Synthesis of ruthenium phenylindenylidene, carbyne, allenylidene and vinylmethylidene complexes from (PPh3)3-4RuCl2: A mechanistic and structural investigation

Article abstract of DOI:10.1016/j.jorganchem.2007.08.005

The reaction of (Ph₃P)₃RuCl₂ with 1,1-diphenyl-2-propyn-1-ol was investigated in various solvents. The reaction in thf under reflux is reported to produce the (PPh₃)₂Cl₂Ru(3-phenylindenylidene) complex (3) which has undergone rearrangement of the allenylidene C₃-spine. We have improved the reliability of the reported synthesis by adding acetyl chloride which converts the formed water of the reaction and thus increases the acidity of the reaction solution. Without the additive, we observed the exclusive formation of an intermediate of the transformation and identified it as dinuclear (PPh₃)₂ClRu(μ-Cl)₃(PPh₃)₂Ru{double bond, long}C{double bond, long}C{double bond, long}CPh₂ complex (5). The reaction of (Ph₃P)_3-4RuCl₂ with 1,1-diphenyl-2-propyn-1-ol in CH₂Cl₂ or C₂H₄Cl₂ under reflux in the presence of excess conc. aqueous HCl afforded the new, neutral (PPh₃)₂Cl₃Ru{triple bond, long}C-CH{double bond, long}CPh₂ carbyne complex (7), an HCl adduct of previously elusive (PPh₃)₂Cl₂Ru{double bond, long}C{double bond, long}C{double bond, long}CPh₂ complex 6 in high yields. In contrast to the formation of complex 3, the reaction in a non-coordinating solvent did not afford the rearrangement of the allenylidene C₃-spine. Complex 7 was converted into complex 3 in thf under reflux under loss of a molecule HCl. Complex 7 was converted with triethylamine under loss of HCl to complex 6. Pentacoordinate complex 6 was crystallized in the presence of O-donor ligands (EtOH, MeOH and H₂O) to give hexacoordinate (PPh₃)₂Cl₂(ROH)Ru{double bond, long}C{double bond, long}C{double bond, long}CPh₂ (R = H, CH₃, C₂H₅) complexes (9)-(11) with the O-donor coordinating in trans-position to the allenylidene moiety. The reaction of complex 7 with 2 equiv. of 4-(N,N-dimethylamino)pyridine (DMAP) gave hexacoordinate (PPh₃)₂Cl₂(DMAP)Ru{double bond, long}C{double bond, long}C{double bond, long}CPh₂complex (12) with one molecule DMAP also coordinating in trans-position to the allenylidene group. Methanol and acetic acid in the absence of strong bases afforded the Fischer-carbene complexes (PPh₃)₂Cl₂Ru{double bond, long}C(OCH₃)-CH{double bond, long}CPh₂ (14) and (PPh₃)₂Cl₂Ru{double bond, long}C(OAc)-CH{double bond, long}CPh₂ (15) where the nucleophile added to the α-carbon atom. The structures of complexes 5, 7, 9-11, 14, and 15 were solved via X-ray crystallography.

Full text of DOI:10.1016/j.jorganchem.2007.08.005

Journal of Organometallic Chemistry 692 (2007) 5221–5233
www.elsevier.com/locate/jorganchem
Synthesis of ruthenium phenylindenylidene, carbyne, allenylidene and
vinylmethylidene complexes from (PPh3)3À4RuCl2: A mechanistic
and structural investigation
a
b
b
c
Erika A. Shaffer , Chun-Long Chen , Alicia M. Beatty , Edward J. Valente ,
a,
*
Hans-Jo¨rg Schanz
a
Department of Chemistry and Biochemistry, The University of Southern Mississippi, 118 College Drive, Hattiesburg, MS 39406-5043, United States
b
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, United States
Department of Chemistry and Biochemistry, Mississippi College, Clinton, MS 39058, United States
c
Received 3 July 2007; received in revised form 7 August 2007; accepted 7 August 2007
Available online 11 August 2007
Abstract
The reaction of (Ph3P)3RuCl2 with 1,1-diphenyl-2-propyn-1-ol was investigated in various solvents. The reaction in thf under reflux is
reported to produce the (PPh3)2Cl2Ru(3-phenylindenylidene) complex (3) which has undergone rearrangement of the allenylidene C3-
spine. We have improved the reliability of the reported synthesis by adding acetyl chloride which converts the formed water of the reaction
and thus increases the acidity of the reaction solution. Without the additive, we observed the exclusive formation of an intermediate of the
transformation and identified it as dinuclear (PPh3)2ClRu(l-Cl)3(PPh3)2Ru@C@C@CPh2 complex (5). The reaction of (Ph3P)3À4RuCl2
with 1,1-diphenyl-2-propyn-1-ol in CH2Cl2 or C2H4Cl2 under reflux in the presence of excess conc. aqueous HCl afforded the new, neutral
(PPh3)2Cl3Ru„C–CH@CPh2 carbyne complex (7), an HCl adduct of previously elusive (PPh3)2Cl2Ru@C@C@CPh2 complex 6 in high
yields. In contrast to the formation of complex 3, the reaction in a non-coordinating solvent did not afford the rearrangement of the alleny-
lidene C3-spine. Complex 7 was converted into complex 3 in thf under reflux under loss of a molecule HCl. Complex 7 was converted with
triethylamine under loss of HCl to complex 6. Pentacoordinate complex 6 was crystallized in the presence of O-donor ligands (EtOH,
MeOH and H2O) to give hexacoordinate (PPh3)2Cl2(ROH)Ru@C@C@CPh2 (R = H, CH3, C2H5) complexes (9)–(11) with the O-donor
coordinating in trans-position to the allenylidene moiety. The reaction of complex 7 with 2 equiv. of 4-(N,N-dimethylamino)pyridine
(DMAP) gave hexacoordinate (PPh3)2Cl2(DMAP)Ru@C@C@CPh2 complex (12) with one molecule DMAP also coordinating in
trans-position to the allenylidene group. Methanol and acetic acid in the absence of strong bases afforded the Fischer-carbene complexes
(PPh3)2Cl2Ru@C(OCH3)–CH@CPh2 (14) and (PPh3)2Cl2Ru@C(OAc)–CH@CPh2 (15) where the nucleophile added to the a-carbon
atom. The structures of complexes 5, 7, 9–11, 14, and 15 were solved via X-ray crystallography.
Published by Elsevier B.V.
Keywords: Ruthenium; Fischer-carbene; Carbyne complexes; Carbene complexes; Carbene rearrangement; X-ray crystal structures
1. Introduction
functional groups, moisture and air [12]. Whereas several
different synthetic strategies had been developed to access
such 16-electron Ru–carbene complexes over the past dec-
ade, including metathesis-active vinylidene [13], allenylidene
[14] and vinylmethylidene complexes [15], today Ru–benzyl-
idene complexes such as Grubbs’ catalyst 1 (Fig. 1) and its
NHC-ligated counterparts [16–19] are the most prominent
representatives of this class of compounds. They are studied
to the greatest detail [20,21], are commercially available, and
Olefin metathesis has become a valuable synthetic tool in
organic [1–5] and polymer chemistry [6–11]. In particular
Ru-based catalysts have proven to be highly applicable in
homogeneous solution due to their high tolerance towards
*
Corresponding author. Tel.: +1 601 2665708; fax: +1 601 2666075.
E-mail address: hans.schanz@usm.edu (H.-J. Schanz).
0022-328X/$ - see front matter Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2007.08.005

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E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
PCy3
Cl
Ru
PCy3
Cl
Ru
PPh3
Cl
Ru
in thf under reflux to obtain complex 3. The modified
Ph
Ph
work-up protocol [27] required the removal of all solvent
and a thorough wash of the residue with diethyl ether.
Although, we were occasionally successful following this
procedure, we had not once obtained complex 3 in recent
years in spite of closely following this protocol. Instead
we isolated a new ruthenium complex on these occasions,
each time in very high yield. We have identified this com-
pound via NMR-spectroscopy and single crystal X-ray dif-
fraction (Fig. 2) as a non-symmetric binuclear complex 5
with two hexacoordinate ruthenium centers which are l-
Cl3-bridged across an octahedral face. Both ruthenium cen-
ters are additionally coordinated by two PPh3 ligands, one
ruthenium atom bears another terminal chloro ligand, the
other a diphenylallenylidene moiety. The complex could
be easily formed upon the reaction of the starting complex
4 and complex 6 (supposedly the initial product of the
addition of 1,1-diphenyl-2-propyn-1-ol to complex 4) and
could represent an early intermediate of the formation of
complex 3 (Scheme 1). A similar non-symmetric dimeric
complex bearing one vinylmethylidene group has been
identified as an intermediate of the thermal degradation
of the corresponding (PPh3)2Cl2Ru(alkylidene) complex
[28]. Cationic, (l-Cl)3-bridged Ru2(allenylidene)2 com-
plexes have also been reported before [22b,29]. Several
dinuclear, (l-Cl)2-bridged ruthenium carbene complexes
have been identified as very effective olefin metathesis initi-
ators [30]. The 31P NMR spectrum in d6-benzene exhibits
the presence of four different phosphorus atoms with the
signals (d = 37.0 ppm, 40.8 ppm, 48.9 ppm and 51.4 ppm)
split in four duplets [2J(31P31P) = 26.6 Hz and 37.8 Hz] of
equal intensity caused by two separate Ru(PPh3)2 units in
the molecule. X-ray quality crystals were obtained by
vapor diffusion of diethyl ether into a solution of complex
5 in CH2Cl2 which contained 4 equivalent of PPh3.
Cl
Cl
Cl
Ph
PCy3
1
PCy3
PPh3
2
3
Fig. 1. Structures of commercially available catalysts 1 and 2 and catalyst
precursor 3.
still are most widely used for many applications. Ruthe-
nium–3-phenylindenylidene complex 2 (Fig. 1) and its
NHC-ligated derivatives also have been produced in a large
variety [21–24]. Their attraction lies in the improved thermal
stability profile [23] paired with catalytic activity reported to
rival, and in some instances surpass their benzylidene coun-
terparts, in particular for use in Ring Closing Metathesis
(RCM) reactions [24]. Complex 2 is also commercially
available.
The synthetic access to complex 2 is reported to be
straightforward from non-hazardous starting materials
[22]. The precursor complex 3 with two PPh3 ligands was
obtained from the reaction of (Ph3P)3À4RuCl2 and 1,1-
diphenyl-2-propyn-1-ol in refluxing thf under elimination
of water and then converted with PCy3. Instead of the orig-
inally proposed allenylidene complex [22], the C3-spine
undergoes, presumably acid induced, rearrangement
involving one of the phenyl groups to form the 3-phenylin-
denylidene complex 3 (Fig. 1) [23]. Complex 3, while lowly
metathesis active by itself, is highly useful. In solid, dry
form, it is highly stable, can be stored for months in air
without noticeable decomposition in contrast to Grubbs’
(PPh3)2Cl2Ru@CHPh complex, precursor to the family of
Grubbs’ catalysts. This stability makes complex 3 an ideal
precursor to access an array of differently substituted olefin
metathesis catalysts. In our experience however, the
reported synthetic procedure lacked reliability. Often, the
same synthetic procedure (sometimes from the same batch
of starting materials) would occasionally afford complex 3
but more often it would afford an unidentified dimeric spe-
cies containing four different kinds of phosphine ligands as
major product. To date, no reliable synthesis for complex 3
has been reported and the nature of dimeric species has not
been identified. Also, despite the proposed mechanisms for
the formation of complex 3, no intermediate of the reaction
has been isolated and characterized. We now wish to report
an improved, reliable and high-yielding synthetic proce-
dure for complex 3, and the synthesis and characterization
of two intermediates of the formation reaction, a dimeric
allenylidene and a carbyne complex. Furthermore, we wish
to report transformations of the carbyne complex to afford
allenylidene and vinylmethylidene complexes which also
were isolated and characterized.
Due to the coordinative saturation of the ruthenium
center not bearing a carbene, further reaction to complete
the formation of complex 3 only can occur by dissociation
of the dimeric complex. Considering three bridging l-Cl
2. Results and discussion
2.1. Complex syntheses
Following the procedure of Hill et al. [22], we reacted
(PPh3)3À4RuCl2 (4) [26] with 1,1-diphenyl-2-propyn-1-ol
Fig. 2. ORTEP diagram of (PPh3)2ClRu(l-Cl)3Ru(PPh3)2@C@C@CPh2
(5) (hydrogen atoms omitted for clarity).

E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
5223
Ph
HCl produced during the reaction is one key to the forma-
tion of the 3-phenylindenylidene carbene. Previous success-
ful syntheses of complex 3 [22–25] may have benefited from
impurities of the acidic HPPh3+ cation, a byproduct of the
synthesis of starting material 4 [26]. However, upon thor-
ough washing during filtration of precursor 4, the catalytic
amounts acid may be removed sufficiently and the synthesis
would not yield the desired complex according to the stan-
dard protocol [22,27].
(PPh3)3-4RuCl2
Ph
Ph
OH
Ph
OH
+ HCl
4
Ph
Ph
OH
thf / reflux
90 min
AcCl (10 %)
thf / reflux
2 h
CH2Cl2 / reflux
90 min
PPh3
Cl
Cl Ru C CH
PPh3
Cl
Ru C
PPh3
Cl
Ru
Ph
C
CPh2
Cl
CPh2
Cl
6
PPh3
7
Cl
PPh3
PPh3
+ (PPh3)3-4RuCl2
3
It should be noted that the reaction of complex 5 with
1 equiv. 1,1-diphenyl-2-propyn-1-ol, 2 equiv. PPh3 and
0.1 equiv. of acetyl chloride in refluxing thf also forms
the desired complex 3 (Scheme 1), however, the reaction
is slow and the conversion does not go to completion
(approx. 50% of 5 are converted into 3 after 4 h). More-
over, the long reaction times additionally afford thermal
degradation products which are apparent in the 31P
NMR spectrum of the crude product. It appears likely, that
the dimeric structure of complex 5 needs to be dissociated
into complexes 4 and 6 in order to successfully form com-
plex 3, and this may be the slow step of this conversion.
Therefore, complex 5 may be one, but rather likely a minor
intermediate formed during the synthesis of complex 3. The
acidic conditions appear to favor a second reaction path-
way which does not include the dimeric complex 5 (vide
infra).
We also have attempted the conversion of complex 4
with 1,1-diphenyl-2-propyn-1-ol in refluxing CH2Cl2, which
is a very good solvent for the starting complex 4 and inert
against concentrated acid. When we used a catalytic
amount of HCl refluxing for 16 h, a mixture of various com-
pounds was produced, among those trace amounts (<10%)
of complex 5 were identified via 31P NMR spectroscopy.
The use of excess HCl (with respect to starter complex 4)
in refluxing CH2Cl2 for 90 min however, yielded the new
carbyne complex 7 as yellow powder in high yields (Scheme
1), which precipitated upon addition of 2-propanol, and
was obtained as the sole isolated Ru-compound after filtra-
tion. Complex 7 obviously had been derived from the
allenylidene complex 6 where one molecule HCl has added
in 1,3-fashion across the Ru@C@C@C spine. A reminiscent
cationic ruthenium monohydride complex with a carbyne
moiety has been reported by Werner et al. [32], produced
by the addition of acid to vinylidene complexes. The struc-
ture of complex 7 was confirmed via NMR spectroscopy
and X-ray diffraction (Fig. 3). The 31P NMR (CD2Cl2)
exhibited one signal at 13.6 ppm (s). The 1H NMR
(CD2Cl2) signal for CbH atom is significantly shifted from
the residual sp2CH atoms with a resonance at 5.67 ppm
and displays coupling to the phosphorus atoms [t,
4J(31P1H) = 2.4 Hz]. The observed coupling constant indi-
cates that phosphine dissociation is slow on the NMR time
scale. X-ray quality crystals were obtained by slow layer-
diffusion of 2-propanol into a solution of complex 7 in
CH2Cl2 which contained 4 equiv. of PPh3.
4
AcCl (10 %)
thf / reflux
4 h
Ph3P
PPh3
Cl Ru
slow
C
C CPh2
Ph3P
Ph
Ph
OH
+ 2 PPh3
Cl
Cl
5
Cl Ru
Ph3P
Scheme 1. Conversion of complex 4 with 1,1-diphenyl-2-propyn-1-ol
under various reaction conditions.
ligands, this may be a very slow process and one reason for
the near-exclusive formation of complex 5 under literature
conditions [22,27]. In those experiments even extended
reaction times up to 12 h did not afford the desired complex
3 as determined by 31P NMR spectroscopy of aliquots.
Instead unidentified decomposition products were formed
in small amounts alongside complex 5. Therefore, a suc-
cessful synthesis of complex 3 requires either avoiding the
formation of complex 5 or applying conditions which favor
its dissociation. A solvent change to refluxing CH2Cl2,
generally a very good solvent for ruthenium carbene
complexes, also yielded the dinuclear complex 5 as the
major product which was isolated in 79% yield from the
reaction, however without noticeable formation of complex
3 according to the 31P NMR spectrum of the crude prod-
uct. We tested adding bases such as triethylamine or pyri-
dine (to prevent the formation of dinuclear species 5) and
acids such as acetyl chloride to facilitate the conversion
into complex 3 in thf under reflux. Whereas the added
bases did yield mixtures of unidentified products, addition
of acetyl chloride indeed dramatically improved the con-
version and we were able to isolate complex 3 in high
yields. In fact, acid-catalyzed rearrangement of allenylidene
to phenylindenylidene moieties has been extensively stud-
ied with 18-electron (p-cymene)Ru complexes [31]. It is
likely that the rearrangement of the C3-spine is also acid-
catalyzed to form 16-electron complex 3. Formation of
complex 3 as the sole product after work-up was accom-
plished when a catalytic amount of acetyl chloride
(0.1 equiv. in respect to propynol) used with a reaction time
of 90 min in refluxing thf (Scheme 1). Upon reaction with
water (residual moisture in thf and water formed from
the reaction) and/or the propynol, the acetyl chloride will
provide HCl and some amounts of acetic acid. The reaction
also yields complex 3 using an excess of acetyl chloride
(2 equiv. in respect to propynol). It seems likely, that the
Protonation of the Cb atom to form carbyne complexes
was reported for Re, Ru and Ir vinylidene complexes using

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E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
tion of the product and/or the intermediates. Such decom-
position is observed when the reaction is conducted
without it via 31P NMR spectroscopy. It should be noted
that thermal degradation is intimately linked to the rate
of phosphine dissociation in 16-electron carbene complexes
and additional phosphine reduces this rate [20,21]. Addi-
tionally, the extra phosphine also serves as oxygen sponge
to prevent oxidative decomposition. The catalytic effect of
ruthenium complexes of the oxidation of phosphines with
molecular oxygen was observed previously [38]. The reac-
tion actually was carried out in a closed vessel under
non-inert conditions with a sufficient excess of phosphine.
Upon work-up, the complex was separated from the excess
phosphine and Ph3PO via filtration of the slurry in 2-
propanol.
Fig. 3. ORTEP diagram of (PPh3)2Cl3Ru„C–CH@CPh2 (7) (hydrogen
atoms omitted for clarity).
The reactivity difference between thf in contrast to the
non-coordinating solvent CH2Cl2 seems likely to be due
to an intermediate formation of a cationic carbyne species
8a (Scheme 3) where the chloro ligand in trans-position to
the carbyne group is replaced by a thf ligand. It is likely
that the a-carbon atom in complex 8a possesses elevated
electrophilicity and therefore, is activated towards internal
nucleophilic attack by one of the benzene rings attached to
Cc to form the 3-phenylindenylidene moiety.
The reversible abstraction of HCl makes complex 7 reac-
tive towards bases and various nucleophiles. In fact, com-
plex 7 was used to provide the catalytic amount acid
needed for the formation of complex 3 from precursor 4
and 1,1-diphenyl-2-propyn-1-ol. The reaction using 10%
complex 7 exclusively yields complex 3 under standard con-
ditions (thf reflux, 2 h) in 90% yield. The reaction of com-
plex 7 with triethylamine as a weakly coordinating base
afforded the abstraction of a molecule HCl resulting in
the formation of deep-red 16-electron allenylidene complex
6 (Scheme 2). The reaction was performed in methanol
with an excess triethylamine under sonication (15 min).
The product was filtered, washed and dried under vacuum.
However, crystallization attempts for complex 6 by slow
diffusion of 2-propanol into a saturated CH2Cl2 solution
did not afford suitable crystals for X-ray analysis. Even
more surprising, crystallization attempts using vapor diffu-
sion of diethyl ether into a saturated CH2Cl2 solution affor-
ded suitable crystals for X-ray analysis, however complex 9
non-coordinating acids [33,34]. Also the addition of non-
nucleophilic acid converted Ru [35,36] and Ir [37] allenylid-
ene complexes into vinylcarbyne complexes. The formation
of a dicationic carbyne complex from a diphenylallenylid-
ene moiety was also observed by Dixneuf et al. via 31P
NMR spectroscopy when converting a 18-electron (p-cym-
ene)Ru diphenylallenylidene complex into the phenylinde-
nylidene analogue with triflic acid at low temperatures
[31]. Hence, it appears likely that complex 7 represents an
intermediate of the formation of complex 3, very likely
one intermediate of the major reaction pathway. In reflux-
ing CH2Cl2 complex 7 could not be converted into complex
3. In contrast, when complex 7 is heated under reflux in thf
in the presence of 2 equiv. of PPh3 for 90 min, the rear-
rangement of the C3-spine with subsequent dehydrohalo-
genation is accomplished quantitatively and complex 3 is
obtained in high yields (Scheme 2). In this transformation,
additional PPh3 is needed as it limits thermal decomposi-
PPh3
PPh3
Cl
Ru
Cl
C
Ph
Me2N
N
Ru
C
CPh2
Cl
Cl
12
PPh3
2 PPh3
PPh3
thf / reflux
3
2 DMAP
- HCl
- DMAP.HCl
2-PrOH
PPh3
Cl
Cl Ru
Cl
C
CH
CPh2
NEt3 (excess)
- Et3N.HCl
MeOH
PPh3
7
MeOH
reflux
AcOH (excess)
2-PrOH
+
Ph
Ph
OH
PPh3
Cl-
PPh3
Cl
Ru
H3C
H
Cl
C
+
PPh3
Cl
Ru
C CPh2
CH3
PPh3
Cl
O
Cl
C CH
CPh2
Cl-
PPh3
Cl
Ru C
thf / reflux
[AcCl]
Cl
HO
6
+ HCl
fast
PPh3
O
Cl
Ru
C
CH
CPh2
PPh3
8b
Cl Ru
Cl
C
CH
CPh2
(PPh3)3-4RuCl2
C
CPh2
slow
vacuum / 60oC
- ROH
Cl
PPh3
8c
PPh3
6
4
+ ROH
PPh3
7
- HCl
PPh3
Cl
Ru
C C CPh2
+ HCl
+ thf
fast
- HCl
R
PPh3
Cl
+ thf
fast
H
O
Cl
C
CPh2
H
PPh3
Cl
Ru
Ru
C
+
H
PPh3
PPh3
Cl
Cl-
PPh3
Cl
Ru
C
OCH3
CPh2
- thf
Cl
Ph
R = Et
9
C
Cl
- HCl
PPh3
Me 10
11
O
Cl
Ru
C
CH
CPh2
14
O
O
H
fast
Cl
15
PPh3
PPh3
PPh3
3
8a
Scheme 2. Conversion of carbyne complex 7 to give 3-phenylindenylidene,
allenylidene, and vinylmethylidene complexes.
Scheme 3. Proposed mechanism for the formation of complex 3.

E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
5225
was obtained with an additional ethanol molecule coordi-
nating trans to the allenylidene moiety instead of complex
6. The ethanol molecule is likely formed as a result from
the hydrolysis of diethyl ether, perhaps catalyzed by
complex 6. Other vapor diffusion crystallization attempts
(Et2O into CH2Cl2) in the presence of methanol or water
(added in a 1:1 v/v mixture with 2-propanol) also afforded
hexacoordinate species, namely complexes 10 and 11 which
were analyzed by X-ray diffraction (Figs. 4–6). On the
other hand, the use of 2-propanol in these experiments
did not yield suitable crystals. Standard drying conditions
(2 h vacuum/60 ꢀC) accomplished the complete removal
of the trans-ligand from all three complexes to afford com-
plex 6. The coordination of the donor ligands (Scheme 2)
can be observed via 31P NMR spectroscopy. The spectrum
(d6-benzene) exhibited one resonance at 30.9 ppm (s) for
complex 6. Addition of excess (>10 equiv.) ethanol, meth-
anol and water to the NMR solution afforded a resonance
shift up-field to 27.0 ppm (s, 9), 27.6 ppm (s, 10) and
27.5 ppm (s, 11), respectively. In contrast, the addition of
2-propanol caused a minimal up-field shift to 30.6 ppm.
It appears likely that 2-propanol is too bulky to coordinate
Fig. 6. ORTEP diagram of (H2O)(PPh3)2Cl2Ru@C@C@CPh2 (11)
(hydrogen atoms omitted for clarity).
to the vacant site in order to form a stable hexacoordinate
complex.
Complexes 9–11 are unprecedented among neutral,
hexacoordinate 18-electron ruthenium carbene complexes.
The fact that hard, neutral O-donor ligands such alcohols
or water coordinate to the soft ruthenium center of com-
plex 6 demonstrates a much higher Lewis-acidity of the
metal center than for other 16-electron ruthenium carbene
complexes. It explains the formation of dimeric complex 5
under non-acidic conditions with the weakly Lewis-basic
complex 4. Under acidic conditions, the catalytic amount
HCl obviously converts complex 6 into complex 7 (or alter-
natively directly into cationic carbyne complex 8a)
instantly after formation which then was demonstrated to
undergo dehydrohalogenation with subsequent rearrange-
ment of the C3-spine to complex 3 in thf. As catalytic
amounts of acetyl chloride (which should form HCl under
reaction conditions), or complex 7 itself, prove sufficient
for a complete conversion into the desired product, it is
obvious that the first step, the formation of complex 6, is
rate determining for the conversion as there must be suffi-
cient amounts of HCl in the reaction mixture to complete
the pathway. The protonation to afford complex 7 (or
directly complex 8a), the trans-chloride substitution to
form complex 8a from complex 7, and the C3-spine rear-
rangement therefore, have to be significantly faster
(Scheme 3).
Fig. 4. ORTEP diagram of (EtOH)(PPh3)2Cl2Ru@C@C@CPh2 (9)
(hydrogen atoms omitted for clarity).
Nucleophilic bases such as N,N-4-dimethylaminopyri-
dine (DMAP) also afforded the loss of one HCl molecule
in complex 7 under restoration of the initial allenylidene
moiety. A second molecule DMAP coordinated to the
metal center in trans-position to the carbene moiety to
form purplish-blue complex 12 (Scheme 2). The use of
<2 equiv. of DMAP will result in a mixture of complexes
6 and 12. Complex 12 was isolated and the structure was
determined via NMR spectroscopy and X-ray diffraction
(Fig. 7). The 31P NMR spectrum (CD2Cl2) exhibited one
resonance at 23.2 ppm (s). The 1H NMR spectrum
Fig. 5. ORTEP diagram of (MeOH)(PPh3)2Cl2Ru@C@C@CPh2 (10)
(hydrogen atoms omitted for clarity).

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E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
tion of 10 equiv. of DMAP to complex 12 afforded a con-
version of approximately 70% after 30 min, however, a
strong increase in the formation of secondary products
was also observed. It is obvious, that both PPh3 ligands
are strongly bonded in complex 12. Pentacoordinate ruthe-
nium allenylidene complexes are known slow metathesis
initiators [14], and this process depends on the rate of phos-
phine dissociation. In addition, the use of an excess of PPh3
during synthesis and crystallization also may have shifted
the equilibrium back to complex 12 that this was the sole
isolated product.
The reaction of complex 7 with methanol without addi-
tion of extra base yielded the Fischer-type vinylmethylidene
complex 14 (Scheme 2). Instead of deprotonation of the Cb
atom, the trans chloride was replaced by a methoxide add-
ing to the Ca-atom converting the carbyne to a carbene
moiety. The product precipitated almost quantitatively
from the reaction solution (refluxing methanol plus
2 equiv. PPh3 open to air) as a brown powder. Complex
14 was characterized via NMR spectroscopy and X-ray dif-
fraction (Fig. 8) and represents the a,b-addition product of
complex 6 with methanol. The 31P NMR spectrum
(CD2Cl2) exhibited one resonance at 29.8 ppm (s), and
Fig. 7. ORTEP diagram of (DMAP)(PPh3)2Cl2Ru@C@C@CPh2 (12)
(hydrogen atoms omitted for clarity).
displayed only one resonance outside the aromatic area at
2.88 ppm (s, 6H) for the NMe2 protons. Complex 12 is
unique as it represents the first hexacoordinate 18-electron
Ru carbene complex bearing two phosphine and only one
N-donor ligand, in contrast to reports where the
reaction of two N-donor ligands replacing one phosphine
forming L(N-donor)2Cl2Ru carbene [19,39,40] or L(N-
donor)3ClRu+ carbene [38] complexes (L = phosphine or
NHC ligand). It should be noted, that dissolution of
crystals of complex 12 in CD2Cl2, (and to a lesser degree in
d6-benzene) did afford trace amounts of several secondary
species which display multiple 31P NMR resonances. Most
notably, resonances are observed at 41.4 ppm (s), 31.9 (s)
and at À4.7 ppm (s, PPh3) with the same integration val-
ues. It appears likely that the signal at 41.4 ppm represents
complex (PPh3)(DMAP)2Cl2Ru@C@C@CPh2 (13) where
one of the PPh3 ligands is replaced by a second DMAP
ligand. Thus, a free PPh3 ligand is formed (d À4.7 ppm)
plus a molecule of complex 6 (d 31.9 ppm). Dissolving pure
complex 12 apparently resulted in the formation of an equi-
librium with complex 13, complex 6 and free PPh3 (Scheme 4)
which are formed in trace amounts as >90% of the mixture
is still present as complex 12. Upon addition of DMAP to
this mixture, the signal intensities of complex 13 (d
41.4 ppm) and PPh3 (d À4.7 ppm) slowly increase in a 1:1
ratio, whereas the signal for complex 6 disappears. Addi-
1
the H NMR spectrum displayed two characteristic reso-
nances outside the aromatic area at 3.15 ppm (s, 3H) for
the methoxy group and 5.33 ppm (s, 1H) for the Cb-hydro-
gen atom. The nucleophile addition proceeds at the
a-carbon atom in contrast to reports of cationic CpRu
vinylcarbyne complexes adding soft nucleophiles to the c-
carbon atom of the C3-spine [36]. Addition of alcohols
across the Ca–Cb bond of cationic vinylidene complexes
to form Fischer-carbene complexes had been reported
before [42]. The mechanism of the addition was not inves-
tigated in these reactions. Very likely the nucleophilic
attack precedes the proton transfer to the Cb atom in these
transformations. It is unlikely the reaction proceeds via the
dicationic carbyne complex as the cationic vinylidene pre-
cursor was obtained by protonation using strong acids
PPh3
Cl
Me2N
N
Ru
C
C
CPh2
Cl
N
13
NMe2
+
PPh3
Cl
PPh3
Cl
Ru
C
C
CPh2
2
Me2N
N
Cl
Ru
C
C
CPh2
12
PPh3
Cl
PPh3
6
> 90 %
+
PPh3
< 10 %
Scheme 4. Equilibrium between mono-DMAP complex 12 and complexes
13, 6 and PPh3 in CD2Cl2.
Fig. 8. ORTEP diagram of (PPh3)2Cl2Ru@C(OMe)–CH@CPh2 (14)
(hydrogen atoms omitted for clarity).

E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
5227
and thus, weakly acidic alcohols should not afford a second
protonation step at the Cb atom. The formation of complex
14 proceeds in reverse order, first protonation of the Cb
atom in complex 6, then nucleophilic attack with subse-
quent deprotonation at the Ca atom, as the protonation
is already accomplished with the formation of complex 7.
Interestingly, we were not able, even after several hours
of reflux in 2-propanol, to obtain the corresponding
Fischer-carbene complex bearing an OiPr substituent. As
it was demonstrated that 2-propanol is too bulky to coor-
dinate to the ruthenium center of complex 6 upon treat-
ment of complex 7 with base, it suggests that trans-
chloride substitution versus methanol may be crucial to
the substitution reaction. The resulting cationic intermedi-
ate carbyne complex 8b certainly possesses a more electro-
philic Ca-atom which could be more readily attacked by the
weakly nucleophilic alcohol.
Fig. 9. ORTEP diagram of (PPh3)2Cl2Ru@C(O–COMe)–CH@CPh2 15
(hydrogen atoms omitted for clarity).
The formation of complex 15 from complex 7 with ace-
tic acid, another weakly basic nucleophile, was accom-
plished by sonication of the slurry of complex 7 in
2-propanol and a large excess of AcOH for 4 h (Scheme 2).
In the same fashion, chloride substitution takes place with
the weakly nucleophilic acetate adding to the Ca-atom. To
the best of our knowledge, this is the first example of the
addition of a carboxylate to a carbyne carbon atom to
form a Fischer-carbene complex. Similar to the formation
of complex 14, we propose that the nucleophilic addition
is preceded by the chloride substitution in trans-position
to the allenylidene group to form the cationic complex
8c. As a result, the ruthenium center became more suscep-
tible towards nucleophilic attack at the Ca atom. The ace-
tate group additionally coordinates back to the metal
center to form a chelating vinylmethylidene group under
trans to cis isomerization of the chloride ligand. Complex
15 was characterized via NMR spectroscopy and X-ray dif-
fraction (Fig. 9). The 31P NMR spectrum (CD2Cl2) exhib-
ited one resonance at 18.3 ppm (s), and the 1H NMR
spectrum displayed one characteristic resonance outside
the aromatic area at 1.01 ppm (s, 3H) for the acetyl methyl
group whereas the signal for the Cb-hydrogen atom is
masked by the aromatic proton signals.
2.2. Structural investigations
The structures in solid state of complexes 5, 7, 9–12, 14
and 15 could be determined via X-ray crystallography.
Relevant bond distances and angles of the allenylidene
complexes 5, 9–12 are summarized in Table 1 and those
of complexes 7, 14 and 15 in Table 2. All complexes exhibit
a distorted octahedral environment at the ruthenium center
with exception of pentacoordinated 16-electron complex 14
which is distorted tetragonal pyramidal.
In complex 5, three bridging l-Cl ligands face-connect
both octahedra. As expected, all (l-Cl)–Ru–(l-Cl) (between
78.18(3)ꢀ and 82.39(3)ꢀ) and Ru–(l-Cl)–Ru angles (between
83.15(3) and 85.90(3)ꢀ) are significantly smaller than 90ꢀ.
Table 1
Selected bond distances (pm) and bond angles (ꢀ) for allenylidene complexes 5, 9, 10, 11 and 12
5c
9
10
11
12
Ru–Ca
Ca–Cb
Cb–Cc
Ru–P
186.0(4)
124.6(5)
135.7(5)
233.52(10)
238.79(11)
243.52(9)
246.24(10)
248.37(9) (Cl)
171.6(3)
183.6(4)
125.0(4)
135.4(5)
183.3(6)
123.6(7)
138.4(8)
184.8(9)
124.4(11)
134.5(11)
238.5(2)
239.2(2)
237.7(2)
237.1(2)
225.7(5) (O)
179.1(8)
177.8(9)
179.41(9)
163.89(8)
190.2(4)
119.0(5)
139.7(5)
242.09(9)
248.37(9)
237.38(9)
235.85(9)
229.8(2) (O)
177.8(3)
176.5(4)
172.41(3)
159.24(3)
238.55(16)
239.02(16)
237.22(16)
236.54(17)
225.5(4) (O)
177.1(5)
178.9(6)
179.01(6)
162.20(6)
239.80(11)
243.93(10)
239.13 (11)
239.32(11)
225.0(3) (N)
179.3(4)
175.3(4)
178.89(4)
172.86(3)
Ru–Cl
Ru–La,b
Ru–Ca–Cb
Ca–Cb–Cc
P–Ru–P
170.1(4)
101.85(4)
79.29 (3)
82.39(3)
Cl–Ru–Cl
78.33(3)
a
Distance to binding atom of the ligand trans to the allenylidene moiety.
Binding atom given in brackets following value.
Distances and angles given for ruthenium center bearing the allenylidene moiety.
b
c

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Table 2
(170.3(9)–176.6(3) pm) [36,45]. The C–C distances in the
C3-spine (Ca–Cb: 137.9(9) pm and Cb–Cc: 137.6(9) pm)
are almost identical and in similar range as the literature
complex. Interestingly, such similar bond distances, despite
different bonding orders in the C3-spine, was also observed
for ruthenium vinylmethylidene complexes [17c].
Selected bond distances (pm) and bond angles (ꢀ) for carbyne complex 7
and vinylmethylidene complexes 14 and 15
7
14
15
Ru–Ca
Ca–Cb
Cb–Cc
Ru–P
172.5(7)
137.9(9)
137.6(9)
244.27(15)
245.79(15)
185.5(5)
146.3(7)
134.9(8)
236.91(17)
241.80(18)
186.2(5)
143.4(7)
134.7(7)
240.96(12)
241.97(12)
Allenylidene complexes 9–11 display the same coordina-
tion sphere around the ruthenium center as expected.
Methanol and water complexes 10 and 11 exhibit very
similar bond distances and angles around the metal center.
Ethanol complex 9 exhibits a slightly longer Ru–O distance
to the ligand (229.8(2) pm) in comparison to complexes 10
(225.5(4) pm) and 11 (225.7(5) pm) presumably due to
increased steric crowding at the metal center. Due to the
same effect, the Ru–P distances are also elongated in com-
plex 9 (242.09(9) pm and particularly 248.37(9) pm)
whereas these distances all lie in between 238.5(2) pm and
239.2(2) pm for complexes 10 and 11. This steric effect is
also visible in the bond angles around the metal center.
The trans-phosphine angles for complex 9 (P–Ru–P:
172.41(3)ꢀ) is smaller by more than 6ꢀ than in complexes
10 and 11, and the trans-chlorine angle (Cl–Ru–Cl:
159.24(3)ꢀ) by approx. 3ꢀ. Additionally, the cis O–Ru–P
angles are also significantly widened in complex 9
(93.77(3)ꢀ and 93.91(6)ꢀ) by an average of approx. 3ꢀ in
comparison to complexes 10 and 11. The angles along
the C3-spine are close to linearity in all complexes (smallest
Ru–Ca–Cb (10): 177.1(5)ꢀ, smallest Ca–Cb–Cc (9): 176.5(4) ꢀ).
The Ru–Cl distances for all three complexes are in a
narrow range between 235.85(11) pm (9) and 237.7(2) pm
(11). The Ru–Ca distances are similarly close between
183.3(6) pm (10) and 184.8(9) pm (11) and like complex 5
(vide supra) at the short end to other 18-electron Ru–
allenylidene complexes (typical range 187–192 pm) [41].
The bond distances along the C3-spine (9: Ca–Cb:
125.0(4) pm and Cb–Cc: 135.4(5) pm; 10: Ca–Cb: 123.6(7)
pm and Cb–Cc: 138.4(8) pm; 11: Ca–Cb: 124.4(11) pm
and Cb–Cc: 134.5(11) pm) are similar to complex 5 and
other ruthenium allenylidene complexes [14,43,44]. The
angles along the C3-spine do not deviate more than 3.5ꢀ
from linearity which should exclude significant C–H p-
interactions to spatially close ligand hydrogen atoms.
In complex 12, all cis-angles vary between 84.87(4)ꢀ and
94.45(4)ꢀ (both Cl–Ru–P) and the three trans-angles (C–
Ru–N: 177.67(15)ꢀ, P–Ru–P: 178.89(4)ꢀ, Cl–Ru–Cl:
172.86(3)ꢀ) are close to linearity, much more so than in iso-
electronic complexes 9–11. The angles along the C3-spine
also are close to linearity (Ru–Ca–Cb: 179.3(4)ꢀ, Ca–Cb–
Cc: 175.3(4)ꢀ). The Ru–N distance (225.0(3) pm) is much
shorter than other reported Ru–N distances for pyridines
coordinated trans to the carbene moiety [19c], and also
shorter than the Ru–O distances in complexes 9–11. This
indicates a very strong interaction between metal and N-
donor ligand. The Ru–Ca distance (190.2(4) pm) is in the
general range (187–192 pm) for 18-electron Ru–allenylid-
ene complexes [41] and somewhat longer than in complexes
5 and 9–11. The C–C distances in the C3-spine, Ca–Cb:
Ru–Cl
235.90(15)
240.93(15)
249.66(17)a
167.1(5)
233.93(17)
235.70(17)
239.63(12)
250.39(13)a
Ru–Ca–Cb
Ca–Cb–Cc
124.0(4)
120.1(5)
134.1(3)
130.3(5)
127.7(7)
P–Ru–P
Cl–Ru–Cl
a
176.33(6)
175.01(6)
166.53(5)
150.06(6)
177.06(4)
98.03(5)
Distance to Cl trans to the carbyne or carbene moiety.
All other cis-angles at the Ru centers between the terminal
ligands vary between 86.40(4)ꢀ and 102.03(4)ꢀ with the P–
Ru–P angles widened to 101.85(4)ꢀ and 99.36(4)ꢀ, respec-
tively. The angles along the C3-spine also are deviating
somewhat from linearity (Ru–Ca–Cb: 171.6(3)ꢀ, Ca–Cb–
Cc: 170.1(4)ꢀ) which could be a consequence of C–H p-
interactions to spatially close ligand hydrogen atoms. This
was been observed for other allenylidene complexes
[14,43]. The Ru-(l-Cl) distances vary between 242.16(8)
pm and 253.10(10) pm which makes them slightly longer
than the Ru–Clterminal distance (239.96(9) pm). The Ru–P
distances are longer at the metal bearing the allenylidene
group (233.52(10) pm and 238.79(11) pm) than for the ter-
minal chloride substituted (227.00(11) pm and 229.80(11)
pm). The Ru–Ca distance (186.0(4) pm) is relatively short
for 18-electron Ru–allenylidene complexes (typical range
187–192 pm) [40,44] but significantly longer than the car-
bene distances (179 pm) observed for the only two reported
16-electron Ru–allenylidene complexes [14]. The C–C dis-
tances in the C3-spine, Ca–Cb: 124.6(5) pm (typical range
125–127 pm) and Cb–Cc: 135.7(5) (typical range 132–135
pm), are in the common range for allenylidene complexes
[14,43,44].
In complex 7, all cis-angles at the metal vary between
84.34(6)ꢀ and 96.60(2)ꢀ and the trans-angles between
175.01(6)ꢀ and 178.90(2)ꢀ, respectively. As expected, the
C3-spine has lost the linearity at the Cb atom (Ru–Ca–Cb:
167.1(5)ꢀ, Ca–Cb–Cc: 127.7(7)ꢀ). However, the angle at
the Ca atom also is somewhat significantly bent and smaller
than any other such angle observed with ruthenium
carbyne complexes (168.8(4)–179.9(7)ꢀ) [36,45]. This may
come as a result of steric interference with the terminal phe-
nyl groups. The closest non-bonding contacts of the Ca and
the Cb atoms are to the ortho-CH of one of the spine-phe-
nyl groups (272.4 pm and 286.9 pm). The Ru–Cl distances
cis to the carbyne moiety are 235.90(15) pm and 240.93(15)
pm whereas the trans-Cl bond is elongated to 249.66 (17)
pm. The Ru–Ca distance (172.5(7) pm) is in the range of
previously reported ruthenium carbyne complexes

E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
5229
119.0(5) pm (typical range 125–127 pm) and Cb–Cc:
139.7(5) (typical range 132–135 pm), exhibit noticeable
shortening of the internal bond and extension of the termi-
nal bond which indicates an increased level of conjugation
in the allenylidene system.
and we have demonstrated that adding catalytic amounts
of acetyl chloride under otherwise similar reaction condi-
tions results in complete and reliable formation of this
compound. We have identified dinuclear allenylidene com-
plex 5 as a low-reactive intermediate which is formed under
non-acidic conditions. Complex 5 can be converted into
complex 3 under acidic conditions with 1,1-diphenyl-2-pro-
pyn-1-ol in thf, but the conversion is only moderately
successful, as long reaction times cause partial formation
of degradation products leaving some unreacted complex
5 in the reaction mixture. We conclude that complex 5
may be an intermediate of a lesser reaction pathway to
the formation of complex 3. The reaction of complex 4
and 1,1-diphenyl-2-propyn-1-ol in CH2Cl2 under reflux in
the presence of excess amounts of conc. HCl afforded the
new carbyne complex 7, an HCl addition product of alleny-
lidene complex 6. Complex 7 can be completely converted
into complex 3 in thf under reflux and thus, complex 7 very
likely represents an intermediate of the major pathway to
the formation of complex 3. Complex 7 is a versatile com-
plex and can be converted to different types of carbene
complexes. A molecule HCl can be abstracted from com-
plex 7 with triethylamine, a non-coordinating base, to form
the new 16-electron allenylidene complex 6 which can be
crystallized as 18-electron complexes adding small alcohols
(MeOH, EtOH) or water to the vacant coordination site
trans to the allenylidene group to give complexes 9–11.
The addition of 2-PrOH does not afford stable coordina-
tion. Stronger N-donor ligand DMAP (2 equiv.) reacts
with complex 7 to give unique diphosphine-mono-N-donor
ruthenium allenylidene complex 12 which is formed in con-
trast to previously reported monophosphine-di-N-donor
ruthenium carbene complexes upon addition of N-donor
ligands. The formation of complexes 9–12 is unique in
comparison to other ruthenium carbene complexes, which
proves the relatively strong Lewis acidity of the allenylid-
ene complex 6. This acidity makes the reaction conditions
for the formation of complex 3 plausible. The acid will
be needed to form intermediate 7, preventing the formation
of slow-reacting side product 5 with nucleophilic complex
4. The solvent thf is needed to replace the trans-chloride
ligand of complex 7 during the reaction to form the cat-
ionic intermediate species 8a. The a-carbon atom of inter-
mediate 8a has an elevated electrophilicity and thus enables
the rearrangement of the allenylidene into the 3-phenylin-
denylidene group. For the first time, evidence has been
produced to formulate a mechanism for the formation of
complex 3. The electrophilicity of the a-carbon atom of
complex 7 is also observed in reaction of weakly basic
nucleophiles such as methanol and acetic acid which also
affords HCl abstraction, however with the nucleophile
attacking the a-carbon atom of the carbyne ligand instead
of the metal center. The formed vinylmethylidene Fischer-
carbene complexes 14 and 15 are produced in high yields.
Due to the fact that 2-propanol is not affording this trans-
formation, it is likely that the reactive species are cationic
intermediates 8b and 8c bearing a methanol or acetic acid
Complex 14 possesses the only pentacoordinate ruthe-
nium center in the series of investigated complexes. The
structure is somewhat distorted tetragonal pyramidal. All
P–Ru–Cl cis angles are smaller than 90ꢀ in the range
between 87.14(6)ꢀ and 89.46(6)ꢀ whereas the Ca–Ru–
P(Cl) cis angles are all larger than 90ꢀ in a range between
93.07(18)ꢀ and 106.89(16)ꢀ. This indicates a strong steric
interference of the vinylmethylidene group with the other
metal ligands pushing them out of co-planarity with the
metal center. This effect can also be seen with the trans-
angles, P–Ru–P: 166.53(5)ꢀ and particularly Cl–Ru–Cl:
150.06(6)ꢀ, which are significantly smaller than 180ꢀ. The
angles in the C3-spine now are very close to the expected
120ꢀ with Ru–Ca–Cb: 124.0(4)ꢀ and Ca–Cb–Cc: 120.1(5)ꢀ.
In comparison to the previously published pentacoordinate
16-electron ruthenium vinylmethylidene complex (Ru–Ca:
176 pm) [17c,46], the Ru–Ca distance (185.5(5) pm) is
somewhat elongated which may be a result of the steric
interference with the other metal ligands and/or a result
of lower conjugation. The C–C distances in the C3-spine,
Ca–Cb: 146.3(7) pm and Cb–Cc: 134.9(8), are elongated
for the internal and shortened for the terminal bond in
comparison the literature complex (Ca–Cb: 138.0 pm and
Cb–Cc: 136.2) [17c] indicating a lower degree of conjuga-
tion along the C3-spine. Such may be a result of the hetero-
atom substitution at Ca which has become part of the
conjugated system.
Due to the chelating acetate ligand, vinylmethylidene
complex 15 is distorted octahedral. All cis-angles vary in
a broad range between 80.11(17)ꢀ (the chelate O–Ru–C)
and 98.03(5)ꢀ (Cl–Ru–Cl) and the three trans-angles (Ca–
Ru–Cl: 167.14(15)ꢀ, P–Ru–P: 177.06(4)ꢀ, O–Ru–Cl:
174.69(10)ꢀ) are deviating more or less strongly from line-
arity. The angles along the C3-spine are larger than 120ꢀ
(Ru–Ca–Cb: 134.1(3)ꢀ, Ca–Cb–Cc: 130.3(5)ꢀ). The Ru–O
distance (210.9(3) pm) is much shorter than the Ru–O dis-
tances in complexes 9-11. The Ru–Ca distance (186.2(5)
pm) is similar to complex 14. The C–C distances in the
C3-spine, Ca–Cb: 143.4(7) pm and Cb–Cc: 134.7(7), are sim-
ilarly elongated for the internal and shortened for the ter-
minal bond as in complex 14 in comparison the literature
vinylmethylidene complex (Ca–Cb: 138.0 pm and Cb–Cc:
136.2) [17c] as a result of lower conjugation in the C3-spine.
3. Conclusions
The primary goal of the presented research was to
investigate the formation of ruthenium 3-phenylindenylid-
ene complex 3, precursor to a powerful class of olefin
metathesis catalysts, from its precursor 4. The originally
described, synthetic procedure from complex 4 and 1,1-
diphenyl-2-propyn-1-ol in thf under reflux lacked reliability

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E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
molecule trans to the carbyne moiety. A similar intermedi-
ate cannot be formed with 2-propanol due to steric con-
straints as shown in reaction with complex 6. To the best
of our knowledge, complex 15 is the first example of the
addition of a carboxylic acid to the a-carbon atom of an
allenylidene complex.
RuCl2 (4) (690 mg, approx. 0.690 mmol) and 1,1-diphe-
nyl-2-propyn-1-ol (178 mg, 0.86 mmol) in thf (40 mL) and
stirred under reflux for 2 h. The work-up procedure was
identical with Method A, using 30 mL and 3 · 10 mL 2-
propanol. Yield (608 mg, 0.684 mmol, approx. 90%).
4.4. (PPh3)2ClRu(l-Cl)3(PPh3)2Ru@C@C@CPh2 (5)
4. Experimental
Method A: A solution of (PPh3)3À4RuCl2 (4) (1.782 g,
approx. 1.78 mmol) and 1,1-diphenyl-2-propyn-1-ol
(385 mg, 1.85 mmol) in 40 mL thf was heated and stirred
under reflux for 45 min. The purple solution was cooled
to room temperature and the solvent was removed under
reduced pressure. Diethyl ether (50 mL) was added and
the residue was dispersed in the solvent under sonication
at 30 ꢀC for 30 min. The slurry was filtered in air and
washed with 3 · 20 mL diethyl ether. The residue was dried
in a vacuum oven for 60 min at 60 ꢀC to yield pure complex
5 (1.218 g, 0.769 mmol, approx. 86%) as reddish-purple
powder. X-ray quality crystals of complex 5 were obtained
from a concentrated solution in CH2Cl2 containing approx.
4 equiv. of PPh3 by vapor diffusion of diethyl ether in a
closed vessel at À20 ꢀC. Method B: A solution of
(PPh3)3À4RuCl2 (4) (278 mg, approx. 0.278 mmol) and
1,1-diphenyl-2-propyn-1-ol (61 mg, 0.293 mmol) in 15 mL
CH2Cl2 was heated and stirred under reflux for 2 h. The
purple solution was cooled to room temperature and the
solvent was removed under reduced pressure. Analogous
to Method A, diethyl ether (20 mL) was added and the res-
idue was dispersed in the solvent under sonication at 30 ꢀC
for 30 min. The slurry was filtered in air and washed with
3 · 10 mL diethyl ether. The residue was dried in a vacuum
oven for 60 min at 60 ꢀC to yield pure complex 5 (176 mg,
0.110 mmol, approx. 79%) as reddish-purple powder.
1H NMR (CD2Cl2, 20 ꢀC, 300.1 MHz) d = 7.66 (d,
3J(1H1H) = 7.5 Hz, 4H), 7.62 (m, 4H), 6.90 (t,
3J(1H1H) = 7.5 Hz, 4H, @C(C6H5)2), 7.28–7.52 (m, 12H),
7.06–7.28 (m, 24H), 6.92–7.06 (m, 18H) 6.76 (m, 6H,
P(C6H5)3); 31P NMR (CD2Cl2, 20 ꢀC, 121.4 MHz) d =
48.3 (s, 2P), 39.8 (d, 2J(31P31P) = 27.8 Hz, 1P), 38.6 (d,
2J(31P31P) = 27.8 Hz, 1P); 31P NMR (CD2Cl2, 20 ꢀC,
121.4 MHz) d = 51.4 (d, 2J(31P31P) = 37.8 Hz), 48.9 (d,
4.1. General procedures
All experiments with organometallic compounds (unless
stated otherwise) were performed under dry nitrogen atmo-
sphere using standard Schlenck techniques or in an
MBraun drybox (O2 < 2 ppm). NMR spectra were
recorded at a Varian Inova Instrument (300.1 MHz for
1H, and 121.4 MHz for 31P). H NMR spectra were refer-
1
enced to the residual solvent (d6-benzene d 7.15 ppm,
CD2Cl2 d 5.32 ppm), 31P NMR spectra were referenced
using H3PO4 (d 0 ppm) as external standard. IR spectra
were recorded with a Nicolet Nexus 470 FT-IR instrument.
For sonication, a Fischer Scientific Ultrasonic Cleaner FS
30 was used. The bath temperature was set to 30 ꢀC. Crys-
tal data was obtained for complex 14 on a Bruker AXS
Smart system, and for complexes 5, 7, 9–12 and 15 on an
Oxford Diffraction Gemini S system.
4.2. Materials and methods
Diethyl ether and thf were dried by passage through
solvent purification (MBraun-Auto-SPS) and CH2Cl2, d6-
benzene and CD2Cl2 were degassed prior to use. No puri-
fication was performed with other solvents. Reagents were
purchased from commercial sources and used without fur-
ther purification. (PPh3)3À4RuCl2 [26] 4 was prepared
according to the literature.
4.3. (PPh3)2Cl2Ru(3-phenylindenylidene) (3) [22]
Method A: Acetyl chloride (0.10 mL, mg, mmol) was
added to a solution of (PPh3)3À4RuCl2 (4) (2.032 g, Mꢁ
1000 g/mol, 2 mmol) and 1,1-diphenyl-2-propyn-1-ol
(434 mg, 2.09 mmol) in thf (70 mL) and stirred under reflux
for 90 min. The purple solution was cooled to room tem-
perature and the solvent was removed under reduced pres-
sure. 2-propanol (50 mL) was added and the residue was
dispersed in the solvent under sonication at 30 ꢀC for
30 min. The slurry was filtered in air and washed with
3 · 20 mL 2-propanol. The residue was dried in a vacuum
oven for 3 h at 60 ꢀC to yield pure complex 3 (1.532 g,
1.72 mmol, approx. 86%) as purple powder. Method B:
Complex 7 (233 mg, 0.252 mmol) was heated in a solution
of PPh3 (103 mg, 0.39 mmol) in thf (15 mL) under reflux
for 90 min. The work-up procedure was identical with
Method A, using 20 mL and 3 · 10 mL 2-propanol. Yield
(186 mg, 0.209 mmol, 83%). Method C: Complex 7
(67 mg, 0.073 mmol) was added to a solution of (PPh3)3–4
2
2J(31P31P) = 37.8 Hz), 40.8 (d, J(31P31P) = 26.6 Hz), 37.0
2
(d, J(31P31P) = 26.6 Hz); IR (20 ꢀC, solid) m (cmÀ1) 1930
(s, C@C@C).
4.5. (PPh3)2Cl3Ru C–CH@CPh2 (7)
Aqueous HClconc. (0.3 mL, approx. 3 mmol) was added
to a solution of (PPh3)3À4RuCl2 (4) (1.678 g, approx.
1.68 mmol) and 1,1-diphenyl-2-propyn-1-ol (376 mg,
1.81 mmol) in 100 mL CH2Cl2 and stirred under reflux
for 90 min. The yellow–brown solution was cooled to room
temperature and transferred in air into 2-propanol
(100 mL). During the transfer, a yellow precipitate was
formed. The resulting slurry was reduced to 80 mL under
reduced pressure and sonicated at 30 ꢀC for 2 min. The

E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
5231
slurry was filtered in air and washed with 2 · 20 mL 2-pro-
panol and once with 20 mL of diethyl ether. The residue
was dried in a vacuum oven for 2 h at 60 ꢀC to yield pure
complex 7 (1.306 g, 1.41 mmol, approx. 84%) as yellow
powder. X-ray quality crystals of complex 7 were obtained
from a concentrated solution in CH2Cl2 containing approx.
4 equiv. of PPh3 by layer-diffusion of an approx. 10-fold
volume of 2-propanol in a closed test tube at room temper-
was filtered in air and washed with 3 · 10 mL methanol.
The residue was dried in a vacuum oven for 3 h at 60 ꢀC
to yield pure complex 12 (91 mg, 0.090 mmol, 57%) as pur-
plish-blue powder. X-ray quality crystals of complex 12
were obtained from a concentrated solution in CH2Cl2 con-
taining approx. 4 equiv. of PPh3 by vapor diffusion of
diethyl ether in a closed vessel at À20 ꢀC. 1H NMR
(CD2Cl2, 20 ꢀC, 300.1 MHz) d = 8.16 (d, 3J(1H1H) =
7.5 Hz, 2H), 5.74 (d, 3J(1H1H) = 7.5 Hz, 2H), 2.88
(s, 6H, DMAP-H), 6.85-7.73 (m, 40H, @C(C6H5)2 and
P(C6H5)3); 31P NMR (CD2Cl2, 20 ꢀC, 121.4 MHz)
d = 23.2; IR (20 ꢀC, solid) m (cmÀ1) 1886 (s, C@C@C).
1
ature. H NMR (CD2Cl2, 20 ꢀC, 300.1 MHz) d = 5.67 (t,
4J(31P1H) = 2.4 Hz, 1H, CbH), 7.21 (m, 2H), 7.66–7.78
(m, 6H), 7.44 (d, 3J(1H1H) = 7.5 Hz, 2H, @C(C6H5)2),
8.56–8.68 (m, 12H), 7.61–7.68 (m, 18H), 6.92–7.06 (m,
18H, P(C6H5)3); 31P NMR (CD2Cl2, 20 ꢀC, 121.4 MHz)
d = 13.6.
4.9. (PPh3)2Cl2Ru@C(OCH3)–CH@CPh2 (14)
4.6. (PPh3)2Cl2Ru@C@C@CPh2 (6)
Complex 7 (245 mg, 0.265 mmol) was dispersed in a
solution of PPh3 (104 mg, 0.40 mmol) in methanol
(15 mL) and heated under reflux open to the air for 15 min-
utes. In that time, the initially yellow solution turned
almost clear and a brown precipitate formed. The precipi-
tate was filtered and washed with 3 · 10 mL methanol. The
residue was dried in a vacuum oven for 3 h at 60 ꢀC to yield
pure complex 14 (239 mg, 0.260 mmol, 98%) as yellowish-
brown powder. X-ray quality crystals of complex 14 were
obtained from a concentrated solution in CH2Cl2 contain-
ing approx. 4 equiv. of PPh3 by vapor diffusion of diethyl
ether in a closed vessel at À20 ꢀC. 1H NMR (CD2Cl2,
20 ꢀC, 300.1 MHz) d = 5.33 (s, 1H, CbH), 3.15 (s, 3H,
OCH3), 6.88–7.66 (m, 40H, @C(C6H5)2 and P(C6H5)3);
31P NMR (CD2Cl2, 20 ꢀC, 121.4 MHz) d = 29.7.
Triethylamine (1.0 mL, 0.7 g, 7 mmol) was added to a
slurry of complex 7 (289 mg, 0.313 mmol) and PPh3
(125 mg, 0.48 mmol) in methanol (25 mL) under non-inert
conditions. After the addition, the vessel was immediately
closed with a septum and sonicated for 15 min at 30 ꢀC.
During that time, the yellow slurry turned deep red. The
slurry was filtered in air and washed with 3 · 10 mL meth-
anol. The residue was dried in a vacuum oven for 3 h at
60 ꢀC to yield pure complex 6 (198 mg, 0.223 mmol, 71%)
as bright red powder. 1H NMR (d6-benzene, 20 ꢀC,
300.1 MHz) d = 7.40 (d,3J(1H1H) = 7.5 Hz, 4H), 7.08 (m,
3J(1H1H) = 7.5 Hz, 2H), 6.70 (m, 4H, @C(C6H5)2), 7.96
(m, 12H), 6.86–7.02 (m, 18H, P(C6H5)3); 31P NMR (d6-
benzene, 20 ꢀC, 121.4 MHz) d = 30.9. IR (20 ꢀC, solid) m
(cmÀ1) 1906 (s, C@C@C).
4.10. (PPh3)2Cl2Ru = C(OAc)–CH@CPh2 (15)
4.7. Crystallization and NMR experiments with complex 6
affording complexes 9–11
Complex 7 (178 mg, 0.193 mmol) was dispersed in a
solution of PPh3 (132 mg, 0.50 mmol), acetic acid
(2.0 mL, 2.1 g, 35 mmol) in 2-propanol (15 mL) in a closed
vessel under non-inert conditions and sonicated for 4 h at
30 ꢀC. During that time, the initially yellowish orange
slurry turned yellowish-green. The precipitate was filtered
and washed with 3 · 10 mL methanol. The residue was
dried in a vacuum oven for 3 h at 60 ꢀC to yield pure com-
plex 15 (117 mg, 0.123 mmol, 64%) as yellowish-green pow-
der. X-ray quality crystals of complex 15 were obtained
from a concentrated solution in CH2Cl2 containing approx.
4 equiv. of PPh3 by vapor diffusion of diethyl ether in a
closed vessel at À20 ꢀC. 1H NMR (CD2Cl2, 20 ꢀC,
300.1 MHz) d = 1.01 (s, 3H, C(O)–CH3), 7.47 (m, 2H),
7.03 (d, 3J(1H1H) = 8.1 Hz, 2H), 6.44 (d, 3J(1H1H) =
8.7 Hz, 2H), 7.64–7.74 (m, 14H), 7.16–7.37 (m, 21H,
@C(C6H5)2, P(C6H5)3 and CbH); 31P NMR (CD2Cl2,
20 ꢀC, 121.4 MHz) d = 18.3.
Complex 6 (20 mg) and approx. 4 equiv. of PPh3 were
dissolved in CH2Cl2 (9), or a 90:10 v/v mixture of CH2Cl2
methanol (10), or in a 90:5:5 v/v mixture of CH2Cl2, water
and 2-propanol (2 mL each) in a scintillation vial and placed
in a closed vessel containing diethyl ether (15 mL). The ves-
sel was stored at À20 ꢀC to afford crystals of complexes 9–11
suitable for X-ray diffraction after 3–6 days. 31P NMR (d6-
benzene, 20 ꢀC, 121.4 MHz) were obtained adding 2.0 lL of
O-donor via microliter syringe to a solution of 2 mg of com-
plex 6 in d6-benzene (0.6 mL) which was placed in an NMR
tube sealed with a rubber septum. 9 (EtOH): d = 27.0, 10
(MeOH): d = 27.6, 11 (H2O): d = 27.5.
4.8. (PPh3)2(C7H10N2)Cl2Ru@C@C@CPh2 (12)
4-N,N-dimethylaminopyridine (39 mg, 0.32 mmol) was
added to a slurry of complex 7 (146 mg, 0.158 mmol) and
PPh3 (87 mg) in 2-propanol (15 mL) under non-inert condi-
tions. After the addition, the vessel was immediately closed
with a septum and sonicated for 90 min at 30 ꢀC. During
that time, the yellow slurry turned deep blue. The slurry
4.11. Crystal structure determinations of complexes
5, 7, 9–12, 15
Crystals of 5, C87H70Cl4P4Ru2, FW = 1583.37, 291(2) K,
ꢀ
Mo Ka radiation, triclinic, space group P1 (#2),

5232
E.A. Shaffer et al. / Journal of Organometallic Chemistry 692 (2007) 5221–5233
˚
˚
˚
a = 14.2366(8) A, b = 15.310(3) A, c = 18.9961(16) A,
gas stream of the diffractometer. Data were collected using
graphite-monochromated Mo Ka (k = 0.71073 A) radia-
˚
a = 96.095(11)ꢀ, b = 107.802(6), c = 96.796(9); V =
3869.9(9) A , Z = 2, dcalc = 1.359 Mg/m3, 18772 reflec-
tion. The structure of complex 14 was solved by direct
methods using SHELXS-97 and refined using SHELXL-97
[48]. Non-hydrogen atoms were found by successive full-
matrix least-squares refinement on F2 and refined with
anisotropic thermal parameters. Hydrogen atoms were
placed in calculated positions and refined using a riding
model. A disordered diethyl ether solvent molecule was
refined isotropically.
3
˚
tions, 874 parameters, S = 0.895, R [I > 2r(I)] = 0.049,
wR2 = 0.096. Crystals of 7, a tris-dichloromethane solvate
(one disordered), C51H39Cl3P2Ru Æ 3CH2Cl2, FW =
1178.06, 293(2) K, Mo Ka radiation, monoclinic,
˚
˚
P21/n (#14), a = 12.1954(3) A, b = 24.6253(7) A, c =
3
˚
˚
18.5432(5) A, b = 102.650(3)ꢀ, V = 5433.6(3) A , Z = 4,
dcalc = 1.440 Mg/m3, 15711 reflections, 602 parameters,
S = 1.136, R [I > 2r(I)] = 0.104, wR2 = 0.194. Crystals of
9, C53H46Cl2OP2Ru, FW = 932.81, 293(2) K, MoKa
Acknowledgements
˚
radiation, monoclinic, P21/c (#14), a = 13.6293(4) A, b =
˚
˚
18.2506(5) A, c = 18.4184(5) A, b = 99.784(3)ꢀ, V =
This work was supported by the National Science Foun-
dation. H.J.S. would like to thank the NSF MRSECenter
for Response Driven Films at USM (DMR-0213883) for
providing the REU (Research Experience for Undergradu-
ates) stipend for E.A.S. E.J.V. acknowledges MRI-0618148
and the W. M. Keck Foundation for crystallographic
resources.
4514.8(2) A , Z = 4, dcalc = 1.372 Mg/m3, 10462 reflec-
3
˚
tions, 539 parameters, S = 0.917, R [I > 2r(I)] = 0.044,
wR2 = 0.065. Crystals of 10, C52H44Cl2OP2Ru, FW =
918.78, 296(2) K, Mo Ka radiation, monoclinic,
˚
˚
C2/c (#15), a = 19.0142(10) A, b = 23.5771(11) A, c =
3
˚
˚
19.5359(6) A, b = 91.000(4)ꢀ, V = 8756.6(7) A , Z = 8,
dcalc = 1.394 Mg/m3, 7800 reflections, 523 parameters,
S = 0.730, R [I > 2r(I)] = 0.048, wR2 = 0.063. Crystals of
11, C51H42Cl2OP2Ru, FW = 904.76, 293(2) K, Mo Ka
Appendix A. Supplementary material
˚
radiation, monoclinic, C2/c (#15), a = 18.907(4) A, b =
CCDC 651174, 651173, 651172, 651171, 651170,
651169, 652073 and 651168 contain the supplementary
crystallographic data for 5, 7, 9, 10, 11, 12, 14 and 15.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.08.005.
˚
˚
23.587(2) A, c= 19.5230(18) A, b = 91.249(17)ꢀ, V =
8704(2) A , Z = 8, dcalc = 1.381 Mg/m3, 9981 reflections,
3
˚
520 parameters, S = 0.892, R [I > 2r(I)] = 0.066, wR2 =
0.108. Crystals of 12, C58H50Cl2N2P2Ru, FW = 1008.98,
293(2) K, Mo Ka radiation, monoclinic, Cc (#9),
˚
˚
˚
a = 10.2434(2) A, b = 20.4633(5) A, c = 22.7544(6) A, b =
91.500(2)ꢀ, V = 4768.0(2) A , Z = 4, dcalc = 1.406 Mg/m3,
3
˚
12506 reflections, 586 parameters, S = 0.911,
R
[I > 2r(I)] = 0.045, wR2 = 0.069. Crystals of 15, an ethoxye-
thane solvate (ordered), C53H44Cl2O2P2Ru. C4H10O,
FW = 1020.98, 293(2) K, Mo Ka radiation, monoclinic,
References
˚
˚
P21/n (#14), a = 13.0221(3) A, b = 16.6652(4) A, c =
3
˚
˚
23.0069(5) A, b = 93.545(2)ꢀ, V = 4983.3(2) A , Z = 4,
dcalc = 1.361 Mg/m3, 14699 reflections, 586 parameters,
S = 1.106, R [I > 2r(I)] = 0.086, wR2 = 0.175. Structures
were solved with SHELXS-86 [47]; non-H atoms were modeled
with anisotropic vibrational parameters, H-atoms were
located in difference electron density maps but placed in ide-
alized positions with isotropic vibrational parameters.
Structures were corrected for absorption, and refined by
full-matrix least-squares using SHELXL-97 [48], and refined
to convergence.
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