The preparation of chiral metal complexes and, specifically, chiral at metal complexes, is a highly sought after goal in current organometallic chemistry due to its relevance in enantioselective metal-mediated processes.¹.

Despite the wealth of metal-fullererene hybrids reported to date, only a few are optically actives.² To the best of our knowledge, only a single case presents a stereogenic metal center,³ while in all of them the chiral information stems from the stoichiometric use of other chiral ligands.⁴ In this regard, the use of asymmetric organo- and metal-catalysis in fullerene chemistry has provided an easy access to optically active derivatives through a precise stereocontrol in the newly formed asymmetric carbon atoms.⁵ Conversely, the control of the metal-centered chirality is not a trivial issue due to the configurational lability of the metals that often undergo rapid ligands exchange.¹

In this communication, we report the first enantioselective synthesis of fullerene hybrids endowed with a stable stereogenic metal center whose configuration can be defined at will by the proper chiral catalyst choice. In these reactions, iridium, rhodium and ruthenium pyrrolidino[3,4:1,2][60]fullerene half-sandwich complexes with four new stereocenters are formed, namely the two C-2 and C-5 chiral car bons at the pyrrolidine ring, the asymmetric nitrogen atom and the transition metal center (Scheme). The suitable functionalization and stereochemistry of the chiral fullerene ligand determine the final configuration of the metal center. Interestingly, the chiral metal center does not undergo any epimerization process as evidenced by temperature dependent NMR analysis as well as by DFT theoretical calculations.⁶

References

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6. J. Marco-Martínez, S. Vidal, I. Fernández, S. Filippone, N. Martín, Angew. Chem. Int. Ed., 2017, accepted for publication.