Matrix photochemistry of syn-(chlorocarbonyl)sulfenyl bromide, syn-ClC(O)SBr: Precursor to the novel species anti-ClC(O)SBr, syn-BrC(O)SCl, and BrSCl

The vapor of (chlorocarbonyl)sulfenyl bromide. CIC(O)SBr, was isolated in s olid Ar. Kr, Nz, and Ar doped with 5% CO at 15 K, and the matrix was subseq uently irradiated with broad-band UV-visible light (200 less than or equal to lambda less than or equal to 800 nm), the changes being followed by refe rence to the IR spectrum of the matrix. The initial spectrum showed the vap or of CIC(O)SBr to consist of more than 99% of the syn form (with the C=O b ond syn with respect to the S-Br bond) in equilibrium with less than 1% of the anti conformer. Irradiation caused various changes to occur. First, con formational randomization took place, leading to a roughly equimolar mixtur e of the two rotamers, and so affording the first spectroscopic characteriz ation of an anti-ClC(O)S-containing compound. Simultaneously, the novel con stitutional isomer syn-BrC(O)SCl was also formed. Continued photolysis resu lted in the decay of all these species while revealing a third reaction cha nnel, leading to the elimination of CO and the formation of the new triatom ic sulfur halide BrSCl. The assignment of the IR bands to the different pro ducts was made on the basis of the usual criteria, taking account (i) of th e effects of the naturally occurring isotopic pairs Cl-35/Cl-37 and Br-79/B r-81, (ii) of the vibrational properties of related molecules, and (iii) of the properties predicted for the relevant molecules by quantum chemical ca lculations.