The RhII-RhII bonded dimer ([(tmtaa)Rh]2) has a 22 kcalmol-1 dissociation enthalpy and reacts with CO and H2 to produce equilibria with  (tmtaa)Rh-H and (tmtaa)Rh-C(O)H that give estimates Rh-H (63 kcal mol-1) Rh-C(O)H (60 kcal mol-1) BDEs.  The structures and reactivity patterns of heterobimetallic complexes of (tmtaa)Rh with metallo-radical units ((tmtaa)Rh-M, M = Co(CO)4, Mn(CO)5, FeCp(CO)2,  CrCp(CO)3, MoCp(CO)3) are currently being evaluated. Presence of a bridged CO unit (Co-C(O)Rh) in the (tmtaa)Rh-Co(CO)4 complex compared to the all terminal Co-CO units in the porphyrin complex provides a vivid illustration of how the increased flexibility of tmtaa can open metal binding sites. DFT calculations place (tmtaa)Rh-Co(CO)4 on a trajectory to form a heterobimetallic dimetal ketone (tmtaa)Rh-C(O)-Co(CO)3 and reactivity studies indicate that the bridged CO is a site for hydrogenation. Structures, reactivity patterns, bond dissociation energetics and DFT calculations for the series of heterobimetallic complexes will be presented and prospects for catalysis discussed.

Bimetallic complexes of rhodium dibenzotetramethylaza[14]annulene ((tmtaa)Rh): Structure, reactivity, and thermodynamic studies

247th National Meeting (2014)

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