Molecular hydride carbonyl clusters and nanoclusters

Syntheses, structures, 1 H NMR features, electrochemical properties, applications to catalysis and electrocatalysis of molecular hydride carbonyl clusters and nanoclusters is reviewed. • Synthesis of molecular hydride carbonyl clusters and nanoclusters is summarized. • Different coordination modes of hydride ligands are analyzed. • NMR features and the problems of detecting hydrides in larger clusters are discussed. • Electrochemical properties of hydride clusters are reviewed. • Applications to catalysis and electrocatalysis are outlined. This minireview outlines the actual status of the chemistry of hydride metal carbonyl clusters (MCCs) by means of pertinent examples, without being comprehensive. After a brief introduction to the topic, the major synthetic routes for the introduction of hydride ligands in MCCs are described, with particular focus on the different typologies of reagents that can be employed. The structures of hydride MCCs and the different coordination modes of hydride ligands are, then presented, based on single-crystal X-ray and neutron diffraction data available. Some general considerations on 1 H NMR studies of hydride MCCs are described, including fluxionality and the problems of detecting hydrides in larger MCCs. Moreover, electrochemical studies of hydride MCCs are summarized, focusing on electrochemistry as an indirect tool for determining the hydride nature of large MCCs, and tuning the redox potentials of MCCs by protonation/deprotonation reactions. Applications of hydride MCCs in catalysis and electrocatalysis are only briefly described at the end of this minireview, since this topic has been recently reviewed.