Keto-enol tautomers of mixed-ligand ruthenium(II) complexes containing α-diamine and azoimine bearing alkyne group ligands

Refluxing azoimine ligand (L = C6H5NNC(COCH3)NC6H4CCH) with RuCl3·3H2O in ethanol resulted in catalytic hydration of the terminal acetylene group to the enol form C6H5NNC(COCH3)NC6H4C(OH)CH2 (L1), the ketone form C6H5NNC(COCH3)NC6H4COCH3 (L2) and the vinyl chloride: C6H5NNC(COCH3)NC6H4C(Cl)CH2 (L3) via Markovnikov selectivity. Ruthenium complexes of the formula trans-[Ru(N-N)(Y)Cl2] (Y = L1, N-N = 4,4′-dimethoxy-2,2′-bipyridine; dmeb (1), 1,10-phenanthroline; phen (2), 3,4,7,8-tetramethyl-1,10-phenanthroline; tmphen (3), Y = L2, N-N = dmeb (4), phen (5), tmphen (6)) were made from L, N-N ligands and RuCl3·3H2O. Complexes 1-6 were characterized by spectroscopic techniques (IR, UV-Vis, 1H, 13C NMR, DEPT-135) and electrochemistry. The crystal structures of trans-[Ru(tmphen)(L1)Cl2] (3) and trans-[Ru(bpy)(L3)Cl2] (7) were determined and found to have distorted octahedral geometry. The catalytic activity of 3 towards the hydration of cinnamaldehyde is described.77