The synthesis of the first singly
bridged non-heme diiron complex with a
-hydroxo
bridging ligand, [{(salten)Fe}
2(OH)][B(C
6H
5)
4]·(CH
3CN)
x·(H
2O)
y (
1) [H
2salten = 4-azaheptane-1,7-
bis(salicylideneiminate)], is reported. The complexhas
been characterized with X-ray crystallography, FTIR, magnetic suscepti
bility measurements, and Möss
bauerspectroscopy. The data have
been compared with the results of DFT calculations on
both
1 and a model with anunsupported
-oxo
bridge (
2) to verify the formulation of the complex as a
-hydroxo-
bridged species. The X-raystructure [Fe-O(H) = 1.997(1) Å and Fe-O(H)-Fe = 159
] is consistent with the DFT-optimized geometry of
1[Fe-O(H) = 2.02 Å and Fe-O(H)-Fe = 151
]; the Fe-O(H) distance in
1 is a
bout 0.2 Å longer than the Fe-Oseparations in the optimized geometry of
2 (1.84 Å) and in the crystallographic structures of diiron(III) compoundswith unsupported
-oxo
bridges (1.77-1.81 Å). The formulation of
1 as a hydroxo-
bridged compound is also supported
by the presence of an O-H stretch
band in the FTIR spectrum of the complex. The magnetic suscepti
bilitymeasurements of
1 reveal antiferromagnetic exchange (
J = 42 cm
-1 and
Hex =
JS1·
S2). Nearly the same
J valueis o
btained
by analyzing the temperature dependence of the Möss
bauer spectra (
J = 43 cm
-1; other parameters:
= 0.49 mm s
-1,
EQ = -0.97 mm s
-1, and
= 0.45 at 4.2 K). The experimental
J values and Möss
bauerparameters agree very well with those o
btained from DFT calculations for the
-hydroxo-
bridged compound (
J =46 cm
-1,
= 0.48 mm s
-1,
EQ = -1.09 mm s
-1, and
= 0.35). The exchange coupling constant in
1 isdistinctly different from the value
J 200 cm
-1 calculated for the optimized
-oxo-
bridged species,
2. The increasedexchange-coupling in
2 arises primarily from a decrease in the Fe-O
bond length.