72476-44-9Relevant academic research and scientific papers
Pyridyl based ruthenium(II) catalyst precursors and their dihydride analogues as the catalytically active species for the transfer hydrogenation of ketones
Zacharopoulos, Nikolaos,Kolovou, Evgenia,Peppas, Anastasios,Koukoulakis, Konstantinos,Bakeas, Evangelos,Schnakenburg, Gregor,Philippopoulos, Athanassios I.
, p. 27 - 38 (2018/08/09)
In this study we describe the one-pot and high yield synthesis of the ruthenium(II) complex cis-dichloride [RuCl2(PPh3)2(L1)] (L1 = 4-methyl-2-(2′-pyridyl)quinoline) (1). The solid state structure of L1 is described. The catalytic activity of 1 in the transfer hydrogenation of various ketones by 2-propanol at 82 °C, has been studied and compared with the activity of the known catalyst precursors cis-[RuCl2(PPh3)2(L2)] (L2 = 2-(2'-pyridyl)quinoline) (2), cis-[RuCl2(PPh3)2(L3)] (L3 = 2-(2′-pyridyl)quinoxaline) (3) and cis-[RuCl2(PPh3)2(bipy)] (bipy = 2,2′-bipyridine) (4). The ruthenium monohydride complex [RuHCl(PPh3)2(L3)] 3-H (Cl cis to H) was prepared from the reaction of 3 with 2.5 equivalents of a KOiPr solution. Reaction of 3 with 10 equivalents of KOiPr yields the cis-[RuH2(PPh3)2(L3)] (3-H2). Treatment of 1, 2 and 4 with KOiPr (in excess) affords the ruthenium cis-dihydride complexes [RuH2(PPh3)2(L1)] (1-H2), [RuH2(PPh3)2(L2)] (2-H2) and [RuH2(PPh3)2(bipy)] (4-H2). The formation of 1-H2, 2-H2, 3-H2 and 4-H2 is supported by NMR spectroscopic data. The cis-dihydrides 1-H2 to 4-H2 catalyze successfully the transfer hydrogenation of benzophenone to benzhydrol in the absence of a base, suggesting that presumably the active catalyst is a ruthenium dihydride complex (RuH2). Catalyst 1 has been potentially recovered and reused at least four times.
Dynamics of H-atom exchange in stable cis-dihydrogen/hydride complexes of ruthenium(ii) bearing phosphine and N-N bidentate ligands
Bera, Barun,Patil, Yogesh P.,Nethaji, Munirathinam,Jagirdar, Balaji R.
, p. 4726 - 4733 (2014/03/21)
Synthesis and characterization of cis,trans-[RuH(η2-H 2)(PPh3)2(N-N)][OTf] (N-N = 2,2′-bipyridyl (bpy) 1a, 2,2′-bipyrimidine (bpm) 2a; OTf = trifluoromethane sulfonate (CF3SO3)) complexes are reported. The cis-H2/hydride ligands are involved in H-atom site exchange between the two moieties. This dynamics was investigated by variable temperature NMR spectral studies based on which the mechanism of the exchange process was deduced. The ΔG≠ for the exchange of H-atoms between the η2-H2 and hydride ligands was determined to be around 8 and 13 kJ mol-1, respectively, for 1a and 2a. The H-H distances (dHH, A) in complexes 1a and 2a have been calculated from the T1(minimum) and 1J(H,D) and are found to be 1.07 A (slow) and 0.95 A for 1a and 1.04 A (slow) and 0.94 A for 2a, respectively. The molecular structure of 1a was determined by X-ray crystallography.
Chemistry of Ruthenium(II) monohydride and dihydride complexes containing pyridyl donor ligands including catalytic ketone H2-hydrogenation
Abdur-Rashid, Kamaluddin,Abbel, Robert,Hadzovic, Alen,Lough, Alan J.,Morris, Robert H.
, p. 2483 - 2492 (2008/10/09)
In this study we determine the changes to the properties of dihydride catalysts for ketone H2-hydrogenation by successively replacing the amine donors in the known dach complex RuH2(PPh3) 2(dach) (2a), dach = 1,2-(R,R)-diaminocyclohexane, with one pyridyl group in the corresponding 2-(aminomethyl)pyridine (ampy) complexes RuH 2(PPh3)2(ampy) (2b) and with two pyridyl groups in the complexes RuH2(PPh3)2(bipy) (2c) and RuH2(PPh3)2(phen) (2d). The ruthenium monohydride complex, (OC-6-54)-RuHCI(PPh3)2(ampy), (1b with CI trans to H) was prepared by the addition of 1 equiv of ampy to RuHCI(PPh3)3 in THF. Treatment of the monohydride complex with K[BH-(sec-Bu)3] in THF or KOtBu/H2 in toluene resulted in the formation of a mixture of at least two isomers of the highly reactive, air-sensitive ruthenium dihydride complex 2b. One is the cis dihydride (OC-6-14)-2b or more simply c,t-2b with trans PPh3 groups and another is the cis dihydride c,c-2b (OC-6-42) that has PPh3 trans to H and PPh3 trans to N(pyridyl). The isomer c,c-2b slowly converts to c,t-2b in solution. The reaction of 1b with KOtBu under Ar results in the formation of a mixture that includes a complex with an imino ligand HN=CH-2-py while the same reaction under H2 leads to c,c-2b and then c,t-2b. The dach complex c,t-2a, reacts with ampy, 2,2′- bipyridine (bipy), and 1,10-phenanthroline (phen) in refluxing THF to form the substituted cis-dihydride complexes c,t-2b, (OC-6-13)-RuH2(PPh 3)2(bipy) (c,t-2c with trans PPh3 groups) and (OC-6-13)-RuH2(PPh3)2(phen), c,t-2d, respectively, The dihydrides containing amino groups and cis-PPh3 groups, i.e., c,c-2a or c,c-2b, are active precatalysts for the H 2-hydrogenation of acetophenone (neat or in benzene) under mild reaction conditions, whereas those with trans-PPh3 groups, c,t-2a and c,t-2b are much less active. The combination of ampy complex 1b and KO tBu also provides a catalyst in benzene that is more active than the corresponding dach system. The complexes without amino groups c,t-2c and c,t-2d are air-stable and inactive as hydrogenation catalysts under comparable conditions. The mechanism of hydrogenation of ketones catalyzed by isomers of 2a,b is thought to be similar and to proceed via a trans-dihydride complex, t,c-2a or t,c-2b, and an amido complex, neither of which are directly observed for the ampy complexes. The dihydride complex c,t-2b reacts with formic acid to give (OC-6-45)-RuH(OCHO)(PPh3)2(ampy), 3b, with formate trans to hydride. The structures of 1b, c,t-2b, c,t-2c, and 3b have been determined by single-crystal X-ray diffraction.
