Alkyne-Functionalized Zirconocene Complexes: Synthesis, Structures

Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People's Republic of China. ‡ State Key ... Publication Date (Web): October ...
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Organometallics 2010, 29, 6092–6096 DOI: 10.1021/om1007677

Alkyne-Functionalized Zirconocene Complexes: Synthesis, Structures, and Reactivities Minxiong Li,† Haibin Song,† Shansheng Xu,† and Baiquan Wang*,†,‡ †

State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China, and ‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China Received August 7, 2010

Reactions of (phenylethynyl)lithium with substituted cyclopentenones gave the corresponding phenylethynyl-substituted cyclopentadienes 1,2-R2-4-(PhCtC)C5H2 (R=Me (1a), Ph (1b)), which underwent subsequent deprotonation and transmetalation with ZrCl4 to yield the corresponding alkynefunctionalized zirconocene complexes {η5-[1,2-R2-4-(PhCtC)C5H2]}2ZrCl2 (R = Me (2a), Ph (2b)). Thermal treatment of 2a,b with Ru3(CO)12 in refluxing benzene afforded the trinuclear complexes (3,4-R2C5H2)2(μ3-C4Ph2)Ru3(CO)6(μ-CO)2 (R=Me (3a), Ph (3b)) and the dinuclear complex (3,4Ph2C5H2)2( μ-C4Ph2)Ru2(CO)5(μ-CO) (3c), via the unexpected cleavage of the two Cp0 -Zr bonds. The crystal structures of 2b and 3a,c were determined by X-ray diffraction. Cyclopentadienyl ligands with one or more alkyne groups as the ring substituents or side chain functional groups have been extensively used to synthesize alkyne-functionalized cyclopentadienyl transition-metal complexes.1-5 The alkyne group in these complexes acts not only as a donor of two π electrons to coordinate with the Lewis acidic metal center2 but also as a reactive group to undergo further reaction.3,4 For double-alkyne-functionalized metallocene complexes, some metal carbonyl complexes and other reagents can couple the two *To whom correspondence should be addressed. Fax: þ86-2223504781. E-mail: [email protected]. (1) (a) Bunel, E. E.; Valle, L.; Jones, N. L.; Carroll, P. J.; Gonzalez, M.; Munoz, N.; Manrlquez, J. M. Organometallics 1988, 7, 789. (b) Bunz, U. H. F.; Enkelmann, V.; Beer, F. Organometallics 1995, 14, 2490. (c) Bunz, U. H. F. Pure Appl. Chem. 1996, 68, 309. (d) Fabian, K. H. H.; Lindner, H.-J.; Nimmerfroh, N.; Hafner, K. Angew. Chem., Int. Ed. 2001, 40, 3402. (e) Sato, M.; Kubota, Y.; Kawata, Y.; Fujihara, T.; Unoura, K.; Oyama, A. Chem. Eur. J. 2006, 12, 2282. (2) (a) Buzinkai, J. F.; Schrock, R. R. Inorg. Chem. 1989, 28, 2831. (b) Baker, M. V.; Brayshaw, S. K. Organometallics 2004, 23, 3749. (3) (a) Onitsuka, K.; Miyaji, K.; Adachi, T.; Yoshida, T.; Sonogashira, K. Chem. Lett. 1994, 23, 2279. (b) Onitsuka, K.; Katayama, H.; Sonogashira, K.; Ozawa, F. J. Chem. Soc., Chem. Commun. 1995, 2267. (c) Pudelski, J. K.; Callstrom, M. R. Organometallics 1994, 13, 3095. (d) Ma, J.; K€ uhn, B.; Hackl, T.; Butensch€on, H. Chem. Eur. J. 2010, 16, 1859. (4) (a) Onitsuka, K.; Tao, X. Q.; Wang, W. Q.; Otsuka, Y.; Sonogashira, K. J. Organomet. Chem. 1994, 473, 195. (b) McAdam, C. J.; Brunton, J. J.; Robinson, B. H.; Simpson, J. J. Chem. Soc., Dalton Trans. 1999, 2487. (c) Scholz, G.; Gleiter, R.; Rominger, F. Angew. Chem., Int. Ed. 2001, 40, 2477. (d) Champeil, E.; Draper, S. M. Dalton Trans. 2001, 1440. (e) Scholz, G.; Schaefer, C.; Rominger, F.; Gleiter, R. Org. Lett. 2002, 4, 2889. (f) Jiao, J.; Long, G. J.; Rebbouh, L.; Grandjean, F.; Beatty, A. M.; Fehlner, T. P. J. Am. Chem. Soc. 2005, 127, 17819. (g) Laus, G.; Schottenberger, H.; Lukasser, J.; Wurst, K.; Sch€ utz, J.; Ongania, K.-H.; Zsolnai, L. J. Organomet. Chem. 2005, 690, 691. (h) Mathur, P.; Chatterjee, S.; Das, A.; Mobin, S. M. J. Organomet. Chem. 2007, 692, 819. (5) (a) Peifer, B.; Milius, W.; Alt, H. G. J. Organomet. Chem. 1998, 553, 205. (b) Reybuck, S. E.; Meyer, A.; Waymouth, R. M. Macromolecules 2002, 35, 637. (c) Licht, A. I.; Alt, H. G. J. Organomet. Chem. 2003, 684, 91. (d) G€ orl, C.; Alt, H. G. J. Organomet. Chem. 2007, 692, 5727. (e) Ivchenko, P. V.; Nifant'ev, I. E.; Mkoyan, S. G. Russ. Chem. Bull. 2007, 56, 70. (f) Chen, L.; Kehr, G.; Fr€ohlich, R.; Erker, G. Eur. J. Inorg. Chem. 2008, 73. pubs.acs.org/Organometallics

Published on Web 10/27/2010

Scheme 1

alkyne groups to form distinct bridged metallocene complexes.3 For example, reactions of 1,10 -dialkynylferrocene with Ru3(CO)12, KOH, and ArOH yielded metallacycles or [4]ferrocenophanes.3a-d Up to now, alkyne-functionalized cyclopentadienyl transition-metal complexes have mainly focused on ferrocene and ruthenocene derivatives; other metal complexes with an alkyne-functionalized cyclopentadienyl ligand are very limited. Recently, the alkynyl-substituted zirconocene complexes bis(2-phenylethynylindenyl)zirconium dichloride and bis[2-(prop-1-ynyl)indenyl]zirconium dichloride have been synthesized.5f They reacted with Co2(CO)8 to form the corresponding heteronuclear (alkyne)Co2(CO)6 complexes. In this work, we will report the synthesis and structures of two new alkyne-functionalized zirconocene complexes. Their reactions with Ru3(CO)12 were also studied, and the Cp0 -Zr bond cleavage products were obtained.

Results and Discussion Following the synthetic route reported previously by the Waymouth group,5b the two new ligand precursors 1a,b were r 2010 American Chemical Society

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Scheme 2

Figure 1. ORTEP diagram of 2b. Thermal ellipsoids are shown at the 30% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (A˚) and angles (deg): Zr(1)-Cl(1) = 2.4161(10), Zr(1)-Cl(2) = 2.3888(8), C(1)-C(6) = 1.426(3), C(6)-C(7) = 1.184(3), C(7)-C(8) = 1.434(3), C(26)C(31) = 1.414(3), C(31)-C(32) = 1.193(3), C(32)-C(33) = 1.427(3); Cl(2)-Zr(1)-Cl(1) = 98.17(3), C(7)-C(6)-C(1) = 178.6(2), C(6)-C(7)-C(8) = 177.2(2), C(32)-C(31)-C(26) = 175.3(3), C(31)-C(32)-C(33)=175.0(3), Cp-Cp=56.0.

synthesized by the reactions of (phenylethynyl)lithium with the corresponding substituted cyclopentenones in 81% and 50% yields, respectively (Scheme 1). 1a,b are both quite soluble in Et2O, CH2Cl2, and THF, while being slightly soluble in pentane and hexane. They have been fully characterized by 1H NMR, 13C NMR, mass spectra, and elemental analysis. In the 1H NMR spectra of 1a,b the signals of the cyclopentadienyl protons appeared as two singlets at 6.50 (1H), 2.96 (2H) ppm and 7.13 (1H), 3.90 (2H) ppm, respectively, indicating that the phenylethynyl groups were attached to the 4-position of the cyclopentadiene rings. By the direct transmetalation of their lithium salts with ZrCl4, the corresponding alkyne-functionalized zirconocene complexes 2a,b were synthesized in 52% and 53% yields, respectively (Scheme 1). Complexes 2a,b are stable to air and moisture in the solid state and could be exposed to air for several hours without obvious decomposition, but they decompose readily in solution when exposed to air. They are quite soluble in Et2O, CH2Cl2, and THF. Their 1H NMR spectra showed one singlet for the four cyclopentadienyl protons at 6.54 and 6.85 ppm for 2a,b, respectively. The signal of the methyl protons in 2a also appeared as a singlet at 2.14 ppm. This indicated that both complexes consist of two equivalent units

and possess C2 symmetry in solution. The EI-MS of 2a,b both showed the molecular ion peaks. The molecular structure of 2b was determined by X-ray diffraction analysis (Figure 1). It showed that the phenylethynyl substituents attached to the cyclopentadienyl rings are almost linear (C(1)-C(6)-C(7) = 178.6(2)°, C(6)-C(7)-C(8) = 177.2(2)°; C(26)-C(31)-C(32) = 175.3(3)°, C(31)-C(32)-C(33)=175.0(3)°), similar to those reported for the 2-phenylethynylindenyl zirconium complexes.5e,f The CtC bond lengths (1.184(3) and 1.193(3) A˚) are typical of acetylene and substituted acetylenes. The two phenylethynyl substituents are oriented toward the same lateral sector of the bent-metallocene wedge. The cyclopentadienyl ring and the phenyl ring of the PhCtC fragment are noncoplanar, with dihedral angles of 73.1 and 24.4°. The Cl-Zr-Cl angle is 98.17(3)°, slightly larger than those observed in (Ph2Cp)2ZrCl2 (94.25°) and (1,2-Ph2-4-Me-C5H2)2ZrCl2 (94.41°).6 The Cent-Zr-Cent angle (130.30°) is close to the values of 129.5° found in (1,2-Ph2-4-Me-C5H2)2ZrCl2 but slightly larger than that in (Ph2Cp)2ZrCl2 (126.6°). The dihedral angles between the two Cp planes (56°) is close to the value of 56.8° for (1,2-Ph2-4-Me-C5H2)2ZrCl2 but smaller than the value of 61.6° for (Ph2Cp)2ZrCl2. The Zr-Cent distances (2.248, 2.245 A˚) are longer than those in (Ph2Cp)2ZrCl2, (1, 2-Ph2-4-Me-C5H2)2ZrCl2, and other bulky zirconocene complexes (2.215-2.223 A˚).7 Our initial idea was to synthesize heteronuclear ruthenacycle-bridged zirconocene complexes through the C-C coupling reactions of the two alkyne groups in 2a,b by Ru3(CO)12. When the reactions were performed in refluxing benzene, C-C coupling reactions occurred indeed for both 2a and 2b; however, to our surprise, the zirconium atoms were decoordinated from the cyclopentadienyl ligands to give the ruthenacycle-bridged biscyclopentadiene derivatives 3a-c (Scheme 2). To the best of our knowledge, no similar chemistry has been reported for group 4 metallocene complexes. In our previous work we reported that reaction of the doubly bridged dinuclear (μ-oxo)titanium complex (Me2C)(Me2Si)(C5H3)2(μ-O)(CpTiCl)2 with concentrated HCl or HBr gave the corresponding Cp-decoordinated products (Me2C)(Me2Si)(C5H3)2[CpTiX(μ-O)TiX2] (X = Cl, Br).8 In that case the decoordination of the Cp ligand could be attributed to the large intramolecular interaction and the strong acidity of concentrated HCl and HBr, and the fate of the decoordinated Cp ligand was unknown. However, in this case the (6) Zhang, F.; Mu, Y.; Zhao, L.; Zhang, Y.; Bu, W.; Chen, C.; Zhai, H.; Hong, H. J. Organomet. Chem. 2000, 613, 68. (7) (a) Grimmond, B. J.; Corey, J. Y.; Rath, N. P. Organometallics 1999, 18, 404. (b) Erker, G.; Nolte, R.; Aul, R.; Wilker, S.; Kr€uger, C.; Noe, R. J. Am. Chem. Soc. 1991, 113, 7594. (8) Luo, S.; Shen, B.; Li, B.; Song, H.; Xu, S.; Wang, B. Organometallics 2009, 28, 3109.

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Figure 2. ORTEP diagram of 3a. Thermal ellipsoids are shown at the 50% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (A˚) and angles (deg): Ru(1)C(6) = 2.214(2), Ru(1)-Ru(2) = 2.6646(5), Ru(1)-Ru(3) = 2.6797(5), Ru(2)-C(6) = 2.283(2), Ru(2)-C(7) = 2.355(2), Ru(3)-C(6) = 2.298(2), Ru(3)-C(7) = 2.327(2), C(6)-C(7) = 1.458(3), C(7)-C(7A) = 1.482(4), C(8)-C(9) = 1.372(3), C(8)C(12)=1.481(3), C(9)-C(10)=1.478(3), C(10)-C(11)=1.349(4), C(11)-C(12)=1.497(3); C(6A)-Ru(1)-C(6)=73.22(12), Ru(2)Ru(1)-Ru(3)=88.612(12), C(7)-C(6)-Ru(1)=119.98(16), C(6)C(7)-C(7A)=113.40(13).

reaction conditions are much milder, and the decoordinated free cyclopentadiene derivatives were obtained. However, the fate of Zr is still unknown; it may be adsorbed by the Al2O3 column. Furthermore, we also do not know where the protons for the cyclopentadienes come from. We are still trying to determine this and extend the reaction scope. Complexes 3a-c are stable to air and moisture in both the solid state and solution. They are quite soluble in common organic solvents. In the 1H NMR spectra of 3a-c nearly all chemical shifts moved toward high field in comparison with their corresponding signals in the zirconocene complexes 2a, b. A remarkable change is the appearance of a singlet for the methylene protons at 2.72 and 3.44 ppm for 3a,b, respectively. In 3c the signal of the methylene protons was split into two doublets at 3.31 and 3.19 ppm, due to its unsymmetrical structure. In the IR spectra 3a,b showed four or three terminal and two bridging carbonyl absorptions at 2063-1959 and 1872-1839 cm-1, respectively, while 3c showed four terminal carbonyl absorptions at 2084-1993 cm-1 and one bridging carbonyl absorption at 1922 cm-1. The CdC double-bond absorptions at 1640-1615 cm-1 are very weak for 3a but strong for 3b,c. The molecular structures of 3a,c were determined by X-ray diffraction analysis (Figures 2 and 3). 3a is a trinuclear ruthenium cluster in which two ruthenium atoms coordinate symmetrically with the ruthenacyclopentadienyl in an η5 mode from the both sides of the ruthenacyclopentadienyl plane. The ruthenacyclopentadiene is obviously the product of a “head-to-head” C-C coupling of the two alkyne groups. This bridges the two cyclopentadienyl rings by the two carbon atoms, as we expected. The ruthenacyclopentadiene ring is coplanar. The dihedral angles between the ruthenacyclopentadiene plane and the cyclopentadienyl and phenyl

Li et al.

Figure 3. ORTEP diagram of 3c. Thermal ellipsoids are shown at the 30% probability level. Hydrogen atoms have been omitted for clarity. Selected bond lengths (A˚) and angles (deg): Ru(1)-Ru(2)=2.7185(7), Ru(2)-C(7)=2.092(5), Ru(2)-C(10)=2.095(5), C(7)-C(8) = 1.421(7), C(8)-C(9) = 1.454(7), C(9)-C(10) = 1.436(7), C(17)-C(21) = 1.367(7), C(17)-C(18) = 1.473(7), C(18)-C(19) = 1.502(7), C(19)-C(20) =1.358(8), C(20)-C(21) = 1.468(7), C(34)-C(35) = 1.355(7), C(34)-C(38) = 1.491(7), C(35)-C(36)=1.464(7), C(36)-C(37)=1.348(7), C(37)-C(38)= 1.505(7); C(7)-Ru(2)-C(10)=77.64(19), C(8)-C(7)-Ru(2)= 116.4(4), C(7)-C(8)-C(9) = 114.6(5), C(10)-C(9)-C(8) = 113.8(4), C(9)-C(10)-Ru(2)=116.3(3).

planes are 70.2 and 49.8°, respectively. The Ru-Ru distances are 2.6646(5) and 2.6797(5) A˚, and the Ru(2)-Ru(1)-Ru(3) angle is 88.612(12)°, which is comparable with those for other trinuclear ruthenacycle complexes.3a,9 The C(7)C(7A) bond length is 1.482(4) A˚, slightly longer than those found in the similar trinuclear ruthenacycle complexes (μ3-C4R4)Ru3(CO)6(μ-CO)2 (R = Ph, Me) (1.460(7), 1.472(6) A˚).9 The C(8)-C(9) and C(10)-C(11) bond lengths (1.372(3), 1.349(4) A˚) are close to the typical CdC double bond and evidently shorter than other C-C bonds (1.4781.497 A˚) in the five-membered ring, supporting the cyclopentadiene structure. The structure of 3c is similar to that of 3a. It is a dinuclear ruthenium complex in which only one ruthenium atom coordinates with the ruthenacyclopentadienyl in an η5 mode. Similar to the known ferrole-type complexes, the [Ru2(CO)6] fragments of 3c have a “non-sawhorse” geometry typified by a semibridging CO ligand and a Ru-Ru bond of 2.7185(7) A˚. The C(8)-C(9) bond length is 1.454(7) A˚, significantly shorter than that of 3a, but it is comparable with those of other similar dinuclear ruthenacycle complexes (1.4161.474 A˚).10 The dihedral angles between the ruthenacyclopentadienyl plane and the two cyclopentadienyl and two phenyl planes are 65.3, 49.0, 82.7, and 67.7°, respectively. In summary, the two alkyne-functionalized zirconocene complexes {η5-[1,2-R2-4-(PhCtC)C5H2]}2ZrCl2 (R = Me (9) (a) Capparelli, M. V.; DeSanctis, Y.; Arce, A. J. Acta Crystallogr., Sect. C 1995, 51, 1819. (b) Ferrand, V.; Neels, A.; Evans, H. S.; Fink, G. S. Inorg. Chem. Commun. 1999, 2, 561. (10) (a) Astier, A.; Daran, J. C.; Jeannin, Y.; Rigault, C. J. Organomet. Chem. 1983, 241, 53. (b) Bruce, M. I.; Matisons, J. G.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1983, 251, 249. (c) Yeh, W. Y.; Hsu, S. C. N.; Peng, S. M.; Lee, G. H. Organometallics 1998, 17, 2477. (d) Adams, R. D.; Fu, W.; Qu, B. J. Cluster Sci. 2000, 11, 55.

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Table 1. Crystal Data and Summary of X-ray Data Collection Details

formula fw T, K λ, A˚ cryst syst space group a, A˚ b, A˚ c, A˚ R, deg β, deg γ, deg V, A˚3 Z Dcalcd, g cm-3 μ, mm-1 F(000) cryst size, mm θ range, deg no. of rflns collected no. of indep rflns/Rint no. of params goodness of fit on F2 R1, wR2 (I > 2σ(I)) R1, wR2 (all data) largest diff peak and hole (e A˚-3)

2b

3a

3c

C50H34Cl2Zr 796.89 113(2) 0.710 73 monoclinic P21/n 13.792(3) 11.672(2) 23.739(5) 90 100.75(3) 90 3754.2(13) 4 1.410 0.471 1632 0.20  0.18  0.12 2.30-25.02 28 935 6606/0.0320 478 1.090 0.0332, 0.0844 0.0369, 0.0868 0.372, -0.590

C38H28O8Ru3 915.81 113(2) 0.710 75 orthorhombic Pnma 18.429(2) 21.069(3) 8.9515(9) 90 90 90 3475.6(7) 4 1.750 1.339 1808 0.28  0.22  0.20 2.21-27.85 23 323 4218/0.0404 235 1.190 0.0321, 0.0773 0.0342, 0.0783 1.855, -1.171

C56H36O6Ru2 1006.99 113(2) 0.710 75 monoclinic P21/n 9.5624(14) 17.547(3) 26.690(4) 90 91.864(2) 90 4476.0(12) 4 1.494 0.728 2032 0.26  0.24  0.22 1.39-26.00 37 068 8788/0.0726 603 1.248 0.0673, 0.1266 0.0759, 0.1300 0.591, -0.656

(2a), Ph (2b)) were synthesized. Their reactions with Ru3(CO)12 did not give a heteronuclear ruthenacycle-bridged ansa-zirconocene complex but afforded ruthenacyclebridged bis(cyclopentadiene) derivatives via the cleavage of the Cp0 -Zr bonds.

Experimental Section General Considerations. Schlenk and vacuum-line techniques were employed for all manipulations of air- and moisturesensitive compounds. All solvents were distilled from appropriate drying agents under argon before use. 1H and 13C NMR spectra were recorded on a Bruker AV400 spectrometer, while EI mass spectra were measured on a VG ZAB-HS instrument. Elemental analyses were performed on a Perkin-Elmer 240C analyzer. IR spectra were recorded as KBr disks on a Nicolet 380 FT-IR spectrometer. 3,4-Dimethyl-2-cyclopenten-1-one11 and 3,4-diphenyl-2-cyclopenten-1-one12 were synthesized according to literature procedures. Synthesis of 1,2-Dimethyl-4-phenylethynylcyclopentadiene (1a). The ligand precursor 1a was synthesized by following the procedure described for 2-phenylethynylindene.5b To a solution of 18.384 g (180 mmol) of phenylacetylene in 120 mL of THF was gradually added 108 mL (180 mmol, 1.67 M) of nBuLi hexane solution at 0 °C. After the mixture was warmed to room temperature and stirred for 5 h, a solution of 19.827 g (180 mmol) of 3,4-dimethyl-2-cyclopenten-1-one in 30 mL of THF was added dropwise. The reaction mixture was stirred overnight and then quenched with 30 mL of a saturated NH4Cl aqueous solution. The aqueous layer was extracted with diethyl ether, and the combined organics were dried over Na2SO4. After removal of solvents the residue was dissolved in 100 mL of diethyl ether, and 70 mL (3 M) of H2SO4 was added, and then this mixture was stirred overnight. The reaction mixture was again quenched with a saturated NH4Cl aqueous solution, separated, extracted with diethyl ether, and dried. After removal of solvents the residue was chromatographed over a silica gel column with hexane as eluent to give 28.324 g (81%) of 1a as a (11) Schwartz, K. D.; White, J. D. Org. Synth. 2006, 83, 49. (12) (a) Plenio, H.; Burth, D. Organometallics 1996, 15, 4054. (b) Polo, E.; Barbieri, A.; Traverso, O. Eur. J. Inorg. Chem. 2003, 324.

yellow solid. Mp: 50-51 °C. Anal. Calcd for C15H14: C, 92.74; H, 7.26. Found: C, 92.66; H, 7.34. 1H NMR (CDCl3): δ 7.32 (d, J = 4.7 Hz, 2H, Ph H), 7.16-7.04 (m, 3H, Ph H), 6.50 (s, 1H, C5H3), 2.96 (s, 2H, C5H3), 1.77 (s, 3H, Me), 1.70 (s, 3H, Me) ppm. 13C NMR (100 MHz, CDCl3): δ 142.6, 137.7, 135.0, 130.9, 128.0, 127.3, 123.8, 122.6, 91.7, 87.1, 48.9, 13.1, 12.0 ppm. MS (EI): m/z 194.1 (100, Mþ). Synthesis of 1,2-Diphenyl-4-phenylethynylcyclopentadiene (1b). Using a procedure similar to that described above for 1a, the ligand precursor 1b was synthesized as an orange solid in 50% yield by using 3,4-diphenyl-2-cyclopenten-1-one instead of 3, 4-dimethylcyclopent-2-enone. Mp: 159-160 °C. Anal. Calcd for C25H18: C, 94.30; H, 5.70. Found: C, 94.21; H, 5.79. 1H NMR (CDCl3): δ 7.65 (d, J=7.4 Hz, 2H, Ph -H), 7.50-7.38 (m, 10H, Ph H), 7.36-7.28 (m, 3H, Ph H), 7.13 (s, 1H, C5H3), 3.90 (s, 2H, C5H3) ppm. 13C NMR (100 MHz, CDCl3): δ 142.5, 141.5, 140.7, 136.3, 136.1, 131.3, 128.5, 128.3, 128.2, 127.9, 127.8, 127.3, 126.8, 125.6, 123.5, 93.7, 86.5, 48.7 ppm. MS (EI): m/z 318.1 (100, Mþ). Synthesis of 2a. To a solution of 8.125 g (41.82 mmol) of 1a in 120 mL of hexane was added dropwise 18 mL (41.94 mmol, 2.33 M) of a nBuLi hexane solution at 0 °C. After it was warmed to room temperature and stirred overnight, the resulting suspension was filtered. To the residue was added 4.873 g (20.91 mmol) of ZrCl4; then the flask was cooled to -78 °C, and 150 mL of CH2Cl2 was added slowly. The mixture was warmed slowly to room temperature and stirred overnight. It was filtered through a Celite pad, and the solvent was removed under reduced pressure. The residue was recrystallized with diethyl ether and hexane to give 5.966 g (52%) of 2a as a yellow solid. Mp: 179-180 °C. Anal. Calcd for C30H26Cl2Zr: C, 65.67; H, 4.78. Found: C, 65.73; H, 4.79. 1H NMR (CDCl3): δ 7.53 (m, 4H, Ph H), 7.37 (m, 6H, Ph H), 6.54 (s, 4H, C5H2), 2.14 (s, 12H, CH3) ppm. 13C NMR (100 MHz, CDCl3): δ 131.4, 128.6, 128.5, 122.6, 121.4, 102.8, 92.8, 83.0, 13.2 ppm. MS (EI): m/z 546.3 (52, Mþ). Synthesis of 2b. Using a procedure similar to that described above for 2a, 2b was synthesized as yellow crystals in 53% yield by using 1b instead of 1a. Mp: 213-215 °C. Anal. Calcd for C50H34Cl2Zr: C, 75.36; H, 4.30. Found: C, 75.48; H, 5.80. 1H NMR (CDCl3): δ 7.42-7.29 (m, 18H, Ph H), 7.20 (t, J=7.2 Hz, 4H, Ph H), 7.13 (t, J = 7.5 Hz, 6H, Ph H), 6.85 (s, 4H, C5H2) ppm. 13C NMR (100 MHz, CDCl3): δ 132.7, 131.7, 131.1, 129.6,

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128.6, 128.3, 127.9, 127.8, 122.5, 120.6, 107.3, 94.6, 82.7 ppm. MS (EI): m/z 794.1 (7, Mþ). Reaction of 2a with Ru3(CO)12. A solution of 0.264 g (0.48 mmol) of 2a and 0.307 g (0.47 mmol) of Ru3(CO)12 in 30 mL of benzene was heated under reflux for 12 h. The solvent was removed under reduced pressure, and the residue was placed in an Al2O3 column. Elution with CH2Cl2/petroleum ether gave 0.072 g (17%) of 3a as orange crystals. Mp: 206-207 °C. Anal. Calcd for C38H28O8Ru3: C, 49.84; H, 3.08. Found: C, 49.63; H, 3.27. 1H NMR (CDCl3): δ 6.96 (m, 6H, Ph H), 6.41 (d, J=6.9 Hz, 4H, Ph H), 6.36 (s, 2H, C5H3), 2.72 (s, 4H, C5H3), 1.81 (s, 6H, CH3), 1.78 (s, 6H, CH3) ppm. 13C NMR (100 MHz, CDCl3): δ 190.1, 146.0, 144.9, 138.7, 134.8, 134.7, 128.1, 127.1, 126.7, 116.9, 116.5, 53.4, 13.4, 12.6 ppm. IR (νCO and νCdC): 2063 (s), 2030 (s), 1997 (s), 1973 (s), 1860 (s), 1839 (s), 1635 (w), 1624 (w) cm-1. Reaction of 2b with Ru3(CO)12. Using a procedure similar to that described above, reaction of 2b with Ru3(CO)12 in refluxing benzene gave 3b (47%) and 3c (8%) as orange and yellow-green crystals, respectively. Data for 3b are as follows. Mp: 225 °C dec. Anal. Calcd for C56H36O8Ru3: C, 59.00; H, 3.18. Found: C, 59.14; H, 3.56. 1H NMR (CDCl3): δ 7.22-7.01 (m, 26H, Ph H), 6.97 (s, 2H, Ph H), 6.58 (s, 1H, Ph H), 6.56 (s, 2H, C5H3), 3.44 (s, 4H, C5H3) ppm. 13C NMR (100 MHz, CDCl3): δ 200.9, 198.8, 189.9, 149.4, 146.1, 144.6, 142.4, 140.9, 138.3, 136.0, 135.7, 130.0, 128.6, 128.4, 128.2, 128.1, 127.7, 127.5, 127.4, 127.2, 116.7, 115.8, 53.3 ppm. IR (νCO and νCdC): 2063 (m), 2013 (s), 1959 (s), 1872 (m), 1856 (m), 1636 (m), 1615 (s) cm-1. Data for 3c are as follows. Mp: 230 °C dec. Anal. Calcd for C56H36O6Ru2: C, 66.79; H, 3.60. Found: C, 66.93; H, 4.07. 1H NMR (CDCl3): δ 7.28-7.19 (m, 12H, Ph H), 7.15-7.10 (m, 12H, Ph H), 7.04-6.99 (m, 6H,

Li et al. Ph H), 6.59 (s, 1H, C5H3), 3.31 (d, J=23.5 Hz, 2H, C5H3), 3.19 (d, J = 23.5 Hz, 2H, C5H3) ppm. 13C NMR (100 MHz, CDCl3): δ 200.9, 195.5, 192.4, 164.7, 149.3, 141.5, 140.6, 140.3, 140.1, 136.4, 136.1, 131.8, 128.4, 128.2, 128.1, 127.9, 127.7, 127.2, 126.8, 125.8, 50.9 ppm. IR (νCO and νCdC): 2084 (m), 2038 (m), 2022 (m), 1993 (s), 1922 (m), 1640 (s), 1615 (s) cm-1. Crystallographic Studies. A single crystal of complex 2b suitable for X-ray diffraction was obtained from hexane/Et2O solutions at -20 °C, while those of complexes 3a,c were obtained from hexane/CH2Cl2 solutions at room temperature. Data collection was performed on a Rigaku MM-OO7/Saturn 70 (for 2b) or a Rigaku Saturn 724 (for 3a and 3c) diffractometer, using graphite-monochromated Mo KR radiation (ω-2θ scans). Semiempirical absorption corrections were applied for all complexes. The structures were solved by direct methods and refined by full-matrix least squares. All calculations were done using the SHELXL-97 program system. Crystal data and a summary of X-ray data collection details are given in Table 1. In 3c a phenyl group at one cyclopentadiene ring is disordered.

Acknowledgment. We thank the National Natural Science Foundation of China (Nos. 20672058, 20872066, and 20721062) and the Research Fund for the Doctoral Program of Higher Education of China (No. 20070055020) for financial support. Supporting Information Available: CIF files giving crystallographic details for 2b and 3a,c. This material is available free of charge via the Internet at http://pubs.acs.org.