Square planar vs tetrahedral geometry in four coordinate iron(II) complexes

Eric J. Hawrelak, Wesley H. Bernskoetter, Emil Lobkovsky, Gordon T. Yee, Eckhard Bill, Paul J. Chirik

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The geometric preferences of a family of four coordinate, iron(II) d 6 complexes of the general form L 2FeX 2 have been systematically evaluated. Treatment of Fe 2(Mes) 4 (Mes = 2,4,6-Me 3C 6H 2) with monodentate phosphine and phosphite ligands furnished square planar trans-P 2Fe(Mes) 2 derivatives. Identification of the geometry has been accomplished by a combination of solution and solid-state magnetometry and, in two cases (P = PMe 3, PEt 2Ph), X-ray diffraction. In contrast, both tetrahedral and square planar coordination has been observed upon complexation of chelating phosphine ligands. A combination of crystallographic and magnetic susceptibility data for (depe)Fe-(Mes) 2 (depe = 1,2- bis(diethylphosphino)ethane) established a tetrahedral molecular geometry whereas SQUID magnetometry and Mössbauer spectroscopy on samples of (dppe)Fe(Mes) 2 (dppe = 1,2-bis(diphenylphosphino)-ethane) indicated a planar molecule. When dissolved in chlorinated solvents, the latter compound promotes chlorine atom abstraction, forming tetrahedral (dppe)Fe(Mes)Cl and (dppe)FeCl 2. Ligand substitution reactions have been studied for both structural types and are rapid on the NMR time scale at ambient temperature.

Original languageEnglish (US)
Pages (from-to)3103-3111
Number of pages9
JournalInorganic Chemistry
Issue number9
StatePublished - May 2 2005
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry


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