Polypyridyl complexes of d6 metals such as Ru(II), Os(II), an Re(I) have been an interest for many years because they often play important roles as intermediates in many catalytic redox reactions, such as hydrogen evolution, water-gas-shift reactions, and the reduction of carbon dioxide (CO2).    Work from our laboratory has resulted in opening a synthetic route to the tris-chelated cis-Re(?3-tpy)(CO)2Cl complex (tpy is 2,2';6',2'-terpyridine) based on the previously reported precursor fac-Re(?2-tpy)(CO)3Cl. Several experimental observations point to the extraordinary chemical, optical, and electrochemical properties of this complex. For example, the reactivity of cis-Re(?3-tpy)(CO)2Cl complex mirrors (or tracks) that of fac-Re(a,?-diimine)(CO)3Cl complexes. The cis-Re(?3-tpy)(CO)2Cl complex absorbs light throughout the entire visible spectrum. The first oxidation potential for this complex occurs reversibly at +0.51 V (vs. SCE) which is ~ 0.85 V less oxidizing compared to established fac-Re(a,?-diimine)(CO)3X (X = Cl, Br) complexes. Indeed, these results suggest that Re(I)-terpyridine complexes are capable of driving catalytic processes using light absorbed throughout the whole visible spectrum at significantly lower oxidation potentials.

Preparation and characterization of tris-chelated Re(I)-terpyridines

243rd National Meeting (2012)

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