Direct observation of free and complexed substrate in a lanthanide shift reagent system

Abstract

The ¹H n.m.r. spectra of mixtures of tris-(1,1,1,2,2,3,3-heptafluoro-7,7-[²H₆]dimethyl[²H₃]octane-4,6-dionato)europium and excess of dimethyl sulphoxide in CD₂Cl₂ have been determined over a range of temperatures; chemical exchange is slow at –80 °C and each mol of shift reagent is found to co-ordinate 2·0 ± 0·2 mol of dimethyl sulphoxide, corresponding to a co-ordination number of 8 for the europium ion.