HYDRIDO(ACYLPHENOLATO)COBALT(III) COMPOUN DS CONTAINING TRIMETHYLPHOSPHANE LIGANDS

Salicylaldehyde derivatives and related beta-hydroxo aldehydes CHO-CR= CR'-OH react with CoMe(PMe3)(4) via oxidative substitution to form low -spin d(6) complexes mer-CoH(CO-CR=CR'-O)(PMe3)(3). Reductive eliminat ion of acyl and hydride functions from cis positions at the metal is l ess favourable than in carbonyl cobalt intermediates through a pronoun ced stabilization by neutral phosphane sigma-donor and dianionic acyle nolato chelate ligands. Reactions of the hydride complexes with iodome thane or with protic acids HX afford octahedral molecular complexes me r-CoX(CO-CR=CR'-O)(PMe3)(3) (X = I, OAc) and mer-CoX(CO-CR=CR'-O)(PMe3 )(2) (X = OAc, O-CR'=CR-CHO) without opening of the acylenolato chelat e ring.