X-ray emission spectra and electronic structure of the sulphate and methyl sulphonate anions, dimethyl sulphone and the trimethylsulphoxonium cation [(CH3)nSO4–n]n–2, (n= 0, 1, 2 and 3)

The S Kβ X-ray emission spectra have been measured for the series [(CH3)nSO4–n]n–2, (n= 0, 1, 2 and 3). Peak shifts and changes in relative peak intensities are rationalised in terms of changes in electronic structure. S 1s and other sulphur orbitals become less tightly bound as methyl substitution increases, which causes a decrease in S 3p participation in ligand 2s orbitals and a decrease in the relative intensity of Kβ′. Evidence is found for increased ‘hyperconjugation’ between C—H and S—O, S—C σ bonds as the number of methyl groups increases.