Alkylidene-Ruthenium-Tin Catalysts for the Formation of Fatty Nitriles

Organometallics 2010, 29, 5257–5262 DOI: 10.1021/om100372b

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Alkylidene-Ruthenium-Tin Catalysts for the Formation of Fatty Nitriles and Esters via Cross-Metathesis of Plant Oil Derivatives† Xiaowei Miao,‡ Anton Blokhin,§ Alexandr Pasynskii,§ Sergey Nefedov,§ Sergey N. Osipov, Thierry Roisnel,‡ Christian Bruneau,‡ and Pierre H. Dixneuf*,‡ ‡

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Institut Sciences Chimiques de Rennes, UMR 6226 CNRS-Universit
e de Rennes, Campus de Beaulieu, 35042 Rennes, France, §N. S. Kurnakov Institute of General and Inorganic Chemistry, 119991 Moscow, Leninskij pr 31, Russia, and A. N. Nesmeyanov Institute of Organoelement compounds, RAS, 119991 Moscow, Vavilov str. 28, Russia Received April 29, 2010

The reaction of SnCl2 with the Ru-Cl bond of the Grubbs I catalyst RuCl2(dCHPh)(PCy3)2 (1) gives the complex {[Ru(dCHPh)(SnCl3)(PCy3)]2(μ-Cl)3}-[HPCy3]þ (2), but containing two diethyl ether solvate molecules. The formal insertion of SnCl2 into one Ru-Cl bond of the Hoveyda II catalyst RuCl2(dCH-C6H4OPri)(H2IMes) (3) (H2IMes = N,N0 -dimesityl-4,5-dihydroimidazol-2-ylidene) results in formation of the new complex RuCl(SnCl3)(dCH-C6H4OPri)(H2IMes) (4). The X-ray analyses of 2 and 4 show the presence of very short Ru-Sn bonds (2.5834(9) A˚ mean bond for 2 and 2.5925(12) A˚ for 4) and the retention of short RudC bonds (1.895(10) and 1.825(8) A˚, respectively). Complex 4 shows an excellent catalytic activity for the cross-metathesis of plant oil derivatives, the C11 ω-unsaturated ester and aldehyde and the unsaturated C18 diester with acrylonitrile, and a good activity for their cross-metathesis with methyl acrylate. Good to excellent yield of R,ω-bifunctional compounds, precursors of polyesters and polyamides, were obtained. Complex 2 shows catalytic activity for the self-metathesis of C11 ω-unsaturated aldehyde at low concentration to produce C20 R,ω-dialdehyde.

Introduction Alkene metathesis has become a key catalytic reaction for the transformation of carbon-carbon double bonds, with useful applications in both organic synthesis1,2 and polymer sciences.3,4 This wide range of applications is currently

motivating the modification of catalysts5 or the discovery of new ones6 to obtain more stable and efficient catalysts in order to decrease their loading. An attractive application of alkene metathesis deals with the transformation of renewable resources, especially for that of plant oil derivatives into added-value molecules.7 Recently, plant oil unsaturated acid derivatives have been successfully transformed into R,ω-bifunctional linear molecules8 with potential as surfactants8a or monomers, precursors of polyesters9 and polyamides.10,11 The cross-metathesis of plant oil unsaturated acids and esters with acrylonitrile in the presence of alkylidene-ruthenium complexes such as Grubbs I and Hoveyda II catalysts has just allowed the direct access to linear

† Part of the Dietmar Seyferth Festschrift. Dedicated to professor Dietmar Seyferth for his tremendous contribution to organometallic chemistry and Organometallics. *To whom correspondence should be addressed. E-mail: pierre.dixneuf@ univ-rennes1.fr. (1) (a) Grubbs, R. H., Ed. Applications in Organic Synthesis. In Handbook of Metathesis; Wiley-VCH: Weinheim, Germany, 2003; Vol. 2. (b) Chatterjee, A. K.; Choi, T.-L.; Sanders, D. P.; Grubbs, R. H. J. Am. Chem. Soc. 2003, 125, 11360. (c) Connon, S. J.; Blechert, S. In Ruthenium Catalysts and Fine Chemistry; Dixneuf, P. H., Bruneau, C., Eds.; Springer: Berlin, 2004; Vol. 11, p 93. (d) Ghosh, S.; Ghosh, S.; Sarkar, N. J. Chem. Sci. 2006, 118, 223. (e) Conrad, J. C.; Fogg, D. E. Curr. Org. Chem. 2006, 10, 185. (2) (a) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42, 4592. (b) Schrock, R. R. Angew. Chem., Int. Ed. 2006, 45, 3748. (c) Sattely, E. S.; Meek, S. J.; Malcolmson, S. J.; Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 943. (3) As examples of ROMP see: (a) Applications in Polymer Synthesis. In Handbook of Metathesis; Grubbs, R. H., Ed.; Wiley-VCH: Weinheim, Germany, 2003; Vol. 3. (b) Bielawski, C. W.; Benitez, D.; Morita, T.; Grubbs, R. H. Macromolecules 2001, 34, 8610. (c) Scherman, O. A.; Rutenberg, I. M.; Grubbs, R. H. J. Am. Chem. Soc. 2003, 125, 8515. (d) Trimmel, G.; Riegler, S.; Fuchs, G.; Slugovc, C.; Stelzer, F. Adv. Polym. Sci. 2005, 176, 43. (f) Vygodskii, Y. S.; Shaplov, A. S.; Lozinskaya, E. I.; Filippov, O. A.; Shubina, E. S.; Bandari, R.; Buchmeiser, M. R. Macromolecules 2006, 39, 7821. (e) Buchmeiser, M. R. Metathesis Polymerization. In Advances in Polymer Science; Springer: Berlin, 2005; Vol. 176. (4) As examples of ADMET see: (a) Schwendeman, J. E.; Church, A. C.; Wagener, K. B. Adv. Synth. Catal. 2002, 344, 597. (b) Baughman, T. W.; Wagener, K. B. Adv. Polym. Sci. 2005, 176, 1.

(5) (a) Vougioukalakis, G. C.; Grubbs, R. H. Chem. Rev. 2010, 110, 1746. (b) Samojlowicz, C.; Bieniek, M.; Grela, K. Chem. Rev. 2009, 109, 3708. (6) (a) Romero, P. E.; Piers, W. E.; McDonald, R. Angew. Chem., Int. Ed. 2004, 43, 6161. (b) Monfette, S.; Fogg, D. E. Organometallics 2006, 25, 1940. (c) Rend
on, N.; Berthoud, R.; Blanc, F.; Gajan, D.; Maishal, T.; Basset, J.-M.; Cop
eret, C.; Lesage, A.; Emsley, L.; Marinescu, S. C.; Singh, R.; Schrock, R. R. Chem. Eur. J. 2009, 15, 5083. (7) (a) Rybak, A.; Meier, M. A. R. ChemSusChem 2008, 1, 542. (b) Bruneau, C.; Fischmeister, C.; Miao, X.; Malacea, R.; Dixneuf, P. H. Eur. J. Lipid Sci. Technol. 2010, 112, 3. (b) Mutlu, H.; Meier, M. A. R. Eur. J. Lipid Sci. Technol. 2010, 112, 10. (8) (a) Rybak, A.; Meier, M. A. R. Green Chem. 2007, 9, 1356. (b) Rybak, A.; Meier, M. A. R. Green Chem. 2008, 10, 1099. (c) Jacobs, T.; Rybak, A.; Meier, M. A. R. Appl. Catal. A: Gen. 2009, 353, 32. (9) Quinzler, D.; Mecking, S. Chem. Commun. 2009, 5400. (10) (a) Malacea, R.; Fischmeister, C.; Bruneau, C.; Dubois, J.-L.; Couturier, J.-L.; Dixneuf, P. H. Green Chem. 2009, 11, 152. (b) Miao, X.; Fischmeister, C.; Bruneau, C.; Dixneuf, P. H. ChemSusChem 2009, 2, 542. (11) (a) Beillon, T.; Gillet, J.-P. (Arkema, France) WO 2008/ 053113A1 (8.5.08), 2008. (b) Dubois, J.-L. (Arkema, France) WO2008/ 104722A2, 2008.

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R,ω-nitrile acid/ester derivatives,10 some known precursors of polyamides.11 The feasibility of this useful transformation has led us to search for related, more stable ruthenium catalytic systems. The influence of tin dihalide additives on alkylideneruthenium catalysts has been shown to favor the cross-metathesis of 1-octene with neohexene and, by suppressing the isomerization, the self-metathesis of 1-octene.12 It was shown that stoichiometric reaction of SnCl2 with ruthenium complexes led to formal insertion of SnCl2 into the Ru-Cl bond of various complexes such as RuCl2(DMSO)4,13 RuCl(COD)Cp*,14 RuCl2(P(OMe)3)(cumene),15 and RuCl2(L)(arene)16 to give a very stable and bulky Cl3Sn-Ru moiety. We have thus investigated the reaction of SnCl2 with Grubbs I and Hoveyda II complexes 1 and 3, respectively, and studied the catalytic efficiency of the resulting complexes for alkene metathesis in the transformation of fatty acid derivatives. We now report the preparation of {[Ru(dCHPh)(SnCl3)(PCy3)]2(μ-Cl)3}-[HPCy3]þ (2) and RuCl(SnCl3)(dCHC6H4OPri)(H2IMes) (4; H2IMes=N,N0 -dimesityl-4,5-dihydroimidazol-2-ylidene) complexes on reaction of SnCl2, respectively, with alkylidene-ruthenium RuCl2(dCHPh)(PCy3)2 Grubbs I (1) and RuCl2(dCHC6H4OPri)(H2IMes) Hoveyda II (3) complexes, their X-ray structure characterization, and their ability to promote the cross-metathesis with acrylonitrile of unsaturated esters and aldehydes arising from plant oils to produce linear R,ω-bifunctional derivatives.

Results and Discussion 1. Preparation and Characterization of Complexes 2 and 4. As the influence of SnX2 additives on alkene metathesis catalysts has been shown,12,17 the reaction of SnCl2 with RuCl2(dCHPh)(PCy3)2 (1) and RuCl2(dCH-C6H4OPri)(H2IMes) (3) complexes was attempted. The purple Grubbs I catalyst (1) was first reacted in THF with an excess of anhydrous SnCl2 at room temperature for 4 h to give the yellow-green complex 2, which was isolated in 75% yield (eq 1).

The 1H and 31P NMR spectra (CDCl3) showed the presence of one type of RudCHPh alkylidene proton at δ 8.67 ppm (d, 2H, 3 JPH=7.3 Hz, CH) and of one (PCy3) 31P singlet at δ (31P) 23.84 (12) Meyer, W. H.; McConnell, A. E.; Forman, G. S.; Dwyer, C. L.; Kirk, M. M.; Ngidi, E. L.; Blignaut, A.; Saku, D.; Slawin, A. M. Z. Inorg. Chim. Acta 2006, 359, 2910. (13) Evans, I. P.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton Trans. 1973, 20. (14) Moreno, B.; Sabo-Etienne, S.; Dahan, F.; Chaudret, B. J. Organomet. Chem. 1995, 498, 139. (15) Hodson, E.; Simpson, S. J. Polyhedron 2004, 23, 2695. (16) Therrien, B.; Thaia, T.-T.; Freudenreich, J.; S€ uss-Fink, G.; Shapovalov, S. S.; Pasynskii, A. A.; Plasseraud, L. J. Organomet. Chem. 2010, 695, 409. (17) In ref 12 it was pointed out (ref 8) that the addition of SnCl2 to the Grubbs I complex in dichloromethane improved the metathesis yield and it was assumed to produce RuCl(SnCl3)(dCHPh)(PCy3)2.

Miao et al.

ppm with a phosphorus HPCy3þ cation singlet (δ 48.13 ppm). The complex 2 afforded single crystals in a dichloromethanehexane-diethyl ether mixture, and its X-ray structure was obtained (Figure 1). It shows the presence of an anionic complex containing two identical [RudCHPh(SnCl3)(PCy3)] units maintained together by three chloride bridges, associated with the HPCy3þ cation. The Ru-Sn distances (2.5899(9) and 2.5770(9) A˚) are similar to that found in the Ru-SnCl3 complex RuSnCl3(COD)Cp*14 (Ru-Sn=2.5855(4) A˚). The alkylidene RudC bond length (1.895(10) A˚) is comparable to that of the mononuclear alkylidene-ruthenium Grubbs I complex, the analogous RuCl2(dCHC6H4Cl)(PCy3)218 (RudC=1.839(3) A˚). Thus, the reaction consists of the formal insertion of SnCl2 into only one Ru-Cl bond, the displacement of one PCy3 from the Grubbs I catalyst with retention of the alkylidene ligand, and the bridging of two [RudCHPh(SnCl3)(PCy3)] units by three chloride atoms to give the diruthenium anion in 2. It is well-established that the Grubbs I catalyst easily loses one PCy3 ligand.1a,b The structure of complex 2 teaches us that 1 equiv of HCl was formally added to 2 equiv of complex 1. HCl formation likely arises from SnCl2 in the presence of residual water, as SnCl2 can react with H2O to give HCl and SnCl(OH). The protonation by HCl of one freed PCy3 is used to generate the PHCy3þ cation, and the bridging chloride is added to two [RudCHPh(Cl)(SnCl3)(PCy3)] units with the additional bridging of the two remaining chlorides. Crystals of a complex similar to 2 were previously obtained by Meyer et al.12 from the reaction of 1 with CuCl in dichloromethane followed by addition of SnCl2. However, there are some structural differences between Meyer’s ruthenium compound12 and complex 2, which gives green prisms instead of Meyer’s yellow prisms and contains two diethyl ether solvate molecules in comparison with dichloromethane and toluene solvate molecules. The differences in unit cell parameters at low temperature (T=100 K) are as follows (complex 2/Meyer’s complex12): a=13.8127(9)/14.560(2) A˚, b=16.6947(9)/16.982(4) A˚, c = 21.1828(14)/20.375(4) A˚, R = 87.934(4)/89.942(14)°, β = 81.224(4)/74.578(9)°, γ = 66.866(3)/82.865(12)o, cell volume 4437.8(5)/4816.3(2) A˚3. The light green Hoveyda II complex 3 was then reacted with a large excess of SnCl2 in THF at 50 °C for 72 h to lead to the dark green complex 4, which was isolated in 70% yield (eq 2).

The 1H NMR (CDCl3) of 4, in addition to the NHC and PrOC6H4 group protons, shows a new alkylidene proton signal at δ 15.60 ppm with broad satellite peaks (3J117Sn-1H ≈ 3J119Sn-1H = 68.7 Hz), whereas complex 3 showed a Rud CH proton at δ 16.6 ppm. A single crystal of 4 obtained in THF with the final recrystallization from dichloromethanehexane allowed determination of its X-ray structure (Figure 2). It shows that the structure of the Hoveyda II complex 3 was retained with the formal insertion of SnCl2 into only one RuCl bond in spite of the long reaction time in the presence of an excess of SnCl2. The structure of 4 shows the distances RudC = 1.831(8) A˚, Ru-C(NHC) = 1.994(8) A˚, Ru-O = 2.255(5) A˚, i

(18) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100.

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Figure 1. Molecular structure of complex 2 with thermal ellipsoids drawn at the 30% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-C(5) =1.897(10), Ru(2)-C(45) =1.893(9), Ru(1)-Sn(1) =2.5899(9), Ru(2)-Sn(41) =2.5770(9), Ru(1)-P(12) =2.352(2), Ru(2)-P(52)=2.351(3), Ru(1)-Cl(35) = 2.494(2), Ru(2)-Cl(35) = 2.482(2), Ru(1)-Cl(36) = 2.597(2), Ru(2)-Cl(36) = 2.430(2), Ru(1)Cl(37) = 2.428(2), Ru(2)-Cl(37) = 2.607(2), Sn(1)-Cl(2) = 2.393(2), Sn(1)-Cl(3) = 2.439(2), Sn(1)-Cl(4) = 2.355(3), Sn(41)-Cl(42) = 2.391(3), Sn(41)-Cl(43) = 2.398(2), Sn(41)-Cl(44) = 2.409(3), C(5)-C(6) = 1.452(12), C(45)-C(46) = 1.447(12); C(5)-Ru(1)-Sn(1) = 86.9(3), C(6)-C(5)-Ru(1) = 134.0(7), P(12)-Ru(1)-Sn(1) = 97.46(6), P(12)-Ru(1)-C(5) = 89.4(3), Ru(1)-Cl(35)-Ru(2) = 85.91(7), Ru(1)-Cl(36)-Ru(2) = 84.77(7), C(5)-Ru(1)-Cl(35) = 92.7(3), P(12)-Ru(1)-Cl(35) = 172.44(8).

Figure 2. Molecular structure of complex 4 with thermal ellipsoids drawn at the 30% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-C(1)=1.825(8), Ru-C(11)=2.000(8), Ru(1)-Sn(1)=2.5925(12), Ru(1)-O(1)=2.255(5), Ru(1)-Cl(1)=2.335(2), Sn(1)Cl(2) = 2.382(2), Sn(1)-Cl(3) = 2.362(2), Sn(1)-Cl(4) = 2.387(2); C(11)-Ru(1)-O(1) = 177.6(3), Cl(1)-Ru(1)-Sn(1) = 164.75(6), C(1)-Ru(1)-C(11)=101.1(3), C(1)-Ru(1)-Cl(1)=103.1(2), C(1)-Ru(1)-Sn(1)=84.2(2), C(1)-Ru(1)-O(1)=79.5(3), C(11)-Ru(1)Cl(1)=93.8(2), O(1)-Ru(1)-Sn(1)=84.39(14), O(1)-Ru(1)-Cl(1)=83.81(15), C(11)-Ru(1)-Sn(1)=98.0(2).

Ru-Cl = 2.333(2) A˚, and Ru-Sn 2.5934(12) A˚, which are similar to those obtained for the X-ray structure of Hoveyda II

complex 319 (RudC=1.828(5) A˚, Ru-C(NHC)=1.981(5) A˚, Ru-O = 2.261(3) A˚; Ru-Cl = 2.328(12) and 2.340(2) A˚).

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However, the Ru-Sn bond length is strongly shortened in comparison with the sum of the covalent radii (2.85 A˚)20 due to an additional Ru-Sn π interaction, and especially the angle SnRu-Cl = 164.75(6)o in 4 is larger than the angle Cl-Ru-Cl= 156.5(5)° in complex 3. This difference between the Cl3SnRu-Cl and Cl-Ru-Cl angles and moieties may be responsible for the change in catalytic properties of 4 with respect to those of 3 in the following cross-metathesis. The SnCl3 group reactivity offers potential for further modification of complexes 2 and 4. 2. Cross- and Self-Metathesis of Fatty Unsaturated Esters and Aldehydes with Catalysts 2 and 4. 2.1. Cross- and SelfMetathesis of Fatty Unsaturated Esters and Aldehydes with Acrylonitrile. The interest in transforming vegetable oil derivatives in linear amino acids as precursors of polyamides10,11 led us to consider the cross-metathesis reaction of several oil derivatives with acrylonitrile as the key step to obtain unsaturated R,ω-bifunctional nitriles, the precursors, via reduction11 of amino acid derivatives. We have investigated the ability of the potential Sn-Ru alkylidene catalysts 2 and 4 in promoting cross-metathesis with acrylonitrile of the unsaturated aldehyde 5 and of the unsaturated ester 6 arising from castor oil and 1-decene 7 arising from ethenolysis of oleic acid (eqs 3-5). The results are displayed in Table 1.

Miao et al. Table 1. Ruthenium-Catalyzed Cross-Metathesis of Terminal Alkenes 5-7 with Acrylonitrilea entry

fatty compd

catalyst

time (h)

conversn (%)c

GC yield (%) (Z/E)c

1 2 3 4 5 6 7 8

5 5 5 5 (0.1 M) 6 6 7 7

2 3 4 4 3 4 3 4

5 2b 3 3 5 6 16 16

0 88.5 91 82 91 98 89 86

8, 88 (3.1) 8, 91 (4.3) 8, 81 (3.1) 9, 91 (3.6) 9, 98 (3.1) 10, 87 (2.1) 10, 85 (3.3)

a Reaction conditions: 0.5 mmol of terminal fatty compounds, 1 mmol of acrylonitrile, 10 mL of distilled toluene, 80 °C, dodecane as internal standard. b A longer reaction time did not give better conversion and yield. c Determined by gas chromatography.

Table 2. Ruthenium-Catalyzed Cross-Metathesis of Functional Terminal Alkenes 5 and 6 with Methyl Acrylatea fatty entry compd catalyst 1 2 3 4 5 6 7 8

5 5 5 5 6 6 6 6

3 3 4 4 3 3 4 4

temp (°C)

conversn (%)b

GC yield (%) (Z/E)b

50 room temp 50 room temp, 1.5 h 50 room temp 50 room temp, 1.5 h

>99 >99 98 88 >99 >99 96 90

11, 98 (1/11.3) 11, 98 (1/12.2) 11, 95 (13.6) 11, 85 (16.0) 12, 99 (1/11.5) 12, 98 (1/11.2) 12, 92 (1/11.3) 12, 89 (1/11.6)

a Reaction conditions: 0.5 mmol of terminal fatty compound, 1 mmol of methyl acrylate, 1 mL of distilled toluene, dodecane as internal standard. b Determined by gas chromatography.

With the unsaturated aldehyde 5 the bis rutheniumalkylidene complex 2 showed no activity for its cross-metathesis with acrylonitrile (entry 1). In contrast, the Hoveyda II modified complex 4 showed activity slightly better than that of the parent Hoveyda II catalyst 3 for the production of the nitrile aldehyde 8 (eq 3) (Table 1, entries 2 and 3). However, dilute solutions have to be used, as an increase in the substrate 5 concentration led to a decrease in the conversion (entries 3 and 4). The cross-metathesis of the unsaturated ester 6 with acrylonitrile led also to slightly better activity and yield of the nitrile ester 9 with catalyst 4 than with 3 (eq 4) (Table 1, entries 5 and 6). Thus, the stable catalyst 4 may offer an alternative for the production of the linear R,ω-nitrile ester derivative 9. (19) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.; Hoveyda, A. H. J. Am. Chem. Soc. 2000, 122, 8168. (20) Cordero, B.; G
omez, V.; Platero-Prats, A. E.; Rev
es, M.; Echeverrı´ a, J.; Cremades, E.; Barrag
an, F.; Alvarez, S. Dalton Trans. 2008, 2832.

Catalysts 3 and 4 both led to similar activities and yields for the transformation of the 1-decene 7 into the C11 alkenylnitrile 10 (eq 5) (entries 7 and 8). It is noteworthy that the terminal alkene 7 cannot be transformed as easily as the functional species 5 and 6 (entries 3, 6, and 8.) All the above reactions gave the Z isomer as the major product. The reactions promoted by catalyst 4 were found to give a Z/E isomer ratio to the profit of the Z isomer (Table 1, entries 3 and 8 vs 2 and 7), although this isomer ratio is not crucial for the production of linear amino alcohol or amino ester monomer from 8 and 9. The influence of substrate concentration was shown to be crucial for the reaction conversion: 91% conversion was obtained by the reaction at 0.05 M, and when the concentration was increased to 0.1 M only 82% conversion was obtained (Table 1, entries 3 and 4). 2.2. Cross-Metathesis of Fatty Derivatives 5 and 6 with Methyl Acrylate. The cross-metathesis of unsaturated aldehyde 5 and ester 6 with methyl acrylate leads to aldehyde ester and diester that have the potential to produce R,ω-diacid or diol monomers on oxidation and reduction, respectively. The reaction of 6 with methyl acrylate was already performed in bulk under mild conditions by Meier.8 The reactions of unsaturated fatty compounds 5 and 6 with 2 equiv of methyl acrylate were performed in toluene with a substrate concentration of 0.5 M at 50 °C and room temperature for 30 min using only 0.5 mol % of ruthenium catalysts 3 and 4 (eq 6 and Table 2).

In this case, we found that the activity of catalyst 3 was better than that of 4. The reaction with catalyst 3 afforded full

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Table 3. Ruthenium-Catalyzed Cross-Metathesis of Internal Alkene 13 with Acrylonitrilea

Table 4. Ruthenium-Catalyzed Self-Metathesis of Unsaturated Aldehyde 5a GC ratio (%)b

GC yield (%) (Z/E)b entry

catalyst (amt (mol %))

time (h)

conversn (%)b

14

15

1 2 3 4

3 (1) 3 (0.5) 4 (1) 4 (0.5)

6 8 8 8

98 88 99 72

91 (2.9) 71 (3.2) 93 (2.5) 48 (3.0)

7 16 6 21

a Reaction conditions: 0.5 mmol of 13, 2 mmol of acrylonitrile, 10 mL of distilled toluene, catalyst 1-0.5 mol %, dodecane as internal standard. b Determined by gas chromatography.

conversions either at 50 °C or at room temperature (Table 2, entries 1 and 2, 5 and 6). The conversion decreased when the catalyst 4 was used for the cross-metathesis at room temperature, and the reaction time had to be prolonged to 1.5 h to get good conversion of 5 and 6 and to reach a decent yield of aldehyde ester 11 and diester 12 (Table 2, entries 4 and 8). In contrast to the reaction with acrylonitrile, all reactions with methyl acrylate gave the E isomer as the major product. 2.3. Cross-Metathesis of Dimethyl Octadec-9-enedioate 13 with Acrylonitrile. The (Z)-dimethyl octadec-9-enedioate 13, obtained via biotransformation or self-metathesis of oleic acid, contains an internal CdC bond which is expected to be less suitable for cross-metathesis than ω-unsaturated esters. Diester 13 was studied as a possible precursor of the C11 nitrile ester 14, a homologue of the C12 derivative 9, by cross-metathesis with acrylonitrile. The reaction of 13 with 4 equiv of acrylonitrile was performed in toluene at 100 °C using catalysts 3 and 4. The results are displayed in Table 3. With 1 mol % of catalyst loading, the two catalysts 3 and 4 promoted the cross-metathesis reaction similarly to afford 14 in good yield with only a small amount of unsaturated ester 15 (eq 7) (Table 3, entries 1 and 3). Catalyst 3 appears to be more active than 4 on decreasing the catalyst loading to 0.5 mol %. An 88% conversion along with 71% yield of nitrile ester 14 were obtained by reaction of diester 13 and acrylonitrile with catalyst 3, while only 72% conversion and a 48% yield of 14 were obtained with catalyst 4 (entries 2 and 4).

2.4. Self-Metathesis of C11 Unsaturated Aldehyde 5. The self-metathesis of the castor oil derivative C11 unsaturated aldehyde 5 has the potential to lead to the C20 dialdehyde 16 (eq 8), a potential precursor of C20 dicarboxylic acid and diol monomers. Previous attempts to perform that selfmetathesis10b actually led to a moderate yield of 16 with high ratio of byproducts due to isomerization. The performance of catalysts 2 and 4 as compared to that of classical catalysts 1 and 3 was then investigated on the transformation 6 f 16 in toluene at 40 °C (eq 8). The results are displayed in Table 4. The Grubbs I catalyst 1 leads to good conversion but for a long reaction time (entries 1 and 2). The dirutheniumalkylidene catalyst 2 shows good conversion after only 4 h

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entry

catalyst (amt (mol %))

time (h)

conversn (%)b

16

byproducts

1 2 3 4 5 6 7 8

1 (1.0) 1 (0.5) 2 (1.65) 2 (0.66) 2 (0.33) 3 (2.5) 4 (1.25) 4 (2.5)

48 48 16 4 48 23 13 22

81 74 72 61 70 84 72 85

67 60 43 39 51 40 51 44

5 6 20 4 2 33 19 20

a Reaction conditions: 0.5 mmol of 5, 2.5 mL of distilled toluene, 40 °C, dodecane as internal standard. b Determined by gas chromatography.

(entry 4), but its concentration should be decreased to reach decent conversion and avoid byproduct formation (entries 3 and 5). NHC-containing catalysts 3 and 4 both afford good conversion but with moderate yield in 16 and too high a ratio of byproduct. Thus, for self-metathesis of 5 into 16 catalysts 1 and 2 both offer a better compromise than catalysts 3 and 4.

In the formation of 16 only the E isomer was observed, in contrast to the case for 10, 12, and 14, which were formed as a mixture of E and Z isomers. This is likely due to the fact that in 5, the only precursor of 16, the functional formyl group is far from the terminal CH2dCH bond which is transformed and cannot interact with the catalyst metal, in contrast to the case for the functional alkenes CH2dCHZ (Z = CN, CO2R) leading to E/Z isomers 10, 12, and 14.

Conclusion The alkylidene-ruthenium complexes of the type RuCl2(dCHR)(L1)(L2), the Grubbs I and Hoveyda II catalysts, behave quite differently on reaction with tin dichloride. In both cases formal insertion of SnCl2 into only one Ru-Cl bond takes place and the active RudCHR moiety is retained. With the Hoveyda II complex 3 the reaction stops at this insertion and leads to a large angle and bulky Cl-Ru-SnCl3 moiety in the stable complex 4. From the Grubbs I catalyst 1, likely due to the lability of one PCy3 ligand, the formed RuCl(SnCl3)(dCHR)PCy3) moiety dimerized and added one chloride to give the anionic binuclear complex 2. The alkene metathesis performance of Cl3Sn-Ru-containing catalysts 2 and 4 with fatty acid derivatives offers the possibility of catalytic transformation of renewable materials. The binuclear catalyst 2 is not suitable for crossmetathesis with electron-withdrawing short olefins but offers a good alternative for self-metathesis of a C11 unsaturated aldehyde into a C20 dialdehyde derivative on the condition that a low concentration of catalyst is used to decrease isomerization and the formation of byproduct. The thermally stable catalyst 4, containing an NHC ligand, is suitable for cross-metathesis of long-chain olefins. It is especially useful for cross-metathesis with acrylonitrile and synthesis of linear bifunctional nitriles with the C11 unsaturated aldehyde 5 and ester 6 as well as for the

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Organometallics, Vol. 29, No. 21, 2010

cross-metathesis of an internal CdC bond diester with acrylonitrile.

Experimental Section General Procedures. All reactions were performed under an argon atmosphere using Schlenk techniques. Reagent grade solvents were dried by the standard procedures and were freshly distilled prior to use. Transmittance FT-IR spectra were recorded using a Bruker IFS 28 spectrophotometer. 1H NMR and 31P{1H} NMR were recorded on a Bruker AM 300WB spectrometer operating at 300.13 and 121.5 MHz, respectively. 31P{1H} NMR spectra were externally referenced against 85% ortho-H3PO4. Elemental analyses were performed with the microanalysis instrument Flash EA1112 CHN/O Thermo Electron at the CRMPO, Unversit
e de Rennes 1. The catalytic reactions were monitored using a Shimadzu 2014 gas chromatograph equipped with Equity-1 fused silica capillary column. RuCl2(dCHPh)(PCy3)2 (1) and RuCl2(dCHC6H4OPri)(H2IMes) (3) and anhydrous SnCl2 98% were purchased respectively from Sigma-Aldrich and AlfaAesar. Fatty derivatives 5 and 7 were purchased from Acros, compound 6 was offered by Arkema France, and the diester 13 was synthesized by esterification of the corresponding diacid offered by Arkema France. All the cross-metathesis products are known int he literature and their obtained spectroscopic data can be found in the Supporting Information. X-ray Diffraction Analysis. Details of the data collection and structure refinement for complexes 2 and 4 are presented in Table S1 (Supporting Information). Single-crystal X-ray diffraction experiments were carried out at T = 100 K on a BrukerAXS APEXII diffractometer (Centre de Diffractom
etrie X, Sciences Chimiques de Rennes) and at T = 150 K on a Bruker SMART APEXII diffractometer, for complexes 2 and 4, respectively. Both diffractometers are equipped with a CCD area detector and use Mo KR radiation (graphite monochromator, λ = 0.710 73 A˚). The semiempirical method SADABS was applied for absorption correction. The structures were solved by direct methods and refined by the full-matrix least-squares technique against F2 with anisotropic displacement parameters for all non-hydrogen atoms. All the hydrogen atoms in the complexes were placed geometrically and included in the structure factor calculations in the riding motion approximation. All of the data reduction and further calculations were performed using the SAINT and SHELXTL program package.21 The crystal structures have been deposited at the Cambridge Crystallographic Data Centre and allocated the deposition numbers CCDC 772944 (2) and 772694 (4). Preparation of [Ru(dCHC 6 H 5 )(SnCl 3 )(PCy 3 )]2 (μ-Cl)3 ]-[HPCy 3 ]þ (2). To a solution of 100 mg (0.12 mmol) of the purple complex RuCl2(dCHPh)(PCy3)2 (1) in 20 mL of THF was added an excess of SnCl2 (70 mg, 0.36 mmol). The solution was stirred for 4 h at room temperature with monitoring by TLC (yellow-green spot, Rf=0.4, 1/1 CH2Cl2/hexane). The solvent was removed under vacuum, the greenish yellow solid was extracted with 30 mL of CH2Cl2, and the solution was filtered. A 15 mL portion of hexane was added to the filtrate, the solution was concentrated until the crystallization started, and then 3 mL of diethyl ether was added. After a night at 0 °C the green crystals that formed were filtered and dried under vacuum (80 mg, 75% yield). 1H NMR (300.13 MHz, CDCl3; δ, ppm): 1.23-1.38 (m, 30H); 1.67-1.87 (m, 60H); 2.19 (s, 1H); 2.35-2.42 (m, 3H), 7.55-7.75 (m, 10H); 8.67 (d, 2H, 3JHH = 7.3 Hz, dCH). 31P{1H} NMR (121.5 MHz, CDCl3; δ, ppm): 23.837 (s), 48.134 (s). IR spectrum (KBr, cm-1): C-H (2929 s, 2852 s, 1297 m, 1259 m, 1205 m 1176 m, 1121 m, 567 w, 517 m), Ph (1446 s, 1077 s, 1005 m, 924 m, 875 m, 850 m, 727 m, 699 m). Anal. Calcd for C68H112Cl9P3Ru2Sn2 3 2(C2H5)2O: C, 47.31; H, 6.90. Found: C, 47.65; H, 6.37. (21) Sheldrick, G. M. SHELXTL-97, Version 5.50; Bruker AXS Inc., Madison, WI 53719. 1997.

Miao et al. Preparation of RuCl(SnCl3)(dCHC6H4OPri)(H2IMes) (4). To a solution of 100 mg (0.16 mmol) of the green complex 3 in 20 mL of THF was added an excess of dry SnCl2 (152 mg, 0.8 mmol). The solution was stirred for 72 h at 50 °C with monitoring by TLC (dark green spot, Rf = 0.25, 1/1 acetone/ hexane). The solvent was removed under vacuum; the solid was extracted three times with 30 mL of CH2Cl2. The green solution was concentrated to 25 mL, and then 15 mL of hexane was added and the mixture was concentrated until the beginning of crystallization. After a night at 0 °C the dark green crystals that formed were filtered and dried under vacuum (92 mg, 70% yield). 1H NMR (300.13 MHz, CDCl3; δ, ppm): 1.34 (d, 3 H, 3JHH = 6.1 Hz, CH3-iPr) ; 1.39 (d, 3 H, 3JHH = 6.1, CH3-iPr); 2.31, 2.37, 2.45, 2.55, 2.66, 2.71 (6 s, 18 H, 6 CH3mesityl); 4.16-4.35 (m, 4 H, NCH2CH2N); 5.00-5.09 (m, 1 H, OCH); 6.86-7.19 (m, 7 H, CH arom); 7.59-7.65 (m, 1 H, CH arom); 15.65 (s þ 2 satellites, 1 H, 3J117Sn-1H= 3J119Sn-1H = 68.7 Hz, RudCH). IR spectrum (KBr, cm-1): C-H (2980 m, 2917 m, 1256 m, 1216 m, 854 m 595 vw, 510 w), Ph (1627 s, 1445 s, 1082 m, 1028 m, 730 w, 696 w). Anal. Calcd for C31H38Cl4N2ORuSn 3 0.5CH2Cl2): C, 44.06; H, 4.58; N, 3.26. Found: C, 43.78; H, 4.64; N, 3.29. General Procedure for Cross-Metathesis of Fatty Derivatives with Acrylonitrile. In a Schlenk tube under argon, 0.5 mmol of fatty derivatives and acrylonitrile (53 mg, 1 mmol) were dissolved in 10 mL of distilled toluene with dodecane as internal standard; ruthenium catalyst (0.0025 mmol, 0.5 mol %) was then added, and the reaction mixture was stirred at 80 °C for various periods of time. A sample of the reaction mixture was taken, filtered on a small pad of silica, and analyzed by GC. The reaction product was purified by column chromatography on silica gel. General Procedure for Cross-Metathesis of Fatty Derivatives with Methyl Acrylate. In a Schlenk tube under argon, 0.5 mmol of fatty derivatives and methyl acrylate (86 mg, 1 mmol) were dissolved in 1 mL of distilled toluene with dodecane as internal standard, ruthenium catalyst (0.0025 mmol, 0.5 mol %) was then added, and the reaction mixture was stirred at 50 °C or at room temperature for various periods of time. A sample of the reaction mixture was taken, filtered on a small pad of silica, and analyzed by GC. The reaction product was purified by column chromatography on silica gel. General Procedure for Self-Metathesis of Undecylenic Aldehyde 5. In a Schlenk tube under argon, 84 mg (0.5 mmol) of aldehyde 5 was dissolved in 2.5 mL of distilled toluene with dodecane as internal standard. The ruthenium catalyst was then added, and the reaction mixture was stirred at 40 °C for various periods of time. The reaction was monitored using gas chromatography.

Acknowledgment. We are grateful to Arkema Co. for a Ph.D. position to X.M., the PICS CNRS-Russian Foundation of Basic Research (RFBR) (Nos. 07-03-92171 and 09-03-00961), the GDRE CNRS-Russia CH2D, the Institut Universitaire de France for support to P.H.D., and the Foundation of President of the Russian Federation (program for support of leading Russian scientific schools NSh-1733.2008.3). Supporting Information Available: CIF files giving full details of the crystal structure analyses for complexes 2 and 4, tables giving crystal data and structure refinement details, atomic coordinates, bond lengths and angles, and hydrogen coordinates, and text giving additional characterization data. This material is available free of charge via the Internet at http:// pubs.acs.org. The data for X-ray diffraction analysis of complexes 2 and 4 can also be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam. ac.uk/data_request/cif.