Diastereoselectivity and catalytic activity in ruthenium complexes chiral at the metal centre Daniele S. Zerla, Isabella Rimoldi, Edoardo Cesarotti, Giorgio Facchetti, Michela Pellizzoni, Marco Fus  e * DISFARM, Sezione di Chimica Generale ed Organica “A. Marchesini”, Universit a degli Studi di Milano, via Venezian 21, 20133 Milano, Italy article info Article history: Received 29 March 2014 Received in revised form 17 June 2014 Accepted 18 June 2014 Available online xxx Keywords: Ruthenium Metal chirality ATH 8-Amino-5,6,7,8-tetrahydroquinoline abstract Cis-RuCl 2 (diphosphine)(CAMPY) complexes, chiral at the metal centre with matching or mismatching chiralities between diphosphine and CAMPY were prepared and the configuration at the metal was determined in solution by a complete set of NMR investigations; CAMPY is (R)-() or (S)-(þ)-8-amino- 5,6,7,8-tetrahydroquinoline. The complexes were used in ATH reactions of different aryl ketones with 2- propanol as hydrogen source. The effects of the chirality at the metal were studied and enantiomeric excesses up to 99% were obtained. © 2014 Elsevier B.V. All rights reserved. Introduction The enantioselective reduction of C]O double bonds is a key synthetic transformation proved as fundamental for the preparation of fine chemicals [1,2], mainly drugs, fragrances and insecticides [3e7]; the reaction has been largely reviewed and a huge bibliog- raphy exists. The ketones' reduction can be realized by asymmetric transfer hydrogenation (ATH) based on the use of hydrogen donors, usually secondary alcohols or formic acid, or with molecular H 2 as reducing agent (asymmetric hydrogenation, AH) [8e10]. The most outstanding results have been obtained by Noyori's group who discovered and developed the catalyst [RuCl 2 (dipho- spine)(diamine)] [11] in which the ruthenium complexes in trans geometry [12,13]. The action mechanism of these catalysts has been studied in details and elucidated by several research groups, first of all by Noyori's one [14,15] and deeply in all its aspects by Morris's one [16e18]. Metal-catalysed hydrogenation of ketones and imines [19] has a great attraction because it replaces the use of stoichiometric hy- drides, usually difficult to handle and with amounts of basic by- products to be disposed off; one of the few counter-indications of this technique is the high pressure vessels necessary. On the contrary ATH is simpler and it avoids handling H 2 gas. The ATH has been studied in details and a great number of catalytic systems have been developed; the most advanced and used are those based on h 6 -arene Ru bis-amido and on h 6 -arene Ru H aminoamido; these complexes are devoid of phosphine ligands and the chiral information is located on an aminoalcohol or a diamine [8,20]. The very active catalysts generated by the addition of diamines to RuCl 2 phosphines in 2-propanol in presence of a base have been essentially studied as hydrogenation catalysts but they have received less attention as catalysts for ATH [21]. An improvement in ATH with this type of complexes was real- ized by Rigo using cis-Ru(II) complexes, [RuCl 2 (PP)(NN)] [22,23], where NN is the 2-(aminomethyl)pyridine. Many strategies have been developed to increase the level of enantioselectivity, partic- ularly by exploring the matching combination between two different chiral ligands but when complexes are in a cis arrange- ment the role of the chirality at the metal centre must be taken in consideration. Experimental General considerations Commercially reagent grade solvents were dried according to standard procedure and freshly distilled under nitrogen before * Corresponding author. Tel.: þ39 (02)50314367. E-mail addresses: marco.fuse@unimi.it, fuse.marco@gmail.com (M. Fus e). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem http://dx.doi.org/10.1016/j.jorganchem.2014.06.016 0022-328X/© 2014 Elsevier B.V. All rights reserved. Journal of Organometallic Chemistry xxx (2014) 1e7 Please cite this article in press as: D.S. Zerla, et al., Journal of Organometallic Chemistry (2014), http://dx.doi.org/10.1016/ j.jorganchem.2014.06.016