Photodecomposition of Trimethylsilyl Azide in Solid Argon

Abstract

WHEN some group IV azide derivatives have been subjected to photodecomposition in argon matrices at cryogenic temperatures, isocyanides have been produced. In the case of methyl azide H3CNNN, hydrogen isocyanide HN≡C was proved to result from a secondary photolysis of methylenimine H₂C = NH (ref. 1). From silyl azide, H₃SiNNN, iminosilicon HNSi has been detected², but the mechanism of formation was uncertain; the vibrational absorptions of other products were not then assigned. From germyl azide H₃GeNNN, HNGe has been tentatively identified (unpublished work with S. Cradock). The force constants of the heavy-atom valence-stretching vibrations of HNSi and HNGe are probably appropriate to what might effectively constitute “double bonds” rather than to a “triple bond” as in the case of HNC. Because π-type bonds of atoms beyond the first row are decreasingly stable because of the reduced overlap of the p-orbitals of the larger atoms, it is interesting to know the results of a situation in which there might be unsaturation either in a chemical bond between only first row atoms or alternatively, in a bond involving a second row atom. Such a case has been discovered following the photolysis of trimethylsilyl azide isolated in solid argon at 17° K.