Synthesis, Reactivity, and Catalytic Transfer Hydrogenation Activity of Ruthenium Complexes Bearing NNN Tridentate Ligands: Influence of the Secondary Coordination Sphere.

ABSTRACT: By the introduction of -OH group(s) into different position(s) of 6-(pyridin-2-ylmethyl)-2,2'-bipyridine, several NNN-type ligands were synthesized and then introduced to ruthenium (Ru) centers by reactions with RuCl₂(PPh₃)₃. In the presence of PPh₃ or CO, these ruthenium complexes reacted with NH₄PF₆ in CH₂Cl₂ or CH₃OH to give a series of ionic products 5-9. The reaction of Ru(L₂)(PPh₃)Cl₂ (2) with CO generated a neutral complex [Ru(L₂)(CO)Cl₂] (10). In the presence of CH₃ONa, 10 was further converted into complex [Ru(L₂)(HOCH₃)(CO)Cl] (11), in which there was a methanol molecule coordinating with ruthenium, as suggested by density functional theory calculations. The catalytic transfer hydrogenation activity of all of these new bifunctional metal-ligand complexes was tested. Dichloride complex 2 exhibits best activity, whereas carbonyl complexes 10 and 11 are efficient for selectively reducing 5-hexen-2-one, suggesting different hydrogenation mechanisms. The results reveal the dramatic influence for the reactivity and catalytic activity of the secondary coordination sphere in transition metal complexes.

SUBMITTER: Shi J 

PROVIDER: S-EPMC6641270 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature