Tetranuclear nickel complexes composed of pairs of dinuclear LNi 2 fragments linked by 4,4′-bipyrazolyl, 1,4-bis(4′- pyrazolyl)benzene, and 4,4′-bipyridazine: Synthesis, structures, and magnetic properties

Article abstract of DOI:10.1002/ejic.200700317

The ability of the ligands 4,4′-bipyrazolyl (H₂bpz), 1,4-bis(4′-pyrazolyl)benzene (H₂bpzb), and 4,4′- bipyridazine (bpdz) to link two dioctahedral LNi₂ units has been examined. The following complexes were prepared: [L

Full text of DOI:10.1002/ejic.200700317

FULL PAPER
DOI: 10.1002/ejic.200700317
Tetranuclear Nickel Complexes Composed of Pairs of Dinuclear LNi2
Fragments Linked by 4,4Ј-Bipyrazolyl, 1,4-Bis(4Ј-pyrazolyl)benzene, and
4,4Ј-Bipyridazine: Synthesis, Structures, and Magnetic Properties
Vasile Lozan,[a] Pavlo Y. Solntsev,[b] Guido Leibeling,[c] Konstantin V. Domasevitch,*[b] and
Berthold Kersting*[a]
Keywords: Macrocyclic ligands / Bipyrazolate ligands / Nickel / Polynuclear complexes / Magnetic properties
The ability of the ligands 4,4Ј-bipyrazolyl (H2bpz), 1,4-bis(4Ј-
pyrazolyl)benzene (H2bpzb), and 4,4Ј-bipyridazine (bpdz) to
link two dioctahedral LNi2 units has been examined. The
following complexes were prepared: [L1NiII2(Hbpz)][BPh4]
(6[BPh4]), [L1NiII2(bpdz)][ClO4]2 (7[ClO4]2), [(L1NiII2)2(bpzb)]-
[BPh4]2 (8[BPh4]2), and [(L2NiII2)2(bpz)][BPh4]2 (9[BPh4]2),
where (L1)2– and (L2)2– represent macrocyclic hexaaza-dithio-
phenolate ligands. All complexes have been characterised by
UV/Vis spectroscopy, IR spectroscopy, and X-ray crystal-
lography. Whereas (Hbpz)– and bpdz in 6[BPh4]2 and
7[ClO4]2 act as bidentate ligands coordinating to only one
[LNi2]2+ unit, in 8[BPh4]2 and 9[BPh4]2 the (bpzb)2– and
(bpz)2– units are tetradentate linkers. This is qualitatively ex-
plained in terms of the absence or presence of steric repul-
sions between the tBu groups of the supporting ligands and
the length of the coligands. The structures of the tetranuclear
complexes differ mainly in the distance between the center
of the Ni···Ni axes of the isostructural [LNi2] units
{14.040(1) Å in 8[BPh4]2, 9.184(1) Å in 9[BPh4]2}. The two Ni2-
pyrazolato planes in 9[BPh4]2 are coplanar. An analysis of the
temperature-dependent magnetic susceptibility data for
9[BPh4]2 reveals the presence of weak ferromagnetic ex-
change interactions between the NiII ions in the binuclear
[L2Ni2] subunits with values for the magnetic exchange con-
stant J1 of 23.97 cm–1 (H = –2JS1S2). The exchange coupling
across the dipyrazolato bridge is less than 0.1 cm–1, suggest-
ing that no significant interdimer exchange coupling occurs
in 9[BPh4]2.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
plexes. The oligonuclear Pd3 and Pd4 complexes reported
by Yu et al. may serve as rather rare examples of this class
of compounds.[14]
Introduction
The coordination chemistry of the potentially quadri-
dentate ligands 4,4Ј-bipyrazolyl (H2bpz)[1,2] and its derivative
3,3Ј,5,5Ј-tetramethyl-4,4Ј-bipyrazolyl (H2Me4bpz)[3–6] has
been studied in some detail, primarily due to their capa-
bility to form porous coordination polymers with potential
uses as solid sorbents, ion exchangers or heterogeneous cat-
alysts.[7–11] In this context, a large body of work has been
carried out concerning the formation of polypyrazolate-
based coordination networks with open framework struc-
tures.[12,13] It is surprising that such ligands have not yet
been used in the construction of discrete polynuclear com-
In previous work, we described a series of dinuclear tran-
sition-metal complexes of the macrocyclic N6S2 ligands L1
and L2 (Scheme 1).[15,16] These complexes have a rich coor-
dination chemistry since the [L1M2]2+ fragments are able to
coordinate a large variety of coligands such as Cl–,[15]
[a] Institut für Anorganische Chemie, Universität Leipzig,
Johannisallee 29, 04103 Leipzig
Fax: +49-341-973-6199
E-mail: b.kersting@uni-leipzig.de
–
–
– [18]
– [19]
–
–
OH–,[17] NO2 , NO3 , N3 ,
BH4 ,
ClO4 , ReO4 ,
[b] Inorganic Chemistry Department, Kiev University,
Volodimirska Street 64, Kiev 01033, Ukraine
E-mail: dk@anorgchemie.univ.kiev.ua
2– [20]
SO42–, MoO4
,
MoO3(OMe)–,[21] and various carboxyl-
ate anions.[16,22,23]
[c] Institut für Anorganische Chemie, Georg-August-Universität
Göttingen,
The magnetic properties of an isostructural series of bio-
ctahedral [L1MII2(OAc)]+ complexes have also been re-
ported.[24] In the MnII2, FeII and CoII complexes of this
37077 Göttingen, Germany
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
2
2
Eur. J. Inorg. Chem. 2007, 3217–3226
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3217

K. V. Domasevitch, B. Kersting et al.
FULL PAPER
Scheme 1. Dinuclear complexes of the hexaaza-dithiophenolate li-
gands (L1)2– and (L2)2–.
series intramolecular antiferromagnetic exchange interac-
tions are present with J values of –5.1, –10.6, and –2.0 cm–1
(H = –2JS1S2). For the corresponding NiII complex, how-
2
ever, a ferromagnetic exchange interaction is observed (J =
+6.4 cm–1). In view of the strong interest in the targeted
design of molecular-based magnetic materials using high-
spin molecules of higher nuclearity,[25–31] we have initiated
a study on the synthesis of complexes in which pairs of
exchange coupled [L1Ni2] units are linked by 4,4Ј-bipyr-
azole (H2bpz) and 1,4-bis(4-pyrazolyl)-benzene (H2bpzb).
The neutral ligand 4,4Ј-bipyridazine (bpdz) was also in-
cluded in this study. We report herein the results of our
investigation together with the single-crystal X-ray structure
determination of the complexes [L1NiII2(Hbpz)][BPh4]
(6[BPh4]), [L1NiII2(bpdz)][ClO4]2 (7[ClO4]2), [(L1NiII2)2-
(bpzb)][BPh4]2 (8[BPh4]2), and [(L2NiII2)2(bpz)][BPh4]2
(9[BPh4]2). The results of temperature-dependent magnetic
susceptibility measurements on [(L2NiII2)2(bpz)][BPh4]2
(9[BPh4]2) are also described.
Scheme 2. Synthesis of the heterocycles H2bpzb and bpdz.
Attempts to link two [L1Ni2]2+ units by a (bpz)2– dianion
did not meet with any success. Treatment of
[L1Ni2Cl][ClO4] with triethylammonium 4,4-bipyrazolate in
methanol in varyingmolar ratios resulted always in the for-
mation of the green 1:1 complex [(L1)Ni2(Hbpz)][ClO4]
(6[ClO4]), presumably as a result of the sterically de-
manding tert-butyl groups. Nickel complexes of the neutral
bpdz ligand were found to be inaccessible from
Results and Discussion
Synthesis of Ligands and Complexes
Of the N-heterocycles used in this study, only 4,4Ј-bipyr- [L1Ni2Cl][ClO4]. The substitution reaction succeeded only
azolyl (H2bpz) was reported previously.[1,2] Scheme 2 depicts with the more labile perchlorato complex [L1Ni2(ClO4)]-
the syntheses of the new compounds H2bpzb and bpdz. The [ClO4], but again only 1:1 complexes formed. Thus, treat-
Diels–Alder reaction of bright-red 1,2,4,5-tetrazine (1) with ment of a dark green acetonitrile solution of [L1Ni2(ClO4)]-
cis-/trans-1,4-bis(dimethylamino)butadiene (2) in a 2.1:1 ra- [ClO4] with bpdz produced a brown-yellow solution, from
tio is accompanied by a vigorous evolution of dinitrogen which brown crystals of [L1Ni2(bpdz)][ClO4]2 (7[ClO4]2)
and affords after thermal elimination of dimethylamine and could be isolated in 80% yield.
recrystallization from methanol colourless 4,4Ј-bipyridazine
It was clear at this stage that tetranuclear Ni4 complexes
(bpdz) in reasonable yields (39%). The route to H2bpzb be- would only be accessible with longer bipyrazolyls or with
gan with a Vilsmeyer–Haack-type reaction of p-phenylene- less bulky LNi2 precursor subunits. Indeed, reaction of
diacetic acid 3 with POCl3/DMF to give the bis(trimethin- [L1Ni2Cl][ClO4] with a 0.5 molar equivalent of (bpzb)2–
ium) salt 4, which was isolated as its perchlorate salt.[32] (prepared in situ from H2bpzb and NEt3) in methanol fol-
Hydrolysis of 4 followed by treatment of the resulting tetra- lowed by addition of an exess of LiClO4 and recrystalli-
aldehyde 5 (not isolated) with hydrazine furnished the new zation from acetonitrile affords the green complex [(L1Ni2)2-
dipyrazole derivative H2bpzb as thin white needles in good (bpzb)][ClO4]2 (8[ClO4]2) in 76% yield. Similarly, reaction of
overall yield (78%). The new compounds were of sufficient [L2Ni2Cl][ClO4] with half a molar equivalent of (bpz)2– in
purity for metal complex syntheses.
methanol followed by addition of an excess of LiClO4 fur-
3218
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3217–3226

Tetranuclear Nickel Complexes
FULL PAPER
nished the tetranuclear species [(L2Ni2)2(bpz)][ClO4]2 = pyrazolate)[18] indicative of µ1,2-bridging pyrazolate func-
(9[ClO4]2) as a dark-green, air-stable solid. Complexes 8 tions and pseudo-octahedral N4S2 coordination environ-
and 9 were also isolated as tetraphenylborate salts.
ments around the Ni atoms. The UV/Vis spectrum of the
All compounds gave satisfactory elemental analyses and bipyridazine complex 7[ClO4] is similar but not identical
were characterized by IR spectroscopy and UV/Vis spec- with that of 6[BPh4], displaying two weak bands at 608 and
troscopy, and compounds 6[BPh4]·1.5MeCN, 7[ClO4]2· 1100 nm. The corresponding absorptions in previously re-
3MeCN, 8[BPh4]2·6MeCN·2H2O, and 9[BPh4]2·2CH2Cl2 ported [L1Ni2(pydz)]2+ (pydz = pyridazine)[18] were observed
also by X-ray structure analysis.
at 615 and 1095 nm. The slight differences in the position
of the d-d transitions indicate that each complex retains its
integrity in solution.
Characterization of the Complexes
X-ray Crystallography
Spectroscopic Characterization. IR and UV/Vis
Spectroscopy
Single-crystals of 6[BPh4]·1.5MeCN were obtained by
The infrared spectra of all compounds display the bands slow evaporation of a 1:1 acetonitrile/ethanol solution of
expected for the macrocyclic ligands and counterions, but 6[BPh4]. The crystal structure is composed of dinuclear
were not informative with respect to the conformations of [L1Ni2(Hbpz)]+ cations, tetraphenylborate anions, and ace-
the supporting or coligands. Only the band at 3385 cm–1 in tonitrile molecules of solvent of crystallization. An Ortep
the IR spectrum of 6[BPh4] can be attributed to the N–H plot of the structure of complex 6 is depicted in Figure 1.
stretching vibration of the protonated pyrazole moiety. The Selected bond lengths and angles are summarized in
electronic absorption spectra of the nickel complexes have Table 1. The bipyrazolato ligand acts only as a bidentate
2+
been recorded in the 300–1600 nm range in acetonitrile ligand towards one dinuclear [L1NiII
]
2
unit through the
solution. The spectra of the pyrazolato complexes 6, 8 and ring atoms N(7) and N(8). The atoms N(9) and N(10) re-
9 display two weak absorption bands around 640 and main uncoordinated, but the hydrogen atom bonded to
1190 nm typical of octahedral NiII (S = 1) ions. The ob- N(9) is involved in a hydrogen bonding interaction with an
served values closely compare with those of [L1Ni2(pz)]+ (pz adjacent acetonitrile solvate molecule [N(9)···N(11)
Eur. J. Inorg. Chem. 2007, 3217–3226
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3219

K. V. Domasevitch, B. Kersting et al.
FULL PAPER
2.975 Å]. The distance between the N atom of the acetoni- cannot link two [L1Ni2]2+ units. This can be attributed to
trile and N(10) is 3.652 Å. The corresponding C–C, C–N, the steric demand of the tBu groups which hinder the for-
and N–N distances of the two five membered rings of the mation of a tetranuclear complex. This assumption is nicely
(bpz)2– dianion do not deviate significantly from each other; corroborated by the crystal structure determination of
the largest difference being in the N–N bonds [N(7)–N(8) 9[BPh4]2.
1.384(2) Å, N(9)–N(10) 1.329(2) Å]. Note that the two het-
Figure 2 shows the structure of the dinuclear NiII com-
2
erocycles are not strictly coplanar. The dihedral angle be- plex 7 in crystals of 7[ClO4]2·3MeCN. Again, the 4,4Ј-bi-
tween the two five-membered rings is 25.6°. The C(40)– pyridazine ligand acts only as a bidentate group coordinat-
C(42) bond is of length 1.472(2) Å indicative of a C–C sin- ing to only one bioctahedral [L1Ni2]2+ entity through the
gle bond. The [L1Ni2]2+ subunits in 6 and the compounds ring nitrogen atoms N(7) and N(8). Metal complexes of
described below are structurally very similar, and the Ni–N 4,4Ј-bipyridazine have not been reported previously. The
and Ni–S distances lie within very narrow ranges (Table 1). average Ni–Npyridazine bond length of 2.159(2) Å is signifi-
The Ni···Ni distance is at 3.373(1) Å, which is nearly iden- cantly longer than the Ni–Npyrazolate distance in
6
tical with that in [L1Ni2(pz)][BPh4] [3.389(1) Å].[18] Overall, [2.043(2) Å], implying that the neutral bipyridazine binds
this structure clearly shows that the bipyrazolate moiety more weakly to the dinuclear [L1Ni2]2+ fragment in 7 than
Figure 1. ORTEP representation of the structure of the
[L1NiII2(Hbpz)]+ cation in crystals of 6[BPh4]·1.5MeCN. Ellipsoids
are represented at the 50% probability level. Hydrogen atoms ex-
cept H(9) have been omitted for clarity.
Figure 2. Structure of the [L1NiII2(bpdz)]2+ dication in crystals of
7[ClO4]2·3MeCN with thermal ellipsoids at the 50% probability
level. Hydrogen atoms are omitted for reasons clarity.
Table 1. Selected bond lengths [Å] and angles [°] in 6–9.
6[BPh4]·1.5MeCN
7[ClO4]2·3MeCN
8[BPh4]2·6MeCN·2H2O
9[BPh4]2·2CH2Cl2
Ni(1)–N(7)
Ni(1)–N(1)
Ni(1)–N(2)
Ni(1)–N(3)
Ni(1)–S(1)
Ni(1)–S(2)
Ni(2)–N(8)
Ni(2)–N(4)
Ni(2)–N(5)
Ni(2)–N(6)
Ni(2)–S(1)
Ni(2)–S(2)
Ni–N
2.050(2)
2.316(2)
2.178(2)
2.307(2)
2.4682(7)
2.4844(9)
2.036(2)
2.319(2)
2.167(2)
2.293(2)
2.4958(8)
2.4754(7)
2.208(2)
2.4810(7)
3.373(1)
–
2.149(3)
2.352(3)
2.125(3)
2.255(3)
2.435(1)
2.4846(9)
2.168(3)
2.410(3)
2.128(3)
2.202(3)
2.4533(9)
2.434(1)
2.224(3)
2.452(1)
3.401(1)
–
2.065(2)
2.276(2)
2.186(2)
2.279(2)
2.4692(5)
2.4878(5)
2.091(2)
2.247(2)
2.236(2)
2.300(2)
2.3983(5)
2.4967(5)
2.210(2)
2.4630(5)
3.349(1)
14.040(1)
90.69(6)
177.04(6)
91.06(5)
170.22(5)
80.46(2)
85.68(2)
2.037(2)
2.430(2)
2.170(2)
2.206(2)
2.5020(5)
2.4493(5)
2.005(2)
2.211(2)
2.142(2)
2.435(2)
2.5307(5)
2.4553(5)
2.205(2)
2.4843(5)
3.373(1)
9.184(1)
90.33(6)
175.70(6)
91.13(2)
171.43(5)
82.10(2)
85.53(2)
Ni–S
Ni···Ni
Ni–Nicent/Ni–Nicent[a]
[b]
N–M–Ncis
90.73(8)
176.63(7)
90.83(7)
170.27(6)
81.62(3)
85.65(2)
90.5(1)
[b]
N–M–Ntrans
176.2(1)
91.22(8)
171.03(8)
81.28(3)
87.83(3)
[b]
S–M–Ncis
[b]
S–M–Ntrans
S–M–S[b]
M–S–M[b]
[a] Distance between center of the Ni···Ni axes of the Ni2 units. [b] Average values.
3220
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3217–3226

Tetranuclear Nickel Complexes
FULL PAPER
does the charged pyrazolato ligand in 6. A similar behav- plane (folding angle: 165.4°). The Ni···Ni distance of
iour has been noted previously for [L1Ni2(pydz)]2+ and 3.448(1) Å is the same as that in 6. The distance d between
[L1Ni2(pz)].[18] As in 6, the coordination of the pyridazine the center of the Ni···Ni axes of the binuclear subunits
ring to the NiII ions results in a slight elongation of the amounts to 9.184(1) Å, which is significantly smaller than
N–N bond length [N(7)–N(8) = 1.336(2) Å vs. N(9)–N(10) the corresponding distance in 8. The bond lengths and
1.366(2) Å]. Likewise, the two six-membered rings are also angles around the Ni atoms within the [L2Ni2]2+ unit reveal
tilted by 25.2° with respect to each other. The Ni···Ni dis- no unusual features. The average Ni–S, Ni–Namine and
tance is at 3.401(1) Å.
Ni–Npyrazolato distances are at 2.018(3), 2.291(3), and
Complex 8[BPh4]2·6MeCN·2H2O crystallizes in the tri- 2.517(1) Å, respectively. Virtually the same distances are
¯
clinic space group P1 with six cocrystallized acetonitrile seen in 6. A large number of polymeric metal complexes
and two water molecules. The [(L1Ni2)2(bpzb)]2+ complex is containing bipyrazolato ligands have been structurally char-
centrosymmetric (Figure 3). Selected bond lengths and acterized;[2–7] to the best of our knowledge, 9 is the first
angles are summarized in Table 1. The structure of 8 unam- discrete species of (bpz)2–. Overall, this structure clearly
biguously confirms the ability of the deprotonated 1,4- shows that two bioctahedral [L2Ni2]2+ units can be linked
2+
bis(4Ј-pyrazolyl)-benzene to link two [L1NiII
]
2
units. The by bipyrazolate dianions.
four six-coordinate Ni atoms are arranged in a rectangular
fashion, the Ni···Ni distances being 3.349(1) Å [Ni(1)···
Ni(2)] and 14.040(1) Å [Ni(1)···Ni(2Ј)], respectively. Note
that the Ni2pyrazolato planes are coplanar with each other,
but that the central aromatic ring is slightly twisted out of
this plane (τ = 23.8°). The metal–ligand bond lengths
within the [L1Ni2(pyrazolato)]2+ units reveal no anomalities
and are very similar to those in 6 [Table 1]. There are no
significant intermolecular interactions between the Ni4
complexes. The shortest intermolecular Ni···Ni distance is
at 7.806[1] Å.
Figure 4. Left: van der Waals plot of the [(L2NiII2)2(µ-bipyrazol-
ato)]2+ dication in crystals of 9[BPh4]2·2CH2Cl2. Middle: ORTEP
representation of the core structure of 9 with the atom labeling
Scheme. Ellipsoids are represented at the 50% probability level.
Symmetry code used to generate equivalent atoms: 1 – x, 2 – y,
– z (Ј). Right: Tilting of the Ni2pyrazolato planes in 9.
Magnetic Properties of 9[BPh4]2
To gain insight into the electronic structure of 9[BPh4]2
variable-temperature magnetic susceptibility data were mea-
Figure 3. Left: Van der Waals plot of the [(L1NiII2)2(bpzb)]2+ dicat-
ion in crystals of 8[BPh4]2·6MeCN·2H2O. Middle: ORTEP repre- sured between 2.0 and 295 K by using a SQUID magne-
sentation of the core structure of 8 with the atom labeling Scheme.
tometer in an applied external magnetic field of 0.2 T. Fig-
Ellipsoids are represented at the 50% probability level. Symmetry
ure 5 shows a plot of the temperature dependence of the
code used to generate equivalent atoms: 1 – x, 1 – y, 1 – z (Ј).
effective magnetic moment for 9[BPh4]2. The effective mag-
Right: Mutual orientation of the Ni2pyrazolato planes in 8.
netic moment increases from 6.75 µB at 295 K to a maxi-
mum value of 7.59 µB at 22 K. On lowering the temperature
Crystals of 9[BPh4]2·2CH2Cl2 are triclinic, space group further the magnetic moment decreases to 6.97 µB at 2.0 K.
¯
P1. Ortep views of the structure of the dication 9 and the Although the effective magnetic moment at 22 K is smaller
central core are provided in Figure 4. A selection of the than expected for the spin-only value of 9.84 µB for ST = 4
most important bond lengths is given in Table 1. Again, 9 resulting from the ferromagnetic coupling of four NiII ions
exhibits crystallographically imposed inversion symmetry. (Si = 1, g = 2.20), it is larger than the value of 6.22 µB
In striking contrast to 6, the bipyrazolate moiety in 9 be- calculated for four noninteracting NiII ions. This behaviour
haves as a tetradentate bridging ligand joining two binu- indicates the presence of weak ferromagnetic exchange in-
clear [L2Ni2] subunits, most likely as a consequence of the teractions between the NiII ions in the binuclear subunits
absence of the tert-butyl groups in (L2)2–. The bipyrazolate but negligible – if any – coupling across the bipyrazolate
ligand assumes a planar conformation and the Ni2N2 pla- bridge. This is not surprising, considering the long distance
nes are only slightly folded with respect to the bipyrazolato between the nickel(II) ions.
Eur. J. Inorg. Chem. 2007, 3217–3226
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3221

K. V. Domasevitch, B. Kersting et al.
FULL PAPER
change couplings in the binuclear [L2Ni2(pyrazolate)]+ sub-
units. Therefore, we also tried to simulate the temperature
dependence of the magnetic data by using an isotropic di-
mer model [Equation (3)] for two NiII (S = 1) ions based
on the Hamiltonian in [Equation (4)].
χ = 2[χdim(1 – ρ) + 2χmonoρ]
(3)
(4)
The magnetic data could be reproduced equally well by
this approach (Figure 5), yielding J1 = +24.14 cm–1, g =
2.19, D = 4.85 cm–1, and ρ = 0.020%. Again, this analysis
reveals a weak ferromagnetic coupling between the two NiII
ions. All of these values are in excellent agreement with
those reported for other dinuclear nickel(II) complexes of
(L1)2– providing further support for the absence of signifi-
cant interdimer exchange coupling in 9[BPh4]2.[18,24]
Figure 5. Temperature dependence of µeff (per tetranuclear com-
plex) for 9[BPh4]2. The full line represents the best theoretical fit
to Equation (1). The dashed line represents the best fit to the dimer
model in Equation (3).
It should be noted that there is much interest in the dis-
tance-dependence of superexchange interactions between
paramagnetic transition metal ions bridged by extended or-
ganic spacer ligands. Thus, a large number of dicarboxyl-
ato-bridged copper(II) dimers with Cu···Cu separations of
5 to 15 Å have been prepared and their magnetic properties
have been determined.[35–41] The magnetic exchange interac-
tions decrease rapidly with increasing Cu···Cu separations
and the experimentally determined J values approach the
values predicted by the Coffman–Buettner relation
[|J|Յ1 cm–1 for d(M···M)Ն9 Å].[42] This finding also ap-
plies to other paramagnetic metal ions than Cu.[43] The ob-
servations made for the nickel(II) complexes presented
herein are in good agreement with the reported trend. It
is also worth mentioning that the coplanarity of the two
Ni2pyrazolato planes in 9 does not strengthen the magnetic
exchange interactions via the bipyrazolate moiety.
The magnetic susceptibility data were fitted to Equa-
tion (1), where χtetra and χmono refer to the molar suscep-
tibilities of a Ni4 complex and a fraction ρ of a mononu-
clear
nickel(II) impurity with Curie constant C = Ng2µB2/3kT.
χ = χtetra(1 – ρ) + 4χmono
ρ
(1)
The molar magnetic susceptibility χtetra was derived from
the appropriate spin-Hamiltonian Equation (2) including
the isotropic HDVV exchange, the single-ion zero-field
splitting and the single-ion Zeeman interaction by a full-
matrix diagonalization approach.
(2)
In this model J1 represents the exchange interaction be-
tween the Ni2+ ions within the dinuclear subunit, whereas
J2 describes the interaction across the bipyrazolate moiety.
Conclusions
In summary, we presented the synthesis of two new het-
The D and g values were considered to be identical for all erocyclic N4-ligands and the first members of a new class
of the four Ni2+ ions. Notice that D represents an effective of tetranuclear nickel(II) complexes in which pairs of dinu-
zero-field splitting parameter, since in Equation (2) and clear LNi2 fragments are united by (bpz)2– and (bpzb)2–
Equation (4) the zero-field splitting tensors of all ions are groups. The isolation of the two dinuclear complexes 6 and
assumed to be collinear. The least-squares fitting of the ex- 7 clearly show that the ease of formation of a tetranuclear
perimental data over the full temperature range led to J1 = cluster depends critically on two factors: (i) the length of
+24.0(1) cm–1, J2 = –0.001(5) cm–1, g = 2.19(1), D = 4.8(2) the bridging coligand and (ii) the steric demand of the sup-
cm–1, and ρ = 0.02(1)%. The inclusion of the D parameter porting ligand. If one pays attention to these two factors
improves the low-temperature fit significantly, but it repre- one can readily prepare higher nuclearity clusters such as 8
sents by no means an accurate value since temperature-de- and 9. These exist as stable and discrete complexes in solu-
pendent magnetic susceptibility measurements are not very tion and in the solid state as ascertained by various spectro-
appropriate for the determination of the sign and magni- scopic methods and X-ray crystallography. The Ni4 com-
tude of D.[33,34] However, this analysis establishes clearly plexes are well separated from each other in the solid state.
that magnetic exchange interactions via the dipyrazolate The magnitude of the exchange interaction J2 across the
moiety are not significant (J2 Ͻ 0.1 cm–1) and that the mag- bipyrazolate was found to be less than 0.1 cm–1, suggesting
netic properties of complex 9 are solely based on the ex- that no interdimer exchange coupling occurs in 9. In this
3222
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3217–3226

Tetranuclear Nickel Complexes
FULL PAPER
2+
colored mixture was cooled to room temp., diluted with 10 mL
water and 10% HCl solution was added to pH = 5, leading to
precipitation of the tetraaldehyde 5. Then 5.0 mL hydrazine hydrate
was added at once with stirring, which effects dissolution of 5 and
after 15–20 min stirring at room temp. the dipyrazole H2bpzb de-
posits as thin white needles. The mixture was left overnight and
filtered to yield 3.22 g (98.5%) of the product. This compound was
used for the preparation of the metal complexes without further
purification.
sense the LNi2 fragments are ideally suited to screen
novel extended bridging ligands for their ability to transmit
magnetic exchange interactions between paramagnetic tran-
sitions metal ions.
Experimental Section
General Remarks: Solvents and reagents were of reagent grade
quality and used as received unless otherwise specified. The com-
pounds 4,4Ј-bipyrazol,[2] [L1NiII2Cl][ClO4],[15] [L1NiII2(ClO4)]-
[ClO4],[20] and [L2NiII2(Cl)][ClO4][16] were prepared according to
the literature procedures. Melting points were determined in capil-
laries and are uncorrected. IR spectra were measured on a Bruker
VECTOR 22 FT-IR spectrophotometer as KBr pellets, electronic
absorption spectra on a Jasco V-570 UV/Vis/near IR spectropho-
tometer. Elemental analysis were performed on a Vario EL ana-
lyzer (Elementaranalysensysteme GmbH). All metal complexes
crystallize with solvent molecules (see crystal structures), but slowly
lose their solvent molecules of crystallization upon standing in air.
This is why the observed microanalytical data do not fit exactly
with the calculated values (for the solvent-free compounds). Tem-
perature-dependent magnetic susceptibility measurements on pow-
dered solid samples were carried out on a SQUID magnetometer
(MPMS Quantum Design) over the temperature range 2.0 –293 K.
The magnetic field applied was 0.20 Tesla. The observed suscep-
tibility data were corrected for underlying diamagnetism by using
Pascal’s constants.
[L1Ni2(Hbpz)][ClO4] (6[ClO4]): To a solution of H2bpz (13.8 mg,
0.103 mmol) in methanol (30 mL) was added triethylamine (20 mg,
0.20 mmol). Complex [L1Ni2Cl][ClO4] (194 mg, 0.210 mmol) was
added and the resulting yellow solution was stirred for 12 h. A
solution of LiClO4·3H2O (160 mg, 1.00 mmol) in methanol (2 mL)
was then added. After further stirring for 12 h, the green precipitate
was filtered, washed with cold ethanol, and dried in air. Yield:
80 mg (76%). M.p. 363–365 °C (decomp.). IR (KBr): ν = 3394 (m),
˜
2961 (s), 2867 (s), 1629 (w), 1463 (s), 1394 (w), 1363 (w), 1311 (w),
–
1265 (w), 1236 (w), 1203 (w), 1151 (m), 1078 [vs, ν3(ClO4 )], 1057
(s), 1041 (s), 1008 (w), 914 (m), 882 (w), 825 (m), 754 (w), 657 (w),
–
626 [m, ν4(ClO4 )], 563 (w), 535 (w), 492 (w), 461 (w), 418 (w). UV/
Vis (CH3CN): λmax/nm (ε/–1 cm–1) = 385 (1064), 634 (13), 1187
(24).
[L1Ni2(Hbpz)][BPh4] (6[BPh4]): To a solution of 6[ClO4] (102 mg,
0.100 mmol) in methanol (50 mL) was added a solution of NaBPh4
(342 mg, 1.00 mmol) in methanol (50 mL). The reaction mixture
was allowed to stir for 3 h. The green product was filtered, washed
with ethanol, and dried in air to give 113 mg (91%) of 6[BPh4] as
a green, air-stable, microcrystalline powder. M.p. 295–297 °C (de-
Safety Note: Caution! Perchlorate salts of transition metal com-
plexes are potentially hazardous and may explode. Only small quanti-
ties should be prepared and handled with great care.
comp.). IR (KBr): ν = 3384 (m), 3123 (w), 3054 (m), 3032 (m),
˜
2963 (s), 2858 (s), 1944 (w), 1877 (w), 1815 (w), 1764 (w), 1622 (w),
1580 (w), 1524 (w), 1462 (s), 1425 (m), 1393 (m), 1363 (m), 1309
(w), 1265 (m), 1235 (m), 1201 (w), 1169 (w), 1151 (w), 1126 (w),
1075 (m), 1040 (s), 1006 (w), 928 (w), 912 (m), 881 (w), 824 (m),
4,4Ј-Bipyridazine (bpdz): A solution of 12.31 g (0.15 mol) 1,2,4,5-
tetrazine (1) in 150 mL of dry 1,4-dioxane was added dropwise for
a period of 40 min to a stirred solution of 10.09 g (0.072 mol) of
cis-trans-1,4-bis(dimethylamino)butadiene (2) in 60 mL of dry 1,4-
dioxane. The immediate evolution of nitrogen gas and discoloration
were accompanied with a pronounced exothermic effect. After the
addition was completed, the red-brown reaction mixture was stirred
at 80 °C for 4 h (elimination of dimethylamine) and then left over-
night at room temp. The precipitate was filtered, washed with 5 mL
CH2Cl2 and twice crystallized from methanol with charcoal yield-
ing a pure product (4.44 g, 39%) as thin colorless needles. 1H NMR
(400 MHz, [D6]DMSO): δ = 9.77 (s, 2 H, 3-CH), 9.37 (d, 2 H, 6-
CH), 8.23 (dd, 2 H, 5-CH) ppm. C8H6N4 (158.16): calcd. C 60.75,
H 3.82, N 35.43; found C 60.44, H 3.89, N 35.17.
–
–
733 [s, ν(BPh4 )], 704 [s, ν(BPh4 )], 628 (m), 611 (m), 562 (w), 534
(w), 492 (w), 467 (w), 430 (w), 417 (w). UV/Vis (CH3CN): λmax/nm
(ε/–1 cm–1) = 382 (1037), 634 (14), 1182 (24). C68H89BN10Ni2S2
(1238.83): calcd. C 65.93, H 7.24, N 11.31, S 5.18; found C 65.50,
H 7.53, N 11.00, S 4.96. Single crystals of 6[BPh4]·1.5MeCN suit-
able for X-ray structure analysis were grown by slow evaporation
of an ethanol/acetonitrile solution of 6[BPh4]. These crystals slowly
lose the solvent molecules of solvent of crystallization at ambient
temperature and become turbid.
[L1Ni2(bpdz)][ClO4]2 (7[ClO4]2): To a solution of [L1Ni2Cl][ClO4]
(92 mg, 0.10 mmol) in methanol (30 mL) was added solid Pb-
(ClO4)2 (80 mg, 0.20 mmol). The color of the reaction mixture im-
1,4-Bis(4Ј-pyrazolyl)benzene. Intermediate 4: 11.2 mL (0.12 mol) mediately turned from yellow to dark green. The reaction mixture
POCl3 was added dropwise to 45 mL of dry DMF at 5–10 °C with
constant stirring. The mixture was stirred for an additional hour
at room temp. Then 3.88 g (20.0 mmol) solid p-phenylenediacetic
acid (3) was added at once and the clear solution formed was
stirred for 4 h at 90–95 °C and then at room temperature overnight.
The resulting black mixture was poured on 100 g crushed ice. After
decomposition of the excess Vilsmeyer reagent a saturated solution
of 15.0 g NaClO4 was added with stirring. The resulting nearly
white crystalline deposit of the bis(trimethinium) diperchlorate
(4[ClO4]2) was filtered and washed with two 15 mL portions of
water. The yield was 8.21 g (79.5%). This compound was used in
the next step without further purification. Intermediate 5: 8.22 g
(15.6 mmol) of the perchlorate salt 4[ClO4]2 were added to a warm
solution of 3.45 g (86 mmol) NaOH in 20 mL water, and the mix-
ture was heated with stirring for 7–8 min (bath temperature 90 °C)
until total dissolution of the organic salt was observed. The yellow-
was stirred for 5 min, filtered off from PbCl2, and to the dark-
green filtrate was added a solution of bpdz (7.9 mg, 0.050 mmol) in
acetonitrile (5 mL) to give a brown-yellow solution. The solution
was kept at room temperature for three days during which time
brown crystals separated. These were isolated by filtration, washed
with a little amount of cold methanol, and dried in air. Yield:
91 mg (80%). M.p. 297–298 °C (decomp.). IR (KBr): ν = 3433 (m),
˜
2962 (s), 2868 (s), 2250 (w), 2017 (w), 1603 (w), 1581 (m), 1464 (s),
1395 (m), 1364 (m), 1310 (m), 1267 (m), 1235 (m), 1199 (w), 1094
–
[vs, ν3(ClO4 )], 912 (m), 887 (m), 850 (w), 824 (s), 755 (w), 688 (w),
–
669 (w), 624 [s, ν4(ClO4 )], 566 (w), 538 (w), 494 (w), 440 (w), 414
(w) cm–1. UV/Vis (CH3CN): λmax/nm (ε/–1 cm–1) = 608 (47), 1094
(51). C46H70Cl2N10Ni2O8S2 (1143.53): calcd. C 48.31, H 6.17, N
12.25, S 5.61; found C 48.25, H 5.98, N 11.95, S 5.32. The crystals
of 7[ClO4]2·3MeCN used for an X-ray structure determination were
picked from the mother liquor.
Eur. J. Inorg. Chem. 2007, 3217–3226
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3223

K. V. Domasevitch, B. Kersting et al.
[(L1Ni2)2(bpzb)][ClO4]2 (8[ClO4]2): To a solution of H2bpzb (21 mg, slowly added resulting in the immediate formation of a green pre-
FULL PAPER
0.10 mmol) in methanol (50 mL) and triethylamine (20 mg,
0.20 mmol) was added solid [L1Ni2Cl][ClO4] (184 mg, 0.200 mmol).
The mixture was stirred for 3 d during which time the colour of
the suspension changed from yellow to green. A solution of
cipitate. After the addition was complete, further LiClO4·3H2O
(320 mg, 2.00 mmol) dissolved in methanol (2 mL) was added, and
stirring was continued for additional 12 h. The green product was
collected by filtration, washed several times with cold methanol,
LiClO4·3H2O (320 mg, 2.00 mmol) in methanol (10 mL) was and dried in air. Yield: 123 mg (73%). M.p. 340–341 °C (decomp.).
added. After stirring for 1 d, the green precipitate was collected by
filtration, washed several times with cold ethanol and dried in air.
IR (KBr): ν = 3521 (m), 2969 (s), 2855 (s), 2245 (w), 2017 (w),
1628 (w), 1587 (m), 1487 (s), 1454 (s), 1435 (s), 1396 (m), 1364 (w),
˜
Yield: 150 mg (76%). M.p. 342–343 °C (decomp.). IR (KBr): ν =
3431 (s), 2962 (s), 2866 (s), 1630 (w), 1579 (w), 1462 (s), 1395 (w), [vs, ν3(ClO4 )], 1042 (s), 999 (m), 956 (w), 916 (s), 897 (w), 828 (s),
1350 (w), 1298 (m), 1268 (s), 1254 (m), 1200 (w), 1170 (m), 1095
˜
–
–
1363 (w), 1310 (w), 1266 (w), 1233 (m), 1201 (w), 1150 (m), 1121 806 (m), 764 (s), 727 (w), 670 (m), 655 (w), 623 [s, ν4(ClO4 )], 566
(s), 1077 [vs, ν(ClO4 )], 1057 (s), 1041 (s), 1000 (w), 956 (w), 928
(w), 537 (w), 489 (w), 462 (w), 433 (w), 412 (w) cm–1. UV/Vis
–
(w), 913 (w), 881 (w), 826 (m), 807 (w), 754 (w), 625 [m, ν4(ClO4 )], (CH3CN): λmax/nm (ε/–1 cm–1) = 294 (23213), 380 (3785), 635 (66),
–
564 (w), 535 (w), 493 (w), 413 (w) cm–1. UV/Vis (CH3CN): λmax
nm (ε/–1 cm–1) = 380 (4989), 627 (57), 1195 (132).
/
1178 (91).
[(L2Ni2)2(bpz)][BPh4]2 (9[BPh4]2): To a warm solution of 9[ClO4]2
(168 mg, 0.100 mmol) in methanol (50 mL) was added a solution of
NaBPh4 (342 mg, 1.00 mmol) in methanol (100 mL). The reaction
mixture was allowed to stir for 3 h. The green microcrystalline pre-
cipitate was filtered, washed with ethanol and dried in air yielding
186 mg (88%) of 9[BPh4]2 as a green powder. M.p. 335–336 °C (de-
[(L1Ni2)2(bpzb)][BPh4]2 (8[BPh4]2): To
a solution of 8[ClO4]2
(198 mg, 0.100 mmol) in methanol (50 mL) was added a solution
of NaBPh4 (684 mg, 2.00 mmol) in methanol (10 mL). The reaction
mixture was allowed to stir for 1 h, and the volume of the solution
reduced in vacuo to about 30 mL. The green product was filtered,
washed with ethanol and dried in air to give 189 mg (78%) of
8[BPh4]2 as a green, air-stable, microcrystalline powder. M.p. 350–
comp.). IR (KBr): ν = 3523 (w), 3054 (m), 2984 (s), 2854 (s), 2247
˜
(w), 1634 (w), 1586 (m), 1484 (m), 1463 (s), 1435 (s), 1396 (m),
351 °C (decomp.). IR (KBr): ν = 3435 (s), 3054 (m), 3027 (m), 2963 1364 (m), 1350 (w), 1337 (w), 1297 (m), 1267 (s), 1255 (m), 1200
˜
(s), 2866 (s), 1636 (w), 1579 (w), 1480 (m), 1462 (s), 1395 (w), 1363 (w), 1169 (m), 1095 (s), 1075 (s), 1041 (s), 998 (m), 956 (m), 916
–
(w), 1310 (w), 1266 (w), 1233 (m), 1201 (w), 1169 (w), 1152 (w), (s), 896 (m), 827 (s), 806 (m), 761 (s), 732 [s, ν(BPh4 )], 704 [s,
–
1122 (w), 1108 (w), 1076 (m), 1056 (m), 1042 (s), 1000 (w), 956 (w), ν(BPh4 )], 669 (m), 623 (s), 612 (m), 565 (w), 536 (w), 488 (w), 465
–
928 (w), 912 (w), 881 (w), 825 (s), 733 [s, ν(BPh4 )], 704 [s,
(w), 433 (w), 412 (w) cm–1. UV/Vis (CH3CN): λmax/nm (ε/–1 cm–1)
–
ν(BPh4 )], 629 (w), 612 (m), 564 (w), 535 (w), 492 (w), 445 (w)
=
294 (27244), 376 (4504), 637 (63), 1183 (111).
cm–1. UV/Vis (CH3CN): λmax/nm (ε/–1 cm–1) = 381 (4626), 631
(53), 1190 (112). C136H176B2N16Ni4S4 (2419.62): calcd. C 67.51, H
7.33, N 9.26, S 5.30; found C 66.92, H 7.39, N 9.15, S 4.82. Single
crystals of 8[BPh4]·6MeCN·2H2O suitable for X-ray structure
analysis were grown by slow evaporation of an ethanol/acetonitrile
solution of 8[BPh4].
C114H140B2N16Ni4S4 (2119.09): calcd. C 64.61, H 6.66, N 10.58, S
6.05; found C 62.79, H 6.81, N 11.43, S 5.92. Single crystals of
9[BPh4]2·2CH2Cl2 suitable for X-ray structure analysis were grown
by recrystallization from dichloromethane.
Collection and Reduction of X-ray Data: Suitable single crystals of
6[BPh4]·1.5MeCN, 7[ClO4]2·3MeCN, 8[BPh4]2·6MeCN·2H2O, and
9[BPh4]2·2CH2Cl2 were selected and mounted on the tip of a glass
fibre using perfluoropolyether oil. The data sets were collected at
[(L2Ni2)2(bpz)][ClO4]2 (9[ClO4]2): To a solution of H2bpz (13.4 mg,
0.100 mmol) in methanol (30 mL) was added triethylamine (20 mg,
0.20 mmol). Complex [L2Ni2Cl][ClO4] (162 mg, 0.200 mmol) was 213(2) K using a STOE IPDS-2T diffractometer. Graphite-mono-
Table 2. Crystallographic data for complexes 6[BPh4]·1.5MeCN, 7[ClO4]2·3MeCN, 8[BPh4]2·6MeCN·2H2O, and 9[BPh4]2·2CH2Cl2.
Compound
6[BPh4]·1.5MeCN
7[ClO4]2·3MeCN
8[BPh4]2·6MeCN·2H2O
9[BPh4]2·2CH2Cl2
Formula
C71H93.50BN11.50Ni2S2
1300.42
P1
C52H79Cl2N13Ni2O8S2
1266.72
P1
C148H198B2N22Ni4O2S4
2701.98
P1
C116H144B2Cl4N16Ni4S4
2288.97
P1
Mr [g/mol]
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
¯
¯
¯
¯
12.5151(13)
16.2376(14)
18.270(2)
98.745(12)
95.316(12)
103.121(11)
3542.4(6)
2
13.2202(9)
15.6825(10)
16.7954(10)
74.250(8)
69.252(8)
66.228(8)
2946.2(3)
2
13.9142(4)
16.0978(5)
18.6102(6)
108.658(2)
107.475(2)
102.448(3)
3536.1(2)
1
12.2969(5)
15.3907(6)
15.5812(7)
73.445(3)
80.928(3)
79.567(3)
2762.2(2)
1
γ [°]
V [Å3]
Z
dcalcd. g/cm3
Cryst. size [mm]
µ(Mo-Kα) [mm–1]
θ limits [°]
Measured reflections
Independent reflections
Observed reflections[a]
Number of parameters
1.219
0.30ϫ0.25ϫ0.25
0.639
2.37–28.04
24520
15783
10159
778
0.0399 (0.0571)
0.1111 (0.1142)
0.994, –0.751
1.428
0.27ϫ0.24ϫ0.18
0.864
5.84–25.98
23694
10610
5881
727
0.0417 (0.0826)
0.0874 (0.0932)
0.602, –0.570
1.269
0.30ϫ0.30ϫ0.15
0.643
3.31–33.29
59533
23987
18472
845
0.0526 (0.0713)
0.1383 (0.1478)
1.105, –1.256
1.376
0.30ϫ0.20ϫ0.15
0.900
3.36–28.00
19250
13319
11233
659
0.0370 (0.0443)
0.1092 (0.1121)
1.349, –1.563
[b]
R1 (R1 all data)
[c]
wR2 (wR2 all data)
Max., min. peaks, [e/Å3]
[a] Observation criterion: I Ͼ 2σ(I). [b] R1 = Σ||Fo| – |Fc||/Σ|Fo|. [c]wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}1/2
.
2
2 2
3224
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3217–3226

Tetranuclear Nickel Complexes
FULL PAPER
[10] S. Kitagawa, S. Noro, T. Nakamura, Chem. Commun. 2006,
701–707.
[11] S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. 2004, 116,
2388–2430; Angew. Chem. Int. Ed. 2004, 43, 2334–2375.
[12] I. Boldog, E. B. Rusanov, A. N. Chernega, J. Sieler, K. V. Dom-
asevitch, Angew. Chem. 2001, 113, 3543–3546; Angew. Chem.
Int. Ed. 2001, 40, 3435–3438.
chromated Mo-Kα radiation (λ = 0.71073 Å) was used throughout.
The data were processed with the program STOE X-AREA.[44] Se-
lected details of the data collection and refinement are given in
Table 2. The structures were solved by direct methods[45] and re-
fined by full-matrix least-squares techniques on the basis of all data
against F2 using SHELXL-97.[46] PLATON was used to search for
higher symmetry.[47] All non-hydrogen atoms were refined aniso-
tropically. H atoms were placed at calculated positions and refined
as riding atoms with isotropic displacement parameters.
[13] K. V. Domasevitch, I. Boldog, Acta Crystallogr., Sect. C 2005,
61, 373–376.
[14] S. Y. Yu, H.-P. Huang, S.-H. Liu, Q. Jia, Y.-Z. Li, B. Wu, Y.
Sei, K. Yamaguchi, Y.-J. Pan, H.-W. Ma, Inorg. Chem. 2005,
44, 9471–9488.
[15] B. Kersting, G. Steinfeld, Chem. Commun. 2001, 1376–1377.
[16] a) G. Steinfeld, V. Lozan, B. Kersting, Angew. Chem. 2003, 115,
2363–2365; Angew. Chem. Int. Ed. 2003, 42, 2261–2263; b) S.
Käss, T. Gregor, B. Kersting, Angew. Chem. 2006, 118, 107–
110; Angew. Chem. Int. Ed. 2006, 45, 101–104.
[17] M. H. Klingele, G. Steinfeld, B. Kersting, Z. Naturforsch., Teil
B 2001, 56, 901–907.
[18] J. Hausmann, M. H. Klingele, V. Lozan, G. Steinfeld, D. Sieb-
ert, Y. Journaux, J. J. Girerd, B. Kersting, Chem. Eur. J. 2004,
10, 1716–1728.
[19] Y. Journaux, V. Lozan, J. Hausmann, B. Kersting, Chem. Com-
mun. 2006, 83–84.
[20] V. Lozan, B. Kersting, Eur. J. Inorg. Chem. 2007, 1436–1443.
[21] V. Lozan, B. Kersting, Inorg. Chem. 2006, 45, 5630–5634.
[22] B. Kersting, Angew. Chem. 2001, 113, 4110–4112; Angew.
Chem. Int. Ed. 2001, 40, 3988–3990.
[23] B. Kersting, G. Steinfeld, Inorg. Chem. 2002, 41, 1140–1150.
[24] Y. Journaux, T. Glaser, G. Steinfeld, V. Lozan, B. Kersting,
Dalton Trans. 2006, 1738–1748.
Some of the solvate molecules in 6 and 7 were found to be disor-
dered or only partially occupied. In the crystal structure of
6[BPh4]2·1.5MeCN the occupancy factor of one MeCN was re-
duced to 0.5. In the crystal structure of 7[BPh4]2·6MeCN·2H2O
the water molecule was found to be disordered over two sites. The
respective orientations were refined by using a split atom model to
give site occupancy factors of 0.59(1) [O(1a)] and 0.41(1) [for
O(1b)]. Water hydrogen atoms were not included in the refinement.
Graphics were produced with Ortep3 for Windows.[48]
CCDC-641207 (for 2), -641208 (for 3), -641209 (for 4), and -641210
(for 5) contain the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac/data_request/
cif.
Supporting Information (see also the footnote on the first page of
this article): Experimental and calculated magnetic values suscep-
tibility data for 9[BPh4]2.
[25] Magnetism: Molecules to Materials (Eds.: J. S. Miller, M. Dril-
lon), Wiley-VCH, Weinheim, 2001.
[26] E. Coronado, P. Delhaes, D. Gatteschi, J. S. Miller (Eds.), Mo-
lecular magnetism: From Molecular Assmblies to Devices,
NATO ASI Series, Kluwer, Dordrecht, The Netherlands, 1995,
vol. 321.
[27] S. P. Watton, P. Fuhrmann, L. E. Pence, A. Caneschi, A.
Cornia, G. L. Abbati, S. J. Lippard, Angew. Chem. 1997, 109,
2917–2919; Angew. Chem. Int. Ed. Engl. 1997, 36, 2774–2776.
[28] J. Larionova, M. Gross, M. Pilkington, H. Andres, H. Stoeckli-
Evans, H. U. Güdel, S. Decurtins, Angew. Chem. 2000, 112,
1667–1672; Angew. Chem. Int. Ed. 2000, 39, 1605–1609.
Acknowledgments
We sincerely thank the Deutsche Forschungsgemeinschaft (DFG)
(priority program 1137 “Molecular Magnetism”) for funding of
this work. We are grateful to Prof. Dr. F. Meyer for providing facili-
ties for magnetic susceptibility measurements.
[1] S. Trofimenko, J. Org. Chem. 1964, 29, 3046–3049.
[2] I. Boldog, J. Sieler, A. N. Chernega, K. V. Domasevitch, Inorg.
Chim. Acta 2002, 338, 69–77.
[3] P. E. Kruger, G. D. Fallon, B. Moubaraki, K. S. Murray, J.
Chem. Soc., Chem. Commun. 1992, 1926–1927.
[4] a) V. V. Ponomarova, V. V. Komarchuk, I. Boldog, A. N. Cher-
nega, J. Sieler, K. Domasevitch, Chem. Commun. 2002, 436–
437; b) I. Boldog, E. B. Rusanov, J. Sieler, S. Blaurock, K. V.
Domasevitch, Chem. Commun. 2003, 740–741; c) E. B. Rus-
anov, V. V. Ponomarova, V. V. Komarchuk, H. Stoeckli-Evans,
E. Fernandez-Ibanez, F. Stoeckli, J. Sieler, K. V. Domasevitch,
Angew. Chem. 2003, 115, 2603–2605; Angew. Chem. Int. Ed.
2003, 42, 2499–2501.
[5] J.-P. Zang, S. Horike, S. Kitagawa, Angew. Chem. 2007, 119,
907–910; Angew. Chem. Int. Ed. 2007, 46, 889–892.
[6] J. He, Y.-G. Yin, T. Wu, D. Li, X.-C. Huang, Chem. Commun.
2006, 2845–2847.
[7] a) M. Eddaoudi, D. B. Moler, H. Li, B. Chen, T. M. Reineke,
M. O’Keeffe, O. M. Yaghi, Acc. Chem. Res. 2001, 34, 319–330;
b) M. Eddaoudi, J. Kim, J. B. Wachter, H. K. Chae, M.
O’Keeffe, O. M. Yaghi, J. Am. Chem. Soc. 2001, 123, 4368–
4369; c) J. L. C. Rowsell, A. R. Millward, K. S. Park, O. M.
Yaghi, J. Am. Chem. Soc. 2004, 126, 5666–5667; d) T. J. Barton,
L. M. Bull, W. G. Klemperer, D. A. Loy, B. McEnaney, M.
Misono, P. A. Monson, G. Pez, G. W. Scherer, J. C. Vartuli,
O. M. Yaghi, Chem. Mater. 1999, 11, 2633–2656.
[8] C. N. R. Rao, S. Natarajan, A. Choudhury, S. Neeraj, A. A.
Ayi, Acc. Chem. Res. 2001, 34, 80–87.
[9] B. Moulton, M. J. Zaworotko, Chem. Rev. 2001, 101, 1629–
1658.
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
A. L. Dearden, S. Parsons, R. E. P. Winpenny, Angew. Chem.
2001, 113, 155–158; Angew. Chem. Int. Ed. 2001, 40, 151–154.
S. Demeshko, G. Leibeling, S. Dechert, F. Meyer, Dalton Trans.
2006, 3458–3465.
B. Kersting, G. Steinfeld, D. Siebert, Chem. Eur. J. 2001, 7,
4253–4258.
C. C. Barton, G. F. Daves, G. Franceschi, J. Chem. Soc., Perkin
Trans. 1980, 643–647.
T. Beissel, T. Glaser, F. Kesting, K. Wieghardt, B. Nuber, Inorg.
Chem. 1996, 35, 3936–3947.
K. K. Nanda, A. W. Addison, N. Paterson, E. Sinn, L. K.
Thompson, U. Sakaguchi, Inorg. Chem. 1998, 37, 1028–1036.
T. R. Felthouse, E. J. Laskowski, D. N. Hendrickson, Inorg.
Chem. 1977, 16, 1077–1089.
a) M. Julve, M. Verdaguer, A. Gleizes, M. Philoche-Levisalles,
O. Kahn, Inorg. Chem. 1984, 23, 3808–3818; b) S. Alvarez, M.
Julve, M. Verdaguer, Inorg. Chem. 1990, 29, 4500–4507.
M. Verdaguer, J. Gouteron, S. Jeannin, Y. Jeannin, O. Kahn,
Inorg. Chem. 1984, 23, 4291–4296.
[37]
[38]
a) E. G. Bakalbassis, C. A. Tsipis, J. Mrozinski, Inorg. Chem.
1985, 24, 4231–4233; b) E. G. Bakalbassis, J. Mrozinski, C. A.
Tsipis, Inorg. Chem. 1986, 25, 3684–3690; c) C. E. Xan-
thopoulos, M. P. Sigalas, G. A. Katsoulos, C. A. Tsipis, A.
Terzis, M. Mentzafos, A. Hountas, Inorg. Chem. 1993, 32,
5433–5436.
[39]
P. Chaudhuri, K. Oder, K. Wieghardt, S. Gehring, W. Haase,
B. Nuber, J. Weiss, J. Am. Chem. Soc. 1988, 110, 3657–3658.
Eur. J. Inorg. Chem. 2007, 3217–3226
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3225

K. V. Domasevitch, B. Kersting et al.
FULL PAPER
[40] K. S. Burger, P. Chaudhuri, K. Wieghardt, B. Nuber, Chem.
Eur. J. 1995, 1, 583–589.
[41] C. Erasmus, W. Haase, Spectrochim. Acta, Ser. A 1994, 50,
2189–2195.
[45] G. M. Sheldrick, Acta Crystallogr., Sect. A 1990, 46, 467–473.
[46] G. M. Sheldrick, SHELXL-97, Computer program for crystal
structure refinement, University of Göttingen, Göttingen, Ger-
many, 1997.
[42] R. E. Coffman, G. R. Buettner, J. Phys. Chem. 1979, 83, 2387– [47] Spek, A. L. PLATON – A Multipurpose Crystallographic Tool,
2392.
Utrecht University, Utrecht, The Netherlands, 2000.
[48] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
[43] J. Cano, G. De Munno, J. L. Sanz, R. Ruiz, J. Faus, F. Lloret,
M. Julve, A. Caneschi, J. Chem. Soc., Dalton Trans. 1997,
1915–1923.
Received: March 22, 2007
Published Online: May 22, 2007
[44] XAREA, Stoe & Cie, Darmstadt, Germany, 2001.
3226
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 3217–3226