Nuclear magnetic resonance study of ring inversion and nitrogen inversion in substituted ethylenediamine complexes of praseodymium

Abstract

At low temperatures, ring inversion is slow on a proton n.m.r. time-scale for the Pr([²H₉]fod)₃–NNN′N′-tetramethylethylenediamine {[²H₉]fod =(CD₃)₃CC(:O)-CHC(:O)CF₂CF₂CF₃} complex (I), and the barrier to ring inversion, ΔG^‡, is 42.2 kJ mol^–1 at – 38 °C; in the corresponding NNN′N′-tetramethyl-1,2-propylenediamine complex (II), interchange of N-Me groups is observed above room temperature.