First detection of a selenenyl fluoride ArSe-F by NMR spectroscopy:: The nature of Ar2Se2/XeF2 and ArSe-SiMe3/XeF2 reagents

Arylselenenyl fluorides ArSeF are obtained from diselenides Ar2Se2 or arylselenotrimethylsilanes ArSe-SiMe3, and XeF2. They are detected by low-temperature F-19 and Se-77 NMR spectroscopy. Substitution in the ortho position of the aromatic ring to provide electronic or steric protection is a requirement for their formation. ArSe-F compounds decompose according to 3ArSe-F-->[ArSe-SeF2Ar] +ArSe-F-->ArSeF3+Ar2Se2. Reaction energies for this disproportionation as well as that of the sulfur and tellurium homologues have been calculated with MP2, CCSD(T,) and B3LYP methods. They were found to be increasingly exothermic in the sequence S