Intramolecular metathesis of a vinyl group with vinylidene C=C double bond in Ru complexes

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Intramolecular Metathesis of a Vinyl Group with Vinylidene

C

_d

C Double Bond in Ru Complexes

Yung-Sheng Yen, Ying-Chih Lin,* Shou-Ling Huang, Yi-Hung Liu, Hui-Ling Sung, and Yu Wang

Contribution from the Department of Chemistry, National Taiwan UniVersity, Taipei, Taiwan 106, Republic of China

Received July 25, 2005; E-mail: yclin@ntu.edu.tw

Abstract:The cationic complex{[Ru]dCdCHCPh2CH2CHdCH2}BF4(3a, [Ru])(η5-C5H5)(PPh3)2Ru) in

solution transforms to{[Ru]dCdCHCH2CPh2CHdCH2}BF4(4a) via a new metathesis process of the terminal

vinyl group with the CdC of the vinylidene group which is confirmed by 13C labeling studies. This

transformation is irreversible as revealed by deuteration and decomplexation studies. The cationic complex {[Ru]dCdCHCPh2CH2CMedCH2}BF4(3b) undergoes a cyclization process yielding 6b containing aη2 -cyclic allene ligand which is fully characterized by single-crystal X-ray diffraction analysis. Analogous

complexes 4a′and 6b′([Ru])(η5_-C

5H5)(dppe)Ru) containing dppe ligands were similarly obtained from

protonation of the corresponding acetylide complexes via formation of vinylidene intermediate. Protonation

of the acetylide complex containing a terminal alkynyl group [Ru]-CtCCPh2CH2CtCH (2c) generates the

vinylidene complex{[Ru]dCdCHCPh2CH2CtCH}BF4(3c) which again undergoes an irreversible

trans-formation to give{[Ru]dCdCHCH2CPh2CtCH}BF4(4c) possibly via a π-coordinated alkynyl complex

followed by hydrogen and metal migration. No similar transformation is observed for the analogous dppe

complex 3c′. With an extra methylene group, complex{[Ru]dCdCHCPh2CH2CH2CHdCH2}BF4(3d) and

complex{[Ru]dCdCHCPh2CH2Ph}BF4(3e) are stable. The presence of a gem-diphenylmethylene moiety

at the vinylidene ligand with the appropriate terminal vinyl or alkynyl group along with the correct steric environment implements such a novel reactivity in the ruthenium vinylidene complexes.

Introduction

Free vinylidene is a high-energy tautomer of alkyne and could be effectively stabilized by coordination to transition metals.1

Novel chemical properties of the resulting metal vinylidene complexes are valuable for organic transformations. For in-stance, vinylidene complexes of various metals commonly function as strategic intermediates for catalytic conversion of alkynes such as cycloaromatization of conjugated enediynes,2

dimerization of terminal alkynes,3 _{and addition of oxygen,}

nitrogen, and carbon nucleophiles to alkynes.4 _Furthermore,

some vinylidene complexes have been exploited as catalyst precursors for olefin-metathesis reactions.5_{Reactivities of metal}

vinylidene complexes are rationalized by taking electrophilicity of vinylidene R-carbon, nucleophilicity of vinylideneβ-carbon, and highly unsaturated structures of the vinylidene ligands into

consideration.1a _{With one more carbon atom, a metal}

alle-nylidene complex6 _{is also of interest for the building of}

innovative carbon-rich architectures7_{and material science.}8

Owing to the invention of a common method of approach by easy activation of propargylic alcohols,9 _{the chemistry of}

metal allenylidenes has been quickly elaborated. Nowadays nucleophilic addition to the allenylidene ligand is considered

(1) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Bruce, M. I. Chem. ReV. 1998, 98, 2797. (c) Davies, S. G.; McNally, J. P.; Smallridge, A. J. AdV. Organomet. Chem. 1990, 30, 1. (d) Bruce, M. I.; Swincer, A. G. AdV. Organomet. Chem. 1983, 22, 59. (e) Antonova, A. B. Russ. Chem. ReV. 1989, 58, 693.

(2) (a) Nicolaou, K. Chem. Ber. 1994, 33. (b) Wang, Y.; Finn, M. G. J. Am. Chem. Soc. 1995, 117, 8045. (c) Ohe, K.; Kojima, M.; Yonehara, K.; Uemura, S. Angew. Chem., Int. Ed. Engl. 1996, 35, 1823.

(3) (a) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311. (b) Bianchini, C.; Frediani, P.; Masi, D.; Peruzzini, M.; Zanobini, F. Orga-nometallics 1994, 13, 4616. (c) Wakatsuki, Y.; Yamazaki, H.; Kumegava, N.; Satoh, T.; Satoh, J. Y. J. Am. Chem. Soc. 1991, 113, 9604. (d) Yi, C. S.; Liu, N. Synlett 1999, 281.

(4) Bruneau, C.; Dixneuf, P. H. Chem. Commun. 1997, 507. (5) Grubbs, R. H. Handbook of Metathesis, Wiley-VCH: 2003.

(6) (a) Werner, H. Chem. Commun. 1997, 903. (b) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Eur. J. Inorg. Chem. 2001, 571. (c) Touchard, D.; Dixneuf, P. H. Coord. Chem. ReV.1998, 178-180, 409. (d) Werner, H.; Ilg, K.; Lass, R.; Wolf, J. J. Organomet. Chem. 2002, 661, 137. (e) Selegue, J. P. Coord. Chem. ReV. 2004, 248, 1543. (f) Winter, R. F.; Za´li, S. Coord. Chem. ReV. 2004, 248, 1565. (g) Rigaut, S.; Touchard, D.; Dixneuf, P. H. Coord. Chem. ReV. 2004, 248, 1585. (h) Bruce, M. I. Coord. Chem. ReV. 2004, 248, 1603. (i) Cadierno, V.; Gamasa, M. P.; Gimeno, J. Coord. Chem. ReV. 2004, 248, 1627. (j) Fischer, H.; Szezni, N. Coord. Chem. ReV. 2004, 248, 1659. (7) (a) Uno, M.; Dixneuf, P. H. Angew. Chem., Int. Ed. 1998, 37, 1714. (b)

Weiss, D.; Dixneuf, P. H. Organometallics 2003, 22, 2209.

(8) (a) Tamm, M.; Jentsche, T.; Werncke, W. Organometallics 1997, 16, 1418. (b) Roth, G.; Fischer, H.; Meyer-Friedrichsen, T.; Heck, J.; Houbrechts, S.; Persons, A. Organometallics 1998, 17, 1511.

(9) (a) Parmantier, M.; Galloy, J.; Van Meerssche, M.; Viehe, H. G. Angew. Chem., Int. Ed. Engl. 1975, 14, 53. (b) Fischer, E. O.; Kalder, H.-J.; Frank, A.; Kohler, H.; Huttner, G. Angew. Chem., Int. Ed. Engl. 1976, 15, 623. (c) Berke, H. Chem. Ber. 1980, 113, 1370. (d) Berke, H. J. Organomet. Chem. 1980, 185, 75. (e) Selegue, J. P. Organometallics 1982, 1, 217.

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as an alternative synthesis of a metal vinylidene complex making various kinds of vinylidene complexes available for exploitation. We previously reported10_{synthesis of ruthenium cyclopropenyl}

complexes by deprotonation reaction of the readily accessible metal vinylidene complex containing a -CH2R group bound

to Cβof the vinylidene ligand.

Our attempts to prepare a four-membered ring ligand have prompted us to synthesize vinylidene complexes containing a -CPh2CH2R group bound to Cβ of the vinylidene ligand. A number of such complexes are successfully prepared via alkylation of metal allenylidene by using Grignard reagents.11

Surprisingly, with the presence of a terminal vinyl group, the metal vinylidene complex [Ru]dCdCHCPh2CH2CHdCH2+

displays novel intramolecular metathesis reactivity between the two CdC double bonds. Unlike electrophilic and nucleophilic additions to the vinylidene ligand, the cycloaddition of the Cd C double bond of a vinylidene ligand is much less studied. It is well-known that the [2 + 2] cycloaddition of alkenes and/or alkynes represents an important approach for the synthesis of cyclobutane derivatives.12_{A thermally forbidden process by the}

Woodward-Hoffmann rules,13 _{this cycloaddition has been}

achieved photochemically,14_{by thermal reactions via biradical}

intermediates,15_{by the use of Lewis acid catalysts,}16 _{and by}

the use of transition metal catalysts.17_{To date, the range of}

substrates which undergo [2 + 2] reactions with transition metals is rather restricted. Reactions of strained alkenes have received the most attention, and further studies to expand the scope of this reaction are needed.26,27 _{Herein we report a novel}

trans-formation of the vinylidene ligand involving metathesis of the CdC double bond of the vinylidene ligand and a terminal vinyl group tethered on the ligand.

Results and Discussion

Preparation of Ruthenium Allenylidene Complexes. The reported preparation of a ruthenium diphenylallenylidene com-plex in the literature28_{is modified to obtain [Ru]dCdCdCPh}

2+,

(1, [Ru] ) Cp(PPh3)2Ru) in high yield. Many other ruthenium

diphenylallenylidene complexes are known in the literatures.9,29

The reaction of 1 with Grignard reagents RsCH2MgBr yield

the acetylide complexes [Ru]sCtCsC(Ph)2CH2R (2a, R )

CHdCH2; 2b, R ) CMedCH2; 2c, R ) CtCH; 2d, R ) CH2

-CHdCH2; 2e, R ) Ph; Scheme 1) all in high yield.

Charac-teristic spectroscopic data of 2a, 2b, 2c, 2d, and 2e are comparable with that of analogous indenyl complexes in the literature.11a _{Complexes 2a-2e are characterized by IR,} 31_P, 1_{H, and} 13_{C NMR spectroscopy. The IR spectra of these}

acetylide complexes show typical ν(CtC) absorption bands within 2077-2084 cm-1. In the13_{C NMR spectra} 13_C

reso-nances of the acetylide ligand fall in the ranges ofδ 97.1-98.6 for CRand 114.4-115.2 for Cβ. In the1H NMR spectrum of 2a, the doublet resonance at δ 3.27 with JH-H ) 6.0 Hz is

assigned to the internal methylene group. Corresponding me-thylene resonances for complexes 2b, 2c, 2d, and 2e appear at δ 3.29, 3.31, 2.58, and 3.79, respectively.

Novel Metathesis Reactions. Protonation of complexes 2a-2e by HBF4in diethyl ether at 0 °C gave the corresponding

vinylidene complexes [Ru]dCdCHC(Ph)2CH2R+ (3a, R )

CHdCH2; 3b, R ) CMedCH2; 3c, R ) CtCH; 3d, R ) CH2

-CHdCH2; 3e, R ) Ph) as a solid precipitate all with over 90%

(10) (a) Ting, P. C.; Lin, Y. C.; Cheng, M. C.; Wang, Y. Organometallics 1994, 13, 2150. (b) Ting, P. C.; Lin, Y. C.; Lee, G. H.; Cheng, M. C.; Wang, Y. J. Am. Chem. Soc. 1996, 118, 6433. (c) Chang, C. W.; Ting, C. P.; Lin, Y. C.; Lee, G. H.; Wang, Y. J. Organomet. Chem. 1998, 553, 417. (d) Lo, Y. H.; Lin, Y. C.; Lee, G. H.; Wang, Y. Organometallics 1999, 18, 982. (e) Chang, C. W.; Lin, Y. C.; Lee, G. H.; Wang, Y. Organometallics 2000, 19, 3211. (f) Huang, C. C.; Lin, Y. C.; Liu, Y. H.; Wang, Y. Organome-tallics 2003, 22, 1512. (g) Chang, K. H.; Lin, Y. C. Chem. Commun. 1998, 1441. (h) Chang, K. H.; Lin, Y. C.; Liu, Y. H.; Wang, Y. J. Chem. Soc., Dalton Trans. 2001, 3154.

(11) (a) Cadierno, V.; Conejero, S.; Gamasa, M. P.; Gimeno, J. Organometallics 2002, 21, 3837. (b) Cadierno, V.; Conejero, S.; Dı´ez, J.; Gamasa, M. P.; Gimeno, J.; Garcı´a-Granda, S. Chem. Commun. 2003, 840.

(12) For reviews on other methods to construct four-membered rings, see: (a) Ginsburg, D. Alicyclic Compounds: Int. ReV. of Science, Organic Chemistry; Butterworth: London, 1976; Series 2, Vol. 5, p 83. (b) Wong, H. M. C.; Lau, K. L.; Tam, K. F. Top. Curr. Chem. 1986, 133, 83. (c) Ghosez, L.; Marchand-Brynaert, J. In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Paquette, L. A., Eds.; Pergamon: Oxford, 1991; Vol. 5, p 85.

(13) (a) Woodward, R. B.; Hoffmann, R. Angew. Chem. 1969, 81, 797. (b) Woodward, R. B.; Hoffmann, R. The ConserVation of Orbital Symmetry; Academic Press: New York, 1970.

(14) Crimmins, M. T. In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Paquette, L. A., Eds.; Pergamon: Oxford, 1991; Vol. 5, p 123. (15) Baldwin, J. E. In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming,

I., Paquette, L. A., Eds.; Pergamon: Oxford, 1991; Vol. 5, p 63. (16) For Lewis acid-catalyzed [2 + 2] cycloadditions, see: (a) Narasaka, K.;

Hayashi, Y. Chem. Lett. 1990, 295. (b) Narasaka, K.; Nihata, S.; Hayashi, Y. Chem. Lett. 1990, 2091. (c) Engler, T. A.; Letavic, M. A.; Reddy, J. P. J. Am. Chem. Soc. 1991, 113, 5068. (d) Ahmad, S. Tetrahedron Lett. 1991, 32, 6997.

(17) For metal-catalyzed dimerization of norbornadiene, see: (a) Schrauzer, G. N.; Ho, R. K. Y.; Schlesinger, G. Tetrahedron Lett. 1970, 543. (b) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1971, 93, 3089. (c) Acton, N.; Roth, R. J.; Katz, T. J.; Frank, J. K.; Maier, C. A.; Paul, I. C. J. Am. Chem. Soc. 1972, 94, 5446. (d) Weissberger, E.; Mantzaris, J. J. Am. Chem. Soc. 1974, 96, 1873. (e) Jennings, P. W.; Voecks, G. E.; Pillsbury, D. G. J. Org. Chem. 1975, 40, 260. (f) Yoshikawa, S.; Kiji, J.; Furukawa, J. Bull. Chem. Soc. Jpn. 1976, 49, 1093.

(18) For metal-catalyzed dimerization of 1,3-butadiene, see: Yoshikawa, S.; Nishimura, S.; Kiji, J.; Furukawa, J. Tetrahedron Lett. 1973, 3071. (19) For nickel-catalyzed [2 + 2] cycloadditions, see: Ishii, Y.; Kawahara, M.;

Noda, T.; Ishigaki, H.; Ogawa, M. Bull. Chem. Soc. Jpn. 1983, 56, 2181.

(20) For ruthenium-catalyzed [2 + 2] cycloadditions, see: Mitsudo, T.; Naruse, H.; Kondo, T.; Ozaki, Y.; Watanabe, Y. Angew. Chem., Int. Ed. Engl. 1994, 33, 580.

(21) For cobalt-catalyzed [2 + 2] cycloadditions, see: Ville, G. A.; Vollhardt, K. P. C.; Winter, M. J. Organometallics 1984, 3, 1177 and references therein.

(22) For iron-catalyzed [2 + 2] cycloadditions, see: Rosenblum, M.; Scheck, D. Organometallics 1982, 1, 397.

(23) Palladium-catalyzed [2 + 2] cycloadditions: (a) Trost, B. M.; Yanai, M.; Hoogsteen, K. J. Am. Chem. Soc. 1993, 115, 5294. (b) Tanaka, H.; Abdul Hai, A. K. M.; Sadakane, M.; Okumoto, H.; Torii, S. J. Org. Chem. 1994, 59, 3040.

(24) For other titanium-catalyzed [2 + 2] cycloadditions, see: Cannell, L. G. J. Am. Chem. Soc. 1972, 94, 6867.

(25) For other tungsten-catalyzed [2 + 2] cycloadditions, see: Gassman, P. G.; Johnson, T. H. J. Am. Chem. Soc. 1976, 98, 861.

(26) For various types of cycloadditions of metal carbene complexes, see: (a) Do¨tz, K. H.; Fischer, H.; Hofmann, P.; Kreissel, F. R.; Schubert, U.; Weiss, K. Transition Metal Carbene Complexes; Verlag Chemie: Deerfield Beach, FL, 1984. (b) Do¨tz, K. H. Angew. Chem., Int. Ed. Engl. 1984, 23, 587. (c) Schore, N. E. Chem. ReV. 1988, 88, 1081. (d) Wulff, W. D. AdVances in Metal-Organic Chemistry; Liebeskind, L. S., Ed.; JAI Press Inc.: Green-wich, CT, 1989; Vol. 1.

(27) For general references on metathesis, see: (a) Ivin, K. J. Olefin Metathesis; Academic Press: London, 1983. (b) Dragutan, V.; Balaban, H. T.; Dimonic, M. Olefin Metathesis and Ring-opening Polymerization of Cyclo-Olefins; Wiley: New York, 1985. (c) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley: New York, 1988; Chapter 7.

(28) Bruce, M. I.; Low, P. J.; Tiekink, E. R. T. J. Organomet. Chem. 1999, 572, 3.

(29) (a) Schanz, H. J.; Jafarpour, L.; Stevens, E. D.; Nolan, S. P. Organometallics 1999, 18, 5187. (b) Harlow, K. J.; Hill, A. F.; Wilton-Ely, J. D. E. T. J. Chem. Soc., Dalton Trans. 1999, 285. (c) Fuerstner, A.; Hill, A. F.; Liebl, M.; Wilton-Ely, J. D. E. T. Chem. Commun. 1999, 601. (d) Werner, H.; Gruenwald, C.; Steinert, P.; Gevert, O.; Wolf, J. J. Organomet. Chem. 1998, 565, 231. (e) Wolf, J.; Stueer, W.; Gruenwald, C.; Gevert, O.; Laubender, M.; Werner, H. Eur. J. Inorg. Chem. 1998, 1827. (f) Werner, H.; Stark, A.; Steinert, P.; Gruenwald, C.; Wolf, J. Chem. Ber. 1995, 128, 49.

A R T I C L E S

18038 J. AM. CHEM. SOC.9VOL. 127, NO. 51, 2005

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yield. Complexes 3d and 3e are stable vinylidene compounds even at 75°C. Interestingly, vinylidene complexes 3a, 3b, and 3c all display interesting reactivity possibly due to the presence of the gem-diphenyl group and the unsaturated functional group at a proper location of the vinylidene ligand.

Treatment of complex 2a with HBF4 affords the cationic

complex [Ru]dCdCHC(Ph)2CH2CHdCH2+(3a) as a light pink

powder. When complex 3a is dissolved in CDCl3or CH2Cl2at

room temperature, a novel transformation takes place and [Ru]d CdCHCH2CPh2CHdCH2+(4a) is isolated in 90% yield in ca.

12 h (see Scheme 2). With a chelating diphenylphosphinoethane (dppe) ligand replacing the two PPh3ligands, complex [Ru′]d

CdCHC(Ph)2CH2CHdCH2+([Ru′] ) (η5-C5H5)(dppe)Ru, 3a′)

undergoes the same metathesis transformation giving 4a′with a much faster rate of reaction.

If the CH3CN solution of complex 3a is heated to reflux,

three products, cationic metal acetonitrile [Ru]NCCH3+,

4,4-diphenyl-hex-1,5-enyne (7a), and 3,3-4,4-diphenyl-hex-1,5-enyne (8a), in a 3:2:1 ratio are isolated in high yield. Complex 4a can be observed at the initial stage of the reaction at room temperature, and eventually 7a, 8a, and [Ru]NCCH3+ are

isolated. Thermolysis of 4a in CH3CN yields only 8a

quanti-tatively indicating that the transformation of 3a to 4a is irreversible (see Scheme 2). Formation of alkyne from metal vinylidene in acetonitrile has been reported in thermolysis of the analogous indenyl vinylidene complex. However the reaction of the indenyl compound yielded only 1,5-enyne 7a.

Characterization of 3a and 4a is achieved by a spectroscopic method as well as elemental analysis. Significant differences in the spectroscopic data of 3a and 4a leading to disclosure of the structural feature can be undoubtedly discerned. Mainly the coupling patterns of 1_{H resonances of vinylidene and vinyl}

protons of the 1_{H COSY NMR spectra reveal important}

structural information. In the1_{H NMR spectrum of 3a, the broad}

triplet resonance of the vinylidene proton atδ 4.45 with JH-P

) 3.0 Hz shows coupling only with the phosphine ligands. For

4a, the corresponding1_{H resonance of the vinylidene proton at}

δ 4.40, in addition to being coupled with two phosphine ligands, is found to be coupled with the methylene protons atδ 3.09 with JH-H ) 7.8 Hz indicating direct connectivity of the

methylene group to Cβ of the vinylidene ligand. For 3a, the multiplet resonance atδ 5.02 assignable to the methyne proton of the vinyl group is coupled to the resonance atδ 3.06 with

JH-H) 6.0 Hz assignable to the saturated internal methylene

group. But in 4a, the corresponding vinyl proton atδ 3.09 only couples with the resonances of the terminal olefinic dCH2group

indicating no neighboring CH2 group thus signifying direct

bonding of the vinyl ligand to the CPh2group. In addition, the

relevant spectroscopic feature of 4a is the characteristic CR resonance as a triplet atδ 345.6 with JP-C) 15.1 Hz in the 13_{C NMR spectrum. All these spectroscopic data support the}

proposed formula for 4a. Spectroscopic data of 7a and 8a, particularly the 1_{H NMR spectra, are consistent with their}

formulas.

Such a transformation could be interpreted by a novel metathesis process between the terminal vinyl group and the CdC of the vinylidene ligand of 3a first giving the possible cyclobutylidene intermediate 5a shown in the Scheme 2. Namely, a regiospecific [2+2] cycloaddition of two double bonds leads to formation of the four-membered ring. This is followed by a retro-cycloaddition to give 4a. A somewhat similar cycloaddition, namely, the first half of our metathesis reaction, has been reported by Gimeno’s group for a ruthenium vinylidene complex containing an allylphosphine ligand.30

However, in 3a, a further step causes complete metathesis of two double bonds.

When a stoichiometric amount of CF3COOD is used in

treating 2a leading to 4a in CDCl3, a mixture of deuterated

products was observed (Scheme 3). The vinylidene proton and the methyne proton of the terminal vinyl group are partly deuterated. No deuterium incorporation takes place at the terminal CH2of the vinyl group or at the saturated methylene

group. In the proton NMR spectrum, the intensity ratio of vinylidene proton to methyne proton is 3:2. If an excess amount of CF3COOD is used in the protonation of 2a, both hydrogen

atoms are replaced by deuterium giving 4a-D2. However,

addition of D+to 4a results in formation of only 4a-Da, but no 4a-Dbis observed. The deuterium incorporation is observed to

(30) (a) Alvarez, P.; Lastra, E.; Gimeno, J.; Bassetti, M.; Falvello, L. R. J. Am. Chem. Soc. 2003, 125, 2386. (b) Diez, J.; Gamasa, M. P.; Gimeno, J.; Lastra, E.; Villar, A. Organometallics 2005, 24, 1410. (c) Do¨tz, K. H.; Pfeiffer, J. Transition Met. Org. Synth. 1998, 1, 335.

Scheme 1

Scheme 2

d A R T I C L E S

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take place only at the vinylidene hydrogen indicating that transformation of 3a to 4a is irreversible. The H-D exchange is proposed to proceed via the pathway shown in Scheme 3. Metathesis of 3a-D before H-D exchange should result in formation of 4a-Db. Fast transformation of both vinylidene

complexes to acetylide complexes and proton and/or deuterium should then create an opportunity for exchange of proton and deuterium leading to the formation of 4a-D0and 4a-D2. It is

less likely to obtain 4a-Dafrom 3a-D with only one deuteration

at the vinylidene group. In the1_{H NMR spectrum of the product}

isolated from 3a-D, we actually observed a vinylidene proton and internal vinyl proton of a mixture of 4a-D0, 4a-Db, and 4a-D2. For a much faster transformation of vinylidene to

acetylide relative to that of metathesis, a statistical distribution of 4a (no 4a-Da) should be obtained and the ratio of the

vinylidene proton to the internal vinyl proton is 2:1. Considering the rate of metathesis is also fast, the observed ratio (3:2) is in reasonable agreement with the theoretical value.

Definite evidence for the metathesis is obtained from a13_C

labeling study of the reaction. The13_{C labeling at both C}_R_and

Cβfor 1 is readily achieved by using TMS13Ct13CH to prepare the propargyl alcohol H13_Ct13_CC(Ph)

2OH for the synthesis of 13_C_R_,13_C

β-allenylidene complex 1 from which the isolated product 4a via 2a and 3a sequentially is found to have 13_C

labeling at CR(triplet atδ 345.6 with JC-P) 15.5 Hz) and an

internal vinyl CH unit (singlet atδ 143.8) with no CsC coupling between the two carbon atoms. Portions of 13_{C spectra of}

complexes 3a (the second trace from the top) and 4a (the middle trace) obtained from 2a (the top trace) with 25%13_{C enrichment}

at CR and Cβ are shown in Figure 1. The JC-C of 60.2 Hz

between two enriched carbon atoms is clearly seen in 3a, indicating direct connectivity. Evidence of intramolecular

me-tathesis leading to separation of two carbon atoms is noticeably observed by the disappearance of such a C-C coupling between resonances of two enriched carbon atoms for 4a.

The indenyl analogue of 3a has been reported11a_{by Gimeno}

and co-workers; however, no such transformation has been observed. Instead, with the presence of a vinylphosphine bound to the ruthenium metal center, the [2+2] cycloaddition of the CdC bond of the vinylidene ligand and the vinyl group of the phosphine ligand readily occurred.30a_{It seems that intricate steric}

or electronic demand is required for an intramolecular metathesis to take place.

Formation of Cyclic Allene from 3b. The vinylidene complex 3b undergoes a different transformation process to give the cyclic allene complex 6b in high yield; see Scheme 4. The reaction takes place as soon as 3b is dissolved in solution, and the reaction is completed in 10 min at room temperature. In the31_{P NMR spectrum of 6b two resonances at}_{δ 41.3 and 40.9}

with an AB pattern are observed indicating the presence of a stereogenic carbon center in the six-membered ring ligand. The

1_{H NMR spectrum of 6b displays resonances attributed to one}

methyl, one diastereotopic methylene, and three methyne groups. Resonances of two allenic hydrogens appear atδ 5.39 and 2.70 with the latter showing JP-H) 9.5 Hz thus assignable to the

coordinated portion of the allene ligand. Resonances of two methyne and a methyl group are overlapped in the region ofδ 1.55 and 1.66. The 1_{H-COSY 2D NMR spectrum reveals}

couplings of all relevant resonances. In addition, the very pertinent spectroscopic feature of 6b is the characteristic doublet of the doublet13_{C resonance at}_{δ 144.7 with J}

P-C) 22.6, 2.5

Hz assignable to the central carbon of the allene ligand in the

13_{C NMR spectrum. Protonation of complex 2b}′_{containing a}

dppe ligand gave 6b′directly in 97% yield. The vinylidene complex was not observed. Both 6b and 6b′in their solid state

Scheme 3 Scheme 4

A R T I C L E S

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are stable, but 6b decomposed in solution in 4 h at room temperature and 6b′is stable.

Single crystals of 6b suitable for X-ray diffraction analysis are obtained by recrystallization from acetone/diethyl ether. The solid-state structure is determined. An ORTEP drawing is shown in Figure 2, and representative bond lengths and angles are listed in Table 1. The coordination around the Ru atom can be described as a three-legged piano stool. The C(1) and Ru-C(2) bond lengths of 2.225(4) and 2.088(4) Å are in the range

of a regular Ru-C bond for a ruthenium-allene coordination in other crystallographically characterized ruthenium allene complexes.3a _{The C(1)-C(2) bond length of 1.396(6) Å is in}

the range of that of a regularly coordinated double bond. The uncoordinated double bond of the allene ligand is slightly shorter (1.326(6) Å). The bond angles C(6)-C(2) and C(1)-C(2)-C(3) of 111.8(4)°and 126.9(4)°, respectively, reveal the effect of metal coordination of one double bond.

Transformation of 3b to 6b could proceed via pathway A or B depicted in Scheme 4. With a methyl group at the vinyl group, complex 3b undergoes a C-C bond formation between the terminal vinyl carbon atom and CRgiving a six-membered ring ligand with a stereogenic carbon center. This is followed by metal and proton migration to give the product (pathway A). However, the transformation could alternatively proceed via the same [2+2] cycloaddition pathway B as that in 3a followed by the same C-C bond formation mentioned above with a 1,3 Figure 1. Part of13_{C NMR spectra of Ru complexes 2a, 3a, 4a, 2b, and a mixture of 3b and 6b prepared from 25%}13_{C enriched [Ru]d}13_Cd13_CdC(Ph)2+ complex. For atom labeling, see inserted structure.

Figure 2. An ORTEP plot of complex 6b drawn at the 30% probability level. Phenyl groups except the C(ipso) atoms on the phosphine ligand have been omitted for clarity.

Table 1. Selected Bond Lengths [Å] and Angles [deg] for Complex 6b Ru(1)-P(1) 2.3724(11) Ru(1)-P(2) 2.3930(12) Ru(1)-C(1) 2.225(4) Ru(1)-C(2) 2.088(4) C(1)-C(2) 1.396(6) C(2)-C(3) 1.326(6) C(1)-C(6) 1.526(6) C(3)-C(4) 1.518(6) C(5)-C(6) 1.549(6) C(4)-C(5) 1.558(6) C(2)-C(1)-C(6) 111.8(4) C(1)-C(2)-C(3) 126.9(4) C(2)-C(3)-C(4) 119.8(4) C(3)-C(4)-C(5) 110.2(4) C(4)-C(5)-C(6) 115.8(4) C(1)-C(6)-C(5) 101.4(3) d A R T I C L E S

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hydrogen shift to yield 6b. Deuteration should cause scrambling of deuterium for the reaction proceeding via the pathway B which is not experimentally observed. Considering the much faster rate of the reaction and the presence of a more stable tertiary carbocation, we believe this transformation could preferably proceed via pathway A.

A labeling study using H13_Ct13_CC(Ph)

2OH for the

prepara-tion of 3b reveals that the reacprepara-tion proceeds via pathway A giving the product 6b with labeling at two neighboring allenyl carbon atoms (δ 144.3, 131.4 with JC-C) 81.4 Hz); see the

bottom trace of Figure 1 which is the13_{C NMR spectrum of a}

mixture containing equal amounts of 3b and 6b. The13_{C NMR}

spectrum of 2b with 25% enriched 13_{C at C}_R _{and C} β is also shown in Figure 1 for comparison.

Protonation of 2c. Vinylidene complex 3c with a terminal alkynyl group on the chain bound at the vinylidene ligand is obtained in almost quantitative yield from the protonation reaction of 2c. Complex 3c is stable at room temperature. However, when heated to 56 °C, complex 3c in solution is converted to 4c in 4 h; see Scheme 5. If the thermolysis is carried out in CH3CN, organic 1,5-diyne 9c is obtained in high yield.

Again1_{H NMR spectra of 3c and 4c are informative illuminating}

their structural features. The coupling pattern on the terminal alkynyl proton and vinylidene proton noticeably discloses the structural information. For 3c, the resonance atδ 4.81 assignable to the vinylidene proton only couples with two phosphine ligands. But the corresponding resonance atδ 4.67 for 4c is observed to have additional coupling to the methylene protons atδ 3.09 with JH-H) 7.8 Hz indicating direct connectivity of

the methylene group with the vinylidene ligand. Transformation of 3c to 4c could proceed via formation of a π-coordinated alkyne complex from 3c followed by metal migration to the terminal alkynyl group (see Scheme 5). Therefore it is not surprising to observe formation of Rω-bisalkynyl compound 9c when the reaction is carried out in CH3CN. The driving force

of such a transformation could be attributed to the steric effect

between the gem-diphenyl group and the metal fraction. Surprisingly, the analogous complex 3c′containing the dppe ligand would not undergo a similar transformation even under thermolytic conditions. This may indicate that, in addition to the steric effect, a proper orientation of two alkynyl groups is required such that the metal moiety could migrate between two CtC triple bonds. A slight difference in steric or electronic environment deters such a transformation.

Treatment of 2d with acid affords the vinylidene complex 3d in almost quantitative yield. However even with a terminal vinyl group tethered on the vinylidene ligand for 3d, no metathesis of the two double bonds is observed. Thermolysis in toluene causes extensive decomposition of 3d. Both 5-methylenebicyclo[2,1,1]hexane and 6-methylenebicyclo[3,1,1]-heptane are known.31_{And a simple calculation seems to indicate}

that the latter has less ring strain. However, we do not see formation of a metathesis product. As expected, complex 3e is also a stable compound. The fact that complex 3d is stable with respect to the metathesis process could reflect that, even with the presence of a gem-diphenyl substituted group imposing the steric effect, proper conditions do not exist in this complex like the situation for the allyl terminus in 3a and 3b. The fact that the vinylidene complex 3d failed to react may exemplify that the reactivity of a given vinylidene is highly sensitive to the structural changes at a site remote from the reacting double bond. Concluding Remark

In summary, ruthenium complexes {[Ru]dCdCHCPh2

-CH2R}BF43a-3e containing vinylidene ligands tethering with

a terminal vinyl or alkynyl group were synthesized. For 3d (R ) CH2CHdCH2) and 3e (R ) Ph), normal behavior of a

vinylidene complex was observed. However, a novel intramo-lecular metathesis process causes irreversible transformation of 3a (R ) CHdCH2) to 4a. Transformation of 3b (R ) CMed

CH2) to the cyclic allene complex 6b involved a CsC bond

formation giving a six-membered ring and a change of coordination to aη2_{-allene mode. For 3c (R ) CtCH), a metal}

moiety could also irreversibly migrate to the terminal alkynyl group to give 4c possibly with less steric demand between the metal center and the ligand. In vinylidene complexes 3a, 3b, and 3c, a gem-diphenyl moiety along with an unsaturated functional group properly aligned with the vinylidene ligand in a particular orientation could be the reason for such a novel reactivity to take place. In contrast, the vinylidene complexes 3d and 3e failed to react, illustrating that the reactivity of a given vinylidene is highly sensitive to the structural changes at a site remote from the reacting double bond.

Experimental Section

General Procedures. The manipulations were performed under an

atmosphere of dry nitrogen using vacuum-line and standard Schlenk techniques. Solvents were dried by standard methods and distilled under nitrogen before use. All reagents were obtained from commercial suppliers (TMS13_Ct13_{CH from Isotec) and used without further}

purification. Compounds [Cp(PPh3)2Ru(dCdCdCPh2)][PF6] (1) and

its dppe analogues [Cp(dppe)Ru(dCdCdCPh2)][PF6] (1′) were

pre-pared by following the methods28_{reported in the literature. Infrared}

(31) (a) Roth, W. R.; Enderer, K. Justus Liebigs Ann. Chem. 1970, 733, 44. (b) Wiberg, K. B.; Chen, W. J. Org. Chem. 1972, 37, 3235. (c) Inoue, Y.; Mukai, T.; Hakushi, T. Chem. Lett. 1982, 1045. (d) Binmore, G. T.; Della, E. W.; Janowski, W. K.; Mallon, P.; Walton, J. C. Aust. J. Chem. 1994, 47, 1285.

Scheme 5 A R T I C L E S

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spectra were recorded on a Nicolet-MAGNA-550 spectrometer. The C, H, and N analyses were carried out with a Perkin-Elmer 2400 microanalyzer. Mass spectra (FAB) were recorded using a JEOL SX-102A spectrometer; 3-nitrobenzyl alcohol (NBA) was used as the matrix. NMR spectra were recorded on a Bruker AC-300 instrument at 300 MHz (1_{H), 121.5 MHz (}31_{P), or 75.4 MHz (}13_{C) using SiMe}

4or

85% H3PO4as a standard or an Avance 500 FT-NMR spectrometers. Synthesis of Complex [Ru]sCtCsC(Ph)2CH2R (2a, R ) CHd CH2). To a 30 mL THF solution of 1 (0.2 g, 0.19 mmol) was added

CH2CHdCH2MgBr (1.0 M in Et2O; 0.19 mL, 0.19 mmol). The mixture

is stirred at -20°C for 30 min. Then the solution was warmed to room temperature, and the solvent was removed under vacuum. The solid residue was first dissolved in CH2Cl2(5 mL), and then MeOH (15

mL) was added. While the volume of the solvent of the resulting yellow-orange solution was reduced to 5 mL, yellow precipitate formed which was filtered and washed with cold MeOH (2× 5 mL) and dried under vacuum to give 2a (yield 85%). Spectroscopic data for 2a: 1_{H NMR}

(C6D6): δ 7.75-6.86 (m, 40H, Ph), 6.34 (m, 1H, dCH), 5.01 (dd, 2H, JHH) 21.0 Hz, JHH) 12.0 Hz, dCH2), 4.46 (s, 5H, Cp), 3.27 (d, 2H, JHH) 6.0 Hz, CH2).31P NMR (C6D6): δ 51.0.13C NMR (C6D6): δ 149.8-125.4 (m, Ph), 138.2 (s, dCH), 115.7 (s, dCH2), 115.1 (s, Cβ), 97.4 (t, JCP) 23.9 Hz, CR), 85.7 (s, Cp), 51.9 (s, Cγ), 48.0 (s, CH2). Mass m/z 922.3 (M+), 881.2 (M+- CH2CHdCH2), 619.2 (M+- CH2

-CHdCH2- PPh3). IR (KBr, cm-1)ν 2083 (CtC). Anal. Calcd for

C59H50P2Ru: C, 76.85; H, 5.47. Found: C, 76.80; H, 5.57.

Complexes 2b-2e (2b, R ) CMedCH2; 2c, R ) CtCH; 2d, R )

CH2CHdCH2; 2e, R ) Ph) were similarly prepared. Spectroscopic data

for 2b (in 85% yield): 1_{H NMR (C}

6D6): δ 7.64-6.86 (m, 40H, Ph), 5.10 (s, 1H, dCH2), 4.97 (s, 1H, dCH2), 4.48 (s, 5H, Cp), 3.29 (s, 2H, CH2), 1.90 (s, 3H, CH3).31P NMR (C6D6): δ 50.3.13C NMR (C6D6): δ 150.0-125.2 (m, Ph), 143.4 (s, dCCH3), 115.2 (s, Cβ), 114.6 (s, dCH2), 96.7 (t, JCP) 24.1 Hz, CR), 51.3 (s, Cγ), 50.8 (s, CH2), 24.9 (s, CH3). Mass m/z 936.0 (M+), 881.0 (M+- CH2CMedCH2), 691.1 (M+- C2CPh2CH2CMedCH2). IR (KBr, cm-1)ν 2082 (CtC). Anal.

Calcd for C60H52P2Ru: C, 76.99; H, 5.60. Found: C, 76.95; H, 5.74.

Spectroscopic data for 2c (yield 87%): 1_{H NMR (C}

6D6): δ 7.76-6.87 (m, 40H, Ph), 4.50 (s, 5H, Cp), 3.31 (d, JHH) 2.1 Hz, CH2), 1.74 (t, JHH) 2.1 Hz, CtCH).31P NMR (C6D6): δ 51.2.13C NMR (C6D6): δ 148.5-125.7 (m, Ph), 114.4 (s, Cβ), 98.6 (t, JCP) 24.1 Hz, CR), 85.6 (s, Cp), 83.5 (s, CtC), 71.0 (s, tCH), 51.4 (s, Cγ), 34.9 (s, CH2). Mass m/z 920.0 (M+), 881.0 (M+- CH2CtCH), 691.2 (M+ - C2 -CPh2CH2CtCH). IR (KBr, cm-1) ν 2084 (CtC). Anal. Calcd for

C59H48P2Ru: C, 77.02; H, 5.26. Found: C, 77.15; H, 5.31.

Spectroscopic data for 2d (in 85% yield): 1_{H NMR (C}

6D6):δ 7.76-6.86 (m, 40H, Ph), 5.90 (m, 1H, dCH), 4.96 (m, 2H, dCH2), 4.46 (s, 5H, Cp), 2.58-2.46 (m, 4H, CH2CH2).31P NMR (C6D6): δ 50.9.13C NMR (C6D6): δ 150.2-125.5 (m, Ph), 140.4 (s, dCH), 115.0 (s, Cβ), 113.8 (s, dCH2), 97.1 (t, JCP) 23.9 Hz, CR), 52.3 (s, Cγ), 42.6 (s, CH2), 31.0 (s, CH2). Mass m/z 936.1 (M+), 881.0 (M+- CH2CH2 -CHdCH2), 691.1 (M+- C2CPh2CH2CH2CHdCH2). IR (KBr, cm-1)

ν 2083 (CtC). Anal. Calcd for C60H52P2Ru: C, 76.99; H, 5.60.

Found: C, 76.95; H, 5.78.

Spectroscopic data for 2e (in 83% yield): 1_{H NMR (C}

6D6):δ

7.55-6.84 (m, 45H, Ph), 4.46 (s, 5H, Cp), 3.79 (s, 2H, CH2). 31P NMR

(C6D6): δ 50.2.13C NMR (C6D6): δ 149.6-125.3 (m, Ph), 114.9 (s,

Cβ), 97.8 (t, JCP) 24.1 Hz, CR), 52.9 (s, Cγ), 49.1 (s, CH2). Mass m/z

972.4 (M+), 881.3 (M+- CH2Ph), 691.2 (M+- C2CPh2CH2Ph). IR

(KBr, cm-1)ν 2077 (CtC). Anal. Calcd for C63H52P2Ru: C, 77.84;

H, 5.39. Found: C, 77.98; H, 5.49.

Dppe analogues 2a′-2d′([Ru] ) Cp(dppe)Ru) were also prepared from 1′and corresponding Grignard reagents using similar methods. Spectroscopic data for 1′: 1_{H NMR (CDCl}

3): δ 7.56-7.00 (m, 30H,

Ph); 5.34 (s, 5H, Cp); 2.80 (m, 4H, CH2of dppe).31P NMR (CDCl3):

δ 82.2.13_{C NMR (CDCl}

3): δ 290.8 (CR); 204.9 (Cβ); 157.7 (Cγ);

142.7-128.1 (Ph); 91.2 (Cp); 28.5 (CH2of dppe). MS (FAB) m/z:

755.2 (M+ - PF6); 565.1 (M+ - PF6, -C3(Ph)2). Anal. Calcd for

C46H39P3F6Ru: C, 61.40; H, 4.36. Found: C, 61.48; H, 4.42.

Spectroscopic data for [Ru]sCtCsC(Ph)2CH2CHdCH2(2a′, [Ru] ) Cp(dppe)Ru, 89% yield): 1_{H NMR (C} 6D6): δ 8.03-7.06 (m, 30H, Ph); 5.95 (m, 1H, CHdCH2); 4.96 (dd, 2H, CHdCH2, JH-H) 10.5, 14.3 Hz); 4.92 (s, 5H, Cp); 2.83 (d, 2H, C(Ph)2CH2, JH-H) 6.55 Hz); 2.49, 2.13 (m, 4H, CH2of dppe).31P NMR (C6D6): δ 87.2.13C NMR (C6D6):δ 149.2-125.2 (Ph); 115.1 (CHdCH2); 112.2 (Cβ); 98.2 (CR); 82.6 (Cp); 51.5 (Cγ); 47.2 (C(Ph)2CH2); 27.9 (CH2of dppe). MS(FAB) m/z: 796.1 (M+); 565.1 (M+- C3(Ph)2, CH2CHdCH2). Anal. Calcd

for C49H44P2Ru: C, 73.94; H, 5.57. Found: C, 74.02; H, 5.63.

Spectroscopic data for 2b′(90% yield): 1_{H NMR (C}

6D6): δ 7.96-7.06 (m, 30H, Ph); 4.94 (s, 5H, Cp); 4.87 (s, 1H, -CH2); 4.61 (s, 1H, -CH2); 2.84 (s, 2H, CH2); 2.28, 1.97 (m, 4H, CH2of dppe); 1.67 (s, 3H, CH3).31P NMR (C6D6): δ 86.8.13C NMR (C6D6): δ 149.7-112.3 (Ph); 114.1 (-CH2); 112.3 (Cβ); 98.5 (CR); 82.3 (Cp); 51.1 (Cγ); 49.6 (CH2); 27.5 (CH2of dppe); 24.7 (CH3). MS(FAB) m/z: 811.2 (M++ 1); 755.1 (M+- CH2C(CH3)CH2); 565.1 (M+- C3(Ph)2CH2C(CH3

)-CH2). Anal. Calcd for C49H46P2Ru: C, 73.75; H, 5.81. Found: C, 73.81;

H, 5.88.

Spectroscopic data for 2c′(88% yield): 1_{H NMR (C}

6D6): δ 8.06-7.06 (m, 30H, Ph); 4.92 (s, 5H, Cp); 2.85 (d, 2H, CH2, JH-H) 2.45 Hz); 2.57, 2.15 (m, 4H, CH2of dppe); 1.67 (t, 1H, tCH, JH-H) 2.45 Hz).31_{P NMR (C} 6D6): δ 87.4.13C NMR (C6D6): δ 148.1-125.5 (Ph); 112.2 (Cβ); 99.4 (CR_{); 83.4 (tC); 82.6 (Cp); 70.3 (tC); 51.1 (C}γ); 33.9 (CH2); 28.1 (CH2of dppe). MS(FAB) m/z: 794.2 (M+); 755.2 (M+- CH2CtCH); 565.1 (M+- C3(Ph)2, CH2CtCH). Anal. Calcd

for C49H42P2Ru: C, 74.13; H, 5.33. Found: C, 74.19; H, 5.39.

Spectroscopic data for 2d′(91% yield): 1_{H NMR (C}

6D6): δ 8.05-7.02 (m, 30H, Ph); 5.96 (m, 1H, dCH); 5.11 (dd, 2H, dCH2); 4.91 (s, 5H, Cp); 2.46, 2.18, 2.10 (m, 4H, 2H, 2H, CH2of dppe, 2CH2).31P NMR (C6D6): δ 87.2.13C NMR (C6D6): δ 149.5-125.1 (Ph); 113.4 (dCH2); 112.3 (Cβ); 97.8 (CR); 82.5 (Cp); 51.7 (Cγ); 41.7 (CH2); 30.7 (CH2); 27.8 (CH2of dppe). MS(FAB) m/z: 810.2 (M+); 755.2 (M+ -CH2CH2CHdCH2); 565.1 (M+- C3(Ph)2, CH2CH2CHdCH2). Anal.

Calcd for C50H46P2Ru: C, 74.14; H, 5.72. Found: C, 74.21; H, 5.80. Synthesis of Vinylidene Complex{[Ru]dCdCHC(Ph)2CH2R} -BF4(3a, R ) CHdCH2). To a Schlenk flask charged with 2a (0.1 g,

0.11 mmol) in diethyl ether (15 mL), HBF4(54% in Et2O) was added

dropwise at 0°C under nitrogen. Immediately, a pink precipitate formed, but addition of HBF4was continued until no further solid formed. The

precipitate was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give 3a (yield 95%). Spectroscopic data for 3a: 1_{H NMR (CDCl}

3): δ 7.40-6.92 (m, 40H, Ph), 5.02 (m, 1H, dCH), 5.00 (s, 5H, Cp), 4.87 (m, 2H, dCH2), 4.45 (t, 1H,4JPH) 3.0

Hz, CdCH), 3.06 (s, 2H, JHH) 6.0 Hz, CH2).31P NMR (CDCl3): δ

42.1. Mass m/z 923.3 (M+- BF4), 691.2 (M+ - BF4- C2HCPh2

-CH2CHdCH2). Anal. Calcd for C59H51BF4P2Ru: C, 70.17; H, 5.09.

Found: C, 70.14; H, 5.12.

Complexes 3b-3e (3b, R ) CMedCH2; 3c, R ) CtCH; 3d, R )

CH2CHdCH2; 3e, R ) Ph) were similarly prepared. Spectroscopic data

for 3b (yield 91%): 1_{H NMR (CDCl}

3): δ 7.56-6.76 (m, 40H, Ph),

4.99 (s, 5H, Cp), 4.62 (s, 1H, dCH2), 4.56 (t, 1H,4JPH) 3.0 Hz, Cd

CH), 4.53 (s, 1H, dCH2), 3.10 (s, 2H, CH2), 0.86 (s, CH3).31P NMR

(CDCl3): δ 42.1.

Spectroscopic data for 3c (yield 94%): 1_{H NMR (CDCl}

3): δ 7.41-6.84 (m, 40H, Ph), 5.05 (s, 5H, Cp), 4.81 (t,4_J PH) 3.0 Hz, CdCH), 3.00 (d,4_J HH) 2.1 Hz, CH2), 1.96 (t,4JHH) 2.1 Hz, CtCH).31P NMR (CDCl3): δ 41.5.13C NMR (CDCl3): δ 346.7 (t, JP-C) 15.1 Hz, CR), 145.7-127.1 (m, Ph), 120.1 (Cβ), 94.5 (Cp), 81.1 (CtCH), 72.6 (≡CH), 50.5 (Cγ), 33.4 (CH2). Mass m/z 920.0 (M+- 1 - BF4),

691.0 (M+- BF4- C2HCPh2CH2CtCH). Anal. Calcd. for C59H49

-BF4P2Ru: C, 70.31; H, 4.90. Found: C, 70.38; H, 5.08.

Spectroscopic data for 3d (yield 96%): 1_{H NMR (CDCl}

3): δ

7.41-6.81 (m, 40H, Ph), 5.69 (m, 1H, dCH), 5.00 (s, 5H, Cp), 4.90 (s, 2H,

dCH2), 4.59 (t, 1H,4_J

PH) 3.0 Hz, CdCH), 2.36 (m, 2H, CH2), 1.54

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(m, 2H, CH2).31P NMR (CDCl3): δ 41.8.13C NMR (CDCl3): δ 347.5

(t, JP-C) 15.1 Hz, CR_{), 146.7-126.7 (Ph), 137.7 (dCH), 120.2 (d} CH2), 115.0 (Cβ), 94.2 (Cp), 50.9 (Cγ), 41.0, (CH2), 29.2 (CH2). Mass

m/z 936.1 (M+- 1 - BF4), 691.1 (M+- BF4- C2HCPh2CH2CH2

-CHdCH2). Anal. Calcd for C60H53BF4P2Ru: C, 70.38; H, 5.22.

Found: C, 70.43; H, 5.20.

Spectroscopic data for 3e (yield 93%): 1_{H NMR (CDCl}

3): δ 7.39-6.39 (m, 45H, Ph), 4.96 (s, 5H, Cp), 4.10 (t, 1H,4_J PH) 3.0 Hz, Cd CH), 3.65 (s, 2H, CH2). 31P NMR (CDCl3): δ 42.0. 13C NMR (CDCl3): δ 346.8 (t, JP-C) 15.1 Hz, CR), 147.0-126.8 (Ph), 118.7 (Cβ), 94.7 (Cp), 53.0 (Cγ), 49.2, (CH2). Mass m/z 973.1 (M+- BF4), 881.1 (M+- BF4- CH2Ph), 691.0 (M+- BF4- C2HCPh2CH2Ph).

Anal. Calcd for C63H53BF4P2Ru: C, 71.39; H, 5.04. Found: C, 71.43;

H, 5.11.

Complexes 3a′, 3c′, and 3d′ were also prepared using similar procedures. Spectroscopic data for 3a′ (96% yield): 1_{H NMR}

(CDCl3): δ 7.47-6.67 (m, 30H, Ph); 5.84 (m, 1H, dCH); 5.23 (s,

5H, Cp); 4.83 (m, 1H, dCH2); 3.45 (s, 1H, CdCH); 2.73 (m, 4H, CH2

of dppe); 2.27 (d, 2H, CH2C(Ph)2).31P NMR (CDCl3): δ 77.6. Complex 3b′was not obtained. Upon protonation of 2b′complex 6b′was directly obtained in 97% yield.

Spectroscopic data for 3c′(95% yield): 1_{H NMR (CDCl}

3): δ 7.50-6.69 (m, 30H, Ph); 5.39 (s, 5H, Cp); 4.96 (s, 1H, CH); 3.75 (s, 1H, CHC(Ph)2); 2.80 (m, 4H, CH2of dppe); 2.15 (d, 2H, CH2; JH-H) 2.4 Hz); 1.94 (t, 1H, tCH, JH-H) 2.4 Hz).31P NMR (CDCl3): δ 77.5. 13_{C NMR (CDCl} 3): δ 343.2 (t, CR, JP-C) 15.5 Hz); 145.9-126.7 (Ph); 120.9 (Cβ); 91.8 (Cp); 81.3 (tC); 72.4 (tCH); 49.7 (Cγ); 31.8 (CH2); 26.9 (CH2of dppe). MS(FAB) m/z: 795.2 (M+); 755.2 (M+ -1, sCH2CtCH); 565.1 (M+ - C3H(Ph)2, CH2CtCH). Anal. Calcd

for C49H43P2BF4Ru: C, 66.75; H, 4.91. Found: C, 66.82; H, 4.98.

Spectroscopic data for 3d′(93% yield): 1_{H NMR (CDCl}

3): δ 7.51-6.56 (m, 30H, Ph); 5.52 (m, 1H, dCH); 5.32 (s, 5H, Cp); 4.89 (d, 1H, dCH2, JH-H) 8.1 Hz); 4.83 (d, 1H, dCH2, JH-H) 17.2 Hz); 3.68 (s, 1H, CH); 2.83, 2.58 (m, 4H, CH2of dppe); 1.56 (br, 4H, 2CH2).31P NMR (CDCl3): δ 77.8.13C NMR (CDCl3): δ 341.5 (t, CR); 147.1-126.0 (Ph); 120.8 (Cβ); 114.6 (dCH2); 91.5 (Cp); 51.4 (Cγ); 39.9 (CH2); 29.5 (CH2); 26.7 (CH2of dppe). MS(FAB) m/z: 811.2 (M+); 755.2 (M+- CH2CH2CHdCH2); 565.1 (M+- C3H(Ph)2, CH2CH2CHdCH2).

Anal. Calcd for C50H47P2BF4Ru: C, 66.89; H, 5.27. Found: C, 66.93;

H, 5.31.

Preparation of Complex {[Ru]dCdCHCH2C(Ph)2CHdCH2} -BF4(4a). A Schlenk flask was charged with 3a (0.1 g, 0.11 mmol)

and CH2Cl2(15 mL). The solution was heated to reflux under nitrogen

for 4 h and then cooled to room temperature. The solvent was reduced to 5 mL under vacuum, and then the residual mixture was added to 30 mL of diethyl ether. The orange precipitate thus formed was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give 4a (yield 90%). Spectroscopic data for 4a: 1_{H NMR (CDCl}

3): δ 7.41-6.78 (m, 40H, Ph), 6.51 (dd, 1H, JHH) 18.0, 10.8 Hz, dCH), 5.29 (d, 1H, JHH) 10.8 Hz, dCH2), 4.87 (s, 5H, Cp), 4.71 (d, 2H, JHH ) 18.0 Hz, dCH2), 4.40 (m, 1H, CdCH), 3.09 (d, 2H, JHH) 7.8 Hz, CH2).31P NMR (CDCl3): δ 43.9.13C NMR (C6D6): δ 345.6 (t, JP-C ) 15.1 Hz, CR_{), 145.4-126.6 (Ph), 143.7 (dCH), 115.3 (dCH}2), 110.5 (s, Cβ), 94.4 (s, Cp), 54.0 (s, Cγ), 31.9 (s, CH2). Mass m/z 923.3 (M+ - BF4), 691.2 (M+ - BF4- C2H CH2CPh2CHdCH2). Anal. Calcd

for C59H51BF4P2Ru: C, 70.17; H, 5.09. Found: C, 70.19; H, 5.15. Thermolysis of 3a in Acetonitrile. Complex 3a (0.1 g, 0.11 mmol)

was dissolved in 15 mL of CH3CN at room temperature. The solution

was heated to reflux for 1 h under nitrogen. Solvent was then removed under vacuum. The solvent was reduced to 5 mL under vacuum, and then the residual mixture was added to 30 mL of diethyl ether. The pale-orange precipitate thus formed was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give{[Ru]NCCH3}BF4.

The filtrate was evaporated to dryness, and the crude product was purified by column chromatography on silica gel with hexanes as eluent. Evaporation of the solvent gave a mixture of terminal enyne 7a and

8a as a colorless oil (yield 87%). Spectroscopic data of 7a are consistent

with that of literature data.

Preparation of 8a. A Schlenk flask was charged with 4a (0.1 g,

0.11 mmol) and CH3CN (15 mL). The solution was heated to reflux

under nitrogen for 1 h and then cooled to room temperature. The solvent was reduced to 5 mL under vacuum, and then the residual mixture was added to 30 mL of diethyl ether. The pale-orange precipitate thus formed was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give {[Ru]NCCH3}BF4. The filtrate was

evaporated to dryness, and crude product was purified by column chromatography on silica gel with hexanes as eluent. Evaporation of the solvent gave terminal enyne 8a as a colorless oil (yield 77%). Spectroscopic data for 8a: 1_{H NMR (CDCl}

3): δ 7.31-7.19 (m, 10H, Ph), 6.52 (dd, 1H, JHH) 17.7 Hz, JHH) 10.8 Hz, dCH), 5.28 (d, 1H, JHH) 10.8 Hz, dCH2), 4.86 (d, 1H, JHH) 17.7 Hz, dCH2), 3.12 (d, 2H, JHH) 2.4 Hz, CH2), 1.90 (t, 1H, JHH) 2.4 Hz, tCH).13C NMR (CDCl3): δ 145.1 (s, Ph), 143.8 (s, dCH), 128.5 (s, Ph), 128.2 (s, Ph), 126.5 (s, Ph), 115.3 (s, dCH2), 81.6 (s, tC), 71.5 (s, tCH), 53.5 (s, CPh2), 30.1 (s, CH2).

Conversion of 3a′to 4a′. Complex 3a′(90 mg, 0.113 mmol) was dissolved in 10 mL of CH2Cl2and stirred for 1 h at room temperature.

Then diethyl ether was added, and 5a was precipitated as an orange solid which was filtered and washed with ether and dried under vacuum to give 4a′(85 mg, 0.106 mmol) in 93% yield. Spectroscopic data for

4a′: 1_{H NMR (CDCl} 3): δ 7.67-6.70 (m, 30H, Ph); 6.00 (m, 1H, d CH, JH-H) 10.8, 16.8 Hz); 5.22 (s, 5H, Cp); 5.03 (d, 1H, dCH2, JH-H) 10.7 Hz); 4.43 (d, 1H, dCH2, JH-H) 17.5 Hz); 3.20 (t, 1H, CdCH, JH-H) 7.25 Hz); 2.76 (m, 4H, CH2of dppe); 2.21 (d, 2H, CH2, JH-H) 7.25 Hz).31P NMR (CDCl3): δ 87.2.13C NMR (CDCl3): δ 341.7 (t, CR, JP-C) 16.3 Hz); 145.2-126.2 (Ph); 114.5 (Cβ); 108.5 (dCH2); 91.4 (Cp); 53.2 (Cγ); 28.7 (CH2); 27.3 (CH2of dppe). MS (FAB) m/z: 796.1 (M+- 1); 565.1 (M+- 1, sC3(Ph)2, CH2CHCH2).

Anal. Calcd for C49H45P2BRuF4: C, 66.59; H, 5.13. Found: C, 66.62;

H, 5.18.

Preparation of 6b. A Schlenk flask was charged with 3b (0.10 g,

0.10 mmol) and CH2Cl2 (15 mL) under nitrogen. The solution was

stirred at room temperature for 1 min. The solvent was reduced to 5 mL under vacuum, and then 30 mL of diethyl ether were added to give an orange precipitate which was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give 6b (yield 83%). Spectroscopic data for 6b: 1_{H NMR (CD}

2Cl2): δ 7.58-6.30 (m, 40H, Ph), 5.39 (br, 1H, dCH), 4.96 (s, 5H, Cp), 2.76 (d, JHH) 14.0 Hz, 1H of CH2), 2.70 (t, JP-H) 10.0 Hz, br, 1H, dCH), 1.66 (m, 1H, CH), 1.56 (d, JHH) 5.5 Hz, CH3+ 1H of CH2).31P NMR (CDCl3): δ 41.3, 40.9 (d, JP-P) 36.4 Hz, 2 PPh3).13C NMR (CD2Cl2, 258K): δ 151.1-125.5 (Ph), 144.7 (dd, JP-C) 22.6, 2.5 Hz, dCd), 131.6 (dCH); 90.4 (Cp), 57.7 (CPh2), 51.2 (CH2), 43.4 (dCH), 35.2 (dCH), 20.3 (CH3).

Mass m/z 937.1 (M+- BF4), 675.1 (M+- BF4- PPh3). Anal. Calcd for C60H53BF4P2Ru: C, 70.38; H, 5.22. Found: C, 70.29; H, 5.17.

Spectroscopic data for 6b′: 1_{H NMR (CDCl}

3): δ 7.68-6.65 (m, 30H, Ph); 5.04 (s, 5H, Cp); 4.96 (s, 1H, CH); 3.25, 2.70, 2.62, 2.25 (m, 4H, CH2of dppe); 2.40, 1.42 (m, 2H, C(Ph)2CH2); 1.17 (m, 1H, CH); 1.14 (m, 1H, CH); 0.82 (d, JH-H) 7.9 Hz, 3H, CH3).31P NMR (CDCl3): δ 78.1, 74.2 (AX, JP-P) 25.1 Hz).13C NMR (CDCl3): δ 151.1-126.4 (Ph); 143.5 (d, JP-C) 24.8 Hz, dCd); 132.7 (dCH); 90.6 (Cp); 58.1 (CPh2); 51.2 (CH2); 43.2 (C(CH3)); 32.9 (dCH); 27.5, 24.8 (CH2of dppe); 19.2 (CH3). MS (FAB) m/z: 811.2 (M+- BF4);

565.1 (M+- BF4, C3(Ph)2CH2C(CH3)CH2). Anal. Calcd for C49H47P2

-BF4Ru: C, 66.44; H, 5.34. Found: C, 66.49; H, 5.41.

Preparation of 4c. A Schlenk flask was charged with 3c (0.1 g,

0.10 mmol) and CHCl3(10 mL)/CH2Cl2(5 mL) under nitrogen. The

resulting solution was heated to reflux for 4 h and then cooled to room temperature. The solvent was reduced to 5 mL under vacuum, and the mixture was added to 30 mL of diethyl ether. The gray precipitate thus formed was filtered and washed with diethyl ether (2× 10 mL) and dried under vacuum to give 4c (yield 74%). Spectroscopic data for 4c: A R T I C L E S

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1_{H NMR (CDCl}

3): δ 7.77-6.79 (m, 40H, Ph), 4.83 (s, 5H, Cp), 4.67

(m, 1H, CdCH), 3.09 (d, JHH) 7.8 Hz, CH2), 2.78 (s, tCH).31P

NMR (CDCl3): δ 43.8. Mass m/z 921.1 (M+- BF4), 691.1 (M+

-BF4 - C2HCH2CPh2CtCH). Anal. Calcd for C59H49BF4P2Ru: C,

70.31; H, 4.90. Found: C, 70.37; H, 5.03.

The same reaction in CH3CN for 1 h gave [Ru]NCCH3+ and

HCtCC(Ph)2CH2CtCH, 9c. Two products were separated by the

method used for the separation of 8a and [Ru]NCCH3+. Spectroscopic

data for 9c (yield 83%): 1_{H NMR (CDCl}

3): δ 7.49-7.21 (m, 10H,

Ph), 3.16 (d, 1H, JHH) 2.4 Hz, tCH), 2.66 (s, 1H, tCH), 2.01 (t,

1H, JHH) 2.4 Hz, CH2).13C NMR (CDCl3): δ 143.3 (s, Ph), 128.3 (s,

Ph), 127.4 (s, Ph), 127.1 (s, Ph), 87.2 (s, tC), 80.7 (s, tC), 73.9 (s,

tCH), 71.4 (s, tCH), 48.9 (s, CPh2), 32.7 (s, CH2).

Single-Crystal X-ray Diffraction Analysis of 6b. Single crystals

of 6b suitable for an X-ray diffraction study were grown as mentioned above. A single crystal of dimensions 0.25× 0.20 × 0.15 mm3_was

glued to a glass fiber and mounted on an SMART CCD diffractometer. The diffraction data were collected using 3 kW sealed-tube Mo KR radiation (T ) 295 K). Exposure time was 5 s per frame. SADABS32

(Siemens area detector absorption) absorption correction was applied, and decay was negligible. Data were processed, and the structure was

solved and refined by the SHELXTL33 _{program. The structure was}

solved using direct methods and confirmed by Patterson methods refining on intensities of all data (33 919 reflections) to give R1 ) 0.0584 and wR2 ) 0.1370 for 11 445 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 hydrogens.

Acknowledgment. This research is supported by the National Science Council of Taiwan, the Republic of China. Valuable suggestions on the mechanism from Professor Kung Wang of West Virginia University and Professor Charles P. Casey of University of Wisconsin at Madison are gratefully acknowl-edged.

Supporting Information Available: Complete crystallo-graphic data for 6b (CIF). This material is available free of charge via the Internet at http://pubs.acs.org.

JA054994A (32) The SADABS program is based on the method of Blessing; see: Blessing,

R. H. Acta Crystallogr., Sect. A 1995, 51, 33-38.

(33) SHELXTL: Structure Analysis Program, version 5.04; Siemens Industrial Automation Inc.: Madison, WI, 1995.