Binuclear nickel(II) and cobalt(III) complexes with dissimilar bridges: Synthesis, spectroscopy, crystal structure, and magnetism

Article abstract of DOI:10.1002/hlca.200390197

Two novel binuclear nickel(II) and cobalt(III) complexes with two or three dissimilar bridges, [Ni₂(tacn)₂(μ-N₃) ₂(μ-O₂CPh)](ClO₄)·H₂O (1) and [Co₂(tacn)₂(μ-N₃)(μ-OH)(μ-O ₂CPh)](ClO₄)₃ (2) (tacn= 1,4,7-triazacyclononane), were synthesized and structurally as well as magnetically characterized. Both compounds have a discrete binuclear structure, bridged by two N₃^- ions and one carboxylato group of the benzoate ion for 1 and one N₃^- ion, one carboxylato group of the benzoate ion, and one hydroxy group for 2; the macrocyclic ligand tacn acts as terminal ligand. The magnetic data of compound 1 were analyzed by means of H=-2JS₁S₂-D(S₁ ²+S₂²), leading to J=19.6cm ^-1, g=2.07, D=4.01cm^-1, and zJ′=-0.32cm ^-1. The ferromagnetic interaction is discussed on the basis of the structural features.

Full text of DOI:10.1002/hlca.200390197

Helvetica Chimica Acta Vol.86 (2003)
2441
Binuclear Nickel(II) and Cobalt(III) Complexes with Dissimilar Bridges:
Synthesis, Spectroscopy, Crystal Structure, and Magnetism
by Qing-Lun Wanga), Li-Hua Yua)b), Dai-Zheng Liao*a), Shi-Ping Yana), Zong-Hui Jianga)c), and
Peng Chenga)
a) Department of Chemistry, Nankai University, Tianjin, 300071, P.R. China
b) State Key Laboratory of Structural Chemistry, Fujian Institute of Research on Structure of Matter, Chinese
Academy of Sciences, Fuzhou, Fujian, 350002, P.R. China
c) State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, 210093, P.R. China
Two novel binuclear nickel(II) and cobalt(III) complexes with two or three dissimilar bridges,
[Ni2(tacn)2(m-N3)2(m-O2CPh)](ClO4) ¥ H2O (1) and [Co2(tacn)2(m-N3)(m-OH)(m-O2CPh)](ClO4)3 (2) (tacn ˆ
1,4,7-triazacyclononane), were synthesized and structurally as well as magnetically characterized.Both
À
compounds have a discrete binuclear structure, bridged by two N3 ions and one carboxylato group of the
benzoate ion for 1 and one N3À ion, one carboxylato group of the benzoate ion, and one hydroxy group for 2; the
macrocyclic ligand tacn acts as terminal ligand.The magnetic data of compound 1 were analyzed by means of
2
HˆÀ2JS1S2 À D(S1 ‡ S22), leading to Jˆ19.6 cmÀ1
,
g ˆ 2.07, Dˆ4.01 cmÀ1
,
and zJ'ˆÀ0.32 cmÀ1.The
√
√ √
√
√
ferromagnetic interaction is discussed on the basis of the structural features.
Introduction. Molecular magnetism of polynuclear complexes is of considerable
interest both for designing new magnetic materials with potential use in information
storage and for investigating the relationship between the sturcture and the role of the
polymetallic active sites in biological systems [1 4].Particular emphasis has been
placed in the magnetisms of m-azidonickel(II) complexes [5 25].From a magnetic
point of view, the most interesting characteristic of these azidonickel systems lies in the
fact that the azido ligand represents a very effective superexchange pathway in its two
coordination modes, end-to-end, which always gives antiferromagnetic behavior, and
end-on, which always gives ferromagnetic coupling.
As for end-on azidonickel(II) complexes, Ribas and co-workers proposed that the
parameter J could be correlated only with the NiÀNÀNi value in the sense that greater
NiÀNÀNi angles correspond to a most effective ferromagnetic superexchange [10].
This result was confirmed by Ruiz et al., who recently reported the density functional
calculations on magnetic coupling in end-on azidonickel(II) complexes, indicating that
J increases upon increasing the NiÀNÀNi angle from 808 to 1048, while J deceases as
the bond distance of NiÀ(m-N) increases [26].Moreover, Christou and co-workers
believe that there is non-dependence of J on the NiÀNÀNi angle or the NiÀNiÀNÀN
torsion angle for these compounds; however, there appears to be a trend for J to
become more ferromagnetic with increasing average NiÀ(m-N) distances [17].
On the other hand, considerable attention has been devoted to dinuclear CuII
complexes with two dissimilar bridges [27 34].Orbital complementary and counter-
complementary effects have been proposed by Nishida and co-workers [28] and Reed
and co-workers [29] to explain the unusual magnetic properties in the mixed-bridged

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Helvetica Chimica Acta Vol.86 (2003)
CuII complexes.However, little work has been attended to the design of other mixed-
bridged metal complexes, except CuII compounds [8][35 38].
With these facts in mind, our synthetic strategy was to construct ferromagnetically
coupled binuclear compounds with dissimilar bridges other than CuII complexes.To
build the desired molecular architecture, we chose NiII and CoII as metal building
blocks, azido and benzoato as bridging ligands, and the macrocyclic ligand 1,4,7-
triazacyclononane (tacn) as terminal ligand due to its rigidity, and succeeded in
obtaining crystalline samples of two binuclear complexes with dissimilar bridges, i.e.,
(m-N3)2(m-O2CPh)[Ni2(tacn)2](ClO4)¥H2O (1) and [Co2(m-N3)(m-OH)m-O2CPh)(tacn)2]-
(ClO4)3 (2).The crystal structures and magnetic properties of 1 and 2 were
investigated.
Results and Discussion. Synthetic Aspects.In a sense, our synthetic strategy
succeeded through a rational assembly: macrocyclic ligand tacn acts as a terminal
ligand, and a benzoato bridge forces two NiII or CoIII centers so close together that the
azido ligand has to bind two metals in an end-on fashion.Comparison can be made to
compounds synthesized by Wieghardt and co-workers in a similar way, but in the
absence of sodium benzoate with the macrocyclic ligands 1,5,9-triazacyclododecane
À
and 1,4,7-trimethyl-1,4,7-triazacyclononane, which show two and three end-to-end N3
bridges, respectively [5].
As for complex 2, we believe that the macrocyclic CoII compound probably was
oxidized to CoIII before and/or when sodium azide was added.The reaction might be
2[Co2(m-O2CPh)(tacn)2]3‡ ‡ 2H2O‡ O2 ! 2[Co2(m-OH)(m-O2CPh)(tacn)2]4‡ ‡ 2OHÀ.
Thus, the final compound is the binuclear compound with three dissimilar bridges:
[Co2(m-N3)(m-OH)(m-O2CPh)(tacn)2] (ClO4)3 (2).
Molecular Structure of [Ni2(m-N3)2(m-O2CPh)(tacn)2](ClO4) ¥ H2O (1).The struc-
‡
ture of complex 1 consists of binuclear [Ni2(m-N3)2(m-O2CPh)(tacn)2] cations,
perchlorate anions, and H2O molecules.A perspective view of the binuclear cation
with two dissimilar bridges is shown in Fig. 1, and selected bond lengths and angles are
listed in Table 1.
In the binuclear cation, two NiII atoms are bridged by two N3 ions and the
À
carboxylato group of the benzoate ion; the macrocyclic ligand tacn acts as terminal
II
ligand.Each Ni
atom is six-coordinated, forming a slightly distorted octahedral
geometry.The Ni ÀN bond distance is in the range of 2.079(4) 2.131(4) ä, which is
normal for NiÀN coordination bonds.The Ni ÀO bond distance is averaged to 2.074 ä,
which is also very close to that of the literature [17][35].The Ni ¥¥¥ Ni distance in the
binuclear cation is averaged to 3.112 ä.
Fig. 2 shows the packing diagram of complex 1.Perchlorate anions and H O
2
‡
molecules lie in the space between binuclear [Ni2(m-N3)2(m-O2CPh](tacn)] cations.H-
Bonds are firstly found between the carboxylato O-atom (O(1A)) and non-coordinated
H2O (O(7A)) molecules with a distance of 2.918 ä. The second kind of H-bonds exists
between the C-atoms of tacn and O-atoms of the perchlorate anions (C(7A)ÀO(6A)
3.478 ä, C(9B)ÀO(5A) 3.309 ä), which link adjacent binuclear [Ni2(m-N3)2(m-
‡
O2CPh)(tacn)] together to form a unique one-dimensional structure. Desiraju
believes that because of the weakness of the interaction, CÀH ¥¥¥ O bonds can be
distorted by other crystal forces and that C ¥¥¥ O distances (D) of 3.0 4.0 ä are

Helvetica Chimica Acta Vol.86 (2003)
2443
‡
Fig.1. Perspective view of the [Ni2(m-N3)2(m-O2CPh)(tacn)2] cation of 1 with the labeling scheme
Table 1. Selected Bond Lengths [ä] and Angles [8] for 1
Ni(1)ÀN(2)
2.082(4)
2.091(4)
2.093(4)
2.096(4)
2.109(3)
Ni(2)ÀO(2)
2.039(3)
2.079(4)
2.090(4)
2.101(4)
2.131(4)
Ni(1)ÀN(4)
Ni(2)ÀN(10)
Ni(1)ÀN(1)
Ni(2)ÀN(12)
Ni(1)ÀN(3)
Ni(2)ÀN(11)
Ni(1)ÀO(1)
Ni(2)ÀN(7)
Ni(1)ÀN(7)
2.131(4)
Ni(2)ÀN(4)
2.131(4)
N(2)ÀNi(1)ÀN(4)
N(2)ÀNi(1)ÀN(1)
N(4)ÀNi(1)ÀN(1)
N(2)ÀNi(1)ÀN(3)
N(4)ÀNi(1)ÀN(3)
N(1)ÀNi(1)ÀN(3)
N(2)ÀNi(1)ÀO(1)
N(4)ÀNi(1)ÀO(1)
N(1)ÀNi(1)ÀO(1)
N(3)ÀNi(1)ÀO(1)
N(2)ÀNi(1)ÀN(7)
N(4)ÀNi(1)ÀN(7)
N(1)ÀNi(1)ÀN(7)
N(3)ÀNi(1)ÀN(7)
O(1)ÀNi(1)ÀN(7)
C(13)ÀO(1)ÀNi(1)
C(13)ÀO(2)ÀNi(2)
96.94(17)
82.94(18)
96.57(17)
83.63(16)
179.37(16)
83.77(17)
173.89(15)
89.06(15)
95.25(15)
90.38(14)
89.18(17)
82.61(15)
171.93(16)
97.12(16)
92.76(14)
126.3(3)
O(2)ÀNi(2)ÀN(10)
O(2)ÀNi(2)ÀN(12)
N(10)ÀNi(2)ÀN(12)
O(2)ÀNi(2)ÀN(11)
N(10)ÀNi(2)ÀN(11)
N(12)ÀNi(2)ÀN(11)
O(2)ÀNi(2)ÀN(7)
N(10)ÀNi(2)ÀN(7)
N(12)ÀNi(2)ÀN(7)
N(11)ÀNi(2)ÀN(7)
O(2)ÀNi(2)ÀN(4)
N(10)ÀNi(2)ÀN(4)
N(12)ÀNi(2)ÀN(4)
N(11)ÀNi(2)ÀN(4)
N(7)ÀNi(2)ÀN(4)
Ni(1)ÀN(4)ÀNi(2)
Ni(1)ÀN(7)ÀNi(2)
174.66(14)
93.48(15)
83.91(16)
91.38(15)
83.72(16)
83.83(16)
87.50(14)
95.14(15)
178.96(16)
96.49(16)
94.00(14)
90.98(16)
97.91(16)
174.23(16)
81.68(15)
94.98(17)
93.79(16)
130.4(3)

2444
Helvetica Chimica Acta Vol.86 (2003)
common [39].For the Ni II complex 1, the average C ¥¥¥ O distance is 3.393 ä, which is
much longer than that of O(7A) ¥¥¥ O(1A) (2.918 ä). Another interesting feature is
that the benzene rings of the benzoato ligands of different cations are parallel, as seen
in Fig. 2.However, we believe that prolably no p-p interaction exists because the
distance between the C-atoms of the benzene rings is too large (6.155 6.426 ä).
Fig.2. Packing diagram of complex 1
Molecular Structure of [Co2(m-N3)(m-OH)(m-O2CPh)(tacn)2](ClO4)3 (2).The
structure of complex 2 consists of binuclear [Co2(m-N3)(m-OH)(m-O2CPh)(tacn)2]3‡
cations and perchlorate anions.A perspective view of the binuclear cation with three
dissimilar bridges is depicted in Fig. 3, and selected bond lengths and angles are listed in
Table 2.
In the binuclear cation, two CoIII atoms are bridged by one N3À ion, one carboxylato
group of the benzoate ion, and one hydroxy group; the macrocyclic ligand tacn acts as
III
terminal ligand.Each Co atom is six-coordinated, forming a distorted octahedron.
The averaged CoÀN and CoÀN bond distances are 1.937 and 1.914 ä, respectively, all
being normal coordination bonds.The Co ¥¥¥ Co distance in the binuclear cation is
averaged to 2.868 ä.
Fig. 4 shows the packing diagram of complex 2.Perchlorate anions lie in the space
between the binuclear [Co2(m-N3)(m-OH)(m-O2CPh)(tacn)2]3‡ cations.H-Bonds are
found between O-atoms from perchlorate anions and N-atoms or C-atoms of the
terminal tacn ligand (O(14A) ¥¥¥ N(1BA) 2.933 ä, O(22A) ¥¥¥ C(5BA) 3.122 ä).
Spectroscopic Properties.The IR spectra of the two complexes 1 and 2 are very
similar, both displaying the presence of the benzoato ligand with nÄasym(OÀCÀO) at
1590vs and 1600vs cmÀ1 as well as the nÄasym(N3 ) bands centered at 2000vs and 2005vs
À
cmÀ1 for 1 and 2, respectively (vs ˆ very strong).The absorptions at 3250 s and 3150s are
assigned to nÄ(NÀH) of the macrocyclic ligand tacn and to H2O for complex 1 or OHÀ
for 2 (s ˆ strong).The absorption at 1100v s cmÀ1 is the characteristic band of ClO4 .
À
À
The other two bands of the N3 ligand (nÄsym and d) are masked by bands of the tacn
ligand and the nÄsym(OÀCÀO) bands and perchlorate bands.

Helvetica Chimica Acta Vol.86 (2003)
2445
Fig.3. Perspective view of [Co2(m-N3)(m-OH)(m-O2CPh)(tacn)2]3‡ cation of 2 with the labeling scheme
Table 2. Selected Bond Lengths [ä] and Angles [8] for 2
Co(1)ÀO(1)
1.902(3)
1.915(4)
1.924(3)
1.939(4)
1.940(4)
Co(2)ÀO(3)
Co(2)ÀO(2)
Co(2)ÀN(7)
Co(2)ÀN(5)
Co(2)ÀN(4)
Co(2)ÀN(6)
1.907(3)
1.922(3)
1.935(4)
1.939(4)
1.942(4)
1.949(4)
Co(1)ÀN(7)
Co(1)ÀO(3)
Co(1)ÀN(2)
Co(1)ÀN(1)
Co(1)ÀN(3)
1.943(4)
Co(1)ÀCo(2)
2.8681(9)
91.13(16)
94.79(14)
79.73(15)
173.63(16)
93.22(17)
90.58(16)
88.07(16)
98.14(18)
176.45(16)
86.70(18)
88.79(16)
174.60(18)
94.89(16)
87.33(17)
87.26(18)
127.6(3)
O(1)ÀCo(1)ÀN(7)
O(1)ÀCo(1)ÀO(3)
N(7)ÀCo(1)ÀO(3)
O(1)ÀCo(1)ÀN(2)
N(7)ÀCo(1)ÀN(2)
O(3)ÀCo(1)ÀN(2)
O(1)ÀCo(1)ÀN(1)
N(7)ÀCo(1)ÀN(1)
O(3)ÀCo(1)ÀN(1)
N(2)ÀCo(1)ÀN(1)
O(1)ÀCo(1)ÀN(3)
N(7)ÀCo(1)ÀN(3)
O(3)ÀCo(1)ÀN(3)
N(2)ÀCo(1)ÀN(3)
N(1)ÀCo(1)ÀN(3)
C(13)ÀO(1)ÀCo(1)
C(13)ÀO(2)ÀCo(2)
O(3)ÀCo(2)ÀO(2)
O(3)ÀCo(2)ÀN(7)
O(2)ÀCo(2)ÀN(7)
O(3)ÀCo(2)ÀN(5)
O(2)ÀCo(2)ÀN(5)
N(7)ÀCo(2)ÀN(5)
O(3)ÀCo(2)ÀN(4)
O(2)ÀCo(2)ÀN(4)
N(7)ÀCo(2)ÀN(4)
N(5)ÀCo(2)ÀN(4)
O(3)ÀCo(2)ÀN(6)
O(2)ÀCo(2)ÀN(6)
N(7)ÀCo(2)ÀN(6)
N(5)ÀCo(2)ÀN(6)
N(4)ÀCo(2)ÀN(6)
Co(2)ÀO(3)ÀCo(1)
Co(1)ÀN(7)ÀCo(2)
93.56(14)
79.64(15)
92.79(16)
175.83(17)
88.96(17)
96.92(18)
90.87(16)
174.45(17)
91.30(18)
86.83(19)
96.15(17)
89.11(17)
175.48(18)
87.2(2)
87.1(2)
96.95(15)
96.31(17)
126.2(3)
The UV and VIS spectra were measured in the 200 1000 nm range.The spectra of
complex 1 show a strong absorption band at 34500 cmÀ1 (e > 103 l ¥ molÀ1 ¥ cmÀ1), which
may be attributed to a charge transfer and the transition of the ligand itself.In addition,

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Helvetica Chimica Acta Vol.86 (2003)
Fig.4. Packing diagram of complex 2
three bands of medium intensity at 11200 (nÄ1; e ˆ 27.1 l ¥ molÀ1 ¥ cmÀ1), 17300 (nÄ2; e ˆ
9.56 l ¥ molÀ1 ¥ cmÀ1), and 28000 cmÀ1 (nÄ3; e ˆ 15.1 l ¥ molÀ1 ¥ cmÀ1) are tentatively attrib-
uted to the transitions of the NiII ions in a symmetry close to an octahedral
3
3
3
3
3
3
environment: nÄ1, A2g ! T2g; nÄ2, A2g ! T1g (F); nÄ3, A2g ! T1g (P); these are in
agreement with those given in the literature for similar octahedral NiII compounds
[16][17][23][35][40].According to the ligand-field theory [41], 10 Dq, B, and nÄ2 can be
obtained by using two observed bands (nÄ1 and nÄ3): 10Dq ˆ 11200 cmÀ1, B ˆ 806.85 cmÀ1,
and nÄ2 (calc.) ˆ 17574 cmÀ1.The calculated value of nÄ2 is close to the observed one,
indicating that the assignments are reasonable.The calculated nephelauxetic param-
eters b ˆ Bcomplex/Bfree ˆ 0.764 (considering B ˆ 1056 cmÀ1 for the gaseous ion (3P) Ni2‡)
shows moderately strong covalent bonding of NiII in this complex.
For complex 2, the spectra also show a strong absorption band at 29000 cmÀ1 (e >
103 l ¥ molÀ1 ¥ cmÀ1) and one band of medium intensity at 19100 cmÀ1 (nÄ2, e ˆ 102 l ¥
molÀ1 ¥ cmÀ1).From comparison with similar compounds, this latter absorption may
be attributed to the d-d transitions of low-spin CoIII ions in an octahedral environment,
1
i.e., to nÄ2 (1A1g ! T1g) according to the strong-field approximation.However, the
former may be attributed to a charge transfer and the transition of the ligand itself,
1
together with the nÄ1 (1A1g ! T2g) transition [42].
Magnetic Properties.The magnetic susceptibility was measured in the temperature
range 4 300 K with an applied magnetic field of 1 T.As shown in Fig. 5, for complex 1,
the room-temperature value for the effective magnetic moment meff (4.32 B.M.) is a
little higher than that expected for two isolated NiII ions (meff ˆ 4.0 B.M.). Upon
cooling, the meff value steadily increases to reach a maximum value of 5.19 B.M. at ca.

Helvetica Chimica Acta Vol.86 (2003)
2447
18 K, suggesting that a ferromagnetic interaction between NiII ions is operative.This
maximum value may be compared to the spin-only value (meff ˆ 4.90 B.M.) calculated
for an S ˆ 4/2 ground-state expected for two ferromagnetically coupled high-spin NiII
ions with g ˆ 2.00; the actual g value for NiII is expected to be a little higher than 2.00,
however.Below 18 K, the meff value slightly decreased on further cooling, which may be
the result of intermolecular interactions.
Fig.5. Experimental and calculated variations of cM (O) and meff (D) vs. T for complex 1
√
The magnetic analysis was carried out by using the spin Hamiltonian H ˆ
2
2
√ √
√
√
À2JS1S2 À D(S1 ‡ S2 ) and involved the intermolecular exchange interaction (zJ') in
the molecular-field approximation; the resulting magnetic susceptibility is given by
Eqn. 1.
"
#
2Nb2g2
4expꢀA† ‡ expꢀB† ‡ expꢀG†
cM ˆ
‡ Na (1)
KT 2expꢀA† ‡ 2expꢀB† ‡ expꢀC† ‡ 2expꢀG† ‡ expꢀE† ‡ expꢀF†
cM
cM' ˆ
1 À ꢀ2zJ'=Ng2b2†cM
A ˆ (6J ‡ 2D)/KT
B ˆ (6J ‡ D)/KT
C ˆ [(3J ‡ D) À (9J2 À 2DJ ‡ D2)1/2]/KT
G ˆ (2J ‡ D)/KT
E ˆ (2J ‡ 2D)/KT
F ˆ [(3J ‡ D) ‡ (9J2 À 2DJ ‡ D2)1/2]/KT

2448
Helvetica Chimica Acta Vol.86 (2003)
Therein, J is the intramolecular exchange integral, D the zero-field splitting parameter,
and Na the temperature-independent paramagnetism (200 ¥ 10À6 cm3 molÀ1), and the
other symbols have their usual meanings.The best fitting for the experimental data
gives J ˆ 19.6 cmÀ1, g ˆ 2.07, D ˆ 4.01 cmÀ1, and zJ' ˆ À0.32 cmÀ1.The agreement factor
R ˆ S(cobs. À ccalc.)2/Sc2 is 8.3 ¥ 10À5.
obs.
On comparison with the known structural data of similar octahedral NiII complexes
containing m-(azido-kN,kN) bridges (see Table 3), we found that both Ni ¥¥¥ Ni and
NiÀNÀNiav of complex 1 are largely different from the corresponding literature values.
There seems to be no obvious correlation between J and the NiÀNÀNiav angle or Ni ¥¥¥
Ni distance in these azidonickel(II) species.Moreover, when we use the assumption of
Christou and co-workers [17], still no simple linear correlation between J and NiÀ(m-
N)av is revealed.Since a − syn-syn× carboxylato bridge provides a small metal-metal
distance and results in a good overlap of the magnetic orbitals, an antiferromagnetic
coupling is always induced [43].Therefore, it is difficult to correlate the J value with the
structural data of complex 1 because only the average value due to the influence of both
the m-(azido-kN,kN) (ferromagnetic) and carboxylato (antiferromagnetic) bridges was
obtained.The observed J value of complex 1 is close to that of other azidonickel(II)
species, which can only indicate that the azido ligand is the dominant factor in the
superexchange interaction, and a moderately ferromagnetic interaction is operative
even in such NiII complexes with dissimilar bridges.A similar ferromagnetic interaction
has been found in a tetranuclear NiII complex with the dissimilar OHÀ and N3À bridges
and 1,3-diaminopropan-2-ol (OHpn) as blocking ligand [8]. Kahn and co-workers
explain the observed ferromagnetism by polarization effects [44][45], and hence, spin
polarization may well be the key feature leading to ferromagnetism in this azidonick-
el(II) complexes.
Table 3. Structural and Magnetochemical Data for Known Octahedral Nickel(II) Complexes Containing the m-
(Azido-kN,kN) Bridge and of Complex 1a)
NiÀ(m-N)av Ni ¥¥¥ Ni NiÀNÀNiav J [cmÀ1
]
Ref.
[ä]
[ä]
[deg]
[Ni2(m-N3)2(en)4] (ClO4)2
[Ni2(m-N3)4(en)2]n
[Ni2(m-N3)4(tn)2]n
[Ni2(m-N3)2(N3)2(terpy)2] ¥ 2H2O
[Ni2(m-N3)2(Me3[12]N3)2] (ClO4)2 ¥ 2H2O
[Ni2(m-N3)2(232-tet)2] (ClO4)2
[Ni2(m-N3)2(232-tet)2] (PF6)2
[Ni2(m-N3)2(N3)2(pepci)2]
[Ni2(m-N3)2(N3)2(Medpt)2]b)
2.134
2.121
2.106
2.118
2.080
2.167
2.180
2.127
2.193
2.202
2.122
3.369
3.241
3.310
3.276
3.273
3.423
3.449
3.297
3.448
3.470
3.206
3.112
104.3
100.6
103.7
101.3
103.8
104.9
104.6
101.6
103.7
104.0
98.1
20.9
14.8
17.6
20.1
43.9
33.8
17.2
36.3
46.7
[13]
[13]
[13]
[6]
[10]
[10]
[20]
[7]
[16]
[Ni4(m-N3)4(Opn)2(OHpn)2] (ClO4)2
[Ni2(m-N3)2(m-O2CPh)(tacn)2] (ClO4) ¥ H2O (1) 2.121
21.3
19.6
[8]
this work
94.4
a) en ˆ Ethane-1,2-diamine, tn ˆ N,N-bis(2-aminoethyl)ethane-1,2-diamine, terpy ˆ 2,2':6',2''-terpyridine,
Me3[12]N3 ˆ 1,5,9-trimethyl-1,5,9-triazacyclododecane, 232-tet ˆ N,N'-bis(2-aminoethyl)-1,3-propanediamine,
pepci ˆ N'-(2-pyridin-2-ylethyl)pyridine-2-carbalimide, Medptˆ methyl-bis(3-aminopropyl)amine, OHpnˆ 1,3-
diaminopropan-2-ol, tacn ˆ 1,4,7-triazacyclononane. b) Complex shows a magnetic transition at 150 120 K.
Parameters given are for the low- and high-temperature forms, respectively.

Helvetica Chimica Acta Vol.86 (2003)
2449
The magnetic properties of complex 2 were determined at both room and liquid-
nitrogen temperatures.The results indicated that this complex is diamagnetic, which is
in agreement with the strong-field approximation for CoIII in the UV/VIS-spectrum
analysis.
Conclusion. Two novel binuclear NiII and CoIII complexes with dissimilar bridges
were synthesized and structurally as well as magnetically characterized.Both
À
compounds have a discrete binuclear structure, bridged by two N3 ions and one
carboxylato group of the benzoate ion for 1, and by one N3À ion, one carboxylato group
of the benzoate ion, and one OH ligand for 2.The magnetic data of 1 was analyzed by
2
2
À1
À1
√
√ √
√
√
means of H ˆ À2JS1S2 À D(S1 ‡ S2 ), leading to J ˆ 19.6 cm , g ˆ 2.07, D ˆ 4.01 cm ,
and zJ' ˆ À0.32 cmÀ1.The observation of a ferromagnetic interaction within complex 1
indicates that in this mixed-bridged complex, the N3À bridge is the dominant factor in
the superexchange interaction, and a moderately ferromagnetic interaction is operative
even in the NiII complexes with dissimilar bridges.
Experimental Part
General.The ligand 1,4,7-triazacyclononane was prepared as previously described [46][47].All other
starting materials were purchased from the Tianjin Chemical Company and were of reagent grade.UV/VIS
Spectra: Shimadzu UV-2101-PC spectrophotometer; in H2O.IR Spectra: KBr discs; Shimadzu IR-408
spectrophotometer; in 4000 600 cmÀ1 region.Variable-temperature magnetic susceptibilities: Quantum-
Design MPMS-7 SQUID magnetometer, applied magnetic field, 1 T; diamagnetic corrections were made with
Pascal×s constants for all the constituent atoms [48].Elemental analyses: Perkin-Elmer analyzer, model 240.
Bis[m-(azido-kN:kN)][m-(benzoato-kO:kO')]bis(1,4,7-triazacyclononane-kN',kN4,kN7)dinickel(1‡) Per-
chlorate Hydrate (1).A MeOH soln.(10 ml) of sodium benzoate (108 mg, 07.5 mmol) was added to an aq.
soln.of (10 ml) of Ni(ClO 4)2 ¥ 6H2O (549 mg, 1.5 mmol). Then 1,4,7-triazacyclononane (193.5 mg, 1.5 mmol)
and NaN3 (97.5 mg, 1.5 mmol) were added in turn. After 1/2 h heating at 50 708, the mixture was filtered.The
filtrate was left undisturbed, and well-formed blue crystals of 1 were obtained by evaporation at r.t. after a week.
Anal.calc.for C 19H37ClNi2N12O7: C 32.67, H 5.30, N 24.07; found: C 32.79, H 5.00, N 23.95.
[m-(Azido-kN:kN)][m-(benzoato-kO:kO')](m-hydroxy)bis(1,4,7-triazacyclononane-kN1,kN4,kN7)dicobalt(3‡)
Triperchlorate (2).Complex 2 was prepared as described for 1, with Co(ClO4)2 ¥ 6H2O (549 mg, 1.5 mmol)
instead of Ni(ClO4)2 ¥ 6H2O.Light red crystals.Anal.calc.for C
found: C 26.60, H 4.47, N 14.97.
19H36Cl3Co2N9O15: C 26.69, H 4.21, N 14.75;
X-Ray Crystallography.Crystals of dimensions 02.5 mm  0.20 mm  0.20 mm for 1 and 0.88 mm Â
0.24 mm  0.22 mm for 2 were mounted on a Bruker Smart-1000 area detector and a Siemens Smart CCD,
resp., and graphite-monochromated MoKa radiation (l ˆ 0.71073 ä) at 293(2) K was applied. The structures
were solved by direct methods and successive Fourier difference syntheses (SHELXS-97) and refined by full-
matrix least-squares procedure on F2 with anisotropic thermal parameters for all non-H-atoms (SHELXL-97)
[49].Crystal data and details of the structure determination are summarized in Table 4.Crystallographic data
(excluding structure factors) for the structure analysis have been deposited with the Cambridge Crystallographic
Data Centre as supplementary publication Nos.200606 for 1 and 200605 for 2, resp.Copies of the data can be
obtained, free of charge, from the CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: ‡44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
This work was supported by the National Natural Science Foundation of China (No.20071019, No.
50172021, No.90101028).

2450
Helvetica Chimica Acta Vol.86 (2003)
Table 4. Crystal Data and Details of the Structure Determination of Complexes 1 and 2
1
2
Empirical formula
Mr
C19H37ClN12Ni2O7
698.48
C19H36Cl3Co2N9O15
854.3
Crystal system
Space group
a [ä]
b [ä]
c [ä]
b [8]
V [ä3]
Z
m(MoKa) [mmÀ1
F(000)
monoclinic
P2(1)/c
monoclinic
P2(1)/n
9.7391(3)
29.5574(9)
11.0734(3)
94.1190(10)
3179.38(16)
4
12.347(4)
14.759(5)
16.624(5)
99.200(5)
2990.5(15)
4
]
1.407
1456
1.414
2324
q Range [8]
Limiting indices
2.17 to 25.03
À 14 ꢁ h ꢁ 9, À16 ꢁ k ꢁ 17,
À19 ꢁ l ꢁ 19
12109
1.38 to 25.05
À 11 ꢁ h ꢁ 11, À 35 ꢁ k ꢁ 22,
À12 ꢁ l ꢁ 13
Total reflections
11067
Unique reflections
5231
5589
R(int)
0.0563
0.0273
5589, 0, 433
Data, restraints, parameters 5231, 0, 370
Refinement method
Weighting scheme
full-matrix least-squares on F2
full-matrix least-squares on F2
w ˆ 1/[s2(Fo2) ‡ (0.0650P)2 ‡ 0.0000P], w ˆ 1/[s2(Fo2) ‡ (0.0714P)2 ‡ 8.4975P],
P ˆ (Fo2 ‡ 2Fc2)/3
P ˆ (Fo2 ‡ 2Fc2)/3
0.0582, 0.1460
0.0754, 0.1572
1.059
Final R indices (I > 2 s(I)) 0.0473, 0.1081
R indices (all data)
Goodness-of-fit on F2
Largest diff.peak
and hole [eäÀ3
0.0900, 0.1263
0.943
0.826, À0.620
0.919, À0.846
]
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Received January 21, 2003