Spontaneous Decomposition of an Extraordinarily Twisted and Trans‐Bent Fully‐Phosphanyl‐Substituted Digermene to an Unusual Ge ^I Cluster

Abstract

Ditetrelenes R ₂E=ER ₂ (E=Si, Ge, Sn, Pb) substituted by multiple N/P/O/S‐donor groups are extremely rare due to their propensity to disaggregate into their tetrylene monomers R ₂E. We report the synthesis of the first fully phosphanyl‐substituted digermene {(Mes) ₂P} ₂Ge=Ge{P(Mes) ₂} ₂ ( 3, Mes=2,4,6‐Me ₃C ₆H ₂), which adopts a highly unusual structure in the solid state, that is both strongly trans‐bent and highly twisted. Variable‐temperature ³¹P{ ¹H} NMR spectroscopy suggests that 3 persists in solution, but is subject to a dynamic equilibrium between two conformations, which have different geometries about the Ge=Ge bond (twisted/non‐twisted) due to a difference in the nature of their π‐stacking interactions. Compound 3 undergoes unprecedented, spontaneous decomposition in solution to give a unique Ge ^I cluster {(Mes) ₂P} ₄Ge ₄⋅5 CyMe ( 7).

Abstract

The first example of a fully phosphanyl‐substituted digermene, {(Mes) ₂P} ₂Ge=Ge{P(Mes) ₂} ₂ ( 3), exhibits a uniquely distorted Ge=Ge double bond. Unexpectedly, 3 is unstable in solution, decomposing to a novel Ge ^I cluster ( 7).