Novel neutral phosphinite bridged dinuclear ruthenium(II) arene complexes and their catalytic use in transfer hydrogenation of aromatic ketones: X-ray structure of a new Schiff base, N3,N3 '-di-2-hydroxybenzylidene-[2,2 ']bipyridinyl-3,3 '-diamine

AYDEMİR M., DURAP F., BAYSAL A., MERİÇ N., Buldag A., Guemguem B., ...Daha Fazla

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, cilt.326, ss.75-81, 2010 (SCI-Expanded, Scopus)

Özet

A novel Schiff base N3,N3'-di-2-hydroxybenzylidene-[2,2']bipyridinyl-3,3'-diamine, 1 was synthesized from condensation of salicylaldehyde with 3,3'-diamino-2,2'-bipyridine. Reaction of 1 with two equivalents of PPh2Cl in the presence of Et3N proceeds in toluene to give N3,N3'-di-2-(diphenylphosphino)benzylidene-[2,2']bipyridinyl-3,3'-diamine, 2 in quantitative yield. Ruthenium(II) dimers [Ru(eta(6)-arene)(mu-Cl)]Cl](2) readily react with phosphinite ligand [(Ph2PO)(2)-C24H16N4], 2 in toluene at room temperature, to afford the neutral derivatives [C24H16N4{OPPh2-Ru(eta(6)-arene)Cl-2}2] {arene: benzene 3, p-cymene, 4}. All the complexes were fully characterized by analytical and spectroscopic methods. P-31-{H-1} NMR, H-1-C-13 HETCOR or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. Molecular structure of the Schiff base, 1 was also determined by X-ray single crystal diffraction study. The catalytic activity of complexes 3 and 4 in the transfer hydrogenation of acetophenone derivatives was tested. Stable ruthenium(II)-phosphinite complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in excellent conversions up to 99% (up to 530 per hour) in the presence of iso-PrOH/KOH. (C) 2010 Elsevier B.V. All rights reserved.