Silver and Gold Trinuclear Complexes Based on 3-Substituted or 3,5-Disubstituted Pyrazolato Ligands. X-Ray Crystal Structure of cyclo-Tris{μ-[3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-κN 1:κN2]}trigold Dichloromethane ([Au(μ-pz pp2)]3·CH2Cl2)

Article abstract of DOI:10.1002/hlca.200490012

Ten new silver and gold trimeric complexes of the type [M ₃(μ-pz′)₃] (M = Au, Ag), where pz′ indicate pyrazolato ligands derived from mesogenic 3,5-disubstituted 1H-pyrazoles Hpz^R2 or non-mesogenic 3-substituted 1H-pyrazoles Hpz^R (R = C₆H₄OC_nH_2n+1), were synthesized and characterized. The gold and silver complexes 7, 8, 10, and 11 containing symmetric pyrazolato ligands as bridging groups (pz^R2; R = C₆H₄OC_nH_2n+1, n = 4 (pz ^bp2) and 8 (pz^op2)) exhibited a trigonal symmetric structure. The same results were obtained for the related silver derivatives 16-18 with 3-substituted pyrazolato ligands (pz^R; R = C ₆H₄OC_nH_2n+1, n = 4 (pz ^bp), 12 (pz^ddp), and 18 (pz^odp)). By contrast the 3-substituted pyrazolato-gold compounds 13-15 adopted an asymmetric molecular structure related to the position of the substituents on the trinuclear core. The thermal behavior of these complexes was investigated by differential scanning calorimetry and polarized-light microscopy. The mesomorphism of the parent 3,5-disubstituted pyrazoles is avoided in their corresponding trinuclear complexes 7, 8, 10, and 11. However, the metal derivatives 14 and 17 containing the asymmetric 3-[4-(dodecyloxy)phenyl]pyrazolato ligand were found to have liquid-crystal properties. These compounds exhibited monotropic behavior with columnar mesophases that could be related to the disc-like shape of the molecular core and the appropriate length of the alkyloxy chain. For comparative purposes, the X-ray structure of the related gold complex [Au₃(μ-pz ^pp2)₃] (9) having phenoxyphenyl substituents at the 3- and 5-positions of the pyrazolato ligand is also described. The molecular structure is formed by a non-planar (Au-N-N)₃ core, containing three Au-atoms bridged by three pyrazolato ligands. The molecular packing is described as a columnar organization, the shortest Au ... Au distance being 4.639(1) A between consecutive trimers.

Full text of DOI:10.1002/hlca.200490012

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Helvetica Chimica Acta Vol. 87 (2004)
Silver and Gold Trinuclear Complexes Based on 3-Substituted or
3,5-Disubstituted Pyrazolato Ligands. X-Ray Crystal Structure of cyclo-
Tris{m-[3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trigold
Dichloromethane ([Au(m-pzpp )]3 ¥ CH2Cl2)
2
by M. Carmen Torralbaa), Paloma Ovejeroa), M. Jose¬ Mayorala), Mercedes Cano*a), Jose¬ A. Campoa),
Jose¬ V. Herasa), Elena Pinillaa)b), and M. Rosario Torresb)
a
¬
) Departamento de QuÌmica Inorganica I, Facultad de Ciencias QuÌmicas, Universidad Complutense,
E-28040 Madrid (e-mail: mmcano@quim.ucm.es)
b
¬
) Laboratorio de Difraccion de Rayos-X, Facultad de Ciencias QuÌmicas, Universidad Complutense,
E-28040 Madrid
Ten new silver and gold trimeric complexes of the type [M3(m-pz')3] (M ˆ Au, Ag), where pz' indicate
pyrazolato ligands derived from mesogenic 3,5-disubstituted 1H-pyrazoles HpzR or non-mesogenic 3-
2
substituted 1H-pyrazoles HpzR (R ˆ C6H4OCnH2n‡1), were synthesized and characterized. The gold and silver
complexes 7, 8, 10, and 11 containing symmetric pyrazolato ligands as bridging groups (pzR ; R ˆ C6H4OCnH2n‡1
,
2
n ˆ 4 (pzbp ) and 8(pz )) exhibited a trigonal symmetric structure. The same results were obtained for the
related silver derivatives 16 18 with 3-substituted pyrazolato ligands (pzR; R ˆ C6H4OCnH2n‡1, n ˆ 4 (pzbp), 12
(pzddp), and 18(pz odp)). By contrast the 3-substituted pyrazolato-gold compounds 13 15 adopted an
asymmetric molecular structure related to the position of the substituents on the trinuclear core. The thermal
behavior of these complexes was investigated by differential scanning calorimetry and polarized-light
microscopy. The mesomorphism of the parent 3,5-disubstituted pyrazoles is avoided in their corresponding
trinuclear complexes 7, 8, 10, and 11. However, the metal derivatives 14 and 17 containing the asymmetric 3-[4-
(dodecyloxy)phenyl]pyrazolato ligand were found to have liquid-crystal properties. These compounds exhibited
monotropic behavior with columnar mesophases that could be related to the disc-like shape of the molecular
core and the appropriate length of the alkyloxy chain. For comparative purposes, the X-ray structure of the
op2
2
related gold complex [Au3(m-pzpp )3] (9) having phenoxyphenyl substituents at the 3- and 5-positions of the
2
pyrazolato ligand is also described. The molecular structure is formed by a non-planar (AuÀNÀN)3 core,
containing three Au-atoms bridged by three pyrazolato ligands. The molecular packing is described as a
columnar organization, the shortest Au ¥¥¥ Au distance being 4.639(1) ä between consecutive trimers.
1. Introduction. Exobidentate N,N'-coordination of pyrazolato ligands has been
extensively used on coordination oligomers and polymers [1 5]. Typical pyrazolato-
silver or -gold(I) derivatives have commonly been found as dimers or trimers [1][2][6
8], the latter being proposed to have a cyclic structure [1][2][9 18] compatible with
the sp2-hybridized N-atoms of the pyrazolato ring, the usual sp-hybridization of the
metal center, and the requirements of a nine-membered planar ring. Other values of
oligomerization have also been established for related complexes. Thus, a cyclic
Ph2
hexanuclear structure has been described for [Au6(m-pzPh )6] (pz ˆ 3,5-diphenylpyr-
2
azolato) [9][19], while bulky ligands such as 3,5-di(t-butyl)pyrazolato or the
asymmetric 3-ethyl-4,5-dimethyl-pyrazolato have given rise to cyclic tetramers [10].
4-i-C3F7
The latter structure has also been found for [Ag4(m-pz4-i-C F )4] (pz
fluoroisopropyl)pyrazolato) [3].
ˆ 4-(hepta-
3
7

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251
Despite the fact that some of these pyrazolato complexes were synthesized a long
time ago, little structural characterization is available. To the best of our knowledge, the
X-ray structures of only some pyrazolato-gold trimers [9][11 14], one pyrazolato-
silver trimer [9] and one pyrazolato-gold hexamer [9][19] have been reported. From
these results, we observed that the nine-membered metallocyclic core of the trimetallic
species was planar or slightly deviating from planarity depending on the substituents on
the pyrazolato ligand. Besides, it was also interesting to note that the trimeric gold and
silver derivatives containing 3,5-diphenylpyrazolato exhibited very different structures,
i.e., while the former was highly symmetric, the silver analogue presented a strong
deviation from idealized geometry [9].
Recently it has been established that trigonal planar molecules with D3h symmetry
are specially prone to develop non-centrosymmetric packings, and they can be used as
octupolar molecules with nonlinear optical (NLO) properties [20 22]. Therefore, the
study of new trinuclear pyrazolato-metal complexes opens new vistas for designing the
required trigonal molecules.
In addition, some trimetallic pyrazolato-gold(I) complexes of the type [Au3(m-pz)3]
have been shown to have liquid-crystal (LC) properties exhibiting columnar
mesophases [12][13][23]. Most of them carry from 12 to 18side chains in the
molecular periphery (4 to 6 for each pyrazolato group), configurating a discotic
shape [12][23]. However, a new type of related complexes containing only three
side chains from 4-substituted pyrazolato groups has also been found to behave
as discotic metallomesogens [13]. These latter compounds exhibited a star-shaped
dimeric structure formed by two alternated triangular molecules through Au ¥¥¥ Au
interactions, the dimers being considered disc-like molecules having six side chains
[13].
Following these considerations, we thought that, by using pyrazolato groups
containing only one side chain at the 3-position, trigonal pyrazolato-metal molecules
with only three arms could be obtained, which could be suitable to rearrange through
supramolecular interactions in discotic six-arms molecules related to those mentioned
above. With this idea in mind, we started to explore the incorporation of a family of 3-
long-chain-substituted pyrazolato ligands (pzR) into gold and silver centers. Related
studies were also carried out with symmetrically 3,5-disubstituted pyrazolato groups
(pzR2 ) derived from the corresponding mesogenic pyrazoles HpzR2 [24 26] to confirm
the proposed behavior.
Our research group has a long-standing interest in the design of LC metal
complexes based on long-chain-substituted pyrazole ligands [24][26 28]. We have
reported the mesomorphic properties of some of those pyrazoles as well as the ability to
generate mesogenic metal derivatives [24][26][27]. Therefore, we thought that these
pyrazoles could be used as candidates to produce trinuclear [M3(m-pz')3] (M ˆ Ag, Au)
compounds (pz' ˆ pyrazolato ligands derived from 3,5-disubstituted 1H-pyrazoles
HpzR or 3-substituted 1H-pyrazoles HpzR), which could behave as discotic metal-
2
lomesogens if they have the appropriate molecular shape. The analysis of the structural
consequences of the substituents on the pyrazole ring should be a useful guide in the
design of new trinuclear metal derivatives for potential LC and NLO molecular
materials. In this work, new trinuclear metal complexes 7 18 derived from the
pyrazole ligands 1 6 were studied.

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2. Results and Discussion. 2.1. Pyrazole Ligands. The following two types of
pyrazole derivatives were used for complexation to silver(I) and gold(I) centers:
symmetric pyrazoles of type A containing (alkyloxy)phenyl or (aryloxy)phenyl
substituents at the 3- and 5-positions of the pyrazol ring, i.e., Hpzbp (1), Hpzop (2),
2
2
and Hpzpp (3), and asymmetric derivatives of type B carrying only one (alkyl-
2
oxy)phenyl substituent at the 3-position with different length of the alkyl chain, i.e.,
Hpzbp (4), Hpzddp (5), and Hpzodp (6). All the type-A and -B ligands, with the exception
of 3, have previously been described, and they were prepared by reported procedures
[24][25][27][29]. The new ligand 3 was characterized by IR and 1H-NMR spectroscopy
and elemental analysis (see Exper. Part). The crystal structure of 3 was also determined
(see below).
Thermal studies by differential scanning microscopy (DSC) and polarized-light
microscopy were carried out for all ligands. At variance with the LC behavior of the 3,5-
disubstituted 1H-pyrazoles 1 and 2, which exhibit smectic mesophases [24][25], the
remaining 1H-pyrazoles (the new symmetric 3 and the asymmetric 4 6 [27][30]) did
not show mesomorphic properties, the absence of those properties being associated
with an inadequate length-to-width ratio of the molecules. This fact is basically
produced by the shortening of the length of the molecule when only one long
substituent was introduced at the 3-position.
2.2. X-Ray Crystal Structure of 3,5-Bis(4-phenoxyphenyl)-1H-pyrazole (Hpzpp ; 3).
2
An X-ray study of 3 was carried out. This pyrazole crystallizes in the P21/c space group
with four molecules per unit cell. Some representative bond distances and angles are
listed in Table 1. Fig. 1 depicts a perspective view of the molecule showing the atom-
numbering scheme. As other pyrazoles [24][29][31], 3 shows the characteristic bond
distances of a delocalized ring. The same feature is observed for the substituent
benzene rings. At variance with the almost linear geometry found in related pyrazoles
with (alkyloxy)phenyl substituents [24], this linearity is disrupted in 3 by the presence
of the second benzene ring at each substituent. Thus, although the pyrazole ring and the
directly bound benzene rings of the substituents are almost planar (dihedral angles of
9.11(6) and 8.12(6)8), the terminal benzene rings are strongly deviated as deduced from

Helvetica Chimica Acta Vol. 87 (2004)
253
Fig. 1. Molecular structure of 3. H-Atoms, except for HÀN(2), have been omitted for clarity. Arbitratry
numbering scheme.
Table 1. Selected Bond Distances [ä] and Angles [8] for Hpzpp (3). For numbering, see Fig. 1.
2
N(1)ÀN(2)
1.354(2)
1.342(2)
1.385(2)
2.885(2)
112.9(1)
105.6(2)
106.4(2)
N(2)ÀC(5)
1.345(2)
1.398(2)
0.85
2.16
105.1(1)
N(1)ÀC(3)
C(3)ÀC(4)
C(5)ÀC(4)
N(2)ÀH(2)
N(2) ¥¥¥ N(1')a)
N(1)ÀN(2)ÀC(5)
N(2)ÀC(5)ÀC(4)
C(3)ÀC(4)ÀC(5)
N(1') ¥¥¥ H(2)a)
C(3)ÀN(1)ÀN(2)
N(1)ÀC(3)ÀC(4)
N(2)ÀH(2) ¥¥¥ N(1')a)
110.1(2)
142.2
a)' means symmetry operation 1 À x, À y, À z.
the angle formed between the O(1)ÀO(2) line and the O(1)ÀC(16) and O(2)ÀC(27)
lines of 49.95(5) and 66.42(4)8, respectively.
The most-interesting feature is related to the presence of a strong NH ¥¥¥ N
intermolecular H-bond between the NH group and the N-atom of neighboring
molecules (Fig. 2). It suggests a dimeric structure, which has already been observed in
other 1H-pyrazoles [24][29]. The crystal packing can be viewed as columns of dimers in
an eclipsed stacking along the b axis (Fig. 2).
2.3. Pyrazolato-Silver or -Gold(I) Complexes. The synthesis of tris(m-pyrazolato-
kN,kN')trigold(I) or -silver(I) complexes [M3(m-pz')3], i.e., of 7 18, is depicted in the
Scheme. The compounds were isolated as white solids, soluble in polar solvents. Those
derivatives containing symmetric ligands are moderately stable both in solution and in
solid state. The remaining complexes are more unstable, exhibiting decomposition with
deposition of free metal, and repeated purification procedures were required to allow
1
their characterization. All complexes were studied by IR and H-NMR spectroscopy,
elemental analysis, and mass spectrometry (see Exper. Part). Because all attempts to
get adequate crystals for X-ray crystal-structure determination of complexes containing
(alkyloxy)phenyl substituents were unsuccessful, we prepared the related derivatives
containing the 3,5-bis(4-phenoxyphenyl)pyrazolato ligand derived from 3. The X-ray
crystal structure of the gold complex [Au3(m-pzpp )3] ¥ CH2Cl2 (9) was used as reference
2
for comparative purposes (see below).
The complexes 7 and 9 (Au) and 10 and 12 (Ag) based on A-type pyrazolato ligands
exhibit the expected signals in their 1H-NMR spectra, consistent with the formation of a
trimetallic product containing three equivalent pyrazolato ligands, with a D3h

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Helvetica Chimica Acta Vol. 87 (2004)
Fig. 2. Molecular packing of 3 through the b axis
Scheme
symmetry, as a consequence of the rotation of the aromatic rings around the
C(pyrazolato)-C(phenyl) bond in solution.
The complexes 8 (Au) and 11 (Ag) containing eight C-atoms in the chain
substituents could not be isolated as solid products. They were formed as an oil from
which a quasi-liquid or waxy material was isolated after repeated attempts. However,
1
the H-NMR spectra are analogous to those of the above-mentioned compounds,
suggesting the same type of trimetallic complexes. The presence of the long-chain
substituents at the 3- and 5-positions of the pyrazole ring appears to be responsible for
the non-solid nature of the compounds.
On the other hand, complexes 13 18 containing the B-type asymmetrically
1
substituted pyrazolato ligands, display different patterns in their H-NMR spectra

Helvetica Chimica Acta Vol. 87 (2004)
255
depending on the metal center. Thus, the gold derivatives 13 15 exhibit three HÀC(4)
and three HÀC(5) pyrazolato signals in a 1:1:1 ratio. In some of these cases, the
HÀC(5) signals have almost identical chemical shifts, giving rise to two 2 d in a 2 :1
ratio. Similar behavior is observed for the aromatic and the CH2O protons of the
substituents which appear as two Ho and two Hm ds (J ꢀ 8Hz) and two t, respectively, in
a 4 :2 ratio. These results agree with the presence of a asymmetric compound of the
type depicted in Fig. 3,a, which contains three nonequivalent pyrazolato ligands. By
contrast, all the silver derivatives 16 18 exhibit a simpler 1H-NMR spectrum showing
single signals for the HÀC(4) and HÀC(5) protons as well as those required for the
aromatic and alkyl protons of the substituent. Thus, we can deduce that these
compounds belong to a family of trimetallic derivatives containing a symmetric C3h
structure (Fig. 3,b).
Fig. 3. a) Asymmetric and b) symmetric isomers of [M3(m-pz')3]
In the mass spectra (FAB-MS or ESI-MS (positive mode)) of the new complexes,
the parent ions of a trimer [M3(m-pz')3] are observed in most cases, in agreement with
the proposed structure for metallocyclic derivatives. In complexes 12 and 18, the
highest mass fragment observed corresponds to the loss of a pyrazolato ligand. Other
fragments from association reactions with the molecular ion were also produced in
some of the silver derivatives.
In summary, we have established the formation of cyclic trimers for all selected
symmetrical and unsymmetric pyrazolato ligands. The silver complexes with 3-
substituted pyrazolato ligands were isolated as symmetrical isomers, while the gold
analogues adopted the asymmetric form (Fig. 3). The presence of a mixture of the two
isomers (a symmetric and an asymmetric one, derived from the disposition of
asymmetric substituents at the pyrazolato ligand) has already been reported for several
pyrazolato-gold(I) complexes [10][12][14]. However, to the best of our knowledge,
this is the first case in which different trinuclear isomers are formed depending on the
metal center.
2.4. Thermal Studies of Complexes 7 18. Thermal studies of complexes 7 18 were
carried out by DSC as well as by polarized-light-microscopy observations (see Exper.
Part). On heating, some of them decomposed, this fact avoiding to get precise results.
On the basis of our and other previous studies, the 3,5-disubstituted 1H-pyrazoles
HpzR with chains containing from 4 to 18C-atoms were shown to be calamitic
2
materials [24 26]. By contrast, the 3-substituted 1H-pyrazoles HpzR did not exhibit

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liquid-crystal properties for the same range of C-atoms in the chains [27][30]. However
the latter ligands were able to induce mesomorphism on rod-like complexes of the type
[PdCl2(HpzR)2] [27]. Now we used both types of ligands in trinuclear [M3(m-pz')3]
complexes with an approximately disc-like shape.
At variance with the mesogenic parent HpzR ligands [24][25], none of their
2
trinuclear gold or silver derivatives 7, 8, 10, and 11 showed LC properties.
Quite interestingly, the coordination of the non-mesogenic Hpzddp as pyrazolato
ligand to gold and silver (complexes 14 and 17) results in the appearence of
mesomorphic behavior. By contrast, the other related complexes with shorter (n ˆ 4)
or longer (n ˆ 18) chains, i.e., 13, 15, 16, and 18, behave as nonliquid-crystal materials. It
appears that the increase to 18C-atoms in the alkyl chains probably disrupts the
ordering on the columnar arrangement in the mesophases. The same results could be
attributed to the presence of substituent chains with only four C-atoms which does not
appear to be long enough to induce mesomorphic properties.
The new complexes 14 and 17 exhibit a monotropic behavior. The observed textures
are fan-like or pseudo-focal-conic, which are typical of columnar mesophases (Fig. 4).
For the gold derivative 14, the mesophase is observed on cooling at 83.58 only when the
temperature is very slowly modified. The DSC thermogram shows a very broad peak
between 100 and 808 for this process. By heating from the mesophase, the mesophase to
isotropic transformation (clearing point) is observed at 90.58. The mesophase texture
remains when the crystallization begins to take place, which is detected by DSC at an
onset temperature of 76.48. The silver complex 17 exhibits a related mesomorphic
behavior. Upon heating and subsequent cooling, a mesophase is detected by micro-
scopy at 968, but the darkness precludes to see clearly the fan-like texture. The
crystallization process is observed at 868. By DSC, only a broad peak on cooling is
found at an onset temperature of 93.48, and it is attributed to the overlapping of the
isotropic-mesophase and crystallization processes. Comparing the thermal behavior of
both the gold and silver complexes 14 and 17 reveals, remarkably, that the latter is
Fig. 4. Photomicrograph of the texture of the mesophase of [Au3(m-pzddp)3] 14 at 818 (on cooling)

Helvetica Chimica Acta Vol. 87 (2004)
257
associated to an increase in the melting and clearing points. This effect may be related
to the differences on the molecular symmetry.
2.5. X-Ray Structure of [Au3(pzpp )3] ¥ CH2Cl2 (9 ¥ CH2Cl2). As mentioned above,
2
the bulky 3,5-bis(4-phenoxyphenyl)pyrazolato ligand was not used as organic ligand
looking for mesogenic compounds but was employed to obtain insights into its
influence on the oligomerized structure of its silver or gold derivatives.
We made different attempts to obtain crystals for all of the pyrazolato complexes
prepared, but unfortunately, we only got adequate crystals for X-ray studies, although
of poor quality, of [Au3(m-pzpp )3] ¥ CH2Cl2 (9 ¥ CH2Cl2). However, the analysis of its
2
structure was considered of interest since it could establish the molecular nuclearity as
well as the crystal packing.
The crystal structure of 9 ¥ CH2Cl2 consists indeed of discrete trimeric molecules
(see Fig. 5 for a perspective view and the atom-numbering scheme). Table 2 lists the
≈
most-relevant bond distances and angles. The complex crystallizes in the P1 space
group. The asymmetric unit consists of one indepedent trimeric molecule. There is also
a CH2Cl2 molecule of crystallization bonded through a weak H-bonding interaction
to the trimetallic unit (Cl(1) ¥¥¥ H(27B) 2.96(1) ä, C(27) ¥¥¥ Cl(1) 3.64(2) ä,
C(27)ÀH(27B) ¥¥¥ Cl(1) 131(1)8). This could be responsible for the decomposition of
the crystals at room temperature and, therefore, the data collection was carried out at
low temperature (see Exper. Part).
The nine-membered ring formed by three Au-atoms and six pyrazolato N-atoms is
nonplanar and slightly nonregular and distorted. Similar features have been found for
the reported complexes [Au3(m-pzR2 )3] (R ˆ CF3, MeOC6H4) [11][12] and [Ag3(m-
Ph2
pzPh )3] [9], while the related [Au3(m-pz )3] showed a planar and symmetric nine-
2
Fig. 5. Molecular structure of 9 ¥ CH2Cl2. H-Atoms and solvent molecule have been omitted for clarity.

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Helvetica Chimica Acta Vol. 87 (2004)
Table 2. Selected Bond Distances [ä] and Angles [8] of [Au3(m-pzpp )3] ¥ Ch2Cl2 (9 ¥ CH2Cl2)
2
Au(A) ¥¥¥ Au(B)
Au(A) ¥¥¥ Au(C)
Au(B) ¥¥¥ Au(C)
3.347(1)
3.358(1)
3.224(1)
1.96(2)
2.09(2)
2.00(2)
Au(B)ÀN(2C)
2.04(2)
1.97(2)
2.00(2)
1.32(2)
1.42(2)
1.40(2)
Au(C)ÀN(1C)
Au(C)ÀN(2A)
Au( A )ÀN(2B)
N(1A)ÀN(2A)
Au( A )ÀN(1A)
N(1B)ÀN(2B)
Au( B )ÀN(1B)
N(1C)ÀN(2C)
N(2B)ÀAu( A )ÀN(1A)
Au( A )ÀN(1A)ÀN(2A)
Au( A )ÀN(1B)ÀN(2B)
N(1B)ÀAu( B )ÀN(2C)
Au( B )ÀN(1B)ÀN(2B)
174.2(6)
Au(B)ÀN(2C)ÀN(1C)
N(2A)ÀAu(C)ÀN(1C)
Au(C)ÀN(2A)ÀN(1A)
Au(C)ÀN(1C)ÀN(2C)
117(1)
115(1)
117(1)
178.6(7)
118(1)
175.3(6)
120(1)
118(1)
membered ring [9]. A linear coordination at the AuI atom is present in the trimer, the
NÀAuÀN angles ranging between 174.2(6)8 and 178.6(7)8. The AuÀN lengths are in
the 1.96 2.09(2) ä interval with a mean distance of 2.01(2) ä, these distances being
very close to those complexes containing phenyl substituents (1.97 2.07 ä)
[9][12][32][33]. The Au ¥¥¥ Au distances in the trimers are 3.224(1), 3.347(1), and
3.358(1) ä (mean value of 3.310 ä), much longer than in metallic gold (2.884 ä) [34],
and similar to those observed in other pyrazolato-gold(I) complexes (3.25 3.43 ä)
[9][11 14]. A weak Au ¥¥¥ Au intramolecular bonding interaction is suggested because
all Au ¥¥¥ Au distances are shorter than the calculated value for a planar nine-
membered metallocycle (ca. 3.4 ä) [12].
The three pyrazole rings are not exactly coplanar among them, the dihedral angles
ranging from 13.5(6) to 30.8(7)8. Additionally, these pyrazole rings and their own
directly bound phenyl groups do not maintain the planarity observed in the free ligand
(angles between 17.1(7) and 49.2(7)8 in 9 ¥ CH2Cl2 and ca. 98 in 3). Besides, the terminal
benzene rings are even more deviated from that planarity, and they are twisted from
55(1) to 88.3(7)8 with respect to interior benzene rings. Despite these features, by
assuming free rotation of the phenyl substituents, a trigonal symmetry could be defined
for the whole molecule, a consequence of the bonds established between the metal and
the pyrazolato ligands.
The molecular packing of the trimers corresponds to a columnar distribution. The
columns are parallel to the crystallographic a axis, and they are formed by trimers that
are stacked in an alternate disposition as depicted in Fig. 6. The Au3 plane of trimers are
not orthogonal to the a axis but deviated by 48.51(2)8. Therefore, the shortest Au ¥¥¥ Au
distance between consecutive trimers of 4.639(1) ä is derived for the orientation of the
trimers along the columns. However the distance between the centroids of the Au3
planes of consecutive trimers in the column is ca. 6.7 ä, longer than that reported for
the related compound with methoxyphenyl as substituents (4.54 ä) [12] which is a
typical intermolecular distance in LC materials with disc-like molecules [35]. This
disposition in 9 ¥ CH2Cl2 could be explained by the presence of the terminal phenyl
group at the pyrazolato substituents, which must be responsible for the generation of a
higher intermolecular separation.
Thus, we established that the intermolecular separation in the columns is the main
difference of the structural features of 9 ¥ CH2Cl2 as compared to other complexes also

Helvetica Chimica Acta Vol. 87 (2004)
259
Fig. 6. Molecular packing of 9 ¥ CH2Cl2 through the b axis. The terminal benzene rings of the pyrazolato ligands
have been omitted for clarity.
containing phenyl substituents at the pyrazolato ligands [9][12]. Therefore, columnar
arrangements with shorter intermolecular separation should not be excluded as
potential structures for the trimers with other (alkyloxy)phenyl substituents than the
phenoxyphenyl groups.
Conclusions.
In this work, we showed that the coordination of different 3-
substituted or 3,5-disubstituted pyrazolato ligands to gold or silver centers does not
modify the formation of trinuclear cyclic complexes. As expected the 3,5-disubstituted
pyrazolato complexes gave rise to a sole isomer consistent with a D3h symmetry. By
contrast, the 3-substituted pyrazolato derivatives yielded an Ag-symmetric or Au-
asymmetric isomer. Of all investigated complexes, only those containing 3-[4-
(dodecyloxy)phenyl] substituents [M3(m-pzddp)3] (M ˆ Ag, Au) displayed mesomorphic
properties associated with the presence of columnar mesophases. This organization is
consistent with the columnar distribution of disc-like nonplanar trimers observed in the
X-ray structure of the Au derivative containing the 3,5-bis(4-phenoxyphenyl)pyrazo-

260
Helvetica Chimica Acta Vol. 87 (2004)
lato ligand, which, in turn, behaves as a non-mesogenic material due to the absence of
alkyl chains at the periphery.
On the other hand, although an increase in the number of alkyl chains at the
bridging pyrazolato ligand should give rise to a higher-occupied surface favoring the
disc-like structure, we found that, for the cyclic trinuclear compounds [M3(m-pz')3], the
presence of bridging 3-substituted pyrazolato ligands could be a sufficient requirement
to get mesomorphic properties when an adequate chain is selected. New complexes will
be prepared to assess these results.
We are grateful to the DGI/MCyT of Spain (Project No. PB98-0766) for financial support. We also thank
the Comunidad de Madrid for a postdoctoral fellowship to M. C. T.
Experimental Part
General. The starting Au-complex [AuCl(tht)] (tht ˆ tetrahydrothiophene) and the 3-substituted and 3,5-
disubstituted [(alkyloxy)phenyl]-1H-pyrazoles were prepared by procedures described in [24][25][27][29][36].
The 1,3-bis(4-phenoxyphenyl)propane-1,3-dione was also prepared by a known method [37]. All commercial
reagents were used as supplied. Phase studies: Olympus BX50 microscope equipped with a Linkam THMS-600
heating stage; temp. assignment on the basis of visual observations with polarized light. Differential scanning
calorimetry (DSC): Perkin-Elmer Pyris-1 calorimeter; sample (1 4 mg) hermetically sealed in aluminium pans;
heating or cooling rate of 5 108/min. IR Spectra: FT-IR Nicolet Magna-550 spectrophotometer; KBr discs;
4000 350 cmÀ1 region; in cmÀ1. 1H- and 13C{1H}-NMR Spectra: Varian VXR-300, Bruker DPX-300, or Bruker
AC-200 spectrophotometers; CDCl3 solns.; chemical shifts d in ppm rel. to SiMe4, with the signal of the
deuterated solvent as reference, J in Hz; d(H) and d(C) accurate to Æ 0.01 and Æ 0.1 ppm, respectively, J(H,H)
to Æ 0.3 Hz; atomic numbering as shown in 1 6. MS: VG AutoSpec spectrometer (FAB), or LC Squire
spectrometer (ESI); dry MeCN, CHCl3, or MeOH as solvents; in m/z. Elemental analyses (C, H, N) were
carried out by the Centre for Elemental Microanalysis of the Complutense University.
3,5-Bis(4-phenoxyphenyl)-1H-pyrazole ꢁHpzpp ; 3). To a suspension of 1,3-bis(4-phenoxyphenyl)propane-
2
1,3-dione (2 mmol) in EtOH (50 ml) was added an excess of hydrazine hydrate (2.2 mmol), and the mixture was
refluxed for 3 h. Then, the soln. was allowed to cool at r.t. and kept overnight at 48. The precipitated product was
filtered and dried in vacuo; 3 (ca. 75%). M.p. 1858. IR (KBr): 3225 (NH), 1588 (CN). 1H-NMR (CDCl3): 10.90
(br. s, NH); 7.67 (d, J ˆ 8.7, Ho); 7.36 (t, J ˆ 7.8, H m'); 7.13 (t, J ˆ 7.5, Hp'); 7.05 (d, J ˆ 8.6, Hm, Ho'); 6.74
(s, HÀC(4)). 13C-NMR (CDCl3): 157.4; 156.8; 148.3; 129.8; 127.1; 126.2; 123.6; 119.2; 118.8; 99.5. FAB-MS: 405
‡
([M ‡ H] ). Anal. calc. for C27H20N2O2: C 80.2, H 5.0, N 6.9; found: C 79.9, H 5.2, N 6.7.
Preparation of [M3(m-pz')3] (M ˆ Au, Ag) Complexes 7 18. To a soln. of the corresponding 1H-pyrazole
(26 mmol) in dry THF (25 ml) under N2 an excess 60% NaH was added. After a few minutes of stirring, AgNO3
or [AuCl(tht)] (26 mmol) was added. After 24 or 6 h for Ag or Au derivatives, resp., the formed solid was
filtered and washed with THF. The soln. was evaporated and the oily solid obtained recrystallized in CH2Cl2/
hexane.
cyclo-Tris{m-[3,5-bis(4-butoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trigold ([Au3(m-pzbp )3]; 7): M.p.: dec.
2
from 1608, complete melting at 2518. IR (KBr): 1612 (CN). 1H-NMR (CDCl3): 7.71 (d, J ˆ 7.8, H o); 6.76
(s, HÀC(4)); 6.65 (d, J ˆ 7.8, H m); 3.90 (t, J ˆ 6.3, CH2O); 1.78( quint., CH2); 1.51 (sext., CH2); 1.00 (t, J ˆ 7.3,
Me). Anal. calc. for C96H81Au3N6O6: C 48.7, H 4.8, N 4.9; found: C 49.0, H 4.9, N 5.0.
cyclo-Tris{m-{3,5-bis[4-(octyloxy)phenyl]-1H-pyrazolato-kN1 :kN2}}trigold ([Au3(m-pzop )3]; 8): M.p. 858.
2
IR (KBr): 1613 (CN). 1H-NMR (CDCl3): 7.74 (d, J ˆ 8.5, Ho); 6.84 (d, J ˆ 8.5, Hm); 6.68( s, HÀC(4)); 3.95
‡
(t, J ˆ 6.4, CH2O); 1.78( m, CH2); 1.6 1.2 (m, (CH2)5); 0.89 (t, J ˆ 6.7, Me). ESI-MS: 2018([Au 3pz3 ‡ H] ),
‡
1345 ([Au2pz2] ). Anal. calc. for C93H129Au3N6O6: C 55.4, H 6.4, N 4.2; found: C 55.6, H 6.5, N 4.2.
cyclo-Tris{m-[3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trigold ([Au3(m-pzpp )3]; 9): M.p. 2208
2
(dec.). IR (KBr): 1588 (CN). 1H-NMR (CDCl3): 7.71 (d, J ˆ 8.4, Ho); 7.31 (t, J ˆ 7.8, H m'); 7.10 (t, J ˆ 7.5, Hp');
‡
‡
7.03 (d, J ˆ 7.8, H o'); 6.78( s, HÀC(4)); 6.77 (d, J ˆ 8.4, Hm). FAB-MS: 1800 ([Au3pz3] ), 1397 ([Au3pz2] ), 1200
‡
([Au2pz2] ). Anal. calc. for C81H57Au3N6O6; C 54.0, H 3.2, N 4.7; found: C 53.8, H 3.2, N 4.7.
cyclo-Tris{m-[3,5-bis(4-butoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trisilver ([Ag3(m-pzbp )3]; 10): M.p. 2198.
2
IR (KBr): 1612 (CN). 1H-NMR (CDCl3): 7.53 (d, J ˆ 8.7, Ho); 6.67 (d, J ˆ 8.7, Hm); 6.59 (s, HÀC(4)); 3.86 (t, J ˆ
6.6, CH2O); 1.72 (quint., CH2); 1.48( sext., CH2); 0.98( t, J ˆ 7.3, Me). 13C-NMR (CDCl3): 158.9; 153.5; 127.4;

Helvetica Chimica Acta Vol. 87 (2004)
261
‡
‡
‡
127.3; 114.6; 100.0; 67.7; 31.4; 19.3; 14.0. FAB-MS: 1414 ([Ag3pz3] ), 1050 ([Ag3pz2] ), 944 ([Ag2pz2] ), 471
‡
([Agpz] ). Anal. calc. for C69H81Ag3N6O6: C 58.6, H 5.8, N 5.9; found: C 58.7, H 5.8, N 5.9.
cyclo-Tris{m-{3,5-bis[4-(octyloxy)phenyl]-1H-pyrazolato-kN1 :kN2}}trisilver ([Ag3(m-pzop )3]; 11): M.p. 80
2
1
1008 (onset at 938). IR (KBr): 1613 (CN). H-NMR (CDCl3): 7.57 (d, J ˆ 8.8, Ho); 6.68( d, J ˆ 8.8, Hm); 6.62
(s, HÀC(4)); 3.88 (t, J ˆ 6.6, CH2O); 1.76 (m, CH2); 1.6 1.2 (m, (CH2)5); 0.91 (t, J ˆ 6.8, Me). ESI-MS: 1750
‡
‡
‡
‡
([Ag3pz3] ), 1273 ([Ag3pz2] ), 1167 ([Ag2pz2] ), 692 ([Ag2pz] ). Anal. calc. for C93H129Ag3N6O6: C 63.8, H 7.4,
N 4.8; found: C 64.0, H 7.5, N 4.9.
cyclo-Tris{m-[3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trisilver ([Ag3(m-pzpp )3]; 12): M.p. 155
2
1
1808 (onset at 1648). IR (KBr): 1588 (CN). H-NMR (CDCl3): 7.61 (d, J ˆ 8.0, Ho); 7.33 (t, J ˆ 7.8, H m'); 7.13
(t, J ˆ 7.4, Hp'); 7.03 (d, J ˆ 7.8, H o'); 6.85 (d, J ˆ 8.1, Hm); 6.70 (s, HÀC(4)). 13C-NMR (CDCl3): 157.4; 156.5;
‡
‡
154.4; 128.8; 128.2; 127.7; 123.6; 119.5; 118.6; 101.0. FAB-MS: 1131 ([Ag3pz2] ), 1022 ([Ag2pz2] ), 510
‡
([Agpz] ). Anal. calc. for C81H57Ag3N6O6: C 63.4, H 3.8, N 5.5; found: C 63.1, H 3.6, N 5.4.
cyclo-Tris{m-[3-(4-butoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trigold ([Au3(m-pzbp)3]; 13): IR (KBr): 1612
(CN). 1H-NMR (CDCl3): 7.91 (d, J ˆ 8.8, Ho); 7.63 (d, J ˆ 8.5, Ho); 7.44 (d, J ˆ 2.3, HÀC(5)); 7.33 (d, J ˆ 2.3,
HÀC(5)); 6.96 (d, J ˆ 8.8, Hm); 6.63 (d, J ˆ 8.5, Hm); 6.61 (d, J ˆ 2.3, HÀC(4)); 6.56 (d, J ˆ 2.3, HÀC(4)); 6.54
(d, J ˆ 2.0, HÀC(4)); 4.02 (t, J ˆ 6.5, CH2O); 3.90 (t, J ˆ 6.5, CH2O); 1.78( m, CH2); 1.55 (m, CH2); 1.00 (t, J ˆ
‡
7.3, Me). ESI-MS: 1236 ([Au3pz3] ). Anal. calc. for C39H45Au3N6O3: C 37.9, H 3.7, N 6.8; found: C 38.1, H 3.7, N
6.8.
cyclo-Tris{m-{3-[4-(dodecyloxy)phenyl]-1H-pyrazolato-kN1 :kN2}}trigold ([Au3(m-pzddp)3]; 14): M.p. 1038.
1
IR (KBr): 1609 (CN). H-NMR (CDCl3): 7.88 (d, J ˆ 8.8, Ho); 7.57 (d, J ˆ 8.5, Ho); 7.28( d, J ˆ 2.2, HÀC(5));
7.18( d, J ˆ 2.4, HÀC(5)); 6.90 (d, J ˆ 8.8, Hm); 6.58( d, J ˆ 8.5, Hm); 6.48( d, J ˆ 2.2, HÀC(4)); 6.44 (d, J ˆ 2.2,
HÀC(4)); 6.43 (d, J ˆ 2.2, HÀC(4)); 4.00 (t, J ˆ 6.3, CH2O); 3.88 (t, J ˆ 6.1, CH2O); 1.80 (m, CH2); 1.6 1.2
‡
(m, (CH2)9); 0.89 (t, J ˆ 6.6, Me). ESI-MS: 1572 ([Au3pz3] ). Anal. calc. for C63H93Au3N6O3: C 48.1, H 6.0, N
5.3; found: C 48.1, H 5.8, N 5.4.
cyclo-Tris{m-{3-[4-(octadecyloxy)phenyl]-1H-pyrazolato-kN1 :kN2}}trigold ([Au3(m-pzodp)3]; 15): M.p. 87
1
928 (dec.). IR (KBr): 1613 (CN). H-NMR (CDCl3): 7.91 (d, J ˆ 8.5, Ho); 7.62 (d, J ˆ 8.8, Ho); 7.42 (d, J ˆ 2.0,
HÀC(5)); 7.41 (d, J ˆ 2.2, HÀC(5)); 7.31 (d, J ˆ 2.4, HÀC(5)); 6.94 (d, J ˆ 8.8, Hm); 6.62 (d, J ˆ 8.5, Hm); 6.59
(d, J ˆ 2.4, HÀC(4)); 6.54 (d, J ˆ 2.2, HÀC(4)); 6.53 (d, J ˆ 2.0, HÀC(4)); 4.01 (t, J ˆ 6.6, CH2O), 3.89 (t, J ˆ
‡
6.8, CH2O); 1.79 (m, CH2); 1.6 1.2 (m, (CH2)15); 0.88 (t, J ˆ 6.1, Me). ESI-MS: 1825 ([Au3pz3 ‡ H] ), 1216
‡
([Au2pz2] ). Anal. calc. for C81H129Au3N6O3: C 53.3, H 7.1, N 4.6; found: C 53.1, H 7.0, N 4.6.
cyclo-Tris{m-[3-(4-butoxyphenyl)-1H-pyrazolato-kN1 :kN2]}trisilver ([Ag3(m-pzbp)3]; 16): M.p. 1628. IR
(KBr): 1613 (CN). 1H-NMR (CDCl3): 7.59 (d, J ˆ 8.5, Ho); 7.50 (d, J ˆ 2.0, HÀC(5)); 6.81 (d, J ˆ 8.3, Hm); 6.50
(d, J ˆ 2.0, HÀC(4)); 3.96 (t, J ˆ 6.3, CH2O); 1.80 (quint., CH2); 1.54 (m, CH2); 1.01 (t, J ˆ 7.3, Me). ESI-MS:
‡
‡
970 ([Ag3pz3] ), 755 ([Ag3pz2] ). Anal. calc. for C39H45Ag3N6O3: C 48.3, H 4.7, N 8.7; found: C 48.5, H 4.5, N
8.5.
cyclo-Tris{m-{3-[4-(dodecyloxy)phenyl]-1H-pyrazolato-kN1 :kN2}}trisilver ([Ag3(m-pzddp)3]; 17): M.p. 1258.
1
IR (KBr): 1612 (CN). H-NMR (CDCl3): 7.59 (d, J ˆ 8.3, Ho); 7.51 (d, J ˆ 1.8, HÀC(5)); 6.78( d, J ˆ 8.3, Hm);
6.50 (d, J ˆ 2.0, HÀC(4)); 3.94 (t, J ˆ 6.3, CH2O); 1.80 (m, CH2); 1.6 1.2 (m, (CH2)15); 0.88 (t, J ˆ 6.5, Me).
‡
ESI-MS: 1306 ([Ag3pz3] ). Anal. calc. for C63H93Ag3N6O3: C 57.9, H 7.2, N 6.4; found: C 58.0, H 7.1, N 6.3.
cyclo-Tris{m-{3-[4-(octadecycloxy)phenyl}-1H-pyrazolato-kN1 :kN2}}trisilver ([Ag3(m-pzodp)3]; 18): M.p.
1088 (dec.). IR (KBr): 1611 (CN). 1H-NMR (CDCl3): 7.48( d, J ˆ 8.3, Ho); 7.32 (d, J ˆ 1.8, HÀC(5)); 6.73
(d, J ˆ 8.3, Hm); 6.39 (d, J ˆ 2.0, HÀC(4)); 3.91 (t, J ˆ 6.6, CH2O); 1.80 (m, CH2); 1.6 1.2 (m, (CH2)9); 0.89
‡
‡
(t, J ˆ 6.9, Me). ESI-MS: 1147 ([Ag3pz2] ), 519 ([Agpz] ). Anal. calc. for C81H129Ag3N6O3: C 62.4, H 8.3, N 5.4;
found: C 62.0, H 8.3, N 5.4.
2.3. X-Ray Structure Determination. Colorless prismatic single crystals of Hpzpp (3) were obtained by
layering CH2Cl2 solns. with Et2O. Light yellow crystals of [Au3(m-pzpp )3] ¥ CH2Cl2 (9 ¥ CH2Cl2) were obtained by
2
2
layering CH2Cl2 solns. with hexane. The data were collected on a Smart Bruker CCD diffractometers. For data,
see Table 3.
The structures were solved by direct methods and conventional Fourier techniques and refined by full-
matrix least-squares treatment on F2 [38]. Final mixed refinements were performed for the two compounds with
the following differences. For 3, all non-H-atoms were refined anisotropically. H-Atoms were calculated and
refined as riding on the C-bonded atom, except for HÀN(2) bonded to N(2), which was found as the first peak in
a Fourier difference, included, and its coordinates fixed. The largest residual peak in the final difference map was
0.19 eäÀ3
.
Many attempts were made to obtain crystals of the trimetallic compounds of good quality. However only
light yellow crystals of [Au3(m-pzpp )3] ¥ CH2Cl2 (9 ¥ CH2Cl2) could be obtained but of poor quality. In spite of this,
2

262
Helvetica Chimica Acta Vol. 87 (2004)
Table 3. Crystal and Refinement Data for Hpzpp (3) and [Au3(m-pzpp )3] ¥ Ch2Cl2 (9 ¥ CH2Cl2)
2
2
3
9
Formula
M
C27H20N2O2
404.45
C82H59Au3Cl2N6O6
1886.15
Crystal system
Space group
monoclinic
P21/c
triclinic
P(-1)
a/ä
b/ä
c/ä
a/8
b/8
g/8
U/ä3
20.7353(5)
5.6467(1)
18.8420(5)
13.343(1)
15.207(1)
17.755(1)
97.996(1)
92.271(1)
106.484(1)
3408.9(4)
2
109.521(1)
2079.32(8)
4
Z
F(000)
Dc/g cmÀ3
848
1.292
1824
1.838
Temp./K
293(2)
173(2)
m(Mo-Ka)/mmÀ1
Crystal size/mm
Scan technique
Data collected
q/8
0.082
6.580
0.21 Â 0.21 Â 0.080.36
 0.10  0.06
q and w
q and w
(À 24, À 6,0) to (23,0,22)
2.08 25.03
3662
3662
3662, 0, 281
1.025
0.047 (3662 refls.)
0.137
0.194
(À 15, À 13, À 20) to (14,18,21)
2.71 25.00
14673
11054 (Rint ˆ 0.1819)
11054, 0, 412
1.030
0.084 (7502 refls.)
0.242
4.164
Refls. collected
Unique refls.
Data, restraints, parameters
G.o.f ( F2)
R(F) [(F2) > 2s(F2)]a)
wR(F2) (all data)b)
Largest residual peak/e äÀ3
b
a) S[jFo j À jFc j]/S j Fo j . ) {S[w(Fo2 À Fc2)2]/S[w(Fo2)2]}1 /2
we considered it of interest to solve the structure to know the nuclearity degree and the molecular packing.
Therefore, data collection and refinement of different crystals were carried out, at r.t. or at 173 K, obtaining
better agreement factors at low temp. The different attempts carried out to solve the structure at r.t. gave rise to
data decay. The weak H-bonding interaction between the CH2Cl2 molecule and a C-atom of one phenyl group
observed could explain the decomposition observed at r.t. The compound crystallized in the triclinic system, and
≈
then the refinement was carried out in the centric (P1) and acentric (P1) space groups. The acentric model led to
poorer agreement factors, and, therefore, we proposed a structural model in the centric space group. The Au-
atoms were refined anisotropically, while the remaining non-H-atoms were refined only isotropically because
some thermal factors became negative. The H-atoms were calculated and refined as riding on the C-bonded
atom with a common isotropic displacement parameter. All of these problems are reflected in the high R factors.
The largest residual peaks in the final difference map were located in the vicinity of one Au-atom.
Supplementary crystallographic data have been deposited with the Cambridge Crystallographic Data
Centre (CCDC deposition numbers 210429 and 210430 for 3 and 9, resp.). These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data
Center, 12 Union Road, Cambridge CB2 EZ, UK; fax: ‡441223336033; e-mail: deposit@ccdc.cam.ac.uk).
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Received August 5,2003