Derivatization of Phosphine Ligands with Bulky Deltahedral <i>Zintl</i> ClustersSynthesis of Charge Neutral Zwitterionic Tetrel Cluster Compounds [(Ge<sub>9</sub>{Si(TMS)<sub>3</sub>}<sub>2</sub>)<sup><i>t</i></sup>Bu<sub>2</sub>P]M(NHC<sup>Dipp</sup>) (M: Cu, Ag, Au)

Reactions of silylated clusters [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>3</sub>]<sup>−</sup> or [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>2</sub>]<sup>2−</sup> with dialkylhalophosphines R<sub>2</sub>PCl (Cy, <sup><i>i</i></sup>Pr, <sup><i>t</i></sup>Bu) at ambient temperature yield the first tetrel <i>Zintl</i> 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- (<sup><i>i</i></sup>Pr) groups and the tris-silylated cluster [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>3</sub>]<sup>−</sup> yield the novel neutral cluster compounds [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>3</sub>PR<sub>2</sub>] (R: Cy (<b>1</b>), <sup><i>i</i></sup>Pr (<b>2</b>)) with discrete Ge–P <i>exo</i> bonds. By contrast, the bulkier phosphine <sup><i>t</i></sup>Bu<sub>2</sub>PCl does not react with [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>3</sub>]<sup>−</sup> due to steric crowding. However, the reaction with the bis-silylated cluster [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>2</sub>]<sup>2</sup><sup>−</sup> yields the novel cluster compound [Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>2</sub>P<sup><i>t</i></sup>Bu<sub>2</sub>]<sup>−</sup> (<b>3</b>). Subsequent reactions of compound <b>3</b> with NHC<sup>Dipp</sup>MCl (M: Cu, Ag, Au) yield the charge neutral zwitterionic compounds [(Ge<sub>9</sub>{Si­(TMS)<sub>3</sub>}<sub>2</sub>)<sup><i>t</i></sup>Bu<sub>2</sub>P]­M­(NHC<sup>Dipp</sup>) (M: Cu, Ag, Au) (<b>4</b>–<b>6</b>), in which compound <b>3</b> acts as a phosphine ligand bearing a bulky tetrel <i>Zintl</i> cluster moiety. Compounds <b>4</b>–<b>6</b> also represent the first uncharged examples for 3-fold substituted tetrel <i>Zintl</i> clusters.