New mono- and tricyclopalladated dendritic systems with encapsulated catalytic sites

The preparation of a series of new macrocyclic carbodiazasilane molecules functionalized with the monoanionic [2,6-(CH2NMe2)2C6H3](-)[triple bond]N,C,N-pincer ligand has been accomplished. Palladation of these systems was possible through oxidative addition with [Pd(dba)2] affording exclusive formation of the meso diastereoisomer. The X-ray crystal structures of these novel ligands and of the palladium(II) complex 10 were determined and confirmed the stereochemistry of the organopalladium cage. Attachment of the para-OH functionalized carbodiazasilane macrocycle 16 to a central core led to the formation of the dendritic structure 18 which was palladated to afford the novel multimetallic dendritic system with encapsulated catalytic sites 1. This cyclopalladated carbosilane dendrimer (1) as well as the mononuclear organopalladium cage 10 can be conveniently converted into active Lewis acid catalysts for the aldol condensation reaction. The catalytic data showed higher reaction rates for the dendritic structure than for the corresponding mononuclear systems.