Metal complexes of unsaturated tertiary phosphines and arsines. Part X. Five-co-ordinate rhodium(I) complexes of ortho-vinylphenyl phosphines and arsines

Abstract

Rhodium(I) complexes of three ligands, tris-o-vinylphenyl-phosphine (tvpp) and -arsine (tvpa) and phenyl (bis-o-vinylphenyl)phosphine (dvpp), have been prepared. All complexes are five-co-ordinate with the empirical formula RhXL, the bis(vinylphenyl) compounds being dimeric with bridging halogen atoms. The tris(vinylphenyl)-arsine rhodium complexes, although apparently structurally similar to those of the phosphine show an unexpected ease of displacement of the olefin groups by many ligands (e.g. CO or PPh₃). The iodo-complex adopts a dimeric halogen-bridged structure with one free olefin group. The halogen bridges in these complexes are easily split by both ordinary σ-type ligands and those which form (σ+π) double bonds, forming five-co-ordinate monomeric species. The relative tendencies of these polydentate ligands to form five-co-ordinate rhodium(I) complexes is discussed.