Abstract
As part of the quest to develop metal-based redox chemistry beyond the d-block, low oxidation state aluminium complexes have gained wide recognition as discrete and versatile 2-electron reductants. Despite reports of monomeric, dimeric and tetrameric neutral structures, as well as a range of charged aluminyl compounds, neutral trimeric structures have remained notably absent. Furthermore, trimeric nuclearity has previously not been considered when investigating reaction mechanisms. Here, we report two neutral AlI trimers, cyclotrialumanes. The molecules are extensively characterised using both experimental and computational techniques, with the Al–Al bonds described as principally covalent in nature and the trimeric structure shown to be retained in solution. The cyclotrialumanes are highly reactive, activating a range of small molecules and unsaturated substrates (e.g. H2, alkyne, benzene). Most significantly, through a series of extraordinary reactions with ethylene, the cyclotrialumanes are shown to react directly as trimers, forming 5- and 7-membered Al–C ring systems.
Data availability
All processed experimental data generated in this study are provided in the Supplementary Information file. All raw data files are available from the corresponding author upon request. The atomic coordinates generated through computational optimisation are included as a separate Supplementary Data (.txt) file. The X-ray crystallographic coordinates for structures reported in this study have been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition numbers 2469911-2469921 and 2503435. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgements
C.B. thanks the Engineering and Physical Sciences Research Council (grant number EP/Y000129/1) for funding. King’s College London NetZero centre is thanked for studentship funding (M.T.). Jeremy Cockcroft (UCL) and Jens Najorka (NHM) are thanked for helping us access SCXRD. Thomas Hicks and the CBS NMR Facility are thanked for support running NMR spectroscopy experiments. Alberto Collauto (Imperial College London) is thanked for assistance with EPR spectroscopy.
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I.S. and M.d.V.T. designed and conducted experiments and collected and analysed all data. M.T. conducted the computational analysis. L.S.M. supported SCXRD data analysis. T.K. provided computational support and direction and hosted M.T. for a research visit. C.B. conceived the project, acquired funding, supervised the research and wrote the manuscript with input from all authors.
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Squire, I., de Vere-Tucker, M., Tritto, M. et al. A neutral cyclic aluminium (I) trimer. Nat Commun (2026). https://doi.org/10.1038/s41467-026-68432-1
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DOI: https://doi.org/10.1038/s41467-026-68432-1
