Heterogenised Rh(I), Ir(I) metal complexes with chiral triaza donor ligands: a cooperative effect between support and complex

Abstract

Rhodium and iridium complexes of the chiral triaza ligands, { N, N ′-bis{[(2 S)-(1-benzylpyrrolidinyl)]methyl}amine ( 2), N, N ′-bis{[(2 S)-(1-benzylpyrrolidinyl)]methyl}-N-propylamine ( 3), N, N ′-bis{[(2 S)-(1-benzylpyrrolidinyl)]methyl}-N-[3-(triethoxysilyl)propyl]amine ( 4)}, are described. All ligands form one to one [ML] species with the above metal ions. The structures of these complexes were elucidated by analytical and spectroscopic data (elemental analysis, mass spectroscopy, IR, 1H and 13C NMR). The fixation of the preformed triethoxysilyl-rhodium and iridium complexes, on mesoporous solids (MCM-41, SBA-15), and their use, under heterogeneous conditions, for the hydrogenation reactions are reported. The catalytic activity and selectivity of heterogenised complexes are higher to that observed under homogeneous conditions, as a consequence of the complex- and/or reagents-to-support interaction. The stable covalent bond between support and complex allows the recovery and recycling of the heterogenised catalysts for a number of cycles, moreover atomic absorption analysis of the reaction solutions shows that there is not any metal leaching into the solutions.