(Left) Partial IR difference spectra of tetrazole 16 at 12 K in Ar matrix at different photolysis times at 254 nm. The positive peaks are due to the photolysis products. The peaks at 2154 and 3137 cm−1 belong to the same compound, N-methyl-N′-phenylcarbodiimide 20. Abscissa 1900−2500 cm−1. (Right) Plots of IR absorbances at different wavenumbers versus photolysis time. The 1375 cm−1 band belongs to the starting material 16. Ordinates in arbitrary absorbance units.

(a, bottom) Calculated IR spectrum of C-phenyl-N-(trimethylsilyl)nitrile imine 23 (B3-LYP/631G*, harmonic wave-numbers scaled by 0.9613; ordinate in arbitrary absorbance units). (b, middle) C-Phenyl-N-(trimethylsilyl)nitrile imine 23 obtained by photolysis of tetrazole 22 at 254 nm for 1 min in Ar matrix at 12 K and then destroyed by photolysis at 314 nm for 7 min, giving rise to the difference spectrum. Negative peaks are due to the nitrile imine 23: 2245, 1394, 1385, 1108, and 851 cm−1. Positive peaks are due to the formed N-phenyl-N′-(trimethylsilyl)carbodiimide 25: 2140−2175, 1590, 1466, 1451, 1256, 1150, 862, and 848 cm−1. (c, top) IR difference spectrum after photolysis of 22 for 45 min in Ar matrix at 12 K.