NEW FE(3) COMPLEXES WITH SULFUR AND SELENIUM LIGANDS

FeL3 complexes, where L = dithiobenzoate C6H5-CSS, dithiophenylacetate C6H5-CH2-CSS, or diethyldiselenocarbamate (C2H5)2N-CSe2, are deeply colored nonelectrolyte inner complexes containing pseudooctahedral [Fe(III)S6] or [Fe(III)Se6] chromophores. They all exhibit low-spin magnetic behaviour, with only a small lower-symmetry splitting of the octahedral 2T2g groundstate, contrarily to the doublet-sextet equilibria known of other [Fe(III)S6] 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 d5 groundstate. Diselenocarbomates dsc forms with iron(III) also a pentacoordinated species Fedsc2Cl, 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. © 1969.