Pyrazolyl Methyls Prescribe the Electronic Properties of Iron(II) Tetra(pyrazolyl)lutidine Chloride Complexes
A series of iron(ii) chloride complexes of pentadentate ligands related to α,α,α',α'-tetra(pyrazolyl)-2,6-lutidine, pz 4lut, 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 CoCl 2-catalyzed rearrangement reaction. The equimolar combination of ligand and FeCl 2 in methanol gives the appropriate 1:1 complexes [FeCl(pz R 4lut)]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.
T. J. Morin and S. Wanniarachchi and C. Gwengo and V. Makura and H. M. Tatlock and S. V. Lindeman and B. K. Bennett and G. J. Long and F. Grandjean and J. R. Gardinier, "Pyrazolyl Methyls Prescribe the Electronic Properties of Iron(II) Tetra(pyrazolyl)lutidine Chloride Complexes," Dalton Transactions, vol. 40, no. 31, pp. 8024-8034, Royal Society of Chemistry, Aug 2011.
The definitive version is available at https://doi.org/10.1039/c1dt10712g
Keywords and Phrases
Chloride Complexes; High Spins; Inductive Effects; Iron Chlorides; Iron Complex; Ligand Field; Lutidine; Mössbauer; Pyrazolyl; Rearrangement Reactions; Spectroscopic Method; Spin-state; Ssbauer Spectroscopies; Steric Effect; Structural Studies; Tetrakis; Thermochromic Properties; Chlorine Compounds; Cyclic Voltammetry; Driers (Materials); Electronic Properties; Iron; Ligands; Methanol; Molybdenum Compounds; Spectroscopic Analysis; X Ray Diffraction; Iron Compounds; 2,6 Lutidine N Oxide; 2,6-lutidine N-oxide; Amine Oxide; Iron; Methanol; Organometallic Compound; Pyrazole Derivative; Chemical Structure; Chemistry; Electrochemistry; X Ray Diffraction; Cyclic N-Oxides; Electrochemistry; Iron; Methanol; Molecular Structure; Organometallic Compounds; Pyrazoles; X-Ray Diffraction
International Standard Serial Number (ISSN)
Article - Journal
© 2011 Royal Society of Chemistry, All rights reserved.
01 Aug 2011