Methylcobaltverbindungen mit nicht chelatisierenden Liganden,IV. Monoolefinkomplexe

Methylcobalt Compounds with Non-chelating Ligands, IV. Monoolefin Complexes Tris(trimethylphosphane)cobalt(I) halides in ether solvents saturated with olefin at low temperatures from monoolefin complexes which are prone to dissociation. Upon reaction with methyl-or phenyllithium more stable compounds are formed of the composition CoR(CC)L₃ ( 1 – 4 ) (R  CH₃; CC  C₂H₄, C₃H₆, cyclo-C₅H₈; R  C₆H₅; CC  C₂H₄; L  P(CH₃)₃). In solution the fluctional molecules adopt a ground state structure containing a σ-bonded group and an olefin ligand in adjacent positions (trigonal-bipyramidal: CH₃ axial and C₂H₄ equatorial or C₆H₅ and C₂H₄ equatorial). The latter arrangement is confirmed for the crystalline state by an X-ray structure determination of (ethene)phenyltris(trimethylphosphane)cobalt ( 4 ). An equatorial plane of coordination along a Co P bond not only contains both ethene-C atoms but also all the atoms of the phenyl group. The compound is thermally decomposed to give biphenyl and (ethene)tris-(trimethylphosphane)cobalt(0). No products of an olefin insertion reaction are observed.