A series of capped metallo-cyclodextrins were synthesized, affording a variety of artificial chiral metallo-pockets through modulation of the space around the metal. Carbene ligands were used as caps for placing a silver, gold, or copper center at a well-defined location inside the cyclodextrin cavity. Multiple weak interactions involving the d 10 metal center and intra-cavity hydrogen atoms, including anagostic interactions, were observed in solution. Thus, the metal was used as a probe for assessing intra-cavity metal-H distances for building 3D models, revealing the very different shapes of capped a-, band nd g-cyclodextrins and the helical shape of the chiral pocket of some modified cyclodextrins. This series of N-heterocyclic-carbene-based cyclodextrins were compared in gold-catalyzed cycloisomerization reactions, for which the 3D models were used to rationalize the observed regio-and stereoselectivities.

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The encapsulation of copper inside ac yclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catcht he elusive monomeric (L)CuH and ac avity-controlled chemoselective copper-catalyzed hydrosilylation of a,b-unsaturated ketones.R emarkably,( a-ICyD)CuCl promoted the 1,2-addition exclusively,w hile (b-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the sizeo ft he cavity and weak interactions between the substrate and internal C À Hb onds of the cyclodextrin.