Theoretical interpretation of the role of the ionic liquid phase in the (R)-Ru-BINAP catalyzed hydrogenation of methylacetoacetate

Abstract

Recently, the work focusing on the role of alkyl chain length in the N[R,222][Tf2N] ionic liquids and its reflection in the kinetic parameters of stereoselective hydrogenation of methylacetoacetate over (R)-[RuCl(binap)(p-cymene)]Cl complex was reported. Irregular trends in the principle parameter of enantioselectivity were observed. Here, a possible theoretical explanation of such irregular trends elucidated with the help of molecular simulations methods is presented. A stepwise approach is proposed for evaluating the energetically most stable conformers of a series of individual N[R,222][Tf2N] for the interpretation of selectivity-structure effects observed experimentally. Initially, Monte Carlo molecular mechanics was used followed by a semi-empirical PM3 method to elucidate also the characteristic thermodynamic functions of state and theoretical molecular spectra. The density functional theory was finally applied. The specific absolute entropy data revealed that due to the partition of the cation and anion twisted closer approach the ionic liquids N[8,222][Tf2N] and N[12,222][Tf2N] may stabilize the structures of the (R)-[RuCl(binap)(p-cymene)]Cl complex.