Dynamic nuclear magnetic resonance and X-ray diffraction studies of tris(diphenylthiophosphoryl)methane and some related compounds

The 31P n.m.r. spectra of (Ph2P)3CH (1), (Ph2P)2[Ph2P(S)]CH (2), (Ph2P)[Ph2P(S)]2CH (3), and [Ph2P(S)]3CH (4) in the temperature range –100 to +40 °C show that internal rotation about the P–methine-C bonds is essentially unhindered in (1) and (2) but restricted in (3) and (4) with Ea values of 29 and 49 kJ mol–1 respectively. An X-ray diffraction study of (4) shows that the preferred conformation has one PS bond along the methine C–H direction and the other two opposed to it, and this persists in solution, even at higher temperatures. The magnitudes of the 31P–31P and 31P–H couplings in (3) and in (Ph2P)[Me2P(S)][Ph2P(S)]CH are used to propose the preferred conformations of these molecules.