On the Nature of Bridging Metal Atoms in Intermetalloid Clusters: Synthesis and Structure of the Metal‐Atom‐Bridged Zintl Clusters [Sn(Ge₉)₂]⁴⁻ and [Zn(Ge₉)₂)]⁶⁻

Abstract

The addition of Sn and Zn ions to [Ge₉ ] clusters by reaction of [Ge₉ ]^4- with SnPh₂ Cl₂ , ZnCp*₂ (Cp*=pentamethylcyclopentadienyl), or Zn₂ [HC(Ph₂ P=NPh)₂ ]₂ is reported. The resulting Sn- and Zn-bridged clusters [(Ge₉ )M(Ge₉ )]^q- (M=Sn, q=4; M=Zn, q=6) display various coordination modes. The M atoms that coordinate to the open square of a C_4v -symmetric [Ge₉ ] cluster form strong covalent multicenter M-Ge bonds, in contrast to the M atoms coordinating to triangular cluster faces. Molecular orbital analyses show that the M atoms of the Ge₉ M fragments coordinate to a second [Ge₉ ] cluster with similar orbitals but in different ways. The [Ge₉ Sn]^2- unit donates two electrons to the triangular face of a second [Ge₉ ]^2- cluster with D_3h symmetry, whereas [Ge₉ Zn]^2- acts as an electron acceptor when interacting with the triangular face of a D_3h -symmetric [Ge₉ ]^4- unit.