Site-specific orthometallation via C–H bond activation and syntheses of ruthenium(III) organometallics: studies on nitric oxide (NO) reactivity and photorelease of coordinated NO

A new family of σ-aryl ruthenium(III) complexes [Ru(L1–4)(PPh3)2Cl] (1–4) (where L1H2 = N-(quinolin-8-yl)benzamide for 1, L2H2 = 4-chloro-N-(quinolin-8-yl)benzamide for 2, L3H2 = 4-nitro-N-(quinolin-8-yl)benzamide for 3, L4H2 = 3-nitro-N-(quinolin-8-yl)benzamide for 4 and H = dissociable protons) derived from bidentate ligands having amide bonds was synthesized through C–H bond activation. These organometallic ruthenium(III) complexes were treated with nitric oxide (NO) to afford the nitrosyl complexes [Ru(NO2L1–4)(PPh3)2(NO)](ClO4) (1a–4a) (where NO2L1H2 = N-(5-nitroquinolin-8-yl)benzamide for 1a, NO2L2H2 = 4-chloro-N-(5-nitroquinolin-8-yl)benzamide for 2a, NO2L3H2 = 4-nitro-N-(5-nitroquinolin-8-yl)benzamide for 3a, NO2L4H2 = 3-nitro-N-(5-nitroquinolin-8-yl)benzamide for 4a and H = dissociable protons). All ruthenium complexes were characterized by various spectroscopic techniques. An X-ray crystallographic study afforded the molecular structure of complex 4a and the site-specific orthometallation was scrutinized. The coordinated NO molecule was found to be photolabile under visible and UV light.