Synthesis, structure, and reactivity of a zirconocene-carboryne precursor.

Transition metal-benzyne complexes have found many applications in organic synthesis, mechanistic studies, and the synthesis of functional materials. In sharp contrast, the reaction chemistry of transition metal-carboryne complexes is virtually unknown although the theoretical calculations indicated that the formation of carboryne (1,2-C2B10H10) and benzyne is very energetically comparable. This communication reports a novel zirconocene-carboranyl complex Cp2Zr(mu-Cl)(mu-C2B10H10)Li(OEt2)2 (1), an efficient precursor of the zirconocene-carboryne species, prepared from the reaction of Cp2ZrCl2 with 1 equiv of Li2C2B10H10 in Et2O. The reactivity studies indicated that 1 resembles zirconocene-benzyne in reactions with polar unsaturated organic molecules. On the other hand, it shows no reactivity toward alkynes and alkenes, a reactivity pattern which is quite different from that of zirconocene-benzyne. This work also furnishes a novel method for the preparation of functional o-carboranes and their metal complexes which cannot be synthesized by other methods presently known.