Synthesis Of Iron, Cobalt, Nickel Complexes Supported By Trimethylphosphine And NHC Ligands And Their Applications In Catalytic Reactions

Transition metal complexes have been widely used in catalytic reactions. Synthesizing new transition metal complexes and exploring their ability as catalysts raised great interests of scientists. The key components of a metal complex are metal center and the ligands. Different combinations can bring out diverse characters of the complexes. Here, we would like to discuss cheap metals with abundant reserves such like nickel, cobalt and iron.1. Amination of-aryl chlorides have been realized using trimethylphosphine supported Ni(0) as catalyst. The aryl chlorides are Schiff bases. Mono-substitution could proceed in high yields because of the anchoring group, the imine group. In the reported selective C, N-coupling reactions, selectivity is poor. The base we had used is NaOH, easier to get compared to NaO’Bu or KO’Bu which are usually used in C, N-coupling reactions. The additive, tetra-^-butylammonium bromide, increased the reaction rate effectively. We proposed the mechanism to be a cooperation of the metal center, base and amine in the rate limiting step.2. A new amine functionalized double chelate [C, N] type NHC nickel complex was synthesized and characterized. [CNC] pincer type NHC nickel complexes were generated through an improved synthetic method after exploring different pathways. Catalytic ability of the three nickel complexes were tested in Kumada coupling reaction. The [C, N] type nickel complex showed the best property in catalytic activity. With only 0.5 mol% of catalyst loading, the coupling of aryl chlorides with Grignard reagents received good yields.3. Metal hydrides of cobalt and iron have been synthesized through OH bond activation and direct reduction by NaBH4. The reaction of HCo(PMe3)4 with triphenyl phosphite generated the coordination product. While Co(PMe3)4 and Fe(PMe3)4 could activate the C-H bond on the benzene ring of triphenyl phosphite, leading to cobalt hydride and iron hydride complexes. Bromopentafluorobenzene reacted with Fe(PMe3)4 and then reduced by NaBR, could generate iron hydride complex. The iron hydride with bromopentafluorobenzene as ligand showed good property in catalytic hydrosilylation of aldehydes and ketones.