Graphical abstract

Introduction• The precursor [RuCl2(p-cymene)]2 polymerize norbornene when activated by

addition of catalytic amounts of (trimethylsilyl)diazomethane.

• In the case of NBE, the Ru-alkylidene is formed without participation of TMSD by the reaction of RuCl2(p-cymene)( PR3) with the monomer. In the case of unstrained cycloolefins the addition of TMSD is necessary.

• Mesoporous molecular sieves are used as excellent supports for different catalysts. Immobilization of soluble metathesis catalysts on siliceous sieves MCM-41 and SBA-15 provides heterogeneous metathesis catalysts with high activity and selectivity and low metal leaching.

• In this contribution, is describe the immobilization of RuCl2(p-cymene)(PCy3) on mesoporous molecular sieves MCM-41 and SBA-15. The immobilized complexes were tested as catalysts for ROMP of NBE, 5-norbornene-2-yl acetate (NBEAc) and dicyclopentadiene.

Monomers

TMSDRuCl2(p-cymene)(PCy3)[RuCl2(p-cymene)]2

Experimental

MCM-41Mobil Composition of Mater) (J. Am. Chem. Soc. 1992, 114, 10834)

SBET = 1032 m2/gAverage pore diameter = 3,7 nmVolume of pores = 0,81 cm3/g

SBA-15Santa Barbara Amorphous (Chemical Communications (13), 1375)

SBET = 829 m2/gAverage pore diameter = 6.6 nmVolume of pores = 1,18 cm3/g

Silica Gel 40 - MerckSBET = 559 m2/gAverage pore diameter = 4,5 nmVolume of pores = 0,473 cm3/g

Mesoporous molecular sieves

MCM-41SBET = 1032 m2/g

SBA-15SBET = 829 m2/g

Sil. Gel 40SBET = 559 m2/g

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Precursor preparation2.0 g RuCl3.3H2O

10 mL -Phellandrene In 100 mL EtOH

Reflux for 4 h

The precipitate was filtered off, washedwith methanol, and dried in uacuo

0.62 g [RuCl2(p-cymene)]2

0.59 g PCy3 In 5 mL CH2Cl2 at 0°C

[RuCl2(p-cymene)](PCy3)82% yield

15 mL Pentane for 3 h

Stirring for 1 h

Filtered off after 3 h, washed with pentane, and dried under vacuum

[RuCl2(p-cymene)]2 65% yield

a) Martin, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974, 233.b) A. Demonceau,, A.W. Stumpf, E. Saive, A.F. Noels, Macromolecules 30 (1997) 3127-3136.

Precursor preparation2.0 g RuCl3.3H2O

10 mL -Phellandrene In 100 mL EtOH

Reflux for 4 h

The precipitate was filtered off, washedwith methanol, and dried in uacuo

0.62 g [RuCl2(p-cymene)]2

0.59 g PCy3 In 5 mL CH2Cl2 at 0°C

[RuCl2(p-cymene)](PCy3) (2)82% yield

15 mL Pentane for 3 h

Filtered off after 3 h, washed with pentane, and dried under vacuum

[RuCl2(p-cymene)]2 (1) 65% yield

a) Martin, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974, 233.b) A. Demonceau,, A.W. Stumpf, E. Saive, A.F. Noels, Macromolecules 30 (1997) 3127-3136.

Stirring for 1 h(2) (1)

Catalyst preparation

With Ru loading of 1 wt. % were stored under argon atmosphere.Content of Ru was determined by ICP-MS.

Mesoporous molecular sieves

pedried at 3 h – 300°C

Schlenk tubefilled w/ Ar

CH2Cl2 + RuCl2(p-cymene)(PCy3)

1 h of stirring, and let to settle down

Mesoporous and RuCl2(p-cymene)(PCy3)

Supernatant very slight yellowWashed out three

time w/ CH2Cl2 and dried in vacuo at RT

RuCl2(p-cymene)(PCy3)/MCM-41

RuCl2(p-cymene)(PCy3)/SBA-15

RuCl2(p-cymene)(PCy3)/silica

Polymerization experiments• Schlenk tube in Ar atmosphere in toluene, NBE (94 mg, 1 mmol) was added

to RuCl2(p-cymene)(PCy3)/SBA-15 (45 mg , 4.5 µmol Ru) in toluene (9 mL) at 40 °C under stirring. [NBE]/[Ru] = 222.

• The polymerization was quenched with ethyl vinyl ether.

• Catalyst was separated by centrifugation and the supernatant was poured into 3 ml of methanol with 2,6-di-tert-butyl-p-cresol as an antioxidant.

• The precipitated polymer was dried in vacuo at 60 °C and polymer yield was determined gravimetrically.

• The NBE conversion was determined by GC using ethyl vinyl ether as an internal standard

Catalyst preparation and characterizationAccording to the analysis of supernatants and washing solutions about 95 % of RuCl2(p-cymene)(PCy3) submitted was attached to the support and catalysts of 1 wt. % of Ru were prepared.

Figure 1. {1H}13C CP MAS NMR spectrum of RuCl2(p-cymene)PCy3/SBA-15.

Results and Discussion

Carbon δ, ppm

CH3 + CH(CH3)2 20

Cyclohexyl CH2 26

CH(CH3)2 28

Cyclohexyl CH2 30sh

Cyclohexyl CH 33sh

Arom. 80

Arom. 99

The presence of PCy3 ligand is further supported by 31P MAS NMR showing a single broad signal at 27 ppm.

Figure 2. UV-VIS spectra of RuCl2(p-cymene)(PCy3)/SBA-15 (1) and RuCl2(pcymene)(PCy3) in CH2Cl2 (c = 0.004 mol/l, l = 0.2 cm).

(1) Diffuse reflectance spectrum of RuCl2(p-cymene)PCy3/SBA-15 exhibits absorption bands at 345 and 422 nm indicating that the coordination sphere of Ru atom is affected as a result of immobilization.

(2) RuCl2(p-cymene)(PCy3) in CH2Cl2 exhibits a MLCT band at 367 nm (which may be ascribed to the Ru (d) – Ph (π) transition) and a shoulder at about 490 nm.

Figure 3. ROMP of NBE with [RuCl2 (p-cymene)]2/SBA-15 + TMSD (triangle) and RuCl2(p-cymene)(PCy3)/SBA-15 (square).

Toluene, t = 60 °C, NBE/Ru molar ratio = 220, co(NBE) = 11mg/ml, numbers at individual experimental points give Mw of polymer in kDa.

Martin, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974, 233.

RuCl2(p-cymene)(PCy3)/SBA-15

RuCl2(p-cymene)2/SBA-15 + TMSD (TMSD/Ru molar ratio = 10)

PDI = 9

PDI = 5,3

PDI 1,8

PDI 1,8

Figure 4. ROMP of NBE with RuCl2(p-cymene)(PCy3) (squares), RuCl2(p-cymene)(PCy3)/MCM-41 (down triangle), RuCl2(p-cymene)(PCy3)/SBA-15 (circles) and RuCl2(p-cymene)(PCy3)/silica (up triangle). Toluene, t = 40 oC, NBE/Ru molar ratio = 220, co(NBE) = 10 mg/ml, numbers at individual experimental points give Mw of polymer in kDa.

RuCl2(p-cymene)(PCy3)

RuCl2(p-cymene)(PCy3)/MCM-41

RuCl2(p-cymene)(PCy3)/SBA-15

RuCl2(p-cymene)(PCy3)/Silica

PDI = 1,7 – 2,0

TurnOver Frequency 15 = Wt NBE produced / 900 s . Wt Ru in catalyst

TOF15 = 0.146 s-1

TOF15 = 0.034 s-1

TOF15 = 0.014 s-1

TOF15 = 0.014 s-1

Figure 5. ROMP of NBE with RuCl2(p-cymene)(PCy3)/MCM-41 with partial separation of the liquid phase at 100 min of the reaction. Polymer yield (solid symbols), monomer conversion (open symbols), system containing solid catalysts (squares) and system containing liquid phase only (circles). Toluene, 40 °C, NBE/Ru molar ratio = 700, co(NBE) = 10 mg/ml.

After 390 min, the polymerization was quenched, the catalyst was removed by centrifugation and the content of Ru in the liquid phase was determined. The Ru amount found was equal to 2.8 % of the amount of Ru present in the catalyst and corresponds to the maximum product contamination 47 ppm.

Solid phase

Liquid phase

Polymer yield

Monomer conversion

Figure 6. 13C NMR spectrum (range of aliphatic C atoms) of PNBE prepared with RuCl2(p-cymene)(PCy3)/MCM-41.

Thus, the immobilization had no effect on catalyst stereoselectivity. It suggests that catalytic centers of similar steric arrangement were operating in both homogeneous and immobilized catalysts.

tc

tt

cc

ct

rc = Icc/Ict and rt = Itt/Itc

PNBE / Homonegeous Catalyst

rc = 0,3 and rt = 5,2

PNBE / Immobilized Catalysts

rc = 0,3 and rt = 4,9

Conclusion• These materials were active as catalysts for ROMP of NBE, NBEAc and DCPD

producing high-molecular-weight polymers (Mw from 200 000 to 400 000) in high yields.

• For NBE, the initial rate increased in the order RuCl2(p-cymene)( PCy3)/silica < RuCl2(p-cymene)(PCy3)/SBA-15 < RuCl2(p-cymene)(PCy3)/MCM- 41.

• Catalysts could be easily separated from the reaction mixture in contrast to the corresponding homogeneous system and polymers with low content of Ru were obtained.