Bis-chelate N-heterocyclic tetracarbene Ru(II) complexes: Synthesis, structure, and catalytic activity toward transfer hydrogenation of ketones

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

“…1-Phenylethanol could also be obtained in excellent yields using 0.1 mol % and 0.01 mol % Ru catalysts when the reaction time was extended to 1 and 3 h, respectively (Table 1, entries 3, 7, 11 and 4, 8, 12). At catalyst loadings of 0.01 mol %, TOF of 1 – 3 are 3000, 3233, and 3200 h −1 for transfer hydrogenation of acetophenone which are nearly identical to that of [Ru( Me CC meth ) 2 (CH 3 CN) 2 ](BF 4 ) 2 ( Me CC meth = 1,1'-dimethyl-3,3'-methylene-diimidazol-2,2'-diylidene) [40]. Ruthenium picolyl–NHC complex [( η 5 -C 5 Me 5 )-Ru(L)(CH 3 CN)][PF 6 ] (L = 3-methyl-1-(2-picolyl)imidazol-2-ylidene) is so far one of the most efficient catalyst for transfer hydrogenation of acetophenone which gave 1-phenylethanol in a conversion of 93% with a catalyst loading of 0.1 mol % [20,41].…”

Hirshfeld and DFT analysis of the N-heterocyclic carbene proligand methylenebis(N-butylimidazolium) as the acetonitrile-solvated diiodide salt

“…For the preparation of the methylenebis(N-butylimidazolium) cation, [H 2 BisBuIm] 2+ , several pathways have been reported over the years. A general synthetic description could be as follows: a mixture of 1-butylimidazole and CH 2 X 2 [X = Cl (Lee et al, 2008;Lai et al, 2013;Li et al, 2015), Br (Cheng et al, 2010;Zou et al, 2014;Sun et al, 2015) or I (Poyatos et al, 2003;Quezada et al, 2003Quezada et al, , 2004Yang et al, 2008Yang et al, , 2010Mercs et al, 2011;Sun et al, 2011;Aliaga-Lavrijsen et al, 2015)] was stirred in refluxing nonpolar or polar aprotic solvents until a white solid precipitated. This product was then isolated by filtration and washed, giving high yields in all cases.…”

“…There, the reaction mixture was heated to 358 K (1 d) using sealed containers. The obtained product was precipitated using either Et 2 O (Lee et al, 2008;Lai et al, 2013) or a mixture of MeOH and tetrahydrofuran (Li et al, 2015). Good yields were also obtained by refluxing 1-butylimidazole and CH 2 I 2 in acetonitrile, followed by filtration and purification with Et 2 O (Sun et al, 2015).…”

“…We report here the characterization of the bis(imidazolium) salt methylenebis(N-butylimidazolium) diiodide, [H 2 BisBuIm]I 2 , and its isolation as the crystalline material [H 2 BisBuIm]I 2 Á-CH 3 CN, (I), in combination with a Hirshfeld surface analysis and density functional theory (DFT) calculations. Although the [H 2 BisBuIm] 2+ cation has been frequently utilized, its solid-state structure has not been described previously (see, for example, Poyatos et al, 2003;Quezada et al, 2003Quezada et al, , 2004Jin et al, 2005;Lee et al, 2008;Yang et al, 2008Yang et al, , 2010 Lai et al, 2013;Zou et al, 2014;Aliaga-Lavrijsen et al, 2015;Cebollada et al, 2015;Li et al, 2015;Krü ger et al, 2015;Sun et al, 2015).…”

Transfer hydrogenation of ketones in the presence of half sandwich ruthenium (II) complexes bearing imidazoline and benzimidazole ligand

“…[1][2][3] In transfer hydrogenation, 2-propanol, glycerol, formic acid, and its salts have been employed as the hydrogen source. [4][5][6][7][8] 2-propanol is a popular reactive solvent for the transfer hydrogenation reactions since it is easy to handle and is relatively non-toxic, environmentally benign and inexpensive. [9][10][11] Transition metal catalyzed transfer hydrogenation of ketones and aldehydes have attracted attention for the relatively benign nature of the reagents and mild reaction conditions employed.…”