Activation parameters for rotation about an M–Ccarbbond from temperature dependent1H n.m.r. spectra of RhIcarbene complexes

Abstract

Restricted rotation on the n.m.r. time scale about the Rh–C_carb bond in complexes [RhL^Et(Y)Y′(Z)][L^Et= [graphic omitted](Et)] is demonstrated; for trans-[Rh(L^Et)₂(CO)Cl], variable temperature observations provid rotational activation parameters including a relatively low activation energy (⩽ 10 kcal mol^–1) and a negative activation entropy.