N-Heterocyclic Carbene Coinage Metal Complexes of the Germanium-Rich Metalloid Clusters Ge9R3− and Ge9RI22− with R = Si(iPr)3 and RI = Si(TMS)3

摘要

We report on the synthesis of novel coinage metal NHC (N-heterocyclic carbene) compounds of the germanium-rich metalloid clusters [Ge9R3]⁻ and [Ge9R^I2]²⁻ with R = Si(ⁱPr)3 and R^I = Si(TMS)3. NHC^DippCu{η³-Ge9R3} with R = Si(ⁱPr)3 (>1) represents a less bulky silyl group-substituted derivative of the known analogous compounds with R = Si(ⁱBu)3 or Si(TMS)3. The coordination of the [NHC^DippCu]⁺ moiety to the cluster unit occurs via one triangular face of the tri-capped trigonal prismatic [Ge9] cluster. Furthermore, a series of novel Zintl cluster coinage metal NHC compounds of the type (NHCM)2{η³-Ge9R^I2} (R^I = Si(TMS)3 M = Cu, Ag and Au; NHC = NHC^Dipp or NHC^Mes) is presented. These novel compounds represent a new class of neutral dinuclear Zintl cluster coinage metal NHC compounds, which are obtained either by the stepwise reaction of a suspension of K₁₂Ge₁₇ with Si(TMS)₃Cl and the coinage metal carbene complexes NHCMCl (M = Cu, Ag, Au), or via a homogenous reaction using the preformed bis-silylated cluster K₂[Ge₉(Si(TMS)₃)₂] and the corresponding NHCMCl (M = Cu, Ag, Au) complex. The molecular structures of NHC^DippCu{η³-Ge₉(Si(ⁱPr)₃)₃} (>1) and (NHC^DippCu)₂{η³-Ge₉(Si(TMS)₃)₂} (>2) were determined by single crystal X-ray diffraction methods. In >2, the coordination of the [NHC^DippCu]⁺ moieties to the cluster unit takes place via both open triangular faces of the [Ge₉] entity. Furthermore, all compounds were characterized by means of NMR spectroscopy (¹H, ¹³C, ²⁹Si) and ESI-MS.