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Iron(II) Tris-[N4-substituted-3,5-di(2-pyridyl)-1,2,4-triazole] complexes: structural, magnetic, NMR, and density functional theory studies

Iron(II) Tris-[N4-substituted-3,5-di(2-pyridyl)-1,2,4-triazole] complexes: structural, magnetic, NMR, and density functional theory studies
Iron(II) Tris-[N4-substituted-3,5-di(2-pyridyl)-1,2,4-triazole] complexes: structural, magnetic, NMR, and density functional theory studies
Eight mononuclear iron(II) complexes of N(4)-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared and characterized. In all cases the iron(II)/ligand ratio used is 1:3, giving red complexes of the general formula [Fe(II)(Rdpt)(3)](BF(4))(2) x solvents, in 55-89% yield. The ligands differ only in the nature of the N(4)-substituent (amino, pyrrolyl, iso-butyl, methyl, phenyl, para-tolyl, 3,5-dichlorophenyl, and 4-pyridyl; for ligands adpt, pldpt, ibdpt, medpt, phdpt, ptdpt, Cldpt, and pydpt, respectively) allowing substituent effects on the properties of the resulting iron(II) complexes to be probed. The low temperature crystal structures of seven of the complexes reveal low spin iron(II) environments. Packing analyses reveal anion-pi and acetonitrile-pi interactions involving the tetrafluoroborate counteranions and interstitial acetonitrile molecules, respectively. Both "pi-pockets" and "pi-sandwiches" are observed. Solid state magnetic susceptibility measurements (4-300 K) indicate the iron(II) is low spin (LS) in all complexes at all temperatures studied, except for [Fe(II)(pldpt)(3)](BF(4))(2) x 1 1/2 H(2)O which has the beginnings of spin crossover (SCO) at elevated temperatures. Downfield shifts and peak broadening observed in the variable temperature (1)H NMR studies indicate that in d(3)-nitromethane solution the LS [Fe(II)(Rdpt)(3)](2+) complexes are in equilibrium with a trace of a high spin (HS) species. (15)N NMR spectra (measured and calculated) of the ligands reveal that altering the N(4)-substituent changes the chemical shift of the N(1) triazole and pyridine nitrogen atoms, allowing probing of the relationship between ligand substituent and the nature of the coordinating nitrogen atoms.
0020-1669
6670-6679
Kitchen, Jonathan A.
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White, Nicholas G.
ebcbc4ca-7e2c-4af7-820d-366956f64762
Boyd, Maruta
0f10c4e5-f611-44d1-a70c-78326727939c
Moubaraki, Boujemaa
eb24a914-5451-4870-8615-cd853a46b864
Murray, Keith S.
091a4624-9b14-4413-923b-7330444e64b2
Boyd, Peter D.W.
ffc40c87-2894-43fa-8253-78d6bdbc47b3
Brooker, Sally
2ee9681a-3ff7-41be-88c5-681f66b953ef
Kitchen, Jonathan A.
3999f5cb-d53e-4c51-b750-627bd2a1b9b6
White, Nicholas G.
ebcbc4ca-7e2c-4af7-820d-366956f64762
Boyd, Maruta
0f10c4e5-f611-44d1-a70c-78326727939c
Moubaraki, Boujemaa
eb24a914-5451-4870-8615-cd853a46b864
Murray, Keith S.
091a4624-9b14-4413-923b-7330444e64b2
Boyd, Peter D.W.
ffc40c87-2894-43fa-8253-78d6bdbc47b3
Brooker, Sally
2ee9681a-3ff7-41be-88c5-681f66b953ef

Kitchen, Jonathan A., White, Nicholas G., Boyd, Maruta, Moubaraki, Boujemaa, Murray, Keith S., Boyd, Peter D.W. and Brooker, Sally (2009) Iron(II) Tris-[N4-substituted-3,5-di(2-pyridyl)-1,2,4-triazole] complexes: structural, magnetic, NMR, and density functional theory studies. Inorganic Chemistry, 48 (14), 6670-6679. (doi:10.1021/ic900634t). (PMID:19534510)

Record type: Article

Abstract

Eight mononuclear iron(II) complexes of N(4)-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared and characterized. In all cases the iron(II)/ligand ratio used is 1:3, giving red complexes of the general formula [Fe(II)(Rdpt)(3)](BF(4))(2) x solvents, in 55-89% yield. The ligands differ only in the nature of the N(4)-substituent (amino, pyrrolyl, iso-butyl, methyl, phenyl, para-tolyl, 3,5-dichlorophenyl, and 4-pyridyl; for ligands adpt, pldpt, ibdpt, medpt, phdpt, ptdpt, Cldpt, and pydpt, respectively) allowing substituent effects on the properties of the resulting iron(II) complexes to be probed. The low temperature crystal structures of seven of the complexes reveal low spin iron(II) environments. Packing analyses reveal anion-pi and acetonitrile-pi interactions involving the tetrafluoroborate counteranions and interstitial acetonitrile molecules, respectively. Both "pi-pockets" and "pi-sandwiches" are observed. Solid state magnetic susceptibility measurements (4-300 K) indicate the iron(II) is low spin (LS) in all complexes at all temperatures studied, except for [Fe(II)(pldpt)(3)](BF(4))(2) x 1 1/2 H(2)O which has the beginnings of spin crossover (SCO) at elevated temperatures. Downfield shifts and peak broadening observed in the variable temperature (1)H NMR studies indicate that in d(3)-nitromethane solution the LS [Fe(II)(Rdpt)(3)](2+) complexes are in equilibrium with a trace of a high spin (HS) species. (15)N NMR spectra (measured and calculated) of the ligands reveal that altering the N(4)-substituent changes the chemical shift of the N(1) triazole and pyridine nitrogen atoms, allowing probing of the relationship between ligand substituent and the nature of the coordinating nitrogen atoms.

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Published date: 17 June 2009
Organisations: Chemistry

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Local EPrints ID: 343590
URI: http://eprints.soton.ac.uk/id/eprint/343590
ISSN: 0020-1669
PURE UUID: 29e92fa2-4b58-465f-8170-910f226cecaa
ORCID for Jonathan A. Kitchen: ORCID iD orcid.org/0000-0002-7139-5666

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Date deposited: 09 Oct 2012 09:04
Last modified: 18 Nov 2019 20:42

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Author: Jonathan A. Kitchen ORCID iD
Author: Nicholas G. White
Author: Maruta Boyd
Author: Boujemaa Moubaraki
Author: Keith S. Murray
Author: Peter D.W. Boyd
Author: Sally Brooker

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