Half-sandwich cycloruthenated complexes from aryloxazolines: synthesis, structures, and catalytic activities

Seven half-sandwich cycloruthenated complexes [Ru(p-cymene)LCl] (2a-2g) (L = 2-phenyl-2-oxazoline (2a), 2-p-tolyl-4,5-dihydrooxazole (2b), 4,4-dimethyl-2-phenyl-2-oxazoline (2c), 2-(4-chlorophenyl)-4,5-dihydrooxazole (2d), 2-(4-bromophenyl)-4,5-dihydrooxazole (2e), 2-(4-fluorophenyl)-4,5-dihydrooxazole (2f) and 2-(4-nitrophenyl)-4,5-dihydrooxazole (2g)) were synthesized and characterized. All half-sandwich cycloruthenated complexes were fully characterized by H-1 and C-13 NMR spectra, elemental analyses and infrared spectroscopy. The molecular structures of 2a, 2d and 2e were confirmed by single-crystal X-ray diffraction methods. These half-sandwich cycloruthenated complexes were employed in nitroarene reduction using sodium borohydride (NaBH4) as a reducing agent in ethanol at room temperature. The catalytic results indicate that half-sandwich cycloruthenated complexes show promising catalytic activity in nitroarene reduction with a broad substrate and varied functional group compatibility.