Year of Publication

2013

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department/School/Program

Chemistry

First Advisor

Dr. Folami T. Ladipo

Abstract

The catalytic activity of ruthenium(II) bis(diimine) complexes cis-[Ru(6,6′-Cl2bpy)2(OH2)2](Z)2 (2, Z = CF3SO3; 3, Z = (3,5-(CF3)2C6H3)4B ,i.e. BArF), cis-[Ru(4,4′-Cl2bpy)2(OH2)2](Z)2 (4, Z = CF3SO3; 5, Z = BArF) and cis-[Ru(bpy)2(PR3)(OH2)](CF3SO3)2 (7, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 8, bpy = 2,2-bipyridine, PR3 = PPh3; 9, bpy = 4,4’-dichloro-2,2’-bipyridine, PR3 = PPh3; 10, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3 = P(C6H4F)3) for the hydrogenation and hydrogenolysis of furfural (FFR), furfuryl alcohol (FFA) and 5-hydroxymethylfurfural (HMF) was investigated. The compounds 2-5 are active and highly selective catalysts for the hydrogenation of FFR to FFA. Using 2 as catalyst at 100 °C, hydrogenation of FFR proceeded to high conversion (≥98%) and with 100% selectivity to FFA in 2 h. The catalyst cis-[Ru(6,6′-Cl2bpy)2(OH2)2](CF3SO3)2 (2) also showed some activity for hydrogenolysis of FFR and FFA at 130 °C in ethanol, giving up to 25% of 2-methylfuran (MF) yield. The catalyst 3 alsodisplayed high catalytic activity for the hydrogenation of FFA to tetrahydrofurfuryl alcohol.

Catalysts 7-10 are also active towards the hydrogenation of furfural (FFR) in NMP giving >90% FFR conversion with 100% selectivity for furfuryl alcohol (FFA) in 12 h. Compounds 7-10 are active C-O bond hydrogenolysis catalysts in presence of bismuth halide Lewis acids. For example, hydrogenolysis of FFA in the presence of 1 mol% of catalyst cis-[Ru(4,4’-Cl2bpy)2(PPh3)(OH2)](CF3SO3)2 (9) and 20 mol% bismuth bromide at 180 °C/51 atm H2 pressure gave >96% conversion of FFA and 55% MF yield. Compounds 7-10 in the presence of bismuth halides, showed almost 100% conversion of HMF with a very high selectivity (65-72%) for 2,5-DMF, along with 10-12% of MF, and trace amount of 5-methylfurfural (MeFFR). In order to test the activity of ruthenium hydrides towards the C-O bond hydrogenation and hydrogenolysis of HMF, series of monocationic ruthenium complexes cis-[Ru(bpy)2(PR3)(H)](CF3SO3) (12, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 13, bpy = 2,2-bipyridine, PR3= PPh3; 14, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3= P(C6H4F)3) were prepared. The hydrogenation of HMF using catalysts 12-14, produced 70-72% of 2,5-DMF and 11% MF, suggesting that ruthenium hydrides are active and efficient catalysts for HMF hydrogenation.

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