On the Immobilization of Ruthenium Metathesis Catalysts in

in these cases, and ionic modified complexes should be used.18 Several .... (30) Sanford, M. S.; Love, J. A.; Grubbs, R. H. Organometallics 2001,. 20,...
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Organometallics 2009, 28, 4527–4533 DOI: 10.1021/om900376c

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On the Immobilization of Ruthenium Metathesis Catalysts in Imidazolium Ionic Liquids Crestina S. Consorti,* Guilherme L. P. Aydos, G€ unter Ebeling, and Ja€ırton Dupont* Laboratory of Molecular Catalysis, Institute of Chemistry-UFRGS, Avenida Bento Gonc-alves, 9500 P.O. Box 15003, 91501-970, Porto Alegre, RS Brazil Received May 11, 2009

New ionophilic Hoveyda-type complexes were prepared by the treatment of Grubbs’ secondgeneration catalyst with the readily obtained 2,3-dimethyl-1-[1-methyl-3-(2-vinylphenoxy)butyl]imidazolium hexafluorophosphate ligand, for example. This new carbene complex immobilized in BMI 3 PF6 ionic liquid presents excellent catalytic activities in 1,7-octadiene, diallyl diethylmalonate, and allylmethallyl dimethylmalonate ring-closing metathesis (RCM) reactions. The ionophilic complex can be recycled up to seven times in the 1,7-octadiene RCM reaction. The structure of this complex has been unambiguously established by NMR and single-crystal X-ray diffraction studies.

Introduction Liquid/liquid biphasic catalysis is one of the most important alternatives to solve the basic problems associated with organometallic homogeneous catalytic processes, i.e., separation of the products from the reaction mixture, the recovery of the catalysts, and the substitution of volatile organic solvents (VOCs).1 One of the greatest challenges in biphasic catalysis is to devise an immobilizing agent that can act as a simple “solvent” for classical organometallic catalysts. In principle, this might enable the direct transposition of the plethora of known homogeneous catalytic reactions to biphasic systems without the design and synthesis of ligands/ complexes.2 Moreover, the mobile phase can be used for the modulation of the reaction selectivity3 and/or to activate dormant catalytically active species.4,5 Among the various fluids investigated for biphasic catalysis, ionic liquids (ILs) or molten salts, especially those derived from the combination of quaternary ammonium salts and weakly coordinating anions, have been demonstrated to be ideal immobilizing agents for various “classical” transition-metal catalyst precursors.6-8 For example, first- and second-generation Grubbs, Hoveyda-type compounds and ruthenium allenyli-

dene catalysts have been used in ionic liquids9-16 for metathesis reactions.17 However, catalyst leaching is a major issue in these cases, and ionic modified complexes should be used.18 Several modifications have been introduced mostly at the carbene16,19-24 (compounds 3-7, Chart 1) or modified phosphine ligands (compound 8, Chart 1)25 in order to rend the complex ionophilic. Although Ru leaching from the ionic liquid to the product(s) phase was quantified25 only in some cases, in these processes, the introduction of the imidazolium moiety apparently guarantees the reuse of the catalysts. Invariably, the preparation of imidazolium-tagged carbene ligands, such as those in compounds 3-7, involves multistep synthesis. Moreover, an efficient ionophilic ruthenium

*To whom correspondence should be addressed. E-mail: dupont@iq. ufrgs.br. (1) Anastas, P. T.; Kirchhoff, M. M. Acc. Chem. Res. 2002, 35, 686– 694. (2) Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev. 2002, 102, 3667–3691. (3) Umpierre, A. P.; Machado, G.; Fecher, G. H.; Morais, J.; Dupont, J. Adv. Synth. Catal. 2005, 347, 1404–1412. (4) da Costa, R. C.; Gladysz, J. A. Adv. Synth. Catal. 2007, 349, 243– 254. (5) Samojlowicz, C.; Bieniek, M.; Zarecki, A.; Kadyrovb, R.; Grela, K. Chem. Commun. 2008, 6282–6284. (6) Olivier-Bourbigou, H.; Magna, L. J. Mol. Catal. A: Chem. 2002, 182, 419–437. (7) Welton, T. Coord. Chem. Rev. 2004, 248, 2459–2477. (8) Dyson, P. J. Trans. Met. Chem. 2002, 27, 353–358. (9) Sledz, P.; Mauduit, M.; Grela, K. Chem. Soc. Rev. 2008, 37, 2433– 2442.

(10) Buijsman, R. C.; van Vuuren, E.; Sterrenburg, J. G. Org. Lett. 2001, 3, 3785–3787. (11) Semeril, D.; Olivier-Bourbigou, H.; Bruneau, C.; Dixneuf, P. H. Chem. Commun. 2002, 146–7. (12) Csihony, S.; Fischmeister, C.; Bruneau, C.; Horvath, I. T.; Dixneuf, P. H. New J. Chem. 2002, 26, 1667–1670. (13) Semeril, D.; Bruneau, C.; Dixneuf, P. H. Adv. Synth. Catal. 2002, 344, 585–595. (14) Mayo, K. G.; Nearhoof, E. H.; Kiddle, J. J. Org. Lett. 2002, 4, 1567–1570. (15) Stark, A.; Ajam, M.; Green, M.; Raubenheimer, H. G.; Ranwell, A.; Ondruschka, B. Adv. Synth. Catal. 2006, 348, 1934–1941. (16) Thurier, C.; Fischmeister, C.; Bruneau, C.; Olivier-Bourbigou, H.; Dixneuf, P. H. ChemSusChem 2008, 1, 118–122. (17) Grubbs, R. H. Handbook of Metathesis, 1st ed.; Wiley-VCH: Weinheim, Germany, 2003. (18) Clavier, H.; Grela, K.; Kirschning, A.; Mauduit, M.; Nolan, S. P. Angew. Chem., Int. Ed. 2007, 46, 6786–6801. (19) Audic, N.; Clavier, H.; Mauduit, M.; Guillemin, J. C. J. Am. Chem. Soc. 2003, 125, 9248–9249. (20) Clavier, H.; Audic, N.; Mauduit, M.; Guillemin, J.-C. Chem. Commun. 2004, 2282–2283. (21) Clavier, H.; Audic, N.; Guillemin, J. C.; Mauduit, M. J. Organomet. Chem. 2005, 690, 3585–3599. (22) Yao, Q.; Sheets, M. J. Organomet. Chem. 2005, 690, 3577–3584. (23) Yao, Q.; Zhang, Y. Angew. Chem., Int. Ed. 2003, 42, 3395–3398. (24) Chen, S.-W.; Kim, J. H.; Ryu, K. Y.; Lee, W.-W.; Hong, J.; Lee, S.-g. Tetrahedron 2009, 65, 3397–3403. (25) Consorti, C. S.; Aydos, G. L. P.; Ebeling, G.; Dupont, J. Org. Lett. 2008, 10, 237–240.

r 2009 American Chemical Society

Published on Web 07/08/2009

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Consorti et al.

Chart 1. Examples of Imidazolium-Tagged Ru Carbene Complexes Used in Metathesis Reactions in Ionic Liquids

metathesis catalyst for the ring-closing metathesis (RCM) of sterically hindered substrates has not yet been reported. Therefore, a simple and efficient route to imidazoliumtagged carbene ruthenium compounds that precludes metal product contamination is still a challenge. We herein report a simple route for the generation of both Grubbs- and Hoveyda-type catalysts containing imidazolium moieties attached to phosphine or carbene derivatives that are stable and active catalysts for the IL biphasic RCM of dienes.

Results and Discussion Our strategy is to introduce the imidazolium moiety at the Hoveyda-type catalyst attached via the ether oxygen atom similar to that used to prepare 6 and 7 and not at the aromatic carbene substituent, such as in 3-5. The imidazolium-tagged styrene 11 has been prepared in 31% overall yield through the coupling of 2-iodophenol with 2,4-pentanediol (1:1 meso: rac mixture) in the presence of PPh3 and diisopropyl azodicarboxylate (DIAD), affording 9 (Scheme 1). The alkylation of 1,2-dimethylimidazole with the mesylated 9 followed by anion metathesis yields 10. The Heck vinylation of 10 with a large excess of ethylene catalyzed by Pd(OAc)2/tris(o-tolylphosphine) using sodium acetate as a base gave the desired styrene derivative 11.26,27 This route;virtually in three steps;is shorter and simpler than that reported earlier for the synthesis of the analogous carbene-modified ligands such as those used to prepare 6 and 7. Of note, this method is one of the few that allows the introduction of a secondary group at the O-phenol position. The presence of this secondary (26) Gruber, A. S.; Pozebon, D.; Monteiro, A. L.; Dupont, J. Tetrahedron Lett. 2001, 42, 7345–7348. (27) Procedure adapted from: Monteiro, A. L.; Nobre, S. M. Personnal communication.

group is necessary in order to achieve maximum catalyst stability and catalytic activity.28 Moreover, this method, based on the Heck vinylation, has been successfully used for the preparation of analogous ligand 14 in only three steps in 58% overall yield starting from the ether derivative 12, which by reaction with 1,2dimetylimidazole affords the intermediate 13 after anion metathesis with KPF6 (Scheme 2). Ligands 11 and 14 have been used to prepare the ruthenium carbene complexes 15-17 (Figure 1) in good yields by simple reaction with the second-generation Grubbs-type catalyst 1 and its analogue 1829 containing the o-tolyl Nheterocyclic carbene ligand appropriate for the RCM of sterically hindered substrates, using well-established procedures.30 The structure of the ionophilic complex 15 was determined by X-ray diffraction analysis, and an ORTEP diagram is presented in Figure 2. Compound 15 crystallizes as a diastereomeric pair, i.e., in the centrosymmetric space group P21/c. The complex is a distorted trigonal bipyramid with the two chlorides and the carbene carbon atom in the equatorial plane. The geometry around the ruthenium and most of the bond angles and bond lengths are similar to the related Hoveyda complex 2. The Cl-Ru-Cl bond angle (161.77(3)°) is larger than the corresponding angle in the analogous Hoveyda complex (156.5(5)°). The Ru-O bond length (2.289(2) A˚) is considerably longer than in the analogous Hoveyda complex 2 (2.261(3) A˚), probably reflecting the steric congestion caused by the 2pentyl group compared to the isopropoxy ligand. (28) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791–799. (29) Stewart, I. C.; Ung, T.; Pletnev, A. A.; Berlin, J. M.; Grubbs, R. H.; Schrodi, Y. Org. Lett. 2007, 9, 1589–1592. (30) Sanford, M. S.; Love, J. A.; Grubbs, R. H. Organometallics 2001, 20, 5314–5318.

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Scheme 1a

Figure 1. Ru-imidazolium-tagged carbene complexes.

a (a) DIAD, PPh3, THF; (b) MeSO2Cl, NEt3, CH2Cl2; (c) 1,2dimethylimidazole, MeCN; (d) KPF6; (e) Pd(OAc)2/tris(o-tolylphosphine), ethylene, NaOAc, DMF.

Scheme 2a

a (a) 1,3-Dibromopropane, KOH; (b) 1,2-dimethylimidazole, MeCN, KPF6; (c) Pd(OAc)2/tris(o-tolylphosphine), ethylene, NaOAc, DMF.

The ionophilic ruthenium carbene complex 20 containing the imidazolium phosphine derivative was prepared by simple ligand exchange reaction (Scheme 3) employing 18, as reported earlier for the preparation of analogous compounds.25 The ionic liquid of choice for the immobilization of ruthenium carbene complexes is the imidazolium salt associated with the hexafluorophosphate anion since, in other ILs containing NTf2 or FAP (tris(perfluoroethyl)trifluorophosphate) anions, the complexes are not stable and/or the RCM is inhibited.25 For example, the catalytic activity is maintained only in the first two recycles in the RCM of diallyldiethylmalonate at 45 °C, using 15 immobilized in BMI.NTf2 or BMPy 3 NTf2 (N,N-butylmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide) ionic liquids comparing reaction yields at 15 min (Table 1). These results are a clear indication that there is an optimized combination between the anion and cations of the ionic liquids that can be stabilized at the same time and retain the ruthenium catalyst precursor in the ionic phase without losing the catalytic activity. In the case of the ionic liquids containing nucleophilic anions such as NTf2 anion, reactions with the electrophilic carbene intermediates can occur.31 In other cases, the low level of miscibility and diffusion of the dienes in the ionic phase may be responsible for the decomposition or very low catalytic activity (for diene miscibility in ILs see for example ref 3). Under the optimized reaction conditions (45 °C, toluene as cosolvent), 90% conversion can be achieved in the model RCM of 1,7-octadiene using as little as 2.5  10-3 mol % (25 ppm) of 15 immobilized in BMI 3 PF6, reflecting turnover (31) Aggarwal, V. K.; Emme, I.; Mereu, A. Chem. Commun. 2002, 1612–1613.

Figure 2. Structure of the cation of complex 15 with 50% probability ellipsoids. H atoms bonded to carbon are omitted for clarity. Selected bond lengths (A˚) and angles (deg) for 15: Ru-C(22) = 1.830(3), Ru-C(12) = 1.976(3), Ru-O = 2.288 (2), Ru-Cl(1) = 2.3319(8), Ru-Cl(2) = 2.3474(8), C(22)Ru-C(12) = 101.73(13), C(22)-Ru-O = 79.68(11), C(12)Ru-O = 178.16(11), C(22)-Ru-Cl(1) = 98.45(10), C(12)Ru-Cl(1) = 91.71(9), O-Ru-Cl(1) = 86.89(6), C(22)-RuCl(2) = 96.29(10), C(12)-Ru-Cl(2) = 95.73(9), O-Ru-Cl(2) = 85.28(6), Cl(1)-Ru-Cl(2) = 161.78(3). The carbon C(32) is disordered over two positions and occupies 50% for each.

frequencies (TOF) of up to 343 000 h-1 (Table 2). Moreover, 15 immobilized in BMI 3 PF6 could be reused at least six times without any losses in the catalytic activity (Table 1, entry 4). The catalytic activity of complex 15 was evaluated for the more sterically challenging substrate 2-allyl-2-methallyl diethylmalonate (see Figure 3A). In this case, more than 90% yield was obtained after 1 h using 2.0  10-2 mol % (200 ppm) of complex 15. Lowering the catalyst loading to 50 ppm has an impact on the reaction yield, and only 50% of the metathesis product was obtained after 2 h. These catalytic activities are higher (in the same range) than those obtained by ruthenium metathesis catalysts bearing highly substituted NHC carbene ligands under homogeneous conditions.32 Interestingly, 15 immobilized in BMI 3 PF6 roughly maintains its rate profile after the third cycle, whereas its analogue 17 smoothly loses its catalytic activity, as for example observed in the RCM of 2-allyl-2-methallyl diethylmalonate (Figures 3B and 3C, respectively) under optimized reaction conditions. This difference is the same observed for analogous compounds under homogeneous conditions, highlighting the necessity for the presence of a secondary carbon (32) Kuhn, K. M.; Bourg, J.-B.; Chung, C. K.; Virgil, S. C.; Grubbs, R. H. J. Am. Chem. Soc. 2009, 131, 5313–5320.

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Consorti et al. Scheme 3. Synthesis of Complex 20

Table 1. Optimization in the Diallyldiethylmalonate RCM with Catalyst Precursor 15 in Ionic Liquids Using Toluene As the Cosolventa cycle/yield (%)b entry

ionic liquid

1

2

3

4

5

6

7

1 2 3 4c

BMI 3 NTf2 >99 93 50 14 99 93 76 45 17 7 BMPy 3 NTf2 98 96 88 74 59 37 18 BMI 3 PF6 BMI 3 PF6 100 100 100 100 100 100 97 a Reaction conditions: diallyldiethylmalonate (2 mmol), toluene (4 g), IL (1.5 g), catalyst (0.0050 mmol), 45 °C, 15 min. b GC yield. c Reaction performed with 1,7-octadiene.

Table 2. 1,7-Octadiene RCM with Catalyst Precursor 15a t (min)

yield (%)b

TON

TOF (h-1)

2 5

25 10 100 303 000 72 28 600 343 000 a Reaction conditions: 1,7-octadiene (4.91 mmol), toluene (2 mL), BMI 3 PF6 (130 mg), catalyst (1.23  10-4 mmol), 45 °C. b GC yield.

group attached at the ether Ru-coordinating group for the stabilization of the catalytically active species.28 Moreover, these results suggest that the degree of substitution in the ether portion of 15 is responsible for the steric congestion that results in a larger Ru-O bond and also reflects the higher catalytic activities obtained. The efficiency of catalyst precursors 16, 18, and 20 dispersed in BMI 3 PF6 IL in the RCM of sterically hindered substrates was investigated using dimethallyl diethylmalonate as a substrate under the reaction conditions optimized earlier (toluene as cosolvent at 45 °C). Under these conditions, only 18, containing the less sterically hindered N-heterocyclic carbene o-tolyl derivative, gave a cyclic alkene but in low yield, (36%) in opposition to the high yield observed in homogeneous conditions (81%, entry 2, Table 3). However, in this case the reaction occurs on the organic phase since nonionophilic complex 18 is extracted by the toluene-containing substrate. Moreover, compounds 16 and 20, containing the imidazolium moiety, are inert even in toluene conditions, and an extensive decomposition of the organometallic precursor was observed (entries 1 and 3, Table 3). These results clearly indicate that the decomposition of the Ru-catalyst precursors is faster than the coordination of the highly hindered substrate to the metal center. In summary the attachment of an imidazolium moiety to either a phosphine or carbene ligand is important, not only for the immobilization of Ru-carbene complexes in ionic liquids but also for the stabilization of the catalytically active species. The presence of a secondary carbon group attached at the ether Ru-coordinating group was found to be essential for the stabilization of the catalytically

Figure 3. Conversion rate for the RCM of 2-allyl-2-methallyl diethylmalonate and recharges. (A) Using 2.0  10-2 mol % (200 ppm) and 5.0  10-3 mol % (50 ppm) of complex 15, diene (2 mmol), toluene (4 mL), BMI 3 PF6 (0.1 g), 45 °C. (B) Reaction performed using 5.0  10-3 mmol of 15, diene (2 mmol), toluene (4 mL), BMI 3 PF6 (1.0 g), 45 °C. (C) Reaction performed with 5.0  10-3 mmol of 17, diene (2 mmol), toluene (4 mL), BMI 3 PF6 (1.0 g), 45 °C.

active species and to maintain a long-living catalytic system.

Experimental Section General Remarks. All manipulations of phosphine ligands and complexes were conducted under Ar using dryboxes or

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Organometallics, Vol. 28, No. 15, 2009 Table 3. RCM of Dimethallyl Diethylmalonatea

entry

complex

yield (%)b

1 2 3

16 6 18 81 20 13 a Reaction conditions: substrate (0.37 mmol), toluene (2 mL), catalyst (0.018 mmol), 45 °C, 2 h. b GC yields.

standard Schlenk techniques. Chemicals were treated as follows: 1,7-octadiene (Acros), toluene, and THF were distilled from Na/benzophenone; CH2Cl2 was distilled from CaCl2 and degassed; 2-iodophenol, triphenylphosphine, DIAD (diisopropyl azodicarboxylate), triethylamine, MeSO2Cl, Pd(OAc)2, triso-tolylphosphine, NaOAc, DMF, KPF6, CuCl, 1,3-dibromopropane, benzyltriethylammonium chloride, 1,2-dimethylimidazole, allyl bromide, (1,3-bis(mes)H2Im)(PCy3)(Cl)2Ru(dCHPh) (1) (all from Aldrich), ethylene (White Martins), diethyl diallylmalonate (Lancaster), acetone-d6, benzene-d6, CDCl3 (Cambridge Isotope), and other solvents were used as received. 2,4-Pentanediol,33 diethyl 2-allyl-2-methallylmalonate,34 diethyl dimethallylmalonate,34 (1,3-bis(mes)H 2Im)(Py)2(Cl)2Ru(dCHPh),30 (1,3-bis(tol)H2Im)(PCy3)(Cl)2Ru(dCHPh) (18), (1,3-bis(tol)H2Im)(Py)2(Cl)2Ru(dCHPh) (19),29 and ILs (BMI 3 PF6, BMI 3 NTf2, and BMPy 3 NTf2)35 were synthesized according to literature procedures. NMR spectra were recorded on 300 MHz Varian spectrometers at ambient probe temperatures and referenced to internal TMS or external H3PO4. GC analyses were performed using an Agilent 6820 instrument equipped with a capillary column (DB-17-0.25 mm; 25 m S 0.32 mm). GC-MS data were recorded with a Shimadzu QP2010 and ESI/MS on a Micromass Q-TOFmicro. Elemental analyses were performed with a Perkin-Elmer M 2400 CHNS/O analyzer. 4-(2-Iodophenoxy)pentan-2-ol (9). A Schlenk flask was charged with 2-iodophenol (4.55 g, 20.7 mmol), 2,4-pentanediol (2.58 g, 24.8 mmol), triphenylphosphine (6.50 g, 24.8 mmol), and dry THF (30 mL) and cooled to 0 °C. After DIAD (5.01 g, 24.8 mmol) was added dropwise, the ice bath was removed and the reaction mixture was stirred overnight at room temperature. The solvent was removed under vacuum and the residue was purified by chromatographic column on silica gel (hexane/ethyl acetate, 80:20). Yield: 4.58 g, 72%. 1H NMR (300 MHz, CDCl3): δ ppm 7.79 (m, 2H), 7.30 (m, 2H), 6.98-6.81 (m, 2H), 6.73 (m, 2H), 4.87-4.56 (m, 2H), 4.24 (m, 1H), 4.10 (m, 1H), 2.19-1.73 (m, 6H), 1.38 (m, 6H), 1.28 (m, 6H). 13C NMR (75 MHz, CDCl3): δ ppm 156.4, 155.8, 139.6, 139.5, 129.4, 129.29, 122.7, 122.5, 113.7, 113.6, 88.0, 87.9, 75.0, 73.1, 66.7, 64.3, 45.5, 45.2, 23.9, 23.7, 19.8, 19.5. Anal. Calcd (%) for C11H15IO2: C, 43.16; H, 4.94. Found: C, 43.35; H, 4.97. 3-[3-(2-Iodophenoxy)-1-methylbutyl]-1,2-dimethylimidazolium Hexafluorophosphate (10). A round-bottom flask was charged with 4-(2-iodophenoxy)pentan-2-ol (2.53 g, 8.27 mmol), triethylamine (1.25 g, 12.4 mmol), and CH2Cl2 (10 mL). MeSO2Cl (1.23 g, 10.75 mmol) was slowly added and the reaction mixture stirred for 10 min at room temperature. The reaction was concentrated to 5 mL and filtered through a short plug of (33) Pritchard, J.; Vollmer, R. L. J. Org. Chem. 1963, 28, 1545–1549. (34) Necas, D.; Tursky, M.; Kotora, M. J. Am. Chem. Soc. 2004, 126, 10222–10223. (35) Cassol, C. C.; Ebeling, G.; Ferrera, B.; Dupont, J. Adv. Synth. Catal. 2006, 348, 243–248. MacFarlane, D. R.; Meakin, P.; Sun, J.; Amini, N.; Forsyth, M. J. Phys. Chem. B 1999, 103, 4164–4170.

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neutral alumina using hexane/ethyl acetate (50:50). 1,2-Dimethylimidazole (0.740 g, 7.72 mmol) was added, and the mixture was concentrated to 10 mL and diluted to 30 mL with CH3CN. The reaction mixture was refluxed for 4 days, after which time the solvent was removed under vacuum and the oily residue was dissolved in ethyl acetate and washed with hexane. The residue was dissolved in water (10 mL), and KPF6 (1.5 g, 8.1 mmol) was added. After extraction with CH2Cl2 (2  20 mL), drying with MgSO4, and solvent removal under vacuum, a colorless viscous oil was obtained. Yield: 2.27 g, 51%. 1 H NMR (300 MHz, acetone-d6): δ ppm 7.81 (m, 4H), 7.717.59 (m, 2H), 7.47-7.27 (m, 2H), 7.06 (d, J = 8.0 Hz, 1H), 6.85 (d, J = 8. 0 Hz, 1H), 6.77 (m, 2H), 5.14-4.94 (m, 2H), 4.94-4.77 (m, 1H), 4.54-4.32 (m, 1H), 3.90 (s, 3H), 3.85 (s, 3H), 2.80 (s, 3H), 2.54 (s, 3H), 2.41 (m, 4H), 1.64 (m, 6H), 1.31 (m, 6H). 13 C NMR (75 MHz, acetone-d6): δ ppm 156.1, 156.0, 144.3, 139.9, 130.1, 130.0, 123.8, 123.5, 123.2, 123.1, 118.0, 117.9, 113.9, 113.8, 87.3, 87.1, 72.4, 71.3, 52.8, 52.1, 43.2, 42.8, 34.8, 21.1, 19.9, 19.2, 19.1, 9.7, 9.1. ESI/MS(þ): m/z calcd [C16H22IN2O]þ 385.0777, expt 385.0782. Anal. Calcd (%) for C16H22F6IN2OP: C, 36.24; H, 4.18; N, 5.28. Found: C, 36.16; H, 4.24; N, 5.25. 2,3-Dimethyl-1-[1-methyl-3-(2-vinylphenoxy)butyl]imidazolium Hexafluorophosphate (11). A stainless steel reactor was charged with 3-[3-(2-iodophenoxy)-1-methylbutyl]-1,2-dimethylimidazolium hexafluorophosphate (0.530 g, 1.0 mmol), Pd(OAc)2 (0.002 g, 0.01 mmol), tris-o-tolylphosphine (0.012 g, 0.04 mmol), NaOAc (0.090 g, 1.1 mmol,) and DMF (10 mL) and pressurized with ethylene (10 kgf/cm2). The reaction mixture was stirred for 48 h at 90 °C. After cooling to room temperature, the ethylene was released and 30 mL of a saturated KPF6 aqueous solution was added. The precipitate was collected by filtration. A second crop of solid was obtained by mother liquor concentration. The solid was collected by filtration, washed with water (5 mL), and dried under vacuum. Yield: 0.43 g 84%. 1H NMR (300 MHz, acetone-d6): δ ppm 7.85 (m, 2H), 7.67 (t, J = 2.0 Hz, 2H), 7.58 (m, 2H), 7.38-6.67 (m, 8H), 5.79 (m, 2H), 5.24 (m, 2H), 4.99 (m, 2H), 4.86 (m, 1H), 4.35 (m, 1H), 3.87 (s, 3H), 3.83 (s, 3H), 2.66 (s, 3H), 2.53 (s, 3H), 2.52-2.25 (m, 4H), 1.66 (m, 6H), 1.29 (m, 6H). 13 C NMR (75 MHz, acetone-d6): δ ppm 155.6, 133.1, 132.7, 130.6, 128.93, 128.4, 128.0, 127.8, 124.8, 122.6, 122.4, 119.3, 115.3, 114.9, 114.7, 114.5, 73.0, 71.3, 54.7, 53.4, 44.5, 44.1, 36.1, 36.0, 22.3, 21.9, 20.6, 20.4, 10.5, 10.2. ESI/MS(þ): m/z calcd [C18H25N2O]þ 285.1967, expt 285.1977. Anal. Calcd (%) for C18H25F6N2OP: C, 50.23; H, 5.86; N, 6.51. Found: C, 49.85; H, 5.76; N, 6.37. 1-(3-Bromopropoxy)-2-iodobenzene (12). A mixture of 1,3dibromopropane (19.4 g, 96 mmol), 2-iodophenol (7.04 g, 32 mmol), KOH (2.2 g, 33 mmol), and benzyltriethylammonium chloride (0.36 g, 1.6 mmol) in 15 mL of water was heated to 90 °C under vigorous stirring for 48 h. After the mixture was cooled to room temperature, CH2Cl2 (50 mL) was added, the organic phase was collected, washed with KOH (3  15 mL, 5 wt % in water), and dried with K2CO3, and the volatiles were removed under vacuum. A light yellow oil was obtained (9.60 g, 28.1 mmol, 89% yield) with enough purity for further work. 1H NMR (300 MHz, acetone-d6): δ ppm 7.81 (dd, J = 7.8, 1.6 Hz, 1H), 7.38 (ddd, J = 8.2, 7.4, 1.6 Hz, 1H), 7.02 (dd, J = 8.2, 1.3 Hz, 1H), 6.79 (dt, J = 7.8, 1.3 Hz, 1H), 4.22 (t, J = 5.7 Hz, 2H), 3.80 (t, J = 6.5 Hz, 2H), 2.37 (m, 2H). 13C NMR (75 MHz, acetone-d6): δ ppm 157.5, 139.5, 130.0, 122.9, 112.7, 86.3, 66.7, 32.5, 30.7. 3-[3-(2-Iodophenoxy)propyl]-1,2-dimethylimidazolium Hexafluorophosphate (13). A mixture of 1-(3-bromopropoxy)-2iodobenzene (5.46 g, 16 mmol) and 1,2-dimethylimidazole (1.54 g, 16 mmol) in CH3CN (5 mL) was heated to 80 °C for 2 h. Ethyl acetate (40 mL) was added and the resulting solid collected by filtration. Recrystallization with 2-propanol yielded 5.50 g (12.6 mmol) of a white solid. The solid was dissolved in water (50 mL), and KPF6 (2.4 g, 13 mmol) was added in

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portions. The resulting solid was collected by filtration, washed with water (2  10 mL), and dried under vacuum. Yield: 5.97 g, 74%. 1H NMR (300 MHz, acetone-d6): δ ppm 7.80 (dd, J = 7.7, 1.5 Hz, 1H), 7.62 (d, J = 2.1 Hz, 1H), 7.5 (d, J = 2.1 Hz, 1H), 7.37 (dt, J = 8.3, 1.5 Hz, 1H), 6.99 (dd, J = 8.3, 1.2 Hz, 1H), 6.78 (dt, J = 7.7, 1.3 Hz, 1H), 4.57 (t, J = 7.0 Hz, 2H), 4.18 (t, J = 5.6 Hz, 2H), 3.91 (s, 3H), 2.79 (s, 3H), 2.49-2.37 (m, 2H). 13C NMR (75 MHz, acetone-d6): δ ppm 157.2, 145.3, 139.5, 130.2, 123.2, 123.0, 121.3, 112.7, 85.9, 65.4, 45.7, 34.9, 29.4, 9.3. ESI/MS(þ): m/z calcd [C14H18IN2O]þ 357.0464, expt 357.0469. Anal. Calcd (%) for C14H18F6IN2OP: C, 33.48; H, 3.61; N, 5.58. Found: C, 33.64; H, 3.84; N, 5.51. 1,2-Dimethyl-3-[3-(2-vinylphenoxy)propyl]imidazolium Hexafluorophosphate (14). A stainless steel reactor was charged with 3-[3-(2-iodophenoxy)-propyl]-1,2-dimethylimidazolium hexafluorophosphate (1.00 g, 2.0 mmol), Pd(OAc)2 (0.005 g, 0.02 mmol), tris-o-tolylphosphine (0.025 g, 0.08 mmol), NaOAc (0.180 g, 2.2 mmol), and DMF (15 mL) and pressurized with ethylene (10 kgf/cm2). The reaction mixture was stirred for 48 h at 90 °C. After cooling to room temperature, the ethylene was released and 30 mL of a saturated KPF6 aqueous solution was added. The precipitate was collected by filtration. A second crop of solid was obtained by concentration of mother liquor. The solid was washed successively with water and dried under vacuum. Yield: 0.704 g, 88%. 1H NMR (300 MHz, acetoned6): δ ppm 7.64 (d, J = 2.1 Hz, 1H), 7.58 (d, J = 2.1 Hz, 1H), 7.57-7.50 (m, 1H), 7.30-7.19 (m, 1H), 7.08-6.90 (m, 3H), 5.77 (dd, J = 17.8, 1.5 Hz, 1H), 5.23 (dd, J = 11.2, 1.5 Hz, 1H), 4.54 (t, J = 6.9 Hz, 2H), 4.14 (t, J = 5.7 Hz, 2H), 3.90 (s, 3H), 2.74 (s, 3H), 2.43 (m, 2H). 13C NMR (75 MHz, acetone-d6): δ ppm 155.7, 145.2, 131.6, 129.4, 126.5, 126.4, 122.9, 121.3, 121.2, 114.0, 112.2, 64.8, 45.9, 34.9, 29.5, 9.0. ESI/MS(þ): m/z calcd [C16H21N2O]þ 257.1654, expt 257.1650. Anal. Calcd (%) for C16H21F6N2OP: C, 47.77; H, 5.26; N, 6.96. Found: C, 47.89; H, 5.26; N, 6.68. (1,3-Bis(mes)H2Im)(11)(Cl)2Ru (15). A Schlenk flask was charged with (1,3-bis(mes)H2Im)(PCy3)(Cl)2Ru(dCHPh) (0.150 g, 0.176 mmol), 11 (0.069 g, 0.16 mmol), CuCl (0.016 g, 0.016 mmol), and CH2Cl2 (5 mL). The reaction mixture was refluxed for 1.5 h, during which time the mixture turned green. The solvent was removed under vacuum, and the residue was dissolved in acetone (5 mL), filtered, and column chromatographed on neutral alumina using acetone as the eluent. Compound 15 was isolated as a dark green solid in 47% yield (0.075 g) after solvent removal under vacuum. 1H NMR (300 MHz, acetone-d6): δ ppm 16.72 (s, 1H), 16.58 (s, 1H), 7.70 (m, 2H), 7.65 (m, 2H), 7.54 (m, 2H), 7.22-7.01 (m, 9H), 7.01-6.89 (m, 4H), 6.79 (d, J = 8.3 Hz, 1H), 5.48-5.29 (m, 1H), 4.88-4.76 (m, 1H), 4.71 (m, 2H), 4.28 (s, 8H), 3.95 (s, 3H), 3.85 (s, 3H), 2.84 (s, 3H), 2.82-2.76 (m, 3H), 2.57-2.34 (m, 40H), 1.42 (m, 6H), 1.22 (m, 6H). 13C NMR (75 MHz, acetone-d6): δ ppm 151.5, 151.4, 145.1, 139.0, 138.8, 130.3, 129.8, 129.6, 129.5, 129.54, 123.5, 123.1, 122.8, 122.2, 117.8, 117.6, 114.2, 113.6, 104.9, 74.7, 74.6, 52.1, 52.0, 51.9, 51.8, 41.8, 41.2, 35.2, 35.2, 22.0, 20.6, 20.5, 20.4, 19.2, 19.1, 9.68. ESI/MS(þ): m/z calcd [C38H49Cl2N4ORu]þ 749.2327, expt 749.2386. Anal. Calcd (%) for C38H49Cl2F6N4OPRu: C, 51.01; H, 5.52; N, 6.26. Found: C, 51.25; H, 5.51; N, 5.91. (1,3-Bis(tol)H2Im)(11)(Cl)2Ru (16). The same procedure for 15 was repeated starting from (1,3-bis(tol)H2Im)(PCy3)(Cl)2Ru(dCHPh) (0.068 g, 0.086 mmol), 11 (0.033 g, 0.078 mmol), and CuCl (0.080 g, 0.078 mmol) and gave compound 16 as a dark green powder. Yield: 0.050 g 69%. 1 H NMR (300 MHz, acetone-d6): δ ppm 16.61 (s), 16.55 (s), 8.62-6.56 (m), 5.54-3.50 (m), 2.97-2.10 (m), 1.92-1.15 (m), compound is too unstable in solution for 13C NMR measurement. ESI/MS(þ): m/z calcd [C34H41Cl2N4ORu]þ 693.1701, expt 693.1702. Anal. Calcd (%) for C34H41Cl2F6N4OPRu: C, 48.69; H, 4.93; N, 6.68. Found: C, 50.36; H, 5.51; N, 5.94.

Consorti et al. (1,3-Bis(mes)H2Im)(14)(Cl)2Ru (17). A Schlenk flask was charged with (1,3-bis(mes)H2Im)(PCy3)(Cl)2Ru(dCHPh) (0.150 g, 0.176 mmol), 14 (0.065 g, 0.16 mmol), CuCl (0.016 g, 0.016 mmol), and CH2Cl2 (5 mL). The reaction mixture was refluxed for 1.5 h, during which time the mixture turned green. The solvent was removed under vacuum, and the residue was dissolved in acetone (5 mL), filtered, and column chromatographed on neutral alumina using acetone as the eluent. Compound 17 was isolated as a dark green solid in 70% yield (0.106 g) after solvent removal under vacuum. 1H NMR (300 MHz, acetone-d6): δ ppm 16.65 (s, 1H), 7.73-7.57 (m, 2H), 7.57-7.23 (m, 2H), 7.11 (s, 4H), 7.09-6.96 (m, 2H), 4.40-4.24 (m, 8H), 3.93 (s, 3H), 2.71 (s, 3H), 2.47 (s, 12H), 2.44 (s, 6H), 2.16 (m, 2H). 13C NMR (75 MHz, acetone-d6): δ ppm 153.7, 145.6, 145.5, 139.2, 130.3, 129.8, 129.1, 129.0, 128.0, 126.9, 124.5, 123.5, 122.3, 121.6, 114.4, 66.8, 52.0, 45.3, 35.5, 29.7, 29.4, 28.5, 20.8, 9.8. ESI/MS(þ): m/z calcd [C36H45Cl2N4ORu]þ 721.2014, expt 721.2011. Anal. Calcd (%) for C36H45Cl2F6N4OPRu: C, 49.89; H, 5.23; N, 6.46. Found: C, 50.40; H, 5.19; N, 5.91. (1,3-Bis(tol)H2Im)(19)(Cl)2Ru(dCHPh) (20). A Schlenk flask was charged with (1,3-bis(tol)H2Im)(Py)2(Cl)2Ru(dCHPh) (0.142 g, 0.21 mmol), 19 (0.130 g, 0.21 mmol), and toluene (3.0 mL). After 15 min of stirring at room temperature, the solvent was removed under vacuum and the residue triturated with pentane. A pink solid was obtained in 85% yield (0.200 g). 1H NMR (300 MHz, benzene-d6): δ ppm 19.3 (s, 1H), 8.89-6.10 (m, 15H), 3.70-0.67 (m, 44H), compound is too unstable for 13C NMR measurement. 31P NMR (121 MHz, benzene-d6): δ ppm 21.75 (br s). ESI/MS(þ): m/z calc [C44H60Cl2N4PRu]þ 847.2976, expt 847.2983. Anal. Calcd (%) for C46H60Cl2F6N5O4PRuS2: C, 48.98; H, 5.36; N, 6.21. Found: C, 49.49; H, 5.67; N, 6.54. Typical Procedure for the RCM Catalytic Reactions. In a glovebox, a two-neck Schlenk flask was charged with 15 (0.0059 g, 0.0050 mmol) and BMI 3 PF6 (1.5 g). A second Schlenk flask was charged with the appropriate substrate (2.0 mmol) and toluene (4 g). After the IL catalyst solution reached the desired temperature, the substrate solution was added in one portion against a stream of argon. The reaction mixture was stirred at the appropriate temperature using an oil bath. Samples were periodically removed by syringe for GC and GC-MS analyses. After the reaction, the upper organic phase was separated and toluene removed under vacuum. A fresh charge of substrate was added to the IL phase. Spectral characteristics of RCM products were in agreement with previously reported data. Procedure for the RCM Reaction with Low Ru Loading. A solution containing 11.05  10-2 mg of complex 15 (1.23  10-4 mmol) in BMI 3 PF6 was prepared by adding BMI 3 PF6 (0.110 g) to 21.5 mg of a solution of 15 (5.5 mg, 0.0061 mmol) in BMI 3 PF6 (1.07 g). A second Schlenk flask was charged with 1,7-octadiene (0.724 mL, 4.4 mmol) and toluene (2 g). After the IL catalyst solution reached 45 °C, the substrate solution was added in one portion against a stream of argon. The reaction mixture was stirred at the appropriate temperature using an oil bath. Samples were periodically removed by syringe for GC and GC-MS analyses. After the reaction, the upper organic phase was separated and toluene removed under vacuum. A fresh charge of substrate was added to the IL phase. Crystallography. Crystals suitable for X-ray diffraction analyses were obtained by slow diffusion of diethyl ether into an acetone solution of compound 15. Compound 15 crystallized in a centrosymmetric space group P21/c, with 1:1 diastereomers inversion related through a symmetry center. The crystallographic information file for 15 has been deposited with the Cambridge Crystallographic Data Centre and allocated to deposition number CCDC 723745. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union

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Road, Cambridge CB2 1EZ, UK (fax: þ44 1223 336033 or e-mail: deposit@ ccdc.cam.ac.uk).

ment of the structure and S. M. Nobre for the Heck reactions.

Acknowledgment. The authors acknowledge CNPq, CAPES and INCT-Catal for scholarships and financial support. We also thank E. S. Lang and D. F. Back from LMI-UFSM for the determination and refine-

Supporting Information Available: Crystallographic data (cif file, table of atomic coordinates, complete bond distances and angles, and anisotropic displacement parameters) for complex 15 and NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org.