Conformational studies of ligand-template assemblies and the consequences for encapsulation of rhodium complexes and hydroformylation catalysis

The second coordination sphere around a transition metal catalyst can contribute to the activity and selectivity that it displays. In this paper we present encapsulated catalysts using a template-ligand assembly strategy based on Zn(II)salphen building blocks, and show that these have significantly different properties in catalysis than previously reported Zn(II)porphyrin-based analogues. The conformational properties of tris-Zn(II)salphen-based capsular catalysts were examined by a combination of solid state and solution phase analytical methods, as well as computational techniques. We found that as a result of the ability of the salphen-based capsules to adopt different conformations compared to porphyrin-based capsules, less stringent constraints are enforced to the catalytic centre, resulting in different catalyst selectivities displayed by the rhodium complexes enclosed.