Carbon Nitride as a Ligand: Selective Hydrogenation of Terminal Alkenes Using [(η⁵ -C₅ Me₅ )IrCl(g-C₃ N₄ -κ² N,N')]Cl

Anchoring a homogeneous catalyst onto a heterogeneous support facilitates separation of the product from the catalyst, and catalyst-substrate interactions can also modify reactivity. Herein we describe the synthesis of composite materials comprising carbon nitride (g-C₃ N₄ ) as the heterogeneous support and the well-established homogeneous catalyst moiety [Cp*IrCl]⁺ (where Cp*=η⁵ -C₅ Me₅ ), commonly used for catalytic hydrogenation. Coordination of [Cp*IrCl]⁺ to g-C₃ N₄ occurs directly at exposed edge sites with a κ² N,N' binding motif, leading to a primary inner coordination sphere analogous to known homogeneous complexes of the general class [Cp*IrCl(NN-κ² N,N')]⁺ (where N,N'=a bidentate nitrogen ligand). Hydrogenation of unsaturated substrates using the composite catalyst is selective for terminal alkenes, which is attributed to the restricted steric environment of the outer coordination sphere at the edge-sites of g-C₃ N₄ .