1H, 13C and 31P NMR studies of some (C 6H 5) 3− nPR n and (C 6H 5) 3− nPR n Cr(CO) 5 ( n = 0–3; R  H, CH 3, C 2H 5, i-C 3H 7, t-C 4H 9) derivatives

Abstract

The 31P chemical shift of the (C 6H 5) 3− n PR n and (C 6H 5) 3− n PR n Cr(CO) 5 ( n = 0–3; R  H, CH 3, C 2H 5, i-C 3H 7, t-C 4H 9) derivatives is dominated by the steric effect. A small inductive effect is also operative but there are no indications of notable ( d Cr→ d P)π back-bonding. The 13C chemical shift of the phenyl carbon atoms indicates that ( p ring- d P)π electron delocalization is unimportant. The 13C chemical shift of the carbonyl carbon atoms, which is mainly governed by the mean excitation energy, confirms the conclusion that there are no notable changes in ( d Cr→ d P)π back-bonding in this series of compounds.