Synthesis and characterization of a family of penta- and tetra-manganese(III) complexes derived from an assembly system containing tert-butylphosphonic acid

Article abstract of DOI:10.1021/ic701343s

A family of manganese complexes, [Mn₅O₃(t-BuPO ₃)₂(MeCOO)₅(H₂O)(phen)₂] (1), [Mn₅O₃(t-BuPO₃)₂(PhCOO) ₅(phen)₂] (2), [Mn₄O₂(t-BuPO ₃)₂(RCOO)₄(bpy)₂] (R = Me, (3); R = Ph, (4)), NBuⁿ₄[Mn₄O₂(EtCOO) ₃(MeCOO)₄(pic)₂] (5), NR′ ₄[Mn₄O₂(i-PrCOO)₇(pic)₂] (R′ = Buⁿ, (6); R′ = Et, (7)), were synthesized and characterized. The seven manganese clusters were all prepared from a reaction system containing tert-butylphosphonic acid, Mn(O₂CR)₂ (R = Me, Ph) and NR′₄MnO₄ (R′ = Buⁿ, Et) with similar procedures except for using different N-containing ligands (1,10-phenanthroline (phen), 2,2′-bipyridine (bpy) and picolinic acid (picH)) as coligands. The structures of these complexes vary with the N-containing donors. Both the cores of complexes 1 and 2 feature three μ₃-O and two capping t-BuPO₃^2- groups bridging five Mn^III atoms to form a basket-like cage structure. Complexes 3 and 4 both have one [Mn₄(μ₃-O) ₂]⁸⁺ core with four coplanar Mn^III atoms disposed in an extended butterfly-like arrangement and two capping μ₃-t-BuPO₃^2- binding to three manganese centers above and below the Mn₄ plane. Complexes 5, 6, and 7 all possess one [Mn₄(μ₃-O)₂]⁸⁺ core just as complexes 3 and 4, but they display a folded butterfly-like conformation with the four Mn^III atoms nonplanar. Thus, the seven compounds are classified into three types, and three representative compounds 1·2H₂O·MeOH·MeCN, 3·6H ₂O·2MeCOOH, and 5·0.5H₂O have been characterized by IR spectroscopy, ESI-MS spectroscopy, magnetic measurements and in situ UV-vis-NIR spectroelectrochemical analysis. Magnetic susceptibility measurements reveal the existence of both ferromagnetic and antiferromagnetic interactions between the adjacent Mn' ions in compound 1·2H ₂O·MeOH·MeCN, and antiferromagnetic interactions in 3·6H₂O·2MeCOOH and 5·0.5H₂O. Fitting the experimental data led to the following parameters: J₁ = -2.18 cm^-1, J₂ = 6.93 cm^-1, J₃ = -13.94 cm^-1, J₄ = -9.62 cm^-1, J₅ = -11.17 cm^-1, g = 2.00 (1·2H₂O·MeOH·MeCN), J₁ = -5.41 cm^-1, J₂ = -35.44 cm^-1, g = 2.13, zJ′ = -1.55 cm_-1 (3·6H₂O· 2MeCOOH) and J₁ = -2.29 cm^-1, J₂ = -35.21 cm^-1, g = 2.02, zJ′ = -0.86 cm^-1 (5·0.5H ₂O).

Full text of DOI:10.1021/ic701343s

Inorg. Chem. 2008, 47, 5580-5590
Synthesis and Characterization of a Family of Penta- and
Tetra-Manganese(III) Complexes Derived from an Assembly System
Containing tert-Butylphosphonic Acid
Mei Wang,†,‡ Cheng-Bing Ma,† Da-Qiang Yuan,† Hui-Sheng Wang,† Chang-Neng Chen,*,†
and Qiu-Tian Liu†
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, The Chinese Academy of Sciences, Fuzhou, Fujian 350002, China, and Graduate School
of the Chinese Academy of Sciences, Beijing 100039, China
Received July 7, 2007
A family of manganese complexes, [Mn5O3(t-BuPO3)2(MeCOO)5(H2O)(phen)2] (1), [Mn5O3(t-BuPO3)2(PhCOO)5(phen)2]
(2), [Mn4O2(t-BuPO3)2(RCOO)4(bpy)2] (R ) Me, (3); R ) Ph, (4)), NBun [Mn4O2(EtCOO)3(MeCOO)4(pic)2] (5),
4
NR′4[Mn4O2(i-PrCOO)7(pic)2] (R′ ) Bun, (6); R′ ) Et, (7)), were synthesized and characterized. The seven manganese
clusters were all prepared from a reaction system containing tert-butylphosphonic acid, Mn(O2CR)2 (R ) Me, Ph)
and NR′4MnO4 (R′ ) Bun, Et) with similar procedures except for using different N-containing ligands
(1,10-phenanthroline (phen), 2,2′-bipyridine (bpy) and picolinic acid (picH)) as coligands. The structures of these
complexes vary with the N-containing donors. Both the cores of complexes 1 and 2 feature three µ3-O and two
capping t-BuPO32- groups bridging five MnIII atoms to form a basket-like cage structure. Complexes 3 and 4 both
have one [Mn4(µ3-O)2]8+ core with four coplanar MnIII atoms disposed in an extended “butterfly-like” arrangement
and two capping µ3-t-BuPO32- binding to three manganese centers above and below the Mn4 plane. Complexes
5, 6, and 7 all possess one [Mn4(µ3-O)2]8+ core just as complexes 3 and 4, but they display a folded “butterfly-like”
conformation with the four MnIII atoms nonplanar. Thus, the seven compounds are classified into three types, and
three representative compounds 1·2H2O · MeOH · MeCN, 3·6H2O · 2MeCOOH, and 5 · 0.5H2O have been character-
ized by IR spectroscopy, ESI-MS spectroscopy, magnetic measurements and in situ UV-vis-NIR spectroelec-
trochemical analysis. Magnetic susceptibility measurements reveal the existence of both ferromagnetic and
antiferromagnetic interactions between the adjacent MnIII ions in compound 1·2H2O · MeOH · MeCN, and
antiferromagnetic interactions in 3·6H2O · 2MeCOOH and 5 · 0.5H2O. Fitting the experimental data led to the following
parameters: J1 ) -2.18 cm-1, J2 ) 6.93 cm-1, J3 ) -13.94 cm-1, J4 ) -9.62 cm-1, J5 ) -11.17 cm-1, g )
2.00 (1·2H2O · MeOH · MeCN), J1 ) -5.41 cm-1, J2 ) -35.44 cm-1, g ) 2.13, zJ′ ) -1.55 cm-1
(3·6H2O · 2MeCOOH) and J1 ) -2.29 cm-1, J2 ) -35.21 cm-1, g ) 2.02, zJ′ ) -0.86 cm-1 (5 · 0.5H2O).
Introduction
reaction to generate dioxygen.1–3 The synthesis and structure
characterization of manganese complexes have provided a
wealth of data to model the photosynthetic water oxidation
center.4 On the other hand, the magnetic behavior of
manganese clusters makes them have potential application
in the design of molecular magnetic materials, which has
been of considerable interest.5–9 Over the past several years,
Manganese complexes are attracting considerable interest
in recent years in the fields of bioinorganic chemistry and
magnetic materials. It is generally accepted that a tetranuclear
manganese cluster resides at the active site of Photosystem
II in green plants to catalyze the light-driven water oxidation
* To whom correspondence should be addressed. E-mail: ccn@
fjirsm.ac.cn.
(1) Mukhopadhyay, S.; Mandal, S. K.; Bhaduri, S.; Armstrong, W. H.
Chem. ReV. 2004, 104, 3981.
†
Fujian Institute of Research on the Structure of Matter, The Chinese
Academy of Sciences.
(2) Photosynthetic water oxidation: Special Dedicated Issue, Nugent, J.,
Ed.; Biochim. Biophys. Acta 2001, 1503, 1.
‡
Graduate School of the Chinese Academy of Sciences.
5580 Inorganic Chemistry, Vol. 47, No. 13, 2008
10.1021/ic701343s CCC: $40.75  2008 American Chemical Society
Published on Web 06/10/2008

Penta- and Tetra-Manganese(III) Complexes
a number of manganese clusters have been reported.3,4,10 So
far, the common strategy to prepare polynuclear manganese
complexes relies mostly on the use of the carboxylate ligand,
and the manganese carboxylate chemistry has been explored
extensively by Christou et al.4a,d,e,g,m,10a–c,11 To synthesize
new polynuclear manganese species, we have tried to develop
new synthetic routes and oriented our research strategy to
the use of phosphonates to substitute some of the carboxylate
ligands.
Phosphonates are a family of ligands in possession of three
O donors that can bind to more than one metal ion
simultaneously. Transition-metal phosphonate complexes
have received a lot of attention in recent years primarily
because of their potential applications in catalysis, ion
exchange, proton conductivity, intercalation chemistry, pho-
tochemistry, and material chemistry.12–15 Several polynuclear
metal phosphonate compounds that contain vanadium,16
aluminum,17 copper,18 cobalt,19 zinc,20 cadmium,21 and
iron22 have been prepared so far. Recently utilization of the
phosphonate to prepare manganese complexes has received
increasing attention, and several types of target clusters with
higher nuclearity, such as hexa-, icosa-, dodeca-, trideca- and
docosa- nuclear manganese aggregates have been ob-
tained.19,23–27 However, smaller manganese clusters, for
example, the pentanuclear and tetranuclear manganese
complexes with phosphonate ligands remain relatively
scarce.28 For the reasons above, we have fully explored the
reaction system containing tert-butylphosphonic acid and
successfully obtained a family of manganese clusters with
lower nuclearity: [Mn5O3(t-BuPO3)2(MeCOO)5H2O(phen)2]
(1), [Mn5O3(t-BuPO3)2(PhCOO)5(phen)2] (2), [Mn4O2(t-
BuPO3)2(RCOO)4(bpy)2] (R ) Me, (3); R ) Ph, (4)),
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4
PrCOO)7(pic)2] (R′ ) Bun, (6); R′ ) Et, (7)). Herein the
synthesis, structures, magnetic properties, and electrochem-
istry of these complexes are presented.
Experimental Section
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Syntheses. All manipulations were performed under aerobic
29
condition. Mn(O2CPh)2 ·2H2O4d and NBun MnO4 were both
4
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Inorganic Chemistry, Vol. 47, No. 13, 2008 5581

Wang et al.
similar manner with NBun MnO4.30 All the other chemical reagents
and solvents were of analytical grade, were purchased commercially,
and were used without further purification.
49.78; H, 6.79; N, 3.31. Selected IR (KBr, cm-1) data: 2967 (m),
1583 (s), 1446 (m), 1399 (s), 1337 (w), 1015 (w), 943 (m), 665
(w).
4
NEt4[Mn4O2(i-PrCOO)7(pic)2]·0.5H2O (7·0.5H2O). This com-
plex was obtained using a procedure similar to that used for
preparing 6, except that NEt4MnO4 was used instead of
[Mn5O3 (t-BuPO3)2 (MeCOO)5 (H2O)(phen)2]·2H2O·MeOH·
MeCN (1 · 2H2O · MeOH · MeCN). To a stirred solution of
Mn(O2CMe)2 ·4H2O (0.245 g, 1 mmol) and MeCOOH (7 mL, 0.122
NBun MnO4. The brown crystals were produced in 19% yield based
mol) in MeCN (15 mL) was added solid NBun MnO4 (0.091 g,
4
4
on Mn. Anal. Calcd (%) for C48H78Mn4N3O20.5: C, 46.27; H, 6.26;
0.25 mmol) in small portions. To the resulting brown solution was
added a solution of 1,10-phenanthroline (0.10 g, 0.5 mmol) and
tert-butylphosphonic acid (t-BuPO3H2) (0.070 g, 0.5 mmol) in
MeOH (5 mL) to yield a dark brown solution which was stirred
for 24 h at room temperature and then filtered. The filtrate was left
to stand at room temperature for about 1 week, during which time
brown crystals were produced in 21% yield based on Mn. Anal.
Calcd (%) for C45H62Mn5N5O23P2: C, 39.20; H, 4.50; N, 5.08.
Found: C, 39.15; H, 4.53; N, 5.12. Selected IR (KBr, cm-1) data:
3417 (s), 1581 (s), 1518 (s), 1407 (s), 1102 (w), 976 (m), 725 (w).
N, 3.37. Found: C, 46.21; H, 6.39; N, 3.24. Selected IR (KBr, cm-1
)
data: 3452 (m), 2967 (w), 1682 (m), 1602 (s), 1406 (s), 1331 (w),
1275 (m), 1094 (w), 676 (w).
Physical Measurements. Elemental analyses (carbon, hydrogen,
and nitrogen) were performed using a vario EL III CHNOS
elemental analyzer. Infrared spectra were recorded on a Nicolet
magna 750 FT-IR spectrophotometer using KBr pellets in the range
of 400∼4000 cm-1. Electrospray mass spectra were recorded with
a DECAX-30000 LCQ Deca XP mass spectrometer. Electrochemi-
cal studies were performed by a CHI630A voltammetric analyzer.
The auxiliary electrode was a Pt wire, the reference electrode a
Ag/AgCl electrode, and the working electrode a glassy carbon disk,
which was carefully polished with gamma alumina powder (0.05
µm) before each voltammogram and then washed carefully with
distilled dichloromethane. In situ UV-vis-NIR absorption spectra
were recorded in a Varian Cary500 spectrophotometer coupled to
a potentiostat using a quartz glass cuvette as spectroelectrochemical
cell. The measurement was recorded at room temperature in distilled
[Mn5O3(t-BuPO3)2(PhCOO)5(phen)2] · H2O · MeCN (2 · H2O ·
MeCN). This complex was obtained using a procedure similar to
that used for preparing 1·2H2O·MeOH ·MeCN, except that
Mn(O2CPh)2 ·2H2O was used instead of Mn(O2CMe)2 ·4H2O,
PhCOOH instead of MeCOOH, and CH2Cl2/MeCN (v/v 2:1, 15
mL) instead of MeCN (15 mL). The brown crystals were produced
in 17% yield based on Mn. Anal. Calcd (%) for C69H64Mn5N5O20P2:
C, 51.11; H, 3.95; N, 4.32. Found: C, 51.04; H, 3.83; N, 4.63.
Selected IR (KBr, cm-1) data: 3413 (s), 1600 (s), 1518 (s), 1384
(s), 1099 (w), 973 (m), 719 (w).
CH2Cl2 solution under argon and 0.1 M NBun PF6 was added as
4
supporting electrolyte. The variable-temperature magnetic suscep-
tibility (2-300 K) was measured with a model PPMS60000
superconducting extraction sample magnetometer under a field of
0.5 T with the crystalline sample kept in a capsule for weighing.
X-ray Crystallography. The diffraction data for the seven
complexes were collected at 293(2) K on a mercury-CCD/AFCR
diffractometer with Mo KR radiation (λ ) 0.71073 Å). Single
crystals were in all cases selected under a microscope and then
attached to the tip of glass capillaries with grease. The empirical
absorption correction was applied by using the SADABS program.31
All the structures were solved by direct methods and refined by
full-matrix least-squares techniques based on F2with all observed
reflections performed with the SHELXTL-97 package.32 The non-
hydrogen atoms were refined anisotropically. The hydrogen atoms
were located by geometrical calculations except for those on the
water molecules which were located from the difference Fourier
syntheses. The SQUEEZE33 instruction in the PLATON software34
was applied to treat the raw data for the cation of compound 6.
Details of the crystal data and structure refinement of the seven
compounds are listed in Table 1.
[Mn4O2(t-BuPO3)2(MeCOO)4(bpy)2] · 6H2O · 2MeCOOH (3 ·
6H2O · 2MeCOOH). The synthetic procedure of 1 · 2H2O ·
MeOH·MeCN was utilized to prepare 3·6H2O·2MeCOOH with
the use of 2,2′-bipyridine in place of 1,10-phenanthroline. The
brown crystals were produced in 26% yield based on Mn. Anal.
Calcd (%) for C40H66Mn4N4O26P2: C, 36.90; H, 5.07; N, 4.31.
Found: C, 36.74; H, 5.02; N, 4.53. Selected IR (KBr, cm-1) data:
3479 (s), 2966 (w), 1703 (m), 1575 (s), 1399 (s), 1342 (w), 979
(w), 943 (m), 665 (m).
[Mn4O2(t-BuPO3)2(PhCOO)4(bpy)2]·H2O·3PhCOOH(4·H2O·
3PhCOOH). This complex was obtained using a procedure similar
to that used for preparing 2·H2O·MeCN, except that 2,2′-bipyridine
was used instead of 1,10-phenanthroline. The brown crystals were
produced in 21% yield based on Mn. Anal. Calcd (%) for
C77H72Mn4N4O23P2: C, 54.25; H, 4.23; N, 3.29. Found: C, 54.12;
H, 4.47; N, 3.45. Selected IR (KBr, cm-1) data: 3479 (s), 2966
(w), 1703 (m), 1575 (s), 1399 (s), 1342 (w), 979 (w), 943 (m), 665
(m).
NBun [Mn4O2(EtCOO)3(MeCOO)4(pic)2]·0.5H2O (5·0.5H2O).
4
This complex was obtained using a procedure similar to that used
for preparing 1·2H2O·MeOH ·MeCN, except that picolinic acid
was used instead of 2,2′-bipyridine, EtCOOH instead of MeCOOH.
The brown crystals were produced in 29% yield based on Mn. Anal.
Calcd (%) for C45H71Mn4N3O20.5: C, 44.93; H, 5.91; N, 3.49. Found:
C, 44.89; H, 5.63; N, 3.74. Selected IR (KBr, cm-1) data: 3452
(m), 2965 (m), 1676 (s), 1464 (w), 1398 (s), 1331 (s), 1284 (m),
649 (m).
Results and Discussion
Synthesis. The ability of phosphonic acid ligands to
support various structures is well demonstrated by the
growing number of reports on phosphonate clusters.16–28
During our investigation, we have explored the reaction
system of tert-butylphosphonic acid with manganese salts
(Mn(O2CR)2 (R ) Me, Ph)) in combination with the
NBun [Mn4O2(i-PrCOO)7(pic)2] (6). This complex was obtained
4
using a procedure similar to that used for preparing 5 · 0.5H2O,
except that i-PrCOOH was used instead of EtCOOH. The brown
crystals were produced in 20% yield based on Mn. Anal. Calcd
(%) for C56H93Mn4N3O20: C, 49.85; H, 6.90; N, 3.12. Found: C,
(31) Sheldrick, G. M. SADABS Software for Empirical Absorption Cor-
rection; University of Go¨ttingen: Go¨ttingen, Germany, 1996.
(32) Sheldrick, G. M. SHELXTL, Structure Determination Software Pro-
grams; Bruker Analytical X-ray System Inc: Madison, WI, 1997.
(33) SQUEEZE: Sluis, P. v. d.; Spek, A. L. Acta Crystallogr., Sect. A 1990,
46, 194.
(30) Karaman, H.; Barton, R. J.; Robertson, B. E.; Lee, D. G. J. Org. Chem.
1984, 49 (23), 4509.
(34) PLATON software: Spek, A. L. A Multipurpose Crystallographic Tool;
Utrecht University: Utrecht, The Netherlands, 1998.
5582 Inorganic Chemistry, Vol. 47, No. 13, 2008

Penta- and Tetra-Manganese(III) Complexes
Table 1. Crystallographic Data for Complexes 1-7
complex
1·2H2O·MeOH·MeCN
2·H2O·MeCN
3·6H2O·2MeCOOH
formulaa
space group
fw
a, Å
b, Å
C45H62Mn5N5O23P2
P1
C69H64Mn5N5O20P2
P21/c
C40H66Mn4N4O26P2
P1
j
j
1377.64
12.1843(4)
15.2634(9)
17.0702(7)
82.720(9)
81.662(9)
79.114(8)
3068.4(2)
2
1619.89
13.939(5)
19.425(8)
29.166(12)
90
94.515(10)
90
7873(5)
4
1300.67
10.652(4)
11.931(4)
13.295(5)
115.296(4)
90.36
113.407(4)
1370.0(9)
1
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
T, K
293(2)
0.71073
1.491
1.129
0.0788
293(2)
0.71073
1.367
0.889
0.0707
293(2)
0.71073
1.577
1.046
0.0368
λ, Åb
F
calcd, g cm-3
µ, mm-1
c
R1
d
wR2
0.1934
0.2022
0.0838
complex
4·H2O·3PhCOOH
5·0.5H2O
6
7·0.5H2O
formulaa
space group
fw
a, Å
b, Å
C77H72Mn4N4O23P2
P21/c
C45H71Mn4N3O20.5
P1
C56H93Mn4N3O20
P1
C48H78Mn4N3O20.5
P21/c
j
j
1703.09
14.308(2
13.0663(18)
23.021(3)
90
106.091(4)
90
4135.1(10)
2
1201.81
12.575(5
12.724(5)
19.455(8)
78.848(9)
84.450(8)
83.593(11)
3026(2)
2
1348.09
12.617(12)
13.145(12)
21.89(2)
89.67(2)
86.989(15)
85.51(2)
3615(6)
2
1244.89
12.221(4)
21.229(6)
23.495(7)
90
104.561(3)
90
5900(3)
4
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
T, K
293(2)
0.71073
1.368
0.709
0.0609
293(2)
0.71073
1.317
0.883
0.0733
293(2)
0.71073
1.238
293(2)
0.71073
1.429
0.912
0.0995
0.2160
λ, Åb
F
calcd, g cm-3
µ, mm-1
0.746
c
R1
wR2
0.0928
0.1686
2
d
0.165
0.2014
a Including solvent molecules. b Graphite monochromator. c R1 ) ∑(||Fo| - |Fc||/∑|Fo|. d wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]0.5
.
2
2
N-containing ligands (phen, bpy, and picH). It is interesting
to note that compounds 1-7 were all prepared in similar
one-port procedures which lead to three species of com-
plexes. Previous work had proved that NR′4MnO4 (R′ ) Bun,
Et) in nonaqueous solvents represents a useful route to
forming higher oxidation state Mn complexes.35,36 The seven
compounds 1-7 were all prepared from the comproportion-
ation reactions between MnII and NR′4MnO4 (R′ ) Bun, Et)
which resulted in the average Mn oxidation state of +3 in
all of the seven compounds. Complexes 1 and 2 contain a
novel [Mn5O3] core, which has not yet been reported so far,
though several pentanuclear manganese(II),37,38 manga-
nese(III),39 and mixed valent manganese(II and III)40–42
clusters have been prepared before. It is worthwhile to point
out that the participation of the N-containing coligands (bpy,
phen, pyridine, etc.) seems necessary to obtain the poly-
nuclear Mn phosphonate clusters in spite of the various
synthetic procedures when we read throughout all the
synthetic reports on the polynuclear Mn phosphonate clusters.
With the variation of the N-containing coligand, a variety
of structures with higher nuclearity were obtained for the
Mn phosphonate cluster family. In this work, the use of phen
has led to a novel Mn5O3 cluster while the use of bpy in
place of phen in the same ratio and in the similar reaction
system has led to a completely different kind of complex
[Mn4O2(t-BuPO3)2(RCOO)4(bpy)2] (R ) Me, (3); R ) Ph,
(4)). Whereas, when picH was used instead of phen, a known
type of the complex NBun [Mn4O2(MeCOO)7(pic)2]4d was
(35) Vincent, J. B.; Chang, H.-R.; Folting, K.; Huffman, J. C.; Christou,
G.; Hendrickson, D. N. J. Am. Chem. Soc. 1987, 109, 5703.
(36) Bouwman, E.; Bolcar, M. A.; Libby, E.; Huffman, J. C.; Folting, K.;
Christou, G. Inorg. Chem. 1992, 31, 5185.
4
obtained, and the tert-butylphosphonate group failed to ligate
to the manganese ion. It is considered that in contrast with
the basicity of phen and bpy, the acidity of picolinic acid
will be unfavorable for the total deprotonation of tert-
butylphosphonic acid while the deprotonation should be
important for tridentate coordination of the alkylphosphonate.
It is also noticed that as a dibasic acid, alkylphosphonic acid
has its pK1 ) 2.8 and pK2 ) 8.443 implying that the total
deprotonation would be difficult in the presence of picolinic
(37) Matthews, C. J.; Thompson, L. K.; Parsons, S. R.; Xu, Z.; Miller,
D. O.; Heath, S. L. Inorg. Chem. 2001, 40, 4448.
(38) Matthews, C. J.; Xu, Z.; Mandal, S. K.; Thompson, L. K.; Biradha,
K.; Poirier, K.; Zaworotko, M. J. Chem. Commun. 1999, 347.
(39) Reynolds, R. A., III; Coucouvanis, D. Inorg. Chem. 1998, 37, 170.
(40) Lah, M. S.; Pecoraro, V. L. J. Am. Chem. Soc. 1989, 111, 7258.
(41) Berlinguette, C. P.; Vaughn, D.; Can˜ada-Vilalta, C.; Gala´n-Mascaro´s,
R. G.; Dunbar, K. R. Angew. Chem., Int. Ed. 2003, 42, 1523.
(42) Yang, C.-I.; Wernsdorfer, W.; Lee, G.-H.; Tsai, H.-L. J. Am. Chem.
Soc. 2007, 129, 456.
Inorganic Chemistry, Vol. 47, No. 13, 2008 5583

Wang et al.
Figure 1. DIAMOND view of (a) compound 1 and (b) compound 2. Hydrogen atoms have been omitted for clarity.
acid with pK ) 5.32.44 Consequently it is comprehensible
that despite many attempts, we failed to introduce tert-
butylphosphonate into the manganese compounds in the
reaction system containing picH and just obtained the Mn4O2
carboxylate complexes 5, 6, and 7. Interestingly, complex 5
contains mixed aliphatic carboxylate ligands in its Mn4O2
core, which is the first example of the family. It is considered
that EtCOOH exhibits similar acidity and structural features
to those of acetic acid; therefore, the substitution of EtCOO-
for AcO- is likely incomplete and leads to mixed aliphatic
carboxylate ligands in complex 5.
triangular planes made up of {Mn(3), Mn(4), Mn(5)},
{Mn(2), Mn(4), Mn(5)}, and {Mn(1), Mn(3), Mn(5)} but
outside of the planes by 0.8150, 0.2018, and 0.3305 Å,
respectively. The five manganese atoms are all six-coordinate
with near-octahedral geometry around each center. The
Mn(1) and Mn(2) atoms are each surrounded by two
phosphonate oxygen atoms, one µ3-O, one acetate oxygen
atom, and two 1,10-phenanthroline nitrogens. The Mn(4) and
Mn(5) atoms are both coordinated by one phosphonate
oxygen atom, two µ3-O, and three acetate oxygen atoms. It
is notable that the coordination environment of Mn(3) is
slightly different from that of Mn(4) and Mn(5) in that one
oxygen atom (O(16)) from the H2O molecule chelates to
Mn(3) instead of the acetate oxygen atom. One acetate group
is monodentate, and O(18) of the acetate group is not
involved in manganese coordination. The average distance
of Mn-Ophosphonate is 2.048(4) Å which is comparable with
that reported for manganese phosphonates.19,23,24
As shown in Figures 1b and 2, complex 2 possesses
analogous molecular structure to that of 1 and the identical
inorganic core structure with 1. However, the peripheral
ligation of complex 2 consists of two t-BuPO32-, six
PhCOO-, and two terminal phen groups, of which the six
PhCOO- are all bidentate bridges and no H2O is coordinated
to Mn. A comparison of selected bonds distances and angles
of 1 with those of 2 is given in Supporting Information, Table
S1.
Description of Crystal Structures.
[Mn5O3(t-BuPO3)2(MeCOO)5(H2O)(phen)2] (1) and
[Mn5O3(t-BuPO3)2(PhCOO)5(phen)2] (2). The molecular
structure of complex 1 is shown in Figure 1a, while selected
bond distances and angles of 1 are listed in Table 2.
Complex 1 possesses a pentanuclear core [Mn5O3]9+ and
the five manganese atoms are all in +3 oxidation state
according to the bond valence sum calculations.45 The
peripheral ligation is composed of two t-BuPO32-, five
MeCOO-, one H2O, and two terminal phen groups. The two
tert-butylphosphonate ligands in 1 adopt two kinds of binding
mode: [4.211] and [3.111] by the Harris notation (Scheme
1).46
Five manganese atoms are bridged by three µ3-O and two
2-
t-BuPO3
to form an unprecedented basket-like cage
structure (Figure 2). The Mn(3), Mn(4), Mn(5) atoms with
intermanganese bond lengths of Mn(3) · · ·Mn(4), 2.9928(12);
Mn(4) · · ·Mn(5), 2.8442(13); Mn(3) · · ·Mn(5), 2.9892(12) (Å)
are linked by µ3-O(1) forming a cone-shaped bottom of the
basket. And the mouth of the basket is composed of the eight-
membered ring of {Mn(1)-O(4)-P(1)-O(5)-Mn(2)-
O(8)-P(2)-O(7)}. Unlike the Mn3O complexes,35,47,48 the
three µ3-O atoms O(1), O(2), O(3) are not in the three
[Mn4O2(t-BuPO3)2(RCOO)4(bpy)2] (R ) Me, (3); R
) Ph, (4)). The Oak Ridge Thermal Ellipsoid Plot (ORTEP)
diagram for complex 3 is illustrated in Figure 3a, while
selected bond lengths and angles for 3 are given in Table 3.
j
Complex 3 crystallizes in triclinic P1 space group with C2V
symmetry. It possesses an [Mn4(µ3-O)2]8+ core with the four
coplanar Mn atoms disposed in an extended “butterfly-like”
arrangement which is similar to that in the previously
reported [Mn4(µ3-O)2]8+ complexes.49,50 However, there are
two capping tert-butylphosphonate ligands above and below
the core, which is markedly different from the reported Mn4
(43) White, J. R. J. Am. Chem. Soc. 1950, 72, 1859.
(44) Stephenson, H. P.; Sponer, H. J. Am. Chem. Soc. 1957, 79, 2050.
(45) Liu, W. T.; Thorp, H. H. Inorg. Chem. 1993, 32, 4102.
(46) Coxall, R. A.; Harris, S. G.; Henderson, D. K.; Parsons, S.; Tasker,
P. A.; Winpenny, R. E. P. Dalton Trans. 2000, 2349.
(47) Baikie, A. R. E.; Hursthouse, M. B.; New, L.; Thornton, P.; White,
R. G. J. Am. Chem. Soc. Commun. 1980, 684.
(49) Wang, S.; Wemple, M. S.; Yoo, J.; Folting, K.; Huffman, J. C.; Hagen,
K. S.; Hendrckson, D. N.; Christou, G. Inorg. Chem. 2000, 39, 1501.
(50) Can˜ada-Vilalta, C.; Huffman, J. C.; Christou, G. Polyhedron. 2001,
20, 1785.
(48) Baikie, A. R. E.; Hursthouse, M. B.; New, D. B.; Thornton, P. J. Am.
Chem. Soc. Commun. 1978, 62.
5584 Inorganic Chemistry, Vol. 47, No. 13, 2008

Penta- and Tetra-Manganese(III) Complexes
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for Complex 1
Mn(1)-O(3)
Mn(1)-O(7)
Mn(1)-O(4)
Mn(1)-N(1)
Mn(1)-O(14)
Mn(1)-N(2)
Mn(2)-O(2)
Mn(2)-O(8)
Mn(2)-O(5)
Mn(2)-N(3)
Mn(2)-O(10)
1.807(4)
1.991(4)
2.007(4)
2.101(5)
2.120(4)
2.190(6)
1.831(4)
1.975(4)
2.006(5)
2.091(5)
2.133(5)
Mn(2)-N(4)
Mn(3)-O(3)
Mn(3)-O(1)
Mn(3)-O(15)
Mn(3)-O(19)
Mn(3)-O(9)
Mn(3)-O(16)
Mn(4)-O(1)
Mn(4)-O(2)
Mn(4)-O(11)
Mn(4)-O(20)
2.206(6)
1.867(4)
1.899(3)
1.938(4)
1.997(4)
2.229(4)
2.246(4)
1.871(4)
1.904(4)
1.912(5)
1.971(4)
Mn(4)-O(13)
Mn(4)-O(9)
Mn(5)-O(6)
Mn(5)-O(1)
Mn(5)-O(2)
Mn(5)-O(17)
Mn(5)-O(12)
Mn(5)-O(3)
Mn(3) · · ·Mn(5)
Mn(3) · · ·Mn(4)
Mn(4) · · ·Mn(5)
2.175(4)
2.250(4)
1.878(4)
1.885(4)
1.970(4)
2.001(5)
2.203(4)
2.208(4)
2.9892(12)
2.9928(12)
2.8442(13)
O(3)-Mn(1)-O(7)
O(3)-Mn(1)-O(4)
O(7)-Mn(1)-O(4)
O(3)-Mn(1)-N(1)
O(7)-Mn(1)-N(1)
O(4)-Mn(1)-N(1)
O(3)-Mn(1)-O(14)
O(7)-Mn(1)-O(14)
O(4)-Mn(1)-O(14)
N(1)-Mn(1)-O(14)
O(3)-Mn(1)-N(2)
O(7)-Mn(1)-N(2)
O(4)-Mn(1)-N(2)
N(1)-Mn(1)-N(2)
O(14)-Mn(1)-N(2)
O(2)-Mn(2)-O(8)
O(2)-Mn(2)-O(5)
O(8)-Mn(2)-O(5)
O(2)-Mn(2)-N(3)
O(8)-Mn(2)-N(3)
O(5)-Mn(2)-N(3)
O(2)-Mn(2)-O(10)
O(8)-Mn(2)-O(10)
O(5)-Mn(2)-O(10)
N(3)-Mn(2)-O(10)
Mn(4)-O(1)-Mn(3)
Mn(2)-O(2)-Mn(5)
Mn(1)-O(3)-Mn(5)
95.83(17)
93.97(16)
98.21(18)
174.3(2)
89.9(2)
84.84(17)
95.35(17)
90.9(2)
166.24(18)
84.88(17)
97.32(18)
166.81(16)
81.98(18)
77.0(2)
86.81(19)
94.14(16)
96.00(17)
101.5(2)
174.26(19)
90.4(2)
O(2)-Mn(2)-N(4)
O(8)-Mn(2)-N(4)
O(5)-Mn(2)-N(4)
N(3)-Mn(2)-N(4)
O(10)-Mn(2)-N(4)
O(3)-Mn(3)-O(1)
O(3)-Mn(3)-O(15)
O(1)-Mn(3)-O(15)
O(3)-Mn(3)-O(19)
O(1)-Mn(3)-O(19)
O(15)-Mn(3)-O(19)
O(3)-Mn(3)-O(9)
O(1)-Mn(3)-O(9)
O(15)-Mn(3)-O(9)
O(19)-Mn(3)-O(9)
O(3)-Mn(3)-O(16)
O(1)-Mn(3)-O(16)
O(15)-Mn(3)-O(16)
O(19)-Mn(3)-O(16)
O(9)-Mn(3)-O(16)
O(1)-Mn(4)-O(2)
O(1)-Mn(4)-O(11)
O(2)-Mn(4)-O(11)
O(1)-Mn(4)-O(20)
O(2)-Mn(4)-O(20)
Mn(5)-O(1)-Mn(3)
Mn(4)-O(2)-Mn(5)
Mn(3)-O(3)-Mn(5)
97.93(18)
166.70(19)
82.89(19)
77.2(2)
O(11)-Mn(4)-O(20)
O(1)-Mn(4)-O(13)
O(2)-Mn(4)-O(13)
O(11)-Mn(4)-O(13)
O(20)-Mn(4)-O(13)
O(1)-Mn(4)-O(9)
O(2)-Mn(4)-O(9)
O(11)-Mn(4)-O(9)
O(20)-Mn(4)-O(9)
O(6)-Mn(5)-O(1)
O(6)-Mn(5)-O(2)
O(1)-Mn(5)-O(2)
O(6)-Mn(5)-O(17)
O(1)-Mn(5)-O(17)
O(2)-Mn(5)-O(17)
O(6)-Mn(5)-O(12)
O(1)-Mn(5)-O(12)
O(2)-Mn(5)-O(12)
O(17)-Mn(5)-O(12)
O(6)-Mn(5)-O(3)
O(1)-Mn(5)-O(3)
O(2)-Mn(5)-O(3)
O(17)-Mn(5)-O(3)
O(12)-Mn(5)-O(3)
Mn(4)-O(1)-Mn(5)
Mn(2)-O(2)-Mn(4)
Mn(1)-O(3)-Mn(3)
Mn(3)-O(9)-Mn(4)
86.9(2)
87.78(17)
88.94(16)
90.35(19)
94.51(17)
84.32(15)
87.29(15)
97.80(18)
88.20(16)
169.34(16)
93.33(17)
82.14(16)
97.2(2)
88.68(18)
167.24(18)
101.52(17)
87.71(16)
84.67(17)
86.15(19)
94.98(15)
76.49(14)
100.47(15)
85.85(18)
162.43(15)
98.45(16)
124.3(2)
82.5(2)
85.09(16)
100.55(18)
173.72(17)
172.00(17)
86.99(17)
87.42(18)
90.66(16)
84.28(14)
98.32(17)
87.42(17)
89.27(16)
88.29(15)
89.01(18)
91.62(17)
172.55(15)
84.27(16)
174.28(18)
101.10(18)
87.82(17)
171.24(18)
104.39(18)
94.46(15)
94.00(16)
86.5(2)
94.06(19)
91.1(2)
163.24(18)
82.3(2)
105.09(17)
137.6(2)
133.01(19)
123.8(2)
83.84(12)
Scheme 1
in 3, adopting a [3.111] binding mode by the Harris notation
(Scheme 1), are above or below the Mn4 plane, each binding
to three manganese centers of the Mn3O triangular unit
(Figure 4). The distance between the two planes formed by
{O(2)-O(3)-O(4)} and {Mn(1)-Mn(2)-Mn(1A)-Mn(2A)}
is 2.0466 Å while the distances of P(1) · · · P(1A) are 5.833
Å. In addition to two capping tert-butylphosphonate ligands,
there are a total of four bridging µ2-MeCO2- groups around
the four Mn atoms and two terminal bpy groups, giving a
six-coordination near-octahedral geometry around each MnIII
with Jahn-Teller elongation.
complexes. The four manganese atoms are all in the +3
oxidation state according to the bond valence sum calcula-
tions.45 The two bicapping µ3-tert-butylphosphonate ligands
As shown in Figures 3b and 4, the molecular structure of
complex 4 closely resembles that of 3, and it possesses an
identical inorganic core structure to 3 but the peripheral
ligation of PhCOO- groups in 4 substitutes MeCO2- groups
in 3. A comparison of selected bonds distances and angles
of 3 with those of 4 is given in Supporting Information, Table
S2.
NBun4[Mn4O2(EtCOO)3(MeCOO)4(pic)2](5),NR′4[Mn4O2(i-
PrCOO)7(pic)2] (R′ ) Bun, (6); R′ ) Et, (7)). The ORTEP
diagram for the anion of complex 5 is shown in Supporting
Information, Figure S1, and selected bond lengths and angles
for 5 are given in Supporting Information, Table S3. The
anion contains a [Mn4(µ3-O)2]8+ core in which the four Mn
atoms display a folded “butterfly-like” conformation just as
in some previously reported [Mn4(µ3-O)2]8+ com-
Figure 2. Inorganic core of compounds 1 and 2 showing 30% probability
displacement ellipsoids.
Inorganic Chemistry, Vol. 47, No. 13, 2008 5585

Wang et al.
Figure 3. Crystal structures of (a) compound 3 and (b) compound 4 at 30% probability displacement ellipsoids. Hydrogen atoms have been omitted for
clarity.
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for
complex 5 that have not been obtained before. Three
Complex 3
EtCOO- groups in 5 replace three of the seven MeCOO-
Mn(1)-O(2A)
Mn(1)-O(1)
Mn(1)-N(2)
Mn(1)-N(1)
Mn(1)-O(7A)
Mn(1)-O(5)
Mn(2)-O(1A)
1.8659(15) Mn(2)-O(1)
1.8693(14) Mn(2)-O(6)
2.0465(19) Mn(2)-O(8)
2.0475(19) Mn(2)-O(3)
2.2086(17) Mn(2)-O(4A)
2.2136(17) Mn(2) · · ·Mn(2A)
1.9055(14)
1.9086(15)
1.9358(16)
1.9401(16)
2.1949(16)
2.3362(16)
2.8380(9)
groups in NBun [Mn4O2(MeCOO)7(pic)2].4d
4
As shown in Supporting Information, Figure S1, the anions
of complexes 6 and 7 possess similar structures to that of 5.
A comparison of selected bond distances and angles of 5
with those of 6 and 7 is given in Supporting Information,
Table S4.
Magnetic Susceptibility Studies. Magnetic susceptibility
data for 1 · 2H2O · MeOH · MeCN, 3 · 6H2O · 2MeCOOH,
and 5 · 0.5H2O were measured in the temperature range
2-300 K under a field of 0.5 T. The resulting plots of ꢁM
and ꢁMT versus T for 1, 3, and 5 are depicted in Figures 5,
top, and 7, top, and in Supporting Information, Figure S2,
respectively.
As the temperature is lowered, the ꢁMT of complex 1
decreases smoothly from a value of 11.04 cm3 mol-1 K at
300 K to 5.50 cm3 mol-1 K at 16 K, and then the value falls
sharply to 3.15 cm3 mol-1 K at 2 K. The ꢁMT value (11.05
cm3 mol-1 K) at room temperature is smaller than that of
14.99 cm3 mol-1 K expected for five independent Mn(III)
ions with S ) 2. This result reveals the overall intramolecular
antiferromagnetic character of the system. As shown in
Figure 5, bottom, a model is used to simulate the exchange
interaction within the complex, which involves five pairwise
couplings on the basis of the bridge angles and the distances
between the Mn atoms. The susceptibility data were fitted
using the magnetism package MAGPACK54,55 based on the
interaction pattern (Figure 5, bottom) and on the correspond-
ing Hamiltonian (eq 1).
O(2A)-Mn(1)-O(1) 95.42(7)
O(2A)-Mn(1)-N(2) 91.39(8)
O(1A)-Mn(2)-O(1) 83.84(6)
O(1A)-Mn(2)-O(6) 177.10(6)
O(1)-Mn(2)-O(6) 96.73(6)
O(1A)-Mn(2)-O(8) 96.34(6)
O(1)-Mn(1)-N(2)
173.18(7)
O(2A)-Mn(1)-N(1) 170.08(7)
O(1)-Mn(1)-N(1)
N(2)-Mn(1)-N(1)
O(2A)-Mn(1)-O(7A) 98.87(7)
O(1)-Mn(1)-O(7A) 92.35(7)
N(2)-Mn(1)-O(7A) 86.42(7)
N(1)-Mn(1)-O(7A
O(2A)-Mn(1)-O(5) 94.01(7)
93.99(7)
79.21(8)
O(1)-Mn(2)-O(8)
O(6)-Mn(2)-O(8)
174.39(7)
83.38(7)
O(1A)-Mn(2)-O(3) 89.54(6)
O(1)-Mn(2)-O(3)
O(6)-Mn(2)-O(3)
O(8)-Mn(2)-O(3)
O(1A)-Mn(2)-O(4A) 86.62(6)
O(1)-Mn(2)-O(4A) 84.18(6)
O(6)-Mn(2)-O(4A) 96.27(7)
O(8)-Mn(2)-O(4A) 90.23(6)
O(3)-Mn(2)-O(4A) 172.00(5)
88.43(6)
87.63(7)
97.18(7)
83.85(7)
O(1)-Mn(1)-O(5)
N(2)-Mn(1)-O(5)
N(1)-Mn(1)-O(5)
95.58(7)
84.08(7)
81.95(8)
O(7A)-Mn(1)-O(5) 164.17(6)
plexes.4d,51–53 The whole structure of 5 is very similar to
that of NBun [Mn4O2(RCOO)7(pic)2] (R ) Me, Et, Ph).4d It
4
is worthwhile to point out that there are two kinds of
carboxylate groups (three EtCOO- and four MeCOO-) in
(51) Wang, B. S.; Huffman, J. C.; Folting, K.; Streib, W. E.; Lobkovsky,
E. B.; Christou, G. Angew. Chem., Int. Ed. Engl. 1991, 30, 1672
.
(52) Wemple, M. W.; Tsai, H. L.; Wang, S.; Claude, J. P.; Streib, W. E.;
Huffman, J. C.; Hendrickson, D. N.; Christou, G. Inorg. Chem. 1996,
35, 6437
.
(53) Huang, D.; Zhang, X.; Ma, C.; Chen, H.; Chen, C.; Liu, Q.; Zhang,
C.; Liao, D.; Li, L. Dalton Trans. 2007, 680
.
(54) Borra´s-Almenar, J. J.; Clemente-Juan, J. M.; Coronado, E.; Tsukerblat,
B. S. J. Comput. Chem. 2001, 22, 985.
Figure 4. DIAMOND view of the core of 3 and 4 showing the planar
(55) Borra´s-Almenar, J. J.; Clemente-Juan, J. M.; Coronado, E.; Tsukerblat,
B. S. Inorg. Chem. 1999, 38, 6081.
parallelogram Mn4 array bicapped by the [t-BuPO3]2-
.
5586 Inorganic Chemistry, Vol. 47, No. 13, 2008

Penta- and Tetra-Manganese(III) Complexes
ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
2 4
H ) -2J S S - 2J S S + S S - 2J S S + S S -
(
)
5
(
3
)
1
3
4
2
3
5
4
1
3
ˆ
2J S Sˆ + S S - 2J S S (1)
ˆ ˆ
ˆ ˆ
(
4
)
5
1
5
2
5 1 2
Several sets of fitted parameters have been obtained by
choosing different starting values of J, two of which with
Figure 7. (top) Temperature dependence ꢁMT (4) and ꢁM (0) values for
3·6H2O·2MeCOOH. The solid lines correspond to the best-fit curves using
the parameters described in the text. (bottom) Spin topology for
3·6H2O·2MeCOOH assuming two different J values.
acceptable convergence values (R) are (i) J1 ) -5.59 cm-1,
J2 ) 15.40 cm-1, J3 ) 16.15 cm-1, J4 ) -46.53 cm-1, J5 )
2.73 cm-1, g ) 2.01, R ) 6.87 × 10-5, and (ii) J1 ) -2.18
cm-1, J2 ) 6.93 cm-1, J3 ) -13.94 cm-1, J4 ) -9.62 cm-1,
J5 ) -11.17 cm-1, g ) 2.00 and R ) 6.27 × 10-4 (Defined
as ∑[(ꢁMT)calcd. - (ꢁMT)obsd.]2/[∑(ꢁMT)obsd.]2). Obviously, the
coupling interactions between the paramagnetic metal ions
are sensitive to the type of bridge between the metal centers,
as well as the related structure parameters. There is no
literature about magnetostructural correlations between the
structure parameters (such as MnIII-O-MnIII angle) and the
sign/magnitude of the exchange constant for such a com-
plicated system; however, we can tentatively discuss the
correlations by comparison with some reported dinuclear
manganese clusters with a [MnIII2O] core.56 In these dinuclear
manganese clusters, the angles of the MnIII-O-MnIII bridges
transmitting the exchange interactions of -6.8, +9, -0.5,
and -120 cm-1 are 122.9°, 118°, 125°, and 168°, respec-
tively, which exhibit some similarities in the MnIII-O-MnIII
angles with those (∼105°, ∼94°, ∼124°, ∼135°, respectively,
found in our compounds) corresponding to the first four
Figure 5. (top) Temperature dependence of ꢁm (0) and ꢁmT (O) values
for 1·2H2O·MeOH·MeCN. The solid lines correspond to the best-fit curves
using the parameters described in the text. (bottom) Spin topology for
1·2H2O·MeOH·MeCN assuming five different J values.
(56) (a) Hotzelmann, R.; Wieghardt, K.; Flo¨rke, U.; Haupt, H.-J.; Weath-
erburn, D. C.; Bonvoisin, J.; Blondin, G.; Girerd, J.-J. J. Am. Chem.
Soc. 1992, 114, 1681. (b) Kipke, C. A.; Scott, M. J.; Gohdes, J. W.;
Armstrong, W. H. Inorg. Chem. 1990, 29, 2193. (c) Wieghardt, K.;
Bossek, U.; Nuber, B.; Weiss, J.; Bonvoisin, J.; Corbella, M.; Vitols,
S. E.; Girerd, J. J. J. Am. Chem. Soc. 1988, 110, 7398. (d) Wieghardt,
K.; Bossek, U.; Ventur, D.; Weiss, J. J. Chem. Soc. Commun. 1985,
347. (e) Me´nage, S.; Girerd, J. J.; Gleizes, A. J. Chem. Soc. Commun.
1988, 431.
Figure 6. Plots of in-phase (ꢁM′T) ac susceptibility versus temperature (T)
for 1·2H2O·MeOH·MeCN.
Inorganic Chemistry, Vol. 47, No. 13, 2008 5587

Wang et al.
interactions (J1-J4). Besides these MnIII-O-MnIII bridges,
the other external bridges in our complex (O-P-O and
O-C-O bridges) exhibit partial similarity to these reported
dinuclear manganese clusters (O-C-O bridges). So we think
that the second set of the fitted parameters is a more
reasonable result. As for J5, there is no MnIII-O-MnIII bridge
between Mn1 and Mn2 but two O-P-O bridges which
usually can mediate the antiferromagnetic exchange.57
As shown in Supporting Information, Figure S3, the
isothermal magnetization values M(H) of complex 1 were
collected at 2 K but no hysteresis loop was observed. The
alternating current (ac) magnetic susceptibility measurement
was carried out with a 3.0 G ac field at frequencies of 111,
311, 511, 711, and 911 Hz without the use of a dc field. As
seen from Figure 6, the in-phase signal (ꢁM′T) is not
frequency-dependent, and the extrapolation of the plot to the
lowest temperature 0 K affords a ꢁM′T value of about 3 cm3
mol-1 K, indicating an S ) 2 ground-state with g ) 2.00.
All the results suggest that complex 1 is not a single
molecular magnet (SMM).
Figure 8. Cyclic voltammogram (100 mV s-1) (top) and differential pulse
voltammetry (100 mV s-1) (bottom) for complex 1 in distilled CH2Cl2 with
0.1 M NBun PF6 as supporting electrolyte.
4
The ꢁMT value at 300 K is 8.08 cm3 mol-1 K for compound
3; upon cooling, the value of ꢁMT gradually decreases to
4.20 cm3 mol-1 K at 30 K, whereupon the value falls sharply
to 0.40 cm3 mol-1 K at 2 K. The ꢁMT per Mn4 at room
temperature (8.08 and 8.04 cm3 mol-1 K for 3 and 5,
of 3 and 5, which are comparable to those of known
tetranuclear Mn(III) complexes,4d,49 though there are obvious
distinctions in structural features between the two types of
Mn4O2 complexes, including 4Mn coplanarity and phospho-
nate coordination. This seems to indicate that the phospho-
nate coordination did not have an essential influence on the
magnetic exchange between the Mn(III) ions, indicating also
that the µ3-O bridge may be the strongest mediator for
transmitting the exchange interaction between the Mn(III)
ions.
respectively) is smaller than that of 12.01 cm3 mol-1
K
expected for four independent Mn(III) ions with S ) 2, which
indicates the overall antiferromagnetic character of the two
systems. As shown in Figure 7, bottom, a model is used to
simulate the antiferromagnetic exchange interaction within
complex 3 which involves two pairwise couplings, J1
corresponding to the interactions between Mn(1) and Mn(2)
joined by one µ3-O, one O-P-O and one O-C-O bridge,
J2 corresponding to the interactions between Mn(2) and
Mn(2A) connected by two µ3-O and two O-P-O bridges.
The susceptibility data of 3 and 5 were fitted over the
temperature range 20-300 K based on the interaction
patterns shown in Figure 7, bottom, and Supporting Informa-
tion, Figure S2, bottom, respectively, and on the correspond-
ing Hamiltonian (eq 2).
Electrochemical Studies. The cyclic voltammetry (CV)
and differential pulse voltammetry (DPV) of 1, 3, and 5 have
been recorded in distilled CH2Cl2 solution under argon in
the presence of 0.1 M NBun PF6 as supporting electrolyte.
4
As the CV and DPV plots (Figure 8) show, compound 1
displays two quasi-reversible waves at E1/2 ) 0.76 V (∆EP
) 190 mV) and E1/2 ) ∼ -1.54 V (∆EP ) 150 mV) versus
Ag/AgCl and one irreversible reduction at ∼ -0.46 V
between both the quasi-reversible redox waves. (Under the
same experimental condition, the Fc/Fc+ couple is at E1/2
)
ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
ˆ ˆ
2 1 4
H ) -2J S S + S S + S S + S S - 2J S S
(2)
(
)
4
0.436 V.) The first two quasi-reversible redox waves with
the relatively small peak separations are comparable to that
of the Fc/Fc+ couple under the same condition, suggesting
that they are all one-electron processes.59 Also, the studies
of the changes in the redox processes at the scan rate of
100, 200, 300, 500, and 800 mV s-1 indicate that the
processes at 0.46 and -1.54 V are quasi-reversible (Sup-
porting Information, Figure S4). The deprotonated ligand
1
1
2
1
3
2
4
3
The molecular field approximation (zJ′)58 is introduced
to estimate the inter-complex interactions, and the best-fit
parameters obtained are J1 ) -5.41 cm-1, J2 ) -35.44
cm-1, g ) 2.13, zJ′ ) -1.55 cm-1, and R ) 2.15 × 10-4
for 3, and J1 ) -2.29 cm-1, J2 ) -35.21 cm-1, g ) 2.02,
zJ′ ) -0.86 cm-1, and R ) 3.15 × 10-4 for 5 (R is defined
as ∑[(ꢁMT)calcd. - (ꢁMT)obsd.]2/[∑(ꢁMT)obsd.]2). The results
reveal the overall antiferromagnetic character of the systems
2-
t-BuPO3 does not display any such peaks as mentioned
above. Thus, the redox processes are all metal-based, which
are consistent with the electrochemistry of the other reported
manganese clusters.4a,d,m The quasi-reversible oxidation at
the E1/2 value of 0.76 V is tentatively assigned to the
oxidation of MnIII5 to MnIII4MnIV. An in situ UV-vis-NIR
(57) (a) Ikotou, O. F.; Armatus, N. G.; Julve, M.; Kruger, P. E.; Lloret, F.;
Nieuwenhuyzen, M.; Doyle, R. P. Inorg. Chem. 2007, 46, 6668. (b)
Sanz, F.; Parada, C.; Rojo, J. M.; Ru´ız-Valero, C. Chem. Mater. 2001,
13, 1334. (c) Bu, X.; Feng, P.; Stucky, G. D. J. Solid State Chem.
1997, 131, 387. (d) Fan, J.; Yee, G. T.; Wang, G.; Hanson, B. E.
Inorg. Chem. 2006, 45, 599.
(58) ꢁ0 is the susceptibility of the noninteracting compounds, z is the number
of nearest neignbors, and J′ is the magnetic interactions between units.
See Kachi-Terajima, C.; Miyasaka, H.; Sugiura, K.-i.; Cle´rac, R.;
Nojin, H. Inorg. Chem. 2006, 45, 4381.
(59) Sessoli, R.; Tsai, H.-L.; Schake, A. R.; Wang, S.; Vincent, J. B.;
Folting, K.; Gatteschi, D.; Christou, G;.; Hendrickson, D. N. J. Am.
Chem. Soc. 1993, 115, 1804.
5588 Inorganic Chemistry, Vol. 47, No. 13, 2008

Penta- and Tetra-Manganese(III) Complexes
spectroelectrochemistry of compound 1 was tested from 0.6
to 1.0 V. Two absorption bands occurred at 235 and 270
nm, and no obvious absorption was observed in the range
>400 nm. Meanwhile, no spectral change was observed in
the testing process. This seems a hint that both the ligands
and the skeleton of the complex may remain intact in the
oxidation. It is noticed that polynuclear Mn(III) clusters may
be insensitive in the visible range to the variation of the Mn
oxidation states because the solutions of these Mn(III)
clusters are usually dark or black. So far UV-vis data for
the polynuclear Mn phosphate clusters still remain absent,
while related UV-vis data60 or studies61 are rarely reported
for other polynuclear Mn clusters. Subsequent irreversible
reduction at -0.46 V implies the occurrence of some
chemical reactions that follow some electrochemical pro-
cesses. A new optical band at 245 nm was observed with in
situ UV-vis-NIR spectroelectrochemistry from -0.2 to
-0.8 V, acompanying the weakening of the original bands
at 233 and 272 nm, which can commonly be attributed to
the variation of metal-ligand linkage (ligand loss or
structural rearrangement, etc.) in the chemical reaction. Also
the ligands (t-BuPO3H2 + phen) showed two bands at 227
and 263 nm in the same testing conditions to that for 1,
implying that the new band seems not to be from the free
ligands. However, it is difficult to analyze what variation
occurs in this irreversible reduction. Interestingly, the second
reduction at -1.54 V is a quasi-reversible one-electron
process. We attempted to isolate the possible species in the
solution but failed.
Figure 9. Cyclic voltammogram (100 mV s-1) (top) and differential pulse
voltammetry (100 mV s-1) (bottom) for complex 3 in distilled CH2Cl2 with
0.1 M NBun PF6 as supporting electrolyte.
4
potential. Consulting the assignment for complex 5, the quasi-
reversible redox can be assigned to the MnIII4/MnIII3MnIV
couple. The studies of the changes in the reduction and
oxidation processes at the sweeping potential range from 0
to 1.5 V and at the scan rate of 100, 200, 300, 500, and 800
mV s-1 also indicate that the MnIII4/MnIII3MnIV couple is
quasi-reversible (Supporting Information, Figure S7). The
in situ UV-vis-NIR spectroelectrochemistry of compound
3 was studied, and there was no obvious change of the spectra
in the reduction (-0.2 ∼ -0.7 V) and oxidation processes
(0.4 ∼ 1.0 V). The unvaried peak at 291 nm implies the
stability of the metal-ligand linkage in the complex.
Complex 3 did not exhibit an obvious signal in the range of
400-900 nm in the whole redox process, owing to the
insensitivity of the polynuclear Mn(III) cluster in visible
range though one of the Mn(III) ions was oxidized.
The CV and DPV plots of compound 5 (Supporting
Information, Figures S5 and S6) show that there is an
irreversible reduction response at ∼ -0.46 V versus Ag/
AgCl which is comparable to that of the similar tetranuclear
Mn(III) complexes.4d In addition, an irreversible oxidation
at about 0.57 V and one quasi-reversible wave at E1/2 ) 1.00
V (∆EP ) 160 mV) were observed. Consulting the electro-
chemical behaviors4d of similar tetranuclear Mn(III) com-
plexes, the latter redox can be assigned to the MnIII
/
4
MnIII3MnIV couple. The difference of the values of last two
peaks is considered to stem from the various carboxylate
ligands.62
The oxidative and reductive electrochemistry of compound
3 was studied using CV and DPV in the potential range from
1.5 to -1 V versus Ag/AgCl (Figure 9). Compound 3 has a
similar electrochemical behavior as that of compound 5 and
other Mn4O2 clusters.4d,m,63 It displays one irreversible
reduction response at ∼ -0.50 V when scanning toward the
The ESI-MS of the CH2Cl2 solution of 1, 3, and 5 gave
major peaks at m/z 1269.7, 1096.7, and 1192.5, which
correspond to [1 + H]+, [3 + Na]+, and [5 + H]+ (positive
mode), suggesting the stability of the complexes in solution,
which also gives support for the assignment of the electro-
chemistry processes of the three complexes.
cathodic potential and one quasi-reversible wave at E1/2
)
∼ 0.74 V (∆EP ) 230 mV) when scanning toward the anodic
(60) (a) Wemple, M. W.; Tsai, H.-L.; Wang, S.; Claude, J. P.; Streib, W. E.;
Huffman, J. C.; Hendrickson, D. N.; Christou, G. Inorg. Chem. 1996,
35, 6437. (b) Vincent, J. B.; Christmas, C.; Chang, H. R.; Li, Q.; Boyd,
P. D. W.; Huffman, J. C.; Hendrickson, D. N.; Christou, G. J. Am.
Chem. Soc. 1989, 111, 2086.
Conclusions
In summary, the t-BuPO3H2-Mn2+-RCOOH reaction
system has been systematically explored, and it is observed
that the use of different N-containing coligands (bpy, phen,
and pic) in this reaction system leads to three completely
different types of manganese clusters (1-7), that is, penta-
nuclear clusters with phosphonate ligands, tetranuclear
(61) Carrell, T. G.; Bourles, E.; Lin, M.; Dismukes, G. C. Inorg. Chem.
2003, 42, 2849.
(62) Chakov, N. E.; Zakharov, L. N.; Rheingold, A. L.; Abboud, K. A.;
Christou, G. Inorg. Chem. 2005, 44, 4555.
(63) (a) Boskovic, C.; Folting, K.; Christou, G. Polyhedron 2000, 19, 2111.
(b) Arom´ı, G.; Bhaduri, S.; Artu´s, P.; Huffman, J. C.; Hendrickson,
D. N.; Christou, G. Polyhedron 2002, 21, 1779.
Inorganic Chemistry, Vol. 47, No. 13, 2008 5589

Wang et al.
clusters with phosphonate ligands, and tetranuclear clusters
without phosphonate ligands, which demonstrates the control
of these N-containing coligands over the framework of the
manganese clusters. The pentanuclear cluster with a basket-
like core is a novel structural type among the manganese
phosphonates. The experimental finding provides an impor-
tant addition to the study of manganese phosphonate
chemistry. The magnetic property of the pentanuclear cluster
1 · 2H2O · MeOH · MeCN shows both ferromagnetic and
antiferromagnetic couplings among the Mn atoms, though
the overall character is antiferromagnetic. It is also a good
example of the influence of O-P-O, µ3-O, and O-C-O
bridges on the magnetic interaction. The results of the
magnetic measurements for the other two tetranuclear species
reveal antiferromagnetic character as expected for their
[Mn4(µ3-O)2]8+ structure. The effect of N-containing coli-
gands in the reaction system of phosphonic acid on the
topology of the manganese clusters and other transition metal
clusters will be further exploited in our future work.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China (No. 20471061
and No. 20633020) and the Science & Technology Innova-
tion Foundation for the Young Scholar of Fujian Province
(No. 2005J059).
Supporting Information Available: X-ray crystallographic files
in CIF format for the seven complexes (CIF), three tables, and five
figures (PDF). This material is available free of charge via the
Internet at http://pubs.acs.org.
IC701343S
5590 Inorganic Chemistry, Vol. 47, No. 13, 2008