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Unexpected structural diversity in alkali metal azide-crown ether complexes: syntheses, X-ray structures, and quantum-chemical calculations

Unexpected structural diversity in alkali metal azide-crown ether complexes: syntheses, X-ray structures, and quantum-chemical calculations
Unexpected structural diversity in alkali metal azide-crown ether complexes: syntheses, X-ray structures, and quantum-chemical calculations
A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N-3)], [Na([15]crown-5)(N-3)], [Na([15]crown-5)(H2O)(2)]N-3, [K([18]crown-6)(N-3)(H2O)], [Rb([18]crown-6)(N-3)(H2O)], [Cs([18]crown-6)(N-3)](2), and [Cs([18]crown-6)(N-3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the M-N-terminal metalazide bond length and charge densities on the metal (M) and terminal nitrogen centre (N-terminal) in these complexes has allowed the nature of the metal-azide bond to be probed in each case. The bonding in these 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. The structures of the crown ether complexes determined in this work show the subtle interplay of such factors. The significant role of hydrogen bonding is also demonstrated, most clearly in the structures of the K and Rb dimers, but also in the chain structure of the hydrated Cs complex.
alkali metals azides, crown ether complexes, density functional calculations, x-ray structures crystal-structure, lithium thiocyanate, nitrogen, density, 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane, approximation, coordination, temperature, energy, n-5(+)
0947-6539
2620-2629
Brown, Michael D.
76a42341-1a1e-4ec9-8cdc-aca9d5e53bf4
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Ferrante, Francesco
5b217df6-ac83-4b5d-85c3-96060e69b89a
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Webster, Michael
f26c6e36-cb2e-486e-b2ed-b0d25a3a71f7
Brown, Michael D.
76a42341-1a1e-4ec9-8cdc-aca9d5e53bf4
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Ferrante, Francesco
5b217df6-ac83-4b5d-85c3-96060e69b89a
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Webster, Michael
f26c6e36-cb2e-486e-b2ed-b0d25a3a71f7

Brown, Michael D., Dyke, John M., Ferrante, Francesco, Levason, William, Ogden, J. Steven and Webster, Michael (2006) Unexpected structural diversity in alkali metal azide-crown ether complexes: syntheses, X-ray structures, and quantum-chemical calculations. Chemistry - A European Journal, 12 (9), 2620-2629. (doi:10.1002/chem.200501072).

Record type: Article

Abstract

A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N-3)], [Na([15]crown-5)(N-3)], [Na([15]crown-5)(H2O)(2)]N-3, [K([18]crown-6)(N-3)(H2O)], [Rb([18]crown-6)(N-3)(H2O)], [Cs([18]crown-6)(N-3)](2), and [Cs([18]crown-6)(N-3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the M-N-terminal metalazide bond length and charge densities on the metal (M) and terminal nitrogen centre (N-terminal) in these complexes has allowed the nature of the metal-azide bond to be probed in each case. The bonding in these 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. The structures of the crown ether complexes determined in this work show the subtle interplay of such factors. The significant role of hydrogen bonding is also demonstrated, most clearly in the structures of the K and Rb dimers, but also in the chain structure of the hydrated Cs complex.

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More information

Published date: 2006
Keywords: alkali metals azides, crown ether complexes, density functional calculations, x-ray structures crystal-structure, lithium thiocyanate, nitrogen, density, 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane, approximation, coordination, temperature, energy, n-5(+)

Identifiers

Local EPrints ID: 44396
URI: https://eprints.soton.ac.uk/id/eprint/44396
ISSN: 0947-6539
PURE UUID: 2036656c-31f9-4af6-a985-594bf5c55de7
ORCID for John M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X
ORCID for William Levason: ORCID iD orcid.org/0000-0003-3540-0971

Catalogue record

Date deposited: 05 Mar 2007
Last modified: 14 Mar 2019 01:56

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