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

Abstract

Two series of triphenylphosphine-stabilized diphenyl-arsenium, -stibenium, and -bismuthenium salts of the types [(Ph 3 P)EPh 2 ]PF 6 (where E ) As, Sb, Bi) and [(Ph 3 P) 2 EPh 2 ]PF 6 (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 [(Ph 3 P)EPh 2 ]-PF 6 (E ) As, Sb, Bi), the theoretical results for the cations are consistent with the dative covalent formulation [Ph 3 PfEPh 2 ] + , especially for E ) As and Sb, but for [(Ph 3 P) 2 EPh 2 ]PF 6 (E ) Sb, Bi) the bonding between the phosphines and the stibenium or bisthmuthenium ion is best described as an induced dipole-ion interaction.

Coordination Complexes of Ph3Sb2+ and Ph3Bi2+: Beyond Pnictonium Cations

“…Cationic frameworks exhibit an enhanced Lewis acidity compared with neutral analogues and recent reports of cationic complexes of p-block acceptors represent a new direction for coordination chemistry. [2,3] For example, complexes of mono-, [4] di-, [5] and tricationic [6] + , through sequential replacement of an anionic substituent (X) by neutral ligand(s) (L). Indeed, a number of cationic complexes containing tetrahedral P V acceptor centers have been structurally characterized, [7][8][9][10][11] although in all but a single case [7] ligand coordination is facilitated by a low coordination number at a phosphorus center involved in multiple bonding.…”

Phosphine complexes of lone pair bearing Lewis acceptors

“…Based on the limited data available, the observed geometries at the acceptor centres are dictated primarily by the balance between the stereochemical presence of the lone pair and the covalent radius of the element. For example, complexes of the form [(PPh 3 ) 2 EPh 2 ] 1+ (E = Sb, Bi) are prepared in high yields, 20 whereas the analogous phosphorus complexes of the form [(PR 3 ) 2 PR′ 2 ] 1+ have not been reported. Attempts to prepare diphosphine chelate complexes of [PR′ 2 ] 1+ result in the diphosphine ligand bridging two phosphorus acceptors as in the example of [Ph 2 P-(dppe)-PPh 2 ] 2+ .…”

Covalently bonded compounds of heavy group 15/16 elements – Synthesis, structure and potential application in material sciences

“…Stibenium (R 2 Sb + ) and bismuthenium ions (R 2 Bi + ), which are six-valence-electron species such as silylenes (R 2 Si) or N-heterocyclic carbenes (NHCs), have a vacant p orbital and one electron lone pair, hence are able to react as Lewis acid and base as was initially shown in homoleptic ([Me 2 Sb(SbMe 3 )]MeSbBr 3 , [132] ) and heteroleptic 1:1 complexes of the type [Ph 2 E(PPh 3 )]PF 6 (E = As, Sb, Bi). [133,134,135,136] In addition, 1:2 complexes such as [Ph 2 E(PPh 3 ) 2 ]PF 6 (E = Sb, Bi) were synthesized for the heavier pnictogens. [133,134,135,136] Tellurenyl ions (RTe + ), which are similar to these compounds since they are also unsaturated six-valence-electron species with one vacant p orbital as well as two electron lone pairs, have been obtained as intramolecular σ-donor-stabilized complexes.…”

“…[133,134,135,136] In addition, 1:2 complexes such as [Ph 2 E(PPh 3 ) 2 ]PF 6 (E = Sb, Bi) were synthesized for the heavier pnictogens. [133,134,135,136] Tellurenyl ions (RTe + ), which are similar to these compounds since they are also unsaturated six-valence-electron species with one vacant p orbital as well as two electron lone pairs, have been obtained as intramolecular σ-donor-stabilized complexes. For instance, di-and trinuclear tellurium compounds [MesTe(TeMes 2 ) n ]SbF 6 (n = 1, 2), in which the mesityltellurenyl cation (MesTe + ) is coordinated by the Lewis base Mes 2 Te (Mes = 2,4,6-Me 3 C 6 H 2 ), as well as mesityltellurenyl cations stabilized by trialkylphosphine selenides [MesTe(SeP-t-Bu 2 -iPr) n ]SbF 6 (n = 1, 2) were synthesized, but no structural information was given.…”