Heterobimetallic Metallaborane Chemistry:  Synthesis and Characterization of a “Lightly Stabilized” Molybdairidahexaborane, [{Cp*Ir}{(CO)₃(THF)Mo}B₄H₈], and Its Direct Conversion to [{Cp*Ir}{(CO)₃(L)Mo}B₄H₈] (L = CO, PPh₃, NCPh, CNBu, NH₃, PPh₃CHC(O)OMe)

The reaction of [Cp*IrB₄H₁₀] (1) with [{η⁶-(C₆H₄)(CH₃)₂}Mo(CO)₃] in tetrahydrofuran (THF) leads to [Cp*Ir(CO)₃(THF)MoB₄H₈] (2), which was characterized by NMR spectroscopy. Intermediate 2 subsequently decomposes to give the tetracarbonyl analogue [Cp*Ir(CO)₄MoB₄H₈] (3). In the presence of free CO, the same reaction constitutes a high-yield synthesis of 3. The treatment of 2 (formed in situ) with different Lewis bases led to the replacement of the THF ligand at the molybdenum center and generation of [Cp*Ir(CO)₃(L)MoB₄H₈] (L = PPh₃ (4), NCPh (5), CNBu (6), NH₃ (7)). Reaction of the benzonitrile derivative 5 with PPh₃CHCO₂Me afforded the ylide compound [Cp*Ir(CO)₃(PPh₃CHCO₂Me)MoB₄H₈] (8). All compounds have been spectroscopically characterized, and 3 and 5−7 have been structurally characterized in the solid state. This work demonstrates that, similarly to metal clusters, metallaboranes with labile metal ligands can serve as versatile synthons.