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

The coordination of Ge 9 Zintl clusters at (carbene)Cu I moieties is explored, and the complexes [(CAAC)Cu] 2 [η 3 -Ge 9 {Si(TMS) 3 } 2 ] ( 1 ), (CAAC)Cu[η 3 -Ge 9 {Si(TMS) 3 } 3 ] ( 2 ), and (MIC)Cu[η 3 -Ge 9 {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 [Ge 9 R 2 ] 2– and [Ge 9 R 3 ] − [R = Si(TMS) 3 ] cluster ligands, respectively, and yields complexes of (carbene)Cu I (carbene = CAAC, MIC) moieties exhibiting η 3 -coordination modes of the Ge 9 deltahedron to the Cu atom. In 1, [Ge 9 R 2 ] 2– acts as a η 3 -bridging unit for two (CAAC)Cu I moieties, and 2 and 3 feature single (carbene)Cu I (CAAC and MIC) fragments η 3 -connected to [Ge 9 R 3 ] − units. Analysis of the bond lengths in comparison with known examples shows a bond expansion within the coordinated Ge 3 triangular faces for all (carbene)Cu I Ge 9 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 Ge 9 clusters with carbene ligands at Cu I atoms.