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2-Diphenylphosphinobenzaldehyde as Chelating Ligand in Trimethylphosphine Complexes of Cobalt and Nickel

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journal contribution
posted on 25.08.1998, 00:00 by Hans-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⌒CO) which occupy OC-axial and P-equatorial positions in the trigonal bipyramidal configuration of nickel(d8) compounds Ni(Ph2P⌒CO)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⌒CO)(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⌒CO)(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⌒CO)(PMe3)2 (10) (17 valence electrons). The molecular structures of compounds 3, 5, 6, and 10 have been solved by X-ray crystallography.