The reaction of [Os₃(µ-H)₃(CO)₉(µ₃-COMe)]1 with a slight excess of the sterically hindered base 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) affords the anion [Os₃(µ-H)₂(CO)₉(µ₃-COMe)]^–3 which has been isolated as its N(PPh₃)₂⁺ salt in high yield. Treatment of 3 with [Au(PPh₃)]Cl in the presence of TIPF₆ gives [Os₃(µ-H)₂(µ-AuPPh₃)(CO)₉(µ₃-COMe)]4 in high yield. The cluster [Os₃(µ-H)₃(CO)₉(µ₃-CCl)]2 reacts with 1 equivalent of dbu to produce a highly unstable species thought to be [Os₃(µ-H)₂(CO)₉(µ₃-CCl)]^– which, in the presence of excess of dbu, gives the yellow compound [Os₃(µ-H)₂(CO)₉(µ₃-CN₂C₉H₁₆)]5 in good yield. This reaction has been found to be general and the reaction of 2 with 1 equivalent of dbu in the presence of a twenty-fold excess of the required nucleophile Y gives the compounds [Os₃(µ-H)₂(CO)₉(µ₃-CY)](Y = pyridine 6, quinoline 7, isoquinoline 8 or trimethyl phosphite 9). The molecular structures of complexes 4, 5, 7 and 9 have been established by single-crystal X-ray analysis. Both structural features and spectroscopic data for compounds 4–9 are consistent with a zwitterionic formulation of these species. Complex 7 exhibits a strong negative solvatochromism in a wide range of organic solvents, suggesting a less-polar excited state upon photoxcitation.