The tetracyanoborate anion as a building block for the heterocubane cluster cage [Cr 4 {B(CN) 4 } 4 ] 4 .

The tetracyanoborate anion [B(CN) 4 ] - (TCB) was utilized as a building block for the synthesis of polynuclear chromium carbonyl compounds upon photolytic reaction with [Cr(CO) 6 ]. Up to four κN-coordinated cyano groups of TCB can be involved in binding to chromium, giving mixtures of [B(CN) 4- x {CN-Cr(CO) 5 } x ] - ( x = 1-4; 1-4) and [{Cr(CO) 4 (B(CN) 4 )} 2 ] 2- (5). The reaction of [B(CN) 4 ] - with fac -[Cr(CO) 3 (MeCN) 3 ] led to isolation of salts of the tetraanionic heterocubane cage [{Cr(CO) 3 (B(CN) 4 )} 4 ] 4- .