title: Pyrazolyl methyls prescribe the electronic properties of iron(II) tetra(pyrazolyl)lutidine chloride complexes.
abstract: A series of iron(II) chloride complexes of pentadentate ligands related to α,α,α',α'-tetra(pyrazolyl)-2,6-lutidine, pz(4)lut, 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**(4)lut, was prepared via a CoCl(2)-catalyzed rearrangement reaction. The equimolar combination of ligand and FeCl(2) in methanol gives the appropriate 1:1 complexes [FeCl(pz(R)(4)lut)]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, 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. Non-intuitive 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.
authors: Department of Chemistry, Marquette University, Milwaukee, WI 53201-1881, USA.
authors: Tyler J
authors: TJ
authors: Morin
authors: Sarath
authors: S
authors: Wanniarachchi
authors: Chengeto
authors: C
authors: Gwengo
authors: Vitales
authors: V
authors: Makura
authors: Heidi M
authors: HM
authors: Tatlock
authors: Sergey V
authors: SV
authors: Lindeman
authors: Brian
authors: B
authors: Bennett
authors: Gary J
authors: GJ
authors: Long
authors: Fernande
authors: F
authors: Grandjean
authors: James R
authors: JR
authors: Gardinier
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry*; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D003497:Cyclic N-Oxides; D009942:Organometallic Compounds; D011720:Pyrazoles; C018089:2,6-lutidine N-oxide; D007501:Iron; D000432:Methanol