none

none

The organometallic chemistry of C60 has attracted much attention concerning the effect of metal coordination on the properties of C60 since the discovery and macroscopic synthesis of C60. In our study, we try to synthesize two analogous ligands which contain two phosphines. And reaction of the new ligands and metal carbonyl clusters will produce new-type of metal complexes. Addition of Ph2(Li)PBH3, prepared by n-BuLi-deprotonation of Ph2(H)PBH3 in THF, to toluene solution of C60 took place to give the adduct C60H2(Ph2PBH3)2 (2) after quenching with HCl in ethyl acetate. Reaction of C60 and sodium 1-propanethiolate in acetonitrile produces C602-, and then adding PPh2Cl to C602- solution to afford C60(PPh2)2 (8). Treatment of the borane complex 2 with diazabicyclo[2.2.2]octane (DABCO) in toluene removes the borane group to give the phosphine C60H2(PPh2)2 (3). Reaction of 3 and Os3(CO)10(NCMe)2 at room temperature produces Os3(CO)10(£g,£b3-(PPh2)C60H) (5) and C60H2(PPh2)2(Os3(CO)10)2 (6). Furthermore, reaction of 3 and Ru3(CO)12 at 85 ¢J produces Ru3(CO)10(£g,£b3-(PPh2)C60H) (7). The resulting compounds are characterized by NMR, IR, Mass, X-ray and EA.

none

A series of aluminia and titania promoted, silica- supported chromium (III) acetate catalysts were characterized using X-ray photoelectron spectroscopy (XPS) prior to, and after, activation in oxygen at 780 C. The results indicated that Cr (VI) was formed in each case as a result of the activation process. Increased promoter metal binding energies implied an interaction between the promoter and silica support. It is proposed that there is insertion of aluminium and titanium atoms into the silica network, which leads to formation of surface silicates. A qualitative measure of the metal dispersions has been made using the XPS results. In general, the chromium dispersion fell on activation, but the greatest decline was seen with the lowest chromium loading (0.5% Cr), Promoter metal dispersion was unchanged on activation, except in the case of the highest titanium loading (4.35% Ti), where small titania clusters are formed. Mass spectral analysis of the gases evolved during thermal decomposition in argon led to a mechanism being proposed for the decomposition of the acetate precursor. The first step is dehydration of the silica support, which is followed by decompositon of acetate ligands to form an intermediate, which was thought to be a carbonate, and the final stage is the decomposition of this intermediate to chromium (III) oxide for the unpromoted catalysts. Where a promoter is present a structural and electronic interaction between the chromium complex and the promoter is proposed, which leads to formation of mixed surface oxides of perovskite (M(^II)Ti(^IV)0(_3)) or spinel (M(^II)Al(_2)(^III)0(_4)) structure, where M = Cr. For activation under oxygen the pattern of decomposition was much simpler. Studies of the promoted catalysts showed the oxidation to occur—in two stages. It was not clear which chromium species were present after the first step, but the second step led to the formation of chromium (VI) oxide for all catalysts. Modelling of the adsorption sites on metal surfaces has also been undertaken with a series of triosmium carbonyl complexes containing ligands derived from aniline, phenol, pyrrole, furan, thiophene and benzene. These complexes have been characterized using Fourier Transform Infra Red spectroscopy and their vibrational spectra assigned in full. The usefulness of these complexes as models, and in the assignment of vibrational spectra of adsorbates on metal surfaces, is discussed.

The reaction of 2-[(diphenylphosphino)methyl]-6-methylpyridine (PN) with Os3(CO)12-n(MeCN)n [where n = 0 (1), 1 (2), 2 (3)] has been investigated. Os3(CO)12 reacts with PN in the presence of Me3NO to afford the clusters Os3(CO)11(1-PN) (4) and 1,2-Os3(CO)10(1-PN)2 (5). X-ray diffraction analyses confirm the equatorial coordination of the phosphine(s) in 4 and 5, with the two phosphines in the latter cluster exhibiting a 1,2-trans orientation about the Os-Os vector that contains the two ligands. Treatment of the MeCN-substituted cluster Os3(CO)11(MeCN) and PN (1:1 ratio) in CH2Cl2 gives clusters 4 and 5, in addition to HOs3(η1-Cl)(CO)10(1-PN) (6) as a result of competitive activation of the reaction solvent. Cluster 6 contains 48e- and the diffraction structure reveals the presence of axial chloride and equatorial phosphine ligands which are located on adjacent osmium atoms. The bridging hydride ligand in 6 spans the Cl,P-substituted Os-Os vector. The reaction of Os3(CO)10(MeCN)2 with PN furnishes 5, 6, and 1,1-Os3(CO)10(2-PN) (7) in yields that are dependent on the reagent stoichiometry and reaction solvent. The solid-state structure of 7 confirms the chelation of the PN ligand to a single osmium atom via the pyridine and phosphine moieties at axial and equatorial sites, respectively. The bonding in 7 relative to other possible stereoisomers has been explored by DFT calculations, and the diffraction structure is computed as the thermodynamically most stable form of this cluster. Cluster 4 is photosensitive and CO loss gives 7, in addition to the formation of the dihydride H2Os3(CO)8[µ-CH(NC5H3)CH2PPh2] (8), whose origin derives from the double metalation of the C-6 methyl group of the PN ligand in 7. Photolysis of 7 yields 8 without detectable observation of the expected intermediate hydride HOs3(CO)9[µ-CH2(NC5H3)CH2PPh2]. The PN ligand in 7 undergoes P-C bond activation in toluene at 110 °C to afford the 50e cluster Os3(CO)9(µ-C6H4)(µ-PPh), which contains face-capping benzyne and phosphinidene moieties. The bonding between the benzyne moiety and the opened Os3 frame in 9 has been examined computationally, and these data are discussed relative to and π bonding contributions from the metalated aryl ring to the cluster polyhedron. Thermolysis of BrRe(CO)5 with 4-(2,2-dimethylhydrazino)dimethylhydrazone-3(Z)-penten-2-one in toluene at 70 °C furnishes the new β-diketimine-substituted complex fac-BrRe(CO)3[(Me2NNCMe)2CH2] (1) in 50-70 isolated yield. Product 1 is also obtained in comparable yield when the same reactants are irradiated at 366 nm at room temperature in fluid solution. Treatment of the parent ligand with the "lightly stabilized" rhenium compound fac-BrRe(CO)3(THF)2 affords 1 as the sole observable rhenium product. Complex 1 has been characterized in solution by IR and 1H NMR spectroscopy, and the molecular structure has been determined by single-crystal X-ray diffraction analysis.

Quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been synthesized as possible specific metal host systems. The synthesis and characterization of quinoxaline-functionalized, cage-annulated oxa- and thiacrown ethers have been described. The characterization of these host systems have been fully achieved in solution by using various techniques such as IR, 1H NMR, and 13C NMR spectroscopic methods, high-resolution mass spectrometry (HRMS), elemental microanalysis, and X-ray crystallographic analysis in case of one quinoxaline-functionalized, cage-annulated oxacrown ether compound. The synthesis of the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) is described. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligand bmi proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(bmi) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)N(tolyl-p)C(O)]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(bmi) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(bmi), whose molecular structure has been determined by X-ray crystallography. The kinetics for the ligand isomerization have been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-348 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Orthometalation of one of the phenyl groups associated with the bmi ligand is triggered by near-UV photolysis of the chelating cluster 1,1- Os3(CO)10(bmi).

The reaction between the formamidine ligand PriN=CHNHPri and the activated cluster Os3(CO)10(MeCN)2 has been studied. A rapid reaction is observed at room temperature, yielding the hydride clusters HOs3(CO)9[μ-OCNPriC(H)NPri] and HOs3(CO)10[μ-NPriC(H)NPri] as the principal products. The spectroscopic data and X-ray diffraction structures of those formamidinate-substituted clusters will be present. The thermal reactivity of the clusters has been investigated, with the face-capped cluster HOs3(CO)9[μ-NPriC(H)NPri] found as the sole observable product. The relationship between these three clusters has been established by kinetic studies, the results of which will be discussed.

Substitution of MeCN ligands in the activated cluster Os3(CO)10(MeCN)2 by the unsaturated diphosphine ligands (Z)-Ph2PCH=CHPPh2 (cDPPEn) or 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) proceeds rapidly at room temperature to furnish the ligand-bridged cluster 1,2-Os3(CO)10(P-P) (P-P represents cDPPEn or bpcd). Heating 1,2-Os3(CO)10(P-P) leads to the formation of the thermodynamically more stable chelating isomer 1,1-Os3(CO)10(P-P). Each compound of Os3(CO)10(P-P) has been characterized by x-ray diffraction, IR, 31P NMR and 1H NMR. Ligand isomerization kinetics have been investigated by UV-VIS and 31P NMR (for cDPPEn) or 1H NMR (for bpcd) spectroscopies. The isomerization mechanism is discussed based on the activation parameters and CO inhibition (for cDPPEn) or ligand trapping experiments (for bpcd). Thermolysis of 1,1-Os3(CO)10(bpcd) in refluxing toluene gives the hydrido cluster HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] and the benzyne cluster HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)]. Photolysis of 1,1-Os3(CO)10(bpcd) using near UV light affords HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] as the sole product. HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)] has been characterized in solution by IR and NMR spectroscopies. Furthermore its molecular structure has been determined by X-ray crystallography. Reversible C-H bond formation in HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] is demonstrated by ligand trapping studies to give 1,1-Os3(CO)9L(bpcd) (where L = CO, phosphine) via the unsaturated intermediate 1,1-Os3(CO)9(bpcd). The kinetics for reductive coupling in HOs3(CO)9[γ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] and DOs3(CO)9[μ-(PPh2-d10)C=C{P(Ph-d5)(C6D4)}C(O)CH2C(O)] in the presence of PPh3 give rise to a kH/kD value of 0.88, whose magnitude supports the existence of a preequilibrium involving the hydride(deuteride) cluster and a transient arene-bound Os3 species that precedes the rate-limiting formation of 1,1-Os3(CO)9(bpcd). Strong proof for the proposed hydride(deuteride)/arene preequilibrium has been obtained from photochemical studies employing the isotopically labeled cluster 1,1-Os3(CO)10(bpcd-d4ortho), whose bpcd phenyl groups each contain one ortho hydrogen and deuterium atom. Equilibrium and kinetic isotope effects in the orthometallation step has been determined by 1H NMR in photochemical studies. Kinetics for the transformation from HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C(O)CH2C(O)] to HOs3(CO)8(μ3-C6H4)[μ2,η1-PPhC=C(PPh2)C(O)CH2C(O)] has been studied by UV-VIS spectroscopy for which the mechanism is discussed.