Activation Of Strong Chemical Bonds With Iron,Cobalt And Nickel Complexes Supported By Trimethylphosphine

1. The C-Cl bond activation of CH2C12with Co(PMe3)4.Co(PMe3)4was found to be a very effective complex in the activation of C-Cl bonds in chloroalkanes and chloroform. A new mechanism like Simmons-Smith reaction was proposed since ethene was found as one of the products.Based on the formation of ethylene in this reaction, we proposed the methylene intermediate was involved in the reaction. In an attempt to confirm our proposal, cyclohexene was added as a carbene trapping agent. The adduct norcarane was detected by GC-MS and characterized by NMR. Similar reaction was performed with fullerene as another carbene trapping agent,[6,6]C6oCH2was monitored by NMR. Although both of the adducts are afforded in trace amount(2%), we have got strong credence to our proposal that the methylene intermediate was involved in the reaction.2. Reactivity of Nickel(O) Complexes Stablized by Trimethylphosphine with CS2, CO2and SCNPh Molecules.The reactivity of heterocumulenes such as carbon dioxide and carbon disulfide, which are promising sources of Cl chemistry, has been shown to produce a variety of chemical transformations. The development of practical methods for the generation of organic compounds from carbon dioxide, an abundant and inexpensive source of carbon, is essential in the future management of this greenhouse gas. Carbon disulfide and phenyl isothiocyanate are highly reactive, and their coordination, addition, cleavage, and insertion reactions are currently being intensively investigated. The interest in the coordination chemistry of carbon sulfide and phenyl isothiocyanate with transition metal complexes stems mainly from the fact that both of them are structurally related to carbon dioxide, although it is clear that these molecules exhibit different reactivity.Reactions of Ni(PMe3)4with carbon disulfide and phenyl isothiocyanate in THF give the tetrahedral coordinate complexes (PMe3)3Ni(η2-CS2) and (PMe3)3Ni(η2-SCNPh), characterized by standard spectroscopic methods and X-ray difffraction. Property of these two complexes have also been studied. Reaction of Ni(PMe3)4with carbon monoxide results in the reduction of CO2to CO, which was trapped as (PMe3)3Ni(CO). Trimethylphosphine served as reductant giving O=PMe3.3. Activation of sp2C-H Bonds by Fe(PMe3)4and Catalytic Study of Iron Hydride ComplexesTreatment of bis(phosphine) ligands1,3-(Ph2PCH2)2C6H4with Fe(PMe3)4furnishes iron PCP-pincer hydride complexes [2,6-(Ph2PCH2)2C6H3]Fe(H)(PMe3)2with two cis-PMe3. This new iron PCP-pincer hydride complexes catalyze the hydrosilylation of aldehydes and ketones with different functional groups. The hydrosilylation reactions are more likely to proceed via the activation of silanes or carbonyl substrates after ligand dissociation from the iron center.