Reactivity of bis(pyrazol-1-yl)methanes functionalized by 2-hydroxyphenyl and 2-methoxyphenyl on the methine carbon atom with W(CO)5THF

Article abstract of DOI:10.1016/j.jorganchem.2011.08.023

Reactions of 2-hydroxyphenyl and 2-methoxyphenylbis(pyrazol-1-yl)methanes as well as 2-hydroxyphenyl and 2-methoxyphenylbis(3,5-dimethylpyrazol-1-yl) methanes with W(CO)₅THF have been carried out. Heating 2-hydroxyphenylbis(pyrazol-1-yl)methane (L¹) with W(CO) ₅THF in THF at reflux yielded complex (L¹)W(CO) ₄.L¹, while similar reaction of 2-hydroxyphenylbis(3,5- dimethylpyrazol-1-yl)methane (L²) with W(CO)₅THF resulted in the cleavage of a C_sp3-N bond to generate 1,2-bis(2-hydroxyphenyl) -1,2-bis(3,5-dimethylpyrazol-1-yl)ethane (L) and pyrazole derivative W(CO) ₅(3,5-Me₂PzH) (Pz = pyrazol-1-yl). These two fragments were connected together through strong O...H-N and O-H...N hydrogen bonds to form complex L.[W(CO)₅(3,5-Me₂PzH)]₂. The analogous results were observed in the treatment of 2-methoxyphenylbis(pyrazol- 1-yl)methane (L³) with W(CO)₅THF, which gave product L′.[W(CO)₅(PzH)]₂ (L′ = 1,2-bis(2- methoxyphenyl)-1,2-bis(pyrazol-1-yl)ethane) as well as certain amount of complex (L³)W(CO)₄. In addition, during the reaction of 2-methoxyphenylbis(3,5-dimethylpyrazol-1-yl)methane (L⁴) with W(CO)₅THF, partial decomposition reactions took place to yield complexes (L⁴)W(CO)₄ and W(CO)₅(3,5-Me ₂PzH), but no hydrogen bond was found between these two moieties.

Full text of DOI:10.1016/j.jorganchem.2011.08.023

Journal of Organometallic Chemistry 696 (2011) 3662e3667
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Reactivity of bis(pyrazol-1-yl)methanes functionalized by 2-hydroxyphenyl and
2-methoxyphenyl on the methine carbon atom with W(CO)5THF
*
Ke Ding, Cai-Hong Cheng, Yan-Xin Yang, Hai-Bin Song, Liang-Fu Tang
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 2-hydroxyphenyl and 2-methoxyphenylbis(pyrazol-1-yl)methanes as well as 2-
hydroxyphenyl and 2-methoxyphenylbis(3,5-dimethylpyrazol-1-yl)methanes with W(CO)5THF have
been carried out. Heating 2-hydroxyphenylbis(pyrazol-1-yl)methane (L1) with W(CO)5THF in THF at
reflux yielded complex (L1)W(CO)4.L1, while similar reaction of 2-hydroxyphenylbis(3,5-
dimethylpyrazol-1-yl)methane (L2) with W(CO)5THF resulted in the cleavage of a Csp3-N bond to
generate 1,2-bis(2-hydroxyphenyl)-1,2-bis(3,5-dimethylpyrazol-1-yl)ethane (L) and pyrazole derivative
W(CO)5(3,5-Me2PzH) (Pz ¼ pyrazol-1-yl). These two fragments were connected together through strong
O.HeN and OeH.N hydrogen bonds to form complex L.[W(CO)5(3,5-Me2PzH)]2. The analogous results
were observed in the treatment of 2-methoxyphenylbis(pyrazol-1-yl)methane (L3) with W(CO)5THF,
which gave product L0.[W(CO)5(PzH)]2 (L0 ¼ 1,2-bis(2-methoxyphenyl)-1,2-bis(pyrazol-1-yl)ethane) as
well as certain amount of complex (L3)W(CO)4. In addition, during the reaction of 2-
methoxyphenylbis(3,5-dimethylpyrazol-1-yl)methane (L4) with W(CO)5THF, partial decomposition
reactions took place to yield complexes (L4)W(CO)4 and W(CO)5(3,5-Me2PzH), but no hydrogen bond was
found between these two moieties.
Received 1 June 2011
Received in revised form
2 August 2011
Accepted 18 August 2011
Keywords:
Bis(pyrazol-1-yl)methane
Heteroscorpionate ligand
Carbonyl tungsten
Crystal structure
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
metal atoms and reaction conditions. Our recent investigations
showed thatfunctionalizedbis(pyrazol-1-yl)methanes bytheorganic
The modification of bis(pyrazol-1-yl)methanes by organic func-
tional groups on the bridgehead carbon atom to form novel hetero-
scorpionate ligands is currently drawing extensive attention [1e3].
The catalyzed Peterson rearrangement [4e6] starting from
substituted pyrazoles and aldehydes, as well as reactions of bis(pyr-
azol-1-yl)methide anion [7] with various electrophilic reagents, has
been exploited to synthesize these heteroscorpionate ligands. Lots of
nitrogen-, oxygen- and sulfur-functionalized bis(pyrazol-1-yl)meth-
anes have been obtained using these two methods. These intriguing
heteroscorpionate ligands usually have N2N0 [8e10], N2O [7,11e16]
and N2S [17e21] coordination environments, which render them
the potential to form novel complexes with various main group and
transition metals, so they have been widely applied in bioinorganic,
coordination chemistry and organometallic fields. For example, the
coordination behavior and reactivity of the phenol-substituted bis(-
pyrazol-1-yl)methanes have been extensively investigated [11,12],
they were found to be good donors to transition metals as bidentate
[11,14,22e25] or tridentate ligands [12,22,26e29], depending on the
groups on the methine carbon atom provided unusual reactivity
[20,21,29,30]. For instance, the reaction of Ph3SnCH(3,5-Me2Pz)2
(Pz ¼ pyrazol-1-yl) with W(CO)5THF resulted in the oxidative addi-
tion reaction of the Sn-Csp3 bond to the tungsten(0) atom to yield
novel four-membered metallacyclic complexes [30], while the anal-
ogous reaction of Ph2(I)SnCH(3,5-Me2Pz)2 led to the oxidative addi-
tion of the relatively electrophilic SneI bond to the tungsten(0) atom
to form five-membered metallacyclic complexes [31]. These results
encourage us to explore the relative reactivity of other bis(pyrazol-1-
yl)methanes substituted on the bridgehead carbon atom with
carbonyl tungsten derivatives. Herein, we report the reaction of 2-
hydroxyphenyl- and 2-methoxyphenyl-substituted bis(pyrazol-1-
yl)methanes with W(CO)5THF.
2. Results and discussion
2.1. Reaction of 2-hydroxyphenylbis(pyrazol-1-yl)methanes with
W(CO)5THF
Reaction of (2-hydroxyphenyl)bis(pyrazol-1-yl)methane (L1)
* Corresponding author. Fax: þ86 22 23502458.
E-mail address: lftang@nankai.edu.cn (L.-F. Tang).
with W(CO)5THF in THF at reflux gave complex (L1)W(CO)4.L1 (1) in
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.08.023

K. Ding et al. / Journal of Organometallic Chemistry 696 (2011) 3662e3667
3663
Fig. 2. The dimeric structure of 1 through hydrogen bonds. O(5)eH.N(6A) 1.973 and
O(6A)eH.N(7B) 1.895 Å. Symmetric code: A ¼ 1ꢀx, 1ꢀy, 1ꢀz; B ¼ 2ꢀx, 1ꢀy, ꢀz.
cleavage of
W(CO)5(3,5-Me2PzH) (Pz
a
C
sp3-N bond of L2 yields pyrazole derivative
pyrazol-1-yl) and 1,2-bis(2-
¼
Scheme 1. Reaction of (2-hydroxyphenyl)bis(pyrazol-1-yl)methanes with W(CO)5THF.
hydroxyphenyl)-1,2-bis(3,5-dimethylpyrazol-1-yl)ethane, which
are linked together through strong O.HeN and OeH.N hydrogen
bonds to form complex 2 in a yield of 47%. This structure is
confirmed by X-ray crystal structural analyses, and presented in
Fig. 3. The hydrogen bond O(6)eH.N(4) and N(2)eH.O(6)
distances are 1.790 and 2.124 Å, respectively. The WeN bond
distance is 2.244(3) Å, comparable to the average WeN bond
distance (2.234 Å) in complex 1.
Complex 2 has been further characterized by IR and NMR
spectroscopy. The characteristic OH and NH absorption peaks are
clearly visible at 3268 and 3160 cmꢀ1, respectively. A nCO band is
observed at 2071 cmꢀ1, which is the same value as the known
pyrazole derivative W(CO)5(3,5-Me2PzH) (6) (Scheme 2) [33]. The
13C NMR spectrum shows two carbonyl carbon signals with a ca. 1:4
intensity ratio, consistent with the W(CO)5 fragment. It is worth
noting that the proton signal of the CH group (6.14 ppm) appears in
downfield region. Some weak hydrogen bond interactions, such as
C(16)eH.O(6A) (2.58(3) Å) and C(16)eH.N(4A) (2.667(3) Å),
possibly lead to the deshielding to this proton.
a yield of 48% (Scheme 1). The reaction was incomplete even
though the reaction time was prolonged to 24 h, possibly since the
hydrogen bond interactions between (L1)W(CO)4 and L1 prevent
the further reaction of L1 with W(CO)5THF. The structure of
complex 1 has been confirmed by X-ray crystal structural analyses.
The molecular structure of complex 1 is presented in Fig. 1, which
contains two ligands. One of them coordinates to the tungsten
atom, while the other is free. These two moieties are linked
together through the strong OeH.N hydrogen bonds in the crystal
packing (Fig. 2) and formed a dimeric structure. The hydrogen bond
O(5)eH.N(6A) and O(6A)eH.N(7B) distances are 1.973 and
1.895 Å, respectively.
The IR and NMR spectra of complex 1 also support the suggested
structure. The IR spectrum displays four bands in the carbonyl
stretching region, implying a typical cis-tetracarbonyl arrangement
[32]. Two sets of proton signals of equal intensities are observed in
its 1H NMR spectrum, attributed to the coordinated and uncoor-
dinated ligands. At the same time, the 13C NMR spectrum of this
complex contains two sets of carbon signals corresponding to L1.
To investigate the effect of the substituents on the pyrazole ring
on the reaction, the reaction of (2-hydroxyphenyl)bis(3,5-
dimethylpyrazol-1-yl)methane (L2) with W(CO)5THF has been
carried out under the same conditions as the reaction of L1. It is
surprising that a markedly different reaction takes place. The
2.2. Reaction of 2-methoxyphenylbis(pyrazol-1-yl)methanes with
W(CO)5THF
Heating 2-methoxyphenylbis(pyrazol-1-yl)methane (L3) or 2-
methoxyphenylbis(3,5-dimethylpyrazol-1-yl)methane (L4) with
W(CO)5THF in THF at reflux resulted in partial decomposition of
these two ligands to give complexes 3e6, in yields of 20% for 3 and
15% for 4 as well as 26% for 5 and 25% for 6, respectively (Scheme 2).
Fig. 1. The molecular structure of 1. The thermal ellipsoids are drawn at the 30%
probability level. The solvent molecule is omitted for clarity. Selected bond distances
(Å) and angles (ꢁ): W(1)eN(1) 2.229(5), W(1)-N(4) 2.249(6), C(11)-N(2) 1.457(8),
C(11)-N(3) 1.476(8), C(11)eC(12) 1.533(10), C(24)-N(5) 1.443(9), C(24)-N(8) 1.473(8) Å;
C(1)-W(1)-C(4) 171.1(3), N(1)-W(1)-N(4) 79.4(2), W(1)eC(1)eO(1) 169.5(5), W(1)-
C(2)-O(2) 179.2(8), W(1)-C(3)-O(3) 178.1(6), W(1)-C(4)-O(4) 174.0(7), N(2)eC(11)-
N(3) 110.9(5), N(3)eC(11)eC(12) 112.2(6), N(5)-C(24)-N(8) 108.1(5)ꢁ.
Fig. 3. The molecular structure of 2. The thermal ellipsoids are drawn at the 30%
probability level. Selected bond distances (Å) and angles (ꢁ): W(1)eN(1) 2.244(3),
C(16)-N(3) 1.458(4), C(16)eC(16A) 1.557(6), C(16)eC(17) 1.518(4), O(6)eH.N(4) 1.790,
N(2)eH.O(6) 2.124 Å; W(1)eC(1)eO(1) 176.1(3), W(1)eC(4)eO(4) 174.8(3), C(2)e
W(1)eC(5) 178.85(13), C(1)eW(1)eC(4) 173.89(12), C(3)eW(1)eN(1) 177.49(10),
C(1)eW(1)eC(2) 87.77(12), C(2)eW(1)eN(1) 91.42(13), N(3)eC(16)eC(17) 113.0(2),
C(17)eC(16)eC(16A) 113.1(3)ꢁ. Symmetric code: A ¼ 1ꢀx, 1ꢀy, ꢀz.

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K. Ding et al. / Journal of Organometallic Chemistry 696 (2011) 3662e3667
Scheme 2. Reaction of (2-methoxyphenyl)bis(pyrazol-1-yl)methanes with W(CO)5THF.
Fig. 4. The molecular structure of 4A. The thermal ellipsoids are drawn at the 30%
probability level. Selected bond distances (Å) and angles (ꢁ): W(1)eN(1) 2.244(2),
W(1)eN(4) 2.240(2), C(11)eN(2) 1.467(3), C(11)eN(3) 1.460(3), C(11)eC(12) 1.508(3)
Å; W(1)eC(1)eO(1) 173.0(2), W(1)eC(2)eO(2) 177.8(3), W(1)eC(3)eO(3) 179.5(2),
W(1)eC(4)eO(4) 172.2(2), C(1)eW(1)eC(4) 168.4(1), N(1)eW(1)eN(4) 78.03(7),
N(3)eC(11)eC(12) 114.0(2), N(2)eC(11)-N(3) 109.9(2)ꢁ.
Some analogous spectroscopic features are observed in both
complexes 3 and 2. For example, the IR spectrum of complex 3
similarly shows a nCO absorption at 2072 cmꢀ1, corresponding to the
A1eq mode for the pseudo C4v metal center in a metal pentacarbonyl
moiety [34]. This value is very close to that in complex 2. Further-
more, the 1H and 13C NMR spectra of these complexes display two
sets of proton and carbon signals attributed to the pyrazole ring. In
addition, the proton signal of the CH group (8.32 ppm) in complex 3
appears in an unusually downfield region, like that in complex 2.
These data illustrate that these two complexes should have similar
structural frameworks.
Complexes 4 and 5 have been characterized by NMR spectros-
copy. Complex 4 shows a set of proton signal as well as carbon
signal corresponding to L3 in CDCl3, and the chemical shifts are
close to those of the free L3. However, two sets of such signals are
observed in DMSO-d6, indicating the presence of isomers (Scheme
3). The assignment of isomers was done with the help of NOESY,
HBQC or HMQC spectra in DMSO-d6. The NOE between Ha and H5 is
observed in isomer 4B, reflecting that the o-methoxyphenyl group
locates on the axial position of the metallacyle [14]. In contrast to
complex 4, complex 5 displays only one set of proton as well as
carbon signals corresponding to L4 both in the CDCl3 and DMSO-d6
solutions. The NOE between Ha and Me5 in complex 5 (see Scheme
3) has been observed in CDCl3. Moreover, a proton of the phenyl
group markedly shifts upfield (6.03 ppm in CDCl3 and 5.89 ppm in
DMSO-d6), compared with that of the free L4. A similar result is
found in isomer 4B, in which the corresponding signal appears at
6.28 ppm in DMSO-d6. The upfield shift of this proton should be
attributed to the shielding effect of one pyrazole ring, disclosed by
the X-ray crystal structural analyses of complex 5 (see Fig. 5), which
reveals that the proton on the 2-postion atom of the phenyl group is
situated over the N(2)eN(1)-C(6)-C(7)-C(8) pyrazolyl plane.
Although the interconversion between the axial isomer and the
equatorial isomer is possible in solution, complex 4 should adopt
the sole equatorial conformer 4A in CDCl3, judged by the fact that
Fig. 5. The molecular structure of 5. The thermal ellipsoids are drawn at the 30%
probability level. Selected bond distances (Å) and angles (ꢁ): W(1)eN(1) 2.273(5),
W(1)eN(4) 2.267(4), C(15)eN(2) 1.459(6), C(15)eN(3) 1.436(7), C(15)eC(16) 1.503(7)
Å; W(1)eC(1)eO(1) 167.1(5), W(1)-C(2)eO(2) 178.8(5), W(1)eC(3)eO(3) 178.2(5),
W(1)eC(4)eO(4) 172.1(5), C(1)eW(1)eC(4) 167.1(2), N(1)eW(1)eN(4) 81.0(2), N(3)e
C(15)eC(16) 117.2(4), N(2)eC(15)eC(16) 112.6(4), N(2)eC(15)eN(3) 109.6(4)ꢁ.
Scheme 3. Interconversion of the isomers of complexes 4 and 5 in solution.

K. Ding et al. / Journal of Organometallic Chemistry 696 (2011) 3662e3667
3665
no proton signal is observed for isomer 4A in the region markedly
upfield relative to the phenyl group like those in isomer 4B and
complex 5. However, the interconversion is observed in DMSO-d6.
Taking into accounts the generally accepted knowledge of DMSO as
a typical kind of coordination solvent, this observation is under-
standable and the interconversion can be explained by a plausible
pathway through the partial dissociation of the nitrogen ligand and
succedent association process (see Scheme 3) [14]. In addition, the
o-methoxyphenyl group in complex 5 is considered to situate on
the axial position of the boat conformation in solution based on the
absence of one downfield proton signal of the phenyl group like
that in isomer 4A. The large steric repulsion in the equatorial
isomer of complex 5, between the o-methoxyphenyl group with the
methyl group in the 5-position of pyrazole ring, maybe prevents the
interconversion of the axial isomer to the equatorial isomer.
The structures of isomer 4A and complex 5 have been confirmed
by X-ray crystal structural analyses, and presented in Figs. 4 and 5,
respectively. L3 and L4 act as N,N-bidentate chelating ligands in
these two complexes, and the tungsten atom adopts a distorted
octahedral coordination geometry, like that in complex 1.
Complexes 1, 4A and 5 share some similar structural parameters,
such as similar bite angle NeWeN of 79.4(2)o in complex 1,
78.03(7)o in complex 4A and 81.0(2)o in complex 5, respectively.
The average WeN bond distance of complex 4A is 2.242 Å, similar
with that in complex 1 (2.239 Å), but slightly shorter than that in
complex 5 (2.271 Å). Two cis-carbonyls in these three complexes
significantly deviate from linearity owing to the steric repulsion
between the ligand and these carbonyls. Moreover, the angle of
W(1)eC(1)eO(1) in complex 5 is 167.1(5)o, considerably smaller
than the corresponding angles in complexes 1 (169.5(5)o) and 4A
(173.0(2)o), reflecting the presence of the larger steric repulsion in
complex 5 compared with complexes 1 and 4A, possibly led by the
2-methoxyphenyl group located on the axial position of the boat
conformation. A significant structural difference is observed in
these three complexes. The aryl groups on the bridgehead carbon
atom in complexes 1 and 4A occupy the equatorial position,
whereas the axial position is favored in complex 5 to avoid the
steric repulsion between the o-methoxyphenyl group with the
methyl group in the 5-position of pyrazole ring.
Scheme 4. Possible reaction pathways of L1eL4 with W(CO)5THF.
In conclusion, reactions of bis(pyrazol-1-yl)methanes function-
alized by 2-hydroxyphenyl and 2-methoxyphenyl on the bridge-
head carbon atom with W(CO)5THF have been carried out. Some
interesting results are obtained. The cleavage of a Csp3eN bond in
these reactions is observed, and the O.HeN and OeH.N
hydrogen bonds play an important role in the formation of the final
products.
3. Experimental
All reactions were carried out under an atmosphere of argon.
Solvents were dried and distilled prior to use according to standard
procedures. NMR (1H and 13C) were recorded on a Bruker 400
spectrometer, and the chemical shifts were reported in ppm with
respect to the reference (internal SiMe4 for 1H and 13C NMR
spectra). These assignments were confirmed by standard Bruker
gradient enhanced HMBC, HMQC and NOE pulse sequences. IR
spectra were recorded as KBr pellets on a Nicolet 380 spectrometer.
Element analyses were carried out on an Elementar Vairo EL
analyzer. (2-Hydroxyphenyl)bis(pyrazol-1-yl)methane (L1) [11],
(2-Hydroxyphenyl)bis(3,5-dimethylpyrazol-1-yl)methane (L2) [11],
(2-methoxyphenyl)bis(pyrazol-1-yl)methane (L3) [13] and (2-
methoxyphenyl)bis(3,5-dimethylpyrazol-1-yl)methane (L4) [13]
were prepared according to the literature methods.
2.3. Possible formation pathway of complexes 2 and 3
Reaction of bis(pyrazol-1-yl)methanes with the main group or
transition metals leading to the cleavage of the Csp3-N bond has
been observed previously [22,35,36]. The pyrolysis of bis(pyrazol-
1-yl)methanes has been reported, and a radical mechanism was
suggested to explain the formation of the corresponding pyrazole
derivatives [37]. Based on these results and other known facts,
plausible reaction pathways of L1-L4 with W(CO)5THF are depicted
in Scheme 4. At first, the THF ligand in W(CO)5THF is replaced by
one pyrazole to give intermediate A. This intermediate faces two
possible reaction pathways in succedent reactions. Complex 4 or 5
is obtained when the other pyrazole substitutes one carbonyl group
of intermediate A. The alternative route is the cleavage of a Csp3eN
bond to generate radicals B and C. Radical C absorbs one hydrogen
atom from the solvent or other species to yield complex E, while
radical B dimerizes to give intermediate D. Complex 2 or 3 is
formed through the hydrogen bond interactions of intermediate D
with complex E. Although the cleavage of a Csp3-N bond was
observed in the reaction of L4 with W(CO)5THF, no corresponding
dimeric complex analogous to 2 or 3 was isolated, which should be
attributed to the decreasing of hydrogen bond interactions like
those in 2 or 3 by the methyl groups of the pyrazole ring and
methoxyl group.
3.1. Reaction of L1 with W(CO)5THF
L1 (0.12 g, 0.5 mmol) was added to a solution of W(CO)5THF in
THF, prepared in situ by the irradiation of a solution of W(CO)6 (0.18,
0.5 mmol) in THF (50 ml) for 8 h, and the mixture was stirred and
heated at reflux for 10 h. Then the solvent was removed under
a reduced pressure, and the residual solid was purified by column
chromatography on silica using ethyl acetate/hexane (2/1 v/v) as
eluent. The eluate was concentrated to dryness and the residual
solid was recrystallized from CH2Cl2/hexane to give yellow crystals
of 1. Yield: 95 mg (48% calculated from ligand). 1H NMR (DMSO-d6):

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K. Ding et al. / Journal of Organometallic Chemistry 696 (2011) 3662e3667
d
6.30 (t, J ¼ 2.0 Hz, 2H, H4 of uncoordinated pyrazole), 7.55 (d,
cmꢀ1): nOH ¼ 3268 (m, br), nNH ¼ 3160 (w), nCO ¼ 2071 (m), 1987 (s),
1954 (sh), 1922 (vs), 1878 (vs). Anal. Calc. for C44H42N8O12W2: C,
42.53; H, 3.41; N, 9.02. Found: C, 42.17; H, 3.85; N, 9.32%.
J ¼ 1.6 Hz, 2H, H3 of uncoordinated pyrazole), 7.65 (d, J ¼ 2.4 Hz, 2H,
H5 of uncoordinated pyrazole), 7.94 (s, 1H, CH of uncoordinated L1),
6.77e6.90, 7.20e7.30 (m, m, 6H, 2H, C6H4), 6.56 (t, J ¼ 2.4 Hz, H4 of
pyrazole coordinated to the tungsten atom), 8.07 (d, J ¼ 2.0 Hz, 2H,
H3 of pyrazole coordinated to the tungsten atom), 8.20 (s, br, 2H, H5
of pyrazole coordinated to the tungsten atom), 8.39 (s, 1H, CH of L1
coordinated to the tungsten atom), 10.10, 10.23 (s, br, s, br, 1H, 1H,
3.3. Reaction of L3 with W(CO)5THF
This reaction was similarly carried out as above-mentioned for
the reaction of L1 with W(CO)5THF while L3 was used instead of L1.
The solvent was removed under a reduced pressure, the residual
solid was purified by column chromatography on silica using ethyl
acetate/hexane (2/3 v/v) as eluent to yield complex 3. After
complex 3 was isolated, ethyl acetate/hexane (2/1 v/v) was used
subsequently as eluent to give complex 4. After removing the
solvents, the solids were crystallized from CH2Cl2/hexane to give
yellow crystals of 3 and 4, respectively.
OH). 13C NMR (DMSO-d6): 72.3 (CH of uncoordinated L1), 105.7 (C4
d
of uncoordinated L1), 129.8 (C5 of uncoordinated L1), 139.8 (C3 of
uncoordinated L1), 72.9 (CH of L1 coordinated to the tungsten
atom),107.3 (C4 of L1 coordinated to the tungsten atom),135.7 (C5 of
L1 coordinated to the tungsten atom), 147.3 (C3 of L1 coordinated to
the tungsten atom), 115.4, 116.4, 117.9, 118.9, 119.5, 122.5, 127.7,
128.6, 130.4, 131.7, 154.6, 155.3 (C6H4), 202.9 (1 C), 203.1 (1 C), 212.1
(2 C) (CO). IR (cmꢀ1): nOH ¼ 3404 (s); nCO ¼ 2011 (s), 1869 (vs, br),
1823 (sh), 1777 (vs). Anal. Calc. for C30H24N8O6W: C, 46.41; H, 3.12;
N, 14.43. Found: C, 45.91; H, 3.35; N, 14.58%.
Data for complex 3: yield: 20%. 1H NMR (CDCl3):
d 3.82 (s, 3H,
OCH3), 6.37 (t, J ¼ 1.6 Hz, 1H, H4 of pyrazole coordinated to the
tungsten atom), 7.43, 7.66 (d, J ¼ 1.9 Hz, d, J ¼ 2.0 Hz, 1H, 1H, H3 and
H5 of pyrazole coordinated to the tungsten atom), 6.39 (t, J ¼ 2.4 Hz,
1H, H4 of uncoordinated pyrazole), 7.50 (d, J ¼ 2.7 Hz, 1H, H5 of
uncoordinated pyrazole), 8.04 (d, J ¼ 1.9 Hz, 1H, H3 of uncoordi-
nated pyrazole), 6.45 (d, J ¼ 7.5 Hz, 1H), 6.93e6.97 (m, 2H),
3.2. Reaction of L2 with W(CO)5THF
This reaction was carried out similarly as above-mentioned for
the reaction of L1 with W(CO)5THF while L2 was used instead of L1.
The eluent was ethyl acetate/hexane (2/3 v/v). After recrystalliza-
tion from CH2Cl2/hexane, yellow crystals of 2 were obtained. Yield:
7.41e7.45 (m, 1H, C6H4), 8.32 (s, 1H, CH). 13C NMR (CDCl3):
d 55.7
(OCH3), 74.0 (CH), 106.9 (C4 of pyrazole coordinated to the tungsten
atom), 131.7, 141.5 (C3 and C5 of pyrazole coordinated to the tung-
sten atom), 107.9 (C4 of uncoordinated pyrazole), 133.0 (C5 of
uncoordinated pyrazole), 149.4 (C3 of uncoordinated pyrazole),
111.2, 120.9, 123.4, 127.0, 129.7, 156.7 (C6H4), 197.7 (4 C), 201.4 (1 C)
(CO). IR (nujol, cmꢀ1): nNH ¼ 3154 (w), nCO ¼ 2072 (s), 1957 (sh),
1923 (vs), 1875 (vs), 1858 (vs). Anal. Calc. for C38H30N8O12W2: C,
39.40; H, 2.61; N, 9.67. Found: C, 39.34; H, 2.63; N, 9.67%.
47%. 1H NMR (CDCl3):
d 2.08 (s, 3H, 3-CH3 of uncoordinated pyr-
azole), 2.14 (s, 3H, 5-CH3 of uncoordinated pyrazole), 5.40 (s, 1H, H4
of uncoordinated pyrazole), 2.23, 2.24 (s, s, 3H, 3H, 3- or 5-CH3 of
coordinated pyrazole), 5.85 (s, 1H, H4 of pyrazole coordinated to the
tungsten atom), 6.14 (s, 1H, CH), 6.55 (dt, J ¼ 1.1 Hz, J ¼ 7.4 Hz, 1H),
6.82 (dd, J ¼ 1.1 Hz, J ¼ 8.1 Hz, 1H), 6.89 (dd, J ¼ 1.3 Hz, J ¼ 7.5 Hz,
1H), 7.04 (dt, J ¼ 1.7 Hz, J ¼ 8.1 Hz, 1H) (C6H4), 9.28 (s, 1H, NH), 12.86
(s, br, 1H, OH). The proton signals of NH and OH disappeared when
Data for complex 4: yield: 15%. 1H NMR (CDCl3):
d 3.88 (s, 3H,
OCH3), 6.31 (t, J ¼ 2.2 Hz, 2H, H4 of pyrazole), 7.17 (d, J ¼ 8.4 Hz, 1H),
7.64e7.70 (m, 2H, C6H4), 7.24e7.28 (m, 2H, CH and C6H4), 7.47 (d,
D2O was added. 13C NMR (CDCl3):
d 10.5 (5-CH3 of uncoordinated
pyrazole), 13.2 (3-CH3 of uncoordinated pyrazole), 104.8 (C4 of
uncoordinated pyrazole), 141.2 (C5 of uncoordinated pyrazole),
147.4 (C3 of uncoordinated pyrazole), 10.9, 16.3 (3- or 5-CH3 of
pyrazole coordinated to the tungsten atom), 63.2 (CH), 106.5 (C4 of
pyrazole coordinated to the tungsten atom), 119.3, 119.4, 122.3,
130.4, 131.7, 156.1 (C6H4), 142.1, 155.1 (C3 and C5 of pyrazole coor-
dinated to the tungsten atom),197.8 (4 C), 201.5 (1 C) (CO). IR (nujol,
J ¼ 2.2 Hz, 2H), 8.08 (d, J ¼ 0.9 Hz, 2H, H3 and H5 of pyrazole). 13
C
NMR (CDCl3):
d
55.6 (OCH3), 77.2 (CH), 107.1 (C4 of pyrazole), 112.7
(2 C), 116.3, 121.4, 133.9, 157.7 (C6H4), 131.8, 147.2 (C3 and C5 of
pyrazole), 201.3 (1 C), 204.3 (1 C), 212.4 (2 C) (CO). Complex 4 in
DMSO-d6 displayed two isomers (4A/4B). The relative ratio of
isomers 4A/4B was ca. 1/18, according to the integration of the
corresponding protons of pyrazole. 1H NMR of isomer of 4B:
d 3.67
Table 1
Crystallographic data and refinement parameters for complexes 1, 2, 4A and 5.
Complex
1.H2O
30H26N8O7W
794.44
2
4A
5
Formula
C
C44H42N8O12W2
1242.54
0.18 ꢂ 0.16 ꢂ 0.10
Monoclinic
P21/c
15.979(3)
9.3448(19)
16.780(3)
90
109.29(3)
90
2364.9(8)
2
C18H14N4O5W
550.18
0.24 ꢂ 0.20 ꢂ 0.18
Monoclinic
P21/n
7.5617(9)
20.824(2)
11.892(1)
90
104.150(4)
90
1815.9(4)
4
2.012
3.92e55.74
1056
6.401
C22H22N4O5W
606.29
0.10 ꢂ 0.08 ꢂ 0.04
Monoclinic
P21/n
9.5823(19
15.130(3)
15.336(3)
90
91.83(3)
90
2222.3(8)
4
1.812
3.78e50.04
1184
5.239
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
0.18 ꢂ 0.16 ꢂ 0.10
Triclinic
ꢀ
Pı
8.4945(17)
12.801(3)
16.458(3)
116.130(2)
91.28(3)
104.00(3)
1620.6(6)
2
b (Å)
c (Å)
a
b
g
(o)
(o)
(o)
V (Å 3
)
Z
DCalc (g cmꢀ3
)
1.628
3.52e50.04
784
1.745
5.06e55.04
1212
2
q
Range (o)
F(000)
(mmꢀ1
m
)
3.621
4.929
Number of reflections measured
12053
16162
17129
16189
Number of reflections observed [Rint
]
5686 [0.0749]
4777
427
5401 [0.0346]
4680
306
4321 [0.0322]
3750
254
3925 [0.0828]
3222
294
Number of reflections observed with (I ꢃ 2
s(I))
Number of parameters
Residuals R, Rw (I ꢃ 2
s(I))
0.0698, 0.1302
1.234
0.0271, 0.0608
1.027
0.0193, 0.0376
0.996
0.0359, 0.0633
0.997
Goodness-of-fit

K. Ding et al. / Journal of Organometallic Chemistry 696 (2011) 3662e3667
3667
(s, OCH3), 6.60 (t, J ¼ 2.8 Hz, H4 of pyrazole), 6.28 (s, br), 6.97 (t,
Appendix A. Supplementary material
J ¼ 7.5 Hz), 7.09 (d, J ¼ 8.3 Hz), 7.44 (t, J ¼ 7.7 Hz) (C6H4), 8.08 (d,
J ¼ 1.1 Hz, H3 of pyrazole), 8.25 (s, br, H5 of pyrazole), 8.50 (s, 1H,
CCDC 825748, 825749, 825750 and 825751 contain the supple-
mentary crystallographic data for 1, 2, 4A and 5, respectively. These
data can be obtained free of charge from The Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
CH). 13C NMR of isomer of 4B:
d
55.6 (OCH3), 72.7 (CH), 107.3 (C4 of
pyrazole), 112.3, 120.9, 128.2, 131.9, 136.0, 139.9, 147.5, 156.8 (C6H4
as well as C3 and C5 of pyrazole), 202.6 (1 C), 203.6 (1 C), 212.0 (2 C)
(CO). 1H NMR of isomer of 4A:
d
3.74 (s, OCH3), 6.32 (t, J ¼ 2.0 Hz, H4
of pyrazole), 6.89 (d, J ¼ 7.6 Hz, one proton of C6H4), 7.55, 7.66 (d,
J ¼ 2.3 Hz, d, J ¼ 1.2 Hz, H3 and H5 of pyrazole), 7.98 (s, CH). The
other three protons of the phenyl group were covered by those of
Appendix. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2011.08.023. These
data include MOL files and InChiKeys of the most important
compounds described in this article.
the phenyl group of isomer 4B. 13C NMR of isomer of 4A:
d 55.8
(OCH3), 72.0 (CH), 105.8 (C4 of pyrazole), 111.5, 118.0, 120.2, 120.3,
124.2, 127.6, 130.7, 156.2 (C6H4 as well as C3 and C5 of pyrazole). The
carbonyl carbon signals overlap with those of isomer 4B. IR (cmꢀ1):
nCO ¼ 2012 (s), 1863 (vs, br), 1810 (vs). Anal. Calc. for C18H14N4O5W:
C, 39.30; H, 2.56; N, 10.18. Found: C, 38.86; H, 2.67; N, 10.15%.
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3.4. Reaction of L4 with W(CO)5THF
This reaction was similarly carried out as above-mentioned for
the reaction of L1 with W(CO)5THF while L4 was used instead of L1.
The solvent was removed under a reduced pressure, and the
residual solid was purified by column chromatography on silica
using ethyl acetate/hexane (1/2 v/v) as eluent to yield complex 6.
After complex 6 was isolated, ethyl acetate/hexane (1/1 v/v) was
used subsequently as eluent to give complex 5. After removing the
solvents, the solids were crystallized from CH2Cl2/hexane to give
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Data for complex 5: yield: 26%. 1H NMR (CDCl3):
d 2.46 (s, 6H, 5-
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CH3 of pyrazole), 2.59 (s, 6H, 3-CH3 of pyrazole), 3.60 (s, 3H, OCH3),
6.10 (s, 2H, H4 of pyrazole), 6.03 (d, J ¼ 7.7 Hz,1H, H2 of phenyl), 6.89
(d, J ¼ 8.3 Hz, 1H, H5 of phenyl), 6.91 (t, J ¼ 7.6 Hz, 1H, H4 of phenyl),
7.35 (t, J ¼ 7.9 Hz,1H, H3 of phenyl), 7.43 (s,1H, CH). 1H NMR (DMSO-
d6):
d 2.46, 2.50 (s, s, 6H, 6H, 3- and 5-CH3 of pyrazole), 3.55 (s, 3H,
OCH3), 6.33 (s, 2H, H4 of pyrazole), 5.89 (d, J ¼ 7.2 Hz, 1H), 6.94 (t,
J ¼ 7.6 Hz, 1H), 7.06 (d, J ¼ 8.3 Hz, 1H), 7.36 (t, J ¼ 7.8 Hz, 1H) (C6H4),
7.80 (s, 1H, CH). 13C NMR (CDCl3):
d 12.0 (5-CH3 of pyrazole), 17.3 (3-
CH3 of pyrazole), 55.7 (OCH3), 66.9 (CH),107.6 (C4 of pyrazole),142.4
(C5 of pyrazole), 155.4 (C3 of pyrazole), 112.6 (C5 of phenyl),121.4 (C1
of phenyl), 121.9 (C4 of phenyl), 128.1 (C2 of phenyl), 131.7 (C3 of
phenyl), 157.1 (C6 of phenyl), 200.6 (1 C), 203.8 (1 C), 212.4 (2 C)
(CO). IR (cmꢀ1): nCO ¼ 2002 (s), 1871 (vs), 1845 (vs), 1803 (vs). Anal.
Calc. for C22H22N4O5W: C, 43.58; H, 3.66; N, 9.24. Found: C, 43.13; H,
4.14; N, 9.40%. Data for complex 6: yield: 25%. 1H NMR (CDCl3):
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d
2.32 (s, 6H, CH3), 5.94 (s, 1H, H4 of pyrazole), 9.33 (s, 1H, NH). IR
(cmꢀ1): nNH ¼ 3365 (m), nCO ¼ 2071 (s), 1922 (vs, br), 1870 (vs).
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Mo-K
a
radiation (
l
¼ 0.71073 Å). Semi-empirical absorption
corrections were applied using the Crystalclear program [38]. The
structures were solved by direct methods and difference Fourier
map using SHELXS of the SHELXTL package and refined with
SHELXL [39] by full-matrix least-squares on F2. All nonhydrogen
atoms were refined anisotropically. A summary of the fundamental
crystal data for these complexes is listed in Table 1.
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Tetrahedron 44 (1988) 6429e6434.
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Acknowledgments
This work is supported by the National Natural Science Foun-
dation of China (Nos. 20672059 & 20972075).