There is an increasing interest in bimetallic complexes due to possible synergistic reactivity between two nearby positioned metal centers. One potential application in which such bimetallic synergistic reactivity may be desirable is the efficient oxidation of CO under mild conditions. Efficient oxidation of CO generally requires (1) high loading of precious metal (Rh, Pt) catalysts; (2) high reaction temperatures. As CO oxidation is carried out on a large scale (every gasoline vehicle employs a catalytic converter, transforming residual CO into CO2), there is a need for efficient earth-abundant catalysts capable of operating under mild conditions. Mechanistically, CO oxidation with O2 requires two different types of active sites in the catalyst: a Lewis basic (LB) site and a Lewis acidic (LA) site. In the case of CO oxidation on Pt surface, CO binds to the LB site (Pt), while a nearby LA site (Pt-O) transfers an [O] atom. We hypothesize that a heterobimetallic system containing two earth-abundant LA and LB sites in the vicinity will catalyze CO oxidation effectively. To test this hypothesis, we have synthesized a new heterodinucleating ligand featuring two different metal-binding sites, iminopyridine and catecholate. We demonstrate that the iminopyridine site selectively binds softer metals (Cu(I)) and the catecholate site selectively binds harder metals (Mo(VI)/W(VI)). We will also discuss the reactivity of these heterobimetallic systems in the oxidation of CO and CO-related substrates.

Heterobimetallic homogeneous catalysts for CO oxidation

255th National Meeting (2018)

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