Synthesis and characterization of N-phenyl pyrrole anchored to Fischer carbene complex through ring closing metathesis oxidative aromatization and various aryl substituted Fischer carbene complexes

Article abstract of DOI:10.1016/j.jorganchem.2012.12.014

Ring closing metathesis of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)carbene]tungsten(0) complex, [(CO)₅W=C(OCH₂CH ₃)C₆H₄N(CH₂CHCH₂) ₂], 1 leads to the formation of pentacarbonyl[(ethoxy)(N-phenyl 2,5-dihydro pyrrolyl)carbene]tungsten(0) complex, [(CO)₅W=C(OCH ₂CH₃)C₆H₄N (CH₂CHCH ₂)₂], 2 in good yield. Further, complex 2 undergoes oxidative aromatization to afford N-phenyl pyrrole anchored to alkoxy carbene, 3. In addition, a number of aryl substituted carbene complexes [(CO) ₅W=C(OCH₂CH₃)C₆H₄R], 4-7 (4: R = OCH₂CH₃; 5: R = OCH₂CH=CH₂; 6: R = OCH=CHCH₂CH₂CH₂CH₂CH ₃; 7: OC₆H₅Br) have been synthesized from the reaction of 1-(allyloxy)-4-bromobenzene with W(CO)₆ in presence of various concentration of n-BuLi and Meerwein's salt. All the complexes have been isolated in moderate to good yields and have been characterized by ¹H NMR, ¹³C NMR, IR, UV-vis spectroscopic techniques and the solid state structures of 1, 2 and 4 have been unequivocally established by X-ray diffraction analysis.

Full text of DOI:10.1016/j.jorganchem.2012.12.014

Journal of Organometallic Chemistry 726 (2013) 56e61
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of N-phenyl pyrrole anchored to
Fischer carbene complex through ring closing metathesis oxidative
aromatization and various aryl substituted Fischer carbene complexes
*
R. Ganesamoorthi, Arunabha Thakur, D. Sharmila, V. Ramkumar, Sundargopal Ghosh
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Ring closing metathesis of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)carbene]tungsten(0) complex,
[(CO)5W]C(OCH2CH3)C6H4N(CH2CH]CH2)2], 1 leads to the formation of pentacarbonyl[(ethoxy)(N-
phenyl 2,5-dihydro pyrrolyl)carbene]tungsten(0) complex, [(CO)5W]C(OCH2CH3)C6H4N (CH2CH]
CH2)2], 2 in good yield. Further, complex 2 undergoes oxidative aromatization to afford N-phenyl pyrrole
anchored to alkoxy carbene, 3. In addition, a number of aryl substituted carbene complexes [(CO)5W]
C(OCH2CH3)C6H4R], 4e7 (4: R ¼ OCH2CH3; 5: R ¼ OCH2CH]CH2; 6: R ¼ OCH]CHCH2CH2CH2CH2CH3; 7:
OC6H5Br) have been synthesized from the reaction of 1-(allyloxy)-4-bromobenzene with W(CO)6 in
presence of various concentration of n-BuLi and Meerwein’s salt. All the complexes have been isolated in
moderate to good yields and have been characterized by 1H NMR, 13C NMR, IR, UVevis spectroscopic
techniques and the solid state structures of 1, 2 and 4 have been unequivocally established by X-ray
diffraction analysis.
Received 4 October 2012
Received in revised form
11 December 2012
Accepted 12 December 2012
Keywords:
Fischer carbene complex
Ring closing metathesis
Oxidative aromatization
N-heterocycle
Group 6 transition metal
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
commanding strategies for the synthesis of carbocyclic and
heterocyclic frameworks is ring closing metathesis (RCM) [14,15].
Since after the discovery of Fischer carbene complex in 1964 [1],
it has been extensively used during past few decades and it is one of
the most versatile organometallic reagents for organic synthesis.
The number and utility of different types of reactions of these
complexes that have been reported [2e4], are far too numerous to
list. It has been widely reported that variations in the substituents
of the carbene-unit often lead to novel and unprecedented reac-
tivity trends. Reports focused on the utility of these organometallic
reagents in the synthesis of heterocyclic compounds have not been
much explored [5]. Therefore, it is desirable to draw the attention of
people involved in organic synthesis mediated or catalyzed by
organometallic reagents to the potential of Fischer-type carbene
complexes for accessing different types of heterocycles.
However, in the context of aromatic and heteroaromatic ring
formation, rationally designed RCM strategies have only recently
been highlighted in the literature [16]. Indeed, many early exam-
ples of the synthesis of aromatic compounds by RCM were viewed
as unwanted degradation reactions [17]. A compound containing
heteroaromatic moiety attached with alkoxy Fischer carbene
complex was found to be highly demandable in the field of
chemistry and biology. In the course of our ongoing investigations
on the reactivity of Fischer carbene complexes, we have observed
the formation of several unusual products and subsequent reaction
of one of the products with Grubb’s catalyst produces a N-hetero-
cycle bearing Fischer carbene complex. We report herein the
synthesis and characterization of pentacarbonyl[(ethoxy)(N-phenyl
In recent years, the metathesis reaction has become one of the
most important CeC bond forming processes and has been utilized
extensively in total synthesis [6e10]. The advent of well defined
catalyst systems, combined with excellent activity and broad
functional group compatibility, has been the major factor for
popularizing the metathesis reaction [11e13]. One of the most
pyrrolyl)carbene]tungsten(0) complex via
aromatization and several aryl substituted Fischer carbene
complexes.
a
RCM-oxidative
2. Results and discussion
2.1. Synthesis and characterization of compounds 1e3
There are several reports available in the literature that depict
the oxidative aromatization of N-aryl dihydropyrroles upon
* Corresponding author. Tel.: þ91 44 2257 4230; fax: þ91 44 2257 4202.
E-mail address: sghosh@iitm.ac.in (S. Ghosh).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.12.014

R. Ganesamoorthi et al. / Journal of Organometallic Chemistry 726 (2013) 56e61
57
Table 1
prolonged exposure to air [18], by treatment with stoichiometric
Synthesis of complex 3 via ring closing metathesis (RCM).
amounts of benzoquinones [18] or MnO2 [19,20] or during Pd-
catalyzed Heck reactions at the endocyclic dihydropyrrole CeC-
double bond [21]. In an attempt to the ring closing metathesis
allylic oxidation sequence for the synthesis of coumarin [22], it was
observed that the reaction became faster in presence of hydroper-
oxides. Schmidt et al. speculated that the use of this chemical
triggered the RCM reactions leading to five membered heterocycles
might result in oxidative aromatization, rather than allylic oxida-
tion. Therefore, we attempted to synthesize complex 3 from 1 using
the same strategy. As shown in Scheme 1, the reaction of N,N-
diallylaminophenyllithium with [W(CO)6] followed by the addi-
tion of 1 equivalent of Meerwein’s salt, [(Et3O)BF4] afforded the red
Fischer carbene complex 1 in 65% yield. After having compound 1 in
good yield, we have performed the Grubb’s catalytic RCM of 1, that
yielded pentacarbonyl[(ethoxy)(N-phenyl 2,5-dihydro pyrrolyl)
carbene]tungsten(0) complex, 2 in moderate yield. Furthermore,
the aromatization of 2 using tert-butyl hydroperoxide in toluene
yielded the complex 3 (Scheme 1b). As shown in Table 1, the
reaction proceeds well in presence of 5 mol% catalyst in toluene in
Entry Solvent
Equivalent of catalyst Temperature Time Yielda
1
2
3
4
5
Ether
Ethyl acetate
Dichloromethane 5 mol%
Toluene
Toluene
5 mol%
5 mol%
RT
RT
40 ꢀC
40 ꢀC
60 ꢀC
12 h NR
12 h 10%
15 h 20%
5 mol%
5 mol%
5 h
3 h
71%
80%
NR: No results.
a
Isolated yield after purification.
aryl ring attached to the carbene carbon of the complex is oriented
orthogonal to the metalcarbene -plane in solid state. The We
p
ꢀ
C(carbene) distance of 2.192(14) A in 1 is typical for alkox-
ycarbene complexes of W(CO)5 and WeC(carbene) distance of
ꢀ
2.245(3) A in 2 is longer due to the presence of less electronegative
N atom attached to aryl ring. As observed in 1 and 2, the N,N-diallyl
and the N-phenyl 2,5-dihydro pyrrole moiety are approximately
coplanar with the carbene moiety (W, C(6), O(6), C(7)), with torsion
angle ranging from 168.5(2)ꢀ to 180.0ꢀ, thus allowing resonance
stabilization between the carbene ligand and the adjacent ring.
t
3 h at 60 ꢀC followed by room temperature reaction with BuOOH
for 30 min. All the carbene complexes, 1e3 were characterized by
standard spectroscopic analysis and the solid state structure of 1
and
analysis.
2 were unambiguously established by X-ray diffraction
2.2. Synthesis and characterization of aryl substituted alkoxy
Fischer carbene complexes, 4e7
The presence of NCH2 protons in 1 and 2 have been confirmed
by 1H NMR spectra, which show the characteristic peaks in the
As shown in Scheme 2, the reaction of 1-(allyloxy)-4-
bromobenzene with W(CO)6 in presence of various concentration
of n-BuLi and Meerwein’s salt leads to the formation of air stable
red alkoxy Fischer carbene complexes, 4e6 in 42e56% yields.
Interestingly, a room temperature reaction of tungsten hex-
acarbonyl with 1-(allyloxy)-4-bromobenzene in presence of 0.5
equivalent of n-BuLi and 3 equivalent of Meerwein’s salt yielded
a red complex, 7 in 30% yield. The formation of 4 requires only 1
equivalent of n-BuLi to generate the aryl lithium complex required
for the formation of the carbene complex. If Meerwein’s salt is
present in excess, it is the source for ethyl cation which will cleave
the O-allyl bond by first coordination of ethyl cation to the oxygen
atom followed by the cleavage of allyl group (Supporting
information Figure S16). This will lead to the formation of the
compound 4. Formation of compound 5 is straight forward, 1
equivalent of n-BuLi is used to generate the aryl lithium and exactly
1 equivalent of Meerwein’s salt is required to ethylate the resulting
range of
CH2 protons of 1 have been confirmed by 1H NMR spectra, which
show the characteristic multiplet at
5.25 ppm respectively. Absence of these two characteristic peaks
and presence of one new peak due to the olefinic protons at
d
¼ 4.03e4.22 ppm. Further, the presence of allylic CH and
d
¼ 5.8e5.90 ppm and 5.16e
d
¼ 5.98 ppm confirms the formation of complex 2. Formation of
complex 3 was confirmed by 1H NMR spectra which show the
chemical shift at
¼ 5.9e6.5 ppm characteristic for aromatic N-
heterocyclic pyrrole ring. The presence of carbene carbon (W]C) in
d
1e3, appeared in the region of
d
¼ 299.5e315.7 ppm, was
confirmed by 13C NMR spectroscopy. The characteristic IR stretch-
ing frequencies for W(C]O) were observed in the range of 2065.4e
2076.4 and 1911.1e1932.7 cmꢁ1 for compounds 1e3.
The solid state X-ray structures of 1 and 2, shown in Figs.1 and 2,
are fully consistent with the spectroscopic data. The crystal struc-
ture of both the Fischer carbene complexes 1 and 2 reveal that an
Scheme 1. a) Synthesis of N-diallyl substituted Fischer carbene complex 1; b) Synthesis of complexes 2 and 3.

58
R. Ganesamoorthi et al. / Journal of Organometallic Chemistry 726 (2013) 56e61
1H NMR spectra of complexes 4e6 show symmetrical patterns
as expected for phenyl ring in the aromatic region at
d
¼ 6.88e
7.87 ppm. Further, the presence of allylic CH and CH2 protons of 5
have been confirmed by 1H NMR spectrum, which shows the
characteristic multiplet at
d
¼ 6.01e6.06 ppm and 5.32e5.45 ppm
respectively. The presence of vinylic proton in complex 6 was
confirmed by 1H NMR. Further, the 2-D NMR spectroscopic study
was performed to confirm the presence of vinylic protons and
aliphatic chain in complex 6. The presence of all the characteristic
peaks were further confirmed by 13C NMR spectroscopy that
confirms the presence of carbene carbon (W]C) appeared in the
region of
d
¼ 310.7e312.4 ppm and the carbonyl groups.
The solid state structure of complex 4, shown in Fig. 3, was
unambiguously established by X-ray diffraction analysis. The
crystal structure of Fischer carbene complexes reveal that an aryl
ring attached to the carbene carbon of the complex is oriented
ꢀ
orthogonal to the metalcarbene
p
-plane. The distance of 1.49(2) A
between C15 and C16 in 4 is slightly longer than the corresponding
ꢀ
distance of C15eC16 (1.42(4) A) in 1. This may be due to the change
of heteroatom oxygen by nitrogen.
The pentacarbonyl[(ethoxy)(4-bromo phenoxy phenyl)carbene]
tungsten(0) complex 7, isolated as an air-stable red solid, represents
a novel mononuclear organometallic compound consisting of
conjugated donoreacceptor systems. Complexes of these charac-
teristics are attractive synthetic goals due to their physical and
chemical properties. 1H NMR spectrum shows the presence of four
symmetrical aromatic resonances (Jortho ¼ 9 Hz) as doublet in the
ꢀ
Fig. 1. Molecular structure and labeling diagram for 1. Selected bond lengths (A) and
angles are (ꢀ):C1eW1 1.95(2), C6eW1 2.28(3), C3eW1 2.041(11), C6eO6 1.321(2), C6e
C7 1.37(4), C10eN1 1.36(3), C11eC12 1.46(3), C15eC16 1.42(4), C15eN1 1.47(3), C13e
O6 1.408(16); O6eC6eW1 124(2), O3eC3eW1 173.2(15), O2eC2eW1 173.4(14), O6e
C6eC7 110(3), C11eC10eN1 122(3), C16eC15eN1 114(2).
carbene intermediate. In presence of 0.5 equivalent of n-BuLi and 3
equivalent of Meerwein’s salt, the compound 5 is forming while
excess of starting material, (1-(allyloxy)-4-bromobenzene) and
Meerwein’s salt are present (as we have taken 0.5 equivalent of
BuLi). The lone pair on the oxygen atom of the excess starting
material will attack (known as Ipso substitution) the aromatic
carbon attached to the O-allyl group to form the complex 7
(Supporting information Figure S16).
region of
d
¼ 6.72e7.80 ppm, which confirms the presence of two
aromatic rings. In addition, 2-D NMR confirms the formation of
proposed complex. The presence of all the characteristic peaks was
further confirmed by 13C NMR spectroscopy that confirms the
presence of W]C carbon appeared at
d
¼ 311.3 ppm. The charac-
teristic IR stretching frequency for W(C]O) appeared at 1917.9 and
2065.2 cmꢁ1 for compound 7. In the infrared spectra, the CO-
absorptions of 7 are shifted to lower wave numbers due to the
electron pushing effect of the aromatic conjugation.
2.3. UVevis absorption spectra of 1e7
The organometallic photochemistry of chromium(0)/tung-
sten(0)carbene complexes is, perhaps, one of the few metal-
mediated photoreactions of general application in organic
synthesis [23e25]. The monometallic carbene complexes, 1e7 are
strongly colored ranging from yellow to deep red. Therefore, the
charge transfer bands in the UVevisible region of the carbene
complexes have been recorded to verify whether they show
behavior compatible with other alkoxy carbene complexes [26].
The UVevis spectra of Fischer metalecarbene complexes show
three well-defined absorptions: a spin-forbidden metaleligand
charge transfer (MLCT) absorption around 500 nm, the spin-
allowed and moderately intense LF absorption in the range of
350e450 nm, and one additional ligand-field (LF) transition in the
range of 300e350 nm [27]. Complexes 1e3 show three major
absorption bands in the visible region (Supporting information
Figure S17). The absorption bands appeared around ca. 450 nm
for complexes 1 and 2 may be attributed to the metal-to-ligand
charge transfer (MLCT) consistent with previous findings on
related Fischer carbene complexes [26]. The less intense absorption
band (MLCT) in ultraviolet (w354 nm) for 1 and 2 originating from
metal carbonyl moiety. For compound 3, both MLCT bands got blue-
shifted due to the aromatic character of attached pyrrole ring.
Interestingly, upon changing nitrogen atom by more electronega-
tive oxygen atom both high energy and weaker low energy band
got shifted bathochromically in complexes 4e7.
ꢀ
Fig. 2. Molecular structure and labeling diagram for 2. Selected bond lengths (A) and
angles are (ꢀ):C1eN1 1.456(4), C2eC3 1.301(5), C5eN1 1.350(3), C11eW1 2.245(3),
C12eO1 1.440(3), C12eC13 1.498(4), C15eW1 2.032(3), C7eC8 1.409(3), C16 O4
1.148(4); C3eC2eC1 112.4(3), N1eC1eC2 101.9(3), N1eC5eC10 121.3(2), O1eC11eW1
125.83(19), C8eC11eW1 126.60(18), O1eC12eC13 106.8(2), O3eC15eW1 179.0(3),
C16eW1eC14 82.84(13), C11eO1eC12 123.4(2).

R. Ganesamoorthi et al. / Journal of Organometallic Chemistry 726 (2013) 56e61
59
Scheme 2. Synthesis of aryl substituted Fischer carbene complexes 4e7.
3. Conclusion
(Triethyloxonium tetrafluoroborate), 4-allyloxyphenyllithium and
N,N0-diallylaminophenyllithium compound were performed
according to the literature procedure [28e30]. Allyl bromide,
epichlorohydrin were purchased and freshly distilled prior to use.
Chromatography was carried out on 3 cm of silica gel in a 2.5 cm dia
column. Thin layer chromatography was carried on 250 mm dia
aluminum supported silica gel TLC plates (MERK TLC Plates). The
NMR spectra were recorded on 400 and 500 MHz Bruker FT-NMR
spectrometer. The Infrared spectra were obtained on a Nicolet
iS10 FT-IR spectrometer. Microanalysis for C, H and N were per-
formed on Perkin Elmer Instruments series II model 2400. The UVe
vis spectra were carried out in CH2Cl2 solutions at c ¼ 1 ꢂ10ꢁ4 M in
JASCO V-650 spectrophotometer.
In conclusion we have reported a novel approach for the
synthesis of N-phenyl pyrrole anchored to Fischer carbene complex
using RCM as a key for CeC bond formation reaction followed by
oxidative aromatization. To the best of our knowledge, the
synthesis of the N-phenyl pyrrole attached to Fischer carbene
complex using this reaction sequence is unprecedented. Further,
we have described the synthesis of several aryl substituted Fischer
carbene complexes containing heteroatom in good yields. In addi-
tion, the solid state structure of these complexes revealed that aryl
ring attached to the carbene carbon of the complex is oriented
orthogonal to the metalcarbene
p-plane in solid state. These
results, in essence, supplement the observation made for their
preferred orthogonal conformation in solution as well. All these
complexes reported in this article could be the crucial intermediate
for the synthesis of various natural product and biologically active
molecules.
4.2. Synthesis of 1
In a dried Schlenk tube, W(CO)6 (0.50 g, 1.5 mmol) was taken in
30 ml dry ether and the suspension was cooled to 0 ꢀC. In an
another Schlenk tube N,N-diallyl-4-bromo aniline (0.43 g,
1.8 mmol) was taken in 10 ml dry ether. The stirred solution was
cooled to ꢁ78 ꢀC and 1.3 ml of n-BuLi (1.6 M in hexane, 2.1 mmol)
was added and continued stirring for 1 h. The lithiated solution was
then added dropwise to the W(CO)6 suspension. The reaction
mixture was stirred at room temperature for 1 h. The ether was
evaporated and the salt was dissolved in minimum amount of
CH2Cl2, to which 0.6 ml of Meerwein’s salt solution (2.5 M,
1.5 mmol) was added. The solvent was removed under vacuum and
the residue was extracted into hexane and passed through neutral
alumina. After removal of solvent, the residue was subjected to
4. Experimental
4.1. General procedures and instrumentation
All the operations were conducted under Ar atmosphere using
standard Schlenk techniques and Glove Box. Solvents were distilled
and degassed prior to use under Argon. 4-bromo phenol, 4-bromo
aniline, W(CO)6, sodium methoxide, Grubb’s catalyst (G-I), tert-
Butyl hydroperoxide and n-BuLi purchased were of analytical grade
and used without further purification. Synthesis of Meerwein’s salt

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R. Ganesamoorthi et al. / Journal of Organometallic Chemistry 726 (2013) 56e61
54.6 (NCH2), 15.2 (CH3). Mp 85 ꢀC; IR (Hexane): 2076.4, 1918.7,
1578.0 cmꢁ1. Elemental analysis (%) calcd for C18H15O7NW: C, 41.22;
H, 2.86; N, 2.67. Found: C, 41.44; H, 2.72; N, 2.79.
4.4. Synthesis of 3
The pentacarbonyl[(ethoxy)(N-phenyl 2,5-dihydro pyrrolyl)
carbene]tungsten(0) complex (0.10 g, 0.20 mmol) was dissolved in
toluene (10 ml) and a 6 M solution of tBuOOH (0.04 ml, 0.26 mmol)
in decane was added drop wise to this solution. After stirring for
30 min at ambient temperature, the solvent was removed under
vacuum and the residue was extracted into CH2Cl2 and passed
through Celite. After removal of solvent, the residue was subjected
to chromatographic work up using flash column chromatography.
Elution with a hexane/CH2Cl2 (80:20 v/v) mixture afforded red oil 3
(0.09 g, 90%).
3: 1H NMR (CDCl3, 500 MHz):
d
¼ 7.81 (d, 2H, ArH, J ¼ 9 Hz), 7.18
(d, 2H, ArH, J ¼ 9 Hz), 7.44 (d, 2H, HPyrrole), 6.39 (d, 2H, HPyrrole), 5.09
(q, 2H, OCH2, J ¼ 7 Hz), 1.73 (t, 3H, CH3, J ¼ 7 Hz); 13C NMR (CDCl3,
125 MHz)
d
¼ 315.0 (W]C), 203.3 (WeCO), 197.5 (WeCO), 132.6
(ArC), 130.0 (ArC), 131.0 (ArC), 129.0 (ArC), 119.0 (CPyrrole), 118.8
(CPyrrole), 68.3 (OCH2), 14.1 (CH3); IR (Hexane): 2065.4, 1932.7,
1597.0 cmꢁ1
.
4.5. Synthesis of 4
In a dried Schlenk tube, W(CO)6 (1 g, 2.9 mmol) was taken in
30 ml dry ether and the suspension was cooled to 0 ꢀC. In a 100 ml
Schlenk tube, 4-allyloxy bromo benzene (0.61 g, 2.9 mmol) was
taken in 10 ml dry ether. The stirred solution was cooled to ꢁ78 ꢀC
and 1.78 ml of n-BuLi in hexane (1.6 M in hexane, 2.9 mmol) was
added drop wise and continued stirring for 1 h. The allyloxy
benzene anion solution was then added to the tungsten hex-
acarbonyl suspension. The temperature was raised to 0 ꢀC and
stirred for 1 h. The ether was evaporated and the salt was dissolved
in minimum amount of CH2Cl2, to which 2.84 ml of Meerwein’s salt
solution (2.5 M, 7.25 mmol) was added. The resulting dark red
solution was extracted in hexane, concentrated and purified by
flash column chromatography (pet ether: CH2Cl2 90:10) to afford
complex 4 (0.79 g, 56%) as an orange solid.
Fig. 3. Molecular structure and labeling diagram for 4. Thermal ellipsoids are shown at
the 30% probability level. Selected bond lengths (A) and angles are (ꢀ): C6eW1
ꢀ
2.192(14), C1eW1 2.030(16), C3eW1 2.014(19), C6eO6 1.298(16), C6eC7 1.498(19),
C10eO7 1.300(17), C11eC12 1.39(2), C15eC16 1.49(2), C3eO3 1.132(19), C13eO6
1.477(18); O6eC6eW1131.6(9), O3eC3eW1178.4(15), O2eC2eW1176.5(14), O6eC6e
C7 104.2(11), O7eC10eC9 119.1(14).
chromatographic work up using flash column chromatography.
Elution with a hexane/CH2Cl2 (95:5 v/v) mixture yielded red solid 1
(0.51 g, 65%).
1: 1H NMR (CDCl3, 500 MHz):
d
¼ 8.03 (d, 2H, ArH, J ¼ 9.2 Hz),
4: 1H NMR (CDCl3, 500 MHz):
d
¼ 7.88 (d, 2H, ArH, J ¼ 9 Hz), 6.90
6.67 (d, 2H, ArH, J ¼ 9.2 Hz), 5.90e5.82 (m, 2H, HC]CH2), 5.25e5.16
(d, 2H, ArH, J ¼ 9 Hz), 5.05 (q, 2H, OCH2, J ¼ 9 Hz), 4.13 (q, 2H, OCH2,
(m, 4H, C]CH2), 5.01 (q, OCH2, J ¼ 9 Hz), 4.04e4.03 (m, NCH2), 1.68
J ¼ 9 Hz), 1.70 (t, 3H, CH3, J ¼ 9 Hz), 1.45 (t, 3H, CH3, J ¼ 9 Hz); 13C
(t, 3H, CH3, J ¼ 9 Hz); 13C NMR (CDCl3, 125 MHz):
¼ 300.1 (W]C),
d
NMR (CDCl3, 125 MHz)
d
¼ 310.7 (W]C), 203.3 (WeCO), 197.9 (We
200.1 (WeCO), 198.4 (WeCO), 153.4 (ArC), 141.3 (ArC), 134.3 (ArC),
132.0 (ArC), 117.0 (C]Callyl), 110.6 (C]Callyl), 78.3 (OCH2), 52.8
(NCH2), 29.8 (CH3); mp 87 ꢀC; IR (Hexane): 2065.6, 1911.2, 1667.2,
1593.4 cmꢁ1. Elemental analysis (%) calcd for C20H19O6NW: C,
43.47; H, 3.44; N, 2.53. Found: C, 43.70; H, 3.38; N, 2.62.
CO), 163.5 (ArC), 146.7 (ArC),132.2 (ArC), 113.9 (ArC), 79.6 (OCH2),
64.0 (OCH2), 15.1 (CH3), 14.9 (CH3); mp 76 ꢀC; IR (Hexane): 2065.4,
1932.7, 1597.0 cmꢁ1. Elemental analysis (%) calcd for C16H14O7W: C,
38.32; H, 2.79. Found: C, 38.58; H, 2.51.
4.3. Synthesis of 2
4.6. Synthesis of 5
To a solution of pentacarbonyl[(ethoxy)(N,N-diallyl anilyl)car-
bene]tungsten(0) complex, 1 (0.30 g, 0.6 mmol) in toluene (10 ml),
Grubb’s catalyst (G-I) (0.024 g, 0.03 mmol) was added. The solution
was stirred for 3 h at 60 ꢀC. After cooling to ambient temperature all
volatiles were removed in vacuo and the residue was purified by
column chromatography. Elution with hexane/CH2Cl2 mixture
(90:10 v/v) yielded red solid 2 (0.23 g, 80%).
The same procedure was adopted as for complex 4 using the
following reagents: W(CO)6, (0.66 g, 1.9 mmol), 4-allyloxy bromo
benzene (0.40 g, 1.9 mmol), n-BuLi in hexane (1.17 ml, 1.9 mmol),
0.75 ml of Meerwein’s salt solution (2.5 M, 1.9 mmol). Yield (0.44 g,
46%).
5: 1H NMR (CDCl3, 500 MHz):
d
¼ 7.87 (d, 2H, ArH, J ¼ 9 Hz), 6.93
(d, 2H, ArH, J ¼ 9 Hz), 6.06e6.01 (m, 1H, CH), 5.45e5.32 (m, 2H, C]
2: 1H NMR (CDCl3, 500 MHz):
d
¼ 8.04 (d, 2H, ArH, J ¼ 9 Hz), 6.47
CH2), 5.05 (q, 2H, OCH2, J ¼ 7 Hz), 4.63e4.61 (m, 2H, CH2), 1.70 (t,
(d, 2H, ArH, J ¼ 9 Hz), 5.98 (s, 2H, CH]CH), 4.22 (s, 4H, NCH2), 4.99
3H, CH3, J ¼ 7 Hz); 13C NMR (CDCl3, 125 MHz):
d
¼ 311.3 (W]C),
(q, 2H, OCH2, J ¼ 7 Hz), 1.66 (t, 3H, CH3, J ¼ 7 Hz); 13C NMR (CDCl3,
203.2 (WeCO), 197.9 (WeCO), 162.9(ArC), 147.1(ArC), 132.4 (ArC),
132.1 (ArC), 118.5 (C]C), 114.1 (C]C), 79.7 (OCH2), 69.1 (OCH2); IR
125 MHz)
d
¼ 299.5 (W]C), 203.2 (WeCO), 198.5 (WeCO), 151.4
(ArC), 134.7 (ArC), 141.1 (ArC), 126.0 (ArC), 110.3 (C]C), 78.3 (OCH2),
(Hexane): 2065.4, 1932.7, 1565.1 cmꢁ1
.

R. Ganesamoorthi et al. / Journal of Organometallic Chemistry 726 (2013) 56e61
61
ꢀ
Table 2
monochromated Mo-K
a
(l
¼ 0.71073 A) radiation at 173 K. The
Crystallographic data for compounds 1, 2 and 4.
structures were solved by heavy atom methods using SHELXS-97
[31] or SIR92 and refined using SHELXL-97 [32].
1
2
4
Empirical formula
Formula weight
Crystal system
Temperature
C
20H19O6NW
C18H15O6WN
525.16
Monoclinic
298 K
C16H14O7W
502.12
Triclinic
298 K
553.21
Triclinic
298 K
Acknowledgment
Generous support of the Department of Science and Technology,
Board of Research in Nuclear Science (BRNS), No-2011/37C/54/
BRNS, Government of India, is gratefully acknowledged. R. G is
grateful to the University Grants Commission (UGC), A. T and D. S
thanks Council of Scientific and Industrial Research (CSIR), India for
research fellowship.
Space group
P-1
P2(1)/c
P-1
ꢀ
a (A)
9.9451(6)
10.1754 (6)
11.8239 (7)
107.994(2)
105.794(2)
94.626(2)
1077.15 (11)
2
1.706
536
2.16e27.71
1.159
9.7908(2)
26.4079(7)
7.11130(10)
90.00
90.5050(10)
90.00
1838.59(7)
4
1.897
6.8017(7)
10.6812(12)
12.7848(15)
93.590(4)
90.557(4)
108.185(4)
880.28(17)
2
1.894
480
1.60e22.01
1.134
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
3
ꢀ
V (A )
Z
Appendix A. Supplementary data
DcaSlc (g/cm3)
F (000)
1008
2.59e28.49
1.051
Range (ꢀ)
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2012.12.014.
q
Goodness-of-fit on F2
Final R indices [I > 2
q(I)]
R1 ¼ 0.0461
R1 ¼ 0.0221
R1 ¼ 0.0532
wR2 ¼ 0.1089
wR2 ¼ 0.0441
wR2 ¼ 0.1274
References
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4.7. Synthesis of 6
The same procedure was used as for complex 4, using the
following reagents: W(CO)6 (1 g, 2.9 mmol), 4-allyloxy bromo
benzene (0.61 g, 2.9 mmol), 2.7 ml of n-BuLi(1.6M, 4.4 mmol),1.14 ml
of Meerwein’s salt solution (2.5 M, 2.9 mmol). Yield (0.66 g, 42%).
6: 1H NMR (CDCl3, 500 MHz):
d
¼ 7.84 (d, 2H, ArCH, J ¼ 7 Hz),
[7] R.H. Grubbs (Ed.), Handbook of Metathesis, vol. 1e3, Wiley-VCH, Weinheim,
2003, p. 1234.
7.01 (d, 2H, ArCH, J ¼ 7 Hz), 5.03 (q, 2H, CH2, J ¼ 7 Hz), 6.43e6.42 (m,
1H, OeHC]CH), 5.01e4.97 (m, 1H, C]CH), 1.717 (t, 3H, CH3,
J ¼ 7 Hz), 2.21 (m, 2H, CH2), 1.41 (m, 2H, CH2), 1.31 (m, 2H, CH2), 0.88
[8] A. Furstner, Angew. Chem. Int. Ed. 39 (2000) 3012e3043.
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121 (1999) 791e799.
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2664e2670.
[17] M.J. Bassindale, P. Hamley, A. Leitner, J.P.A. Harrity, Tetrahedron Lett. 40
(1999) 3247e3250.
(m, 3H, CH3); 13C NMR (CDCl3, 125 MHz)
d
¼ 312.4 (W]C), 203.1
(WeCO), 197.7 (WeCO), 161.2 (ArC), 148.3 (ArC), 138.5 (C]C), 116.0
(C]C), 131.3 (ArC), 115.1 (ArC), 77.7 (OCH2), 31.3 (CH2), 28.9 (CH2),
23.9 (CH2), 22.4 (CH2), 15.0 (CH3), 14.0 (CH3); IR (Hexane): 2065.6,
1911.1, 1593.4 cmꢁ1; Elemental analysis (%) calcd for C21H22O7W: C,
44.28; H, 3.86; Found: C, 44.51; H, 3.67.
4.8. Synthesis of 7
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Med. Chem. Lett. 13 (2003) 4173e4177.
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M.A. Weidner-Wells, H.M. Werblood, K. Bush, M.J. Macielag, Bioorg. Med.
Chem. Lett. 16 (2006) 4537e4542.
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143e153.
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Metal Carbene Complexes, Verlag Chemie, Deerfield Beach, FL, 1983.
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5253e5258.
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[31] SHELXS-97 G.M. Sheldrick, Program for Crystal Structure Solution, University
of Göttingen, Germany, 1997.
The same procedure was used as for complex 4, using the
following reagents: W(CO)6, (1.0 g, 2.9 mmol), 4-allyloxy bromo
benzene (0.61 g, 2.9 mmol), 0.89 ml of n-BuLi in hexane (1.6 M,
1.45 mmol), 3.40 ml of Meerwein’s salt solution (2.5 M, 8.7 mmol).
Yield (0.53 g, 30%).
7: 1H NMR (CDCl3, 500 MHz):
d
¼ 7.83 (d, 2H, ArH, J ¼ 9 Hz), 7.33
(d, 2H, ArH, J ¼ 9 Hz), 6.83 (d, 2H, ArH, J ¼ 9 Hz), 6.73 (d, 2H, ArH,
J ¼ 9 Hz), 5.05 (q, 2H, OCH2, J ¼ 7 Hz), 1.70 (t, 3H, CH3, J ¼ 7 Hz); 13
C
NMR (CDCl3, 125 MHz):
d
¼ 311.3 (W]C), 203.3 (WeCO),197.8 (We
CO), 132.6 (ArC), 132.2 (ArC), 117.3 (ArC), 115.0 (ArC), 160.4 (ArC),
154.7 (ArC), 147.3 (ArC), 112.9 (ArC), 79.7 (OCH2), 15.1 (CH3); IR
(Hexane): 2065.2, 1917.9 cmꢁ1; Elemental analysis (%) calcd for
C
20H13O7BrW: C, 38.21; H, 2.07. Found: C, 38.48; H, 2.31.
4.9. X-ray structure determination
The crystal data for 1 (CCDC 902381), 2 (CCDC 902382) and 4
(CCDC 902383), shown in Table 2, were collected and integrated
using a Bruker Axs kappa apex2 CCD diffractometer, with graphite
[32] SHELXL-97 G.M. Sheldrick, Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1997.