Phosphorus donor complexes of bismuth(III). Structural characterisation of [Bi2Cl6(Ph2PCH2PPh2)2], [Bi2Cl6(Ph2PCH2CH2PPh2)2] and [Bi2Cl6(Ph2PCH2CH2PPh2)3]

Abstract

The reactions of the diphosphines dppm [bis(diphenylphosphino)methane] and dppe [1,2-bis(diphenylphosphino)ethane] with bismuth(III) chloride in acetonitrile solution have been studied. The resulting complexes [Bi₂Cl₆(dppm)₂]1 and [Bi₄Cl₁₂(dppe)₅]2 respectively, have been structurally identified by X-ray diffraction studies. The centrosymmetric structure 1·2MeCN consists of coplanar halide-bridged Bi₂Cl₆ units with each of the two dppm ligand molecules in a bidentate bridging mode between the two metal sites. The overall co-ordination geometry at each bismuth atom is approximately octahedral with four (equatorial) chlorine atoms and two (axial) phosphorus atoms: Bi–Cl (terminal) 2.475(3), 2.530(4), Bi–Cl (bridging) 2.808(4), 2.820(3), Bi–P 2.872(3), 3.090(3)Å. In 2 there are two separate and independent molecules in the asymmetric unit cell identified as [Bi₂Cl₆(dppe)₂]2a and [Bi₂Cl₆(dppe)₃]2b respectively. For 2a the centrosymmetric structure is made up of halide-bridged Bi₂Cl₆ units with bidentate chelate attachment of a dppe ligand molecule to each bismuth atom giving rise to an overall edge-shared bioctahedral geometry: Bi–Cl (terminal) 2.409(9), 2.470(11), Bi–Cl (bridging) 2.619(9), 2.945(9), Bi–P 2.699(8), 2.956(10)Å. In the case of 2b the centrosymmetric dimer contains two BiCl₃(dppe) moieties connected by a bridging dppe ligand; thus both bidentate chelate and bidentate bridging bonding modes are observed. Each bismuth atom is surrounded by three terminal chlorine atoms, Bi–Cl 2.514(8), 2.521(9), 2.555(9)Å, and three phosphorus atoms, two from the chelating ligand, Bi–P 2.654(8), 2.916(9)Å, and one from the bridging ligand, Bi–P 2.973(9)Å, in an approximately mer-octahedral arrangement.