On the Variable Reactivity of Phosphine‐Functionalized [Ge 9 ] Clusters: Zintl Cluster‐Substituted Phosphines or Phosphine‐Substituted Zintl Clusters

The reaction of [(Ge 9 {Si(TMS) 3 } 2 P t Bu 2 )] − with NHC Mes CuCl yields [(Ge 9 {Si(TMS) 3 } 2 )( t Bu 2 P)]Cu(NHC Mes ) ( 1 ), which is a new derivative of the recently reported monomeric zwitterionic tetrel cluster compounds [(Ge 9 {Si(TMS) 3 } 2 )( t Bu 2 P)] M (NHC Dipp ) ( M : Cu, Ag, Au). By contrast, the reaction of the same anion [(Ge 9 {Si(TMS) 3 } 2 P t Bu 2 )] − with the more labile copper phosphine complex Cy 3 PCuCl leads to the formation of [Ge 9 {Si(TMS) 3 } 2 {( t Bu) 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 PR 2 ] − [R: Mes ( 3 ) and N i Pr 2 ( 4 )], reactions with NHC Dipp CuCl yielded the complexes NHC Dipp Cu[η 3 ‐Ge 9 {Si(TMS) 3 } 2 (PR 2 )] [R: Mes ( 5 ) and N i Pr 2 ( 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 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.