Chemistry of ferroverdin: trinuclear species of type [M(FeL₃)₂](M = Mg, Ca, Mn, Fe, Co, Ni, Zn, or Cd; L = 4-methyl-1,2-benzoquinone 2-oximate)

Abstract

Reaction of sodium tris (4-methyl-1,2-benzoquinone 2-oximato) ferrate(II), Na[FeL₃], with M²⁺(M = Mg, Ca, Mn, Fe, Co, Ni, Zn, or Cd) in methanol furnishes trinuclear species of type [M(FeL₃)₂]. Upon treatment with NaOH, M(OH)₂ is precipitated and Na[FeL₃] is regenerated. The iron(II) atoms of the two [FeL₃]^– moieties in the trinuclear complexes are low spin but M²⁺ is high spin (S=5//₂, 2, 3/2, and 1 in the cases of M = Mn, Fe, Co, and Ni respectively). The M²⁺ site can be doped with Mn²⁺ and e.s.r. data for the doped complexes are compatible with a near octahedral environment of the M²⁺ site. It is proposed that this environment is created by the six oximato oxygen atoms of the two facial [FeL₃]^– moieties. The significance of the present work in relation to the reported variation of the iron content in different preparations of ferroverdin is noted.