Reactions of Ruthenium Bipyridine Catalyst Precursors:  Synthetic, Structural, and Theoretical Studies on Ruthenium Mono(bipyridine) Carbonyls in Ethylene Glycol Solutions

Abstract

Carbonyl-containing ruthenium mono(bipyridines) are effective catalysts or catalyst precursors in processes such as the water-gas shift reaction. Ethylene glycol solutions provide versatile solvent systems for synthesizing the mono(bipyridines) from [Ru(CO) 3 Cl 2 ] 2 and 2,2‘-bipyridine. These starting compounds were used here in the preparation of three primary products, Ru(bpy)(CO) 2 Cl(C(O)OCH 2 CH 2 OH), Ru(bpy)(CO) 2 ClH, and [Ru(bpy)(CO) 2 Cl] 2, which were formed consecutively and isolated by adjusting the reaction conditions. Reactions were studied by analyzing the solid products and monitoring the evolution of gases in each reaction step. Computational nonlocal density functional methods were applied to estimate the total reaction energies and to study isomerism of the compounds. Ethylene glycol solvent plays an active role in the synthesis reactions. It provides a reactive alkoxy group, - OCH 2 CH 2 OH, which is able to act as a nucleophile attacking the carbon of a Ru−CO group. The first product, Ru(bpy)(CO) 2 Cl(C(O)OCH 2 CH 2 OH), is formed under mild conditions at room temperature. The alkoxy carbonyl complex reacts further to Ru(bpy)(CO) 2 ClH and CO 2 when heated. Formation of the hydride complex requires the presence of water. Ru(bpy)(CO) 2 ClH can be further converted to dimeric [Ru(bpy)(CO) 2 Cl] 2 . Ru(bpy)(CO) 2 Cl 2 is a side product which is also obtained from [Ru(CO) 3 Cl 2 ] 2 and 2,2‘-bipyridine. Crystal data: Ru(bpy)(CO) 2 Cl(C(O)OCH 2 CH 2 OH)· 1 / 4 (HOCH 2 CH 2 OH) ( 1 ), space group C 2/ c, cell constants a = 27.889(3) Å, b = 10.270(2) Å, c = 26.563(2) Å, β = 112.01(3)°, V = 7053.7(17) Å 3, Z = 16; Ru(bpy)(CO) 2 ClH ( 2 ), P 1̄, a = 6.3871(10) Å, b = 8.132(2) Å, c = 12.693(3) Å, α = 89.20(3)°, β = 81.37(3)°, γ = 81.20(3)°, V = 644.2(2) Å 3, Z = 2; [Ru(bpy)(CO) 3 Cl][Cl]·(H 5 O 2 )(Cl) ( 3 ), Pbcn, a = 20.856(4) Å, b = 13.523(3) Å, c = 13.203(3) Å, V = 3723.7(14) Å 3, Z = 8.