Synthesis and properties of the indenyl ruthenium (II) complex [Ru{(E)-η1-C(C≡CPh)=CHPh}(η5-C9H 7)(κ2-P-dppm)] (dppm = bis(diphenylphosphino)methane). An organometallic intermediate in the catalytic d

Article abstract of DOI:10.1021/om020483a

The reaction of the hydride complex [RuH(η⁵-C₉H₇)(κ²-P-dp-pm)] (1) with an excess of 1,4diphenyl-1,3-butadiyne, PhC≡C-C≡CPh, yields complex [Ru{E)-η¹-C(C≡CPh)=CHPh}(η⁵C₉H _7<

Full text of DOI:10.1021/om020483a

Organometallics 2002, 21, 4815-4822
4815
Syn th esis a n d P r op er ties of th e In d en yl Ru th en iu m (II)
Com p lex
[Ru {(E)-η1-C(CtCP h )dCHP h }(η5-C9H7)(K2-P -d p p m )]
(d p p m ) bis(d ip h en ylp h osp h in o)m eth a n e). An
Or ga n om eta llic In ter m ed ia te in th e Ca ta lytic
Dim er iza tion of P h en yla cetylen e
Mauro Bassetti* and Silvia Marini
Istituto CNR di Chimica dei Composti Organo Metallici, Sezione di Roma,
c/ o Dipartimento di Chimica, Universita` La Sapienza, 00185 Roma, Italy
J osefina D´ıaz, M. Pilar Gamasa, J ose´ Gimeno,* and Yolanda Rodr´ıguez-AÄ lvarez
Instituto de Quı´mica Organometa´lica Enrique Moles (Unidad Asociada al CSIC),
Departamento de Quı´mica Orga´nica e Inorga´nica, Facultad de Quı´mica,
Universidad de Oviedo, 33071 Oviedo, Spain
Santiago Garc´ıa-Granda
Departamento de Quı´mica Fı´sica y Analı´tica, Facultad de Qu´ımica,
Universidad de Oviedo, 33071 Oviedo, Spain
Received J une 19, 2002
The reaction of the hydride complex [RuH(η5-C9H7)(κ2-P-dppm)] (1) with an excess of 1,4-
diphenyl-1,3-butadiyne, PhCtC-CtCPh, yields complex [Ru{(E)-η1-C(CtCPh)dCHPh}(η5-
C9H7)(κ2-P-dppm)] (3), formed by regio- and stereoselective insertion of the alkyne into the
Ru-H bond, in toluene or benzene-d6. The reaction, about 4 times slower than with the
terminal alkyne phenylacetylene, proceeds via an associative mechanism, characterized by
the following activation parameters: ∆Hq ) 11 kcal mol-1; ∆Sq ) -44 cal mol-1 K-1. The
σ-enynyl complex 3 is protonated with an equimolar amount of HBF4‚Et2O to give the cationic
alkynylalkylidene complex [Ru{dC(CtCPh)CH2Ph}(η5-C9H7)(κ2-P-dppm)][BF4] (4), which in
t
turn is deprotonated by BuOK to regenerate quantitatively complex 3. Both complexes 3
and 4 have been characterized by X-ray structural analysis. Complex 3 catalyzes the
dimerization of PhCtCH to give (E)- and (Z)-1,4-diphenyl-1-buten-3-yne under milder
conditions than analogous indenyl complexes [RuX(η5-C9H7)(dppm)] (X ) H, CtCPh, (E)-
CHdCHPh), while complex 4 is inactive. The σ-metathesis reaction between complex 3 and
PhCtCH is not the rate-determining step in the catalytic cycle.
In tr od u ction
dissymmetric species without waste products.2 Of main
concern is still the regioselectivity due to competitive
head-to-tail 1,3 or head-to-head 1,4 disubstitution, and
to competitive formation of the two geometric isomers
or of oligomers versus dimers. Significant progress
regarding the catalytic efficiency has been obtained
upon the use of ruthenium complexes bearing N-
heterocyclic carbene ligands, which allow the dimeriza-
tion reaction to proceed very rapidly at room tempera-
ture, rather than in refluxing solvents.3 Although the
process has not been developed as a useful synthetic
procedure, we have recently shown the possibility of
obtaining and isolating from phenylacetylene both the
E and Z isomers of 1,4-diphenyl-1-buten-3-yne, as an
alternative to the Heck reaction or to more elaborate
reaction sequences.4
Various ruthenium complexes have been shown to be
active catalysts for the dimerization of terminal alkynes
to form disubstituted enynes (eq 1).1
2RCtCH f RCtC-CHdCHR (E + Z)
(1)
This reaction, of potential synthetic utility, involves
C-H activation and satisfies the criteria of “atom
economy”, where one substrate is converted into a
(1) (a) Qu, J .-P.; Masui, D.; Ishii, Y.; Hidai, M. Chem. Lett. 1998,
10, 1003. (b) Bruce, M. I.; Hinchliffe, J . R.; Humphrey, P. A.; Surynt,
R. J .; Skelton, B. W.; White, A. H. J . Organomet. Chem. 1998, 552,
109. (c) Yi, C. S.; Liu, N.; Rheingold, A. L.; Liable-Sands, L. M.
Organometallics 1997, 16, 3910. (d) Slugovc, C.; Mereiter, K.; Zobetz,
E.; Schmid, R.; Kirchner, K. Organometallics 1996, 15, 5275. (e)
Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J . Am. Chem.
Soc. 1994, 116, 8105. (f) Bianchini, C.; Peruzzini, M.; Zanobini, F.;
Frediani, P.; Albinati, A. J . Am. Chem. Soc. 1991, 113, 5453. (h)
Echavarren, A. M.; Lo´pez, J .; Santos, A.; Montoya, J . J . Organomet.
Chem. 1991, 414, 393. (g) Dahlenburg, L.; Frosin, K.-M.; Kerstan, S.;
Werner, D. J . Organomet. Chem. 1991, 407, 115.
(2) Trost, B. M. Chem Ber. 1996, 129, 1313.
(3) Baratta, W.; Herrmann, W. A.; Rigo, P.; Schwarz, J . J . Orga-
nomet. Chem. 2000, 593-594, 489.
10.1021/om020483a CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/04/2002

4816 Organometallics, Vol. 21, No. 22, 2002
Bassetti et al.
Sch em e 1
Sch em e 2
Various authors have proposed a mechanistic scheme
of the catalytic process, which can therefore be rational-
ized according to Scheme 1.1 The key steps are genera-
tion of a free coordination site in a Ru-acetylide species,
coordination of the alkyne, rearrangement of the π-com-
plexed molecule to a vinylidene species,5 intramolecular
acetylide migration to the R-vinylidene carbon to give
a labile η3- or η1-butenynyl complex, and σ-bond meta-
thesis with an incoming alkyne molecule to form the
organic enyne and the catalytic species. An alternative
and short-cut step is the direct alkyne insertion into the
Ru-acetylide bond, although the intermediacy of vi-
nylidene species is highly favored. Since an acetylide
complex can form by insertion of the alkyne into the
Ru-H bond of dihydride species and subsequent trans-
formations, ruthenium hydride complexes are also pre-
catalysts of the dimerization process.6 The mechanistic
features of the sequential formation of a diacetylide
compound from the cis-dihydride complex [RuH2(PP3)]
(PP3 ) P(CH2CH2PPh2)3) and the role of 1-alkyne as
hydrogen donor to the acetylide fragment have been
described in the dimerization of phenylacetylene.6
The formulation of the catalytic cycle as shown in
Scheme 1 is based essentially on the logic assembly of
known stoichiometric reactions, rather than on experi-
mental evidence of intermediates or sequence of steps.
As a consequence, the current understanding of the
process does not allow the design of an efficient and
selective precatalyst, nor to know which are the rate-
and stereo-determining steps. For instance, the reason-
able assumption that the catalytic precursor bearing a
Ru-acetylide moiety, i.e., one partner of the coupling
step,1c,6 may more efficiently enter the catalytic cycle
has not met with the experimental results, except for
the case of the bis-acetylide complex [Ru(CtCPh)2-
(PP3)].6 In fact, comparable results have been obtained
using an alkynyl complex containing a hemilabile ligand
[Ru(CtCPh)Tp(κ2(P,O)-Ph2PCH2CH2OMe)] (Tp ) hy-
dridotrispyrazolylborate) or the complexes [RuHTp-
(PPh3)2], [Ru(dCdCHPh)TpCl], and [RuH3(η5-C5Me5)-
(PR3)].7 We have also observed that the nature of the
anionic η1-ligand does not affect significantly the cata-
lytic activity of the indenyl complexes [RuX(η5-C9H7)-
(dppm)] (X ) H, CtCPh, (E)-CHdCHPh).4
Since Ru-σ-enynyl species have been proposed as
intermediates and many complexes of this type have
been isolated,1c,d,7 we have focused our attention on this
species, as a potential source of information about the
catalytic cycle. We report now (a) the synthesis and
structural characterization of [Ru{(E)-η1-C(CtCPh)d
CHPh}(η5-C9H7)(dppm)] (3), formed by insertion of 1,4-
diphenylbutadiyne (2) into the Ru-H bond of [RuH(η5-
C9H7)(dppm)] (1), (b) the kinetics of this reaction, and
(c) the catalytic properties of 3 in the dimerization of
phenylacetylene. We have previously described a kinetic
study of the insertion of phenylacetylene into the Ru-H
bond of [RuH(η5-C9H7)(dppm)] to give the corresponding
vinyl derivative.8
Resu lts a n d Discu ssion
Syn th esis of th e En yn yl Com p lex [Ru {(E)-η1-
C(CtCP h )dCHP h }(η5-C9H7)(K2-P -d p p m )] (3). The
reaction of the hydride complex [RuH(η5-C9H7)(κ2-P-
dppm)] (1) with a 10-fold excess of diphenylbutadiyne
(2) in refluxing toluene leads to the formation of the
enynyl complex 3 (58%). The low yield of recovered
complex is due to the separation procedure from the
diyne, which involves washings with pentane of the
crude product. On the other hand, the reaction of 1 with
an equimolar amount of 2 gave in addition to complex
3 consistent formation of an uncharacterized species
(31P{1H} NMR signal at δ 22.9 ppm). This byproduct is
still formed when using a 5-fold amount of diyne, but it
is not detected at larger excesses. Complex 3 is easily
protonated with an equimolar amount of HBF4‚Et2O in
diethyl ether to give the alkynylalkylidene complex 4
(see below) in nearly quantitative yield. The sequence
of protonation of 3 in the crude reaction mixture to give
4 followed by deprotonation of 4 to give back 3 has been
employed to improve the yield of 3 (81%) (see Scheme 2
and Experimental Section).
Complex 3 has been isolated as an air-stable yellow-
orange solid and characterized by mass spectrum (FAB)
and IR and NMR spectroscopy. The 31P{1H} NMR
spectrum shows a singlet signal at δ 19.68, indicating
the chemical equivalence of both phosphorus atoms. The
(4) Bassetti, M.; Marini, S.; Tortorella, F.; Cadierno, V.; D´ıez, J .;
Gamasa, M. P.; Gimeno, J . J . Organomet. Chem. 2000, 593-594, 292.
(5) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Gonza´lez-Bernardo,
C.; Pe´rez-Carren˜o, E.; Garc´ıa-Granda, S. Organometallics 2001, 20,
5177.
(6) Bianchini, C.; Frediani, P.; Masi. D.; Peruzzini, M.; Zanobini, F.
Organometallics 1994, 13, 4616.
1
IR and H and 13C{1H} NMR spectra show the expected
resonances arising from the presence of the indenyl,
(7) Pavlik, S.; Gemel, C.; Slugovc, C.; Mereiter, K.; Schmid, R.;
Kirchner, K. J . Organomet. Chem. 2001, 617-618, 301.
(8) Bassetti, M.; Casellato, P.; Gamasa, M. P.; Gimeno, J .; Gonzales-
Bernardo, C.; Martin-Vaca, B. Organometallics 1997, 16, 5470.

Catalytic Dimerization of Phenylacetylene
Organometallics, Vol. 21, No. 22, 2002 4817
Ta ble 1. Selected Bon d Dista n ces a n d Slip
P a r a m eter ∆a (Å) a n d Bon d An gles a n d Dih ed r a l
An gles HA,b F A,c a n d CAd (d eg) for Com p lex 3
Distances
Ru-C*
1.976(10)
2.094(7)
2.302(3)
2.265(3)
2.241(9)
2.246(10)
2.395(9)
0.130(10)
Ru-C(24)
Ru-C(25)
C(1)-C(2)
C(1)-C(3)
C(3)-C(4)
C(4)-C(11)
C(2)-C(5)
2.404(10)
2.291(10)
1.349(10)
1.422(11)
1.182(10)
1.438(13)
1.482(10)
Ru-C(1)
Ru-P(1)
Ru-P(2)
Ru-C(17)
Ru-C(18)
Ru-C(19)
∆
Angles
P(1)-Ru-P(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
C*-Ru-P(1)
C*-Ru-P(2)
C*-Ru-C(1)
HA
71.31(8)
81.3(2)
94.6(2)
143.7(3)
131.4(3)
117.9(4)
4.4(8)
Ru-C(1)-C(3)
Ru-C(1)-C(2)
C(3)-C(1)-C(2)
C(1)-C(3)-C(4)
C(3)-C(4)-C(11)
C(1)-C(2)-C(5)
CA
108.6(6)
129.3(6)
122.0(7)
174.5(9)
174.6(10)
130.8(7)
5.9(5)
FA
8.7(7)
a
b
∆ ) d[Ru-C(19),C(24)] - d[Ru-C(18),C(25)]. HA (hinge
angle) ) angle between normals to least-squares planes defined
by [C(25), C(17), C(18)] and [C(18), C(19), C(24), C(25)]. c FA (fold
angle) ) angle between normals to least-squares planes defined
by [C(25), C(17), C(18)] and [C(19), C(20), C(21), C(22), C(23),
F igu r e 1. ORTEP view of complex [Ru{(E)-η1-C(CtCPh)d
CHPh}(η5-C9H7)(κ2-P-dppm)] (3). Thermal ellipsoids are
shown at the 30% level. For clarity, the H atoms, except
that of the enyne moiety, and the phenyl rings of bis-
(diphenylphosphino)methane are omitted.
d
C(24)]. CA (confomational angle) ) angle between normals to
least-squares planes defined by [C**, C*, Ru] and [C*, Ru, C(1)].
C* ) centroid of C(17), C(18), C(19), C(24), C(25). C** ) centroid
of C(19), C(20), C(21), C(22), C(23), C(24).
phosphine, and enynyl groups. Significantly, the pres-
ence of the enynyl moiety was identified on the basis of
(i) a ν(CtC) absorption in the IR spectrum (KBr) at 2154
i.e., Ru-P(1) ) 2.302(3) Å, Ru-P(2) ) 2.265(3) Å, Ru-
C* ) 1.976(10) Å (C* ) centroid of the five-membered
indenyl ring), hinge angle (HA) ) 4.4(8)°, fold angle (FA)
) 8.7(7)°, slippage parameter (∆) ) 0.130(10) Å, can be
compared with those found in analogous indenyl-phos-
phinoruthenium(II) complexes reported by us and do not
merit further comment.12 The most remarkable struc-
tural feature is the E configuration of the alkenyl group
showing the alkynyl substituent attached to the CR
atom. It is also worth noting the nearly trans orientation
of the alkenyl group with respect to the benzo ring of
the indenyl ligand (CA ) 5.9(5) Å) and the orientation
of the alkynyl substituent of the alkenyl group, defined
by the dihedral angle (52.1(5)°) formed by the planes
Ru-C(1)-C(3) and Ru-C(1)-C*.
1
cm-1, (ii) a singlet signal in the H NMR spectrum at δ
5.56 (CdCH), (iii) two singlet resonances at 99.91 and
102.32 ppm for tCPh and CtCPh, respectively, and
two triplets at δ 134.35 (2J CP ) 13.7 Hz) and 145.01
(3J CP ) 5.8 Hz) ppm for the carbon atoms of the alkenyl
group in the 13C{1H} NMR spectrum. To assign the
regio- and stereochemistry of the alkenyl group, an
X-ray crystal structure determination of complex 3 has
been carried out. An ORTEP type view is shown in
Figure 1, and selected bond distances and angles are
listed in Table 1.
The molecular structure shows the typical pseudooc-
tahedral three-legged piano-stool geometry around the
ruthenium atom, which is linked to the η5-indenyl
group, to the two phosphorus atoms of the chelate
diphosphine, and to the C(1) of the enynyl ligand,
resulting from a regio- and stereoselective (cis) insertion
of diphenylbutadiyne into the Ru-H bond.
The bite angle of the chelate dppm ligand P(1)-Ru-
P(2) (71.31(8)°) shows a value similar to the one in
complex [RuH(η5-C9H7)(κ2-P-dppm)] (71.28(2)°)9 and in
the analogous chelate S-peap of the alkenyl complex
[Ru{(E)-η1-C(CO2Me)dCH(CO2Me)}(η5-C9H7){κ2-P-(S-
peap)}] (70.53(9)°) (S-peap ) (-)-N,N-bis(diphenylphos-
phine)-S-R-phenylethylamine).10 The bond length dis-
tance Ru-C(1), 2.094(7)°, is analogous to those reported
in other alkenyl ruthenium complexes.10 The C(1)-C(2)
(1.349(10)°) and C(3)-C(4) (1.182(10)°) distances are
typical of a double and triple carbon-carbon bond,
respectively, such as those found in other σ-butenynyl
ligands.11 The rest of the main structural parameters,
The preparation of complex 3 via reaction of the
hydride complex 1 with diphenylbutadiyne to form
σ-butenynyl complexes is not common. These species are
obtained by reaction of alkynyl ruthenium derivatives
with a terminal alkyne,1f,7 by reaction of a vinylidene
complex with LiCtCtBu,11 by protonation of a bis(σ-
alkynyl) ruthenium complex and subsequent coupling,6
or by carbon-carbon coupling in alkynyl-vinylidene
complexes.13 When [Ru(CtCPh)(η5-C9H7)(dppm)] is al-
lowed to react with PhCtCH in toluene, (E)- and (Z)-
1,4-diphenyl-1-buten-3-yne form at elevated tempera-
tures as the only organic products, while the alkynyl
complex is the only organometallic species observed by
1
31P and H NMR, maintaining constant concentration
throughout the reaction. This implies rate-limiting
reaction of the alkynyl with the alkyne followed by fast
σ-metathesis with a second alkyne molecule to form the
organic products, the presumed σ-enynyl complex not
(9) Hung, M. Y.; Ng, S. M.; Zhou, Z.; Lau, C. P.; J ia, G. Organome-
tallics 2000, 19, 3692.
(10) Bieger, K.; D´ıez, J .; Gamasa, M. P.; Gimeno, J .; Pavlista, M.;
Rodr´ıguez-AÄ lvarez, Y.; Garc´ıa-Granda, S.; Santiago-Garc´ıa, R. Eur. J .
Inorg. Chem. 2002, 7, 1647.
(11) Wakatsuki, Y.; Yamazaki H.; Kumegawa, N.; Satoh, T.; Satoh,
J . Y. J . Am. Chem. Soc. 1991, 113, 9604.
(12) Cadierno, V.; D´ıez, J .; Gamasa, M. P.; Gimeno, J .; Lastra, E.
Coord. Chem. Rev. 1999, 193-195, 147.
(13) Albertin, G.; Antoniutti, S.; Bordignon, E.; Cazzaro, F.; Ianelli,
S.; Pelizzi, G. Organometallics 1995, 14, 4114.

4818 Organometallics, Vol. 21, No. 22, 2002
Bassetti et al.
being detectable (Scheme 1). In the case of [Ru(PP3)-
(CtCSiMe3)][BF4] reacting with Me3SiCtCH,1f or of
[Ru(CtCPh)Tp(κ2(P,O)-Ph2PCH2CH2OMe)] reacting with
PhCtCH,7 η3-butenynyl complexes are stable and isol-
able materials. It is possible that such enynyl complexes
via this route are stabilized by the η3-coordination mode,
which is allowed by the four-donor system (P4) in one
case1f and by the hemilabile character of the phosphi-
noether ligand in the other.7
The insertion of a 1,4-butadiyne into Ru-H has been
used to form [Ru{(E)-η1-C(CtCtBu)dCHtBu}Cl(CO)-
(PPh3)2] from (tBuCtC)2 and [RuClH(CO)(PPh3)3].14
This η1-enynyl complex decomposed thermally to release
(Z)-1,4-di-tert-butylbutatriene.
Syn th esis of th e Alk yn yla lk ylid en e Com p lex
[R u {dC(CtCP h )CH 2P h }(η5-C9H 7)(K2-P -d p p m )]-
[BF 4] (4). Complex 3 reacts with HBF4‚Et2O at -40 °C,
in diethyl ether, producing instantaneously the precipi-
tation of complex 4, which is isolated from the reaction
mixture as an air-stable red solid (94%). This complex
is easily deprotonated with an equimolar amount of KOt-
Bu in THF to give the enynyl complex 3 in quantitative
yield.
F igu r e 2. ORTEP view of complex [Ru{dC(CtCPh)CH2-
Ph}(η5-C9H7)(κ2-P-dppm)][BF4] (4). Thermal ellipsoids are
shown at the 30% level. For clarity, the H atoms and the
phenyl rings of bis(diphenylphosphino)methane are omit-
ted.
Complex 4 has been characterized by mass spectrum
(FAB), conductance measurement, and IR and NMR
spectroscopy, which support the proposed formulation.
Conductivity data, in acetone solution, are in the range
expected for a 1:1 electrolyte, and the IR spectrum
exhibits the typical ν(B-F) strong absorption at 1062
cm-1. 1H and 13C{1H} NMR spectra reveal the presence
of the alkenylalkylidene group; the most relevant data
arise from the 13C{1H} NMR spectrum, which shows a
typical low-field resonance at δ 293.78 (t, 2J CP ) 6.4 Hz)
for the CR atom and the higher field resonances assigned
to the remaining carbon atoms of the hydrocarbon chain
Ta ble 2. Selected Bon d Dista n ces a n d Slip
P a r a m eter ∆a (Å) a n d Bon d An gles a n d Dih ed r a l
An gles HA,b F A,c a n d CAd (d eg) for Com p lex 4
Distances
Ru-C*
1.974(7)
1.931(6)
2.265(2)
2.266(2)
2.238(8)
2.247(7)
2.389(6)
0.140(6)
Ru-C(24)
Ru-C(25)
C(1)-C(2)
C(1)-C(3)
C(3)-C(4)
C(4)-C(11)
C(2)-C(5)
2.401(7)
2.264(9)
1.522(8)
1.407(8)
1.199(8)
1.445(9)
1.497(10)
Ru-C(1)
Ru-P(1)
Ru-P(2)
Ru-C(17)
Ru-C(18)
Ru-C(19)
∆
3
at δ 63.75 (s) (CH2Ph), 108.78 (t, J CP ) 3.1 Hz), and
122.6 (s) (CtCPh). These assignments can be compared
to those recently reported for the rhenium complex [Re-
{dC(CtCC6H4-p-CH3)(C6H4-p-CF3)}(η5-C9H7)(CO)2].15
The formation of 4 is in accordance with the expected
reactivity of alkenyl complexes, which are prone to
undergo electrophilic additions at the Câ atom.16 Alky-
nylalkylidene complexes are scarcely found in the
literature, and to the best of our knowledge, only the
complex [Ru{dC(CtCPh)CHdCPh2}(η5-C5H5)(CO)(Pi-
Pr3)][BF4], with ruthenium, has been reported.17 The
structure of complex 4 has been confirmed by an X-ray
diffraction study. An ORTEP type view of the cation
complex is shown in Figure 2, and selected bond
distances and angles are collected in Table 2.
Angles
P(1)-Ru-P(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
C*-Ru-P(1)
C*-Ru-P(2)
C*-Ru-C(1)
HA
72.64 (6)
92.5(2)
91.5(2)
123.2(2)
124.9(2)
133.5(3)
5.4(6)
Ru-C(1)-C(3)
Ru-C(1)-C(2)
C(2)-C(1)-C(3)
C(1)-C(3)-C(4)
C(3)-C(4)-C(11)
C(1)-C(2)-C(5)
CA
127.7(4)
119.2(4)
113.1(5)
177.0(7)
175.4(7)
115.4(5)
5.5(4)
FA
10.2(5)
a
b
∆ ) d[Ru-C(19),C(24)] - d[Ru-C(18),C(25)]. HA (hinge
angle) ) angle between normals to least-squares planes defined
by [C(25), C(17), C(18)] and [C(18), C(19), C(24), C(25)]. c FA (fold
angle) ) angle between normals to least-squares planes defined
by [C(25), C(17), C(18)] and [C(19), C(20), C(21), C(22), C(23),
d
C(24)]. CA (confomational angle) ) angle between normals to
The pseudooctahedral geometry around the ruthe-
nium atom is quite similar to that found for complex 3,
wherein the alkylidene group occupies the position of
the former alkenyl moiety. Bonding distances, Ru-C*
) 1.974(7) Å, Ru-P(1) ) 2.265(2) Å, Ru-P(2) ) 2.266-
(2) Å, the chelating bite angle, P(1)-Ru-P(2) ) 72.64-
least-squares planes defined by [C**, C*, Ru] and [C*, Ru, C(1)].
C* ) centroid of C(17), C(18), C(19), C(24), C(25). C** ) centroid
of C(19), C(20), C(21), C(22), C(23), C(24).
(6)°, and all the distortion parameters of the indenyl
group (HA, FA, and ∆) are comparable to those shown
for complex 3 (see Table 1).
Of special interest is the nearly cis orientation of the
alkylidene chain relative to the benzo ring of the indenyl
ligand (CA ) 5.5(4) Å). A relevant feature is the
orientation of the alkynyl substituent determined by the
value of the dihedral angle defined by the planes Ru-
C(1)-C(3) and Ru-C(1)-C* (176.5(5)°), which are nearly
coplanar in 4. This value contrasts with that shown in
complex 3 (52.1(5)°), and the difference probably arises
(14) Wakatsuki Y.; Yamazaki, H. J . Organomet. Chem. 1995, 500,
349.
(15) Casey, C. P.; Kraft, S.; Powell, D. R. Organometallics 2001, 20,
2651.
(16) (a) Gamasa, M. P.; Gimeno, J .; Mart´ın-Vaca, B. M. Organome-
tallics 1998, 17, 3707. (b) Harlow, K. J .; Hill, A. F.; Welton, T. J . Chem.
Soc., Dalton Trans. 1999, 1911. (c) Kostic, N. M.; Fenske, R. F.
Organometallics 1982, 1, 974.
(17) Esteruelas, M. A.; Go´mez, A. K.; Lo´pez, A. M.; Modrego, J .;
On˜ate, E. Organometallics 1997, 16, 5826.

Catalytic Dimerization of Phenylacetylene
Organometallics, Vol. 21, No. 22, 2002 4819
Ta ble 3. Cr ysta llogr a p h ic Da ta for th e Com p lexes
3 a n d 4
3
4
formula
fw
cryst syst
space group
a (Å)
C
50H40P2Ru
C50H41BF4P2Ru
891.65
monoclinic
P21/c
20.638(4)
11.067(5)
18.819(5)
90
95.319(12)
90
803.83
monoclinic
P21/c
13.255(5)
17.082(10)
17.651(6)
90
96.98(3)
90
3967(3)
4
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
4280(2)
4
1.384
Z
calcd density (g cm-3
F(000)
)
1.346
1656
1824
radiation (λ, Å)
cryst size (mm)
temp (K)
monochromator
Mo KR (0.71073)
Mo KR (0.71073)
0.20 × 0.13 × 0.07 0.33 × 0.20 × 0.20
293(2)
graphite cryst
0.510
ω-2θ
1.55-25.97
293(2)
graphite cryst
0.493
ω-2θ
2.30-25.98
µ (mm-1
)
F igu r e 3. Plot of concentration values vs time for the
reaction of complex [RuH(η5-C9H7)(κ2-P-dppm)] (b, 1) with
PhCtC-CtCPh (1.05 M) to give complex [Ru{(E)-η1-C(Ct
CPh)dCHPh}(η5-C9H7)(κ2-P-dppm)] ([, 3), in benzene-d6
at 69 °C, by 31P{1H} NMR spectroscopy.
diffraction geom
θ range for data
collection (deg)
index ranges for data
collection
-16 e h e 16
-25 e h e 25
-21 e k e 0
-21 e l e 0
8038
7772
484
0 e k e 13
-23 e l e 0
8679
8390
517
from the greater steric hindrance between the indenyl
and the alkenyl group in 4.
no. of reflns measd
no. of indep reflns
no. of variables
agreement between
equiv reflns
Kin etics of th e Reaction of [Ru H(η5-C9H7)(dppm )]
w ith P h CtC-CtCP h . The reaction of the hydride
complex with 1,4-diphenylbutadiyne (2) in benzene-d6
can be followed conveniently by 31P{1H} NMR spectros-
copy, monitoring the disappearance of 1 (δ 20.3 ppm)
as well as the formation of the σ-enynyl complex 3 (δ
19.7 ppm), while intermediate species are not detected.
This is shown graphically in Figure 3.
0.0630
0.0348
final R factors (I < 2σ(I)) R1 ) 0.0483
R1 ) 0.0554
wR2 ) 0.1390
R1 ) 0.1531
wR2 ) 0.1741
wR2 ) 0.0850
final R factors (all data) R1 ) 0.3175
wR2 ) 0.1362
Ta ble 4. Obser ved Ra te Con sta n ts, kobs (s-1), for
th e Rea ction of [Ru H(η5-C9H7)(d p p m )] (1) w ith
a
The solid line represents the best exponential decay
fitted to the data set of concentration values (c) vs time
(t), according to the first-order rate equation (eq 2):
P h CtC-CtCP h (2) in Ben zen e-d 6
b
T (°C)
[1], M
[2], M
-d[1]/dt (s-1
)
k1 (M-1, s-1
)
69
69
69
69
0.034
0.037
0.035
0.042
0.35
0.53c
0.76
1.05
7.3 × 10-5
8.5 × 10-5
1.3 × 10-4
1.8 × 10-4
ct ) c∞ + (c0 - c∞) exp -(kobst)
(2)
The experiment of Figure 3 yields a value of the
observed rate constant, kobs ) 1.1 × 10-2 min-1 at [2] )
1.05 M, corresponding to τ1/2(half time) ) 1 h (T ) 69
°C). The reaction is first-order in the hydride complex.
The reaction order on the diyne was investigated by
varying the initial concentration of 2 in different experi-
ments. Values of kobs are reported in Table 4.
69
1.6 × 10-4 d
1.06 × 10-4
0.41 × 10-4
56
43.5
0.036
0.044
0.77
0.73
8.2 × 10-5
0.30 × 10-4
a
Method: 31P{1H} NMR spectroscopy (1, 20.3 ppm). b All values
(10%. kobs ) 10 × 10-5 s-1 for the reaction of 2 (0.54 M) with
c
[RuD(η5-C9H7)(dppm)] (0.046 M). Value obtained from the slope
d
of kobs vs [2].
A plot of kobs vs time is linear, which indicates first-
order dependence on 1,4-diphenylbutadiyne as well;
therefore that the reaction is overall second-order. The
reaction of the deuteride complex [RuD(η5-C9H7)(dppm)]
proceeded at a rate similar to that of complex 1 (footnote
c in Table 4). From the measurements carried out in
the temperature range 43-69 °C, the following activa-
tion parameters were obtained: ∆Hq ) 11 ( 2 kcal
mol-1; ∆Sq ) -44 ( 5 cal mol-1 K-1. The data are
consistent with the occurrence of an associative mech-
anism, as represented in Scheme 3 and described by eq
3,
scheme was proposed earlier for the insertion reaction
of BuCtCH with the iridium hydride complex [IrH-
t
(Me)(η5-C9H7)(PMe3)].18 The intermediate of Scheme 3
may involve rate-determining π-coordination of the
alkyne assisted by an η5- to η3-haptotropic shift of the
indenyl ligand.19 The reactivity of the diyne toward 1
is about 4 times lower than that of the terminal alkyne
(k1 ) 0.41 × 10-4 M-1 s-1 for (PhCtC)2 at 43.5 °C in
benzene-d6 vs k1 ) 1.8 × 10-4 M-1 s-1 for PhCtCH at
40 °C in toluene-d8), in a process that proceeds with
identical stereochemical features and similar kinetic
pattern. This may be due to greater steric hindrance of
the diyne, as pointed out by the larger negative value
k1k2[(PhCtC)2]
kobs
)
(3)
k-1 + k2
(18) Foo, T.; Bergman, R. G. Organometallics 1992, 11, 1811.
(19) (a) O’Connor, J . M.; Casey, C. P. Chem. Rev. 1987, 87, 307. (b)
Calhorda, M. J .; Romao, C. C.; Veiros, L. F. Chem. Eur. J . 2002, 8,
868. (c) Veiros, L. F. Organometallics 2000, 19, 3127.
in analogy with the results obtained for the reaction of
complex 1 with phenylacetylene.8 This mechanistic

4820 Organometallics, Vol. 21, No. 22, 2002
Bassetti et al.
Sch em e 3
reaction, the σ-metathesis step is not rate determining
in the catalytic process. Figure 4 shows no evidence of
an induction period, suggesting that the formation of
the catalytic species is rapid, of lower energy, with
respect to the rate of formation of the enyne products.
1
Inspection of the H NMR spectra reveals the disap-
pearance of the indenyl protons of 3 but gives no clean
spectral evidence of the organometallic products, while
more information is obtained by 31P NMR. After 14 h
of reaction, when the solution is still active, the spec-
trum shows the resonance of complex 3 (δ 19.74 ppm),
in addition to that of the alkynyl complex [Ru(η5-C9H7)-
(dppm)(CtCPh)] (19.49 ppm), as well as two doublets
at δ 62.6 and 40.9 (J P-P ) 135 Hz) and smaller doublets
at 104.7 and -24.2 (J P-P ) 41 Hz) ppm, due to the
presence of uncharacterized species bearing nonequiva-
lent phosphorus atoms. Especially the latter peaks are
typical of dppm ruthenium complexes where the bis-
phosphine is monodentate,20 which may leave an open
coordination site on the metal for catalytic activity.
F igu r e 4. Reaction profile for the catalytic dimerization
of phenylacetylene (4.2 M) in the presence of complex [Ru-
{(E)-η1-C(CtCPh)dCHPh}(η5-C9H7)(κ2-P-dppm)] (0.059 M,
1.4%, 3), showing the disappearance of 3 (0) and the
formation of (E, b)- and (Z, [)-1,4-diphenyl-1-buten-3-yne,
in benzene-d6 at 77 °C.
Conversely, the η3-enynyl complexes [(PP3)Ru{(E)-η3-
C(CtCR)dCHR}]BF4 (R ) SiMe3, Ph) were the only
organometallic species observable in the course of the
catalytic dimerization of RCtCH by [Ru(σ-CtCR)-
(PP3)].1f
of entropy of activation (PhCtCH: ∆Sq ) -21 ( 4 cal
mol-1 K-1).
The disappearance of 3 follows clean first-order
behavior. A plot of ln[3] vs time is linear and yields a
value of kobs ) 7.7 × 10-5 s-1 for [PhCtCH] ) 4.2 M.
The rate is dependent on the concentration of PhCt
CH (2.6 M, kobs ) 3.5 × 10-5 s-1), indicating that the
transformation of the σ-enynyl complex is induced by
the alkyne, and it is not due to complex decomposition.
The transformation of complex 3 can therefore be
represented as in Scheme 4.
Ca ta lytic P r op er ties of [Ru {(E)-η1-C(CtCP h )d
CHP h }(η5-C9H7)(d p p m )]. Complex 3 was found to
catalyze the dimerization of phenylacetylene. The reac-
tion of PhCtCH (4.2 M) in the presence of 3 (0.059 M,
1.4%), in benzene-d6, was monitored by 1H NMR, at
constant temperature (77 °C). Figure 4 shows the
disappearance of complex 3 and the formation of the
products of homocoupling, (E)- and (Z)-1,4-diphenylbut-
1-en-3-yne. After 15 h of reaction, more than 10 mol of
enyne per mole of ruthenium complex has formed, with
44% conversion of the alkyne. The cationic complex 4
yields traces of the enyne products only after heating
for 1 day at 120 °C, the Z isomer being the major
component.
The catalytic reaction also proceeds at lower concen-
tration of both alkyne (2.58 M) and complex 3 (0.039
M, 1.5%), with 31% conversion of phenylacetylene after
40 h of reaction. On the other hand, in the presence of
[Ru(CtCPh)(η5-C9H7)(dppm)] (0.042 M, 1.6%) under
similar experimental conditions ([PhCtCH] ) 2.64 M,
77 °C), the formation of [(E)-1,4-diphenylbut-1-en-3-yne]
does not exceed 3 mol per mole of the alkynyl complex.
The geometric selectivity in the reaction catalyzed by
3 favors the isomer with trans geometry of the double
bond (E/Z ) 6), being the same in the early stages of
the reaction, which indicates that the isomers neither
interconvert nor become involved in further processes.
Since only the E isomer is detected in the first spectra,
it appears that the σ-bond metathesis process occurs
preferentially with a change of configuration with
respect to complex 3. The catalytic activity of the
solution endures after complete transformation of com-
plex 3, implying that the complex has changed into the
catalytic species and it is not the resting state of the
catalyst. Since 3 is consumed during the dimerization
In conclusion, the σ-enynyl complex involves a lower
energy pathway as well as additional formation of the
active species, resulting in a better catalyst precursor
than the alkynyl, the hydride, or the styryl derivatives
[RuX(η5-C9H7)(dppm)] (X ) H, CtCPh, (E)-CHdCHPh),
which exhibit consistent catalytic activity only at high
temperatures.
(20) (a) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Lanfranchi, M.;
Tiripicchio, A. J . Organomet. Chem. 1992, 430, C39. (b) Gamasa, M.
P.; Gimeno, J .; Lastra, E.; Lanfranchi, M.; Tiripicchio, A. J . Organomet.
Chem. 1991, 405, 333.

Catalytic Dimerization of Phenylacetylene
Organometallics, Vol. 21, No. 22, 2002 4821
Sch em e 4
of diethyl ether, cooled at -40 °C, was treated dropwise with
dilute solution of HBF4 in diethyl ether (0.13 mmol).
Exp er im en ta l Section
a
Gen er a l Da ta . The reactions were carried out under dry
nitrogen using standard Schlenk techniques. Solvents were
dried by standard methods and distilled under nitrogen before
use. The complex [RuH(η5-C9H7)(κ2-P-dppm)] was prepared by
published methods.8 Infrared spectra were recorded on a
Perkin-Elmer FT-1720-Y spectrometer. Mass spectra (FAB)
were recorded using a VG-Autospec spectrometer, operating
in the positive mode; 3-nitrobenzyl alcohol (NBA) was used
as the matrix. The conductivities were measured at room
temperature, in ca. 10-3 mol‚dm-3 acetone solutions, with a
J enway PCM3 conductimeter. NMR spectra were recorded on
a Bruker DPX-300 or AC-300 instrument operating at 300
MHz (1H), 121.5 MHz (31P), and 75.4 MHz (13C) or a Bruker
AC-200 instrument operating at 200 MHz (1H), 81.01 MHz
(31P), and 50.32 MHz (13C), using SiMe4 or 85% H3PO4 as
standard. Inconsistent C, H elemental analyses were found
for complexes 3 and 4 due to incomplete combustion.
Immediately, a red solid precipitated. The solution was
decanted and the solid washed with diethyl ether (3 × 20 mL)
and vacuum-dried. Yield: 94%. 31P{1H} NMR (CD2Cl2):
δ
1
16.09 s. H NMR [CO(CD3)2]: δ 2.85 (s, 2H, CH2Ph), 4.87 (bs,
2
1H, H-2), 5.65 (dt, J HH ) 16.0 Hz, J HP ) 12.8 Hz, 1H,
PCHaHbP), 6.23 (d, J HH ) 2.6 Hz, 2H, H-1,3), 6.27 (m, 1H,
PCHaHbP), 6.41 and 6.98 (m, 2H each, H-4,5 and H-6,7), 7.09-
7.96 (m, 30H, PPh2, CH2Ph, tCPh). 13C{1H} NMR (CD2Cl2):
δ 47.82 (t, J CP ) 26.3 Hz, PCH2P), 63.75 (s, CH2Ph), 86.13 (s,
C-1,3), 93.55 (s, C-2), 108.78 (t, 3J CP ) 3.1 Hz, CtCPh), 114.85
(s, C-3a,7a), 122.60 (s, CtCPh), 124.32 (s, C-4,5 or C-6,7),
127.01-134.42 (m, PPh2, CH2Ph, tCPh, C-4,5 or C-6,7), 134.76
(t, J CP ) 24.6 Hz, PCipso), 138.39 and 143.11 (s, CCipso), 293.78
2
(t, J CP ) 6.4 Hz, RudC). ∆δ (C-3a,7a) ) -15.85. IR (KBr,
cm-1): ν (CtC) 2132 w; (BF4-) 1062 b. Conductivity (acetone,
20 °C): 108 Ω-1 cm2 mol-1. MS (FAB, m/e): 805 (M+), 689 (M+
- C9H7 - 1), 601 (M+ - C16H12), 485 (M+ - C9H7 - C16H12
-
Syn th esis of th e En yn yl Com p lex [Ru {(E)-η1-C(Ct
CP h )dCHP h }(η5-C9H7)(K2-P -d p p m )] (3). A solution of the
hydride complex 1 (0.25 g, 0.39 mmol) and a large excess of
diphenylbutadiyne (0.789 g, 3.9 mmol) in toluene (40 mL) was
heated under reflux for 90 min. The solvent was then evapo-
rated to dryness, and the brown solid residue was repeatedly
washed with pentane (4 × 15 mL), to eliminate the excess of
diyne, and dried under vacuum, yielding 3 as a yellow-orange
solid (0.181 g, 58%). The yield of 3 was improved by proceeding
as follows: the solid residue was dissolved in 50 mL of diethyl
ether, cooled at - 40 °C, and treated dropwise with an ethereal
solution of HBF4 (0.40 mmol). Immediately, the cationic
complex 4 precipitated as a red solid. The solution was
decanted and the solid washed with diethyl ether (3 × 20 mL)
to eliminate the excess diyne. A solution of 4 in THF (10 mL)
was treated with an equimolar amount of KOtBu, the mixture
stirred for 30 min, and the solvent removed to dryness. The
residue obtained was extracted with diethyl ether and filtered
to give the enynyl complex 3 in 81% yield. 31P{1H} NMR
1), 421 (M+ - dppm) (correct isotope patterns observed for each
fragment).
Ra te Mea su r em en ts. The ruthenium complex 1 or 3 and
[(PhCtC)2] or PhCtCH were dissolved in benzene-d6 into an
NMR tube, under argon. 1H or 31P NMR spectra were collected
immediately after mixing, using a macro sequence. The
temperature in the NMR probe was determined from the
chemical shift difference between OH and CH2 signals of a
solution of ethylene glycol containing 20% DMSO-d6. The first-
order rate constants were obtained from nonlinear least-
squares regression analysis by fitting the exponential depen-
dence of concentration, c, calculated via peak intensities (31P)
or integration with mesitylene as internal standard (1H),
against time. The procedure yields values of c∞, kobs, and
correlation coefficient (R). The kobs values were checked against
those obtained from straight line plots of ln c vs time.
X-r a y Cr yst a l St r u ct u r e Det er m in a t ion of 3 a n d 4.
X-ray-suitable single crystals were obtained by slow diffusion
of pentane into toluene or of diethyl ether into dichloromethane
solutions of 3 or 4, respectively. Diffraction data were recorded
on a Nonius CAD4 single-crystal diffractometer. The intensi-
ties were measured using the ω-2θ scan technique. Three
standard reflections were monitored every 60 min. On all
reflections, profile analysis was performed.21 Some double-
measured reflections were averaged, and Lorentz and polar-
ization corrections were applied. The structure was solved by
Patterson interpretation and phase expansion using DIRDIF.22
Isotropic least-squares refinement on F2 was done using
1
(CDCl3): δ 19.68 s. H NMR (CDCl3): δ 4.30 (dt, J HH ) 14.0
2
Hz, J HP ) 11.1 Hz, 1H, PCHaHbP), 4.70 (dt, J HH ) 14.0 Hz,
2J HP ) 9.8 Hz, 1H, PCHaHbP), 5.03 (d, J HH ) 2.6 Hz, 2H,
H-1,3), 5.47 (t, J HH ) 2.6 Hz, 1H, H-2), 5.56 (s, 1H, dCH),
6.78-7.54 (m, 34H, PPh2, dCPh, tCPh, H-4,5,6,7). 13C{1H}
NMR (CDCl3): δ 47.83 (t, J CP ) 21.0 Hz, PCH2P), 70.28 (s,
C-1,3), 91.57 (s, C-2), 99.91 (s, CtCPh), 102.32 (s, CtCPh),
108.86 (s, C-3a,7a), 122.70 and 123.58 (s, C-4,5 and C-6,7),
123.88-132.44 (m, PPh2, dCPh, tCPh), 134.35 (t, 2J CP ) 13.7
Hz, Ru-C), 135.46 (t, J CP ) 21.3 Hz, PCipso), 139.20 (t, J CP
)
3
20.4 Hz, PCipso), 145.01 (t, J CP ) 5.8 Hz, dCHPh). ∆δ (C-3a,-
7a) ) -21.84. IR (KBr, cm-1): ν (CtC) 2154 w. MS (FAB,
m/e): 804 (M), 689 (M - C9H7), 601 (M - C16H11), 485 (M -
C9H7 - C16H11) (correct isotope patterns observed for each
fragment).
(21) (a) Lehman, M. S.; Larsen, F. K. Acta Crystallogr. A 1974, 30,
580. (b) Grant, D. F.; Gabe, E. J . J . Appl. Crystallogr. 1978, 11, 114.
(22) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF Program System; Technical Report of the Crystallographic
Laboratory; University of Nijimegen: Nijimegen, The Netherlands,
1996.
Syn t h esis of t h e Alk yn yla lk ylid en e Com p lex [R u {d
C(CtCP h )CH2P h }(η5-C9H7)(K2-P -dppm )][BF4] (4). A stirred
solution of the enynyl complex 3 (0.1 g, 0.12 mmol) in 20 mL

4822 Organometallics, Vol. 21, No. 22, 2002
Bassetti et al.
SHELXL97.23 Absorption correction was applied to 3 by means
of XABS2.24 During the final stages of the refinements, all
positional parameters and the anisotropic temperature factors
of all the non-H atoms were refined. The H atoms were
geometrically located and refined riding with common isotropic
thermal parameters. Atomic scattering factors were taken from
International Tables for X-ray Crystallography.25 Plots were
made with the EUCLID package.26 Geometrical calculations
were made with PARST.27 All calculations were made at the
Scientific Computer Centre of the University of Oviedo. The
most relevant crystal and refinement data are collected in
Table 3.
Ack n ow led gm en t. We thank COST CHEMISTRY
Action D12 (WG D12/0025/99), Ministerio de Ciencia y
Tecnolog´ıa of Spain (MCT-00-BQU-0227), CICYT
(BQU2000-0219), and FICYT (PR-01-GE-4) for financial
support.
(23) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, 1997.
(24) Parkin, S.; Moezzi, B.; Hope, H. J . Appl. Crystallogr. 1995, 28,
53.
(25) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham (Present distrubutor: Kluwer Academic Publishers:
Dordrecht), 1974; Vol. IV.
(26) Spek, A. L. PLATON, a multipurpose crystallographic tool;
Utrecht University: Utrecht, The Netherlands, 2000.
(27) Nardelli, M. Comput. Chem. 1983, 7, 95.
Su p p or tin g In for m a tion Ava ila ble: NMR spectra of
complexes 3 and 4, kinetic plots, X-ray crystallographic data
of 3 and 4, including tables of atomic coordinates, thermal
parameters, bond distances, and bond angles. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM020483A