New Fe(III) complexes with sulfur and selenium ligands

Abstract

FeL 3 complexes, where L = dithiobenzoate C 6H 5-CSS, dithiophenylacetate C 6H 5-CH 2-CSS, or diethyldiselenocarbamate (C 2H 5) 2N-CSe 2, are deeply colored nonelectrolyte inner complexes containing pseudooctahedral [Fe(III)S 6] or [Fe(III)Se 6] chromophores. They all exhibit low-spin magnetic behaviour, with only a small lower-symmetry splitting of the octahedral 2T 2g groundstate, contrarily to the doublet-sextet equilibria known of other [Fe(III)S 6] chromophores like Fe(III) dithiocarbamates. The low-spin behaviour is produced here by the relatively high ligand-field strength of dithiocarboxylates, respectively by the pronounced nephelauxetic effect of selenium ligands, both effects favoring magnetic crossover to the spin-paired d 5 groundstate. Diselenocarbomates dsc forms with iron(III) also a pentacoordinated species Fe dsc 2Cl, whose existence and properties stress the close similarity between dithio- and diselenocarbamato complexes. Mössbauer spectra of iron(II) dithiocarboxylates exhibit rather large quadrupole splitting of the order of 1·8 mm/ sec.