Alkyne-functionalized zirconocene complexes: Synthesis, structures, and reactivities

Article abstract of DOI:10.1021/om1007677

Reactions of (phenylethynyl)lithium with substituted cyclopentenones gave the corresponding phenylethynyl-substituted cyclopentadienes 1,2-R ₂-4-(PhC≡C)C₅H₂ (R = Me (1a), Ph (1b)), which underwent subsequent deprotonation

Full text of DOI:10.1021/om1007677

6092 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 phe-
nylethynyl-substituted cyclopentadienes 1,2-R2-4-(PhCtC)C5H2 (R=Me (1a), Ph (1b)), which under-
went subsequent deprotonation and transmetalation with ZrCl4 to yield the corresponding alkyne-
functionalized 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 (3,4-
Ph2C5H2)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.
Scheme 1
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: þ86-22-
23504781. E-mail: bqwang@nankai.edu.cn.
(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,
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(c) Pudelski, J. K.; Callstrom, M. R. Organometallics 1994, 13, 3095.
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 cyclo-
pentadienyl transition-metal complexes have mainly focused
on ferrocene and ruthenocene derivatives; other metal com-
plexes 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 corre-
sponding 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.
€
(d) Ma, J.; K€uhn, B.; Hackl, T.; Butenschon, H. Chem. Eur. J. 2010, 16,
1859.
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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.
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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.
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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.
Results and Discussion
€
(d) Gorl, C.; Alt, H. G. J. Organomet. Chem. 2007, 692, 5727. (e) Ivchenko,
Following the synthetic route reported previously by the
Waymouth group,5b the two new ligand precursors 1a,b were
P. V.; Nifant'ev, I. E.; Mkoyan, S. G. Russ. Chem. Bull. 2007, 56, 70.
(f) Chen, L.; Kehr, G.; Frohlich, R.; Erker, G. Eur. J. Inorg. Chem. 2008, 73.
€
r
pubs.acs.org/Organometallics
Published on Web 10/27/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 22, 2010 6093
Scheme 2
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 phenyl-
ethynyl 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)2-
ZrCl2 (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
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.
˚
(2.248, 2.245 A) are longer than those in (Ph2Cp)2ZrCl2, (1,
2-Ph2-4-Me-C5H2)2ZrCl2, and other bulky zirconocene com-
7
˚
plexes (2.215-2.223 A).
Our initial idea was to synthesize heteronuclear ruthena-
cycle-bridged zirconocene complexes through the C-C cou-
pling 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).
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 character-
1
ized by H NMR, 13C NMR, mass spectra, and elemental
1
analysis. In the H NMR spectra of 1a,b the signals of the
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 decoordi-
nated Cp ligand was unknown. However, in this case 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 com-
plexes 2a,b were synthesized in 52% and 53% yields, respec-
tively (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 solu-
tion 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
(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. Organo-
metallics 2009, 28, 3109.

6094 Organometallics, Vol. 29, No. 22, 2010
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-
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)-
˚
(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).
˚
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).
planes are 70.2 and 49.8°, respectively. The Ru-Ru distances
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, respec-
tively. 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 termi-
nal 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.
˚
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),
9
˚
1.472(6) A). 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 (1.478-
1.497 A) in the five-membered ring, supporting the cyclo-
pentadiene 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 (1.416-
1.474 A). The dihedral angles between the ruthenacyclo-
10
˚
pentadienyl 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
The molecular structures of 3a,c were determined by X-ray
diffraction analysis (Figures 2 and 3). 3a is a trinuclear ru-
thenium 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 ruthena-
cyclopentadiene plane and the cyclopentadienyl and phenyl
(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.

Article
Organometallics, Vol. 29, No. 22, 2010 6095
Table 1. Crystal Data and Summary of X-ray Data Collection Details
2b
3a
3c
formula
fw
T, K
λ, A
cryst syst
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
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
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
˚
space group
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
Dcalcd, g cm-3
μ, mm-1
F(000)
cryst size, mm
θ range, deg
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
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
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
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)
-3
˚
largest diff peak and hole (e A
)
(2a), Ph (2b)) were synthesized. Their reactions with Ru3-
(CO)12 did not give a heteronuclear ruthenacycle-bridged
ansa-zirconocene complex but afforded ruthenacycle-
bridged bis(cyclopentadiene) derivatives via the cleavage
of the Cp0-Zr bonds.
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).
Experimental Section
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).
General Considerations. Schlenk and vacuum-line techniques
were employed for all manipulations of air- and moisture-
sensitive compounds. All solvents were distilled from appro-
priate 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 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 suspen-
sion 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
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
1
C50H34Cl2Zr: C, 75.36; H, 4.30. Found: C, 75.48; H, 5.80. H
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,
(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.

6096 Organometallics, Vol. 29, No. 22, 2010
Li et al.
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).
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
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),
(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) diffractom-
eter, 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.
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,
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 crystal-
lographic details for 2b and 3a,c. This material is available free
of charge via the Internet at http://pubs.acs.org.