Formation and Ring Expansion of Germaplatinacycles via Dehydrogenative Ge−Ge and Ge−Pt Bond-Forming Reactions

The bis(germyl)platinum complex [Pt(GeHPh<sub>2</sub>)<sub>2</sub>(dmpe)] (<b>1</b>) (dmpe = 1,2-bis(dimethylphosphino)ethane) reacts with a small excess of H<sub>2</sub>GePh<sub>2</sub> at 90 °C to produce four-membered germaplatinacycle [Pt(GePh<sub>2</sub>GePh<sub>2</sub>GePh<sub>2</sub>)(dmpe)] (<b>2</b>). Further reaction of <b>2</b> with excess H<sub>2</sub>GePh<sub>2</sub> at 90 °C forms tetragermaplatinacyclopentane [Pt(GePh<sub>2</sub>GePh<sub>2</sub>GePh<sub>2</sub>GePh<sub>2</sub>)(dmpe)] (<b>3</b>), while <b>3</b> is obtained also by the direct reaction of excess H<sub>2</sub>GePh<sub>2</sub> with <b>1</b> for a prolonged period. Complexes <b>1</b>−<b>3</b> were characterized by X-ray crystallography and NMR spectroscopy. Germaplatinacycles <b>2</b> and <b>3</b> react with H<sub>3</sub>GePh to cause cleavage of the Pt−Ge bonds and formation of the oligogermanes H(GePh<sub>2</sub>)<sub>3</sub>H and H(GePh<sub>2</sub>)<sub>4</sub>H, respectively.