Σ-GeH and Germyl Cationic Pt(II) Complexes

The low electron count Pt(II) complexes [Pt(NHC ')(NHC)]-[BArF] (where NHC is a N-heterocyclic carbene ligand and NHC ' its metalated form) react with tertiary hydrogermanes HGeR3 at room temperature to generate the 14-electron platinum(II) germyl derivatives [Pt(GeR3)(NHC)2][BArF]. Low-temperature NMR studies allowed us to detect and characterize spectroscopically some of the cr-GeH intermediates [Pt(q2-HGeR3)(NHC ')(NHC)][BArF] that evolve into the platinum-germyl species. One of these compounds has been characterized by X-ray diffraction studies, and the interaction of the H-Ge bond with the platinum center has been analyzed in detail by computational methods, which suggest that the main contribution is the donation of the H-Ge to a cr*(Pt-C) orbital, but backdonation from the platinum to the cr*(Ge-H) orbital is significant. Primary and secondary hydrogermanes also produce the corresponding platinum-germyl complexes, a result that contrasts with the reactivity observed with primary silanes, in which carbon-silicon bond-forming reactions have been reported. According to density functional theory calculations, the formation of Pt-Ge/C-H bonds is both kinetically and thermodynamically preferred over the competitive reaction pathway leading to Pt-H/C-Ge bonds.

Automated summary

The study revealed that low electron count Pt(II) complexes react with tertiary hydrogermanes to generate platinum(II) germyl derivatives. Through low-temperature NMR studies, some of the cr-GeH intermediates were detected and characterized, which further evolved into platinum-germyl species. Computational analysis suggested that the interaction between the H-Ge bond and the platinum center involves both donation and backdonation of electrons. Additionally, primary and secondary hydrogermanes also produced platinum-germyl complexes.