Synthesis, structure and magnetic properties of oxo-centered trinuclear manganese complex [Mn3O(O2CC3H7)6(C 5H5N)3]·ClO4

Article abstract of DOI:10.1016/S0020-1693(99)00278-9

The reaction of N-n-Bu₄MnO₄ with Mn(OAc)₂·4H₂O, pyridine and butyric acid in absolute EtOH leads to the high-yield formation of the oxo-centered trinuclear Mn complex, [Mn₃O(O₂CC₃H₇)₆(C ₅H₅N)₃]·ClO₄. The complex crystallizes in orthorhombic, space group Pna2₁ with a=19.588(7), b=20.194(6), c=12.491(5) A. Variable temperature solid state magnetic susceptibility study shows that the antiferromagnetic exchange interaction is weak, and the exchange integral J=-12.36 cm^-1.

Full text of DOI:10.1016/S0020-1693(99)00278-9

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 294 (1999) 109–113
Note
Synthesis, structure and magnetic properties of oxo-centered
trinuclear manganese complex [Mn3O(O2CC3H7)6(C5H5N)3]·ClO4
Jun Li a,*, Shuming Yang a, Fengxing Zhang a, Zongxun Tang a, Shulin Ma b,
Qizhen Shi a, Qiangjin Wu c, Zixiang Huang c
a Chemistry Department, Northwest Uni6ersity, Xi’an 710069, People’s Republic of China
b Tianjin Uni6ersity of Commerce, Tianjin 300400, People’s Republic of China
c Fujian Institute of Research on the Structure of Matter, Chinese Academy of Science, Fuzhou 350002, People’s Republic of China
Received 9 February 1999; accepted 11 June 1999
Abstract
The reaction of N-n-Bu4MnO4 with Mn(OAc)2·4H2O, pyridine and butyric acid in absolute EtOH leads to the high-yield
formation of the oxo-centered trinuclear Mn complex, [Mn3O(O2CC3H7)6(C5H5N)3]·ClO4. The complex crystallizes in orthorhom-
,
bic, space group Pna21 with a=19.588(7), b=20.194(6), c=12.491(5) A. Variable temperature solid state magnetic susceptibility
study shows that the antiferromagnetic exchange interaction is weak, and the exchange integral J= −12.36 cm−1. © 1999
Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Manganese complexes; Oxo complexes; Trinuclear complexes
tion [Mn3O(O2CR)6L3]0,+ (L=a neutral donor group).
In previous literature [8–11], these complexes with R=
1. Introduction
Me,Ph,CMe3 and L=pyridine, 3-Clpyridine, imidazole
have been reported. In this paper, we describe the
synthesis and crystal structure of [Mn3O(O2CC3H7)6
The coordination chemistry of manganese in the +2,
+3 and +4 oxidation states is receiving considerable
attention due to the biological importance of these ions
(C5H5N)3]·ClO4, together with the results of variable
[1–4]. It is now firmly established that at least three
temperature magnetic susceptibility and IR spectrum.
enzymes (manganese superoxide dismutase [5], azide
insensitive catalase [6], and the photosynthetic oxygen-
evolving complex [7]) use manganese in redox roles at
2. Experimental
their catalytic center to facilitate the metabolism of the
n−
O2
unit. All the three enzymes probably contain
2.1. Materials
Mn(III) in at least one of their catalytic forms. There-
fore, an important area of investigation of the bioinor-
ganic chemistry of manganese is the study of the
structure and properties of Mn(III) complexes com-
posed of biologically relevant donor ligands.
An attractive system for modeling the structure and
properties of these manganoenzymes is trinuclear oxo-
centered manganese complexes of the general formula-
All reagents used were of analytical grade and pur-
chased from Xi’an Chemical Company.
2.2. Preparation
N-n-Bu4MnO4 was prepared by a literature method
[12]. N-n-Bu4Br (12.00 g, 37.2 mmol) was added to an
aqueous solution of KMnO4 (5.00 g, 31.6 mmol) with
vigorous stirring. The immediate purple precipitate was
* Corresponding author.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00278-9

110
J. Li et al. / Inorganica Chimica Acta 294 (1999) 109–113
collected by filtration, washed thoroughly with distilled
water and diethyl ether and then dried in vacuo at
room temperature. Yield \90%.
Warning N-n-Bu4MnO4 is potentially explosive and
must be treated with care.
was operated at a magnetic field strength of 20 kG.
Diamagnetic corrections were estimated from Pascal’s
constants and substrated from the experimental suscep-
tibility data to obtain the molar paramagnetic suscepti-
bilities of the compound. These molar paramagnetic
susceptibilities were fitted to the appropriate theoretical
expressions by means of a least-squares fitting com-
puter program. Infrared spectra were recorded on a
Mattson High Res FTIR spectrometer with sample
prepared as KBr pellets.
The trinuclear manganese butyrate complex was syn-
thesized as follows. Mn(O2CMe)2·4H2O (2.00 g, 8.15
mmol) was dissolved in a solvent mixture comprising
absolute EtOH (20 ml), pyridine (3 ml) and n-butyric
acid (12 ml). The resulting solution was stirred while
solid N-n-Bu4MnO4 (1.14 g, 3.15 mmol) was added in
small portions to give a deep brown homogeneous
solution. To this was added a solution of NaClO4 (0.69
g, 5.65 mmol) in EtOH (5 ml). This solution was stored
at room temperature for 2 weeks, and a brown–black
crystalline material was isolated by filtration. Crystals
for X-ray crystallographic analysis were obtained
straight from the mother liquor. Elemental analysis was
performed on a polycrystalline sample. Anal. Found: C,
44.82; H, 5.43; N, 3.56. Calc. for [Mn3O(O2CC3H7)6-
(C5H5N)3]·ClO4: C, 45.02; H, 5.48; N, 4.04%.
3. Results and discussion
3.1. Structure
Fig. 1 shows an ORTEP projection of the complex
molecule [Mn3O(O2CC3H7)6(C5H5N)3]·ClO4. Fractional
coordinates and isotropic thermal parameters are listed
in Table 2. Selected bond lengths and bond angles are
given in Table 3. The charge on the complex is a Mn3III
description. From Table 3, we found that the Mn(1,3)–
2.3. Crystallographic study
,
O(1) distances are almost the same (1.91, 1.93 A), but
,
Mn(2)–O(1) distance is a little shorter (1.84 A). Again
The data were collected on a Rigaku–AFC5R-
diffractometer using graphite-monochromated Mo Ka
,
radiation (0.71069 A) at room temperature. A crystal of
Table 1
dimensions 0.50×0.50×0.25 mm was attached to a
thin glass fibre and mounted on the diffractometer. Cell
parameters and an orientation matrix for data collec-
tion were obtained from least-squares refinement, using
the setting angles of 20 reflections in the range 205
2q521.4°. The systematic absences (0kl, k+l=2n+1,
hol, h=2n+1, hoo, h=2n+1, oko, k=2n+1, and
ool, l=2n+1) allow the space groups to be Pna21 and
Pnam. The structure could be solved successfully only
in the noncentrosymmetric space group Pna21. The
intensities were corrected for Lorentz polarization ef-
fects, and empirical absorption correction based on a
series of c scans was applied. After averaging, 5969
unique data were used to solve the structure by a direct
method and subsequent difference Fourier syntheses.
The final cycle of refinement led to a final convergence
at R=0.069, Rw=0.086, for 427 variables and 2384
reflections with I\3|(I). All calculations were carried
out with computer software TEXSAN on a Micro
VAXII. No attempts were made to locate hydrogen
atoms. Crystal data of the complex are given in Table
1.
Summary of crystallographic data
Empirical formula
Formula weight
Crystal system
Space group
C39H57N3O17Cl1Mn3
1040.16
orthorhombic
Pna21
19.588(7)
20.194(6)
12.491(5)
4941(3)
4
296
2160
1.40
0.5×0.5×0.25
Mo Ka, 0.71069
8.44
ꢀ–2q
54.0
,
a (A)
,
b (A)
,
c (A)
3
,
V (A )
Z
T (K)
F(000)
Dcalc (g cm−3
)
Crystal size (mm)
,
Radiation (A)
v (cm−1
)
Scan type
2qmax (°)
Index ranges
05h535, 05k537,
05l523
6041
5969
2385
No. of reflections measured
No. of unique reflections
Reflections used, I\3|(I)
R
0.069
0.086
Rw
S (goodness-of-fit)
w
2.02
2.4. Physical measurements
1/|2(F)
0.42
Highest peak in final difference
−3
,
map (e A
)
Variable temperature magnetic susceptibility data
were measured with a Maglab System 2000 susceptome-
ter (made in Oxford, UK), maintained by the chemistry
department of Peking University. The susceptometer
Lowest peak in final difference
−0.40
−3
,
map (e A
)
No. of parameters refined
427

J. Li et al. / Inorganica Chimica Acta 294 (1999) 109–113
111
Table 2
Fractional coordinates and isotropic thermal parameters
Atom
x
y
z
Biso
3.8(1)
Mn(1)
Mn(2)
Mn(3)
Cl(1)
O(01)
O(02)
O(03)
O(04)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
O(13)
N(1)
0.8048(1)
0.7860(1)
0.7377(1)
0.0649(3)
0.121(2)
0.005(2)
0.072(2)
0.063(2)
0.7751(5)
0.7197(7)
0.677(1)
0.8531(8)
0.813(1)
0.7611(9)
0.7434(7)
0.8946(7)
0.8830(8)
0.6573(6)
0.6928(7)
0.7900(8)
0.833(1)
0.8378(8)
0.6958(9)
0.7948(9)
0.901(1)
0.924(1)
0.877(2)
0.816(1)
0.795(1)
0.737(1)
0.711(1)
0.643(2)
0.603(1)
0.627(1)
0.855(1)
0.859(1)
0.803(1)
0.744(1)
0.741(1)
0.915(1)
0.989(1)
1.006(2)
0.970(3)
0.675(1)
0.612(1)
0.564(2)
0.594(2)
0.826(1)
0.875(2)
0.866(3)
0.915(2)
0.651(1)
0.586(2)
0.584(2)
0.627(2)
0.739(1)
0.699(1)
0.741(2)
0.720(3)
0.854(1)
0.914(2)
0.948(2)
0.981(2)
0.1694(1)
0.1243(1)
0.0250(1)
0.2417(4)
0.208(1)
0.211(1)
0.272(2)
0.301(2)
0.1078(5)
0.1636(7)
0.0670(6)
0.1002(8)
0.0078(8)
0.2474(7)
0.2145(7)
0.1859(8)
0.168(1)
0.5911
0.8405(3)
0.6473(3)
0.1072(7)
0.065(3)
0.110(3)
0.191(4)
0.036(3)
0.697(1)
0.503(1)
0.538(1)
0.503(1)
0.551(2)
0.673(1)
0.835(1)
0.666(1)
0.830(1)
0.748(1)
0.882(1)
0.762(2)
0.872(1)
0.479(1)
0.598(1)
1.008(1)
0.440(2)
0.358(2)
0.323(2)
0.362(3)
0.438(2)
0.579(2)
0.542(2)
0.522(2)
0.541(2)
0.577(2)
1.058(2)
1.171(2)
1.227(2)
1.175(2)
1.063(2)
0.753(2)
0.774(2)
0.725(4)
0.736(4)
0.495(2)
0.435(2)
0.401(3)
0.322(4)
0.829(2)
0.858(4)
0.945(6)
0.967(3)
0.836(2)
0.894(3)
1.005(3)
1.035(4)
0.764(2)
0.780(2)
0.734(4)
0.755(5)
0.506(2)
0.442(3)
0.491(4)
0.602(4)
3.7(1)
3.9(1)
8.6(4)
17(1)
18(1)
24(2)
23(1)
3.8(5)
7.0(8)
10(1)
8(1)
13(1)
9(1)
6.8(7)
7.8(9)
10(1)
7.4(9)
7.7(9)
10(1)
9(1)
5.2(8)
5.4(8)
5.1(9)
7(1)
8(1)
8(2)
10(2)
7(1)
6(1)
7(1)
8(2)
7(1)
6(1)
6(1)
7(1)
7(1)
7(1)
Fig. 1. ORTEP projection of complex cation [Mn3O(O2CC3H7)6-
(C5H5N)3]·ClO4.
0.0274(7)
0.0854(9)
−0.0318(6)
0.0387(8)
0.2390(8)
−0.0649(6)
0.1399(8)
0.233(1)
comparing the Mn–N distances, we found that the
Mn(1)–N(1) and Mn(3)–N(2) distances are the same
,
,
(2.09 A), while the Mn(2)–N(3) distance of 2.12 A is
apparently longer than the other two. These are differ-
ent from an acetate and pivalate counterpart [8,11], in
which three bonds of Mn–O(central) are equal in dis-
tance within experimental error. In addition, Jahn–
Teller distortion of each metal ion in this complex is
negligible. So this distortion may be caused by n-bu-
tyrate space factor. The Mn3O triangle is very close to
an equilateral triangle, with Mn(1)–Mn(2), Mn(2)–
Mn(3) and Mn(1)–Mn(3) distances of 3.272, 3.283, and
N(2)
N(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
0.277(1)
0.322(1)
0.328(1)
0.283(1)
−0.1177(9)
−0.176(1)
−0.182(1)
−0.128(1)
−0.0678(9)
0.129(1)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(21)
C(22)
C(23)
C(24)
C(31)
C(32)
C(33)
C(34)
C(41)
C(42)
C(43)
C(44)
C(51)
C(52)
C(53)
C(54)
C(61)
C(62)
C(63)
C(64)
C(71)
C(72)
C(73)
C(74)
,
3.279 A, respectively. The Mn(1)–Mn(2)–Mn(3),
0.131(1)
0.150(1)
0.163(1)
0.156(1)
0.1856(8)
0.209(1)
0.270(2)
0.324(3)
0.120(1)
Mn(2)–Mn(3)–Mn(1), Mn(3)–Mn(1)–Mn(2) angles
are 60.03, 59.82, and 60.15°, respectively. Central oxy-
,
gen O(1) lies slightly above the Mn3 plane (0.0330 A).
6(1)
The Mn coordination geometry is slightly distorted
octahedral with any other four oxygen atoms from
bridging acetate groups and one terminal pyridine ni-
trogen atom completing the coordination to each metal.
The overall structure is thus of the common ‘basic
carboxylate’ type seen for many transition metals
[13,14]
4.4(3)
8.6(6)
16(1)
19(2)
4.9(4)
8.2(6)
13(1)
16(1)
6.8(5)
16(1)
22(2)
13(1)
4.6(3)
9.4(7)
13(1)
15(1)
4.6(4)
8.1(6)
15(1)
18(2)
6.6(5)
13(1)
16(1)
18(1)
0.141(1)
0.089(2)
0.053(2)
−0.013(1)
−0.082(2)
−0.104(3)
−0.169(2)
0.0499(9)
0.043(1)
3.2. Magnetic susceptibility
Variable temperature (ꢀ10 to ꢀ278 K) magnetic
susceptibility data were collected for microcrystalline
0.027(2)
−0.026(2)
0.2548(9)
0.318(1)
sample of the compound. The  versus T plots are
M
shown in Fig. 2. The magnetic moments decrease with
decreasing temperature, implying the existence of an
antiferromagnetically coupling of MnI3II pairs.
The spin Hamiltonian which describes the isotropic
magnetic exchange interaction in a triangulated trinu-
clear complex is given in Eq. (1). In this compound,
0.378(2)
0.444(3)
0.043(1)
0.011(2)
−0.034(2)
−0.014(2)

112
J. Li et al. / Inorganica Chimica Acta 294 (1999) 109–113
Table 3
,
Selected bond lengths (A) and bond angles (°) involving the non-hy-
drogen atoms
Mn(1)–O(1)
Mn(1)–O(2)
Mn(1)–O(4)
Mn(1)–O(8)
Mn(1)–O(6)
Mn(1)–N(1)
Mn(2)–O(1)
Mn(2)–O(13)
Mn(2)–O(7)
1.91(1)
2.00(1)
2.01(2)
2.02(1)
2.07(2)
2.09(2)
1.84(1)
2.00(1)
2.01(1)
Mn(2)–O(11)
Mn(2)–O(9)
Mn(2)–N(3)
Mn(3)–O(1)
Mn(3)–O(5)
Mn(3)–O(3)
Mn(3)–O(10)
Mn(3)–N(2)
Mn(3)–O(12)
2.06(1)
2.09(2)
2.12(2)
1.93(1)
1.93(2)
2.00(1)
2.02(1)
2.09(1)
2.11(2)
O(1)–Mn(1)–O(2)
O(1)–Mn(1)–O(4)
O(1)–Mn(1)–O(8)
O(1)–Mn(1)–O(6)
O(1)–Mn(1)–N(1)
O(2)–Mn(1)–O(4)
O(2)–Mn(1)–O(8)
O(2)–Mn(1)–O(6)
O(2)–Mn(1)–N(1)
O(4)–Mn(1)–O(8)
O(4)–Mn(1)–O(6)
O(4)–Mn(1)–N(1)
O(8)–Mn(1)–O(6)
O(8)–Mn(1)–N(1)
O(6)–Mn(1)–N(1)
O(1)–Mn(2)–O(13)
O(1)–Mn(2)–O(7)
O(1)–Mn(2)–O(11)
O(1)–Mn(2)–O(9)
O(1)–Mn(2)–N(3)
95.1(5)
94.1(5)
93.0(5)
91.5(5)
178.2(5)
92.9(7)
171.8(5)
88.4(7)
85.9(6)
87.7(8)
174.2(6)
87.4(6)
90.2(8)
86.0(6)
87.0(6)
95.2(5)
94.7(5)
94.1(5)
97.0(5)
177.1(6)
O(7)–Mn(2)–O(11)
O(7)–Mn(2)–O(9)
O(7)–Mn(2)–N(3)
89.2(7)
89.8(7)
86.2(6)
O(11)–Mn(2)–O(9) 168.9(6)
Fig. 2. Plots of effective magnetic moment per Mn3O molecule, and
molar paramagnetic susceptibility vs. temperature for
[Mn3O(O2CC3H7)6(C5H5N)3]·ClO4. The solid lines represent a least-
squares fit of the data to the theoretical Eq. (2).
O(11)–Mn(2)–N(3)
O(9)–Mn(2)–N(3)
O(1)–Mn(3)–O(5)
O(1)–Mn(3)–O(3)
O(1)–Mn(3)–O(10)
O(1)–Mn(3)–N(2)
O(1)–Mn(3)–O(12)
O(5)–Mn(3)–O(3)
83.2(6)
85.7(6)
93.7(6)
94.4(5)
94.2(5)
178.4(5)
93.8(5)
96(1)

M
parameters J= −12.36 cm−1, q=6.18 K and g=
2.01. The solid line in Fig. 2 represents this fit. The
agreement factor F defined here is 8.97×10−6. This
result shows the existence of intramolecular antiferro-
magnetic interaction and intermolecular ferromagnetic
interaction. In this type of m3-oxo-bridged trinuclear
complex, it is very likely that the majority of this
interaction is propagated by the oxide bridge, not by
O(5)–Mn(3)–O(10) 171.1(6)
O(5)–Mn(3)–N(2)
O(5)–Mn(3)–O(12)
O(3)–Mn(3)–O(10)
O(3)–Mn(3)–N(2)
O(3)–Mn(3)–O(12) 170.8(6)
O(10)–Mn(3)–N(2) 84.3(6)
O(10)–Mn(3)–O(12) 88.0(8)
N(2)–Mn(3)–O(12) 85.5(6)
87.7(6)
87(1)
87.3(8)
86.1(6)
the n-butyrate bridges. At
a lower temperature
O(13)–Mn(2)–O(7) 170.0(6)
O(13)–Mn(2)–O(11) 91.8(7)
O(13)–Mn(2)–O(9)
O(13)–Mn(2)–N(3)
(B14.06 K), the magnetic susceptibility versus temper-
ature curves do not fit well, mainly because of zero field
interaction. The J value of this complex approxi-
mates to the J values of other oxo-bridged trinuclear
MnIII complexes, and the antiferromagnetic exchange
interaction of this complex is weaker than the FeI3IIO
complexes which have been described in the literature
[10].
Mn(2)–O(1)–Mn(3) 121.1(6)
Mn(2)–O(1)–Mn(1) 121.5(6)
Mn(1)–O(1)–Mn(3) 117.3(6)
87.3(8)
84.0(6)
.
.
.
.
.
.
.
H= −2[J12(S1·S2)+J23(S2·S3)+J31(S3·S1)]
(1)
(2)
M=[2Ng2i2/k(T−q)]A/B
A=91+110 exp(−12J/kT)+90 exp(−22J/kT)
+56 exp(−30J/kT)+25 exp(−36J/kT)
+3 exp(−40J/kT)
B=13+22 exp(−12J/kT)+27 exp(−22J/kT)
+28 exp(−30J/kT)+25 exp(−36J/kT)
+9 exp(−40J/kT)+exp(−42J/kT)
S1=S2=S3=2, and if all three MnIII ions are equiva-
lent, J12=J31=J23=J. The molar paramagnetic sus-
ceptibility for such a trinuclear complex is given in Eq.
(2), where  denotes the susceptibility per trinuclear
M
complex, q is the Curie–Weiss parameter, g is the
average g-value, and the other symbols have their usual
meanings.
The paramagnetic susceptibility data for this complex
were least-squares fit to Eq. (2) to give the fitting
Fig. 3. Solid state IR spectra of [Mn3O(O2CC3H7)6(C5H5N)3]·ClO4.
Bands 2 and 3 (shaded black) are assigned to vibrations of coordi-
nated pyridine molecules. Unshaded bands: 5, l(CO2); 8, y(CO2);
hatched band: 10, was(Mn3O).

J. Li et al. / Inorganica Chimica Acta 294 (1999) 109–113
113
3.3. IR spectrum
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Fig. 3 shows the IR spectrum of the complex. Bands
are assigned and numbered by comparison with previ-
ous work on this and the corresponding Cr3O and Fe3O
complexes [15,16]. After vibrations of pyridine, bu-
tyrate, and ionic perchlorate are accounted for, one
broad band (10) is assigned to was(Mn3O), the doubly
degenerate in-plane vibration of the central oxygen.
4. Supplementary material
[6] W.F. Beyer Jr., I. Fridovich, Manganese in Metabolism and
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Tables with atomic coordinates, bond lengths, bond
angles and thermal parameters for all atoms, including
hydrogen atoms, may be obtained from the authors on
request. Crystallographic data (excluding structure fac-
tors) for the structure in this paper have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication No. CCDC-122161. Copies
of the data can be obtained free of charge on applica-
tion to CCDC, 12 Union Road, Cambridge CB2 IEZ,
UK (fax: (int.) +44(1223)336-033; e-mail: deposit@
ccdc.cam.ac.uk).
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[10] J.B. Vicent, H.-R. Chang, K. Folting, J.C. Huffman, G. Chris-
tou, D.N. Hendricleson, J. Am. Chem. Soc. 109 (19) (1987) 5703.
[11] W. Ruowen, P. Mehmet, F.E. Sowrey, C.E. Anson et al. Inorg.
Chem. 37 (1998) 1913.
[12] T. Sala, M.V. Sargent, J. Chem. Soc., Chem. Commun. (1978)
253.
[13] J. Catterick, P. Thornton, Adv. Inorg. Chem. Radiochem. 20
(1977) 291.
[14] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, 4th
edn, New York, 1980, p. 154.
[15] L. Messuk, R.P. White, B. Templeton, U.A. Jayasooriya, R.D.
Cannon, Inorg. Chem. 29 (1990) 2389.
[16] M.K. Johnson, D.B. Powell, R.D. Cannon, Spectrochim. Acta,
Part A 37 (11) (1981) 995.
Acknowledgements
We are very grateful for the financial support from
The National Natural Science Foundation of China
and The Educational Committee Foundation of
Shaanxi Province.
.