Syntheses, structures, electrochemistry and magnetic properties of chain-like dicyanamide manganese(III) and iron(III) complexes with salen ligand

Article abstract of DOI:10.1039/b200907b

Two dicyanamide (dca) M^III complexes with salen ligand, [Mn^III(salen)(dca)]_n (1) and [Fe^III(salen)(dca)]_n (2), were synthesized and characterized. X-Ray diffraction analyses revealed the two complexes have a similar one-dimensional zig-zag chain structure constructed by μ_1,5-dca bridge. Magnetic susceptibility measurements indicate the presence of antiferromagnetic interactions between two intra-chain high-spin Mn^III ions and between two intra-chain low-spin Fe^III ions via the dca bridge. The electrochemical properties of the two complexes were studied by cyclic voltammetry.

Full text of DOI:10.1039/b200907b

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Syntheses, structures, electrochemistry and magnetic properties
of chain-like dicyanamide manganese(III) and iron(III)
complexes with salen ligand
Qian Shi,ab Rong Cao,*a Xing Li,a Junhua Luo,a Maochun Hong*a and Zhongning Chena
a
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure
of Matter, The Chinese Academy of Sciences, Fuzhou 350002, P. R. China.
E-mail: hmc@ms.fjirsm.ac.cn
Department of Chemistry, Wenzhou Teachers College, Wenzhou 325000, P. R. China
b
Received (in Montpellier, France) 24th January 2002, Accepted 3rd May 2002
First published as an Advance Article on the web 21st August 2002
III
III
III
Two dicyanamide (dca) M complexes with salen ligand, [Mn (salen)(dca)]n (1) and [Fe (salen)(dca)]n (2),
were synthesized and characterized. X-Ray diffraction analyses revealed the two complexes have a similar one-
dimensional zig-zag chain structure constructed by m1,5-dca bridge. Magnetic susceptibility measurements
III
indicate the presence of antiferromagnetic interactions between two intra-chain high-spin Mn ions and
III
between two intra-chain low-spin Fe ions via the dca bridge. The electrochemical properties of the two
complexes were studied by cyclic voltammetry.
Dicyanamide (dca) bridged polynuclear transition metal com-
plexes constitute a hot subject of research, due to their rich
structural and topological features along with the magnetic
properties related to this ligand. Surprisingly, most of the
reported dca bridged transition metal complexes have focused
nol (30 mL) was added 120 mg of ethylenediamine (2 mmol).
After stirring at 60 ꢂC for 0.5 h, the solution color changed
from yellow to brown; a methanol solution (10 mL) of Na(dca)
(180 mg, 2 mmol) was added dropwise into the mixture. After
the solution stood at room temperature for 3 days, dark brown
cubic crystals were obtained and washed with diethyl ether,
yield 69%. Found (calcd) % for C18H14MnN5O2 : C, 55.8
(55.8); H, 3.5 (3.6); N, 18.2 (18.1). IR (KBr, cmꢀ1):
I
II
on low-oxidation state systems such as M and M . For
I
instances, the reactions of M (M ¼ Cu, Ag) with dca yielded
a series of discrete or polymeric structures;1–3 the reactions
[N(CN)2]ꢀ, n (C N) 2170(s), n (C N) 2227(s), ns(C–N)
II
of M with dca resulted in a great number of interesting struc-
=
=
=
=
s
as
II
II
tures, which usually possess the formulas M (dca)2 or M (d-
ca)2L (M ¼ Cu, Co, Ni, Mn, Zn or Fe, L ¼ co-ligand)4–9
and show 0 to 3-D dimensional structures. To date, the high-
904(s), nas(C–N) 1292(s); n(C=N) 1622(s), n(Mn–N) 467(s),
n(Mn–O) 386(s).
III
oxidation state transition metal dca complexes, such as M
or M complexes, have been almost neglected.10 As is well-
[Fe(salen)(dca)]n 2. To a mixture of FeCl3ꢁ6H2O (320 mg, 2
mmol) and salicylaldehyde (540 mg, 4 mmol) in methanol
(30 mL) was added 120 mg of ethylenediamine (2 mmol). After
stirring at 60 ꢂC for 0.5 h, an ethanol solution (10 mL) of
Na(dca) (180 mg, 2 mmol) was added dropwise into the mix-
ture. Red-brown cubic crystals along with a great-amount of
red powder were obtained after 5 days. The red powder may
be a mixture of by-products and efforts to characterize it were
unsuccessful. The cubic crystals were separated manually and
washed with diethyl ether, yield 33%; Found (calcd) % for
IV
known, six-coordinate manganese(III) and iron(III) Schiff base
complexes display interesting structural and electronic
effects;11–13 the variation of in-plane chelating and axial sites
often leads to a change in the spin state of the metal ions:
high-spin, low-spin or spin-crossover state.14–16 Accordingly,
III
introducing a dca ligand into these M -Schiff base (M ¼ Fe,
Mn) systems will combine their interesting characteristics
III
and result in the formation of M -dca complexes along with
a rich coordination chemistry. In this work, salen anion
[salen2ꢀ ¼ N,N’-ethylenebis(salicylaldiiminato)] was selected
as the Schiff base ligand, because upon deprotonation of the
two hydroxyl groups it usually acts as a dianionic tetradentate
C18H14FeN5O2 : C, 55.6 (55.7); H, 3.6 (3.6); N, 18.1 (18.0).
ꢀ
IR (KBr, cmꢀ1): [N(CN) ] , n (C N) 2177(s), n (C N)
=
=
=
=
2
s
as
2245(s), ns(C–N) 906(s), nas(C–N) 1294(s); n(C=N) 1626(s),
n(Mn–N) 432(s), n(Mn–O) 382(s).
III
ligand coordinating to a M ion, and the two remaining coor-
III
dination sites of M are easily accessible to dca ligands to gen-
erate one-dimensional complexes with a single end-to-end dca
bridge. This paper will report details of the syntheses and char-
acterizations of two one-dimensional complexes, [Mn(salen)(d-
ca)]n (1) and [Fe(salen)(dca)]n (2).
Physical measurements
Elemental analyses were determined on an Elementar Vario
ELIII elemental analyzer. IR spectra were measured as KBr
pellets on a Nicolet Magna 750 FT-IR spectrometer in the
range of 200–4000 cmꢀ1. UV-visible spectra were recorded
on a Lambda 35 spectrometer. ESR spectra were recorded as
powder samples at the X-band frequency on a Bruker
ER420 spectrometer at room temperature. The temperature-
dependent magnetic measurements were determined in the
temperature range 300–4 K on a SQUID magnetometer in
an external field of 10 kG. Cyclic voltammetry was performed
Experimental
Syntheses
[Mn(salen)(dca)]n 1. To a mixture of Mn(OAc)2ꢁ4H2O (492
mg, 2 mmol) and salicylaldehyde (540 mg, 4 mmol) in metha-
DOI: 10.1039/b200907b
New J. Chem., 2002, 26, 1397–1401
1397
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a
ꢂ
˚
Table 2 Selected bond distances (A) and angles ( ) for 1 and 2
on a PE-236A potentiostat with a three-electrode cell under an
inert atmosphere, consisting of a platinum wire working elec-
trode, Ag–AgCl reference electrode and a platinum auxiliary
Complex 1
Mn–O(1)
1.882(2)
1.983(3)
2.304(3)
Mn–O(2)
Mn–N(5)
Mn–N(3A)
1.882(2)
1.986(3)
2.317(3)
electrode; 0.1 molꢁdmꢀ3 [NBun ][PF6] was used as supporting
4
Mn–N(4)
Mn–N(1)
electrolyte and the scan rate was 0.1 V sꢀ1
.
O(1)–Mn–O(2)
O(2)–Mn–N(4)
O(2)–Mn–N(5)
O(1)–Mn–N(1)
N(4)–Mn–N(1)
O(1)–Mn–N(3A)
N(4)–Mn–N(3A)
N(1)–Mn–N(3A)
Complex 2
95.46(19)
173.22(11)
91.43(10)
91.26(11)
89.03(12)
91.84(10)
88.53(12)
176.10(11)
O(1)–Mn–N(4)
O(1)–Mn–N(5)
N(4)–Mn–N(5)
O(2)–Mn–N(1)
N(5)–Mn–N(1)
O(2)–Mn–N(3A)
N(5)–Mn–N(3A)
91.31(11)
173.10(10)
81.80(12)
90.47(11)
88.93(11)
91.60(11)
87.71(11)
Crystallographic measurements
X-Ray intensities of 1 and 2 were collected on a Siemens Smart
CCD diffractometer with graphite-monochromated Mo-Ka
˚
radiation (l ¼ 0.71073 A) with the o ꢀ 2y scan mode. Empiri-
cal absorption correction was applied to the data using
SADABS program.17 The structures were solved by direct
methods.18 Non-hydrogen atoms were refined anisotropically.
In the two complexes, the C(10) atom was treated with disor-
der in two positions [C(10A) and C(10B)], and the hydrogen
atoms on the C(10A), C(10B) and C(11) atoms were generated
from successive difference Fourier syntheses, while the other
hydrogen atoms were generated in idealized positions. All cal-
culations were performed using the SHELXTL program.19
The crystallographic data and other pertinent information
are summarized in Table 1 and the selected bond lengths and
angles for the two complexes are given in Table 2.
Fe–O(1)
Fe–N(4)
Fe–N(1)
1.892(3)
2.105(4)
2.157(4)
Fe–O(2)
Fe–N(5)
Fe–N(3A)
1.892(3)
2.107(4)
2.171(4)
O(1)–Fe–O(2)
O(2)–Fe–N(4)
O(2)–Fe–N(5)
O(1)–Fe–N(1)
N(4)–Fe–N(1)
O(1)–Fe–N(3A)
N(4)–Fe–N(3A)
N(1)–Fe–N(3A)
105.81(13)
165.63(15)
88.21(14)
92.20(14)
88.10(16)
92.29(14)
86.39(16)
172.19(16)
O(1)–Fe–N(4)
O(1)–Fe–N(5)
N(4)–Fe–N(5)
O(2)–Fe–N(1)
N(5)–Fe–N(1)
O(2)–Fe–N(3A)
N(5)–Fe–N(3A)
88.40(15)
165.98(14)
77.58(16)
93.37(14)
86.95(15)
90.83(14)
87.33(15)
CCDC reference numbers 178127 and 178128. See http://
www.rsc.org/suppdata/nj/b2/b200907b/ for crystallographic
files in CIF or other electronic format.
a
Symmetry code A: ꢀx + 3/2, y ꢀ 1/2, z for 1 and ꢀx + 1/2, y ꢀ 1/2,
z for 2.
Results and discussion
EtOH and MeCN. Upon formation 1 is easily deposited in
crystalline form from the reaction mixture, resulting in a high
yield of 1. Interestingly, the synthetic reaction of 2 is much
more complicated, and the solvent used in the reaction plays
a crucial role in the formation of different products. If the reac-
tion is carried out in a single solvent such as methanol, ethanol
or acetonitrile, the major product is [Fe(salen)Cl], as confirmed
by elemental analysis and IR spectrum. Complex 2 can only be
Synthesis
II
III
In the preparation of complex 1, Mn was oxidized to Mn by
air under basic conditions during the synthetic reaction11 and
pure product with a composition of [Mn(salen)(dca)] was iso-
lated in high yield. In the preparation of complex 2, large
quantities of by-products were observed, indicating that there
might be different species in the reaction mixture. The forma-
tion of the isolated complexes can be understood from the
successfully isolated in
Although the reason why dca does not coordinate to the
a mixed solvent, MeOH–EtOH.
III
solution behavior of the simple salen-M (M ¼ Mn, Fe) com-
plexes.20–23
III
Fe -salen complex in single solvent systems is still unclear,
the difficult synthesis of 2 may be caused by its high solubility
in solvents such as MeOH or CH3CN. Thus, during the reac-
tion many Fe(salen)(dca) species, which may change confor-
mation as shown by the CV determination (see below), may
be present in the solution leading to a complex system and ren-
dering the synthesis of 2 more difficult. Using the MeOH–
EtOH mixed solvent may change the polarity of the solvent
and lower the solubility of 2, allowing the successful precipita-
tion of 2 in crystalline form from the solution.
Owing to the rich coordination mode of dca (e.g., mono-, di-
or tridentate) and the presence of an equilibrium between
III
monomer and dimer of the salen-M complex, the addition
III
of the dca ligand into the salen-M system may induce pro-
ducts with different configurations. In our experiment, com-
plex 1 composed of a monomer unit is the major product
isolated from the synthetic reaction, which may be attributed
to the low solubility of 1 in common solvents such as MeOH,
Table 1 Crystallographic data for 1 and 2
Electronic spectra
1
2
The electronic spectra of the two complexes in MeOH were
recorded in the range of 200–800 nm, as shown in Fig. 1.
The intense absorption bands at short wavelengths, 202
(e ¼ 5900 dm3 molꢀ1 cmꢀ1) and 241 nm (e ¼ 3077 dm3 molꢀ1
cmꢀ1) for complex 1, 204 (e ¼ 5900 dm3 molꢀ1 cmꢀ1) and 234
nm (e ¼ 4336 dm3 molꢀ1 cmꢀ1) for complex 2, may be
assigned to intraligand p-p* transitions in the ꢀc1omplexes.24
The absorptions at 282 nm (e ¼ 1349 dm3 mol cmꢀ1) for
complex 1 and 320 nm (e ¼ 1035 dm3 molꢀ1 cmꢀ1) for com-
plex 2 may be assigned to a Schiff base to metal ion charge-
transfer band (LMCT).23
Empirical formula
Formula weight
T/K
C18H14MnN5O2
387.28
293(2)
C18H14FeN5O2
388.19
293(2)
˚
Wavelength/A
Crystal system
0.71073
Orthorhombic
Pbca
0.71073
Orthorhombic
Pbca
Space group
˚
a/A
˚
11.2826(1)
17.0485(2)
17.5949(3)
3384.40(8)
8
11.4946(3)
16.5213(4)
17.8642(1)
3392.51(12)
8
b/A
˚
c/A
3
˚
m/A
Z
m/mmꢀ1
Reflections collected
Independent reflections
Rint
0.803
10 087
0.912
10 389
Crystal structures
2983
0.0405
2989
0.0684
Complex 1 possesses a one-dimensional zig-zag chain struc-
III
ture, which is constructed by square-planar Mn -salen species
˚
(the average deviation is 0.005 A) bridged by dca ligands in an
III
anti-anti configuration, as shown in Fig. 2(A). The Mn ion is
R1[I > 2s(I)]
wR2 (all data)
0.0446
0.1079
0.0530
0.1264
1398
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Fig. 3 Adjacent tightly packed chains in 2.
bond N(1)–Fe–N(3A) angle is 172.19(16)ꢂ. The in-plane Fe–
O and Fe–N bond lengths are 1.892(3), 1.892(3), 2.105(4)
and 2.107(4) A, respectively, similar to that in [Fe (sale-
n)(OAc)]n .13 The axial Fe–N(dca) bond lengths [2.157(4) and
Fig. 1 UV-Vis absorption spectra of [Mn(salen)(dca)]n (solid line)
and [Fe(salen)(dca)]n (dashed line) in MeOH.
III
˚
in a slightly distorted octahedral geometry where the donor
atoms from the salen ligand [O(1), O(2), N(4) and N(5)] form
the equatorial plane with the angles subtended at the Mn ion
varying from 81.80(12)ꢂ to 95.46(9)ꢂ (see Table 2), and the two
nitrogen atoms from different dca ligands [N(1) and N(3A)]
occupy the axial positions with the N(1)–Mn–N(3A) angle
being 176.10(11)ꢂ. The in-plane bond distances of Mn–O
˚
2.170(4) A] are significantly shorter than the corresponding
value of Mn–N(dca) in 1, which may be due to different
III
4
Jahn–Teller effects in octahedral Mn (3d ) and Fe (3d5)
III
III
complexes. Interestingly, the inter-chain M–M distances in
˚
the two complexes (7.633 to 7.525 A for 1 and 7.710 to 7.751
˚
A for 2) are shorter than the corresponding intra-chain values
˚
˚
(8.555 A for 1 and 8.326 A for 2). Fig. 3 shows the adjacent
tightly packed chains in 2.
˚
˚
[1.882(2) A] and Mn–N [1.983(3) and 1.986(3) A] show typical
values for a high-spin Mn ion.25,26 The axial Mn–N(dca)
III
˚
bond lengths [2.304(3) and 2.317(3) A] are significant longer
III
than the corresponding values in salen-Mn complexes {such
Magnetic properties
14
as 2.25(3) A in [Mn(salen)CN]n , 2.278(5) A in {Mn[1,4-
˚
˚
di(1-inidazolyl)butane](salen)},27 2.162(7)
A
in [Mn(sa-
˚
The plots of the molar magnetic susceptibility wM versus tem-
perature T and the effective magnetic moment meff versus T
for complexes 1 and 2 are shown in Fig. 4.
len)(NCS)]25}, and also much longer than the Mn–N(dca)
II
bond lengths in [Mn (m1,5-dca)(NO3)(terpy)]n [2.196(3) and
II
˚
For complex 1, the meff value of 4.70 mB at room temperature
is slightly lower than the spin-only value for high-spin Mn
2.218(3) A] and [Mn (m1,5-dca)(H2O)(terpy)]n [2.162(2) and
8
2.182(2) A]. This axial elongation may be attributed to a
III
˚
(4.90 mB). On lowering the temperature, the meff value decreases
smoothly from 300 to 90 K, and then increases gradually from
90 to 22 K before abruptly reaching the minimum value of 4.23
mB at 5 K. This behavior indicates the presence of a weak anti-
Jahn–Teller distortion, which is commonly observed in octahe-
dral Mn complexes.28
III
III
Complex 2 is the isomorph of 1 with replacement of Mn by
III
Fe [Fig. 2(B)]. However, the octahedral polyhedron around
III
III
Fe is highly distorted as compared to that of Mn . The
III
ferromagnetic interaction between two high-spin Mn ions via
III
angles subtended at the Fe ion in the equatorial plane (the
the dca bridge. The X-band ESR spectrum recorded on a pow-
der sample prepared from the crystals at room temperature
shows no signal, due to non-Kramer spin states (S ¼ 2) of
˚
average deviation is 0.019 A) formed by donor atoms from
the salen ligand vary from 77.58(16)ꢂ to 105.81(13)ꢂ, and the
III
the Mn ion, as a result of either large zero-field splitting or
fast relaxation processes.24
For complex 2, the meff value of 1.728 mB at room tempera-
ture is in agreement with the spin-only value for low-spin Fe
III
(1.73 mB). The ESR spectrum of 2 recorded on a powder sam-
ple prepared from the crystals at room temperature shows a
broad isotropic signal centered at g ¼ 2.0140 (peak-to-peak
III
line width 1833 G), confirming the low-spin state of the Fe
ion in 2.29 On lowering the temperature, the meff value
decreases slowly to reach the minimum value of 1.15 mB at 5
K, indicating the presence of an antiferromagnetic interaction
between two magnetic centers via the dca bridge.
The magnetic data of 1 and 2, were analyzed by means of the
analytical expression derived by Fisher:30
Ng2b2SðS þ 1Þ 1 þ u
wM
¼
:
ð1Þ
3kT
JSðS þ 1Þ
kT
1 ꢀ u
kT
u ¼ coth
ꢀ
JSðS þ 1Þ
for the magnetic susceptibility of an infinite chain of classical
spins based on the Hamiltonian H ¼ ꢀJSSiSi+1 for local spin
III
III
values S ¼ 2 for Mn in 1 and S ¼ 1/2 for Fe in 2. The best
fit parameters are: J ¼ ꢀ0.24 cmꢀ1
,
g ¼ 1.99, R ¼
1.24 ꢃ 10ꢀ6; J ¼ ꢀ7.65 cmꢀ1, g ¼m 2.01, R ¼ 4.01 ꢃ 10ꢀ6 for
Fig. 2 ORTEP plots for the title complexes: (A) [Mn(salen)(dca)]n ,
(B) [Fe(salen)(dca)]n .
m
P
P
ðwci alc ꢀ wiexpÞ = ðwiexpÞ :
2
2
1 and 2, respectively, where R ¼
i¼1
i¼1
New J. Chem., 2002, 26, 1397–1401
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Fig. 4 Plots of wM vs. T (K) and meff vs. T (X) for: (A) [Mn(salen)(dca)]n , (B) [Fe(salen)(dca)]n . The solid lines show the best fits to the model.
Cyclic voltammetry studies
which is also present as different species in DMF solution.23
This lends support to our discussion on the formation of 2
(see above).
The cyclic voltammogram of 1 was obtained in DMF solution
(Fig. 5). Only one quasi-reversible redox couple at ꢀ0.274/
ꢀ0.068 V is observed. This result indicates that only a single
species of 1 is present in solution and the redox process maꢀy
III
II
Conclusion
be assigned to the [Mn (salen)(dca)] $ [Mn (salen)(dca)]
reductive process.11,31,32 Surprisingly, the cyclic voltammo-
gram of 2 in DMF is rather complicated; several irreversible
peaks (ꢀ1.546, 1.004 and 1.178 V) and a quasi-reversible cou-
ple (ꢀ0.396/ꢀ0.758 V) are observed. A detailed explanation
remains unavailable as the redox behavior of 2 in DMF is very
complicated different species accompanied by some irreversible
chemical process may be present in DMF solution. This result
We have successfully synthesized two one-dimensional zig-zag
III
chain-like M -dca polymeric complexes with the salen ligand,
III III
[Mn (salen)(dca)]n (1) and [Fe (salen)(dca)]n (2). Magnetic
susceptibility measurements indicate the presence of antiferro-
III
magnetic interactions between two intra-chain high-spin Mn
III
ions in 1 and between two intra-chain low-spin Fe ions in 2
via the dca bridge. The cyclic voltammetry studies indicate that
there is only a single species for 1 but there are several species
for 2 in solution.
ꢀ
III
is in agreement with those reported for [Fe (salen)(ox)]
Acknowledgements
The authors thank for the financial support from NNSFC,
Natural Foundation of Fujian Provice and the key project of
CAS.
References
1
K. E. Bessier, L. L. Romualdo, V. M. Dellon and A. Hagenbach,
Z. Anorg. Allg. Chem., 2000, 626, 1942.
2
3
D. Britton, Acta Cryst. allogr., Sect. C, 1990, 46, 2297.
S. R. Batten, A. R. Harris, P. Jensen, K. S. Murray and A.
Ziebell, J. Chem. Soc., Dalton Trans., 2000, 3829.
P. Jensen, D. J. Price, S. R. Batten, B. Moubaraki and K. S.
Murray, Chem. Eur. J., 2000, 17, 3186.
4
5
J. L. Manson, D. W. Lee, A. L. Rheingold and J. S. Miller, Inorg.
Chem., 1998, 37, 5966.
Fig. 5 Cyclic voltammogram of 1 in DMF.
1400
New J. Chem., 2002, 26, 1397–1401

View Article Online
6
7
8
9
I. Dasna, S. Golhen, L. Ouahab, O. Pen˜a, J. Guillevic and M.
Fettouhi, J. Chem. Soc., Dalton Trans., 2000, 129.
18 G. M. Sheldrick, SHELXS 97, Program for Crystal Structure
Solution, University of Go¨ttingen, Germany, 1997.
19 G. M. Sheldrick, SHELXTL 97, Program for Crystal Structure
Refinement, University of Go¨ttingen, Germany, 1997.
20 H.-L. Shyu, H.-H. Wel and Y. Wang, Inorg. Chim. Acta, 1999,
290, 8.
´
S. Triki, F. Thetiot, J.-R. Galan-Mascaros, J. S. Pala and K. R.
Dunbar, New J. Chem., 2001, 25, 954.
´
´
A. Clar´amunt, A. Escuer, F. A. Mautner, N. Sanz and R. Vicente,
J. Chem. Soc., Dalton Trans., 2000, 2627.
B.-W. Sun, S. Gao, B.-Q. Ma, D.-Z. Niu and Z.-M. Wang,
J. Chem. Soc., Dalton Trans., 2000, 4187.
21 M. D. Hobday and T. C. Smith, Coord. Chem. Rev., 1972, 9, 311.
¯
22 H. Miyasaka, N. Matsumoto, H. Okawa, N. Re, E. Gallo and C.
10 H. Miyasaka, R. Clerac and C. S. Campoe-Fernandez, Inorg.
Chem., 2001, 40, 1663.
11 M. Hirotsu, K. Nakajima, M. Kojima and Y. Yoshikawa, Inorg.
Chem., 1995, 34, 6173.
Floriani, J. Am. Chem. Soc., 1996, 118, 981.
23 A. Geiß and H. Vahrenkamp, Eur. J. Inorg. Chem., 1999, 1793.
24 X. S. Tan, J. Chen, Z. N. Chen, P. J. Zheng and W. X. Tang,
Inorg. Chim. Acta, 1995, 234, 27.
12 C. E. Hulme, M. Watkinson, M. Haynes, R. G. Pritchard, C. A.
McAuliffe, N. Jaiboon, B. Beagley, A. Sousa, M. R. Bermejo and
M. Fondo, J. Chem. Soc., Dalton Trans., 1997, 1805.
13 G. Liu, A. M. Arif, F. W. Bruenger and S. C. Miller, Inorg. Chim.
Acta, 1999, 287, 109.
25 M. Mikuriya, Y. Yamato and T. Tokii, Bull. Chem. Soc. Jpn.,
1992, 65, 1466.
26 M. Mikuriya, S. Kida and I. Murase, Chem. Lett., 1988, 35.
27 N. Matsumoto, N. Takemoto, A. Ohyosi and H. Okawa, Bull.
Chem. Soc. Jpn., 1988, 61, 2984.
¯
14 N. Matsumoto, Y. Sunatsuki, H. Miyasaka, Y. Hashimoto, D.
Luneau and J.-P. Tuchagues, Angew. Chem., Int. Ed., 1999, 38,
171.
15 H. Miyasaka, H. Ieda, N. Matsumoto, N. Re, R. Crescenzi and C.
Floriani, Inorg. Chem., 1998, 37, 255.
28 F. A. Cotton, G. Wilkinson, C. A. Murillo and M. Bochmann,
Advanced Inorganic Chemistry, John Wiley & Sons, 6th edn., 1999.
29 B. J. Kennedy, G. Brain, E. Horn, K. S. Murray and M. R. Snow,
Inorg. Chem., 1985, 24, 1647.
30 M. E. Fisher, Am. J. Phys., 1964, 32, 343.
´
´
16 N. Re, R. Crescenzi, C. Floriani, H. Miyasaka and N.
Matsumoto, Inorg. Chem., 1998, 37, 2717.
17 G. M. Sheldrick, SADABS, Program for Empirical Absorption
Correction of Area Detector Data, University of Go¨ttingen,
Germany, 1996.
31 M. R. Bermejo, A. M. Gonzalez, M. Fondo, A. Garcıa-Deibe, M.
Maneiro, J. Sanmart´ın, O. L. Hoyos and M. Watkinson, New. J.
Chem., 2000, 24, 235.
32 S.-B. Yu, C.-P. Wang, E. P. Day and R. H. Holm, Inorg. Chem.,
1991, 30, 4067.
New J. Chem., 2002, 26, 1397–1401
1401