Syntheses, structures and catalytic activity for Friedel-Crafts reactions of substituted indenyl rhenium carbonyl complexes

Article abstract of DOI:10.1080/00958972.2016.1276573

The complexes [(η⁵-C₉H₆R)Re(CO)₃] [R?=?ⁿBu (8), ^tBu (9), CH(CH₂)₄ (10), Ph (11), Bz (12), 4-methoxyphenyl (13), 4-chlorophenyl (14)] were synthesized by refluxing substituted indenyl ligands [C₉H₇R] [R?=?ⁿBu (1), ^tBu (2), CH(CH₂)₄ (3), Ph (4), Bz (5), 4-methoxyphenyl (6), 4-chlorophenyl (7)], and Re₂(CO)₁₀ in decalin. The molecular structures of 9, 10, 12, and 13 were determined by X-ray diffraction analysis. These four crystals have similar molecular structures of the mononuclear carbonyl complex. In each of these molecules, Re is η⁵-coordinated to the five-membered ring of the indenyl group. Complexes 8–14 have catalytic activity for Friedel-Crafts reactions of aromatic compounds with a variety of alkylation and acylation reagents. Compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as high activities, mild reaction conditions, high selectivity, and environmentally friendly chemistry.

Full text of DOI:10.1080/00958972.2016.1276573

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Syntheses, structures and catalytic activity for
Friedel-Crafts reactions of substituted indenyl
rhenium carbonyl complexes
Zhihong Ma, Xinli Zhang, Hong Wang, Zhangang Han, Xuezhong Zheng & Jin
Lin
To cite this article: Zhihong Ma, Xinli Zhang, Hong Wang, Zhangang Han, Xuezhong Zheng & Jin
Lin (2017) Syntheses, structures and catalytic activity for Friedel-Crafts reactions of substituted
indenyl rhenium carbonyl complexes, Journal of Coordination Chemistry, 70:4, 709-721, DOI:
10.1080/00958972.2016.1276573
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Date: 02 February 2017, At: 00:00

Journal of Coordination Chemistry, 2017
Vol. 70, no. 4, 709–721
http://dx.doi.org/10.1080/00958972.2016.1276573
Syntheses, structures and catalytic activity for Friedel-Crafts
reactions of substituted indenyl rhenium carbonyl complexes
Zhihong Maa, Xinli Zhangb, Hong Wangc, Zhangang Hanb, Xuezhong Zhengb and
Jin Linb
aCollege of Basic medicine, hebei medical university, shijiazhuang, Pr China; bthe College of Chemistry &
materialscience, hebeinormaluniversity, shijiazhuang, Pr China; chebeiinstituteoffoodQualitysupervision
inspection and research, shijiazhuang, Pr China
ABSTRACT
ARTICLE HISTORY
received 10 march 2016
accepted 8 november 2016
The complexes [(η5-C9H6R)Re(CO)3] [R = nBu (8), Bu (9), CH(CH2)4
(10), Ph (11), Bz (12), 4-methoxyphenyl (13), 4-chlorophenyl (14)]
were synthesized by refluxing substituted indenyl ligands [C9H7R]
[R = nBu (1), tBu (2), CH(CH2)4 (3), Ph (4), Bz (5), 4-methoxyphenyl (6),
4-chlorophenyl (7)], and Re2(CO)10 in decalin. The molecular structures
of 9, 10, 12, and 13 were determined by X-ray diffraction analysis.These
four crystals have similar molecular structures of the mononuclear
carbonyl complex. In each of these molecules, Re is η5-coordinated to
the five-membered ring of the indenyl group. Complexes 8–14 have
catalytic activity for Friedel-Crafts reactions of aromatic compounds
with a variety of alkylation and acylation reagents. Compared with
traditional catalysts, these mononuclear metal carbonyl complexes
have obvious advantages such as high activities, mild reaction
conditions, high selectivity, and environmentally friendly chemistry.
t
KEYWORDS
synthesis; mononuclear
rhenium carbonyl complex;
indenyl; friedel-Crafts
reaction
CONTACT Zhihong ma
mazhihong-1973@163.com; Jin lin
linjin@hebtu.edu.cn
supplemental data for this article can be accessed at http://dx.doi.org/10.1080/00958972.2016.1276573.
© 2017 informa uK limited, trading as taylor & francis Group

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Z. MA ET AL.
1. Introduction
Transition metal complexes containing indenyl have various metal-indenyl bonding modes,
enhanced reactivity, and catalytic ability as compared with the cyclopentadienyl analogs
[1–10]. Steric and electronic effects of indenyl ring substituents greatly influence catalytic
activity and stability of the substituted indenyl complexes [5]. Thus, variation of indenyl
ligands is the first strategy for efficient catalysts. In previous work, we studied reactions of
substituted indenes with Ru3(CO)12 and obtained a series of dinuclear and trinuclear ruthe-
nium carbonyl complexes involving intramolecular C–H activation [11–13]. These substitu-
ents with special electronic and steric effect on the complexes have important effects on
the physicochemical properties of the complexes [14–18]. To explore the relationship
between structure and reactivity of the substituents in indenyl metal complexes, a series of
substituted indenyl rhenium carbonyl complexes was synthesized and characterized. Their
catalytic reactivity for Friedel-Crafts alkylation and acylation was also studied.
2. Experimental
2.1. General considerations
Schlenk and vacuum line techniques were employed for all manipulations. All solvents were
distilled from appropriate drying agents under argon prior to use. 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. Agilent 6820 gas chromatograms were recorded
t
for analysis of samples. The ligand precursors [C9H7R] [R = nBu (1), Bu (2), CH(CH2)4 (3), Ph
(4), Bz (5), 4-methoxyphenyl (6), 4-chlorophenyl (7)] were synthesized according to the lit-
erature [19–25].
2.2. Synthesis of 8
A solution of 1 (0.106 g, 0.614 mmol) and Re2(CO)10 (0.2 g, 0.307 mmol) in decalin (6 mL) was
refluxed for 24 h. After removal of solvent, the residue was loaded on an alumina column.
After elution with petroleum ether/CH2Cl2 (6:1), a yellow band was collected and concen-
n
trated. [(η5-C9H6 Bu)Re(CO)3] (8) was afforded as a yellow solid; yield: 0.194 g (71.6%). M.p.
92 °C. Anal. Calcd for C16H15O3Re: C, 43.53; H, 3.42. Found (%): C, 43.50; H, 3.39; 1H NMR (CDCl3,
500 MHz): δ 0.99 (t, 3H, J = 7.0 Hz, CH3), 1.42–1.67 (m, 4H, (CH2)2), 2.68–2.95 (m, 2H, C9H6CH2),
5.62 (s, 2H, C9H6), 7.08–7.13 (m, 2H, C9H6), 7.46 (d, 1H, J = 7.0 Hz, C9H6), 7.56 (d, 1H, J = 7.5 Hz,
C9H6); 13C NMR (CDCl3, 125 MHz): δ 13.9, 22.6, 26.6, 34.2, 67.6, 90.7, 95.3, 106.7, 108.0, 122.5,
123.5, 125.4, 126.3, 194.1; IR (vCO, cm−1): 2015(s), 1950(s).
2.3. Synthesis of 9
Using a procedure similar to that described above, 2 reacted with Re2(CO)10 in refluxing
t
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-C9H6 Bu)
Re(CO)3] (9) was obtained (0.175 g, 64.6% yield) as yellow crystals. M.p.: 90 °C; Anal. Calcd
for C16H15O3Re: C, 43.53; H, 3.42. Found (%): C, 43.57; H, 3.44; 1H NMR (CDCl3, 500 MHz): δ 1.49
(s, 9H, (CH3)3), 5.63 (d, 2H, J = 6.5 Hz, C9H6), 7.02 (t, 1H, J = 7.0 Hz, C9H6), 7.12 (t, 1H, J = 8.0 Hz,
C9H6), 7.49 (d, 1H, J = 8.5 Hz, C9H6), 7.74 (d, 1H, J = 8.5 Hz, C9H6); 13C NMR (CDCl3, 125 MHz):

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711
δ 32.4, 32.5, 68.1, 90.7, 105.5, 106.8, 107.6, 123.3, 124.8, 125.2, 126.1, 194.0; IR (vCO, cm−1):
2009(s), 1896(s).
2.4. Synthesis of 10
Using a procedure similar to that described above, 3 reacted with Re2(CO)10 in refluxing
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-
C9H6CH(CH2)4)Re(CO)3] (10) was obtained (0.210 g, 75.5% yield) as yellow crystals. M.p.: 80 °C;
1
Anal. Calcd for C17H15O3Re: C, 45.02; H, 3.33. Found (%): C, 45.12; H, 3.23; H NMR (CDCl3,
500 MHz): δ 1.38–2.17 (m, 8H, (CH2)4), 3.29 (t, 1H, J = 8.0 Hz, CH), 5.59 (d, 2H, J = 7.5 Hz, C9H6),
7.04–7.11 (m, 2H, C9H6), 7.44 (d, 1H, J = 8.0 Hz, C9H6), 7.57 (d, 1H, J = 8.5 Hz, C9H6); 13C NMR
(CDCl3, 125 MHz): δ 25.3, 25.8, 34.9, 35.7, 37.6, 67.7, 89.3, 99.4, 107.2, 107.7, 122.6, 123.7,
125.5, 126.1, 194.1; IR (vCO, cm−1): 2015(s), 1919(s).
2.5. Synthesis of 11
Using a procedure similar to that described above, 4 reacted with Re2(CO)10 in refluxing
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-
C9H6C6H5)Re(CO)3] (11) was obtained (0.194 g, 68.6% yield) as yellow solid. M.p.: 94 °C; Anal.
Calcd for C18H11O3Re: C, 46.85; H, 2.40. Found (%): C, 46.87; H, 2.52; 1H NMR (CDCl3, 500 MHz):
δ 5.77 (d, 1H, J = 3.0 Hz, C9H6), 5.95 (d, 1H, J = 3.0 Hz, C9H6), 7.11–7.18 (m, 2H, C9H6Ph), 7.36
(t, 1H, J = 7.5 Hz, C9H6Ph), 7.43 (t, 2H, J = 7.5 Hz, C9H6Ph), 7.52 (d, 1H, J = 8.5 Hz, C9H6Ph), 7.60
(d, 2H, J = 7.5 Hz, C9H6Ph), 7.76 (d, 1H, J = 8.0 Hz, C9H6Ph); 13C NMR (CDCl3, 125 MHz): δ 69.5,
91.8, 95.2, 106.9, 107.3, 122.4, 124.0, 126.3, 126.5, 128.0, 128.9, 129.6, 133.3, 193.5; IR (vCO
,
cm−1): 2011(s), 1919(s).
2.6. Synthesis of 12
Using a procedure similar to that described above, 5 reacted with Re2(CO)10 in refluxing
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-
C9H6CH2C6H5)Re(CO)3] (12) was obtained (0.189 g, 64.7% yield) as yellow crystals. M.p.: 144 °C;
1
Anal. Calcd for C19H13O3Re: C, 47.99; H, 2.76. Found (%): C, 47.83; H, 2.67; H NMR (CDCl3,
500 MHz): δ 4.14 (dd, 2H, J = 89.5, 15.5 Hz, CH2), 5.45 (d, 1H, J = 2.5 Hz, C9H6), 5.59 (d, 1H,
J = 2.5 Hz, C9H6), 7.07–7.13 (m, 2H, CH2), 7.23–7.34 (m, 5H, C9H6CH2Ph), 7.45 (d, 1H, J = 7.5 Hz,
C9H6CH2Ph), 7.59 (d, 1H, J = 8.5 Hz, C9H6CH2Ph); 13C NMR (CDCl3, 125 MHz): δ 33.2, 68.0, 91.8,
93.7, 107.1, 108.2, 122.2, 125.8, 126.4, 126.9, 128.6, 128.7, 139.3, 193.7; IR (vCO, cm−1): 2017(s),
1903(s).
2.7. Synthesis of 13
Using a procedure similar to that described above, 6 reacted with Re2(CO)10 in refluxing
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-C9H-
6C6H4OCH3)Re(CO)3] (13) was obtained (0.151 g, 50.0% yield) as yellow crystals. M.p.: 105 °C;
1
Anal. Calcd for C19H13O4Re: C, 46.43; H, 2.67. Found (%): C, 46.52; H, 2.56; H NMR (CDCl3,
500 MHz): δ 3.86 (s, 3H, OCH3), 5.74 (d, 1H, J = 2.5 Hz, C9H6), 5.89 (d, 1H, J = 2.5 Hz, C9H6), 6.96
(d, 2H, J = 9.0 Hz, C9H6C6H4), 7.09–7.16 (m, 2H, C9H6C6H4), 7.51 (t, 3H, J = 8.5 Hz, C9H6C6H4),

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Z. MA ET AL.
7.72 (d, 1H, J = 8.5 Hz, C9H6C6H4); 13C NMR (CDCl3, 125 MHz): δ 55.4, 69.0, 91.6, 95.5, 106.8,
107.2, 114.3, 122.5, 123.9, 125.3, 126.2, 126.3, 130.9, 159.4, 193.7; IR (vCO, cm−1): 2011(s),
1909(s).
2.8. Synthesis of 14
Using a procedure similar to that described above, 7 reacted with Re2(CO)10 in refluxing
decalin for 24 h; after chromatography and elution with petroleum ether/CH2Cl2, [(η5-
C9H6C6H4Cl)Re(CO)3] (14) was obtained (0.132 g, 43.4% yield) as yellow solid. M.p.: 110 °C;
Anal. Calcd for C18H10O3ClRe: C, 43.59; H, 2.03. Found (%): C, 43.72; H, 2.12; 1H NMR (CDCl3,
500 MHz): δ 5.78 (d, 1H, J = 2.5 Hz, C9H6), 5.93 (d, 1H, J = 3.0 Hz, C9H6), 7.12–7.20 (m, 2H,
C9H6C6H4), 7.40 (d, 2H, J = 8.5 Hz, C9H6C6H4), 7.52–7.55 (m, 3H, C9H6C6H4), 7.71 (d, 1H, J = 8.5 Hz,
C9H6C6H4); 13C NMR (CDCl3, 125 MHz): δ 69.8, 91.8, 93.6, 106.9, 107.2, 122.0, 124.1, 126.4,
126.8, 129.1, 130.8, 132.0, 133.8, 193.2; IR (vCO, cm−1): 2013(s), 1909(s).
2.9. Crystallographic studies
Single crystals of 9, 10, 12, and 13 suitable for X-ray diffraction were obtained from slow
evaporation of hexane-dichloromethane solutions. All X-ray crystallographic data were col-
lected on a Bruker Smart APEX diffractometer with graphite monochromated Mo Kα
Table 1. Crystal data and structure refinement parameters for 9, 10, 12, and 13.
Complex
9
10
12
13
empirical formula
formula weight
temperature (K)
Wavelength (Å)
Crystal system
space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C
16h15o3re
441.48
298(2)
0.71073
C17h15o3re
453.49
298(2)
0.71073
monoclinic
P2(1)/c
10.7799(10)
8.6629(8)
16.5270(16)
90
102.575(2)
90
1506.4(2)
4
2.000
8.073
C19h13o3re
475.49
298(2)
0.71073
monoclinic
P2(1)/n
8.9367(4)
12.1360(7)
14.6388(8)
90
96.339(5)
90
1577.96(14)
4
2.002
7.712
C19h13o4re
491.49
298(2)
0.71073
monoclinic
C2(1)/c
32.844(3)
7.0582(6)
14.3171(12)
90
101.120(2)
90
3256.7(5)
8
2.005
7.482
monoclinic
P2(1)/c
8.8485(5)
13.8341(7)
12.1274(6)
90
97.106(5)
90
1473.13(14)
4
γ (°)
V (Å3)
Z
DCalcd (g cm−3
)
1.991
8.252
840
μ (mm−1
F (0 0 0)
)
864
904
1872
Crystal size (mm)
θ range (°)
reflections collected/unique
R(int)
0.37 × 0.32 × 0.08
3.07–26.37
9081/3007
0.0484
0.42 × 0.40 × 0.33
2.53–25.01
7253/2663
0.0397
0.37 × 0.27 × 0.06
3.05–26.37
7152/3222
0.0905
0.40 × 0.27 × 0.14
2.53–25.02
8086/2873
0.0943
Completeness to θ
absorption correction
max./min. transmission
refinement method
data/restraints/parameters
Goodness of fit on F2
R1, wR2 [I > 2σ(I)]
99.9%
99.9%
99.8%
99.8%
semi-empirical from equivalents
0.1759/0.1326 1.00000/0.04008
full-matrix least-squares on F2
2663/0/190
1.063
0.0323, 0.0734
0.0531, 0.0806
2.141
1.00000/0.37965
0.4206/0.1538
3007/0/184
1.037
0.0337, 0.0799
0.0396, 0.0843
1.433
3222/0/209
1.049
0.0648, 0.1582
0.0753, 0.1708
3.817
2873/0/218
1.063
0.0615, 0.1541
0.0749, 0.1653
4.208
R1, wR2 (all data)
max. peak (e Å−3
)
min. peak (e Å−3
)
−1.492
−0.996
−4.064
−3.236
CCdC
1424780
1424779
1424777
1424778

JOURNAL OF COORDINATION CHEMISTRY
713
(λ = 0.71073 Å) radiation using the φ/ω scan technique at room temperature. The structures
were solved by direct methods and refined by full-matrix least-squares based on F2 using
SHELXL-97. All hydrogens were placed at their calculated positions and treated as riding.
The molecular graphics in this manuscript were done using Diamond software [26]. The
crystal data and summary of X-ray data collection are presented in table 1.
2.10. Catalytic tests
The catalytic reactions were carried out under an argon atmosphere with magnetic stirring;
the required complexes (0.02 mmol) were mixed with 1,2-dichloroethane (3.5 mL) in a 25 mL
round-bottom flask at room temperature. Aromatic compounds and alkylation/acylation
reagents were added by syringe. The reaction mixture was heated in an oil bath at 84 °C for
15 and 24 h. After cooling to room temperature, the solid catalyst was separated from the
reaction mixture by filtration, solvent was removed through rotary evaporation, and the
residue was purified by Al2O3 column chromatography, eluting with petroleum ether to give
the corresponding products. The progress of the reaction was monitored using an Agilent
6820 gas chromatograph.
3. Results and discussion
3.1. Preparation of the complexes
The ligand precursors [C9H7R] [R = nBu (1), tBu (2), CH(CH2)4 (3), Ph (4), Bz (5), C6H4OCH3 (6),
C6H4Cl (7)] were reacted with Re2(CO)10 in refluxing decalin for 24 h to give the corresponding
complexes [(η5-C9H6R)Re(CO)3] [R = nBu (8), tBu (9), CH(CH2)4 (10), Ph (11), Bz (12), C6H4OCH3
(13), C6H4Cl (14)] (scheme 1). These reactions were carried out in refluxing decalin, which
indicates that these ligands have low reactivity towards Re2(CO)10. IR spectra of 8–14 showed
1
similar patterns and displayed strong absorptions in the terminal v(CO) region. H NMR
spectra of 8–14 were similar and showed peaks at 5.45–5.95 ppm for the C5-ring protons of
1
the indenyl ligands. H NMR spectrum of 9 showed a singlet at 1.49 ppm for the t-butyl
protons. 1H NMR spectrum of 12 showed two doublets at 4.03–4.24 ppm for the methylene
protons. 1H NMR spectra of 13 showed a singlet at 3.86 ppm for the methoxy protons.
3.2. Crystal structures of 9, 10, 12, and 13
The crystal structures of 9, 10, 12, and 13 were determined by X-ray diffraction. Selected
bond parameters for these complexes are presented in table 2 and their structures are
depicted in figure 1.
Scheme 1. synthesis of 8–14.

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Z. MA ET AL.

JOURNAL OF COORDINATION CHEMISTRY
715
Figure 1. the molecular structures of 9, 10, 12, and 13. ellipsoids correspond to 50% probability. hydrogens
are omitted for clarity.
X-ray diffraction analyses confirm that 9, 10, 12, and 13 are similar mononuclear-substi-
tuted indenyl rhenium carbonyl complexes, in which rhenium is η5-coordinated to the
five-membered ring of the indenyl group and three terminal CO ligands. The Re–C distances
to the indenyl ring carbons in these complexes show the typical pattern of longer distances
to the ring fusion carbons than to the three“allylic”carbons. These differences are similar to
values found for similar Re indenyl complexes, like (CMe2)(C9H7)(η5-C9H6)Re(CO)3 [27]. Of the
three Re–C distances to the“allylic”carbons, the Re(1)–C(1) distance is longer than the other
two, which is attributed to the bulky substituent on C(1). The Re–CEN (CEN means centroid
of the cyclopentadienyl ring) distances are 1.982 Å for 9, 1.975 Å for 10, 1.980 Å for 12 and
1.984 Å for 13, respectively, which are attributed to the steric effect of the indenyl substitu-
ents. The dihedral angles between the five- and six-membered indenyl fragments are 3.84°
for 9, 4.19° for 10, 3.20° for 12 and 2.20° for 13.
In the crystal of 9, there are two π–π interactions with centroid–centroid distances of
3.831(4) and 3.454(3) Å (symmetry operation: 2 − x, −y, 2 − z). These distances in 10 are
3.441(5) and 3.430(4) Å (symmetry operation: −x, 2 −y, −z). The dihedral angles between
them are α = 3.9(3)° in 9 and 0.0(5)° in 10, and the corresponding slipping angles are β = 24.7,
γ = 25.6° in 9 and β = γ = 4.6° in 10. The intermolecular π–π stacking interactions affect the
molecular distortions of these complexes in which the smallest bond angle of C–Re–C is
35.10(17)° for 9, 35.7(3)° for 10, 34.4(5)° for 12 and 35.4(4)° for 13.

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Z. MA ET AL.
3.3. Catalytic studies
To develop an optimal catalytic system, we investigated substituted indenyl rhenium car-
bonyl complex 12 as a precatalyst on the Friedel-Crafts reaction of anisole and tert-butyl
chloride (scheme 2 and table 3). A solution of anisole (2 mmol) and tert-butyl chloride
(6 mmol) in 1,2-dichloroethane (3.5 mL) was refluxed in the presence of a catalytic amount
of the precatalyst (2 mol%) under argon. By refluxing in 1,2-dichloroethane, mixtures of
mono- and di-substituted products were obtained. The conversion rate reached as high as
89.5% for para-selectivity with 5 h reaction time (table 3, entry 3). The effect of different
solvents on catalytic efficacy was also studied, with the reaction conversion rate decreasing
significantly, when cyclohexane (boiling point of 80.7 °C) was chosen as the solvent under
the same conditions. The lower yield was ascribed to the lower polarity of cyclohexane. The
experiment was carried out in the absence of 12 and no products were obtained, which
suggested that electrophilic-substitution mechanism was involved in 12; further studies will
be needed to elucidate the mechanism of these catalytic reactions.
In order to test the capability of Friedel-Crafts alkylation reactions (scheme 2) catalyzed
by these substituted indenyl rhenium carbonyl complexes, influencing factors such as reac-
tion time, yield, and economic considerations were considered. The following experimental
conditions were chosen for further work: 1,2-dichloroethane as solvent; the molar ratio 1:3
of aromatic substrates and alkylation reagents; the amount 0.02 mmol of catalyst; temper-
ature 84 °C; reaction time 15 h. The catalytic results are shown in table 4. The catalytic activ-
ities of the reported complexes were determined from % yield and the turnover (T.O.)
conversion of substrate as follows:
Yield (%) = [Wt. of alkylation substrate (product)/Wt. of theoretical yield] × 100
(1)
Scheme 2. friedel-Crafts alkylation reactions of anisole, phenol, and toluene with alkylation reagents.
Table 3. optimization of 12 catalyzed friedel-Crafts alkylation reaction.
Entry
Solvent
T (°C)
t (h)
Yield (%) (mono-/di-)
1
2
3
4
5
6
ClCh2Ch2Cl
25
60
84
84
61
80
24
24
5
15
15
15
3.0 (100 : 0)
10.6 (95 : 5)
89.5 (65 : 35)
90.3 (61 : 39)
88.3 (22 : 78)
15.8 (91 : 9)
ChCl3
Cyclohexane
notes: reagents and conditions: anisole (2 mmol); tert-butyl chloride (6 mmol); [(η5-C9h6Ch2C6h5)re(Co)3] (2 mol%); solvent
(3.5 ml).

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Z. MA ET AL.
TON = turnover number [(mol of product)/(mol of catalyst)]
TOF = TON/reaction time (15 h)
(2)
(3)
All seven complexes were capable of catalyzing Friedel-Crafts alkylation reactions; the
yields and turnovers vary with the different catalysts used, as indicated in table 4. In no case
was there any detectable alkylation product in the absence of the rhenium complexes. The
relatively higher product yield obtained for alkylation of anisole and phenol than for toluene
was due to the fact that aromatic substrates containing electron-donating groups tend to
improve the yield of these Friedel-Crafts reactions. The smaller influence of the different
substituents on the catalytic behavior may be due to their modest variations in steric and
electronic properties. 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 [28, 29]. Tert-butyl halides 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-products. The reactivity of tert-butyl bromide was
higher than that of tert-butyl chloride, since bromide is a better leaving group. The order of
increasing reactivity was n-butyl bromide < tert-butyl chloride < tert-butyl bromide, which
was consistent with the classical Friedel-Crafts mechanism.
With the promising results of catalytic Friedel-Crafts alkylation reactions, the study was
then extended to the Friedel-Crafts acylation (scheme 3) using these complexes as catalysts.
Three acylation reagents were employed, including benzoyl chloride, phenylacetyl chloride,
and cinnamoyl chloride. The acylation reactions were carried out under the following con-
ditions: 1,2-dichloroethane as solvent; the molar ratio 1 :3 of aromatic substrates and acyl-
ation reagents; the amount 0.02 mmol of catalyst; temperature 84 °C; reaction time 24 h.
The catalytic results are shown in table 5.
With the above studies, all seven complexes catalyze Friedel-Crafts acylation reactions.
The yields and turnovers vary with the different catalysts used as indicated in table 5.
Compared with the alkylation reaction, TONs and TOFs of acylation are much lower than
alkylation, thus the yields of alkylation are much higher than acylation. Friedel-Crafts reac-
tions are electrophilic substitution reactions, however, the halogen and the carbonyl caused
p-pi conjugation in the acylating agent, thus loss of the halogen to form the carbocation
was difficult. Benzoyl chloride and phenylacetyl chloride were used as acylation reagents in
these reactions and the corresponding acyl products were obtained with high selectivity
for the para-products without detection of di-substituted products, suggesting that the
Scheme 3. friedel-Crafts acylation reactions of anisole and methylbenzene with acylation reagents.

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Z. MA ET AL.
catalytic reaction has high regioselectivity. Toluene exhibited less reactivity in the Friedel-
Crafts acylation reactions than anisole. The results showed that the reaction was favored by
the presence of electron-donating groups in the aromatic substrate, consistent with the
characteristics of the aromatic electrophilic substitution reaction [30].
4. Conclusion
Reactions of substituted indenyl ligands [C9H7R] [R = nBu (1), tBu (2), CH(CH2)4 (3), Ph (4), Bz
(5), C6H4OCH3 (6), C6H4Cl (7)] with Re2(CO)10 in refluxing decalin were studied. A series of new
mononuclear indenyl rhenium carbonyl complexes were obtained and showed their obvious
catalytic activity in Friedel-Crafts reactions of aromatic substrates with alkylation and acyl-
ation reagents catalyzed by these complexes. Tert-butyl halides could be used as alkylation
reagents in these reactions. It is consistent with an aromatic electrophilic substitution reac-
tion that aromatic substrates containing electron-donating groups were beneficial for
improving the reactivity. Compared with traditional catalysts, the present system has a sig-
nificant practical advantage: lower amounts of catalysts, mild reaction conditions, high
selectivity, and ease of use. To elucidate the reaction mechanism and expand the synthetic
utility of these catalysts, further studies are in progress.
Supplementary material
Crystallographic data for the structural analysis have been deposited with the Cambridge
Crystallographic Data Center, CCDC Nos. 1424780, 1424779, 1424777 and 1424778 for 9, 10, 12, and
13, 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 or
www: http://www.ccdc.cam.ac.uk.
Supplementary information
The structure and characterization data for related catalytic products.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the National Natural Science Foundation of China [grant number
21372061]; the Hebei Natural Science Foundation of China [grant number B2013205025], [grant
number B2014205018], [grant number B2015205116]; and the Key Research Fund of Hebei Normal
University [grant number L2012Z02].
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