Article (Scientific journals)
Monofluoride Bridged, Binuclear Metallacycles of First Row Transition Metals Supported by Third Generation Bis(1-pyrazolyl)methane Ligands: Unusual Magnetic Properties
Reger, Daniel; Watson, R. P.; Foley, E. A. et al.
2009In Inorganic Chemistry, 48, p. 10658
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Keywords :
Magnetic properties
Abstract :
[en] The reaction of M(BF4)2•xH2O, where M is Fe, Co, Cu, and Zn, and the bitopic, bis(pyrazolyl)methane ligand m-[CH(pz)2]2C6H4, Lm, where pz is a pyrazolyl ring, yields the monofluoride bridged, binuclear [M2(μ-F)(μ-Lm)2](BF4)3 complexes. In contrast, a similar reaction of Lm with Ni(BF4)2•6H2O yields dibridged [Ni2(μ-F)2(μ-Lm)2](BF4)2. The solid state structures of seven [M2(μ-F)(μ-Lm)2](BF4)3 complexes, with M = Fe, Co, Cu, and Zn, indicate that the divalent metal ion is in a five-coordinate, trigonal bipyramidal, coordination environment with either a linear M–F–M bridging arrangement in five of the complexes, or with a slightly bent Cu–F–Cu bridge in two of the complexes. NMR results indicate that [Zn2(μ-F)(μ-Lm)2](BF4)3 retains its dimeric structure in solution. The [Ni2(μ-F)2(μ-Lm)2](BF4)2 complex has a dibridging fluoride structure that has a six-coordination environment about each nickel(II) ion. In the solid state, the [Fe2(μ-F)(μ-Lm)2](BF4)3 and [Co2(μ-F)(μ-Lm)2](BF4)3 complexes show weak intramolecular antiferromagnetic exchange coupling between the two metal(II) ions with J values of –10.4 and –0.67 cm–1, respectively; there is no observed long-range magnetic order. Three different solvates of [Cu2(μ-F)(μ-Lm)2](BF4)3 are diamagnetic between 5 and 400 K, thus showing strong antiferromagnetic exchange interactions of –600 cm–1 or more negative. Mössbauer spectra indicate that [Fe2(μ-F)(μ-Lm)2](BF4)3 exhibits no long-range magnetic order between 4.2 and 295 K and isomer shifts that are consistent with the presence of five-coordinate, high-spin iron(II).
Disciplines :
Chemistry
Author, co-author :
Reger, Daniel;  University of North Carolina
Watson, R. P.;  University of North Carolina
Foley, E. A.;  University of North Carolina
Pelecchia, P. J.;  University of North Carolina
Smith, M. D.;  University of North Carolina
Grandjean, Fernande ;  Université de Liège - ULiège > Département de physique > Département de physique
Long, Gary J.
Language :
English
Title :
Monofluoride Bridged, Binuclear Metallacycles of First Row Transition Metals Supported by Third Generation Bis(1-pyrazolyl)methane Ligands: Unusual Magnetic Properties
Publication date :
2009
Journal title :
Inorganic Chemistry
ISSN :
0020-1669
eISSN :
1520-510X
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
48
Pages :
10658
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 11 August 2010

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