Grubbs-type catalysts immobilized on SBA-15: A novel heterogeneous catalyst for olefin metathesis

Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Contents lists available at SciVerse ScienceDirect

Journal of Molecular Catalysis A: Chemical journal homepage: www.elsevier.com/locate/molcata

Grubbs-type catalysts immobilized on SBA-15: A novel heterogeneous catalyst for olefin metathesis Huan Zhang, Ying Li, Songxue Shao, Haihong Wu ∗ , Peng Wu ∗ Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062, China

a r t i c l e

i n f o

Article history: Received 15 September 2012 Received in revised form 18 January 2013 Accepted 19 January 2013 Available online 18 February 2013 Keywords: Heterogeneous catalysis Grubbs-type catalyst SBA-15 mesoporous silica Ring-closing olefin metathesis Immobilization

a b s t r a c t A series of novel heterogeneous olefin metathesis catalysts have been developed by immobilizing Ru species on SBA-15 mesoporous silica with tunable ordered pores and different textural properties. Various techniques such as X-ray diffraction, N2 adsorption–desorption, high resolution transmission electron microscopy have been used to characterize the physicochemical properties of the catalysts. The catalytic activity of thus prepared Ru-based catalysts has been studied in ring closing metathesis (RCM) and other metathesis reactions. Among these immobilized catalysts, the SBA-15 support with the largest pore size gives rise to the highest catalytic activity because the large pores are benefit for the diffusion of reactants and products. The immobilized Ru catalysts prove to be reusable in RCM reactions. Their catalytic activity is closely related to the confinement effect and high hydrophobicity of SBA-15 mesopores. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Olefin metathesis, a transition metal-catalyzed interexchange reaction of alkylidene units between two substituted alkenes, is an effective and useful method for constructing carbon–carbon double bonds, which attracts growing research attentions in organic synthesis in recent years [1]. It opens up new industrial routes to synthesize valuable petrochemicals, polymers, oleochemicals and specialty chemicals. As remarkable olefin metathesis catalysts, ruthenium-based carbene complexes developed by Grubbs [2] have significantly broadened the scope of the olefin metathesis reaction (Scheme 1). Lately, several modified Grubbs-type catalysts have also been developed and intensively studied [3]. Despite of the successes to ring construction, there is still a large room to improve this general approach in terms of scope, convenience and generality. Most of homogeneous Grubbs-type catalysts are hard to be reused and recycled after reactions. Furthermore, the homogeneous systems suffer the difficulty of removing residual ruthenium byproducts from the reaction products [4]. Nowadays, the use of environmentally friendly heterogeneous catalysts has become an important research target for green chemistry. Immobilizing homogeneous catalytic species on solid supports and scavenging residual catalysts are the most effective ways to solve the problems. Several immobilized Grubbs-type catalysts

∗ Corresponding authors. Tel.: +86 21 62238510; fax: +86 21 62238510. E-mail addresses: [email protected] (H. Wu), [email protected] (P. Wu). 1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molcata.2013.01.034

have been reported by using polymer supports including vinyl polystyrene [5], polyethylene glycol [6], PEGA-NH2 resin [7], Poly (fluoroalkyl acrylate) [8], PolyHIPE [9], and so on [10]. The polymers possess usually a relatively low thermal stability, making the recovered catalysts less active in reuse. Since the discovery of the M41S family [11], ordered mesoporous silica materials are widely investigated because of their high surface area, large adsorption capacity, diverse morphologies and tunable mesopores [12]. Thereafter, these ordered mesoporous silica materials such as MCM-41 [13], siliceous mesocellular foam [14], etc., are used as supports for the Grubbs-type catalysts. Among these materials, SBA-15, a kind of important hexagonal mesoporous silicas [15], has been developed and investigated in various applications as it has larger pore size, thicker silica walls and higher hydrothermal stability [16]. Using these mesoporous materials as supports, several generations immobilized Grubbs catalysts have been reported [17]. In 2005, Shi and coworkers anchored first generation of Grubbs catalyst on the inner pore surface of SBA15 through the N-heterocyclic carbene ligands, which effectively prevented the decomposition of the catalytic species. SBA-15supported catalysts thus prepared achieved a durable catalytic activity [17a]. The supported catalysts prepared from the second generation Grubbs complex gave much higher reaction rates than those from the first generation one. A second generation Hoveyda–Grubbs catalyst was once immobilized on silica without any linkers but simply by mixing the Ru complex with silica in a suspension [18]. Hoveyda–Grubbs-type complexes were also covalently bonded to a silica matrix by sol-gel processes. They were shown to be superior

36

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Mes N

PCy3 Cl Cl

Mes N

Cl

Ph

Ru

Cl

Ph PCy3

1

Cl Cl

Ru

Ru Ph PCy3

3

2 PCy3

N Mes

Cl

Cl

Ru PCy3

N Mes

Mes N

N Mes

Cl Cl

Ru

O

O

4

5

Scheme 1. Grubbs-type catalysts.

to those prepared through anchoring the complexes to commercial silica or meso-structured MCM-41 in the ring-closing metathesis reactions of dienes (II) and enyne (IV) [19]. However, most of supported catalysts exhibit a lower activity in comparison to homogeneous counterparts and suffer substantial leaching of the ruthenium species. The supported catalytic species should have suitable interactions with the surface, whether functionalized or not, in order to obtain a desired catalytic activity [20]. Therefore, a proper understanding of the nature on inorganic support surface would provide deep insights into the activity of the supported metathesis catalysts. Polarz et al. proved that the covering of surface silanols may stabilize the Grubbs catalyst [17c]. Recently, Fontaine and coworkers further demonstrated the pore surface functionalities of mesoporous SBA-15 silica influenced the stability of first generation Grubbs catalyst. The presence of surface silanols significantly decreases the longevity of the ring-closing metathesis catalyst, whereas total passivation of the surface with trimethylsilyl groups prevents the catalyst from deactivating, but slows down the reaction rate [17d]. Compared to organic polymers, mesoporous silica material is a common support for immobilization due to its higher thermal and chemical stability. It has already been discussed that a confining reaction field affects intermolecular equilibrium reactions very strongly [17c]. In this context, we design new method for immobilization and use SBA-15 with different pore sizes as supports for the heterogenization of the first-generation or second-generation Grubbs catalyst. The surface hydrophilicity/hydrophobicity of SBA15 with variable pore sizes is quite different because of the various synthesis conditions. It will allow a different loading of these large catalytic species throughout the matrix, which results in different catalytic conversions of bulky organic reactants. In this study, with purpose to prepare active and stable heterogeneous Grubbs catalysts, we synthesized a series of SBA-15 ordered mesoporous silica materials with variable pore sizes, and then immobilized the Grubbs-type catalysts on them. We prepared a series of new supported catalysts and studied the catalytic activity of them in ring-closing metathesis (RCM), self-metathesis and cross-metathesis (CM) reactions. 2. Experimental 2.1. General All reagents were commercially available (Aldrich) and were directly used without further purification. All reactions were carried out in Argonaut advantage seriesTM 2410 personal screening synthesizer. All non-aqueous reactions were performed under an

argon atmosphere. 1 H spectra were acquired on a Bruker DRX500 spectrometer at 500 MHz in CDCl3 . TMS was used as an internal standard for 1 H spectra. Flash column chromatography was performed using silica gel 60 (230–400 mesh). The X-ray diffraction (XRD) patterns were collected on a Bruker D8 ADVANCE instru˚ at 40 kV and 40 mA. ment using Cu-K␣ radiation ( = 1.5418 A) Nitrogen adsorption–desorption isotherms were recorded on a Quancachrome Autosorb-3B instrument. The specific surface areas were evaluated using Brunauer–Emmett–Teller (BET) method. The TEM images were recorded using a JEOL-JEM-2010 microscope. IR analyses were obtained with Nicolet NEXUS 670 infrared spectrometer. N elemental analyses were performed on an Elementar VarioEL III CHN elemental analyzer. The bulk loading amount of Ru was determined by ICP (Thermo Electron Corporation IRIS Intrepid II XSP). 2.2. Synthesis of SBA-15 mesoporous materials in different conditions Four kinds of SBA-15 mesoporous materials with different pore sizes were synthesized according to the literatures [15,21]. Both the gel compositions and the condensation temperature were varied changed in order to change pore size or surface. In a typical synthesis, copolymer surfactant P123 was dissolved in deionized water and 2 M HCl solution, followed by the addition of TEOS. Four weight ratios of P123/H2 O/HCl/TEOS actually used in gram were 8.0/72/288/20.4, 6.0/45.2/180/12.3, 6.24/45/180/12.8 and 6.0/187.5/112.5/16.8. The four gels were first stirred at 35 ◦ C for 24 h, and then autoclaved for further condensation for 24 h at 60 ◦ C,100 ◦ C,130 ◦ C and 180 ◦ C, respectively. The products were collected by filtration, dried and calcined at 550 ◦ C for 6 h to remove the surfactant. The samples were denoted as SBA-15-n (n = a, b, c and d). 2.3. Synthesis of amino-functionalized SBA-15 mesoporous materials (1a–1d)

SBA-15-a (2.0 g) mesoporous materials were evacuated at 90 ◦ C for 4 h in a three-necked flask, into which dry toluene (60 mL) and 3-aminopropyl triethoxysilane (0.9 g, 4 mmol) were added through a syringe. The mixture was then refluxed at 110 ◦ C for 24 h. After cooling to room temperature, the mixture was filtrated and washed repeatedly with toluene, ethanol and acetone in turns to afford 1a as a light yellow solid 2.2 g. 1b–1d were obtained by the same method. 2.4. Immobilization of Hoveyda-type ligand on SBA-15 (6a–6d)

To a solution of 3-(3-vinyl-4-isopropoxyphenyl) propionic Acid 5 (0.80 g, 3.42 mmol) in 50 mL of DMF was added DCC (0.78 g, 3.76 mmol), DMAP (0.125 g, 1.03 mmol) and TsOH (65.0 mg, 0.342 mmol). This solution was stirred at room temperature for 1 h and then amino-functionalized SBA-15-a mesoporous materials 1a (800 mg) were added in one portion. The mixture was stirred at 70 ◦ C for 72 h. The resulting suspension was filtered and washed repeatedly with CH2 Cl2 , DMF and acetone in turns to afford 6a as a yellow solid 0.96 g. 6b–6d were obtained by the same method.

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

37

2.5. Preparation of SBA-15 supported Hoveyda–Grubbs 1st type catalyst (7a–7d)

6a (400 mg) and CuCl (24 mg, 0.24 mmol) was charged to a 50 mL tube-flask. In the glove box, Grubbs Catalyst 1st Generation (198 mg, 0.24 mmol) was added to the above tube flask, and the flask was evacuated and charged with N2 for three times. Then, 15 mL of CH2 Cl2 was added and the reaction mixture was stirred at 40 ◦ C for 24 h. After the reaction, the mixture was filtrated and washed repeatedly with CH2 Cl2 to afford 7a as a gray green solid 0.5 g. 7b–7d was obtained by the same method.

Intersity

(100)

(110)

SBA-15-c

SBA-15-a

1

In a typical experiment, a mixture of olefins (0.5 mmol) and 7a (5 mol%) in CH2 Cl2 (5 mL) was stirred at 38 ◦ C under Ar. The reaction was monitored by TLC. After the completion of the reaction, the catalyst was filtered off and washed with CH2 Cl2 . The filtrate was evaporated under vacuum and the residue was purified by column chromatography on silica gel to give the pure RCM product. The catalyst was dried and reused without any further activation. 2.8. Typical procedure for other metathesis reaction In a typical experiment, a mixture of styrene (1 mmol) or styrene (0.5 mmol) and ethyl acrylate (0.5 mmol) and 8d (5 mol%) in CH2 Cl2 (5 mL) was stirred at 38 ◦ C under Ar. The reaction was monitored by TLC. After the completion of the reaction, the catalyst was filtered off and washed with CH2 Cl2 . The filtrate was evaporated under vacuum and the residue was purified by column chromatography on silica gel to give the pure product. 3. Results and discussion According to the literatures [15,21], four kinds of SBA-15 mesoporous materials with different pore sizes were synthesized by changing the condensation temperature. The four samples were denoted as SBA-15-n (n = a, b, c or d), corresponding to the condensation temperature of 80, 100, 130 and 180 ◦ C, respectively. As shown in small-angle XRD patterns (Fig. 1), four SBA-15 samples all exhibit three peaks, which can be indexed to (1 0 0), (1 1 0) and (2 0 0) reflections that associated with a 2D hexagonal (p6mm) structure.

2

3

4

2Theta(deg) Fig. 1. Small angle XRD patterns for SBA-15 samples.

The N2 adsorption/desorption isotherms of four calcined SBA-15 samples are shown in Fig. 2. All four SBA-15 samples have typical type IV isotherms with the H1-type hysteresis loop, clearly indicating that these materials possess a mesoporous structure. The relative pressure position for the mutilayer adsorption step increases gradually with synthesis temperature, suggesting an enlargement of pore size. As listed in Table 1, the pore size of SBA-15 samples increased with an increase in hydrothermal temperature. SBA-15-a synthesized at 80 ◦ C has the smallest pore size of 3.7 nm, while SBA-15-d at 180 ◦ C has the biggest pore size of 10.1 nm. These results are in agreement with those of microwave-assisted synthesis of SBA-15 reported by Jaroniec et al. [22]. At the same time, the BET surface area and pore volume varied with the hydrothermal temperature. The synthesis of amino-functionalized SBA-15 ordered mesoporous materials is illustrated in Scheme 2. The silylation of four SBA-15 samples, including SBA-15-a, SBA-15-b, SBA-15-c and SBA15-d, with 3-(triethoxysilyl) propan-1-amine correspondingly gave rise to four amino-functionalized SBA-15 ordered mesoporous materials 1a–1d [23]. Scheme 2 also illustrates the novel route to synthesize the new SBA-15 supported Grubbs-type catalysts, where the commercially available Methyl-3-(4-hydroxyphenyl) propionate 2 start the esterification of carboxylic acid with methanol in the presence of acid and the etherification of phenol group with isopropyliodide offered 3, followed by bromination of the aromatic ring and then introduction of the vinyl group by a Pdcatalyzed Still coupling offered 4. 5 was accomplished by hydrolysis

SBA-15-d

SBA-15-c

Volume(cm 3/g)

2.7. Typical procedure for RCM reaction

SBA-15-d

SBA-15-b

2.6. Preparation of SBA-15 supported Hoveyda–Grubbs 2nd type catalyst (8a–8d)

6a (400 mg), CuCl (24 mg, 0.24 mmol) was charged to a 50 mL tube-flask. In the glove box, Grubbs Catalyst 2nd Generation (204 mg, 0.24 mmol) was added to the above tube flask, and the flask was evacuated and charged with N2 for three times. Then, 15 mL of CH2 Cl2 was added and the reaction mixture was stirred at 40 ◦ C for 24 h. After the reaction, the mixture was filtrated and washed repeatedly with CH2 Cl2 to afford 8a as a yellow green solid 0.49 g. 8b–8d was obtained by the same method.

(200)

SBA-15-b

SBA-15-a

0.0

0.2

0.4

0.6

0.8

1.0

P/P0 Fig. 2. The Nitrogen adsorption–desorption isotherms for SBA-15 samples.

38

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Table 1 Nitrogen adsorption–desorption for SBA-15 samples.a Sample

P123/H2 O/HCl/TEOSb

Condensation temp. (◦ C)

SBET (m2 /g)

Vp (cm3 /g)

dp (nm)

SBA-15-a SBA-15-b SBA-15-c SBA-15-d

8.0:72:288:20.4 6.0:45.2:180:12.3 6.24:45:180:12.8 6.0:187.5:112.5:16.8

60 100 130 180

469 567 679 450

0.50 0.84 1.40 1.20

3.70 6.18 8.06 10.1

a b

Given by N2 sorption at 77 K. Weight ratios.

Scheme 2. Synthesis of SBA-15 supported Grubbs-type catalysts.

with KOH and then acidification with HCl [24,2f], then was coupled to the 1a–1d by amidation and thus offered precursor 6a–6d. 6a–6d was then treated with the first-generation Grubbs catalyst or second-generation Grubbs catalyst in the presence of CuCl to provide the desired heterogeneous catalysts 7a–7d or 8a–8d [25]. The key step of the synthesis is to prepare amidation 6a–6d, which is confirmed by FT-IR and elemental analysis. Fig. 3 shows the IR spectra of amino-functionalized SBA-15 1b and 6b. The peak at 3302 cm−1 assigns as stretching vibration absorption of N H, meanwhile the characteristic peaks at 1656 cm−1 could be related to the stretching vibration absorption of C O, indicating that the product of amidation was obtained.

Results of elemental analysis are shown in Table 2. After amidation, nitrogen content of the samples all has a reduction between 0.15 mmol/g and 0.19 mmol/g. It indicates that 4 products of amidation were obtained in success. Ruthenium content in catalytic materials is determined by inductively coupled plasma (ICP) analysis, summarized in Table 3. All immobilized catalysts contain a certain amount of Ru with some differences. Ruthenium content of immobilized catalysts prepared from the second generation Grubbs complexes gave much lower Ru content than those prepared from the first generation Grubbs complexes. As reported by Polarz et al. [17c] and Staub et al. [17d]

Table 3 Ruthenium content in catalytic materials of 7a–7d and 8a–8d.a

Table 2 Nitrogen content of 1a–1d and 6a–6d. Substrate

N (mmol/g)

Substrate

N (mmol/g)

1a 1b 1c 1d

1.15 1.58 1.49 0.92

6a 6b 6c 6d

1.00 1.39 1.32 0.77

Substrate

Ru (mmol/g)

Substrate

Ru (mmol/g)

7a 7b 7c 7d

0.0935 0.1452 0.1656 0.1208

8a 8b 8c 8d

0.0504 0.0630 0.1050 0.0828

a

Determined by ICP.

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Transmission

1b

6b

3302 cm-1

3500

1656 cm -1

3000

2500

2000

1500

1000

Wavenumber/ (cm-1) Fig. 3. FT-IR spectra of 1b and 6b.

respectively, there is an interaction between the tricyclohexylphosphine and the surface silanols. Small-angle XRD patterns shows that most functionalized SBA15 samples, including 1a–1d, 6a–6d, 7a–7d and 8a–8d, exhibit three peaks indexed to (1 0 0), (1 1 0) and (2 0 0) reflections that associat with a 2D hexagonal (p6mm) structure. Therefore, supported catalysts almost maintain the ordering of mesoporous materials (Fig. S1). The N2 adsorption–desorption isotherms and the data of samples are shown in Fig. 4 and Table 4. The well-defined type IV isotherm curves clearly indicate that these materials possess a mesoporous structure. After the immobilization, the BET surface area of SBA-15 and the average pore size decreased due to the loading of the Ru complex in the mesoporous structure. However, the pore size is still large enough to permit the diffusion of large organic molecule in it. Fig. 5 shows the TEM image of the sample 7c after immobilization taken with the electron beam along and perpendicular to pore channels. The hexagonal pore structure of SBA-15 remained intact after the immobilization. The activity of the immobilized catalysts is shown in Table 5. When a solution of the disubstituted dienes 9a in CH2 Cl2 was treated with 5 mol% immobilized catalysts at 38 ◦ C under the protect of Ar. Importantly, the supported catalysts can be cleanly recovered by filtration, washing and repeatedly reused. As shown in Table 5, 7d and 8d can be recycled up to 8 times, while the isolated yields remain at about 85%, although the reaction time has been extended. Meanwhile, larger pore sizes of SBA-15 ordered mesoporous materials are benefit for the immobilized catalysts. In all 8 kinds of immobilized catalysts, 7d and 8d using the

Table 4 The N2 adsorption–desorption isotherms of a series of SBA-15 supported catalysts.a Sample

SBET (m2 /g)

Vp (cm3 /g)

dp (nm)

SBA-15-b 1b 6b 7b 8b SBA-15-c 1c 6c 7c 8c

539 331 258 179 135 601 393 305 169 171

0.87 0.58 0.48 0.33 0.25 1.40 0.90 0.60 0.31 0.31

6.18 5.41 4.76 4.19 3.71 8.06 7.05 5.41 4.76 4.76

a

Given by N2 sorption at 77 K.

39

SBA-15 with the largest pore size as support have the highest catalytic activity – shortest reaction time and reused most cycles. It has already been discussed that a confining reaction field affects intermolecular equilibrium reactions very strongly. It seems that the unusual reactivity of 7d and 8d is a combination of a confinement effect and a surface effect [17c]. The main reason lies in that large pore is benefit for the diffusion of reactants and products and small pore size restrict the diffusion of reactants and product. At the same time, the surface hydrophilicity/hydrophobicity is quite different because the reaction conditions are varied in the synthesis of SBA-15. In general, high temperature favors the silica condensation and thus leads to the reduction of surface silanols, which could be proved by 29 Si NMR. As shown in 29 Si NMR spectrum and their fitting with multiple peaks of Fig. 6, all SBA-15 samples show three signals at around −90, −100 and −110 ppm that are assigned to Q2 [Si(OSi)2 (OH)2 ], Q3 [Si(OSi)3 (OH)] and Q4 [Si(OSi)4 ] substructures, respectively. With the aging temperature increasing, SBA-15-d synthesized at 180 ◦ C exhibits highest silica condensation degree, as the percentage of Q4 in SBA-15-d reached ∼81%. Meanwhile, other three samples synthesized at lower aging temperature show similar Q4 /Q3 /Q2 ratio with much lower percentage of Q4 of ∼60–65%. Staub et al. considered that the masking of the surface silanol groups lead to the stabilization of the Grubbs catalyst [17d]. Furthermore, the pore diameter of SBA-15 samples increased with an increase aging temperature, as listed in Table 1. Lager mesopore could reduce diffusion limitation and thus favor the reaction, because one major limitation with the grafting of Grubbs catalyst on a solid support is the diffusion of the catalyst to the liquid phase. These results are also coincident with those reported by Polarz [17c]. Hence, SBA-15 samples synthesized at high temperature that show high hydrophobicity and less silanol groups along with large pore diameter are benefit for the reaction. Besides the recyclability and reusability of the immobilized catalysts, we further examine the performance of immobilized catalyst 8d in the RCM of a variety of di-, tri-, and tetrasubstituted diene substrates leading to the formation of various carbocyclic and heterocyclic olefins. As listed in Table 6, ring-closing metathesis of di-, trisubstituted diene substrates can go cleanly with high isolated yields except 9f. Tetrasubstituted diene substrate has a low conversion and isolated yield because of steric hindrance. As the immobilized catalyst 8d showed a good activity for RCM, we further examined the self-metathesis and crossmetathesis reactions of olefins. As shown in Table 7, self-metathesis reaction went cleanly in case of styrene (Entry 1) and pmethoxy styrene (Entry 2), and the corresponding products were formed in high yields (>90%). However, CM reaction between styrene and ethyl acrylate were ended with 2 products (Entry 3). The reaction time is extended with the catalysts further cycled and reused, so three assumptions were investigated for the phenomenon: (I) the loss of Ru content causes the immobilized catalyst activity decreased; (II) the collapse of SBA-15 mesopore structure worsen the diffusion limitation of reactants and products; and (III) the catalysts deteriorate due to the air and water, and thus result in a decrease in the activity. Ru content in catalysts before and after cycle was analyzed by ICP. At the end of the reaction, the catalyst solid was gathered by filtration, and the Ru content in the recycled catalyst was determined by ICP analysis. The larger pore SBA-15 support was used for immobilizing the Ru catalysts, the more Ru species were released (7a: 0.006 mmol/g; 7b: 0.006 mmol/g; 7c: 0.048 mmol/g; 7d: 0.026 mmol/g; 8a: 0 mmol/g; 8b: 0.011 mmol/g; 8c: 0.034 mmol/g; 8d: 0.04 mmol/g). Filtration test was also examined using RCM of 9a with 7b as catalyst. After 6 h of the reaction,

40

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Table 5 Recycling and reuse of the immobilized catalyst 7a–7d and 8a–8d in the ring-closing metathesis of dinen 9a. N Ts

9a

5mol% cat. CH2Cl2, 38oC

N

10a

Ts

Cat. Cyclea

7a Yieldb (timec )

8a Yieldb (timec )

7b Yieldb (timec )

8b Yieldb (timec )

7c Yieldb (timec )

8c Yieldb (timec )

7d Yieldb (timec )

8d Yieldb (timec )

1 2 3 4 5 6 7 8 9

92 (24) 76 (24)

96 (24) 64 (24)

98 (12) 95 (16) 92 (20) 89 (24)

98 (12) 94 (12) 93 (12) 97 (16) 92 (20) 63 (24)

96 (10) 98 (10) 95 (12) 98 (20) 93 (20) 87 (20) 87 (24)

97 (6) 98 (6) 97 (8) 95 (12) 92 (24) 42 (24)

96 (5) 95 (5) 97 (5) 95 (6) 96 (8) 95 (10) 92 (12) 87 (24) 64 (24)

98 (4) 96 (5) 96 (5) 97 (6) 97 (8) 94 (10) 90 (12) 83 (24) 70 (24)

a b c

9 (1 mmol), cat (5 mol% Ru), CH2 Cl2 , 38 ◦ C, Ar. Isolated yield (%). Reaction time (h), detected by TLC.

the catalyst 7b was separated by filtration and the liquid phase was kept under the same conditions as the standard reaction. Only 52% yield was achieved after 12 h whereas in the presence of 7b this reaction gave 98% yield. For all catalysts, filtration tests gave the similar results, indicating the catalytic activity was contributed by the heterogeneous catalysts but not by those Ru species leached into the reaction solution.

Whether or not the pore structure was maintained during the cycle is an important factor for the catalytic activity. So we choose 7c and 8c after the recycling and reusing to investigate their pore structure by XRD and BET. Small-angle XRD patterns for recycled supported catalysts 7c and 8c samples all exhibit three peaks, which can be indexed to (1 0 0), (1 1 0) and (2 0 0) reflections that associated with a 2D hexagonal (p6mm) structure. It proves that the

SBA-15-c

Volume(cm 3/g)

1b

6b 7b

Volume(cm 3/g)

SBA-15-b

1c

6c 7c

8b

0.0

0.2

0.4

0.6

P/P0

0.8

8c

1.0

0.2

0.4

0.6

0.8

P/P0

Fig. 4. The N2 adsorption–desorption isotherms of a series of SBA-15 supported catalyst samples.

Fig. 5. TEM images of SBA-15 supported catalysts 7c.

1.0

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

41

Table 6 RCM of dienes catalyzed by the immobilized catalyst 8d in CH2 Cl2 . Entrya

Time (h)b

Substrate

Yield (%)c

Product

CO2Et

EtO2C

CO2Et

1

CO2Et 6

9b

10b

Ts N SBA-15-a

N Ts

2

4

93

10c

9c Ts N

N Ts 4

3

9d

4

78

10d

Ts N

N Ts 14

95

10e

9e

SBA-15-b

92

Ts N

N Ts

5

12

10f

9f Ts N

N Ts 12

6

Ts N

N Ts 24

7

9h a b c

SBA-15-d

-80

-90

-100

-110

-120

-130

Chemical Shift (ppm) Fig. 6.

29

Si NMR spectra of SBA-15 samples and their fitting with multiple peaks.

92

10g

9g

SBA-15-c

88

37

10h

Substrate (1 mmol), 8d (5 mol%), CH2 Cl2 , 38 ◦ C, Ar. Detected by TLC. Isolated yield.

recycled supported catalysts also keep their ordered mesoporous structure (Fig. S2). The N2 adsorption/desorption isotherms of recycled supported catalysts 7c and 8c are also studied. The type IV isotherm curves with a well defined step clearly indicate that these materials possess mesoporous structure (Fig. S3). At last, the valences of Ru before and after recycle were investigated by XPS. As the Ru 3d band is overlapped with that of C 1 s in XPS spectra (Fig. S4), the Ru 3p band is thus used to characterize the status of the Ru species. The binding energy of Ru 3p3/2 is almost the same before and after the reaction (∼462.3 eV), although there is a slight decrease in Ru 3p band intensity because of partial leaching of the Ru species. Thus, the Ru valence does not change during the catalytic reaction.

42

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43

Table 7 Self-metathesis or cross-metathesis of styrene derivatives catalyzed by 8d. Entrya

Time (h)b

Substrate

1

Yield (%)c

Product

6

+

91

11 MeO

MeO

2

+

OMe

18

MeO

12

+ 3

90

+

18

O

O

40 O

13

O 32 a b c

◦

Substrate (1 mmol), 8d (5 mol%), CH2 Cl2 , 38 C, Ar. Detected by TLC. Isolated yield.

4. Conclusions In conclusion, we have synthesized 8 novel Ru-based olefin catalysts using SBA-15 ordered mesoporous materials with different pore size as support. The immobilized catalysts have good activities in RCM and other metathesis reactions. The reactivity of the catalyst is a combination of a confinement effect and a surface effect. SBA-15 with large pore size is benefit for the immobilized catalysts. In view of diversity and excellent stability of ordered mesoporous materials, Grubbs-type catalysts can immobilized on other functionalized ordered mesoporous materials, such investigations are currently underway in our laboratories and will be disclosed shortly.

[3]

Acknowledgements We gratefully acknowledge the financial supports by NSFC (20925310 and U1162102), National Key Technology R&D Program (2012BAE05B02), Innovation Program of Shanghai Municipal Education Commission (13zz038), Key Project of the Shanghai Committee of Science and Technology (12JC1403600) and Shanghai Leading Academic Discipline Project (No. B409). We also would like to thank Dr. Yimeng Wang for valuable discussion.

[4]

Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.molcata. 2013.01.034. References [1] (a) M. Schuster, S. Blechert, Angew. Chem. Int. Ed. Engl. 36 (1997) 2036; (b) R.H. Grubbs, S. Chang, Tetrahedron 54 (1998) 4413; (c) A. Fürstner, Angew. Chem. Int. Ed. 39 (2000) 3012. [2] (a) P. Schwab, R.H. Grubbs, J.W. Ziller, J. Am. Chem. Soc. 118 (1996) 100; (b) M. Scholl, S. Ding, C.W. Lee, R.H. Grubbs, Org. Lett. 1 (1999) 953;

[5]

[6]

[7] [8] [9]

(c) J. Huang, E.D. Stevens, S.P. Nolan, J.L. Petersen, J. Am. Chem. Soc. 121 (1999) 2674; (d) M. Scholl, T.M. Trnka, J.P. Morgan, R.H. Grubbs, Tetrahedron Lett. 40 (1999) 2247; (e) J.S. Kingsbury, J.P.A. Harrity, P.J. Bonitatebus Jr., A.H. Hoveyda, J. Am. Chem. Soc. 121 (1999) 791; (f) S.B. Garber, J.S. Kingsbury, B.L. Gray, A.H. Hoveyda, J. Am. Chem. Soc. 122 (2000) 8168; (g) Si. Gessler, S. Randl, S. Blechert, Tetrahedron Lett. 41 (2000) 9973. (a) H. Wakamatsu, S. Blechert, Angew. Chem. Int. Ed. 41 (2002) 794; (b) H. Wakamatsu, S. Blechert, Angew. Chem. Int. Ed. 41 (2002) 2403; (c) K. Grela, S. Harutyunyan, A. Michrowska, Angew. Chem. Int. Ed. 41 (2002) 4038; (d) T.M. Trnka, J.P. Morgan, M.S. Sanford, T.E. Wilhelm, M. Scholl, T.L. Choi, S. Ding, M.W. Day, R.H. Grubbs, J. Am. Chem. Soc. 125 (2003) 2546; (e) S. Maechling, M. Zaja, S. Blechert, Adv. Synth. Catal. 347 (2005) 1413; (f) D.R. Anderson, V. Lavallo, D.J. O’Leary, G. Bertrand, R.H. Grubbs, Angew. Chem. Int. Ed. 46 (2007) 7262; (g) J.M. Berlin, K. Campbell, T. Ritter, T.W. Funk, A. Chlenov, R.H. Grubbs, Org. Lett. 9 (2007) 1339; (h) G.C. Vougioukalakis, R.H. Grubbs, J. Am. Chem. Soc. 130 (2008) 2234; (i) N. Ledoux, A. Linden, B. Allaert, H. Vander, F. Mierde, Verpoorta, Adv. Synth. Catal. 349 (2007) 1692; (j) N. Ledoux, B. Allaert, A. Linden, P.V.D. Voort, F. Verpoort, Organometallics 26 (2007) 1052. (a) T.A. Kirkland, D.M. Lynn, R.H. Grubbs, J. Org. Chem. 63 (1998) 9904; (b) H.D. Maynard, R.H. Grubbs, Tetrahedron Lett. 40 (1999) 4137; (c) L.A. Paquette, J.D. Schloss, I. Efremov, F. Fabris, F. Gallou, J.M. Andino, J. Yang, Org. Lett. 2 (2000) 1259; (d) Y.M. Ahn, K.L. Yang, G.I. Georg, Org. Lett. 3 (2001) 1411; (e) J.C. Conrad, H.H. Parnas, J.L. Snelgrove, D.E. Fogg, J. Am. Chem. Soc. 127 (2005) 11882; (f) T. Nicola, M. Brenner, K. Donsbach, P. Kreye, Org. Process Res. Dev. 9 (2005) 513; (g) A. Michrowska, Ł. Gułajski, K. Grela, Chem. Commun. 42 (2006) 841. (a) S.T. Nguyen, R.H. Grubbs, J. Organomet. Chem. 497 (1995) 195; (b) M. Ahmed, A.G.M. Barrett, D.C. Braddock, S.M. Cramp, P.A. Procopiou, Tetrahedron Lett. 40 (1999) 8657; (c) S.C. Schürer, S. Gessler, N. Buschmann, S. Blechert, Angew. Chem. 112 (2000) 4062. (a) Q.W. Yao, A.R. Motta, Tetrahedron Lett. 45 (2004) 2447; (b) J.P. Gallivan, J.P. Jordan, R.H. Grubbs, Tetrahedron Lett. 46 (2005) 2577; (c) S. Zaman, An.D. Abell, Tetrahedron Lett. 50 (2009) 5340. S.J. Connon, S. Blechert, Bioorg. Med. Chem. Lett. 12 (2002) 1873. Q.W. Yao, Y.L. Zhang, J. Am. Chem. Soc. 126 (2004) 74. S. Cetinkaya, E. Khosravi, R. Thompson, J. Mol. Catal. A: Chem. 254 (2006) 138.

H. Zhang et al. / Journal of Molecular Catalysis A: Chemical 372 (2013) 35–43 [10] (a) J. Dowden, J. Savovic, Chem. Commun. 37 (2001) 37; (b) F. Michalek, D. Mädge, J. Rühe, W. Bannwarth, J. Organomet. Chem. 691 (2006) 5172; (c) D. Rix, F. Caijo, I. Laurent, F. Boeda, H. Clavier, S.P. Nolan, M. Mauduit, J. Org. Chem. 73 (2008) 4225; (d) B.H. Lipshutz Subir Ghorai, Tetrahedron 66 (2010) 1057. [11] (a) C.T. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359 (1992) 710; (b) J.S. Beck, J.C. Vartuli, W.J. Roth, M.E. Leonowicz, C.T. Kresge, K.D. Schmitt, C.T.W. Chu, D.H. Olson, E.W. Sheppard, S.B. McCullen, J.B. Higgins, J.L. Schlenker, J. Am. Chem. Soc. 114 (1992) 10834. [12] (a) P. Behrens, Angm. Chem. lnt. Ed Engl. 35 (1996) 515; (b) N.K. Raman, M.T. Anderson, C.J. Brinker, Chem. Mater. 8 (1996) 1682; (c) A. Sayari, Chem. Mater. 8 (1996) 1840; (d) A. Corma, Chem. Rev. 97 (1997) 2373. [13] (a) K. Melis, D. De Vos, P. Jacobs, F. Verpoort, J. Mol. Catal. A: Chem. 169 (2001) 47; (b) X. Elias, R. Pleixats, M.W.C. Man, J.J.E. Moreau, Adv. Synth. Catal. 348 (2006) 751; (c) B.D. Clercq, F. Lefebvreb, F. Verpoort, New J. Chem. 26 (2002) 1201; (d) D. Bek, H. Balcar, N. Zilková, A. Zukal, M. Horácek, J. Cejka, ACS Catal. 1 (2011) 709; (e) T. Shindea, N. Zilková, V. Hanková, H. Balcar, Catal. Today 179 (2012) 123. [14] J. Lim, S.S. Lee, S.N. Riduan, J.Y. Ying, Adv. Synth. Catal. 349 (2007) 1066. [15] (a) D.Y. Zhao, J.L. Feng, Q.S. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Science 279 (1998) 548; (b) D.Y. Zhao, Q.S. Huo, J.L. Feng, B.F. Chmelka, G.D. Stucky, J. Am. Chem. Soc. 120 (1998) 6024; (c) M. Kruk, M. Jaroniec, C.H. Ko, R. Ryoo, Chem. Mater. 12 (2000) 1961.

43

[16] (a) J.Y. Ying, C.P. Mehnert, M.S. Wong, Angew. Chem. Int. Ed. 38 (1999) 56–77; (b) R. Sayah, K. Glegoła, E. Framery, V. Dufaud, Adv. Synth. Catal. 349 (2007) 373; (c) K. Wang, X.J. Li, S.F. Ji, B.Y. Huang, C.Y. Li, ChemSusChem 1 (2008) 527; (d) J.N. Zhang, Z. Maa, J. Jiao, H.F. Yin, W.F. Yan, E.W. Hagaman, J.H. Yu, S. Dai, Micropor. Mesopor. Mater. 129 (2010) 200; (e) L. Wang, X.J. Meng, B. Wang, W.Y. Chi, F.S. Xiao, Chem. Commun. 46 (2010) 5003; (f) B. Naika, S. Hazra, V.S. Prasad, N.N. Ghosh, Catal. Commun. 12 (2011) 1104. [17] (a) L. Li, J.L. Shi, Adv. Synth. Catal. 347 (2005) 1745; (b) X. Elias, Roser Pleixats, M.W.C. Man, Tetrahedron 64 (2008) 6770; (c) S. Polarz, B. Völker, F. Jeremias, Dalton Trans. 39 (2010) 577; (d) H. Staub, R.G. Nicolas, N. Even, L. Kayser, F. Kleitz, F.G. Fontaine, Chem. Eur. J. 17 (2011) 4254. [18] V.B. Berlo, K. Houthoofd, B.F. Sels, P.A. Jacobs, Adv. Synth. Catal. 350 (2008) 1949. [19] X. Ellas, R. Pleixats, M.W.C. Man, J.J.E. Moreau, Adv. Synth. Catal. 349 (2007) 1701. [20] M.S. Sanford, M. Ulman, R.H. Grubbs, J. Am. Chem. Soc. 123 (2001) 749. [21] N. Xiao, L. Wang, S. Liu, Y.C. Zou, C.Y. Wang, Y.Y. Ji, J.W. Song, F. Li, X.J. Meng, F.S. Xiao, J. Mater. Chem. 19 (2009) 661. [22] E.B. Celer, M. Jaroniec, J. Am. Chem. Soc. 128 (2006) 14408. [23] P. Sreekanth, S.W. Kim, T. Hyeon, B.M. Kima, Adv. Synth. Catal. 345 (2003) 936. [24] N. Audic, H. Clavier, M. Mauduit, J.C. Guillemin, J. Am. Chem. Soc. 125 (2003) 9248. [25] C. Che, W.Z. Li, S.Y. Lin, J.W. Chen, J. Zheng, J.C. Wu, Q.X. Zheng, G.Q. Zhang, Z. Yang, B.W. Jiang, Chem. Commun. 45 (2009) 5990.