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.