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Synthesis, structures and DFT calculations on alkaline-earth metal azide-crown ether complexes

Synthesis, structures and DFT calculations on alkaline-earth metal azide-crown ether complexes
Synthesis, structures and DFT calculations on alkaline-earth metal azide-crown ether complexes
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional theory (DFT). This has allowed the effects of the crystal lattice to be investigated. A study of the MNterminal metal-azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal-azide bond to be investigated in each case. As in our earlier work on alkali metal azide-crown ether complexes, the bonding in the alkaline-earth complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre, and minimising ligand-ligand repulsions.
density functional, crown compounds, stucture elucidation, stability, azides, approximation, calculations, polyazide chemistry, alkaline earth metals, magnesium, crystal-structure, constants, calcium, ions, coordination, barium thiocyanates
0947-6539
2615-2624
Brown, M.D.
785195da-02f2-46c7-b482-d8c8516f09ff
Davis, M.F.
22d05b77-e973-4ca6-9148-bf63a99c6316
Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f
Ferrante, F.
cff3f6ec-876e-45c4-bb06-ac2734fdd3ee
Levason, W.
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ogden, J.S.
d022e70d-b424-4100-9517-64a46486dd8c
Webster, M.
f26c6e36-cb2e-486e-b2ed-b0d25a3a71f7
Brown, M.D.
785195da-02f2-46c7-b482-d8c8516f09ff
Davis, M.F.
22d05b77-e973-4ca6-9148-bf63a99c6316
Dyke, J.M.
46393b45-6694-46f3-af20-d7369d26199f
Ferrante, F.
cff3f6ec-876e-45c4-bb06-ac2734fdd3ee
Levason, W.
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ogden, J.S.
d022e70d-b424-4100-9517-64a46486dd8c
Webster, M.
f26c6e36-cb2e-486e-b2ed-b0d25a3a71f7

Brown, M.D., Davis, M.F., Dyke, J.M., Ferrante, F., Levason, W., Ogden, J.S. and Webster, M. (2008) Synthesis, structures and DFT calculations on alkaline-earth metal azide-crown ether complexes. Chemistry - A European Journal, 14 (8), 2615-2624. (doi:10.1002/chem.200701502).

Record type: Article

Abstract

The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional theory (DFT). This has allowed the effects of the crystal lattice to be investigated. A study of the MNterminal metal-azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal-azide bond to be investigated in each case. As in our earlier work on alkali metal azide-crown ether complexes, the bonding in the alkaline-earth complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre, and minimising ligand-ligand repulsions.

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More information

e-pub ahead of print date: 28 January 2008
Published date: 7 March 2008
Keywords: density functional, crown compounds, stucture elucidation, stability, azides, approximation, calculations, polyazide chemistry, alkaline earth metals, magnesium, crystal-structure, constants, calcium, ions, coordination, barium thiocyanates

Identifiers

Local EPrints ID: 54431
URI: https://eprints.soton.ac.uk/id/eprint/54431
ISSN: 0947-6539
PURE UUID: a41751ca-8a7f-4f99-8367-0a2b07eb13b1
ORCID for J.M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X
ORCID for W. Levason: ORCID iD orcid.org/0000-0003-3540-0971

Catalogue record

Date deposited: 05 Aug 2008
Last modified: 14 Mar 2019 01:56

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Contributors

Author: M.D. Brown
Author: M.F. Davis
Author: J.M. Dyke ORCID iD
Author: F. Ferrante
Author: W. Levason ORCID iD
Author: J.S. Ogden
Author: M. Webster

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