Direct electrochemical synthesis and crystallographic characterization of metal diphenylphosphido and diphenylthiophosphinato compounds, and some derivatives

Abstract

The electrochemical oxidation of a number of metals in acetonitrile solutions of PPh₂H gives rise to M(PPh₂)_n compounds (M = Co, Zn or Cd, n= 2; M = Cu, Ag or Au, n= 1). With anodic nickel the product is Ni(PPh₂)·PPh₂H. In the presence of elemental sulphur such oxidation reactions yield [M(S₂PPh₂)₂](M = Co, Zn or Cd). The electrochemical processes involved have been identified. The crystal structure of the addition compound [Cu₄(PPh₂)₄(dppm)₂]·4MeCN 1[dppm = bis(diphenylphosphino)methane] has been determined by X-ray crystallography, which reveals a Cu₄P₄ ring, capped by Cu₂PCP'₂ rings. Crystal parameters: triclinic, space group P, a= 14.719(4), b= 13.649(5), c= 17.112(5)Å, α= 112.40(3), β= 106.22(2), γ= 115.39(2)° and Z= 1; R= 0.0632 for 3622 observed reflections [I 3σ(I)]. The compound Ni(PPh₂)·PPh₂H is oxidized by elemental oxygen, sulphur or selenium to give [Ni(E₂PPh₂)₂](E = O, S or Se), and also reacts with PhNCS to yield [Ni{PPh₂(SCNPh)}₂]2. Crystal parameters: triclinic, space group P, a= 8.950(6), b= 9.745(4), c= 10.366(7)Å,α= 112.28(4), β= 99.09(5), γ= 90.88(4)° and Z= 1. Disorder prevented this structure from being refined beyond R= 0.1612, but the essential features of the square-planar NiS₂P₂ core were identified. The crystal parameters of [Ni(O₂PPh₂)₂(HO₂PPh₂)₂(MeCN)₂]3 are monoclinic, space group P2₁/c, a= 12.420(5), b= 9.737(7), c= 20.729(16)Å, β= 100.29(5)° and Z= 2. The nickel atom is co-ordinated by two monodentate Ph₂PO(O)^– ligands and two monodentate Ph₂(O)OH ligands which are hydrogen-bonded to their anionic analogues, and by two MeCN molecules, to give a NiO₂O′₂N₂ core.