Wei Zhou and Dehua He* - Royal Society of · PDF fileRh-P complex activities in 1-octene...

Lengthen alkyl spacer to increase SBA-15-anchored Rh-P complex activities in 1-octene hydroformylation

Wei Zhou and Dehua He*

Innovative Catalysis Program, Key Lab of Organoelectronics & Molecular Engineering

of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing

100084, People’s Republic of China

*Corresponding author. Professor Dehua He, E-mail: [email protected];

Tel & Fax: +86(10)62773346

CONTENTS

1. Preparation of SARC catalysts ..................................................................................0

2. Characterization of SARC catalysts .........................................................................2 2.1 Transmission electron microscopy (TEM) ................................................................... 2 2.2 Powder X-ray diffraction (XRD) ................................................................................... 3 2.3 Isothermal N2 sorption analysis...................................................................................... 4

3. 1-Octene hydroformylation.........................................................................................4 3.1 Reaction operation............................................................................................................. 4 3.2 Rh loss in catalytic 1-octene hydroformylation .......................................................... 6 3.3 Other rhodium precursors............................................................................................... 6 3.4 13C CP-MAS NMR spectroscopy.................................................................................... 7

4. References .................................................................................................................... 10

1. Preparation of SARC catalysts Please refer to Scheme 1 in the manuscript for sample correspondence.

Supplementary Material (ESI) for Chemical CommunicationsThis journal is (c) The Royal Society of Chemistry 2008

Electronic Supplementary Information (ESI)

1

Ordered silica-based mesoporous molecular sieve SBA-15 was synthesized in a

three-necked flask1. P123 (PEO20PPO70PEO20, Mn = 5800, Aldrich) was dissolved in

HCl (2 mol·L-1). Tetraethyl orthosilicate (TEOS, Acrös) was added dropwise. The

mixture was stirred for 20 h under 308 K. The flask was then sealed and kept under

353 K for 24 h. Molar ratio of the initial gel was 0.017P123:aH2O:4.78HCl:1TEOS.

The resultant solid was recovered and washed. As-synthesized SBA-15 was calcined

at 773 K for 6 h. To preserve as much as possible sufficient hydroxyls on the SBA-15

surface and consequently to achieve better grafting, the following calcination program

with a ramp of 1 K·min-1 is recommended2:

Time (min)

Fig. E1 Recommended calcination program for P123-bearing SBA-15. Three steps lasted for 60 mins, 60 mins, and 360 mins, respectively.

The following experiments were carried out under Schlenk operation. Solvents

(toluene, THF, and ether) were in advance refluxed with sodium under nitrogen.

Haloalkylation was finished by the grafting method3. Parent SBA-15 was suspended

in toluene and excessive silane X(CH2)nSi(OCH3)3 was added (silanes with n = 1, 3,

and 11 were purchased from ABCR GmbH & Co. KG; silanes with n = 5 and 8 were

prepared according to the literatures4,5. For n = 11, X = Br, others X = Cl). The

mixture was refluxed for 24 h. The resulting solid was recovered and washed by

CH2Cl2 in a Soxhlet’s extractor for 12 h to remove physisorbed species. Phosphine

ligand preparation and connection: PPh3 (Ph = phenyl, Fluka) was dissolved in

THF. Li meanings (Sinopharm Chemical Reagent Co., Ltd) were added. The mixture

was stirred at room temperature and in dry nitrogen’s atmosphere for 3 h. After

removing the surplus metal, t-C4H9Cl (Sinopharm Chemical Reagent Co., Ltd) was

added at 273 K to decompose LiPh. Stir was held at 273 K for 1 h and then at room

Tem

pera

ture

(K)

298 383

513

773



2

temperature for 2 h. Haloalkylated SBA-15 (S-Cn-X) was afterwards mixed with the

red LiPPh2 solution and the continuous stir was held for 16 h under room temperature.

Molar ratio of LiPPh2 and silane was 4. The resulting solid was recovered, and then

washed by CH2Cl2 in a Soxhlet’s extractor and in N2 for 12 h. Rhodium anchor:

S-Cn-PPh2 was mixed with RhCl3 (6 w.t.% of S-Cn-PPh2, Aldrich) in ethanol. The

mixture was refluxed under syngas (H2/CO = 1) for 6 h. The successful formation of

Rh-P complex was evidenced by the observation that the mixture turned from red to

brown in several minutes. Resultant SARC catalyst (S-Cn-PPh2-Rh) was washed with

ethanol by an ultra-sonic device6 to free uncoordinated ions.

Owing to raw materials limit, the preparation of 8-chlorooctyltrimethoxylane

started from the reaction of 8-chloro-1-octanol (98%, Acrös) with PBr3 (99%, Acrös)

in toluene. α-Br, ω-Cl alkane and Mg were of the same molar. Scheme E1 showed the

preparation of silanes with spacer n = 5 and 8. Pyridine was in advance dried by

calcined (573 K for 3 h) 4A molecular sieves overnight and was employed for the

absorption of acid. 1-bromo-5-chloropentane, Mg, SiCl4, and NaOCH3 were

purchased form Alfa Aesar. Detailed preparation could be acquired from literatures4,5.

Scheme E1 Preparation of 5-chloropentyltrimethoxysilane and 8-chlorooctyltrimethoxysilane.

2. Characterization of SARC catalysts

2.1 Transmission electron microscopy (TEM)

TEM measurements were performed with a PHILIP EM400ST electron micro-

scope operated at 100 kV. Sample material was mounted on a holey carbon film

supported on a Cu grid by drying a droplet of a suspension of ground sample in

ethanol on the grid.



3

Fig. E2 TEM micrographs of parent SBA-15 at different focuses.

Fig. E2 showed TEM micrographs of parent SBA-15. Very ordered and regular

honeycomb-like hexagonal mesopores (ca. 5-6 nm in pore size) were clearly observed.

The particle size of SBA-15 at lower focus revealed ca. 0.5 μm × 0.8 μm.

2.2 Powder X-ray diffraction (XRD)

XRD data at low angles were collected on a Rigaku D/max-RB diffractometer at a

scan solution of 2°·min-1 with CuKα radiation (λ = 0.154 2 nm). XRD characterization

was powered at 40 kV and 100 mA.

Fig. E3 shows XRD patterns of SARC catalysts with different alkyl spacers. The

well-resolved d100 reflection at ca. 2Theta = 1° indicated all SARC catalysts preserved

typical hexagonal symmetry2 from the support. Unit cell parameter a0 of hexagonal

structure (see Table 1 in the manuscript) was calculated by the equation7:

1000 32 da =



4

Fig. E3 Powder XRD patterns of SARC catalysts S-Cn-PPh2-Rh.

2.3 Isothermal N2 sorption analysis

Isothermal nitrogen sorption at 77 K was performed on a Micromeritics ASAP

2010 analysis system. The BET (Brunauer-Emmett-Teller) and the BJH (Barrett-

Joyner-Halenda) methods were applied for the specific surface area and pore size

distribution calculations, respectively.

Fig. E4 (on next page) shows the isotherms of parent SBA-15 and SARC catalysts.

Inserts are corresponding pore size distribution plot. Type IV according to the IUPAC

classification and narrow pore size distribution are shown (see corresponding inserts),

indicating the ordered regular mesopores were preserved during the Rh-P complex

anchor. N2 sorption analysis results are in accordance with XRD characterization.

3. 1-Octene hydroformylation

3.1 Reaction operation

Hydroformylation of 1-octene was carried out as follows. 5 mL 1-octene (Acrös,

99%) was mixed with 15 mL toluene (as solvent, sodium-refluxed, A.R.) in a 100 mL

autoclave and the SARC catalyst was added. The autoclave was then firmly sealed



5

and syngas (H2/CO = 1) was injected at lower than 278 K to replace the air inside the

autoclave (3×). The autoclave was heated to 393 K and the syngas was injected to 5

MPa. The electromagnetic stir was started and lasted for 2.5 h. At the end of the

reaction, the autoclave was cooled to lower than 278 K and the pressure was released.

1 mL isopropyl alcohol (A.R.) was added as internal standard. The resulting mixture

was analyzed by a GC equipped with an SE-30 capillary column (0.32 mm × 0.25 μm

× 30 m). In the recycle experiments, the separated catalysts were above all washed by

toluene under ultrasonic washing.

Fig. E4 Isotherms of parent SBA-15 and SARC catalysts; Inserts: corresponding pore size

distribution plot.

Parent SBA-15



6

3.2 Rh loss in catalytic 1-octene hydroformylation

Fig. E5 Rh leaching during the recycle of SARC catalysts S-Cn-PPh2-Rh. The percentage in the insert is the sum of Rh leaching from SARC catalyst recycles.

Immobilized Rh contents of SARC catalysts were received by an IRIS Intrepid II

ICP-AES spectrometer. Leached Rh contents in reaction liquids were analyzed by an

X series In 20000CPS/ppb (1.5%RSD) ICP-MS spectrometer. 2 mL reaction liquid

was calcined at 573 K to evaporate all liquids. 0.5 mL concentrated H2SO4 (98%) was

added to the residue and heated for eliminating residue organics. Then, 1 mL HNO3

(63%) was added. The resulting acidic liquid mixture was then diluted to 25 mL for

ICP-MS analysis. Rhloss% equals to the ratio of Rh in reaction liquids (sum of recycles)

and immobilized Rh of the SARC catalyst.

Fig. E5 reveals the leaching of Rh from SARC catalysts gradually decreases

along with catalyst runs. The leaching of Rh of the several beginning recycles might

be original from the external surface of SBA-15.

3.3 Other rhodium precursors

Table E1 shows 1-octene hydroformylation over SBA-15 anchored Rh catalyst

with spacer C11. Four rhodium precursors were employed, including rhodium acetate

dimer, rhodium chloride, a rhodium complex, and Wilkinson’s catalyst. It is obvious

the immobilized catalyst shows higher activity if more active rhodium precursor was

used. All four heterogeneous catalysts showed comparable activity to corresponding

homogeneous counterpart, but they gave higher selectivity of nonyl aldehydes. This

indicates the absolute activity of SARC catalyst could be promoted by using more

active rhodium precursor, which evidenced the general preparative strategy to



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increase immobilized catalyst activity – adopting more efficient ligands8. Noticeably,

the molar ratio of normal and branched nonyl aldehyde is increased if the rhodium

precursor has more PPh3 ligands. This is in accordance with previous researches in

homogeneous process9. The preparation of S-C11-PPh2-anchored RhCl(CO)(PPh3)2 or

RhCl(PPh3)3 catalyst was carried out by stirring S-C11-PPh2 with rhodium complex

(Strem) in CH2Cl2 for 24 h at room temperature (N2 atmosphere). The resulting

catalyst was washed by CH2Cl2 under ultra-sonic for removing physisorbed species.

Table E1 1-Octene hydroformylation over S-C11-PPh2-anchored Rh catalysts: a comparison among four rhodium precursors.

Rhodium precursors

[Rh(CH3COO)2]2

(Rh = 1.8 w.t.%)

RhCl3

(Rh = 1.5 w.t.%)

RhCl(CO)(PPh3)2

(Rh = 0.35 w.t.%)

RhCl(PPh3)3

(Rh = 0.28 w.t.%)

TON Sel. n/i TON Sel. n/i TON Sel. n/i TON Sel. n/i

Homogeneous 755 92% 0.5 965 91% 0.7 2931 91% 1.8 3008 93% 2.5 S-C11-PPh2-Rh 688 99% 0.4 922 99% 0.5 2755 98% 1.6 2976 98% 2.2 aReaction temperature 393 K, reaction time 2.5 h, initial syngas pressure 5 MPa (see section 3.1). bTON = 1-octene turnover number (molar ratio of converted 1-octene and immobilized rhodium). Sel. = selectivity of nonyl aldehydes. n/i = ratio of linear and branched nonyl aldehyde. cData from the heterogenized catalysts refer to the first catalyst cycle.

3.4 13C CP-MAS NMR spectroscopy

13C{1H} cross polarization-magic angle spinning (CP-MAS) NMR spectroscopy

was applied to fresh and recycled SARC catalysts on a Bruker 300 MHz spectrometer.

The 5 mm probe was set to 5.5 KHz. Fig. E6 is the NMR spectra of fresh (a) and

recycled (b) SARC catalyst with spacer C3 as example. In the spectrum of fresh

S-C3-PPh2-Rh (a), the coordinated carbonyl showed a signal at 179.9 ppm. The

phenyl rings gave a signal at 126.8 ppm, original from C=C bond. These resonances

were broadened by the influences of coordinated Rh. The propyl spacer showed

peaks10 at 21.6, 14.9, and 8.3 ppm. The peaks at 57.3 and 44.6 ppm might be original

from the hydrogen-bonded solvent ethanol or non-bonded methoxyls of the silane10.

In the spectrum of recycled S-C3-PPh2-Rh catalyst (b), a broadened resonance

was found at 185.8 ppm. Since no coordinated carbonyl could observed in the IR

spectrum of the recycled catalyst, this peak can be accordingly assigned to the

carbonyl in the –(C=O)-(C=C)- structure of the alfa,beta-unsaturated aldehyde. The

resonance from C=C carbon was slightly shifted to 129.1 ppm. This is might because

the influence of the C=C bond in the alfa,beta-unsaturated aldehyde, which cannot be

distinguished from the phenyl resonance in the NMR spectrum. Noticeably, the



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recycled S-C3-PPh2-Rh catalyst spectrum gave more signals of alkyl carbon in the

range 50 – 0 ppm, indicating the dehydrated product of the aldol condensation of

nonyl aldehyde, an 18-carbon alfa,beta-unsaturated aldehyde. However the alkyl

carbons of the by-product cannot be finely resolved owing to the similar chemical

surroundings of the carbons. Similar conclusions can be received from 13C CP-MAS

NMR spectra of SARC catalysts with other spacers.



9

Fig. E6 13C Cross Polarization-Magic Angle Spinning NMR spectra of fresh S-C3-PPh2-Rh (a) and

recycled S-C3-PPh2-Rh (b) catalyst.



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4. References 1. X.-Y. Hao, W. Zhou, J.-W. Wang, Y.-Q. Zhang, S. Liu, Chem. Lett., 2005, 34,

1000. 2. D. Zhao, Q. Huo, J. Feng, B. F. Chmelka and G. D. Stucky, J. Am. Chem. Soc.,

1998, 120, 6024. 3. C. Zhang, W. Zhou and S. Liu, J. Phys. Chem. B, 2005, 109, 24319. 4. R. A. Benkeser, S. D. Smith, J. L. Noe, J. Org. Chem., 1968, 33, 597. 5. C. S. Marvel, W. E. Garrison, Jr, J. Am. Chem. Soc., 1959, 81, 4737. 6. X.-Y. Hao, Y.-Q. Zhang, J.-W. Wang, W. Zhou, C. Zhang, S. Liu, Micropor.

Mesopor. Mater., 2006, 88, 38. 7. 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. Schlenke, J. Am. Chem. Soc., 1992, 114, 10834.

8. A. J. Sandee, L. A. van der Veen, J. N. H. Reek, P. C. J. Kamer, M. Lutz, A. L. Spek, P. W. N. M. van Leeuwen, Angew. Chem. Int. Ed., 1999, 38, 3231.

9. D. Evans, J. A. Osborn, G. Wilkinson, J. Chem. Soc. (A), 1968, 3133. 10. J. Kramer, E. Nöllen, W. Buijs, W. L. Driessen, J. Reedijk, React. Funct. Polym.,

2003, 57, 1.


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