3,7,10-Trichalcogenaoctasila[3.3.3]propellanes

Abstract

The reaction of hexakis(trimethylsilyl)disilane with acetyl chloride and aluminum chloride yields hexakis(chlorodimethylsilyl)disilane (5a) under carefully controlled reaction conditions. Treatment of 5a with either H 2 S/NEt 3 or Li 2 E (E = Se, Te) gives the dodecamethyl-3,7,10-trichalcogenaoctasila-[3.3.3]propellanes Si 2 (SiMe 2 ) 6 E 3 (6a E = S, 6b E = Se, 6c E = Te). The products have been characterized by multinuclear NMR spectroscopy ( 1 H, 13 C, 29 Si, 77 Se, 125 Te). The central silicon atoms are very deshielded in comparison with other

Organosilicon chalcogenides with trisilane units – bicyclo[3.3.1]nonanes, bicyclo[3.2.2]nonanes and spiro[4.4]nonanes

“…Starting from methylchlorooligosilanes reactions with either H 2 S/NEt 3 or Li 2 E (E ¼ S, Se, Te) led to the characterization of a variety of new cyclic and polycyclic organosilicon chalcogenides with disilane [26][27][28][29][30][31], trisilane [32][33][34] (and related disilylmethane [28,34]), isotetrasilane [35] (and related trisilylmethane [36]), branched hexasilane [29] as well as octasilane [37] units, see Scheme 1. The structures of the compounds formed as well as DFT calculations on model systems suggest that five-membered rings (Si 3 E 2 or Si 4 E) are the most stable ring size.…”

“…Atoms In addition to compounds 5a-h the six-membered ring compounds (R 2 ME) 3 [38] are always formed as by-products in 20-50% amount, see Fig. 3.…”

“…This is evident from a comparison of d Si A in the spiro [4.4] [42]) also reveals low field shifts due to the incorporation into five-membered rings. These low field shifts even exceed by some 5 ppm those of monosilanyl units in the simple five-membered rings R 2 Si(E) 2 Si 2 Me 4 [38].…”

“…If the formation of five-membered rings is not possible, six-membered rings are formed, whereas the formation of four-membered rings is favored by more bulky substituents. Besides information from crystal structure analyses the formation of different ring sizes can also be deduced from the 29 Si NMR chemical shifts [38].…”

Organosilicon hypersilylchalcogenolates and related compounds

“…Again, the bond angle at selenium is relatively large, e.g. in comparison with the cyclic six-membered ring compound Se(SiMe 2 SiMe 2 ) 2 Se (\Si-Se-Si: 105.14(3)°) [7].…”