Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes

Article abstract of DOI:10.1007/s11243-015-0014-3

The reactions of five dinuclear carbonyl complexes [(η ⁵-C₅Me₄R)Mo(CO)₃]₂ [R = allyl, ⁿ Bu, ^t Bu, Ph, Bz] with I₂ in chloroform solution gave the corresponding mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes [(η ⁵-C₅Me₄R)MoI(CO)₃] [R = allyl (1), ⁿ Bu (2), ^t Bu (3), Ph (4), Bz (5)]. The molecular structures of complexes 2, 3 and 5 were determined by X-ray diffraction analysis. The results show that the substituent in the ring can directly affect the Mo-I bond distances; the more sterically hindered the substituent, the longer the Mo-I bond. Friedel-Crafts reactions of aromatic compounds with a variety of alkylation reagents catalyzed by the complexes showed that all of these mononuclear molybdenum carbonyl complexes have catalytic activity in Friedel-Crafts alkylation reactions. Indeed, compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as higher activities, mild reaction conditions, high selectivity, simple post-processing, and environmentally friendly chemistry.

Full text of DOI:10.1007/s11243-015-0014-3

Transition Met Chem
DOI 10.1007/s11243-015-0014-3
Synthesis and catalytic reactivity of mononuclear substituted
tetramethylcyclopentadienyl molybdenum carbonyl complexes
Zhi-Hong Ma2 Lin-Qian Lv1 Hong Wang3 Zhan-Gang Han1 Xue-Zhong Zheng1 Jin Lin1
•
•
•
•
•
Received: 13 October 2015 / Accepted: 1 December 2015
Ó Springer International Publishing Switzerland 2015
Abstract The reactions of five dinuclear carbonyl com-
Keywords Synthesis Á Friedel–Crafts alkylation
reaction Á Mononuclear molybdenum carbonyl complex Á
Chloranil
plexes [(g5-C5Me4R)Mo(CO)3]2 [R = allyl, Bu, Bu, Ph,
Bz] with I2 in chloroform solution gave the correspond-
ing mononuclear substituted tetramethylcyclopentadienyl
molybdenum carbonyl complexes [(g5-C5Me4R)MoI(CO)3]
[R = allyl (1), nBu (2), tBu (3), Ph (4), Bz (5)]. The molec-
ular structures of complexes 2, 3 and 5 were determined by
X-ray diffraction analysis. The results show that the sub-
stituent in the ring can directly affect the Mo–I bond dis-
tances; the more sterically hindered the substituent, the
longer the Mo–I bond. Friedel–Crafts reactions of aromatic
compounds with avariety of alkylation reagents catalyzed by
the complexes showed that all of these mononuclear
molybdenum carbonyl complexes have catalytic activity in
Friedel–Crafts alkylation reactions. Indeed, compared with
traditional catalysts, these mononuclear metal carbonyl
complexes have obvious advantages such as higher activi-
ties, mild reaction conditions, high selectivity, simple post-
processing, and environmentally friendly chemistry.
n
t
Introduction
Friedel–Crafts alkylation is one of the most important
chemical processes for the production of value-added
aromatic compounds through the formation of new C–C
bonds between aromatic molecules and alkylation reagents
such as alkyl halides, alkenes and alcohols [1–3].
Many of the products of these reactions are used as key
intermediates for the production of petrochemicals, cos-
metics, dyes and pharmaceuticals [2–5].
Conventional Friedel–Crafts alkylations are catalyzed
by Lewis acids such as AlCl3, FeCl3 and ZnCl2. However,
the separation and handling of the acid waste in these
homogeneous processes present undesirable economic,
environmental and safety issues [6]. Therefore, consider-
able effort has been devoted to the development of envi-
ronmentally friendly alternatives. One promising method is
the ortho metalation/alkylation approach, which provides
access to ortho-substituted benzene derivatives with pre-
cise regiocontrol [7–9]. However, this strategy also has
certain disadvantages. The use of a stoichiometric amount
of strong base results in salt waste. Moreover, this method
is incompatible with a wide range of reactive functional
groups. To resolve these issues, the transition-metal-cat-
alyzed direct C-H alkylation of benzenes with olefins has
been utilized since the first truly efficient catalysts were
identified by Murai et al. [10–12]. Although catalytic C–H
alkylation reactions enable the introduction of an alkyl
chain under neutral conditions, most existing methods
require aromatic substrates bearing a directing group and/
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-015-0014-3) contains supplementary
material, which is available to authorized users.
& Jin Lin
linjin64@126.com
1
The College of Chemistry and Material Science, Hebei
Normal University, Shijiazhuang 050024, China
2
College of Basic Medicine, Hebei Medical University,
Shijiazhuang 050017, China
3
Hebei Institute of Food Quality Supervision Inspection and
Research, Shijiazhuang 050091, China
123

Transition Met Chem
or specific olefins, thereby limiting the scope of this
methodology [13–16]. The strong demand for an environ-
mentally friendly and versatile synthesis for alkylbenzenes
has led to the recent innovative development of catalytic
Friedel–Crafts alkylation reactions.
the methylene protons. The 1H NMR spectrum of complex
3 showed a singlet at 1.38 ppm for the t-butyl protons. The
1H NMR spectra of 4 and 5 each showed a multiplet at
7.28–7.48 and 7.11–7.34 ppm, respectively, for the phenyl
protons.
Yamamoto and co-workers reported molybdenum com-
plexes that can catalyze Friedel–Crafts alkylations of ben-
zene derivatives in the presence of an organic oxidant,
namely o-chloranil [17]. Our team previously reported many
substituted tetramethylcyclopentadienyl binuclear molyb-
denum carbonyl complexes [(g5-C5Me4R)Mo(CO)3]2 [18–
21]. We at first studied the reactions of dinuclear metal
carbonyl complexes [(g5-C5Me4R)Mo(CO)3]2 [R = allyl,
nBu, tBu, Ph, Bz] with I2 in chloroform solution and obtained
the corresponding mononuclear substituted tetramethylcy-
clopentadienyl molybdenum carbonyl complexes [(g5-C5-
Me4R)MoI(CO)3] [R = allyl (1), nBu (2), tBu (3), Ph (4), Bz
(5)]. Next, we investigated the reactions of complex (2) with
toluene, tert-butyl bromide and o-chloranil in 1,2-dichlor-
oethane under reflux in order to observe electrophilic sub-
stitution products. To our delight, para/ortho substitution
products were detected; furthermore, we concluded that the
molybdenum species formed in situ was involved in this
reaction because no reaction took place in the absence of o-
chloranil. Therefore, this work is focused on this interesting
catalytic system, which is a combination of substituted
tetramethylcyclopentadienyl mononuclear molybdenum
carbonyl complexes and o-chloranil, for the alkylation of
aromatic derivatives. Some important reaction variables,
such as time and amount of catalyst, as well as various aro-
matic compounds and alkylating reagents, were investi-
gated. The obtained results and a possible reaction
mechanism are presented in this paper.
Crystal structures of complexes 2, 3 and 5
(Scheme 1)
The crystal structures of complexes 2, 3 and 5 were
determined by X-ray diffraction. Selected bond parameters
for these complexes are presented in Table 1, and their
structures are depicted in Figs. 1, 2 and 3. All three are
mononuclear substituted tetramethylcyclopentadienyl
molybdenum carbonyl complexes and have similar struc-
tures, in which the molybdenum atom is coordinated by an
g5-cyclopentadienyl, three terminal CO ligands and one
iodine atom. For complex 2, disorder in the location of
C(11) and C(12) is shown in Fig. 1; there was also disorder
˚
at the iodine atom. The I(1)–Mo(2) distance is 2.835(2) A,
˚
and the I(2)–Mo(2) distance is 2.8259(8) A. The Mo–I
bond distances for complexes 3 and 5 are 2.8556(3) and
˚
2.844(3) A, respectively, which are longer than in complex
2. This may be due to the steric effect of the bulkyl ligands.
Optimization of the catalytic system
To develop an optimal catalytic system, we first investi-
gated substituted complex (2) as a precatalyst for Friedel–
Crafts reaction of toluene and tert-butyl bromide
(Scheme 2; Table 2). A solution of toluene (4 mmol) and
tert-butyl bromide (12 mmol) in 1,2-dichloroethane
(3.5 mL) was heated in the presence of a catalytic amount
of the precatalyst (2.5 mol %) and different amounts of o-
chloranil under an argon atmosphere. Using refluxing 1,2-
dichloroethane, mixtures of the corresponding para and
ortho products were obtained. The conversion rate reached
69.7 % with higher para selectivity, when the reaction time
was 12 h and the ratio of complex (2) to o-chloranil was
1:2 (Table 2, entry 3). Upon increasing the proportion of
oxidant, the conversion rate was improved (Table 2, entries
5–8). With an extended reaction time, the yield reached
89.9 % (Table 2, entry 8). No product was obtained in the
absence of o-chloranil (Table 2, entry 9), suggesting
that an electrophilic substitution mechanism was involved
Results and discussion
Preparation of the complexes
The dinuclear carbonyl complexes [(g5-C5Me4R)Mo-
t
(CO)3]2 [R = allyl, nBu, Bu, Ph, Bz] were prepared
according to the literature [22, 23]. These molybdenum
dimers were reacted with excess I2 in chloroform to give
the new complexes. The IR spectra of complexes 1–5 were
similar and displayed characteristic strong peaks assigned
to terminal CO ligands. The 1H NMR spectra of complexes
1 and 3–5 showed two groups of singlets peak for the four
methyl protons, respectively, while complex 2 showed one
doublet for the four methyl protons. The 1H NMR spectrum
of complex 1 showed one multiplet at 7.29–7.38 ppm for
R
CO
OC
Mo
CO
I
CO
R
CO
CO
I2
CHCl3
Mo
Mo
2
Na2S2O3
OC
R
CO
CO
1
the allyl protons. The H NMR spectrum of complex 2
showed a triplet at 0.93 ppm for the methyl protons, a
multiplet at 1.34–1.38 ppm and a triplet at 2.42 ppm for
Scheme 1 Synthesis of complexes 1–5. R = allyl (1), nBu (2), Bu
(3), Ph (4), Bz (5)
t
123

Transition Met Chem
˚
Table 1 Selected bond distances (A) and angles (°) for complexes 2, 3 and 5
2
3
5
Bond distances
I(1)–Mo(2)
2.835(2)
2.8259(8)
2.323(5)
1.530(9)
1.004(7)
1.026(8)
C(1)–Mo(1)
C(2)–Mo(1)
C(3)–Mo(1)
C(15)–O(1)
C(16)–O(3)
Mo(1)–I(1)
2.386(3)
2.424(3)
2.339(3)
1.138(4)
1.140(4)
2.8556(3)
C(8)–Mo(1)
C(9)–Mo(1)
C(17)–O(1)
C(19)–O(3)
I(1)–Mo(1)
I(10)–Mo(1)
2.310(5)
2.308(5)
1.137(6)
1.12(2)
I(2)–Mo(2)
C(1)–Mo(2)
C(11)–C(12)
C(15)–O(1)
2.844(3)
2.815(2)
C(14)–O(2)
Bond angles
C(2)–C(3)–Mo(2)
C(4)–C(3)–Mo(2)
C(1)–Mo(2)–C(4)
C(16)–Mo(2)–C(3)
C(1)–Mo(2)–I(1)
I(1)–Mo(2)–I(1)
71.9(3)
70.5(3)
C(1)–C(2)–Mo(1)
C(3)–C(2)–Mo(1)
C(1)–Mo(1)–I(1)
C(2)–Mo(1)–I(1)
O(1)–C(15)–Mo(1)
O(2)–C(14)–Mo(1)
71.20(16)
69.28(16)
104.77(7)
84.74(7)
174.3(3)
179.8(3)
C(9)–C(10)–Mo(1)
C(15)–C(10)–Mo(1)
C(17)–Mo(1)–I(1)
O(1)–C(17)–Mo(1)
O(2)–C(18)–Mo(1)
I(10)–Mo(1)–I(1)
70.5(3)
127.6(4)
77.47(15)
176.7(5)
175.3(5)
133.65(5)
59.56(19)
141.2(4)
85.17(16)
131.36(4)
Fig. 3 Molecular structure of complex 5. Ellipsoids correspond to
30 % probability. Hydrogen atoms are omitted for clarity
Fig. 1 Molecular structure of complex 2. Ellipsoids correspond to
30 % probability. Hydrogen atoms are omitted for clarity
CH3
[CpMoI(CO)3] (2.5 mol%)
CH3
CH3
o-Chloranil
Br
+
+
ClCH2CH2Cl (3.5 mL), 80°C
a
6
6a
6a'
Scheme 2 [(g5-C5Me4nBu)MoI(CO)3]/o-chloranil-catalyzed Friedel–
Crafts alkylation reaction of toluene with tert-butyl bromide.
Cp = g5-C5Men4Bu
in the [[(g5-C5Me4nBu)MoI(CO)3]/o-chloranil catalytic
system.
From the above studies, considering factors such as the
reaction time, yield, and economic considerations, the
following experimental conditions were chosen for further
work: 1,2-dichloroethane as solvent; the molar ratio of
aromatic substrates and alkylation reagents was 1:3; the
Fig. 2 Molecular structure of complex 3. Ellipsoids correspond to
30 % probability. Hydrogen atoms are omitted for clarity
123

Transition Met Chem
Catalytic activities of the other complexes
Table 2 Optimization of the complex (2)/o-chloranil-catalyzed
reaction
Given the promising results obtained with complex (2), we
turned our attention to use of the other complexes as
Friedel–Crafts alkylation catalysts. The four remaining
Entry o-chloranil (mol%) t (h) Yield (%) para 6a/ortho 6a’
1
2
3
4
5
6
7
8
9
2.5
2.5
5
12
24
12
24
12
24
12
24
24
35.5
50.9
69.7
79.5
76.9
87
95:5
91:9
97:3
95:5
94:6
91:9
97:3
94:6
–
t
complexes [(g5-C5Me4R)MoI(CO)3] [R = allyl (1), Bu
(3), Ph (4), Bz (5)] with o-chloranil were examined under
the optimal conditions, with the results shown in
Tables 6–9 (Supporting Information). Overall, these com-
plexes gave similar results to (2). The small influence of
the different substituents on the catalytic behavior may be
due to their modest variations in steric and electronic
properties.
5
7.5
7.5
10
85
10
0
89.9
–
Reagents and conditions: toluene: 4 mmol, tert-butyl bromide:
12 mmol, [(C5Men4Bu)MoI(CO)3]: 2.5 mol %, 80 °C, – = not
detected
Reuse of catalyst
Catalyst reuse experiments were carried out using complex
(2) (2.5 mol%) and o-chloranil (5 mol%) to catalyze a
model reaction of substitution of toluene (4 mmol) with
tert-butyl bromide (12 mmol) in refluxing 1,2-dichlor-
oethane. After completion of the reaction, the catalyst was
recovered by filtration, washed three times with petroleum
ether and then reused for further cycles. The results are
summarized in Table 4. Yields of 37.1–63.9 % were
obtained over three consecutive cycles. These experiments
showed that the catalyst can be easily recovered from the
reaction mixture and gave modest yields upon reuse.
amount of catalyst was 2.5 mol % (substrate as reference);
the molar ratio of catalyst to oxidant was 1:2; reflux tem-
perature; reaction time 12 h.
Activity of aromatic substrates and alkylation
reagents
In order to test the scope of Friedel–Crafts alkylation
reactions catalyzed by complex (2) with o-chloranil, dif-
ferent aromatic substrates were chosen under the optimal
conditions, as shown in Table 3. Seven different alkylation
reagents including halohydrocarbons, alkenes and alcohols
were chosen as electrophilic reagents. Different functional
groups were included in the aromatic ring of the substrates
including electron-donating and electron-withdrawing
groups. The relevant reaction equations are shown in
Schemes 3, 4 and 5.
Catalytic reaction mechanism
All five of these complexes proved to be capable of cat-
alyzing Friedel–Crafts alkylation reactions. The aryl
products were obtained in moderate-to-good yields with
high para selectivities. The pattern of results suggests that
the reactions proceed by an electrophilic substitution
mechanism. The classical Markovnikov alkylation prod-
ucts obtained from the reactions of styrene with aromatic
substrates strongly support the intermediacy of carbocation
Tert-butyl halides, styrene and benzyl chloride could be
used as alkylation reagents in these reactions, and the
corresponding aryl products were obtained in good yields
with high selectivity for the para isomers. Two or three
substituted products could only be obtained with highly
active substrates and higher excess of alkylation reagent
(Table 3, entries 9, 17 and 25), suggesting that the catalytic
reaction has high regioselectivity. The reactivity of tert-
butyl bromide was higher than that of tert-butyl chloride,
since bromide is a better leaving group. The reactivity of n-
butyl bromide is poor, suggesting carbocation formation in
the reaction. The poor reactivities of alcohols in general
were ascribed to the activity of hydroxyl as leaving group.
Aromatic substrates containing electron-donating groups
tend to improve the yield of these Friedel–Crafts reactions,
consistent with the characteristics of the aromatic elec-
trophilic substitution reaction.
1
species. The H NMR spectrum of the recovered catalyst
was almost the same as that before reaction, but the IR
spectrum showed only two terminal strong carbonyl peaks,
different from the three terminal strong carbonyl peaks
before reaction. These results indicate that whereas the
molybdenum remains coordinated to the cyclopentadienyl
ring, one carbonyl group is lost during the catalytic reac-
tion. A probable catalytic mechanism can be proposed
according to reference 17 (Scheme 6). First, the mononu-
clear molybdenum carbonyl complex is oxidized by o-
chloranil to produce a higher-oxidation-state molybdenum
catecholate species 10. As a result of its electrophilic
character, 10 reacts with alkylation reagents to form a
clathrate R?X[Mo]-. This species reacts further to give the
123

Transition Met Chem
Table 3 [(g5-C5Me4nBu)
MoI(CO)3]/o-chloranil-
catalyzed reaction of aromatic
substrates with different
alkylation reagents
Entry
Arene
PhMe
Reagent
tBuBr
Mole ratio
T (°C)
T (h)
Yielda (%)
para/ortho
1
1:8
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:8
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:8
1:3
1:3
1:3
1:3
1:3
1:3
1:3
1:8
1:3
1:3
1:3
1:3
1:3
1:3
1:3
80
12
69.7
63.9
65.8
7.9
97:3
98:2
93:7
100c
100c
–
2
3
tBuCl
4
nBuBr
tBuOH
nBuOH
BzCl
5
12.4
–
6
7
77.9
65.5
97.9
96.1
94.5
6.3
94:6
91:9
95:5b
98:2
98:2
100c
99:1
100c
93:7
90:10
90:10b
97:3
96:4
–
8
PhCHCH2
tBuBr
9
PhOMe
80
80
80
8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
a
tBuCl
nBuBr
tBuOH
nBuOH
BzCl
12
8.9
1.3
90.2
80.1
25.1
21.3
17.2
–
PhCHCH2
tBuBr
PhBr
12
tBuCl
nBuBr
tBuOH
nBuOH
BzCl
1.1
100
–
–
35.8
22.2
92.9
91.0
90.3
–
94:6
100c
88:12b
92:8
92:8
–
PhCHCH2
tBuBr
PhOH
12
tBuCl
nBuBr
tBuOH
nBuOH
BzCl
6.1
100c
–
–
75.9
57.7
93:7
90:10
PhCHCH2
Separation rate of column chromatography
b
c
Containing a small amount of two or three substituted products
Only para product
Mole ratio: arene/reagent. – = not detected
R1
R1
R2
R1
[CpMoI(CO)3] (2.5 mol%)
R2
/ o-Chloranil (5.0mol%)
+
R2X
+
ClCH2CH2Cl (3.5 mL), 80°C
4 mmol
12 mmol
Scheme 3 [(g5-C5Me4nBu)MoI(CO)3]/o-chloranil-catalyzed Friedel–Crafts alkylation reactions of halohydrocarbons. Cp = g5-C5Men4Bu,
t
n
t
R1 = CH3(6); OCH3(7); Br(8); OH(9), X = Br, R2 = Bu(a); Bu(b), X = Cl, R2 = Bu(c); PhCH2(d)
123

Transition Met Chem
Scheme 4 [(g5-
R
R
C5Men4Bu)MoI(CO)3]/o-
chloranil-catalyzed Friedel–
Crafts alkylation reactions of
styrene. Cp = g5-C5Me4nBu,
R = CH3(6); OCH3(7); Br(8);
OH(9)
R
[CpMoI(CO)3] (2.5 mol%)
/ o-Chloranil (5.0mol%)
+
+
ClCH2CH2Cl (3.5 mL), 80°C
e
4 mmol
12 mmol
R1
R1
R1
[CpMoI(CO)3] (2.5 mol%)
R2
/ o-Chloranil (5.0mol%)
R2OH
12 mmol
+
+
ClCH2CH2Cl (3.5 mL), 80°C
4 mmol
R2
Scheme 5 [(g5-C5Me4nBu)MoI(CO)3]/o-chloranil-catalyzed Friedel–Crafts alkylation reactions of alcohols. Cp = g5-C5Me4nBu, R1 = CH3(6);
t
n
OCH3(7); Br(8); OH(9), R2 = Bu(f); Bu(g)
Cl
Cl
Table 4 Reuse of the catalyst
Cl
Cl
Cl
Cl
O
Cl
Cl
Recycle number
T (h)
Yield (%)
para/ortho
O
[Mo]
[Mo]
Br
O
H
10
R
O
H
1st
24
24
24
63.9
51.5
37.1
98:2
97:3
95:5
2nd
3rd
11
12
R
[Mo]
H
H
C
-[Mo], -HBr
Br
R
H
R
Cl
Cl
CO
Cl
O
[Mo]
O
13
CO
o-chloranil
-CO, -I
Cp' Mo
I
CO
Cl
Scheme 7 Possible mechanism of C–H activation in the substitution
process
10
R
R1
catecholate species 10 as before. As a result of its elec-
trophilic character, 10 then reacts with aromatic substrates
by activation of a C–H bond of the aromatic ring zwitte-
rionic intermediate 11. Subsequent proton abstraction gives
a Brønsted acid species 12. Because of the nucleophilicity
of the carbon atom attached to the metal center, 12 reacts
with n-butyl bromide to form the transition state 13 via an
SN2 reaction. Finally, the alkylation products are obtained
along with [Mo] and HBr.
R2
[Mo]
R1 X[Mo]
R1
R2
X
+ HX
-[Mo]
R2
[Mo]
R2
[
]
Mo
-[Mo]
Scheme 6 Possible mechanism involving carbonium ion intermedi-
t
ate in the substitution process. R1 = Bu, Bz; R2 = CH3, OCH3, Br,
OH; X = Br, Cl
carbonium ion R?, which attacks the aromatic substrate to
give the alkylation product.
Conclusions
The reactivity of n-butyl bromide is poor; moreover,
isomerization products of n-butyl were not found. Alkyla-
tions with n-butyl bromide may proceed via an immediate
C–H activation mechanism (Scheme 7). First, the
molybdenum carbonyl complex is oxidized by o-chloranil
to produce the higher-oxidation-state molybdenum
A new Friedel–Crafts alkylation catalyst is reported in this
study, consisting of various substituted tetramethylcy-
clopentadienyl mononuclear molybdenum carbonyl com-
plexes and an organic oxidant, namely o-chloranil. Tert-
butyl halides, styrene and benzyl chloride could be used as
alkylation reagents in these reactions, whereas the
123

Transition Met Chem
n
C5Me4R)MoI(CO)3] (R = Bu), complex (2) as purple-red
reactivity of alcohols was generally poor. Aromatic sub-
strates containing electron-donating groups were beneficial
for improving the alkylation yields, consistent with an
aromatic electrophilic substitution reaction. On the basis of
the para/ortho and Markovnikov selectivities observed for
the products, the oxidation of the molybdenum complex by
o-chloranil to give an intermediate molybdenum cate-
cholate species is postulated. Compared with traditional
catalysts, the present system has significant practical
advantages: lower amounts of catalyst, mild reaction con-
ditions, high selectivity, avoidance of isomerization, and
ease of use. Further studies to elucidate the reaction
mechanism and expand the synthetic utility of these alky-
lation catalyses are ongoing.
crystals in 82.8 % yield. M.p.: 104–105 °C; Anal. Calc. for
C16H21MoIO3: C, 39.7; H, 4.3. Found (%): C, 39.5; H, 4.4;
1H NMR (CDCl3, 500 MHz): d 0.93 (t, 3H, J = 6.75 Hz,
CH3), 1.34-1.38 (m, 4H, (CH2)2), 2.16 (d, 12H, J = 2.0 Hz
C5Me4), 2.42 (t, 2H, J = 7.25 Hz, C5Me4CH2); 13C
NMR(CDCl3, 125 MHz):d 11.3, 11.4, 13.9, 22.8, 26.1,
33.2, 106.6, 108.5, 110.6; IR (KBr): 2021(s), 1938(s),
1921(w), 2955, 2928, 2866(w), 1465(w), 1450(w),
1380(w) cm-1
.
Synthesis of complex (3)
Using a procedure similar to that described above, reaction
of the molybdenum dimer [(g5-C5Me4R)Mo(CO)3]2
t
(R = Bu) with I2 in chloroform afforded [(g5-C5Me4-
R)MoI(CO)3] (R = Bu), complex 3 as purple-red crystals
Experimental
t
in 56.6 % yield. M.p.: 99-100 °C; Anal. Calc. for C16-
H21MoIO3: C, 39.7; H, 4.3. Found (%): C, 39.5; H, 4.2; 1H
NMR (CDCl3, 500 MHz): d 1.38 (s, 9H, C(CH3)3), 2.09 (s,
6H, C5Me2), 2.31 (s, 6H, C5Me2); 13C NMR (CDCl3,
125 MHz): d 11.5, 15.1, 32.5, 34.6, 108.2, 108.3, 120.1; IR
(KBr): 1380(w), 1390, 1396, 1456(w), 2870, 2969 (w),
All reactions were carried out under an argon atmosphere
using standard Schlenk techniques. Solvents were distilled
from appropriate drying agents under an argon atmosphere.
1H and 13C NMR spectra were recorded on a Bruker AV
500 instrument in CDCl3, while IR spectra were recorded
as KBr disks on an IR FT 8900 spectrometer. Gas chro-
matograms were recorded with an Agilent 6820 gas chro-
matograph. Mass spectrometric measurements were
1932 (s), 1953 (s), 2017 (s) cm-1
.
Synthesis of complex (4)
performed on
spectrometer.
a
DSQ(II) gas chromatograph–mass
Using a procedure similar to that described above, reaction
of [(g5-C5Me4R)Mo(CO)3]2 (R = Ph) with I2 in chloro-
form afforded [(g5-C5Me4R)MoI(CO)3] (R = Ph), com-
plex 4 as purple-red solid in 75.4 % yield. M.P.:
112–113 °C; Anal. Calc. for C18H17MoIO3: C, 42.9; H,
3.8. Found (%): C, 42.6; H, 3.7; 1H NMR (CDCl3,
500 MHz): d 2.18 (s, 6H, C5Me2), 2.19 (s, 6H, C5Me2),
7.28–7.43 (m, 5H, C6H5); 13C NMR (CDCl3, 125 MHz): d
11.3, 12.5, 107.6, 108.6, 113.1, 128.4, 128.5, 130.9, 131.2;
IR (KBr): 702(s), 762(s), 1465(w), 1580, 3248(w), 1930
Synthesis of complex (1)
[(g5-C5Me4R)Mo(CO)3]2 (R = allyl) (0.068 g, 0.10 mmol)
was mixed with excess I2 (0.033 g, 0.13 mmol) in chlo-
roform (20 mL). The solution was stirred at room tem-
perature overnight and then washed with 10 % sodium
thiosulphate (10 mL). After removal of solvent, the residue
was placed on an alumina column. Elution with petroleum
ether/CH2Cl2 (2:1) developed a purple-red band that
afforded [(g5-C5Me4R)MoI(CO)3] (R = allyl) (1) as a
purple-red solid, yield: 0.08 g (85.5 %). M.p. 90–91 °C.
Anal. Calc. for C15H17MoIO3: C, 38.5; H, 3.6. Found (%):
C, 38.6; H, 3.7; 1H NMR (CDCl3, 500 MHz): d 2.11 (br s,
6H, C5Me2), 2.24 (br s, 6H, C5Me2), 7.29–7.38 (m, 5H,
C3H5); 13C NMR(CDCl3, 125 MHz): d 11.3, 11.4, 30.4,
107.5, 107.6, 108.2, 116.4, 134.9; IR (KBr): 1950(s),
2025(s), 2048(w), 3171(vw), 1654 (w), 2856, 2922, 883(s),
(s), 1955 (s), 2019 (s) cm-1
.
Synthesis of complex (5)
Using a procedure similar to that described above, reaction
of [(g5-C5Me4R)Mo(CO)3]2 (R = Bz) with I2 in chloro-
form afforded [(g5-C5Me4R)MoI(CO)3] (R = Bz), com-
plex 5 as purple-red crystals in 65.8 % yield. M.P:
115–116 °C; Anal. Calc. for C19H19MoIO3: C, 44.0; H,
3.7. Found(%): C, 44.1; H, 3.5; 1H NMR (CDCl3,
500 MHz): d 2.13 (s, 6H, C5Me2), 2.15 (s, 6H, C5Me2),
3.77 (s, 2H, CH2), 7.11-7.34(m, 5H, C6H5); 13C NMR
(CDCl3, 125 MHz):d 11.5, 11.8, 32.0, 107.7, 108.4, 108.7,
126.7, 127.8, 128.8, 139.4; IR (KBr): 3024, 1580, 1490,
914(s) cm-1
.
Synthesis of complex (2)
Using a procedure similar to that described above, reaction
of the molybdenum dimer [(g5-C5Me4R)Mo(CO)3]2
2920, 2858, 1460, 2019(s), 1944(s), 1925(w) cm-1
.
n
(R = Bu) with I2 in chloroform afforded [(g5-
123

Transition Met Chem
Table 5 Crystal data and
structure refinement parameters
for complexes 2, 3 and 5
Complex
2
3
5
Empirical formula
Formula weight
Temperature (K)
C16H21IMoO3
484.17
C16H21IMoO3
484.17
C19H19IMoO3
518.18
298(2)
100.01(10)
0.71073
Monoclinic
P21/n
99.97(15)
0.71073
Monoclinic
P21/c
´
˚
Wavelength (A)
0.71073
Triclinic
P¯ı
Crystal system
space group
˚
a (A)
7.4065(4)
8.7021(5)
15.4797(10)
74.132(5)
86.385(5)
74.433(5)
924.41(10)
2
9.1696(2)
12.5559(3)
15.1348(4)
90
7.2772(3)
15.3194(6)
17.1132(8)
90
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
93.199(2)
90
91.149(4)
90
3
˚
V(A )
1739.79(8)
4
1907.45(14)
4
Z
Dcalc (g cm-3
)
1.739
1.848
1.804
l (mm-1
)
2.385
2.535
2.319
F (000)
472
944
1008
Crystal size (mm)
h range (°)
Reflections collected/unique
0.31 9 0.14 9 0.02
3.17–25.49
11695/3426
0.0543
0.21 9 0.09 9 0.02
3.01–26.37
8052/3559
0.0269
0.18 9 0.07 9 0.02
2.91–26.37
11799/3886
0.0436
R(int)
Completeness to h
Absorption correction
Max and min transmission
Refinement method
Data/restraints/parameters
Goodness of fit on F2
R1, wR2 [I [ 2r(I)]
R1, wR2 (all data)
99.8 %
99.9 %
99.8 %
Semiempirical from equivalents
1.00000/0.33963
Full-matrix least-squares on F2
1.00000/0.86994
1.00000/0.81882
3426/30/224
1.084
3559/0/197
3886/0/248
1.143
1.045
0.0478, 0.1071
0.0736, 0.1278
0.566
0.0244, 0.0504
0.0312, 0.0552
0.571
0.0413, 0.1034
0.0561, 0.1120
1.023
´
-3
)
˚
Max. peak/(eÁA
´
-3
)
˚
Mini. peak/(eÁA
CCDC
-0.635
-0.616
-0.695
990,573
1,028,696
993,212
Crystallographic studies
General procedure for catalyzed alkylation
of toluene and tert-butyl bromide
Single crystals of complexes 2, 3 and 5 suitable for X-ray
diffraction were obtained from the slow evaporation of
hexane-dichloromethane solutions. All X-ray crystallo-
graphic data were collected on a Bruker Smart APEX
diffractometer with graphite monochromated Mo Ka
Under an argon atmosphere, the required Mo complex
(0.1 mmol) and o-chloranil (0.05 g, 0.200 mmol) were
mixed with 1,2-dichloroethane (3.5 mL) in a 25-mL round-
bottom flask at room temperature. The solution immedi-
ately darkened. After the mixture had been stirred for
40 min at room temperature, toluene (0.44 mL, 4 mmol)
and tert-butyl bromide (1.88 mL, 12 mmol) were added by
syringe. The reaction mixture was heated on an oil bath at
80 °C for 12 h. After cooling to room temperature, the
˚
(k = 0.71073 A) radiation using the u/x scan technique.
The structures were solved by direct methods and refined
by full-matrix least-squares procedures based on F2 using
the SHELXL-97 program system. The crystal data and
summary of X-ray data collection are presented in Table 5.
123

Transition Met Chem
2. Olah GA (1963) Friedel-crafts and related reactions. Wiley-In-
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solid catalyst was separated from the reaction mixture by
filtration, washed three times with petroleum ether, dried at
room temperature and reused if necessary. The solvent was
removed through rotary evaporation, and the residue was
purified by Al2O3 column chromatography, eluting with
petroleum ether to give a colorless liquid. The product
identity was further confirmed by GC–MS.
3. Olah GA (1973) Friedel-crafts chemistry. Wiley, New York
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Supplementary material
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Cen-
tre, CCDC Nos. 990573, 1028696 and 993212 for com-
plexes 2, 3 and 5, respectively. Copies of this information
may be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ, UK, fax: ?44 1223
336 033, e-mail: deposit@ccdc.cam.ac. uk of www: http://
www.ccdc.cam.ac.uk.
11. Kakiuchi F, Sekine S, Tanaka Y, Kamatani A, Sonoda M, Cha-
tani N, Murai S (1995) Bull Chem Soc Jpn 68:62
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(2000) J Am Chem Soc 122:7414
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tallics 25:1801
17. Yamamoto Y, Itonaga K (2008) Chem Eur J 14:10705
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Chim Acta 359:4503
Acknowledgments The authors gratefully acknowledge the finan-
cial support from the National Natural Science Foundation of China
(No. 21372061), the Hebei Natural Science Foundation of China
(Nos. B2013205025 and B2014205018), and the Key Research Fund
of Hebei Normal University (No. L2012Z02).
19. Ma ZH, Zhao MX, Li F, Liu XH, Lin J (2009) Chin J Inorg Chem
25:1699
20. Ma ZH, Zhao MX, Lin LZ, Han ZG, Lin J (2010) Chin J Inorg
Chem 26:1908
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Acta 399:126
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123