31P-NMR-Untersuchungen VII

Abstract

All members of the series LnPh3-nPY and n-Bu3PY; L = Me2N, MeO; n = 0, 1, 2, 3; Y = O, S, Se, nil, have been prepared and converted to the methylchalkogeno-phosphonium ions LnPh3-nPYMe⊕ and n-Bu3PYMe⊕ respectively. For the accompaning change in the 31P chemical shift both positive and negative values are found. They depend on Y and n, are most negative for Y=O, and increase approximately linearly with n. To interpret the shift differences it is suggested, that Y on methylation decreases and L increases the shielding of P by altering their (p→d)π electron contributions. The 1H-NMR and IR spectra are also considered.