Confinement of Metal–N‐Heterocyclic Carbene Complexes to Control Reactivity in Catalytic Reactions

: Confinement of a metal complex is a promising way to induce reactivity modulation and selectivity. Combining this principle with the properties of N-heterocyclic carbenes (NHC) used as ligands is therefore of great interest. NHCs metal complexes have been encapsulated in polymeric structures (metal-organic frameworks, metal organic polymers and porous organic polymers), and in molecular containers (capsules, cages or cavitands). This confinement induced reactivity change, on and off switching of reactions, substrate selection, stereoselectivity, regioselectivity, and product distribution variation. The syntheses and the influence of confinement on reactivity will be discussed in this Minireview.