Silylated Ge 9 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 [Ge9 R2 ]2- and [Ge9 R3 ]- [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, [Ge9 R2 ]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 [Ge9 R3 ]- units. Analysis of the bond lengths in comparison with known examples shows a bond expansion within the coordinated Ge3 triangular faces for all (carbene)CuI Ge9 complexes (carbene = NHC, MIC, CAAC). All compounds are characterized by single-crystal X-ray diffractometry, NMR spectroscopy [1 H, 13 C{1 H}, and 29 Si{1 H}], 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.