Reactions of ruthenium acetylide and vinylidene complexes containing a 2-pyridyl group

Article abstract of DOI:10.1021/om800253e

Two ruthenium acetylide complexes [Ru]C≡C(C₅H ₃RN) (1a, R = H; 1b, R = Me; [Ru] = Cp(PPh₃) ₂Ru) containing 2-pyridyl groups are prepared and their chemical reactivities are explored. Protonation of the ruthenium acetylide complex 1a with HBF₄ takes place at both the nitrogen atom and Css, giving the dicationic pyridiniumvinylidene complex {[Ru]=C=C(H)(C₅H ₄NH)}(BF₄)₂ (3a). Addition of BF₃ to la yields the Lewis acid/base adduct [Ru]OC(C₅H₄N← BF₃) (4a). In the presence of moisture both complexes 3a and 4a in solution transform into the cationic heterocyclic carbene complex {[Ru]=C(O)CH2(C₅H₄N←BF₂)}BF₄ (6a), for which the structure is confirmed by X-ray structure determination. The formation of 6a involves the intermediate {[Ru]=C=C(H)(C₅H ₄N←BF₂OH)}BF₄ (5a), characterized by spectroscopic methods. DFT calculations show that the Gibbs free energy change of the exothermic transformation of 5a to 6a is -20.59 kcal/mol. N-Alkylation reactions of 1b with two alkyl bromides BrCH₂R′ (R′ = CH=CHCO₂Me and CO₂Me) yield two pyridiniumacetylide complexes {[Ru]C≡ C(C₅H₃MeNCH₂R′)} Br (7b, R′ = CH=CHCO₂Me; 7c, R′ = CO₂Me, respectively). Complex 7c, characterized by X-ray structure determination, undergoes further protonation to give the pyridiniumvinylidene complex {[Ru]=C=C(H)(C₅H₄NCH₂R′)²⁺ (8c). Interestingly, the acetylide complex 7b undergoes a C-C coupling reaction of the acetylic Css with the C=C double bond to give the vinylidene complex 9b, characterized also by X-ray structure determination.

Full text of DOI:10.1021/om800253e

5212
Organometallics 2008, 27, 5212–5220
Reactions of Ruthenium Acetylide and Vinylidene Complexes
Containing a 2-Pyridyl Group
Hsien-Hsin Chou, Ying-Chih Lin,* Shou-Ling Huang, Yi-Hong Liu, and Yu Wang
Department of Chemistry, National Taiwan UniVersity, Taipei, Taiwan 106, Republic of China
ReceiVed March 18, 2008
Two ruthenium acetylide complexes [Ru]Ct C(C5H3RN) (1a, R ) H; 1b, R ) Me; [Ru] ) Cp(PPh3)2Ru)
containing 2-pyridyl groups are prepared and their chemical reactivities are explored. Protonation of the
ruthenium acetylide complex 1a with HBF4 takes place at both the nitrogen atom and Cꢀ, giving the
dicationic pyridiniumvinylidene complex {[Ru]dCdC(H)(C5H4NH)}(BF4)2 (3a). Addition of BF3 to 1a
yields the Lewis acid/base adduct [Ru]Ct C(C5H4NfBF3) (4a). In the presence of moisture both complexes
3a and 4a in solution transform into the cationic heterocyclic carbene complex {[Ru]dC(O)CH2-
(C5H4NfBF2)}BF4 (6a), for which the structure is confirmed by X-ray structure determination. The
formation of 6a involves the intermediate {[Ru]dCdC(H)(C5H4NfBF2OH)}BF4 (5a), characterized by
spectroscopic methods. DFT calculations show that the Gibbs free energy change of the exothermic
transformation of 5a to 6a is -20.59 kcal/mol. N-Alkylation reactions of 1b with two alkyl bromides
BrCH2R′ (R′ ) CHdCHCO2Me and CO2Me) yield two pyridiniumacetylide complexes {[Ru]Ct
C(C5H3MeNCH2R′)}Br (7b, R′ ) CHdCHCO2Me; 7c, R′ ) CO2Me, respectively). Complex 7c,
characterized by X-ray structure determination, undergoes further protonation to give the pyridiniumvi-
nylidene complex {[Ru]dCdC(H)(C5H4NCH2R′)2+ (8c). Interestingly, the acetylide complex 7b undergoes
a C-C coupling reaction of the acetylic Cꢀ with the CdC double bond to give the vinylidene complex
9b, characterized also by X-ray structure determination.
metathesis reactivity of CdC double bonds so that skeletal
Introduction
rearrangement and cyclization are observed.3
During the past decade, chemistry of transition metal
complexes containing vinylidene ligands has attracted a great
deal of attention because of their occurrence as key intermediates
in many stoichiometric and catalytic transformations of organic
molecules.1 Since the method for the preparation of cationic
bisubstituted vinylidene complexes via electrophilic attack of
metal acetylides was established, the diversity and applications
of these metal vinylidene complexes have further expanded.
Previously we have shown that ruthenium vinylidene complexes
[Ru]dCdC(Ph)CH2R+ ([Ru] ) Cp(PPh3)2Ru) bearing an
electron-withdrawing group R attached at Cγ undergo intramo-
lecular cyclization under mild basic conditions.2 On the basis
of this approach, various mono- and multinuclear neutral metal
cyclopropenyl or furyl complexes have been prepared. Recently,
serendipitous results showed that the ruthenium vinylidene
complex with a pendant terminal vinyl group exhibits excellent
Rich chemistry has been demonstrated for molecules contain-
ing various pyridyl moieties. For example, ortho-substituted
pyridyl groups usually act as building blocks in templating metal
centers by means of coordination, which leads to supramol-
ecules.4 Very recently the metal-mediated C-H activation was
reported to cause formation of pyridine/quinolidene ortho-
carbene complexes.5 ortho-Substitution of an ethynyl group on
pyridine has been under investigation in the development of
nonlinear optics.6 The coordination ability of the N atom of
platinum acetylide complexes with 2-pyridyl functional groups
has also been investigated.4d,e We therefore set a goal to study
* Corresponding author. E-mail: yclin@ntu.edu.tw.
(1) (a) Bruce, M. I. Chem. ReV. 1991, 91, 197. (b) Werner, H. Angew.
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10.1021/om800253e CCC: $40.75
2008 American Chemical Society
Publication on Web 09/26/2008

Reactions of Ruthenium Acetylide
Organometallics, Vol. 27, No. 20, 2008 5213
Scheme 1
Figure 1. ORTEP drawing (30% thermal ellipsoid) of 1b with
phenyl groups on phosphine ligands (except ipso carbon) and
hydrogen atoms eliminated for clarity. Selected bond distances (Å)
and bond angles (deg): Ru1-C1, 2.007(3); C1-C2, 1.216(4);
C2-C3, 1.422(4); Ru1-C1-C2, 174.7(2); C1-C2-C3, 172.5(3).
the chemistry of ruthenium acetylide and vinylidene complexes
containing ortho-pyridyl groups. Herein we report the synthesis
and reactivities of these acetylide and vinylidene complexes
toward protic acids, Lewis acids, and electrophilic alkyl groups.
Results and Discussion
Preparation and Reactions of Ruthenium Pyridylacetyl-
ides. A convenient method was utilized to prepare a ruthenium
pyridylacetylide complex from ruthenium chloride. Thus the
reaction of [Ru]-Cl ([Ru] ) Cp(PPh3)2Ru) with 2-ethynylpy-
ridine in a mixed solvent (CHCl3/MeOH/NEt3) at room tem-
perature exclusively gave the pyridylacetylide complex 1a as a
yellow powder in good yield. Complex 1a shows a 31P
analogue Cp(PPh3)NiCt C(C5H3N-p-NO2) (III, 1.215(7) Å),7b
but is slightly longer than that in II (1.202(8) Å).
resonance at δ 51.0 and CR resonance at δ 124.30 with JCP
)
On the other hand, when the reaction was carried out in a
mixed solvent of CH2Cl2/MeOH at room temperature, the
2-picolylmethoxycarbene complex 2a was obtained (Scheme 1).
This result is different from that in the ruthenium 4-pyridy-
lacetylide complex reported by Lin et al.8a The cationic complex
2a exhibits spectroscopic features different from those of 1a.
The 13C NMR spectrum shows a characteristic carbenoic triplet
resonance of CR at δ 306.0 with JCP ) 12.8 Hz. The 31P NMR
spectrum of 2a shows a singlet at δ 46.6. Furthermore the 31P
NMR results indicate that during the reaction a singlet resonance
at δ 42.0 appeared and diminished as 2a gradually formed. This
intermediate is proposed to be the pyridylvinylidene complex
{[Ru]dCdC(H)(C5H4N)}+. Because of its instability in the
presence of alcohol and in the absence of NEt3, the intermediate
complex will spontaneously undergo nucleophilic addition to
yield the cationic methoxycarbene complex. The electron-
withdrawing ortho-pyridine substituent seems to play a role in
this reaction. Similar reactions involving various vinylidenes
of the type Cp(PR3)2RudCdCRH can lead to alkoxycarbene
in the presence of alcohol, albeit at elevated temperature.9 This
phenomenon prompted us to study the reactivities of the pyridine
moiety implanted in the ruthenium acetylide backbone. The
reactions of complex 1 toward protic acids, Lewis acids, and a
25.8 Hz in the 31P and 13C NMR spectra, respectively. These
are comparable with those of analogous phenylacetylide
derivatives.7a,b The mass spectrum of 1a shows parent peaks at
m/z ) 794.0 for M+ + 1. Similarly the reaction of [Ru]-Cl with
6-methyl-2-ethynylpyridine yielded complex 1b, which has been
characterized by single-crystal X-ray diffraction analysis. The
molecular structure of complex 1b with selected bond lengths
and bond angles is shown in Figure 1. The coordination sphere
surrounding the ruthenium center of 1b adopts a three-legged
piano-stool structure with a typical acetylide skeleton. The
methyl and N atom in the pyridyl group face the same direction
as the bonding of Ru toward the Cp ring centroid. The Ru-C(1)
distance of 2.007(3) Å is a typical Ru-C single bond and is
comparable to the corresponding one in [Ru]Ct CPh (I, 2.017(5)
Å)7a and [Ru]Ct C(C6H4-p-NO2) (II, 1.994(5) Å).7b The
C(1)-C(2) distance of 1.216(4) Å, which is a Ct C triple bond,
is also comparable to that in I (1.214(7) Å) and the nickel
(5) (a) Alvarez, E.; Conejero, S.; Paneque, M.; Petronilho, A.; Poveda,
M. L.; Serrano, O.; Carmona, E. J. Am. Chem. Soc. 2006, 128, 13060. (b)
Esteruelas, M. A.; Ferna´ndez-Alvarez, F. J.; On˜ate, E. J. Am. Chem. Soc.
2006, 128, 13044. (c) Wiedemann, S. H.; Lewis, J. C.; Ellman, J. A.;
Bergman, R. G. J. Am. Chem. Soc. 2006, 128, 2452. (d) Chen, D; Li, Y.;
Wang, B.; Xu, S.; Song, H. Organometallics 2006, 25, 307.
(6) (a) Powell, C. E.; Humphrey, M. G. Coord. Chem. ReV. 2004, 248,
725. (b) Marder, T. B.; Lesley, G.; Yuan, Z.; Fyfe, H. B.; Chow, P.; Stringer,
G.; Jobe, I. R.; Taylor, N. J.; Williams, I. D.; Kurtz, S. K. In Materials for
Nonnlinear Optics: Chemical PerspectiVes; Marder, S. R., John, S., Stucky,
G. D., Eds.; ACS Symp. Ser. A; 1991; Vol. 455, p 605. (c) Naulty, R. H.;
Cifuentes, M. P.; Humphrey, M. G.; Houbrechts, S.; Boutton, C.; Persoons,
A.; Heath, G. A.; Hockless, D. C. R.; Luther-Davies, B.; Samoc, M. J. Chem.
Soc., Dalton Trans. 1997, 4167.
(7) (a) Bruce, M. I.; Humphrey, M. G.; Snow, M. R.; Tiekink, E. R. T.
J. Organomet. Chem. 1986, 314, 213. (b) Whittall, I. R.; Humphrey, M. G.;
Hockless, D. C. R.; Skelton, B. W.; White, A. H. Organometallics 1995,
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(8) (a) Wu, I. Y.; Lin, J. T.; Luo, J.; Sun, S. S.; Li, C. S.; Lin, K. J.;
Tsai, C.; Hsu, C.-C.; Lin, J.-L. Organometallics 1997, 16, 2038. (b) Bruce,
M. I.; Ke, M.; Kelly, B. D.; Low, P. J.; Smith, M. E.; Skelton, B. W.;
White, A. H. J. Organomet. Chem. 1999, 590, 184. (c) Szesni, N.; Drexler,
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(9) (a) Takagi, Y.; Matsuzaka, H.; Ishii, Y.; Hidai, M. Organometallics
1997, 16, 4445. (b) Bruce, M. I.; Duffy, D. N.; Humphrey, M. G.; Swincer,
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A. G. Aust. J. Chem. 1980, 33, 1471.

5214 Organometallics, Vol. 27, No. 20, 2008
Chou et al.
few alkyl halides are thus investigated. Their further transforma-
tions into vinylidene and heterocyclic carbene complexes are
also studied.
Although many reports deal with the coordination ability
of the N atom of the transition metal 2-pyridylacetylides,4d,e
their interaction with protic acids and Lewis acids have not
been thoroughly described. Furnished with acetylide and
pyridyl groups both complexes 1a and 1b are expected to
undergo electrophilic addition. Treatment of complex 1a with
excess HBF4 in diethyl ether produces the bright orange
pyridiniumvinylidene complex {[Ru]dCdC(H)(C5H4NH)}-
(BF4)2 (3a) in high yield (Scheme 1). The 31P NMR spectrum
of 3a shows a singlet resonance at δ 37.3. The 1H NMR
spectrum shows the characteristic broad proton resonance of
NH at δ 12.7 and the relatively downfield singlet resonance
of the vinylidene proton at Cꢀ at δ 5.90. This reveals that
both the pyridyl group and Cꢀ are protonated; thus the
basicity of the pyridine moiety is not diminished in forming
a complex of this system.8 Addition of D2O causes the
exchange of the pyridinium and vinylidene protons of 3a as
shown in the 1H NMR spectrum. Surprisingly, this two-proton
adduct is sufficiently acidic and can even protonate D2O to
effectively restore 1a if excess D2O was added (observed in
nearly 100% NMR yield). In a similar vein, protonation of
complex 1b also gives the dicationic complex {[Ru]dCd
C(H)(C5H3MeNH)}(BF4)2 (3b).
Figure 2. ORTEP drawing (30% thermal ellipsoid) of 6a with
phenyl groups on the phosphine ligands (except the ipso carbon)
and hydrogen atoms eliminated for clarity. Selected bond distances
(Å) and bond angles (deg): Ru1-C1, 1.944(3); C1-C2, 1.520(4);
C2-C3, 1.484(5); C1-O1, 1.308(4); O1-B1, 1.484(5); B1-F1,
1.369; B1-F2, 1.352; Ru1-C1-C2, 123.4(2); C1-C2-C3,
113.7(3);Ru1-C1-O1,124.7(2);C2-C1-O1,111.8(3);C1-O1-B1,
125.4(3); O1-B1-N1, 105.9(3); F1-B1-F2, 112.8(3).
resonance of the methoxy derivative 2a at δ 306.0. The IR
spectrum of 6a reveals an absorption band at ν ) 1350.5 cm-1
,
indicating the presence of a C-O single bond skeleton.10g
Complex 6a has been characterized by X-ray structural deter-
mination. Figure 2 displays an ORTEP drawing and selected
bond lengths and angles of 6a. The Ru-C(1) bond distance of
1.944(3) Å is a typical RudC carbenoic double bond but is
slightly longer than that of the methoxy derivative {[Ru]d
C(OMe)Me}+ (V, 1.931(9) Å),10e whereas the C(1)-O(1) bond
length of 1.308(4) Å is shorter than that in complex V (1.321(9)
Å). The partial delocalization of the cationic charge around
Ru-C(1)-O(1) bonds can be rationalized by the much upfield-
shifted CR resonance of 6a in the 13C spectrum. The O(1)-B(1)
bond distance of 1.484(5) Å is slightly shorter than those in
iron complexes10d and in rhodium complexes.10a For compari-
son, in a trinuclear Ru cluster the bond distances between B-O,
O-C, and average C-Ru10b are 1.508(5), 1.262(4), and 2.004
Å, respectively.
On the other hand, a Lewis acid/base interaction was
observed only at the pyridyl group, and the BF3 adduct of
the pyridiniumacetylide complex [Ru]Ct C(C5H4NfBF3)
(4a) was obtained when complex 1a was treated with excess
BF3-OEt2 (Scheme 1). Binding of the BF3 group is indicated
by the singlet resonance at δ -152.2 in the 19F NMR
spectrum, which is similar to that of the structurally similar
BF4- group at δ -152.0. The 31P NMR spectrum of 4a shows
a singlet resonance at δ 50.9, which is comparable to that of
BF3-free 1a at δ 51.0. The 13C NMR triplet resonance of
CR at δ 173.98 with JCP ) 23.0 Hz is closer to the carbene
region (generally at ca. δ 200) than that of complex 1a (δ
124.30 with JCP ) 25.8 Hz), which is attributed to the partial
contribution of the allenylidene structure (IV) in the ground-
state geometry of complex 4a (Scheme 1).8c
In addition to complex 4a, the pyridiniumvinylidene complex
3a with two BF4- counteranions in solution also yielded 6a in
the presence of moisture. Upon NMR monitoring of a sealed
tube containing a CDCl3 solution of 3a under nitrogen, complex
6a, [Ru]-CO+, and triphenylphosphine oxide were observed in
a 2:1:1 ratio based on 31P NMR integration after 5 days at room
temperature. The 31P NMR resonances of [Ru]-CO+ and
OdPPh3 appear at δ 42.5 and 30.0, respectively.11 The 1H and
13C signals of the Cp group at δ 5.00 and 91.4, respectively,
confirm the formation of [Ru]-CO+. Perhaps trace moisture in
the solution caused decomposition of the BF4- anion of complex
3a to form BF3,12 which then reacted with 3a to result in the
formation of 5a and finally 6a. The methyl derivative 1b
sequentially gave complexes 3b and 5b. However, complex 5b
Complex 4a is air and moisture sensitive and in chloroform
can be cleanly transformed to 5a in the presence of moisture.
In addition, treatment of 3a or 1a with an excess amount of
BF3-OEt2 in the presence of moisture also affords complex
5a (Scheme 1). The reaction of complex 4a with HBF4 in
the presence of H2O at room temperature also gives 5a as a
brown solid in good yield. Complex 5a is believed to be the
cationic pyridiniumvinylidene complex {[Ru]dCdC(H)-
(C5H4NfBF2OH)}BF4 with a BF2OH group on the pyridine
N atom. The 1H NMR spectrum of 5a shows a singlet
resonance at δ 5.90 and a broad peak at δ 12.33 assigned to
the vinylidene ꢀ-proton and the OH group, respectively. The
vinylidene backbone of 5a is reflected by the 13C NMR
resonances of R- and ꢀ-carbons at δ 344.56 and 112.46,
respectively. A 2D NMR 13C-1H HSQC experiment also
confirms the vinylidene group by displaying a cross-peak
between δH of 5.90 and δC of 112.46.
(10) (a) Yeston, J. S.; Bergman, R. G. Organometallics 2000, 19, 2947.
(b) Chipperfield, A. K.; Housecroft, C. E.; Raithby, P. R. Organometallics
1990, 9, 479. (c) Lukehart, C. M.; Raja, M. Inorg. Chem. 1982, 21, 2100.
(d) Butts, S. B.; Strauss, S. H.; Holt, E. M.; Stimson, R. E.; Alcock, N. W.;
Shriver, D. F. J. Am. Chem. Soc. 1980, 102, 5093. (e) Bellachioma, G.;
Cardaci, G.; Foresti, E.; Macchioni, A.; Sabatino, P.; Zuccaccia, C. Inorg.
Chim. Acta 2003, 353, 245. (f) Nakazawa, H.; Yamaguchi, Y.; Miyoshi,
K. Organometallics 1996, 15, 4661. (g) Butts, S. B.; Strauss, S. H.; Holt,
E. M.; Stimson, R. E.; AIcock, N. W.; Shriver, D. F. J. Am. Chem. Soc.
1980, 102, 5093.
Interestingly, in CDCl3 solution, complex 5a further trans-
forms into the new complex 6a in 4 days at room temperature
in ca. 60% yield (Scheme 1). The cationic complex 6a contains
a heterocyclic carbene ligand with a boron atom in the ring.10
The carbenoic triplet resonance of 6a at δC 292.65 with JCP
12.7 Hz shifts slightly upfield than the corresponding CR
)
(11) Bruce, M. I.; Swincer, A. G.; Wallis, R. C. J. Organomet. Chem.
1979, 171, C5.

Reactions of Ruthenium Acetylide
Organometallics, Vol. 27, No. 20, 2008 5215
Figure 3. Optimized geometries and relative Gibbs free energies (kcal/mol) for the conversion of {Cp(PH3)2RudCdC(H)(C5H4NfBF2OH)}+
(A) to heterocyclic carbene {Cp(PH3)2RudCCH2(C5H4Nf BF2O)}+ (D). Values in parentheses are relative electronic energies.
is relatively more stable toward cyclization in solution. Attempts
to promote cyclization of 5b led to decomposition.
reaction. The reaction of [Ru]-Cl with 2-ethynylpyridine in the
presence of CH3I leads to [Ru]-I only.
Given that the aforementioned transformations require the
existence of moisture (either from the air or the solvent), a
deuterium labeling experiment was carried out. To the complex
4a was added an equivalent amount of HBF4 in the presence of
excess D2O. The 31P NMR spectrum of the product shows the
resonance at δ 46.9 of 6a, while the disappearance of the
methylene resonance at δ 5.15 in the 1H NMR spectrum reveals
the doubly deuterated complex (6a-d2). As described below,
because the protonation of a pyridiniumacetylide complex to
give a pyridiniumvinylidene complex is easily achieved, we
believe that the protonation of 4a here involves the formation
of the pyridiniumvinylidene intermediate. Interestingly, no
alkoxycarbene product from the addition at CR was observed
during the reaction. This probably indicates that the pyridyl-
BF3 group is more reactive than the vinylidene group so that
the substitution of F by OH proceeds faster than the nucleophilic
attack at CR. When the 2-pyridyl group is bound to a less
electron-deficient BH3 group, no substitution was observed.
Namely, by treating the pyridylacetylide complex 1a with excess
BH3-THF we prepared the pyridylacetylide complex [Ru]Ct
C(C5H4NfBH3) (4c), which is sufficiently stable at ambient
temperature even in solution for at least 1 week.13
Theoretical Calculations. DFT calculations at the B3LYP/
LanL2DZ16 level by Gaussian 03 were performed to study the
reaction of 5 to 6 in an effort to distinguish two pathways for
the addition of OH to the CdC bond.17 The phenyl groups of
the PPh3 were replaced by hydrogen in our study. Figure 3
displays the optimized geometries and corresponding Gibbs free
energy changes of the conversion of A to D, modeling the
transformation of complex 5 to 6. The Ru-C bond of 1.95 Å,
C-O bond of 1.35 Å, and O-B bond of 1.50 Å of the optimized
structure reasonably match the experimental result obtained from
(12) (a) Cole-Hamilton, D. J. Science 2003, 299, 1702. (b) Ignat’ev,
N. V.; Welz-Biermann, U.; Kucheryna, A.; Bissky, G.; Willner, H. J. Fluor.
Chem. 2005, 126, 1150. (c) Sellin, M. F.; Webb, P. B.; Cole-Hamilton,
D. J. Chem. Commun. 2001, 781. (d) Limmert, M.; Lorenz, I.-P.; Neubauer,
J.; No¨th, H.; Habereder, T. Eur. J. Inorg. Chem. 2001, 1593.
(13) Lesley, M. J. G.; Woodward, A.; Taylor, N. J.; Marder, T. B.;
Cazenobe, I.; Ledoux, I.; Zyss, J.; Thornton, A.; Bruce, D. W.; Kakkar,
A. K. Chem. Mater. 1998, 10, 1355.
(14) The boron-water complex BF3-H2O has been studied for more
than a decade. Decomposition of this complex into B(OH)3 and BF4 anion
has also been reported; see for example: (a) Evans, D. G.; Yeo, G. A.;
Ford, T. A Faraday Discuss. Chem. Soc. 1988, 86, 55. (b) Jacox, M. E.;
Irikura, K. K.; Thompson, W. E. J. Chem. Phys. 2000, 113, 5705. (c)
Ghaemy, M.; Khandani, M. H. Iran. Polym. J. 1997, 6, 5.
The mechanism for the formation of 6a is thus suggested as
followed. Treatment of 4a with HBF4 immediately affords the
vinylidene intermediate {[Ru]dCdC(H)(C5H4NfBF3)}+ (VI).
Substituting one fluoride of the pyridinium-BF3 group by a
hydroxyl group subsequently gives the OH-substituted py-
ridylvinylidene 5a with the formation of a B-OH bond.14 Then
two possible pathways were considered, namely, intramolecular
nucleophilic addition of the OH group onto the vinylidene CR
and 1,3-proton shift and direct nucleophilic addition of the O-H
group onto the vinylidene CRdCꢀ bond, affording the final
product 6a.15
According to this mechanism, it can be visualized that
complex 6 can be prepared directly via a one-pot procedure
from [Ru]-Cl. Actually, in chloroform solution, 10 molar equiv
of BF3-OEt2 and 2-ethynylpyridine were first mixed for 10 min
followed by the addition of [Ru]-Cl. The resulting solution was
stirred for 3 days at room temperature. Workup of the solution
afforded complex 6a in high yield. However, without an excess
amount of BF3, only [Ru]-Cl was obtained. Excess BF3 probably
induces dissociation of the chloride ligand and initiates the
(15) (a) Li, W. T.; Pan, M. H.; Wu, Y. R.; Wang, S. L.; Liao, F. L.;
Liu, R. S. J. Org. Chem. 2000, 65, 3761. (b) Chen, M. J.; Chang, S. T.;
Liu, R. S. Tetrahedron 2000, 56, 5029. (c) Chen, M. J.; Lo, C. Y.; Chin,
C. C.; Liu, R. S. J. Org. Chem. 2000, 65, 6362.
(16) (a) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys 1980, 58, 1200.
(b) Becke, A. D. Phys. ReV. A 1988, 38, 3098. (c) Lee, C.; Yang, W.; Parr,
R. G. Phys. ReV. B 1988, 37, 785. (d) Hay, P. J.; Wadt, W. R. J. Chem.
Phys. 1985, 82, 299.
(17) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y. ; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A.
D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S. ; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,
Revision D.02; Gaussian, Inc.: Wallingford, CT, 2004.

5216 Organometallics, Vol. 27, No. 20, 2008
Chou et al.
Scheme 2
the crystal structure of complex 6a (1.944(3), 1.308(4), and
1.484(5) Å, respectively). In addition, the Ru-C-O bond angle
of 121.4° and C-O-B bond angle of 124.6° also resemble
those of 6a (123.4(2)° and 125.4(3)°, respectively). NBO
analysis18 of D, the modeling complex of 6a, reveals that the
Ru-C and C-O bond orders are 1.46 and 1.95, respectively,
indicating partial delocalization of π-electrons and positive
charge at the carbene moiety. For compound A, the modeling
complex of 5a, the LUMO and LUMO+1 orbitals are largely
localized at CR, showing that an electrophilic attack might take
place there (see Figure S1 in the Supporting Information).
Consequently, the approach of the hydroxyl group of BF2OH
to CR in A caused the formation of the intermediate B, which
is lower in Gibbs free energy than A by -1.66 kcal/mol. B is
formally an intramolecular cyclization product of A, where the
oxygen atom is bound to boron, CR, and a proton. The transition
state (TSAB) is 5.87 kcal/mol higher in free energy than A.
Following the reaction coordinate, the conversion of B to D
first requires the rotation of the Ru-C bond to become the
rotamer C, which is higher in free energy than B by 1.66 kcal/
mol. This can be rationalized by the metal-carbon π-bonding
resulted from different preferred orbital overlap of metal dπ-
orbital with the carbene and vinylidene p-orbital.19 The conver-
sion of C to D is exothermic by -20.59 kcal/mol. However,
this conversion via the transition state TSCD has an activation
free energy of 42.07 kcal/mol. Since experimentally we have
observed that complex 5 spontaneously undergoes isomerization
to give 6 at room temperature in solution, the pathway C f
TSCD f D is thus unfavorable. That is, the direct O-H addition
is less likely. Alternatively, another pathway via a stepwise
deprotonation-protonation process through the intermediate E
is suggested. Although we cannot accurately calculate the
relative energy of E in this system, this C f E f D pathway
is much preferred due to the fact that the spontaneous
transformation of 5 to 6 often occurs in acidic conditions, i.e.,
in the presence of an excess amount of HBF4 during the
synthesis of 6. The overall conversion of A to D is exothermic
by a free energy of -20.59 kcal/mol, which reasonably matches
our experimental observation.
The molecular structure of complex 7c established by single-
crystal X-ray diffraction analysis is shown in Figure 4 with
selected bond lengths and bond angles. Bonding of the pyri-
dinium N-C bond faces the direction parallel to that of the Ru
center to the Cp centroid. The Ru-C(1) single bond distance
(1.977(4) Å) is slightly shorter than that in complex 1b (2.007(3)
Å), whereas the C(1)-C(2) triple bond distance (1.219(5) Å)
is slightly longer than that in 1b (1.216(4) Å) but is shorter
that in the chromium allenylidene complex.8c The Ru-C1-C2
bond angle is approximately the same as that in 1b (174.4(7)°).
This fact might indicate partial contribution of the allenylidene
resonance structure VII shown in Scheme 2 in the solid state.
The 13C resonance of CR of 7d at δ 181.8 compared to that of
1b at δ 117.6 provides further support.
Alkylation Reactions. Reactions of 1 with various alkyl
halides are also studied. At room temperature, treatment of 1a
with 4-bromomethylcrotonate produces the air-stable golden-
yellow product 7a in high yield. The alkylation takes place at
the nitrogen atom. Similarly, facile N-alkylation is observed in
the case of 1b. Treatment of 1b with functionalized alkyl halides
also generates 7b, 7c, and 7d in high yield (Scheme 2).
Complexes 7a-7d were characterized by 1H, 31P, and 13C NMR
and mass spectra. 2D NMR HMBC and HSQC techniques were
also applied to confirm the connectivity between the pyridiyl
and the alkylated group. For example, the 13C NMR spectrum
of 7c shows a triplet resonance assigned to the Ru-CR carbon
The fact that complexes 1a and 1b underwent addition
exclusively at the N atom rather than at Cꢀ might stem from
the intrinsic reactivity of the pyridyl group. A similar event was
observed in the alkylation reaction of tungsten and chromium
pyridylacetylide and indolylacetylide complexes to give alle-
1
at δ 181.8 with JCP ) 22.3 Hz. The H NMR spectrum of 7c
displays a singlet downfield shift resonance of the methylene
protons of the ester group at δ 5.96. Of the most important is
1
the H-13C HMBC spectrum, which shows long-range cou-
plings between the methylene protons at δ 5.96 of the ester
group to both Cꢀ at δ 114.9 and one of the pyridyl carbons at
δ 153.7, but no cross-peak is observed with the CR resonance
at δ 181.8. This demonstrates that the methylene protons of
the ester group are not in the vicinity of CR.
Figure 4. ORTEP drawing (30% thermal ellipsoid) of 7c with
phenyl groups on the phosphine ligands (except the ipso carbon),
hydrogen atoms and the anion eliminated for clarity. Selected bond
distances (Å) and bond angles (deg): Ru1-C1 1.977(4), C1-C2
1.219(5), C2-C3 1.400(5), N1-C9 1.458(5), Ru1-C1-C2 174.7(2),
C1-C2-C3 174.1(3).
(18) Martin, F.; Zipse, H. J. Comput. Chem. 2005, 26, 97.
(19) (a) Schilling, B. E. R.; Hoffmann, R.; Lichtenberger, D. L. J. Am.
Chem. Soc. 1979, 101, 585. (b) Kostic´, N. M.; Fenske, R. F. Organometallics
1982, 1, 974.

Reactions of Ruthenium Acetylide
Organometallics, Vol. 27, No. 20, 2008 5217
Å reveal a typical vinylidene skeleton. The Ru(1)-C(1)-C(2)
bond angle of 166.0(5)° is bent from linear arrangement, which
is possibly due to the steric effect between the CO2Me group
and two PPh3 ligands.2h Attempts to promote a similar coupling
reaction for complex 7d failed to yield the desired product,
indicating the requirement of the activating ester group in this
C-C bond forming reaction.
On the basis of the aforementioned protonation reactions of
pyridylacetylides 1 and pyridiniumacetylides 7, it is reasonable
to assume that formation of 9b from 7b proceeds via an addition
of the activated olefin to Cꢀ, leading to C-C bond formation
generating the RudCdC vinylidene moiety. Addition of a
proton possibly from acid or moisture at the other olefinic carbon
atom then gave the final product. This C-C coupling reaction
occurs between the internal carbon of the allylic moiety and
the acetylide Cꢀ without cleavage of the C-N bond. Reactions
involving coupling of the allylic terminal carbon with transition
metal acetylide complexes have been reported in the literature.21
Preparations of transition metal vinylidene complexes with
monosubstituted Cꢀ are well known in the literature. Yet
preparation of vinylidenes with quarternary Cꢀ directly via
highly substituted alkyl halides5a,b were only scarcely demon-
strated.22 The established alkylating protocol for metal acetylides
provided by Bruce11,23 in reactions with alkyl halides is limited
to primary ones. To our knowledge, these highly branched
ruthenium pyridiniumvinylidenes are unprecedented. Our ob-
servation in the formation of 9b unequivocally serves as an
alternative approach to prepare Cꢀ,Cꢀ-disubstituted vinylidenes
with a stereogenic center simultaneously generated at Cγ.
Figure 5. ORTEP drawing (30% thermal ellipsoid) of 9b with
phenyl groups of PPh3 ligands (except ipso carbon atoms), hydrogen
atoms and the anion are eliminated for clarity. Selected bond
distances (Å) and bond angles (deg): Ru1-C1, 1.820(6); C1-C2,
1.330(9); C2-C3, 1.447(9); C3-N1, 1.333(8); N1-C9, 1.473(9);
Ru1-P1, 2.3715(16); Ru1-P2, 2.3560(16); Ru1-C1-C2, 166.0(5);
C1-C2-C3, 126.3(6); C3-C2-C10, 108.3(5); P1-Ru1-P2,
99.93(5); C1-Ru1-P1, 97.94(17); C1-Ru1-P2, 94.01(19).
nylidene complexes.8c Also in ruthenium 4-pyridylacetylide
complexes, the dangling pyridine was protonated, methylated,
or ligated to tungsten carbonyl fragments to give various
pyridiniumacetylide complexes.8a Interestingly, when the alky-
lation reaction of 1b was carried out in methanol at 60 °C, no
reaction was observed. On the other hand, protonation took place
when strong acid-like HBF4 was used. Treatment of 7a, 7b,
7c, and 7d with excess HBF4 in CH2Cl2 at 0 °C produced
various dicationic pyridiniumvinylidene complexes 8. However,
among these spectroscopically observed pyridiniumvinylidene
complexes only complex 8c, with the CH2CO2Me group, was
isolated. The 31P resonance of phosphorus ligands and 1H
resonance of the Cp group of complex 8c resemble that of
complex 3. Other protonated products could not be isolated,
since the ꢀ-hydrogen of the product is relatively acidic, and
these revert rapidly to pyridiniumacetylides in the presence of
a weak base such as trace amounts of water in the solvent.20
Surprisingly, addition of KPF6 to an acidic solution of 7b at
room temperature resulted in the formation of the brown
dicationic ruthenium vinylidene complex 9b (Scheme 2). A
cyclization by the formation of a C-C bond takes place between
Cꢀ of the vinylidene ligand and one of the olefinic carbons,
leading to a heterocyclic fused-ring ligand. The 31P NMR
spectrum of 9b displays a set of doublets of doublets at δ 41.3
and 39.6 with JPP ) 24.6 Hz due to the presence of a stereogenic
Conclusion
Protonation of the two ruthenium pyridylacetylide complexes
1a and 1b gave pyridiniumvinylidene complexes 3a and 3b,
respectively. Additions of BF3 to 1a take place at the N atom
of the pyridyl group, yielding 4a. This reaction is rationalized
by the Lewis acid/base interaction. Subsequent protonation of
4a in the presence of moisture caused substitution of one F in
the BF3 bonded to the 2-pyridyl group of 4a by an OH group,
giving the vinylidene complex 5a. This is followed by a
spontaneous cyclization reaction, resulting in the formation of
the cationic carbene complex 6a. This spontaneous transforma-
tion of 5a to 6a is further confirmed by DFT calculations using
model complexes. Analogous vinylidene complex 5b could be
obtained from 1b. However, the cyclization process is not
observed in the case of complex 5b. Alkylation of 1a and 1b
also took place preferentially at the N atom of the pyridyl group,
yielding the pyridiniumacetylide complexes 7, which could be
protonated to give pyridiniumvinylidene complexes 8 detected
1
center. The H NMR spectrum shows this methine resonance
at δ 4.72, while the 13C NMR spectrum displays a resonance
of this carbon at δ 32.62. The two methylene groups both split
1
into multiplets in the H NMR spectrum (δ 2.14 and 2.42 for
NCH2; δ 2.38 and 2.42 for the other CH2) because of the
adjacent stereogenic center. Finally, the characteristic R-carbon
resonance at δC of 343.42 and the downfield-shifted Cp
resonance at δH of 5.77 and δC of 97.55 indicate the presence
of a vinylidene structure. 2D NMR COSY, HSQC, and HMBC
techniques are also applied in the structure determination of
9b. The HSQC spectrum clearly displays C-H cross-peaks of
the two methylene groups, and cross-peaks in the HMBC
between the methine and two methylene groups clearly indicate
their connectivity. The structure of 9b is confirmed by X-ray
diffraction analysis. Figure 5 shows an ORTEP drawing and
selected bond lengths and angles of 9b. The Ru(1)-C(1) bond
length of 1.820(6) Å and the C(1)-C(2) bond length of 1.330(9)
(21) (a) George, D. S. A.; Hilts, R. W.; McDonald, R.; Cowie, M.
Organometallics 1999, 18, 5330. (b) Winter, R. F.; Klinkhammer, K.-W;
Za´lisˇ, S. Organometallics 2001, 20, 1317.
(22) (a) Chang, C. W.; Lin, Y. C.; Lee, G. H.; Wang, Y. J. Chem. Soc.,
Dalton Trans. 1999, 4223. (b) Chang, C. W.; Lin, Y. C.; Lee, G. H.; Huang,
S. L.; Wang, Y. Organometallics 1998, 17, 2534. (c) Ipaktschi, J.; Mu¨ller,
B. G.; Glaum, R. Organometallics 1994, 13, 1044. (d) Birdwhistell, K. R.;
Templeton, J. L. Organometallics 1985, 4, 2062. (e) Bruce, M. I.;
Koutsantonis, G. A.; Liddell, M. J.; Tiekink, E. R. T. J. Organomet. Chem.
1991, 420, 253. (f) Bruce, M. I.; Cifuentes, M. P.; Snow, M. R.; Tiekink,
E. R. T. J. Organomet. Chem. 1989, 359, 379. (g) Fischer, H.; Scheck,
P. A. Chem. Commun. 1999, 1031. (h) Lugan, N.; Kelley, C.; Terry, M. R.;
Geoffroy, G. L.; Rheingold, A. L. J. Am. Chem. Soc. 1990, 112, 3220. (i)
Werner, H.; Schneider, D.; Schulz, M. J. Organomet. Chem. 1993, 451,
175.
(23) (a) Davison, A.; Selegue, J. P. J. Am. Chem. Soc. 1978, 100, 7763.
(b) Abbott, S.; Davies, S. G.; Warner, P. J. Organomet. Chem. 1983, 246,
C65. (c) Bianchini, C.; Peruzzini, M.; Vacca, A.; Zanobini, F. Organome-
tallics 1991, 10, 3697.
(20) Bustelo, E.; Jime´nez-Tenorio, M.; Mereiter, K.; Puerta, M. C.;
Valerga, P. Organometallics 2002, 21, 1903.

5218 Organometallics, Vol. 27, No. 20, 2008
Chou et al.
reprecipitation with 60 mL of diethyl ether. The precipitate thus
formed was collected in a glass frit, washed with diethyl ether,
and dried under vacuum. The final product can be obtained as a
brown powder and was identified as complex 2a (255.7 mg, 75%
yield). Anal. (%) Calcd for C49H44F6NOP3Ru: C, 60.62; H, 4.57;
N, 1.44. Found: C, 60.71; H, 4.71; N, 1.32. FAB mass (m/z): 826.3
(M+), 719.2, 564.1 (M+ - PPh3), 429.1 ([Cp(PPh3)Ru]+). IR (KBr,
cm-1): ν 1588.9 (RudC), 1263.7 (br, C-O). 1H NMR (CDCl3): δ
spectroscopically. For the pyridiniumacetylide complex 7d,
containing an unsaturated functional group CH2CHdCHCO2Me
on the pyridinium moiety, the C-C coupling of the acetylide
Cꢀ with the CdC double bond yielded 9b.
Experimental Section
General Procedures. All manipulations were performed under
nitrogen using vacuum-line, glovebox, and standard Schlenk
techniques unless mentioned otherwise. Hexanes and CH2Cl2 were
distilled from CaH2, diethyl ether and THF from sodium benzophe-
none ketyl, and methanol from Mg/I2. All other solvents were of
reagent grade and were used as received. NMR spectra were
recorded on Bruker Avance-400 and DMX-500 FT-NMR spec-
trometers at room temperature (unless stated otherwise) and are
reported in units of δ with residual protons in the solvents as a
standard (CDCl3, δ 7.24; d6-acetone, δ 2.04). FAB mass spectra
were recorded using a JEOL SX-102A spectrometer using 3-ni-
trobenzyl alcohol (NBA) as the matrix. Infrared spectra were
recorded on a Nicolet-MAGNA-550 spectrometer. X-ray diffraction
studies were carried out at the Regional Center of Analytical
Instrument at the National Taiwan University. All reagents were
obtained from commercial suppliers. RuCl3 · xH2O was purchased
from Strem Chemicals. Cp(PPh3)2RuCl24 was prepared following
the method reported in the literature.
3
3
8.26 (d, JHH ) 6.8 Hz,1H, Py), 7,90 (t, JHH ) 6.8 Hz, 1H, Py),
3
7.65 (t, JHH ) 6.8 Hz, 1H, Py), 7.96-6.38 (Ph and Py), 4.99 (s,
2H, CH2), 4.78 (s, 5H, Cp), 3.38 (s, 3H, OCH3). 13C NMR (CDCl3):
2
δ 306.0 (t, JCP ) 12.8 Hz, RuC), 154.77, 148.91, 137.82 (Py)
136.16-127.62 (Ph), 124.49, 122.30 (Py), 91.84 (s, Cp), 64.05 (s,
CH2), 62.23 (s, OCH3). 31P NMR (CDCl3): δ 46.6.
Protonation of 1a and 1b. Complex 1a (182.2 mg, 0.23 mmol)
was dissolved in 80 mL of diethyl ether. The resulting solution
was cooled to 0 °C followed by addition of HBF4 (54 wt % in
diethyl ether, 0.5 mL) via a syringe, and the solution was allowed
to warm to room temperature and stirred for 1 day. After that, the
precipitate was collected by a glass frit, washed with diethyl ether,
and dried under vacuum to afford 3a as an orange powder (211.7
mg, 95% yield). Anal. (%) Calcd for C48H41B2F8NP2Ru: C, 59.53;
H, 4.27; N, 1.45. Found: C, 59.83; H, 4.10; N, 1.52. 1H NMR
(CDCl3): δ 12.7 (br, 1H, NH), 8.29 (1H, Py), 8.14 (1H, Py), 7.93
(1H, Py), 7.59-6.89 (Ph), 5.90 (s, 1H, dCdCH), 5.51 (s, 5H, Cp).
2
13C NMR (CDCl3): δ 346.41 (t, JCP ) 14.6 Hz, RuC), 145.96,
Synthesis of [Ru]Ct C(C5H3RN) (R ) H, 1a; R ) CH3, 1b).
In a Schlenk flask containing a mixed solvent of CHCl3/MeOH/
NEt3 (15:15:1 mL) were added at ambient temperature [Ru]Cl (1.03
g, 1.42 mmol) and 2-ethynyl-6-methylpyridine (406 mg, 3.1 mmol),
and the resulting solution was stirred for 18 h. After that the volatiles
were removed to obtain an oily product, which was redissolved in
10 mL of CH2Cl2 followed by filtration via a small pack of Celite
into 60 mL of methanol. The precipitate thus formed was collected
by filtration and dried under vacuum to afford 1b as a yellow
powder (824 mg, 72.0% yield). The rest of the methanol solution
was evaporated to dryness, and the residue was recrystallized from
CH2Cl2/cold pentane to bring about more desired product 1b as a
brown microcrystal, 34.09 mg (yield ca. 18.3%). Anal. (%) Calcd
for C49H41NP2Ru: C, 72.94; H, 5.12; N, 1.74. Found: C, 72.78; H,
5.10; N, 1.82. FAB mass (m/z): 807.3 (M+), 546.1 (M+ - PPh3),
468.1, 429.1 ([Cp(PPh3)Ru]+). IR (KBr, cm-1): ν 2064.6 (Ct C).
139.47 (Py), 133.22-128.00 (Ph), 125.86, 122.35 (Py), 112.40
(RuCC), 96.58 (Cp). 31P NMR (CDCl3): δ 37.3 (s).
Complex 3b was similarly obtained from 1b in 91% yield.
Spectroscopic data for3b: Anal. (%) Calcd for C49H43B2F8NP2Ru:
1
C 59.90, H 4.41, N 1.43. Found: C, 59.78; H, 4.50; N, 1.52. H
NMR (CDCl3): δ 12.28 (br, 1H, NH), 8.13 (t, 3JHH ) 7.8 Hz, 1H,
Py), 7.59 (d, 3JHH ) 7.8 Hz, 1H, Py), 7.60-7.03 (Ph and Py), 6.10
(s, 1H, RuCCH), 5.50 (s, 5H, Cp), 2.65 (s, 3H, CH3). 31P NMR
(CDCl3): δ 37.8 (s).
Synthesis of [Ru]Ct C(C5H4NfBY3) (Y ) F, 4a; Y ) H,
4c). At room temperature complex 1a (90.3 mg, 0.11 mmol) was
weighted into a Schlenk flask under nitrogen. Diethyl ether (80
mL) was added into the flask via a cannula followed by addition
of BF3-OEt2 (ca. 48%, 0.02 mL) under nitrogen. The resulting
orange cloudy solution was then stirred for 8 h. After that, the
mixture was filtered through a glass frit under nitrogen, and the
solid was washed with diethyl ether and dried under vacuum to
afford 4a as a golden powder (85.9 mg, 88% yield). Anal. (%)
Calcd for C48H39BF3NP2Ru: C, 66.99; H, 4.57; N, 1.63. Found: C,
3
1H NMR (CDCl3): δ 7.46-7.04 (Ph and Py), 6.70 (d, JHH ) 7.7
3
Hz, 1H, Py), 6.43 (d, JHH ) 7.7 Hz, 1H, Py), 4.35 (s, 5H, Cp),
2.50 (s, 3H, CH3). 13C NMR (CDCl3): δ 132.86, 131.98, 131.22,
128.98 (Py), 138.66-127.35 (Ph), 123.38 (Py), 117.57 (RuCC),
115.38 (t, 2JCP ) 5.2 Hz, RuC), 86.02 (Cp), 23.39 (CH3). 31P NMR
(CDCl3): δ 51.2 (s).
1
3
66.79; H, 4.60; N, 1.52. H NMR (CDCl3): δ 8.29 (d, JHH ) 8.3
3
Hz, 1H, Py), 7.68 (t, JHH ) 8.3 Hz, 1H, Py), 7.11-7.39 (Ph),
3
3
7.04 (t, JHH ) 8.3 Hz, 1H, Py), 6.70 (d, JHH ) 8.3 Hz, 1H, Py),
4.54 (s, 5H, Cp). 13C NMR (CDCl3): δ 173.98 (t, 2JCP ) 23.0 Hz,
RuC), 142.53, 139.58, 136.41 (Py), 137.78-127.45 (Ph), 117.15
(Py), 113.08 (RuCC), 87.44 (Cp). 31P NMR (CDCl3): δ 50.9. 19F
NMR (CDCl3): δ -152.2.
Complex 1a was prepared in 73% yield from 2-ethynylpyridine
following the same procedure as that of 1b. Spectroscopic data for
1a: Anal. (%) Calcd for C48H39NP2Ru: C, 72.71; H, 4.96; N, 1.77.
Found: C, 71.88; H, 4.91; N, 1.63. ESI mass (m/z): 794.0 (M+
+
1). 1H NMR (CDCl3): δ 8.39 (d, 3JHH ) 7.6 Hz, Py), 7.30 (t, 3JHH
3
Complex 4c was similarly synthesized from 1a and BH3-THF
in 61% yield. Spectroscopic data for 4c: Anal. (%) Calcd for
C48H42BNP2Ru: C, 71.47; H, 5.25; N, 1.74. Found: C, 71.68; H,
) 7.6 Hz, Py), 7.43-7.05 (Ph), 6.83 (t, JHH ) 7.6 Hz, Py), 6.64
3
(d, JHH ) 7.6 Hz, Py), 4.36 (s, 5H, Cp). 13C NMR (CDCl3): δ
149.03, 147.81 (Py), 139.11-127.01 (Ph), 125.51 (Py), 124.30 (t,
2JCP ) 25.8 Hz, RuC), 117.73 (Py), 116.52 (RuCC), 85.65 (Cp).
31P NMR (CDCl3): δ 51.0.
1
3
5.10; N, 1.62. H NMR (CDCl3): δ 8.51 (d, JHH ) 8.0 Hz, 1H,
Py), 7.07-7.44 (Ph and Py), 6.82 (d, 3JHH ) 8.0 Hz, 1H, Py), 4.51
(s, 5H, Cp), 2.5-3.5 (br, 3H, BH3). 13C NMR (CDCl3): δ 153.47
Synthesis of {[Ru]dC(OMe)CH2(C5H4N)}PF6 (2a). To a
Schlenk flask charged with [Ru]Cl (254.2 mg, 0.35 mmol) and
NaPF6 (56.0 mg, 0.47 mmol) were added 2-ethynylpyridine (0.5
mL, 0.5 mmol) and 35 mL of mixed solvent (CH2Cl2/methanol,
3:4, v/v) under nitrogen. The resulting solution was stirred at room
temperature for 13 h. After that, volatiles were removed and the
solid residue was extracted with 5 mL of CH2Cl2 followed by
2
(t, JCP ) 23.5 Hz, RuC), 147.37, 143.20, 136.55, 128.23 (Py),
138.71-127.39 (Ph), 117.03 (Py), 115.39 (RuCC), 86.58 (Cp). 31
NMR (CDCl3): δ 51.5.
P
Synthesis of {[Ru]dCdC(H)(C5H3RNfBF2OH)}BF4 (5a, R
) H; 5b; R ) Me). To a Schlenk flask containing a CH2Cl2
solution (25 mL) of complex 1a (139.8 mg, 0.18 mmol) was added
BF3-OEt2 (1.25 mL) at room temperature, and the resulting solution
was stirred for 12 h, while the color of the solution turned from
yellow to orange-red. Then volatiles of the solution were removed
(24) Bruce, M. I.; Hameister, C.; Swincer, A. G.; Wallis, R. C. Inorg.
Synth. 1990, 28, 270.

Reactions of Ruthenium Acetylide
Organometallics, Vol. 27, No. 20, 2008 5219
Table 1. Crystal Data and Refinement Parameters for Complexes 1b, 6a, 7c, and 9b
1b
6a
7c
9b
formula
C49H41NP2Ru
806.84
P21/n
8.83500(10)
18.3860(2)
24.0340(2)
90
94.5170(1)
90
3891.96(7); 4
1.40 to 27.49
27 035
8922
0.0387
C52H51B2F6NO2P2Ru
1020.57
P21/c
10.34010(10)
18.5289(2)
25.4882(2)
90
92.3180(10)
90
4879.31(8); 4
1.60 to 27.49
33 479
11 035
0.0513
C53H50BrCl2NO3P2Ru
1062.76
P1
C58H57F12NO3P4Ru
1269.00
P1
mass (amu)
space group
a (Å)
b (Å)
c (Å)
j
j
11.4830(3)
11.9140(3)
20.4030(4)
95.1040(10)
103.5170(10)
112.4140(10)
2459.21(10); 2
1.05 to 27.47
15 898
10 814
0.0512
0.1575
1.094
12.0479(2)
15.3359(2)
16.6007(3)
72.3710(10)
81.1360(10)
86.1200(10)
2887.56(8); 2
1.71 to 27.46
23 576
13 211
0.0877
0.2862
1.110
R (deg)
ꢀ (deg)
γ (deg)
V (Å3); Z
θ range (deg)
no. of data
no. of indep data
R1 for I > 2σ(I)
wR2, all data
goodness-of-fit on F2
0.1140
1.124
0.1560
1.090
under vacuum, and 60 mL of diethyl ether was added into the flask.
The resulting mixtures were stirred vigorously under nitrogen for
1.5 h. Precipitates thus formed were collected by a glass frit, washed
with diethyl ether, and dried in vacuo to give complex 5a as a pale
orange powder (120.9 mg, 72%). Anal. (%) Calcd for
C48H41B2F6NOP2Ru: C, 60.91; H, 4.37; N, 1.48. Found: C, 60.74;
H, 4.10; N, 1.48. 1H NMR (CDCl3): δ 12.33 (br, 1H, OH), 8.14 (t,
to 5 mL and was added into 50 mL of diethyl ether. A bright yellow
precipitate thus formed was filtered through a glass frit, washed
three times with diethyl ether and hexane, and dried under vacuum
to obtain complex 7d (432 mg, 81% yield). Method B: to a Schlenk
flask containing 50 mL of a diethyl ether solution of 1b (47.5 mg,
0.06 mmol) was added 0.1 mL of allyl iodide and the resulting
solution stirred overnight. The golden precipitate thus formed was
collected, washed, and dried under vacuum to afford 7d. The yield
is comparable. Anal. (%) Calcd for C52H46INP2Ru: C, 64.07; H,
4.76; N, 1.44. Found: C, 64.18; H, 4.60; N, 1.52. FAB mass (m/z):
3
3JHH ) 7.2 Hz, Py), 7.71 (d, JHH ) 7.2 Hz, Py), 7.43-6.95 (Ph
and Py), 5.90 (s, 1H, dCdCH), 5.49 (s, 5H, Cp). 13C NMR
(CDCl3): δ 344.56 (t, 2JCP ) 15.7 Hz, RuC), 146.02, 145.94, 139.46
(Py), 133.48-126.50 (Ph), 125.93, 122.42 (Py), 112.46 (RuCC),
96.62 (Cp). 31P NMR (CDCl3): δ 37.6 (s). 19F NMR (CDCl3): δ
-149.6 (br, BF2), -150.7 (BF4).
1
3
848 (M+). H NMR (CDCl3): δ 7.68 (t, JHH ) 7.8 Hz, 1H, Py),
3
7.41-7.05 (Ph and Py), 6.57 (d, JHH ) 7.8 Hz, 1H, Py), 5.89 (s,
2H, CH2), 5.03 (s, 1H, dCH), 4.45 (s, 5H, Cp), 3.71 (s, 2H, dCH2),
2
2.82 (s, 3H, CH3). 13C NMR (CDCl3): δ 181.33 (t, JCP ) 22.5
Complex 5b was prepared using the same procedure as that of
1
Hz,RuC),166.86(dCH2),152.97,141.26,139.26(Py),137.40-127.75
(Ph), 127.38, 120.53 (Py), 114.32 (RuCC), 90.82 (dCH), 87.05
(Cp), 55.01 (CH2), 53.18 (CH2), 22.46 (CH3). 31P NMR (CDCl3):
δ 49.8.
5a in 79% yield. Spectroscopic data for 5b: H NMR (CDCl3): δ
12.14 (br, 1H, OH), 7.99-7.67 (m, Py), 7.54-6.99 (Ph and Py),
6.09 (s, 1H, dCH), 5.46 (s, 5H, Cp), 2.58 (s, 3H, CH3). 13C NMR
(CDCl3): δ 345.82 (t, 2JCP ) 16.2 Hz, RuC), 151.96, 145.77, 145.46
(Py), 134.58-128.55 (Ph), 123.05, 122.59 (Py), 112.48 (RuCC),
96.44 (Cp), 19.47 (CH3). 31P NMR (CDCl3): δ 37.7 (s). 19F NMR
(CDCl3): δ -150.4 (BF4).
Complexes 7a, 7b, and 7c were prepared following the same
procedure as that in 7d. Spectroscopic data for 7a (method B, in
85% yield): Anal. (%) Calcd for C53H46BrNO2P2Ru: C, 65.50; H,
4.77; N, 1.44. Found: C, 65.74; H, 4.81; N, 1.32. 1H NMR (CDCl3):
Synthesis of {[Ru]dC(O)CH2(C5H4NBF2)}BF4 (6a). To a 10
mL chloroform solution of 2-ethynylpyridine (0.4 mL, 3.96 mmol)
at room temperature was added an aliquot of BF3-OEt2 (ca. 48%
in ether, 2 mL, 7.57 mmol). The solution was stirred for 10 min
under nitrogen. Subsequently the solution was transferred to a 25
mL chloroform solution containing [Ru]Cl (514.3 mg, 0.71 mmol)
under nitrogen. After stirring for 2 days the solvent of the resulting
solution was removed and the crude product was extracted with
CH2Cl2. The solution was concentrated and added into diethyl ether,
and the precipitate thus formed was collected by a glass frit, washed
with diethyl ether and hexane, and dried under vacuum to afford
the yellow product 6a (485.2 mg; 85% yield). Anal. (%) Calcd for
C49H43B2F6NOP2Ru: C, 61.27; H, 4.51; N, 1.46. Found: C, 61.51;
H, 4.60; N, 1.42. FAB mass (m/z): 860.4 (M+). IR (KBr, cm-1):
ν 1350.5 (νCO), 1081.9 (m, BF), 1030.2 (m, BF). 1H NMR
3
3
δ 9.30 (d, JHH ) 8.1 Hz, 1H, Py), 7.72 (t, JHH ) 8.1 Hz, 1H,
Py), 7.40-6.89 (Ph and Py), 6.75 (d, 3JHH ) 8.1 Hz, 1H, Py), 6.17
3
(d, JHH ) 15.6 Hz, 1H, dCH), 5.89 (s, 2H, NCH2), 4.45 (s, 5H,
Cp), 3.67 (s, 3H, OCH3). 13C NMR (CDCl3): δ 181.15 (t, JCP
)
2
22.6 Hz, RuC), 165.56, 141.39, 140.05 (Py), 137.41-127.23 (Ph),
124.56, 118.82 (Py), 113.39 (RuCC), 86.85 (Cp), 57.01 (NCH2),
51.60 (OCH3). 31P NMR (CDCl3): δ 49.5.
Spectroscopic data for 7b (method B, in 98% yield): Anal. (%)
Calcd for C54H48BrNO2P2Ru: C 65.79, H 4.91, N 1.42. Found: C,
65.78; H, 5.04; N, 1.41. FAB mass (m/z): 906.3 (M+), 719.3, 645.3,
1
429.0. H NMR (CDCl3): δ 7.62-6.98 (Ph, dCH and Py), 6.66
3
3
(d, JHH ) 8.2 Hz, 1H, Py), 6.03 (d, JHH ) 2.7 Hz, 2H, CH2),
5.77 (m, 1H, dCHCO2Me), 4.47 (s, 5H, Cp), 3.67 (s, 3H, OCH3),
2.91 (s, 3H, CH3). 13C NMR (CDCl3): δ 180.27 (t, JCP ) 22.5
2
3
3
(CDCl3): δ 8.46 (d, JHH ) 7.2 Hz, 1H, Py), 8.30 (t, JHH ) 7.2
Hz,RuC),165.35(CdO),152.48,140.86,140.15(Py),137.40-127.24
(Ph), 122.81, 120.69 (Py), 114.18 (RuCC), 97.50 (dCH), 90.78
3
3
Hz, 1H, Py), 8.03 (d, JHH ) 7.2 Hz, 1H, Py), 7.51 (t, JHH ) 7.2
Hz, 1H, Py), 7.31-6.95 (Ph), 5.15 (s, 2H, CH2), 4.94 (s, 5H, Cp).
(dCH), 86.93 (Cp), 54.62 (CH2), 51.69 (OCH3), 22.08 (CH3). 31
NMR (CDCl3): δ 49.6.
P
13C NMR (CDCl3): δ 292.65 (t, JCP ) 12.7 Hz, RuC), 148.54,
2
145.31, 140.21 (Py), 135.96-128.04 (Ph), 126.60, 124.16 (Py),
92.18 (Cp), 63.11 (CH2). 31P NMR (CDCl3): δ 46.9 (s). 19F NMR
(CDCl3): δ -155.8 (br, 2F, BF2), -152.4 (4F, BF4).
Synthesis of Complexes {[Ru]Ct C(C5H3RNCH2R′)}X (R )
H, R′ ) CHdCHCO2CH3, 7a; R ) Me, R′ ) CHdCHCO2CH3,
7b; R ) Me, R′ ) CO2CH3, 7c; R ) Me, R′ ) CHdCH2, 7d).
Two synthetic methods are used. Method A for 7d: an aliquot of
allyl iodide (1 mL) was added into a 20 mL of CH2Cl2 solution of
1b (507 mg, 0.63 mmol) under nitrogen, and the solution was stirred
at 0 °C overnight. The volume of the resulting solution was reduced
Spectroscopic data for 7c (method A, in 86% yield): Anal. (%)
calcd for C52H46BrNO2P2Ru: C, 65.07; H, 4.83; N, 1.46. Found:
1
C, 65.17; H, 4.91; N, 1.48. FAB mass (m/z): 880.1 (M+ + 1). H
NMR (CDCl3): δ 7.70 (d, 3JHH ) 8.1 Hz, 1H, Py), 7.26-7.12 (Ph
and Py), 6.56 (d, 3JHH ) 8.1 Hz, 1H, Py), 5.96 (s, 2H, CH2), 4.46
(s, 5H, Cp), 3.72 (s, 3H, OCH3), 2.87 (s, 3H, CH3). 13C NMR
(CDCl3): δ 181.76 (t, 2JCP ) 22.3 Hz, RuC), 167.54 (CdO), 153.74,
141.90, 139.95 (Py), 138.06-128.37 (Ph), 128.00, 121.18 (Py),
114.95 (RuCC), 87.68 (Cp), 55.76 (CH2), 53.78 (OCH3), 23.15
(CH3). 31P NMR (CDCl3): δ 49.8.

5220 Organometallics, Vol. 27, No. 20, 2008
Chou et al.
Synthesis of {[Ru]dCdC(H)(C5H3MeNCH2CO2CH3)}(BF4)2
(8c). To a Schlenk flask containing a solution of 7c (45.5 mg, 0.05
mmol) in 20 mL of CH2Cl2 at 0 °C was added HBF4 (54 wt %
diethyl ether solution, 0.1 mL) via a syringe. The resulting solution
was allowed to warm to room temperature in 10 min, and the color
of the solution turned from yellow to brown. Volatiles were
removed under vacuum, and the residue was washed with diethyl
ether. A brown solid thus formed was collected and dried in vacuo
was solved using direct methods and confirmed by Patterson
methods, and refining on intensities of all data gave R1 and wR2
for unique observed reflections (I > 2σ(I)). Hydrogen atoms were
placed geometrically using the riding model with thermal parameters
set to 1.2 times that for the atoms to which the hydrogen is attached
and 1.5 times that for the methyl hydrogens. Structures of complexes
6a, 7c, and 9b were similarly determined. Table 1 lists the crystal
data and refinement parameters for complexes 1b, 6a, 7c, and 9b.
Computational Methods. Theoretical calculations have been
carried out using the Gaussian 03 program17 at the DFT level by
means of the Becke 3 and Lee-Yang-Parr (B3LYP) composite
exchange-correlation functional.16 The LanL2DZ basis sets was
used throughout the calculation, where for the Ru atom the
innermost electrons are replaced by a relativistic ECP and the 18
valence electrons are explicitly treated by a double-ꢁ basis set. Full
geometry optimization without symmetry restrictions was performed
for all structure. Before performing optimization of ground-state
geometries at the B3LYP/LanL2DZ level of theory, the molecular
structures were initially optimized at the semiempirical PM326 level
of calculation. Harmonic frequencies were calculated at the
optimization level using the same basis sets, and the nature of the
stationary points was determined in each case according to the right
number of negative eigenvalues of the Hessian matrix. For each of
the stationary points, the presence of one imaginary frequency
indicates a transition state, while no imaginary frequency indicates
a local minimum. The intrinsic reaction coordinate (IRC) path-
ways27 from the transition structures have been followed using a
second-order integration method28 to verify the expected connec-
tions of the first-order saddle points with the correct local minima
found on the potential energy surface.
1
to afford 8c (38.3 mg, 77% yield). H NMR (CDCl3): δ 8.20 (t,
3
3JHH ) 8.2 Hz, Py), 7.72-6.98 (Ph, Py), 5.85 (d, JHH ) 8.2 Hz,
1H, Py), 5.58 (s, 5H, Cp), 5.01 (s, 2H, NCH2), 4.27 (m, 1H,
dCdCH), 3.77 (s, 3H, OCH3), 2.65 (s, 3H, CH3). 13C NMR
3
(CDCl3): δ 341.77 (t, JCP ) 14.6 Hz, RuC), 189.28 (CdO),
153.58-129.03 (Ph, Py), 101.38 (RuCC), 97.82 (Cp), 54.03
(OCH3),19.85 (CH3). 31P NMR (CDCl3): δ 38.9.
Transformation of Complex 7b to 9b. A CHCl3 solution (4
mL) containing complex 7b (80.4 mg, 0.08 mmol) and KPF6 (33.9
mg, 0.18 mmol) was stirred at ambient atmosphere for 3 days.
Volatiles were removed and the residue was extracted with CH2Cl2
(10 mL), which was added into diethyl ether to form a precipitate,
which was collected, washed with diethyl ether and cold THF, and
dried under vacuum to afford 9b as a brown powder (48.4 mg,
50% yield). Anal. (%) Calcd for C54H49F12NO2P4Ru: C, 54.19; H,
4.13; N, 1.17. Found: C, 54.07; H, 4.10; N, 1.12. FAB mass (m/z):
906.4 (M+ + 1), 726.1, 644.2 (M2+ - PPh3), 429 ([Cp(PPh3)Ru]+).
1H NMR (CDCl3): δ 7.40-6.90 (Ph and Py), 5.77 (s, 5H, Cp),
3
5.59 (m, 1H, NCH), 4.72 (br, 1H, CH), 4.42 (d, JHH ) 11.3 Hz,
1H, NCH), 3.53 (s, 3H, OCH3), 2.74 (s, 3H, CH3), 2.42 (m, 2H)
3
and 2.38 (dd, JHH ) 7.0 Hz, 1H, CH), 2.14 (d, JHH ) 16.1 Hz,
3
1H, CH). 13C NMR (CDCl3): δ 343.42 (t, JCP ) 13.4 Hz, RuC),
171.38 (CO), 152.21, 149.21, 143.44 (Py), 133.87-128.43 (Ph),
124.75, 120.70 (Py), 97.55 (Cp), 61.03 (NCH2), 52.01 (OCH3),
39.59 (CH2), 32.62 (CH), 20.79 (CH3). 31P NMR (CDCl3): δ 41.3,
Acknowledgment. This research is supported by the
National Science Council and National Center for High-
Performance Computing of Taiwan, Republic of China.
2
39.6 (2 d, JPP ) 24.6 Hz).
X-ray Structure Determinations. Details of the structure
analyses carried out on complexes 1b, 6a, 7c, and 9b are given in
Table 1. A single crystal of 1b suitable for an X-ray diffraction
study was glued to a glass fiber and mounted on a Nonius Kappa
CCD diffractometer. The diffraction data were collected using 3
kW sealed-tube molybdenum KR radiation (T ) 295 K). Exposure
time was 5 s per frame. Multiscan absorption correction was applied,
and decay was negligible. Data were processed, and the structures
were solved and refined by the SHELXTL program.25 The structure
Supporting Information Available: Complete crystallographic
data for 1b, 6a, 7c, and 9b (CIF) and detailed computational results.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM800253E
(26) (a) Stewart, J. J. P. J. Comput. Chem. 1989, 10, 207. (b) Stewart,
J. J. P. J. Comput. Chem. 1989, 10, 221.
(27) Fukui, K. Acc. Chem. Res. 1981, 14, 363.
(28) Gonzalez, C.; Schlegel, H. B. J. Phys. Chem. 1990, 94, 5523.
(25) SHELXTL: Structure Analysis Program, version 5.04; Siemens
Industrial Automation Inc.: Madison, WI, 1995.