Reaction of [Cp*MoCl4], 1 (Cp*= eta(5)-C5Me5), with [LiBH4 center dot thf] in toluene at -70 degrees C, followed by pyrolysis with excess dichalcogenides RE-ER (R = Ph, CH2Ph, 2,6-(Bu-t)(2)-C6H2OH, (CH3)(3)C=Bu-t); E=S, Se) yielded a new class of hybrid clusters, 3-8: (3, [(Cp*Mo)(2)(mu-eta(1)-SPh)(2)(mu(3)-S)(H2BSPh)]; 4, [(CP*Mo)(2)B5H8(SPh)]; 5, [(CP*Mo)(2)B6H8(SePh)]; 6, [(CP*Mo)(2)B2S2H2(mu-eta(1)-S)]; 7, [(CP*Mo)(2)B2H5(BSR)(2)(mu-eta(1)-SR)], (R = 2,6-(Bu-t)(2)-C6H2OH); and 8, [(Cp*Mo)(2)B2H5(BSePh)(2)(mu-eta(1)-SePh)]. Compounds 3-8 have been isolated in modest yields as green or brown crystalline solids. In parallel with 3-8, [(CP*Mo)(2)B5H9] was isolated as a major product in all cases. The isolation and structural characterization of compounds 3 and 6-8 provided the first direct evidence of the existence of [(Cp*Mo)(2)B4H8], 2, an intermediate in the formation of [(Cp*Mo)(2)B5H9]. These new compounds have been characterized in solution by mass spectrometry, H-1, B-11, C-13 NMR, and IR spectroscopy, and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 3-8.