245529-71-9Relevant academic research and scientific papers
Novel P-stereogenic PCP pincer-aryl ruthenium(II) complexes and their use in the asymmetric hydrogen transfer reaction of acetophenone
Medici, Serenella,Gagliardo, Marcella,Williams, Scott B.,Chase, Preston A.,Gladiali, Serafino,Lutz, Martin,Spek, Anthony L.,Van Klink, Gerard P.M.,Van Koten, Gerard
, p. 694 - 705 (2007/10/03)
Achiral P-donor pincer-aryl ruthenium complexes ([RuCl(PCP)(PPh 3)]) 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)2C6H 3}(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-(Me2NCH 2)2C6H3}(PPh3)], (3; Scheme 3). The crystal structures of achiral [RuCl(iPr,iPrPCP) (PPh3)] 4c and of chiral (S,S)-[RuCl-(tBu,PhPCP)(PPh 3)] 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.
Carbon-Carbon vs Carbon-Hydrogen Bond Activation by Ruthenium(II) and Platinum(II) in Solution
Van Der Boom, Milko E.,Kraatz, Heinz-Bernhard,Hassner, Lawrence,Ben-David, Yehoshoa,Milstein, David
, p. 3873 - 3884 (2008/10/08)
Reaction of RuCl2(PPh3)3 with the bisphosphine {1,3,5-(CH3)3-2,6-(iPr2PCH 2)2C6H} (1) under 30 psi H2 results in quantitative C-C activation of an Ar-CH3 bond to afford Ru(Cl)-(PPh3){2,6-(iPr2PCH2) 2-3,5-(CH3)2C6H} (2) and CH4, whereas reaction of RuCl2(PPh3)3 with 1 in the presence of NaOtBu results in selective ArCH2-H bond activation to afford the benzylic complex Ru(Cl)(PPh3H{1-CH2-2,6-(iPr2PCH 2)2-3,5-(CH3)2C6H} (7). The identity of the 16-electron complex 2 was confirmed by reaction of the bisphosphine {2,6-(iPr2PCH2)2-3,5-(CH 3)2C6H2} (3), lacking the Ar-CH3 group between the phosphine arms, with RuCl2(PPh3)3. Metal insertion into an Ar-Et bond was observed as well. Follow-up of the reaction of RuHCl-(PPh3)3 with 1 by NMR and deuterium labeling studies reveal that the kinetic products of ArCH2-H bond activation (7 and H2) are irreversibly converted into the thermodynamically more stable products of Ar-C bond activation (2 and CH4) via reversal of the C-H activation process. Reaction of (COD)PtCl2 (COD = cycloocta-1,5-diene) with a stoichiometric amount of 1 at room temperature results in the exclusive formation of the benzylic Pt(II) complex Pt(Cl){1-CH2-2,6-(iPr2PCH2) 2-3,5-(CH3)2C6H} (8) and HCl. The iodide analogue of 8 has been characterized by X-ray analysis. Reaction of 8 with a 10-fold excess of HCl results in selective C-C bond activation to afford Pt(Cl){2,6-(iPr2PCH2)2-3,5-(CH 3)2C6H} (10) and MeCl. The activation parameters for the overall process are ΔH? = 10.6 kcal/mol, ΔS? = -40.1 eu, and ΔG?(298) = 23.1 kcal/mol in a benzene/dioxane solution (5.5:1 v/v) and ΔH? = 2.1 kcal/mol, ΔS? = -65.4 eu, and ΔG?(298) = 21.6 kcal/mol in dioxane.
