The tetracyanoborate anion as a building block for the heterocubane cluster cage [Cr{B(CN)}].

The tetracyanoborate anion [B(CN)] (TCB) was utilized as a building block for the synthesis of polynuclear chromium carbonyl compounds upon photolytic reaction with [Cr(CO)]. Up to four κN-coordinated cyano groups of TCB can be involved in binding to chromium, giving mixtures of [B(CN){CN-Cr(CO)}] ( = 1-4; 1-4) and [{Cr(CO)(B(CN))}] (5). The reaction of [B(CN)] with -[Cr(CO)(MeCN)] led to isolation of salts of the tetraanionic heterocubane cage [{Cr(CO)(B(CN))}].