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

Two series of triphenylphosphine-stabilized diphenyl-arsenium, -stibenium, and -bismuthenium salts
of the types [(Ph3P)EPh2]PF6 (where E = As, Sb, Bi) and [(Ph3P)2EPh2]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)EPh2]PF6 (E = As, Sb, Bi), the theoretical results for the cations are consistent with the dative covalent
formulation [Ph3P→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.