The Synthesis And Properties Of New Methyl Cobalt Complexes. Trimethylphosphine Support

Cobalt belongs to VIII family of transition metals. It has unsaturated d-orbits, and presents different oxidation states, so it holds particular reaction performance. Cobalt can activate small molecule such as N₂, CO, CO₂, H₂, SO₂,olefin, alkine, alkane through coordination. It can stabilize many complexes by σ and π coordination .Cobalt may provide electrons to organic complex and accept electrons from organic complex. All these characters play an important role in organic synthesis especially in catalytic reaction. Further more, it is widely used in organic synthesis and industrial catalysis and so on since it is cheap.Trimethylphosphine coordinates with transition metals very strongly and forms steady compounds. Trimethylphosphine can stabilize M-C bond. The organic compounds of cobalt coordinated with trimethylphosphine have high reaction activity and selectivity.The central atom of vitamin B₁₂ was proved to be cobalt(III). Recently, much attention has been devoted to this field about it. Methyl cobalt complexes often are used as methylation agents for germanium, tin and lead compounds in environmental chemistry. In this paper four novel dimethylcobalt complexes through the reaction of CoL₃Me₃ with substituted salicylaldehydes or enolated malonic dialdehydes. These complexes were characterized with IR, ¹H NMR, ¹³C NMR, ¹P NMR and elemental analyses. The crystal structure was determined with X-ray diffraction. The reaction of dimethylcobalt(III) complexes with CO was discussed.Olefin can be obtained by nucleophilic addition of Wittig agents with aldehyde or ketone containing C=O. Acyl cobalt complexes also contain C=O group. If they can react with phosphorous ylide at room temperature, π -coordinate olefin cobalt chelating complex with phenoxy oxygen as anchoring group could be obtained.. But it was proved that cobalt(II) complexes were obtained and the anticipated reaction didn't occur. Supposed reaction mechanisms is that one methylcobalt intermediate is firstly produced and then two intermediates eliminates one ethane to afford the cobalt(II) complexes.