REACTIONS OF A TRIPLET ARYLNITRENIUM ION - LASER FLASH-PHOTOLYSIS ANDPRODUCT STUDIES OF N-TERT-BUTYL(2-ACETYL-4-NITROPHENYL)NITRENIUM ION

Photolysis of 1e (N-tert-butyl-5-nitro-3-methylanthranilium ion) (ClO4 - or BF4- salt) generates the isomeric tert-butyl(4-nitro-2-acetylphen yl)nitrenium ion (2e). The latter further reacts to form iminium ion 4 e and parent amine 5e as stable products. On the basis of triplet sens itization and quenching studies, it is shown that 4e is a product of t he singlet state of 2e and 5e is a product of the triplet state of 2e. Laser flash photolysis experiments on 1e give a short-lived (ca. 300 ns) transient spectrum having maxima at 390 and 540 nm which is assign ed to the excited triplet state of 1e. It was not possible to directly detect nitrenium ion 2e under these conditions. However, its lifetime and reactivity could be studied through the use of a probe substrate. Triphenylmethane does not affect the decay of triplet 1e. However, it s addition causes a new transient species to grow in over much longer time scales than the decay of triplet 1e. The new, longer lived specie s is identified as the triphenylmethyl radical (Ph(3)C(.)). Its format ion is attributed to hydrogen atom abstraction by the triplet state of 2e. Analysis of the growth kinetics for Ph(3)C(.) shows that 2e lives for ca. 2 mu s in CH2Cl2. On the basis of this observation as well as several other mechanistic and kinetic considerations, it is argued th at arylnitrenium ion 2e has a triplet ground state.