The Insertion of Ruthenium into Porphyrins Revisited and Improved: Proof of Concept Results with a Ruthenium(II) Monocarbonyl Compound, and the Spectacular Effect of Propionic Acid

This contribution, that readdresses the insertion of the Ru(II)–CO fragment into model porphyrins (i.e. ruthenation), has a Janus character, with one speculative and one practical side. As a proof of concept we demonstrate that ruthenation of a porphyrin can be performed under relatively mild conditions using the Ru(II) monocarbonyl complex [Ru(CO)(dmso)5][PF6]2 that – besides CO – features exclusively labile dmso ligands. Even though this finding might seem trivial, it is only the second example that uses a Ru(II) carbonyl for porphyrin ruthenation, the first one having been reported almost 50 years ago and then neglected. From a practical point of view, we show the spectacular effect of propionic acid as solvent for performing the ruthenation of neutral and anionic model porphyrins with Ru3(CO)12 (1). This process turned out to be extremely efficient and advantageous in terms of both reaction rates and yields (e.g. 100% ruthenation of TPP in 30 min at 140°C) compared to the procedures described in the literature.