A series of four structurally relate
d cis-
dithiolate-ligate
d Fe(III) complexes, [Fe
III(DITpy)
2]Cl (
1), [Fe
III(DITIm)
2]Cl (
2), [Fe
III(ADIT)
2]Cl (
3), an
d [Fe
III(AMIT)
2]Cl (
4), are
describe
d. The structural characterization of
3 as wellas the spectroscopic properties of
3 an
d 4 has been previously reporte
d. Crystal
data for
1,
2, an
d 4 are asfollows:
1·3H
2O crystallizes in the orthorhombic space group
Pca2
1 with
a = 19.800(4) Å,
b = 18.450(4) Å,
c= 14.800(3) Å, an
d Z = 8.
2·
1/
2EtOH·
1/
2H
2O crystallizes in the monoclinic space group
Cc with
a = 24.792(4)Å,
b = 14.364(3) Å,
c = 17.527(3) Å,
ddle"> = 124.91(2)
deg.gif">, an
d Z = 8.
4 crystallizes in the triclinic space group
Pwith
a = 8.0152(6) Å,
b = 10.0221(8) Å,
c = 11.8384(10) Å,
= 73.460(3)
deg.gif">,
ddle"> = 71.451(5)
deg.gif">,
= 72.856(4)
deg.gif">,an
d Z = 2. Complexes
1-
4 share a common S
2N
4 coor
dination environment that consists of two
cis-thiolates,two
trans-imines, an
d two
cis-terminal nitrogen
donors: N
term = pyri
dine (
1), imi
dazole (
2), an
d primary amine(
3 an
d 4). The crystallographically
determine
d mean Fe-S bon
d distances in
1-
4 range from 2.196 to 2.232 Åan
d are characteristic of low-spin Fe(III)-thiolate complexes. The low-spin
S =
1/
2 groun
d state was confirme
dby both EPR an
d magnetic susceptibility measurements. The electronic spectra of these complexes are characterize
dby broa
d absorption ban
ds centere
d near ~700 nm that are consistent with ligan
d-to-metal charge-transfer (CT)ban
ds. The complexes were further characterize
d by cyclic voltammetry measurements, an
d all possess highlynegative Fe(III)/Fe(II) re
dox couples (~ -1 V vs SCE, saturate
d calomel electro
de) in
dicating that alkyl thiolate
donors are effective at stabilizing Fe(III) centers. Both the re
dox couple an
d the 700 nm ban
d in the visiblespectra show solvent-
depen
dent shifts that are
depen
dent upon the H-bon
ding ability of the solvent. The implicationsof these results with respect to the active site of the iron-containing nitrile hy
dratases are also
discusse
d.