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

Abstract

A new family of σ-aryl ruthenium(III) complexes [Ru(L^1–4)(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(NO₂L^1–4)(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.