Ru(II)Porphyrinate-Based Molecular Nanoreactor with Unusual Coordinative Properties and Extraordinary Chemical Selectivity in N–H Bond Carbene Insertion Reactions

A 5,15-bis(1,1’-biphenyl)porphyrin-based molecular clip covalently-linked to a stiff phenanthrene appended moiety yields a porphyrin-based macrocycle with a well-defined and relatively small cavity in the solid-state and in solution. Introduction of a Ru(II) ion into the porphyrin moiety followed by axial coordination of the inert and bulky diphenylcarbene ligand exo-to the macrocycle’s cavity affords a Ru(II)porphyrinate-based macrocycle able to promote the active-metal template [2]rotaxane synthesis in quantitative yield through the challenging single N–H bond carbenoid insertion. A detailed structural investigation of the Ru(II)porphyrinate-based macrocycle and the resulting asymmetrical [2]rotaxanes reveals that the synergy between the steric shielding provided by the hollow macrocyclic structure and the kinetic stabilization of otherwise labile coordinative bonds, warranted by the mechanical bond, can be used as principles for the design of molecular nanoreactors.