THE GAS-PHASE RNX-NO- NITROSO ONIUM CATIONS VERSUS ION-MOLECULE COMPLEXES( (X = O, N, S) CATIONS )

Collisional activation (CA) and ion-molecule reaction experiments maki ng use of a hybrid tandem mass spectrometer provide evidence for the d ilute gas-phase existence of the nitroso sulfonium cation (H2SNO+). Ab initio molecular orbital calculations using the coupled-cluster metho d, CCSD(T), with both 6-31G(d,p) and 6-311 + + G(3df,2p) basis sets co nfirm that, while H2SNO+ is relatively stable with respect to fragment ation, it can best be regarded as a strong molecular complex between N O+ and SH2 rather than an onium cation. Other nitroso onium cations ha ve also been generated by ionization of mixtures incorporating NO. and water, methanol, ammonia and alkane thiols and characterized by colli sional activation and by neutralization-reionization (NR) mass spectro metry. (C) 1998 Elsevier Science B.V.