Synthesis, Structure, and Reactivity of Mixed-Ligand Dinuclear Ruthenium Polyhydrido Complexes Supported by 1,4,7-Trimethyl-1,4,7-triazacyclononane and Bulky Phosphine Ligands

Abstract

To construct electronically and sterically anisotropic reaction sites of dinuclear cluster, mixed-ligand diruthenium pentahydrido complexes [Cn*Ru(μ-H)3Ru(H)2(PR3)2]+ (Cn* = 1,4,7-trimethyl-1,4,7-triazacyclononane; R = Cy (3a), iPr (3b), cyclopentyl (Cyp, 3c)) were synthesized by the reaction of [Cn*RuH(H2)2]+ (1) with Ru(H)2(H2)2(PR3)2 (R = Cy (2a) iPr (2b), Cyp (2c)). The treatment of 3a–c with KH afforded the corresponding neutral tetrahydrido complexes Cn*Ru(μ-H)3RuH(PR3)2 (R = Cy (4a), iPr (4b), Cyp (4c)). The structures of 3 and 4 were confirmed by X-ray diffraction studies. Introduction of the Cn* ligand into the cluster increased the electron density at the Cn*-ligated metal center and significantly stimulated reactivitiy toward molecular nitrogen and carbon dioxide. Complexes 3a–c reacted with molecular nitrogen to produce the terminal dinitrogen complexes [Cn*Ru(N2)(μ-H)2RuH(PR3)2]+ (R = Cy (5a), iPr (5b), Cyp (5c)), which readily underwent dimerization to form the bridging dinitrogen complexes ...