Synthesis and Electrochemical Properties of Tetranuclear Di-mu-oxo-bis[di-mu-phenolatodiiron(III)]Complexes

摘要

A series of tetrairon(III)complexes of di-mu-oxo-bis[di-mu-phenolatodiiron(III)]core,[{Fe2(L)(L')}2(mu-O)2](PF6)2(1-11),where L~(2-)is the phenol-based macrocyclic compartmental ligand and(L')~-is acetate,monochloroacetate,dichloroacetate,trifluoroacetate,pentafluoropropionate,benzoate,p-nitrobenzoate,pentafluorobenzoate,diethyl phosphate,diphenyl phosphate,or diethyldithiophosphate for 1-11,respectively,were synthesized.X-ray crystallographic studies for 4,7,and 9 indicated that two{Fe2(L)(L')}units were connected by two oxo bridges to afford a tetranuclear di-mu-oxo-bis[di-mu-phenolatodiiron(III)]core.Cyclic voltammograms of 1-11 in acetonitrile showed a quasi-reversible or irreversible reduction wave between-332 and-620 mV(vs.Ag/Ag~+),which were attributed to a two-electron process involving the Fe_4~(II,II,III,III).The Fe_4~(III,III,III,III)/Fe_4~(II,II,III,III)potential shifted positive with a decrease in the electron-donating ability of the end-cap ligand,and a good linear correlation was found between the potentials and the pK_a values of HL'.The Fe_4~(II,II,III,III)species were generated in acetonitrile by electrochemical reduction and showed broad intervalence transition bands in the range of 900-1500 nm.