Metal-rich metallaboranes: Synthesis and structure of nido-[(Cp*Rh)<inf>3</inf>B<inf>6</inf>H<inf>8</inf>(μ-CO)]

This work reports the results of a thermally driven cluster expansion reaction of [(Cp*Rh)2B3H7] (Cp* = η5-C5Me5), nido-1 with metal carbonyl compounds. In addition to the previously reported products, the reactivity of nido-1 with [Mn2(CO)10] led to the isolation of a new rhodaborane cluster [(Cp*Rh)3B6H8CO], 4, in modest yield. Electron counting rules predict the geometry of 4 to be a nido-rhodaborane having a core similar to a decaborane with one vertex missing. These predictions were further confirmed experimentally by spectroscopic characterization in solution and structure determinations in the solid state. On the other hand, the reaction of nido-1 with [Fe2(CO)9] yielded a trinuclear metal carbonyl cluster [(Cp*Rh){Fe(CO)3}{Fe(CO)4}(μ-CO)2], 7. Both compounds 4 and 7 have been characterized in solution by IR, 1H, 11B NMR and mass spectrometry and the structural types were unequivocally established by crystallographic analysis.