Derivatization of Phosphine Ligands with Bulky Deltahedral Zintl Clusters—Synthesis of Charge Neutral Zwitterionic Tetrel Cluster Compounds [(Ge9{Si(TMS)3}2)tBu2P]M(NHCDipp) (M: Cu, Ag, Au)

Reactions of silylated clusters [Ge9{Si(TMS)3}3]− or [Ge9{Si(TMS)3}2]2− with dialkylhalophosphines R2PCl (Cy, iPr, tBu) at ambient temperature yield the first tetrel Zintl cluster compounds bearing phosphine moieties. Varying reactivity of the dialkylhalophosphines toward the silylated clusters is observed depending on the bulkiness of the phosphine’s alkyl substituents and on the number of hypersilyl groups at the tetrel cluster. Reactions between phosphines with small cyclohexyl- (Cy) or isopropyl- (iPr) groups and the tris-silylated cluster [Ge9{Si(TMS)3}3]− yield the novel neutral cluster compounds [Ge9{Si(TMS)3}3PR2] (R: Cy (1), iPr (2)) with discrete Ge–P exo bonds. By contrast, the bulkier phosphine tBu2PCl does not react with [Ge9{Si(TMS)3}3]− due to steric crowding. However, the reaction with the bis-silylated cluster [Ge9{Si(TMS)3}2]2− yields the novel cluster compound [Ge9{Si(TMS)3}2PtBu2]− (3). Subsequent reactions of compound 3 with NHCDippMCl (M: Cu, Ag, Au) yield the charge neutral zwitterionic compounds [(Ge9{Si(TMS)3}2)tBu2P]M(NHCDipp) (M: Cu, Ag, Au) (4–6), in which compound 3 acts as a phosphine ligand bearing a bulky tetrel Zintl cluster moiety. Compounds 4–6 also represent the first uncharged examples for 3-fold substituted tetrel Zintl clusters.