Rhodium(III) complexes of N-{2-(arylseleno/telluro)ethyl} morpholine: Synthesis, structure and applications as efficient catalyst for transfer hydrogenation reaction of ketones

Abstract

N-{2-(Arylseleno/telluro)ethyl}morpholine ( L1 / L2 ) synthesized by reacting PhSe − /ArTe − (generated insitu) with (2-chloroethyl)morpholine hydrochloride, reacts with RhCl 3 ·3H 2 O resulting in complexes [RhCl 2 ( L1 / L2 ) 4 ][ClO 4 ] ( 1 / 2 ). 1 H, 13 C{ 1 H} and 77 Se{ 1 H}/ 125 Te{ 1 H} NMR spectra of L1 , L2 , 1 and 2 were found characteristic. The single crystal structure of 2 has been solved. The L2 binds with Rh in 2 as a monodentate ligand. The geometry around Rh is distorted octahedral. The Rh–Te distances are in the range 2.6509(9)–2.6688(8) Ǻ. Both the complexes efficiently catalyze transfer hydrogenation reaction of acetophenone (TON/TOF up to 9.9 × 10 4 /9.9 × 10 3 h − 1 ) and benzophenone (TON up to 9.8 × 10 4 and TOF up to 9.8 × 10 3 h − 1 ). N-{2-(arylseleno/telluro)ethyl}morpholine ( L1 / L2 ) and complexes [Rh(III)Cl 2 ( L1 / L2 ) 4 ][ClO 4 ] ( 1 / 2 ) have been synthesized and characterized with 1 H, 13 C{ 1 H} and 77 Se{ 1 H}/ 125 Te{ 1 H} NMR spectra. The 2 has trans structure and octahedral geometry around Rh. constituted by four Te and two Cl. The 1 and 2 show good catalytic activity for transfer hydrogenation reaction of acetophenone and benzophenone (TON/TOF ≤ 9.9 × 10 4 /9.9 × 10 3 h − 1 ).