A novel route to functionalized terminal alkynes through η1-vinylidene to η2-alkyne tautomerizations in indenyl-ruthenium(II) monosubstituted vinylidene complexes: Synthetic and theoretical studies

Article abstract of DOI:10.1021/om990194v

Heating under reflux solutions of the monosubstituted vinylidene complex [Ru{=C=C(H)-Ph}(η⁵-C₉H₇)(PPh ₃)₂][PF₆] (1) in nitriles yields the complexes [Ru(N≡CR)(η⁵-C₉H₇)(PPh ₃)₂]-[PF₆] (R = Me (2a), Et (2b), Ph (2c)) and phenylacetylene. The process proceeds via an initial η¹-vinylidene-η²-alkyne tautomerization followed by the displacement of the coordinated π-alkyne by the solvent. Vinylidene complexes [Ru{=C=C(H)R}(η⁵-C₉H₇)(PPh ₃)₂][PF₆] (R = (η⁵-C₅H₄)Fe(η⁵-C ₅H₅) (3), 4-NO₂-C₆H₄ (4)) also react with acetonitrile to yield the nitrile derivative 2a and the corresponding terminal alkynes HC≡CR. Cationic alkenyl-vinylidene derivatives [RU{=C=C(H)CH=CR¹R²}(η⁵-C₉H ₇)(PPh₃)₂][BF₄] (R¹ = R² = Ph (7a), R¹ = H; R² = 4-OMe-C₆H₄ [(Z)-Tb], 4-NO₂-C₆H₄ [(E,Z)-7c], (η⁵-C₆H₄)Fe(η⁵-C ₅H₅) [(E)-7d]) behave similarly. Thus, the treatment of 7a-d with acetonitrile at reflux results in the formation of complex 2a and the liberation of the corresponding terminal 1,3-enyne HC≡CCH=CR¹R² (8a-d). The formation of the enynes 8b-d is stereoselective, giving rise to the E stereoisomer. The allenylidene complex [Ru{=-C=C-C(C₁₃H₂₀)}(η⁵-C₉H ₇)(PPh₃)₂][PF₆] (9), containing the bicyclic [3.3.1]non-2-en-9-ylidene moiety C₁₃H₂₀, reacts with NaC≡CH in THF at -20°C to yield the neutral σ-alkynyl derivative [Ru{C≡CC(C≡CH)C₁₃H₂₀}(η⁵-C ₉H₇)(PPh₃)₂] (10) in a regioselective manner. Protonation of 10 with HBF₄·Et₂O, in diethyl ether at -20°C, affords the vinylidene complex [Ru{=C=C(H)C(C≡CH)C₁₃H₂₀}(η⁵-C ₉H₇)(PPh₃)₂][BF₄] (11), which can be easily demetalated by heating in refluxing acetonitrile to give 2a and the unprecedented diyne (HC≡C)₂CC₁₃H₂₀ (12). These demetalation processes allow the quantitative recovery of the metal auxiliary as the labile complex 2a, which can be used as starting material for further reactions. Ab initio molecular orbital calculations on the η¹-vinylidene to η²-alkyne tautomerization have been performed. It is shown that the process proceeds through a 1,2-[H] shift mechanism showing that the conversion requires an energy barrier of 29.9 kcal/ mol. This is a value low enough to be overcome under the experimental reaction conditions allowing the formation of the labile η²-alkyne complex and the subsequent exchange of the coordinated alkyne by acetonitrile.

Full text of DOI:10.1021/om990194v

Organometallics 1999, 18, 2821-2832
2821
A Novel Rou te to F u n ction a lized Ter m in a l Alk yn es
th r ou gh η1-Vin ylid en e to η2-Alk yn e Ta u tom er iza tion s in
In d en yl-Ru th en iu m (II) Mon osu bstitu ted Vin ylid en e
Com p lexes: Syn th etic a n d Th eor etica l Stu d ies
Victorio Cadierno, M. Pilar Gamasa, and J ose´ Gimeno*,†
Departamento de Quı´mica Orga´nica e Inorga´nica, Instituto Universitario de Quı´mica
Organometa´lica “Enrique Moles” (Unidad Asociada al CSIC), Facultad de Qu´ımica,
Universidad de Oviedo, E-33071 Oviedo, Spain
Enrique Pe´rez-Carren˜o and Santiago Garc´ıa-Granda
Departamento de Quı´mica Fı´sica y Analı´tica, Facultad de Qu´ımica, Universidad de Oviedo,
E-33071 Oviedo, Spain
Received March 18, 1999
Heating under reflux solutions of the monosubstituted vinylidene complex [Ru{dCdC(H)-
Ph}(η5-C9H7)(PPh3)2][PF6] (1) in nitriles yields the complexes [Ru(NtCR)(η5-C9H7)(PPh3)2]-
[PF6] (R ) Me (2a ), Et (2b), Ph (2c)) and phenylacetylene. The process proceeds via an initial
η1-vinylidene-η2-alkyne tautomerization followed by the displacement of the coordinated
π-alkyne by the solvent. Vinylidene complexes [Ru{dCdC(H)R}(η5-C9H7)(PPh3)2][PF6] (R )
(η5-C5H4)Fe(η5-C5H5) (3), 4-NO2-C6H4 (4)) also react with acetonitrile to yield the nitrile
derivative 2a and the corresponding terminal alkynes HCtCR. Cationic alkenyl-vinylidene
derivatives [Ru{dCdC(H)CHdCR1R2}(η5-C9H7)(PPh3)2][BF4] (R1 ) R2 ) Ph (7a ), R1 ) H;
R2 ) 4-OMe-C6H4 [(Z)-7b ], 4-NO2-C6H4 [(E,Z)-7c], (η5-C5H4)Fe(η5-C5H5) [(E)-7d ]) behave
similarly. Thus, the treatment of 7a -d with acetonitrile at reflux results in the formation
of complex 2a and the liberation of the corresponding terminal 1,3-enyne HCtCCHdCR1R2
(8a -d ). The formation of the enynes 8b-d is stereoselective, giving rise to the E stereoisomer.
The allenylidene complex [Ru{dCdCdC(C13H20)}(η5-C9H7)(PPh3)2][PF6] (9), containing the
bicyclic [3.3.1]non-2-en-9-ylidene moiety C13H20, reacts with NaCtCH in THF at -20 °C to
yield the neutral σ-alkynyl derivative [Ru{CtCC(CtCH)C13H20}(η5-C9H7)(PPh3)2] (10) in a
regioselective manner. Protonation of 10 with HBF4‚Et2O, in diethyl ether at -20 °C, affords
the vinylidene complex [Ru{dCdC(H)C(CtCH)C13H20}(η5-C9H7)(PPh3)2][BF4] (11), which can
be easily demetalated by heating in refluxing acetonitrile to give 2a and the unprecedented
diyne (HCtC)2CC13H20 (12). These demetalation processes allow the quantitative recovery
of the metal auxiliary as the labile complex 2a , which can be used as starting material for
further reactions. Ab initio molecular orbital calculations on the η1-vinylidene to η2-alkyne
tautomerization have been performed. It is shown that the process proceeds through a 1,2-
[H] shift mechanism showing that the conversion requires an energy barrier of 29.9 kcal/
mol. This is a value low enough to be overcome under the experimental reaction conditions
allowing the formation of the labile η2-alkyne complex and the subsequent exchange of the
coordinated alkyne by acetonitrile.
In tr od u ction
carbon2a,3 coupling reactions, and they have been also
proposed as key intermediates in a number of catalytic
transformations involving terminal alkynes.4 Although
several methods are known for the preparation of
Transition metal vinylidene complexes [M]dCdCR2
have attracted increasing attention in recent years since
they display a rich and versatile reactivity of potential
utility in organic synthesis.1 In this respect, ruthenium-
(II) vinylidene derivatives have proven to be appropriate
promoters for selective carbon-heteroatom2 and carbon-
(2) See for example: (a) Davies, S. G.; McNally, J . P.; Smallridge,
A. J . Adv. Organomet. Chem. 1990, 30, 1, and references therein. (b)
Bianchini, C.; Glendenning, L.; Peruzzini, M.; Romerosa, A.; Zanobini,
F. J . Chem. Soc., Chem. Commun. 1994, 2219. (c) Bianchini, C.;
Peruzzini, M.; Romerosa, A.; Zanobini, F. Organometallics 1995, 14,
3152. (d) Nombel, P.; Lugan, N.; Mathieu, R. J . Organomet. Chem.
1995, 503, C22. (e) Bianchini, C.; Casares, J . A.; Peruzzini, M.;
Romerosa, A.; Zanobini, F. J . Am. Chem. Soc. 1996, 118, 4585, and
references therein. (f) Chang, K. H.; Lin, Y. C. Chem. Commun. 1998,
1441. (g) Yam, V. W.-W.; Chu, B. W.-K.; Cheung, K.-K. Chem. Commun.
1998, 2261.
† E-mail: jgh@sauron.quimica.uniovi.es.
(1) For comprehensive reviews see: (a) Bruce, M. I. Chem. Rev. 1991,
91, 197; 1998, 98, 2797. (b) Antonova, A. B.; Ioganson, A. A. Russ.
Chem. Rev. (Engl. Transl.) 1989, 58, 693. (c) Werner, H. J . Organomet.
Chem. 1994, 475, 45.
10.1021/om990194v CCC: $18.00 © 1999 American Chemical Society
Publication on Web 06/30/1999

2822 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
Ch a r t 1
have been isolated as stable intermediates in the
formation of the corresponding vinylidene complexes.
Moreover, both tautomers have been found to be in
equilibrium at room temperature in complexes contain-
ing the ruthenium(II) fragments [Ru(η5-C5H5)(CO)-
(PPh3)]+ 2d and [Ru(η5-C9H4Me3)(CO)(PPh3)]+,8 showing
that the conversion of the η2-alkyne into the vinylidene
complexes depends on the electronic properties of the
metallic fragment. Although the reverse process, i.e., the
transformation of the vinylidene complex into the cor-
responding η2-alkyne, has not been so extensively
studied, it has also been described in a few cases. Thus,
the reaction of [Ru{dCdC(H)Ph}Cl(κ2P,O-Pri PCH2-
2
CH2OMe)2]+9a and [Ru{dCdC(H)Ph}{dC(NHPh)(CH2-
Ph)}Cl(PNP)]+9b (PNP ) PrnN(CH2CH2PPh2)2) with CO
in THF leads to the elimination of HCtCPh and
formation of the carbonyl compounds [RuCl(CO)(κ2P,O-
transition metal vinylidene derivatives, the most gen-
eral approach is the addition of electrophiles to the
nucleophilic Câ atom of σ-alkynyl complexes.1 An alter-
native procedure widely used in the chemistry of ru-
thenium(II) complexes is the direct activation of termi-
nal alkynes, which proceeds through the initial formation
of the corresponding η2-alkyne complex. The subsequent
tautomerization via either the 1,2-[H] shift (see Chart
1; path A) or formation of the hydride-alkynyl ruthe-
nium(IV) complex (see Chart 1; path B)5 gives rise to
the thermodynamically favored vinylidene isomer.1
Theoretical studies6 support both mechanisms which
have been also experimentally proved through the
spectroscopic characterization or isolation of the corre-
sponding intermediate complexes. As far as the η2-
terminal alkyne species are concerned, derivatives such
as [Ru(η2-HCtCR)(η5-C5H5)L2]+ (R ) H, L ) PMe2Ph;
R ) Me, L ) PMe3)7 and [Ru(η2-HCtCH)(η5-C5H5)-
(dippe)]+ (dippe ) 1,2-bis(diisopropylphosphino)ethane)5
Pri PCH2CH2OMe)2]+ and [Ru{)C(NHPh)(CH2Ph)}Cl-
2
(CO)(PNP)]+, respectively. Similarly, the terminal alkyne
is obtained when [RuI2{dCdC(H)Ph}(κ2P,O-Pri PCH2-
2
CH2OMe)(κP-Pri PCH2CH2OMe)] is heated at a high
2
temperature.9a The vinylidene moiety is also displaced
from the reaction of [Ru(CtCR){dCdC(H)R}P4]+ (P )
phosphites) with P(OMe)3 and isocyanides3a as well as
in half-sandwich ruthenium(II) complexes of the type
[Ru{HB(pz)3}Cl(PPh3){dCdC(H)R}] by nucleophiles (L)
such as PMe3, PPh3, MeCN, pyridine, and CO to give
[Ru{HB(pz)3}Cl(PPh3)L] and the free terminal alkyne.10
It is, therefore, apparent that the transformation of
the vinylidene moiety into the corresponding terminal
alkyne in ruthenium(II) complexes is a feasible process
which is accessible in ordinary reaction conditions.
Although in the above-mentioned examples there is no
valuable synthetic approach of alkynes (the resulting
terminal alkynes are themselves the precursors of the
vinylidene complexes), we believed it to be of interest
to investigate the utility of these processes as a synthetic
methodology for the preparation of functionalized ter-
minal alkynes.
(3) For recent references see: (a) Albertin, G.; Antoniutti, S.;
Bordignon, E.; Cazzaro, F.; Ianelli, S.; Pellizi, G. Organometallics 1995,
14, 4114. (b) Wang, Y.; Finn, M. G. J . Am. Chem. Soc. 1995, 117, 8045.
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H. Organometallics 1996, 15, 4075. (e) Ting, P. C.; Lin, Y. C.; Lee, G.
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C. P. J . Organomet. Chem. 1998, 565, 37, and references therein. (i)
Slugovc, C.; Mauthner, K.; Kacetl, M.; Mereiter, K.; Schmid, R.;
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J . C.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 4700.
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Organomet. Chem. 1995, 500, 349, and references therein. (b) Trost,
B. M. Chem. Ber. 1996, 129, 1313, and references therein. (c) Merlic,
C. A.; Pauly, M. E. J . Am. Chem. Soc. 1996, 118, 11319. (d) Yi, C. S.;
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Slugovc, C.; Kremel, S.; Mereiter, K.; Schmid, R.; Kirchner, K.
Organometallics 1996, 15, 3998. (f) Slugovc, C.; Mereiter, K.; Zobetz,
E.; Schmid, R.; Kirchner, K. Organometallics 1996, 15, 5275. (g) Gemel,
C.; Kickelbick, G.; Schmid, R.; Kirchner, K. J . Chem. Soc., Dalton
Trans. 1997, 2113. (h) Bruneau, C.; Dixneuf, P. H. Chem. Commun.
1997, 507, and references therein. (i) Tokunaga, M.; Wakatsuki, Y.
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B.; Thommen, M. Chem. Eur. J . 1999, 5, 1055.
As part of our continuing studies on the reactivity
patterns of unsaturated carbene ruthenium(II) com-
plexes,11 here we report that functionalized indenyl-
(8) Gamasa, M. P.; Gimeno, J .; Gonza´lez-Bernardo, C.; Borge, J .;
Garc´ıa-Granda, S. Organometallics 1997, 16, 2483.
(9) (a) Mart´ın, M.; Gevert, O.; Werner, H. J . Chem. Soc., Dalton
Trans. 1996, 2275. (b) Bianchini, C.; Purches, G.; Zanobini, F.;
Peruzzini, M. Inorg. Chim. Acta 1998, 272, 1.
(10) Other metal-η1-vinylidene to metal-η2-alkyne isomerizations
have been also reported: (a) Ru: Slugovc, C.; Sapunov, V. N.; Wiede,
P.; Mereiter, K.; Schmid, R.; Kirchner, K. J . Chem. Soc., Dalton Trans.
1997, 4209. (b) Fe: Bly, R. S.; Zhong, Z.; Kane, C.; Bly, R. K.
Organometallics 1994, 13, 899, and references therein. (c) Mo, W:
Ipaktschi, J .; Demuth-Eberle, G. J .; Mirzaei, F.; Mu¨ller, B. G.; Beck,
J .; Serafin, M. Organometallics 1995, 14, 3335.
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Garc´ıa-Granda, S.; Pe´rez-Carren˜o, E. Organometallics 1994, 13, 4045.
(b) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Borge, J .; Garc´ıa-Granda,
S. J . Chem. Soc., Chem. Commun. 1994, 2495. (c) Cadierno, V.;
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Garc´ıa-Granda, S. Organometallics 1996, 15, 2137. (d) Cadierno, V.;
Gamasa, M. P.; Gimeno, J .; Borge, J .; Garc´ıa-Granda, S. Organome-
tallics 1997, 16, 3178. (e) Cadierno, V.; Gamasa, M. P.; Gimeno, J .;
Lo´pez-Gonza´lez, M. C.; Borge, J .; Garc´ıa-Granda, S. Organometallics
1997, 16, 4453. (f) Crochet, P.; Demerseman, B.; Vallejo, M. I.; Gamasa,
M. P.; Gimeno, J .; Borge, J .; Garc´ıa-Granda, S. Organometallics 1997,
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Ricart, S.; Roig, A.; Molins, E. Organometallics 1998, 17, 697. (h)
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Doctoral Thesis, University of Oviedo, 1996.
(5) Hydrido-alkynyl ruthenium(IV) derivatives [Ru(H)(CtCR)(η5-
C5Me5)(dippe)]+ (dippe ) 1,2-bis(diisopropylphosphino)ethane) have
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Functionalized Terminal Alkynes
Organometallics, Vol. 18, No. 15, 1999 2823
Ch a r t 2
Sch em e 1
ruthenium(II) vinylidene derivatives [Ru{dCdC(H)R}-
(η5-C9H7)(PPh3)2]+ react with nitriles to give the cationic
complexes [Ru(η5-C9H7)(NtCR′)(PPh3)2]+ (R′ ) Me, Et,
Ph) and the corresponding functionalized terminal
alkyne HCtCR (R ) C6H5, 4-NO2-C6H4, (η5-C5H4)Fe-
(η5-C5H5), C(CtCH)C13H20) (see Chart 2). Similarly
terminal (E)-1,3-enynes HCtCCHdCR1R2 (R1 ) R2 )
Ph; R1 ) H, R2 ) 4-OMe-C6H4, 4-NO2-C6H4, (η5-C5H4)-
Fe(η5-C5H5)) can be obtained starting from the alkenyl-
vinylidene complexes [Ru{dCdC(H)CHdCR1R2}(η5-
C9H7)(PPh3)2]+, which have been synthesized by proto-
nation of the neutral σ-enynyl derivatives [Ru(CtCCHd
CR1R2)(η5-C9H7)(PPh3)2].
To study the electronic properties of the indenyl-
ruthenium(II) fragment [Ru(η5-C9H7)(PPh3)2] which en-
able the lability of the vinylidene moiety via conversion
to the η2-alkyne complex, ab initio molecular orbital
calculations are also reported.
η2-alkyne tautomer [Ru(η2-HCtCPh)(η5-C9H7)(PPh3)2]-
[PF6] under the reaction conditions (ca. temperature
65-97 °C). Although at room temperature complex 1 is
more stable (see Theoretical Calculations below), the
rapid substitution in the transient π-alkyne species of
the labile coordinated phenylacetylene by the more basic
nitrile ligands favors the displacement of the equilib-
rium to afford complexes 2a -c and the free alkyne. To
get information on the existing species in solution, the
reaction of complex 1 with CD3CN has been monitored
by 31P{1H} and 1H NMR spectroscopy (from 20 to 70
°C). However, the presence of the π-alkyne species is
not observed12,13 since the spectra show only the reso-
nances of the precursor complex 1 along with those
assigned to the nitrile complex [Ru(NtCCD3)(η5-C9H7)-
(PPh3)2][PF6].
Resu lts a n d Discu ssion
Rea ction s of Mon osu bstitu ted Vin ylid en e Ru -
th en iu m (II) Com p lexes w ith Nitr iles. Although the
monosubstituted vinylidene derivative [Ru{dCdC(H)-
Ph}(η5-C9H7)(PPh3)2][PF6] (1)11a is obtained from phe-
nylacetylene itself, we have first explored the feasibility
of the vinylidene to π-alkyne transformation using the
easily accessible complex 1 as precursor. Thus, the
treatment of 1 with nitriles at high temperature results
in the formation of the cationic nitrile complexes [Ru-
(NtCR)(η5-C9H7)(PPh3)2][PF6] (R ) Me (2a ), Et (2b), Ph
(2c)), which were isolated in 75-85% yield, via pheny-
lacetylene elimination (Scheme 1). Compounds 2a -c
have been characterized by elemental analysis, conduc-
tance measurements, and IR and NMR (1H, 31P{1H},
and 13C{1H}) spectroscopy (details are given in the
Experimental Section). The presence of the nitrile
ligands is unambiguosly confirmed by the appearance
in the IR spectra (KBr) of a ν(CtN) absorption in the
(12) The existence of this equilibrium is confirmed in the reaction
of the analogous vinylidene complex [Ru{dCdC(H)R}(η5-C9H7)(PPh3)2]-
[PF6] (R ) 1-cyclohexenyl) with triphenylphosphine in refluxing
methanol, which leads to the formation of the alkenyl-phosphonio
complex (E)-[Ru{CHdC(PPh3)R}(η5-C9H7)(PPh3)2][PF6] (R ) 1-cyclo-
hexenyl) via nucleophilic addition of PPh3 to the coordinated π-alkyne
(see ref 11d). Similarly, complex 1 reacts with PPh3 in refluxing
methanol to give the analogous alkenyl-phosphonio complex [Ru{CHd
C(PPh3)Ph}(η5-C9H7)(PPh3)2][PF6] (Unpublished results).
range 2226-2271 cm-1
.
(13) Variable-temperature 31P{1H} and 1H NMR experiments were
also carried out with both CD3OD and CD3NO2 solutions of the
vinylidene complex 1. No products other than 1 could be detected.
The formation of 2a -c may be understood assuming
that the vinylidene complex 1 is in equilibrium with its

2824 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
Sch em e 2
Sch em e 3
To find out to what extent the electronic density of
the vinylidene ligand may affect this η1-vinylidene-η2-
alkyne tautomerization, the behavior of the vinylidene
derivatives [Ru{dCdC(H)(η5-C5H4)Fe(η5-C5H5)}(η5-C9H7)-
(PPh3)2][PF6] (3) and [Ru{dCdC(H)-4-NO2-C6H4}(η5-
C9H7)(PPh3)2][PF6] (4)14 toward acetonitrile was ex-
plored. Compound 3 containing the electron-donor
ferrocenyl fragment was prepared (82%) by reaction of
[RuCl(η5-C9H7)(PPh3)2] with ethynylferrocene and NaPF6
in refluxing methanol (Scheme 2), as previously de-
scribed for analogous indenyl-ruthenium(II) vinylidene
complexes.11a,14 Analytical and spectroscopic data (IR
to indicate that the process is kinetically favorable for
the vinylidene groups bearing electron-releasing sub-
stituents.
R ea ct ion s of Mon osu b st it u t ed Alk en yl-Vin yl-
id en e Ru th en iu m (II) Com p lexes w ith Aceton i-
tr ile: Syn th esis of Ter m in a l 1,3-En yn es. Since the
vinylidene ligand in complexes 1, 3, and 4 has been
found to be easily converted into the corresponding
terminal alkyne in refluxing acetonitrile, we became
interested in extending this reactivity to functionalized
vinylidene derivatives. Providing that these derivatives
are not accessible from the corresponding terminal
alkyne, this approach could lead to a new route of
terminal functionalized alkynes. We have previously
shown11b,g,14 that alkynyl-phosphonio complexes [Ru-
{CtCCH(R1)(PR3)}(η5-C9H7)(PPh3)2][PF6] (R1 ) H, PR3
) PPh3; R1 ) Ph, PR3 ) PMe3) are excellent substrates
for Wittig reactions, leading to the formation of new
carbon-carbon double bonds. Thus, functionalized neu-
tral σ-enynyl derivatives such as [Ru(CtC-C(Ph)d
CR1R2)(η5-C9H7)(PPh3)2] (R1 ) R2 ) Ph; R1 ) H, R2 )
Me)11b and [Ru(CtC-CHdCH-CtCPh)(η5-C9H7)-
(PPh3)2]11g can be obtained in good yields. Following this
synthetic methodology novel σ-enynyl derivatives have
been prepared in order to use them as potential precur-
sors of the corresponding alkenyl-vinylidene complexes.
The treatment of a THF solution of the alkynyl-
phosphonio complex [Ru{CtCCH2(PPh3)}(η5-C9H7)-
(PPh3)2][PF6]14b (5) with 1 equiv of LinBu at -20 °C,
adding the corresponding aldehyde or ketone and warm-
ing the mixture up to room temperature resulted in the
formation of the σ-enynyl complexes 6a ,b (98% and 62%
yield, respectively) (Scheme 4). IR and NMR (1H, 31P-
{1H}, and 13C{1H}) spectroscopic data (see Experimental
Section) support the proposed formulations and are in
accordance with the presence of the novel carbon-
carbon double bonds. It is worth mentioning that
complex 6b was stereoselectively obtained as the pure
1
and H, 31P{1H}, and 13C{1H} NMR) are in agreement
with the proposed formulation. In particular, the pres-
ence of the vinylidene moiety was identified, as usual,
on the basis of the low-field triplet resonance in 13C-
{1H} NMR of the carbene carbon RudCR (δ 352.30 ppm,
2J CP ) 13.4 Hz).11
Complex 3 readily reacts with acetonitrile at reflux
(ca. 1 h), like the vinylidene derivative 1, to yield the
expected nitrile complex [Ru(NtCMe)(η5-C9H7)(PPh3)2]-
[PF6] (2a ) and ethynylferrocene in almost quantitative
yield (Scheme 3). In contrast, vinylidene complex 4,
containing the electron-withdrawing p-nitrophenyl group,
reacts slowly with acetonitrile at reflux to afford after
6 h a complicated mixture of products including 2a and
PPh3, along with p-nitroethynylbenzene and additional
uncharacterized organic and organometallic species. It
is likely that competitive processes occur in the course
of the long reaction period, among others the substitu-
tion of the coordinated PPh3 ligands by acetonitrile.
Although it is apparent that the η1-vinylidene-η2-
alkyne tautomerization takes place, since for both
reactions the free alkyne is obtained, these results seem
(14) (a) Houbrechts, S.; Clays, K.; Persoons, A.; Cadierno, V.;
Gamasa, M. P.; Gimeno, J . Organometallics 1996, 15, 5266. (b)
Cadierno, V.; Conejero, S.; Gamasa, M. P.; Gimeno, J .; Asselberghs,
I.; Houbrechts, S.; Clays, K.; Persoons, A.; Borge, J .; Garc´ıa-Granda,
S. Organometallics 1999, 18, 582.

Functionalized Terminal Alkynes
Organometallics, Vol. 18, No. 15, 1999 2825
Sch em e 4
Z stereoisomer, as clearly indicated by the coupling
constant (J HH ) 13.0 Hz) for the olefinic protons in the
1H NMR spectrum. The presence of the enynyl moiety
was identified on the basis of (i) the presence of a ν(Ct
C) absorption band in the IR spectra (KBr) at 2049 (6a )
and 2045 (6b) cm-1 and (ii) the triplet resonance of the
Ru-CR atom (6a : δ 123.96 (2J CP ) 24.2 Hz) ppm; 6b:
δ 116.90 (2J CP ) 25.0 Hz) ppm), the singlet resonance
of the Câ atom (δ 116.36 (6a ) and 115.77 (6b) ppm), and
the olefinic carbon resonances (ca. δ 114-145 ppm)
observed in the 13C{1H} NMR spectra.
As expected, the protonation of 6a ,b with HBF4‚Et2O
in THF at -20 °C leads to the formation of the alkenyl-
vinylidene derivatives 7a ,b (98% and 88% yield, respec-
tively) (Scheme 4). The analytical and spectroscopic
data of 7a ,b, which are similar to those reported for
other indenyl-ruthenium(II) alkenyl-vinylidene com-
plexes,11b,d,g,14 are consistent with the proposed formula-
tions (see Experimental Section). Since no isomerization
of the CdC bond takes place in the course of these
protonations, complex 7b has been isolated as the pure
Z stereoisomer. Similarly, complex 7c has been obtained
from the previously reported σ-enynyl complex 6c14 and
isolated (73% yield) as a mixture of the corresponding
E and Z stereoisomers in accordance with the isomeric
mixture of the precursor derivative 6c (ca. 2:1 ratio).
Complexes 7a -c react rapidly with refluxing MeCN,
resulting in the quantitative formation of the nitrile
complex 2a , isolated as an unsoluble tetrafluoroborate
salt, and the elimination of the 1,3-enynes 8a -c, which
are readily isolated from the reaction mixture by extrac-
tion with diethyl ether (Scheme 4). If we compare the
behavior of the vinylidene complexes 4 and 7c, both
containing the strong acceptor p-nitrophenyl group, we
can conclude that the presence of a conjugated CdC
double bond in the vinylidene group of the latter seems
to favor the initial η1-vinylidene-η2-alkyne tautomer-
ization. The enyne HCtC-CHdCH-(η5-C5H4)Fe(η5-
C5H5) (8d ) has been similarly obtained following an
analogous sequence of reactions from the known σ-eny-
nyl (E)-6d and alkenyl-vinylidene (E)-7d complexes.14b
Enynes 8a -d were easily purified by column chroma-
tography on silica gel (60-77% isolated yield) and
spectroscopically characterized (see Experimental Sec-
tion).15 Thus, the IR spectra show the expected ν(CtC)
absorptions in the range 2092-2106 cm-1. The acety-
1
lenic CtCH proton resonances appear, in the H NMR
spectra, as doublets (J HH ) 2.1-2.5 Hz) at δ 2.80-3.22
ppm, and the CtCH carbons resonate, in 13C{1H} NMR,
in the ranges δ 78.42-83.94 (tCH) and 81.49-89.92
(tC) ppm, respectively.
The most remarkable feature of this synthesis is that
1,3-enynes 8b-d were stereoselectively obtained as the
thermodynamically stable E stereoisomers, as inferred
clearly from the values of the coupling constant for the
olefinic protons (ca. J HH ) 16 Hz). Given the stereo-
chemistry of the starting vinylidene complexes, (Z)-7b
and (E,Z)-7c, it is probable that during the demetalation
process, the isomerization of the CdC double bond takes
place in the intermediate coordinated enyne derivatives.
Despite the plethora of methods that have been used
for the preparation of terminal 1,3-enynes,16 those based
on a simple Wittig reaction for the generation of the
(15) Enynes 8a ,b have been previously reported. 8a : (a) J asiobedzki,
W.; Zimniak, A.; Glinka, T. Rocz. Chem. 1975, 49, 111. 8b: (b) Gibson,
A. W.; Humphrey, G. R.; Kennedy, D. J .; Wright, S. H. B. Synthesis
1991, 414.
(16) See for example: (a) Pattenden, G. In Comprehensive Organic
Chemistry, Vol 1; Stoddart, J . F., Ed.; Pergamon: Oxford, 1979; p 205.
(b) Yamamoto, H. In Comprehensive Organic Synthesis, Vol 2; Trost,
B. M., Fleming, I., Eds.; Pergamon: Oxford, 1991; p 91. (c) Cheshire,
D. R. In Comprehensive Organic Synthesis, Vol 3; Trost, B. M., Fleming,
I., Eds.; Pergamon: Oxford, 1991; p 217. (d) Sonogashira, K. In
Comprehensive Organic Synthesis, Vol 3; Trost, B. M., Fleming, I., Eds.;
Pergamon: Oxford, 1991; p 521. (e) Coveney, D. J . In Comprehensive
Organic Synthesis, Vol 3; Trost, B. M., Fleming, I., Eds.; Pergamon:
Oxford, 1991; p 878.

2826 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
Sch em e 5
Ch a r t 3
Syn th esis of th e Diyn e (HCtC)2CC13H20. In the
search for the versatility and potential utility of this
methodology for the synthesis of functionalized terminal
alkynes, we have investigated the reactivity of other
types of σ-alkynyl ruthenium(II) derivatives. Thus, we
have recently reported that the activation of 1-ethynyl-
1-cyclohexanol by [RuCl(η5-C9H7)(PPh3)2] gives the al-
lenylidene complex [Ru{dCdCdC(C13H20)}(η5-C9H7)-
(PPh3)2][PF6] (9), which contains the bicyclic [3.3.1]non-
2-en-9-ylidene moiety C13H20 (Scheme 5). This spiro
bicycle results from the formal addition of two molecules
of the 1-alkyn-3-ol via an unprecedent metal-promoted
double dehydration of 1-ethynyl-1-cyclohexanol.19 Since
all attempts to liberate the organic fragment in 9
through the cleavage of the RudC bond using standard
oxidative reagents (e.g., DMSO, ammonium cerium(IV)
nitrate (CAN)) were unsuccessful, we decided to trans-
form the allenylidene chain into a vinylidene ligand,
which would enable the subsequent elimination of the
terminal alkyne by the treatment with acetonitrile, as
has been described above. The overall transformations
which are based on the initial generation of a σ-alkynyl
derivative and subsequent conversion into a vinylidene
complex are shown in Scheme 5. The allenylidene
complex 9 reacts in THF with a large excess of NaCt
CH at -20 °C to generate, via the typical regioselective
nucleophilic addition11b-i at the Cγ of the allenylidene
group, the σ-alkynyl complex 10 isolated as an air-stable
orange solid (61% yield). Elemental analyses and spec-
troscopic data are in accordance with the formulation
as an σ-yninyl derivative. The IR spectrum (KBr) of 10
shows the expected ν(CtC) absorption bands at 2082
and 2275 cm-1 assigned to the coordinated and terminal
CtC bonds, respectively. The most remarkable features
carbon-carbon double bond are scarce (see Chart 3).
Thus, it is known that the phosphorus ylide derived
from triphenyl (2-propynyl)phosphonium bromide reacts
with aldehydes to produce largely (Z)-1,3-enynes in poor
yields (path A).17 The Horner-Wadsworth-Emmons
variant of the Wittig reaction, starting from (3-trimeth-
ylsilyl-2-propynyl)phosphonate and aldehydes or ke-
tones, has been also reported and gives terminal 1,3-
enynes in excellent yields but as mixtures of the E and
Z stereoisomers (path B).15b With these precedents in
mind, the results reported here provide a useful meth-
odology for the stereoselective generation of terminal
(E)-1,3-enynes based on the Wittig reaction. Further-
more, taking into account that the precursor alkynyl-
phosphonio complex 5 is obtained in a one-pot synthesis
by treatment of [RuCl(η5-C9H7)(PPh3)2] with 2-propyn-
1-ol and NaPF6 in the presence of PPh3,14b this synthetic
route of enynes can be regarded as a formal ruthenium-
mediated coupling of 2-propyn-1-ol with aldehydes or
ketones without precedent in the literature.18
(18) The related coupling of propargyl alcohols with ketones contain-
ing R-hydrogens, via [Co2(CO)6]-stabilized propargylium ions, is known
to yield γ-keto-substituted alkynes. (a) Nicholas, K. M. Acc. Chem. Res.
1987, 20, 207. (b) Smit, W. A.; Caple, R.; Smoliakova, I. P. Chem. Rev.
1994, 94, 2359.
(19) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Lastra, E.; Borge, J .;
Garc´ıa-Granda, S. Organometallics 1994, 13, 745.
(17) Eiter, K.; Oediger, H. Liebigs Ann. Chem. 1965, 682, 62. The
use of the trimethylsilyl-protected phosphonium salt and LiBun as base
has been reported to yield trimethylsilyl-protected (E)-1,3-enynes in
good yields. Corey, E. J .; Ruden, R. A. Tetrahedron Lett. 1973, 1495.

Functionalized Terminal Alkynes
Organometallics, Vol. 18, No. 15, 1999 2827
of the NMR spectra are (i) (1H NMR) the singlet
resonance at δ 2.02 ppm of the CtCH proton and (ii)
(13C{1H} NMR) the Ru-CR resonance, which appears
suki’s previous studies on Ru(II) complexes,6b we have
assumed that the isomerizations in our indenyl-ruthe-
nium(II) complexes proceed through the 1,2-hydrogen
shift mechanism. In fact, no hydrido-alkynyl complexes
were detected under the experimental conditions used
in the described vinylidene to η2-alkyne conversions.
Geometry optimization and vibrational analysis on
the C2H2 unit with the [Ru(η5-C9H7)(PH3)2]+ moiety
were performed. The optimized structures and main
geometric parameters are shown in Figure 1, while their
relative energies are summarized in Figure 2. Minimum
energies for complexes A and E and three transition
states B, C, and D were found. The indenyl ligands were
located in a trans orientation with respect to the η2-
alkyne or vinylidene groups, in accord with the preferred
conformation found in our previous reported theoretical
studies.11a The X-ray structures of the vinylidene inde-
nyl-ruthenium(II) complexes [Ru{dCdC(R1)R2}(η5-
C9H7)(PPh3)2]+ (R1 ) Me, R2 ) 1-cyclohexenyl, Me; R1
) H, R2 ) Ph) are known.11a,d,j The calculated Ru-CR
(1.844 Å) and the CR-Câ (1.308 Å) distances in E are
very close to those experimentally determined (average
values: 1.834(5) and 1.290(6) Å, respectively). The
Ru-P (2.375 Å) and Ru-C* (2.007 Å) (C* ) centroid of
the five-membered ring of the indenyl group) bond
lengths in E are also in agreement with the observed
values (average values: 2.364(3) and 1.97(1) Å, respec-
tively).
The η2-HCtCH complexes A and B are rotational
isomers with the alkyne group either perpendicular to
the molecular plane characteristic of the Cs symmetry
or in the same plane, respectively. Analogously, the
vinylidene complexes D and E are rotational isomers
(by rotation around the ruthenium-CR bond) in which
the vinylidene group is also contained or perpendicular
to the molecular plane, respectively. Finally complex C
is the transition state associated with the transforma-
tion of A to E.
As shown in Figure 2 rotamers A and E, in which
the alkyne and vinylidene groups are located perpen-
dicular to the molecular plane, are more stable than
rotamers B and D (4.3 and 5.8 kcal/mol, respectively).
This is in accord with previous molecular orbital calcu-
lations23 which showed for these orientations the most
efficient π-back-bonding from the metal to the π-alkyne
or vinylidene ligand. Therefore, the less stable rotational
isomers B and D, generated from the rotation of the η2-
alkyne and the vinylidene groups, may be considered
as transition states in the isomerization process.
Although the calculated energy difference between D
and E is 5.8 kcal/mol, as shown in Figure 2, this value
2
as a virtual triplet at δ 89.41 ppm (2J CP ) J CP′ ) 24.9
Hz) due to the coupling with the two unequivalent
phosphorus atoms, as well as the expected Câ and Ct
CH singlet resonances (δ 113.65 (Câ), 90.48 (tC), 71.20
(tCH) ppm). As expected, the treatment of a diethyl
ether solution of complex 10 with HBF4‚Et2O at -20
°C leads to the formation of the monosubstituted vi-
nylidene derivative 11 (79% yield). Analytical and
spectroscopic data are fully consistent with the proposed
structure (see Experimental Section).
The demetalation of complex 11 by reaction with
acetonitrile at 60 °C proceeds smoothly and gives,
besides the nitrile complex 2a , the diyne 12, which was
isolated after column chromatography as a colorless oil
in 70% yield. Spectroscopic data of this unprecedented
alkyne supports this formulation (see Experimental
Section). The most significant spectroscopic features are
(a) (1H NMR) two unequivalent tCH proton resonances
at δ 2.22 and 2.50 ppm and (b) (13C{1H} NMR) acety-
lenic carbon resonances at δ 69.88 (tC), 72.55 (tC),
87.00 (tCH), and 89.29 (tCH) ppm.
Th eor et ica l Ca lcu la t ion s. The 1-alkyne to vi-
nylidene tautomerization in the coordination sphere of
a transition metal is at present well-documented by
theoretical studies which show that the process is
energetically favorable.6 This transformation takes place
after the coordination of the terminal alkyne and may
proceed via two mechanisms: (a) the initial formation
of an intermediate hydrido-alkynyl species, through the
oxidative addition of the coordinated alkyne, followed
by a hydrogen shift to the â carbon atom of the alkynyl
group to afford the vinylidene complex (Chart 1; path
B), and (b) a direct 1,2-hydrogen shift from the R to â
carbon in the η2-coordinated terminal alkyne (Chart 1;
path A). The former mechanism has been experimen-
tally supported by the identification of hydrido-alkynyl
species in a series of Co, Rh, Ir,20 and Ru5 complexes.
Recent ab initio calculations and kinetic studies have
shown that these transformations proceed either by a
bimolecular hydrogen shift (i.e., [RhCl(PH3)2(H)(Ct
CH)])6c or by an intramolecular 1,3-hydrogen shift (i.e.,
[Co(H)(CtCH)(P(CH2CH2PPh2)3)].20a The 1,2-hydrogen
shift mechanism seems to be more favorable for d6 metal
complexes such as [Mn(η5-C5H5)(CO)2(η2-C2H2)]6a and
[RuCl2(PH3)2(η2-C2H2)],6b as it was found by extended
Hu¨ckel or ab initio calculations, respectively.21
Since these studies are relevant for the knowledge of
energy barriers, it seemed therefore of interest to carry
out theoretical simulations on the isomerization pro-
cesses described in this paper. In accord with Wakat-
(21) In the experimental studies on the mechanism of the isomer-
ization of [Ru(η5-C5Me5)(η2-HCtCH)(dippe)]+ to the vinylidene complex
[Ru(η5-C5Me5)(dCdCH2)(dippe)]+ (dippe ) 1,2-bis(diisopropylphosphi-
no)ethane) C. Puerta and co-workers have also isolated a metastable
hydrido-alkynyl intermediate (see ref 5). However, since this reaction
is inhibited in solution by strong acids, the mechanism seems to be
dissociative in contrast to the usual 1,3-[H] shift, indicating that the
isomerization proceeds in a nonconcerted fashion.
(22) We have explored the alternative mechanism (path B; Chart
1) with a single calculation of the optimized structure energy of the
corresponding hydrido-alkynyl species, and we have found an energy
comparable to the transition state C. This fact allows us to predict
that the energy barrier needed for this mechanism should be higher
than that of the [1, 2]-H shift process and could explain why this
intermediate was not detected.
(20) [Co]: (a) Bianchini, C.; Peruzzini, M.; Vacca A.; Zanobini, F.
Organometallics 1991, 10, 3697. [Rh]: (b) Wolf, J .; Werner, H.; Sehadli,
O.; Ziegler, M. L. Angew. Chem., Int. Ed. Engl. 1983, 22, 414. (c)
Werner, H.; Garc´ıa Alonso, F. J .; Otto, H.; Wolf, J . Z. Naturforsch.
1988, 43b, 722. (d) Werner, H.; Brekau, U. Z. Naturforsch. 1989, 44b,
1438. (e) Rappert, T.; Nurnberg, O.; Mahr, N.; Wolf, J .; Werner, H.
Organometallics 1992, 11, 4156. (f) Werner, H.; Baum, M.; Schneider,
D.; Windmuller, B. Organometallics 1994, 13, 1089. (g) Werner, H.;
Rappert, T.; Baum, M.; Stark, A. J . Organomet. Chem. 1993, 459, 319.
[Ir]: (h) Hoehn, A.; Otto, H.; Dziallas, M.; Werner, H. Angew. Chem.,
Int. Ed. Engl. 1985, 24, 406. (i) Hoehn, A.; Otto, H.; Dziallas, M.;
Werner, H. J . Chem. Soc., Chem. Commun. 1987, 852. (j) Hoehn, A.;
Werner, H. J . Organomet. Chem. 1990, 382, 255. (k) Werner, H.;
Hoehn, A.; Schulz, M. J . Chem. Soc., Dalton Trans. 1991, 777.
(23) (a) Kitaura, K.; Sakaki, S.; Morokuma, K. Inorg. Chem. 1981,
20, 2292. (b) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.

2828 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
F igu r e 1. Optimized ab initio (B3LYP) structures (Å, deg) of reactants, products, and transition states for the formation
of [Ru(η5-C9H7)(dCdCH2)(PH3)2]+ from [Ru(η5-C9H7)(PH3)2]+ and C2H2.
should be less in the actual complexes since a maximum
steric repulsion between the vinylidene substituents and
the triphenylphosphine ligands should be expected for
E. In fact, the X-ray structures of [Ru{dCdC(R1)R2}-
(η5-C9H7)(PPh3)2]+ (R1 ) Me, R2 ) 1-cyclohexenyl, Me;
R1 ) H, R2 ) Ph)11a,d,j show orientations of the vi-
nylidene group that deviate more than 18° away from
the preferred perpendicular orientation. Similarly, an
important steric repulsion can be predicted for the
rotamer η2-C2H2 complex A, which therefore should lead
to a less stable energy level than that shown in Figure
2. Providing the existence of these steric repulsions and
the small differences in the energy values of the
rotational isomers (which may be easily overcome in
solution), it can be assumed that B and D are the acting
species in the 1,2-[H] shift mechanism.
structure and the energy (18.9 kcal/mol less stable than
B) are shown in Figures 1 and 2, respectively. The
distances Ru-CR (2.225 Å), CR-Câ (1.220 Å), Ru-H
(1.958 Å), and CR-H (1.112 Å) and the angles Ru-CR-
Câ (154.5°) and Câ-CR-H (143.9°) are very similar to
those found by Wakatsuki6b in the analogous intermedi-
ate complex [RuCl2(η2-H-C2H)(PH3)2] (distances: Ru-
CR (2.087 Å), CR-Câ (1.225 Å), Ru-H (1.763 Å), and
CR-H (1.130 Å); angles: Ru-CR-Câ (154.9°) and Câ-
CR-H (147.5°)). Nevertheless, this complex in the
Wakatsuki’s model is a relative minimum state with
respect to two close transition states, while in our case
the structure C is a transition state itself.
The following interesting features are relevant in the
η1-vinylidene-η2-alkyne tautomerization reaction path,
back and forth (Figure 2): (i) The vinylidene species are
thermodynamically more stable than the η2-alkyne
complexes (11.0 kcal/mol), (ii) the calculated activation
In this migration only the transition state C has been
found along the reaction path. The calculated optimized

Functionalized Terminal Alkynes
Organometallics, Vol. 18, No. 15, 1999 2829
F igu r e 2. Energy diagram (kcal/mol) for the formation of [Ru(η5-C9H7)(dCdCH2)(PH3)2]+ from [Ru(η5-C9H7)(PH3)2]+ and
C2H2.
energy to reach C from B is 18.9 kcal/mol, and (iii) the
reverse process from D requires 29.9 kcal/mol. There-
fore, since the energy barrier to reach the η2-alkyne
species from the stable vinylidene complex can be
overcome under the experimental reaction conditions,
the transformation to the kinetically labile π-alkyne
complexes may be readily achieved.
afford stereoselectively terminal (E)-1,3-enynes HCtC-
CHdCRR′. They are formed in good yields through the
initial tautomerization at the ruthenium center of the
η1-vinylidene group to the η2-terminal alkyne and
subsequent elimination from the ruthenium center
(Scheme 4) by exchange with CH3CN. These syntheses
can be regarded as a formal metal-mediated coupling
of 2-propyn-1-ol with aldehydes or ketones without
precedent in the literature.
Con clu d in g Rem a r k s
As part of our continuing interest in studying the
reactivity of allenylidene ruthenium(II) complexes, we
have recently reported the synthesis of a wide series of
functionalized indenyl-ruthenium(II) vinylidene de-
rivatives.11,14 The synthetic methodology is based on the
nucleophilic additions at the Cγ of the allenylidene chain
in the cationic complexes [Ru(dCdCdCRR′)(η5-C9H7)-
L2]+ to give the corresponding neutral σ-alkynyl deriva-
tives [Ru{CtCC(Nu)RR′}(η5-C9H7)L2], which can be
easily converted into the corresponding vinylidene
complexes [Ru{dCdC(H)C(Nu)RR′}(η5-C9H7)L2]+ after
typical proton additions. In addition, we have reported
the synthesis of a large series of alkenyl-vinylidene
complexes [Ru{dCdC(H)C(R)dCRR′}(η5-C9H7)(PPh3)2]+,
which can be obtained in high yields from the reaction
of alkynyl-phosphonio complexes with ketones or al-
dehydes, via Wittig type processes, and subsequent
protonation of the corresponding σ-enynyl [Ru{CtCC-
(R)dCRR′}(η5-C9H7)(PPh3)2] intermediates. This paper
illustrates for the first time the utility of these processes
in stoichiometric organic synthesis. Thus, it is shown
that the readily accessible indenyl-ruthenium(II) alk-
enyl-vinylidene complexes are able to undergo demeta-
lation reactions by heating in CH3CN under reflux to
HCtCCH2OH + RCOR′ [Ru]8 (E)-HCtCCHdCRR′
Since these processes take place under mild reaction
conditions and have proven to be general for other
vinylidene complexes (Schemes 1 and 3-5), they provide
a useful synthetic methodology of functionalized alkynes
and diynes. Furthermore, it should be mentioned that
the metal auxiliary is recovered as the acetonitrile
complex [Ru(NtCMe)(η5-C9H7)(PPh3)2]+ (2a ), which can
be used as starting material for further reactions, taking
into account the well-known lability of the nitrile
ligands.
In this paper we also describe a theoretical simulation
of the η1-vinylidene to η2-alkyne tautomerization in
these indenyl-ruthenium(II) complexes, which is shown
to proceed through the classical 1,2-[H] shift mecha-
nism. Although the η2-alkyne to η1-vinylidene tautomer-
ization is well-known to occur for several transition
metal complexes1 and has been calculated to be ther-
modynamically favorable,6 the reverse transformation
has hardly been described experimentally.9,10 It is
apparent from the processes described above that the
energy barrier associated in the conversion of η1-

2830 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
vacuum-dried. 2a : yield 0.723 g (78%); IR (KBr) ν ) 835 cm-
1
vinylidene to η2-alkyne can be readily overcome in the
reaction conditions (refluxing acetonitrile). Ab initio
molecular orbital calculations are consistent with the
experimental results and show that the energy barrier
is 29.9 kcal/mol, allowing the formation of the kinetically
labile π-alkyne complex under relatively mild reaction
conditions.
In summary, this work reports theoretical and ex-
perimental studies on the tautomerization of indenyl-
ruthenium(II) vinylidene complexes in the correspond-
ing η2-alkyne derivatives which readily undergo exchange
of the coordinated alkyne by nitriles. It is shown that
this process discloses a new entry for the synthesis of
functionalized terminal alkynes, which are obtained in
good yields and stereoselectively. This synthetic meth-
odology also allows the quantitative recovery of the
metal fragment, which may be used for further trans-
formations. Studies directed to the extension of this
methodology are currently in progress.
(PF6-), 2270 cm-1 (CtN); Λ (acetone, 20 °C) ) 104 Ω-1 cm2
1
mol-1
;
31P{1H} (CDCl3, 121.5 MHz) δ ) 48.16 (s); H (CDCl3,
300 MHz) δ ) 2.20 (s, 3H, CH3), 4.49 (d, 2H, J HH ) 1.7 Hz,
H-1,3), 4.73 (t, 1H, J HH ) 1.7 Hz, H-2), 6.89-7.37 (m, 34H,
Ph, H-4,7 and H-5,6); 13C{1H} (CDCl3, 75.4 MHz) δ ) 4.14 (s,
CH3), 67.90 (s, C-1,3), 93.64 (s, C-2), 109.60 (s, C-3a,7a), 124.63
and 129.43 (s, C-4,7 and C-5,6), 128.08-135.01 (m, Ph and
CtN). RuC47H40F6P3N (926.8): calcd C 60.91, H 4.35, N 1.51;
found C 60.40, H 4.49, N 1.48. 2b: yield 0.705 g (75%); IR (KBr)
ν ) 840 cm-1 (PF6-), 2271 cm-1 (CtN); Λ (acetone, 20 °C) )
108 Ω-1 cm2 mol-1 31P{1H} (CDCl3, 121.5 MHz) δ ) 47.93 (s);
;
1H (CDCl3, 300 MHz) δ ) 0.91 (t, 3H, J HH ) 7.6 Hz, CH3),
2.64 (d, 2H, J HH ) 7.6 Hz, CH2), 4.51 (bs, 2H, H-1,3), 4.75 (bs,
1H, H-2), 6.90-7.45 (m, 34H, Ph, H-4,7 and H-5,6); 13C{1H}
(CDCl3, 75.4 MHz) δ ) 9.55 (s, CH3), 13.09 (s, CH2), 67.95 (s,
C-1,3), 93.52 (s, C-2), 109.55 (s, C-3a,7a), 124.55 and 129.32
(s, C-4,7 and C-5,6), 127.96-134.91 (m, Ph and CtN).
RuC48H42F6P3N (940.8): calcd C 61.28, H 4.50, N 1.49; found
C 61.54, H 4.66, N 1.57. 2c: yield 0.840 g (85%); IR (KBr) ν )
834 cm-1 (PF6-), 2226 cm-1 (CtN); Λ (acetone, 20 °C) ) 112
1
Ω-1 cm2 mol-1
;
31P{1H} (CDCl3, 121.5 MHz) δ ) 47.83 (s); H
(CDCl3, 300 MHz) δ ) 4.59 (d, 2H, J HH ) 2.1 Hz, H-1,3), 4.83
(t, 1H, J HH ) 2.1 Hz, H-2), 6.86-7.61 (m, 39H, Ph, H-4,7 and
H-5,6); 13C{1H} (CDCl3, 75.4 MHz) δ ) 68.75 (s, C-1,3), 93.80
(s, C-2), 109.54 (s, C-3a,7a), 110.88 (s, CtN), 124.28 (s, C-4,7
Exp er im en ta l Section
All reactions were carried out under an atmosphere of dry
nitrogen using vacuum-line and standard Schlenk tube tech-
niques. All reagents were obtained from commercial suppliers
and used without further purification. Solvents were dried by
standard methods and distilled under nitrogen before use. The
compounds [RuCl(η5-C9H7)(PPh3)2],24 [Ru{dCdC(H)R}(η5-
C9H7)(PPh3)2][X] (R ) Ph,11a 4-NO2-C6H4,14 -CHdCH-(η5-
C5H4)Fe(η5-C5H5)14b), [Ru(CtCCHdCHR)(η5-C9H7)(PPh3)2] (R
) 4-NO2-C6H4,14 (η5-C5H4)Fe(η5-C5H5)14b), [Ru{CtCCH2(PPh3)}-
(η5-C9H7)(PPh3)2][PF6],14 [Ru{dCdCdCC13H20}(η5-C9H7)(PPh3)2]-
[PF6]19 and (η5-C5H5)Fe(η5-C5H4-CtCH)25 were prepared by
following the methods reported in the literature.
Infrared spectra were recorded on a Perkin-Elmer 1720-XFT
spectrometer. The conductivities were measured at room
temperature, in ca. 10-3 mol dm-3 acetone solutions, with a
J enway PCM3 conductimeter. The C, H, and N analyses were
carried out with a Perkin-Elmer 240-B microanalyzer. High-
resolution mass spectra were recorded using a MAT-95
spectrometer. NMR spectra were recorded on a Bruker AC300
instrument at 300 MHz (1H), 121.5 MHz (31P), or 75.4 MHz
(13C) using SiMe4 or 85% H3PO4 as standards. DEPT experi-
ments have been carried out for all the compounds. Abbrevia-
tions used: s, singlet; bs, broad singlet; d, doublet; t, triplet;
vt, virtual triplet; m, multiplet.
or C-5,6), 128.13-134.56 (m, Ph and C-4,7 or C-5,6). RuC52H42
-
F6P3N (988.8): calcd C 63.16, H 4.28, N 1.41; found C 63.02,
H 4.32, N 1.44.
Syn t h esis of [R u {dCdC(H)F c}(η5-C9H7)(P P h 3)2][P F 6]
(F c ) (η5-C5H4)F e(η5-C5H5)) (3). A mixture of [RuCl(η5-C9H7)-
(PPh3)2] (0.776 g, 1 mmol), NaPF6 (0.336 g, 2 mmol), and
ethynylferrocene (0.273 g, 1.3 mmol) in MeOH (50 mL) was
heated under reflux for 1 h. The solvent was then removed
under vacuum, and the solid residue was extracted with
dichloromethane (ca. 25 mL) and filtered. The resulting
solution was then concentrated (ca. 5 mL), and diethyl ether
(100 mL) was added, yielding a brown solid, which was washed
with diethyl ether (3 × 20 mL) and vacuum-dried: yield 0.898
g (82%); IR (KBr) ν ) 833 cm-1 (PF6-); Λ (acetone, 20 °C) )
106 Ω-1 cm2 mol-1 31P{1H} (CDCl3, 121.5 MHz) δ ) 41.27 (s);
;
1H (CDCl3, 300 MHz) δ ) 4.44 (m, 10H, C5H5, C5H4 and Rud
CdCH), 5.47 (m, 3H, H-1,3 and H-2), 6.24 (m, 2H, H-4,7 or
H-5,6), 6.89-7.68 (m, 32H, Ph and H-4,7 or H-5,6); 13C{1H}
(CDCl3, 75.4 MHz) δ ) 67.58 and 69.92 (s, CH of C5H4), 71.58
(s, C5H5), 73.42 (s, C of C5H4), 83.81 (s, C-1,3), 98.63 (s, C-2),
113.59 (s, Câ), 114.73 (s, C-3a,7a), 122.97 and 130.06 (s, C-4,7
2
and C-5,6), 126.93-142.43 (m, Ph), 352.30 (t, J CP ) 13.4 Hz,
RudCR). FeRuC57H47F6P3 (1095.8): calcd C 62.47, H 4.32;
found C 62.21, H 4.18.
Syn th esis of [Ru (CtCCHdCR1R2)(η5-C9H7)(P P h 3)2] (R1
) R2 ) P h (6a ); R1 ) 4-OMe-C6H4, R2 ) H [(Z)-6b]). LiBun
(1.6 M in hexane; 0.625 mL, 1 mmol) was added at -20 °C to
a solution of complex 5 (1.186 g, 1 mmol) in THF (30 mL).
The reaction mixture was stirred for 10 min., and benzophe-
none (0.546 g, 3 mmol) or p-anisaldehyde (0.365 mL, 3 mmol)
was then added. Upon warming to room temperature, the
solution was stirred for an additional 30 min. The solvent was
then removed under vacuum and the orange solid residue
dissolved in dichloromethane (ca. 5 mL) and transferred to an
Al2O3 (neutral; activity grade I) chromatography column.
Elution with a mixture hexane/diethyl ether (3:1) gave an
orange band, which was collected and evaporated to give the
desired compounds. Complex 6b was obtained as the Z
stereoisomer only. 6a : yield 0.925 g (98%); IR (KBr) ν ) 2049
cm-1 (CtC); 31P{1H} (C6D6, 121.5 MHz) δ ) 51.33 (s); 1H (C6D6,
300 MHz) δ ) 4.68 (d, 2H, J HH ) 2.1 Hz, H-1,3), 5.59 (t, 1H,
J HH ) 2.1 Hz, H-2), 6.25 and 6.68 (m, 2H each one, H-4,7 and
H-5,6), 6.73 (s, 1H, dCH), 6.86-8.21 (m, 40H, Ph); 13C{1H}
(C6D6, 75.4 MHz) δ ) 75.51(s, C-1,3), 96.28 (s, C-2), 110.26 (s,
C-3a,7a), 115.81 (s, dCH), 116.36 (s, Câ), 123.79 and 126.46
Syn th esis of [Ru (NtCR)(η5-C9H7)(P P h 3)2][P F 6] (R )
Me (2a ), Et (2b), P h (2c)). A solution of complex 1 (0.987 g,
1 mmol) in the corresponding nitrile (50 mL) (for 2a ,b), or in
methanol (50 mL) and in the presence of PhCtN (1.010 mL,
10 mmol) (for 2c), was heated under reflux for 90 min. The
solution was then evaporated to dryness and the resulting
yellow solid washed with diethyl ether (2 × 20 mL) and
(24) Oro, L. A.; Ciriano, M. A.; Campo, M.; Foces-Foces, C.; Cano,
F. H. J . Organomet. Chem. 1985, 289, 117.
(25) Behrens, U.; Brussaard, H.; Hagenau, U.; Heck, J .; Hendrickx,
E.; Ko¨rnich, J .; van der Linden, J . G. M.; Persoons, A.; Spek, A. L.;
Veldman, N.; Voss, B.; Wong, H. Chem. Eur. J . 1996, 2, 98.

Functionalized Terminal Alkynes
Organometallics, Vol. 18, No. 15, 1999 2831
(s, C-4,7 and C-5,6), 123.96 (t, 2J CP ) 24.2 Hz, Ru-CR), 126.93-
145.04 (m, Ph and dC). RuC61H48P2 (944.0): calcd C 77.60, H
5.12; found C 77.01, H 5.20. 6b: yield 0.556 g (62%); IR (KBr)
ν ) 2045 cm-1 (CtC); 31P{1H} (C6D6, 121.5 MHz) δ ) 51.88
7a), 122.60-133.54 (m, Ph, C-4,7, C-5,6, dCH and CH of
4-NO2-C6H4), 143.58 and 145.81 (s, C of 4-NO2-C6H4), 355.70
2
(t, J CP ) 16.2 Hz, RudCR).
Syn th esis of HCtCCHdCR1R2 (R1 ) R2 ) P h (8a ); R1
)
1
H, R2 ) 4-OMe-C6H 4 (8b), 4-NO2-C6H 4 (8c), F c (8d )). A
solution of the corresponding vinylidene complex 7a -d (1
mmol) in acetonitrile (50 mL) was heated under reflux for 90
min. The solution was then evaporated to dryness, and the
resulting solid residue was extracted with diethyl ether (ca.
150 mL) (a yellow solid containing mainly the complex [Ru-
(NtCMe)(η5-C9H7)(PPh3)2][BF4] remains insoluble). The ex-
tract was evaporated to dryness and the crude product was
purified by column chromatography on silica gel with hexane
as eluent. Enynes 8b-d were obtained as the E stereoisomer
only. Quantities used: 7a , 1.031 g (1 mmol); 7b, 1.074 g (1
mmol); 7c, 1.000 g (1 mmol); 7d , 1.063 g (1 mmol). 8a : yield
0.157 g (77%) as a colorless oil; IR (Nujol) ν ) 2092 cm-1 (Ct
C); 1H (CDCl3, 300 MHz) δ ) 3.02 (d, 1H, J HH ) 2.5 Hz, t
CH), 6.03 (d, 1H, J HH ) 2.5 Hz, dCH), 7.27-7.48 (m, 10H,
Ph); 13C{1H} (CDCl3, 75.4 MHz) δ ) 81.43 (s, tCH), 82.39 (s,
tC), 105.93 (s, dCH), 127.92, 127.94, 128.27, 128.50 and
129.88 (s, CH of Ph), 138.78 and 141.04 (s, C of Ph), 154.44 (s,
dC); HRMS m/z calcd for C16H12 (found) M+) 204.094289
(204.093900). 8b: yield 0.094 g (60%) as a colorless oil; IR
(s); H (C6D6, 300 MHz) δ ) 3.30 (s, 3H, OCH3), 4.75 (d, 2H,
J HH ) 1.9 Hz, H-1,3), 5.72 (t, 1H, J HH ) 1.9 Hz, H-2), 6.34 and
6.69 (m, 2H each one, H-4,7 and H-5,6), 6.77 and 7.33 (d, 2H
each one, J HH ) 8.7 Hz, 4-OMe-C6H4), 6.82 (d, 1H, J HH ) 13.0
Hz, dCH), 6.92-7.49 (m, 31H, Ph and dCH); 13C{1H} (C6D6,
75.4 MHz) δ ) 55.42 (s, OCH3), 75.71 (s, C-1,3), 96.19 (s, C-2),
110.22 (s, C-3a,7a), 114.55 and 132.51 (s, dCH), 115.02 and
127.20 (s, CH of 4-OMe-C6H4), 115.77 (s, Câ), 116.90 (t, 2J CP
)
25.0 Hz, Ru-CR), 123.83 and 126.63 (s, C-4,7 and C-5,6),
128.10-139.75 (m, Ph), 133.32 and 159.53 (s, C of 4-OMe-
C6H4). RuC56H46P2O (897.9): calcd C 74.90, H 5.16; found C
73.98, H 5.22.
Syn th esis of [Ru{dCdC(H)CHdCR1R2}(η5-C9H7)(P P h 3)2]-
[BF 4] (R1 ) R2 ) P h (7a ); R1 ) 4-OMe-C6H4, R2 ) H [(Z)-
7b]; R1 ) H, R2 ) 4-NO2-C6H4 [(E, Z)-7c]). A solution of
HBF4‚Et2O (1.9 mL, 1.5 mmol) in diethyl ether (10 mL) was
added dropwise, at -20 °C, to a solution of the corresponding
σ-enynyl complex 6a -c (1 mmol) in THF (30 mL). The reaction
mixture was gradually warmed to room temperature and then
concentrated (ca. 5 mL). Addition of diethyl ether (100 mL)
gave a brown solid, which was washed with diethyl ether (3
× 20 mL) and vacuum-dried. Quantities used: 6a , 0.944 g (1
mmol); 6b, 0.898 g (1 mmol); 6c, 0.913 g (1 mmol). 7a : yield
1.011 g (98%); IR (KBr) ν ) 1059 cm-1 (BF4-); Λ (acetone, 20
1
(Nujol) ν ) 2101 cm-1 (CtC); H (CDCl3, 300 MHz) δ ) 3.03
(d, 1H, J HH ) 2.1 Hz, tCH), 3.83 (s, 3H, OCH3), 6.00 (dd, 1H,
J HH ) 16.3 Hz, J HH ) 2.1 Hz, dCH), 7.00 (d, 1H, J HH ) 16.3
Hz, dCH), 6.87 and 7.34 (d, 2H each one, J HH ) 8.7 Hz,
4-OMe-C6H4); 13C{1H} (CDCl3, 75.4 MHz) δ ) 55.24 (s, OCH3),
78.42 (s, tCH), 83.25 (s, tC), 104.46 and 142.67 (s, dCH),
114.07 and 127.67 (s, CH of 4-OMe-C6H4), 128.64 and 160.21
(s, C of 4-OMe-C6H4); HRMS m/z calcd for C11H10O (found)
M+) 158.073165 (158.073804). 8c: yield 0.119 g (69%) as a
yellow oil; IR (Nujol) ν ) 2106 cm-1 (CtC); 1H (CDCl3, 300
MHz) δ ) 3.22 (d, 1H, J HH ) 2.4 Hz, tCH), 6.31 (dd, 1H, J HH
) 16.3 Hz, J HH ) 2.4 Hz, dCH), 7.09 (d, 1H, J HH ) 16.3 Hz,
dCH), 7.54 and 8.22 (d, 2H each one, J HH ) 7.8 Hz, 4-NO2-
C6H4); 13C{1H} (CDCl3, 75.4 MHz) δ ) 81.86 (s, tCH), 89.92
(s, tC), 111.82 and 140.46 (s, dCH), 124.04 and 168.47 (s, C
of 4-NO2-C6H4), 124.10 and 126.82 (s, CH of 4-NO2-C6H4);
°C) ) 127 Ω-1 cm2 mol-1
;
31P{1H} (CDCl3, 121.5 MHz) δ )
1
39.34 (s); H (CDCl3, 300 MHz) δ ) 5.22 (dt, 1H, J HH ) 10.6
4
Hz, J HP ) 1.7 Hz, RudCdCH), 5.50 (d, 2H, J HH ) 2.4 Hz,
H-1,3), 5.98 (m, 3H, H-2 and H-4,7 or H-5,6), 6.51 (d, 1H, J HH
) 10.6 Hz, dCH), 6.79-7.52 (m, 42H, Ph and H-4,7 or H-5,6);
13C{1H} (CDCl3, 75.4 MHz) δ ) 83.92 (s, C-1,3), 98.62 (s, C-2),
109.37 and 115.11 (s, Câ and dCH), 115.22 (s, C-3a,7a), 122.94
(s, C-4,7 or C-5,6), 127.12-141.30 (m, Ph, dC and C-4,7 or
2
C-5,6), 358.48 (t, J CP ) 16.8 Hz, RudCR). RuC61H49F4P2B
(1031.8): calcd C 71.00, H 4.78; found C 70.82, H 4.70. 7b:
yield 0.945 g (88%) as pure (Z) product; IR (KBr) ν ) 1060
cm-1 (BF4-); Λ (acetone, 20 °C) ) 117 Ω-1 cm2 mol-1
;
31P{1H}
HRMS m/z calcd for
C
10H7O2N (found) M+) 173.047678
1
(CDCl3, 121.5 MHz) δ ) 39.86 (s); H (CDCl3, 300 MHz) δ )
3.78 (s, 3H, OCH3), 5.37 (d, 1H, J HH ) 9.1 Hz, RudCdCH),
5.50 (d, 2H, J HH ) 2.6 Hz, H-1,3), 5.82 (t, 1H, J HH ) 2.6 Hz,
H-2), 5.93-6.06 (m, 4H, dCH and H-4,7 or H-5,6), 6.75-7.49
(m, 36H, Ph, 4-OMe-C6H4 and H-4,7 or H-5,6); 13C{1H} (CDCl3,
75.4 MHz) δ ) 55.30 (s, OCH3), 84.18 (s, C-1,3), 98.88 (s, C-2),
108.50 and 125.01 (s, dCH), 113.86, 123.00, 127.28 and 130.27
(s, C-4,7, C-5,6 and CH of 4-OMe-C6H4), 115.23 (s, C-3a,7a),
118.13 (s, Câ), 128.60-133.53 (m, Ph), 129.61 and 158.96 (s,
(173.048423). 8d : yield 0.170 g (72%) as a red oil; IR (Nujol) ν
) 2100 cm-1 (CtC); 1H (CDCl3, 300 MHz) δ ) 2.80 (d, 1H,
J HH ) 2.1 Hz, tCH), 3.86 (s, 5H, C5H5), 3.97 and 4.03 (m, 2H
each one, C5H4), 5.70 (dd, 1H, J HH ) 16.1 Hz, J HH ) 2.1 Hz,
dCH), 6.78 (d, 1H, J HH ) 16.1 Hz, dCH); 13C{1H} (CDCl3, 75.4
MHz) δ ) 67.31 and 69.93 (s, CH of C5H4), 69.67 (s, C5H5),
78.35 (s, C of C5H4), 81.49 (s, tC), 83.94 (s, tCH), 104.25 and
142.75 (s, dCH); HRMS m/z calcd for FeC14H12 (found) M+)
236.028839 (236.028878).
2
C of 4-OMe-C6H4), 360.22 (t, J CP ) 16.4 Hz, RudCR).
Syn th esis of [Ru {CtCC(CtCH)C13H20}(η5-C9H7)(P P h 3)2]
(10). A large excess (ca. 1:10) of NaCtCH (suspension in
xylene) was added at -20 °C to a solution of the allenylidene
complex 9 (1.098 g, 1 mmol) in THF (50 mL). Upon warming
to room temperature, the solvent was removed in vacuo, and
the resulting orange solid residue dissolved in dichloromethane
(ca. 5 mL) and transferred to an Al2O3 (neutral; activity grade
I) chromatography column. Elution with a mixture of hexane/
diethyl ether (4:1) gave an orange band, which was collected
and evaporated to give complex 10: yield 0.597 g (61%); IR
(KBr) ν ) 2082 and 2275 cm-1 (CtC); 31P{1H} (C6D6, 121.5
RuC56H47F4P2BO (1074.5): calcd C 68.23, H 4.80; found C
68.35, H 4.72. 7c: yield 0.730 g (73%) as a 2:1 (E/Z) mixture;
IR (KBr) ν ) 1062 cm-1 (BF4-); Λ (acetone, 20 °C) ) 116 Ω-1
cm2 mol-1. RuC55H44F4O2P2BN (1000.7): calcd C 66.00, H 4.43,
N 1.40; found C 65.41, H 4.22, N 1.52. (E isomer): 31P{1H}
1
(CDCl3, 121.5 MHz) δ ) 38.47 (s); H (CDCl3, 300 MHz) δ )
5.58 (m, 3H, H-1,3 and H-2), 5.91 (m, 2H, H-4,7 or H-5,6), 6.25
(d, 1H, J HH ) 10.2 Hz, RudCdCH), 6.81-7.50 (m, 34H, Ph,
dCH and H-4,7 or H-5,6), 7.05 and 8.03 (d, 2H each one, J HH
) 8.8 Hz, 4-NO2-C6H4); 13C{1H} (CDCl3, 75.4 MHz) δ ) 83.85
(s, C-1,3), 99.33 (s, C-2), 115.89 (s, C-3a,7a), 117.71 and 117.84
(s, dCH and Câ), 122.60-133.54 (m, Ph, C-4,7, C-5,6, dCH
and CH of 4-NO2-C6H4), 143.70 and 145.81 (s, C of 4-NO2-
C6H4), 356.50 (t, 2J CP ) 16.5 Hz, RudCR). (Z isomer): 31P{1H}
2
2
MHz) δ ) 50.52 (d, J PP ) 31.0 Hz, PPh3), 52.98 (d, J PP
)
1
31.0 Hz, PPh3); H (C6D6, 300 MHz) δ ) 1.46-1.80 (m, 14H,
CH2), 2.02 (s, 1H, tCH), 2.26-2.52 (m, 3H, CH2 and CH), 2.68
(m, 1H, CH), 4.73 and 4.77 (m, 1H each one, H-1 and H-3),
5.68 (m, 1H, H-2), 5.82(dd, 1H, J HH ) 10 Hz, J HH ) 6.0 Hz,
dCHCH), 6.02 (d, 1H, J HH ) 10 Hz, dCH), 6.32 and 6.66 (m,
2H each one, H-4, H-5, H-6 and H-7), 6.29-7.53 (m, 30 H, Ph);
13C{1H} (C6D6, 75.4 MHz) δ ) 17.86, 22.83, 23.02, 24.92, 26.40,
26.97, 36.86 and 37.54 (s, CH2), 38.49 and 39.49 (s, C), 42.68
and 42.91 (s, CH), 71.20 (s, tCH), 73.75 (d, 2J CP ) 7.6 Hz, C-1
1
(CDCl3, 121.5 MHz) δ ) 38.77 (s); H (CDCl3, 300 MHz) δ )
5.58 (m, 3H, H-1,3 and H-2), 5.72 (d, 1H, J HH ) 11.2 Hz, d
CH), 6.10 (m, 3H, dCH and H-4,7 or H-5,6), 6.30 (d, 1H, J HH
) 10.2 Hz, RudCdCH), 6.81-7.50 (m, 34H, Ph, 4-NO2-
C6H2H2 and H-4,7 or H-5,6), 8.15 (d, 2H, J HH ) 8.7 Hz, 4-NO2-
C6H2H2); 13C{1H} (CDCl3, 75.4 MHz) δ ) 83.85 (s, C-1,3), 99.49
(s, C-2), 113.13 and 116.69 (s, dCH and Câ), 115.89 (s, C-3a,-

2832 Organometallics, Vol. 18, No. 15, 1999
Cadierno et al.
2
2
or C-3), 74.56 (d, J CP ) 7.4 Hz, C-1 or C-3), 89.41 (vt, J CP
)
41.43 (s, CH), 69.88 and 72.55 (s, tCH), 87.00 and 89.29 (s,
tC), 124.24 and 138.68 (s, dCHCH and dCH); HRMS m/z
calcd for C18H22 (found) M+) 238.172151 (238.172233).
Com p u ta tion a l Deta ils. Ab initio calculations were car-
ried out with the Gaussian 94 set of programs26 within the
framework of DFT at the B3LYP level.27 LANL2DZ effective
core potentials (quasi relativistic for the metal centers) were
used to replace the 28 innermost electrons of Ru, as well as
the 10 core electrons of P.28 The associated double-ú basis set
of P atoms was augmented by a d function.29 The other atoms
were represented by a 6-31G(d,p) basis set.30 PH3 and indenyl
hydrogen atoms were represented at the STO-3G level.31 In
our calculations we replace the PPh3 ligand and the mono-
subtituted acetylene by PH3 and HCtCH, respectively.
Full geometry optimization and frequency calculations were
performed with Cs symmetry without any further symmetry
constraints. A vibrational analysis was performed for the three
transition states B, C, and D to confirm that they have only
one imaginary frequency, while for A and E no imaginary
frequency was found. The transition-state structures were
relaxed after introducing small perturbations to ensure that
they are actually connected to the corresponding reactants and
the products.
2J CP′ ) 24.9 Hz, Ru-CR), 90.48 (s, tC), 91.15 (s, C-2), 109.25
and 109.98 (s, C-3a and C-7a), 113.65 (s, Câ), 123.15, 123.45,
125.46, 125.87 and 126.42 (s, C-4, C-5, C-6, C-7 and dCHCH
or dCH), 127.18-139.64 (m, Ph), 138.54 (s, dCHCH or dCH).
RuC63H58P2 (978.7): calcd C 77.36, H 5.98; found C 77.32, H
6.33.
Syn th esis of [Ru {dCdC(H)C(CtCH)C13H20}(η5-C9H7)-
(P P h 3)2] [BF 4] (11). A solution of the σ-alkynyl complex 10
(0.979 g, 1 mmol) in diethyl ether (100 mL), at -20 °C, was
treated dropwise by strong stirring with a diluted solution of
HBF4‚Et2O in diethyl ether. Immediately, an insoluble solid
precipitated, but the addition was continued until no further
solid was formed. The solution was then decanted and the
brown solid washed with diethyl ether (3 × 20 mL) and
vacuum-dried: yield 0.842 g (79%); IR (KBr) ν ) 1057 cm-1
(BF4-), 2197 cm-1 (CtC); Λ (acetone, 20 °C) ) 108 Ω-1 cm2
mol-1
;
31P{1H} (CD2Cl2, 121.5 MHz) δ ) 39.25 (d, J PP ) 23.5
2
Hz, PPh3), 40.62 (d, J PP ) 23.5 Hz, PPh3); 1H (CD2Cl2, 300
2
MHz) δ ) 1.38-2.35 (m, 18H, CH2 and CH), 2.54 (s, 1H, t
4
4
CH), 4.29 (vt, 1H, J HP ) J HP′ ) 2.3 Hz, RudCdCH), 5.32-
5.70 (m, 5H, H-1, H-2, H-3, dCHCH and dCH), 6.01 and 6.25
(m, 2H each one, H-4, H-5, H-6 and H-7), 6.64-7.50 (m, 30 H,
Ph); 13C{1H} (CD2Cl2, 75.4 MHz) δ ) 17.35, 22.79, 24.98, 25.92,
26.39, 36.57 and 37.85 (s, CH2), 38.69 and 39.39 (s, C), 42.00
and 43.93 (s, CH), 75.24 (s, tCH), 82.71 (d, 2J CP ) 5.9 Hz, C-1
Ack n ow led gm en t. This work was supported by the
Ministerio de Educacio´n y Cultura of Spain (DGICYT,
Projects PB96-0556 and PB96-0558) and the EU (Hu-
man Capital Mobility program, Project ERBCHRXCT
940501). V.C. thanks the Fundacio´n para la Investiga-
cio´n Cient´ıfica y Te´cnica de Asturias (FICYT) for a
fellowship.
2
or C-3), 84.60 (d, J CP ) 5.7 Hz, C-1 or C-3), 89.78 (s, tC),
98.45 (s, C-2), 113.04 (s, C-3a and C-7a), 119.07 (s, Câ), 122.26,
122.54, 125.14 and 125.25 (s, C-4, C-5, C-6 and C-7), 128.81-
138.23 (m, Ph, dCHCH and dCH), 344.26 (vt, J CP ) J CP′
15.7 Hz, RudCR). RuC63H59F4P2B (1065.9): calcd C 70.98, H
5.58; found C 70.21, H 5.69.
2
2
)
Syn th esis of (HCtC)2CC13H20 (12). A solution of complex
11 (1.066 g, 1 mmol) in acetonitrile (25 mL) was heated at 60
°C for 2 h. The solution was then evaporated to dryness, and
the resulting yellow residue was extracted with diethyl ether
(ca. 150 mL) (a yellow solid containing mainly the complex
[Ru(NtCMe)(η5-C9H7)(PPh3)2][BF4] remains insoluble). The
extract was evaporated to dryness, and the crude product was
purified by column chromatography on silica gel with hexane
as eluent. Evaporation of the solvent gave 12 as a colorless
OM990194V
(26) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
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G. A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.;
Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.; Cioslowski, J .;
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Stewart, J . P.; Head-Gordon, M.; Gonzalez, C.; Pople, J . A. Gaussian
94; Gaussian Inc.: Pittsburgh, PA, 1995.
1
oil: yield 0.166 g (70%); IR (Nujol) ν ) 2113 cm-1 (CtC); H
(27) Becke, A. D. J . Chem. Phys. 1993, 98, 5648.
(CDCl3, 300 MHz) δ ) 1.23-1.71 (m, 13H, CH2), 2.02-2.21
(m, 3H, CH2), 2.22 and 2.50 (s, 1H each one, tCH), 2.36 and
(28) Hay, P. J .; Wadt, W. R. J . Chem. Phys. 1985, 82, 299.
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A.; J onas, V.; Ko¨hler, K.; Stegmann, R.; Veldkamp, A.; Frenking, G.
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51, 2657.
2.61 (m, 1H each one CH), 5.56 (dd, 1H, J HH ) 10.2 Hz, J HH
)
6.2 Hz, dCHCH), 5.74 (d, 1H, J HH ) 10.2 Hz, dCH); 13C{1H}
(CDCl3, 75.4 MHz) δ ) 16.77, 21.83, 22.35, 23.80, 25.04, 26.05,
35.89 and 36.88 (s, CH2), 35.36 and 38.76 (s, C), 40.57 and