Neutral carbene and vinylidene cyclopentadienyl ruthenium complexes with PPh2(2-MeC6H4)

Article abstract of DOI:10.1016/S0022-328X(00)00675-6

The complex [RuCl(η⁵-C₅H₅){PPh₂(2-MeC ₆H₄)}₂] (1), unlike the triphenylphosphine analog [RuCl(η⁵-C₅H₅)(PPh₃) ₂], reacts und

Full text of DOI:10.1016/S0022-328X(00)00675-6

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Journal of Organometallic Chemistry 617–618 (2001) 511–519
Neutral carbene and vinylidene cyclopentadienyl ruthenium
complexes with PPh2(2-MeC6H4)
Walter Baratta a,*1, Alessandro Del Zotto a, Eberhardt Herdtweck b, Sara Vuano a,
Pierluigi Rigo a,*2
a Dipartimento di Scienze e Tecnologie Chimiche, Uni6ersita` di Udine, Via Cotonificio 108, I-33100 Udine, Italy
b Anorganisch-chemisches Institut, Technische Uni6ersita¨t Mu¨nchen, Lichtenbergstrasse 4, D-85747 Garching, Germany
Received 7 August 2000; accepted 19 September 2000
Abstract
The complex [RuCl(h5-C5H5){PPh2(2-MeC6H4)}2] (1), unlike the triphenylphosphine analog [RuCl(h5-C5H5)(PPh3)2], reacts
under mild conditions with CO, N2CPh2 and HCꢀCPh to give the neutral carbonyl, carbene and vinylidene derivatives
[RuCl(h5-C5H5)(L){PPh2(2-MeC6H4)}] (L=CO 2, CPh2 5, CꢁCHPh 6), respectively, via displacement of one phosphine ligand.
The vinylidene complex 6 promptly reacts with benzylamine affording the aminocarbene [RuCl(h5-C5H5){ꢁC(NHCH2Ph)CH2Ph}
{PPh2(2-MeC6H4)}] (7). Moreover, the cyclometalated derivative [¸R¹u(¹h¹5-¹C¹5H¹5¹){¹P¹P¹h2¹(2¹-CºH2C6H4)}{PPh2(2-MeC6H4)}]
(4) has been obtained from the methyl complex [RuMe(h5-C5H5){PPh2(2-MeC6H4)}2] (3) by intramolecular C–H bond cleavage
and methane elimination. Complex 1, whose X-ray structure analysis is also reported, has been found to catalyze alkyne coupling
reactions. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ruthenium; Carbenes; Vinylidenes; Cyclometalation
applications of [RuCl(h5-C5H5)(PPh3)2]. Thus, displace-
ment of one PPh3 and formation of neutral vinylidene
1. Introduction
complexes has not been observed in the reaction with
1-alkynes, whereas this process readily occurs in the
case of [RuCl(h5-C5Me5)(PPh3)2] [4]. Werner success-
fully synthesized the first neutral cyclopentadienyl vi-
nylidene complex [RuCl(h5-C5H5)(ꢁCꢁCHCO2Me)-
(PPh3)], but in a stepwise process starting from the allyl
derivative [Ru(h3-C3H5)(h5-C5H5)(PPh3)] [5]. By con-
trast, cationic complexes of general formula [Ru(h5-
C5H5)(ꢁCꢁCHR)(PPh3)2]+ have been obtained by ready
dissociation of the halide, especially in polar solvents
[6].
Recently, we have reported that the complexes
[RuCl(h5-C5H5)(PR3)2] can act as effective catalysts in a
variety of reactions involving diazocompounds, such as
stereoselective carbene–carbene coupling [7], cyclo-
propanation [8], carbene insertion into N–H and S–H
bonds [9], and nitrogen ylide generation [10]. The key
step of these catalytic processes is the formation of the
carbene intermediate [RuCl(h5-C5H5)(ꢁCHR)(PR3)]
from the 16-electron species [RuCl(h5-C5H5)(PR3)].
The easily accessible half-sandwich ruthenium com-
plex [RuCl(h5-C5H5)(PPh3)2] exhibits a rich chemistry,
which is an area of current active interest [1]. Its high
reactivity appears to be related to the facile displace-
ment of one of the coordinate ligands, affording neutral
or cationic 16-electron unsaturated species. In polar
solvents the chloride is readily exchanged with neutral
ligands (L), providing a convenient entry for a variety
of cationic complexes of the type [Ru(h5-C5H5)-
(PPh3)2(L)]+ (L=CO, RCN, PR3, etc.) [1c]. In non-po-
lar solvents, dissociation of one PPh3 leads to the
transient [RuCl(h5-C5H5)(PPh3)] complex, which can
add p-acceptor ligands such as CO [2] and monodentate
phosphines [3]. However, the extrusion of PPh3 to
create coordinative unsaturation requires severe condi-
tions [2], and this limits the synthetic and catalytic
1 *Corresponding author. E-mail: inorg@dstc.uniud.it
2 *Corresponding author. Tel.: +39-432-558801; fax: +39-432-
558803; e-mail: pierluigi.rigo@dstc.uniud.it
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00675-6

512
W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
from [RuMe(h5-C5H5){PPh2(2-MeC6H4)}2] (3) through
Bulky phosphines favor the reaction as shown by the
fact that [RuCl(h5-C5H5){PPh2(2-MeC6H4)}2] (1) is cat-
alytically active below 20°C, whereas the PPh3 analog
needs heating at 60°C [7b]. The facile displacement of
one phosphine in complex 1 is also apparent in the
reaction with diethyl maleate (DEM) which leads to the
formation of complex [RuCl(h5-C5H5)(h2-DEM){PPh2-
(2-MeC6H4)}] [7b]. The easy cleavage of one Ru–P
bond in 1 prompted us to carry out a specific investiga-
tion on its properties and its ability to form isolable
neutral carbene and vinylidene derivatives. Ruthenium
organometallic compounds of this type continue to
attract interest, because of their potential use in stoi-
chiometric and catalytic C–C bond forming reactions
[11] and alkyne dimerization [12].
We report herein the preparation in high yield of
the new carbene and vinylidene derivatives [RuCl
(h5-C5H5)(ꢁCPh2){PPh2(2-MeC6H4)}] (5) and [RuCl-
(h5-C5H5)(ꢁCꢁCHPh){PPh2(2-MeC6H4)}] (6) from the
easily available precursor 1. Complex 6 reacts with
benzylamine affording the aminocarbene [Ru-
Cl(h5 - C5H5){ꢁC(NHCH2Ph)CH2Ph}{PPh2(2 - MeC6-
H4)}] (7). Furthermore, complex 1, whose X-ray struc-
ture is also reported, was found to catalyze the cy-
clotrimerization of dimethyl ac¸et¹yl¹en¹e¹d¹ic¹ar¹b¹ox¹yºlate.
The cyclometalated derivative [Ru(h5-C5H5){PPh2(2-
CH2C6H4)}{PPh2(2-MeC6H4)}] (4) is easily formed
methane elimination.
2. Results and discussion
2.1. Structural characterization and reacti6ity of
[RuCl(p5-C5H5){PPh2(2-MeC6H4)}2] (1)
During studies directed towards the synthesis of cy-
clopentadienylruthenium complexes containing bulky
phosphines, we have recently isolated the complex
[RuCl(h5-C5H5){PPh2(2-MeC6H4)}2] (1) in high yield in
a one-pot reaction from ruthenium trichloride, cy-
clopentadiene and PPh2(2-MeC6H4) [7b]. Among the
few cyclopentadienylruthenium compounds bearing
phosphines with a cone angle larger than that of PPh3
(145°), 1 has been found to be the most reactive in
several catalytic reactions [7b,8]. With the aim of com-
paring structurally the PPh3 and the PPh2(2-MeC6H4)
systems, complex 1 was investigated by X-ray single-
crystal analysis. The crystallographic parameters are
collected in Table 1, whereas an ORTEP view of 1 is
shown in Fig. 1 with selected bond distances and
angles.
The geometry of 1 is distorted octahedral about the
ruthenium center due to the severe steric interactions
between the phosphines. The two phosphorus ligands
are not equivalent and one methyl group of the tolyl
substituent is directed towards the chloride ligand. The
Ru–P and Ru–Cl distances are very similar to those
reported for the PPh3 analog but with a slightly smaller
P–Ru–P angle (101.12° versus 103.99° [13]).
Table 1
Crystallographic data for 1·C2H6O
Empirical formula
Formula weight
Crystal system
C45H45ClOP2Ru
800.27
Monoclinic
P21/c (no. 14)
Complex 1 is thermally stable in toluene solution
under inert atmosphere even at 100°C, but decomposes
in air within a few minutes at room temperature with
the formation of phosphine oxide and brown insoluble
products. The 31P-NMR spectra of 1 show that the
compound has a fluxional behavior in solution on the
NMR time-scale. Thus, at 20°C the 31P{1H}-NMR
spectrum shows a sharp singlet at l=37.9 and no
phosphine dissociation is observed even at 100°C. On
cooling, the signal broadens and at −80°C the spec-
trum displays an AX pattern with two doublets at
Space group
Unit cell parameters
,
a (A)
11.446(1)
11.797(1)
28.238(2)
98.01(1)
3775.7(5)
4
1.408
1656
0.606
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
Dcalc (g cm−3
F(000)
)
v (mm−1
)
q range for data collection (°)
Limiting hkl indices
Reflections collected
2.26–25.67
913, 914, 934
52576
2
l=43.2 and 35.6, and J(P,P)=35.4 Hz. The observed
Independent reflections (all data)
Observed reflections (Io\2|(Io))
Data/restraints/parameters
6847
5118
6847/0/469
0.0327/0.0453
0.0943
0.936
0.0686/0
0.60, −0.26
behavior is reversible and may be explained by the low
temperature restricted rotation of the phenyl and tolyl
rings that leads to the magnetic inequivalence of the
two phosphorus atoms.
Although there is no significant structural difference
between the PPh3 and the PPh2(2-MeC6H4) derivatives,
their behavior in phosphine-substitution reactions is
markedly different. It has been reported that one PPh3
ligand in [RuCl(h5-C5H5)(PPh3)2] can be replaced by
CO under forcing carbonylation conditions (150 atm
carbon monoxide, 70°C, 48 h) [2], whereas at lower CO
a
R1 (Io\2|(Io)/all data)
b
wR2
GOF c
d
Weights a/b
−3
,
Largest difference peak and hole (e A
)
a R1=ꢀ(ꢁꢁFoꢁ−ꢁFcꢁꢁ)/ꢀꢁFoꢁ.
b wR2=[ꢀw (Fo2−Fc2)2/ꢀw(Fo2)2]1/2
.
c GOF=[ꢀw(F2o−Fc2)2/(NO−NV)]1/2
.
d w=1/[|2(F2o)+(aP)2+bP] with P: [max (0 or Fo2)+2F2c]/3.

W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
513
Fig. 1. ORTEP representation of the molecular structure of 1 in the solid state. Thermal ellipsoids are at the 50% probability level. Hydrogens
,
omitted for clarity. Selected bond lengths [A] and angles [°]: Ru–Cl 2.4372(8), Ru–P1 2.3271(7), Ru–P2 2.3390(8), Ru–C1 2.167(3), Ru–C2
2.167(3), Ru–C3 2.198(3), Ru–C4 2.204(3), Ru–C5 2.203(3); C1–Ru–P1 92.92(3), C1–Ru–P2 87.85(3), P1–Ru–P2 101.12(2), Ru–P1–C11
111.34(9), Ru–P1–C21 125.20(11), Ru–P1–C31 114.18(9), Ru–P2–C41 114.67(9), Ru–P2–C51 112.45(9), Ru–P2–C61 119.71(8), P1–Ru–Cen
120.9, P2–Ru–Cen 122.8, Cl–Ru–Cen 123.2. Cen: centroid of the C5H5–ligand.
Scheme 1.
The 13C{1H}-NMR spectrum of 2 in CDCl3 shows a
pressure (2 atm) sulfur is needed to remove the phos-
phine as SꢁPPh3 [14]. By contrast, the monocarbonyl
derivative [RuCl(h5-C5H5)(CO){PPh2(2-MeC6H4)}] (2)
was obtained quantitatively by stirring 1 under 1 atm
CO at room temperature within a few minutes (Scheme
1).
doublet at l=203.8 (2J(C,P)=20.0 Hz), whereas the
wCO appears at 1946 cm−1, and is shifted 12 cm−1
to lower wavenumbers compared to [RuCl(h5-
C5H5)(CO)(PPh3)] [14], in agreement with the more
basic character of the ortho-methylated phosphine.

514
W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
Moreover, treatment at 25°C of 1 in C6D6 with an
equimolar amount of PPh3 promptly affords the mixed
phosphine complex [RuCl(h5-C5H5)(PPh3){PPh2(2-
MeC6H4)}], whose 31P{1H}-NMR spectrum exhibits
(PPh3)2] for which heating at 100°C for 6 h is necessary.
In both cases cyclometalation probably occurs by in-
tramolecular C–H bond cleavage, induced by the gen-
eration of a vacant coordination site at the metal
center. Therefore, formation of 4 is favored by the
more facile dissociation of one phosphine to give the
2
two doublets at l=40.8 and 38.8 with J(P,P)=41.7
Hz. Addition of a twofold molar amount of PPh3 to 1
at 50°C gives [RuCl(h5-C5H5)(PPh3)2] quantitatively, as
result of complete displacement of PPh2(2-MeC6H4).
Aryl phosphines with methyl groups in ortho posi-
tion have been extensively employed to synthesize cy-
clometalated complexes [15], which result from
intramolecular C–H activation of methyl groups, and
coordinatively
unsaturated
16-electron
species
[RuMe(h5-C5H5)(PR3)]. W¸e ¹ca¹n¹¹ob¹s¹er¹vºe that a related
cyclometalated complex [RuCl{PPh2(2-CH2C6H4)}(h6-
C6Me6)] was obtained by the reaction of [RuCl2{PPh2-
(2-MeC6H4)}(h6-C6Me6)] with Na2CO3 in 2-propanol
[19]. However, attempts to obtain 4 by treatment of 1
with Na2CO3 in 2-propanol or CaH2 in toluene resulted
in the formation of only trace amounts of the cy-
clometalated product.
more recently to prepare
a 14-electron complex
[RuCl2{PPh2(2,6-Me2C6H3}2] stabilized by two agostic
interactions [16]. In the case of 1, cyclometalation was
not observed even when it was refluxed in toluene and
in the presence of base. However, starting from the
methyl derivative [RuMe(h5-C5H5){PPh2(2-MeC6H4)}2]
2.2. Preparation of carbene and 6inylidene complexes
¸¹¹¹¹¹¹¹¹¹¹º
(3), the cyclometalated complex [Ru(h5-C5H5){PPh2(2-
CH2C6H4)}{PPh2(2-MeC6H4)}] (4) can be easily ob-
tained according to the procedure adopted by
The synthesis of electrophilic carbene complexes of
ruthenium still remains an area of great interest because
of the manifold applications in organic synthesis for
C–C carbon bond forming reactions. We have now
Lehmkuhl for the synthesis of the orthometalated
¸¹¹¹¹¹¹¹¹¹¹¹¹º
product
[Ru(h5-C5H5){PPh2(2-C6H4)}(PPh3)]
[17].
found that compound
1 reacts with diphenydi-
Treatment of 1 in toluene at −40°C with a slight
excess of methylmagnesium bromide in diethyl ether
gave complex 3, which was isolated as yellow powder in
78% yield (Scheme 1). The most characteristic feature
in the 1H-NMR spectrum of 3 is the presence of a
azomethane in toluene at 40°C affording the green
carbene complex [RuCl(h5-C5H5)(ꢁCPh2){PPh2(2MeC6-
H4)}] (5), which was isolated in 81% yield and charac-
terized by elemental analysis and NMR spectroscopy
(Scheme 1). The presence of a carbene ligand in 5 was
unambiguously established by the 13C{1H}-NMR spec-
trum which contains a typical doublet at l=319.3 with
3
triplet at l=0.82 with a J(H,P)=6.1 Hz, whereas the
13C-NMR DEPT spectrum shows a singlet at l=1.5,
attributed to the Ru–CH3 methyl. This product slowly
decomposes in solution at room temperature with
methane evolution and the reaction can be readily
monitored by 31P{1H}-NMR. When heated in toluene
at 70°C, 3 is quantitatively converted into complex 4
within 30 min (Scheme 1). The yellow complex 4 was
isolated and fully characterized. Consistent with the
cyclometalated structure, the 31P{1H}-NMR spectrum
shows two doublets at l 75.2 and 59.4 with a 2J(P,P)=
34.2 Hz. The strongly downfield-shifted resonance is
attributed to the P atom of the cyclometalated phos-
phine that is part of a five-membered chelate ring [18].
2
a J(C,P)=15.3 Hz, attributed to the RuꢁC carbon;
these values are similar to those reported for [RuCl(h5-
C5H5)(ꢁCPh2)(PPh3)] [11b]. It should be mentioned that
we have recently reported that complex 1 and the PPh3
analog efficiently catalyze the cyclopropanation of sty-
rene and other electron-rich alkenes in the presence of
ethyl diazoacetate. Moreover, when diphenyldiazo-
methane is employed as carbene source, the reaction
with styrene affords mainly 1,1,3-triphenylpropene, as
result of a formal :CPh2–:CHCH2Ph coupling. For
these catalytic reactions there is strong evidence that
complexes of type 5 are key intermediates in the C–C
coupling processes [8].
1
In the H-NMR spectrum the two signals due to the
Ru–CH2 methylene appear as a doublet at 4.44 ppm
with a J(H,H)=15.5 Hz and a doublet of doublets at
4.26 ppm with a J(H,P)=7.0 Hz as inferred by
1H{31P}-NMR experiments. Furthermore, the 13C{1H}-
NMR signal at l=13.1 (part of an AXY spin system,
Complex 1 is also an excellent starting material to
give neutral alkyne or vinylidene ruthenium complexes.
Indeed, selective dimerization of alkynes [12] is thought
to occur via ruthenium vinylidene intermediates which
are also involved in various other ruthenium catalyzed
reaction of acetylenes [20].
2
2J(C,P)=12.3 Hz, J(C,P%)=8.4 Hz) was attributed to
the RuCH2 carbon through a 13C-NMR DEPT experi-
ment. Complex 4 is relatively stable in solution and no
phosphine displacement was observed by reaction with
CO or CNtBu ligand.
Treatment of 1 in CDCl3 with an equimolar amount
of internal alkynes RCꢀCR containing electron-with-
drawing groups such as R=CO2Me leads to the alkyne
complex
[RuCl(h5-C5H5)(h2-MeO2CCꢀCCO2Me)-
It should be noted that cyclometalation in 3 proceeds
{PPh2(2-MeC6H4)}] which was found in equilibrium
more easily than in the PPh3 analog [RuMe(h5-C5H5)
with the starting product. The 31P{1H}-NMR spectrum

W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
515
exhibits a signal at l=45.5, whereas the 1H-NMR
spectrum shows a resonance at l=5.08 for the cy-
clopentadienyl ligand and a broad signal at 3.52 ppm
for the methyl protons of the coordinated alkyne. It
should be noted that a similar p-alkyne complex
sion into the vinylidene complex (30%) and prolonged
heating of the reaction mixture led to catalytic alkyne
dimerization. The results here obtained for 1 can be
compared with those previously reported for the 16-
electron derivatives [RuCl(h5-C5Me5)(L)] (L=N-hete-
rocyclic carbene). With the latter, we observed highly
efficient catalytic dimerization of terminal alkynes, with
no detection of the corresponding vinylidene complexes
[24]. The systems [RuCl(h5-C5H5)(PR3)2] with bulky
phosphines are currently under investigation to estab-
lish their potential in catalytic alkyne coupling reac-
tions. On the other hand, stoichiometric C–C coupling
reactions of terminal alkynes in cyclopentadienyl ruthe-
nium complexes have been extensively described [25].
Finally, we tested the reactivity of the ruthenium-
vinylidene 6 towards nucleophiles such as amines. Due
to the electrophilic character of the a-carbon atom in
vinylidene complexes, it is well known that these species
promptly react with primary amines to give aminocar-
bene complexes via intermolecular nucleophilic attack
of the nitrogen atom [26]. Thus, treatment of 6 with an
equimolar amount of benzylamine at room temperature
in toluene led to complex [RuCl(h5-C5H5){ꢁC(NHCH2-
Ph)CH2Ph}{PPh2(2-MeC6H4)}] (7), which was isolated
in 55% yield after appropriate work-up (Scheme 1). The
formation of the aminocarbene ligand was unequivo-
cally established by 1H and 13C-NMR spectroscopy.
[OsCl(h5-C5H5)(h2-MeCO2CꢀCCO2Me)(PiPr3)]
has
been obtained by reaction of the alkyne with [OsCl(h5-
C5H5)(PiPr3)2] [21], which also shows a high tendency to
release a phosphine ligand in solution. When complex 1
(3 mol%) is added to a CDCl3 solution of dimethyl
acetylenedicarboxylate, a catalytic cyclotrimerization
occurs at room temperature with 90% conversion of the
alkyne into hexamethyl benzenehexacarboxylate after 1
day [22].
By contrast, the reaction of 1 with terminal alkynes
leads to formation of neutral vinylidene derivatives.
Thus, treatment of a CHCl3 solution of 1 with phenyl-
acetylene in excess at reflux affords the neutral vinyli-
dene
complex
[RuCl(h5-C5H5)(ꢁCꢁCHPh){PPh2-
(2-MeC6H4)}] (6), isolated as a pale brown powder in
63% yield (Scheme 1). The most characteristic feature
in the 13C{1H}-NMR spectrum of 6 is the presence of a
doublet at l=345.6 with a J(P,C)=20.4 Hz for the
carbon bound to ruthenium, whereas the 1H-NMR
spectrum shows a singlet at 4.74 ppm for the vinylidene
proton, and these values are close to those given by
[RuCl(h5-C5Me5)(ꢁCꢁCHPh)(PPh3)] [4a]. It should be
noted that the reaction of the above-mentioned
[OsCl(h5-C5H5)(PiPr3)2] with phenylacetylene initially
gives [OsCl(h5-C5H5)(h2-HCꢀCPh)(PiPr3)] which subse-
quently isomerizes to [OsCl(h5-C5H5)(ꢁCꢁCHPh)-
(PiPr3)] [21]. By contrast, in the formation of 6 from 1,
the p-alkyne intermediate was not detected. The nature
of the solvent seems to play a delicate role for the
isolation of the vinylidene complexes. In fact, if toluene
is used instead of CHCl3, complex 6 is formed in low
amounts along with catalytic conversion of phenyl-
acetylene into the dimers arising from head-to-head and
head-to-tail alkyne coupling. Also the type of alkyne
seems to be important for the isolation of the vinyli-
dene derivative. Although the reaction of 1 with a series
of terminal alkynes HCꢀCR (R=CH2Ph, SiMe3,
CO2Me) in CHCl3 leads to mixtures of products, with
HCꢀCtBu we were able to detect the corresponding
vinylidene complex. Reaction of a CDCl3 solution of 1
with HCꢀCtBu in the presence of CuCl, which has been
used as phosphine scavenger for ruthenium complexes
[23], in 1:10:2 molar ratio at 70° C for 5 min, afforded
1
The H-NMR spectrum of 7 exhibits a signal at l=
10.39 for the NH proton with two doublets at l=4.83
and 3.89 for the diasterotopic ꢁCCH2 protons, whereas
the 13C{1H}-NMR spectrum shows a doublet at 255.0
ppm with J(C,P)=16.3 Hz for the RuꢁC carbon,
which agree well with the literature data [27].
3. Concluding remarks
This study has revealed that the use of PPh2(2-
MeC6H4) as auxiliary ligand in cyclopentadienylruthe-
nium complexes gives rise to a derivative related to
[RuCl(h5-C5H5)(PPh3)2], but with a remarkably higher
reactivity. The easily accessible complex 1 is a conve-
nient starting material for the preparation of neutral
cyclopentadienylruthenium carbene and vinylidene
derivatives. This results from the high tendency of 1 to
release one phosphine ligand to give the coordinatively
unsaturated [RuCl(h5-C5H5){PPh2(2-MeC6H5)}] species
which can add a variety of p-acceptor ligands. Proba-
bly, as suggested by Nolan et al. on the basis of
thermochemical studies on [RuCl(h5-ligand)(PR3)2]
complexes [28], the high steric requirements of the
PPh2(2-MeC6H4) ligand are responsible for the weaken-
ing of the Ru–P bond in 1, allowing easier formation
of the 16-electron complex intermediate. The new
ruthenium complexes 5 and 6, which have been iso-
lated, are thought to be key intermediates in C–C bond
almost
quantitatively
the
complex
[RuCl(h5-
C5H5)(ꢁCꢁCHtBu){PPh2(2-MeC6H4)}] as inferred by
1H and 31P-NMR data. The 31P{1H}-NMR spectrum
shows a signal at l=51.1, whereas the H-NMR spec-
1
trum shows singlets at l=5.02 for the cyclopentadienyl
ring and l=3.74 for the CꢁCH vinylidene proton,
which can be compared with those of 6. In the reaction
performed without CuCl we observed a lower conver-

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W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
forming reactions. Thus, the carbene derivative 5 has
been found to be involved in the catalytic synthesis of
the trisubstituted olefin 1,1,3-triphenylpropene from
diphenyldiazomethane and styrene [8], whereas complex
6 is formed in the catalytic phenylacethylene dimeriza-
tion. It is noteworthy that in the reactions of alkynes
with [RuCl(h5-C5H5)(PR3)2] systems, displacement of
one PR3 ligand and formation of a neutral complex
have not been observed prior to this work. In conclu-
sion, complex 1 provides a useful alternative to the
widely employed PPh3 analog in catalytic processes
which occur through phosphine displacement.
C5H5), 23.2 (d, J(C,P)=5.9 Hz; CH3). 31P{1H}-NMR
(CDCl3, 25°C): l=46.9. IR (nujol): w(CO)=1946 cm−1
.
4.2. Synthesis of [RuMe(p5-C5H5){PPh2(2-MeC6H4)}2]
(3)
Methylmagnesium bromide (0.21 ml of a 3.0 M
solution in diethyl ether, 0.630 mmol) was added drop-
wise to 1 (0.400 g, 0.530 mmol) dissolved in toluene (20
ml) at −40°C. The yellow mixture was allowed to
attain room temperature and stirred for 15 min. After
filtration on alumina, the solvent was removed and
pentane (5 ml) was added affording a yellow product,
which was filtered, recrystallized from toluene–heptane
and dried under reduced pressure. Yield: 0.304 g (78%).
Anal. Calc. for C44H42P2Ru: C, 72.02; H, 5.77. Found:
C, 71.35; H, 5.65%.
4. Experimental
All reactions were carried out under an argon atmo-
sphere using standard Schlenck techniques. Solvents
were carefully dried by conventional methods and dis-
tilled under argon before use. Phenylacetylene, benzyl-
amine and methylmagnesium bromide 3.0 M solution
in diethyl ether were purchased from Aldrich Chemical
Co. The compounds 1 [7b] and N2CPh2 [29] were
prepared according to the literature. NMR measure-
ments were carried out using a Bruker AC 200 spec-
trometer. Chemical shifts, in ppm, are relative to TMS
1
Spectroscopic data: H-NMR (C6D6, 25°C): l=8.0–
6.7 (m, 28H; aromatic protons), 4.23 (s, 5H; C5H5),
1.77 (s, 6H; CH3), 0.82 (t, J(H,P)=6.1 Hz, 3H;
RuCH3). 13C{1H}-NMR (C6D6, 5°C): l=138.0–124.9
(aromatic carbons), 84.5 (t, J(C,P)=2.0 Hz; C5H5),
23.5 (s; CCH3), 1.5 (s; RuCH3). 31P{1H}-NMR (C6D6,
25°C): l=53.9.
¸¹¹¹¹¹¹¹¹¹¹¹¹º
4.3. Synthesis of [Ru(p5-C5H5){PPh2(2-CH2C6H4)}-
1
for H and 13C, and to external 85% H3PO4 for 31P. IR
{PPh2(2-MeC6H4)}] (4)
spectra were recorded with a Nicolet Magna 550 FT
spectrometer. Elemental analyses (C, H, N) were per-
formed by the Microanalytical Laboratory of our
department.
The complex 3 (0.300 g, 0.409 mmol) was dissolved
in toluene (5 ml) and the solution was heated at 70°C
for 30 min. The solvent was eliminated and the oily
product was treated with pentane (5 ml) affording a
yellow precipitate. The product was filtered, recrystal-
lized from toluene–heptane and dried under reduced
4.1. Synthesis of
[RuCl(p5-C5H5)(CO){PPh2(2-MeC6H4)}] (2)
pressure. Yield: 0.220
g (75%). Anal. Calc. for
C43H38P2Ru: C, 71.95; H, 5.34. Found: C, 71.61; H,
5.29%.
Spectroscopic data: H-NMR (C6D6, 25°C): l=8.0–
The complex 1 (260 mg, 0.345 mmol) was dissolved
in 5 ml of toluene and the solution was stirred under
CO (1 atm) at room temperature for 1 h. The volume
was reduced to 2 ml and heptane was added affording
a yellow precipitate. After filtration the product was
washed with heptane and dried under reduced pressure.
Yield: 151 mg (86%). Anal. Calc. for C25H22ClOPRu:
C, 59.35; H, 4.38. Found: C, 58.90; H, 4.41%.
1
6.6 (m, 28H; aromatic protons), 4.44 (d, J(H,H)=15.5
Hz, 1H; RuCH2), 4.26 (s, 5H; C5H5), 3.08 (dd,
J(H,H)=15.5 Hz, J(H,P)=7.0 Hz, 1H; RuCH2), 1.77
(s, 3H; CH3). 13C{1H}-NMR (C6D6, 25°C): l=146.0–
124.5 (aromatic carbons), 83.5 (t, J(C,P)=2.0 Hz;
C5H5), 23.4 (d, J(C,P)=4.5 Hz; CH3), 13.1 (dd,
J(C,P)=12.3 Hz, J(C,P)=8.4 Hz; RuCH2). 31P{1H}-
NMR (C6D6, 25°C): l=75.2 (d, J(P,P)=34.2 Hz),
59.4 (d, J(P,P)=34.2 Hz).
Spectroscopic data: 1H-NMR (CDCl3, 25°C): l=
7.42–6.63 (m, 14H; aromatic protons), 4.65 (s, 5H;
C5H5), 2.08 (s, 3H; CH3). 13C{1H}-NMR (CDCl3,
25°C): l=203.8 (d, J(C,P)=20.0 Hz; CO), 141.5 (d,
J(C,P)=9.6 Hz; CMe), 134.8 (d, J(C,P)=11.2 Hz;
o-C6H5), 134.0 (d, J(C,P)=46.1 Hz; ipso-C6H5), 133.4
(d, J(C,P)=10.4 Hz; o-C6H5), 132.9 (d, J(C,P)=10.4
Hz; o-C6H4), 132.0 (d, J(C,P)=7.8 Hz; m-C6H4), 131.5
(d, J(C,P)=45.0 Hz; ipso-C6H4), 130.5–130.2 (p-C6H4
and p-C6H5), 128.4 (d, J(C,P)=10.4 Hz; m-C6H5),
128.2 (d, J(C,P)=10.4 Hz; m-C6H5), 125.7 (d,
J(C,P)=9.7 Hz; m-C6H4), 85.6 (d, J(C,P)=1.9 Hz;
4.4. Synthesis of [RuCl(p5-C5H5)(ꢁCPh2)-
{PPh2(2-MeC6H4)}] (5)
The complex 1 (260 mg, 0.345 mmol) and diphenyldi-
azomethane (150 mg, 0.772 mmol) were dissolved in 10
ml of toluene and the red solution was stirred at 45°C
overnight. Diphenyldiazomethane (75 mg, 0.386 mmol)

W. Baratta et al. / Journal of Organometallic Chemistry 617–618 (2001) 511–519
517
was added to the resulting green solution, which was
stirred at 55°C for 2 h and concentrated to 1 ml.
Addition of heptane (10 ml) afforded a green precipi-
tate which was recrystallized from toluene–heptane and
dried under reduced pressure. Yield: 180 mg (81%).
Anal. Calc. for C37H32ClPRu: C, 69.00; H, 5.01.
Found: C, 69.30; H, 5.16%.
10.38 (s broad, 1H; NH), 8.7–6.8 (m, 24H, aromatic
protons), 4.83 (d, J(H,H)=15.2 Hz, 1H; CH2Cꢁ), 4.37
(s, 5H, C5H5), 4.01 (dd, J(H,H)=14.5 Hz, J(H,H)=
6.1 Hz, 1H; CH2NH), 3.89 (d, J(H,H)=15.2 Hz, 1H;
CH2Cꢁ), 3.30 (dt, J(H,H)=15.0 Hz, J(H,H)=3.0 Hz,
1H; CH2NH), 1.85 (s, 3H; CH3). 13C{1H}-NMR (C6D6,
25°C): l=255.0 (d, J(C,P)=16.3 Hz; RuꢁC); 142.3–
125.6 (aromatic carbons), 81.6 (d, J(C,P)=2.0 Hz;
C5H5), 51.2 (s; NCH2), 32.2 (s; CH2Ph), 23.6 (d,
J(C,P)=5 Hz; CH3). 31P{1H}-NMR (C6D6, 25°C):
l=54.1.
Spectroscopic data: 1H-NMR (C6D6, 25°C): l=
7.75–6.75 (m, 24H; aromatic protons), 4.69 (s, 5H;
C5H5), 1.73 (s, 3H; CH3). 13C{1H}-NMR (C6D6, 25°C):
l=319.3 (d, J(C,P)=15.3 Hz; RuꢁC), 165.2 (d,
J(C,P)=4.3 Hz; ipso-C6H5), 144.2–125.3 (aromatic
carbons), 90.7 (d, J(C,P)=3.0 Hz; C5H5), 23.4 (d,
J(C,P)=4.3 Hz; CH3). 31P{1H}-NMR (C6D6, 25°C):
l=44.9.
4.7. X-ray structure determination for the complex
1·C2H6O
Crystal data and details of the structure determina-
tion are presented in Table 1. Suitable single crystals
for the X-ray diffraction study were grown by cooling a
concentrated solution of 1 in dichloromethane–ethanol.
A clear red–brown fragment (0.34×0.42×0.57 mm)
was stored under perfluorinated ether, transferred in a
Lindemann capillary, fixed and sealed. Preliminary ex-
amination and data collection were carried out on an
imaging plate diffraction system (Ipds; Stoe&Chi)
equipped with a rotating anode (Nonius; Fr951) and
graphite monochromated Mo–Ka radiation (u=
4.5. Synthesis of [RuCl(p5-C5H5)(ꢁCꢁCHPh)-
{PPh2(2-MeC6H4)}] (6)
Phenylacetylene (1.5 ml, d=0.93 g ml−1, 13.7 mmol)
was added to 1 (1.00 g, 1.33 mmol) dissolved in chloro-
form (20 ml). The solution was heated at the reflux
point for 1 h and the solvent was completely removed
under reduced pressure. The resulting oily product was
treated with 50 ml of heptane and the suspension was
stirred overnight. After filtration, the product was dis-
solved in chloroform (20 ml) and phenylacetylene (1.5
ml, 13.7 mmol) was added. The solution was refluxed
for 1 h and the solvent was removed under reduced
pressure. The product was suspended in heptane (50
ml) and stirred overnight. After filtration the pale
brown product was recrystallized from CH2Cl2–hep-
tane and dried under reduced pressure. Yield: 0.487 g
(63%). Anal. Calc. for C32H28ClPRu: C, 66.26; H, 4.87.
Found: C, 66.10; H, 4.84%.
,
0.71073 A). The unit cell parameters were obtained by
full-matrix least-squares refinement of 4705 reflections.
Data collection were performed at 293 K (q range
2.26°BqB25.67°; exposure time 300 s per image; os-
cillation scan modus €=0° to 360° with D€=1.0°). A
total number of 52576 reflections were collected. Raw
data were corrected for Lorentz, polarization, decay
and absorption effects. After merging (Rint=0.042) a
sum of 6847 independent reflections remained and were
used for all calculations. The structure was solved by a
combination of direct methods and difference Fourier
syntheses. All non-hydrogen atoms of the compound
1·C2H6O were refined anisotropically. All hydrogen
atoms were calculated in ideal positions (riding model).
Full-matrix least-squares refinements with 469 parame-
ters were carried out by minimizing ꢀw(F2o−Fc2)2 with
the SHELXL-97 weighting scheme and stopped at shift/
errB0.001. Neutral atom scattering factors for all
atoms and anomalous dispersion corrections for the
non-hydrogen atoms were taken from International
Tables for Crystallography. All calculations were per-
formed on a DEC 3000 AXP workstation and an Intel
Pentium II PC, with the STRUX-V system, including the
Spectroscopic data: 1H-NMR (CDCl3, 25°C): l=
7.8–6.8 (m, 19H; aromatic protons), 5.17 (s, 5H; C5H5),
4.74 (s, 1H; CꢁCH), 2.19 (s, 3H; CH3). 13C{1H}-NMR
(CDCl3, 25°C): 345.6 (d, J(C,P)=20.4 Hz; RuꢁC),
142.2–124.8 (aromatic carbons), 118.2 (s; ꢁCHPh), 92.5
(d, J(C,P)=2.5 Hz; C5H5), 23.3 (d, J(C,P)=5.1 Hz;
CH3). 31P{1H}-NMR (CDCl3, 25°C): l=50.5.
4.6. Synthesis of [RuCl(p5-C5H5){ꢁC(NHCH2Ph)-
CH2Ph}{PPh2(2-MeC6H4)}] (7)
Benzylamine 45 ml (d=0.98 g ml−1, 0.412 mmol)
was added to 6 (0.200 g, 0.345 mmol) dissolved in
toluene (6 ml) and the solution was stirred for 30 min.
After filtration the solution was concentrated to 1 ml
and heptane (4 ml) was added affording a yellow
precipitate. The product was recrystallized from tolu-
ene–heptane and dried under reduced pressure. Yield:
0.13 g (55%). Anal. Calc. for C39H37ClNPRu: C, 68.16;
H, 5.43; N, 2.04. Found: C, 67.94; H, 5.28; N, 1.93%.
Spectroscopic data: 1H-NMR (C6D6, 25°C): l=
programs PLATON, SIR92, and SHELXL-97 [30].
5. Supplementary material
Crystallographic data (excluding structure factors)
for the structure reported in this paper have been

518
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deposited with the Cambridge Crystallographic Data
Centre as supplementary publication CCDC no. 149912
(1). Copies of the data can be obtained, free of charge
on application to The Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (Fax: +44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
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This work was supported by the Italian Ministero
dell’Universita` e della Ricerca Scientifica e Tecnologica
(MURST), Regione Friuli Venezia Giulia and the
Bayerische Forschungsstiftung (FORKAT). The au-
thors thank Dr P. Martinuzzi of the Dipartimento di
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for assistance in NMR measurements.
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