Transfer hydrogenation reaction using novel ionic liquid based Rh(I) and Ir(III)-phosphinite complexes as catalyst.

Hydrogen transfer reduction methods are attracting increasing interest from synthetic chemists in view of their operational simplicity. Thus, interaction of [Rh(μ-Cl)(cod)] 2 and Ir(η 5 -C 5 Me 5 )(μ-Cl)Cl] 2 with phosphinite ligand [(Ph 2 PO)-C 7 H 11 N 2 Cl]Cl, 1 gave new monodendate (1-chloro-3-(3-methylimidazolidin-1-yl)propan-2-yl diphenylphosphinite chloride) (chloro ɳ 4 -1,5-cyclooctadiene rhodium(I))], 2 and (1-chloro-3-(3-methylimidazolidin-1-yl)propan-2-yl diphenylphosphinite chloride) (dichloro ɳ 5 -pentamethylcyclopentadienyl iridium(III))], 3 complexes, which were characterized by a combination of multinuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. 1 H-{ 31 P} NMR, 1 H- 13 C HETCOR or 1 H- 1 H COSY correlation experiments were used to confirm the spectral assignments. The novel catalysts were applied to transfer hydrogenation of acetophenone derivatives using 2-propanol as a hydrogen source. The results showed that the corresponding alcohols could be obtained with high activity (up to 99%) under mild conditions. Notably, (1-chloro-3-(3-methylimidazolidin-1-yl)propan-2-yl diphenylphosphinite chloride) (chloro ɳ 4 -1,5-cyclooctadiene rhodium(I))], 2 complex is much more active than the other analogous complex, 3 in the transfer hydrogenation. Furthermore, compound, 2 acts as excellent catalysts, giving the corresponding alcohols in 97–99% conversions in 5 min (TOF ≤ 1176 h −1 ). [ABSTRACT FROM AUTHOR]