Abstract
Low-oxidation-state complexes of type (BDI)Mg–Mg(BDI) (BDI, β-diketiminate) show broad reactivity, finding application as soluble, universal reducing agents, enriching the field of early main group metal chemistry. Attempts to isolate similar, but considerably more reactive, Ca–Ca bound complexes have so far failed. As the metal–metal bond strength descending group 2 rapidly decreases, BDI complexes of the heavier AeI (alkaline earth) ions (Ae = Ca, Sr, Ba) probably exist as (BDI)Ae· radicals of untamed reactivity. Here we describe a facile method to prepare stable but highly reactive complexes with heterobimetallic Mg–Ae bonds. Mixing [(BDI)MgˉNa+]2 and [Ae(NR2)2]2 dimers led to anion–cation exchange and exclusive formation of mixed species: (BDI)MgˉNa+/Ae(NR2)2 (Ae = Ca, Sr, Ba; R = SiMe3). Crystal structures feature examples of Mg–Ca and Mg–Sr bonding with formal oxidation states of Mg0–AeII. Best described as polarized Mgδˉ–Aeδ+ bonds, these complexes show potential as alkane-soluble reductants for bond activation, which readily react with benzene by C–H bond cleavage and are oxidized to discrete complexes with N2O.
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Data availability
X-ray data are available free of charge from the Cambridge Crystallographic Data Centre under reference CCDC 2269821 (1), 2269822 (2), 2269823 (4), 2269824 (5), 2269631 (7), 2269632 (8), 2269633 (9), 2269634 (10) and 2269648 (Na(MgN″3)). Copies of the data can be obtained free of charge at https://www.ccdc.cam.ac.uk/structures/. Spectroscopic data that support the findings of this study as well as complementary crystallographic and computational details are included in Supplementary Information. Raw data are also available from corresponding author on reasonable request.
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Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (DFG) for funding (HA 3218/11-1).
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J. Mai: conceptualization, investigation, validation, formal analysis, writing—original draft, and visualization. J. Maurer: conceptualization, investigation, validation, formal analysis, writing—original draft, and visualization. J.L.: investigation, formal analysis and validation. S.H.: conceptualization, writing—original draft, review and editing, visualization, validation, supervision and project administration.
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Supplementary information
Supplementary Information
Experimental details and Supplementary Figs. 1–74 and Tables 1–9.
Supplementary Data 1
Crystallographic data for compound 1, CCDC 2269821.
Supplementary Data 2
Crystallographic data for compound 2, CCDC 2269822.
Supplementary Data 3
Crystallographic data for compound 4, CCDC 2269823.
Supplementary Data 4
Crystallographic data for compound 5, CCDC 2269824.
Supplementary Data 5
Crystallographic data for compound 6.
Supplementary Data 6
Crystallographic data for compound 7, CCDC 2269631.
Supplementary Data 7
Crystallographic data for compound 8, CCDC 2269632.
Supplementary Data 8
Crystallographic data for compound 9, CCDC 2269633.
Supplementary Data 9
Crystallographic data for compound 10, CCDC 2269634.
Supplementary Data 10
Crystallographic data for compound Na(MgN″3), CCDC 2269648.
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Mai, J., Maurer, J., Langer, J. et al. Heterobimetallic alkaline earth metal–metal bonding. Nat. Synth 3, 368–377 (2024). https://doi.org/10.1038/s44160-023-00451-y
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DOI: https://doi.org/10.1038/s44160-023-00451-y
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