On the Variable Reactivity of Phosphine-Functionalized [Ge9 ] Clusters: Zintl Cluster-Substituted Phosphines or Phosphine-Substituted Zintl Clusters.

The reaction of [(Ge9 {Si(TMS)3 }2 PtBu2 )]- with NHCMes CuCl yields [(Ge9 {Si(TMS)3 }2 )(tBu2 P)]Cu(NHCMes ) (1), which is a new derivative of the recently reported monomeric zwitterionic tetrel cluster compounds [(Ge9 {Si(TMS)3 }2 )(tBu2 P)]M(NHCDipp ) (M: Cu, Ag, Au). By contrast, the reaction of the same anion [(Ge9 {Si(TMS)3 }2 PtBu2 )]- with the more labile copper phosphine complex Cy3 PCuCl leads to the formation of [Ge9 {Si(TMS)3 }2 {(tBu)2 PCu}2 Ge9 {Si(TMS)3 }2 ] (2), which is a neutral dimeric twofold-bridged [Ge9 ] 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 [Ge9 {Si(TMS)3 }2 PR2 ]- [R: Mes (3) and NiPr2 (4)], reactions with NHCDipp CuCl yielded the complexes NHCDipp Cu[η3 -Ge9 {Si(TMS)3 }2 (PR2 )] [R: Mes (5) and NiPr2 (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 [Ge9 ] clusters with three different ligands bound to the [Ge9 ] cluster core. All compounds were characterized by 1 H, 13 C, 31 P, and 29 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.