Electronegativity and crystal field splittings in rare earth compounds

Crystal field studies in a variety of 4f-and some 5f electron-systems reveal a correlation between crystal field splittings, i.e. sign and charge strength of simple ligands and their electronegativities. Deviations occur in several very dilute f.c.c. noble metals, as well as noble metal compounds presumably due to the d-electron contribution and perhaps ill-defined valence states, in particular in transition metal compounds.