Synthesis and N.M.R. Studies of New Unsymmetrically Substituted Ditertiary Phosphines

Abstract

The synthesis and characterization of rac- and meso-(E)-1,2-C₂H₂( PMePh )₂ (1), 1,2-C₆H₄( PMePh )(PPh₂)(2),1,2-C₆H₄( PBuPh )(PPh₂)(3) and 1,2-C₆H₄(Pme₂)(PPh₂) (4) are reported. Reaction of (1) with MeI (1:2) gives [(E)-1,2-C₂H₂(Pme₂Ph)₂]I₂ (5). The compound [(E)-1,2-C₂H₂(PPh₂)(PmePh₂)]I (6) was synthesized from (E)-1,2-C₂H₂(PPh₂)₂ and MeI (1:1). ¹H n.m.r. spectra are reported for (2), (3), (5) and 6. ³¹P n.m.r. spectra are reported for (1)-(3), (5), (6) and [(E)-1,2-C₂H₂(PmePh₂)₂]I₂ (7). ₂J(P^V,H) and trans ³J(H,H) coupling were observed in the ¹H n.m.r. spectra of (6). Substitution of one Ph group for one Me group at phosphorus in a ditertiary phosphine produces a change in chemical shift of 19.5 and 21.8 ppm for (E)-CH=CH and 1,2-C₆H₄ interphosphorus linkages respectively. The interphosphorus linkage in a ditertiary phosphine produces large ³J(P,P) coupling constants (c. 155 Hz), and an increase in screening of the phosphorus nuclei (c. 10 ppm ).