Phosphorus-31 Chemical Shifts in Secondary and Tertiary Phosphines

Abstract

ALTHOUGH several theoretical and empirical attempts^1–4 have been made to predict the ³¹P chemical shifts of phosphorus compounds, these have seldom achieved an accuracy of better than 10–20 p.p.m. For example, Van Wazer et al.³ assigned to alkyl groups the ‘group shift’ of +20 p.p.m. in tervalent phosphorus compounds. On this basis a tertiary phosphine should have a ³¹P chemical shift of about +60 p.p.m. However, the known values for twenty tertiary phosphines (Table 1) vary widely from this prediction, ranging from −19.3 to +62 p.p.m.