Cyanido Antimonate(III) and Bismuthate(III) Anions.

Abstract

The reaction of in situ generated E(CN)3 (E = Sb, Bi) with different amounts of [Ph4P]CN and [PPN]CN ([PPN]+ = [Ph3P-N-PPh3]+) was studied, affording salts bearing the novel ions [E(CN)5]2-, [Bi2(CN)11]5-, and [Bi(CN)6]3-. The valence lone pair of electrons on the central atom of antimony and bismuth(III) compounds can be either sterically active in an unsymmetric fashion (three shorter bonds + x longer bonds) or symmetric (with rather long averaged bonds). In the presence of weakly coordinating cations (e.g., [Ph4P]+ and [PPN]+), the solid-state structures of salts with [E(CN)5]2- anions contain well-separated cations and monomeric anions, which display a sterically active lone pair and a monomeric square-based pyramidal (pseudo-octahedral) structure. The [Bi(CN)5·MeCN]2- acetonitrile adduct ion exhibits a strongly distorted octahedral structure, which is better understood as a [5 + 1] coordination. The intriguing [Ph4P]6[Bi2(CN)11]CN salt consists of separated cations and anions as well as well-separated [Bi2(CN)11]5- and CN- ions. The structure of the molecular [Bi2(CN)11]5- ion can be described as two square-based-pyramidal [Bi(CN)5]2- fragments connected by a disordered bridging CN- ion, thereby leading to a distorted-octahedral environment around the two Bi centers. Here the steric effect of the lone pair is much less pronounced but still present.