The Riordan laboratory focuses on frontier synthetic and mechanistic problems in bioinorganic and coordination chemistry that may be probed through chemical synthesis, reactivity and kinetic studies. This bioinspired approach requires the tools of both synthetic and physical inorganic chemistry. Specifically, we are interested in using low valent nickel complexes to activate small molecules, in particular dioxygen, so as to understand the pathways of dioxygen activation and utilization as an abundant and environmentally responsible oxidant. In intellectually related pursuits, the oxidation of metal hydroxide complexes as a strategy to investigate homogenous water oxidation is another area of current interest. Objectives include deducing the geometric and electronic structures of new molecules, in particular reactive intermediates, via application of a wide range of contemporary physical methods and correlating structure with chemical reactivity.

Students in the laboratory are trained in the areas of synthesis, including anaerobic techniques, spectroscopy, reaction kinetics and mechanism. Recent Riordan group alumni are employed in industry, academia and government laboratories.

DIOXYGEN ACTIVATION O₂ is the ideal oxidant for a wide range of homogeneous catalytic processes. We have discovered that a series of readily accessible nickel(I) complexes react avidly with O₂, reducing the O=O bond to varying degrees, generating metastable intermediates, Figure 1. The geometric and electronic structures and reactivity of these new complexes are of current interest. A surprising observation is that the sulfur-containing ancillary ligands are not oxidized during the reaction.

Nickel-dioxygen complexes prepared via reaction of nickel(I) precursors with O2

SULFUR AND SELENIUM ACTIVATION In expanding the bioinspired approach of O₂ activation by nickel(I) complexes, activation of the heavier congeners, sulfur and selenium, has led to the isolation of a wide range of new chemical entities with interesting electronic and geometric structures, in which the nature of the sulfur or selenium bridging ligand is determined by the identity of the supporting ligand AND the metal-to-chalcogen stoichiometry. A sampling of recently deduced structures is provided in Figure 2.

Nickel-sulfur and -selenium complexes prepared via reaction of nickel(I) precursors with S8 or Se