The reaction of diphenylphosphine, PPh 2H, with an alkyne-bridged dicobalt carbonyl complex; the synthesis crystal structure and reactivity of the complex [CO 2{μ-C(CO 2Me)CHCO 2Me}(μ-PPh 2)(CO) 4

Abstract

The reaction between [Co 2(μ-C 2(CO 2Me) 2)(CO) 6] and diphenylphosphine gives the mono- and di-substituted complexes [Co 2{μ-C 2}(CO 2Me) 2 (CO) 6- n (PPh 2H) n ] [ n = 1 ( 1), 2 ( 2)]. Thermolysis of ( 1) leads to phosphorus-hydrogen bond cleavage and formation of the phosphido-, vinyl-bridged complex [Co 2{μ-C(CO 2Me)CHCO 2Me}(μ-PPh 2(CO) 4] ( 3) together with the trinuclear cobalt complex [Co 3{μ-C 2(CO 2Me) 2}(μ-PPh 2(CO) 7 ( 4). An X-ray diffraction study of 3 reveals that one of the methylcarboxylate substituents of the vinyl ligand is coordinated via oxygen to cobalt, forming an almost planar M-C-C-C-O five-membered metallacyclic ring. The reactions of ( 3) with a tertiary phosphine and with phenylacetylene are described.