Coordination Compounds of Electron-Deficient Boron Cluster Anions BnHn2- (n=6, 10, 12)

This survey concerns the coordination ability of BnHn2- (n = 6, 10, 12) boron cluster anions and their derivatives in complex formation. Boron cluster anions form four types of compounds: salts of organic cations and alkali-metal cations, including Cat(2)B(n)H(n), where specific interactions can be observed between a cation Cat and a boron cluster anion; salts of protonated anions CatB(6)H(7) and CatB(10)H(11), analogues of Cat[MBnHn] complexes, where an extra hydrogen atom appears bound with the BBB face of a boron poly-hedron and performs as a hard acceptor; metal complexes with outer-sphere boron cluster anions where specific ligand-ligand interactions may be observed between a boron cluster anion and an inner-sphere ligand; and true metal complexes with boron cluster anions that enter the inner coordination sphere. The last case characterizes closo-hydroborate anions as polydentate ligands whose denticity can vary widely under the effect of substituents or other ligands in the complex.