Enhancing Reactivity of Directly íObservable B–H–Pt Interactions through Conformational Rigidity

We report for the first time the direct syntheses of trimethylplatinum(IV) complexes supported by bis(pyrazolyl)dihydridoborate (Bp) and bis(3,5-dimethylpyrazolyl)dihydridoborate (Bp*) ligands from the corresponding dimethylplatinum(II) complexes. X-ray crystallographic and multinuclear NMR characterization of the trimethylplatinum(IV) complexes reveal agostic B–H–Pt interactions. Solid-state analysis reveals that BpPtIVMe3 adopts a dinuclear structure featuring an intermolecular B–H–Pt bridge, whereas Bp*PtIVMe3 adopts a mononuclear structure containing an intramolecular B–H–Pt bridge. Addition of acetonitrile leads to cleavage of the weakly coordinating B–H–Pt interactions, and in the case of Bp*PtIVMe3, leads to hydroboration of acetonitrile. The B–H fragment interacting with the PtIV center in Bp*PtIVMe3 was also found to react with methanol to form a methoxy-bridged complex. DFT calculations were employed to investigate the structural contributions to the difference in the reactivity of the Bp- and Bp*-supported complexes.