Boron and Phosphorus Containing Heterosiliconoids: Stable p- and n-Doped Unsaturated Silicon Clusters

Abstract

Unsaturated silicon clusters (siliconoids) are short-lived intermediates during the transition from molecules to the elemental bulk; stable representatives reiterate surface features of silicon materials. The incorporation of suitable heteroatoms into the cluster scaffold of stable siliconoids extends this analogy to the technological process of silicon doping. Here, we report boron- and phosphorus-containing heterosiliconoids with BSi₅ and PSi₅ core based on the global minimum Si₆R₆ platform (dubbed benzpolarene for its relationship to benzene). The reductive cleavage of an SiR₂ moiety (R = 2,4,6-iPr₃C₆H₂) from Si₆R₆ selectively yields a dianionic Si₅R₄²⁻ cluster as its lithium salt. Treatment with Me₃SiCl affords the corresponding trimethylsilyl-substituted (Me₃Si)₂Si₅R₄. Reaction of Si₅R₄²⁻ with iPr₂NECl₂ (E = B, P) yields the unprecedented p- and n-doped heterosiliconoids iPr₂NESi₅R₄. Their peculiar electronic features are compared to those of the hexasilabenzpolarene starting material on grounds of NMR spectroscopy, X-ray diffraction and DFT calculations.