Multiply Bonded Silicon: Matrix Isolation and Chemical Trapping of Products of Pyrolysis and Photolysis of Triazidophenylsilane

Triazidophenylsilane (1) yields phenyl isosilacyanide (3) upon irradiation in matrix isolation and by pyrolysis followed by trapping in noble gas matrix. Annealing from 12 to 15 K causes significant changes in the IR spectrum of photochemically produced 3, attributed to the release of hydrostatic pressure in the matrix. The matrix reaction of pyrolytically produced 3 with t-BuOH to yield an independently synthesized trapping adduct 4 has been followed spectrally. An aligned sample of 3 was produced by photoselection and polarized IR spectra were recorded. The UV and IR absorption spectra of 3 have been interpreted and agree well with ab initio and semiempirical calculations. In contrast, the intermediacy of benzenesilonitrile (2), a representative of a so far unknown class of species with a -Si=N triple bond, in the photofragmentation of matrix-isolated 1, is merely strongly suggested but not proven by trapping of the photoproducts from matrix-isolated 1 with t-BuOH to yield the adduct 5 in addition to 4. The silonitrile 2 did not accumulate in the matrix in amounts sufficient for spectral characterization.