Synthesis and characterization of nickel dithiocarbamate complexes bearing ferrocenyl subunits

Kenichi Oyaizu, Kimihisa Yamamoto, Yurie Ishii, Eishun Tsuchida

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Abstract

Syntheses of a unique molecule, nickel(II) dithiocarbamate bearing two ferrocenyl groups (3), and its oxidized product, nickel(IV) dithiocarbamate bearing three ferrocenyl groups (4+), are reported. Spectroelectrochemical investigations have shown that the complex 4+ undergoes a three-electron oxidation process, according to two quasireversible steps ([NiIV(FeII)3]+⇌ [NiIV(FeII)2FeIII] 2++e-, [NiIV(FeII)2-FeIII]2+ ⇌ [NiIV(FeIII)3]4++2e-), whose redox potentials are separated by ΔE = 250 mV. The value ΔE is related to the comproportionation equilibrium ([NiIV(FeII)3]++[Ni IV(FeIII)2FeII]3+⇌ 2 [NiIVFeIII(FeII)2]2+) and results from the combination of a statistical contribution and a term which reflects the electrostatic repulsive interaction between the metal centers. In spite of the chemical equivalence of the three ferrocenyl groups, the mixed-valence state [NiIV-FeIII(FeII)2]2+ (42+) substantially persists in solution. Model studies with ethylenebridged bis(ferrocenylimine) (6) have revealed that the electrostatic term is much lower in the absence of the nickel(IV) center. Preliminary force-field simulations on 4+ have shown that enhanced electrostatic repulsion caused by the oxidation of the ferrocenyl subunits affects the conformation of the molecule, which results in a significant dimensional increment. Stereochemical features of the molecules are related to the electrostatic interaction and ΔG0 associated with the comproportionation process is affected by such strong deformation that a decrease in electrostatic repulsion results.

Original languageEnglish
Pages (from-to)3193-3201
Number of pages9
JournalChemistry - A European Journal
Volume5
Issue number11
Publication statusPublished - 1999 Nov 1

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Keywords

  • Electrochemistry
  • Metallocenes
  • N ligands
  • Nickel
  • S ligands
  • Sandwich complexes

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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