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

The reaction of in situ generated E(CN) (E = Sb, Bi) with different amounts of [PhP]CN and [PPN]CN ([PPN] = [PhP-N-PPh]) was studied, affording salts bearing the novel ions [E(CN)], [Bi(CN)], and [Bi(CN)]. 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., [PhP] and [PPN]), the solid-state structures of salts with [E(CN)] 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)·MeCN] acetonitrile adduct ion exhibits a strongly distorted octahedral structure, which is better understood as a [5 + 1] coordination. The intriguing [PhP][Bi(CN)]CN salt consists of separated cations and anions as well as well-separated [Bi(CN)] and CN ions. The structure of the molecular [Bi(CN)] ion can be described as two square-based-pyramidal [Bi(CN)] 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.