Triplet States of Tetrazoles, Nitrenes, and Carbenes
from Matrix Photolysis of Tetrazoles, and Phenylcyanamide as a Source
of Phenylnitrene
Manabu Abe
Didier Bégué
Hugo Santos Silva
Alain Dargelos
Curt Wentrup
10.1021/acs.jpca.8b06960.s001
https://acs.figshare.com/articles/journal_contribution/Triplet_States_of_Tetrazoles_Nitrenes_and_Carbenes_from_Matrix_Photolysis_of_Tetrazoles_and_Phenylcyanamide_as_a_Source_of_Phenylnitrene/7053599
Photolysis
of 1- and 5-aryltetrazoles at 5–10 K using a
266 nm laser immediately generates their triplet excited states, which
are characterized by their electron spin resonance (ESR) spectra with
zero-field splitting parameters <i>D</i> = 0.12–0.13
cm<sup>–1</sup> and <i>E</i> = 0.002–0.008
cm<sup>–1</sup>. Further photolysis of all of the aryltetrazoles
affords arylnitrenes (<i>D</i> ≅ 1 cm<sup>–1</sup>), and in the case of 5-aryltetrazoles also arylcarbenes (<i>D</i> ≅ 0.5 cm<sup>–1</sup>). The formation of
arylnitrenes from 5-aryltetrazoles, where no aryl–N bond is
present, is explained by the photochemical rearrangement of initially
formed nitrile imines ArCN<sup>+</sup>N<sup>–</sup>R to carbodiimides.
The monosubstituted carbodiimide PhNCNH isomerizes
to phenylcyanamide, PhNH–CN, and photolysis of the latter causes
rapid elimination of HCN and formation of phenylnitrene. When <i>N</i>-methyl groups are present in the tetrazoles, methylnitrene,
CH<sub>3</sub>–N, is formed too. In the case of 5-phenyltetrazole,
additional hydrogen shift and fragmentation afford cyano- and isocyanonitrenes,
NCN and CNN.
2018-08-30 00:00:00
Tetrazole
5- aryltetrazoles
carbodiimide
formation
HCN
cm
CH
arylnitrene
Photolysi
photolysi
266 nm laser
ESR
CNN
zero-field splitting parameters D
nitrile imines ArCN
NCN