Adducts of trimethylaluminium with phosphine ligands; electronic and steric effects

Abstract

Complexes of the type Me₃AlPR₂R′ have been synthesised and studied by ¹H, ¹³C, and ³¹P n.m.r. spectroscopy. The change in ³¹P chemical shift on co-ordination, Δ(³¹P), decreases, becoming more negative, with sterically bulkier phosphines and with increasing donor ability. The aluminiummethyl ¹³C resonance shifts downfield with increasing phosphine steric bulk, and with increased donor ability. Steric effects, however, are found to be the major factor contributing to the changes in both Δ(³¹P) and methyl ¹³C chemical shifts.