On the Variable Reactivity of Phosphine-Functionalized [Ge ] Clusters: Zintl Cluster-Substituted Phosphines or Phosphine-Substituted Zintl Clusters.

The reaction of [(Ge {Si(TMS) } PtBu )] with NHC CuCl yields [(Ge {Si(TMS) } )(tBu P)]Cu(NHC ) (1), which is a new derivative of the recently reported monomeric zwitterionic tetrel cluster compounds [(Ge {Si(TMS) } )(tBu P)]M(NHC ) (M: Cu, Ag, Au). By contrast, the reaction of the same anion [(Ge {Si(TMS) } PtBu )] with the more labile copper phosphine complex Cy PCuCl leads to the formation of [Ge {Si(TMS) } {(tBu) PCu} Ge {Si(TMS) } ] (2), which is a neutral dimeric twofold-bridged [Ge ] cluster compound, with the exo-bonded phosphine substituent being involved in the cluster bridging. In case of the presence of sterically more demanding phosphines in [Ge {Si(TMS) } PR ] [R: Mes (3) and NiPr (4)], reactions with NHC CuCl yielded the complexes NHC Cu[η -Ge {Si(TMS) } (PR )] [R: Mes (5) and NiPr (6)], comprising exclusively Cu-Ge bonds. Compounds 5 and 6 show varying reactivity in dependence of the identity of the phosphine group and represent the first examples of fourfold-substituted [Ge ] clusters with three different ligands bound to the [Ge ] cluster core. All compounds were characterized by H, C, P, and Si NMR spectroscopy. Additionally, compounds 3 and 4 were analyzed by ESI-MS, and the structures of compounds 1, 2, and 5 were characterized by single-crystal X-ray diffraction.