Three-dimensional cubic mesoporous materials with a built-in N-heterocyclic carbene for Suzuki–Miyaura coupling of aryl chlorides and C(sp 3)-chlorides

Abstract

New cubic cage-like mesoporous materials with a bulky N-heterocyclic carbene [IPr, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] precursor in the framework were synthesized by a co-condensation of IPr precursor-bridged organosilane and TEOS in the presence of template. N 2 sorption, XRD and TEM characterizations revealed that the mesostructural orderings of the synthesized materials depended on the molar fraction of the bridged organosilane in the initial gel mixture. With the increase in the molar fraction of the organosilane from 2.5% to 15%, the mesostructure of the synthesized material changed from a well-ordered 3D ordered structure to a amorphous structure. FT-IR and solid-state NMR characterizations confirmed that IPr carbene precursor was covalently integrated with the solid materials. Such hybrid materials were able to coordinate Pd(acac) 2, leading to active solid catalysts for Suzuki–Miyaura couplings of less reactive aryl chlorides. The solid catalyst could be reused 8 times without a significant decrease in activity. Furthermore, the solid catalyst was active for the coupling of C(sp 3)-chlorides and arylboronic acids.