Noble metals such as Pd or Rh are the workhorses of chemical industry due to their ability to engage in substrate coordination and organometallic redox events during catalysis. However, supply and price instability of noble metals pose a tremendous challenge. This has led to a shift towards exploring the realm of main group elements.[1] Within this realm, heavy main group elements present themselves as versatile elements with multiple oxidation states that remain underexplored in the field of redox catalysis.[2]
We have recently introduced a new class of zwitterionic pnictogen compounds stabilized by bis(NHC)borate ligands, enabling the isolation and characterization of Sb and Bi species in oxidation states +1, +2, and +3.[3,4] Computational studies reveal an electronic structure analogous to tetrylones, with unique electronic properties that underpin their stability and reactivity. We demonstrate Sb(I) species engage in key organometallic transformations, including oxidative addition and reductive elimination. These stoichiometric studies on antimony-mediated fundamental organometallic events laid the foundation for the development of two proof-of-concept catalytic cycles based on the Sb(I)/Sb(III) redox couple, expanding the scope of heavy pnictogen redox catalysis beyond the constraints of conventional N,C,N-pincer scaffolds and offering a new approach in main-group catalysis. Additionally, zwitterionic In(II) complexes were isolated and investigated using the same ligand scaffold,[5] revealing promising avenues for the stabilization of elusive In(II) hydride species and highly reactive In(I) analogues. This work highlights the potential of heavier main group elements in redox organometallic chemistry as an alternative to noble metals in synthesis.
[1] (a) P. P. Power, Nature, 2010, 463, 171-177. (b) R. L. Melen, Science, 2019, 363, 479-484.
[2] K. Oberdorf, C. Lichtenberg, Chem. Commun., 2023, 59, 8043-8058.
[3] S. Fernando, Y.-C. Chan, S. Fernandez, E. Sabater, G. Tizzard, S. J. Coles, D. M. Andrada, O. Planas. Angew. Chem. Int. Ed. 2025, 64, e202505697
[4] I. Sanchez-Sordo, S. Fernandez, S. Fernando, D. M. Andrada, O. Planas. Angew. Chem. Int. Ed. 2026, accepted, e6579940.
[5] O. Mouriki, G. Tizzard, S. J. Coles, D. M. Andrada, O. Planas. J. Am. Chem. Soc. 2026, 148, 5783
