SiNCO+ and SiNCS+ and their neutral counterparts

[Si,C,N,O](+) and [Si,C,N,S](+) cations formed upon electron ionization of trimethylsilyl isocyanate and iosthiocyanate, respectively, are probed by t andem mass spectrometry. In the case of [Si,C,N,O](+), the experimental dat a suggest that the isocyanato group remains intact upon ionization such tha t silicon isocyanate SiNCO+ is formed. Neutralization-reionization mass spe ctrometry indicates that also neutral SiNCO is a viable molecule in the gas phase. instead, partial isomerization to SiSCN+ is indicated for the sulfu r analog. Because of this structural dichotomy, the nature of the [Si,C,N,S ](+) species giving rise to the recovery signal in the neutralization-reion ization experiments remains uncertain. (C) 2000 Elsevier Science B.V. All r ights reserved.