Pincer CNN Ruthenium(II) Complexes with Oxygen-Containing Ligands (O2CR, OAr, OR, OSiR3, O3SCF3): Synthesis, Structure, and Catalytic Activity in Fast Transfer Hydrogenation

The pincer complexes [RuX(CNN)(dppb)](55-11: X = carboxylate. phenoxide. alkoxide, silanolate, triflate; HCNN = 1-[6-(4'-methylphenyl)pyridin-2-yl]methanamine; dppb = Ph2P(CH2)(4)PPh2), containing the Ru-NH2 functionality and monodentate oxygen donor ligand. have been prepared in high yield starting from [RuCl(CNN)(dppb)] (1) Via Substitution of the Chloride With sodium Or thallium compounds or protonation of the alkoxide [Ru(OiPr)(CNN)(dppb)]center dot n(iPrOH) (3). In the solid state the formate 5 shows intermolecular C NH center dot center dot center dot O hydrogen bonds, Whereas the acetate 6 displays all intramolecular interaction, as inferred from X-ray studies. Addition of phenol and alcohol Compounds to the phenoxide and alkoxide complexes leads to fast ligand exchange through hydrogen bond interactions. The corresponding pincer complexes [RuX(CNN')(dppb)] (12, 13b: X = phenoxide, alkoxide; HCNN' = N,N-dimethyl-1-[6-(4'-methylphenyl)pyridin-2-yl]methanamine), containing the Ru-NMe2, moiety, have been obtained from [RuCl(CNN')(dppb)] (4) and sodium phenoxide or alkoxide. All the NH2 Complexes 5-11 are highly active Catalysts ill the transfer hydrogenation of ketones in 2-propanol with NaOiPr. affording complete conversion ill it few minutes and achieving TOF values Of Up to 3.8 x 10(6) h(-1) with 0.005 mol % of clatalyst.