Synthesis and catalytic activity of monobridged bis(cyclopentadienyl)rhenium carbonyl complexes

Article abstract of DOI:10.1007/s11243-016-0064-1

Thermal treatment of three monobridged biscyclopentadienes (C₅H₅)R(C₅H₅) [R?=?C(CH₃)₂ (1), C(CH₂)₅ (2), Si(CH₃)₂ (3)] with Re₂(CO)₁₀ in refluxing mesitylene gave the corresponding complexes [(η⁵-C₅H₄)₂R][Re(CO)₃]₂ [R?=?C(CH₃)₂ (4), C(C₅H₁₀) (5), Si(CH₃)₂ (6)], which were separated by chromatography, and characterized by elemental analysis, IR, and ¹H NMR spectroscopy. The molecular structures of complexes 5 and 6 were characterized by X-ray crystal diffraction analysis and show that both are monobridged bis(cyclopentadienyl)rhenium carbonyl complexes in which the molecule consists of two [(η⁵-C₅H₄)Re(CO)₃] moieties linked by a single bridge, in which each of the two Re(CO)₃ units is coordinated to the cyclopentadienyl ring in an η⁵ mode. All three of these monobridged bis(cyclopentadienyl)rhenium carbonyl complexes have good catalytic activities in Friedel–Crafts alkylation reactions.

Full text of DOI:10.1007/s11243-016-0064-1

Transition Met Chem
DOI 10.1007/s11243-016-0064-1
Synthesis and catalytic activity of monobridged
bis(cyclopentadienyl)rhenium carbonyl complexes
Zhen Li1 Zhi-Hong Ma2 Hong Wang3 Zhan-Gang Han1 Xue-Zhong Zheng1
Jin Lin1
•
•
•
•
•
Received: 30 March 2016 / Accepted: 17 May 2016
Ó Springer International Publishing Switzerland 2016
Abstract Thermal treatment of three monobridged biscy-
clopentadienes (C5H5)R(C5H5) [R = C(CH3)2 (1),
C(CH2)5 (2), Si(CH3)2 (3)] with Re2(CO)10 in refluxing
mesitylene gave the corresponding complexes [(g5-C5
H4)2R][Re(CO)3]2 [R = C(CH3)2 (4), C(C5H10) (5),
Si(CH3)2 (6)], which were separated by chromatography,
Introduction
Metallocene catalysts have been an actively investigated
research topic for more than 20 years [1–8]. Bridged
bis(cyclopentadienyl) ligands have been extensively stud-
ied as frameworks for dinuclear metal complexes that are
resistant to fragmentation and maintain two metal centers
in close proximity even after metal–metal bond cleavage
[9–13]. In particular, rhenium carbonyl complexes have
received attention due to their catalytic activity for many
reactions, such as Friedel–Crafts alkylations. In compar-
ison with mononuclear rhenium complexes, bridged dicy-
clopentadienyl dirhenium analogs, in which the bridging
ligand binds two reactive metal centers, may promote the
distinctive chemical reactivity and catalytic properties.
However, their chemistry has been rarely reported. To the
best of our knowledge, only a few examples of Friedel–
Crafts alkylation reactions catalyzed by rhenium carbonyl
complexes have been reported so far [14, 15]. Hence, in
order to develop a deeper understanding of the structures
and reactivities of bridged bis(cyclopentadienyl)rhenium
carbonyl complexes, here we report the synthesis, struc-
tures, and catalytic reactivities of three monobridged bis
(cyclopentadienyl)rhenium carbonyl complexes.
1
and characterized by elemental analysis, IR, and H NMR
spectroscopy. The molecular structures of complexes 5 and
6 were characterized by X-ray crystal diffraction analysis
and show that both are monobridged bis(cyclopentadi-
enyl)rhenium carbonyl complexes in which the molecule
consists of two [(g5-C5H4)Re(CO)3] moieties linked by a
single bridge, in which each of the two Re(CO)3 units is
coordinated to the cyclopentadienyl ring in an g5 mode. All
three of these monobridged bis(cyclopentadienyl)rhenium
carbonyl complexes have good catalytic activities in Frie-
del–Crafts alkylation reactions.
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-016-0064-1) contains supplementary
material, which is available to authorized users.
& Zhi-Hong Ma
mazhihong-1973@163.com
Results and discussion
& Jin Lin
linjin64@126.com
Preparation of the complexes
1
The College of Chemistry and Material Science, Hebei
Normal University, Shijiazhuang 050016, China
When monobridged ligand precursors (C5H5)R(C5H5)
[R = C(CH3)2 (1), C(CH2)5 (2), Si(CH3)2 (3)] were reacted
with Re2(CO)10 in refluxing mesitylene for 48 h, the
corresponding complexes [(g5-C5H4)2R][Re(CO)3]2 [R =
C(CH3)2 (4), C(C5H10) (5), Si(CH3)2 (6)] were obtained in
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
˚
73–84 % yields (Scheme 1). The IR spectra of complexes
4–6 are very similar, and all exhibit characteristic strong
peaks assigned to terminal CO ligands. The 1H NMR
spectra of 4 and 5 are also similar; both show two groups of
peaks at 5.23 and 5.41 ppm for the cyclopentadienyl pro-
tons. However, the 1H NMR spectrum of complex 6 shows
two groups of peaks at 5.44 and 5.46 for the cyclopenta-
dienyl protons and a strong singlet at 0.46 for the methyl
protons.
Table 1 Selected bond distances (A) and angles (°) for complexes 5
and 6
Complex 5
Complex 6
Bond distances
Re(1)–C(1)
2.330(6)
2.301(7)
2.290(7)
2.281(7)
2.294(7)
1.901(8)
1.919(9)
1.899(8)
1.957(6)
1.959(7)
Re(1)–C(1)
2.304(10)
2.275(12)
2.304(13)
2.285(11)
2.272(11)
1.919(14)
1.899(13)
1.915(13)
1.946(0)
Re(1)–C(2)
Re(1)–C(2)
Re(1)–C(3)
Re(1)–C(3)
Re(1)–C(4)
Re(1)–C(4)
Re(1)–C(5)
Re(1)–C(5)
Re(1)–C(17)
Re(1)–C(13)
Re(1)–C(14)
Re(1)–C(15)
Re(1)–Cp(centroid)
Re(2)–Cp(centroid)
Crystal structures of complexes 5 and 6
Re(1)–C(18)
Re(1)–C(19)
The crystal structures of complexes 5 and 6 were deter-
mined by X-ray diffraction. Selected bond parameters are
presented in Table 1 and their structures are depicted in
Figs. 1 and 2, respectively.
Re(1)–Cp(centroid)
Re(2)–Cp(centroid)
Bond angles
1.952(2)
C(1)–C(11)–C(6)
C(1)–C(11)–C(12)
O(1)–C(17)–Re(1)
O(2)–C(18)–Re(1)
O(3)–C(19)–Re(1)
108.1(6)
110.6(6)
178.6(8)
176.6(8)
177.7(8)
C(1)–Si(1)–C(6)
105.6(5)
111.7(6)
177.8(14)
177.5(11)
177.2(11)
Both structures show monobridged bis(cyclopentadi-
enyl)rhenium carbonyl complexes in which the molecule
consists of two [(g5-C5H4)Re(CO)3] moieties linked by a
single bridge, with each of two Re(CO)3 units coordinated
to the cyclopentadienyl ring in an g5 mode. Re–Re bonds
are not observed in these complexes. Complex 5 has an
asymmetric structure; the molecule consists of two [(g5-
C5H4)Re(CO)3] moieties linked by a cycloalkylidene
C(CH2)5 ring, which takes the standard chair conformation.
The two angles at the tetrahedral bridging carbon atom
[C(1)–C(11)–C(6) = 108.1(6)° and C(12)–C(11)–C(16) =
108.4(7)°] are close to the tetrahedral value. The distances
of Re1–CEN and Re2–CEN (CEN denotes the centroid of
C(11)–Si(1)–C(12)
O(1)–C(13)–Re(1)
O(2)–C(14)–Re(1)
O(3)–C(15)–Re(1)
˚
the cyclopentadienyl ring) are 1.957 and 1.960 A, respec-
tively. The dihedral angle between the two Cp ring planes
is 70.4°, and the torsion angle Re(1)–Cp(centroid)ÁÁÁCp(-
centroid)–Re(2) is -173.4°. Complex 6 has an approxi-
mate C2 symmetrical axis. The molecule consists of two
[(g5-C5H4)Re(CO)3] moieties linked by a Si(CH3)2 bridge.
The distances of Re1–CEN and Re2–CEN are 1.946 and
˚
1.952 A, respectively. The dihedral angle between the two
Cp ring planes is 82.2°, indicating that two Cp rings are
almost perpendicular to each other. The torsion angle
Re(1)–Cp(centroid)ÁÁÁCp(centroid)–Re(2) is 117.4°, show-
ing that the Cp planes of the bridging [Si(CH3)2(g5-C5H4)2]
ligand are significantly twisted with respect to each other.
From these data, we can conclude that the different ligand
bridges in these complexes have a significant effect on their
structures.
Fig. 1 Molecular structure of complex 5. Ellipsoids correspond to
30 % probability. Hydrogen atoms are omitted for clarity
Catalysis of Friedel–Crafts reactions
We have investigated the use of complex 6 as a precatalyst
for the Friedel–Crafts reaction of anisole with tert-butyl
bromide (Scheme 2; Table 2). A solution of anisole (4 mmol)
and tert-butyl bromide (8 mmol) in 1,2-dichloroethane
(3.5 mL) was heated in the presence of different amounts of
the precatalyst under an argon atmosphere. The expected
product was obtained. Using refluxing 1,2-dichloroethane,
mixtures of the corresponding monosubstituted and disubsti-
tuted products were obtained. The conversion rate reached
R
R
mesitylene
48 h
Re2(CO)10
+
Re
Re
CO
OC
OC
CO
OC
CO
Scheme 1 Synthesis of complexes 4–6. R = C(CH3)2 (4), C(C5H10
(5), and Si(CH3)2 (6)
)
123

Transition Met Chem
the optimized conditions, and several alkylation reagents were
employed, including halohydrocarbons, styrene, and alcohols,
as shown in Table 3. As expected, tert-butyl halides and
benzyl chloride could be used as alkylation reagents in these
reactions and the corresponding aryl products were obtained
in good yields with high selectivities for the para products.
The order of increasing reactivity was found to be n-butyl
bromide \tert-butyl chloride \tert-butyl bromide, which is
consistent with the classical Friedel–Crafts mechanism. As
expected, the reactivity of tert-butyl bromide was higher than
that of tert-butyl chloride. The reactivity of n-butyl bromide
was poor, suggesting carbocation formation in the reaction.
The poor reactivity of alcohols in general can be ascribed to
the low activity of hydroxyl as a leaving group. Trisubstituted
products could only be obtained with highly active substrates
and alkylation reagents (Table 3, entries 11, 12), suggesting
that the catalytic reaction has high regioselectivity. It should
be noted that complex 6 exhibited no catalytic activity for the
alkylation of toluene/anisole with styrene. Also, an unex-
pected product was obtained with phenol and styrene
(Table 3, entry 16). Further studies will be needed to eluci-
date the mechanism of these catalytic reactions; however, the
relevant reaction equations are shown in Schemes 3–5.
Given the promising results obtained with complex 6,
we turned our attention to the use of the other complexes as
Friedel–Crafts alkylation catalysts. The remaining
Fig. 2 Molecular structure of complex 6. Ellipsoids correspond to
30 % probability. Hydrogen atoms are omitted for clarity
OCH3
+
OCH3
OCH3
+
Complex 6
Br
ClCH2CH2Cl (3.5 mL), 80
a
7
7a
7b
Scheme 2 [(g5-C5H4)2R][Re(CO)3]2 [R = Si(CH3)2 (6)] catalyzed
Friedel–Crafts alkylation reaction of anisole with tert-butyl bromide
Table 2 Optimization of the complex 6 catalyzed reaction
Entry (C5H4)2Si(CH3)2Re2(CO)6/mol% t (h) Yield (%) 7a/7b
1
2
3
4
5
6
7
8
9
10
0.25
0.5
1.0
1.5
2.0
12
24
12
24
12
24
12
24
12
24
67.0
92.1
75.0
96.5
73.5
93.8
71.0
91.2
65
73:27
63:37
72:28
68:32
75:25
70:30
86:14
74:26
82:18
76:23
Table 3 [(g5-C5H4)2R][Re(CO)3]2 [R = Si(CH3)2 (6)] catalyzed
reactions of aromatic substrates with different alkylation reagents
Entry Arene
Reagent
Yield (%) Product
Ratio
1
PhOMe t-BuBr
t-BuCl
96.5
93.2
10.1
98.6
4.3
7a 7b
7a 7b
7a
7c 7c0
7d 7e
8a 8a0
8a 8a0
8a
8c 8c0
8d 8e
9a 9b
9a 9b
9a 9b
9c 9c0
9d 9e
9f 100
68:32
65:35
100a
2
3
t-BuOH
4
BzCl
51:49
48:52
94:6
5
n-BuBr
89.2
6
PhMe
PhOH
t-BuBr
t-BuCl
t-BuOH
BzCl
95.6
91.7
6.7
7
95:5
100a
Reagents and conditions: anisole: 4 mmol, tert-butyl bromide:
8 mmol, 80 °C
8
9
98.1
2.8
49:51
57:43
32:66:2b
30:69:1b
78:22
45:55
53:47
10
11
12
13
14
15
16
n-BuBr
t-BuBr
t-BuCl
t-BuOH
BzCl
96.5 % when the reaction time was 24 h and the amount of
complex 6 was 0.5 mol% (Table 2, entry 4).
99.5
95.1
12.7
99.1
5.9
From these preliminary 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; a molar ratio
of aromatic substrates and alkylation reagents of 1:2; cat-
alyst amount 0.5 mol% (substrate as reference); reflux
temperature; and reaction time 24 h.
n-BuBr
PhCH = CH2 35.7
No products detected for PhOMe plus nBuOH or PhCH = CH2; or for
n
PhMe plus BuOH or PhCH = CH2; or for PhOH plus BuOH
n
a
The catalytic study was then extended to the Friedel–
Crafts alkylation of other substrates using complex 6 as
catalyst. Different aromatic substrates were chosen under
Only para product
b
Small amount of three substituted product, mole ratio: arene/
reagent = 1:2, 80 °C
123

Transition Met Chem
R1
R2
R1
alkylation and acylation reagents showed that these rhe-
nium carbonyl complexes have catalytic activity. Tert-
butyl halides and benzyl chloride could be used as alky-
lation reagents in these reactions. Compared with tradi-
tional catalysts, these complexes have significant practical
advantages, namely lower amounts of catalyst, mild reac-
tion conditions, and high selectivity. Further studies to
elucidate the reaction mechanism and expand the synthetic
utility of these catalysts are in progress.
R1
R1
R2
R2
Complex 6
R2X
+
+
+
R2
a
a'
b
R1
R3
R1
R1
R3
Complex 6
R3X
+
+
c
c'
Experimental
Scheme 3 [(g5-C5H4)2R][Re(CO)3]2 [R = Si(CH3)2 (6)] catalyzed
Friedel–Crafts alkylation reactions of halohydrocarbons. R1 = OMe
All reactions were carried out under argon 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
FTIR 8900 spectrometer. Gas chromatograms were recorded
with an Agilent 6820 gas chromatograph. Mass spectro-
metric measurements were performed on a DSQ(II) gas
chromatograph–mass spectrometer.
t
(7), Me (8), OH (9); R2 = Bu, X = Br, Cl, OH; and R3 = Bz,
X = Cl
R1
R1
R1
Complex 6
+
+
X
e
Synthesis of complex 4
d
Scheme 4 [(g5-C5H4)2R][Re(CO)3]2 [R = Si(CH3)2 (6)] catalyzed
Friedel–Crafts alkylation reactions of n-butyl bromide. R1 = OMe
(7), Me (8), OH (9); X = Br
A solution of free ligand 1 (0.258 g, 1.50 mmol) and Re2(-
CO)10 (0.5 g, 0.75 mmol) in mesitylene (10 mL) was refluxed
for 48 h. After removal of solvent, the residue was placed on an
alumina column. Elution with petroleum ether/CH2Cl2 (1:1)
developed a colorless band, which was collected, and after
concentration, afforded [(g5-C5H4)2(CMe2)][Re(CO)3]2 (4) as
a white solid, yield: 0.438 g (80.1 %). M.P: 106 °C; Anal.Calc.
for C19H14O6Re2: C, 32.1; H, 2.0. Found (%): C, 32.3; H, 2.2.
1H NMR (CDCl3, 500 MHz): d 1.48 (s, 6H, CMe2), 5.23 (t, 4H,
J = 1.8 Hz, C5H4), 5.41 (t, 4H, J = 1.8 Hz, C5H4); 13C
NMR(CDCl3, 125 MHz): d 32.2, 34.4, 82.3, 85.2, 117.9,
194.1(CO); and IR (KBr): 1348(s), 1888(s), 1921(s), 1950(s),
OH
O
Complex 6
+
f
Scheme 5 [(g5-C5H4)2R][Re(CO)3]2 [R = Si(CH3)2 (6)] catalyzed
Friedel–Crafts alkylation reactions of phenol with styrene
2019(s), 2856(s), 2926(s), 2983(s) cm-1
.
complexes [(g5-C5H4)2R][Re(CO)3]2 [R = C(CH3)2 4,
C(C5H10) 5] were investigated under the optimal condi-
tions, with the results as shown in Tables 4 and 5. Overall,
these complexes gave similar results to that of complex 6,
showing that the different ligand bridges have only a small
influence on the catalytic behavior.
Synthesis of complex 5
Using a procedure similar to that described above, ligand
precursor 2 was reacted with Re2(CO)10 in refluxing
mesitylene for 48 h. After chromatography with petroleum
ether/CH2Cl2, [(g5-C5H4)2(C(CH2)5)][Re(CO)3]2 (5) was
obtained (0.421 g, 73.2 % yield) as white crystals. M.P:
125 °C; Anal. Calc. for C22H18O6Re2: C, 35.2; H, 2.4.
Found (%): C, 35.5; H, 2.2. 1H NMR (CDCl3, 500 MHz): d
1.51–1.52 (m, 6H, C6H10), 1.89 (t, 4H, J = 6 Hz, C6H10),
5.22 (t, 4H, J = 2.3 Hz, C5H4), 5.53 (t, 4H, J = 2.3 Hz,
C5H4); 13C NMR(CDCl3, 125 MHz): d 22.5, 25.2, 36.7,
38.8, 81.7, 85.8, 121.2, 194.4(CO); and IR (KBr): 1401(s),
Conclusions
Reactions of monobridged biscyclopentadienes (C5H5)
R(C5H5) [R = C(CH3)2 (1), C(CH2)5 (2), Si(CH3)2 (3)]
with Re2(CO)10 in refluxing mesitylene gave three new
bridged bis(cyclopentadienyl)rhenium carbonyl com-
plexes. Friedel–Crafts reactions of aromatic substrates with
1888(s), 1906(s), 2015(s), 2859(s), 2930(s), 3131(s) cm-1
.
123

Transition Met Chem
Table 4 Catalytic data for
complex 4
Arene
Reagent
Molar ratio
1:2
T/°C
Yield (%)
Product
Ratio
PhOMe
t-BuBr
t-BuCl
t-BuOH
n-BuBr
BzCl
80
95.8
93.5
9.3
7a
7a
7a
7d
7c
8a
8a
8a
8d
8c
9a
9a
9a
9d
9f
7b
7b
69:31
63:37
100b
3.6
7e
49:51
53:47
95:5
2:1
1:2
70
84
96.1
93.1
90.3
7.3
7c0
8a0
8a0
PhMe
PhOH
t-BuBr
t-BuCl
t-BuOH
n-BuBr
BzCl
97:3
100a
3.1
8e
55:45
52:48
31:64:5b
31:67:2b
85:15
57:43
2:1
1:2
70
84
97.4
97.9
94.3
10.4
6.7
8c0
9b
9b
9b
9e
t-BuBr
t-BuCl
t-BuOH
n-BuBr
PhCH = CH2
BzCl
41.2
98.3
100
9c0
2:1
70
9c
43:57
No products detected for PhOMe plus nBuOH or PhCH = CH2; or for PhMe plus nBuOH or PhCH = CH2;
n
or for PhOH plus BuOH
a
Only para product
b
Small amount of three substituted product
Table 5 Catalytic data for
complex 5
Arene
Reagent
Molar ratio
1:2
T/°C
Yield (%)
Product
Ratio
PhOMe
t-BuBr
t-BuCl
t-BuOH
n-BuBr
BzCl
84
96.5
94.1
8.9
7a
7a
7a
7d
7c
8a
8a
8a
8d
8c
9a
9a
9a
9d
9f
7b
7b
67:33
62:38
100a
5.4
7e
43:57
54:46
97:3
2:1
1:2
70
84
97.3
95.3
92.7
8.1
7c0
8a0
8a0
PhMe
PhOH
t-BuBr
t-BuCl
t-BuOH
n-BuBr
BzCl
9:46
100a
4.9
8e
48:52
51:49
53:46:1b
46:52:2b
83:17
57:43
2:1
1:2
70
84
98.5
98.5
94.9
11.3
3.9
8c0
9b
9b
9b
9e
t-BuBr
t-BuCl
t-BuOH
n-BuBr
PhCH = CH2
BzCl
40.5
98.9
100
9c0
2:1
70
9c
44:56
No products detected for PhOMe plus nBuOH or PhCH = CH2; or for PhMe plus nBuOH or PhCH = CH2;
n
or for PhOH plus BuOH
a
Only para product
b
Small amount of three substituted product
ether/CH2Cl2, [(g5-C5H4)2(Si(CH3)2)][Re(CO)3]2 (6) was
obtained (0.375 g, 84.3 % yield) as white crystals. M.P:
Synthesis of complex 6
Using a procedure similar to that described above, ligand
precursor 3 was reacted with Re2(CO)10 in refluxing
mesitylene for 48 h. After chromatography with petroleum
116 °C; Anal. Calc. for C18H14O6Re2Si: C, 29.8; H, 1.9.
Found (%): C, 29.6; H, 1.8. 1H NMR (CDCl3, 500 MHz): d
0.46 (s, 6H, SiMe2), 5.44 (t, 4H, J = 1.0 Hz, C5H4), 5.46
123

Transition Met Chem
Table 6 Crystal data and
structure refinement parameters
for complexes 5 and 6
Complex
5
6
Empirical formula
Formula weight
Temperature (K)
C22H18O6Re2
C18H14O6Re2Si
726.78
750.76
298(2)
298(2)
˚
Wavelength (A)
0.71073
0.71073
Crystal system
Space group
Monoclinic
Triclinic
P ¯ı
C2/c
˚
a (A)
24.270(2)
7.7760(6)
11.0313(9)
12.3164(11)
97.8340(10)
105.490(2)
96.9320(10)
994.87(14)
2
˚
b (A)
8.0794(6)
˚
c (A)
21.7675(18)
a (°)
b (°)
c (°)
90
90.3120(10)
90
3
˚
V (A )
4268.3(6)
Z
8
Dcalc (g cm-3
)
2.337
2.426
l (mm-1
)
11.369
12.247
F (000)
2784
668
Crystal size (mm)
h range (°)
Reflections collected/unique
0.32 9 0.31 9 0.28
2.51–25.02
0.30 9 0.27 9 0.13
2.33–25.02
5111/3461
0.0401
10,305/3762
0.0654
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 %
98.5 %
Semiempirical from equivalents
0.1430/0.1217
Full-matrix least-squares on F2
3762/0/272
1.048
0.2989/0.1203
3461/0/247
1.038
0.0322, 0.0724
0.0458, 0.0773
2.131
0.0447, 0.1118
0.0587, 0.1182
1.994
-3
˚
Max. peak/(e A
)
-3
˚
Min. peak/(e A
)
-1.777
-3.657
CCDC
1,437,148
1,437,147
(t, 4H, J = 1.0 Hz, C5H4); 13C NMR(CDCl3, 125 MHz): d
0.04, 87.1, 88.8, 92.9, 194.1(CO); and IR (KBr): 1357(s),
1911(s), 1943(s), 2018(s), 2846(s), 2922(s), 2960(s),
the SHELXL-97 program system. The crystal data and
summary of X-ray data collection are presented in Table 6.
3090(s), 3117(s) cm-1
.
General procedure for catalytic tests
Crystallographic studies
The catalytic reactions were carried out under an argon
atmosphere with magnetic stirring. The required complex
(0.02 mmol) was mixed with 1,2-dichloroethane (3.5 mL) in
a 25-mL round-bottom flask at room temperature. Aromatic
compounds and alkylation reagents were added by syringe.
The reaction mixture was heated at 80 °C for 24 h. After
cooling to room temperature, the solid catalyst was separated
from the reaction mixture by filtration. The solvent was
removed by rotary evaporation, and the residue was purified
by Al2O3 column chromatography, eluting with petroleum
Single crystals of complexes 5 and 6 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
˚
(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
123

Transition Met Chem
ether to give a colorless liquid. The course of the reaction was
monitored using an Agilent 6820 gas chromatograph. The
identities of the products were confirmed by GC–MS.
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Acknowledgments The authors gratefully acknowledge the financial
support from the National Natural Science Foundation of China (No.
21372061), the Hebei Natural Science Foundation of China (Nos.
B2013205025, B2014205018 and B2015205116), and the Key
Research Fund of Hebei Normal University (No. L2012Z02).
123