Stepwise Introduction of Cyano Groups into nido- and closo-Undecaborate Clusters.

Eleven-vertex closo and nido boron clusters with one or two exo-cyano groups were obtained by a series of consecutive cage-opening and cage-closure reactions starting from K [closo-B H ] (K 1). In the first step, K 1 reacts with KCN in water at elevated temperatures to yield [7-NC-nido-B H ] (5 a). Oxidation of 5 a with PbO gives [NC-closo-B H ] (2).