Preparation of Heterobimetallic Ketimido-Actinide-Molybdenum Complexes.

During our attempts to prepare paddlewheel actinide-molybdenum complexes of the type [(X)An(MesNPR2)3Mo(CO)3] (Mes= 2,4,6-trimethylphenyl; X = Cl or I; An = U or Th; R = iPr or Ph) we have found that under certain conditions acetonitrile insertion reactions occur to give the heterobimetallic bridging ketimido species [ClAn(μ-MesNPiPr2)2(μ-MesNPiPr2{μ-NCMe})Mo(CO)3] (An = U, 1; Th, 2), [ClAn(μ-MesNPPh2)2(μ-MesNPPh2{μ-NCMe})Mo(CO)3] (An = U, 3; An = Th, 4), and [IAn(η2-MesNPiPr2)(μ-MesNPiPr2){μ-NC(Me)N(Mes)PiPr2}Mo(CO)3] (An = U, 5; Th, 6). Structural and spectroscopic data confirm the assignment of a ketimido ligand bridging An(IV) and Mo(0) centers. The isolation of 1-6 is in contrast to our previously reported preparations of [(X)An(MesNPPh2)3Mo(CO)3] (An = U or Th; X= Cl or I; Chem. Commun. 2018, 54, 13515-13518) with the difference in reactivity being attributable to a combination of ancillary phosphino-amide, reaction solvent, and temperature variation. Complexes 1-5 represent the first examples of structurally characterized ketimido-bridged actinide-transition metal linkages and demonstrate the profound differences in reaction outcomes that can occur from relatively minor experimental changes.