1H nuclear magnetic resonance study of para-substituted derivatives of triphenylphosphine

Abstract

A ¹H n.m.r. investigation into para-substituted triarylphosphine derivatives is reported. For compounds showing a small chemical shift difference between ortho- and meta-protons, spectral analysis proved difficult owing to the relatively small number of observable transitions; in the cases of the tri-para-deuterio-derivative and the corresponding phosphonium salt, only approximate values of chemical shifts are reported. The electronic behaviour of the groups P, (O), and ⁺ interacting with a phenyl ring, derived from chemical shift measurements is interpreted in terms both of substituent additivity constants and of Hammett substituent parameters. Long-range ³¹P–¹H coupling constants are discussed in terms of hybridization at the phosphorus atom, d-orbital participation in (p–d)_π conjugation, and molecular geometry by comparing the experimental results with semiempirically calculated values.