Triphenylphosphine-Stabilized Diphenyl-Arsenium, -Stibenium, and -Bismuthenium Salts

Abstract

Two series of triphenylphosphine-stabilized diphenyl-arsenium, -stibenium, and -bismuthenium salts of the types [(Ph3P)EPh2]PF 6 (where E = As, Sb, Bi) and [(Ph3P)2EPh 2]PF6 (where E = Sb, Bi) have been synthesized and their structures and bonding investigated by X-ray crystallography and density functional theory at the PBE/TZP level. The coordination geometries around the central group 15 elements are distorted trigonal pyramidal in the mono(triphenylphosphine) complexes and distorted trigonal bipyramidal in the bis(triphenylphosphine) complexes, where in each case the stereochemically active lone pair of the six-electron, angular diphenyl-arsenium, -stibenium, or -bismuthenium ion occupies an equatorial position in the trigonal plane containing the C-E-C bonds. For the complexes [(Ph3P)EPh 2]-PF6 (E = As, Sb, Bi), the theoretical results for the cations are consistent with the dative covalent formulation [Ph 3P→EPh2]+, especially for E = As and Sb, but for [(Ph3P)2EPh2]PF6 (E = Sb, Bi) the bonding between the phosphines and the stibenium or bisthmuthenium ion is best described as an induced dipole-ion interaction.