Reference : Pyrazolyl methyls prescribe the electronic properties of iron(II) tetra(pyrazolyl)lut...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Pyrazolyl methyls prescribe the electronic properties of iron(II) tetra(pyrazolyl)lutidine chloride complexes
[en] Les groupes méthyl-pyrazolyl gouvernent les propriétés électroniques des complexes de fer(II) tetra(pyrazolyl)lutidine chlorure.
Morin, Tyler J [Marquette University > Chemistry > > >]
Wanniarachchi, Sarath [Marquette University > Chemistry > > >]
Gwengo, Chengeto [Marquette University > Chemistry > > >]
Makura, Vitales [Marquette University > Chemistry > > >]
Tatlock, Heidi M [Marquette University > Chemistry > > >]
Lindeman, Sergey V [Marquette University > Chemistry > > >]
Bennett, Brian mailto [Medical College of Wisconsin > Biophysics > > >]
Long, Gary J mailto [Missouri University of Science and Technology > Chemistry > > >]
Grandjean, Fernande mailto [Université de Liège - ULiège > Département de physique > Département de physique >]
Gardinier, James R mailto [> >]
Journal of the Chemical Society. Dalton Transactions
Royal Society of Chemistry
[en] x-ray diffraction ; Mössbauer spectroscopy
[en] A series of iron(II) chloride complexes of pentadentate ligands related to α,α,α’,α’-tetra(pyrazolyl)-2,6-lutidine, pz4lut, has been prepared to evaluate whether pyrazolyl substitution has any systematic impact on the electronic properties of the complexes. For this purpose, the new tetrakis(3,4,5-trimethylpyrazolyl)lutidine ligand, pz**4lut, was prepared via a CoCl2-catalyzed rearrangement reaction. The equimolar combination of ligand and FeCl2 in methanol gives the appropriate 1:1 complexes [FeCl(pzR4lut)]Cl that are each isolated in the solid state as a hygroscopic solvate. In solution, the iron(II) complexes have been fully characterized by several spectroscopic methods and cyclic voltammetry. In the solid state, the complexes have been characterized by X-ray diffraction, magnetic measurements and, in some cases, by Mössbauer spectroscopy. The Mössbauer studies show that the complexes remain high spin to 4 K and exclude spin-state changes as the cause of the surprising solid-state thermochromic properties of the complexes. Counterintuitive results of spectroscopic and structural studies showed that methyl substitution at the 3- and 5- positions of the pyrazolyl rings reduces the ligand field strength through steric effects whereas methyl substitution at the 4-position of the pyrazolyl rings increases the ligand field strength through inductive effects.

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