Phenylantimony(V) oxalates: isolation and crystal structures of [SbPh4][SbPh2(ox)2], [SbPh3(OMe)]2ox and (SbPh4)2ox

Abstract

The course of the reaction between triphenylantimony dichloride and silver oxalate depends on both the solvent and temperature at which the reaction is carried out. No reaction occurs in toluene at room temperature, but on refluxing the solution, crystals of [SbPh₄][SbPh₂(ox)₂]1[ox = oxalate(2–)], an ionic form of SbPh₃(ox), are obtained. Covalent SbPh₃(ox), on the other hand, is probably the initial product of reaction in methanol at room temperature, but on recrystallisation from hot methanol, crystals of a methoxy derivative, [SbPh₃(OMe)]₂ox 2, are obtained. Structures have been determined for both compounds. Compound 1 consists of tetrahedral [SbPh₄]⁺ cations and octahedral [SbPh₂(ox)₂]^– anions containing two chelating oxalate groups and phenyl groups in cis positions. The methoxy derivative 2 is centrosymmetric, with a quadridentate oxalate group and each antimony octahedrally co-ordinated to three phenyl groups, one methoxy group and two oxygens from the oxalate group. A quadridentate oxalate group is also present in (SbPh₄)₂ox 3, obtained from [SbPh₄]Br and silver oxalate. The structure contains two essentially identical, independent, centrosymmetric molecules with antimony again in distorted-octahedral co-ordination.