Chemistry Department Seminar

Polyols of the general composition HOCH2(CHOH)nCH2OH (n = 1-4) are among the most abundant biomolecules on the planet and in principle constitute a renewable resource of C3 to C6 polymer building blocks, if new pathways and catalysts for their selective deoxygenation to the corresponding diols HOCH2(CH2)nCH2OH can be developed. The deoxygenations can be achieved through an iterative cascade of acid-catalyzed dehydration and metal catalyzed hydrogenation and hydrogenolysis reactions in the same reactor vessel. Some principle pathways of these reactions and specific guidelines for the design of catalysts capable of operating under the required acidic aqueous conditions will be discussed. A series of new metal-ligand bifunctional homogeneous catalysts meeting these guidelines are ruthenium complexes that incorporate chelating 2,2’-bipyridine and 1,10-phenanthroline ligands, ortho-functionalized with amino groups acting as internal proton acceptors/donors. The complexes are postulated to activate hydrogen gas in a heterolytic fashion and thus effect the hydrogenation and/or hydrogenolysis through a proton/hydride transfer, an ionic mechanism that should enable both a ionic hydrogenation of C=O and C=C double bonds and a ionic hydrogenolysis of aliphatic C-O ether bonds by the same catalyst system.