Pyridine-based tridentate triamine compounds ( 0 N kNkN 0 ) are very attractive ligands for coordination chemistry, and their transition-metal (TM) complexes have been successfully applied in homogeneous catalysis. 1À28 Although examples of the related Ru complexes are scarce, such complexes recently gained attention due to their use in catalysis and in other chemical applications. 29À48 For example, d N k N k N d -containing neutral Ru(II) complexes of the general formula [RuCl 2 ( d N k N k N d )L] (L = monodentate ligands such as CH 3 CN, PPh 3 , and CO) are effective catalysts for the transfer hydrogenation (TH) of ketones. 29,32 During the preparation of this paper, a report on unsymmetrical and asymmetrical [RuCl( 0 N k N k N 00 )(PPh 3 ) 2 ]Cl complexes which showed excellent TH activity has appeared. 49 On the other hand, Ru(II) complexes bearing chelating amine ligands such as N-sulfonated 1,2-diamines have been successfully used in the TH of acetophenone by Noyori and others. 50À63 However, in spite of these developments, there is still demand for stable and easily handled complexes prepared from cheap starting materials which make them preferred catalyst precursors. In comparison with the extensive chemistry of sulfonated 1,2-diamines, little research has been performed on pyridylsulfonamide compounds of the type C 5 H 4 NCH 2 NHSO 2 Ar, which are versatile bidentate ligands due to their ease of synthesis and variability of Ar groups. 64À68 Neutral sulfonamide ligands are expected to be poor ligands. Thus, the pyridyl-2-alkylsulfonamides generally coordinate to the metal center through the pyridyl nitrogen atom and the deprotonated nitrogen of the sulfonamide group. 69 However, Soltani et al. have recently shown that cationic Ir complexes containing neutral sulfonamide ligands are active catalysts for the TH of acetophenone derivatives in water. 70 More recently, Baratte and co-workers have shown that Ru(II) complexes containing nonsulfonated (2-aminomethyl)-pyridine ligands display excellent catalytic activity in the TH of ketones. 71 With the aim of contributing to the understanding of how geometric and electronic factors imposed by a combination of mixed tri-and bidentate ligands influence the catalyst performance, herein a series of novel Ru(II) complexes (1À10) were characterized and employed as catalysts for the TH of ketones.

No abstract

No abstract

No abstract

No abstract