posted on 1998-08-25, 00:00authored byHans-Friedrich Klein, Ute Lemke, Mathias Lemke, Alexandra Brand
Methylnickel complexes activate the C(O)−H function of 2-diphenylphosphinobenzaldehyde
to form five-membered chelate rings Ni(Ph2P⌒CO) which occupy OC-axial and P-equatorial
positions in the trigonal bipyramidal configuration of nickel(d8) compounds Ni(Ph2P⌒CO)X(PMe3)2 (X = Cl (1), Br (2), I (3), Me (4)). Methylcobalt complexes react with
2-diphenylphosphinobenzaldehyde to afford an isoelectronic species Co(Ph2P⌒CO)(PMe3)3
(5) of similar configuration, while cobalt halides CoX(PMe3)3 oxidatively add the aldehyde
function to produce octahedral compounds mer-CoH(X)(Ph2P⌒CO)(PMe3)2 (X = Cl (6), Br
(7), I (8)). Carbon monoxide replaces an axial trimethylphosphine in 5, while iodomethane
gives rise to an oxidative substitution producing CoI(Ph2P⌒CO)(PMe3)2 (10) (17 valence
electrons). The molecular structures of compounds 3, 5, 6, and 10 have been solved by X-ray
crystallography.