Niobium and Tantalum Halocyanide Clusters: The Complete Family.

Synthetic procedures providing straightforward access to the whole family of Nb and Ta halide clusters with terminal cyanide ligands have been developed. Corresponding [M 6 X 12 (CN) 12 ] 4- (M = Nb, Ta; X = Cl, Br) can be accessed by ligand-exchange procedures from K 4 Nb 6 X 18 (X = Cl, Br) and Bu 4 NCN, (Et 4 N) 2 [Ta 6 Cl 18 ] and Bu 4 NCN and from [Ta 6 Br 12 (H 2 O) 4 Br 2 ]·4H 2 O and KCN in moderate to high yields (50-80%). The products were isolated as Bu 4 N salts. The compounds were investigated both experimentally and by quantum chemistry, revealing correlations between structural, electrochemical, electrostatic, electronic, and topological features as a function of type of metal, halide, and charge.