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

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.