The neutral trinuclear iron-thiolate-nitrosyl, [(ON)Fe(
![](/images/entities/mgr.gif)
-S,S-C
6H
4)]
3 (
1), and its oxidation product,[(ON)Fe(
![](/images/entities/mgr.gif)
-S,S-C
6H
4)]
3[PF
6] (
2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption,electron paramagnetic resonance (EPR), and magnetic measurement. The five-coordinated, squarepyramidal geometry around each iron atom in complex
1 remains intact when complex
1 is oxidized toyield complex
2. Magnetic measurements and EPR results show that there is only one unpaired electronin complex
1 (
Stotal =
1/
2) and no unpaired electron (
Stotal = 0) in
2. The detailed geometric comparisonsbetween complexes
1 and
2 provide understanding of the role that the unpaired electron plays in the chemicalbonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances aroundFe(1) is observed when complex
1 is oxidized to
2. This result implicates that the removal of the unpairedelectron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. Asignificant shift of the
NO stretching frequency from 1751 cm
-1 (
1) to 1821, 1857 cm
-1 (
2) (KBr) also indicatesthe strengthening of the N-O bonds in complex
2. The EPR, X-ray absorption, magnetic measurements,and molecular orbital calculations lead to the conclusion that the unpaired electron in complex
1 is mainlyallocated in the Fe(1) fragment and is best described as {Fe(1)NO}
7, so that the unpaired electron isdelocalized between Fe and NO via d-
* orbital interaction; some contributions from [Fe(2)NO] and[Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations,the spin density of complex
1 is predominately located at the Fe atoms with 0.60, -0.15, and 0.25 atFe(1), Fe(2), and Fe(3), respectively.