NITRILE N-SELENIDE (RC-NSE) AND ISOSELENOCYANATE (RN=C=SE) NEUTRALS AND RADICAL CATIONS BY SELENATION OF NITRILES AND ISONITRILES - TANDEM MASS-SPECTROMETRY AND AB-INITIO STUDIES

Cyanogen N-selenide radical cations, NCCNSe.+ (4(.+)), have been produ ced by dissociative ionization of 3,4-dicyano-1,2,5-selenadiazole (3). By using a new hybrid tandem mass spectrometer, it is shown that thes e ions are excellent agents of selenation of nitriles and isonitriles, producing nitrile N-selenide ions (RCNSe.+) and isoselenocyanate ions (RNCSe.+), respectively. The connectivities of these ions have been e stablished by collisional activation, and the stabilities of the corre sponding neutrals were probed by neutralization-reionization experimen ts and ab initio G2(MP2,SVP) calculations. The neutral nitrile N-selen ides are found by experiment and theory to be observable species in th e gas phase. All the cations are potential energy minima, and their ca lculated fragmentation energies are in accord with experimental observ ations. NCCNSe.+ is found to be an effective Se.+ transfer agent becau se of its low N-Se bond dissociation energy and exceptional low-lying LUMO. The effect of substituents (CH3, NH2, OH, F, Cl, Br, I, CN, and SCH3) on the structures and stabilities of RCNSe neutrals is also repo rted.