Synthesis And Reactivity Of Novel Iron, Cobalt And Nickel Hydride Complexes Supported By Trimethylphosphine

Transition metal hydrides occupy an essential place in organometallic chemistry because hydrides are intermediates or catalysts in many important reactions such as hydrogenation, hydrosilylation, hydroformylation and transfer hydrogenation. A number of iron, cobalt, and nickel hydrido complexes have been prepared and many catalytic transformations involving these hydrides have been reported. Many of these hydrides were supported by pincer (e.g. PCP or PNP) ligands. Moreover, the cobalt hydrido complexes used as catalysts for hydrosilylation are very rare.The insertion reaction of triple carbon-carbon bond into transition metal-hydrogen bond is the key intermediate process in functionalization of triple carbon-carbon bond, producing vinyl complexes. Most of the transition metals are Ir, Os and Ru. Although nickel hydride complexes were synthesized and used in many catalytic reactions, few of nickel hydride complexes react with alkyne to produce metal-alkenyl complexes were reported.Reaction of the N-benzylidene-1-naphthylamine with CoMe(PMe3)4 afforded the hydrido CNC pincer cobalt complex of CoH(PMe3)2[(C6H4)CH=N(C10H6)] (1) via double C-H bond activation. Complex 1 reacted with haloalkane (CH3I and EtBr) delivered CoX(PMe3)2((C6H4)CH=N(C10H6)) (X=I (2); Br (3)). However, the reactions of complex 1 with HCl and trifluoroacetic acid (TFA) delivered HCoCl(PMe3)2((C6H4)CH=N(C10H7)) (4) and HCo(OCOCF3)(PMe3)2((C6H4)CH=N(C10H7)) (5) with the cleavage of the Co-C(naphthyl) bond. A reaction of complex 1 with DCl was carried out to prove that the hydrogen atom eliminated to the naphthyl carbon comes from HCl. Complex 1 reacted with acetylacetone resulted in the formation of Co(acac)(PMe3)2((C6H5)CHNH(C10H6)) (7). Complex 1 was found to be an efficient catalyst for hydrosilylation of aldehydes and ketones.The treatment of 2-(diphenylphosphino)benzeneselenol with Ni(PMe3)4 at -78℃ afforded the hydrido nickel(II) complex 11 bearing a chelate [P,Se]-ligand. The insertion reactions of 11 with phenylacetylene and 1-phenyl-1-propyne afforded the vinyl nickel(Ⅱ) complexes 12 and 13, while the combination of 1 with diphenylacetylene, trimethylsilylacetylene and 1-phenyl-2-(trimethylsilyl)acetylene delivered nickelacyclopropane complexes 14,15,16A and 16B containing a ylidic ligand through 1,2 phosphine shift.Reaction of 2-(diphenylphosphino)benzeneselenol with Fe(PMe3)4 afforded the hydrido complex 17 bearing a chelate [P,Se]-ligand. Bischelate product 18 was obtained in the presence of Bronsted Acids.