Understanding the Solution and Solid-State Structures of Pd and Pt PSiP Pincer-Supported Hydrides

The PSiP pincer-supported complex (CyPSiP)PdH [CyPSiP = Si(Me)(2-PCy2-C6H4)2] has been implicated as a crucial intermediate in carboxylation of both allenes and boranes. At this stage, however, there is uncertainty regarding the exact structure of (CyPSiP)PdH, especially in solution. Previously, both a Pd(II) structure with a terminal Pd hydride and a Pd(0) structure featuring an η2-silane have been proposed. In this contribution, a range of techniques were used to establish that (CyPSiP)PdH and the related Pt species, (CyPSiP)PtH, are true M(II) hydrides in both the solid state and solution. The single-crystal X-ray structures of (CyPSiP)MH (M = Pd and Pt) and the related species (iPrPSiP)PdH [iPrPSiP = Si(Me)(2-PiPr2-C6H4)2] are in agreement with the presence of a terminal metal hydride, and the exact geometry of (CyPSiP)PtH was confirmed using neutron diffraction. The 1H and 29Si{1H}NMR chemical shifts of (CyPSiP)MH (M = Pd and Pt) are consistent with a structure containing a terminal hydride, especial...