Versatile formation of Ru(II) hydrazone complexes: Structure, theoretical studies and catalytic activity in α-alkylation

Abstract

New 1-(anthracen-10-yl)methylene)-2-(benzo[d]thiazol-2-yl)hydrazine (BHA) and 1-(anthracen-10-yl)methylene)-2-(quinolin-2-yl)hydrazine (QHA) ligands were reacted with [RuHCl(CO)(E)3] (E = PPh3 or AsPh3) or [RuCl2(AsPh3)3] in a 1:1 mol ratio in chloroform-ethanol medium to synthesis new ruthenium complexes. All the new ruthenium complexes were analyzed by elemental analysis, IR, NMR (1H, 13C and 31P) spectroscopy, ESI-Mass spectrometry and single crystal XRD techniques. The single crystal XRD study reveals the octahedral geometry around the ruthenium ion. The study also shows that the ligands coordinate with the Ru metal as monoanionic bidentate N^N donors in complexes 1, 3 and 4 and as a neutral bidentate N^N donor in complex 2 by forming five or four member chelate rings. The intramolecular interactions in the crystal lattices were studied by Hirshfeld surface analysis. The results indicate that π-stacking contacts play an important role in the crystal lattices. DFT calculations were carried out to explain the solid structures of complexes 1–3. Moreover, the synthesized complexes were screened as catalysts for the α-alkylation of ketones with alcohols. The effect of various parameters, such as base, solvent, temperature, time, substituents and also catalyst loading, on the catalytic activity were analyzed. The results depict that the complex 3 was found to be an efficient catalyst for the synthesis of α-alkylation products.