Reaction of the ruthenium(II) indenyl complex [Ru(η55-C 9H7){κ3(P,C,C)-PPh2(CH2CH=CH2)}(PPh3)][PF6] with terminal alkynes. Mechanisms of 1-alkyne to η1-vinylidene transformation and kinetic detection of hemilability of the allylphosphine ligand

Article abstract of DOI:10.1021/om040068d

A kinetic investigation of the reaction of terminal alkynes with a ruthenium indenyl complex bearing an hybrid allyphosphine ligand was carried out to yield η¹-vinylidene derivatives. The 18 electron complex of the Ru compounds reacted well through parallel pathways characterized by rate determining bimolecular interaction with the alkyne. It was found that the other pathway that involved intramolecular rate determining dissociation of the allylic double bond formed a transient 16-electron intermediate. The proposed arm-off mechanism regarding the allylphosphine ligand was given an experimental support, since it was found to be independent of the alkyne structure and also of the specific reaction involved.

Full text of DOI:10.1021/om040068d

Organometallics 2004, 23, 5127-5134
5127
Articles
Rea ction of th e Ru th en iu m (II) In d en yl Com p lex
[Ru (η5-C9H7){K3(P ,C,C)-P P h 2(CH2CHdCH2)}(P P h 3)][P F 6]
w ith Ter m in a l Alk yn es. Mech a n ism s of 1-Alk yn e to
η1-Vin ylid en e Tr a n sfor m a tion a n d Kin etic Detection of
Hem ila bility of th e Allylp h osp h in e Liga n d
Mauro Bassetti,*,† Patricia Alvarez,‡ J ose´ Gimeno,‡ and Elena Lastra‡
Istituto CNR di Metodologie Chimiche, Sezione Meccanismi di Reazione, Dipartimento di
Chimica, Universita` La Sapienza, 00185 Roma, Italy, and Departamento de
Quı´mica Orga´nica e Inorga´nica, Instituto de Quı´mica Organometa´lica “Enrique Moles”
(Unidad Asociada al CSIC), Universidad de Oviedo, Oviedo, Principado de Asturias, Spain
Received May 13, 2004
The reaction of the complex [Ru(η5-C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}(PPh3)][PF6] (1)
with p-XC6H4CtCH (X ) H, Cl) yields the transient and observable vinylidene species
[Ru(η5-C9H7){κ1(P)-PPh2(CH2CHdCH2)}(PPh3)(dCdCH(p-XC6H4))]+, which react further by
an intramolecular [2 + 2] cycloaddition process, forming bicyclic alkylidene compounds. The
formation of the vinylidene intermediates, associated with a change of the binding mode of
the allylphosphine ligand from κ3(P,C,C) to monodentate κ1(P) coordination, has been
investigated by kinetic measurements carried out in chloroform-d at 38 °C. Plots of first-
order kobs values vs concentration of arylalkyne are linear with a positive intercept on the
y axis. The reaction proceeds via two parallel pathways, one which is first order in complex
1 and first order in arylalkyne, second order overall, and one which is zero order in arylalkyne,
overall first order. The second-order pathway implies rate-determining nucleophilic attack
of the arylalkyne on complex 1, k2 ) [5.5((0.4)] × 10-4 (X ) H) and [2.8((0.3)] × 10-4 M-1
s-1 (X ) Cl) being the corresponding rate constants, associated with displacement of the
allylic double bond or a haptotropic shift of the indenyl ring. The first-order pathway involves
rate-determining formation of a transient 16-electron intermediate arising from complex 1
by reversible decoordination of the allylic double bond and rapid reaction with the incoming
arylalkyne. The rate of this route is independent of the concentration and nature of the
alkyne (k1 ) [9.5((2.5)] × 10-5 s-1 for X ) H; [6.9((1.5)] × 10-5 s-1 for X ) Cl) and
corresponds to the rate of formation of the intermediate species [Ru(η5-C9H7){κ1(P)-
PPh2(CH2CHdCH2)}(PPh3)]+. The vinylidene complexes [Ru(η5-C9H7)(CdCdRR′){κ1(P)-
PPh2(CH2CHdCH2)}(PPh3)][BF4] (R′ ) H, R ) Ph (3a ), p-MeC6H4 (3b), p-ClC6H4 (3c); R′ )
Me, R ) Ph (4a ), p-MeC6H4 (4b)) have been independently synthesized by electrophilic attack
of HBF4 or MeSO3CF3 on the alkynyl derivatives [Ru(η5-C9H7)(CtCR){κ1(P)-PPh2(CH2-
CHdCH2)}(PPh3)] (R ) Ph (2a ), p-MeC6H4 (2b ), p-ClC6H4 (2c)), obtained in turn from
[Ru(η5-C9H7)Cl{κ1(P)-PPh2(CH2CHdCH2)}(PPh3)].
In tr od u ction
reactions3 or for further synthetic elaboration of the
organic fragment.4
The transformation of terminal alkynes into ruthe-
nium cumulenylidene derivatives represents a conve-
nient method of alkyne functionalization,1 as well as a
direct access into metal-vinylidene species (eq 1).2
The interaction of the 1-alkyne with the metal com-
plex involves first the formation of an η2 adduct, which
(1) Bruce, M. I. Chem. Rev. 1991, 91, 197-257; 1998, 98, 2797-
2858.
(2) Cadierno, V.; Gamasa, M. P.; Gimeno, J . Eur. J . Inorg. Chem.
2001, 571-591.
(3) (a) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 311-323.
(b) Naota, T.; Takaya, H.; Murahashi, S.-I. Chem. Rev. 1998, 98, 2599-
2660.
RCtCH + RuLn h Ru(dCdCHR)Ln-1 + L (1)
These compounds are extremely useful for catalytic
* To whom correspondence should be addressed. E-mail:
mauro.bassetti@uniroma1.it.
(4) (a) Wakatsuki, Y.; Yamazaki, H.; Kumegawa, N.; Satoh, T.;
Satoh, J . Y. J . Am. Chem. Soc. 1991, 113, 9604-9610. (b) Bianchini,
C.; Casares, J . A.; Peruzzini, M.; Romerosa, A.; Zanobini, F. J . Am.
Chem. Soc. 1996, 118, 4585-4594.
† Universita` La Sapienza.
‡ Universidad de Oviedo.
10.1021/om040068d CCC: $27.50 © 2004 American Chemical Society
Publication on Web 09/30/2004

5128 Organometallics, Vol. 23, No. 22, 2004
Bassetti et al.
Sch em e 1
Sch em e 2. Rea ction of Com p lex 1 w ith Ter m in a l
Alk yn es
complex and the mechanisms by which the metal center
can be accessed.
We have recently described that the complex [Ru(η5-
C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}(PPh3)][PF6] (1) re-
acts with RCtCH (R ) Ph, p-MeC6H4, SiMe3), yielding
bicyclic compounds containing a cyclobutylidene ring
(Scheme 2).11a,b It has been proved that the reaction
proceeds through the formation of vinylidene intermedi-
ates which undergo an intramolecular [2 + 2] cycload-
dition of the allylic and vinylidene C-C double bonds.
This reaction stems from the presence in the precursor
complex 1 of allylphosphine, PPh2(CH2CHdCH2), which
acts as a hemilabile κ3(P,C,C) ligand, allowing the
π-coordination of the incoming alkyne and subsequent
tautomerization to afford the vinylidene species.
Hybrid hemilabile ligands are gaining increasing
relevance in coordination and organometallic chemis-
try,12 since they can reversibly create and/or occupy a
vacant coordination site at the metal, with consequent
stabilization of reactive intermediates or enhancement
of reactivity in catalytic reactions.12c The chemistry of
ruthenium complexes containing hemilabile ligands is
well documented.13 One key feature of the hybrid
phosphine-olefin ligands is in fact the presumed ability
to easily dissociate the C-C double bond and allow
interaction between the metal center and the organic
rearranges into an η1-vinylidene species. Various mech-
anisms have been proposed for this tautomerization
process (Scheme 1). In most cases, the η2 adduct moves
toward a σ-η1 coordination, which is followed by a 1,2-
hydrogen shift (path A).5 In the reaction of the complex
[Ru(η5-C5Me5)Cl(dippe)] (dippe ) 1,2-bis(diisopropyl-
phosphino)ethane) with terminal alkynes, the hydrido-
alkynyl complexes [RuH(η5-C5Me5)(CtCR)(dippe)] have
been isolated and shown to be intermediates in the
subsequent formation of the η1-vinylidene compounds.6
The process occurs by proton dissociation from ruthe-
nium and protonation at the â-carbon atom (path B).
In the case of ruthenium hydride complexes, the reac-
tion of [RuHX(H2)(PtBu2Me)2] (X ) Cl, I) proceeds by
an alternative mechanism involving insertion of the
alkyne into the Ru-H bond to form a vinyl species,
which changes into a hydrido vinylidene complex by a
hydrogen shift from carbon(1) to ruthenium (path C).7
In the description of a novel synthetic route to func-
tionalized terminal alkynes from the corresponding η1-
vinylidene ruthenium complexes, ab initio molecular
orbital calculations have been reported on the η2-alkyne/
η1-vinylidene tautomerization proceeding through a 1,2-
hydrogen shift mechanism, for the model structure
[Ru(η5-C9H7)(PH3)2(η2-HCtCH)].8 Several theoretical
studies have dealt with this η2/η1 rearrangement,5,7-9
and some kinetic experiments have been reported.6,10
A specific point addressed in this work regards instead
the initial interaction of the free alkyne with the metal
(11) (a) Alvarez, P.; Lastra, E.; Gimeno, J .; Bassetti, M.; Falvello,
L. R. J . Am. Chem. Soc. 2003, 125, 2386-2387. (b) Bran˜a, P.; Gimeno,
J .; Sordo, J . A. J . Org. Chem. 2004, 124, 2544. (c) The reaction of
complex 1 with p-ClC6H4CtCH in refluxing dichloromethane leads
after workup to a yellow solid characterized spectroscopically as a
mixture of the vinylidene [Ru(dCdCH(p-ClC6H4))(η5-C9H7){κ1(P)-
PPh2(CH2CHdCH2)}(PPh3)][BF4] (3c) and the corresponding cycload-
dition product. IR and 31P{1H} NMR spectra of this solid mixture are
consistent with the presence of both vinylidene and cyclobutylidene
derivatives. Thus, the ν(BF4) absorption at 1100 cm-1 and the weak
ν(CdC) band at 1635 cm-1 are observed in the IR spectrum (Nujol),
while the 31P{1H} NMR spectrum shows two AB sets of resonances at
δ 43.6 and 32.2 ppm (J PP ) 25.4 Hz) for the vinylidene complex and at
δ 42.1 and 82.5 ppm (J PP ) 34.2 Hz) corresponding to the cycloaddition
product. All attempts to separate both complexes by crystallization
failed.
(12) (a) Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40,
680-699. (b) Slone, C. S.; Weinberger, D. A.; Mirkin, C. A. Prog. Inorg.
Chem. 1999, 48, 233-350. (c) Espinet, P.; Soulantica, K. Coord. Chem.
Rev. 1999, 193-195, 499-556.
(13) (a) Martin, M.; Gevert, O.; Werner, H. J . Chem. Soc., Dalton
Trans. 1996, 2275-2284. (b) Mauthner, K.; Slugovc, C.; Mereiter, K.;
Schmid, R.; Kirchner, K. Organometallics 1997, 16, 1956-1961. (c)
Barthel-Rosa, L. P.; Maitra, K.; Nelson, J . H. Inorg. Chem. 1998, 37,
633-639. (d) Lindner, E.; Pautz, S.; Fawzi, R.; Steiman, M. Organo-
metallics 1998, 17, 3006-3014. (e) Cadierno, V.; Crochet, P.; Diez, J .;
Garcia-Alvarez, J .; Garcia-Garrido, S. E.; Gimeno, J .; Garcia-Granda,
S.; Rodriguez, M. A. Inorg. Chem. 2003, 42, 3293-3307.
(5) (a) Silvestre, J .; Hoffmann, R. Helv. Chim. Acta 1985, 68, 1461-
1506. (b) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J .
Am. Chem. Soc. 1994, 116, 8105-8111.
(6) de los R´ıos, I.; Tenorio, M. J .; Puerta, M. C.; Valerga, P. J . Am.
Chem. Soc. 1997, 119, 6529-6538.
(7) Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organome-
tallics 1998, 17, 3091-3100.
(8) Cadierno, V.; Gamasa, M. P.; Gimeno, J . Organometallics 1999,
18, 2821-2832.
(9) (a) Wakatsuki, Y.; Koga, N.; Werner, H.; Morokuma, K. J . Am.
Chem. Soc. 1997, 119, 360-366. (b) Stegmann, R.; Frenking, G.
Organometallics 1998, 17, 2089-2095. (c) De Angelis, F.; Sgamellotti,
A.; Re, N. Organometallics 2002, 21, 5944-5950.
(10) (a) Bullock, R. M. J . Chem. Soc., Chem. Commun. 1989, 165-
166. (b) In cobalt complexes: Bianchini, C.; Peruzzini, M.; Vacca, A.;
Zanobini, F. Organometallics 1991, 10, 3697-3707.

Reactions of a Ru(II) Complex with Terminal Alkynes
Organometallics, Vol. 23, No. 22, 2004 5129
Sch em e 3. In d ep en d en t Syn th esis of th e
Vin ylid en e Com p lexes [Ru (η5-C9H7){dCdC(R)H}-
{K1(P )-P P h 2(CH2CHdCH2)}(P P h 3)][BF 4] a n d
[Ru (η5-C9H7){(CdCdR(Me)}-
substrate. The specific hemilabile character of PPh2-
(CH2CHdCH2) in the indenyl complex 1 has been shown
in the reactions with nitriles, which yield the cationic
complexes [Ru(η5-C9H7)(NtCR){κ1(P)-Ph2P(CH2CHd
CH2)}(PPh3)][PF6] (R ) Me, benzyl), featuring a P-
monodentate coordination of allylphosphine.14 In the
same context, the reactions of the Cp* complex [Ru(η5-
C5Me5){κ1(P)-PPh2CH2CHdCH2}{κ3(P,C,C)-PPh2CH2-
CHdCH2}][PF6] with two-electron ligands (L), yielding
monodentate phosphine-allyl complexes [Ru(η5-C5Me5)-
{κ1(P)-PPh2CH2CHdCH2)}2L][PF6], occur readily thr-
ough substitution of the coordinated olefin.13c
{K1(P )-P P h 2(CH2CHdCH2)}(P P h 3)][CF 3SO3]
We report here on the reaction of the complex [Ru(η5-
C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}(PPh3)][PF6] with
terminal alkynes and, in particular, on rate measure-
ments for the first step of Scheme 2, in which the
corresponding η1-vinylidene complex is formed. The
kinetic study is focused on the specific role of the
allylphosphine ligand, as a bidentate hemilabile donor
system, in the mechanism of the 1-alkyne/vinylidene
transformation (eq 1). To identify the intermediate
species observed in the kinetics, the synthesis and
characterization of the vinylidene complexes are also
reported. Part of the synthetic work here presented has
been reported in a preliminary communication.11a
ppm (2b) in the 13C{1H} NMR spectra. Alkynyl CR and
Câ resonances are found at δ 89.9 (br s) and 109.8 ppm
(2a ) or at δ 73.9 (d, J CP ) 20.5 Hz) and 92.9 (2b). All
attempts to obtain 2c with analytical purity have failed,
including those samples obtained by the reaction of the
parent complex with p-ClC6H4CtCH and KOtBu in
refluxing dichloromethane. Nevertheless, spectroscopic
characterization has been obtained from IR and NMR
data. The most significant features are as follows: (i)
two dCH2 resonances at δ 3.90 and 4.62 ppm and one
dCH at δ 4.57 ppm in the 1H NMR spectrum; (ii)
resonances of the olefinic groups dCH2 at δ 118.2 ppm
and dCH at δ 122.5 ppm and CR and Câ resonances at
δ 92.0 (br s) and 113.5 ppm in the 13C{1H} NMR
spectrum.
Resu lts a n d Discu ssion
Although terminal alkynes are appropriate sources
of the vinylidene group in metal complexes, the reaction
of complex 1 with terminal alkynes yields cycloaddition
products (Scheme 2).11 Therefore, we devised an alter-
native synthetic procedure to obtain vinylidene deriva-
tives via protonation of alkynyl precursors, thus avoid-
ing the consecutive cycloaddition reaction.
Syn th esis of th e Vin ylid en e Com p lexes [Ru -
{dCdCR(R′)}(η5-C9H7){K1(P )-P P h 2(CH2CHdCH2)}-
(P P h 3)][BF 4] (R′ ) H, R ) P h (3a ), p-MeC6H4 (3b);
R′ ) Me, R ) P h (4a ), p-MeC6H4 (4b)). The treatment
of a solution of the alkynyl derivatives 2a ,b in diethyl
ether with HBF4‚Et2O at room temperature leads to the
precipitation of a solid identified as the vinylidene
complexes [Ru{dCdCR(H)}(η5-C9H7){κ1(P)-PPh2(CH2-
CHdCH2)}(PPh3)][BF4] (R ) Ph, (3a ), p-MeC6H4 (3b))
in 80-95% yields. Similarly, the vinylidene derivatives
[Ru{(CdCdR(Me)}(η5-C9H7){κ1(P)-PPh2(CH2CHdCH2)}-
(PPh3)][CF3SO3] (R ) Ph (4a ), p-MeC6H4 (4b)) are
obtained in 85-90% yields from 2a ,b by the addition of
MeSO3CF3 (Scheme 3). However, the addition of HBF4‚
Et2O at room temperature to a solution of 2c in diethyl
ether leads to decomposition products. Complexes 3a ,b
and 4a ,b have been isolated as air-stable brown solids
and characterized by elemental analysis and spectro-
scopic methods. The IR spectra show strong ν(BF4)
Syn th esis of th e Alk yn yl Com p lexes [Ru (η5-
C9H 7)(CtCR ){K1(P )-P P h 2(CH 2CH dCH 2)}(P P h 3)]
(R ) P h (2a ), p-MeC6H4 (2b), p-ClC6H4 (2c)). Treat-
ment of [Ru(η5-C9H7)Cl{κ1(P)-Ph2P(CH2CHdCH2)}-
(PPh3)]14 with terminal alkynes and KOH in methanol
allows, after chromatographic workup, the isolation of
the alkynyl derivatives [Ru(η5-C9H7)(CtCR){κ1(P)-
PPh2(CH2CHdCH2)}(PPh3)] (R ) Ph (2a ), p-MeC6H4
(2b), p-ClC6H4 (2c)) as yellow air-stable solids (80-95%
yields). The alkynyl complexes can be also obtained by
reaction of [Ru(η5-C9H7)Cl{κ1(P)-PPh2(CH2CHdCH2)}-
(PPh3)] with the terminal alkyne in the presence of
KOtBu in refluxing dichloromethane. Complexes 2a ,b
were characterized by elemental analyses and 1H,
31P{1H}, and 13C{1H} NMR spectroscopy. The 31P{1H}
NMR spectra show two doublet resonances in the ranges
δ 44.1-43.5 and 53.2-53.5 ppm, in accord with the
expected AB system arising from the inequivalent
phosphorus nuclei of the two monodentate phosphines.
The 1H and 13C{1H} NMR spectra confirm the κ1(P)
coordination mode of allylphosphine, displaying reso-
nances of the uncoordinated allylic group: (i) two dCH2
resonances at δ 3.97 and 4.61 ppm (2) or δ 3.56 and 4.45
ppm (2b) and one dCH at δ 4.71 ppm (2a ) or δ 4.57
ppm (2b) in the 1H NMR spectra; (ii) resonances of
dCH2 at δ 119.8 ppm (d, J CP ) 8.4 Hz, 2a ) or δ 121.9
ppm (s, 2b) and of dCH at δ 123.2 ppm (2a ) or δ 127.5
(1055-1063 cm-1) and ν(CF3SO3) (1198-1203 cm-1
)
absorptions along with a weak ν(CdC) band at 1628-
1641 cm-1. 1H, 31P{1H}, and 13C{1H} NMR data support
the presence of the vinylidene group. In particular,
13C{1H} NMR spectra show the characteristic low-field
CR and Câ resonances at respectively δ 360.1 and 116.1
ppm (3a ), δ 369.2 and 117.2 ppm (3b), δ347.6 and 117.3
1
ppm (4a ), and δ 348.4 and 121.9 ppm (4b). H NMR
spectra exhibit the expected peaks arising from the
proton of the vinylidene group at δ 5.34 (3a ) and 5.31
ppm (3b) as broad signals and those of the methyl
group, which appear as singlet signals at δ 2.40 (4a )
and 1.92 ppm (4b).
(14) Alvarez, P.; Lastra, E.; Gimeno, J .; Bran˜a, P.; Sordo, J . A.;
Gomez, J .; Falvello, L. R.; Bassetti, M. Organometallics 2004, 23,
2956-2966.

5130 Organometallics, Vol. 23, No. 22, 2004
Bassetti et al.
Rea ction s of Ru (η5-C9H7){K3(P ,C,C)-P P h 2(CH2-
CHdCH2)}(P P h 3)][P F 6] (1) w ith Ter m in a l Alk yn es.
Complex 1 reacts with an excess of phenylacetylene or
p-tolylacetylene, in dichloromethane at reflux, to give
the corresponding bicyclic alkylidene compound [Ru-
(η5-C9H7){κ2(P,C)-(dCC(R)HCH2CHCH2PPh2)}(PPh3)][PF6]
(R ) Ph, p-MeC6H4). The complex obtained from the
reaction with PhCtCH has been fully characterized by
X-ray analysis.11a The reaction with (trimethylsilyl)-
acetylene in the presence of NH4PF6 affords [Ru(η5-
C9H7){κ2(P,C)-(dCCH2CH2CHCH2PPh2)}(PPh3)][PF6]
(85%), in which the acidic ammonium ion has assisted
the protodemetalation of the C-Si bond.15 To get
information on the possible steps leading to the cycload-
dition products, the reactions of complex 1 with
PhCtCH, Me3SiCtCH, and p-ClC6H4CtCH in chloro-
form-d have been monitored at 38.1 °C by 1H and
31P{1H} NMR until completion. A large excess of the
alkyne with respect to the ruthenium complex was used
in order to ensure pseudo-first-order conditions and
allow us to obtain rate data. In the 31P{1H} NMR
spectra, the disappearance of the two doublets of
F igu r e 1. Plot of concentration values of complex 1 vs time
for the reaction with p-ClC6H4CtCH in chloroform-d at
38.1 °C, as obtained by 31P NMR. The experimental points
are fitted with eq 2.
2
complex 1 (δ 55.1 and - 69.8 ppm; J ) 35 Hz)14 is
accompanied by the formation of two doublets at δ 43.9
and 32.7 ppm (2J ) 25 Hz) in the case of the reaction
with PhCtCH and of two doublets at δ 43.8 and 32.8
ppm (2J ) 24 Hz) in the case of p-ClC6H4CtCH,
indicating the formation of the vinylidene species
[Ru(η5-C9H7){dCdC(R)H}{κ1(P)-PPh2(CH2CHdCH2)}-
(PPh3)]+ as the only intermediates observed.11c At about
30 min of reaction, the vinylidene species appears as
the most abundant in solution with respect to both
starting material and final product. Each vinylidene
complex evolves further to give the bicyclic alkylidene
compound. This has allowed us to treat independently
the disappearance of complex 1 and that of the vi-
nylidene intermediate and to obtain rate data for the
[2 + 2] coupling process, as the second step of two
consecutive reactions.11a The identification of vinylidene
complexes as reaction intermediates has been confirmed
by the independent synthesis and characterization of
the tetrafluoroborate salts [Ru(η5-C9H7){dCdC(R)H}-
{κ1(P)-PPh2(CH2CHdCH2)}(PPh3)][BF4] (R ) Ph, (3a ),
p-MeC6H4 (3b)), which yield the corresponding bicyclic
alkylidene products when kept in dichloromethane at
reflux for 15 min.11a In the reaction of 1 with Me3SiCt
CH, only the peaks of the starting material and of the
product of [2 + 2] coupling, at δ 89.4 and 42.5 ppm
(2J PP ) 32 Hz), are observed in the 31P{1H} NMR
spectra. The trialkylsilyl substitution in the expected
vinylidene intermediate renders such species very reac-
tive, and therefore not detectable, with respect to the
more stable aryl-vinylidene complexes. The reaction is
accompanied by formation of a precipitate under the
above experimental conditions, which has halted the
kinetic study.
F igu r e 2. Plot of kobs values for the reaction of [Ru(η5-
C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}(PPh3)][PF6] (1) with
PhCtCH (b) or p-ClC6H4CtCH (9), vs concentration of
the alkyne, in chloroform-d at 38.1 °C.
-70.0 ppm (PPh2CH2CHdCH2 resonance) decays expo-
nentially until complete consumption, thus allowing us
to calculate values of observed rate constants, kobs
.
Figure 1 shows the disappearance of complex 1 (0.022
M) with time, in the presence of an excess of p-ClC6H4Ct
CH (0.176 M), in which the solid line represents the best
fit with the first-order rate equation (eq 2). The reaction
ct ) c∞ + (c0 - c∞) exp(-kobst)
(2)
is first order in complex 1, and in this case, the
calculated value of kobs is 1.27 × 10-4 s-1, implying a
τ1/2 value of 90 min at 38.1 °C. Various experiments have
been performed at different concentrations of PhCtCH
and p-ClC6H4CtCH, and the values of kobs are reported
in Table 1. Figure 2 shows a plot of kobs versus the
concentration of the alkynes. In both cases, the linear
dependence of kobs on [alkyne] indicates the presence of
a reaction pathway which is also first order in alkyne,
overall second order, and the slopes of the lines yield
the values of the corresponding rate constants, which
are k2 ) [5.5((0.4)] × 10-4 M-1 s-1 for phenylacetylene
Ra te Stu d ies. Rate measurements have been per-
formed for the reaction of complex 1 with PhCtCH or
p-ClC6H4CtCH toward the formation of the vinylidene
species. In a series of 31P{1H} NMR spectra, the
intensity of the low-frequency peak of complex 1 at
(15) (a) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Martin-Vaca, B. M.;
Anillo, A.; Tiripicchio, A. Organometallics 1992, 11, 1373-1381. (b)
Braun, T.; Mu¨nch, G.; Windmu¨ller, B.; Gevert, O.; Laubender, M.;
Werner, H. Chem. Eur. J . 2003, 9, 2516-2530 and references therein.

Reactions of a Ru(II) Complex with Terminal Alkynes
Organometallics, Vol. 23, No. 22, 2004 5131
Ta ble 1. Va lu es of Obser ved Ra te Con sta n ts,
Ch a r t 1. P r op osed In ter m ed ia te Ad d u cts in th e
Secon d -Or d er P a th w a y of th e Rea ction betw een
Com p lex 1 a n d Ar CtCH (Ar ) P h , p-ClC6H4)
k
obs, for th e Rea ction of [Ru (η5-C9H7)-
{K3(P ,C,C)-P P h 2(CH2CHdCH2)}(P P h 3)][P F 6] w ith
P h CtCH a n d p-ClC6H4CtCH, in Ch lor ofor m -d , a t
38.1 °C, Obta in ed fr om th e Disa p p ea r a n ce of
Com p lex 1
[PhCtCH],
kobs
,
[p-ClC6H4CtCH],
kobs,
M
10-4 s-1
M
10-4 s-1
0.350
0.515
0.674
0.828
0.975
3.04
3.74
4.45
5.58
6.46
0.176
0.439
0.718
0.908
1.25
1.92
2.61
3.40
route, while no reaction is observed for the cyclopenta-
dienyl complex [RuH(η5-C5H5)(dppm)], as in a typical
case of “indenyl effect”.19 Similar mechanistic features
had been previously reported for the reaction of [IrH(η5-
C9H7)Me(PMe3)] with tert-butylacetylene.20 A mecha-
nistic scheme involving the formation of an intermediate
adduct between complex 1 and the alkyne is represented
in Scheme 4.
Ta ble 2. Va lu es of Kin etic Con sta n ts for th e
Rea ction of [Ru (η5-C9H7)-
{K3(P ,C,C)-P P h 2(CH2CHdCH2)}(P P h 3)][P F 6]
w ith Ar yla lk yn es a n d w ith CD3CN (L), in
Ch lor ofor m -d , a t 38.1 °C
L
k1, s-1
k2, M-1 s-1
Ra
PhCtCH
[9.5((2.5)] × 10-5 [5.5((0.4)] × 10-4 0.994
1.5 (( 0.6) × 10-4 [4.2((0.2)] × 10-3 0.998
p-ClC6H4CtCH [6.9((1.5)] × 10-5 [2.8((0.3)] × 10-4 0.993
Sch em e 4
CD3CNb
k3 (slow)
k4
a
b
Correlation coefficient. Reference 14.
1 + ArCCH y
z intermediate adduct 98
k-3
and [2.8((0.3)] × 10-4 M-1 s-1 for p-chlorophenylacety-
lene. In addition, the positive value of the linear
intercept on the y axis implies a contribution to kobs
arising from a pathway which is zero order in alkyne,
overall first order, with the value k1 ) [9.5((2.5)] × 10-5
s-1 for phenylacetylene and [6.9((1.5)] × 10-5 s-1 for
(p-chlorophenyl)acetylene (Table 2).16 The latter values
are the same within the experimental error, in agree-
ment with the inferred zero-order dependence on the
reagent. This situation is represented by the kinetic
equation (3), which shows how the two pathways
contribute to the observed reactivity.
vinylidene
Inclusion of the corresponding rate equation into eq
3 yields eq 4.
k3k4[alkyne]
kobs ) k1 + k2[alkyne] ) k1 +
(4)
k-3 + k4
If the forward transformation of the adduct is faster
than its reversal to the starting material (k4 . k-3), then
the second-order rate constant k2 corresponds to the
formation of this intermediate from complex 1 and the
alkyne (k3). Therefore, the second-order pathway ex-
hibited by complex 1 in the reactions of Scheme 2 should
imply a rate-determining nucleophilic attack by the
alkyne to induce either a ring slippage of the indenyl
five-membered ring with formation of an η3 intermedi-
ate species, or the displacement of the allylic double
bond, according to a SN2 mode. In fact, upon attack at
the metal involving formation of the metal-π-alkyne
bond, the metal complex can respond either by a
haptotropic ring shift or by olefin dissociation. This slow
step is followed by a fast 1,2-hydrogen shift within the
η2-alkyne species. According to this picture, Chart 1
shows the structures of the proposed intermediates in
the second-order route. The nucleophilic character of the
alkyne in this step is indicated by the greater reactivity
of phenylacetylene with respect to (p-chlorophenyl)-
acetylene.
kobs ) k1 + k2[alkyne]
(3)
(a ) Secon d -Or d er P a th w a y. The route represented
by the second-order rate constant implies participation
of both complex 1 and alkyne in the rate-determining
step and can be regarded as an associative process,
which is common in the reactions of indenyl com-
plexes.17 The higher reactivity often observed with
respect to cyclopentadienyl analogues is explained in
terms of favorable ring slippage of the indenyl ligand
from an η5 toward an η3 coordination, upon attack of
the nucleophilic reagent at the metal center.18 We have
reported that the insertion reactions of PhCtCH and
(PhCtC-)2 into the Ru-H bond of the complex [RuH(η5-
C9H7)(dppm)] (dppm ) bis(diphenylphosphino)methane),
with formation of the (E)-alkenyl complexes [Ru{(E)-
CHdCHPh}(η5-C9H7)(dppm)] and [Ru{(E)-CH(CtCPh)d
CHPh}(η5-C9H7)(dppm)], proceed via an associative
(b) F ir st-Or d er P a th w a y. A pathway which is zero
order in alkyne implies rate-determining intramolecular
rearrangement of complex 1 with formation of a tran-
sient intermediate, able to react rapidly in the following
step with the alkyne. This is indicated by the fact that
neither the concentration nor the nature of the alkyne
influences the k1 value. Due to its higher reactivity with
(16) (a) Maskill, H. The Physical Basis of Organic Chemistry; Oxford
University Press: New York, 1985; p 276. (b) Atwood, J . D. Inorganic
and Organometallic Reaction Mechanisms; Brooks/Cole: Monterey, CA,
1985; p 14.
(17) (a) Rerek, M. E.; Basolo, F. J . Am. Chem. Soc. 1984, 106, 5908.
(b) Kakkar, A. K.; Taylor, N. J .; Marder, T. B.; Shen, J . K.; Hallinan,
N.; Basolo, F. Inorg. Chim. Acta 1992, 198-200, 219-231. (c) Bonifaci,
C.; Carta, G.; Ceccon, A.; Gambaro, A.; Santi, S. Organometallics 1996,
15, 1630-1636.
(18) (a) Merola, J . S.; Kacmarcik, R. T.; Van Engen, D. J . Am. Chem.
Soc. 1986, 108, 329-331. (b) O’Connor, J . M.; Casey, C. P. Chem. Rev.
1987, 87, 307-318. (c) Calhorda, M. J .; Veiros, L. F. Coord. Chem.
Rev. 1999, 185-186, 37-51.
(19) (a) Bassetti, M.; Casellato, P.; Gamasa, M. P.; Gimeno, J .;
Gonza´lez-Bernardo, C.; Mart´ın-Vaca, B. Organometallics 1997, 16,
5470-5477. (b) Bassetti, M.; Marini, S.; D´ıaz, J .; Gamasa, M. P.;
Gimeno, J .; Rodriguez-AÄ lvarez, Y. Organometallics 2002, 21, 4815-
4822.
(20) Foo, T.; Bergman, R. G. Organometallics 1992, 11, 1811-1819.

5132 Organometallics, Vol. 23, No. 22, 2004
Bassetti et al.
indicated as “arm-off” mechanism.12 It should be pointed
out that observation of ligand hemilability by kinetic
means is rare21 and that the concept of kinetic detection
of hemilability has been introduced only recently.22 We
have previously described that the reaction of complex
1 with nitriles yields the cationic complexes [Ru(η5-
C9H7)(NtCR){κ1(P)-PPh2(CH2CHdCH2)}(PPh3)][PF6] (R
) Me, benzyl) by displacement of the double bond of
allylphosphine.14 The kinetics of the reaction with
acetonitrile-d3 have displayed the presence of parallel
second- and first-order pathways, the latter taken as
an indication of the occurrence of an arm-off mechanism
of the allylphosphine system. At this stage, it should
be considered that the rate of formation of the coordi-
natively unsaturated species [Ru(η5-C9H7){κ1(P)-PPh2-
(CH2CHdCH2)}(PPh3)]+, the y intercept in the plots,
should be independent not only of the nature of the
alkyne, as observed in the present study, but, in
principle, also of the final destination of the complex,
i.e., of the actual reaction in which it is involved. In
agreement with this concept, the k1 value found in the
reaction of complex 1 with acetonitrile-d3 ((1.5 ( 0.6) ×
10-4 s-1) is within experimental error of the values
found for the reaction with the arylacetylenes (Table 2),
under identical conditions of solvent and temperature
(see the graph in the Supporting Information).23
Sch em e 5. Over a ll Mech a n ism of th e Rea ction of
Com p lex 1 w ith Ar yla cetylen es
respect to complex 1, this species reacts with the alkyne
as soon as it forms and does not accumulate in the
reaction medium. In light of the structure of complex
1, in particular of the hemilabile character of the
allylphosphine ligand, such a reactive intermediate may
be regarded as arising from reversible dissociation of
the allylic double bond, to yield the 16-electron species
[Ru(η5-C9H7){κ1(P)-PPh2(CH2CHdCH2)}(PPh3)]+. Such
a species would form as a transient under steady-state
conditions, being as such not detectable by spectroscopic
means. In fact, it may either return to complex 1 by
recoordination of the allylic double bond or react with
the alkyne, both processes being rapid. The occurrence
of an η5-η3 haptotropic equilibration of the indenyl ring
as rate limiting along the first-order pathway can be
reasonably excluded. In fact, rate-determining indenyl
rearrangements only occur in the case of second-order
reactions, when the reagent is part of the activated
complex.17-20 Another hypothesis compatible with the
formation of a reactive species arising from complex 1
implies the release of PPh3 to form the 16-electron
species [Ru(η5-C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}]+,
in intermolecular equilibrium with the starting mate-
rial. When complex 1 (0.012 M) was reacted with
PhCtCH (0.675 M) in the presence of an excess of PPh3
(0.10 M), a kobs value of 4.8 × 10-3 s-1 was found, which
compares with the value kobs ) 4.4 × 10-3 s-1 observed
in the absence of free phosphine. A rate depression
should occur if rate-determining dissociation of PPh3
plays any role along the first-order route. This result
does not rule out the presence of a dissociative equilib-
rium of PPh3 in complex 1 but indicates that it is not
productive toward the activation of the alkyne molecule.
The concept that the 16-electron bis(phosphine) inter-
mediate [Ru(η5-C9H7){κ1(P)-PPh2(CH2CHdCH2)}(PPh3)]+
is reactive toward a terminal alkyne in the formation
of a vinylidene species rather than the monophosphine
species [Ru(η5-C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}]+
agrees nicely with the fact that electron-rich ruthenium
centers are required to assist the η2-alkyne/η1-vinylidene
rearrangement.1,3a
The second-order and first-order pathways in the
reaction of complex 1 with alkynes can be regarded as
parallel associative and dissociative routes, respectively.
The contribution of the arm-off mechanism to the overall
reactivity can be estimated from the graph of Figure 2,
by comparison of the interpolated kobs value at a chosen
concentration of arylalkyne with the corresponding k1
value. For instance, at [p-XC6H4CtCH] = 0.5 M, the
reaction proceeds via the first-order pathway to an
extent of about 25% (X ) H) and 33% (X ) Cl),
respectively. The contribution of the arm-off mechanism
becomes relatively large at low concentration of alkyne
and smaller at increasing values. While associative
reactions are typical of indenyl complexes, some cases
have also been reported of ligand substitution reactions
which occur by dissociative mechanisms.24 In particular,
we have reported that the exchange of triphenylphos-
phine in the complex [RuCl(η5-C9H7)(PPh3)2] with phos-
phines of smaller cone angle proceeds exclusively by
rate-determining PPh3 dissociation and that the indenyl
complex reacts 1 order of magnitude faster than the
corresponding cyclopentadienyl analogue.25 Mixed as-
sociative and dissociative modes for substitution reac-
tions in indenyl complexes have also been reported.26
(21) (a) Knebel, W. J .; Angelici, R. J . Inorg. Chem. 1974, 13, 627-
631. (b) Romeo, R.; Monsu` Scolaro, L.; Plutino, M. R.; Romeo, A.; Nicolo`,
F.; Del Zotto, A. Eur. J . Inorg. Chem. 2002, 629-638.
(22) Bassetti, M.; Capone, A.; Salamone, M. Organometallics 2004,
23, 247-252.
(23) The larger reactivity of acetonitrile-d3 with respect to the
arylacetylenes in the second-order pathway corresponds to a steeper
slope of the line in the graph of kobs vs concentration of the reagent,
implying a larger error in the estimate of the y intercept.14
(24) (a) J ones, D. J .; Mawby, R. J . Inorg. Chim. Acta 1972, 6, 157-
160. (b) Pevear, K. A.; Banaszak Holl, M. M.; Carpenter, G. B.; Rieger,
A. L.; Rieger, P. H.; Sweigart, D. A. Organometallics 1995, 14, 512-
523.
A mechanistic description of the overall reactivity of
complex 1 with terminal alkynes is represented in
Scheme 5.
The first-order route would therefore arise from the
reversible intramolecular dissociation of the allylic
double bond from the metal center, a phenomenom
(25) Gamasa, M. P.; Gimeno, J .; Gonzalez-Bernardo, C.; Mart´ın-
Vaca, B.; Monti, D.; Bassetti, M. Organometallics 1996, 15, 302-308.
(26) (a) Hart-Davis, A. J .; White, C.; Mawby, R. J . Inorg. Chim. Acta
1970, 4, 441-446. (b) Turaki, N. N.; Huggins, J . M.; Lebioda, L. Inorg.
Chem. 1988, 27, 424-427.

Reactions of a Ru(II) Complex with Terminal Alkynes
Organometallics, Vol. 23, No. 22, 2004 5133
an orange solid which was purified on a chromatographic
column, recovering the fraction eluted with diethyl ether, to
afford the complex [Ru(η5-C9H7)(CtCR){κ1(P)-PPh2P(CH2CHd
CH2)}(PPh3)] in 85-90% yield. R ) Ph (2a ): 85% yield. Anal.
Calcd for C50H42P2Ru: C, 74.51; H, 5.25. Found: C, 74.99; H,
5.61. 31P{1H} NMR (CDCl3): δ 53.5 (d, J PP ) 31.7 Hz, PPh3),
Con clu sion s
This work reports a kinetic investigation of the
reaction of terminal alkynes with a ruthenium indenyl
complex bearing an hybrid allylphosphine ligand to yield
η1-vinylidene derivatives. The study does not give
information about the η2-alkyne/η1-vinylidene transfor-
mation at the metal center (Scheme 1), which has been
previously investigated in various ruthenium systems,
but discloses the interactive modes of the metal complex
with the incoming alkyne molecule. The 18-electron
complex [Ru(η5-C9H7){κ3(P,C,C)-PPh2(CH2CHdCH2)}-
(PPh3)][PF6] reacts via parallel pathways, one charac-
terized by rate-determining bimolecular interaction with
the alkyne and one involving intramolecular rate-
determining dissociation of the allylic double bond to
form a transient 16-electron intermediate. The proposed
arm-off mechanism regarding the allylphosphine ligand
finds in this work a sound experimental support, since
it has been found to be independent of the alkyne
structure and also of the specific reaction involved. The
data here presented along with those from the reaction
of complex 1 with nitriles represent the first case of
detection and quantitative evaluation by kinetic means
of the hemilability of a hybrid olefin-phosphine ligand.
1
44.1 ppm (d, J PP ) 31.7 Hz, ADPP). H NMR (CDCl3): δ 1.98
(m, 2H, CH2), 2.37 (m, 1H, CH2), 3.97 (m, 1H, dCH2), 4.49 (s,
1H, H1), 4.61 (m, 1H, dCH2), 4.71 (m, 1H, dCH), 4.99 (s, 1H,
H3), 5.49 (s, 1H, H2), 6.41-8.12 ppm (m, 34H, Ar H). 13C{1H}
NMR (CDCl3): δ 33.1 (d, J CP ) 27.2 Hz, CH2), 75.8 (s, C1, 3),
89.9 (br s, CR), 97.8 (s, C2), 109.8 (s, Câ), 111.0 (s, C3a, C7a),
115.7 (s, C3a, C7a), 119.8 (d, J CP ) 8.4 Hz, dCH2), 123.2 (s,
dCH), 127.0-142.0 ppm (m, Ar). R ) p-MeC6H4 (2b): 90%
yield. Anal. Calcd for C51H44P2Ru: C, 74.70; H, 5.40. Found:
C, 74.38; H, 5.50. 31P{1H} NMR (CDCl3): δ 53.2 (d, J PP ) 31.7
Hz, PPh3), 43.5 ppm (d, J PP ) 31.7 Hz, ADPP). 1H NMR
(CDCl3): δ 1.85 (m, 1H, CH2), 2.38 (s, 3H, Me), 2.45 (m, 1H,
CH2), 3.56 (m, 1H, dCH2), 4.34 (s, 1H, H1), 4.45 (m, 1H,
dCH2), 4.57 (m, 1H, dCH), 4.85 (s, 1H, H2), 5.31 (s, 1H, H3),
6.30-8.11 ppm (m, 33H, Ar H). 13C{1H} NMR (CDCl3): δ 22.6
(s, Me), 31.8 (d, J CP ) 31.2 Hz, CH2), 73.9 (d, J CP ) 20.5 Hz,
CR), 79.4 (d, J CP ) 5.6 Hz, C1), 84.3 (d, J CP ) 7.8 Hz, C3), 92.9
(s, Câ), 99.8 (s, C2), 113.8 (s, C3a, C7a), 114.5 (s, C3a, C7a),
121.9 (s, dCH2), 127.5 (s, dCH), 127.0-140.0 ppm (m, Ar).
R ) p-Cl (2c): 90% yield. 31P{1H} NMR (CDCl3): δ 53.4 (d,
1
J PP ) 32.0 Hz, PPh3), 44.2 ppm (d, J PP ) 32.0 Hz, ADPP). H
NMR (CDCl3): δ 1.96 (m, 1H, CH2), 2.45 (m, 1H, CH2), 3.90
(m, 1H, dCH2), 4.46 (s, 1H, H1), 4.62 (m, 1H, dCH2), 4.57 (m,
1H, dCH), 4.99 (s, 1H, H2), 5.31 (s, 1H, H3), 6.30-8.11 ppm
(m, 33H, Ar H). 13C{1H} NMR (CDCl3): δ 30.9 (s, br, CH2),
74.1(s, C1), 79.4 (s, C3), 92.0 (br s, CR), 95.4 (s, C2), 107.6 (s,
C3a, C7a), 108.6 (s, C3a, C7a), 113.5 (s, Câ), 118.2(s, dCH2),
122.5 (s, dCH), 124.0-139.5 ppm (m, Ar). IR (Nujol): 1055
(BF4), 1632 (CdC) cm-1. No analytically pure samples were
obtained.
Syn th esis of [Ru (η5-C9H7){dCdC(R)H}{K1(P )-P P h 2(CH2-
CHdCH2)}(P P h 3)][BF 4] (R ) P h (3a ), p-MeC6H4 (3b)). A
stirred solution of the alkynyl complexes 2a -c (1 mmol) in
diethyl ether (20 mL), at room temperature, was treated
dropwise with a dilute solution of HBF4‚Et2O in diethyl ether
(ca. 7%). Immediately, an insoluble solid precipitated. The
addition was continued until no further solid was formed (ca.
3 mL). The resulting brown solid was recovered by filtration,
washed with diethyl ether (3 × 20 mL), and vacuum-dried.
R ) Ph (3a ): 80% yield. Anal. Calcd for C50H43BF4P2Ru: C,
67.19; H, 4.84. Found: C, 66.85; H, 4.51. 31P{1H} NMR
Exp er im en ta l Section
Gen er a l Con d ition s. The manipulations were performed
under an atmosphere of dry nitrogen using vacuum-line and
standard Schlenk techniques. All reagents were obtained from
commercial suppliers and used without further purification.
Solvents were dried by standard methods and distilled under
nitrogen before use. [Ru(η5-C9H7)Cl(PPh3)],27 [Ru(η5-C9H7){κ3-
(P,C,C)-PPh2P(CH2CHdCH2)}(PPh3)][PF6],14 and PPh2P(CH2-
CHdCH2)28 were prepared by previously reported methods.
Infrared spectra were recorded on a Perkin-Elmer 1720-XFT
or a Perkin-Elmer 599 IR spectrometer. The C, H, and N
analyses were carried out with a Perkin-Elmer 240-B micro
analyzer. NMR spectra were recorded on Bruker AC300 or
300DPX instruments at 300 MHz (1H), 121.5 MHz (31P), or
75.4 MHz (13C) using SiMe4 or 85% H3PO4 as standard. DEPT
experiments have been carried out for all the compounds.
Coupling constants J are given in hertz. ADPP is allyldiphe-
nylphosphine.
Syn th esis of [Ru (η5-C9H7){CtCR}{K1(P )-P P h 2(CH2CHd
CH2)}(P P h 3)] (R ) P h (2a ), p-MeC6H4 (2b), p-ClC6H4 (2c)).
Meth od a . A mixture of [Ru(η5-C9H7)Cl{κ1(P)-Ph2P(CH2CHd
CH2)}(PPh3)] (0.44 g, 0.45 mmol) and the corresponding
terminal alkyne (2.7 mmol) in MeOH (25 mL) was heated until
complete dissolution of the ruthenium complex occurred.
Afterward, KOH (0.06 g, 1.2 mmol) was added and the mixture
was refluxed for 45 min. The solvent was removed under
vacuum, and the resulting solid was purified by chromato-
graphic column, recovering the fraction eluted with diethyl
ether. Evaporation of the solvent afforded the yellow solid
[Ru(η5-C9H7)(CtCR){κ1(P)-PPh2(CH2CHdCH2)}(PPh3)] in 80-
90% yield.
(CDCl3): δ 43.4 (d, J PP ) 23.9 Hz, PPh3), 32.4 ppm (d, J PP
)
1
23.9 Hz, ADPP). H NMR (CDCl3): δ 2.81 (m, 2H, CH2), 4.32
(m, 1H, dCH2), 4.58 (m, 1H, dCH2), 4.82 (m, 1H, dCH), 5.34
(br s, dCdCH), 5.61 (s, 1H, H1), 5.65 (s, 1H, H3), 5.82 (s, 1H,
H2), 6.51-7.9 ppm (m, 34H, Ar H). 13C{1H} NMR (CDCl3): δ
33.9 (d, J CP ) 31.6 Hz, CH2), 81.3 (s, C1), 85.8 (s, C3), 100.9
(s, C2), 114.2 (s, C3a, C7a), 115.7 (s, C3a, C7a), 116.1 (s, Câ),
120.1 (d, J CP ) 20.0 Hz, dCH), 121.9 (s, C9H7), 123.2 (d, J CP
)
27.4 Hz, dCH2), 125.1 (s, C9H7), 126.0-138.2 (m, Ar), 360.1
ppm (s, br, CR). IR (Nujol): 1063 (BF4), 1628 cm-1 (dCdC).
R ) p-MeC6H4 (3b): 95% yield. Anal. Calcd for C51H45BF4P2-
Ru: C, 67.48; H, 4.99. Found: C, 67.11; H, 4.76. 31P{1H} NMR
Meth od b. To a solution of [Ru(η5-C9H7)Cl{κ1(P)-PPh2-
(CH2CHdCH2)}(PPh3)] (0.75 g, 1 mmol) in CH2Cl2 at reflux
(10 mL) were added phenylacetylene or p-tolylacetylene (2
mmol) and KOtBu (0.11 g, 1 mmol). The mixture was refluxed
for 10 min to form an orange solution. Solvents were then
evaporated, and the resulting solid was extracted with CH2Cl2
(2 × 10 mL). The solution was evaporated to dryness to afford
(CDCl3): δ 43.6 (d, J PP ) 25.4 Hz, PPh3), 32.2 ppm (d, J PP
)
25.4 Hz, ADPP). 1H NMR (CDCl3): δ 2.31 (s, Me), 2.82 (m,
2H, CH2), 4.29 (m, 1H, dCH2), 4.57 (m, 1H, dCH2), 5.12 (m,
1H, dCH), 5.31 (br s, dCdCH), 5.52 (s, 1H, H1), 5.61 (s, 1H,
H2), 5.71 (s, 1H, H3), 6.21-7.93 (m, 33H, Ar H). 13C{1H} NMR
(CDCl3): δ 21.2 (d, J CP ) 13.6 Hz, Me), 32.9 (d, J CP ) 28.7 Hz,
CH2), 80.8 (d, J CP ) 9.6 Hz, C1), 85.8 (s, C3), 100.9 (s, C2),
112.8 (s, C3a, C7a), 114.2 (s, C3a, C7a), 117.2 (s, Câ), 120.2
(d, J CP ) 21.3 Hz, dCH), 122.9 (s, C9H7), 123.7 (d, J CP ) 27.0
Hz, dCH2), 125.3 (s, C9H7), 126.0-139.9 (m, Ar), 369.2 ppm
(br s, CR). IR (Nujol): 1055 (BF4), 1632 cm-1 (dCdC).
(27) Oro, L. A.; Ciriano, M. A.; Campo, M.; Foces-Foces, C.; Cano,
F. H. J . Organomet. Chem. 1985, 289, 117-131.
(28) Clark, P. W.; Curtis, J . L. S.; Garrou, P. E.; Hartwell, G. E.
Can. J . Chem. 1974, 52, 1714-1720.

5134 Organometallics, Vol. 23, No. 22, 2004
Bassetti et al.
Syn th esis of [Ru (η5-C9H7){dCdC(R)Me}{K1(P )-P P h 2-
(CH2CHdCH2)}(P P h 3)][BF 4] (R ) P h (4a ), p-MeC6H4 (4b)).
A stirred solution of the alkynyl complexes 2a ,b (1 mmol) in
diethyl ether (20 mL), at room temperature, was treated
dropwise with a dilute solution (ca. 5%) of MeOSO2CF3.
Immediately, an insoluble solid precipitated. The addition was
continued until no further solid was formed. The solvents were
decanted, and the resulting solid was recrystallized from
CH2Cl2/diethyl ether and vacuum dried. R ) Ph (4a ): yield
85%. Anal. Calcd for C52H45F3O3P2RuS: C, 64.38; H, 4.67.
Found: C, 63.97; H, 4.44.31P{1H} NMR (CDCl3): δ 44.4 (d,
added using a microsyringe in the case of PhCtCH or
Me3SiCtCH or as a weighed solid in the case of p-ClC6H4-
CtCH. The samples were shaken to obtain clear solutions just
before introduction into the NMR probe, and the experiment
was started immediately afterward, after allowing about 1 min
for thermal equilibration and experiment setup. A macro
sequence of the Aspect 3000 software was used for the
collection of fids at regular interval times, each one with
identical acquisition parameters. The observed rate constants
for consumption of complex 1 were obtained from nonlinear
least-squares regression analysis by fitting the exponential
dependence of concentration, c, calculated from the peak
intensities of the 31P{1H} NMR resonance of complex 1 at
-70.0 ppm, against time, according to the first-order rate
equation (eq 2). The procedure yields values of c∞, kobs, and
correlation coefficient (R), which were g0.99. The kobs values
were checked against those obtained from straight-line plots
of ln c vs time and found to be in good agreement.
1
J PP ) 24.4 Hz, PPh3), 32.2 ppm (d, J PP ) 24.4 Hz, ADPP). H
NMR (CDCl3): δ 2.40 (s, 3H, Me), 2.51 (m, 2H, CH2), 4.21 (m,
1H, dCH2), 4.52 (m, 1H, dCH2), 4.73 (m, 1H, dCH), 5.32 (s,
1H, H1), 5.45 (s, 1H, H3), 5.73 (s, 1H, H2), 6.01-7.70 ppm
(m, 34H, Ar H). 13C{1H} NMR (CDCl3): δ 9.3 (s, Me), 32.5 (d,
J CP ) 29.9 Hz, CH2), 81.4 (s, C1), 83.2 (s, C3), 97.7 (s, C2),
111.4 (s, C3a, C7a), 111.6 (s, C3a, C7a), 117.3 (s, Câ), 120.1
(d, J CP)20.0 Hz, dCH), 122.3 (d, J CP ) 25.6 Hz, dCH2), 127.0-
142.0 (m, Ar), 347.6 ppm (t, J CP ) 21.5 Hz, CR). IR (Nujol):
1198 (CF3SO3), 1641 cm-1 (dCdC). R ) p-MeC6H4 (4b): yield
90%. Anal. Calcd for C53H47F3O3P2RuS: C, 64.69; H, 4.81.
Found: C, 64.38; H, 5.01. 31P{1H} NMR (CDCl3): δ 44.5 (d,
Ack n ow led gm en t. This work has been carried out
under the auspices of the European program COST
CHEMISTRY, under the projects WG D12/0025/99
(STSM to P.A.) and D24/0014/02, entitled “Stereoselec-
tive Catalysis by Ruthenium Complexes”.
1
J PP ) 26.4 Hz, PPh3), 32.5 ppm (d, J PP ) 26.4 Hz, ADPP). H
NMR (CDCl3): δ 1.92 (s, 3H, Me), 2.42 (s, 3H, Me), 2.61 (m,
2H, CH2), 4.25 (m, 1H, dCH2), 4.55 (m, 1H, dCH2), 4.70 (s,
1H, dCH), 5.41 (s, 1H, H1), 5.69 (s, 1H, H3), 5.89 (s, 1H, H2),
6.10-7.66 ppm (m, 33H, Ar H). 13C{1H} NMR (CDCl3): δ 12.6
(s, Me), 21.1 (s, Me), 32.1 (d, J CP ) 27.6 Hz, CH2), 81.5 (s, br,
C1), 83.2 (br s, C3), 98.3 (s, C2), 112.1 (s, C3a, C7a), 117.0 (s,
C3a, C7a), 119.9 (d, J CP ) 20.0 Hz, dCH), 121.9 (s, Câ), 123.2
(d, J CP ) 25.6 Hz, dCH2), 124.3 (s, C9H7), 126.0-138.2 (m,
Ar), 348.4 ppm (br s, CR). IR (Nujol): 1203 (CF3SO3), 1639
cm-1 (dCdC).
Note Ad d ed a fter ASAP . Due to a production error,
the version of the paper that was published on the Web
on Sept. 30, 2004, contained errors in some of the
chemical formulas. The version that now appears is
correct.
Su p p or tin g In for m a tion Ava ila ble: A figure giving a
plot of kobs values for the substitution reaction of complex 1
with CD3CN and for the reactions of complex 1 with PhCtCH
and p-ClC6H4CtCH. This material is available free of charge
via the Internet at http://pubs.acs.org.
Kin etic Mea su r em en ts. 1H and 31P NMR spectra were
obtained using a Bruker AC 300 P instrument. Manipulations
were performed under argon. A weighed amount of complex 1
(11-13 mg) was dissolved in chloroform-d (0.500 mL) into a 5
mm NMR tube, and the appropriate amount of alkyne was
OM040068D