Ab-initio MCSCF study of the homolytic S-S bond dissociation in disulphides, thiosulphinates and α-disulphoxides.

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The geometrical and electronic properties of RSSR, RS(O)SR and RS(O)S(O)R (with RH,CH 3) molecules and the energy profile for SS bond cleavage were calculated with ab-initio MO MCSCF wavefunctions at 3–21G* level. The results show that the electronic structure of α—disulphoxides is more likely that of two paired radicals with net spin population localized on the oxygen atoms. Also in terms of bond-length and bond-index the SS bond in α—disulphoxides appears to be much weaker than in the other molecules, as also confirmed by the calculated bond dissociation energy (DE) which turns out much lower than expected for a true SS bond.