Synergistic C-H Bond Activation Across Molybdenum-Iridium Multiply Bonded Complexes: a Cascade of Transformations

Abstract

Heterobimetallic compounds offer unique opportunities for activating substrates through cooperative interactions between two distinct metal centers, potentially leading to catalytic reactivity beyond the reach of monometallic systems. The pairing of molybdenum with iridium has recently shown remarkable performance in heterogeneous catalytic and electrocatalytic processes, yet remains surprisingly unexplored in the context of homogeneous catalysis and well-defined molecular complexes. In this work, we address this gap by reporting the synthesis and characterization of complexes featuring rare molybdenum-iridium multiple bonds: Cp*Ir(H)Mo(NMe₂)₃, 1 and (Cp*IrH2)2Mo(NMe2)₂, 2. Both complexes undergo electrophilic insertions of heteroallenes (CO₂, tBuNCO) into the ancillary amido ligands. In the case of compound 1, the insertion of tert-butyl isocyanate initiates a unique cascade of bond breaking/forming events – including triple C-H activations and Csp3-Csp3 coupling – ultimately yielding a Mo(VI) metallacyclopropane complex, 5. Addition of multiple equivalents of isocyanate instead interrupts this mechanism, leading to C-N and C-O bonds cleavage and the formation of aminocarbyne and imido ligands bridging the Ir and Mo centers, along with a molybdenum(VI)-oxo moiety. This unprecedented reactivity, mediated by a key reaction intermediate featuring an unsupported Mo-Ir quadruple bond, illustrates the interest of heterobimetallic compounds for complex bond activation and reorganization.