Alkyne-alkyne coupling reactions with W(CO)(PhC≡CPh)3 and W(NCMe)(PhC≡CPh)3

Article abstract of DOI:10.1021/om9702340

Heating W(CO)(PhC≡CPh)₃ (1) and diphenylacetylene in a sealed tube leads to alkyne-alkyne coupling to yield W(CO)(PhC≡CPh)₂(η⁴C₄Ph₄) (2), W(CO)(PhC≡CPh)(η⁵-C₃Ph₃(C ₅Ph₅)) (3), and W(CO)(PhC≡CPh)(η⁶-C₃Ph₃(C ₅Ph₅)) (4) together with the tungstenocene oligomer [W(C₅Ph₅)₂]_x (5). Oxidation of 5 by diiodine affords W(η⁵-C₅Ph₅)₂(I)₂ (6), which is converted into the oxo complex W(η⁵-C₅Ph₅)2(=O) (7) by treating with AgBF₄ in wet dichloromethane solution. Reaction of W(NCMe)(PhC≡CPh)a (8) and 1 equiv of diphenylacetylene produces W(NCMe)(PhC≡CPh)₂(η⁴-C₄Ph ₄) (9), whereas a similar reaction in the presence of excess diphenylacetylene gives mainly the metallacyclic complex W(PhC≡CPh)(η⁸-C₈Ph₈), (10). Compound 10 reacts with carbon monoxide to afford 3 and 4, while thermolysis of pure 10 results in 5 exclusively. The reaction mechanism has been explored by C-13 labeling experiments. The structures of 7 and 10 have been established by an X-ray diffraction study. The bonding of pentaphenylcyclopentadienyl ligands of 7 is best described as a localized η³:η² fashion. Compound 10 contains a tungstenacyclononapentaene ring with two tungstencarbon double bonds.

Full text of DOI:10.1021/om9702340

2698
Organometallics 1997, 16, 2698-2708
Alk yn e-Alk yn e Cou p lin g Rea ction s w ith
W(CO)(P h CtCP h )3 a n d W(NCMe)(P h CtCP h )3
Wen-Yann Yeh,* Chi-Lin Ho, Michael Y. Chiang,† and I-Ting Chen
Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 80424
Received March 24, 1997X
Heating W(CO)(PhCtCPh)3 (1) and diphenylacetylene in a sealed tube leads to alkyne-
alkyne coupling to yield W(CO)(PhCtCPh)2(η4-C4Ph4) (2), W(CO)(PhCtCPh)(η5-C3Ph3(C5Ph5))
(3), and W(CO)(PhCtCPh)(η6-C3Ph3(C5Ph5)) (4) together with the tungstenocene oligomer
[W(C5Ph5)2]x (5). Oxidation of 5 by diiodine affords W(η5-C5Ph5)2(I)2 (6), which is converted
into the oxo complex W(η5-C5Ph5)2(dO) (7) by treating with AgBF4 in wet dichloromethane
solution. Reaction of W(NCMe)(PhCtCPh)3 (8) and 1 equiv of diphenylacetylene produces
W(NCMe)(PhCtCPh)2(η4-C4Ph4) (9), whereas a similar reaction in the presence of excess
diphenylacetylene gives mainly the metallacyclic complex W(PhCtCPh)(η8-C8Ph8) (10).
Compound 10 reacts with carbon monoxide to afford 3 and 4, while thermolysis of pure 10
results in 5 exclusively. The reaction mechanism has been explored by C-13 labeling
experiments. The structures of 7 and 10 have been established by an X-ray diffraction study.
The bonding of pentaphenylcyclopentadienyl ligands of 7 is best described as a localized
η3:η2 fashion. Compound 10 contains a tungstenacyclononapentaene ring with two tungsten-
carbon double bonds.
In tr od u ction
derivative have also been produced and structurally
characterized.
Mechanistic steps involving the formation of metalla-
cycles, and their interconversions and subsequent decay,
are implicated in a number of important catalytic
transformations.1 It has been shown that reactions of
alkynes with transition-metal compounds can lead to
di-, tri-, or tetramerization of the alkyne ligands, and
in doing so they lose their individuality, forming met-
allacyclic systems or carbocycles.2 Nevertheless, an
isolable metal complex, which would confirm the linking
of acetylene units, is not obtained in all cases. We
previously communicated the reaction of W(L)-
(PhCtCPh)3 (L ) CO, NCMe) and diphenylacetylene
to yield cyclobutadiene complexes, W(L)(PhCtCPh)2(η4-
C4Ph4),3 and a cyclopentadienylpropenylidene complex,
W(CO)(PhCtCPh)(η5-C3Ph3(C5Ph5)).4 Two questions
were raised: whether the butadiene group is derived
from the coordinated PhCtCPh ligands or the added
diphenylacetylene is involved and how the five-mem-
bered cyclopentadiene ring is assembled. Presented in
this article are complete characterizations of the reac-
tion products and information concerning the alkyne-
alkyne coupling mechanism. A novel metallacyclo-
nonapentaene intermediate and a tungstenocene oxo
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under an atmosphere of purified nitrogen with standard
Schlenk and syringe techniques.5 Solvents were distilled from
the appropriate drying agent before use.6 W(CO)(PhCtCPh)3
(1)7 and W(NCMe)(PhCtCPh)3 (8)8 were prepared by litera-
ture methods. Ph13CtCPh was prepared from Ph213C(dO) as
described in the literature.9 Diphenylacetylene, diiodine, and
silver tetrafluoroborate (AgBF4) were purchased from Aldrich
and used as received. Preparative thin-layer chromatographic
(TLC) plates were prepared from silica gel (Merck, GF 254).
1H and 13C NMR spectra were obtained on a Varian VXR-300
spectrometer at 300 and 75.4 MHz, respectively. IR spectra
were taken on a Hitachi-2001 spectrometer. Fast-atom bom-
bardment (FAB) and electron impact (EI) mass spectra were
obtained on a VG-5022 mass spectrometer. Elemental analy-
ses were performed at the National Science Council Regional
Instrumentation Center at National Chen-Kung University,
Tainan, Taiwan. Single-crystal X-ray diffraction studies were
conducted on a Rigaku AFC6S diffractometer with graphite-
monochromated Mo KR radiation using the ω-2θ scan tech-
nique.
Reaction of 1 an d Molten P h CtCP h . W(CO)(PhCtCPh)3
(1; 500 mg, 0.67 mmol) and diphenylacetylene (340 mg, 1.91
mmol) were mixed, ground, and sealed in a glass tube under
vacuum (0.1 mmHg). The tube was placed in a silicon oil bath
at 120 °C. During the first 1 min of reaction, vigorous bubbling
of CO gas was observed with formation of a dark red solution
(Note: diphenylacetylene melts at 60 °C). After 25 min, the
† To whom inquiries concerning the X-ray crystallographic work
should be addressed.
X Abstract published in Advance ACS Abstracts, May 15, 1997.
(1) (a) Parshall, G. W. Homogeneous Catalysis; Wiley: New York,
1980. (b) Crabtree, R. H. The Organometallic Chemistry of the
Transition Metals; Wiley: New York, 1994. (c) Katz, T. J . Adv.
Organomet. Chem. 1977, 16, 283. (d) Chapell, S. D.; Cole-Hamilton,
D. J . Polyhedron 1982, 1, 739. (e) Chisholm, M. H.; Heppert, J . A. Adv.
Organomet. Chem. 1986, 26, 97. (f) Chien, J . C. W. Coordination
Polymerization; Academic Press: New York, 1975. (g) Collman, J . P.;
Hegedus, L. S.; Norton, J . R.; Finke, R. G. Principles and Applications
of Organotransition Metal Chemistry; University Science Books: Mill
Valley, CA, 1987.
(5) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-Sensitive
Compounds, 2nd ed.; Wiley: New York, 1986.
(6) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, U.K., 1988.
(7) (a) Tate, D. P.; Augl, J . M. J . Am. Chem. Soc. 1963, 85, 2174. (b)
Tate, D. P.; Augl, J . M.; Ritchey, W. M.; Rose, B. L.; Grasselli, J . G. J .
Am. Chem. Soc. 1964, 86, 3261.
(8) Yeh, W.-Y.; Ting, C.-S.; Chih, C.-F. J . Organomet. Chem. 1991,
427, 257.
(9) Colvin, E. W.; Hamill, B. J . J . Chem. Soc., Perkin Trans. I 1977,
869.
(2) Grotjahn, D. B. In Comprehensive Organometallic Chemistry II;
Pergamon: Oxford, U.K., 1995; Vol. 12, p 741, and references therein.
(3) Yeh, W.-Y.; Liu, L.-K. J . Am. Chem. Soc. 1992, 114, 2267.
(4) Yeh, W.-Y.; Peng, S.-M.; Lee, G.-H. J . Chem. Soc., Chem.
Commun. 1993, 1056.
S0276-7333(97)00234-3 CCC: $14.00 © 1997 American Chemical Society

Alkyne-Alkyne Coupling Reactions
Organometallics, Vol. 16, No. 12, 1997 2699
tube was removed from the bath, cooled to room temperature,
and opened in air. The resulting brown-red residue was
extracted with dichloromethane (3 × 10 mL) to give a deep
red solution and orange-red solids. The extract was concen-
trated to ca. 5 mL on a rotary evaporator and applied to TLC
with hexane/dichloromethane (3:1, v/v) as eluant. The unre-
acted diphenylacetylene was recovered from the first, colorless
band. The material from the second, orange-red band afforded
W(CO)(PhCtCPh)2(η4-C4Ph4) (2; 249 mg, 0.27 mmol, 40%). The
third, red band gave W(CO)(PhCtCPh)(η5-C3Ph3(C5Ph5)) (3;
98 mg, 0.09 mmol, 13%). The material from the fourth, purple
band yielded W(CO)(PhCtCPh)(η6-C3Ph3(C5Ph5)) (4; 45 mg,
0.04 mmol, 6%).
The dichloromethane-insoluble solids were washed with
methanol, THF, and n-hexane and dried under vacuum
overnight. This orange-red material was formulated as
[W(C5Ph5)2]x (5; 230 mg, 32%), on the basis of spectroscopic
characterization and reaction with I2 to give W(η5-C5Ph5)2(I)2
(6).
solution was filtered, concentrated to ca. 3 mL under vacuum,
layered with benzene (10 mL), and placed in a freezer at -20
°C overnight to give dark green crystals of W(η5-C5Ph5)2(dO)
(7; 42 mg, 0.038 mmol, 56%). IR (KBr): 3064, 1604, 1504,
1448, 1182, 1076, 1028, 802, 778, 740, 700 (CsC, CsH), 906
(ν(WdO)) cm-1
.
1H NMR (CD2Cl2, 20 °C): δ 7.70-6.65 (m,
Ph). 13C{1H} NMR (CD2Cl2, 20 °C): δ 134.2 (C5Ph5), 133.1,
130.6, 129.3, 128.8 (Ph). Mass spectrum (FAB): m/ z 1090
(M+, 184W), 1074 (M+ - O). Anal. Calcd for C70H50OW: C,
77.06; H, 4.62. Found: C, 77.42; H, 4.60.
Crystals of 7 found suitable for an X-ray diffraction study
were grown from dichloromethane/benzene at -20 °C.
Rea ction of 8 a n d 1 Equ iv of P h CtCP h . A 50 mL
Schlenk flask containing W(NCMe)(PhCtCPh)3 (8; 500 mg,
0.66 mmol) and diphenylacetylene (118 mg, 0.66 mmol) were
purged with dry N2. 1,2-Dichloroethane (20 mL) was added,
and the flask was attached to a reflux condenser equipped with
a mineral oil bubble. The mixture was heated to reflux (101
°C) for 15 min, cooled to room temperature, and evaporated
to dryness under vacuum. The residue was dissolved in
dichloromethane and separated by TLC, with hexane/dichlo-
romethane (4:1, v/v) as eluant. Isolation of the material
forming the major orange-red band gave W(NCMe)(PhCtCPh)2-
(η4-C4Ph4) (9; 480 mg, 0.51 mmol, 77%). Mp: 175-177 dec.
IR (KBr): 1591 (ν(CtC)) cm-1. Mass spectrum (FAB): m/ z
937 (M+, 184W), 896 (M+ - NCMe), 718 (M+ - NCMe - C2Ph2),
540 (M+ - NCMe - 2C2Ph2). 1H NMR (CD2Cl2, 25 °C): δ
7.33-6.78 (m, Ph), 1.90 (s, CH3CN). 13C{1H} NMR (CD2Cl2,
25 °C): δ 186.5, 174.8 (CtC), 140.8-124.8 (Ph, NtC), 86.2
(C4Ph4), 4.4 (CH3). Anal. Calcd for C58H43NW: C, 74.28; H,
4.62; N, 1.49. Found: C, 74.49; H, 4.70; N, 1.47.
Ch a r a cter iza tion of 2. IR (KBr disk): 2030 (ν(CO)) 1595
(ν(CtC)) cm-1. Mass spectrum (FAB): m/ z 924 (M+, 184W),
896 (M+ - CO), 718 (M+ - CO - C2Ph2), 540 (M+ - CO -
2C2Ph2). 1H NMR (CD2Cl2, 25 °C): δ 7.25-6.77 (m, Ph).
13C{1H} NMR (CDCl3, 25 °C): δ 214.9 (CO), 175.9, 158.9
(CtC), 140.6-125.1 (m, C6H5), 83.8 (C4 Ph4). Anal. Calcd for
C
57H40OW: C, 74.03; H, 4.36. Found: C, 74.33; H, 4.60.
Ch a r a cter iza tion of 3. IR (KBr disk): 2005 (ν(CO)), 1602
(ν(CtC)) cm-1. Mass spectrum (FAB): m/ z 1102 (M+, 184W),
1074 (M+ - CO), 1025 (M+ - Ph), 997 (M+ - PhsCO), 896
((M+ - CO - C2Ph2). 1H NMR (CDCl3, 20 °C): δ 7.78-5.15
1
(m, Ph). 13C{1H} NMR (CDCl3, 20 °C): δ 300.8 (W)C, J W-C
Rea ction of 8 a n d 1 Equ iv of P h 13CtCP h . This reaction
was carried out and worked up in a fashion identical with that
above. The 13C{1H} NMR spectrum of the product revealed
an intense signal at δ 86.2 corresponding to the resonance of
cyclobutadiene ring carbons. The intensities of other 13C
resonance signals were not affected.
) 140 Hz), 220.0 (CO), 197.4, 190.0 (CtC), 159.7, 150.3, 111.8,
98.5, 95.1, 81.9, 29.7 (C8Ph8), 142.7-120.89 (m, C6H5). Anal.
Calcd for C71H50OW: C, 77.31; H, 4.57. Found: C, 77.12; H,
4.60.
Ch a r a cter iza tion of 4. IR (C6H12, ν(CO)): 1932 cm-1
.
Mass spectrum (FAB): m/ z 1102 (M+, 184W), 1074 (M+ - CO),
896 (M+ - CO - C2Ph2). 1H NMR (CDCl3, 20 °C): δ 8.30-
5.40 (m, Ph). 13C{1H} NMR (CDCl3, 20 °C): δ 236.4 (s, CO),
206.3 (s, Ct), 204.2 (s, Ct), 172.6, 157.7, 127.0, 126.1, 117.6,
93.6, 68.0, 29.7 (C8Ph8), 150.6-124.1 (m, C6H5). Anal. Calcd
for C71H50OW: C, 77.31; H, 4.57; O, 1.45. Found: C, 77.46;
H, 4.79; O, 1.17.
Rea ction of 8 w ith Excess P h CtCP h . A 50 mL Schlenk
flask containing W(NCMe)(PhCtCPh)3 (8; 200 mg, 0.26 mmol)
and diphenylacetylene (240 mg, 1.34 mmol) was purged with
dry N2. Toluene (10 mL) was added, and the flask was
attached to a reflux condenser equipped with a mineral oil
bubble. The mixture was heated to reflux (110 °C) for 8 min
and then quickly cooled down by placing the flask in an ice
bath. The solution was evaporated to dryness under vacuum.
The residue was extracted with dichloromethane (2 × 10 mL)
to give a dark red solution and orange-red solids [W(C5Ph5)2]x
(5; 20 mg, 7%). The extract was concentrated to ca. 3 mL on
a rotary evaporator and subjected to TLC, with hexane/
dichloromethane (7:3, v/v) as eluant. The unreacted diphenyl-
acetylene was recovered from the first, colorless band. The
material forming the third, orange-red band gave W(NCMe)-
(PhCtCPh)2(η4-C4Ph4) (9; 46 mg, 0.049 mmol, 19%). Isolation
of the material from the second, red band afforded
W(PhCtCPh)(η8-C8Ph8) (10; 116 mg, 0.108 mmol, 42%). Mass
Ch a r a cter iza tion of 5. Mass spectrum (EI, 350 °C, 70
eV): m/ z 1074 (184W(C5Ph5)2). IR (KBr pellet): 3060, 1602,
1505, 1448, 1072, 1026, 800, 780, 736, 702, 556 cm-1. Anal.
Calcd for (C70H50W)x: C, 78.21; H, 4.68. Found: C, 77.84; H,
4.72.
P r ep a r a tion of 6. An oven-dried, three-necked spherical
flask (100 mL) was equipped with a magnetic stirbar, a rubber
serum stopper, a reflux condenser, and a nitrogen inlet. When
the stopper was briefly removed, a sample of [W(η5-C5Ph5)2]x
(5; 300 mg, 0.28 mmol based on W) and benzene (40 mL) were
introduced against a nitrogen flow. The mixture was brought
to reflux under nitrogen, and I2 (89 mg, 0.35 mmol) in benzene
(10 mL) was added dropwise over 10 min via a syringe. The
mixture was kept refluxing for 1 h, cooled to ambient temper-
ature, and filtered. The green residue was washed with
benzene (2 × 5 mL) and then extracted with dichloromethane
(2 × 15 mL) to give a dark green solution. The extract was
filtered, concentrated to ca. 5 mL under vacuum, and layered
with benzene (15 mL), resulting in dark green crystals of W(η5-
C5Ph5)2(I)2 (6; 327 mg, 0.25 mmol, 88%). IR (KBr): 3064, 1604,
1506, 1450, 1408, 1264, 1078, 1028, 968, 906, 800, 778, 740,
1
spectrum (FAB): m/ z 1074 (M+, 184W), 896 (M+ - C2Ph2). H
NMR (CDCl3, 20 °C): δ 7.42-6.16 (m, Ph). 13C{1H} NMR
1
(CDCl3, 20 °C): δ 240.3 (W)C, J W-C ) 96 Hz), 196.8, 189.5
(CtC), 130.0, 126.5, 93.5 (s, C8Ph8), 150.0-124.6 (m, Ph). Anal.
Calcd for C70W50W: C, 78.21; H, 4.68. Found: C, 77.69; H,
4.80.
Crystals of 10 found suitable for X-ray diffraction study were
grown by slow diffusion of benzene into dichloromethane
solution at -20 °C for 1 week.
710, 700 cm-1 1H NMR (CDCl3, 20 °C): δ 7.10-6.79 (m, Ph).
.
Rea ction of 9 a n d P h CtCP h . A 50 mL Schlenk flask
was attached to a reflux condenser equipped with a mineral
oil bubble. W(NCMe)(PhCtCPh)2(η4-C4Ph4) (9; 100 mg, 0.1
mmol), diphenylacetylene (127 mg, 0.7 mmol), and toluene (5
mL) were added into the flask. The mixture was heated to
reflux under nitrogen for 15 min, cooled to ambient temper-
ature, and evaporated to dryness under vacuum. The residue
was dissolved in dichloromethane and separated by TLC, with
Mass spectrum (FAB): m/ z 1074 (M+ - 2 I). Anal. Calcd for
C
70H50I2W: C, 63.27; H, 3.79. Found: C, 62.63; H, 3.90.
P r ep a r a tion of 7. A 50 mL Schlenk flask was charged
with W(η5-C5Ph5)2(I)2 (6; 90 mg, 0.068 mmol), AgBF4 (26 mg,
0.13 mmol), dichloromethane (10 mL), and water (100 µL). The
mixture was stirred at room temperature for 1 h, affording a
deep green solution and pale yellow precipitates of AgI. The

2700 Organometallics, Vol. 16, No. 12, 1997
Yeh et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for
dichloromethane/hexane (3:7, v/v) as eluant. W(PhCtCPh)-
(η8-C8Ph8) (10) was obtained in 16% yield (17 mg, 0.016 mmol).
(η5-C5P h 5)2W(dO) (7) a n d W(P h CtCP h )
(η8-C8P h 8) (10)
Th er m olysis of 10. A red solution of W(PhCtCPh)(η8-
C8Ph8) (10; 15 mg) in toluene (5 mL) was refluxed under
nitrogen for 90 min, resulting in orange-red precipitates. The
solids were filtered, washed with dichloromethane, and dried
under vacuum. The product was characterized as [W(C5Ph5)2]x
(5; 13 mg, 87%).
7
10
chem formula
cryst solvents
fw
temp, °C
space group
a, Å
C70H50OW
C70H50W
1/2 CH2Cl2 + 3/2C6H6
1234.65
23
1091.01
23
P1h (No. 2)
12.663(2)
12.759(3)
18.702(3)
104.55(2)
91.87(2)
117.64(1)
2551(1)
2
P1h (No. 2)
11.853(3)
13.372(3)
21.584(4)
89.74(2)
87.65(2)
64.85(2)
3093(1)
2
Rea ction of 10 a n d Ca r bon Mon oxid e. A 100 mL three-
necked, round-bottomed flask was equipped with a magnetic
stirbar. One neck was stopped, one had a reflux condenser
topped with a stopcock connected to an oil bubble, and the
third neck had an inlet tube for introduction of carbon
monoxide. A solution of W(PhCtCPh)(η8-C8Ph8) (10; 50 mg,
0.046 mmol) in THF (10 mL) was transferred into the flask
and saturated with carbon monoxide gas. With carbon mon-
oxide bubbling through the solution, it was heated at 50 °C
for 10 min. The solution was concentrated to ca. 3 mL and
subjected to TLC, with dichloromethane/hexane (3:7, v/v) as
eluent. The material forming the first, red band afforded
W(CO)(PhCtCPh)(η5-C3Ph3(C5Ph5)) (3; 36 mg, 0.032 mmol,
70%). The material forming the second, purple band gave
W(CO)(PhCtCPh)(η6-C3Ph3(C5Ph5)) (4; 11 mg, 0.1 mmol, 22%).
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
Ra
Rw
0.034
0.092
b
0.030
0.121
GOF
D
λ, Å
1.59
1.420
3.23
1.325
calc, g cm-3
0.710 69
0.710 69
a
b
2 1/2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑wFo
] .
Str u ctu r e Deter m in a tion for 7. A suitable crystal of
W(η5-C5Ph5)2(dO) (7) with approximate dimensions of 0.33 ×
0.35 × 0.40 mm was mounted on a glass fiber and aligned on
the diffractometer. Lattice parameters were determined from
18 carefully centered reflections in the range 9.2° < 2θ < 16.7°.
On the basis of a statistical analysis of intensity distribution,
and successful solution and refinement of the structure, the
space group was determined to be P1h (No. 2). The data were
collected at 23 °C with a maximum 2θ value of 47.1°. Scans
of width (1.26 + 0.34 tan θ)° were made at a speed of 8.0°/min
(in ω). Of the 7981 reflections which were collected, 7586 were
unique (Rint ) 0.038). The intensities of three representative
reflections were measured after every 150 reflections; no decay
was observed. The linear absorption coefficient, µ, for Mo KR
radiation was 23.1 cm-1. An empirical absorption correction
based on azimuthal scans of several reflections was applied,
which resulted in transmission factors ranging from 0.78 to
1.00. The data were corrected for Lorentz and polarization
effects. The structure was solved by direct methods10 and
expanded using Fourier techniques.11 The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
included but not refined. The final cycle of full-matrix least-
squares refinement was based on 5631 observed reflections (I
> 3.00σ(I)) and 649 variable parameters. All calculations were
carried out with the TEXSAN crystallographic software pack-
age of the Molecular Structure Corp.12 A summary of relevant
crystallographic data is provided in Table 1.
Str u ctu r e Deter m in a tion for 10. A suitable crystal of
W(PhCtCPh)(η8-C8Ph8) (10) with approximate dimensions of
0.26 × 0.33 × 0.41 mm was mounted on a glass fiber and
aligned on the diffractometer. Lattice parameters were de-
termined from 16 carefully centered reflections in the range
9.5° < 2θ < 14.7°. On the basis of a statistical analysis of
intensity distribution, and successful solution and refinement
of the structure, the space group was determined to be P1h (No.
2). The data were collected at 23 °C with a maximum 2θ value
of 45.4°. Scans of width (1.42 + 0.34 tan θ)° were made at a
speed of 16.0°/min (in ω). Of the 7424 reflections which were
collected, 6993 were unique (Rint ) 0.068). The intensities of
three representative reflections were measured after every 150
reflections. Over the course of data collection, the standards
decreased by 18% due to solvent loss. A polynomial correction
factor was applied to the data to account for this phenomenon.
The linear absorption coefficient, µ, for Mo KR radiation was
20.0 cm-1
.
An empirical absorption correction based on
azimuthal scans of several reflections was applied, which
resulted in transmission factors ranging from 0.86 to 1.00. The
data were corrected for Lorentz and polarization effects. The
structure was solved by direct methods and expanded using
Fourier techniques. Due to the ill nature (solvent loss) of the
data, all carbon atoms were refined isotropically. Only the
tungsten and chloride atoms (of solvent) were refined aniso-
tropically. Hydrogen atoms were put in at their idealized
positions before the last cycle of refinement. The final cycle
of full-matrix least-squares refinement was based on 5068
observed reflections (I > 3.00σ(I)) and 347 variable parameters.
The maximum and minimum peaks on the final difference
Fourier map corresponded to 5.01 and -2.44 e/Å3, respectively.
A summary of relevant crystallographic data is provided in
Table 1.
Resu lts a n d Discu ssion
Rea ction s of W(CO)(P h CtCP h )3 a n d W(NCMe)-
(P h CtCP h )3 w it h Dip h en yla cet ylen e. W(CO)-
(PhCtCPh)3 (1) shows little reactivity toward diphenyl-
acetylene in refluxing toluene solution. It appears that
the W(CO)(RCtCR′)3 stoichiometry is particularly stable,
as suggested by theoretical analyses.13 However, under
harsher conditions by heating 1 and diphenylacetylene
in a sealed tube at 120 °C, reactions involving alkyne-
alkyne coupling occur to produce the carbocyclic and
metallacyclic complexes W(CO)(PhCtCPh)2(η4-C4Ph4)
(2; 40%), W(CO)(PhCtCPh)(η5-C3Ph3(C5Ph5)) (3; 13%),
and W(CO)(PhCtCPh)(η6-C3Ph3(C5Ph5)) (4; 6%) to-
gether with the tungstenocene oligomer [W(C5Ph5)2]x (5)
in 32% yield.
Interestingly, replacement of the carbonyl group of 1
by a labile acetonitrile ligand facilitates the coupling
reaction, and different products are obtained depending
on the ratio of substrates and the reaction conditions,
such that treating W(NCMe)(PhCtCPh)3 (8) with
equimolar diphenylacetylene affords W(NCMe)-
(PhCtCPh)2(η4-C4Ph4) (9) in high yield, while a similar
reaction in the presence of 2 equiv (or more) of di-
(10) SIR92: Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi,
A. J . Appl. Crystallogr. 1993, 26, 343.
(11) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J . M. M. DIRDIF 94, Technical Report
of the Crystallography Laboratory; University of Nijmegen, Nijmegen,
The Netherlands, 1994.
(12) TEXSAN: Crystal Structure Analysis Package; Molecular
Structure Corp., The Woodlands, TX, 1985, 1992.
(13) (a) King, R. B. Inorg. Chem. 1968, 7, 1044. (b) Wink, D. J .;
Greagan, T. Organometallics 1990, 9, 328.

Alkyne-Alkyne Coupling Reactions
Organometallics, Vol. 16, No. 12, 1997 2701
Sch em e 1
phenylacetylene leads to the nine-membered metalla-
cyclic complex W(PhCtCPh)(η8-C8Ph8) (10) as the major
product. Reaction of 9 and diphenylacetylene also
produces 10, but in low yield. Compound 10 transforms
into 5 upon prolonged standing in hot toluene. How-
ever, in the presence of carbon monoxide, complexes 3
and 4 are obtained as the only metal-containing prod-
ucts. The results are summarized in Scheme 1.
Oligomerization of alkynes mediated by transition
metals generally leads to cyclobutadiene, arene, and
cyclooctatetraene complexes or the corresponding met-
allacycles.14 Thus, formation of five-membered cyclo-
pentadiene and cyclopentadienyl derivatives 3, 4, and
5 is unique.15 Compound 10 contains a metallacyclo-
nonapentaene unit, which apparently arises from cou-
pling of four diphenylacetylene ligands at the tungsten
center. Linking of four alkyne molecules at a dimolyb-
denum system was previously observed, but a bridging
metallacyclononatetraene moiety was formed.16 It is of
interest to note that the skeletal carbons of 10 rearrange
to give two cyclopentadienyl groups in 5 instead of
releasing a cyclooctatetraene (C8Ph8)17 or a cyclodeca-
pentaene (C10Ph10) species. In this transformation,
mononuclear tungstenocene W(C5Ph5)2 is likely the
reactive intermediate generated in situ.
Ch a r a cter iza tion of Com p ou n d s 2, 3, 4, a n d 9.
Spectroscopic properties of W(CO)(PhCtCPh)2(η4-C4Ph4)
(2), W(NCMe)(PhCtCPh)2(η4-C4Ph4) (9), and W(CO)-
(PhCtCPh)(η5-C3Ph3(C5Ph5))(3) were briefly described
in previous communications,3,4 and the structures of 2
and 3 were established by X-ray diffraction studies.
If we take the centers of the alkyne and cyclobutadi-
ene ligands, the geometry of 2 and 9 can be viewed as
a distorted tetrahedron. The terminal CO (or NCMe)
and η4-cyclobutadiene ligands are normally counted as
two- and four-electron donors, respectively; thus, the
remaining two alkyne ligands must provide six electrons
to the neutral tungsten atom to satisfy the 18-electron
rule.18 Since the two alkyne ligands are equivalent, as
evidenced by equal CtC bond lengths and 13C chemical
shifts, the actual structure is best regarded as a
resonance hybrid with two canonical forms involving one
four-electron-donor (π| + π ) and one two-electron-donor
(π|) alkyne ligand. Rotation of alkyne ligands is slow
on the NMR time scale, thus displaying two 13C reso-
nances for the CtC carbons, whereas the cyclobutadiene
ligand is fluxional with facial ring rotation and only one
13C resonance is observed down to -50 °C.
(14) (a) Schore, N. E. Chem. Rev. 1988, 88, 1081 and references
therein. (b) Vollhardt, K. P. C. Acc. Chem. Res. 1977, 10, 1.
(15) Reinheimer, H.; Moffat, J .; Maitlis, P. M. J . Am. Chem. Soc.
1970, 92, 2285.
(16) (a) Green, M.; Norman, N. C.; Orpen, A. G. J . Am. Chem. Soc.
1981, 103, 1269. (b) Connelly, N. G.; Metz, B.; Orpen, A. G. J . Chem.
Soc., Chem. Commun. 1994, 2109. (c) Bott, S. G.; Brammer, L.;
Connelly, N. G.; Green, M.; Orpen, A. G.; Paxton, J . F.; Schaverien, C.
J . J . Chem. Soc., Dalton Trans. 1990, 1957.
Compound 3 contains a terminal CO, a diphenyl-
acetylene, and a cyclopentadienylpropenylidene (dCPh-
(17) Colborn, R. E.; Vollhardt, K. P. C. J . Am. Chem. Soc. 1986, 108,
5470.
(18) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th
ed.; Wiley: New York, 1988.

2702 Organometallics, Vol. 16, No. 12, 1997
Yeh et al.
Ch a r a cter iza tion of 10. W(PhCtCPh)(η8-C8Ph8)
(10) is an air-stable, dark red, crystalline solid. The
FAB mass spectrum presents the molecular ion at m/ z
1074 for 184W plus an ion corresponding to loss of a
diphenylacetylene. The 13C{1H} NMR spectrum of the
13C-enriched complex W(Ph*CtCPh)(η8-*C8Ph8) (10′′′)
is illustrated in Figure 2b. The two resonances at δ
196.8 and 189.5 are assigned to the alkyne carbons. The
C8Ph8 skeletal carbons give rise to only four resonance
signals, implying a plane of symmetry passing through
the molecule. The low field resonance at δ 240.3 with
183W satellites (1J W-C ) 96 Hz) is characteristic of
alkylidene type carbons,19,21 while the remaining signals
at δ 130.0, 126.5, and 93.5 are in the range for alkene
carbons coordinated to transition metals. Due to the
absence of diagnostic spectral features to reveal the
structure, a single-crystal X-ray diffraction study was
performed.
Cr ysta l Str u ctu r e of 10. An ORTEP drawing of 10
is shown in Figure 4, where the phenyl groups have
been artificially omitted for clarity. Selected bond
distances and bond angles are given in Table 2. There
are one and a half benzene molecules and a half
dichloromethane molecule cocrystallized with each tung-
sten complex in the asymmetric unit cell. Compound
10 consists of a central tungsten atom bonded to one
diphenylacetylene and one octaphenyloctatetraenyl group.
Although the molecule has no crystallographically im-
posed symmetry in the solid state, it exhibits the
expected idealized Cs symmetry in solution, as evidenced
by 13C NMR.
F igu r e 1. 13C{1H} NMR spectra of the 13C-enriched
compounds (a) W(CO)(Ph*CtCPh)(η5-*C3Ph3(*C5Ph5)) (3*)
and (b) W(CO)(Ph*CtCPh)(η6-*C3Ph3(*C5Ph5)) (4*), ob-
tained from the reaction of W(CO)(Ph*CtCPh)3 and
Ph*CtCPh (ca. 10% 13C).
The W(η8-C8Ph8) moiety forms a metallacycle. It
appears to have tungsten-carbon double bonds at both
ends (W1-C3 ) 2.01(2) Å and W1-C10 ) 2.03(2) Å),
and π-donation from the triene unit (C4-C9) to the
tungsten atom. The atoms W1, C3, C4, and C23 are
coplanar to within (0.05(2) Å and the W1, C9, C10, and
C65 atoms to within (0.04(2) Å; the dihedral angle
between the two planes is 20.5°. Furthermore, the
angles C4-C3-C23) 123(1)° and C9-C10-C65 )
125(1)° are consistent with the expected value for sp2-
hybridized alkylidene carbons. The W-C distances to
the triene linkage (C4-C9) are variable, such that the
two terminal alkenes are bonded to the tungsten atom
asymmetrically, with W1-C4 ) 2.48(2) Å and W1-C9
) 2.46(2) Å being significantly longer than W1-C5 )
2.25(2) Å and W1-C8 ) 2.23(2) Å, while the W-C
distances to the internal alkene carbons, C6 and C7,
are equal, being 2.38(2) Å. The C4, C5, C29, and C35
atoms, the C5, C6, C7, C8, C41, and C53 atoms, and
the C8, C9, C47, and C59 atoms are also coplanar.
CPhdCPhC5Ph5) ligand, with each group formally
donating two, four, and six electrons, respectively, to
the neutral tungsten atom. The 13C{1H} NMR spectrum
of 3*, obtained from reaction of W(CO)(Ph*CtCPh)3 and
Ph*CtCPh (each ca. 10% 13C), is shown in Figure 1a.
The downfield signal at δ 300.8 is assigned to the
alkylidene carbon.19 The signals at δ 197.4 and 190.0
are assigned to the tCPh resonances, which are char-
acteristic of four-electron-donor alkyne ligands.20 The
signals at δ 159.7 and 150.3 are comparable with those
of free alkenes and are assigned to the two uncoordi-
nated allyl carbons. The remaining four resonances
ranging from δ 111.8 to 81.9, and a upfield signal at δ
29.7, are assigned to the butadiene carbons and the sp3-
hybrid carbon of the cyclopentadienyl group, respec-
tively.
W(CO)(PhCtCPh)(η6-C3Ph3(C5Ph5)) (4) forms air-
stable, purple solids. The FAB mass spectrum shows
the molecular ion at m/ z 1102 for 184W and fragments
resulting from successive loss of a CO and a diphenyl-
acetylene. We were not able to obtain crystals suitable
for an X-ray diffraction study. However, the 13C{1H}
NMR spectrum of 4* (Figure 1b) shows great resem-
blance to that of 3*, indicating that their structures
might be closely related. Since compound 4 reveals no
alkylidene carbon resonance and an additional upfield
resonance at δ 68.0 is observed, the propenylidene
moiety of 3 probably appears as a metallacyclobutene
ring for 4. We have tried to interconvert compounds 3
and 4 thermally, but this leads to no reaction.
The diphenylacetylene carbons are bonded to the
tungsten atom equally. The W1-C1, W1-C2, and C1-
C2 distances are 2.09(2), 2.10(2), and 1.31(3) Å, respec-
tively. The phenyl groups are bent away from the CtC
axis by angles averaging 46(2)°. The dihedral angles
between the plane of the alkyne moiety (W1, C1, and
C2) and the planes of alkylidene moieties (W1, C3, C23)
and (W1, C10, C65) are 69.7 and 74.7°, respectively.
Ch a r a cter iza tion of 5. Solid [W(C5Ph5)2]x (5) is
thermally robust to 350 °C. It presents essentially no
solubility to all common solvents. Thus, characteriza-
tion is based on elemental analyses, IR and mass
(19) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: New York, 1981.
(20) (a) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1. (b)
Templeton, J . L.; Ward, B. C. J . Am. Chem. Soc. 1980, 102, 3288.
(21) Yeh, W.-Y.; Peng, S,-M.; Liu, L.-K. Inorg. Chem. 1993, 32, 2965.

Alkyne-Alkyne Coupling Reactions
Organometallics, Vol. 16, No. 12, 1997 2703
F igu r e 2. 13C{1H} NMR spectra of (a) W(PhCtCPh)(η8-C8Ph8) (10) and (b) 13C-enriched W(Ph*CtCPh)(η8-*C8Ph8) (10′′′),
obtained from the reaction of W(NCMe)(Ph*CtCPh)3 and 2 equiv of Ph*CtCPh (ca. 10% 13C).
F igu r e 4. Molecular structure of W(PhCtCPh)(η8-C8Ph8)
(10). The phenyl groups have been artificially omitted,
except the ipso carbon atoms, for clarity.
nuclear products.25 Mo(η5-C5Ph5)2 was previously iso-
F igu r e 3. IR spectra of (a) [W(C5Ph5)2]x (5) and (b) W(η5-
lated as a side product from the reaction of PhCtCPh
C5Ph5)2(I)2 (6) in KBr pellets.
with either Mo(CO)6 or Mo(CO)3(η6-C6H5Me),26 with not
very extensive characterization; this complex is practi-
cally insoluble in all common solvents and is presumably
also polymeric.
spectroscopy, and its reaction with I2 to give W(η5-
C5Ph5)2(I)2 (6).
The IR spectrum of 5 (Figure 3a) is very similar to
that of 6 (Figure 3b), suggesting an η5-bonding mode
for the C5Ph5 groups of 5. In addition, the absence of
strong W-H stretching bands22 in the region 2000-1700
cm-1 could preclude a dihydrido formula, W(C5Ph5)2(H)2,
for 5. The EI mass spectrum of 5, obtained at 350 °C
and 70 eV, displays the highest ion peak at m/ z 1074
for 184W, corresponding to the mononuclear tung-
stenocene W(C5Ph5)2. Thus, it is likely that compound
5 persists a dimeric or trimeric structure with a regular
W(η5-C5Ph5)2 unit.
P r ep a r a tion a n d Ch a r a cter iza tion of 6 a n d 7.
Heating solid [W(C5Ph5)2]x (5) and I2 in benzene affords
a dark green powder, which is recrystallized from
dichloromethane/benzene to yield essentially pure W(η5-
C5Ph5)2(I)2 (6). It appears that diiodine undergoes an
oxidative-addition reaction at the tungsten center, lead-
ing to cleavage of the oligomer (presumably breaking
tungsten-tungsten bonds). Subsequent treatment of 6
with AgBF4 in wet dichloromethane solution affords the
oxo complex W(η5-C5Ph5)2(dO) (7) in good yield (eq 1).
Analogous group 6 “bent metallocene” MCp2X2 can be
prepared by stirring the corresponding dihydrides in
CHCl3 or other appropriate halogenating agent.22a,27
The simple mononuclear complex MCp2 (M ) Mo,
W),23 analogous to chromocene,24 is unstable. All at-
tempts to prepare it and its analogues containing alkyl-
and arylcyclopentadienyls have led to isolation of poly-
(24) (a) Robbins, J . L.; Edelstein, N.; Spencer, B.; Smart, J . C. J .
Am. Chem. Soc. 1982, 104, 1882. (b) O’Hare, D.; Murphy, V. J .;
Kaltsoyannis, N. J . Chem. Soc., Dalton Trans. 1993, 383. (c) Castellani,
M. P.; Geib, S. J .; Rheingold, A. L.; Trogler, W. C. Organometallics
1987, 6, 1703.
(25) (a) Thomas, J . L. J . Am. Chem. Soc. 1973, 95, 1838. (b) Thomas,
J . L.; Brintzinger, H. H. J . Am. Chem. Soc. 1972, 94, 1386.
(26) Hu¨bel, W.; Mere´nyi, R. J . Organomet. Chem. 1964, 2, 213.
(22) (a) Dub, M. Organometallic Compounds, 2nd ed.; Springer-
Verlag: Berlin, 1966; Vol. 1. (b) Girling, R. B.; Grebenik, P.; Perutz,
R. N. Inorg. Chem. 1986, 25, 31.
(23) Grebenik, P.; Downs, A. J .; Green, M. L. H.; Perutz, R. N. J .
Chem. Soc., Chem. Commun. 1979, 742.

2704 Organometallics, Vol. 16, No. 12, 1997
Yeh et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) of W(P h CtCP h )(η8-C8P h 8) (10)
Distances
W1-C1
W1-C3
W1-C5
W1-C7
W1-C9
C1-C2
C2-C17
C3-C23
C4-C29
C5-C35
C6-C41
C7-C53
C8-C47
C9-C59
2.09(2)
2.01(2)
2.25(2)
2.38(2)
2.46(2)
1.31(3)
1.47(3)
1.42(3)
1.50(3)
1.46(3)
1.47(3)
1.47(3)
1.50(3)
1.51(3)
W1-C2
W1-C4
W1-C6
W1-C8
W1-C10
C1-C11
C3-C4
C4-C5
C5-C6
C6-C7
C7-C8
C8-C9
C9-C10
C10-C65
2.10(2)
2.48(2)
2.39(2)
2.23(2)
2.03(2)
1.47(3)
1.43(3)
1.46(3)
1.52(3)
1.46(3)
1.48(3)
1.38(3)
1.36(3)
1.51(3)
Angles
36.4(9)
C1-W1-C2
C1-W1-C4
C1-W1-C6
C1-W1-C8
C1-W1-C10
C2-W1-C4
C2-W1-C6
C2-W1-C8
C2-W1-C10
C2-C1-C11
W1-C2-C1
W1-C3-C23
W1-C4-C3
W1-C4-C29
C3-C4-C29
W1-C5-C4
W1-C5-C35
C4-C5-C35
W1-C6-C5
W1-C6-C41
C5-C6-C41
W1-C7-C6
W1-C7-C53
C6-C7-C53
W1-C8-C7
W1-C8-C47
C7-C8-C47
W1-C9-C8
W1-C9-C59
C8-C9-C59
W1-C10-C9
C9-C10-C65
C1-W1-C3
C1-W1-C5
C1-W1-C7
C1-W1-C9
C2-W1-C3
C2-W1-C5
C2-W1-C7
C2-W1-C9
C1-C2-C17
W1-C1-C2
W1-C3-C4
C4-C3-C23
W1-C4-C5
C3-C4-C5
C5-C4-C29
W1-C5-C6
C4-C5-C6
C6-C5-C35
W1-C6-C7
C5-C6-C7
C7-C6-C41
W1-C7-C8
C6-C7-C8
C8-C7-C53
W1-C8-C9
C7-C8-C9
C9-C8-C47
W1-C9-C10
C8-C9-C10
C10-C9-C59
W1-C10-C65
94.2(9)
130.7(8)
158.7(8)
101.7(8)
108.6(9)
104.9(8)
137.6(8)
95.1(8)
136(2)
72(1)
90(1)
123(1)
63(1)
108(1)
122(1)
75(1)
110(1)
121(1)
71(1)
117(1)
120(1)
66(1)
119(1)
120(1)
82(1)
107(1)
123(1)
55(1)
112(2)
122(1)
141(1)
105.3(8)
165.5(8)
125.4(8)
90.9(9)
97.7(8)
140.9(8)
101.4(8)
105.2(9)
131(2)
71(1)
142(1)
54(1)
142(1)
127(1)
80(1)
135(1)
120(1)
66(1)
139(1)
121(1)
72(1)
131(1)
119(1)
76(1)
131(1)
121(1)
64(1)
(1)
Reduction of WCp′Cl4(PMe3) (Cp′ ) C5Me5) with mag-
nesium and reaction with LiCp′ also provides a conve-
nient route to W(Cp′)2(Cl)2, from which a range of other
derivatives can be prepared.28 For example, the oxo
complexes MCp′2(dO) were synthesized by treating
MCp′2Cl2 with aqueous KOH.28
W(η5-C5Ph5)2(I)2 (6) forms an air-stable, dark green
crystalline solid. It decomposes readily in solution.
Compound 6 gives satisfactory C, H microanalyses,
though the FAB mass spectrum displays the highest
mass at m/ z 1074, corresponding to the M+ - 2I
fragment. The oxo complex W(η5-C5Ph5)2(dO) (7) also
forms air-stable, dark green crystals. The FAB mass
spectrum of 7 gives the parent ion at m/ z 1090 and an
ion at m/ z 1074 for loss of an oxygen atom. The
tungsten-oxygen double bond is characterized by a
147(1)
125(1)
90(1)
125(2)
bond distances and bond angles are given in Table 3.
The unit cell consists of two molecules related by
inversion center symmetry. Each molecule has a for-
mally W(IV) atom surrounded by two pentaphenyl-
cyclopentadienyl groups and an oxo ligand. The overall
geometry can be viewed as a bent sandwich where the
two cyclopentadienyl groups are splayed with respect
to the oxo ligand, with an interplanar angle of 26°.
Ignoring the phenyl groups, the molecule has an ap-
proximate Cs symmetry with a mirror plane passing
through the W1, O1, C7, and C47 atoms and the middle
point of the C1-C2 bond. The tungsten atom is not
situated right behind the centroid of the two cyclopen-
tadienyl rings. Its projection point is 0.26 Å away from
the centroid of the C1-C5 ring, leaning toward the C1-
C2 edge, and 0.39 Å away from the centroid of the C6-
C10 ring, leaning toward the C7 atom. There appears
to be considerable steric repulsions between the two
C5Ph5 moieties such that the cyclopentadienyl groups
are staggered. The phenyl groups are canted to each
cyclopentadienyl ring in a paddlewheel fashion. The
phenyl groups on the cyclopentadienyl rings are dis-
placed outward from the tungsten atom.
strong ν(WdO) band in its IR spectrum at 906 cm-1
which is comparable with those recorded for W(η5-
C5Me5)2(dO) (860 cm-1 29
,
)
and W(η5-C5Me5)(η1-C5Me5)-
(dO)2 (895 and 935 cm-1).30 Apparently, the tungsten
center of 7 persists in a closed-shell configuration (18e-)
without oxygen lone-pair donation; otherwise, an ab-
sorption in the range 930-1000 cm-1 would be observed
for the more common -WtO+ bonding mode.31
Cr ysta l Str u ctu r e of 7. An ORTEP drawing of
W(η5-C5Ph5)2(dO) (7) is shown in Figure 5. Selected
(27) Davis, R.; Kane-Maguire, L. A. P. in Comprehensive Organo-
metallic Chemistry; Pergamon Press: Oxford, U.K., 1982; Vol. 3, p
1321, and references therein.
(28) Parkin, G.; Bercaw, J . E. Polyhedron 1988, 7, 2053.
(29) Parkin, G.; Bercaw, J . E. J . Am. Chem. Soc. 1989, 111, 391.
(30) Parkin, G.; Marsh, R. E.; Schaefer, W. P.; Bercaw, J . E. Inorg.
Chem. 1988, 27, 3262.
(31) (a) Herrmann, W. A.; Serrano, R.; Bock, H. Angew. Chem., Int.
Ed. Engl. 1984, 23, 383. (b) Besecker, C. J .; Klemperer, W. G. J . Am.
Chem. Soc. 1980, 102, 7598. (c) Day, V. W.; Fredrich, M. F.; Thompson,
M. R.; Klemperer, W. G.; Liu, R.-S.; Shum, W. J . Am. Chem. Soc. 1981,
103, 3597.

Alkyne-Alkyne Coupling Reactions
Organometallics, Vol. 16, No. 12, 1997 2705
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for (η5-C5P h 5)2W(dO) (7)
Distances
W1-O1
W1-C2
W1-C4
W1-C6
W1-C8
W1-C10
C1-C5
C2-C3
C3-C4
C4-C5
C5-C35
C6-C10
C7-C8
C8-C9
C9-C10
C10-C65
1.714(4)
2.494(6)
2.476(6)
2.355(6)
2.374(6)
2.618(6)
1.449(8)
1.435(8)
1.451(8)
1.437(8)
1.504(8)
1.463(8)
1.440(8)
1.467(8)
1.402(8)
1.498(8)
W1-C1
W1-C3
W1-C5
W1-C7
W1-C9
C1-C2
C1-C11
C2-C17
C3-C23
C4-C29
C6-C7
2.527(6)
2.421(6)
2.460(6)
2.322(6)
2.646(6)
1.416(8)
1.498(8)
1.488(8)
1.486(8)
1.475(8)
1.440(8)
1.504(8)
1.501(8)
1.504(8)
1.485(8)
C6-C41
C7-C47
C8-C53
C9-C59
Angles
O1-W1-C1
O1-W1-C3
O1-W1-C5
O1-W1-C7
O1-W1-C9
C1-W1-C2
C2-W1-C3
C4-W1-C5
C6-W1-C10
C8-W1-C9
W1-C1-C2
W1-C1-C11
C2-C1-C11
W1-C2-C1
W1-C2-C17
C1-C2-C17
W1-C3-C2
W1-C3-C23
C2-C3-C23
W1-C4-C29
W1-C4-C5
C3-C4-C29
W1-C5-C1
W1-C5-C35
C1-C5-C35
W1-C6-C7
W1-C6-C41
C7-C6-C41
W1-C7-C6
W1-C7-C47
C6-C7-C47
W1-C8-C7
W1-C8-C53
C7-C8-C53
W1-C9-C8
W1-C9-C59
C8-C9-C59
W1-C10-C6
W1-C10-C65
C6-C10-C65
80.4(2)
108.4(2)
112.0(2)
78.6(2)
130.6(2)
32.7(2)
33.9(2)
33.8(2)
33.7(2)
33.4(2)
O1-W1-C2
O1-W1-C4
O1-W1-C6
O1-W1-C8
O1-W1-C10
C1-W1-C5
C3-W1-C4
C6-W1-C7
C7-W1-C8
C9-W1-C10
W1-C1-C5
C2-C1-C5
C5-C1-C11
W1-C2-C3
C1-C2-C3
C3-C2-C17
W1-C3-C4
C2-C3-C4
C4-C3-C23
W1-C4-C3
C3-C4-C5
C5-C4-C29
W1-C5-C4
C1-C5-C4
C4-C5-C35
W1-C6-C10
C7-C6-C10
C10-C6-C41
W1-C7-C8
C6-C7-C8
C8-C7-C47
W1-C8-C9
C7-C8-C9
C9-C8-C53
W1-C9-C10
C8-C9-C10
C10-C9-C59
W1-C10-C9
C6-C10-C9
C9-C10-C65
78.3(2)
132.7(2)
98.6(2)
98.1(2)
131.1(2)
33.7(2)
34.4(2)
35.8(2)
35.7(2)
30.9(2)
F igu r e 5. Molecular structure of W(η5-C5Ph5)2(dO) (7).
The W1-O1 distance of 1.714(4) Å is typical for a
tungsten-oxygen double bond. The interesting feature
of the two η5-C5Ph5 groups is that they show unusual
π-coordination to the tungsten atom and are more aptly
described as asymmetric η3-allyl/η2-olefin-type ligands
(Figure 6). In the C1-C5 ring, the atoms C1, C2, C3,
and C5 are coplanar to within 0.002(6) Å and only the
C4 atom is displaced from the plane, away from W1, by
0.1 Å; this gives a dihedral angle of 6.6° between the
olefinic plane C1, C2, C3, C5 and the allylic plane C3,
C4, C5. Among all W-Cring bond distances, the W1-
C1 and W2-C2 distances (2.527(6) and 2.495(6) Å) are
significantly longer than those to the allylic carbon
atoms C3, C4, and C5 (2.421(6), 2.476(6), and 2.460(6)
Å, respectively). The Cring-Cring distances are varied.
They range from 1.435(8) to 1.451(8) Å with the C1-
C2 length of 1.416(8) Å being the shortest. The ipso
carbon atoms C11 and C17 of the phenyl rings are
essentially on the olefin plane, whereas the ipso atoms
C23, C29, and C35 are displaced away from the allyl
plane (C3-C5) by 9.8(6), 9.5(6), and 9.4(6)°, respectively.
The bent η3:η2-bonding mode of the cyclopentadienyl
ligand is unambiguously substantiated by the C6-C10
ring. It appears as an opened envelope with the allyl
fragment (C6, C7, C8, C47) and olefin fragment (C6,
C10, C9, C8) being planar to within 0.002(6) and
0.003(6) Å, respectively, and the dihedral angle between
the two planes is 10.4(6)°. The bonding of C6, C7, and
C8 atoms is typical of η3-allyl: the central carbon (W1-
C7 ) 2.322(6) Å) is ca. 0.04 Å closer to the metal than
the end carbons (W1-C6 ) 2.355(6) Å and W1-C8 )
2.374(6) Å). The W-C distances to the olefinic carbon
atoms C9 and C10 are substantially longer, being
2.646(6) and 2.618(6) Å. There appears to be a consid-
erable localized feature of the ring bonds, such that the
C9-C10 length (1.402(8) Å) is ca. 0.06 Å shorter than
the lengths of C6-C10 and C8-C9 (1.463(8) and
1.467(8) Å) and is ca. 0.04 Å shorter than the lengths of
C6-C7 and C7-C8 (1.440(8) Å). The phenyl ipso
carbon atoms C41 and C53 are bent outward from the
allyl plane (away from W1) by 5.8(6) and 10.4(6)°. The
72.3(4)
70.6(3)
124.7(4)
126.8(6)
74.9(4)
122.0(4)
123.8(6)
75.9(4)
128.1(4)
124.3(6)
132.2(4)
72.4(4)
126.9(6)
75.7(4)
128.8(4)
121.5(6)
70.8(3)
124.6(4)
123.2(6)
73.3(4)
124.7(4)
126.9(6)
70.2(4)
129.1(4)
124.5(6)
63.1(3)
108.0(6)
125.1(6)
70.2(4)
109.2(6)
127.0(6)
74.9(4)
107.0(6)
126.6(6)
70.7(3)
107.9(6)
124.0(6)
73.7(4)
107.4(6)
129.1(6)
83.0(4)
106.3(5)
128.2(6)
74.1(4)
108.4(5)
124.2(6)
83.5(4)
107.0(5)
124.8(6)
73.4(4)
137.8(4)
124.0(6)
63.3(3)
135.5(4)
122.5(5)
107.8(6)
127.0(6)
75.7(4)
109.4(5)
127.2(6)
atoms C59 and C65 are bent away from the olefin plane
by 12.5(6) and 10.6(6)°, respectively.
The structure of the analogous complex Mo(η5-MeCp)2-
(dO) was previously described,32 whereas the MeCp
rings are essentially flat, with no indication of a “local-
ized” fashion. Thus, the occurrence of an η3:η2-bonding
mode for the C5Ph5 ligands in 7 is probably due to strong
steric repulsions between the phenyl groups. A flat η3-
allyl/η2-olefin-type coordination has been observed for
the pentamethylcyclopentadienyl rings of Re(η5-
C5Me5)(Cl)2(dO), Re(η5-C5Me5)(I)2(dO), and Re(η5-C5Me5)-
(CH3)2(dO).33 Another example of asymmetric ring
(32) Silavwe, N. D.; Chiang, M. Y.; Tyler, D. R. Inorg. Chem. 1985,
24, 4219.

2706 Organometallics, Vol. 16, No. 12, 1997
Yeh et al.
Sch em e 2
configuration is provided by (η5-C5Me5)W(dO)2(OC5-
Me5),30 in which the W-(η5-C5Me5) interaction is a
mixture of η5 and η1 bonding and the ligand is better
described as an η4:η1 fashion.
F igu r e 6. Another view of W(η5-C5Ph5)2(dO) (7), showing
the bent configuration for the cyclopentadienyl rings. The
phenyl groups have been artificially omitted for clarity.
Mech a n istic Stu d y of th e Alk yn e-Alk yn e Cou -
p lin g Rea ction . The harsh reaction conditions re-
quired for W(CO)(PhCtCPh)3 (1) disables detailed
mechanistic study. Thus, C-13 labeling experiments
were only performed on W(NCMe)(PhCtCPh)3 (8). The
results, analyzed by 13C NMR spectroscopy, are dis-
played in Scheme 2. It is found that treating 8 with
equimolar Ph*CtCPh (the asterisk indicates the posi-
tions of the 13C label) leads to W(NCMe)(PhCtCPh)2(η4-
*CC3Ph4) (9′), where the 13C label is located exclusively
at the cyclobutadiene fragment. Succeeding reaction of
9′ and PhCtCPh affords 10′, showing the 13C label in
the γ-, δ-positions of the metallacycle. Similar reaction
of 9 and Ph*CtCPh produces 10′′, with the 13C label in
the alkyne ligand and R-, â-positions of the metallacycle.
However, direct treatments of W(NCMe)(PhCtCPh)3 (8)
with 2 equiv of Ph*CtCPh or of W(NCMe)(Ph*CtCPh)3
(8′) with 2 equiv of PhCtCPh or Ph*CtCPh yield
essentially identical results (10′′′), in which the 13C label
scrambles over the alkyne ligand and all the metalla-
cyclic positions.
Obviously, the η4-C4Ph4 group of 9 is derived from a
coordinated and an added diphenylacetylene. Theoreti-
cal analyses of d6 M(alkyne)3(L) complexes suggest
that13 the three alkyne ligands can donate a total of only
10 electrons to the tungsten atom, while one of the
symmetry-adapted alkyne π orbitals has no match
among the metal s, p, or d orbitals. It is probable that
this unused alkyne π orbital of 8 interacts with a π
orbital of incoming diphenylacetylene to generate a
metallacyclopentadiene intermediate, (WC4Ph4)(NCMe)-
(PhCtCPh)2 (i), followed by ring closing to yield 9
(Scheme 3). Alternative pathways via concomitant
coupling of two coordinated PhCtCPh ligands when the
incoming diphenylacetylene is added to the metal or by
preformation of a tetraalkyne complex, W(NCMe)-
(PhCtCPh)4, would show the 13C label in the alkyne
ligands of 9. Apparently, transformation from 8 to i
involves an oxidative-addition reaction, where the alkynes
are reduced with concomitant carbon-carbon bond
formation and the metal loses two electrons. Thus, the
(33) Herrmann, W. A.; Herdtweck, E.; Floel, M.; Kulpe, J .; Ku¨st-
hardt, U.; Okuda, J . Polyhedron 1987, 6, 1165.

Alkyne-Alkyne Coupling Reactions
Organometallics, Vol. 16, No. 12, 1997 2707
Sch em e 3
Sch em e 4
involves insertion of two alkyne ligands into the metal-
carbocycle bonds, thus bringing the cyclobutadiene
carbons regiospecifically into the γ- and δ-positions of
the metallacycle. On the other hand, the left path from
ii to 10 involves alkyne insertion into the metallacycle
randomly and would scramble the 13C label, consistent
with the observations.
Formation of metallacyclopentadiene from oxidative
cyclization of two alkynes with metal has been well
established.34 For instance, Singleton35 reported cyclo-
dimerization of phenylacetylene at a ruthenium(II)
center to generate CpBr(RuC4H2Ph2). Transformation
of metallacyclopentadienes into cyclobutadienes is also
known, as exemplified by the thermolysis of Cp(CoC4-
Ph4)(PPh3), which gives CpCo(η4-C4Ph4).36 The conver-
sion 9 f 10 represents an interesting ring expansion
reaction. Green37 has previously reported the reaction
of [CpRu(NCMe)(η4-C4Ph4)]+ and PhCtCPh to afford
the arene complex [CpRu(η6-C6Ph6)]+, presumably
through an intermediate analogous to v.
P ossible Mech a n ism for Tr a n sfor m a tion of 10
in to 3, 4, a n d 5. We do not have mechanistic informa-
tion. It is likely that thermolysis of compound 10
induces further alkyne insertion to generate the met-
allacycloundecahexaene species WC10Ph10, followed by
C-C bond activation to produce spiro-W(C5Ph5)2 (Scheme
4). Subsequent steps apparently involve 1,1′-cyclization
to yield tungstenocene, W(η5-C5Ph5)2, and oligomeriza-
tion to afford 5. However, the reaction pathways
involving two or more tungsten centers or involving
alkylidyne intermediates cannot be ruled out. Schrock
has shown38 the formation of substituted cyclopentadi-
enide complexes of W by coupling of alkynes with
alkylidyne ligands.
In the presence of CO, the metallacycle of 10 might
switch its bonding mode, thus providing a coordination
site for a carbonyl ligand. Succeeding reactions are
likely 1,5-cyclization to generate 3 or rearrangement of
fact that compound 8 presents higher reactivity toward
diphenylacetylene than 1 can be due to the stronger
σ-donating and weaker π-accepting ability of the NCMe
ligand relative to CO, making the tungsten center of 8
more electron rich to be oxidized.
It is apparent i is a reactive molecule, which im-
mediately undergoes reductive cyclization to give 9 or,
in the presence of free diphenylacetylene, undergoes
alkyne substitution and insertion reactions to lead to
10. Two pathways shown in Scheme 3 can then be
drawn, which differ only with respect to the crucial
insertion reactions. The right path from iv to 10
(34) (a) Agh-Ataby, N. M.; Davidson, J . L.; Muir, K. W. J . Chem.
Soc., Chem. Commun. 1990, 1399. (b) Davidson, J . L. J . Chem. Soc.,
Chem. Commun. 1983, 1667. (c) Davidson, J . L. J . Chem. Soc., Dalton
Trans. 1987, 2715. (d) Hirpo, W.; Curtis, M. D. J . Am. Chem. Soc. 1988,
110, 5218. (e) Porschke, K.-R. Angew. Chem., Int. Ed. Engl. 1987, 26,
1288.
(35) Albers, M. O.; de Waal, D. J . A.; Liles, D. C.; Robinson, D. J .;
Singleton, E.; Wiege, M. B. J . Chem. Soc., Chem. Commun. 1986, 1680.
(36) Yamazaki, H.; Nagihara, N. J . Organomet. Chem. 1970, 21, 431.
(37) Crocker, M.; Green, M.; Orpen, A. G.; Thomas, D. M. J . Chem.
Soc., Chem. Commun. 1984, 1141.
(38) Schrock, R. R.; Pedersen, S. F.; Churchill, M. R.; Ziller, J . W.
Organometallics 1984, 3, 1574.

2708 Organometallics, Vol. 16, No. 12, 1997
Yeh et al.
Sch em e 5
the propenylidene moiety into a metallacyclobutene ring
followed by 1,5-cyclization to yield 4 (Scheme 5).
afford 10. Insertion of alkyne ligands into the metal-
carbocycle bonds of 9 also leads to 10.
An unusual η3:η2-bonding mode has been observed for
the C5Ph5 groups of 7. This “localized” feature is likely
due to steric repulsions between bulky phenyl groups.
Con clu sion s
The results presented here describe interesting prod-
ucts from oligomerization of diphenylacetylene at a
tungsten center, where cyclobutadiene complexes (2, 9),
cyclopentadiene complexes (3, 4), cyclopentadienyl com-
plexes (5, 6, and 7), and a metallacyclononapentaene
complex (10) are obtained.
It is clear that the cyclobutadiene group of 9 is derived
from a coordinated and an added diphenylacetylene. A
metallacyclopentadiene intermediate is likely involved,
followed by ring closing to give 9 or alkyne insertion to
Ack n ow led gm en t. We are grateful for support of
this work by the National Science Council of Taiwan.
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
crystallographic data, positional parameters, anisotropic ther-
mal parameters, bond lengths and angles, and torsional angles
of 7 and 10 (76 pages). Ordering information is given on any
current masthead page.
OM9702340