Arene ruthenium complexes incorporating immine/azine hybrid-chelating N-N donor ligands: synthetic, spectral, structural aspects and DFT studies

New series of mono and binuclear arene ruthenium complexes [{(η⁶-arene)RuCl(L)}]⁺ and [{(η⁶-arene)RuCl}₂(μ-L)₂]²⁺ (arene=benzene, p-cymene or hexamethylbenzene), {L=pyridine-2-carbaldehyde azine (paa), p-phenylene-bis(picoline)-aldimine (pbp) and p-bi-phenylene-bis(picoline)-aldimine (bbp)} are reported. The complexes have been fully characterized and molecular structure of the representative mononuclear complex [(η⁶-C₆Me₆)RuCl(paa)]BF₄ (1), binuclear complexes [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-paa)](BF₄)₂ (3) and [{(η⁶-C₁₀H₁₄)RuCl}₂(μ-pbp)](BF₄)₂ (6) have been determined by single crystal X-ray diffraction analyses. Single crystal X-ray structure determination revealed that in the binuclear complexes the [(η⁶-C₁₀H₁₄)RuCl]⁺ units are trans disposed. Further, the crystal packing in the complexes 1, 3 and 6 is stabilized by C-H?X type (X=Cl, F) inter, intramolecular hydrogen bonding and π-π stacking (3). To explore the ambiguous nature of the bonding between pyridine-2-carbaldehyde azine (paa) with ruthenium containing units [(η⁶-arene)RuCl]⁺, DFT/B3LYP calculations have been performed on the complexes [(η⁶-arene)RuCl(paa)]⁺ (arene=C₆H₆, I; C₆Me₆, II; C₁₀H₁₄, III).