Symmetrically bridged bis-N-heterocyclic carbene rhodium (I) complexes and their catalytic application for transfer hydrogenation reaction

Symmetric and dissymmetric N‐heterocyclic carbene rhodium(I) complexes: a comparative study of their catalytic activities in transfer hydrogenation reaction

“…The characteristic downfield signals for the NC H N + protons of the imidazol(in)ium salts disappeared in the 1 H NMR spectra of complexes 4a , 4b , 5a , 5b , 6a , 6b . These complexes exhibit 13 C chemical shifts and coupling constants that are comparable to those of other reported NHC–rhodium(I) complexes . 13 C chemical shifts showed that C carbene is substantially deshielded.…”

Strong Solvent Effects on Catalytic Transfer Hydrogenation of Ketones with [Ir(cod)(NHC)(PR3)] Catalysts in 2-Propanol-Water Mixtures

“…The structures of the catalysts together with their numbering scheme are shown in Figure 1. (11) and Ir(2)-C(29) 2.043(10); C(9)=C(10) 1.306 (18) (15); Ir(1)-C(9)-Cl(1) 89.18 (16). (11) and Ir(2)-C(29) 2.043(10); C(9)=C(10) 1.306 (18) and C(30)=C(31) 1.297 (19); Ir(1)-Cl(1) 2.181 (11) and Ir(2)-Cl(2) 2.349(3); Ir(1)-C(9)-Cl(1) 89.2(3) and Ir(2)-C(29)-Cl(2) 88.4(3).…”

“…An important advantage of transfer hydrogenations over reductions with H 2 is in the use of an H-donor which is usually a liquid and much less flammable than gaseous H 2 . No wonder, that transfer hydrogenation has a long and fruitful history, and complexes of several transition metals, such as those of Ru [1][2][3][4][5][6][7][8][9][10][11][12][13], Rh [14][15][16] and Ir [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], and many others have been used to catalyse hydrogen transfer reductions. The various aspects of transfer hydrogenation are covered by several excellent reviews [1][2][3][4][20][21][22]35].…”

Catalytic racemization of secondary alcohols with new (arene)Ru(II)-NHC and (arene)Ru(II)-NHC-tertiary phosphine complexes

“…First examples of such complexes were described by Öfele [1], and Wanzlik and Schönherr [2] already in 1968, and since then N-heterocyclic carbene complexes have been applied in almost all fields of chemistry and biochemistry [3][4][5][6]. Herrmann [7][8][9][10][11], Kühn [8][9][10], Nolan [3,6,[12][13][14][15][16], Glorius [17,18], and Perís [19,20] -among others-have been instrumental in developing this area of homogeneous catalysis. Hydrogenation [9,18,21], transfer hydrogenation [8,22], redox isomerization [23], hydrodehalogenation [24,25], hydroformylation [7,11,26] and various C-C coupling reactions [27,28] were frequent targets of investigations and could be carried out with high yields under mild conditions.…”