Silylated Ge9 Clusters as New Ligands for Cyclic (Alkyl)amino and Mesoionic Carbene Copper Complexes

The coordination of Ge9 Zintl clusters at (carbene)­CuI moieties is explored, and the complexes [(CAAC)­Cu]2[η3-Ge9{Si­(TMS)3}2] (1), (CAAC)­Cu­[η3-Ge9{Si­(TMS)3}3] (2), and (MIC)­Cu­[η3-Ge9{Si­(TMS)3}3] (3) are compared with their known N-heterocyclic carbene (NHC) derivatives (A and B), where CAAC = cyclic (alkyl)­amino carbene, MIC = mesoionic carbene, and TMS = trimethylsilane. In analogy to the NHC derivatives, the synthesis of 1–3 proceeds by single-step reactions of (CAAC)­CuCl or (MIC)­CuCl with the [Ge9R2]2– and [Ge9R3]− [R = Si­(TMS)3] cluster ligands, respectively, and yields complexes of (carbene)­CuI (carbene = CAAC, MIC) moieties exhibiting η3-coordination modes of the Ge9 deltahedron to the Cu atom. In 1, [Ge9R2]2– acts as a η3-bridging unit for two (CAAC)­CuI moieties, and 2 and 3 feature single (carbene)­CuI (CAAC and MIC) fragments η3-connected to [Ge9R3]− units. Analysis of the bond lengths in comparison with known examples shows a bond expansion within the coordinated Ge3 triangular faces for all (carbene)­CuIGe9 complexes (carbene = NHC, MIC, CAAC). All compounds are characterized by single-crystal X-ray diffractometry, NMR spectroscopy [1H, 13C­{1H}, and 29Si­{1H}], electrospray ionization mass spectometry, elemental analysis (C, H, and N), and for the first time also by IR and Raman investigations (for 2 and 3). The new complexes add to the known NHC derivatives and extend the exploration of Ge9 clusters with carbene ligands at CuI atoms.