Synthesis, characterization and catalytic transfer hydrogenation properties of Ru(II) complexes

Three half-sandwich Ru(II) complexes with the general formulae of [Ru(eta(6)-p-cymene)(L)Cl-2] (where L: 2a (diethyl-4-aminobenzylphosphonate), 2b (4-aminoethylbenzoate) and 2c (4-methoxybenzylamine) containing an aniline ligands were synthesized and their structures were characterized. The Crystal structure of complex [Ru(eta(6)-p-cymene)(2c)Cl-2] was investigated by single crystal X-ray diffraction studies. Each Ru(II) ion in both complexes is coordinated with a 6-p-cymene nitrogen atom, two chloride and aniline derivatives. This results in a distorted piano-stool geometry. The catalytic performances of the complexes were investigated in transfer hydrogenation reactions. The complexes catalyze the transfer hydrogenation of cyclohexanone and 2-hexanone in the presence of a base. For 2-hexanone to 2-hexanol reduction, complex [Ru(eta(6)-p-cymene)(2a)Cl-2] showed the highest conversion rate (at the end of 6 h) with 97% conversion. The complexes were found to be more active catalysts in the transfer hydrogenation of cyclohexanone than that of 2-hexanone.

Automated summary

In this study, three half-sandwich Ru(II) complexes were synthesized and their structures and catalytic performances were investigated. The complexes exhibited high activity in transfer hydrogenation reactions.