Unusual Organic Chemistry of a Metallaborane Substrate: Formation of a Tantalaborane Complex with a Bridging Acyl Group (μ-η2)

The addition of LiBH4 center dot THF to (CpTaCl4)-Ta-star (1; Cp-star = eta(5)-C5Me5) at -40 degrees C, followed by mild pyrolysis with excess BH3 center dot THF, results in the formation of the mu-acyl complex ((CpTa)-Ta-star)(2)B4H8(mu-eta(2)-COCH3) (2). The title compound represents a novel class of mu-acyl complexes in which the bicapped-tetrahedral unit ((CpTa)-Ta-star)(2)B4H8 is bridged by a mu-eta(2)-COCH3 acyl ligand.