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Abstract
The {Fe(,4)(SPh)(,6)X(,4)}('2-) (X = Cl, Br) clusters have been synthesized in excellent yields and the structure of the chloro analogue has been determined. These iron-thiolates have been utilized in the synthesis of the mixed ligand {Ph(,4)P}(,2)Fe(,4)S(,4)(SPh)(,2)(O-Ph-Me)(,2) (I) and {Ph(,4)P}(,2)Fe(,4)S(,4)(XPh)(,2)Cl(,2) {X = S (II), X = O (III)} cubanes. The structure of these complexes have been determined and it was found that their Fe(,4)S(,4) cores show idealized D(,2d) non-compressed geometry. The electronic and ('1)H-NMR spectra and solution magnetic studies are presented. Zero field Mossbauer spectra of (I), (II) and (III) show one quadrupole doublet which consists of two poorly resolved quadrupole doublets with very similar isomer shift values.
Cyclic voltametric studies show that (I) and (II) reduce reversibly by one electron while (III) shows quasi-reversiblereduction. The biological implications of the mixed terminal ligand environment {Fe(,4)S(,4)L(,2)L'(,2)}('2-) clusters are discussed.
Subsequently the mixed ligand complexes {Ph(,4)P}(,2)Fe(,4)S(,4)(X)(,2)(Et(,2)Dtc)(,2) (X = SPh, Cl) and {Ph(,4)P}(,2)Fe(,4)S(,4)Cl(,3)(Et(,2)Dtc) have been synthesized and their crystal structures are reported. These compounds contain the {Fe(,4)S(,4)}('2+) core with some of the iron sites possessing five coordination. The electrochemical, ('1)H-NMR, magnetic and electrochemical properties are reported. The Mossbauer spectra show two distinct quadrupole doublets. The doublet with the highest isomer shift (nested configuration) is attributed to the five coordinate iron site.
The {Ph(,4)P}Fe(,4)S(,4)(Et(,2)Dtc)(,4) was prepared and it is the first complex to formally contain the {Fe(,4)S(,4)}('3+) core. The electrochemical, magnetic and Mossbauer spectroscopic properties as well as the crystal structure of this complex are reported. The {Fe(,4)S(,4)}('3+) core in the crystal is found in a highly distorted state.
The synthesis of {Et(,4)N}(,3)Fe(,6)S(,6)Cl(,6)(.)CH(,3)CN (IV) was accomplished. The paramagnetic complex (S = 1/2) crystallized in the monoclinic space group C2/C. The crystal structure of (IV) shows that it contains the hitherto unknown {Fe(,6)S(,6)}('3+) hexagonal prismatic core. The {Fe(,6)S(,6)}('3+) core can be described by the coupling of two Fe(,3)S(,3) cyclohexane chairs or the trimerization of three Fe(,2)S(,2) rhombii. There are two kinds of Fe-Fe distances with mean values at 2.765(3) (ANGSTROM) and 3.790(8) (ANGSTROM). The synthesis of these {Fe(,6)S(,6)(L)(,6)}('3-) clusters is described (L = Br, I, SC(,6)H(,4)-p-Me, O-C(,6)H(,4)-p-Me). The chemical, spectroscopic (electronic, Mossbauer, EPR) and electrochemical properties are described.
