Reactivity study of arene(azido)ruthenium N∩O-base complexes with activated alkynes

Abstract

Substitution reaction of chloro η6-arene ruthenium N∩O-base complexes [(η6-arene)Ru(N∩O)Cl] [N∩O=pyrazine-2-carboxylic acid (pca-H), 8-hydroxyquinoline (hq-H); arene=p-iPrC6H4Me, N∩O=hq (1); arene=C6Me6, N∩O=hq (2)] with NaN3 yield the neutral arene ruthenium azido complexes of the general formula [(η6-arene)Ru(N∩O)N3] [N∩O=pca, arene=p-iPrC6H4Me (3), arene=C6Me6 (4); N∩O=hq, arene=p-iPrC6H4Me (5), arene=C6Me6 (6)]. These complexes undergo [3+2] dipolar cycloaddition reaction with activated alkynes dimethyl and diethyl acetylenedicarboxylates to yield the arene triazole complexes [(η6-arene)Ru(N∩O){N3C2(CO2R)2}] [N∩O=pca, R=Me, arene=p-iPrC6H4Me (7), C6Me6 (8); R=Et, arene=p-iPrC6H4Me (9), C6Me6 (10); N∩O=hq, R=Me, arene=p-iPrC6H4Me (11) C6Me6 (12); R=Et, arene=p-iPrC6H4Me (13), C6Me6 (14)]. On the bases of proton NMR study, in the above triazole complexes N(2) isomers are assigned with dimethylacetylenedicarboxylate whereas N(1) isomers with diethylacetylenedicarboxylate. All complexes have been characterized by IR and NMR spectroscopy as well as by elemental analysis. The molecular structures of the azido complexes [(η6-p-iPrC6H4Me)Ru(pca)N3] (3), [(η6-p-iPrC6H4Me)Ru(hq)N3] (5) and [(η6-C6Me6)Ru(hq)N3] (6) have been established by single crystal X-ray diffraction studies.