Condensed Tantalaborane Clusters: Synthesis and Structures of [(Cp*Ta)2B5H7{Fe(CO)3}2] and [(Cp*Ta)2B5H9{Fe(CO)3}4]

The reaction of [(Cp*Ta)(2)B4H9(mu-BH4)] (1; Cp* = eta(5)-C5Me5) with [Fe-2(CO)(9)] in hexane yielded [(Cp*Ta)(2)B5H7{Fe(CO)(3)}(2)] (2) and [(Cp*Ta)(2)B5H9{Fe(CO)(3)}(4)] (3) in moderate yield. Cluster 2 represents the first example of a bicapped pentagonal-bipyramidal metallaborane with a deformed equatorial plane, and 3 can be described as a fused cluster in which two pentagonal-bipyramidal units are fused through a common 3-vertex triangular face. Compounds 2 and 3 have been characterized by mass spectrometry and IR, H-1, B-11, and C-13 NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis.