Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride

Alex Bowles; James Quirk; Yu Liu; George Morritt; Marina  Freitag; George Whitehead; Adam Woodward; Adam Brookfield; Conrad Goodwin; David Collison; Floriana Tuna; Claire McMullin; James Dawson; Erli Lu; Fabrizio Ortu

doi:10.1021/jacs.4c09408

Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride

Alex Bowles, James Quirk, Yu Liu, George Morritt, Marina Freitag, George Whitehead, Adam Woodward, Adam Brookfield, Conrad Goodwin, David Collison, Floriana Tuna, Claire McMullin, James Dawson, Erli Lu, Fabrizio Ortu

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

3 Citations (SciVal)

Abstract

A new calcium-based Room temperature Stable Electride (RoSE), K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] (2), is successfully synthesized from the reaction of a calcium tris-amide, [Ca{N(Mes)(SiMe3)}3K] (1) (Mes = 2,4,6-trimethylphenyl), with potassium under mechanochemical treatment. The dimeric structure of K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] is calculated using ab initio random structure searching (AIRSS) methods. This shows the existence of highly localized anionic electrons (e–) and suggests poor electrical conductance, as confirmed via electroconductivity measurements. The two anionic electrons in 2 are strongly antiferromagnetically coupled, thus in agreement with the largely diamagnetic response from magnetometry. Reaction of 2 with pyridine affords 4,4′-bipyridine, while reaction with benzene gives C–H activation and formation of a calcium hydride complex, [K(η6-C6H6)4][{Ca[N(Mes)(SiMe3)](H)}2K3] (3). Computational DFT analysis reveals the crucial role played by the ligand framework in the stabilization of this new Ca-hydride complex.

Original language	English
Pages (from-to)	28914-28924
Number of pages	11
Journal	Journal of the American Chemical Society
Volume	146
Issue number	42
Early online date	8 Oct 2024
DOIs	https://doi.org/10.1021/jacs.4c09408
Publication status	Published - 23 Oct 2024

Acknowledgements

For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to the Author Accepted Manuscript version arising from this submission.

Funding

F.O. thanks the Engineering and Physical Sciences Research Council for a PhD scholarship (A.W.J.B.) and a New Investigator Award (EP/W00691X/1). NMR spectroscopy at the University of Leicester was supported by the Engineering and Physical Sciences Research Council (EP/W02151X/1). X-ray diffraction at the University of Leicester and University of Manchester were supported by the Engineering and Physical Sciences Research Council (EP/V034766/1) and (EP/K039547/1), respectively. E.L., J.A.D. and F.T. thank the Leverhulme Trust for financial support (RPG-2022-231, RPG-2023-159). J.A.Q. and J.A.D. gratefully acknowledge the EPSRC (EP/V013130/1) for funding via membership of the UK’s HEC Materials Chemistry Consortium, which is funded by the EPSRC (Nos. EP/L000202, EP/L000202/1, EP/R029431 and EP/T022213), this work used the ARCHER2 UK National Supercomputing Service. A.W.W. was supported by the Engineering and Physical Sciences Research Council (EP/T011289/1). We would also like to thank Dr. Louise S. Natrajan for providing access to a spectrofluorimeter (funded through The Royal Society, EPSRC Career Acceleration Fellowship EP/G004846/1, and Leverhulme Trust Research Leadership Award RL-2012-072). C.A.P.G. acknowledges The Royal Society for a University Research Fellowship (URF\211271). We thank the EPSRC National Research Facility for EPR Spectroscopy at The University of Manchester for support with EPR and magnetic measurements (EPSRC grants EP/W014521/1, EP/V035231/1 and EP/X034523/1). This research made use of the Anatra High Performance Computing (HPC) Service at the University of Bath. C.L.M. gratefully acknowledges the University of Bath’s Research Computing Group (doi.org/10.15125/b6 cd-s854) for their support in this work, and also thanks the Royal Society of Chemistry for a Research Enablement Grant (E21-8355738114).

Funders	Funder number
EPSRC National Research Facility
Royal Society	URF\211271, EP/G004846/1, RL-2012-072
National Supercomputing Service	EP/T011289/1
Royal Society of Chemistry	E21-8355738114
Engineering and Physical Sciences Research Council	EP/R029431, EP/K039547/1, EP/W02151X/1, EP/W00691X/1, EP/T022213, EP/L000202/1, EP/V013130/1, EP/L000202, EP/V034766/1
University of Bath	doi.org/10.15125/b6 cd-s854
University of Manchester	EP/V035231/1, EP/X034523/1, EP/W014521/1
Leverhulme Trust	RPG-2022-231, RPG-2023-159

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10.1021/jacs.4c09408Licence: CC BY

Cite this

Bowles, A., Quirk, J., Liu, Y., Morritt, G., Freitag, M., Whitehead, G., Woodward, A., Brookfield, A., Goodwin, C., Collison, D., Tuna, F., McMullin, C., Dawson, J., Lu, E., & Ortu, F. (2024). Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride. Journal of the American Chemical Society, 146(42), 28914-28924. https://doi.org/10.1021/jacs.4c09408

Bowles, A, Quirk, J, Liu, Y, Morritt, G, Freitag, M, Whitehead, G, Woodward, A, Brookfield, A, Goodwin, C, Collison, D, Tuna, F, McMullin, C, Dawson, J, Lu, E & Ortu, F 2024, 'Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride', Journal of the American Chemical Society, vol. 146, no. 42, pp. 28914-28924. https://doi.org/10.1021/jacs.4c09408

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abstract = "A new calcium-based Room temperature Stable Electride (RoSE), K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] (2), is successfully synthesized from the reaction of a calcium tris-amide, [Ca{N(Mes)(SiMe3)}3K] (1) (Mes = 2,4,6-trimethylphenyl), with potassium under mechanochemical treatment. The dimeric structure of K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] is calculated using ab initio random structure searching (AIRSS) methods. This shows the existence of highly localized anionic electrons (e–) and suggests poor electrical conductance, as confirmed via electroconductivity measurements. The two anionic electrons in 2 are strongly antiferromagnetically coupled, thus in agreement with the largely diamagnetic response from magnetometry. Reaction of 2 with pyridine affords 4,4′-bipyridine, while reaction with benzene gives C–H activation and formation of a calcium hydride complex, [K(η6-C6H6)4][{Ca[N(Mes)(SiMe3)](H)}2K3] (3). Computational DFT analysis reveals the crucial role played by the ligand framework in the stabilization of this new Ca-hydride complex.",

author = "Alex Bowles and James Quirk and Yu Liu and George Morritt and Marina Freitag and George Whitehead and Adam Woodward and Adam Brookfield and Conrad Goodwin and David Collison and Floriana Tuna and Claire McMullin and James Dawson and Erli Lu and Fabrizio Ortu",

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AU - Woodward, Adam

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AB - A new calcium-based Room temperature Stable Electride (RoSE), K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] (2), is successfully synthesized from the reaction of a calcium tris-amide, [Ca{N(Mes)(SiMe3)}3K] (1) (Mes = 2,4,6-trimethylphenyl), with potassium under mechanochemical treatment. The dimeric structure of K[{Ca[N(Mes)(SiMe3)]3(e–)}2K3] is calculated using ab initio random structure searching (AIRSS) methods. This shows the existence of highly localized anionic electrons (e–) and suggests poor electrical conductance, as confirmed via electroconductivity measurements. The two anionic electrons in 2 are strongly antiferromagnetically coupled, thus in agreement with the largely diamagnetic response from magnetometry. Reaction of 2 with pyridine affords 4,4′-bipyridine, while reaction with benzene gives C–H activation and formation of a calcium hydride complex, [K(η6-C6H6)4][{Ca[N(Mes)(SiMe3)](H)}2K3] (3). Computational DFT analysis reveals the crucial role played by the ligand framework in the stabilization of this new Ca-hydride complex.

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Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride

Abstract

Acknowledgements

Funding

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Sub-Valent Alkaline Earth Reagents (SubVAR)

Improving Computational Models for Anions in Solution

Anatra HTC cluster

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Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride

Abstract

Acknowledgements

Funding

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Projects

Sub-Valent Alkaline Earth Reagents (SubVAR)

Improving Computational Models for Anions in Solution

Equipment

Anatra HTC cluster

Cite this