The activation of carbon monoxide, hydrogen, silanes, and alkynes with transition metal complexes

Complexes (Ir(PPh{dollar}sb3)sb2{dollar}(biph)Cl) and (Ir(PMe{dollar}sb3)sb3{dollar}(biph)Cl) (biph = biphenyl-2,2{dollar}spprime{dollar}-diyl), prepared from C-C cleavage of biphenylene show catalytic activity for the unusual head-to-head coupling of terminal alkynes. The cis/trans ratio of the product enynes can be controlled in a way not previously possible. A mechanism is proposed. The complex (Ir(PPh{dollar}sb3)sb2{dollar}(biph)Cl) has an unusual structure lying between Y and T geometries, and is closer to a Y. This geometric preference is discussed. The biph ligand proved to be stable under most reaction conditions, and can also stabilize Ir(IV). The synthesis and structural characterization of an Ir(IV) boryl complex, (Ir(PMe{dollar}sb3)sb3{dollar}(biphBF)Cl) {dollar}sp+{dollar}, is presented. The origin of the easy oxidation of the Ir center as a result of the presence of a high lying HOMO of the Ir(biph) fragment is probed by EHT (Extended Huckel) calculations.; A series of Ni(II) complexes with a biologically relevant O, N, S ligation environment is synthesized and characterized. The use of iminothiolate in these complexes avoids the problems of normal thiolates, especially their bridging tendency. Bridge avoidance is rationalized on a dipole-dipole interaction model. These are the first functional model complexes for the CO oxidation site of Ni CODH, in which CO can be oxidized by either methylviologen or O{dollar}sb2{dollar} to produce CO{dollar}sb2{dollar} in an aqueous solution at room temperature. In contrast to the mechanism of the common water gas shift reaction (WGSR), we propose that a Ni-H is not an intermediate so that protonation to produce H{dollar}sb2{dollar} cannot take place. Kinetic and inhibition properties of the model complexes and the enzyme are in good agreement. Geometric and electronic studies of Ni(II) complexes reveal that five coordination is the most favorable structure for binding CO.; Silane alcoholysis with similar Ni(II) coordination compounds as catalysts is also described. Mechanistic studies are consistent with the silane being activated via a two-electron three-center (Si-H{dollar}cdots{dollar}Ni) binding, followed by nucleophilic attack of alcohol on Si. A Ni(II) complex also catalyzes H{dollar}sp+{dollar}/D{dollar}sb2{dollar} exchange.