Abstract Viewer

Medici, S.; Gagliardo, M., Williams, S. B.; Chase, P. A.; Gladiali, S.; Lutz, M; Spek, A. L.; van Klink, G. P. M.; van Koten, G. 2005. Novel P-Stereogenic PCP Pincer-Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone. Helv. Chim. Acta 88: 694 - 705. Full Article

Achiral P-donor pincer-aryl ruthenium complexes ([RuCl(PCP)(PPh3)]) 4c,d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3-phenylenebis(methylene)]bis[diisopropylphosphine] (2c) or [1,3-phenylenebis(methylene)]bis[diphenylphosphine] (2d) and the N-donor pincer-aryl complex [RuCl{2,6-(Me2NCH2)2C6H3}(PPh3)], (3; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P-donor pincer-aryl ruthenium complexes [RuCl(P*CP*)(PPh3)] 4a,b by reacting P-stereogenic pincer-arenes (S,S)-[1,3-phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a,b (alkyl=iPr or tBu, P*CHP*) and the complex [RuCl{2,6-(Me2NCH2)2C6H3}(PPh3)], (3; Scheme 3). The crystal structures of achiral [RuCl(iPr,iPrPCP)(PPh3)] 4c and of chiral (S,S)-[RuCl(tBu,PhPCP)(PPh3)] 4a were determined by X-ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh3)] complexes and chiral [RuCl(P*CP*)(PPh3)] complexes were tested as catalyst in the H-transfer reduction of acetophenone with propan-2-ol. With the chiral complexes, a modest enantioselectivity was obtained.

Close This Window