition of CO to 2 causes the cluster to open to that of a spiked, square pyramid. Direct reaction of CO to 2 provided 3 in a good yield (72%). A DMAD ligand was added to the cluster of 2 as a simple triply-bridging ligand to form open Ru6 clusters in compounds 5 and 6. Addition of DMAD to 3 yielded the DMAD derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)[μ−C2(CO2Me)2], 8 which contains a DMAD ligand bridging a basal edge of an opened spiked-square pyramidal Ru6 cluster. Compound 5 was thermally converted to the new complex Ru6(μ5-C)(CO)14[μ4−η6−CHCHCHCC(CO2Me)C(CO2Me)](μ-H), 9 that contains a bridging CHCHCHCC(CO2Me)C(CO2Me) ligand formed by a coupling of the DMAD ligand to the bridging C4H4 ligand in 5 accompanied by a cleavage of one CH bond and formation of a bridging hydrido ligand. Decarbonylation of 3 with Me3NO yielded the NMe3 derivative Ru6(μ5-C)(CO)15(μ−η4−C4H4)(NMe3), 10 in which the NMe3 ligand is coordinated to the spiked metal atom on the square-pyramidal Ru5 cluster. Treatment of 4 and 7 with CO at 25 °C induced elimination of the 1,2−C6H4(CO2Me)2 ligand to yield free dimethyl phthalate, 11 and formation of the known parent carbonyl complex Ru6(μ6-C)(CO)17. All of the new cluster compounds were characterized by single-crystal X-ray diffraction analyses.

C – C coupling of alkynes to the CH2 group in a 1-phosphonioethenyl ligand in a zwitterionic dirhenium carbonyl complex

Reactions of the zwitterionic dirhenium complex Re2(CO)8[μ-η2-1-C(CH2)(PMePh2)], 3 with the terminal alkynes, HCC(OEt) and HCCPh, have yielded two new isomeric ethoxy-substituted dirhenium complexes, Re2(CO)7[µ-η3-C(H)C(OCH2CH3)CH2C(PMePh2)], 5 and Re2(CO)7[µ-η3-C(OCH2CH3)C(H)CH2C(PMePh2)], 6 and one phenyl-substituted dirhenium complex Re2(CO)7[µ-η3-C(H)CPhCH2C(PMePh2)], 7, respectively, with each containing a bridging, substituted 1-phosphonio-3,4-butenyl ligand formed by loss of CO and the addition and coupling of one alkyne to the CH2 group of the 1-phosphonioethenyl ligand in 3. The bridging 1-phosphonio-3,4-butenyl ligand in compound 6 exhibits a dynamical “flip-flop” exchange for the phosphonio-3,4-butenyl ligand between the two rhenium atoms that leads to an averaging of the inequivalent protons on its methylene group that is rapid on the NMR timescale. When heated to 70oC, compound 5 was converted to two new compounds: Re2(CO)6(µ-H)[µ-η4-C(H)C(OCH2CH3)CHC(PMePh2)], 8, by loss of a CO ligand and a CH activation at the CH2 group in its C(H)C(OCH2CH3)CH2C(+PMePh2) ligand and an isomer Re2(CO)6(PMePh2)[µ-η4-C(H)C(OCH2CH3)CHCH], 9. Compound 9 was also obtained from 8 by heating to 80 °C for 5 days by shifting the PMePh2 group from its phosphonium carbon atom in 8 to one of the rhenium atoms to become a PMePh2 ligand in 9 and then shifting the hydrido ligand back to the same carbon atom to form a bridging η4-2-ethoxybutadiendiyl, [C(H)C(OCH2CH3)CHCH], ligand. All new products were characterized structurally by single-crystal X-ray diffraction analyses.

Interstitial Hydrides in Nanoclusters can Reduce M(I) (M=Cu, Ag, Au) to M(0) and Form Stable Superatoms.

High-nuclearity clusters resemble the closest model between the determination of atomically precise chemical species and the bulk metallic version thereof, and both impacts on a variety of applications, including catalysis, optics, sensors, and new energy sources. Our interest lies with the nanoclusters of the Group 11 (Cu, Ag, Au) metals stabilized by dichalcogenido and hydrido ligands. Herein, we describe superatoms formed by the clusters and their relationship with precursor hydrido clusters. Specifically, our concept seeks to demonstrate a possible correlation that exist between hydrido clusters (and nanoalloys) and the formation of superatoms, with the loss of hydrides and typically with release of H2 gas. These reactions appear to be internal self-redox reactions and require no additional reducing agent, but does seem to require a similar core structure. Knowledge of such processes could provide insight into how clusters grow and an understanding in bridging the atomically precise cluster - metal nanoparticle mechanism.

Rare-earth-metal half-sandwich complexes incorporating methyl, methylidene, and hydrido ligands.

Complexes Cp*3Ln3(μ2-CH3)3(μ3-CH2)(μ3-H)(thf)3 (Ln = Y, Dy; Cp* = C5Me5) are formed via elimination of CH4 and C2H4 from the respective trinuclear polymethyl complexes [Cp*Ln(μ2-CH3)2]3, involving the methyl/methylidene complex Cp*3Ln3(μ2-CH3)3(μ3-CH2)(μ3-CH3)(thf)2 as an intermediate. Compound Cp*3Y3(μ2-CH3)3(μ3-CH2)(μ3-H)(thf)3 displays "Schrock-type" nucleophilic carbene reactivity, converting ketones into the corresponding terminal alkenes. Treatment of Cp*3Y3(μ2-CH3)3(μ3-CH2)(μ3-H)(thf)3 with [D4]methanol proved accessibility of all small-group functionalities as indicated by the simultaneous formation of deuterated HD and deuterated methanes CH3D and CH2D2.

Copper carbene complexes. Synthesis and structural analysis of a chloro-bridged dicopper cation and the triosmium-copper carbene cluster complex HOs3(CO)11[µ-Cu(IPr)

The chloro-bridged carbene-substituted dicopper salt [{(IPr)Cu}2(µ-Cl)][PF6], 1, IPr = [N,N′-bis(2,6-diisopropylphenyl)imidazolin-2- ylidene], was synthesized by the reaction of (IPr)CuCl with Tl[PF6]. Reaction of 1 with the anion, [HOs3(CO)11]− of the salt [PPN][HOs3(CO)11], 2 yielded the Cu - Os heterometallic cluster complex, HOs3(CO)11[µ-Cu(IPr)], 3, the first example of Cu - Os bimetallic cluster complex containing a N-heterocyclic carbene ligand. Compounds 1 and 3 were characterized by IR, 1H NMR and structurally by single-crystal X-ray diffraction analysis. Compound 3 contains a triosmium carbonyl cluster with a bridging Cu(IPr) group on one edge of the cluster and a terminally-coordinated hydrido ligand on one of the Cu-bridged osmium atoms.

Scandium and lanthanum hydride complexes stabilized by super-bulky penta-arylcyclopentadienyl ligands.

Hydrogenolysis of the half-sandwich penta-arylcycopentadienyl-supported rare-earth metal dibenzyl complexes [(CpAr5)Ln(p-CH2-C6H4-Me)2(THF)] (CpAr5 = C5Ar5, Ar = 3,5-iPr2-C6H3; Ln = Sc, La) afforded a bimetallic scandium complex [(CpAr5)Sc(H)(μ-OC4H9)]2 (2) with two terminal hydrido ligands, and a double-sandwich bimetallic lanthanum hydride complex [(CpAr5)La(μ-H)]2 (4) bearing the reduced CpAr5 ligand. DFT calculations were conducted to elucidate the reaction profiles.

A mononuclear divalent ytterbium hydrido complex supported by a super-bulky scorpionate ligand.

The first mononuclear divalent ytterbium hydride complex [(TpAd,iPr)Yb(H)(THF)] (TpAd,iPr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) (2) bearing a terminal hydrido ligand was obtained by hydrogenolysis of the benzyl precursor in hexane. Complex 2 exhibited two different reaction patterns towards allenes: Yb-H addition with cyclohexylallene and deprotonation of 1,1-dimethylallene.

Rhodium Complexes in P-C Bond Formation: Key Role of a Hydrido Ligand.

Olefin hydrophosphanation is an attractive route for the atom-economical synthesis of functionalized phosphanes. This reaction involves the formation of P-C and H-C bonds. Thus, complexes that contain both hydrido and phosphanido functionalities are of great interest for the development of effective and fast catalysts. Herein, we showcase the excellent activity of one of them, [Rh(Tp)H(PMe3)(PPh2)] (1), in the hydrophosphanation of a wide range of olefins. In addition to the required nucleophilicity of the phosphanido moiety to accomplish the P-C bond formation, the key role of the hydride ligand in 1 has been disclosed by both experimental results and DFT calculations. An additional Rh-H···C stabilization in some intermediates or transition states favors the hydrogen transfer reaction from rhodium to carbon to form the H-C bond. Further support for our proposal arises from the poor activity exhibited by the related chloride complex [Rh(Tp)Cl(PMe3)(PPh2)] as well as from stoichiometric and kinetic studies.

Rhodium(I) Complexes as Useful Tools for the Activation of Fluoroolefins

In this account we describe studies on the reactivity of rhodium(I) complexes of the type [Rh(E)(PEt3)3], where E represents hydrido, fluorido, germyl, boryl or silyl ligands, towards fluorinated olefins. The results are compared with those reported by other research groups on fluoroolefins, as well as with the chemistry of compounds [Rh(E)(PEt3)3] towards fluoroaromatics in terms of selectivity and mechanisms.1 Introduction2 Reactivity Towards Fluoroolefins2.1 Reactivity of Hexafluoropropene2.2 Reactivity of (E)-1,2,3,3,3-Pentafluoropropene2.3 Reactivity of 2,3,3,3-Tetrafluoropropene and (E)-1,3,3,3-Tetrafluoropropene2.4 Reactivity of 3,3,3-Trifluoropropene2.5 Reactivity of Pentafluorostyrene3 Conclusion and Perspective

The activation and transformations of vinyl acetate at a dirhenium carbonyl center

The reaction of Re2(CO)8(μ-C6H5)(μ-H), 1 with vinyl acetate in methylene chloride by heating at 40 °C yielded three new products: Re3(CO)13(μ-η2-C2H3), 3, (24% yield), Re2(CO)8(μ-η2-O2CCH3)(μ-H), 4, (9% yield) and Re2(CO)8(μ-η2-CHCHO2CCH3)(μ-H), 5, (13% yield). Compound 3 was also obtained in a similar yield from the reaction of Re2(CO)8(μ-H)[μ-η2-C(H) = C(H)Bun], 2 with vinyl acetate, but compounds 4 and 5 were not obtained. All of the products were characterized structurally by single-crystal X-ray diffraction analysis. Compound 3 consists of an open trirhenium cluster containing two rhenium – rhenium bonds. One of the rhenium – rhenium bonds contains a μ-η2-(σ+π)-coordinated C2H3 (vinyl) ligand. Compound 4 contains two rhenium atoms with a bridging η2-acetate ligand and a bridging hydrido ligand. Compound 5 contains two mutually bonded Re–Re atoms with a bridging (σ+π)-coordinated acetate-substituted vinyl group and a bridging hydrido ligand by the cleavage of one of the CH bonds on the β–carbon atom of the vinyl group of the vinyl acetate. The reaction of compound 3 with I2 resulted in cleavage of the Re(CO)5 group to yield the known complex Re(CO)5I and the new dirhenium complex Re2(CO)8I(μ-η2-C2H3), 6 containing a μ-η2-(σ+π)-coordinated vinyl group.

Reductive coupling of diisopropylcarbodiimide by a dirhenium carbonyl complex

The reaction of Re2(CO)8(μ-H)[μ-η2-C(H) = C(H)Bun] with N,N′-diisopropylcarbodiimide yielded the new rhenium diamidinate complex [Re(CO)4]2[(μ-C2(N{iPr})4], 2, in 59% yield that was formed by the reductive coupling of two of carbodiimide molecules at the central carbon atom. The diamidinate ligand is nonplanar and four iminyl nitrogen atoms are coordinated to two Re(CO)4 groups in two chelating groups that have formed five-membered rings. Density functional molecular orbital analyses were used to explain the bonding of the diamidinate ligand to the two rhenium atoms. A second product Re2(CO)8(μ-OH)(μ-H), 3 was obtained from the reaction of N,N′-diisopropylcarbodiimide and Re2(CO)8(μ-C6H5)(μ-H), 1. Compound 3 was subsequently found to be a product of the reaction of 1 with traces of H2O in the original reaction and was independently obtained in 60% yield from the reaction of 1 with H2O. Compound 3 contains a bridging hydroxo ligand and a bridging hydrido ligand across the Re–Re bond between two mutually bonded Re(CO)4 groups. Both new compounds were characterized structurally by single-crystal X-ray diffraction analysis.

Synthesis and Properties of a Triruthenium Hydrido Complex Capped by a μ3-Oxoboryl Ligand

A triruthenium hydrido complex in which one of the Ru3 planes is capped by a μ3-BO ligand, [{Cp*Ru(μ-H)}3(μ3-BO)(μ3-H)] (3; Cp* = η5-C5Me5), was synthesized by the reaction of the μ3-borylene complex [{Cp*Ru(μ-H)}3(μ3-BH)] (2a) with water in the presence of Et2NH. The face-capping coordination of the oxoboryl ligand was unambiguously established by X-ray diffraction and exhibited short B–O (1.231(6) A) and long Ru–B bonds (average 2.31 A). Density functional theory (DFT) calculations of 3 reproduced the observed structure well, and the multiplicity of the BO bond suggested by the value of the Wiberg bond index is 1.62. The four hydrido ligands in 3, three μ-hydrides and one μ3-hydride, underwent site exchange on the NMR time scale via the formation of a μ3-hydroxyborylene intermediate, [{Cp*Ru(μ-H)}3(μ3-BOH)] (2c). The DFT calculations showed that 2c lies above 3 by 10.5 kcal mol–1 at 25 °C. The basic oxygen atom in 3 allowed the formation of a B(C6F5)3 adduct, [{Cp*Ru(μ-H)}3{μ3-BO···B(C6F5)3}(μ3-H)] (5),...

Computational Thermochemistry of Mono- and Dinuclear Tin Alkyls Used in Vapor Deposition Processes.

Hexamethylditin has been reported to be a more effective precursor compared to monotin analogs in hybrid molecular beam epitaxy depositions of perovskite oxides. To understand the differences, a library of 68 monotin- and ditin-containing molecules bearing hydrido and/or carbon-based ligands was generated, and their structures were optimized using density functional theory. On the basis of a modified W1-F12 composite thermochemical method, thermochemical data (enthalpy of formation, entropy, and heat capacity) were calculated for each structure over a range of temperatures (298-5000 K). The application of the modified W1-F12 method to heavy element compounds was benchmarked against existing experimental and computational studies of mononuclear hydrido, alkyl, and mixed hydridoalkyl complexes of silicon, germanium, and tin. The library of thermodynamic data was used in partial equilibrium calculations from 300 to 1500 K to determine gas phase compositions resulting from the pyrolysis of tetramethyltin and hexamethylditin at 10-6 and 760 Torr.

Crystal structures of two PCN pincer iridium complexes and one PCP pincer carbodi-phospho-rane iridium inter-mediate: substitution of one phosphine moiety of a carbodi-phospho-rane by an organic azide.

The structure of [Ir{(4-Cl-C6H4N3)C(dppm)-κ3 P,C,N}(dppm-κ2 P,P')]Cl·1.5CH2Cl2·0.5C7H8 (C57H48Cl2IrN3P4·1.5CH2Cl2·0.5C7H8) (2), dppm = bis-(di-phenyl-phosphino)methane {systematic name: [7-(4-chloro-phen-yl)-1,1,3,3-tetra-phenyl-5,6,7-tri-aza-κN 7-1,3λ4-diphospha-κP 1-hepta-4,6-dien-4-yl][methyl-ene-bis(di-phenyl-phosphine)-κ2 P,P']iridium(I) chloride-di-chloro-methane-toluene (2/3/1)}, resulting from the reaction of [IrClH{C(dppm)2-κ3 P,C,P)(MeCN)]Cl (1a) with 1-azido-4-chloro-benzene, shows a monocationic five-coordinate IrI complex with a distorted trigonal-bipyramidal geometry. In 2, the iridium centre is coordinated by the neutral triazeneyl-idene-phospho-rane (4-Cl-C6H4N3)C(dppm) acting as a PCN pincer ligand, and a chelating dppm unit. The structure of the coordination compound [IrCl(CN)H(C(dppm)2-κ3 P,C,P)]·CH3CN, (C52H45ClIrNP4·CH3CN) (1b) [systematic name: chlorido-cyanidohydrido(1,1,3,3,5,5,7,7-octa-phenyl-1,3λ5,5λ4,7-tetra-phospha-κ2 P 1,P 7-hept-3-en-4-yl)iridium(III) aceto-nitrile monosolvate], prepared from 1a and KCN, reveals an octa-hedral IrIII central atom with a meridional PCP pincer carbodi-phospho-rane (CDP) ligand; the chloride ligand is located trans to the central carbon of the CDP functionality while the hydrido and cyanido ligands are situated trans to each other. The chiral coordination compound [Ir(CN)((4-Cl-C6H4N3)CH(CH(P(Ph)2)2)-κ3 P,C,N)(dppm-κ2 P,P')]·2CH3OH, (C58H48ClIrN4P4·2CH3OH) (3) (systematic name: {4-[3-(4-chloro-phen-yl)triazenido-κN 3]-1,1,3,3-tetra-phenyl-1,3λ5-diphospha-κP 1-but-2-en-4-yl}cyanido[methyl-enebis(di-phenyl-phosphine)-κ2 P,P']iridium(III) methanol disolvate), formed via prolonged reaction of 1-azido-4-chloro-benzene with 1b, features a six-coordinate IrIII central atom. The iridium centre is coordinated by the dianionic facial PCN pincer ligand [(4-Cl-C6H4N3)CH(CH(P(Ph2)2)2)], a cyanido ligand trans to the central carbon of the PCN pincer ligand and a chelating dppm unit. Complex 2 exhibits a 2:1 positional disorder of the Cl- anion. The CH2Cl2 and C7H8 solvent mol-ecules show occupational disorder, with the toluene mol-ecule exhibiting additional 1:1 positional disorder with some nearly overlying carbon atoms.

Synthesis of a heterometallic spiked tetrahedral cluster of ruthenium and nickel containing multiple hydrido ligands and its degradation to a tetrahedral NiRu3 cluster

A bimetallic spiked tetrahedral cluster of Ni and Ru, {Cp*Ru(H)(μ-H)3}-{Ni(Cp*Ru)3(μ3-H)3(μ-H)3} (2) (Cp* = η5-C5Me5), was synthesized by reaction of Cp*Ru(μ-H)4RuCp* (1) with Ni(cod)2 under an atmosphere of H2. Cluster 2 comprises monomeric (Cp*RuH) and tetrahedral {Ni(Cp*Ru)3(μ3-H)3(μ-H)3} fragments linked by three bridging hydrogen atoms. Although site exchange of hydrides between the (Cp*RuH4) and {Ni(Cp*Ru)3H6} moieties does not occur on the NMR time scale, incorporation of deuterium into the NiRu3 fragment upon treatment of 2 with 1 atm of D2 establishes that interfragment migration of hydrides does take place. Although reaction of 2 with ethylene results in the replacement of two hydrides in the spiked Ru center by an η2-ethylene ligand, reaction with cyclopentadiene results in the degradation of the pentanuclear skeleton to a tetrahedral cluster, (CpNi)(Cp*Ru)3(μ3-H)3(μ-H)3 (4) (Cp = η5-C5H5), and a mixed-ligand ruthenocene, Cp*CpRu (5).