Probing the Intrinisic Structure and Dynamics of Aminoborane Coordination at Late Transition Metal Centers: Mono(σ-BH) Binding in [CpRu(PR3)2(H2BNCy2)]+

Aminoboranes, H2BNRR′, represent the monomeric building blocks from which novel polymeric materials can be constructed via metal-mediated processes. The fundamental capabilities of these compounds to interact with metal centers have been probed through the coordination of H2BNCy2 at 16-electron [CpRu(PR3)2]+ fragments. In contrast to the side-on binding of isoelectronic alkene donors, an alternative mono(σ-BH) mode of aminoborane ligation is established for H2BNCy2, with binding energies only ∼8 kcal mol–1 greater than those for analogous dinitrogen complexes. Variations in ground-state structure and exchange dynamics as a function of the phosphine ancillary ligand set are consistent with chemically significant back-bonding into an orbital of B–H σ* character.