Synthesis and structural characterization of di-μ-phenoxo-bridged dinuclear iron(III) complexes with ferromagnetic or weak antiferromagnetic coupling

Article abstract of DOI:10.1246/bcsj.74.1425

Dinuclear phenoxo-bridged iron(III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H₂L^a), N-salicylidene-2-hydroxy-5-chlorobenzylamine (H₂L^b), and N- salicylidene- 2-hydroxybenzylamine (H₂L^c): [Fe₂(L^a)₂(CH₃CO₂) ₂] (1), [Fe₂(L^a)₂(C₆H₅CO ₂)₂] (2), [Fe₂(L_a){(CH₃)₃CCO₂} ₂] (3), [Fe₂(L^a)2{(C₆H₅O)₂PO ₂}₂] (4), [Fe₂(L^a)₂(CH₃COCHCOCH ₃)₂] (5), [Fe₂(L^b)₂(CH₃CO₂) ₂] (6), and [Fe₂(L^c)₂(CH₃CO₂) ₂] (7), have been synthesized and characterized by measurements of the infrared and electronic spectra as well as the magnetic susceptibilities. Single-crystal X-ray analysis has revealed that all of the complexes are dinuclear iron(III) complexes having a dinuclear iron(III) core bridged by two phenoxo-oxygen atoms of the Schiff-base ligands. The magnetic-susceptibility data show that a ferromagnetic interaction is operative within a dinuclear core in 1-4, 6, and 7 with J values ranging from 0.17(5) to 1.56(15) cm^-1, whereas an antiferromagnetic coupling is operative in 5 with a J value of -9.24(6) cm^-1. The magnetic properties are discussed in relation to the crystal structures.

Full text of DOI:10.1246/bcsj.74.1425

c. Jpn.
© 2001 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 74, 1425–1434 (2001) 1425
e Chemical
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Synthesis and Structural Characterization of Di- -Phenoxo-Bridged
Dinuclear Iron(Ⅲ) Complexes with Ferromagnetic or Weak
Antiferromagnetic Coupling
Dinuclear Iron(Ⅲ) Complexes
M. Mikuriya et al.
01
25
Masahiro Mikuriya,* Yoshihisa Kakuta, Ryoji Nukada, Takanori Kotera, and Tadashi Tokii†
34
Department of Chemistry, School of Science, Kwansei Gakuin University, Uegahara, Nishinomiya 662-8501
SJA8
09-2673
028
†Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University,
Honjo 1, Saga 840-8502
(Received January 29, 2001)
01
01
Dinuclear phenoxo-bridged iron(Ⅲ) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H2La), N-
salicylidene-2-hydroxy-5-chlorobenzylamine
(H2Lb),
and
N-salicylidene-2-hydroxybenzylamine
(H2Lc):
[Fe2(La)2(CH3CO2)2] (1), [Fe2(La)2(C6H5CO2)2] (2), [Fe2(La){(CH3)3CCO2}2] (3), [Fe2(La)2{(C6H5O)2PO2}2] (4),
[Fe2(La)2(CH3COCHCOCH3)2] (5), [Fe2(Lb)2(CH3CO2)2] (6), and [Fe2(Lc)2(CH3CO2)2] (7), have been synthesized and
characterized by measurements of the infrared and electronic spectra as well as the magnetic susceptibilities. Single-
crystal X-ray analysis has revealed that all of the complexes are dinuclear iron(Ⅲ) complexes having a dinuclear iron(Ⅲ)
core bridged by two phenoxo-oxygen atoms of the Schiff-base ligands. The magnetic-susceptibility data show that a fer-
romagnetic interaction is operative within a dinuclear core in 1–4, 6, and 7 with J values ranging from 0.17(5) to
1.56(15) cm−1, whereas an antiferromagnetic coupling is operative in 5 with a J value of −9.24(6) cm−1. The magnetic
properties are discussed in relation to the crystal structures.
Dinuclear iron complexes have been of wide interest and
relevance to studies of biological iron-containing proteins.1
Today, it is well known that dinuclear iron centers have impor-
tant functional roles in the active sites of iron-containing pro-
teins, such as hemerythrin, ribonucleotide reductase, methane
monooxygenase, and purple acid phosphatases.2 During the
last decade, a large number of dinuclear iron complexes have
been synthesized as models for biological systems. These
complexes are interesting not only from a bioinorganic-chemi-
cal point of view, but also from a magneto-chemical stand
point. As for dinuclear copper(Ⅱ) and chromium(Ⅲ) complex-
es, semiquantative relationships have been established between
the magnetic exchange coupling constants and the structural
parameters.3 Several attempts to correlate the magnetic ex-
change parameters to the structural parameters have been made
for dinuclear iron(Ⅲ) complexes.4 Gorun and Lippard corre-
lated the strength of antiferromagnetic coupling in dinuclear
iron(Ⅲ) centers incorporating a ligand oxygen atom bridge
with parameter P, defined as half the distance of the shortest
superexchange pathway between the iron centers, according to
the relation −J = Aexp (BP), with A = 8.763 × 1011 and B =
−12.663.4a However, there seems to exist no clear relationship
between magnetic and structural parameters, such as J and M–
O–M angles for iron systems. This may come from the fact
that most of the reported dinuclear iron(Ⅲ) complexes are µ-
oxo-bridged iron(Ⅲ) dimers containing µ-oxo-,5 di-µ-oxo-,6 µ-
oxo-µ-carboxylato-,7 µ-oxo-di-µ-carboxylato-,8 µ-oxo-µ-car-
bonato-,9 µ-oxo-di-µ-carbonato-,10 µ-oxo-µ-molybdato-,11 µ-
oxo-µ-phosphato-,12 and µ-oxo-µ-phosphinato-13 bridges, and
that examples of other types of dinuclear species are very lim-
ited.14–18 As part of a continuing project on metal complexes
with tridentate Schiff-base ligands,19,20 we have reported on the
synthesis and characterization of several manganese and vana-
dium complexes with N-salicylidene-2-hydroxybenzylamine
and its substituted analogues. During this activity, we found
that novel di-µ-phenoxo-bridged iron(Ⅲ) complexes are
formed in reactions of these Schiff-base ligands with iron salts.
It is important to develop syntheses of di-µ-phenoxo-bridged
iron(Ⅲ) species with a view to studying the magneto-structural
relationship for iron systems. Herein we report on the synthe-
sis, magnetic properties, and crystal structures of dinuclear
iron(Ⅲ) complexes with N-salicylidene-2-hydroxy-5-bro-
mobenzylamine (H2La), N-salicylidene-2-hydroxy-5-chlo-
robenzylamine (H2Lb) and N-salicylidene-2-hydroxybenzyl-
amine (H2Lc). A preliminary account of this study was previ-
ously reported.21
Experimental
Synthesis of the Complexes. o-Hydroxybenzylamine was
prepared by a published procedure.22 2-Hydroxy-5-chlorobenzy-
lamine and 2-hydroxy-5-bromobenzylamine were synthesized ac-
cording to a method reported by Yamaguchi.23
[Fe2(La)2(CH3CO2)2] (1). 2-Hydroxy-5-bromobenzylamine
(20 mg, 0.099 mmol) and salicylaldehyde (12 mg, 0.098 mmol)
were dissolved in 10 cm3 of acetonitrile. The solution was stirred
and heated at ca. 70 °C. To the resulting solution were successive-
ly added acetic acid (12 mg, 0.20 mmol), triethylamine (22 mg,
0.22 mmol), and iron(Ⅲ) chloride hexahydrate (27 mg, 0.10
mmol). After the reaction mixture had been stirred and filtered
while hot, the filtrate was placed at room temperature for several

1426 Bull. Chem. Soc. Jpn., 74, No. 8 (2001)
Dinuclear Iron(ꢀ) Complexes
days. Black crystals were deposited and collected by filtration and
dried in vacuo over P2O5: Yield, 26 mg (31%). Found: C, 45.94;
H, 3.16; N, 3.53%. Calcd for C32H26Br2Fe2N2O8: C, 45.86; H,
3.13; N, 3.34%. IR (KBr, cm−1) ν(CwN) 1615, νas(COO−) 1538,
νs(COO−) 1400. µeff (295 K) per molecule/B.M. 8.64. Diffuse re-
flectance spectrum: λmax/nm 255, 319, 509. Electronic spectrum
in dmf (N,N-dimethylformamide): λmax/nm (ε per Fe/dm3 mol−1
cm−1) 293 (10960), 418 (3130), 455sh (2880).
reflectance spectrum: λmax/nm 257, 319, 466. Electronic spectrum
in dmf: λmax/nm(ε per Fe/dm3 mol−1 cm−1) 310sh (13500), 430sh
(3200), 477 (3900).
[Fe2(Lb)2(CH3CO2)2] (6). After 2-hydroxy-5-chlorobenzyl-
amine (16 mg, 0.10 mmol) and salicylaldehyde (12 mg, 0.098
mmol) were dissolved in acetonitrile (10 cm3), acetic acid (12 mg,
0.20 mmol), triethylamine (22 mg, 0.22 mmol), and iron(Ⅲ) chlo-
ride hexahydrate (27 mg, 0.10 mmol) were added. After the solu-
tion had been filtered, the filtrate was allowed to stand for several
days at room temperature. Black crystals resulted, which were fil-
tered and dried in vacuo over P2O5: Yield, 21 mg (28%). Found:
C, 51.37; H, 3,44; N, 3.74%. Calcd for C32H26Cl2Fe2N2O8: C,
51.30; H, 3.50; N, 3.74%. IR (KBr, cm−1) ν(CwN) 1618,
νas(COO−) 1539, νs(COO−) 1400. µeff (295 K) per molecule/B.M.
8.38. Diffuse reflectance spectrum: λmax/nm 255, 315, 500. Elec-
tronic spectrum in dmf: λmax/nm(ε per Fe/dm3 mol−1 cm−1) 292
(16900), 415 (4580), 450sh (4130).
[Fe2(La)2(C6H5CO2)2] (2). 2-Hydroxy-5-bromobenzylamine
(20 mg, 0.099 mmol) and salicylaldehyde (12 mg, 0.098 mmol)
were dissolved in acetonitrile (20 cm3). While the solution was
being stirred, sodium benzoate (29 mg, 0.20 mmol) and iron(Ⅲ)
chloride hexahydrate (27 mg, 0.10 mmol) were added, and the re-
sulting solution was filtered. After the filtrate was allowed to
stand for several days at room temperature, black crystals resulted,
which were filtered and dried in vacuo over P2O5: Yield, 31 mg
(32%). Found: C, 52.42; H, 2.91; N, 3.14%. Calcd for
C42H30Br2Fe2N2O8: C, 52.43; H, 3.14; N, 2.91%. IR (KBr, cm−1
)
[Fe2(Lc)2(CH3CO2)2] (7). This complex was prepared in the
same way as that for 6, except for using an equimolar amount of
2-hydroxybenzylamine instead of 2-hydroxy-5-chlorobenzy-
lamine. Yield, 21 mg (31%). Found: C, 56.20; H, 4.18; N, 4.34%.
Calcd for C32H28Fe2N2O8: C, 56.50; H, 4.15; N, 4.12%. IR (KBr,
cm−1) ν(CwN) 1615; νas(COO−) 1531, νs(COO−) 1400. µeff(295
ν(CwN) 1617, νas(COO−) 1540, νs(COO−) 1391. µeff (295 K) per
molecule/B.M. 8.34. Diffuse reflectance spectrum: λmax/nm 255,
318, 516. Electronic spectrum in dmf: λmax/nm(ε per Fe/dm3
mol−1 cm−1) 290sh (4180), 420sh (1100), 470sh (790).
[Fe2(La){(CH3)3CCO2}2] (3). After 2-hydroxy-5-bromoben-
zylamine (20 mg, 0.099 mmol) and salicylaldehyde (12 mg, 0.098
mmol) were dissolved in acetonitrile (10 cm3), pivalic acid (20
mg, 0.20 mmol), triethylamine (30 mg, 0.30 mmol), and iron(Ⅲ)
chloride hexahydrate (27 mg, 0.10 mmol) were added. After the
resulting solution was filtered, the filtrate was left standing for
several days at room temperature to give black crystals. These
were collected by filtration and dried in vacuo over P2O5:Yield, 34
mg (37%). Found: C, 49.34; H, 4.12; N, 3.09%. Calcd for
K) per molecule/B.M. 8.69. Diffuse reflectance spectrum: λmax
/
nm 250, 323, 506. Electronic spectrum in dmf: λmax/nm(ε per Fe/
dm3 mol−1 cm−1) 280sh (6250), 314sh (4630), 422 (1860), 452sh
(1800).
Measurements. Carbon, hydrogen, and nitrogen analyses
were carried out using a Perkin-Elmer 2400 Series Ⅱ CHNS/O
Analyzer. Infrared spectra were measured with a JASCO Infrared
Spectrophotometer model IR700 in the 4000–400 cm−1 region on
a KBr disk. The electronic spectra were measured with a Shimad-
zu UV-vis-NIR Recording Spectrophotometer Model UV-3100.
The temperature dependence of magnetic susceptibilities was
measured with a Quantum Design MPMS-5S SQUID susceptom-
eter operating at a magnetic field of 0.5 T between 2 and 300 K.
The field dependence of magnetization was measured up to 4.8 T
at 4.5 K. The susceptibilities were corrected for the diamagnetism
of the constituent atoms using Pascal’s constants.24 The effective
C38H38Br2Fe2N2O8: C, 49.49; H, 4.15; N, 3.04%. IR(KBr, cm−1
)
ν(CwN) 1618, νas(COO−) 1518, νs(COO−) 1413. µeff (295 K) per
molecule/B.M. 8.37. Diffuse reflectance spectrum: λmax/nm 254,
324, 510. Electronic spectrum in dmf: λmax/nm(ε per Fe/dm3
mol−1 cm−1) 293 (11560), 420 (3200), 460sh (3120).
[Fe2(La)2((C6H5O)2PO2)2] (4). 2-Hydroxy-5-bromobenzyl-
amine (20 mg, 0.099 mmol) and salicylaldehyde (12 mg, 0.098
mmol) were dissolved in a mixture of acetonitrile (15 cm3) and
N,N-dimethylformamide (3 cm3). While the soltuion was being
stirred, diphenyl phosphate (25 mg, 0.10 mmol), triethylamine (5
mg, 0.05 mmol), and iron(Ⅲ) chloride hexahydrate (27 mg, 0.10
mmol) were added, and the resulting solution was filtered. The fil-
trate was left standing for several days at room temperature to give
black crystals. They were collected by filtration and dried in vac-
uo over P2O5: Yield, 17 mg (14%). Found: C, 50.81; H, 3.25; N,
2.76%. Calcd for C52H40Br2Fe2N2O12P2: C, 51.26; H, 3.31; N,
2.30%. IR (KBr, cm−1) ν(CwN) 1618, ν(P–O) 1178, 1063.
µeff(295 K) per molecule/B.M. 8.47. Diffuse reflectance spec-
magnetic moments were calculated from the equation µeff
2.828 χmT , where χm is the magnetic susceptibility per mole.
=
X-ray Crystal Structure Analysis. The crystal data and de-
tails of the data collection are given in Table 1. The crystals were
sealed in a glass capillary together with the mother liquor and
mounted on an Enraf-Nonius CAD4 diffractometer, using graph-
ite-monochromated Mo-Kα radiation at 25 1 °C. The unit-cell
parameters were determined by a least-squares refinement based
on 25 reflections with 20 ≤ 2θ ≤ 30°. Intensitiy data were correct-
ed for Lorentz-polarization effects. The structures were solved by
direct methods and refined by full-matrix least-squares methods.
All of the non-hydrogen atoms were refined with anisotropic ther-
mal parameters. The hydrogen atoms were inserted at their calcu-
lated positios and fixed at their positions. The final discrepancy
factors, R = Σ||Fo| − |Fc||/Σ|Fo|, Rw = [Σw(|Fo| − |Fc|)2/
trum: λmax/nm 262, 319, 520. Electronic spectrum in dmf: λmax
/
nm(ε per Fe/dm3 mol−1 cm−1) 295 (12300), 317sh (11300), 434sh
(2380), 487 (3110).
[Fe2(Lb)2(CH3COCHCOCH3)2] (5). After 2-hydroxy-5-bro-
mobenzylamine (20 mg, 0.099 mmol) and salicylaldehyde (12
mg, 0.098 mmol) were dissolved in acetonitrile (15 cm3), iron(Ⅲ)
acetylacetonate (35 mg, 0.10 mmol) was added with stirring. Af-
ter the solution had been filtered, the filtrate was left at room tem-
perature for several days to give black crystals. Yield, 27 mg
(29%). Found: C, 49.74; H, 3.73; N, 3.13%. Calcd for
2
Σw|Fo| ]1/2, are listed in Table 1. The weighting scheme, w = 1/
[σ2(|Fo|) + (0.02|Fo|)2 + 1.0], was employed. All of the calcula-
tions were carried out on a Micro-VAXⅡ computer using a Enraf–
Nonius SDP program package.25 The atomic coordinates and
thermal parameters of the atoms and the anisotropic thermal pa-
rameters of the non-hydrogen atoms have been deposited as Docu-
ment No. 74045 at the Office of the Editor of Bull. Chem. Soc.
Jpn. Crystallographic data have been deposited at the CCDC, 12
C38H34Br2Fe2N2O8: C, 49.71; H, 3.73; N, 3.05%. IR (KBr, cm−1
ν(CwN) 1617; ν(CwC
CwO(acac−)) 1581; ν(CwC
CwO(acac−)) 1528. µeff (295 K) per molecule/B.M. 7.38. Diffuse
)
+
+

M. Mikuriya et al.
Bull. Chem. Soc. Jpn., 74, No. 8 (2001) 1427
α
σ
θ
α
β
γ
µ

1428 Bull. Chem. Soc. Jpn., 74, No. 8 (2001)
Dinuclear Iron(ꢀ) Complexes
Union Road, Cambridge CB2, 1EZ, UK and copies can be ob-
tained on request, free of charge, by quoting the publication cita-
tion and the deposition numbers 163629–163635.
Results and Discussion
Complexes 1–7 were prepared via one-pot synthesis, given
in the Experimental Section. In previous papers, we described
the synthesis and characterization of other related metal com-
plexes with the present Schiff-base ligands. The Schiff-base
ligands afforded mononuclear Mn(Ⅳ) species, [Mn(L)2] (H2L
= H2La, H2Lb, and H2Lc);19 mononuclear V(Ⅳ) species,
[VO(HLc)2]; and dinuclear V(Ⅴ) species, [(VO)2(Lc)2O],20 sta-
bilizing such a higher oxidation state owing to the presence of
the two phenolic-oxygen donors. In the present cases, the re-
action of the Schiff-base ligands with iron(Ⅲ) in the presence
of exogenous ligands gave black crystals of dinuclear Fe(Ⅲ)
species,
which
have
the
general
composition
−
[Fe2L2X2]•nCH3CN (L = La, Lb, and Lc; X = CH3CO2
,
−
−
−
C6H5CO2
,
(CH3)3CCO2
,
(C6H5O)2PO2
,
and
CH3COCHCOCH3−; n = 0, 2, and 4). This is in contrast with
the cases for the manganese and vanadium systems, and is
probably due to the unstable property of the Fe(Ⅳ) state. Sim-
ilarly, we could isolate dinuclear Cu(Ⅱ) species, [Cu2(L)2(dm-
so)2] (H2L = H2La and H2Lb, dmso = dimethyl sulfoxide) for
copper systems by using the same Schiff-base ligands (Scheme
1).21
Fig. 1. ORTEP drawing of the structure of [Fe2(La)2(CH3-
CO2)2]•2CH3CN (1•2CH3CN) showing the 50% probabili-
ty thermal ellipsoids and atom labeling scheme. Hydrogen
atoms and solvent molecules are omitted for clarity.
Primed and unprimed atoms are related by the inversion.
phenoxo-oxygen atom (O1ꢀ) of the other ligand La. The fifth
and sixth coordination sites are occupied by the two acetato
oxygen atom (O3 and O4). The iron centers are arranged in an
approximate octahedral geometry with distances of Fe–O1
2.107(3), Fe–O1ꢀ 2.021(3), Fe–O2 1.885(3), Fe–O3 2.039(2),
Fe–O4 2.055(3), Fe–N 2.083(4) Å. The Fe–Fe separation and
Fe–O–Fe angle are 2.957(1) Å and 91.5(1)°, respectively.
These values are significantly smaller than those yet found for
Ⅲ
complexes with the Fe 2(OR)2 complexes [di-µ-hydroxo-
Ⅲ
bridged Fe 2 complexes:14 Fe–Fe 3.078(2)–3.155(3) Å, Fe–O–
Fe 100.7(4)–105.3(4)°; di-µ-alkoxo-bridged Fe 2 complexes:15
Ⅲ
Scheme 1.
Fe–Fe 3.049(3)–3.21(1) Å, Fe–O–Fe 101.8(3)–107.4(6)°; di-
Ⅲ
µ-phenoxo-bridged Fe 2 complexes:16 Fe–Fe 3.06–3.186(4) Å,
The X-ray crystallography of 1 reveals a dinuclear structure
where two iron(Ⅲ) ions are doubly bridged by phenoxo-oxy-
gen atoms of the Schiff-base ligands, La. A perspective view
of the molecule is shown in Fig. 1. Selected bond distances
and angles are listed in Table 2. Only a few examples of strc-
turally characterized Fe(Ⅲ) complexes with di-µ-phenoxo-ox-
ygen-bridging are known.16 The dinuclear molecule is cen-
trosymmetric with a crystallographic inversion center in the
middle of the Fe2O2 core. The two iron atoms are further
bridged by two acetate bridging in a syn–syn configuration.
The antisymmetric and symmetric C–O stretching bands of the
acetate ions were found at 1530 and 1400 cm−1, respectively.
This feature is in harmony with the syn–syn bridging mode of
the acetate group.26 The unique bridging mode of the two ace-
tate ions was already found in [Mn2(spa)2(CH3CO2)2] (H2spa
= 3-salicylideneamino-1-propanol).27 Each iron atom (Fe) is
coordinated to two phenoxo-oxygen and one imino-nitrogen
atoms (O1, O2, and N1) of the Schiff-base ligand La and one
Fe–O–Fe 97.06(9)–105.64(3)°].
The crystal structures of 2 and 3 consist of similar cen-
trosymmetric dinuclear molecules to that of 1, as shown in
Figs. 2 and 3, respectively. The two Fe atoms are bridged by
two phenoxo-oxygen atoms of La to form an equatorial co-
plane. The carboxylate groups of benzoate and pivalate ions
are positioned above and below the equatorial plane containing
the Schiff-base moiety, and is involved in the bridges in a syn–
syn configuration. The Fe–Fe separation and Fe–O–Fe angle
for 2 and 3 are 2.953(2) Å and 91.6(2)° and 2.959(3) Å and
92.3 (4)°, respectively; these values are significantly smaller
Ⅲ
than those for the reported Fe 2(OR)2 complexes.14–16
The crystal structure of 4 is shown in Fig. 4. The molecule
is crystallographically centrosymmetric. The two Fe atoms are
bridged by two phenoxo-oxygen atoms of the Schiff-base
ligands La. The Fe atoms are further bridged by two diphenyl
phosphate ions with a similar triatomic bridging mode to the
syn–syn acetate bridge. The Fe–Fe distance and the Fe–O–Fe

M. Mikuriya et al.
Bull. Chem. Soc. Jpn., 74, No. 8 (2001) 1429
Table 2. Selected Bond distances (Å) and Angles (°) of with Their Estimated Standard Deviations in Parentheses
[Fe2(La)2(CH3CO2)2]•2CH3CN (1•2CH3CN)
[Fe2(La)2(CH3COCHCOCH3)2] (5)
Fe–Feꢀa)
Fe–O1
Fe–O1ꢀ
Fe–O2
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N1
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
2.957(1)
2.107(3)
2.021(3)
1.885(3)
88.5(1)
172.3(1)
82.0(1)
81.5(1)
86.0(1)
97.6(1)
85.1(1)
83.4(1)
Fe–O3
Fe–O4
Fe–N1
2.039(2)
2.055(3)
2.083(4)
FeA–FeAꢀd)
FeA–O1A
FeA–O1Aꢀ
FeA–O2A
FeA–O3A
FeA–O4A
FeA–NA
O1A–FeA–O1Aꢀ
O1A–FeA–O2A
O1A–FeA–O3A
O1A–FeA–O4A
O1A–FeA–NA
O1Aꢀ–FeA–O2A
O1Aꢀ–FeA–O3A
O1Aꢀ–FeA–O4A
O1Aꢀ–FeA–NA
O2A–FeA–O3A
O2A–FeA–O4A
O2A–FeA–NA
O3A–FeA–O4A
O3A–FeA–NA
O4A–FeA–NA
FeA–O1A–FeAꢀ
3.270(1)
2.036(4)
2.051(4)
1.901(4)
1.998(5)
2.010(4)
2.149(6)
73.7(2)
165.2(2)
96.9(2)
91.8(2)
83.5(2)
95.7(2)
91.8(2)
165.0(2)
96.7(2)
93.6(2)
99.3(2)
87.8(2)
86.1(2)
171.3(2)
85.2(2)
106.3(2)
FeB–FeBꢁe)
FeB–O1B
FeB–O1Bꢁ
FeB–O2B
FeB–O3B
FeB–O4B
FeB–NB
O1B–FeB–O1Bꢁ
O1B–FeB–O2B
O1B–FeB–O3B
O1B–FeB–O4B
O1B–FeB–NB
O1Bꢁ–FeB–O2B
O1Bꢁ–FeB–O3B
O1Bꢁ–FeB–O4B
O1Bꢁ–FeB–NB
O2B–FeB–O3B
O2B–FeB–O4B
O2B–FeB–NB
O3B–FeB–O4B
O3B–FeB–NB
O4B–FeB–NB
FeB–O1B–FeBꢁ
3.275(1)
2.043(5)
2.051(4)
1.888(5)
2.013(5)
2.019(5)
2.133(5)
73.8(2)
164.7(2)
96.9(2)
90.7(2)
84.4(2)
94.1(2)
91.4(2)
163.6(2)
98.6(2)
92.4(2)
102.1(2)
88.5(2)
85.1(2)
169.9(2)
84.8(2)
O1ꢀ–Fe–N1
O2–Fe–O3
O2–Fe–O4
O2–Fe–N1
O3–Fe–O4
O3–Fe–N1
O4–Fe–N1
Fe–O1–Feꢀ
173.9(1)
103.2(1)
94.5(1)
88.1(1)
160.0(1)
91.5(1)
98.4(1)
91.5(1)
[Fe2(La)2(C6H5CO2)2] (2)
Fe–Feꢀa)
Fe–O1
Fe–O1ꢀ
Fe–O2
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N1
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
2.953(2)
Fe–O3
Fe–O4
Fe–N
2.044(8)
2.055(8)
2.089(7)
2.081(6)
2.037(6)
1.875(7)
88.4(2)
173.8(3)
83.8(3)
81.3(3)
86.1(3)
96.9(3)
83.4(3)
84.5(3)
O1ꢀ–Fe–N
O2–Fe–O3
O2–Fe–O4
O2–Fe–N
O3–Fe–O4
O3–Fe–N
O4–Fe–N
Fe–O1–Feꢀ
174.5(3)
100.1(3)
95.9(3)
88.6(3)
160.9(3)
95.5(3)
95.2(3)
91.6(2)
106.2(2)
[Fe2(Lb)2{(CH3CO2)2]•2CH3CN (6•2CH3CN)
Fe–Feꢀf)
Fe–O1
Fe–O1ꢀ
Fe–O2
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N1
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
2.960(1)
2.103(3)
2.021(3)
1.883(3)
88.3(1)
172.3(1)
81.6(1)
81.7(1)
86.1(1)
98.1(1)
84.9(1)
83.3(1)
Fe–O3
Fe–O4
Fe–N1
2.037(2)
2.053(2)
2.089(4)
[Fe2(La)2{(CH3)3CCO2}2] (3)
Fe–Feꢀb)
Fe–O1
Fe–O1ꢀ
Fe–O2
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
2.959(3)
2.079(10)
2.024(10)
1.873(11)
87.7(4)
174.0(5)
81.4(4)
82.6(4)
86.4(4)
98.2(5)
85.0(4)
83.0(4)
Fe–O3
Fe–O4
Fe–N
2.014(11)
2.061(10)
2.095(13)
O1ꢀ–Fe–N1
O2–Fe–O3
O2–Fe–O4
O2–Fe–N1
O3–Fe–O4
O3–Fe–N1
O4–Fe–N1
Fe–O1–Feꢀ
173.7(1)
103.3(1)
94.6(1)
87.8(1)
159.8(1)
91.5(1)
98.7(1)
91.7(1)
O1ꢀ–Fe–N
O2–Fe–O3
O2–Fe–O4
O2–Fe–N
O3–Fe–O4
O3–Fe–N
O4–Fe–N
Fe–O1–Feꢀ
173.6(4)
100.2(5)
96.9(5)
87.7(5)
160.4(5)
91.6(5)
98.7(5)
92.3(4)
[Fe2(Lc)2(CH3CO2)2] (7)
Fe–Fea)
2.930(1)
Fe–O3
Fe–O4
Fe–N
2.060(3)
2.053(3)
2.106(3)
Fe–O1
Fe–O1ꢀ
Fe–O2
2.093(3)
2.017(2)
1.877(3)
89.1(1)
173.9(1)
81.9(1)
81.6(1)
86.3(1)
96.7(1)
84.8(1)
84.6(1)
[Fe2(La)2{(C6H5O)2PO2}2]•4CH3CN(4•4CH3CN)
Fe–Feꢀc)
Fe–O1
Fe–O1ꢀ
Fe–O2
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N1
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
3.091(1)
2.115(5)
2.030(4)
1.877(5)
83.6(2)
174.8(2)
83.8(2)
83.7(2)
Fe–O3
Fe–O4
Fe–N1
2.029(5)
2.047(5)
2.076(6)
O1–Fe–O1ꢀ
O1–Fe–O2
O1–Fe–O3
O1–Fe–O4
O1–Fe–N
O1ꢀ–Fe–O2
O1ꢀ–Fe–O3
O1ꢀ–Fe–O4
O1ꢀ–Fe–N
O2–Fe–O3
O2–Fe–O4
O2–Fe–N
O3–Fe–O4
O3–Fe–N
O4–Fe–N
Fe–O1–Feꢀ
171.8(1)
100.4(1)
97.0(1)
88.2(1)
160.5(1)
87.8(1)
101.4(1)
90.9(1)
O1ꢀ–Fe–N1
O2–Fe–O3
O2–Fe–O4
O2–Fe–N1
O3–Fe–O4
O3–Fe–N1
O4–Fe–N1
Fe–O1–Feꢀ
170.8(2)
99.8(2)
93.2(2)
88.9(2)
165.3(2)
92.1(2)
95.0(2)
96.4(2)
87.3(2)
100.3(2)
86.0(2)
85.0(2)
a) Prime refers to the equivalent position (1−x, −y, −z). b) Prime refers to the equivalent position (2−x, 1−y, 1−z). c) Prime
refers to the equivalent position (1−x, 1−y, 1−z). d) Prime refers to the equivalent position (1−x, 1−y, −z). e) Double prime
refers to the equivalent position (2−x, −y, 2−z). f) Prime refers to the equivalent position (1−x, −y, 1−z).
angle are 3.091(1) Å and 96.4(2)°, respectively. The elonga-
tion of the Fe–Fe distance and the obtuse Fe–O–Fe angle com-
pared with those of 1–3 may be caused by the bigger triatomic
bridging groups. The coordination geometry of each iron atom
is a distorted octahedral with Fe–O1 (2.115(5) Å), Fe–O2
(1.877(5) Å), Fe–O3 (2.029(5) Å), Fe–O4ꢀ (2.047(5) Å), Fe–
O1ꢀ (2.030(4) Å), and Fe–N1 (2.076(6) Å).
The crystal of 5 contains two crystallographically indepen-
dent dinuclear molecules; they are abbreviated as A and B.
Figure 5 shows the structure of molecule A. Both comprise a

1430 Bull. Chem. Soc. Jpn., 74, No. 8 (2001)
Dinuclear Iron(ꢀ) Complexes
Fig. 4. ORTEP drawing of the structure of [Fe2(La)2{(C6H5-
O)2PO2}2]•4CH3CN (4•4CH3CN) showing the 50% proba-
bility thermal ellipsoids and atom labeling scheme. Hy-
drogen atoms and solvent molecules are omitted for clarity.
Primed and unprimed atoms are related by the inversion.
Fig. 2. ORTEP drawing of the structure of [Fe2(La)2(C6H5-
CO2)2] (2) showing the 50% probability thermal ellipsoids
and atom labeling scheme. Hydrogen atoms are omitted
for clarity. Primed and unprimed atoms are related by the
inversion.
Fig. 5. ORTEP drawing of the structure (molecule A) of
[Fe2(La)2(CH3COCHCOCH3)2] (5) showing the 50% prob-
ability thermal ellipsoids and atom labeling scheme. Hy-
drogen atoms are omitted for clarity. Primed and unprimed
atoms are related by the inversion.
axial and equatorial positions of the distorted octahedral geom-
etry. No significant difference in the geometries of the two di-
nuclear molecules can be recognized between A and B. The
Fe–Fe separation and Fe–O–Fe angle are 3.270(1) Å and
106.3(2)° for A and 3.275(1) Å and 106.2(2)° for B, respec-
tively. These values are much larger than those of 1–4 and
Fig. 3. ORTEP drawing of the structure of [Fe2(La)2{(CH3)3-
CCO2}2] (3) showing the 50% probability thermal ellip-
soids and atom labeling scheme. Hydrogen atoms and sol-
vent molecules are omitted for clarity. Primed and
unprimed atoms are related by the inversion.
Ⅲ
comparable to those of the usual Fe 2(OR)2 complexes.14,15,16b
similar centrosymmetric dinuclear molecule. In the complex,
the two iron atoms are bridged by only phenoxo-oxygen atoms
of the Schiff-base ligands. The acetylacetonato group is coor-
dinated to each iron atom in a didentate fashion to occupy the
As shown in Figs. 6 and 7, the molecular structures of 6 and
7 are very similar to that of 1. The two Fe atoms are bridged
by two phenoxo-oxygen atoms of the Schiff-base ligands Lb or
Lc and two acetate ions. The Fe–Fe sepapration and Fe–O–Fe

M. Mikuriya et al.
Bull. Chem. Soc. Jpn., 74, No. 8 (2001) 1431
angle for 6 and 7 are 2.960(1) Å and 91.7(1)° and 2.930(1) Å
and 90.9(1)°, respectively.
µ-phenoxo-di-µ-carboxylato-bridged complexes may be due to
constraints imposed by the incorporation of bridging carboxy-
late groups.
For the di-µ-phenoxo-di-µ-carboxylato-bridged complexes,
1–3, 6, 7, the Fe–O–Fe angle varies from 90.9(1) to 92.3(4)°
and the Fe–Fe separation from 2.930(1) to 2.960(1) Å; for the
di-µ-phenoxo-di-µ-phosphato-bridged complex 4, the Fe–O–
Fe angle is 96.4(2)° and the Fe–Fe separation is 3.091(1) Å.
The Fe–O–Fe angles for the di-µ-phenoxo-bridged complex 5
are 106.3(2) and 106.2(2)° and the Fe–Fe separations are
3.270(1) and 3.275(1) Å, respectively. These facts show that
the short Fe–Fe separation and small Fe–O–Fe angle in the di-
The diffuse reflectance spectra of the present complexes are
similar, and are characterized by intense absorptions around
255, 320 and 510 nm. The diffuse reflectance spectrum of 1 is
shown in Fig. 8 as a representative example. Since all d–d
transitions are expected to be spin forbidden, the observed ab-
sorptions are most likely to arise from charge-transfer transi-
tions and/or intraligand transitions. Especially, the band
around 510 nm can be assigned as a charge-transfer transition
from bridging phenoxo-oxygen to iron(Ⅲ). For the present di-
µ-phenoxo-bridged iron(Ⅲ) dimers, there is no evidence for a
substantial intensity enhancement of the spin-forbidden d–d
bands, such as that found in certain oxo-bridged iron(Ⅲ)
dimers.28 The absorption spectra in dmf for the complexes are
in generally agreement with the solid-state spectra. All com-
plexes show a shoulder at 450–487 nm, followed by two strong
absorptions beginning at about 420 nm up to the peak maxi-
mum at about 290 nm. The large values of the molar extinc-
tion coefficient of these absorptions indicates that these may be
due to ligand to iron(Ⅲ) charge-transfer bands. The higher en-
ergy band at around 290 nm may be assigned as ligand π→π*
transitions.
The room-temperature magnetic moments of these com-
plexes [1, 8.64 B.M. (295 K); 2, 8.34 B.M. (295 K); 3, 8.37
B.M. (295 K); 4, 8.47 B.M. (295 K); 5, 7.32 B.M. (295 K); 6,
8.38 B.M. (295 K); 7, 8.69 B.M. (295 K)] are close to the spin-
only value (8.37 B.M.) for non-interacting two high-spin d5
ions, except for 5. The high-spin character of the present
iron(Ⅲ) complexes is in harmony with the electronic spectra.
The magnetic moment of 5 is considerably lower than those of
the usual high-spin Fe(Ⅲ) complexes, suggesting an antiferro-
magnetic behavior of this complex. The magnetic susucepti-
bilities were measured over the temperature range 2–300 K.
As expected, 5 is antiferromagnetic, since the magnetic mo-
ment decreases with lowering the temperature (Fig. 9). On the
other hand, the profiles of the temperature dependence of the
magnetic moments of the other complexes, 1–3, 5–7, show that
a ferromagnetic interaction is operative, as illustrated in Figs.
Fig. 6. ORTEP drawing of the structure of [Fe2(Lb)2(CH3-
CO2)2]•2CH3CN (6•2CH3CN) showing the 50% probabili-
ty thermal ellipsoids and atom labeling scheme. Hydrogen
atoms and solvent molecules are omitted for clarity.
Primed and unprimed atoms are related by the inversion.
Fig. 7. ORTEP drawing of the structure of [Fe2(Lc)2(CH3-
CO2)2] (7) showing the 50% probability thermal ellipsoids
and atom labeling scheme. Hydrogen atoms are omitted
for clarity. Primed and unprimed atoms are related by the
inversion.
Fig. 8. Diffuse reflectance spectrum of [Fe2(La)2(CH3CO2)2]
(1).

1432 Bull. Chem. Soc. Jpn., 74, No. 8 (2001)
Dinuclear Iron(ꢀ) Complexes
Fig. 11. Magnetic susceptibity data and effective magnetic
moments of [Fe2(La)2{(CH3)3CCO2}2] (3) (ꢂ, ꢃ),
[Fe2(La)2{(C6H5O)2PO2}2] (4) (ꢄ, ꢅ), and [Fe2(Lb)2(CH3-
CO2)2] (6) (ꢀ, ꢁ).
Fig. 9. Magnetic susceptibity data (ꢀ) and effective magnet-
ic moments (ꢁ) of [Fe2(La)2(CH3COCHCOCH3)2] (5).
The J values for the present di-µ-phenoxo-bridged complexes
range from −9.24(6) cm−1 for the acetylacetonate complex 5
to 1.56(15) cm−1 for the acetate complex 7. Complexes 1–4, 6,
and 7 exhibit ferromagnetic coupling with J values of 0.17(5)
to 1.56(15) cm−1, while 5 exhibits an antiferromagnetic behav-
ior with a J value of −9.24(6) cm−1. To confirm the ferromag-
netic or antiferromagnetic nature of the ground state, the field
dependence of the magnetization M at 4.5 K was measured. In
Fig. 12, the experimental values of M are compared to the cal-
culated curve of the Brillouin functions for an S = 5 state. For
any value of the field, the experimental magnetization of 1–4, 6
and 7 is larger than that for an isolated S = 5/2 state, and close
to the value expected for an S = 5 spin state. On the other
hand, the magnetization data of 5 show an S = 0 ground state.
A comparison of these complexes with related complexes
provides some insight into the factors that affect the magnetic
coupling interaction. The J value (−9.24(6) cm−1) obtained
for 5 implies a much weaker coupling than those usually ob-
served for singly bridged µ-oxo-diiron(Ⅲ) compounds, which
exhibit J values of −80 to −190 cm−1,5 and is significantly
smaller than those typically found for µ-oxo-µ-carboxylato-,
µ-oxo-bis(µ-carboxylato)-, µ-oxo-µ-carbonato-, µ-oxo-di-µ-
carbonato-, µ-oxo-µ-molybdato-, µ-oxo-µ-phosphato-, and µ-
Fig. 10. Magnetic susceptibity data and effective magnetic
moments of [Fe2(La)2(CH3CO2)2] (1) (ꢀ, ꢁ), [Fe2(La)2-
(C6H5CO2)2] (2) (ꢂ, ꢃ) and [Fe2(Lc)2(CH3CO2)2] (7) (ꢄ,
ꢅ).
10 and 11. In the case of 4, the magnetic moment is almost
constant from 30 to 300 K, as shown in Fig. 11, indicating that
the magnetic interaction between the metal ions is small. The
magnetic-susceptibility data were analyzed with the Van Vleck
equation based on the Heisenberg model (H = −2JS1•S2 (S1 =
S2 = 5/2)):
oxo-µ-phosphinato-diiron(Ⅲ) complexes (J
= −83–134
cm−1).7–13 In the case of the di-µ-oxo-bridged complex, a J
value of −27 cm−1 was found.6 Studies of several di-µ-hy-
droxo- and di-µ-alkoxo-bridged dinuclear iron(Ⅲ) complexes
also have been reported. The J values in these complexes
range from −5.5 to −11.7 cm−1 and −6.5 to −28.6 cm−1, re-
spectively.14,15 The strength of the antiferromagnetic interac-
tions through the oxygen bridge is dependent on the nature of
the bridge, the exchange for µ-oxo-bridged complexes being
much stronger than for µ-hydroxo- or µ-alkoxo-bridged com-
plexes. The values of the exchange integral of the present anti-
ferromagnetic complex 5 is comparable to those of µ-hydroxo
or µ-alkoxo-bridged dinuclear iron(Ⅲ) systems. It is clear that
χm = Ng2β2/k(T − θ)(2e2x + 10e6x + 28e12x + 60e20x
+
110e30x)/(1 + 3e2x + 5e6x + 7e12x + 9e20x + 11e30x),
where x = J/kT and the other symbols have their usual mean-
ings.
The values for the three independent parameters (g, J, and
θ) determined by the fitting procedure are listed in Table 3.
The small values of θ suggest that second-order effects, such
as intermolecular interaction and zero-field splitting, are weak.

M. Mikuriya et al.
Bull. Chem. Soc. Jpn., 74, No. 8 (2001) 1433
Table 3. Structural and Magnetic Data of Di-µ-Phenoxo-Bridged Dinuclear Iron(Ⅲ) Complexes
Complex
Fe–O–Fe/°
90.9(1)
Fe≥Fe/Å
2.930(1)
J/cm−1
1.56(15) 2.05(2)
g
θ/K
0.33(7)
Ref.
[Fe2(Lc)2(CH3CO2)2] (7)
[Fe2(La)2(CH3CO2)2] (1)
[Fe2(La)2(C6H5CO2)2] (2)
[Fe2(Lb)2{(CH3CO2)2](6)
[Fe2(La)2{(CH3)3CCO2}2] (3)
[Fe2(La)2{(C6H5O2)2PO2}2] (4)
[Fe2(salmp)2]
This work
91.5(1)
91.6(2)
91.7(1)
92.3(4)
96.4(2)
97.06(9)
105.64(4)
2.957(1)
2.953(2)
2.960(1)
2.959(3)
3.091(1)
3.063
1.40(13) 2.02(2) −0.92(11) This work
1.53(1)
1.34(1)
1.23(4)
0.17(5)
1.21
1.96(1) −0.32(1)
1.97(1) −0.33(6)
1.97(1) −0.17(3)
2.02(2) −0.49(4)
This work
This work
This work
This work
16a
[Fe2(chphn)2Cl2]
3.186(4)
−10.9
−9.24(6)
16b
This work
[Fe2(La)2(CH3COCHCOCH3)2] (5) 106.3(2), 106.2(2) 3.270(1), 3.275(1)
2.04(1) −0.21(6)
thylphenol)16a and [Fe2(chphn)2Cl2] (H2chphn = N-(4-chloro-
2-hydroxyphenyl)-3-hydroxy-2-naphthaldimine),16b where J =
1.21 cm−1 and Fe–O–Fe angle of 97.06(9)° and J = −10.9
cm−1 and Fe–O–Fe angle of 105.64(4)° were described, re-
spectively. The correlations between the Fe–O–Fe angle and
the J values are listed in Table 3 for di-µ-phenoxo-bridged di-
nuclear iron(Ⅲ) complexes. From this, we can say that a
crossover from ferromagnetism (S = 5) to antiferromagnetism
(S = 0) has been observed at a Fe–O–Fe angle of ~98°, like in
the case for di-µ-hydroxo-bridged copper(Ⅱ) complexes.29
Conclusions
The phenolic-oxygen-containing ligands, N-salicylidene-2-
hydroxy-5-bromobenzylamine (H2La), N-salicylidene-2-hy-
droxy-5-chlorobenzylamine (H2Lb) or N-salicylidene-2-hy-
droxybenzylamine (H2Lc), have proved to be good ligands for
the synthesis of a series of di-µ-phenoxo-bridged dinuclear
iron(Ⅲ) complexes containing either two bridging groups (car-
boxylato, phosphato) or a chelating acetylacetonato group
which cover the small Fe–O–Fe angle region in dinuclear
iron(Ⅲ) systems.
Fig. 12. Field dependence of the magnetization: experimen-
tal data for [Fe2(La)2(CH3CO2)2] (1) (ꢃ), [Fe2(La)2(C6H5-
CO2)2] (2) (ꢀ), [Fe2(La)2{(CH3)3CCO2}2] (3) (ꢆ),
[Fe2(La)2{(C6H5O)2PO2}2] (4) (ꢇ), and [Fe2(La)2(CH3CO-
CHCOCH3)2] (5) (ꢄ), [Fe2(Lb)2(CH3CO2)2] (6) (ꢅ), and
[Fe2(Lc)2(CH3CO2)2] (7) (ꢁ); theoretical curves for an S =
5 spin state (g = 2.0) (—) and a non-interacting spin state
(S = 5/2 + S = 5/2) (---).
References
1
2
K. S. Murray, Coord. Chem. Rev., 12, 1 (1974).
a) S. J. Lippard, Angew. Chem., Int. Ed. Engl., 27, 344
(1988). b) I. M. Klotz and D. M. Kurtz, Acc. Chem. Res., 17, 16
(1984). c) P. C. Wilkins and R. G. Wilkins, Coord. Chem. Rev.,
79, 195 (1987). d) J. B. Vincent, G. L. Oliver-Lilley, and B. A.
Averill, Chem. Rev., 90, 1447 (1990). e) D. M. Kurtz, Chem. Rev.,
90, 585 (1990).
the strength of the ferromagnetic coupling between the iron
centers in a di-µ-phenoxo-di-µ-carboxylato diiron(Ⅲ) unit is
not significantly affected by the substituent group on the
Schiff-base ligand nor the carboxylate bridges: J = 1.23(4)–
1.56(15) cm−1 for 1–3, 6, and 7. Although the superexchange
pathways within the diiron(Ⅲ) core consist of various orbital
overlaps, the exchange interaction via the phenoxo-bridges
should be important because of the monatomic bridges. In
these complexes, the Fe–O–Fe angles are close to 90° and may
be a major factor of the observed ferromagnetic coupling,
since interactions of magnetic orbitals with orthogonal bridges
will promote a ferromagnetic behavior. The substitution of
carboxylate with diphenyl phosphate, however, weakens the
ferromagnetic interaction in 4 to J = 0.17(5) cm−1. The diphe-
nyl phosphate substitution in the di-µ-phenoxo-di-µ-carboxy-
lato complexes results in a slight elongation of the Fe–Fe dis-
tance and an increasing Fe–O–Fe angle [96.4(2)°], which
might cancel the ferromagnetic coupling to some extent by
causing an antiferromagnetic interaction between the Fe cen-
ters. Only two examples of complexes containing di-µ-phe-
noxo-diiron(Ⅲ) cores have been previously reported, namely,
[Fe2(salmp)2]•2dmf (H2salmp = 2-bis(salicylideneamino)me-
3
“Magneto-Structural Correlations in Exchange Coupled
Systems,” ed by R. D. Willett, D. Gatteschi, and O. Kahn, Reidal
Publishing Co., Dordrecht (1985).
4
a) S. M. Gorun and S. J. Lippard, Inorg. Chem., 30, 1625
(1991). b) J. R. Hart, A. K. Rappe, S. M. Gorun, and T. H. Upton,
Inorg. Chem., 31, 5254 (1992). c) H. Weihe and H. U. Gudd, J.
Am. Chem. Soc., 119, 6539 (1997).
5
a) M. G. B. Drew, V. McKee, and S. M. Nelson, J. Chem.
Soc., Dalton Trans., 1978, 80. b) J. E. Plowman, T. M. Loehr, C.
A. Schauer, and O. P. Anderson, Inorg. Chem., 23, 3553 (1984).
c) R. N. Mukherjee, T. D. P. Stack, and R. H. Holm, J. Am. Chem.
Soc., 110, 1850 (1988). d) P. Gomez-Romero, E. H. Witten, W.
M. Reiff, G. Backes, J. Sanders-Loehr, and G. B. Jameson, J. Am.
Chem. Soc., 111, 9039 (1989). e) P. Gomez-Romero, E. H.
Witten, W. M. Reiff, and G. B. Jameson, Inorg. Chem., 29, 5211
(1990). f) G. Haselhorst, K. Wieghardt, S. Keller, and B.
Schrader, Inorg. Chem., 32, 520 (1993). g) R. M. Buchanan, R. J.
O’Brien, J. F. Richardson, and J.-M. Latour, Inorg. Chim. Acta,

1434 Bull. Chem. Soc. Jpn., 74, No. 8 (2001)
Dinuclear Iron(ꢀ) Complexes
214, 33 (1993). h) J. C. Plakatouras, T. Bakas, C. J. Huffman, J.
C. Huffman, V. Papaefthymiou, and S. P. Perlepes, J. Chem. Soc.,
Dalton Trans., 1994, 2737. i) A. Hazell, K. B. Jensen, C. J.
McKenzie, and H. Toftlund, Inorg. Chem., 33, 3127 (1994). j) M.
Lausmann, I. Zimmer, J. Lex, H. Lueken, K. Wieghardt, and E.
Vogel, Angew. Chem., Int. Ed. Engl., 33, 736 (1994). k) J. Li, J.
Zou, M. Wu, Z. Xu, X. You, and T. W. Mak, Polyhedron, 14, 23
(1995). l) J. Wang, M. S. Mashuta, Z. Sun, J. F. Richardson, D. N.
Hendrickson, and R. M. Buchanan, Inorg. Chem., 35, 6642
(1996). m) G. Roelfes, M. Lubben, K. Chen, R. Y. N. Ho, A.
Meetsma, S. Genseberger, R. M. Hermart, R. Hage, S. K. Mandal,
V. G. Young, Y. Zang, H. Kooijman, A. L. Spek, L. Que, and B. L.
Feringa, Inorg. Chem., 38, 1929 (1999). n) A.-R. Li, H.-H. Wei,
and L.-L. Gang, Inorg. Chim. Acta, 290, 51 (1999). o) Y.-G. Wei,
S.-W. Zhang, and M.-C. Shao, Polyhedron, 16, 2307 (1997). p) D.
F. Xiang, X. S. Tan, S. W. Zhang, Y. Han, K. B. Yu, and W. X.
Tang, Polyhedron, 17, 2095 (1995). q) H. Matsushima, K.
Iwasawa, K. Ide, M. Y. Reza, M. Koikawa, and T. Tokii, Inorg.
Chim. Acta, 274, 224 (1998).
11 R. C. Holz, T. E. Elgren, L. L. Pearce, J. H. Zhang, C. J.
O’Connor, and L. Que, Inorg. Chem., 32, 5844 (1993).
12 S. Drueke, K. Wieghardt, B. Naber, J. Weiss, H.-P.
Fleischhauer, S. Gehring, and W. Haase, J. Am. Chem. Soc., 111,
8622 (1989).
13 P. N. Turowski, W. H. Armstrong, M. E. Roth, and S. J.
Lippard, J. Am. Chem. Soc., 112, 681 (1990).
14 a) J. A. Thich, C. C. Ou, D. Powers, B. Vasiliou, D.
Mastropaolo, J. A. Potenza, and H. J. Schugar, J. Am. Chem. Soc.,
98, 1425 (1976). b) C. C. Ou, R. A. Lalancette, J. A. Potenza, and
H. J. Schugar, J. Am. Chem. Soc., 100, 2053 (1978). c) L. Borer,
L. Thalken, C. Ceccarelli, M. Glick, J. H. Zhang, and W. M. Reiff,
Inorg. Chem., 22, 1719 (1983). d) K. K. Nanda, S. K. Dutta, S.
Baitalik, K. Venkatsubramanian, and K. Nag, J. Chem. Soc., Dal-
ton Trans., 1995, 1239.
15 a) B. Chiari, O. Piovesana, T. Tarantelli, and P. F. Zanazzi,
Inorg. Chem., 21, 1396 (1982). b) B. Chiari, O. Piovesana, T.
Tarantelli, and P. F. Zanazzi, Inorg. Chem., 23, 3398 (1984). c) S.
Menage and L. Que., Jr, Inorg. Chem., 29, 4293 (1990). d) G. D.
Fallon, A. Markiewicz, K. S. Murray, and T. Quach, J. Chem.
6
H. Zheng, Y. Zang, Y. Dong, V. G. Young, and L. Que, J.
Am. Chem. Soc., 121, 2226 (1999).
a) S. Yan, L. Que, L. F. Taylor, and O. P. Anderson, J. Am.
Soc., Chem. Commun., 1991, 198.
e) M. Leluk, B. J.
7
Trzebiatowska, T. Lis, Polyhedron, 11, 1923 (1992). f) A. J.
Blake, C. M. Grant, S. Parsons, G. A. Solan, and R. E. P.
Winpenny, J. Chem. Soc., Dalton Trans., 1996, 321. g) F. L. Gall,
F. F. Biani, A. Caneschi, P. Cinelli, A. Corma, A. C. Fabretti, and
D. Gatteschi, Inorg. Chim. Acta, 262, 123 (1997).
16 a) B. S. Snyder, G. S. Patterson, A. J. Abrahamson, and R.
H. Holm, J. Am. Chem. Soc., 111, 5214 (1989). b) A. Elmali, Y.
Elerman, I. Svoboda, and H. Fuess, Acta Crystallogr., C49, 965
(1993).
17 a) P. N. Turowski, W. H. Armstrong, S. Liu, S. N. Brown,
and S. J. Lippard, Inorg. Chem., 33, 636 (1994). b) B. Bremer, K.
Schepers, P. Fleischhauer, W. Haase, G. Henkel, and B. Krebs, J.
Chem. Soc., Chem. Commun., 1991, 510.
18 P. Chaudhuri, M. Winter, K. Wieghardt, S. Gehring, W.
Haase, B. Nuber, and J. Weiss, Inorg. Chem., 27, 1564 (1988).
19 a) M. Mikuriya, S. Shigematsu, K. Kawano, T. Tokii, and
H. Oshio, Chem. Lett., 1990, 729. b) M. Mikuriya, D. Jie, Y.
Kakuta, and T. Tokii, Bull. Chem. Soc. Jpn., 66, 1132 (1993).
20 a) J. Dai, S. Akiyama, M. Munakata, and M. Mikuriya,
Polyhedron., 13, 2495 (1994). b) J. Dai, H. Wang, and M.
Mikuriya, Polyhedron., 15, 1801 (1996).
21 M. Mikuriya, Y. Kakuta, K. Kawano, and T. Tokii, Chem.
Lett., 1991, 2031.
22 L. C. Raiford and E. P. Clark, J. Am. Chem. Soc., 45, 1738
(1923).
23 M. Yamaguchi, Nippon Kagaku Zasshi, 73, 393 (1952).
24 P. W. Selwood, “Magnetochemistry,” Interscience Publish-
ers, New York (1956), pp. 78, 91.
25 B. A. Frenz, “The SDP-User’s Guide,”Enraf-Nonius, Delft,
The Netherlands (1985).
Chem. Soc., 110, 5222 (1988). b) R. E. Norman, R. C. Holz, S.
Menage, C. J. O’Connor, J. H. Zhang, and L. Que, Inorg. Chem.,
29, 4629 (1990). c) R. E. Norman, S. Yan, L. Que, G. Backes, J.
Ling, J. Sanders-Loehr, J. H. Zhang, and C. J. O’Conner, J. Am.
Chem. Soc., 112, 1554 (1990). d) A. Hazell, K. B. Jensen, C. J.
McKenzie, and H. Toftlund, J. Chem. Soc., Dalton Trans., 1993,
3249. e) N. Arulsamy, D. J. Hodgson, and J. Glerup, Inorg. Chim.
Acta, 209, 61 (1993). f) N. Arulsamy, P. A. Goodson, D. J.
Hodgson, J. Glerup, and K. Michelsen, Inorg. Chim. Acta, 216, 21
(1994). g) S. Wang, Q. Luo, X. Wang, L. Wang, and K. Yu, J.
Chem. Soc., Dalton Trans., 1995, 2045. h) S. Yan, X. Pan, L. F.
Taylor, J. H. Zhang, C. J. O’Connor, D. Britton, O. P. Anderson,
and L. Que, Inorg. Chim. Acta, 243, 1 (1996). i) B. Graham, B.
Moubaraki, K. S. Murray, L. Spiccia, J. D. Cashion, and D. C. R.
Hockless, J. Chem. Soc., Dalton Trans., 1997, 887. j) J. Glerup,
K. Michelsen, N. Arulsamy, and D. J. Hodgson, Inorg. Chim. Ac-
ta, 274, 155 (1998).
8
a) W. H. Armstrong, A. Spool, G. C. Papaefthymiou, R. B.
Frankel, and S. J. Lippard, J. Am. Chem. Soc., 106, 3653 (1984).
b) J. R. Hartman, R. L. Rardin, P. Chaudhuri, K. Pohl, K.
Wieghardt, B. Nuber, J. Weiss, G. C. Papaefthymiou, R. B.
Frankel, and S. J. Lippard, J. Am. Chem. Soc., 109, 7387 (1987).
c) P. Gomez-Romero, N. Casan-Pastor, A. Ben-Hussein, and G. B.
Jameson, J. Am. Chem. Soc., 110, 1988 (1988). d) J. B. Vincent, J.
C. Huffman, G. Christou, Q. Li, M. A. Nanny, D. N. Hendrickson,
R. H. Fong, and R. H. Fish, J. Am. Chem. Soc., 110, 6898 (1988).
e) R. H. Beer, W. B. Tolman, S. G. Bott, and S. J. Lippard, Inorg.
Chem., 28, 4557 (1989). f) X. Feng, S. G. Bott, and S. J. Lippard,
J. Am. Chem. Soc., 111, 8046 (1989). g) R. H. Beer, W. B.
Tolman, S. G. Bott, and S. J. Lippard, Inorg. Chem., 30, 2082
(1991). h) K. J. Oberhausen, J. F. Richardson, R. J. O'Brien, R.
M. Buchanan, J. K. McCusker, R. J. Webb, and D. N.
Hendrickson, Inorg. Chem., 31, 1125 (1992). i) M. Kotera, H.
Shimakoshi, M. Nishimura, H. Okawa, S. Iijima, and K. Kano, In-
org. Chem., 35, 4967 (1996). j) V. A. Grillo, G. R. Hanson, T. W.
Hambley, L. R. Gahan, K. S. Murray, and B. Moubaraki, J. Chem.
Soc., Dalton Trans., 1997, 305.
26 K. Nakamoto, “Infrared and Raman Spectra of Inorganic
and Coordination Compounds,” 4th ed, Wiley interscience, New
York (1986).
27 a) N. Torihara, M. Mikuriya, H. Okawa, and S. Kida, Bull.
Chem. Soc. Jpn., 53, 1610 (1980). b) M. Mikuriya, N. Torihara,
H. Okawa, and S. Kida, Bull. Chem. Soc. Jpn., 54, 1063 (1981).
28 H. J. Schugar, G. R. Rossman, J. Thibeault, and H. B.
Gray, Chem. Phys. Lett., 6, 26 (1970).
9
T. Fujita, S. Ohba, Y. Nishida, and A. Goto, Acta Crystal-
29 a) D. J. Hodgson, Prog. Inorg. Chem., 19, 173 (1975). b)
W. E. Hatfield, “Theory and Applications of Molecular Paramag-
netism,” ed by E. A. Boudreaux and L. N. Mulay, Wiley-Inter-
sciecne, New York (1976).
logr., Sect C, 50, 544 (1994).
10 S. Drueke, K. Wieghardt, B. Nuber, and J. Weiss, Inorg.
Chem., 28, 1414 (1989).