Naphthyl C8-H hydrogen activation and synthesis of organometallic ruthenium complex: Crystal structure of hydride intermediates and catalytic transfer hydrogenation

Organometallic ruthenium(II) complex [Ru(L1C∧N∧N)(PPh3)2(CO)] (1) [where L1H2 is (E)N-((1H-pyrrol-2-yl)methylene)naphthalen-1-amine] [H represents dissociable proton] was synthesized via CH bond activation using different synthetic strategies. Ruthenium hydrido carbonyl complexes [Ru(L1N∧N)(PPh3)2(CO)H] (2) [where L1H2 is (E)N-((1H-pyrrol-2-yl)methylene)naphthalen-1-amine] and [Ru(L2N∧N)(PPh3)2(CO)H] (3) [where L2H2 is (E)N-((1H-pyrrol-2-yl)methylene)-1-phenylmethanamine] were isolated. All the complexes were characterized by UV–Vis, IR and NMR spectral studies. Molecular structures of complexes 1, 2 and 3 were authenticated using X-ray crystallography. Geometry optimisation of the complexes 1–3 have been performed using Density Functional Theory (DFT) studies. Time-dependent DFT calculations were performed to better understand the electronic properties of complexes 1–3. Complex 1 was utilized as catalyst in transfer hydrogenation of ketones. On the basis of literature study, the plausible mechanisms were proposed for hydride formation and catalytic transfer hydrogenation.