Isolation of Ce(IV) centered polyoxoalkoxide sandwich-type complexes allows comparison of metal-oxygen bond covalency

Abstract

The new CeIII centered sandwich-type complex (TBA)3[Ce{W4O13(OMe)4MoNO}2] is reported. The redox properties of this molecule, and its all-molybdenum analogue, (TBA)3[Ce{Mo5O13(OMe)4NO}2], were investigated using cyclic voltammetry. The data reveals the presence of reversible CeIV/CeIII redox couples at modest potentials. One electron oxidation of the complexes provides facile access to the corresponding CeIV derivatives, which were fully characterized. 17O NMR spectroscopy reveals that the chemical shifts of the oxygen nuclei directly bound to CeIV are much higher than the corresponding signals in isostructural, diamagnetic, ZrIV, HfIV, or ThIV centered complexes. Density functional theory (DFT) calculations indicate that the increase in chemical shift correlates with an increase in the covalency of the MIV-O bonds, illustrating that 17O NMR spectroscopy is a powerful experimental tool for interrogating the nature of metal oxygen bonding in diamagnetic complexes.