Arene C–H insertion catalyzed by ferrocene covalently heterogenized on graphene acid

The heterogenation of molecular catalysts on solid supports is a viable route for the preparation of hybrid materials that combine the high selectivity and activity of homogeneous active species with the enhanced stability and recyclability imparted by the heterogeneous nature of the support. In this work we describe the covalent functionalization with ferrocene (Fc) of two graphene derivatives: graphene acid (GA), a graphene layer whose basal plane is modified with COOH groups, and graphene oxide (GO). The surface modification is performed exploiting the carbodiimide chemistry, which allows introducing up to 3.6% at. of iron in the GA-based material. Compared to GO, GA owns a superior functionalization degree, which is attributed to its controlled surface chemistry. Both Fc-modified materials are tested as catalysts in the C–H insertion of diazonium salts employing arene substrates. The materials are active, versatile and recyclable catalysts that show a catalytic performance comparable to or even better than molecular Fc, together with a 100% recyclability which does not alter the catalytic performance. The GA-based hybrid catalyst results more active than that based on GO due to the presence of more extended aromatic domains that facilitate the adsorption of the reagents close to the active sites.