The search for sustainable alternatives to precious transition metals has driven a paradigm shift toward main group redox catalysis. Among p-block elements, low-valent group 14 compounds, such as tetrylenes and tetryliumylidenes, are particularly attractive because their ambiphilic nature, featuring a lone pair of electrons and a vacant p-orbital, closely mimics the electronic configuration of transition metals. Despite their well-established ability to activate inert bonds in stoichiometric reactions, translating this reactivity into genuine catalytic redox cycles has remained a formidable challenge, primarily due to the often prohibitive reductive elimination from the high-valent state that precludes catalyst turnover.
Over the past three years, Prof. Zhaowen Dong's group at the College of Chemistry, Sichuan University, has focused on the efficient synthesis and functional modulation of low-valent germanium and tin reagents. Through the innovative design of carbodiphosphorane (CDP) and acridine-based PNP pincer ligands, they have successfully stabilized a series of divalent group 14 compounds with tunable redox properties, and pioneered novel main-group catalytic platforms featuring complete E(II)/E(IV) or E(II)/E(III)/E(IV) (E = Ge, Sn) redox cycles (J. Am. Chem. Soc. 2026, 148, 11176; J. Am. Chem. Soc. 2025, 147, 36752; Angew. Chem., Int. Ed. 2026, 65, e7786614; Angew. Chem., Int. Ed. 2025, 64, e202515638; Nat. Commun. 2026, DOI: org/10.1038/s41467-026-74699-1; Nat. Commun. 2024, 15, 9849; JACS Au 2025, 5, 1289; Inorg. Chem. 2026, 65, 2060).
Recently, their Account published in Accounts of Chemical Research systematically summarizes these advances in establishing divalent germanium and tin compounds as a new class of main group redox catalysts. By employing rigid pincer ligands, the group has stabilized a series of Sn(II) and Ge(II) species that exhibit tunable electronic properties and reversible E(II)/E(IV) or E(II)/E(III)/E(IV) redox cycling. These platforms enable a range of catalytic transformations, including hydrodefluorination of C(sp2)–F and C(sp3)–F bonds, chemodivergent reduction of nitroarenes, and transfer hydrogenation of unsaturated N‑containing compounds, with selectivities that can be modulated by varying the central element, reductant, solvent or temperature. Mechanistic studies have uncovered unexpected diversity within this platform: whereas Sn(II) catalysts operate exclusively through two‑electron Sn(II)/Sn(IV) cycles, the lighter germanium congener exhibits a remarkable ability to switch between Ge(II)/Ge(IV) and Ge(II)/Ge(III)/Ge(IV) pathways depending on the substrate. This represents a rare example of a main group catalyst engaging in both one‑electron and two‑electron transfer manifolds.
This work has been published in Acc. Chem. Res. entitled "Main Group Redox Catalysis: New Frontiers with Germanium and Tin" (https://doi.org/10.1021/acs.accounts.6c00386). Prof. Zhaowen Dong is the corresponding author, and Ph.D. candidate Zhuchunguang Liu is the first authors. This work was financially supported by the National Natural Science Foundation of China, the National Key R&D Program of China, the Fundamental Research Funds for the Central Universities, the Sichuan Science and Technology Program, and the Institutional Research Fund from Sichuan University.
