Selenium‐77 NMR chemical shifts of five‐membered selenium and sulphur heterocycles with CSe, CS, and CO groups

Abstract

Abstract This paper reports the 77 Se NMR chemical shifts of 1,3‐dithiole‐, 1,3‐thiaselenole‐ and 1,3‐diselenole‐2‐ones, ‐thiones and ‐selones, of the corresponding saturated compounds 1,3‐diselenolane‐2‐one, ‐thione and ‐selone, and the 1,3‐thiaselenolium tetrafluoroborates, either unsubstituted or substituted by morpholino, ethylthio or ethylseleno groups in the 2‐position. The 77 Se chemical shift values of the ring selenium and the CSe groups are compared with the 13 C chemical shift values of neighbouring carbon atoms. The relationships between the 77 Se chemical shifts of the CSe groups and the wavelengths of their n→* absorption in the UV‐visible spectrum are discussed with respect to the significance of the δE term in the contribution of the paramagnetic screening and the electron density distribution.