Selenenylphosphonium ions as intermediates in the phosphane assisted methylation of elemental selenium

(Methylseleno)tri-n-butylphosphonium iodide has been prepared and was characterized by heteronuclear NMR spectra, ESI-MS and chemical analysis. The charge distribution and bond situation of its cation has been explored by quantum chemical methods at Hartree–Fock, DFT(B3LYP) and MP2 level. The results support a description as a selenenylphosphonium ion rather than as a donor stabilized selenenium ion. Treatment with methyl iodide yields Me3Se+I−, the crystal structure of which was reinvestigated.