Synthesis and Reactivity of Ruthenium Azido Complexes Containing a

May 12, 2009 - Michael. T. HuxleyAlexandre BurgunHanieh GhodratiCampbell J. CoghlanAnthony LemieuxNeil R. ChampnessDavid M. HuangChristian J...
0 downloads 0 Views 252KB Size
Download PDF
3358

Organometallics 2009, 28, 3358–3368

Synthesis and Reactivity of Ruthenium Azido Complexes Containing a Hydridotris(pyrazolyl)borate Ligand and Dimerization of Terminal Alkynes in Organic and Aqueous Media Chien-Kai Chen,† Hung-Chun Tong,† Chih-Yung Chen Hsu,† Chia-Yi Lee,† Yih Hsuan Fong,‡ Yao-Shun Chuang,‡ Yih-Hsing Lo,*,‡ Ying-Chih Lin,§ and Yu Wang§ Department of Chemical Engineering, Tatung UniVersity, Taipei 104, Taiwan, Republic of China, Department of Natural Science, Taipei Municipal UniVersity of Education, Taipei 100, Taiwan, Republic of China, and Department of Chemistry, National Taiwan UniVersity, Taipei 106, Taiwan, Republic of China ReceiVed October 2, 2008

Facile ligand substitution is observed when the ruthenium azido complex (PPh3)[Ru]-N3 (1; [Ru] ) Tp(PPh3)Ru) is treated with CH3CN, yielding the nitrile-substituted ruthenium azido complex (CH3CN)[Ru]-N3 (2). Alkylation, [3 + 2] cycloaddition, and catalytic reactions of complex 2 have been investigated. In the case of [3 + 2] cycloaddition reactions, the metal-bound heterocyclic complexes (CH3CN)[Ru]-N3C2(CO2Me)2 (3a), (CH3CN)[Ru]-N3C2HCO2Me (5), and (CH3CN)[Ru]N3C2HCN (6) are obtained from dimethyl acetylenedicarboxylate, methyl propiolate, and fumaronitrile, respectively. The tetrazolato complex [(CN)2CdC(CN)2][Ru]-N4C[C(CN)dC(CN)2] (8) is prepared from 2 and TCNE. Alkylation of 3a with organic bromides affords N-alkylated five-membered-ring organic triazoles. The reaction of CS2 with 2 produces the thermally unstable thiothiatriazolate (CH3CN)[Ru]-N3CS(S) (10), which decomposes to the isothiocyanate (CH3CN)[Ru]-NCS (11). On the other hand, several cationic imine complexes {(CH3CN)[Ru]-(NHdCHR)}+ (12a, R ) H; 12b, R ) CH3; 12c, R ) HCdCH2) are formed by the reaction of RCH2X with the negatively charged nitrogen atom of the azido ligand on RuII. The reaction proceeds via formation of an alkylimido intermediate followed by N2 evolution and proton transfer from the alkyl group to the imido nitrogen atom. Preliminary results on the catalytic activity of 2 are also presented. Interestingly, complex 2 catalyzes the dimerization of some terminal alkynes HCtCR in organic and aqueous medium. Whereas with R ) Ph, SiMe3, t-Bu isomeric mixtures of head-to-head and head-to-tail coupling products are obtained, in the case of R ) COOMe, E-selective head-to-head dimerization takes place exclusively. The structures of 1, 8, and 12c have been determined by X-ray diffraction analysis. Introduction Organic azides are synthetically useful reagents.1 Among their many transformations, perhaps the most important ones are 1,3dipolar cycloaddition reactions with acetylenes to synthesize triazoles.2 Triazoles are nitrogen heteroarenes which have found a range of important applications in the pharmaceutical and agricultural industries.3 Analogously, metal-coordinated azido ligands can also undergo 1,3-dipolar cycloaddition reactions with carbon-carbon and carbon-heteroatom multiple bonds, fre†

Tatung University. Taipei Municipal University of Education. National Taiwan University. (1) (a) The Chemistry of the Azido Group; Patai, S., Ed.; Interscience: New York, 1971. (b) Azides and Nitrenes: ReactiVity and Utility; Scriven, E. F. V., Ed.; Academic: New York, 1984. (2) (a) Huisgen, R. Proc. Chem. Soc. 1961, 357. (b) Huisgen, R. Angew. Chem., Int. Ed. Engl. 1963, 2, 565. (c) Huisgen, R. Angew. Chem., Int. Ed. Engl. 1963, 2, 633. (d) Huisgen, R. J. Org. Chem. 1976, 41, 403. (e) Labbe, G. Chem. ReV. 1969, 69, 345. (f) Kauffmann, T. Angew. Chem., Int. Ed. Engl. 1974, 13, 627. (g) Padwa, A. Angew. Chem., Int. Ed. Engl. 1976, 15, 123. (3) For reviews of 1,2,3-triazoles, see: (a) Fan, W. Q.; Katritzky, A. R. In ComprehensiVe Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.; Pergamon Press: Oxford, U.K., 1996; Vol. 4, pp 1-126. (b) Dehne, H. In Methoden der Organischen Chemie (HoubenWeyl); Schaumann, E., Ed.; Thieme: Stuttgart, Germany, 1994; Vol. E8d, pp 305-405. (c) Krivopalov, V. P.; Shkurko, O. P. Russ. Chem. ReV. 2005, 74, 339. ‡ §

quently under very mild conditions.4-11 Although such reactions have been studied extensively in synthetic organic chemistry, (4) Fruhauf, H. W. Chem. ReV. 1997, 97, 523. (5) (a) Treichel, P. M.; Knebel, W. J.; Hess, R. W. J. Am. Chem. Soc. 1971, 93, 5424. (b) Beck, W.; Burger, K.; Fehlhammer, W. P. Chem. Ber. 1971, 104, 1816. (c) Fehlhammer, W. P.; Dahl, L. F. J. Am. Chem. Soc. 1972, 94, 3370. (d) Fehlhammer, W. P.; Kemmerich, T.; Beck, W. Chem. Ber. 1979, 112, 468. (6) (a) Beck, W.; Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl. 1967, 6, 169. (b) Beck, W.; Fehlhammer, W. P.; Pollmann, P.; Schachl, H. Chem. Ber. 1969, 102, 1976. (c) Beck, W.; Fehlhammer, W. P.; Bock, H.; Bander, M. Chem. Ber. 1969, 102, 3637. (d) Beck, W.; Bander, M.; Fehlhammer, W. P.; Pohlmann, P.; Schachl, H. Inorg. Nucl. Chem. Lett. 1968, 4, 143. (e) Washburne, S. S.; Peterson, W. R., Jr. J. Organomet. Chem. 1970, 21, 427. (f) Sisido, K.; Nabika, K.; Isida, T.; Kozima, S. J. Organomet. Chem. 1971, 33, 337. (g) Kemmerich, T.; Beck, W.; Spencer, C.; Mason, R. Z. Naturforsch., B: Anorg. Chem., Org. Chem., Biochem., Biophys., Biol. 1972, 27B, 745. (h) Gaughan, A. P.; Browman, K. S.; Dori, Z. Inorg, Chem. 1972, 11, 601. (i) Busetto, L.; Palazzi, A.; Ros, R. Inorg. Chim. Acta 1975, 13, 233. (j) Beck, W.; Schropp, K. Chem. Ber. 1975, 108, 3317. (k) Rigby, W.; Bailey, P. M.; McCleverty, J. A.; Maitlis, P. M. J. Chem. Soc., Dalton Trans. 1979, 371. (l) Ellis, W. R., Jr.; Purcell, W. L. Inorg. Chem. 1982, 21, 834. (m) Hall, J. H.; De La Vega, R. L.; Purcell, W. L. Inorg. Chim. Acta 1985, 102, 157. (7) (a) Gorth, H.; Henry, M. C. J. Organomet. Chem. 1967, 9, 117. (b) Kozima, S.; Itano, T.; Mihara, N.; Sisido, K.; Isida, T. J. Organomet. Chem. 1972, 44, 117. (8) Erbe, J.; Beck, W. Chem. Ber. 1983, 116, 3867. (9) (a) Rosen, A.; Rosenblum, M. J. Organomet. Chem. 1974, 80, 103. (b) Ziolo, R. F.; Dori, Z. J. Am. Chem. Soc. 1968, 90, 6560. (c) Ziolo, R. F.; Thich, J. A.; Dori, Z. Inorg. Chem. 1972, 11, 626. (10) Sato, F.; Etoh, M.; Sato, M. J. Organomet. Chem. 1974, 70, 101.

10.1021/om800952t CCC: $40.75  2009 American Chemical Society Publication on Web 05/12/2009

Ruthenium Azido Complexes

dipolar cycloaddition reactions of azide-coordinated metal complexes have been relatively unexplored. A few reports have appeared in recent years on the cycloaddition of alkynes to ruthenium azido complexes.12 It has been reported that an azide ion, coordinated to a metal center, could be photochemically and thermally decomposed to afford a nitrogen-containing compound, which retains a nitrogen atom of the azido ligand. The reaction proceeds via a reactive intermediate such as a nitrene and/or a nitride complex, and N2 is generated.13 Although azide compounds are explosive as a result of rapid dinitrogen evolution, azido-metal complexes can potentially be converted into various nitrogen-containing complexes such as imido and cycloaddition compounds.14 Ruthenium-catalyzed dimerization reactions of terminal alkynes are attractive, atom-economic C-C bond forming reactions that can give products containing key structural units in natural products and materials.15 Alkyne dimerization reactions are also potentially useful for making conjugated polymers or oligomers from diynes.16 Dimerization reactions of RCtCH can produce several isomeric products, and the most common ones include (Z)-RCHdCHCtCR, (E)-RCHdCHCtCR, CH2dC(R)CtCR, cis-RHCdCdCdCHR, and trans-RHCdCdCdCHR. For practical applications in organic synthesis, ideally, one needs a catalytic system that gives only one desired isomer for a wide range of substrates. However, many of the reported catalytic systems actually give a mixture of isomeric products, and the selectivities of the isomeric products often vary with the substituents of the alkynes. Recently, there have been considerable efforts devoted to the understanding of the origins of the selectivity and the development of selective dimerization of terminal alkynes.17 During the course of investigations into ruthenium cyclopropenyl chemistry, we previously established the formation of a neutral ruthenium tetrazolate complex.18 For example, the cyclopropenyl complex Tp(PPh3)(CH3CN)Ru-CdC(Ph)CHCN (11) Kreutzer, P. H.; Weis, J. C.; Bock, H.; Erbe, J.; Beck, W. Chem. Ber. 1983, 116, 2691. (12) (a) Chang, C. C.; Lee, G. H. Organometallics 2003, 22, 3107. (b) Govindaswamy, P.; Mobin, S. M.; Tho¨ne, C.; Mohan Rao, K. J. Organomet. Chem. 2005, 690, 1218. (13) (a) Brown, G. M.; Callahan, R. W.; Mayer, T. J. Inorg. Chem. 1975, 14, 1915. (b) Weaver, R. T.; Basolo, F. Inorg. Chem. 1974, 13, 1535. (c) Suzuki, T.; DiPasquale, A. G.; Mayer, J. M. J. Am. Chem. Soc. 2003, 125, 10514. (d) Grapperhaus, C. A.; Mienert, B.; Bill, E.; Weyhermu¨ller, T.; Wieghardt, K. W. Inorg. Chem. 1974, 39, 5306. (e) Reed, J. L.; Gafney, H. D.; Basolo, F. J. Am. Chem. Soc. 1974, 96, 1363. (f) Ferraudi, G.; Endicott, J. F. Inorg. Chem. 1973, 12, 2389. (g) Gafney, H. D.; Reed, J. L.; Basolo, F. J. Am. Chem. Soc. 1973, 95, 7998. (h) Brown, S. D.; Peters, J. C. J. Am. Chem. Soc. 2005, 127, 1913. (i) Weaver, T. R.; Lane, B. C.; Basolo, F. Inorg. Chem. 1972, 11, 2277. (j) Lane, B. C.; McDonald, J. W.; Basolo, F.; Pearson, R. G. J. Am. Chem. Soc. 1972, 94, 3786. (14) (a) Kim, Y. J.; Lee, S.-H.; Lee, S.-H.; Jeon, S. I.; Lim, M. S.; Lee, S. W. Inorg. Chim. Acta 2005, 358, 650. (b) Kim, Y. J.; Chang, X.; Han, J. T.; Lim, M. S.; Lee, S. W. Dalton Trans. 2004, 3699. (c) Hsu, S. C.; Lin, Y. C.; Huang, S. L.; Liu, Y. H.; Wang, Y.; Liu, H. Eur. J. Inorg. Chem. 2004, 459. (d) Kim, Y. J.; Joo, Y. S.; Han, J. T.; Han, W. S.; Lee, S. W. Dalton Trans. 2002, 3611. (15) Reviews: (a) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311. (b) Ritleng, V.; Sirlin, C.; Pfeffer, M. Chem. ReV. 2002, 102, 1731. (c) Katayama, H.; Ozawa, F. Coord. Chem. ReV. 2004, 248, 1703. (d) Yi, C. S.; Liu, N. Synlett 1999, 281. (16) Katayama, H.; Nakayama, M.; Nakano, T.; Wada, C.; Akamastsu, K.; Ozawa, F. Macromolecules 2004, 37, 13. (17) (a) Schafer, M.; Wolf, J.; Werner, H. Organometallics 2004, 23, 5173. (b) Horacek, M.; Stepnicka, P.; Kubista, J.; Gyepes, R.; Mach, K. Organometallics 2004, 23, 3388. (c) Yang, C.; Nolan, S. P. J. Org. Chem. 2002, 67, 591. (d) Rubina, M.; Gevorgyan, V. J. Am. Chem. Soc. 2001, 123, 11107. (e) Lee, C. C.; Lin, Y. C.; Liu, Y. H.; Wang, Y. Organometallics 2005, 24, 136. (18) Lo, Y. H.; Lin, Y. C.; Huang, G. C. J. Organomet. Chem. 2008, 693, 117.

Organometallics, Vol. 28, No. 12, 2009 3359 Scheme 1

was found to react with an excess amount of Me3SiN3 to afford the zwitterionic tetrazolate complex Tp(PPh3)(CH3CN)RuN4CCH(Ph)CH2CN. We thought that a similar TpRu complex containing the azido ligand would be a logical extension. Herein, we report the [3 + 2] cycloaddition reactions of alkynes and alkenes with the ruthenium azido complex (CH3CN)[Ru]-N3 (2; [Ru] ) Tp(PPh3)Ru). The stable triazolato and tetrazolato products obtained in all cases were N(2)-bound. We also describe the reaction of 2 with CH3I to give a rare methyleneimine complex of ruthenium, and a preliminary account of the catalytic activity of 2 is given.

Results and Discussion Preparation of the Azido Complex. Treatment of the Tp complex (PPh3)[Ru]-Cl ([Ru] ) Tp(PPh3)Ru) with an excess of sodium azide (NaN3) in methanol under reflux conditions for 24 h affords the yellow ruthenium azido complex Tp(PPh3)2RuN3 (1) with an isolated yield of 78% (Scheme 1). The azido complex 1 is soluble in polar solvents such as CH2Cl2, CHCl3, and acetone, moderately soluble in diethyl ether, and stable in solution and in air. The IR spectrum of the complex exhibits a strong band at 2046 cm-1 due to the terminal azido group, and the 31P NMR spectrum of 1 displays a singlet resonance at δ 44.1 assigned to the triphenylphosphine groups. Bright yellow crystals of 1 were obtained by slow diffusion of n-hexane into a CH2Cl2 solution of 1 at 0 °C for 72 h, and the molecular structure of 1 has been determined by X-ray diffraction analysis (Table 1). An ORTEP diagram is shown in Figure 1, and Table 2 gives selected bond distances and angles. The solid-state structure of 1 contains two crystallographically distinct molecules, although there is no essential structural difference between them. The environment about the ruthenium metal center corresponds to a slightly distorted octahedron, and the bite angle of the Tp ligand produces an average N-Ru-N angle of 85.6°, only slightly distorted from 90°. The three Ru-N(Tp) bond lengths (2.140(3), 2.151(3), and 2.106(3) Å) are slightly longer than the average distance of 2.038 Å in other ruthenium Tp complexes.19 The linear azide ligand adopts an end-on terminal coordination mode with a relatively long Ru-N bond of 2.207(3) Å, which is considerably longer than Ru-N(Tp). Typically, the coordinated azide is either symmetric (the two N-N distances are nearly equal) or asymmetric in such a way that the N-N bond between the coordinated and the central N atoms is longer than the other N-N bond, owing to the two canonical structures (A and B in Scheme 1) contributing to the ground-state geometry of the coordinated azide.20 The copper(19) (a) Christian, S.; Kurt, M.; Roland, S.; Kari, K. Organometallics 1998, 17, 827. (b) Christian, S.; Kurt, M.; Roland, S.; Kari, K. J. Chem. Soc., Dalton Trans. 1997, 4209. (c) Gemel, C.; Trimmel, G.; Christian, S.; Kurt, M.; Roland, S.; Kari, K. Organometallics 1996, 15, 3998. (d) Gemel, C.; Trimmel, G.; Christian, S.; Kurt, M.; Roland, S.; Kari, K. Inorg. Chem. 1997, 36, 1076. (20) (a) Dori, Z.; Ziolo, R. F. Chem. ReV. 1973, 73, 247. (b) Gaughan, A. P.; Ziolo, R. F.; Dori, Z. Inorg. Chem. 1971, 10, 2776. (c) Hu¨cksta¨dt, H.; Homborg, H. Z. Anorg. Allg. Chem. 1998, 624, 980.

3360 Organometallics, Vol. 28, No. 12, 2009

Chen et al.

Table 1. Crystal and Intensity Collection Data for Compounds 1, 8 · CH2Cl2, and 12c 8 · CH2Cl2

1 mol formula mol wt space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z cryst dimens, mm3 Mo KR radiation: λ, Å θ range, deg limiting indices no. of rflns collected no. of indep rflns max, min transmissn refinement method no. of data/restraints/params GOF final R indices (I > 2σ(I)) R indices (all data) largest diff peak and hole

C36H20BN6P2Ru 742.40 P21/c 20.3520(2) 22.5816(2) 19.4934(2) 90.00 111.7890(10) 90.00 8318.75(14) 8 0.30 × 0.25 × 0.20 0.710 73 1.08-25.00 -24 e h e24 -26 e k e 25 -23 e l e 23 46 548 14 612 0.909, 0.850 14 612/2/1058 1.037 R1 ) 0.0417, wR2 ) 0.1131 R1 ) 0.0571, wR2 ) 0.1337 1.332 and -0.995 e Å-3

azide complex Cu2(N3)2[(CH2PPh2)2]3, with the N1-N2 bond (1.196(18) Å) adjacent to the Cu-N1 bond and N2-N3 bond (1.076(18) Å) is a clear case of A being the dominant form.20b

Figure 1. ORTEP drawing of 1 with thermal ellipsoids shown at the 50% probability level. Table 2. Selected Bond Distances (Å) and Angles (deg) of Tp(PPh3)2Ru-N3 (1) Ru(1)-N(2) Ru(1)-N(4) Ru(1)-N(6) N(7)-N(8) N(6)-Ru(1)-N(2) N(2)-Ru(1)-N(4) N(2)-Ru(1)-N(7) N(6)-Ru(1)-P(2) N(4)-Ru(1)-P(2) N(6)-Ru(1)-P(1) N(4)-Ru(1)-P(1) P(2)-Ru(1)-P(1) N(4)-Ru(1)-N(7) N(7)-N(8)-N(9)

2.140(3) 2.151(3) 2.106(3) 1.054(5) 87.89(11) 80.21(10) 90.25(10) 94.01(8) 89.63(7) 88.69(8) 168.92(7) 101.29(3) 86.48(10) 174.1(4)

Ru(1)-N(7) Ru(1)-P(1) Ru(1)-P(2) N(8)-N(9) N(6)-Ru(1)-N(4) N(6)-Ru(1)-N(7) N(4)-Ru(1)-N(7) N(2)-Ru(1)-P(2) N(7)-Ru(1)-P(2) N(2)-Ru(1)-P(1) N(7)-Ru(1)-P(1) N(6)-Ru(1)-N(7) N(2)-Ru(1)-N(7) N(8)-N(7)-Ru(1)

2.207(3) 2.3675(9) 2.3525(8) 1.235(6) 88.67(11) 175.04(10) 86.48(10) 169.62(8) 87.01(7) 88.95(8) 95.88(7) 175.04(10) 90.25 123.6(3)

C40H27BCl2N17PRu 959.54 P21/c 16.0435(12) 13.2513(12) 21,3258(17) 90.00 110.051(5) 90.00 4259.0(6) 4 0.22 × 0.16 × 0.03 0.710 73 1.35-25.02 -19 e h e 19 -9 e k e 15 -25 e l e 25 29 686 7481 0.9827, 0.8822 full-matrix least squares on F2 7481/0/559 1.003 R1 ) 0.0668, wR2 ) 0.1328 R1 ) 0.1557, wR2 ) 0.1669 1.081 and -0.820 e Å-3

12c C32H33BI3N8PRu 1053.21 P1j 10.9119(2) 13.0330(3) 15.0779(3) 92.503(2) 104.852(2) 108.897(2) 1942.04(7) 2 0.20 × 0.20 × 0.10 0.710 73 2.98-27.50 -14 e h e 14 -16 e k e 16 -19 e l e 19 15 905 8834 1.000 00, 0.775 22 8834/0/421 1.020 R1 ) 0.0333, wR2 ) 0.0803 R1 ) 0.0438, wR2 ) 0.0852 2.034 and -1.679 e Å-3

In contrast, in the case of compound 1, the two N-N bonds (1.054(5) Å for N(7)-N(8) and 1.235(6) Å for N(8)-N(9)) are significantly different. A similar tendency was also observed in [n-Bu4N][Ir(pc)(N3)(aC)] (where pc is phthalocyaninate and aC is acetonato; 0.94(1)/0.88(1) Å versus 1.22(2)/ 1.35(2) Å).20c The third canonical form, in which the bond between the coordinated and the central N atoms is a triple bond as shown Scheme 1, would be possible, but in this case the M-N-N linkage should be linear, similar to the case for organic diazo or nitrile complexes. The Ru1-N7-N8 linkage is apparently not linear, with Ru1-N7-N8 ) 123.6(3)°. Although we cannot explain appropriately the unusual nature of the coordinated azide ligand on 1 at present, the contribution from the third canonical form may be important to some extent for the weakly bound azide ligand. The Tp ligand is often compared with the Cp (Cp ) η5-C5H5) ligand due to their charge and number of electrons donated in the formation of a complex. This comparison notwithstanding, differences in size and electronic properties are obvious. Thus, the cone angle of Tp at close to 180° is well above the 100° calculated for Cp. The steric bulk of the Tp ligand appears to disfavor higher coordination numbers or bulky structure of the metal center. The analogous Cp complex of 112a is stable with respect to the ligand substitution reaction; that is, the phosphine ligand bonds strongly to the ruthenium center, making the coordination site unavailable for an incoming substrate. In contrast, the Tp complex 1 is susceptible to ligand substitution reactions under relatively mild conditions. This may be attributed to the increased steric bulkiness of the Tp ligand relative to Cp. Facile ligand substitution is observed when the neutral ruthenium azido complex (PPh3)[Ru]-N3 (1; [Ru] ) Tp(PPh3)Ru) is treated with CH3CN, yielding the nitrile-substituted ruthenium azido complex (CH3CN)[Ru]-N3 (2). Complex 2 is stable in ether, THF, and CH3CN but decomposes in CDCl3. The IR spectrum of 2 shows a medium-intensity band at 2046 cm-1 due to the terminal azido group and a strong band at 2256 cm-1 characteristic of the N-coordinated nitrile ligand. The 31P NMR spectrum of 2 displays a singlet resonance at δ 54.2, and the 1H NMR resonance attributed to the CH3CN ligand appears at δ 2.24.

Ruthenium Azido Complexes Scheme 2

Reaction of 2 with DMAD or DEAD. Treatment of complex 2 with an excess of dimethyl acetylenedicarboxylate (DMAD) in CH2Cl2 at room temperature for 3 h affords the N(2)-bound 4,5-bis(methoxycarbonyl)-1,2,3-triazolato complex (CH3CN)[Ru]N3C2(CO2Me)2 (3a) in 91% isolated yield (Scheme 2). The formation of 3a was readily confirmed by the disappearance of the characteristic azide IR absorption and the appearance of sharp peaks at 1736 and 1438 cm-1 corresponding to the characteristic stretching frequency of CdO and NdN groups, respectively. However, attempts to synthesize the corresponding triazole complexes (PPh3)[Ru]-N3C2(CO2Me)2 from 1 have failed so far. It is possible that the more sterically demanding bis triphenylphosphine groups compared to CH3CN may prevent cycloaddition at the terminal azide around the ruthenium center. Complex 3a is soluble in polar solvents but insoluble in nonpolar solvents and is air stable. The structure of 3a is clearly established as the N(2)-bound isomer from the appearance of its 1H NMR spectrum, which shows a singlet at δ 3.63 for the six methoxycarbonyl protons. The 1H NMR spectrum of an N(1)-bound isomer would exhibit two resonances for its anisochronous methoxycarbonyl groups. When the reaction was monitored by 31P NMR spectroscopy, two singlet resonances at δ 51.9 and 51.7 attributed to the N(1)- and N(2)-bound isomers, respectively, were observed at the initial stage of the reaction. The N(1)-bound isomer, in hours at room temperature, converted to the N(2)-bound isomer. The FAB mass spectrum displays a parent peak at m/z 802.2 (M+). It should be noted that the triazole and tetrazole anion could be coordinated to the metal through either its N(1) or N(2) nitrogen atoms,21 which are essentially isoenergetic, as indicated by molecular orbital calculations.22 Evidence obtained to date indicates that either the two N(1)- and N(2)-bonded isomers are formed simultaneously23 or only the N(2)-bound isomer is produced exclusively.24 In our case, the N(2)-bound isomer is produced exclusively. Significantly, the reaction of 2 with either dimethyl fumarate or dimethyl maleate gives 3a, identical with the reaction of 2 with DMAD. The yields of the reactions are 99% and 83%, respectively. The reaction is completed in 2 days at room temperature. A small sharp peak of free H2 at δ 4.61 was observable in the 1H NMR spectrum and confirmed by GC. In (21) Paul, P.; Nag, K. Inorg. Chem. 1987, 26, 2969. (22) (a) Nelson, J. H.; Schmitt, D. L.; Henty, R. A.; Moore, D. W.; Jonassen, H. B. Inorg. Chem. 1970, 9, 2678. (b) Redfield, D. A.; Nelson, J. H.; Henry, R. A.; Moore, D. W.; Jonassen, H. B. J. Am. Chem. Soc. 1974, 96, 6298. (23) Kieft, R. L.; Peterson, W. M.; Blundell, G. L.; Horton, S.; Henry, R. A.; Jonasson, H. B. Inorg. Chem. 1976, 15, 1721. (24) Kemmerich, T.; Nelson, J. H.; Takach, N. E.; Boeheme, H.; Jablonski, B.; Beck, W. Inorg. Chem. 1982, 21, 1226.

Organometallics, Vol. 28, No. 12, 2009 3361

both reactions, complex 3a is formed by [3 + 2] cyclization between the azido ligand and a CdC double bond following removal of a H2 molecule. There are a few examples of cycloaddition of alkenes to coordinated azides,25 but most of the alkenes investigated did not produce pure products and the triazolinates produced were generally thermally unstable and base sensitive. Generally, these reactions occur over a long period of time, as is the case for the corresponding alkyne reactions.8 Similarly, the preparation of the N(2)-bound 4,5-bis(ethoxycarbonyl)-1,2,3-triazolato complex (CH3CN)[Ru]-N3C2(CO2CH2CH3)2 (3b) was accomplished in high yield by treating 2 with diethyl acetylenedicarboxylate (DEAD). The formation of the complex was readily confirmed by the disappearance of the characteristic azide peak and the subsequent appearance of sharp peaks at 1733 and 1435 cm-1 corresponding to the characteristic stretching frequencies of CdO and NdN, respectively. The 1H NMR spectrum shows a quartet at δ 4.11 and a triplet at δ 1.16 indicating the ethoxy protons. The 31P NMR resonance of 3b appears at δ 51.1. The FAB mass spectrum displays a parent peak at m/z 830.2 (M+). Reactions of Triazolato Complexes with Electrophiles. No alkylation is observed when 3a is treated with CH3I, CH3CH2I, and CH2dCHCH2I, but treatment of 3a with BrCH2C6F5 in CDCl3 at room temperature in a 5 mm NMR tube causes cleavage of the Ru-N bond and affords (CH3CN)[Ru]-Br and the N(1)-alkylated five-membered-ring organic triazole N3(CH2C6F5)C2(CO2Me)2 (4a) (Scheme 2). The alkylation was monitored by NMR spectroscopy. In the 31P NMR spectrum, the resonance of 3a at δ 51.7 disappeared and a resonance at δ 42.29 attributed to (CH3CN)[Ru]-Br appeared. In the 1H NMR spectrum two singlet resonances appear at δ 3.98 and 3.86, attributed to two anisochronous methoxycarbonyl groups of 4a. The FAB mass spectrum of the crude mixture displayed parent peaks at m/z 697.1 and 366.1, attributed to [Ru]-Br and 4a, respectively. Similar reaction of 3a with other organic bromides gives [Ru]-Br and the N(1)-alkylated five-membered-ring organic triazoles N3(R)C2(CO2Me)2 (4b, R ) CH2Ph; 4c, R ) CH2CH3). The structures of these free triazoles are clearly established as N(1)-alkylated from the appearance of their 1H NMR spectra, which exhibit two proton resonances for their anisochronous methoxycarbonyl groups. The free triazoles 4a-c, which mix with excess organic halides in n-hexane, are hard to isolate. Alkylation of triazolato cobalt chelate complexes was carried out by Nelson and co-workers,24 but isolation of the free triazole was not successful either. Reaction of 2 with Methyl Propiolate. Treatment of complex 2 with a 11-fold excess of methyl propiolate in CH2Cl2 at room temperature for 8 h affords the N(2)-bound 4-(methoxycarbonyl)-1,2,3-triazolato complex (CH3CN)[Ru]-N3C2HCO2Me (5), in 85% isolated yield. When the reaction was monitored by 31P NMR spectroscopy, two singlet resonances at δ 51.5 and 51.8, attributed to the N(1)- and N(2)-bound isomers, respectively, were observed at the initial stage of the reaction. The N(1)-bound isomer, over about 2 h at room temperature, converted to the N(2)-bound isomer. The 1H NMR spectrum displays a characteristic singlet resonance at δ 7.02 assigned to the CH proton of the triazole group;12a in addition, a singlet resonance at δ 3.64 is attributed to the three methoxycarbonyl protons. Reaction of 2 with Fumaronitrile. Treatment of 2 with fumaronitrile at room temperature for 12 h affords the N(2)(25) Paul, P.; Chakladar, S.; Nag, K. Inorg. Chim. Acta 1990, 170, 27.

3362 Organometallics, Vol. 28, No. 12, 2009

Chen et al.

Scheme 3

bound 4-cyano-1,2,3-triazolato complex (CH3CN)[Ru]-N3C2HCN] (6), in 86% isolated yield (Scheme 3). The infrared spectrum of the complex shows sharp peaks at 2242 and 1436 cm-1 assignable to the stretching frequencies of the CtN and NdN groups, respectively. The 1H NMR spectrum displays a characteristic singlet resonance at δ 7.04, assigned to the CH proton of the triazole group,12a and a singlet resonance at δ 2.24, attributed to the protons of the CH3CN ligand. The 31P NMR resonance of this complex appears at δ 51.7. In the 13C NMR, a resonance at δ 113.8 is assigned to C(CN). The FAB mass spectrum displays a parent peak at m/z 711.2 (M+). When the reaction was monitored by 31P NMR spectroscopy, two singlet resonances at δ 51.8 and 51.7, attributed to the N(1)- and N(2)bound isomers, respectively, were observed at the initial stage of the reaction. The N(1)-bound isomer, over hours at room temperature, converted to the N(2)-bound isomer. The complex is soluble in polar solvents such as acetone, chloroform, methanol, etc. and is also air-stable. The cycloaddition reaction of fumaronitrile to coordinated azide can take place via the CdC or CtN bond. The product 6, formed by [3 + 2] cyclization between the azido ligand and a CdC double bond following removal of a HCN molecule, is clearly established. In addition, the reaction of the coordinated azide ligand in the Ni(II) complex with CH2dCHCN gave a triazolinato complex.5a A pathway via direct cyclization of HCtCCN with azide, resulting in the formation of triazolate, has been reported.26 The formation of 6 can also be readily confirmed by the disappearance of the azide peak at 2046 cm-1 and the simultaneous appearance of the peak for the CtN group at 2221 cm-1. Reaction of 2 with TCNE. The azido complex 2 was reacted with excess tetracyanoethylene in dichloromethane at room temperature. The reaction mixture turned deep green after 1 h. Continued stirring up to 36 h ensured complete reaction. This afforded the tetrazolato complex (CH3CN)[Ru]-N4C[C(CN)d C(CN)2] (7) in good yield. When the reaction was monitored by 31P NMR spectroscopy, two singlet resonances at δ 52.9 and 52.6, attributed to the N(1)- and N(2)-bound isomers, respectively, were observed at the initial stage of the reaction. The N(1)-bound isomer, over hours at room temperature, converted to the N(2)-bound isomer. The infrared spectrum exhibits sharp peaks at 2242 and 1430 cm-1 assigned to the stretching frequencies of CtN and NdN groups, in good

(26) Huisgen, R.; Szeimies, G.; Mobius, L. Chem. Ber. 1966, 99, 475.

Figure 2. ORTEP drawing of 8 with thermal ellipsoids shown at the 50% probability level. Dichloromethane molecules are omitted for clarity. Table 3. Selected Bond Distances (Å) and Angles (deg) of [(CN)2CdC(CN)2][Ru]-N4C[C(CN)dC(CN)2] (8) Ru(1)-N(1) Ru(1)-N(5) Ru(1)-N(14) N(7)-N(8) N(8)-N(9) C(28)-N(10) N(8)-N(7)-Ru(1) N(10)-C(28)-N(9) N(9)-N(8)-N(7) N(7)-Ru(1)-N(3) N(7)-Ru(1)-N(5) N(1)-Ru(1)-N(5) N(10)-C(28)-N(9) N(14)-Ru(1)-P(1) N(1)-Ru(1)-P(1) N(5)-Ru(1)-P(1) N(14)-C(34)-C(35)

2.111(6) 2.095(5) 1.946(6) 1.335(7) 1.326(7) 1.319(9) 126.3(4) 112.9(6) 108.3(5) 173.6(2) 87.3(2) 84.4(2) 112.9(6) 90.64(15) 95.70(16) 179.92(17) 178.7(7)

Ru(1)-N(3) Ru(1)-N(7) Ru(1)-P(1) N(7)-N(10) N(9)-C(28) N(14)-C(34) N(7)-N(10)-C(28) C(28)-N(9)-N(8) N(7)-Ru(1)-N(1) N(7)-Ru(1)-N(3) N(1)-Ru(1)-N(3) N(3)-Ru(1)-N(5) C(28)-N(9)-N(8) N(7)-Ru(1)-P(1) N(3)-Ru(1)-P(1) C(34)-N(14)-Ru(1) C(37)-C(35)-C(34)

2.071(5) 2.044(5) 2.3532(18) 1.329(6) 1.336(9) 1.153(8) 103.8(6) 104.6(5) 93.6(3) 173.6(2) 87.5(2) 86.6(2) 104.6(5) 92.65(15) 93.45(15) 175.6(5) 122.4(7)

agreement with the reported values.27 The 1H NMR spectrum shows a singlet at δ 2.11 for the CH3CN protons, where the upfield shift here is due to the increased electron density on the metal center. The 31P NMR spectrum of this complex displays a singlet at δ 52.6. The formation of complex 7 is also conformed by the disappearance of the terminal azide peak and by the appearance of the stretching frequency of CtN groups. If the reaction is carried out at 35 °C, the new N(2)-bound product [(CN)2CdC(CN)2][Ru]-N4C[C(CN)dC(CN)2] (8) could be isolated in moderate yield. That the product 8 is obtained when CtN adds to coordinated azide is established by a singlecrystal X-ray diffraction study. An ORTEP diagram is shown in Figure 2, and selected bond distances and bond angles are given in Table 3. The planar five-membered tetrazolato ring is coordinated to the Ru center via the N(7) atom. Although the variation in bond distances is larger than those of triazolates,12 the bonding mode of this tetrazolate is probably best described as a π-delocalized bond in this five-membered ring. The analogous Cp complex of 712a is stable with respect to the ligand substitution reaction; that is, the phosphine ligand bonds strongly (27) (a) Sarjit Singh, K.; Kreisel, K. A.; Yap, G. P. A.; Mohan Rao, K. J. Organomet. Chem. 2006, 691, 3509. (b) Sarjit Singh, K.; Tho¨ne, C.; Mohan Rao, K. J. Organomet. Chem. 2005, 690, 4222. (c) Sarjit Singh, K.; Kreisel, K. A.; Yap, G. P. A.; Mohan Rao, K. J. Coord. Chem. 2007, 60, 505.

Ruthenium Azido Complexes

Organometallics, Vol. 28, No. 12, 2009 3363 Scheme 4

to the ruthenium center, making the coordination site unavailable for an incoming TCNE substrate. The reactivity is highly related to the nature of the nitrile. Benzonitrile, acetonitrile, CF3CN, and HPhCdC(CN)2 do not react with complex 2, even under drastic, vigorous conditions. Typically, tetrazoles are prepared from the corresponding nitriles by reaction with a hydrazoic source (e.g., sodium azide and ammonium chloride).28,29 Alternative strategies, involving different azide anion sources such as trimethylsilyl azide in the presence of dialkyltin oxide,30 have been developed for the conversion of amides into 1,5disubstituted tetrazoles.31 In addition, reaction of a cyanosubstituted cyclopropenyl complex with trimethylsilyl azide reportedly gave a tetrazolato complex.18,32 Intriguingly, treatment of the yellow complex 2 with excess ICH2CN at room temperature afforded the brown N-coordinated iodoacetonitrile complex {(CH3CN)[Ru]-NCCH2I}[N3] (9). Surprisingly, no iodide addition was observed; instead, the coordinated N3- is readily replaced by ICH2CN without cleavage of the C-I bond. In the 1H NMR spectrum of 9, two singlet resonances at δ 4.50 and 2.18 are assigned to CH2 and CH3CN, respectively. The 31P NMR spectrum displays a singlet resonance at δ 41.1. Complex 9 is stable in air, soluble in most polar solvents such as CH2Cl2, acetone, acetonitrile, THF, and MeOH, and moderately soluble in n-pentane and n-hexane. Apparently, not only the steric effect but also the inductive effect should be considered as important driving forces for the reaction of the complex 2 with nitrile. Reaction of 2 with CS2. CS2 reacts with 2 to give the thiothiazolinate product (CH3CN)[Ru]-N3CS(S) (10); however, the thiothiazolinate product could not be isolated in pure form due to its low thermal stability; instead, the thiocyanato complex (CH3CN)[Ru]-NCS (11) was obtained after a prolonged reaction time. The formation of complex 11 is also confirmed by the disappearance of the terminal azide peak and by the appearance of the stretching frequency of the NCS group (observed at 2116 cm-1). In the 1H NMR spectrum of 11, one singlet resonance at δ 2.24 is assigned to CH3CN and the 31P NMR spectrum displays a singlet resonance at δ 43.8. The FAB mass spectrum (28) Palazzi, A.; Stagni, S.; Bordoni, S.; Monari, M.; Selva, S. Organometallics 2002, 21, 3774. (29) (a) Koguro, K.; Oga, T.; Mitsui, S.; Orita, R. Synthesis 1998, 910. (b) Demko, Z. P.; Sharpless, K. B. J. Org. Chem. 2001, 66, 7954. (30) Wittenberger, S. J.; Donner, B. G. J. Org. Chem. 1993, 58, 4139. (31) (a) Duncia, J. V.; Pierce, M. E.; Santella, J. B., III. J. Org. Chem. 1991, 56, 2395. (b) Thomas, E. W. Synthesis 1993, 676, 34. (32) Chang, K. H.; Lin, Y. C.; Liu, Y. H.; Wang, Y. Dalton Trans. 2001, 3154.

shows the parent peak at m/z 676.1 as well as peaks at m/z 635.2 and 618.1 due to loss of a CH3CN and an NCS ligand, respectively. Reactions of 2 with Electrophiles. The methyleneimine complex [Tp(PPh3)(CH3CN)Ru(NHdCH2)]I (12a) was synthesized by the reaction of 2 with 5-fold excess CH3I in CH2Cl2 (Scheme 4). Significantly, when the reaction was repeated using only 1 equiv of CH3I, much lower yields of the product (ca. 15%) were obtained. The IR spectrum of 12a shows characteristic bands at 3183 and 2241 cm-1, assigned to ν(NH) and ν(CN), respectively. The 31P NMR spectrum of this complex displays a singlet at δ 54.4. The 1H NMR spectrum in CDCl3 shows a broad signal for the hydrogen atom of the imine function (NHdCH2) at δ 12.41 as a doublet of doublets owing to coupling with two protons at δ 7.89 and 6.89 (NHdCH2). These two signals overlap with the Ph signals in the aromatic region and were revealed by the H,H COSY spectrum. The δ value of the hydrogen atom of the imine group is similar to that of the CH2dNH-κN and -κ2N,C groups.33 The 13C NMR spectrum shows a signal at δ 169.31, which is assigned to the carbon atoms of the methyleneimine, analogous to that of the known Os complex.34 A few metal complexes containing a methyleneimine moiety (NHdCH2) have been synthesized by the reaction of a methylhydrazine or methylimido complex.35 Methyleneimine is known to be a reactive molecule, and its existence can be recognized only at low temperatures by IR spectroscopy.36 We believe that the methyleneimine ligand is formed by the reaction of CH3I with the negatively charged nitrogen atom of the azido ligand on Ru via a methylimido intermediate with N2 evolution and proton transfer from the methyl group to the imido nitrogen atom, as in the formation of a methyleneimine-κ2N,C osmium complex from a methylimido-κN analogue.34 Similarly, treatment of 2 with 5-fold excess CH3CH2Br and H2CdC(H)CH2I in CH2Cl2 at room temperature for 5 h afforded the cationic imine complexes [Tp(PPh3)(CH3CN)Ru(NHdCH(CH3))]Br (12b) and [Tp(PPh3)(CH3CN)Ru(NHdCH (CdCH2))][I3] (12c), respectively. Good analytical data were obtained for cationic imine complexes 12b,c, which are bright yellow solids (33) Albertin, G.; Antoniutti, S.; Bacchi, A.; Fregolent, B.; Pelizzi, G. Eur. J. Inorg. Chem. 2004, 1922. (34) Shapley, P. A.; Shusta, J. M.; Hunt, J. L. Organometallics 1996, 15, 1622. (35) Albertin, G.; Antoniutti, S.; Giorgi, M. T. Eur. J. Inorg. Chem. 2003, 2855. (36) (a) Milligan, D.; Jacox, M. E. J. Chem. Phys. 1963, 39, 712. (b) Milligan, D. E. J. Chem. Phys. 1961, 35, 1491.

3364 Organometallics, Vol. 28, No. 12, 2009

Chen et al. Table 5. Conversion and Product Distribution of the Catalytic Dimerization of Terminal Alkynesa

R

solvent

%a

%b

Phb Phc SiMe3b t -Bud COOMee

CH2Cl2 water CH2Cl2 CH2Cl2 CH2Cl2

96 96

4 4 86 100

100

%c

% conversn

14

96 95 25 10 80

a

Yields are for isolated products. The product distribution has been determined by NMR spectroscopy. b Reactions were performed in boiling CH2Cl2 for 20 h. c Reactions were performed in boiling water for 20 h. d Reaction was performed in boiling CH2Cl2 for 68 h. e Reaction was performed in CH2Cl2 at room temperature for 24 h.

Figure 3. ORTEP drawing of 12c with thermal ellipsoids shown at the 50% probability level. Table 4. Selected Bond Distances (Å) and Angles (deg) of [Tp(PPh3)(CH3CN)Ru(NHdCH(CHdCH2))][I3] (12c) Ru(1)-N(1) Ru(1)-N(5) Ru(1)-N(7) N(7)-C(12) C(13)-C(14) C(10)-C(11) N(8)-Ru(1)-N(7) N(7)-Ru(1)-N(1) N(7)-Ru(1)-N(3) N(8)-Ru(1)-N(5) N(1)-Ru(1)-N(5) N(8)-Ru(1)-P(1) N(1)-Ru(1)-P(1) N(5)-Ru(1)-P(1) N(7)-C(12)-C(13) C(10)-N(8)-Ru(1)

2.080(3) 2.105(3) 2.036(3) 1.282(5) 1.331(7) 1.447(5) 89.27(11) 92.64(11) 173.35(11) 86.59(10) 85.53(10) 94.88(8) 92.98(8) 178.32(7) 125.6(4) 172.9(3)

Ru(1)-N(3) Ru(1)-N(8) Ru(1)-P(1) C(12)-C(13) N(8)-C(10) N(8)-Ru(1)-N(1) N(8)-Ru(1)-N(3) N(1)-Ru(1)-N(3) N(7)-Ru(1)-N(5) N(3)-Ru(1)-N(5) N(7)-Ru(1)-P(1) N(3)-Ru(1)-P(1) C(12)-N(7)-Ru(1) C(14)-C(13)-C(12) N(8)-C(10)-C(11)

2.092(3) 2.017(3) 2.3425(8) 1.434(6) 1.131(4) 171.81(11) 88.88(10) 88.32(10) 87.77(11) 85.74(10) 93.05(8) 93.47(8) 130.9(3) 121.0(5) 177.5(4)

stable in air and in solution of polar organic solvents. The IR spectrum of 12c shows a weak-intensity band at 3184 cm-1, due to the NH of the imine group. The 31P NMR spectrum of this complex displays a singlet at δ 54.6. The 1H NMR spectrum of 12c in CDCl3 shows a broad signal for the hydrogen atom of the imine function (NHdCH) at δ 11.80 as a doublet owing to coupling with the signals at δ 6.77 (NHdCH). Conclusive support for the formulation of 12c came from the X-ray diffraction analysis (Table 1). An ORTEP diagram is shown in Figure 3, and Table 4 gives selected bond distances and angles. The allylimine ligand coordinates to the ruthenium center in a bent fashion with Ru-N7-C12 ) 130.9(3)° and with Ru-N7 ) 2.036(3) and N7-C12 ) 1.282(5) Å. This coordination fashion is similar to that of the reported κN-mode coordination rhenium complex.37 Interestingly, the Ru-N7-C12 and N7-C12-C13 angles, 130.9(3) and 125.6(5)°, respectively, are remarkably large. Dimerization of Terminal Alkynes in Organic and Aqueous Media. Reaction of 2 with an excess of Et3N and HCtCPh in CH2Cl2 at reflux for 24 h did not yield the expected N(2)bound 4-phenyl-1,2,3-triazolato complex (CH3CN)[Ru]N3C2HPh but instead gave the head to-head dimer (E)-1,4(37) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bordignon, E.; Giorgi, M. T.; Pelizzi, G. Angew. Chem. 2002, 114, 2296; Angew. Chem., Int. Ed. 2002, 41, 2192.

diphenyl-1-buten-3-yne (13a) and small amounts of the Z isomer (13b) in high yields (Table 5). The Z isomer is characterized by well-resolved doublets at δ 5.79 with JHH ) 11.8 Hz and δ 6.40 with JHH ) 11.8 Hz, while the E isomer has a distinct resonance at δ 6.30 with JHH ) 16.2 Hz and δ 7.04 with JHH ) 16.2 Hz. It should be mentioned that the coupling reactions take place in both nonprotic and protic solvents. The conversion decreases from 96% in CH2Cl2 to 74% in toluene and 48% in MeOH. High conversion in CH2Cl2 could be due to the high solubility of ruthenium complex 2. Chemical reactions in aqueous medium are of growing importance because of many potential advantages, such as the alleviation of environmental problems associated with the use of organic solvents.38 Since the complex 2 has some solubility in polar solvents, the dimerization reactions were attempted in water. Surprisingly, HCtCPh could be dimerized in water with a selectivity for the E isomers essentially identical with that observed in organic medium. To our knowledge, this is the first example that dimerization of alkynes with the ruthenium azido complex to give (E)-enynes has been carried out in water. It is known that ruthenium complexes (e.g., CpRuCl(PPh3)2 and (PNP)RuCl2(PPh3)) can promote either the hydration39 or the hydrolysis of alkynes.40 In our case, no product resulting from either reaction was detected by 1H NMR and confirmed by GC/MS. For HCtCSiMe3 the regioselectivity is reversed with respect to R ) Ph, giving no 14a but instead 14b (86%) together with the head-to-tail dimer 2,4-bis(trimethylsilyl)-1-buten-3-yne (14c; 14%) with slightly reduced conversion relative to R ) Ph. For R ) t-Bu, finally, only the formation of the head-to-head isomer 15b is observed, with the conversion dropping to about 10% even after a reaction time of 68 h. Significantly, reaction of 2 with excess HCtCCO2Me in CH2Cl2 at room temperature afforded the N(2)-bound 4-(methoxycarbonyl)-1,2,3-triazolato complex (CH3CN)[Ru]N3C2HCO2Me (5), but the reaction carried out in the presence of Et3N produced exclusiVely the linear dimer (E)-MeO2CCHdCHCtCCO2Me (16a) in an 80% isolated yield. The rate of the formation of 16a at room temperature was faster than that of the formation of 13a, and no other dimeric or higher oligomeric products were detected by 1H NMR. Normally, a (38) Joo, F. Aqueous Organometallic Catalysis; Kluwer: Dordrecht, The Netherlands, 2001. (39) (a) Tokunaga, M.; Suzuki, T.; Koga, N.; Fukushima, T.; Horiuchi, A.; Wakatsuki, Y. J. Am. Chem. Soc. 2001, 123, 11917. (b) Grotjahn, D. B.; Lev, D. A. J. Am. Chem. Soc. 2004, 126, 12232. (40) Bianchini, C.; Casares, J. A.; Peruzzini, M.; Romerosa, A.; Zanobini, F. J. Am. Chem. Soc. 1996, 118, 4585.

Ruthenium Azido Complexes

Organometallics, Vol. 28, No. 12, 2009 3365 Scheme 5

metal-mediated homocoupling reaction of HCtCCO2Me has been well-known to preferentially give the cyclotrimerization products.41 A detailed mechanism for the dimerization reactions mediated by the (CH3CN)[Ru]-N3 system is not yet clear, as the intermediates of the dimerization reactions have not been identified. It has been established that dimerization of HCtCR mediated by the very similar precursor Tp(PPh3)2Ru-Cl proceeds through the coupling of vinylidene and acetylide ligands.42 We believe that HCtCR species react as CH acids and undergo a ligand substitution reaction rather than a 1,3dipolar cycloaddition with 2 in the presence of Et3N to produce acetylide complexes (CH3CN)[Ru]-CtCR with liberation of HN3. Thus, it is very likely that the present formation of enynes may involve a similar mechanism (Scheme 5). However, unlike Tp(PPh3)2Ru-Cl, HCtCR could be dimerized by the complex 2 in protic solvents such as H2O and CH3OH. At present, the mechanism of dimerization reactions can only be speculated upon. Further work is in progress and will be reported in a forthcoming paper. Concluding Remarks. The reaction of the ruthenium azido complex (CH3CN)[Ru]-N3 (2; [Ru] ) Tp(PPh3)Ru) and alkynes or alkenes with electron-withdrawing substituents yielded a series of addition products via a [3 + 2] cycloaddition of a CtC or CdC bond with the azido group. However, addition of a TCNE molecule to 2 resulted in a [3 + 2] cycloaddition via (41) (a) Vollhart, K. P. C. Angew. Chem., Int. Ed. Engl. 1984, 23, 539. (b) Schore, N. E. Chem. ReV. 1988, 88, 1081. (42) Slugovc, C.; Mereiter, K.; Zobetz, E.; Schmid, R.; Kirchner, K. Organometallics 1996, 15, 5275.

the CtN and azido group and afforded a tetrazolato product. Complete characterization of these triazolato and tetrazolato complexes elucidates the structures and establishes the N(2)bonding type of the addition products. Reaction of (CH3CN)[Ru]N3C2(CO2Me)2 (3a) with organic bromides gave (CH3CN)[Ru]Br and a series of 1,4,5-trisubstituted organic triazoles, N3(R)C2(CO2Me)2 (R ) CH2C6F5, 4a; R ) CH2Ph, 4b; R ) CH2CH3, 4c). On the other hand, several cationic imine complexes {(CH3CN)[Ru]-(NHdCHR)}+ (12a, R ) H, 12b, R ) CH3, 12c, R ) HCdCH2) are formed by the reaction of RCH2X with the negatively charged nitrogen atom of the azido ligand on RuII. The reaction proceeds via formation of an alkylimido intermediate followed by N2 evolution and proton transfer from the alkyl group to the imido nitrogen atom. The complex 2 effectively catalyzes the dimerization of terminal alkynes in high regio- and stereoselectivity. The catalyst is reasonably air stable and can tolerate a number of functional groups, which allows for its use in organic and aqueous media.

Experimental Section General Procedure. All manipulations were performed under nitrogen using vacuum-line, drybox, and standard Schlenk techniques. CH3CN and CH2Cl2 were distilled from CaH2 and diethyl ether and THF from Na/ketyl. All other solvents and reagents were of reagent grade and were used without further purification. NMR spectra were recorded on Bruker AC-200 and AM-300WB FTNMR spectrometers at room temperature (unless stated otherwise) and are reported in δ units with residual protons in the solvent as an internal standard (CDCl3, δ 7.24; CD3CN, δ 1.93; C2D6CO, δ 2.04). FAB mass spectra were recorded on a JEOL SX-102A

3366 Organometallics, Vol. 28, No. 12, 2009 spectrometer. Tp(PPh3)2RuCl43 was prepared by following the method reported in the literature. Elemental analyses and X-ray diffraction studies were carried out at the Regional Center of Analytical Instrument at National Taiwan University. Preparation of Tp(PPh3)2Ru-N3 (1). To a solution of Tp(PPh3)2RuCl (2.00 g, 2.28 mmol) in 50 mL of MeOH was added excess NaN3 (2.00 g, 30 mmol), and the solution was heated to reflux for 24 h. The yellow precipitates formed and, after cooling, were filtered off and washed with CH2Cl2 and n-hexane. This yellow solid product was dried under vacuum to give compound 1 (1.58 g, 78% yield). Spectroscopic data for 1 are as follows. IR (KBr, cm-1): ν(B-H) 2478 (br), ν(N3) 2046 (vs). 1H NMR (CDCl3): δ 7.59 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.55 (d, JH-H ) 2.1 Hz, 2H, Tp), 7.24-6.91 (m, PPh3), 6.67 (d, JH-H ) 2.1 Hz, 2H, Tp), 5.74 (t, JH-H ) 2.1 Hz, 2H, Tp), 5.31 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.17 (d, JH-H ) 2.1 Hz, 1H, Tp). 13C NMR (acetone): δ 148.3-122.7 (m, Tp, PPh3). 31P NMR (CDCl3): δ 44.1. MS (FAB): m/z 881.2 (M+), 853.1 (M+ - N2), 839.1 (M+ - N3). Anal. Calcd for C45H40BN9P2Ru (880.69): C, 61.37; H, 4.58; N, 14.31. Found: C, 61.07; H, 4.54; N, 14.45. SynthesisoftheNitrile-SubstitutedAzidoComplexTp(PPh3)(CH3CN)Ru-N3 (2). To a solution of 1 (0.20 g, 0.23 mmol) in 30 mL of THF was added 10 mL of CH3CN. The solution was stirred for 22 h, the color changed from yellow to orange-yellow, and then the solution was filtered through Celite. The solvent of the filtrate was removed under vacuum, and the residue was washed with n-hexane to give 2 (0.13 g, 89% yield). Spectroscopic data for 2 are as follows. IR (KBr, cm-1): ν(B-H) 2474 (br), ν(CtN) 2256 (m), ν(N3) 2046 (vs). 1H NMR (acetone): δ 7.89 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.82 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.65 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.57-7.07 (m, Ph), 6.88 (1H, Tp), 6.72 (1H, Tp), 6.76 (1H, Tp), 6.02 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.98 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.85 (t, JH-H ) 2.2 Hz, 1H, Tp), 2.24 (s, 3H, CH3CN). 13 C NMR (CDCl3): δ 146.9 -105.6 (m, PPh3, Tp), 123.7 (CH3CN), 3.6 (CH3CN). 31P NMR (acetone): δ 54.2. MS (FAB): m/z 660.2 (M+), 619.3 (M+ - CH3CN), 577.1 (M+ - CH3CN, N3). Anal. Calcd for C29H28BN10PRu (659.45): C, 52.82; H, 4.28; N, 21.24. Found: C, 52.81; H, 4.21; N, 21.08. Synthesis of N(2)-Bound Tp(PPh3)(CH3CN)Ru-N3C2(CO2Me)2 (3a). To a Schlenk flask charged with 2 (0.10 g, 0.15 mmol) were added dimethyl acetylenedicarboxylate (234 mg, 1.65 mmol) and 20 mL of CH2Cl2. The mixture was stirred at room temperature for 3 h, and then the solvent was reduced to 2 mL under vacuum. To the residue was added 20 mL of n-hexane, giving a yellow precipitate. After filtration, the precipitate was washed with 2 × 10 mL of n-hexane and dried under vacuum to give the N(2)-bound Tp(PPh3)(CH3CN)Ru-N3C2(CO2Me)2 (3a; 0.11 g, 91% yield). The same product was formed by reaction of 2 (0.20 g, 0.30 mmol) with dimethyl fumarate (0.19 g, 0.825 mmol) at room temperature for 48 h. The yield was 99% (0.24 g, 0.29 mmol). Spectroscopic data for 3a are as follows. IR (KBr, cm-1): ν(B-H) 2472 (br), ν(CtN) 2248 (m), ν(CdO) 1736 (vs), ν(NdN) 1438 (s), ν(C-O) 1245 (m). 1H NMR (CDCl3): δ 7.92 (d, JH-H ) 2.3 Hz, 1H, Tp), 7.83 (d, JH-H ) 2.3 Hz, 1H, Tp), 7.71 (d, JH-H ) 2.3 Hz, 1H, Tp), 7.4-6.9 (m, Tp, Ph), 6.83 (d, JH-H ) 2.3 Hz, 1H, Tp), 5.81 (d, JH-H ) 2.2 Hz, 1H, Tp), 5.66 (d, JH-H ) 2.2 Hz, 1H, Tp), 5.63 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.54 (t, JH-H ) 2.2 Hz, 1H, Tp), 3.63 (s, 6H, OCH3), 2.22 (s, 3H, CH3CN). 13C NMR (CDCl3): δ 162.3 (CO2), 136.2 (C(CO2CH3)), 135.3-107.2 (m, Tp, PPh3), 121.9 (CH3CN), 51.6 (OCH3), 3.8 (CH3CN). 31P NMR (CDCl3): δ 51.7. MS (FAB): m/z 802.2 (M+), 761.3 (M+ - CH3CN), 577.1 (M+ CH3CN, N3C2(CO2Me)2). Anal. Calcd for C35H34BN10O4PRu (802.16): C, 52.44; H, 4.28; N, 17.47. Found: C, 52.41; H, 4.26; N, 16.98. (43) Nathaniel, W.; Alock, N. W.; Burns, I. D.; Claire, K. S.; Hill, A. F. Inorg. Chem. 1992, 31, 2906.

Chen et al. The N(2)-bound complex Tp(PPh3)(CH3CN)Ru-N3C2(CO2CH2CH3)2 (3b; 0.18 g, 72% yield from 0.20 g of 2) was prepared by using a procedure similar to that for 3a. Spectroscopic data for 3b are as follows. IR (KBr, cm-1): ν(B-H) 2468 (br), ν(CtN) 2246 (m), ν(CdO) 1733 (vs), ν(NdN) 1435 (s), ν(C-O) 1248 (m). 1H NMR (CDCl3): δ 8.01 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.86 (d, JH-H ) 2.3 Hz, 1H, Tp), 7.75 (d, JH-H ) 2.3 Hz, 1H, Tp), 7.49-7.07 (m, Tp, Ph), 6.85 (d, JH-H ) 2.2 Hz, 1H, Tp), 5.85 (d, JH-H ) 2.2 Hz, 1H, Tp), 5.70 (d, JH-H ) 2.2 Hz, 1H, Tp), 5.68 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.56 (t, JH-H ) 2.2 Hz, 1H, Tp), 4.11 (q, JH-H ) 7.1 Hz, 4H, OCH2), 2.22 (s, 3H, CH3CN), 1.16 (q, JH-H ) 7.1 Hz, 6H, OCH2CH3). 13C NMR (CDCl3): δ 162.8 (CO2), 140.2 (C(CO2CH2CH3)2), 139.2-107.3 (m, Tp, PPh3), 119.9 (CH3CN), 60.5 (OCH2), 14.2 (OCH2CH3), 3.6 (CH3CN). 31P NMR (CDCl3): δ 51.1. MS (FAB): m/z 830.2 (M+), 789.1 (M+ - CH3CN), 577.1 (M+ - CH3CN, N3C2(CO2CH2CH3)2). Anal. Calcd for C35H34BN10O4PRu (829.62): C, 53.57; H, 4.62; N, 16.88. Found: C, 53.61; H, 4.56; N, 16.78. Synthesis of N3(CH2C6F5)C2(CO2Me)2 (4a) and Other Organic Triazoles. To a solution of complex 3a (10 mg, 0.012 mmol) in CDCl3, prepared under N2 in an NMR tube, was added 1 drop (5 µL) of BrCH2C6F5. The reaction was carried out at 50 °C for 24 h, and the color changed from bright yellow to orange. Then the solvent and excess BrCH2C6F5 were removed under vacuum and washed with 1 mL of cold n-hexane. After filtration, the orange precipitate was washed with 1 mL of n-hexane and dried under vacuum to give the product Tp(PPh3)(CH3CN)Ru-Br (9.97 mg, 0.01 mmol, 86% yield). The filtrate was dried and extracted with 2 mL of cold n-hexane. The extract was filtered, and the filtrate was dried under vacuum to give a mixture of the organic triazole N3(CH2C6F5)C2(CO2Me)2 (4a). Spectroscopic data for 4a are as follows. 1H NMR (CDCl3): δ 5.86 (s, 2H, CH2), 3.98 (s, 3H, OCH3), 3.86 (s, 3H, OCH3). 13C NMR (CDCl3): δ 160.1 (CO2), 158.6 (CO2), 140.1 (C(CO2CH3)), 132.0 (C(CO2CH3)), 53.6 (OCH3), 52.8 (OCH3), 41.3 (CH3), 34.7 (NCH3). MS (m/z): 366.1 (M+ + 1). The complex N3(CH2Ph)C2(CO2Me)2 (4b) was prepared by a procedure similar to that for 4a. Spectroscopic data for 4b are as follows. 1H NMR (CDCl3): δ 7.86-7.14 (m, 5H, Ph), 5.78 (s, 2H, CH2), 3.98 (s, 3H, CH3), 3.88 (s, 3H, CH3). 13C NMR (CDCl3): δ 160.3 (CO2), 158.7 (CO2), 140.1 (C(CO2CH3)), 133.8 (C(CO2CH3)), 137.9-127.8 (Ph), 53.8 (OCH3), 52.6 (OCH3), 53.2 (CH2). MS (m/ z): 276.1 (M+ + 1). The complex N3(CH2CH3)C2(CO2Me)2 (4c) was prepared by a procedure similar to that for 4a. Spectroscopic data for 4c are as follows. 1H NMR (CDCl3): δ 3.95 (s, 3H, CH3), 3.87 (s, 3H, CH3), 2.89 (q, 2H, CH2, JH-H ) 7.6 Hz), 1.32 (t, 3H, CH3, JH-H ) 7.6 Hz). 13C NMR (CDCl3): δ 164.4 (CO2), 156.0 (CO2), 143.1 (C(CO2CH3)), 132.4 (C(CO2CH3)), 52.7 (OCH3), 52.3 (OCH3), 46.8 (CH2), 13.8 (CH3). MS (m/z): 214.1 (M+ + 1). Preparation of N(2)-Bound Tp(PPh3)(CH3CN)Ru-N3C2HCO2Me (5). To a Schlenk flask charged with 2 (0.10 g, 0.15 mmol) were added methyl propiolate (0.14 g, 148.2 µL, 1.69 mmol) and CH2Cl2 (20 mL). The mixture was stirred at room temperature for 8 h, and then the solvent was reduced to 2 mL under vacuum. To the residue was added 20 mL of n-hexane, giving a yellow precipitate. After filtration, the precipitate was washed with 10 mL of n-hexane and dried under vacuum to give the N(2)-bound Tp(PPh3)(CH3CN)Ru-N3C2HCO2Me (5; 0.095 g, 85% yield). Spectroscopic data for 5 are as follows. IR (KBr, cm-1): ν(B-H) 2465 (br), ν(CtN) 2242 (m), ν(CdO) 1728 (vs), ν(NdN) 1436 (s), ν(C-O) 1230 (m). 1H NMR (CDCl3): δ 7.84 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.83 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.43-7.10 (m, Ph, Tp), 7.02 (s, 1H, CH), 6.98 (d, JH-H ) 2.1 Hz, 1H, Tp), 6.68 (d, JH-H ) 2.1 Hz, 1H, Tp), 6.17 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.97 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.85 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.61 (t, JH-H ) 2.1 Hz, 1H, Tp), 3.64 (s, 3H, CH3), 2.24 (s, 3H, CH3CN). 13 C NMR (acetone): δ 163.8 (CO2), 147.4-127.1 (Ph, PPh3, Tp),

Ruthenium Azido Complexes 138.8 (C(CO2CH3)), 134.2 (CH), 122.5 (CH3CN), 50.6 (OCH3), 3.6 (CH3CN). 31P NMR (acetone): δ 51.8. MS (FAB): m/z 744.2 (M+), 703.1 (M+ - CH3CN), 577.1 (M+ - CH3CN, N3C2HCO2Me). Anal. Calcd for C33H32BN10O2PRu (933.53): C, 53.31; H, 4.34; N, 18.84. Found: C, 52.97; H, 4.37; N, 18.60. Preparation of N(2)-Bound Tp(PPh3)(CH3CN)Ru-N3C2HCN (6). To a Schlenk flask charged with 2 (0.10 g, 0.15 mmol) were added fumaronitrile (0.13 g, 1.603 mmol) and CH2Cl2 (20 mL). The mixture was stirred at room temperature for 24 h, and then the solvent was reduced to 2 mL under vacuum. To the residue was added 20 mL of n-hexane, giving a yellow precipitate. The precipitate was filtered, washed with 10 mL of n-hexane, and dried under vacuum to give the N(2)-bound Tp(PPh3)(CH3CN)RuN3C2HCN (6; 0.92 g, 86% yield). Spectroscopic data for 6 are as follows. IR (KBr, cm-1): ν(B-H) 2469 (br), ν(CtN) 2242 (m), ν(CtN) 2221 (vs), ν(NdN) 1436 (s). 1H NMR (CDCl3): δ 8.03 (br, 1H, Tp), 7.96 (br, 1H, Tp), 7.83 (br, 1H, Tp), 7.65 (br, 1H, Tp), 7.43-7.10 (m, Ph), 7.04 (s, 1H, CH), 6.53 (br, 1H, Tp), 6.24 (br, 1H, Tp), 6.03 (br, 1H, Tp), 5.83 (br, 1H, Tp), 5.40 (br, 1H, Tp), 2.24 (s, 3H, CH3CN). 13C NMR (CDCl3): δ 140.6 (C(CN)), 138.2 (CH), 139.2-117.3 (m, Tp, PPh3), 119.4 (CH3CN), 113.8 (C(CN)), 3.9 (CH3CN). 31P NMR (acetone): δ 51.7. MS (FAB): m/z 711.2 (M+), 670.1 (M+ - CH3CN), 577.1 (M+ - CH3CN, N3C2HCN). Anal. Calcd for C32H29BN11PRu (710.5): C, 54.09; H, 4.11; N, 21.69. Found: C, 53.97; H, 4.07; N, 21.40. Synthesis of Tp(PPh3)(CH3CN)Ru-N4C[C(CN)dC(CN)2] (7). Dichloromethane (20 mL) was added to a round-bottomed flask charged with complex 2 (0.10 g, 0.15 mmol) and tetracyanoethylene (0.076 g, 0.60 mmol). The reaction mixture was stirred at room temperature for 36 h. The solvent was evaporated under reduced pressure to 5 mL. To the solution was added 20 mL of n-hexane, whereupon a deep blue compound precipitated. The precipitate was filtered, washed with 10 mL of n-hexane, and dried under vacuum to yield Tp(PPh3)(CH3CN)Ru-N4C[C(CN)dC(CN)2] (7; 1.08 g, 92% yield). Spectroscopic data for 7 are as follows. IR (KBr, cm-1): ν(B-H) 2464 (br), ν(CtN) 2242 (m), ν(CtN) 2228 (vs), ν(CtN) 2196 (vs), ν(NdN) 1430 (s). 1H NMR (CD3C(O)CD3): δ 7.65 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.57 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.49 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.42-7.17 (m, Ph), 6.98 (1H, Tp), 6.78 (1H, Tp), 6.76 (1H, Tp), 6.33 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.98 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.85 (t, JH-H ) 2.2 Hz, 1H, Tp), 2.11 (s, 3H, CH3CN). 13C NMR (CDCl3): δ 154.6 (C(CN)2), 146.8 (C(CN)), 139.2-129.3 (m, Tp, PPh3), 128.2 (CdN), 119.4 (CH3CN), 112.6, 110.4, 108.5 (CN), 3.9 (CH3CN). 31P NMR (acetone): δ 52.6. MS (FAB): m/z 788.3 (M+), 747.2 (M+ - CH3CN), 577.1 (M+ CH3CN, N3C2(CN)4). Anal. Calcd for C35H28BN14PRu (787.55): C, 53.48; H, 3.58; N, 24.90. Found: C, 53.37; H, 3.41; N, 24.46. Synthesis of Tp(PPh3)[(CN)2CdC(CN)2]Ru-N4C[C(CN)d C(CN)2] (8). Dichloromethane (20 mL) was added to a roundbottomed flask charged with complex 2 (0.10 g, 0.15 mmol) and tetracyanoethylene (0.076 g, 0.60 mmol). The reaction mixture was stirred at 35 °C for 36 h. The solvent was evaporated under reduced pressure to 5 mL. To the solution was added 20 mL of n-hexane, whereupon a deep blue compound precipitated. The precipitate was filtered, washed with 10 mL of n-hexane, and dried under vacuum to yield Tp(PPh3)[(CN)2CdC(CN)2]Ru-N4C[C(CN)dC(CN)2] (8; 0.093 g, 71% yield). Spectroscopic data for 8 are as follows. IR (KBr, cm-1): ν(B-H) 2461 (br), ν(CtN) 2236 (m), ν(CtN) 2226 (vs), ν(CtN) 2186 (vs), ν(NdN) 1432 (s). 1H NMR (CD3C(O)CD3): δ 7.85 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.62 (d, JH-H ) 2.0 Hz, 1H, Tp), 7.45 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.38-7.12 (m, Ph), 6.86 (1H, Tp), 6.67 (1H, Tp), 6.56 (1H, Tp), 6.36 (t, JH-H ) 2.0 Hz, 1H, Tp), 6.01 (t, JH-H ) 2.0 Hz, 1H, Tp), 5.82 (t, JH-H ) 2.0 Hz, 1H, Tp). 31P NMR (acetone): δ 54.6. MS (FAB): m/z 875.3 (M+), 747.1 (M+ - C6N4), 577.1 (M+ - C6N4, N3C2(CN)4). Anal. Calcd for C35H28BN14PRu (875.1): C, 53.56; H, 2.88; N, 27.23. Found: C, 53.47; H, 2.81; N, 27.19.

Organometallics, Vol. 28, No. 12, 2009 3367 Synthesis of {Tp(PPh3)(CH3CN)Ru-NCCH2I}[N3] (9). A Schlenk flask was charged with ICH2CN (100 µL, 1.45 mmol) and 2 (0.10 g, 0.15 mmol) in 20 mL of CH2Cl2. The mixture was stirred at room temperature for 24 h. The solvent was reduced to about 2 mL under vacuum and added to 20 mL of vigorously stirred n-hexane. The orange-yellow powder thus formed was filtered, washed with 5 mL of n-hexane, and dried under vacuum to give 9 (0.066 g, 56% yield). Spectroscopic data for 9 are as follows. IR (KBr, cm-1): ν(B-H) 2467 (br), ν(CtN) 2245 (m), ν(CtN) 2243 (m). 1H NMR (CDCl3): δ 7.81 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.80 (d, JH-H ) 2.2 Hz, 1H, Tp), 7.69 (d, JH-H ) 2.0 Hz, 1H, Tp), 7.40-7.07 (m, Ph), 6.86 (br, 1H, Tp), 6.78 (br, 1H, Tp), 6.76 (br, 1H, Tp), 6.02 (t, JH-H ) 1.8 Hz, 1H, Tp), 5.98 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.85 (t, JH-H ) 2.2 Hz, 1H, Tp), 4.50 (s, 2H, CH2), 2.18 (s, 3H, CH3CN). 31P NMR (acetone): δ 41.1. 13C NMR (CDCl3): δ 141.2-123.4 (m, Tp, PPh3), 122.5 (NCCH2I), 119.1 (CH3CN), 50.6 (CH2), 3.6 (CH3CN). MS (FAB): m/z 786.1 (M+ + 1 - I3), 745.2 (M+ + 1 - I3 - CH3CN), 577.1 (M+ + 1 - I3 - CH3CN, ICH2CN). Anal. Calcd for C31H30BI4N8PRu (826.4): C, 31.96; H, 2.60; N, 9.62. Found: C, 31.37; H, 2.61; N, 9.46. Synthesis of Tp(PPh3)(CH3CN)Ru-NCS (11). A Schlenk flask was charged with CS2 (0.7 mL, 0.25 mmol) and 2 (0.10 g, 0.15 mmol) in 20 mL of CH2Cl2. The mixture was stirred at room temperature for 2 h. The solvent was reduced to about 2 mL under vacuum and added to 20 mL of vigorously stirred n-hexane. The orange powder thus formed was filtered, washed with 5 mL of n-hexane, and dried under vacuum to give Tp(PPh3)(CH3CN)RuNCS (11; 0.079, 69% yield). Spectroscopic data for 11 are as follows. IR (KBr, cm-1): ν(B-H) 2469 (br), ν(CtN) 2248 (m), ν(NCS) 2116 (s). 1H NMR (CDCl3): δ 7.91 (d, JH-H ) 2.2 Hz, 2H, Tp), 7.69-7.03 (m, Ph), 6.97 (br, 1H, Tp), 6.78 (br, 1H, Tp), 6.06 (br, 1H, Tp), 6.02 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.90 (t, JH-H ) 2.0 Hz, 1H, Tp), 2.24 (s, 3H, CH3CN). 31P NMR (acetone): δ 43.8. 13 C NMR (CDCl3): δ 156.3 (NCS), 149.3-121.3 (m, Ph, Tp), 119.5 (CH3CN), 50.6 (CH2), 3.6 (CH3CN). MS (FAB): m/z 676.1 (M+), 635.2 (M+ - CH3CN), 618.1 (M+ - NCS). Anal. Calcd for C30H28BN8PRuS (675.5): C, 53.34; H, 4.18; N, 16.59. Found: C, 53.31; H, 4.11; N, 16.46. The intermediate Tp(PPh3)(CH3CN)Ru-N3CS(S) (10) was observed if the reaction was monitored by NMR spectroscopy within 20 min. Spectroscopic data for 10 are as follows. 1H NMR (acetone): δ 7.96 (br, 1H, Tp), 7.86 (br, 1H, Tp), 7.80 (br, 1H, Tp), 7.45-7.10 (m, Ph, Tp), 7.08 (br, 1H, Tp), 6.51 (br, 1H, Tp), 6.24 (br, 1H, Tp), 6.03 (br, 1H, Tp), 5.83 (br, 1H, Tp), 5.40 (br, 1H, Tp), 2.21 (s, 3H, CH3CN). 31P NMR (acetone): δ 52.7. Synthesis of [Tp(PPh3)(CH3CN)Ru(NHdCH2)]I (12a). Dichloromethane (20 mL) was added to a round-bottomed flask charged with complex 2 (0.10 g, 0.15 mmol) and CH3I (1 mL). The reaction mixture was stirred at room temperature for 2 h. The solvent was evaporated under reduced pressure to 5 mL. To the solution was added 20 mL of n-hexane, whereupon a yellow compound precipitated. The precipitate was filtered, washed with 10 mL of n-hexane, and dried under vacuum to yield [Tp(PPh3)(CH3CN)Ru(NHdCH2)]I (12a; 0.11 g, 95% yield). Spectroscopic data for 12a are as follows. IR (KBr, cm-1): ν(N-H) 3183 (s), ν(B-H) 2468 (br), ν(CtN) 2241 (m). 1H NMR (CDCl3): δ 12.4 (dd, JH-H ) 13 Hz, JH-H ) 20 Hz, 1H, NH), 7.89 (d, JH-H ) 13 Hz, 1H, NdCH), 7.75 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.74 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.42-7.17 (m, Ph), 6.89 (d, JH-H ) 20 Hz, 1H, NdCH), 6.48 (1H, Tp), 6.22 (1H, Tp), 5.98 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.83 (t, JH-H ) 2.2 Hz, 1H, Tp), 2.24 (s, 3H, CH3CN). 13C NMR (CDCl3): δ 169.3 (NdC), 143.2-129.3 (m, Tp, PPh3), 121.4 (CH3CN), 4.1 (CH3CN). 31P NMR (acetone): δ 54.4. MS (FAB): m/z 647.3 (M+ - I), 606.2 (M+ - I - CH3CN), 577.1 (M+ CH3CN, NHdCH2). Anal. Calcd for C30H31BIN8PRu (773.4): C, 46.59; H, 4.04; N, 14.49. Found: C, 46.47; H, 4.01; N, 14.27.

3368 Organometallics, Vol. 28, No. 12, 2009 The complex [Tp(PPh3)(CH3CN)Ru(NHdCHCH3)]Br (12b; 0.087 g, 0.11 mmol, 77% yield from 0.10 g of 2) was similarly prepared from BrCH2CH3. Spectroscopic data of 12b are as follows. IR (KBr, cm-1): ν(N-H) 3188 (s), ν(B-H) 2463 (br), ν(CtN) 2248 (m). 1H NMR (CD3C(O)CD3): δ 11.81 (d, JH-H ) 20 Hz, 1H, NH), 7.87 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.67 (d, JH-H ) 2.1 Hz, 1H, Tp), 7.58 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.49-7.11 (m, Ph), 6.95 (1H, Tp), 6.87 (d, JH-H ) 20 Hz, 1H, NdCH), 6.73 (1H, Tp), 6.68 (1H, Tp), 6.43 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.96 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.84 (t, JH-H ) 2.2 Hz, 1H, Tp), 2.28 (s, 3H, CH3CN), 2.13 (NdCHCH3). 13C NMR (CDCl3): δ 171.3 (NdC), 144.9-127.4 (m, Tp, PPh3), 125.4 (CH3CN), 22.6 (NdCHCH3), 4.3 (CH3CN). 31 P NMR (acetone): δ 54.2. MS (FAB): m/z 660.3 (M+ - Br), 619.2 (M+ - Br - CH3CN), 577.1 (M+ - Br - CH3CN, NHdCHCH3). Anal. Calcd for C31H33BBrN8PRu (740.4): C, 50.29; H, 4.49; N, 15.13. Found: C, 50.17; H, 4.41; N, 15.06. The complex [Tp(PPh3)(CH3CN)Ru(NHdCH(CHdCH2))][I3] (12c; 0.13 g, 0.11 mmol, 85% yield from 0.10 g of 2) was similarly prepared from ICH2CHdCH2. Spectroscopic data of 12c are as follows. IR (KBr, cm-1): ν(N-H) 3184 (s), ν(B-H) 2459 (br), ν(CtN) 2241 (m). 1H NMR (CDCl3): δ 11.80 (d, JH-H ) 20 Hz, 1H, NH), 7.81 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.61 (d, JH-H ) 2.0 Hz, 1H, Tp), 7.52 (d, JH-H ) 1.9 Hz, 1H, Tp), 7.41-7.10 (m, Ph), 6.85 (1H, Tp), 6.77 (d, JH-H ) 20 Hz, 1H, NdCH), 6.71 (1H, Tp), 6.61 (1H, Tp), 6.42 (t, JH-H ) 2.1 Hz, 1H, Tp), 5.92 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.82 (t, JH-H ) 2.2 Hz, 1H, Tp), 5.53 (m, 1H, CHd), 5.05 (dd, JH-H ) 10.2 Hz, JH-H ) 2.7 Hz, 1H, 1H of dCH2), 4.95 (dd, JH-H ) 15.3 Hz, JH-H ) 2.7 Hz, 1H, 1H of dCH2), 2.28 (s, 3H, CH3CN). 13C NMR (CDCl3): δ 175.2 (NdC), 153.8 (dCH), 146.3-131.1 (m, Tp, PPh3), 126.9 (CH3CN), 105.8 (dCH2), 4.7 (CH3CN). 31P NMR (acetone): δ 54.6. MS (FAB): m/z 673.1 (M+ - I3), 632.2 (M+ - I3 - CH3CN), 577.1 (M+ - I3 - CH3CN, NHdCH(CHdCH2)). Anal. Calcd for C32H33BI3N8PRu (1053.9): C, 36.49; H, 3.16; N, 10.64. Found: C, 36.37; H, 3.11; N, 10.46. General Procedure of the Ruthenium-Catalyzed Dimerization of RCtCH (R ) Ph, SiMe3, t-Bu, CO2Me). In a 25 mL Schlenk tube equipped with a Teflon stopcock, the ruthenium catalyst 2 (2 mol %) was mixed with Et3N (22 µL, 10 equiv) in 10 mL of CH2Cl2. Excess alkyne (0.60 mmol) was added to the solution, and the reaction mixture was heated in an oil bath either for 20 h (R ) Ph, SiMe3) or for 68 h (R ) t-Bu) and at room temperature for 24 h (R ) COOMe). After that time, the solution was evaporated under high vacuum. The residue was extracted with Et2O, and the Et2O solution was chromatographed on silica gel (n-hexane/Et2O) in air. The rotary evaporation led to the dimeric products as a pale yellow oil. The spectroscopic data for both 13a and 13b have been previously reported.42 Spectroscopic data for (E)-PhCHdHCtCPh (13a) are as follows. 1 H NMR (CDCl3): δ 8.10-6.80 (m, Ph), 7.04 (d, J ) 16.2 Hz, dCHPh), 6.30 (d, J ) 16.2 Hz, dCHCtC). 13C NMR (CDCl3): δ 142.3 (dCHPh), 137.3, 132.2, 129.7, 129.4, 129.2, 127.3, 124.4 (Ph carbons), 109.0 (dCHCtC), 92.3 (dCHCtC), 89.8 (dCHCtCPh). GC-MS: m/z 204 (M+).

Chen et al. Spectroscopic data for (Z)-PhCHdHCtCPh (13b) are as follows. H NMR (CDCl3): δ 8.10-6.80 (m, Ph), 6.40 (d, J ) 11.8 Hz, dCHPh), 5.79 (d, J ) 11.8 Hz, dCHCtC). 13C NMR (CDCl3): δ 139.1 (dCHPh), 137.1, 131.7, 129.2, 128.7, 128.5, 128.4, 124.0 (Ph carbons), 107.7 (dCHCtC), 96.7 (dCHCtCPh), 88.9 (dCHCtCPh). GC-MS: m/z 204 (M+). Spectroscopic data for (Z)-SiMe3CHdHCtCSiMe3 (14b) are as follows. 1H NMR (CDCl3): δ 6.26 (d, J ) 15.2 Hz, dCHSiMe3), 6.16 (d, J ) 15.2 Hz, dCHCtC), 0.19 (s, 18H, SiMe3). 13C NMR (CDCl3): δ 146.8, 125.4, 105.8, 99.2, 0.3, -0.5. Spectroscopic data for CH2dC(SiMe3)CCSiMe3 (14c) are as follows. 1H NMR (CDCl3): δ 6.14 (d, J ) 3.5 Hz), 5.71 (d, J ) 3.5 Hz), 0.16 (s, 18H, SiMe3). 13C NMR (CDCl3): δ 135.6, 135.4, 125.8, 108.2, 99.1, 0.7, -1.8. Spectroscopic data for (Z)-Me3CCHdHCtCCMe3 (15b) are as follows. 1H NMR (CDCl3): δ 5.73 (d, J ) 12.2 Hz, dCHCMe3), 5.38 (d, J ) 12.2 Hz, dCHCtC), 1.28 (s, 9H, CMe3), 1.22 (s, 9H, CMe3). Spectroscopic data for (E)-MeO2CCHdCHCtCCO2Me (16a) are as follows. 1H NMR (CDCl3): δ 6.45 (d, J ) 16.2 Hz, dCHCO2Me), 6.03 (d, J ) 16.2 Hz, dCHCtC), 3.23, 3.21 (s, CO2Me). 13C NMR (CDCl3): δ 164.6 (dCHCO2Me), 153.4 (CtCCO2Me), 135.1 (dCHCO2Me), 121.3 (dCHCtCCO2Me), 87.3 (CtCCO2Me), 81.9 (CtCCO2Me), 52.6, 51.5 (CO2Me). GCMS: m/z 168 (M+). Structure Determination of Complexes 1, 8, and 12c. Singlecrystal X-ray diffraction data were measured on a Bruker SMART Apex CCD diffractometer using µ(Mo KR) radiation (λ) 0.710 73 Å). The data collection was executed using the SMART program; cell refinement and data reduction were performed with the SAINT program. The structure was determined using the SHELXTL/PC program and refined using full-matrix least squares.44 Crystallographic refinement parameters45 of complexes 1, 8, and 12c and selected bond distances and angles are given in the Supporting Information. 1

Acknowledgment. We gratefully acknowledge partial financial support from the National Science Council of Taiwan (NSC 97-2113-M-036-001-MY2) and partial support from the project of the specific research fields in the Tatung University of Taiwan (B96-C07-081). Supporting Information Available: CIF files giving complete crystallographic data for 1, 8, and 12c. This material is available free of charge via the Internet at http://pubs.acs.org. OM800952T (44) (a) The SADABS program is based on the method of Blessing; see: Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33. (b) SHELXTL: Structure Analysis Program, version 5.04; Siemens Industrial Automation Inc., Madison, WI, 1995. (45) GOF ) [∑[w(Fo2- Fc2)2]/(n- p)]1/2, where n and p denote the number of data and parameters. R1 ) (∑||Fo||-||Fc||)/∑||Fo|| and wR2 ) [∑[w(Fo2- Fc2)2]/∑[w(Fo2)2]]1/2, where w ) 1/[σ2(F2o) + (aP)2 + bP] and P ) [(max; 0, Fo2) + 2Fc2]/3.