Tetrasilane-Bridged Bicyclo[4.1.0]heptasil-1(6)-ene

Abstract

Tetrasilane-bridged bicyclo[4.1.0]heptasil-1(6)-ene 1 was synthesized by the reduction of 1,1,2,2-tetrachlorocyclohexasilane 2 in 12% yield as red-orange crystals. The structure and properties of 1 were studied by spectroscopy, X-ray crystallography, and theoretical calculations. The linkage of the cyclotrisilene moiety with two tetrasilane chains with tert-butyl groups remarkably affects its structure and (29)Si NMR spectrum.

Effect of Ring Sizes of Cyclooligosilanes on Construction of Organosilicon Clusters

“…This term contributes to the deshielding effect and is roughly inversely proportional to the averaged transition energy between occupied and unoccupied molecular orbitals (Equation 1). 37 The down eld shift of the 29 Si signal of Si7 is probably due to its contribution to the HOMO and the LUMO (Figure 11). …”

“…The similar trigonal monopyramidal silicon atoms have been found in other oligosilanes. 31 34 The solid state 29 Si CP/MAS NMR spectrum of 4 shows eight signals ( Figure 10). These signals were essentially reproduced by GIAO calculation using the optimized structure and can be assigned as follows.…”

“…These signals were essentially reproduced by GIAO calculation using the optimized structure and can be assigned as follows. Three characteristic signals shifted up eld at 71.8, 62.4, and 56.6 ppm are due to the 29 Si nuclei of the cyclotrisilane rings (Si1, Si4, and Si8). 35 The signals at 25.0, 29.1, 35.4, and 39.0 ppm can be assigned to any of 29 Si nuclei of Si2, Si3, Si5, and Si6.…”

“…Three characteristic signals shifted up eld at 71.8, 62.4, and 56.6 ppm are due to the 29 Si nuclei of the cyclotrisilane rings (Si1, Si4, and Si8). 35 The signals at 25.0, 29.1, 35.4, and 39.0 ppm can be assigned to any of 29 Si nuclei of Si2, Si3, Si5, and Si6. 36 The 29 Si signal of Si7 at 66.4 ppm is shifted rather downeld.…”

“…35 The signals at 25.0, 29.1, 35.4, and 39.0 ppm can be assigned to any of 29 Si nuclei of Si2, Si3, Si5, and Si6. 36 The 29 Si signal of Si7 at 66.4 ppm is shifted rather downeld. A possible explanation may be given by the large paramagnetic term (σ p ) of Si7.…”