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

## TL;DR

Scientists isolated a new cerium-based complex and used NMR and theory to study how strongly cerium bonds with oxygen.

## Contribution

The study introduces a method to assess metal–oxygen bond covalency using 17O NMR and DFT in diamagnetic complexes.

## Key findings

- Ceiv derivatives show higher 17O NMR chemical shifts compared to Zr, Hf, or Th analogs.
- The chemical shift increase correlates with higher covalency in Miv–O bonds.
- One-electron oxidation provides stable Ceiv complexes for detailed characterization.

## 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.

Ce(iv) centered polyoxoalkoxide sandwich-type complexes have been isolated. Combining 17O NMR spectroscopy and density functional theory calculations reveals a relationship between the observed chemical shift and M(IV)–O bond covalency.