Multinuclear (¹³C, ³¹P, ⁷⁷Se) Magnetic Resonance Studies on Organophosphorus Selenides and Sulfides. II. Tri- and Tetra-Tertiary Phosphines

Abstract

Selenium and sulfur have been reacted in various stoichiometries with two tritertiary phosphines Ph₂P(CH₂)₂P(Ph)(CH₂)₂PPh₂(P₂P′) and MeC (CH₂PPh₂)₃ (P₃), and two tetratertiary phosphines Ph₂P(CH₂)₂P(Ph)(CH₂)₂P(Ph)(CH₂)₂PPh₂ (P₂P′₂) and P({CH₂}₂PPh₂)₃ (P₃P′). The products have been fully characterized in solution by multinuclear (¹³C, ³¹P, ⁷⁷Se) magnetic resonance spectroscopic studies. Reaction of P₂P′ with one mole of selenium gives almost exclusively the product with the central phosphorus selenated (P₂P′Se′) and reaction with greater quantities leads to the identification of P₂P′SeSe′ and P₂P′Se₃ by their phosphorus-31 and selenium-77 n.m.r. spectra. The reactions between P₂P′₂ and various mole equivalents of selenium are similar to those of P₂P′, leading to the identification of P₂P′₂Se′, P₂P₂.′Se′₂, P₂P′₂SeSe′₂ and P₂P′₂Se₄ by both phosphorus-31 and selenium-77 n.m.r. spectroscopies although carbon-13 n.m.r. spectroscopy is required to unambiguously determine their structures. P₃ reacts with three moles of selenium to give P₃Se₃. When P₃ is reacted with less than 3 mole equiv. of selenium, phosphorus-31 and selenium-77 n.m.r. spectra cannot distinguish between pure selenides and mixtures of selenides. However, carbon-13 n.m.r. spectra show that reaction of P₃ with less than 3 mole equiv. of selenium leads to almost tatistical distributions of P₃, P₃Se, P₃Se₂ and P₃Se₃. The reactions between P₃P′ and selenium give a combination of the above behaviours. The central phosphorus is selenated first, but subsequent additions of selenium lead to a distribution of selenium among the terminal phosphorus atoms to give mixtures of P₃P′SeSe′, P₃P′Se₂Se′ and P₃P′Se₃Se′ which cannot be distinguished by phosphorus-31 n.m.r. spectroscopy, but can be by selenium-77 n.m.r. spectroscopy. Reaction of P₂P′ (and P₂P′₂) with sulfur in any proportion is quite different to that with selenium, and gives only P₂P′S₃ (and unreacted P₂P′). The reactions between P₃ or P₃P′ and sulfur are similar to those between these compounds and selenium. Reactions between selenium or sulfur and a series of ditertiary phosphines have been investigated in an attempt to clarify the different reactions of the elements with P₂P′ and P₂P′₂.