New Heterogenized Gold(I)‐Heterocyclic Carbene Complexes as Reusable Catalysts in Hydrogenation and Cross‐Coupling Reactions

Abstract

Abstract:Mononuclear unsymmetrical N-heterocyclic carbene-gold complexes and the corresponding solid catalysts in which a gold-carbene complex has been immobilized on silica gel, ordered mesoporous silica (MCM-41), and delaminated zeolite (ITQ-2) have been prepared. These new catalysts have been tested in the hydrogenation of alkenes and the Suzuki cross-coupling reaction to afford selectively non-symmetrical biaryls. These reactions were studied with the soluble as well as with the heterogenized counterpart catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs up to 400 h À1. Moreover, the heterogenized complexes were reused and no deactivation of the catalysts can be observed.

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…Corma et al [227] prepared Au/MCM-41 (loading of 0.20-30 mmol-Au/g support) using a gold-carbene complex [(carbene)AuCl] as Au precursor. The resulting catalysts were active for the hydrogenation of alkenes and the Suzuki cross-coupling reaction between halobenzene and arylboronic acids.…”

Layered zeolitic materials: an approach to designing versatile functional solids

“…144 Interestingly, mononuclear NHC carbine-gold complexes were also covalently grafted on delaminated ITQ-2 zeolite for hydrogenation of alkenes and for Suzuki cross-coupling reaction, yielding selectively non-symmetrical biaryls. 145 Related with this last approach, Au(I) and Pd(II) complexes were heterogenized onto ITQ-2, obtaining effective catalysts for Sonogashira cross-coupling reactions between iodobenzene and arylboronic acids or alkynes. 146 Stabilized enzymes were also covalently supported onto MWW layers which are forming ITQ-2 zeolites, generating novel biocatalysts.…”

One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

“…In most of the cases, the steps required are: a) synthesis of the layered inorganic precursor; b) swelling and pillarization of starting layered precursors; c) extraction and post-functionalization processes. 28,29,30,31 As can be seen, the multi-step synthesis method involves a long route that, on top, requires recovery and isolation of intermediate lamellar hybrid solids. Moreover, it is difficult to avoid an inhomogeneous distribution of organic pillars located in the interlayer space, which could be a problem during the catalytic reactions.…”