Tuning the Porphyrin Building Block in Self-Assembled Cages for Branched-Selective Hydroformylation of Propene

In this study unprecedented regio-selectivity to the branched aldehyde product in hydroformylation of propene is attained upon embedding a rhodium complex in a supramolecular assembly, L2, formed by coordination-driven self-assembly of tris-(meta-pyridyl)-phosphine and zinc(II) porpholactones. The design of the new capsule is based on the ligand-template approach, in which the ligand acts as a template for the capsule formation. Previously we have reported the first generation capsule L1, in which zinc(II) porphyrin units were utilized instead of porpholactones. Binding studies demonstrate that the association constant for the formation of the second generation capsule L2 is nearly an order of magnitude higher than for L1. This strengthened binding keeps the new capsule L2 intact in polar and industrially interesting solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be retained in polar and coordinating solvents when using the second-generation assembly.