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 [Ge₉RI₂]²- with R = Si(iPr)₃ and RI = Si(TMS)₃. NHCDippCu{η³Ge₉R₃} 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 [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{η³Ge₉RI₂} (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 NHCDippCu{η³Ge₉(Si(iPr)₃)₃} (1) and (NHCDippCu)₂{η³-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.