Abstract
Molecular species containing multiple bonds to aluminium have long been challenging synthetic targets. Despite recent landmark discoveries in this area, heterodinuclear Al–E multiple bonds (where E is a group-14 element) have remained rare and limited to highly polarized π-interactions (Al=E ↔ +Al–E–). Here we report the isolation of three alumanyl silanide anions that feature an Al–Si core stabilized by bulky substituents and a Si–Na interaction. Single-crystal X-ray diffraction studies, spectroscopic analysis and density functional theory calculations show that the Al–Si interaction possesses partial double bond character. Preliminary reactivity studies support this description of the compounds through two resonance structures: one that displays a predominant nucleophilic character of the sodium-coordinated silicon centre in the Al–Si core, as shown by silanide-like reactivity towards halosilane electrophiles and the CH-insertion of phenylacetylene. Moreover, we report an alumanyl silanide with a sequestered sodium cation. Cleavage of the Si–Na bond by [2.2.2]cryptand increases the double bond character of the Al–Si core to produce an anion with high aluminata-silene (–Al=Si) character.
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Data availability
All data generated or analysed during this study are included in this published Article and its Supplementary Information files. The structures of compounds 2·IMes, 3·NMe3, 4·NMe3, 5·Na·(15-c-5), 5·Na·IiPr, Na·crypt[5], Na·(DME)3[6] and 7 were determined by single-crystal XRD. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2170414 (2·IMes), 2170415 (3·NMe3), 2170416 (4·NMe3), 2170417 (5·Na·(15-c-5)), 2170418 (5·Na·IiPr), 2170419 (Na·crypt[5]), 2170420 (Na·(DME)3[6]) and 2170421 (7). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. The Cartesian coordinates of all optimized and calculated structures as well as electronic energies are summarized in the supplementary document ‘calculated structures.txt’. The files comprise all necessary data for reproducing the values. All non-default parameters for the computational studies are given in the Supplementary Information together with the corresponding references of the methods used. Further details are provided in the Supplementary Information.
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Acknowledgements
We acknowledge K. Kollmannsberger (R. A. Fischer) for the IR measurements. We thank R. Ebner for assistance with initial reactivity studies and M. Roy for proofreading. A.E.F. thanks the Servicio de Cálculo Científico at the University of Murcia for technical support and computational resources used. The authors are grateful to the European Research Council (ALLOWE101001591) for financial support. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
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M.L. and D.F. conceived and performed the synthetic experiments and analysed the data. A.E.F. designed and performed the theoretical analyses. M.B. and F.H. solved and revised the XRD data. S.I. conceived and supervised the project. M.L., D.F. and S.I. wrote the manuscript with input and critical revision from all authors.
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Supplementary information
Supplementary Information
Supplementary Figs. 1–69, Tables 1–6, synthetic procedures for all compounds, crystallographic and computational details.
Supplementary Data 1
Crystallographic data for compound 2·IMes, CCDC 2170414.
Supplementary Data 2
Crystallographic data for compound 3·NMe3, CCDC 2170415.
Supplementary Data 3
Crystallographic data for compound 4·NMe3, CCDC 2170416.
Supplementary Data 4
Crystallographic data for compound 5·Na(15-c-5), CCDC 2170417.
Supplementary Data 5
Crystallographic data for compound 5·NaIiPr, CCDC 2170418.
Supplementary Data 6
Crystallographic data for compound Na·crypt[5], CCDC 2170419.
Supplementary Data 7
Crystallographic data for compound Na·(DME)3[6], CCDC 2170420.
Supplementary Data 8
Crystallographic data for compound 7, CCDC 2170421.
Supplementary Data 9
Source data for Supplementary Fig. 67.
Supplementary Data 10
Cartesian coordinates of optimized and calculated structures, electronic energies for calculated structures.
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Ludwig, M., Franz, D., Espinosa Ferao, A. et al. Anions featuring an aluminium–silicon core with alumanyl silanide and aluminata-silene characteristics. Nat. Chem. 15, 1452–1460 (2023). https://doi.org/10.1038/s41557-023-01265-3
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DOI: https://doi.org/10.1038/s41557-023-01265-3
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