Cyclization Accompanied with 1, 2-Phenyl Migration in the Protonation

Nov 24, 2010 - Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan 116, Republic of China. Organometallics , 2010, 29 (24), ...
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Organometallics 2010, 29, 6829–6836 DOI: 10.1021/om101017p

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Cyclization Accompanied with 1,2-Phenyl Migration in the Protonation of Ruthenium Acetylide Complex Containing an Allenyl Group Kuo-Hao Chen,† Yi Jhen Feng,† Hao-Wei Ma,† Ying-Chih Lin,*,† Yi-Hong Liu,† and Ting-Shen Kuo‡ †

‡

Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China, and Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan 116, Republic of China Received October 28, 2010

Reaction of the ruthenium allenylidene complex [Ru]dCdCdCPh2 (1, [Ru] = Cp(PPh3)2Ru) with the propargylic Grignard reagent R-CtCCH2MgBr (R = CH3, CH2CH3, Ph) yielded a mixture of two acetylide complexes. The major products, [Ru]CtCCPh2C(R)dCdCH2 (2a, R = CH3; 2b, R = CH2CH3; 2c, R = Ph), have an allenyne moiety, and the minor ones, [Ru]CtCCPh2CH2CtCR (3a, R = CH3; 3b, R = CH2CH3; 3c, R = Ph), have a diyne ligand. The reaction of similar propargyl Grignard reagent HCtCCH2MgBr with 1 yielded only the diyne complex 3d. Treatment of complexes 2a-2c with HBF4 afforded the cyclization complexes 5a-5c, respectively, proceeding via a vinylidene intermediate. The cyclization of the allenyl and the vinylidene groups is accompanied with a phenyl group migration. Complex 5b is fully characterized by a single-crystal X-ray diffraction analysis. Similar cyclization of complexes 2a and 2b, catalyzed by a Au phosphine complex, gave the ruthenium vinylidene complexes 6a and 6b, respectively, with different selectivity from that of the protonation reaction. Au-catalyzed cyclization of the diyne complex 3d yielded 6d, which is fully characterized by a single-crystal X-ray diffraction analysis.

Introduction Transition metal-catalyzed cycloisomerization of alkynecontaining polyunsaturated compounds, such as enyne, diyne, and dienyne, has been a focus of substantial attention due to the

considerable increase in molecular intricacy accomplished in a single synthetic step.1 Recently, a large number of research on gold- and platinum-catalyzed cycloisomerization2 has been published for both intramolecular and intermolecular applications. Now it is recognized that gold and platinum complexes are useful catalysts and can deliver a diverse array of cyclic products under mild conditions.3 These products can be obtained with high efficiency and excellent chemoselectivity. Unsaturated systems, such as 1,5-, 1,6-, and 1,7-enyne compounds, provide access to various products by reacting with a transition metal catalyst.4 It is also known that reactions of functionalized alkyne catalyzed also by a transition metal complex system could yield complex organic compounds.5 In the past few years, our group and others have reported several examples of enyne cycloisomerizations on metals to form various cyclic compounds.6 Allenes are highly valuable synthetic precursors in organic chemistry.

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Their exceptional structure is an indispensable requirement for the synthesis of many structurally appealing and biologically functional compounds.7 It is known that the CdC bond of allenes is around 10 kcal/mol less stable than that of simple alkenes,8 making them appreciably more reactive. In transition metal-catalyzed reactions their reactivity is closer to that of alkynes than that of simple alkenes. Nonetheless, allenes display a distinct and complementary reactivity profile.9 It has been well known that the functionalized allenynes can be catalyzed by Au(I) to yield cycloaddition organic compounds.10 Over the past 30 years, the use of organometallic reagents for the synthesis of allenes has been highly developed.11 One common method for the preparation of various allenes is the metal-mediated SN2 nucleophilic substitution of propargylic electrophiles. The leaving group on the electrophilic propargylic moiety can be an acetal,12 an acetate,13 an epoxide,14 an ether,15 a halide,16 or a sulfonate.17,18 The corresponding organometallic nucleophile can be either a Grignard reagent,19 an organocopper,20 an organozinc,21 or an organoboronate22 derivative. We reported that 1,5-enyne and 1,5-diyne could bind with ruthenium to form metal acetylide complexes, which undergo novel cyclization and/ or metal migration reactions.6 Noticing several recent reports mentioning cyclization reactions of organic allenyl and alkynyl compounds,23 we imagined developing procedures employing allenes for the synthesis of cyclic compounds. In particular, we concentrated our attention on the reactivity of an allenyl group bonded to another unsaturated ligand, which is also coordinated (7) (a) Krause, N.; Hashmi, A. S. K., Eds. Modern Allenes Chemistry; Wiley-VCH: Weinheim, 2004. (b) Hoffmann-R€oder, A.; Krause, N. Angew. Chem., Int. Ed. 2002, 41, 2933–2935. (c) Krause, N.; Hoffmann-R€oder, A.; Canisius, J. Synthesis 2002, 1759–1774. (d) Marshall, J. A. J. Org. Chem. 2007, 72, 8153–8166. (8) (a) Saget. T.; Cramer. N. Angew. Chem., Int. Ed. 2010, 49, DOI: 10.1002/anie.201004795. (b) Padwa, A.; Filipkowski, M. A.; Meske, M.; Murphree, S. S.; Watterson, S. H.; Ni, Z. J. Org. Chem. 1994, 59, 588– 596. (9) (a) Zimmer, R.; Dinesh, C. U.; Nandanan, E.; Khan, F. A. Chem. Rev. 2000, 100, 3067–3125. (b) Hashmi, A. S. K. Angew. Chem., Int. Ed. 2000, 39, 3590–3593. (c) Ma, S. Acc. Chem. Res. 2003, 36, 701–712. (d) Ma, S. Top. Organomet. Chem. 2005, 14, 1–33. (e) Ma, S. Chem. Rev. 2005, 105, 2829–2871. (10) (a) Oh, C. H.; Karmakar, S. J. Org. Chem. 2009, 74, 370–374. (b) Lin, G. Y.; Yang, C. Y.; Liu, R. S. J. Org. Chem. 2007, 72, 6753–6757. (11) (a) Pasto, D. J. Tetrahedron 1984, 40, 205–2827. (b) Brummond, K. M.; DeForrest, J. E. Synthesis 2007, 6, 795–818. (c) Krause, N.; Hoffmann-R€ oder, A. Tetrahedron 2004, 60, 11671–11694. (12) Alexakis, A.; Mangeney, P.; Normant, J. F. Tetrahedron Lett. 1985, 26, 4197–4200. (13) Rona, P.; Crabbe, P. J. Am. Chem. Soc. 1968, 90, 4733–4734. (14) Herr, R. W.; Wieland, D. M.; Johnson, C. R. J. Am. Chem. Soc. 1970, 92, 3813–3814. (15) Alexakis, A.; Marek, I.; Mangeney, P.; Normant, J. F. J. Am. Chem. Soc. 1990, 112, 8042–8047. (16) Mae, M.; Hong, J. A.; Xu, B.; Hammond, G. B. Org. Lett. 2006, 8, 479–482. (17) Westmuze, H.; Vermeer, P. Synthesis 1979, 390–392. (18) (a) Macomber, R. S. J. Am. Chem. Soc. 1977, 99, 3072–3075. (b) Myers, A. G.; Zheng, B. J. Am. Chem. Soc. 1996, 118, 4492–4493. (c) Chedid, R. B.; Brummer, M.; Wibbeling, B.; Frohlich, R.; Hoppe, D. Angew. Chem., Int. Ed. 2007, 46, 3131–3134. (19) Nantz, M. H.; Bender, D. M.; Janaki, S. Synthesis 1993, 577–578. (20) (a) Macdonald, T. L.; Reagan, D. R. J. Org. Chem. 1980, 45, 4740–4747. (b) Deutsch, C.; Lipshutz, B. H.; Krause, N. Angew. Chem., Int. Ed. 2007, 46, 1650–1653. (21) Bertozzi, F.; Crotti, P.; Macchia, F.; Pineschi, M.; Arnold, A.; Feringa, B. L. Tetrahedron Lett. 1999, 40, 4893–4896. (22) Ito, H.; Sasaki, Y.; Sawamura, M. J. Am. Chem. Soc. 2008, 130, 15774–15775. (23) (a) Gockel, B.; Krause, N. Eur. J. Org. Chem. 2010, 311–316. (b) Ueda, M.; Sato, A.; Ikeda, Y.; Miyoshi, T.; Naito, T.; Miyata, O. Org. Lett. 2010, 12, 2594–2597. (c) Teng, T. M.; Liu, R. S. J. Am. Chem. Soc. 2010, 132, 9298–9300. (d) Toullec, P. Y.; Blarre, T.; Michelet, V. Org. Lett. 2009, 11, 2888–2891.

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to a transition metal. We thus explored the cyclization reaction of ligands on transition metals as well as the catalytic reaction of the ruthenium allenyne complex. Herein we report the reaction of the ruthenium allenyne complex with HBF4, causing formation of the carbene complex containing a five-membered ring. This cyclization reaction is accompanied with a 1,2-phenyl migration.24 Gold-complex-catalyzed cyclization of the same ruthenium allenyne as well as diyne complexes leading to the formation of different types of five-membered rings is also reported.

Results and Discussion Phenyl Migration in Cyclization. Treatment of the diphenyl allenylidene ruthenium complex 125 with the propargylic Grignard reagent CH3CtCCH2MgBr, which was prepared from propargylic bromide, CH3CtCCH2Br, and magnesium in diethyl ether,26-29 yielded a mixture of two yellow acetylide complexes, 2a and 3a, in a ratio of 10:1. The major complex, 2a, contains an allenyne ligand on the ruthenium metal with two phenyl groups at Cγ and one methyl group at Cδ. The diyne ligand in 3a, however, has a terminal methyl group. Similarly reactions of 1 with two other propargylic Grignard reagents, CH3CH2CtCCH2MgBr and PhCtCCH2MgBr, also afforded mixtures of 2b and 3b in a ratio of 5:1 and 2c and 3c in a ratio of 10:7, respectively (Scheme 1). The results may imply that all these propargylic Grignard reagents exist in two tautomeric forms, which presumably are in fast equilibrium,26 leading to the formation of 2 and 3.30 Interestingly, when the propargyl Grignard reagent HCtCCH2MgBr was used, only the diyne complex 3d was isolated. Complexes 2a-2c were purified by chromatography using a column packed with Al2O3. Complexes 2 and 3 were characterized by spectroscopic methods. In addition, complex 2b was further characterized by a singlecrystal X-ray diffraction analysis. In the 1H NMR spectrum of 2a, the quartet resonance at δ 4.51, coupling with the methyl protons with JH-H = 2.7 Hz, is assigned to the terminal allenyl protons of the ligand. The corresponding resonances for the allenyl protons of 2b and 2c appear at δ 4.48 as a triplet with JH-H = 3.6 Hz and δ 4.67 as a singlet, respectively. In the 1H NMR spectrum of 3a from the mixture of 2a and 3a, the quartet resonance of the methylene group is at δ 3.07 with 5JH-H = 2.4 Hz, coupling with the CH3 resonance at δ 1.45. The corresponding resonances for (24) Gheorghe, A.; Quiclet-Sire, B.; Vila, X.; Zard, S. Z. Tetrahedron 2007, 63, 7187–7212. (25) Bruce, M. I.; Low, P. J.; Tiekink, E. R. T. J. Organomet. Chem. 1999, 572, 3–10. (26) (a) Acharya, H. P.; Miyoshi, K.; Kobayashi, Y. Org. Lett. 2007, 9, 3535–3538. (b) Karunakar, G. V.; Periasamy, M. Tetrahedron Lett. 2006, 47, 3549–3552. (c) Reich, H. J.; Holladay, J. E.; Walker, T. G.; Thompson, J. L. J. Am. Chem. Soc. 1999, 121, 9769–9780. (27) (a) Stadler, P. A.; Nechvatal, A.; Frey, A. J.; Eschenmoser, A. Helv. Chim. Acta 1957, 40, 1373–1409. (b) Sondheimer, F.; Wolovsky, R.; Ben-Efraim, D. A. J. Am. Chem. Soc. 1961, 83, 1686–1691. (c) Sondheimer, F.; Amiel, Y.; Gaoni, Y. J. Am. Chem. Soc. 1962, 84, 270–274. (d) Viola, A.; MacMillan, J. H. J. Am. Chem. Soc. 1968, 90, 6141–6145. (28) (a) Mesnard, D.; Miginiac, L. J. Organomet. Chem. 1990, 397, 127–137. (b) Eckenberg, P.; Groth, U.; K€ohler, T. Liebigs Ann. Chem. 1994, 673–677. (c) Hernandez, E.; Soderquist, J. A. Org. Lett. 2005, 7, 5397–5400. (d) Zhang, L.; Kozmin, S. A. J. Am. Chem. Soc. 2004, 126, 10204–10205. (29) Yanagisawa, A.; Habaue, S.; Yamamoto, H. Tetrahedron 1992, 48, 1969–1980. (30) (a) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Coord. Chem. Rev. 2004, 248, 1627–1657. (b) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2004, 104, 3079–3159.

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Organometallics, Vol. 29, No. 24, 2010 Scheme 1

Figure 1. ORTEP plot of 2b. Hydrogens and phenyl groups except the C(ipso) atoms on the phosphorus ligands have been omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1)-P(1), 2.2871(5); Ru(1)-P(2), 2.2837(5); Ru(1)-C(1), 2.0212(18); C(1)-C(2), 1.207(2); C(2)-C(3), 1.483(2); C(3)-C(4), 1.562(3); C(4)-C(5), 1.305(3); C(5)-C(6), 1.298(3); C(4)-C(7), 1.506(3); C(7)-C(8), 1.508(3); C(2)-C(1)-Ru(1), 170.79(16); C(1)-C(2)-C(3), 173.5(2); C(7)-C(4)-C(3), 117.38(17); C(4)C(7)-C(8), 115.72(19); C(6)-C(5)-C(4), 177.6(2).

the methylene protons of 3b and 3c appear at δ 3.11 and 3.34, respectively. Single crystals of 2b were obtained from a mixture of CH3OH/CH2Cl2. The molecular structure of 2b was determined by an X-ray diffraction analysis, and an ORTEP drawing is shown in Figure 1. In this acetylide complex, the bond length of Ru(1)-C(1) of 2.0212(18) A˚ shows a (31) Bustelo, E.; Tenorio, M. J.; Puerta, M. C.; Valerga, P. Organometallics 1999, 18, 4563–4573.

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typical Ru-C single bond.31 The bond angle for Ru(1)C(1)-C(2) is 170.79(16)°. The C(1)-C(2) bond length is 1.207(2) A˚, and the corresponding bond angle for C(1)C(2)-C(3) is 173.5(2)°, showing a CtC triple-bond character. The bond angle for C(6)-C(5)-C(4) is 177.6(2)°, and bond lengths for C(4)-C(5) and C(5)-C(6) are 1.305(3) and 1.298(3) A˚, respectively, indicating the allenyl character. The application of propargylic bromide to form a mixture of propargylic and allenylic Grignard reagents via tautomerization has been reported, and treatment of cyclohexanone with this Grignard reagent produced the homopropargylic alcohol compound in good yield. Addition of the propargylic tautomer shows a high selectivity over that of the allenylic tautomer.26 However, in our system, treatment of the allenylidene complex with the propargylic Grignard reagent generated the allenyne products 2a-2c, with a different selectivity favoring addition of the allenylic tautomer of the Grignard reagent. Treatment of complex 2b with HBF4 in diethyl ether gave a pink powder (4b) in about 3 min as a precipitate at -78 °C, which was purified by filtration. Presumably complex 4b is a cationic vinylidene complex on the basis of its 1H and 31P NMR data. Complex 4b appeared in solution for only a short period of time at room temperature. The 1H NMR spectrum of 4b shows two triplet peaks at δ 4.96 and 4.75 both with JH-H = 3.3 Hz, assigned to the methylene protons of the allenyl group and the proton of the vinylidene ligand, respectively. In the 31P NMR spectrum, the singlet peak at δ 41.78 assigned to 4b appears within the normal chemical shift range of a ruthenium vinylidene complex. In the 1H NMR spectrum of the deuteration product obtained from CF3COOD, the triplet vinylidene resonance at δ 4.75 was not observed. When a CHCl3 solution of complex 4b was stirred continually for about 3 h at room temperature, the dark red complex 5b, containing a five-membered ring, was isolated in high yield. Similarly two analogous derivatives, 5a and 5c, were obtained from protonations of 2a and 2c, respectively (Scheme 1). In the 1H NMR spectrum of 5b, two singlet peaks at δ 6.34 and 5.87 are assigned to the terminal methylene protons of the vinyl group and two mutiplet peaks at δ 2.61 and 2.24 are assigned to methylene protons of the ethyl group. The 31P NMR spectrum of 5b shows two doublet resonances at δ 45.51 and 43.89 with JP-P = 30.0 Hz. Both spectra reveal the presence of a stereogenic carbon center in 5b. Comparison of the 1H,13C-HSQC and 1H,13CHMBC spectra of 2b and 5b disclose important structure information of two phenyl groups. On the basis of the 1 H,13C-HSQC spectrum of 2b, the 13C resonance at δ 57.30 is assigned to the tertiary Cγ, which, in the 1H,13C-HMBC spectrum of 2b, correlates with two 1H resonance peaks at δ 7.31 and 7.42, assigned to two aromatic protons at different phenyl groups. This indicates that two phenyl groups are bonded to the same carbon atom. However, in the 1H,13CHMBC spectrum, the 1H resonance at δH 6.76 correlates to that at δC 163.26, assigned to Cγ, and the other 1H resonance at δH 6.81 correlates to a relatively upfield 13C resonance at δC 64.25 assigned to Cδ. This clearly reveals that, in 5b, two phenyl groups are separately bonded to two different neighboring carbon atoms, with a significantly dissimilar chemical shift of δ 64.25 versus 163.26, resulting from migration of one phenyl group from Cγ to Cδ. Also in the 1H,13C-HMBC spectrum of 5b, the resonance of the carbene carbon at δC 292.68 correlates to two vinyl proton resonances at δH 5.87

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Chen et al. Scheme 2

Figure 2. ORTEP plot of 5b. Hydrogens and phenyl groups except the C(ipso) atoms on the phosphorus ligands have been omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1)-P(1), 2.3439(9); Ru(1)-P(2), 2.3478(9); Ru(1)-C(1), 1.980(3); C(1)-C(2), 1.484(4); C(2)-C(3), 1.546(4); C(3)-C(4), 1.512(5); C(4)-C(5), 1.354(5); C(1)-C(5), 1.451(5); C(2)-C(6), 1.327(5); C(3)-C(7), 1.558(5); C(7)-C(8), 1.520(5); C(2)C(1)-Ru(1), 130.9(2); C(1)-C(2)-C(3), 110.3(3); C(4)C(3)-C(2), 100.9(3); C(5)-C(4)-C(3), 110.8(3); C(4)-C(5)C(1), 114.2(3); C(5)-C(1)-C(2), 103.2(3); C(2)-C(3)-C(7), 111.4(3); C(8)-C(7)-C(3), 114.7(3).

and 6.34. Therefore, CR is now neighboring the terminal vinyl moiety, revealing that 5b is a cyclic complex. Hence transformation from 2b to 5b involves formation of a fivemembered ring accompanied with a 1,2-phenyl migration. Complexes 5a and 5c show similar characteristic data in their NMR spectra. The resonance of the vinyl proton at Cβ of 5a at δ 7.25 is overlapped in the aromatic region but is observable in the 2D-HSQC NMR spectrum. Single crystals of 5b were obtained from a mixture of hexane/CH2Cl2 at 5 °C, and the structure was determined by an X-ray diffraction analysis. An ORTEP drawing of complex 5b is shown in Figure 2. One of two phenyl groups originally at Cγ is indeed migrated to Cδ, and this indicates that the cyclization reaction is accompanied with a 1,2phenyl migration.32 The Ru(1)-C(1) bond distance of 1.980(3) A˚ is in the range of typical RudC carbene double (32) (a) Madhushaw, R. J.; Lin, M. Y.; Sohel, S. M. A.; Liu, R. S. J. Am. Chem. Soc. 2004, 126, 6895–6899. (b) Yuan, L. M.; Madhushaw, R. J.; Liu, R. S. J. Org. Chem. 2004, 69, 7700–7704. (c) Bakalbassis, E. G.; Spyroudis, S.; Tsiotra, E. J. Org. Chem. 2006, 71, 7060–7062. (d) Schmittel, M.; Mahajan, A. A.; Bucher, G.; Bats, J. W. J. Org. Chem. 2007, 72, 2166– 2173. (e) Luzung, M. R.; Mauleon, P.; Toste, F. D. J. Am. Chem. Soc. 2007, 129, 12402–12403. (f) Otto, S.; Roodt, A. Inorg. Chem. Commun. 2008, 11, 114–116. (g) Nakazaki, S. A.; Usuki, J.; Tomooka, K. Synlett 2008, 2064– 2068. (h) Agrawal, M. K.; Ghosh, P. K. J. Org. Chem. 2009, 74, 7947–7950. (i) Siebert, M. R.; Osbourn, J. M.; Brummond, K. M.; Tantillo, D. J. J. Am. Chem. Soc. 2010, 132, 11952–11966.

bonds, and the bond lengths of C(2)-C(6) of 1.327(5) A˚ and C(4)-C(5) of 1.354(5) A˚ are typical of CdC double bonds. The presence of the five-membered ring reveals that a C-C bond formation took place between CR and the central carbon of the allenyl moiety of 2b. Furthermore, two adjacent phenyl groups of 5b are now bound separately with C(3) and C(4), a result of a 1,2-phenyl migration. A possible mechanism for the transformation from complex 2b to 5b is shown in Scheme 2. In this mechanism, protonation of complex 2b from HBF4 leads first to formation of the vinylidene complex 4b, and then cyclization30,32 occurs, leading to C-C bond formation between the central carbon atom of the terminal allenyl moiety and CR, giving the cationic five-membered-ring ligand in A. Then a 1,2phenyl migration33,34 could take place for one of the geminal phenyl groups to give C with a stereogenic carbon center. Eventually, establishment of a ruthenium carbene bond results in the formation of 5b. When one of the phosphine ligands is replaced by a phosphite P(OPh)3, the same nucleophilic addition of propargylic Grignard reagents to the analogous allenylidene complex was also observed, giving similar allenyne complexes.30 From [Ru0 ]dCdCdCPh2 (10 [Ru0 ] = Cp(PPh3)(P(OPh)3)Ru) and corresponding propargylic Grignard reagents, analogous mixtures of 2a0 and 3a0 (10:1) and 2b0 and 3b0 (1:1) could be isolated. In the 1H NMR spectrum of 2b0 , the resonance at δ 4.44 is assigned to the terminal allenyl protons of the ligand, and that of the methylene group is at δ 2.22 and 2.07. The corresponding resonances for the allenyl protons of 2a0 appear at δ 4.33. The 31 P NMR spectrum of 2b0 shows two doublet resonances at δ 139.07 and 52.81 with JP-P = 67.0 Hz; the two doublet 31P resonances of 2a0 are at δ 139.31 and 53.02 with Jp-p = 67.1 Hz. In the 1H NMR spectrum of 3b0 , the broad singlet resonance at δ 2.99 is assigned to the methylene group. Two doublet 31P (33) Bruneau, C.; Dixneuf, P. H. Chem. Commun. 1997, 507–512. (34) (a) Cordaro, J. G.; Stein, D.; Gr€ utzmacher, H. J. Am. Chem. Soc. 2006, 128, 14962–14971. (b) Takahashi, M.; Sekine, N.; Fujita, T.; Watanabe, S.; Yamaguchi, K.; Sakamoto, M. J. Am. Chem. Soc. 1998, 120, 12770–12776. (c) Zimmerman, H. E.; Wilson, J. W. J. Am. Chem. Soc. 1964, 86, 4036–4042. (d) Zimmerman, H. E.; Rieke, R. D.; Scheffer, J. R. J. Am. Chem. Soc. 1967, 89, 2033–2047. (e) Zimmerman, H. E.; Lewin, N. J. Am. Chem. Soc. 1969, 91, 879–886. (f) Zimmerman, H. E.; Hancock, K. G. J. Am. Chem. Soc. 1968, 90, 3749–3760.

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Scheme 3

Figure 3. ORTEP plot of 6d. Hydrogens and phenyl groups except the C(ipso) atoms on the phosphorus ligands have been omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1)-P(1), 2.3326(12); Ru(1)-P(2), 2.3710(15); Ru(1)-C(1), 1.851(5); C(1)-C(2), 1.313(6); C(2)-C(3), 1.569(7); C(3)-C(4), 1.570(7); C(4)-C(5), 1.465(9); C(5)-C(6), 1.339(8); C(2)-C(6), 1.449(7); C(3)-C(7), 1.532(8); C(3)-C(13), 1.537(7); C(2)C(1)-Ru(1), 169.8(4); C(1)-C(2)-C(3), 129.9(5); C(6)C(2)-C(3), 105.3(4); C(5)-C(6)-C(2), 113.9(6); C(6)-C(5)C(4), 111.1(6); C(5)-C(4)-C(3), 106.0(5); C(2)-C(3)-C(4), 102.9(4).

resonances at δ 140.01 and 53.35 with Jp-p = 66.7 Hz are assigned to P(OPh)3 and PPh3, respectively. Complex 3a0 shows similar characteristic data in the 1H and 31P spectra. Treatment of 2a0 with HBF4 also gave the cationic five-membered-ring complex 5a0 , which has two stereogenic centers. Complex 5a0 , produced in two diastereomers, is identified by two sets of two doublet 31P resonances appearing at δ 135.41/51.87 with Jp-p = 55.1 Hz and δ 134.97/49.28 with Jp-p = 55.3 Hz. Similarly complex 5b0 was obtained from 2b0 . The 31P resonances of 5b0 appear at δ 132.28/51.34 and 125.03/47.02, both with Jp-p = 54.2 Hz. However, complexes 5a0 and 5b0 are unstable in chloroform and, in 3 h, decomposed to give unidentifiable products. When a chelating diphenylphosphinoethane (dppe) ligand replaces the two PPh3 ligands, even the allenyne complexes are too reactive to be isolated. No further attempt was made to isolate or to explore the reactivity of these products. Cyclization by Au Complex. As illustrated in Scheme 1, transformation of the yellow acetylide complex [Ru]Ct CC(Ph)2CH2CtCH (3d) to give complex 6d, containing a vinylidene ligand with a five-membered ring, was catalyzed by AuPPh3SbF6,3,4 which was prepared from AgSbF6 and AuPPh3Cl in hydrous CH2Cl2. The pink ruthenium vinylidene complex 6d was obtained in 88% yield. This product is characterized by NMR and single-crystal X-ray diffraction analysis. The 1H NMR spectrum of complex 6d displays two multiplet resonances at δ 5.77 and 5.00 assigned to olefinic protons, and the resonance at δ 3.37 is assigned to the unique methylene group of the ring. In order to gain further information supporting the proposed structure of complex 6d, 2D-NMR techniques, including 1H,1H-COSY, 1H,13CHSQC, and 1H,13C-HMBC, are employed. The 1H,1H-COSY spectrum of complex 6d shows cross-peaks correlating three resonances at δ 3.37 and 5.00, 5.77. The HSQC spectrum shows two sets of cross-peaks correlating resonances of the two olefinic protons at δH 5.00 and 5.77 to the 13C resonances of different carbons at δC 123.97 and 119.38, respectively. In the

HMBC spectrum of 6d, long-range C-H correlations are observed between the resonances of the methylene group at δ 3.37 and four remaining carbon atoms of the five-membered ring at δ 142.65, 123.97, 119.38, and 61.41. These NMR data clearly reveal formation of a five-membered ring from cycloaddition of the terminal alkynyl group with the acetylide ligand. Single crystals of 6d were obtained by diffusion of diethyl ether into a solution of 6d in dichloromethane. The structure was confirmed by an X-ray diffraction analysis. Figure 3 shows an ORTEP drawing of 6d with selected bond lengths and angles. The molecular structure reveals a typical vinylidene skeleton with the a bond length of Ru(1)-C(1) of 1.851(5) A˚ and C(1)-C(2) of 1.313(6) A˚. The Ru(1)-C(1)-C(2) bond angle of 169.8(4)° is slightly bent from a linear arrangement, which is possibly due to the steric effect between the two phenyl groups of the five-membered ring and two PPh3 ligands. The bond length of C(5)-C(6) is 1.339(8) A˚, indicating a double bond. It is well known that the cationic Au(PPh3)þ catalyst could effectively activate the terminal CtC triple bond.3 A mechanism for the formation of complex 6d is thus suggested as follows. First, the terminal alkynyl group of complex 3d may coordinate to the unsaturated gold complex to form the intermediate D with a π-coordination mode; see Scheme 3. Cyclization of this alkynyl group with the acetylide β-carbon results in C-C bond formation to give the intermediate E. Finally, extrusion of gold catalyst from the intermediate E leads to formation of the cationic ruthenium vinylidene complex 6d with a cyclopentene ring (Scheme 3).3 The C-C bond formation takes place between Cβ of the acetylide ligand and the methyne carbon of the terminal triple bond. This regioselectivity is different from that of the C-C bond formation occurring in the protonation reactions of the allenyne complexes mentioned above. Therefore, in addition to the cyclization of the diyne ligand of 3d, reactions of complexes 2a and 2b, containing an allenyne moiety, were explored under the same reaction conditions in the presence of gold catalyst, and cyclization, involving similar C-C bond formation to that in the goldcomplex-catalyzed reaction of 3d, was observed yielding 6a and 6b, respectively. As shown in Scheme 4, treatment of complexes 2a and 2b containing the allenyne moiety with a catalytic amount of gold complex Au(PPh3)Cl/AgSbF6 in CH2Cl2 at room temperature afforded complexes 6a and 6b, respectively. Scheme 4 also shows a plausible mechanism for the transformation. The reaction pathway is proposed on the basis of the fact that the cationic Au(PPh3)þ catalyst preferably

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Organometallics, Vol. 29, No. 24, 2010 Scheme 4

Chen et al.

Protonation of these complexes affords 5a-5c by a cyclization involving the terminal allenyl group and the CdC bond of the vinylidene group of the intermediate complex 4, followed by a 1,2-phenyl migration. Cyclization of 3d catalyzed by a gold complex involves a cyclization of diyne, giving the vinylidene complex 6d with a cyclopentene ring. The π-coordination of the terminal CtC triple bond of 3d to Au, followed by a cyclization, results in formation of 6d. Cyclization of the allenyne moiety of 2a and 2b by a gold catalyst similarly proceeds via coordination of the allenyl moiety to Au.

Experimental Section triggered allenyl coordination to form the intermediate F.27,35-37 Cyclization of the acetylide CtC triple bond with the Au-complexed allenyl group of the intermediate F possibly proceeds by an electrophilic addition of the allenyl group to the acetylide β-carbon leading to G. Then, hydrolysis of the intermediate G occurred, causing extrusion of the gold catalyst and formation of the cationic ruthenium vinylidene complex 6 with a cyclopentene moiety; see Scheme 4. Previously reported goldcatalyzed reactions in the literature revealed that the goldcatalyzed rearrangement and/or cyclization of 1,5-allenynes could produce cross-conjugated trienes containing a five- or six-membered ring.35a Hydrative carbocyclization of 1,5-allenynes catalyzed by a gold catalyst gave cyclized ketones chemoselectively containing a five-membered ring.35b With a σ-coordinated acetylide ligand in 2a, we were interested in how the allenyne was activated. Two complexes were thus prepared for this purpose. The reported preparation6 of 3d is slightly modified to obtain the vinylidene complex with a terminal triple bond, {[Ru]dCdCHCPh2CH2CtCH}BF4 (7, [Ru]dCp(PPh3)2Ru). The acetylide complex with a terminal double bond, [Ru]CtCCPh2CH2CHdCH2 (8), was also prepared. Interestingly, treatment of these two complexes with the same gold catalyst mentioned above resulted in no reaction. Thus the mechanism of the gold catalyst could proceed via a π-coordination of either acetylene or allene in the substrate. Accordingly, the terminal vinyl moiety of 8 may not coordinate to the Au(PPh3)þ catalyst. Hence, we suggest that the formation of 6a and 6b proceeds preferably via π-coordination of the allenyl moiety of the ligand to the gold catalyst. When the gold-catalyzed cycloaddition reaction of 3d was carried out using a mixture of CD2Cl2 and D2O as a solvent under nitrogen, the monodeuterated complex 6d-D, where the deuteration took place at the olefinic site, was obtained. From the 1H NMR spectrum of 6d-D, one of two olefinic protons is substituted by deuterium, as evidenced by a 46% decrease in intensity of the proton signal at δ 5.00. Similarly the reaction of complex 2b in the presence of D2O also caused 37% deuterium substitution as determined from the intensity decrease of the unique olefinic proton signal at δ 5.31 of 6b. These results support the formation from 3d to 6d via the hydration substitution. In summary, we report the synthesis of three acetylide complexes, 2a-2c, each tethering a terminal allenyl group. (35) (a) Cheong, P. H. Y.; Morganelli, P.; Luzung, M. R.; Houk, K. N.; Toste, F. D. J. Am. Chem. Soc. 2008, 130, 4517–4526. (b) Yang, C. Y.; Lin, G. Y.; Liao, H. Y.; Swarup, D.; Liu, R. S. J. Org. Chem. 2008, 73, 4907–4914. (36) Zhang, Z.; Liu, C.; Kinder, R. E.; Han, X.; Qian, H.; Widenhoefer, R. A. J. Am. Chem. Soc. 2006, 128, 9066–9073. (37) Nieto-Oberhuber, C.; L opez, S.; Echavarren, A. M. J. Am. Chem. Soc. 2005, 127, 6178–6179.

General Procedures. All manipulations were performed under an atmosphere of dry nitrogen using vacuum-line, drybox, and standard Schlenk techniques. Solvents were dried by standard methods and distilled under nitrogen before use. All reagents were obtained from commercial suppliers and used without further purification. Complexes [Ru]Cl ([Ru] = Cp(PPh3)2Ru),6,38a [Ru0 ]Cl ([Ru0 ] = Cp(PPh3)(P(OPh)3)Ru),6b Cp(dppe)RuCl,6,38b [[Ru]dCdCdCPh2][PF6] (1),6 and [[Ru0 ]dCdCdCPh2][PF6] (10 )6b and its dppe analogue [Cp(dppe)RudCdCdCPh2][PF6] (100 )6a were prepared by literature methods. NMR spectra were recorded on Bruker Avance-400 and DMX-500 FT-NMR spectrometers at room temperature unless stated otherwise and were reported in units of δ with residual protons in the solvent as a standard (CDCl3, 7.26). Electrospray ionization mass spectrometry, elemental analyses, and X-ray diffraction studies were carried out at the Regional Center of Analytical Instrument located at National Taiwan University. All reagents were obtained from commercial suppliers. Synthesis of 2 and 3. To a flask charged with 1 (291 mg, 0.28 mmol) in THF (25 mL) at -78 °C under nitrogen was added dropwise the Grignard reagent MgBrCH2CtCCH3 until the solution become yellow. This solution was continually stirred at room temperature for 10 min, and the solvent was removed under rotary evaporation to give the yellow crude precipitates of the acetylide complexes 2a and 3a (the ratio of 2a and 3a is about 10:1 from the 31P NMR spectrum). This mixture was purified by column chromatography on an Al2O3-packed column with hexane/diether ethyl (10:9) as eluent. A yellow band was collected and the solvent was removed to give the major product, [Ru]-CtCC(Ph)2CMedCdCH2 (2a) (171 mg, in 65% yield). A mixture of compounds 2a and 3a (51 mg) was also obtained from the second yellow band for spectroscopic data of 3a. Spectroscopic data for 2a are as follows. 1H NMR (CDCl3): δ 7.78-6.85 (m, 40H, Ph), 4.51 (q, JH-H = 2.7 Hz, 2H, dCH2), 4.42 (s, 5H, Cp), 2.19 (t, JH-H = 2.7 Hz, 3H, CH3). 31P NMR (CDCl3): δ 50.13 (s, PPh3). 13C NMR (C6D6): δ 207.98 (CdCH2), 147.67-125.88 (Ph), 113.94 (Cδ), 107.73 (Cβ), 97.62 (t, JC-P = 24.0 Hz, CR), 85.62 (Cp), 75.91 (CdCH2), 57.99 (Cγ), 18.79 (CH3). Mass ESI: m/z 935.2653 (Mþ þ 1). A solid sample with one diethyl ether molecule trapped in the crystal confirmed by 1 H NMR was used for elmental analysis. Anal. Calcd for C64H60OP2Ru: C, 76.24; H, 6.00. Found: C, 76.46; H, 6.31. Spectroscopic data for 3a from the mixture of 2a and 3a are as follows. 1H NMR (CDCl3): δ 7.78-6.85 (m, 40H, Ph), 4.27 (Cp), 3.07 (q, 5JH-H = 2.4 Hz, 2H, CH2), 1.45 (t, 5JH-H = 2.4 Hz, 3H, CH3). 31P NMR (CDCl3): δ 51.20 (s, PPh3). 13C NMR (C6D6): δ 149.17-125.72 (Ph), 115.25 (Cβ), 85.83 (Cp), 78.86 (CtC), 77.68 (CtC), 52.18 (Cγ), 35.53 (CH2), 3.82 (CH3). Complexes 2b (R = CH2CH3 in 51% yield) and 2c (R = Ph in 38% yield) were also prepared using similar procedures. Spectroscopic data for 2b are as follows. 1H NMR (CDCl3): δ (38) (a) Bruce, M. I.; Windsor, N. J. Aust. J. Chem. 1977, 30, 1601– 1604. (b) Ashby, G. S.; Bruce, M. I.; Tomkins, I. B.; Wallis, R. C. Aust. J. Chem. 1979, 32, 1003–1016.

Article 7.39-6.96 (m, 40H, Ph), 4.48 (t, JH-H = 3.6 Hz, 2H, dCH2), 4.29 (s, 5H, Cp), 2.18 (m, 2H, CH2), 0.95 (t, JH-H = 7.4 Hz, 3H, CH3). 31P NMR (CDCl3): δ 50.36 (s, PPh3). 13C NMR (CDCl3): δ 206.47 (CdCH2), 147.37-125.26 (Ph), 114.30 (Cδ), 113.21 (Cβ), 97.02 (t, JC-P = 24.1 Hz, CR), 85.13 (Cp), 78.08 (CdCH2), 57.30 (Cγ), 22.85 (CH2), 12.62 (CH3). Mass ESI: m/z 949.2762 (Mþ þ 1), 732.1670 ([Ru] þ CH3CN). A solid sample with one diethyl ether molecule trapped in the crystal, confirmed by NMR, was used for elmental analysis. Anal. Calcd for C65H62OP2Ru: C, 76.37; H, 6.11. Found: C, 76.20; H, 6.04. Spectroscopic data for 2c are as follows. 1H NMR (CDCl3): δ 7.82-6.96 (m, 40H, Ph), 4.67 (s, 2H, CdCH2), 4.04 (s, 5H, Cp). 31P NMR (CDCl3): δ 50.47 (s, PPh3). 13C NMR (CDCl3): δ 210.22 (CdCH2), 147.58-125.33 (Ph), 114.31 (Cδ), 113.52 (Cβ), 99.02 (t, JC-P = 24.0 Hz, CR), 85.05 (Cp), 78.83 (CdCH2), 55.55 (Cγ). Mass ESI: m/z 997.2697 (Mþ þ 1), 732.1560 ([Ru] þ CH3CN). We used NMR spectra to identify complexes 3b and 3c from the corresponding mixtures. Spectroscopic data for 3b are as follows. 1H NMR (CDCl3): δ 4.31 (Cp), 3.11 (br, 2H, CH2), 1.94 (m, 2H, CH2CH3), 0.96 (t, 3H, CH3 overlapped with that of 2b). 31P NMR (CDCl3): δ 51.13 (s, PPh3). 13C NMR (CDCl3): δ 148.46-125.25 (Ph), 114.42 (Cβ), 97.67 (t, JC-P = 24.5 Hz, CR), 85.29 (Cp), 83.72 (tC), 78.53 (tC), 51.40 (Cγ), 34.78 (CH2), 19.90 (CH3), 12.04 (CH2). Spectroscopic data for 3c are as follows. 1H NMR (CDCl3): δ 7.81-6.95 (m, 40H, Ph), 4.25 (s, 5H, Cp), 3.34 (s, 2H, CH2). 31P NMR (CDCl3): δ 51.33 (s, PPh3). 13C NMR (CDCl3): δ 148.25-125.37 (Ph), 114.20 (Cβ), 99.01 (t, JC-P = 21.3 Hz, CR), 89.97 (tC), 85.28 (Cp), 78.84 (tC), 51.52 (Cγ), 35.42 (CH2). Synthesis of 20 and 30 . Mixtures of complexes 2a0 /3a0 and 2b0 / 3b0 were also prepared from 10 using similar procedures. Spectroscopic data for 2a0 are as follows. 1H NMR (CDCl3): δ 7.73-6.80 (m, 40H, Ph), 4.37 (s, 5H, Cp), 4.33 (q, JHH = 2.7 Hz, 2H, dCH2), 1.83 (t, JHH = 2.7 Hz, 3H, CH3). 31P NMR (CDCl3): δ 139.31 (d, JP-P = 67.1 Hz, P(OPh)3), 53.02 (d, JP-P = 67.1 Hz, PPh3). Spectroscopic data for 2b0 are as follows. 1H NMR (CDCl3): δ 7.72-6.78 (m, 40H, Ph), 4.44 (br, 2H, dCH2), 4.36 (s, 5H, Cp), 2.22 (m, 1H, CH2), 2.07 (m, 1H, CH2), 0.83 (t, JH-H = 7.3 Hz, 3H, CH3). 31P NMR (CDCl3): δ 139.07 (d, JP-P = 67.0 Hz, P(OPh)3), 52.81 (d, Jp-p = 67.0 Hz, PPh3). 13C NMR (CDCl3): δ 206.44 (CdCH2), 152.02-121.77 (Ph), 114.67 (Cδ), 110.83 (Cβ), 84.47 (Cp), 77.88 (CdCH2), 57.20 (Cγ), 22.48 (CH2), 12.45 (CH3). Spectroscopic data for 3a0 are as follows. 1H NMR (CDCl3): δ 7.63-6.82 (m, 40H, Ph), 4.35 (s, 5H, Cp), 2.99 (q, 5JH-H = 2.2 Hz, 2H, CH2), 1.53 (t, JH-H = 2.2 Hz, 3H, CH3). 31P NMR (CDCl3): δ 140.26 (d, JP-P = 65.8 Hz, P(OPh)3), δ 53.52 (d, JP-P = 65.8 Hz, PPh3). Spectroscopic data for 3b0 are as follows. 1H NMR (CDCl3): δ 7.72-6.78 (m, 40H, Ph), 4.35 (s, 5H, Cp), 2.99 (br, 2H, CH2), 2.06 (m, 2H, CH2), 0.96 (t, JH-H = 7.4 Hz, 3H, CH3). 31P NMR (CDCl3): δ 140.01 (d, JP-P = 66.7 Hz, P(OPh)3), 53.35 (d, JP-P = 66.7 Hz, PPh3). 13C NMR (CDCl3): δ 152.14-121.68 (Ph), 112.46 (Cβ), 84.74 (Cp), 83.50 (CtC), 78.57 (CtC), 51.38 (Cγ), 34.79 (CH2), 14.05 (CH3), 12.58 (CH2). Synthesis of 5a. To a flask charged with 2a (71.1 mg, 0.07 mmol) in diethyl ether (30 mL) at -78 °C under nitrogen was added dropwise HBF4 (54% in Et2O) to cause the formation of pink precipitates. The addition of HBF4 was continued until no pink solid is further formed. The pink precipitates were filtered and washed with hexane to give presumably the vinylidene intermediate 4a. This precipitates were dried under vacuum, and then the dried product was dissolved in CHCl3 and the solution was stirred at room temperature for 3 h under nitrogen, becoming dark red. No attempt was made to collect spectroscopic data of 4a. The solvent was removed, and CH2Cl2 (3 mL) and hexane (40 mL) were sequentially added to cause formation of dark red precipitates, which were filtered and washed with hexane and then dried under vacuum to afford 5a (70.3 mg, 91% yield). Spectroscopic data for 5a are as follows. 1H NMR (CDCl3): δ 7.73-6.67 (m, 40H, Ph), 7.25 (s, 1H, dCH observed

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from HSQC), 6.51 (s, 1H, CdCH2), 5.83 (s, 1H, CdCH2), 4.76 (s, 5H, Cp), 1.73 (CH3). 31P NMR (CDCl3): δ 46.03, 45.50 (2 d, AB, JP-P = 28.9 Hz, 2 PPh3). 13C NMR (CDCl3): δ 289.27 (t, JC-P = 11.5 Hz, CR), 176.64 (CdCH2), 164.70 (dCPh), 156.15 (t, JC-P = 6.9 Hz, Cβ), 143.04-127.04 (Ph), 125.99 (dCH2), 125.79 (Ph), 92.95 (Cp), 60.12 (PhC), 23.69 (CH3). Mass ESI: m/z 935.2643 (Mþ), 732.1595 ([Ru] þ CH3CN). Anal. Calcd for C60H51BF4P2Ru: C, 70.52; H, 5.03. Found: C, 70.29; H, 5.21. Complexes 5b (in 88% yield) and 5c (in 85% yield) were also prepared using similar procedures. The 1H and 31P NMR data of the slightly more stable intermediate 4b, obtained from protonation using CF3COOH, was collected. Spectroscopic data for 4b are as follows. 1H NMR (CDCl3): δ 7.44-6.80 (m, 40H, Ph), 4.96 (t, 2H, JH-H = 3.3 Hz, dCH2), 4.77 (s, 5H, Cp), 4.75 (t, 1H, JH-H = 3.3 Hz, dCH), 1.58 (m, 2H, CH2), 0.89 (t, 3H, JH-H = 7.3 Hz, CH3). 31P NMR (CDCl3): δ 41.78 (s, PPh3). Spectroscopic data for 5b are as follows. 1H NMR (CDCl3): δ 7.70 (s, 1H, dCH), 7.46-6.75 (m, 40H, Ph), 6.34 (s, 1H, dCH2), 5.87 (s, 1H, dCH2), 4.76 (s, 5H, Cp), 2.61 (m, 1H, CH2), 2.24 (m, 1H, CH2), 0.33 (t, 3H, JH-H = 7.1 Hz, CH3). 31P NMR (CDCl3): δ 45.51, 43.89 (2 d, JP-P = 30.0 Hz, 2 PPh3). 13C NMR (CDCl3): δ 292.68 (t, JC-P = 10.5 Hz, CR), 173.51 (CdCH2), 163.26 (dCPh), 159.29 (t, JC-P = 6.4 Hz, Cβ), 143.36-125.69 (Ph), 125.65 (CdCH2), 92.57 (Cp), 64.25 (PhC), 28.75 (CH2), 8.96 (CH3). Mass ESI: m/z 949.2697 (Mþ). Anal. Calcd for C61H53BF4P2Ru: C, 70.73; H, 5.16. Found: C, 70.57; H, 5.45. Spectroscopic data for 5c are as follows. 1H NMR (CDCl3): δ 7.47-6.77 (m, 40H, Ph), 6.13 (s, 1H, dCH2), 5.80 (s, 1H, dCH2), 4.70 (s, 5H, Cp). 31P NMR (CDCl3): δ 45.80 (s, PPh3). Reactions of 2a0 and 2b0 . Reaction of 2a0 with HBF4 was similarly carried out using the procedure for 5a. A mixture of the crude product contained 5a0 in ca. 65% yield by NMR. Complex 5a0 is not stable for purification; only 31P NMR spectroscopic data were obtained. With two stereogenic centers, two diastereomers are expected. 31P NMR (CDCl3): δ 135.41, 51.87 (2 d, JP-P = 55.1 Hz, P(OPh)3, PPh3); 134.97, 49.28 (2 d, JP-P = 55.3 Hz, P(OPh)3, PPh3) with a ratio of 1:1. Similarly complex 5b0 in 76% NMR yield was obtained from 2b0 . 31P NMR (CDCl3): δ 132.28, 51.34 (2 d, JP-P = 54.2 Hz, P(OPh)3, PPh3); 125.03, 47.02 (2 d, JP-P = 54.2 Hz, P(OPh)3, PPh3) with a ratio of 1:1. Synthesis of 6d. A flask was charged with AgSbPF6 (1.87 mg, 0.05 mmol) and AuPPh3Cl (2.69 mg, 0.05 mmol) in wet CH2Cl2 (a small amount of H2O in 1.22 mL of CH2Cl2) under nitrogen, and the solution was stirred at room temperature for 10 min. The other flask was charged with complex 3d (0.10 g, 0.11 mmol) in CH2Cl2 (a small amount of H2O in 1.33 mL of CH2Cl2) under nitrogen; then the latter solution was added into the former one. The solution was stirred at room temperature for 1.5 h, and then the solution was filtered through a sintered glass with Celite. The solid was dissolved with 10 mL of CH2Cl2, and then the solvent was reduced to about 3 mL under rotary evaporation and 30 mL of diethyl ether was added to cause precipitation. The precipitates were filtered and washed with diethyl ether/hexane and dried under vacuum to give 6d (110.6 mg, yield 88%). Spectroscopic data for 6d are as follows. 1H NMR (CDCl3): δ 7.65-6.85 (m, 40H, Ph), 5.77 (m, 1H, dCH), 5.00 (m, 1H, dCH), 4.67 (s, 5H, Cp), 3.37 (br, 2H, CH2). 31P NMR (CDCl3): δ 41.09 (s, PPh3). 13C NMR (CDCl3): δ 372.91 (t, JC-P = 15.2 Hz, CR), 142.65 (Cβ), 137.79-125.22 (Ph), 123.97 (dC), 119.38 (Cd), 94.00 (Cp), 61.41 (Cγ), 57.83 (CH2). Mass ESI: m/z 921.05 (Mþ). Anal. Calcd for C59H49F6P2RuSb: C, 61.26; H, 4.27. Found: C, 61.04; H, 4.26. Complexes 6a and 6b were also prepared from 2a and 2b, respectively, using similar procedures. Spectroscopic data for 6a (in 87% yield) are as follows. 1H NMR (CDCl3): δ 7.51-6.86 (m, 40H, Ph), 5.22 (q, 4JH-H = 1.3 Hz, 1H, CH), 4.53 (s, 5H, Cp), 3.79 (br, 2H, CH2), 1.33 (t, 4JH-H = 1.3 Hz, 3H, CH3). 31P NMR (CDCl3): δ 41.59 (s, PPh3). 13C NMR (CDCl3): δ 357.75

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(t, JC-P = 16.2 Hz, CR), 144.12 (Cβ), 143.88-126.95 (Ph), 121.76 (HCd), 93.30 (Cp), 69.65 (Cγ), 34.43 (CH2), 13.12 (CH3). Mass ESI: m/z 935.2519 (Mþ). Anal. Calcd C60H51F6P2RuSb: C, 61.55; H, 4.39. Found: C, 61.61; H, 4.50. Spectroscopic data for 6b (in 85% yield) are as follows. 1H NMR (CDCl3): δ 7.44-6.88 (m, 40H, Ph), 5.31 (s, 1H, CH), 4.62 (s, 5H, Cp), 3.89 (br, 2H, CH2), 1.59 (m, 2H, CH2), 0.93 (t, 3H, J = 7.2 Hz, CH3). 31P NMR (CDCl3): δ 41.02 (s, PPh3). 13C NMR (CDCl3): δ 356.96 (t, JC-P = 16.0 Hz, CR), 150.44 (Cβ), 144.30-126.92 (Ph), 119.22 (HCd), 93.41 (Cp), 69.96 (Cγ), 34.74 (CH2), 19.86 (CH2), 11.99 (CH3). Mass ESI: m/z 949.2667 (Mþ). Anal. Calcd for C61H53F6P2RuSb: C, 61.84; H, 4.51. Found: C, 61.63; H, 4.33. Single-Crystal X-ray Diffraction Analysis of 2b, 5b, and 6d. Single crystals suitable for X-ray diffraction study were grown via slow diffusion of diethyl ether into a CH2Cl2 solution of 2b at room temperature. A single crystal of dimensions 0.25  0.15  0.10 mm3 was glued to a glass fiber and mounted on a Nonius Kappa CCD diffractometer. The diffraction data were collected (39) SHELXTL: Structure Analysis Program, version 5.04; Siemens Industrial Automation Inc.: Madison, WI, 1995.

Chen et al. using 3 kW sealed-tube molybdenum KR radiation. Exposure time was 5 s per frame. Multiscan absorption correction was applied, and decay was negligible. Data were processed, and the structures were solved and refined by the SHELXTL program.39 The structure was solved using direct methods and confirmed by Patterson methods refining on intensities of all data (35 888 reflections) to give R1 = 0.0310 and wR2 = 0.0688 for 10 768 unique observed reflections (I > 2σ(I)). Hydrogen atoms were placed geometrically using the riding model with thermal parameters set to 1.2 times that for the atoms to which the hydrogen is attached and 1.5 times that for the methyl hydrogen. Solidstate structure determinations were similarly carried out for 5b and 6d.

Acknowledgment. This research is supported by the National Science Council and National Center of HighPerformance Computing of Taiwan, Republic of China. Supporting Information Available: CIF files giving crystallographic data for complexes 2b, 5b, and 6d. This material is available free of charge via the Internet at http://pubs.acs.org.