Synthesis, structures and electrochemical properties of Group 6 metal carbonyl complexes containing ferrocenylpyrazole ligands

Article abstract of DOI:10.1016/S0022-328X(01)00907-X

A series of carbonylchromium, molybdenum and tungsten complexes containing ferrocenylpyrazole ligands, (M(CO)₅L) (M=Cr, Mo or W; L represents ferrocenyl pyrazole), have been prepared by the photochemical reactions of ferrocenylpyrazole ligands with M(CO)₆. Their electrochemical behaviors have also been investigated by cyclic voltammetry, indicating that chromium complexes exhibit two one-electron reversible or quasi-reversible couples, while molybdenum and tungsten complexes have one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum or tungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazole pentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and 3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octahedral coordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolecular hydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similar intermolecular hydrogen bond interactions. The N-H?O distances in complexes 3 and 6 are 2.932(11) and 2.900 ?, respectively. All new compounds have been characterized by elemental analyses, IR, ¹H-NMR. ¹³C-NMR spectra of molybdenum and tungsten complexes have also been determined.

Full text of DOI:10.1016/S0022-328X(01)00907-X

Journal of Organometallic Chemistry 637–639 (2001) 209–215
www.elsevier.com/locate/jorganchem
Synthesis, structures and electrochemical properties of Group 6
metal carbonyl complexes containing ferrocenylpyrazole ligands
Liang-Fu Tang *, Wen-Li Jia, Zhi-Hong Wang, Jian-Fang Chai, Ji-Tao Wang
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai Uni6ersity, Tianjin 300071, People’s Republic of China
Received 28 December 2000; received in revised form 19 February 2001; accepted 26 March 2001
Abstract
A series of carbonylchromium, molybdenum and tungsten complexes containing ferrocenylpyrazole ligands, (M(CO)5L)
(M=Cr, Mo or W; L represents ferrocenyl pyrazole), have been prepared by the photochemical reactions of ferrocenylpyrazole
ligands with M(CO)6. Their electrochemical behaviors have also been investigated by cyclic voltammetry, indicating that
chromium complexes exhibit two one-electron reversible or quasi-reversible couples, while molybdenum and tungsten complexes
have one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum or
tungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazole
pentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and
3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octa-
hedral coordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolec-
ular hydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similar
,
intermolecular hydrogen bond interactions. The N–H···O distances in complexes 3 and 6 are 2.932(11) and 2.900 A, respectively.
All new compounds have been characterized by elemental analyses, IR, 1H-NMR. 13C-NMR spectra of molybdenum and tungsten
complexes have also been determined. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ferrocenylpyrazole; Metal carbonyl complexes; Cyclic voltammetry; Crystal structures
1. Introduction
ing interest in the use of ferrocenylpyrazole ligands to
produce polymetallic species owing to their versatile
coordination possibility [11–19]. In these complexes,
ferrocenylpyrazoles can act as mono-, bi- and polyden-
tate ligands. In this paper, we report the photochemical
reaction of ferrocenylpyrazole ligands with M(CO)6 to
yield novel M(CO)5L complexes (M=Cr, Mo or W; L
represents ferrocenylpyrazole ligands). The single crys-
tal X-ray analysis shows that substituents on the pyra-
zole ring affect significantly the solid structures of
complexes. The electrochemical properties of M(CO)5L
complexes have also been investigated by cyclic
voltammetry.
Due to its high stability and reversible redox charac-
teristics, ferrocence has been extensively used as starting
materials in the synthesis of versatile ferrocenyl deriva-
tives [1]. For example, ferrocenyl derivatives are very
important electron-transfer systems for molecular elec-
tronics owing to its characteristic redox behaviors [2],
and they could also be expected to play a key role of an
electron chemical probe of the electron-transfer process
in biological molecules [3]. The aromatic heterocyclic
systems covalently linked to ferrocenyl fragment have
shown some interesting electrochemical behaviors,
which allows electronic communication between fer-
rocene and another coordinated metal center through
the p-conjugated systems [4–11]. Ferrocenylpyrazole is
one of above systems. Recently, there has been increas-
2. Experimental
All reactions were carried out under an oxygen-free
atmosphere. Solvents were dried by standard methods
and distilled prior to use. NMR spectra were recorded
* Corresponding author Fax: +86-22-2350-2458.
E-mail address: tanglf@eyou.com (L.-F. Tang).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00907-X

210
L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
on BRUKER AC-P-200 spectrometer using CDCl3 as
solvent unless otherwise noted, and chemical shifts were
2074.2 (m), 1976.2 (sh), 1923.8 (vs), 1858.2 (vs), 1827.6
(vs) (CO); wpyrazole ring=1596.1 (m) cm−1. Anal. Calc.
for C18H12FeN2O5W: C, 37.50; H, 2.08; N, 4.86.
Found: C, 37.35; H, 2.12; N, 5.00%.
1
referenced to Me4Si for H- and 13C-NMR spectra. IR
spectral data were obtained from a Bio-Rad FTS 135
spectrometer in KBr pellets. Elemental analyses were
carried out on a Perkin–Elmer 240C analyzer. 3(5)-Fer-
rocenylpyrazole (L1) [18], 3(5)-methyl-5(3)-ferro-
cenylpyrazole (L2) and 3(5)-phenyl-5(3)-ferrocenyl
pyrazole (L3) [20] were prepared according to the litera-
ture methods.
2.1.4. 3-Methyl-5-ferrocenylpyrazole
pentacarbonylchromium (4)
1H-NMR: l 2.26 (s, 3H, CH3), 4.13 (br, 9H, C5H5+
C5H4), 6.00 (s, 1H, H4 of pyrazole), 9.09 (br, s, 1H,
NH). IR: wNH=3446.7 (s), 3426.3 (sh); wCO=2068.3
(m), 1981.2 (m), 1947.2 (vs), 1900.4 (vs), 1842.0 (m),
1873.5 (vs); wpyrazole ring=1594.2 (m) cm−1. Anal. Calc.
for C19H14CrFeN2O5: C, 49.78; H, 3.06; N, 6.11.
Found: C, 49.64; H, 2.97; N, 6.60%.
2.1. Reaction of ferrocenylpyrazoles with M(CO)6
(M=Cr, Mo and W)
As all the reactions are similar, a general procedure is
described as follows. The solution of M(CO)6 (1 mmol)
and ferrocenylpyrazole (1 mmol) dissolved in THF (20
ml) was irradiated with a 400 W high-pressure mercury
lamp for 6–12 h at room temperature (r.t.). The reac-
tion mixture was monitored by TLC. After the reaction
completed, the solvent was removed in vacuo, and the
residual was purified by column chromatography on
silica using CH3CO2C2H5:hexane (v:v=1:4) as eluent.
The yellow eluent was concentrated to dryness under a
reduced pressure. The residue was recrystallized from
CH2Cl2–hexane to give a yellow crystalline solid.
2.1.5. 3-Methyl-5-ferrocenylpyrazole
pentacarbonylmolybdenum (5)
1H-NMR: l 2.32 (s, 3H, CH3), 4.14 (s, 5H, C5H5),
4.36, 4.51 (m, m, 2H, 2H,C5H4), 6.12 (s, 1H, H4 of
pyrazole), 9.15 (br, s, 1H, NH). 13C-NMR: l 15.5
(CH3), 66.7, 69.5, 71.6 (C5H4), 69.7 (C5H4+C5H5),
104.2 (C4 of pyrazole), 145.0 (C5 of pyrazole), 154.3 (C3
of pyrazole), 204.0, 210.2 (CO). IR: wNH=3407.9 (m),
3386.3 (m); wCO=2075.7 (m), 1994.8 (m), 1932.1 (vs),
1892.8 (vs), 1870.5 (vs), 1843.6 (vs); wpyrazole ring=1599.1
(m) cm−1. Anal. Calc. for C19H14FeMoN2O5: C, 45.42;
H, 2.79; N, 5.58. Found: C, 45.30; H, 3.20; N, 6.02%.
2.1.1. 3-Ferrocenylpyrazole pentacarbonylchromium (1)
1H-NMR: l 4.11 (s, 5H, C5H5), 4.36, 4.51 (s, s, 2H,
2H, C5H4), 6.25 (br, s, 1H, H4 of pyrazole), 7.37 (br, s,
2.1.6. 3-Methyl-5-ferrocenylpyrazole
pentacarbonyltungsten (6)
1H, H5 of pyrazole), 9.35 (br, s, 1H, NH). IR: wNH
=
1H-NMR: l 2.34 (s, 3H, CH3), 4.14 (s, 5H, C5H5),
4.37, 4.52 (m, m, 2H, 2H, C5H4), 6.08 (s, 1H, H4 of
pyrazole), 9.18 (br, s, 1H, NH). 13C-NMR: l 16.4
(CH3), 66.8, 69.7, 71.3 (C5H4), 69.9 (C5H4+C5H5),
104.2 (C4 of pyrazole), 145.8 (C5 of pyrazole), 155.3 (C3
of pyrazole), 197.8, 201.7 (CO). IR: wNH=3390.7 (m),
3363.9 (m); wCO=2073.1 (m), 1985.2 (m), 1921.4 (vs),
3446.2 (s); wCO=2068.2 (m), 1981.2 (m), 1949.4 (vs),
1898.9 (vs), 1873.4 (vs); wpyrazole ring=1593.8 (m) cm−1
.
Anal. Calc. for C18H12CrFeN2O5: C, 48.65; H, 2.70; N,
6.31. Found: C, 49.04; H, 2.45; N, 6.39%.
2.1.2. 3-Ferrocenylpyrazole pentacarbonylmolybdenum
(2)
1867.5 (vs), 1829.2 (vs); wpyrazole ring=1598.8 (m) cm−1
.
1H-NMR: l 4.09 (s, 5H, C5H5), 4.39, 4.57 (s, s, 2H,
2H, C5H4), 6.65 (d, 1H, H4 of pyrazole), 8.13 (d, 1H,
H5 of pyrazole), 9.34 (br, s, 1H, NH). 13C-NMR: l
66.6, 69.4, 71.6 (C5H4), 69.7 (C5H5), 104.2 (C4 of pyra-
zole), 145.0 (C5 of pyrazole), 154.2 (C3 of pyrazole),
204.0, 210.5 (CO). IR: wNH=3384.7 (m); wCO=2074.0
(w), 1974.5 (sh), 1948.0 (vs), 1928.1 (s), 1857.8 (vs),
1827.3 (vs); wpyrazole ring=1596.0 (m) cm−1. Anal. Calc.
for C18H12FeMoN2O5: C, 44.26; H, 2.46; N, 5.74.
Found: C, 44.44; H, 2.92; N, 6.29%.
Anal. Calc. for C19H14FeN2O5W: C, 38.64; H, 2.37; N,
4.75. Found: C, 38.70; H, 1.95; N, 5.05%.
2.1.7. 3-Phenyl-5-ferrocenylpyrazole
pentacarbonyltungsten (7)
Two conformational isomers (an analog is shown in
Fig. 3) were obtained. The relative ratio of isomers is
ca. 44:56 calculated from the integration of H4 signals
of the pyrazole ring in 1H-NMR spectrum. 1H-NMR of
the mixtures: l 4.18, 4.20 (s, s, C5H5), 4.41, 4.59, 4.64
(m, m, m, C5H4), 6.32, 6.72 (s, s, H4 of pyrazole),
7.47–7.55 (m, C6H5), 9.44, 9.64 (s, s, NH). 13C-NMR: l
66.8, 68.2, 69.0, 69.4, 70.6, 70.9 (C5H4), 69.8, 69.9
(C5H5), 104.4, 106.2 (C4 of pyrazole), 125.8, 126.9,
128.3, 128.7, 129.3, 129.5, 129.9, 132.8 (C6H5), 145.3,
145.9 (C5 of pyrazole), 158.4, 159.6 (C3 of pyrazole),
197.6, 197.8, 201.5 (CO). IR: wNH=3394.3 (sh), 3383.6
(m); wCO=2072.5 (m), 1976.5 (m), 1924.9 (vs), 1856.6
2.1.3. 3-Ferrocenylpyrazole pentacarbonyltungsten (3)
1H-NMR: l 4.14 (s, 5H, C5H5), 4.39, 4.56 (s, s, 2H,
2H, C5H4), 6.24 (d, 1H, H4 of pyrazole), 7.58 (d, 1H,
H5 of pyrazole), 9.54 (br, s, 1H, NH). 13C-NMR: l
66.8, 69.6, 70.9 (C5H4), 69.9 (C5H4+C5H5), 104.8 (C4
of pyrazole), 146.1 (C5 of pyrazole), 148.5 (C3 of pyra-
zole), 197.9, 201.8 (CO). IR: wNH=3384.4 (s); wCO
=

L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
211
(vs), 1825.0 (vs); wpyrazole ring=1591.7, 1571.6 (w) cm−1
.
2.3. Crystal structures determination
Anal. Calc. for C24H16FeN2O5W: C, 44.17; H, 2.45; N,
4.29. Found: C, 44.20; H, 2.67; N, 4.37%.
Crystals of complexes 3 and 6 suitable for X-ray
analysis were grown from CH2Cl2–hexane at 4 °C. All
intensity data were collected at r.t. with an Enraf-Non-
ius CAD4 diffractometer using graphite monochro-
2.2. Electrochemical experimental
,
Cyclic voltammetric experiments were performed on
a BAS-100B electrochemical analyser equipped with a
three-electrode assembly with 0.1 M Bu4NPF6 as sup-
port electrolyte and CH3CN as solvent. The working
electrode was a platinum disk (ƒ=1 mm). The refer-
ence electrode was 0.1 M AgNO3 ꢀ Ag prepared in a 0.1
M Bu4NPF6–CH3CN solution. A Pt filament was used
as an auxiliary electrode. The ferrocenium ferrocene
redox couple was taken as an internal standard. E1/2
values were determined as (Epa+Epc)/2.
mated Mo–Ka radiation (u=0.71073 A). The
correction for empirical absorption was applied to in-
tensity data, structures were resolved by direct method
and refined by full-matrix least-squares on F2. All
non-hydrogen atoms were refined anisotropically. All
calculations were performed on a PDP11/44 computer
using SDP-PLUS program system. A summary of the
fundamental crystal data for complexes 3 and 6 is listed
in Table 1.
3. Results and discussion
Table 1
Crystal data and structure refinement parameters for complexes 3 and
6
3.1. Synthesis and characterization of the complexes
3
6
The photochemical reactions of ferrocenylpyrazoles
with M(CO)6 (M=Cr, Mo and W) in the molar ratio
1:1 or 2:1 (ligand:metal) at room temperature yielded
M(CO)5L complexes (L=ferrocenylpyrazole) as the
major products (Scheme 1). However, the reaction of
3(5)-phenyl-5(3)-ferrocenylpyrazole with Cr(CO)6 or
Mo(CO)6 did not take place in this reaction conditions,
possibly owing to bulky steric hindrance of substituents
on the pyrazole ring decreasing the donor ability of this
ligand. Some M(CO)4L2 complexes were also obtained
during the reactions, but their stability was poor, and
no pure products were isolated. The stability of mono-
substituted complexes is in the order Cr(0)ꢀW(0)\
Mo(0), which is similar with the order of Cr(0)ꢀ
W(0)\Mo(0) in M(CO)5L complexes of L=pyrim-
idine or triazine [21], but remarkably different from the
stability order of W(0)\Mo(0)\ \Cr(0) in M(CO)5L
complexes of pyrazine [22]. All complexes are soluble in
chlorinated solvents, and they are slightly air-sensitive
in solution.
Empirical formula
Formula weigh
Crystal size (mm)
Crystal system
Space group
Unit cell dimensions
C18H12FeN2O5W
576.00
0.30×0.30×0.25
monoclinic
P21/n
C
590.02
0.20×0.20×0.30
monoclinic
P21/n
19H14FeN2O5W
,
a (A)
7.0910(10)
23.129(5)
11.192(2)
98.89(3)
1813.5(6)
2.110
9.787(2)
21.459(4)
18.749(4
92.84(3)
3932.8(14)
1.993
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Dcalc (g cm−3
)
Absorption coefficient
7.170
6.615
(mm−1
)
Z
F(000)
Reflections collected
Independent reflections
4
1096
3357
3184 (0.0604)
8
2256
7101
6882 (0.0367)
(Rint
)
No. of parameters
R, Rw [I\2s(I)]
245
505
0.0555, 0.1503
0.993
0.0335, 0.0805
0.929
Goodness-of-fit on F2
The IR spectra of complexes 1–3 show the character-
istic absorption peak of N–H stretching band nearby
3446 and 3384 cm−1. However, two N–H bands are
observed in complexes 4–7, which is consistent with the
existence of two conformational isomers in these solid
complexes (Fig. 3). Two N–H bonds of conformational
isomers in complexes 4–7 are remarkably different
owing to only one N–H bond forming N–H···O hydro-
gen bond. The carbonyl spectra are also interesting.
Five to six wCO bands are observed in all complexes,
which is different from other monosubstituted Group 6
metal carbonyl complexes [23–26]. This is probably due
to a superposition of the absorption of the two different
W(CO)5 fragments.
Scheme 1. Fc=ferrocenyl; 1, R=H, M=Cr; 2, R=H, M=Mo; 3,
R=H, M=W; 4, R=Me, M=Cr; 5, R=Me, M=Mo; 6, R=Me,
M=W; 7, R=Ph, M=W.

212
L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
Table 2
protons of the pyrazole ring and ferrocenyl group,
respectively, are observed in the H-NMR spectrum at
Electrochemical data for ligands and complexes 1–7
1
room temperature. The ratio of the isomers is ca. 44:56,
determined by integration of H4 signals of the pyrazole
ring. The 13C-NMR spectrum of complex 7 also shows
two sets of signals for the carbon atoms of ferrocenyl
group and pyrazole ring, but only three signals for the
carbonyl carbon atoms from two isomers are observed,
this may be the result of low contents of one isomer.
The bulky steric hindrance of phenyl and ferrocenyl
groups on pyrazole ring should be responsible for the
Compound 6 (mV s−1
)
Epa (mV)
Epc (mV)
E1/2 (mV)
L1
L2
L3
1
100
100
100
100
62
40
−30
−30
−27
83
335
92
16
5
47
133
388
136
390
146
120
184
442
181
440
197
739
192
736
182
750
183
744
178
435
180
425
182
767
181
724
199
735
200
100
200
100
200
100
200
100
100
100
340
96
2
3
4
1
two sets of signals for H and 13C resonances, which
77
92
87
134
137
135
slows down the conformational conversion between the
two isomers of complex 7. The time-averaging signal of
two isomers on the NMR time scale was not appeared.
However, attempts to separate the two isomers at room
temperature were not successful.
98
346
95
334
104
138
390
137
379
143
3.2. Electrochemical properties of the complexes
5
6
7
The electrochemical properties of the complexes were
investigated by cyclic voltammetry at room temperature
in CH3CN solution. The voltammetric data are listed in
Table 2. A typical CV curve of complex 4 is illustrated
in Fig. 1. The electrochemical behaviors of M(CO)5
fragments are significantly different from those of
M(CO)4 fragments (M=Cr, Mo and W). One re-
versible or quasi-reversible one-electron oxidation pro-
cess is observed in complexes N–NM(CO)4 (N–N
represents bis(pyrazol-1-yl)alkanes) [27]. However, in
the present work, chromium complexes exhibit two
pairs of reversible or quasi-reversible redox peaks, one
is attributed to the ferrocenyl group and the other to
the chromium center, respectively. A reversible one-
electron oxidation process for ferrocenyl group and an
irreversible oxidation for the other metal center are
observed in molybdenum and tungsten complexes. The
irreversible oxidation process of molybdenum and tung-
sten center was also observed in many other systems
containing M(CO)5 fragments [28,29]. The poor chemi-
cal stability of the oxidation products of molybdenum
and tungsten complexes at room temperature may be
responsible for the irreversible oxidation of the metal
centers. The peak potential (E1/2) of the ferrocenyl
groups in the complexes lies in the range of 133–147
mV, which varies only slightly with different metals in
complexes indicating that there may be no electronic
communication between ligands with metal centers.
This is possibly owing to bulky steric hindrance leading
to relatively weak conjugation effects of ferrocenyl
group with pyrazole plane in the oxidation products
especially to complexes 4–7 (Fig. 3) [4]. Large positive
shifts compared with free ligands are observed, and we
suggest that inductive effects may be the major factors
owing to the electron-withdrawing effect of M(CO)5
fragments [23,24].
100
87
140
143
Fig. 1. Cyclic voltammogram at a potential sweep rate of 200 mV s−1
for complex 4.
1
The H-NMR spectra of all the complexes indicate
expected the signals of pyrazole protons. These pyra-
zole protons in the complexes are shifted downfield
compared with those of the free ligands. Although
X-ray analyses show that complexes 4–6 have two
conformational isomers in solid, only one set of signals
of pyrazole ligand are observed in solution, which can
be easily understood possibly owing to the rapid con-
formational conversion existing in solution. The 13C-
NMR spectra of complexes 2, 3, 5 and 6 exhibit two
signals of the carbonyl carbon atoms with ca. a 1:4
intensity ratio, which is consistent with the formula
1
M(CO)5L [24]. It is also noteworthy that the H- and
13C-NMR spectra of complex 7 clearly show a mixture
of two isomers compared with the conformational iso-
mers of complex 6 (Fig. 3). Two sets of signals for the

L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
213
Table 4
3.3. Crystal structures of complexes 3 and 6
,
Selected bond lengths (A) and bond angles (°) for complex 6
The molecular structures of complexes 3 and 6 were
confirmed by single crystal X-ray diffraction analyses.
Selected bonds distances and angles for complexes 3
and 6 are listed in Tables 3 and 4, respectively.
The crystal structure of complex 3 is shown in Fig. 2.
It clearly shows that ferrocenylpyrazole ligand acts as a
monodentate ligand, which coordinates to tungsten
center through the nitrogen atom away from bulky
ferrocenyl group, in order to avoid the steric repulsion
of ferrocenyl group. The tungsten atom is six-coordi-
nate with a quasi-octahedral coordination geometry.
A
B
Bond lengths
W(1)–C(4)
W(1)–C(2)
W(1)–C(5)
W(1)–C(1)
W(1)–C(3)
W(1)–N(25)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
C(5)–O(5)
C(13)–C(23)
N44…O4
1.940(9)
1.992(12)
2.014(9)
2.030(8)
2.050(11)
2.258(6)
1.139(9)
1.171(12)
1.138(11)
1.161(10)
1.159(11)
1.464(11)
2.900
W(2)–C(6)
W(2)–C(10)
W(2)–C(9)
W(2)–C(8)
W(2)–C(7)
W(2)–N(45)
C(6)–O(6)
C(7)–O(7)
C(8)–O(8)
C(9)–O(9)
C(10)–O(10)
C(43)–C(51)
1.950(8)
2.011(11)
2.031(9)
2.039(10)
2.044(8)
2.249(6)
1.161(10)
1.127(9)
1.130(10)
1.136(10)
1.167(12)
1.440(10)
,
The W–N distance is 2.204(8) A, which is comparable
to those found in other octahedral W(0) complexes with
,
pyrazole ligands (such as average 2.255 A in CH2(3,5-
,
Bond angles
Me2-4-ClPz)2W(CO)4 [27] and 2.275 A in (CH2)2(3,5-
C(4)–W(1)–C(2)
C(4)–W(1)–C(5)
C(2)–W(1)–C(5)
C(4)–W(1)–C(1)
C(2)–W(1)–C(1)
C(5)–W(1)–C(1)
C(4)–W(1)–C(3)
C(2)–W(1)–C(3)
C(5)–W(1)–C(3)
C(1)–W(1)–C(3)
C(4)–W(1)–N(25) 177.5(3)
C(2)–W(1)–N(25) 92.9(3)
C(5)–W(1)–N(25) 92.9(3)
C(1)–W(1)–N(25) 91.6(3)
C(3)–W(1)–N(25) 94.7(3)
86.6(4)
89.6(4)
89.9(5)
86.0(3)
89.3(4)
175.5(3)
85.8(4)
172.3(4)
88.9(4)
91.3(3)
C(6)–W(2)–C(10)
C(6)–W(2)–C(9)
C(10)–W(2)–C(9)
C(6)–W(2)–C(8)
C(10)–W(2)–C(8)
C(9)–W(2)–C(8)
C(6)–W(2)–C(7)
C(10)–W(2)–C(7)
C(9)–W(2)–C(7)
C(8)–W(2)–C(7)
C(6)–W(2)–N(45)
C(10)–W(2)–N(45)
C(9)–W(2)–N(45)
C(8)–W(2)–N(45)
C(7)–W(2)–N(45)
O(6)–C(6)–W(2)
O(7)–C(7)–W(2)
O(8)–C(8)–W(2)
O(9)–C(9)–W(2)
O(10)–C(10)–W(2)
89.5(4)
89.0(3)
89.8(4)
85.4(3)
174.8(4)
90.9(4)
89.2(3)
85.8(3)
175.3(4)
93.3(3)
174.8(3)
95.7(3)
90.5(3)
89.5(3)
91.7(3)
176.8(8)
176.0(7)
173.5(8)
175.9(9)
174.6(10)
Me2Pz)2W(CO)4 [30], respectively, Pz=pyrazole). It is
noteworthy that the W–C distance trans to the pyra-
,
zole ligand is 1.947(11) A, and shorter than the other
four W–C distances, while the C(1)–O(1) distance is
,
1.147(16) A, and is longer than other four C–O dis-
tances. It is also interesting that C(4)O(4) carbonyl
bends toward pyrazole ligand with the W(1)–C(4)–
O(4) angle of 176.1(12)°.
It is well-known that the interactions of hydrogen
bonds play a key role in self-assembly of metal com-
plexes into supramolecular architectures. Hydrogen
bonds formed by metal carbonyl as hydrogen bond
acceptors have been observed in several systems [31–
34]. The crystal packing of complex 3 shows that the
O(1)–C(1)–W(1)
O(2)–C(2)–W(1)
O(3)–C(3)–W(1)
O(4)–C(4)–W(1)
O(5)–C(5)–W(1)
174.7(7)
176.2(10)
172.4(9)
179.0(7)
175.8(9)
Table 3
,
Selected bond lengths (A) and bond angles (°) for complex 3
Bond lengths
W(1)–C(2)
W(1)–C(1)
W(1)–C(5)
W(1)–C(3)
W(1)–C(4)
W(1)–N(1)
N(2)···O(2)a
1.947(11)
1.969(17)
2.016(13)
2.025(14)
2.036(12)
2.204(8)
C(1)–O(1)
C(2)–O(2)
C(3)–O(3)
C(4)–O(4)
C(5)–O(5)
C(8)–C(11)
1.147(16)
1.128(13)
1.112(13)
1.086(14)
1.093(14)
1.444(13)
molecules are linked into a one-dimensional chain via
intermolecular hydrogen bonds interactions between
the N–H groups and the oxygen atoms of metal car-
bonyls trans to pyrazole ligands in different adjacent
molecules. The hydrogen bond N···O distance is
2.932(11)
,
2.932(11) A, and the angle N–H···O is Ú166.6°.
Bond angles
The X-ray crystal structure of complex 6 is presented
in Fig. 3, which consists of two crystallographically
independent molecules (A and B). The two molecules
are essentially the same, and similar to complex 3. The
main difference between them is the dihedral angles
formed by cyclopentadienyl rings and pyrazole planes.
The dihedral angle between the C5H5 and C5H4 rings in
molecule A (Fig. 3) is 1.6°, similar to that in molecule B
(1.5°), but slightly lower than that in complex 3 (2.6°).
The dihedral angle between the C5H4 ring and the
pyrazole plane in molecule B is 40.1°, considerably
larger than those in molecule A (19.2°) and complex 3
(3.4°), respectively. The significantly different dihedral
angles between the C5H4 rings and pyrazole planes in
C(2)–W(1)–C(1)
C(2)–W(1)–C(5)
C(1)–W(1)–C(5)
C(2)–W(1)–C(3)
90.9(5)
89.1(5)
93.2(6)
89.3(5)
C(3)–W(1)–N(1)
C(4)–W(1)–N(1)
O(1)–C(1)–W(1)
O(2)–C(2)–W(1)
O(3)–C(3)–W(1)
O(4)–C(4)–W(1)
O(5)–C(5)–W(1)
C(7)–C(8)–C(11)
N(2)–C(8)–C(11)
C(6)–N(1)–W(1)
N(2)–N(1)–W(1)
C(15)–C(11)–C(8)
C(12)–C(11)–C(8)
90.4(4)
89.2(4)
178.8(10)
178.2(10)
175.9(10)
176.1(12)
173.2(10)
133.1(9)
122.3(8)
130.6(7)
125.1(5)
129.3(8)
127.2(9)
C(1)–W(1)–C(3) 179.6(5)
C(5)–W(1)–C(3)
C(2)–W(1)–C(4)
C(1)–W(1)–C(4)
C(5)–W(1)–C(4) 179.2(5)
C(3)–W(1)–C(4) 93.7(5)
C(2)–W(1)–N(1) 179.6(4)
C(1)–W(1)–N(1)
C(5)–W(1)–N(1)
N(2)–H···O(2)a
87.1(6)
90.7(5)
86.0(5)
89.5(4)
91.0(3)
166.6
a x+1/2, −y+1/2, z+1/2.

214
L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
Fig. 2. The molecular structure of complex 3.
these molecules obviously came from the results of the
different steric effects in ferrocenylpyrazole ligands. The
In conclusion, a series of Group 6 metal carbonyl
complexes containing ferrocenylpyrazole ligands have
been synthesized successfully by photochemical reac-
tions. Their electrochemical behaviors have also been
investigated by cyclic voltammetry. Hydrogen bonds,
formed by metal carbonyl as hydrogen bond acceptors,
have also been found in these complexes. Complex 3
shows a one-dimensional chain structure in the solid
state by this kind of hydrogen bond interactions. It is
also shown that the substituents of pyrazole ring affect
significantly the conformations of complexes.
,
W(1)–N(25) distance (2.258(6) A) in molecule A is
,
similar to the W(2)–N(45) distance (2.249(6) A) in
molecule B, slightly longer than the W–N distance in
,
complex 3 (2.204(8) A). The four carbonyls cis to the
pyrazole ligands in molecules A and B deviate from
linearity, and bend away from the pyrazole ligands. In
addition, hydrogen bonds formed by metal carbonyl as
hydrogen bond acceptors still exist in complex 6, but no
one-dimensional chain via intermolecular hydrogen
bonds is formed in complex 6, possibly owing to more
steric hindrance in complex 6 due to a methyl group
adjacent to the coordinated nitrogen atom. Molecules
A and B, through hydrogen bond, only form a dimer.
4. Supplementary information
,
The hydrogen bond N44···O4 distance is 2.900 A.
Crystallographic data (CIF files) for the structural
analysis have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC no. 154098 for com-
plex 3 and CCDC no. 154099 for complex 6. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
This work is supported by the National Natural
Science Foundation of China (no. 29902002) and Visit-
ing Scholar Foundation of Key Lab. In University.
References
[1] A. Togni, T. Hayashi (Eds.), Ferrocenes, VCH, Weinheim, 1995.
[2] D. Astruc, Acc. Chem. Res. 30 (1997) 383.
Fig. 3. The molecular structure of complex 6.

L.-F. Tang et al. / Journal of Organometallic Chemistry 637–639 (2001) 209–215
215
[3] P.D. Beer, Acc. Chem. Res. 31 (1998) 71.
[4] T.L. Rose, A.B. Kon, Inorg. Chem. 32 (1993) 781.
[5] B. Farlow, T.A. Nile, J.L. Walsh, A.T. McPhail, Polyhedron 12
(1993) 2891.
[6] I.R. Butler, Organometallics 11 (1992) 74.
[7] U. Siemeling, U. Vorfeld, B. Neumann, H.G. Stammler, Chem.
Ber. 128 (1995) 481.
[8] I.R. Butler, S.J. McDonald, M. Hursthouse, K.M. Abdul Malik,
Polyhedron 14 (1995) 529.
[9] A.M. Santos, F.E. Ku¨hn, W.M. Xue, E. Herdtweck, J. Chem.
Soc. Dalton Trans. (2000) 3570.
[10] J.D. Carr, S.J. Coles, M.B. Hursthouse, M.E. Light, E.L.
Munro, J.H.R. Tucker, J. Westwood, Organometallics 19 (2000)
3312.
[11] W.R. Thiel, T. Priermeier, D.A. Fiedler, A.M. Bond, M.R.
Mattner, J. Organomet. Chem. 514 (1996) 137.
[12] J.A. Campo, M. Cano, J.V. Heras, E. Pinilla, M.R. Bermejo, R.
Torres, J. Organomet. Chem. 582 (1999) 173.
[13] N. Chabert-Couchouron, C. Marzin, G. Tarrago, New J. Chem.
21 (1997) 355.
[14] A. Schnyder, A. Togni, U. Wiesli, Organometallics 16 (1997)
255.
[15] R.J. Less, J.L.M. Wicks, N.P. Chatterton, M.J. Dewey, N.L.
Cromhout, M.A. Halcrow, J.E. davies, J. Chem. Soc. Dalton
Trans. (1996) 4055.
[19] L.F. Tang, Z.H. Wang, Y.M. Xu, J.T. Wang, Synth. React.
Inorg. Met.-Org. Chem. 30 (2000) 1129.
[20] C.R. Hauser, J.K. Lindsay, J. Org. Chem. 22 (1957) 482.
[21] T.W. Stringfield, R.E. Shepherd, Inorg. Chim. Acta 292 (1999)
225.
[22] T.W. Stringfield, Y. Chen, R.E. Shepherd, Inorg. Chim. Acta
285 (1999) 157.
[23] F.A. Cotton, C.S. Kraihanzel, J. Am. Chem. Soc. 84 (1962)
4432.
[24] C.S. Kraihanzel, F.A. Cotton, Inorg. Chem. 2 (1963) 533.
[25] M.A. Reynolds, I.A. Guzei, B.C. Logsdon, L.M. Thomas, R.A.
Jacobson, R.J. Angelici, Organometallics 18 (1999) 4075.
[26] E. Peris, J.A. Mata, V. Moliner, J. Chem. Soc. Dalton Trans.
(1999) 3893.
[27] L.F. Tang, Z.H. Wang, Y.M. Xu, J.T. Wang, H.G. Wang, X.K.
Yao, Polyhedron 18 (1999) 2383.
[28] W.Y. Wong, S.H. Cheung, S.M. Lee, S.Y. Leung, J. Organomet.
Chem. 596 (2000) 36.
[29] F.E. Ku¨hn, I.S. Goncalves, A.D. Lopes, J.P. Lopes, C.C. Ro-
ma˜o, W. Wachter, J. Mink, L. Hajba, A.J. Parola, F. Pina, J.
Sotomayor, Eur. J. Inorg. Chem. (1999) 295.
[30] L.F. Tang, Z.H. Wang, Y.M. Xu, J.T. Wang, H.G. Wang, X.K.
Yao, Transition Met. Chem. 24 (1999) 708.
[31] S. Camiolo, S.J. Coles, P.A. Gale, M.B. Hursthouse, T.A.
Mayer, M.A. Paver, J. Chem. Soc. Chem. Commun. (2000) 275.
[32] P.Y. Yang, F.C. Chang, M.C. Suen, J.D. Chen, T.C. Keng, J.C.
Wang, J. Organomet. Chem. 596 (2000) 226.
[33] S.E. Kabir, E. Rosenberg, Organometallics 14 (1995) 721.
[34] C.P. Casey, A.J. Shusterman, N.W. Vollendorf, K.J. Haller, J.
Am. Chem. Soc. 104 (1982) 2417.
[16] N. Chabert, L. Jacquet, C. Marzin, G. Tarrago, New J. Chem.
19 (1995) 443.
[17] C. Lopez, R.M. Claramunt, S. Trofimenko, J. Elguero, Can. J.
Chem. 71 (1993) 678.
[18] K. Niedenzu, J. Serwatowski, S. Trofimenko, Inorg. Chem. 30
(1991) 524.