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Turkish Journal of Chemistry

DOI

10.3906/kim-1604-62

Abstract

A series of unsymmetrical imidazolinium bromides (3a-d) bearing naphthyl and benzyl groups (R' = CH$_{2}$C$_{6}$H$_{2}$(CH$_{3})_{3}$-2,4,6 (a); CH$_{2}$C$_{6}$H(CH$_{3})_{4}$-2,3,5,6 (b); CH$_{2}$C$_{6}$(CH$_{3})_{5}$ (c); CH$_{2}$C$_{6}$F$_{5\, }$(d)) at the N$^{1}$ and N$^{3}$ positions were successfully synthesized. [RuCl$_{2}$(NHC)($p$-cymene)] (NHC= N-heterocyclic carbene) complexes (4a-d) were prepared by the reaction of [RuCl$_{2}(p$-cymene)]$_{2}$ with imidazolinium salts (3a-d). The new salts (3a-d) and their ruthenium(II) complexes (4a-d) were characterized by $^{1}$H, $^{13}$C, $^{19}$F NMR, and elemental analysis. The ruthenium(II) complexes (4a-d) were employed as catalysts for the transfer hydrogenation (TH) of ketones in the presence of KOH using 2-propanol as a hydrogen source and the results were compared. The best results in the transfer hydrogenation of ketones were obtained with 4b. [MCl(NHC)L] (M = Ir, L = Cp$^{\ast })$ (5b), cod (6b); M = Rh, L= Cp$^{\ast}$ (5b'), and cod (6b') complexes were prepared and investigated in the TH of ketones. The reactivity of Rh complexes in comparison to those of Ir also appears to be somewhat better. The catalysis appears to be homogeneous.

Keywords

Arene ruthenium(II) complexes, N-heterocyclic carbene, transfer hydrogenation, naphthyl substituent

First Page

29

Last Page

39

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