Identification of a Heteroleptic Pd<sub>6</sub>L<sub>6</sub>L′<sub>6</sub> Coordination Cage by Screening of a Virtual Combinatorial Library
Sylvain Sudan, Ru‐Jin Li, Suzanne M. Jansze, André Platzek, Robin Rudolf, Guido H. Clever, Farzaneh Fadaei‐Tirani, Rosario Scopelliti, Kay Severin
Abstract
The design of structurally defined heteroleptic coordination cages is a challenging task, and only few examples are known to date. Here we describe a selection approach that allowed the identification of a novel hexanuclear Pd cage containing two types of dipyridyl ligands. A virtual combinatorial library of [PdnL2n](BF4)2n complexes was prepared by mixing six different dipyridyl ligands with substoichiometric amounts of [Pd(CH3CN)4](BF4)2. Analysis of the equilibrated reaction mixture revealed the preferential formation of a heteroleptic [Pd6L6L′6](BF4)12 assembly. The complex was prepared on a preparative scale by a targeted synthesis, and its structure was elucidated by single-crystal X-ray diffraction. It features an unprecedented trigonal-antiprismatic cage structure with two triangular Pd3L3 macrocycles bridged by six L′ ligands. A related but significantly larger [Pd6L6L′6](BF4)12 cage was obtained by using metalloligands instead of organic dipyridyl ligands.