Ladder Oxygenation of Group VIII Metal Clusters and the Formation of Metalloxocubes M13O8+

The diversity of valence and bonding of transition metals makes their oxidation processes perplexing at reduced sizes. Here we report a comprehensive study on the oxidation reactions of rhodium clusters Rh-n(+/-) (n = 3- 30) and find that Rh3,4O4+, Rh5-7O6+, and Rh8-13O8+ always dominate the mass distributions showing size-dependent ladder oxygenation which is closely associated with the O-binding modes. While the Rh8-13O8+ clusters display a mu(3)-O binding mode (hollow site adsorption), Rh3-4O4+ and Rh5-7O6+ favor the mu(2)-O binding mode (edge-site adsorption) or a mixture of the two modes. The mu(3)-O binding mode is inclined to yield a cubic Rh13O8, while the mu(2)-O binding mode gives rise to oxygen-bridge protection for the metal clusters. Such ladder oxidation was also observed for Pt-n(+), Fe-n(+), Co-n(+), and Ni-n(+) clusters. We propose a three-dimensional diagram for the oxidation states and O-binding modes of metals, and highlight the metalloxocubes M13O8+ for cluster-genetic materials.

Automated summary

A comprehensive study on the oxidation reactions of Rh-n(+) (n = 3-30) rhodium clusters reveals a size-dependent ladder oxygenation phenomenon, with Rh3,4O4+, Rh5-7O6+, and Rh8-13O8+ clusters dominating the mass distributions. The oxygen binding modes are closely associated with the ladder oxidation, with different clusters exhibiting different binding modes. The findings have implications for the design of cluster-genetic materials.