Low-coordinate And Low-valent Cobalt Complexes With N-heterocyclic Carbene Ligation: Synthesis, Structure, Reactivity And Catalytic Reaction

The dissertation presents the synthesis, structure and reactivity study of low valent three-coordinate cobalt complexes with N-heterocyclic carbene(NHC) ligation.1. Three-coordinate cobalt(I) complexes. The cobalt(I) complex [Co(IAd)(PPh3)(CH2Ph)](2), [Co(IAd)(PPh3)(?3-CH2C(Me)CH2)](6) and [(Cp)Co(PPh3)2](7) were synthesized from the reactions of [Co(IAd)(PPh3)Cl](1) with Ph CH2 K, 2-methylallylmagnesiumchloride and CpNa, respectvely. The three-coordinate cobalt(0) complex [Co(IAd)(PPh3)2](4) was prepared from the reaction of 2 and tert-butylmagnesium chloride. [Co(IAd)(PPh3)(?2-PhC≡CPh)](10) and [Co(IAd)(PPh3)(SiHPh2)](9) were prepared from the reactions of 2 with diphenylacetylene and Ph2SiH2, respectively. The cobalt(I) complex [Co(IAd)(PPh3)(CH2Ph)] can catalyze regioselective hydrosilylation of 1-octyne with Ph2SiH2 at room temperature.2. Three-coordinate cobalt(0) complexes. Three-coordinate cobalt(0) complexes [Co(L)(η2-vtms)2](L = IMes, 11; IPr, 12; IAd, 13) were prepared in good yield from the reactions of CoCl2 with the corresponding NHC ligand, vtms, and KC8. The three-coordinate cobalt(0) complex [Co(IPr)(η2:η2-L)](L: 1-ethenyl-1-methyl-4-methylenecyclohexane)(14) was obtained through the reaction of 12 with isoprene. The dimeric cobalt(I) silyl complex [{Co(IPr)}2(μ-(SiHPh2)2](15) was prepared by the reaction of 12 with Ph2SiH2. The three coordinate cobalt(0) complex [Co(IPr)(η2: η2-dvtms)](14) was obtained through the reaction of 12 with dvtms. Complex 12 can effectively catalyze the polymerization of Ph2SiH2.