Mesoporous Metal Complex–Silica Aerogels for Environmentally Friendly Amination of Allylic Alcohols

Two series of mesoporous hybrid iron(III) complex–silica aerogels were prepared in one-pot synthesis by using the sol–gel coordination chemistry approach. The use of the ligands 3-(2-aminoethylamino)propyltrimethoxysilane and 2-(diphenylphosphino)ethyltriethoxysilane, both with terminal triethoxysilyl groups, were used to incorporate metal complexes in situ into the framework of silica, through their co-condensation with a silicon alkoxide during the aerogel formation. This methodology yielded optically translucent hybrid mesoporous gels with homogeneous metal incorporation and excellent textural properties. The catalytic performance of these materials was tested in the direct amination of allylic alcohols in water as a target reaction, with activities comparable or even higher than those corresponding to the homogeneous iron(III) complex. Furthermore, these catalysts were stable and maintained their catalytic activity after six reaction cycles.

We thank the Spanish MICINN (project CTQ2011-28954-C02-01) and the University of Alicante (project VIGROB-194) for financial support. E.S. would like to thank UA (project GRE-39) and GV (project GV/2014/093). A.B. would like to thank MICINN for a Juan de la Cierva contract (JCI-2009-03710) and the University of Alicante (project GRE12-03).