A new periodic mesoporous organosilica containing diimine-phloroglucinol, Pd(ii)-grafting and its excellent catalytic activity and trans-selectivity in C–C coupling reactions

Abstract

A new organosilane precursor has been designed via Vilsmeier–Haack formylation of phloroglucinol followed by its Schiff base condensation with 3-aminopropyl-triethoxysilane (APTES). A novel organic–inorganic hybrid periodic mesoporous organosilica (PMO) LHMS-3 containing the highly coordinating bis(propyliminomethyl)-phloroglucinol moiety inside the pore wall has been synthesized by using this precursor organosilane molecule. Phenolic-OH and imine-N donor sites present in this PMO material have been utilized to anchor Pd(II) species at the surface of the mesopores. Small angle neutron scattering, XRD, HR TEM, SEM, ¹³C and ²⁹Si solid state MAS NMR, UV-vis and FT IR spectroscopic tools are utilized to characterize the 2D-hexagonal mesophase and the presence of the bis(propyliminomethyl)-phloroglucinol moiety inside the pore wall. This Pd-anchored material Pd-LHMS-3 showed excellent catalytic activity and trans-selectivity in Heck C–C bond formation reactions for the synthesis of a series of value-added aromatic and aliphatic olefins.