N-Heterocyclic Carbene Coinage Metal Complexes of the Germanium-Rich Metalloid Clusters [Ge9R3]- and [Ge9RI2]2- with R = Si(iPr)3 and RI = Si(TMS)3

We report on the synthesis of novel coinage metal NHC (N-heterocyclic carbene) compounds of the germanium-rich metalloid clusters [Ge9R3] and [Ge9R2] with R = Si(Pr)3 and RI = Si(TMS)3. NHCCu{η-Ge9R3} with R = Si(Pr)3 (1) represents a less bulky silyl group-substituted derivative of the known analogous compounds with R = Si(Bu)3 or Si(TMS)3. The coordination of the [NHCDippCu]+ 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{η-Ge9R2} (RI = Si(TMS)3 M = Cu, Ag and Au; NHC = NHCDipp or NHCMes) 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 NHCCu{η-Ge9(Si(Pr)3)3} (1) and (NHCCu)2{η-Ge9(Si(TMS)3)2} (2) were determined by single crystal X-ray diffraction methods. In 2, the coordination of the [NHCDippCu]+ 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.