NMR spectra of seleninium and 1- and 2-benzoseleninium cations†

The analysis of the NMR spectra of seleninium and 1-and 2-benzoseleninium cations, recorded in deuterotrifluoroacetic acid, is reported. The effects of condensation on the spectral parameters of the protons of the seleninium ring were examined with particular reference to the shift to higher values of δ: this was consistent with the q values calculated by the HMO method. The 3J(HH) and 4J(HH) variations, including an interesting variation regarding the through-selenium 4J coupling, are also discussed.