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

The reaction of [(Ge-9{Si(TMS)(3)}(2)PtBu2)](-) with (NHCCuCl)-Cu-Mes yields [(Ge-9{Si(TMS)(3)}(2))(tBu(2)P)]Cu(NHCMes) (1), which is a new derivative of the recently reported monomeric zwitterionic tetrel cluster compounds [(Ge-9{Si(TMS)(3)}(2))(tBu(2)P)]M(NHCDipp) (M: Cu, Ag, Au). By contrast, the reaction of the same anion [(Ge-9{Si(TMS)(3)}(2)PtBu2)](-) with the more labile copper phosphine complex Cy3PCuCl leads to the formation of [Ge-9{Si(TMS)(3)}(2){(tBu)(2)PCu}(2)Ge-9{Si(TMS)(3)}(2)] (2), which is a neutral dimeric twofold-bridged [Ge-9] 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-9{Si(TMS)(3)}(2)PR2](-) [R: Mes (3) and NiPr2 (4)], reactions with (NHCCuCl)-Cu-Dipp yielded the complexes (NHCCu)-Cu-Dipp[eta(3)-Ge-9{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 [Ge-9] clusters with three different ligands bound to the [Ge-9] cluster core. All compounds were characterized by H-1, C-13, P-31, and Si-29 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.