Polyhedral Platinaborane Chemistry. Interaction of PMe2Ph with [(PMe2Ph)2PtB10H12]

In solution, [(PMe2Ph)2PtB10H12] (1) and PMe2Ph exist in dynamic equilibrium with [(PMe2Ph)3PtB10H12] (2). The activation energy for the dynamic process, ΔG ⧧, is ca. 63 kJ mol–1 at +17 °C, with ΔS being ca. 335 J mol–1 deg–1 and ΔH ca. 105 kJ mol–1 for the equilibrium. At low temperatures a rocking fluxionality of the {Pt­(PMe2Ph)3} unit versus the {η4-B10H12} unit in 2 becomes apparent, with an activation energy ΔG ⧧ of ca. 28 kJ mol–1 at ca. −105 °C. Compound 2 is characterized by NMR spectroscopy and by a single-crystal X-ray diffraction analysis, for which the results suggest that, in contrast to the common view, the extra electron pair gained by the metal-atom center in going from 1 to 2 does not disrupt the cluster electron count proper nor the observed nido electronic structure and geometry.