Coordination of ortho and para quinones and oxidation reduction processes in trimethylphosphine complexes of cobalt and nickel

The ortho-quinones 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 3,5-di -tert-butyl-benzoquinone-1,2 oxidatively substitute trimethylphosphine into Ni(PMe3)(4) affording molecular compounds containing chelating dioxo ligan ds of the catecholate type. Using CoMe(PMe3)(4) as a substrate the synthesi s was extended to tetrachlorobenzoquinone-1,2 and dibenzoyl with retention of the CoMe group. Formally omitting the methyl group, odd-electron complex es were obtained from Co(cyclopentene)(PMe3)(3) by reaction with 9,10-phena nthrenequinone or dibenzoyl. The para-quinones 2,5-di-tert-butyl-benzoquino ne-1,4 and 2-tert-butylnaphthoquinone-5,10 displace two trimethylphosphines in Ni(PMe3)(4) to form diene complexes of zerovalent nickel. X-ray crystal structures establish the presence of O:O coordinated catecholato ligands f or nickel(II) and cobalt(III) and reveal an eta(4)-diene type quinone ligan d coordinated to nickel(0). (C) 1999 Elsevier Science S.A. All rights reser ved.