SBA-15-supported N-coordinate ruthenium(II) materials bearing sulfonamide-type ligands: Effect of ligand backbones on catalytic transfer hydrogenation of ketones and aldehydes

[RuLCl(p-cymene)] (L=N-arylsulfonylphenylenediamine) complexes (2(a-d)) were synthesized from the reaction between [Ru(p-cymene)Cl-2](2) and ligand. Additionally, SBA-15-[RuLCl(p-cymene)] derived catalysts (3(a-d)) were successfully immobilized onto mesoporous silica (SBA-15) by an easily accessible approach. The structural elucidations of 2(a-d) and 3(a-d) were carried out with various methods such as H-1 NMR, C-13 NMR and infrared spectroscopies, elemental analysis, thermogravimetric/differential thermal analysis, nitrogen adsorption-desorption and scanning electron microscopy/energy-dispersive X-ray analysis. The Ru(II) complexes and materials were found to be highly active and selective catalysts for the transfer hydrogenation (TH) reaction of aldehydes and ketones. The influence of various 1,2-phenylenediamines on the reactivity of the catalysts (complexes or materials) was studied and the catalysts (2(d) and 3(d)) with a 4,5-dichlorophenylenediamine substituent showed the best activity (the maximum turnover frequencies are 2916 and 2154h(-1) for TH of 4-fluoroacetophenone, and 6000 and 4956h(-1) for TH of 4-chlorobenzaldehyde).