Synthesis and X-ray crystal structures of dimeric nickel(0) and tetrameric copper(I) iodide complexes of 2-diphenylphosphino-3-methylphosphinine

The dimer [Ni-2(mu-CO)(CO)(2)(mu-1)(2)] 2 has been prepared by two different procedures which involve the reaction of the 2-diphenyl-phosphino-3-methylphosphinine ligand 1 with either Ni(COD)(2) or NiBr2 . DME/Zn under CO atmosphere. The crystal structure of 2 has been determined by X-ray crystallography. As the analogous dppm complex, 2 adopts a W-frame structure with two bridging ligands 1, two terminal carbonyl ligands and one bridging carbonyl ligand. An electrochemical study reveals that the electron density in the Ni-2 core is considerably reduced in 2 compared to the dppm complex. The reaction of 1 with two equivalents of copper iodide yields the tetranuclear complex [Cu-4(mu-I)(2)(mu(4)-I)(2)(mu-1)(2)] 3 which has been identified by an X-ray diffraction study. The structure of 3 consists of an octahedron having a square planar Cu-4 base bridged by two ligands 1 and two mu(2)-iodo atoms. The most surprising feature of this structure concerns the coordination of the two other iodide atoms respectively located at each apex of the octahedron, which display a face mu(4)-face-bridging bonding mode. (C) 1997 Elsevier Science S.A.