Heterobimetallic Complexes of Rhodium Dibenzotetramethylaza[14]annulene [(tmtaa)Rh-M]: Formation, Structures, and Bond Dissociation Energetics

A rhodium­(II) dibenzotetramethylaza[14]­annulene dimer ([(tmtaa)­Rh]2) undergoes metathesis reactions with [CpCr­(CO)3]2, [CpMo­(CO)3]2, [CpFe­(CO)2]2, [Co­(CO)4]2, and [Mn­(CO)5]2 to form (tmtaa)­Rh-M complexes (M = CrCp­(CO)3, MoCp­(CO)3, FeCp­(CO)2, Co­(CO)4, or Mn­(CO)5). Molecular structures were determined for (tmtaa)­Rh-FeCp­(CO)2, (tmtaa)­Rh-Co­(μ-CO)­(CO)3, and (tmtaa)­Rh-Mn­(CO)5 by X-ray diffraction. Equilibrium constants measured for the metathesis reactions permit the estimation of several (tmtaa)­Rh-M bond dissociation enthalpies (RhCr = 19 kcal mol–1, RhMo = 25 kcal mol–1, and RhFe = 27 kcal mol–1). Reactivities of the bimetallic complexes with synthesis gas to form (tmtaa)­Rh-C­(O)H and M-H are surveyed.