Chemistry of ferroverdin: Trinuclear species of type [M(FeL < inf > 3 < /inf > ) < inf > 2 < /inf > ] (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.