Formation and characterization of the gallium and indium subhydride molecules Ga2H2 and In2H2: a matrix isolation study

Ga2 reacts spontaneously with H2 in solid Ar matrixes at 12 K to form the cyclic molecule Ga(mu-H)2Ga. In2 does not react with H2 under similar conditions, but irradiation at wavelengths near 365 nm induces the formation of the corresponding indium hydride, In(mu-H)2In. The molecules have been identified and characterized by the IR spectra displayed by matrixes containing the metal and H2, D2, HD, or H2 + D2; they each have planar, dihydrido-bridged structures with D2h symmetry, as endorsed by comparison of the measured spectra (i) with the properties forecast by quantum chemical calculations and (ii) with the spectra of known gallium and indium hydrides. Both are photolabile under visible light (lambda > 450 nm): green light (lambda = ca. 546 nm) causes Ga(mu-H)2Ga to isomerize to a mixture of HGaGaH and H2GaGa, whereas broad-band visible irradiation (lambda > 450 nm) of In(mu-H)2In gives rise to the isomer HInInH, together with InH. The isomerization can be reversed by UV photolysis (lambda = ca. 365 nm) of HGaGaH, H2GaGa, and HInInH or by near-IR photolysis (lambda > 700 nm) of HGaGaH and H2GaGa.     

Cleavage of hydrazine and 1,1-dimethylhydrazine by dinuclear tantalum hydrides: formation of imides, nitrides, and N,N-dimethylamine

The complexes (RPh[NPN]Ta)2(mu-H)4 (RPh[NPN] = RP(CH2SiMe2NPh)2) activate molecular nitrogen to give (RPh[NPN]Ta)2(mu-eta1-eta2-N2)(mu-H)2; however, addition of hydrazine to (CyPh[NPN]Ta)2(mu-H)4 promotes cleavage of the N-N bond and N-H activation to give the bridging bisimide complex (CyPh[NPN]Ta)2(mu-H)2(mu-NH)2. Substitution of the phosphine substituent from cyclohexyl to phenyl allows for characterization of (PhPh[NPN]Ta)2(mu-H)2(mu-NH)2 crystallographically. Addition of the substituted hydrazine Me2NNH2 results in formation of a mono(nitride) complex, (RPh[NPN]Ta)2(mu-H)3(mu-N). The N-N bond has again been cleaved, but the second nitrogen atom has been functionalized and ejected as Me2NH.     

Strong optical limiting capability of a triosmium cluster bonded indium porphyrin complex [(TPP)InOs3(mu-H)2(CO)9(mu-eta2-C5H4N)

The metal-metal bonded indium porphyrin-osmium cluster complex [(TPP)InOs3(mu-H)2(CO)9(mu-eta2-C5H4N)] was first synthesized and characterized using the indium porphyrin hydride as the precursor. The complex has very good optical limiting performance with determined optical limiting threshold of 0.4 J cm(-2).     

Structural factors influencing linear M-H-M bonding in bis(dialkylphosphino)methane complexes of nickel

Structural data for four closely related dinuclear nickel hydride complexes have been compared in order to gain insight into the factors governing the Ni-H-Ni geometries. The derivatives [(dippm)2Ni2X2](mu-H) [dippm = 1,2-bis(diisopropylphosphino)methane] were found to contain a linear Ni-H-Ni bridge, whereas the derivatives [(dcpm)2Ni2X2](mu-H) [dcpm = 1,2-bis(dicyclohexylphosphino)methane] were found to contain a bent Ni-H-Ni bridge. The number of internal and interatomic CH-to-halide contacts of the former were much shorter and more numerous than the latter, suggesting an important role of external forces in bridging hydride geometries.     

Synthesis and nonlinear optical absorption of novel porphyrin-osmium-cluster complexes

Reaction of azido(tetra-p-tolylporphyrinato)indium(III) [TTPInN(3)] and [Os(3)(mu-H)(2)(CO)(10)] in toluene at 80 degrees C overnight gave two major products, complexes 1 and 2. Complex 1 had an axial bridge of "NH", while 2 had an axial bridge of "N" between the porphyrin and osmium cluster moieties. Complex 1 could be converted to 2 when refluxed in toluene. These two novel porphyrin-osmium clusters are the first axially linked porphyrin-metal cluster complexes. UV/Vis spectroscopy revealed the significant ground state electronic perturbation in the capped complex 2, demonstrating that the remarkable electronic interaction of the moieties within the molecule was achieved by this special structural arrangement. In addition, the electrochemistry of 1 and 2 were investigated and their oxidation current voltage curves are similar to those of indium(III)-porphyrins with a metal-metal sigma bond such as [TPPInRe(CO)(5)] (TPP=tetraphenylporphyrin). The two new molecules also exhibit large nonlinear optical absorption at 532 nm with a ns pulse laser and are potential optical limiting materials for sensor protection in the visible region.     

Synthesis and structure of Ca(18)Li(5)In(25.07): a novel intergrowth of Li-centered in(12) icosahedral clusters and electron-precise Zintl layers

A new ternary polar intermetallic, Ca(18)Li(5)In(25.07), was obtained from high-temperature reactions of the elements in welded Nb tubes. Its crystal structure, established by single-crystal X-ray diffraction, was found to crystallize in the orthorhombic space group Cmmm (No. 65). Unit cell parameters are a = 9.9151(6) A, b = 26.432(2) A, and c = 10.2116(6) A; Z = 2. The structure of Ca(18)Li(5)In(25.07) features two distinct types of indium anionic layers. An "electron-deficient" layer is made up of Li-centered In(12) icosahedra that are interconnected by bridging planar In(4) units and In atoms. A second In(3)(5-) layer is an electron-precise Zintl layer formed by fused four-, five-, and six-membered rings of three- and four-bonded indium atoms. The two distinct layers are alternately stacked and linked into a complex three-dimensional network. Vacancies are observed to occur only at the In(12) icosahedral and the bridging indium units within the "electron-deficient" layers. Magnetic property measurements indicate that Ca(18)Li(5)In(25.07) exhibits temperature-independent paramagnetism consistent with metallic behavior. Band structure calculations were performed to elucidate the role of defects and vacancies in the electronic structure of the electron-deficient "metallic" Zintl phase.     

Preparation and characterization of novel Os-diolefin dimers: new entry to Os-cyclooctadiene complexes

The complex [H(EtOH)2][{OsCl(eta4-COD)}2(mu-H)(mu-Cl)2] (1) has been prepared in high yield by treatment of OsCl3.3H2O (54% Os) with 1,5-cyclooctadiene in ethanol under reflux. Under air, it is unstable and undergoes oxidation by action of O2 to afford the neutral derivative {OsCl(eta4-COD)}2(mu-H)(mu-Cl)2 (2). The terminal chlorine ligands of the anion of 1 are activated toward nucleophilic substitution. Thus, reaction of the salt [NBu4][{OsCl(eta4-COD)}2(mu-H)(mu-Cl)2] (1a) with NaCp in toluene gives [NBu4][{Os(mu1-C5H5)(eta4-COD)}(mu-H)(mu-Cl)2{OsCl(eta4-COD)}] (3) as a result of the replacement of one of the terminal chlorine atoms by the cyclopentadienyl ligand. The CH2 group of the latter can be deprotonated by the bridging methoxy ligand of the iridium dimer [Ir(mu-OMe)(eta4-COD)]2. The reaction leads to the trinuclear derivative [NBu4][{(eta4-COD)Ir(mu5-C5H4-mu1)Os(eta4-COD)}(mu-H)(mu-Cl)2{OsCl(eta4-COD)}] (4) containing a bridging C5H4 ligand that is eta1-coordinated to an osmium atom of the dimeric unit and mu5-coordinated to the Ir(eta4-COD) moiety. Salt 1a also reacts with LiC[triple bond]CPh. In this case, the reaction produces the substitution of both terminal chlorine ligands to afford the bis(alkynyl) derivative [NBu4][{Os(C[triple bond]CPh)(eta4-COD)}2(mu-H)(mu-Cl)2] (5). Complexes 1, 2, 3, and 4 have been characterized by X-ray diffraction analysis. Although the separations between the osmium atoms are short, between 2.6696(4) and 2.8633(5) A, theoretical calculations indicate that only in 2 is there direct metal-metal interaction, as the bond order is 0.5.     

An intramolecular N-H...(mu-H)Re2 dihydrogen bond and a novel mu 3-eta 2 coordination mode of the pyrazolate anion on a triangular cluster face

The quantitative addition of pyrazole (Hpz) to the 44 valence-electron, triangular cluster anion [Re3(mu 3-H)-(mu-H)3(CO)9]- gives the novel unsaturated anion [Re3(mu-H)4(CO)9(Hpz)]- (1, 46 valence electrons), which contains a pyrazole molecule that is terminally coordinated on a cluster vertex. Solidstate X-ray and IR analyses reveal a rather weak hydrogen-bonding interaction between the NH proton and one of the hydrides bridging the opposite triangular cluster edge (delta H degree = -3.1 kcal mol-1 from the Iogansen equation). Both IR and NMR data indicate that such a proton-hydride interaction is maintained in the major conformer present in CD2Cl2, but also provide evidence of the presence of minor conformers of 1 in which the NH proton is involved in an intermolecular hydrogen bond with the solvent. The mu-H...HN bond length evaluated in solution through the T1 minimum value (2.07 A) and that determined in the solid state by X-ray diffraction (2.05 A) are in good agreement. NMR experiments show that, in acetone, intermolecular N-H...solvent interactions replace the intramolecular dihydrogen bond. At room temperature in CH2Cl2, the pyrazole ligand in 1 is labile and 1 slowly "disproportionates" to [Re3(mu 3-H)-(mu-H)3(CO)9]- and [Re3(mu-H)3(CO)9-(mu-eta 2-pz)(Hpz)]-, with H2 evolution. Slow H2 evolution also leads to the formation of the anion [Re3(mu-H)3-(CO)9(pz)]- (5), in which the pyrazolate anion adopts a novel mu 3-eta 2-coordination mode, as revealed by a single-crystal X-ray analysis. The analysis of the bond lengths indicates that the pyrazolate anion in 5 acts as a six-electron donor, with loss of the aromaticity. The formation of 5 from 1 is much faster in solvents with a high dielectric constant, such as acetone or DMF. Anion 5 was also obtained from the reaction of pyrazole with [Re3(mu-H)3(CO)9(mu 3-CH3)]- through the intermediate formation of two isomeric addition derivatives and following CH4 evolution.     

Synthesis and structure of two tetranuclear osmium carbonyl isotopomers: a crystallographic isotope effect

A synthetic route to [Os4(mu-H)(mu-OH)(mu-CO)(CO)12] ( 1) has been devised through the activation of [Os4(CO)14] with Me3NO. The pyrolysis and photolysis of the reactant in the presence of a trace amount of water produces 1 in low yield. The solid-state structure of [Os4(mu-H)(mu-OH)(mu-CO)(CO)12 x H2O] (1 x H2O) reveals a butterfly Os4 skeleton with bridging H, OH and CO ligands as well as hydrogen-bonded molecules of water in the crystal lattice. A low-temperature 13C{1H} NMR spectroscopic study revealed a merry-go-round exchange of CO ligands around the Os3 plane containing the asymmetric bridging CO. The exposure of 1 x H2O to D2O yielded [Os4(mu-H)(mu-OD)(mu-CO)(CO)12]2. Although the solid-state, intramolecular structure of 2 closely matched that of 1 x H2O, the intermolecular structure did not: its crystal lattice contained no water of crystallization, a previously unreported crystallographic isotope effect.     

Oxidative addition of phosphine-tethered thiols to iron carbonyl: binuclear phosphinothiolate complexes, (mu-SCH(2)CH(2)PPh(2))(2)Fe(2)(CO)(4), and hydride derivatives

The mononuclear complex Fe(CO)(4)(PPh(2)CH(2)CH(2)SH), 1, is isolated as an intermediate in the overall reaction of PPh(2)CH(2)CH(2)SH with [Fe(0)(CO)(4)] sources to produce binuclear bridging thiolate complexes. Photolysis is required for loss of CO and subsequent S-H activation to generate the metal-metal bonded Fe(I)-Fe(I) complex, (mu-SCH(2)CH(2)PPh(2))(2)Fe(2)(CO)(4), 2. Isomeric forms of 2 derive from the apical or basal position of the P-donor ligand in the pseudo square pyramidal S(2)Fe(CO)(2)P coordination spheres. This position in turn is dictated by the stereochemistry of the mu-S-CH(2) bond, designated as syn or anti with respect to the Fe(2)S(2) butterfly core. Addition of strong acids engages the Fe(I)-Fe(I) bond density as a bridging hydride, [(mu-H)-anti-2](+)[SO(3)CF(3)](-) or [(mu-H)-syn-2](+)[SO(3)CF(3)](-), with formal oxidation to Fe(II)-H-Fe(II). Molecular structures of anti-2, syn-2, and [(mu-H)-anti-2](+)[SO(3)CF(3)](-) were determined by X-ray crystallography and show insignificant differences in distance and angle metric parameters, including the Fe-Fe bond distances which average 2.6 A. The lack of coordination sphere rearrangements is consistent with the ease with which deprotonation occurs, even with the weak base, chloride. The Fe(I)-Fe(I) bond, supported by bridging thiolates, therefore presents a site where a proton might be taken up and stored as a hydride without impacting the overall structure of the binuclear complex.     

Dihydrogen activation by a diruthenium analogue of the Fe-only hydrogenase active site

The photochemical reaction of Ru2(S2C3H6)(CO)4(PCy3)2 (1) and H2 gives the dihydride Ru2(S2C3H6)(mu-H)(H)(CO)3(PCy3)2 (2). NMR and crystallographic studies reveal mutually trans basal phosphine ligands and both bridging and terminal hydrides. Ru2(S2C2H4)(CO)4(PCy3)2 behaves similarly. Other HX substrates undergo photoaddition to 1, affording Ru2(S2C3H6)(mu-H)(X)(CO)3(PCy3)2 for X = OTs (3a), Cl (3b), and SPh (3c). Treatment of Ru2(S2C3H6)(mu-H)(H)(CO)3(PCy3)2 with [H(OEt2)]BArF4 (ArF = B(C6H3-3,5-(CF3)2) in CD2Cl2 gives [Ru2(S2C3H6)(mu-H)(CO)3(PCy3)2(H2)]+ (4), which catalyzes H2-D2 exchange. The reaction of 2 with [D(OEt2)]BArF4 gave [Ru2(S2C3H6)(mu-H)(CO)3(PCy3)2(HD)]+ (JH-D = 31 Hz). These studies provide the first models for the Fe-only hydrogenases that bear dihydrogen and terminal hydrido ligands.     

Activation of metal hydride complexes by tri-tert-butylphosphine-platinum and -palladium groups

The compounds HM(CO)4SnPh3, M = Os (10), Ru (11) are activated in the presence of Pt(PBut3)2 and Pd(PBu(t)3)2 toward the insertion of PhC2H into the M-H bond. The compounds PtOs(CO)4(SnPh3)(PBu(t)3)[mu-HCC(H)Ph], 12, and PtOs(CO)4(SnPh3)(PBu(t)3)[mu-H2CCPh], 13, were obtained from the reaction of 10 with PhC2H in the presence of Pt(PBu(t)3)2. Compounds 12 and 13 are isomers containing alkenyl ligands formed by the insertion of the PhC2H molecule into the Os-H bond at both the substituted and unsubstituted carbon atoms of the alkyne. Both compounds contain a Pt(PBu(t)3) group that is bonded to the osmium atom and a bridging alkenyl ligand that is pi-bonded to the osmium atom. The reaction of 11 with PhC2H in the presence of Pt(PBu(t)3)2 yielded the products PtRu(CO)4(SnPh3)(PBu(t)3)[mu-HC2(H)Ph], 14, and PtRu(CO)4(SnPh3)(PBut3)[mu-H2C2Ph], 15, which are also isomers similar to 12 and 13. The reaction of 11 with PhC2H in the presence of Pd(PBu(t)3)2 yielded the product PdRu(CO)4(SnPh3)(PBu(t)3)[mu-H2C2Ph], 16. Compound 16 contains a Pd(PBu(t)3) group bonded to the ruthenium atom and a bridging H2C2Ph ligand that is pi-bonded to the palladium atom. Compound 10 reacted with Pt(PBu(t)3)2 in the absence of PhC2H to yield the compound PtOs(CO)4(SnPh3)(PBu(t)3)(mu-H), 17. Compound 17 is a Pt(PBu(t)3) adduct of 10. It contains a Pt-Os bond with a bridging hydrido ligand. Compound 17 reacted with PhC2H to yield 12. Compound 12 reacted with PhC2H to yield the compound PtOs(CO)3(SnPh3)(PBu(t)3)[mu-HCC(Ph)C(H)C(H)Ph], 18. Compound 18 contains a bridging 2,4-diphenylbutadienyl ligand, HCC(Ph)C(H)C(H)Ph, that is pi-bonded to the osmium atom and sigma-bonded to the platinum atom. Fenkse-Hall molecular orbitals of 17 were calculated. The LUMO of 17 exhibits an empty orbital on the platinum atom that appears to be the most likely site for PhC2H addition prior to its insertion into the Os-H bond.     

High-nuclearity ruthenium carbonyl cluster complexes derived from 2-amino-6-methylpyridine: synthesis of nonanuclear derivatives containing mu4- and mu5-oxo ligands

Nonanuclear cluster complexes [Ru9(mu3-H)2(mu-H)(mu5-O)(mu4-ampy)(mu3-Hampy)(CO)21] (4) (H2ampy = 2-amino-6-methylpyridine), [Ru9(mu5-O)2(mu4-ampy)(mu3-Hampy)2(mu-CO)(CO)20] (5), [Ru9(mu5-O)2(mu4-ampy)(mu3-Hampy)2(mu-CO)2(CO)19] (6), and [Ru9(mu4-O)(mu5-O)(mu4-ampy)(mu3-Hampy)(mu-Hampy)(mu-CO)(CO)19] (7), together with the known hexanuclear [Ru6(mu3-H)2(mu5-ampy)(mu-CO)2(CO)14] (2) and the novel pentanuclear [Ru5(mu4-ampy)(2)(mu-CO)(CO)12] (3) complexes, are products of the thermolysis of [Ru3(mu-H)(mu3-Hampy)(CO)9] (1) in decane at 150 degrees C. Two different and very unusual quadruply bridging coordination modes have been observed for the ampy ligand. Compounds 4-7 also feature one (4) or two (5-7) bridging oxo ligands. With the exception of one of the oxo ligands of 7, which is in a distorted tetrahedral environment, the remaining oxo ligands of 4-7 are surrounded by five metal atoms. In carbonyl metal clusters, quadruply bridging oxo ligands are very unusual, whereas quintuply bridging oxo ligands are unprecedented. By using 18O-labeled water, we have unambiguously established that these oxo ligands arise from water.     

Synthesis of PtRu5(CO)14(PBu(t)3)(mu-H)2(mu6-C) and its reactions with Pt(PBut3)2, HGePh3, and HSnPh3

Reaction of PtRu5(CO)15(PBut3)(C), 3, with hydrogen at 97 degrees C yielded the new dihydride-containing cluster compound PtRu5(CO)14(PBut3)(mu-H)2(mu6-C), 5. Compound 5 was characterized crystallographically and was shown to contain an octahedral cluster consisting of one platinum and five ruthenium atoms with a carbido ligand in the center. Two hydrido ligands bridge two oppositely positioned PtRu bonds. Compound 5 reacts with Pt(PBut3)2 to yield Pt2Ru5(CO)14(PBut3)2(mu-H)2(mu6-C), 6, a Pt(PBut3) adduct of 5, by adding a Pt(PBut3) group as a bridge across one of the Ru-Ru bonds in the square base of the Ru5 portion of the cluster. Compound 6 is dynamically active on the NMR time scale by a mechanism that appears to involve a shifting of the Pt(PBut3) group from one Ru-Ru bond to another. Two new complexes, PtRu5(CO)13(PBut3)(mu-H)3(GePh3)(mu5-C), 7, and PtRu5(CO)13(PBut3)(mu-H)2(mu-GePh2)(mu6-C), 8, were obtained from the reaction of 5 with HGePh3. The cluster of 7 has an open structure in which the Pt(PBut3) group bridges an edge of the square base of the square pyramidal Ru5 cluster. Compound 7 also has three bridging hydrido ligands and one terminal GePh3 ligand. When heated to 97 degrees C, 7 is slowly converted to 8 by cleavage of a phenyl group from the GePh3 ligand and elimination of benzene by its combination with one of the hydrido ligands. The PtRu5 metal cluster of 8 has a closed octahedral shape with a GePh2 ligand bridging one of the Ru-Ru bonds. Two tin-containing compounds, PtRu5(CO)13(PBut3)(mu-H)3(SnPh3)(mu5-C), 9, and PtRu5(CO)13(PBut3)(mu-H)2(mu-SnPh2)(mu6-C), 10, which are analogous to 7 and 8 were obtained from the reaction of 5 with HSnPh3.     

Nonlinear optically active polymeric coordination networks based on metal m-pyridylphosphonates

A family of polymeric coordination networks based on meta-pyridylphosphonate bridging ligands has been synthesized and characterized by single-crystal X-ray crystallography. Compounds [M(2)(L-Et)(4)(mu-H(2)O)] (M = Mn, 1; Co, 2; Ni, 3; L-Et = ethyl-4-[2-(3-pyridyl)ethenyl]phenylphosphonate) were obtained by hydro(solvo)thermal reactions between diethyl-4-[2-(3-pyridyl)ethenyl]phenylphosphonate (L-Et(2)) and corresponding metal salts, while [Cd(L-H)(2)], 4 (L-H is monoprotonated 4-[2-(3-pyridyl)ethenyl]phenylphosphonate), was obtained by a hydro(solvo)thermal reaction between (L-H(2)).HBr and Cd(CF(3)SO(3))(2).6H(2)O. Compounds 1-3 are isostructural and crystallize in noncentrosymmetric space group Fdd2, and they adopt a complicated 3D framework structure composed of [M(2)(L-Et)(4)(mu-H(2)O)] building units, while compound 4 adopts a centrosymmetric 3D network structure resulted from linking 1D sinusoidal cadmium phosphate chains with L-H bridging ligands. Consistent with their polar structures, compounds 1-3 exhibit powder second harmonic generation signals larger than that of potassium dihydrogen phosphate.     

High-nuclearity iridium carbonyl clusters containing phenylgermyl ligands: synthesis, structures, and reactivity

The reaction of Ir4(CO)12 with Ph3GeH at 97 degrees C has yielded the new tetrairidium cluster complexes Ir4(CO)7(GePh3)(mu-GePh2)2[mu3-eta3-GePh(C6H4)](mu-H)2 (10) and Ir4(CO)8(GePh3)2(mu-GePh2)4 (11). The structure of 10 consists of a tetrahedral Ir4 cluster with seven terminal CO groups, two bridging GePh2) ligands, an ortho-metallated bridging mu3-eta3-GePh(C6H4) group, a terminal GePh3 ligand, and two bridging hydrido ligands. Compound 11 consists of a planar butterfly arrangement of four iridium atoms with four bridging GePh2 and two terminal GePh3 ligands. The same reaction at 125 degrees C yielded the two new triiridium clusters Ir3(CO)5(GePh3)(mu-GePh2)3(mu3-GePh)(mu-H) (12) and Ir3(CO)6(GePh3)3(mu-GePh2)3 (13). Compound 12 contains a triangular Ir3 cluster with three bridging GePh2), one triply bridging GePh, and one terminal GePh3 ligand. The compound also contains a hydrido ligand that bridges one of the Ir-Ge bonds. Compound 13 contains a triangular Ir3 cluster with three bridging GePh2 and three terminal GePh3 ligands. At 151 degrees C, an additional complex, Ir4H4(CO)4(mu-GePh2)4(mu4-GePh)2 (14), was isolated. Compound 14 consists of an Ir4 square with four bridging GePh2, two quadruply bridging GePh groups, and four terminal hydrido ligands. Compound 12 reacts with CO at 125 degrees C to give the compound Ir3(CO)6(mu-GePh2)3(mu3-GePh) (15). Compound 15 is formed via the loss of the hydrido ligand and the terminal GePh3 ligand and the addition of one carbonyl ligand to 12. All compounds were fully characterized by IR, NMR, single-crystal X-ray diffraction analysis, and elemental analysis.     

Catalysis of H(2)/D(2) scrambling and other H/D exchange processes by [Fe]-hydrogenase model complexes

Protonation of the [Fe]-hydrogenase model complex (mu-pdt)[Fe(CO)(2)(PMe(3))](2) (pdt = SCH(2)CH(2)CH(2)S) produces a species with a high field (1)H NMR resonance, isolated as the stable [(mu-H)(mu-pdt)[Fe(CO)(2)(PMe(3))](2)](+)[PF(6)](-) salt. Structural characterization found little difference in the 2Fe2S butterfly cores, with Fe.Fe distances of 2.555(2) and 2.578(1) A for the Fe-Fe bonded neutral species and the bridging hydride species, respectively (Zhao, X.; Georgakaki, I. P.; Miller, M. L.; Yarbrough, J. C.; Darensbourg, M. Y. J. Am. Chem. Soc. 2001, 123, 9710). Both are similar to the average Fe.Fe distance found in structures of three Fe-only hydrogenase active site 2Fe2S clusters: 2.6 A. A series of similar complexes (mu-edt)-, (mu-o-xyldt)-, and (mu-SEt)(2)[Fe(CO)(2)(PMe(3))](2) (edt = SCH(2)CH(2)S; o-xyldt = SCH(2)C(6)H(4)CH(2)S), (mu-pdt)[Fe(CO)(2)(PMe(2)Ph)](2), and their protonated derivatives likewise show uniformity in the Fe-Fe bond lengths of the neutral complexes and Fe.Fe distances in the cationic bridging hydrides. The positions of the PMe(3) and PMe(2)Ph ligands are dictated by the orientation of the S-C bonds in the (mu-SRS) or (mu-SR)(2) bridges and the subsequent steric hindrance of R. The Fe(II)(mu-H)Fe(II) complexes were compared for their ability to facilitate H/D exchange reactions, as have been used as assays of H(2)ase activity. In a reaction that is promoted by light but inhibited by CO, the [(mu-H)(mu-pdt)[Fe(CO)(2)(PMe(3))](2)](+) complex shows H/D exchange activity with D(2), producing [(mu-D)(mu-pdt)[Fe(CO)(2)(PMe(3))](2)](+) in CH(2)Cl(2) and in acetone, but not in CH(3)CN. In the presence of light, H/D scrambling between D(2)O and H(2) is also promoted by the Fe(II)(mu-H)Fe(II) catalyst. The requirement of an open site suggests that the key step in the reactions involves D(2) or H(2) binding to Fe(II) followed by deprotonation by the internal hydride base, or by external water. As indicated by similar catalytic efficiencies of members of the series, the nature of the bridging thiolates has little influence on the reactions. Comparison to [Fe]H(2)ase enzyme active site redox levels suggests that at least one Fe(II) must be available for H(2) uptake while a reduced or an electron-rich Fe(I)Fe(I) metal-metal bonded redox level is required for proton uptake.     

Interpenetrated networks from a novel nanometer-sized pseudopeptidic ligand, bridging water, and transition metal ions with cds topology

The combination of a new pseudopeptidic ligand, transition metal ions, and bridging water molecules results in the formation of [M(mu-TBG)(mu-H2O)(H2O)2].2H2O (M: Cu, Co and H2TBG: terephthaloylbisglycine); both compounds show rare two-fold interpenetrated three-dimensional cds-nets and reversible loss of coordinated and lattice water molecules.     

High nuclearity ruthenium-tin clusters from the reactions of triphenylstannane with pentaruthenium carbonyl carbido cluster complexes

The reaction of Ru(5)(CO)(15)(mu(5)-C), 1, with Ph(3)SnH in the presence of UV irradiation has yielded the Ph(3)SnH adduct Ru(5)(CO)(15)(SnPh(3))(mu(5)-C)(mu-H), 3, by SnH bond activation and cleavage of one Ru-Ru bond in the cluster of 1. The reaction of 1 with Ph(3)SnH at 127 degrees C yielded the high nuclearity cluster compound Ru(5)(CO)(10)(SnPh(3))(mu-SnPh(2))(4)(&mu(5)-C)(mu-H), 4, that contains five tin ligands. Four of these are SnPh(2) groups that bridge each edge of the base of the Ru(5) square pyramidal cluster. The reaction of Ph(3)SnH with the benzene-substituted cluster Ru(5)(CO)(12)(C(6)H(6))(mu(5)-C), 2, at 68 degrees C yielded two products: Ru(5)(CO)(11)(SnPh(3))(C(6)H(6))(mu(5)-C)(mu-H), 5, and Ru(5)(CO)(10)(SnPh(3))(2)(C(6)H(6))(mu(5)-C)(mu-H)(2), 6. Both contain square pyramidal Ru(5) clusters with one and two SnPh(3) groups, respectively. At 127 degrees C, the reaction of 2 with an excess of Ph(3)SnH has led to the formation of two new high-nuclearity cluster complexes: Ru(5)(CO)(8)(mu-SnPh(2))(4)(C(6)H(6))(mu(5)-C), 7, and Ru(5)(CO)(7)(mu-SnPh(2))(4)(SnPh(3))(C(6)H(6))(mu-H), 8. Both compounds contain square pyramidal Ru(5) clusters with SnPh(2) groups bridging each edge of the square base. Compound 8 contains a SnPh(3) group analogous to that of compound 4. When treated with CO, compound 8 is converted to 4. When heated to 68 degrees C, compound 5 was converted to the new compound Ru(5)(CO)(11)(C(6)H(6))(mu(4)-SnPh)(mu(3)-CPh), 9, by loss of benzene and the shift of a phenyl group from the tin ligand to the carbido carbon atom to form a triply bridging benzylidyne ligand and a novel quadruply bridging stannylyne ligand.     

Tetranuclear platinum phosphido complexes with different structures

The addition of [NBu4]Br or [NBu4][BH4] to solutions of [Pt4(mu-PPh2)4(C6F5)4(CO)2] yields the complexes [NBu4]2[Pt4(mu-PPh2)4(mu-X)2(C6F5)4] (X=Br, H,) in which the two CO groups have been replaced by two anionic, bridging X ligands. The total valence electron counts are 64 and 60, respectively; thus, complex does not require Pt-Pt bonds, while two metal-metal bonds are present in, as their NMR spectra confirm. Also, the NMR spectra indicate a nonsymmetrical "Pt(mu-PPh2)2Pt(mu-PPh2)(mu-X)Pt(mu-PPh2)(mu-X)Pt" disposition for and. Treatment of with HX (X=Cl, Br) yields the complexes [NBu4]2[Pt4(mu-PPh2)4(mu-H)2(C6F5)3X] (X=Cl, Br,). These complexes react with [Ag(OClO 3)PPh3] with displacement of the halide and formation of [NBu4][Pt4(mu-PPh2)4(mu-H)2(C6F5)3PPh3]. Complexes maintain the same basic skeleton as, with two Pt-Pt bonds. Complex is, however, an isomer of the symmetric [NBu4]2[{(C6F5)2Pt(mu-PPh2)2Pt(mu-Br)}2], which has been prepared by a metathetical process from the well-known [NBu4]2[{(C6F5)2Pt(mu-PPh2)2Pt(mu-Cl)}2]. The comparison of the X-ray structures of and confirms the different disposition of the bridging ligands, and their main structural differences seem to be related to the size of Br- and its position in the skeleton.