Reactions of [Cp*Ru(H2O)(NBD)]+ with dihydrogen, silanes, olefins, alkynes, and allenes

Article abstract of DOI:10.1021/om0600285

Formal [2+2+2] addition reactions of the NBD ligand in [Cp*Ru(H ₂O)(NBD)]BF₄ (NBD = norbornadiene) with H₂, Ph₃SiH, ArCH=C=CH₂, and RC≡CPh were observed. In contrast, olefins such as styrene and NBD d

Full text of DOI:10.1021/om0600285

2344
Organometallics 2006, 25, 2344-2354
Reactions of [Cp*Ru(H2O)(NBD)]+ with Dihydrogen, Silanes,
Olefins, Alkynes, and Allenes
Peng Xue, Jun Zhu, Sheng Hua Liu, Xin Huang, Weng Sang Ng, Herman H. Y. Sung,
Ian D. Williams, Zhenyang Lin,* and Guochen Jia*
Department of Chemistry and Open Laboratory of Chirotechnology of the Institute of Molecular
Technology for Drug DiscoVery and Synthesis, The Hong Kong UniVersity of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong
ReceiVed January 10, 2006
Formal [2+2+2] addition reactions of the NBD ligand in [Cp*Ru(H2O)(NBD)]BF4 (NBD )
norbornadiene) with H2, Ph3SiH, ArCHdCdCH2, and RCtCPh were observed. In contrast, olefins such
as styrene and NBD do not undergo similar [2+2+2] addition reactions with [Cp*Ru(H2O)(NBD)]BF4.
[Cp*Ru(H2O)(NBD)]BF4 reacts with H2 in benzene to give [Cp*Ru(η6-C6H6)]BF4 and nortricyclene.
Similarly, [Cp*Ru(H2O)(NBD)]BF4 reacts with Ph3SiH to give [Cp*Ru(η6-C6H5SiPh2OH)]BF4 and
nortricyclene. Treatment of [Cp*Ru(H2O)(NBD)]BF4 with styrene produces [Cp*Ru(η6-C6H5-CHdCH-
C7H9)]BF4, [Cp*Ru(η6-C6H5-CHdCH2)]BF4, C6H5-CHdCH-C7H9, and Cp*Ru(η5-C5H4-C9H11). The latter
complex is also produced from the reaction of [Cp*Ru(H2O)(NBD)]BF4 with NBD. Treatment of [Cp*Ru-
(H2O)(NBD)]BF4 with ArCHdCdCH2 produces [Cp*Ru(η6-Ar-C10H11)]BF4. Reactions of [Cp*Ru(H2O)-
(NBD)]BF4 with RCtCC6H5 (R ) Ph, Me) give [Cp*Ru(η6-C6H5-C10H8R)]BF4. The reaction pathways
of the coupling reactions have been studied by computational chemistry.
ing electron pairs to an empty orbital of the metal and metal-
ligand π-bonds by back-donation of metal dπ-electrons to the
σ*-orbitals.6 Alkenes, allenes, and alkynes form metal-ligand
σ-bonds by donating their π-bonding electron pairs to an empty
orbital of the metal and metal-ligand π-bonds by back-donation
of metal dπ-electrons to the π*-orbitals. It is then of interest to
see if these ligands could also undergo mechanistically related
organometallic reactions. Such a comparative study may help
to develop the chemistry or catalytic reactions of less-developed
systems based on the knowledge of well-developed related
systems.
Introduction
Dihydrogen, silanes, alkenes, allenes, and alkynes are im-
portant ligands in organometallic chemistry.1 As illustrated
below by structures A-E, they can form metal complexes
through coordination of a single, double, or triple bond,
respectively.
In this work, we have studied the coupling reactions of H2,
Ph3SiH, olefins, allenes, and PhCtCR with norbornadiene
(NBD) mediated by [Cp*Ru]+. Cyclopentadienienyl-ruthenium
fragments have been used widely in organometallic chemistry7
and have found increasing applications in catalysis.8,9 Experi-
mentally, we found that formal [2+2+2] addition reactions
occur between NBD and substrates such as H2, Ph3SiH, ArCHd
In terms of their bonding interactions with transition metal
centers, these ligands are quite similar. Dihydrogen2,3 and
silanes4,5 form metal-ligand σ-bonds by donating their σ-bond-
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10.1021/om0600285 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/30/2006

Reactions of [Cp*Ru(H2O)(NBD)]+
Organometallics, Vol. 25, No. 9, 2006 2345
Scheme 1
CdCH2, and PhCtCR, while a similar reaction is not observed
for the reactions with olefins. To understand the origin of the
similarity and difference in the reactivity, we have also carried
out computational studies on the intramolecular coupling
reactions of the model complex [CpRu(substrate)(NBD)]+. The
preliminary results have been communicated,10 and we now
report the details of this study.
Results and Discussion
Reaction with Dihydrogen. Exposure of a solution of
[Cp*Ru(H2O)(NBD)]BF4 (1)11 to H2 in the presence of benzene
produced [Cp*Ru(η6-C6H6)]BF4 (2) and nortricyclene (3) (eq
1). In the reaction, benzene was purposely added to trap the
[Cp*Ru]+ fragment by forming complex 2. In the absence of
benzene, the reaction of 1 with H2 in THF produced unidentified
hydride species. Complex 212 and nortricyclene (3)13 could be
readily identified by comparing their 1H and 13C NMR
spectroscopic data with those reported.
(M ) Cr, Mo, and W) have been characterized by IR
spectroscopy and were proposed as the intermediates in pho-
tocatalytic hydrogenation of norbornadiene to nortricyclene.15,16
The reaction pathway shown in Scheme 1 has been studied
computationally with the model complex [CpRuH2(NBD)]+.10
The calculations suggest that [CpRuH2(NBD)]+ is indeed a
dihydrogen complex with a H-H distance of 0.857 Å and that
the stepwise intramolecular hydrogen transfer reaction of the
dihydrogen complex [CpRu(H2)(NBD)]+ can proceed readily
with a very low reaction barrier (ca. 5.5 kcal/mol, see Figure
1a), confirming the proposed mechanism shown in Scheme 1.
Nortricyclene can be thought of as formed by a formal
[2+2+2] addition reaction of H2 with NBD. A plausible
mechanism for the reaction is shown in Scheme 1. As complex
[Cp*Ru(H2)(COD)]+ is known to contain a dihydrogen ligand,14
it is reasonable to assume that reaction of [Cp*Ru(H2O)(NBD)]+
with H2 initially gave the dihydrogen complex [Cp*Ru(H2)-
(NBD)]+ (F) (rather than the dihydride [Cp*RuH2(NBD)]+),
which undergoes a hydrogen transfer reaction to give intermedi-
ate G. The intermediate G may then undergo an insertion
reaction to give H. A reductive elimination reaction of H would
give 3 and the [Cp*Ru]+ fragment. Further reaction of the
[Cp*Ru]+ fragment with benzene would produce complex 2.
The related dihydrogen complexes fac-[M(H2)(η4-NBD)(CO)3]
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Figure 1. Schematic illustration of the stepwise reaction pathways
for [CpRu(η2-H2)(NBD)]+ (a) and [CpRu(η2-Me3SiH)(NBD)]+ (b)
together with calculated relative energies (kcal/mol) and free
energies (kcal/mol, in parentheses) for species involved in the
reactions.
Reaction with Ph3SiH. Silanes R3SiH are similar to dihy-
drogen in that both of them may form σ-complexes with the
same metal fragment.4 Thus, we expect that reaction of silanes
(14) Jia, G.; Ng, W. S.; Lau, C. P. Organometallics 1998, 17, 4538.

2346 Organometallics, Vol. 25, No. 9, 2006
Xue et al.
Scheme 2
Figure 2. X-ray structure of the cation of [Cp*Ru(η6-C6H5-SiPh2-
OCH3)]BPh4 (4). The counteranion is omitted for clarity.
(I), which undergoes a stepwise hydrogen transfer reaction to
give intermediate J. The stepwise hydrogen transfer reaction
can occur by either first transferring an H followed by SiPh3 or
first transferring SiPh3 followed by an H. A reductive elimina-
tion reaction of J followed by coordination of an aryl group to
ruthenium would give K, which reacts with water to give
nortricyclene 3 and complex 4OH. Although we have failed to
identify the η2-silane intermediate, reported complexes closely
related to the intermediate I including [Cp(PMe3)2Ru(η2-
HSiCl3)]+,17a,b Cp*RuCl(η2-HSiClMe2)(PiPr3),17c and [Cp(CO)-
(PEt3)Fe(η2-HSiEt3)]+ 17d are known. We noted that hydrosila-
tion of alkynes catalyzed by [CpRu(CH3CN)3]+ has been
reported recently. η2-Silane intermediates were also suggested
as the reaction intermediates in the hydrosilation reactions.18
To verify the proposed mechanism and to compare the
reaction profile with that of the hydrogenation reaction, a
computational study was carried out. The results confirm that
the model complex [CpRu(H-SiMe3)(NBD)]+ (PC-silane) is a
nonclassical silane complex with an Si-H bond distance of
1.717 Å.
with [Cp*Ru(H2O)(NBD)]BF4 would give [Cp*Ru(η2-R3SiH)-
(NBD)]BF4, which may undergo a similar [2+2+2] addition
reaction.
To test this hypothesis, we have studied the reaction of
[Cp*Ru(H2O)(NBD)]BF4 with Ph3SiH. Treatment of [Cp*Ru-
(H2O)(NBD)]BF4 (1) in dichloromethane or acetone with
Ph3SiH produced [Cp*Ru(η6-C6H5SiPh2OH)]BF4 (4OH) and
nortricyclene (3) (eq 2). We have tried to grow single crystals
of 4OH in order to confirm its structure by X-ray diffraction.
However, all of our attempts to grow crystals of 4OH from
various solvent systems failed. The crystallization process often
leads to the formation of an oily residue. With the hope of
obtaining crystalline material, we have tried to exchange the
-
-
counteranion BF4 in 4OH with BPh4 by treatment with
NaBPh4. When the metathesis reaction was carried out in
methanol, the OH group in 4OH is changed to OMe, due to
the reaction of the Si-OH functional group with MeOH (eq
2). Thus we have isolated compound 4 in good yield from the
reaction of 4OH with NaBPh4 in methanol.
We have examined the reaction profile of the formal [2+2+2]
addition reaction of Me3SiH with the NBD ligand in PC-silane.
Figure 1b shows two possible pathways for the conversion of
PC-silane to PR-silane, a model precursor complex to addition
products. Path a starts with the hydride migration with the
cleavage of the H-SiMe3 bond to form the IN1-silane-a
intermediate. Then the silyl migration gives the PR-silane
intermediate. Path b starts with the silyl migration to form the
IN1-silane-b intermediate. Then the hydride migration leads
to the formation of PR-silane. One can see that not only is the
barrier of the first step of path a lower than that of path b, but
also the first intermediate (IN1-silane-a) is more stable than
that of path b. It is understandable that a hydride migration is
easier than a silyl transfer due to the bulky group of the latter.
Moreover, the higher stability of IN1-silane-a versus IN1-
silane-b is apparently related to the agostic bonding found in
the former. Thus, path a was calculated to be more favorable.
It is worth noting that at first glance the conversion of PC-
silane to PR-silane seems thermodynamically unfavorable. A
thermodynamic driving force for the experimental addition
The structure of 4 has been determined by X-ray diffraction.
A view of the cation of 4 is shown in Figure 2, and selected
bond distances and angles are given in Table 1. The solid-state
structure is consistent with the solution NMR data. In particular,
1
the H NMR spectrum in CDCl3 showed the OMe signal at
3.67 ppm and the η6-C6H5 signal at 4.91 (1H), 4.98 (2H), and
5.48 (2H) ppm.
Scheme 2 shows a plausible mechanism for the formation of
complex 4OH. Reaction of [Cp*Ru(H2O)(NBD)]+ with Ph3SiH
can initially give the σ-complex [Cp*Ru(η2-Ph3SiH)(NBD)]+
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2002, 21, 2030. (b) Lemke, F. R. J. Am. Chem. Soc. 1994, 116, 11183. (c)
Osipov, A. L.; Vyboishchikov, S. F.; Dorogov, K. Y.; Kuzmina, L. G.;
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123, 12726.

Reactions of [Cp*Ru(H2O)(NBD)]+
Organometallics, Vol. 25, No. 9, 2006 2347
Table 1. Crystal Data and Structure Refinement for [Cp*Ru(η6-C6H5-SiPh2OCH3)]BPh4 (4), [Cp*Ru(η6-C6H5-C10H11)]BPh4
(12BPh4), and [Cp*Ru(η6-p-CH3C6H4-C10H11)]BPh4 (12BPh4)
4
11BPh4
12BPh4
empirical formula
fw
C53H53BORuSi
845.92
C50H51BRu
763.79
C51H53BRu‚0.25CH3OH
785.82
wavelength, Å
cryst syst
space group
a, Å
0.71073
monoclinic
P21/c
13.5964(10)
0.71073
orthorhombic
P212121
12.6430(9)
0.71073
triclinic
P1h
11.4214(8)
b, Å
15.9305(12)
16.8636(13)
12.2316(8)
c, Å
19.8104(15)
90
94.9360(10)
90
4275.0(6)
4
1.314
0.433
17.9064(13)
90
90
90
3817.8(5)
4
1.329
0.446
16.3587(11)
99.6840(10)
103.7620(10)
109.4750(10)
2014.8(2)
R, deg
â, deg
γ, deg
volume, Å3
Z
2
density (calcd), g/cm3
abs coeff, mm-1
F(000)
1.295
0.425
825
1768
1600
cryst size, mm3
θ range, deg
index ranges
0.40 × 0.25 × 0.15
1.50 to 26.00
-15 e h e 16, -19 e k e 19,
-23 e l e 24
28 177
0.35 × 0.15 × 0.10
1.66 to 28.36
-16 e h e 16, -22 e k e 19,
-23 e l e 23
26 318
0.40 × 0.15 × 0.10
1.33 to 26.00
-12 e h e 14, -14 e k e 15,
-20 e l e 20
12 961
no. of rflns collected
no. of indep rflns
max./min. transmn
8339 [R(int) ) 0.0350]
1.00/0.91
9107 [R(int) ) 0.0439]
1.00/0.91
7732 [R(int) ) 0.0174]
1.00/0.90
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
largest diff peak and hole, e Å-3
8339/0/514
1.021
R1 ) 0.0325, wR2 ) 0.0781
0.616 and -0.324
9107/0/471
1.002
R1 ) 0.0355, wR2 ) 0.0732
0.740 and -0.295
7732/1/486
1.073
R1 ) 0.0285, wR2 ) 0.0707
0.527 and -0.323
reaction is that the silyl-substituted nortricyclene ligand, resulting
from the reductive elimination of PR-silane, is able to rearrange
in such a way that the [Cp*Ru]+ fragment coordinates with one
of the phenyl rings (H-SiPh3 was used in the experiments) in
the silyl substituent, giving a much more stable η6-aryl metal
complex.
It is clear from Figure 1 that the hydrosilyation reaction is
more difficult than the hydrogenation reaction, primarily due
to the formation of the weaker Ru-Si and C-Si bonds in the
hydrosilation reaction in comparison with the strong Ru-H and
C-H bonds in the hydrogenation reaction and the inability of
the formed C-Si bond to interact with Ru â-agostically in the
hydrosilation reaction.
Reactions with Olefins. H2 and Ph3SiH undergo formal
[2+2+2] addition reactions with the NBD ligand in [Cp*Ru-
(H2O)(NBD)]BF4. The reactivity is associated with the H-H
or Si-H single bond. To see how a substrate with a CdC double
bond may react with [Cp*Ru(H2O)(NBD)]BF4, we have studied
the reaction of CH2dCHPh with [Cp*Ru(H2O)(NBD)]BF4 (1).
No appreciable reactions were observed when a mixture of 1
and styrene in dichloromethane was stored at room temperature
for 3 h. When the reaction mixture was stored at room
temperature for 2 days, a mixture of species was produced, from
which complexes 5BPh4 (after treatment with NaBPh4), 6BF4,
7, and 8 can be isolated (Scheme 3). Unlike the reaction of H2
or Ph3SiH, the product due to [2+2+2] addition of styrene to
NBD was not detected in the styrene reaction. Formation of
5-8 is unusual because addition products are usually obtained
in metal-promoted coupling reactions of norbornadiene with
olefins.19
The new compounds 5BPh4, 6BF4, and 7 have been
characterized by NMR spectroscopy and elemental analysis. The
structure of 5BPh4 has been confirmed by X-ray diffraction as
mentioned in our preliminary report.10 The complex cation
[Cp*Ru(styrene)]+ (6+) was previously made from the reaction
of [Cp*Ru(CH3CN)3]+ with styrene.20 Complex 8 is also a
known complex and was previously obtained by Girolami et
al. from the reaction of [Cp*RuCl2]2 with NBD in refluxing
ethanol.21 Our NMR data are fully consistent with those
reported.
Compounds 5 and 7 can be thought of as being formally
formed by addition of a C-H bond of styrene across one of
the double bonds of NBD. Mechanistically, the production of
compounds 5-7 can be rationalized by the sequence shown in
Scheme 4. Reaction of [Cp*Ru(H2O)(NBD)]+ with PhCHdCH2
initially could give the olefin complex [Cp*Ru(η2-PhCHdCH2)-
(NBD)]+ (L), which undergoes an oxidative coupling reaction
to give intermediate M. Oxidative coupling reactions of allenes
with olefins on a [CpRu]+ fragment to give metallacyclopen-
tanes have been proposed previously for the coupling reactions
of allenes with olefins mediated by CpRuCl(COD) (COD )
1,5-cyclooctadiene) or [CpRu(CH3CN)3]+.22 Closely related
metallacycles, namely, ruthenacyclopentadienes with CpRu or
Cp*Ru, have been isolated previously from the oxidative
coupling of alkynes on a CpRu or Cp*Ru fragment.23 Interme-
diate M can undergo a â-H elimination reaction to give the
Scheme 3
(19) Lautens, M.; Klute, W.; Tam, W. Chem. ReV. 1996, 96, 49.
(20) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc. 1989,
111, 1698.
(21) Brumaghim, J. L.; Girolami, G. S. J. Organomet. Chem. 1999, 586,
258.
(22) (a) Trost, B. M.; Pinkerton, A. B. J. Am. Chem. Soc. 1999, 121,
4068. (b) Trost, B. M., Pinkerton, A. B.; Seidel, M. J. Am. Chem. Soc.
2001, 123, 12466.

2348 Organometallics, Vol. 25, No. 9, 2006
Xue et al.
Scheme 4
Scheme 5
key intermediate N. A recent study shows that a â-H elimination
reaction involving five-membered ruthenacyclopentanes can
occur easily.24 A reductive elimination reaction of N followed
by coordination of the Ph group of the coupled organic ligand
to [Cp*Ru]+ would give 5BF4, and by coordination of the Ph
group of styrene present in solution to [Cp*Ru]+ would give
6BF4.
It is interesting to note that a small amount of complex 8
was also produced in the reaction of [Cp*Ru(H2O)(NBD)]BF4
with styrene. Apparently, complex 8 is formed from the reaction
of [Cp*Ru(H2O)(NBD)]BF4 with NBD, which may be released
from substitution reaction of [Cp*Ru(H2O)(NBD)]BF4 with
styrene. In fact, it can be demonstrated that complex 8 was
produced cleanly when a mixture of [Cp*Ru(H2O)(NBD)]BF4
and NBD was stood at room temperature overnight.
Scheme 5 shows a plausible mechanism for the formation of
8 in the reaction of [Cp*Ru(H2O)(NBD)]BF4 with NBD.
Reaction of [Cp*Ru(H2O)(NBD)]+ with NBD initially could
give the olefin complex [Cp*Ru(η2-NBD)(η4-NBD)]+ (O),
which undergoes an oxidative coupling reaction to give inter-
mediate P. Although we have not being able to identify P in
our case, a few complexes related to intermediate P, i.e., formed
from oxidative coupling of two NBD ligands, have been
previously isolated and well characterized.25 Intermediate P can
undergo a C-C bond cleavage reaction to give the allyl complex
Q. The allyl complex Q could undergo olefin insertion to give
another allyl complex R, which can undergo a â-H elimination
reaction to give the cyclopentadiene complex S. A reductive
(23) (a) Yamamoto, Y.; Arakawa, T.; Itoh, K. Organometallics 2004,
23, 3610. (b) Yamamoto, Y.; Arakawa, T.; Ogawa, R.; Itoh, K. J. Am. Chem.
Soc. 2003, 125, 12143. (c) Kirchner, K.; Calhorda, M. J.; Schmid, R.; Veiros,
L. F. J. Am. Chem. Soc. 2003, 125, 11721. (d) Yamada, Y.; Mizutani, J.
Kurihara, M.; Nishiyama, H. J. Organomet. Chem. 2001, 637-639, 80. (e)
Ernst, C.; Walter, O.; Dinjus, E. J. Organomet. Chem. 2001, 627, 249. (f)
Ernst, C.; Walter, O.; Dinjus, E.; Arzberger, S.; Gorls, H. J. Prakt. Chem.
1999, 341, 801. (g) Gemel, C.; Lapensee, A.; Mauthner, K.; Mereiter, K.;
Schmid, R.; Kirchner, K. Monatsch. Chem. 1997, 128, 1189. (h) Albers,
M. O.; de Waal, D. J. A.; Liles, D. C.; Robinson, D. J.; Singleton, E.; Wiege,
M. B. J. Chem. Soc., Chem. Commun. 1986, 1680. (i) Yi, C. S.; Torres-
Lubian, J. R.; Liu, N. Organometallics 1998, 17, 1257.
(24) Huang, X.; Zhu, J.; Lin, Z. Organometallics 2004, 23, 4154.
(25) See for example: (a) Itoh, K.; Oshima, N.; Jameson, G. B.; Lewis,
H. C.; Ibers, J. A. J. Am. Chem. Soc. 1981, 103, 3014. (b) Itoh, K.; Oshima,
N. Chem. Lett. 1980, 1219. (c) Bezman, S. A.; Bird, P. H.; Fraser, A. R.;
Osborn, J. A. Inorg. Chem. 1980, 19, 3755. (d) Brumaghim, J. L.; Feldhoff,
U.; Grevels, F. W.; Grubbs, R. H.; Miyashita, A. J. Organomet. Chem.
1979, 173, 253.
elimination reaction of S would give T, which can be depro-
tonated by water to give 8. Although rare, other examples of
skeletal rearrangements of NBD or norbornenyl ligands on
coordinated unsaturated metal centers to form organic ligands
with a five-membered ring are known, for example, in the
reaction of Cp*RuCl(NBD) with AgBF4 to give [Cp*Ru(η6-
C5H4dCHCH3)]BF411 and in the reaction of CpCo(NBD) with
HBF4 to form [CpCo(C5H6CHdCH2)]BF4.26
(26) (a) Bennett, M. A.; Nicholis, J. C.; Rahman, A. K. F.; Redhouse,
A. D.; Spencer, J. L.; Willis, A. C. J. Chem. Soc., Chem. Commun. 1989,
1328. (b) Nicholis, J. C.; Redhouse, A. D.; Spencer, J. L. Organometallics
1994, 13, 1781.

Reactions of [Cp*Ru(H2O)(NBD)]+
Organometallics, Vol. 25, No. 9, 2006 2349
Scheme 6
Scheme 7
[Cp*Ru(H2O)(NBD)]BF4 with ArCHdCdCH2 were carried out.
Reactions of [Cp*Ru(H2O)(NBD)]BF4 with phenylallenes PhCHd
CdCH2 produced a mixture of species, from which complex
11BF4 can be isolated. Complex 11BF4 can be converted to
11BPh4 on treatment with NaBPh4. Similarly, reactions of
p-tolylCHdCdCH2 produced 12BF4, which can be converted
to 12BPh4 on treatment with NaBPh4 (Scheme 7).
The structures of complexes 11BPh4 and 12BPh4 have been
determined by X-ray diffraction studies. The structures of the
cations of these two complexes are shown in Figures 3 and 4,
respectively. Selected bond distances and angles are given in
Table 2. The X-ray structures clearly reveal that an allene
molecule is cycloadded to the NBD ligand through the aryl-
Reactions with Alkynes. Both alkynes and olefins are
unsaturated organic substrates. However, alkynes are slightly
different from olefins in that olefins have only one π-bond but
alkynes have one extra π-bond. It is therefore interesting in
knowing whether alkynes will have similar or different reactivity
toward [Cp*Ru(H2O)(NBD)]BF4 compared with olefins. It was
found that alkynes are more reactive toward 1 than styrene or
NBD. [Cp*Ru(H2O)(NBD)]BF4 in dichloromethane rapidly
reacted with MeCtCPh to give 9BF4 (Scheme 6), which has
been characterized by NMR as well as X-ray diffraction, as
reported in our preliminary report.10 Similarly, reaction with
PhCtCPh also gave the analogous complex 10BF4, the structure
of which can be readily assigned on the basis of its NMR
spectroscopy.
1
substituted CdC bond of allenes. The solution H NMR data
are consistent with the solid structures. It is interesting to note
that the aryl-substituted CdC bond rather than the nonsubstituted
CdC bond is coupled with NBD. The higher reactivity of the
aryl-substituted CdC bond versus the nonsubstituted CdC bond
Overall, the reaction between RCtCPh and 1 is similar to
that between hydrogen or Ph3SiH and 1 in that a formal
[2+2+2] addition of RCtCPh to NBD also occurred. It is
assumed that complexes 9 and 10 are formed through the alkyne
complexes U, which evolve to the isolated products through
intermediates V and W by oxidative coupling of alkyne and
NBD, followed by olefin insertion, reductive elimination, and
coordination of an aryl group. The reaction pathway is supported
by theoretical calculations (see discussion below). Ruthenacyclo-
pentene complexes have been proposed as the key intermediates
in alkyne-alkene coupling reactions catalyzed by ruthenium
complexes such as CpRuCl(COD) and [CpRu(CH3CN)3]PF6.8
Formation of complexes 9 and 10 is probably not surprising,
as catalytic [2+2+2] homo-Diels-Alder cycloadditions of
RCtCR′ to NBD have been achieved with complexes such as
[Co(acac)3]/PR3/Et2AlCl.19 Homo-Diels-Alder cycloadditions
of RCtCR′ to COD could also be effected by ruthenium
complexes such as (η5-C9H7)RuCl(COD) and CpRuCl(COD).27
Interestingly, Cp*RuCl(COD) catalyzed [2+2] cycloadditions
of alkynes to NBD.28
Figure 3. X-ray structure of the cation of [Cp*Ru(η6-C6H5-C10H11)]-
BPh4 (11BPh4). The counteranion is omitted for clarity.
Reactions with Arylallenes. Allenes RCHdCdCH2 have
two adjacent double bonds. Allenes are structurally similar to
olefins in that they all have a CdC double bond. Allenes RCHd
CdCH2 can also be related to alkynes RCtCR′ in that they
have two π-bonds. One may wonder whether the reactivity of
allenes toward [Cp*Ru(H2O)(NBD)]BF4 is similar to that of
olefins or alkynes. To address this question, the reactions of
(27) (a) Trost, B. M.; Imi, K.; Indolese, A. F. J. Am. Chem. Soc. 1993,
115, 8831. (b) Butenschon, H. Angew. Chem., Int. Ed. Engl. 1994, 33, 636.
(c) Alvarez, P.; Gimeno, J.; Lastra, E.; Garc´ıa-Granda, S.; Van der Maelen,
J. F. Bassetti, M. Organometallics 2001, 20, 3762. (d) Huang, X.; Lin, Z.
Organometallics 2003, 22, 5478.
(28) Mitsudo, T.; Naruse, H.; Kondo, T.; Ozaki, Y.; Watanabe, Y. Angew.
Chem., Int. Ed. Engl. 1994, 33, 580.
Figure 4. X-ray structure of the cation of [Cp*Ru(η6-p-CH3C6H4-
C10H11)]BPh4 (12BPh4). The counteranion is omitted for clarity.

2350 Organometallics, Vol. 25, No. 9, 2006
Xue et al.
Figure 5. Energy profiles for the [2+2+2] addition between NBD and allene in the ruthenium cationic complex [CpRu(NBD)(allene)]+.
The relative energies and free energies (in parentheses) are given in kcal/mol.
Table 2. Selected Bond Lengths [Å] for
[Cp*Ru(η6-C6H5-SiPh2OCH3)]BPh4 (4),
Scheme 8
[Cp*Ru(η6-C6H5-C10H11)]BPh4 (11BPh4), and
[Cp*Ru(η6-p-CH3C6H4-C10H11)]BPh4 (12BPh4)
4
11BPh4
12BPh4
Ru(1)-C(1)
Ru(1)-C(2)
Ru(1)-C(3)
Ru(1)-C(4)
Ru(1)-C(5)
Ru(1)-C(11)
Ru(1)-C(12)
Ru(1)-C(13)
Ru(1)-C(14)
Ru(1)-C(15)
Ru(1)-C(16)
2.194(2)
2.189(2)
2.173(2)
2.166(2)
2.183(2)
2.253(2)
2.200(2)
2.204(2)
2.214(2)
2.202(2)
2.223(2)
2.185(3)
2.186(3)
2.173(2)
2.177(3)
2.176(3)
2.271(3)
2.233(3)
2.195(3)
2.197(3)
2.200(3)
2.214(3)
2.1831(18)
2.1771(18)
2.1838(18)
2.1811(18)
2.1736(18)
2.2449(18)
2.2195(18)
2.2013(19)
2.2361(19)
2.2081(18)
2.1994(18)
is likely related to the electron-withdrawing property of the aryl
substituent. The addition reaction presumably starts with an
oxidative coupling step (see the discussion below). It is expected
that electron-deficient CdC bonds undergo oxidative coupling
reactions more easily.
Mechanistically, complexes 11 and 12 could be formed
through a reaction sequence similar to those of the alkyne
reactions, as illustrated in Scheme 8, starting from allene
complexes X. There are two possible pathways for the coupling
reactions to proceed. The NBD ligand could initially link to
the central carbon of the allene or to one of the terminal carbons.
Unfortunately, we have not been able to identify the intermedi-
ates. Thus the two pathways cannot be differentiated experi-
mentally.
To gain more insight into the reaction mechanism, the two
reaction pathways relevant to the [2+2+2] addition of allene
with the NBD ligand of [Cp*Ru(H2O)(NBD)]+ (1) have been
examined by density functional theory calculations at the
Becke3LYP level using model complex [CpRu(NBD)(allene)]+.
The energy profiles for the reactions are illustrated in Figure 5.
As shown in Figure 5, path a starts with the middle carbon
and then one of the terminal carbons of the allene ligand in the
first and second C-C couplings, giving intermediates IN1-
allene-a and IN2-allene, respectively. In path b, one of the
terminal carbons and the middle carbon of the allene take turns
to have the first and second carbon-carbon coupling steps,
giving intermediates IN1-allene-b and IN2-allene, respectively.
Finally, a reductive elimination from IN2-allene leads to the
formation of PR-allene. It is interesting to note that although
the energy difference (0.6 kcal/mol) between TS1-allene-a and
TS1-allene-b for the two reaction pathways is small, the energy
difference (18.3 kcal/cal) between IN1-allene-a and IN1-
allene-b is large. The higher stability of IN1-allene-a is
apparently related to the Ru-η3-allyl interaction, while in IN1-
allene-b, no Ru-η3-allyl interaction is possible. The results
shown in Figure 5 clearly indicate that path a is kinetically more
favorable than path b.
Comments on the Reactivity of H
2, Ph3SiH, Olefins, RCt
CPh, and ArCHdCdCH2. It is noted that H2, Ph3SiH, RCt
CPh, and ArCHdCdCH2
readily undergo formal [2+2+2]
addition reactions with the NBD ligand of 1. However olefins
such as styrene and NBD are much less reactive toward 1 and
do not react in a similar manner to give the [2+2+2] addition
products. The differences can be understood by careful exami-
nation of the energy profiles of the relevant addition reactions.

Reactions of [Cp*Ru(H2O)(NBD)]+
Organometallics, Vol. 25, No. 9, 2006 2351
membered ring structural arrangement. In addition, IN-ene
shows greater H- - -H repulsions because two hydrogens orig-
inally from H2CdCH2 orient in such a way that creates
significant repulsion with the hydrogens on the Cp ring.
The barriers for the oxidative coupling reactions (the first
step in the coupling reactions) are in the order H2 (5.5 kcal/
mol) < Me3SiH (9.8 kcal/mol) < HCtCH (11.9 kcal/mol) <
CH2dCdCH2 (13.0 kcal/mol) < CH2dCH2 (16.2 kcal/mol).
The low barriers for TS1-H2 and TS1-silane-a can be related
to the spherical property of hydrogen’s 1s orbital. The spherical
property of hydrogen’s 1s orbital increases the tendency of its
orbital to overlap with the receiving carbon.29 The lower barrier
of TS1-yne can be related to the extra π -bonding orbital of
alkyne. The extra π -bonding orbital of alkyne is oriented in
such a way that it is ready to interact with the orbitals from the
receiving carbon. The barriers of the reactions involving CH2d
CdCH2 (14.4 kcal/mol) and CH2dCH2 (16.2 kcal/mol) are
higher than those involving H2, Me3SiH, and HCtCH.
The barriers for the second step of the coupling reactions are
in the order of HCtCH (1.3 kcal/mol) < H2 (3.1 kcal/mol) <
Me3SiH (10.8 kcal/mol) < CH2dCdCH2 (16.0 kcal/mol) <
CH2dCH2 (16.7 kcal/mol). When TS2 is considered, very small
barriers are calculated for the reactions of the H2 and HCtCH
cases. For the H2 case, the easy C-H bond formation is again
due to hydrogen’s spherical σ-type orbital. The calculated
structure of IN-yne shows that the R-carbon of the η2-alkenyl
unit has a pyramidal geometry. The orientation of the hydrogen
associated with the R-carbon indicates that the Ru-C σ-bond
bends toward the adjacent olefinic carbon. Apparently, the
bending of the Ru-C σ-bond facilitates orbital overlap between
the R-carbon and the adjacent olefinic carbon, and thus favors
the C-C formation and lowers the reaction barrier from IN-
yne to PR-yne. The slightly higher barrier for TS2-silane-a
can be related to the weaker C-Si bond. The barriers of TS2-
allene-a (16.0 kcal/mol) and TS2-ene (16.7 kcal/mol) are
significantly higher than those of TS2-H2, TS2-silane-a, and
TS2-yne, but are similar to those of the first step.
Overall, the reaction barriers for the conversion of [CpRu-
(L)(NBD)]+ to the complexes that are precursors to the [2+2+2]
addition products are relatively small (5-15 kcal/mol) for L )
H2, HCtCH, and CH2dCdCH2, or moderate (22 kcal/mol) for
L ) Me3SiH, and significantly high for CH2dCH2 (ca. 30 kcal/
mol). Thus we see that H2, Ph3SiH, RCtCPh, and RCHdCd
CH2 readily undergo formal [2+2+2] addition reactions with
the NBD ligand of 1, but olefins such as styrene and NBD are
much less reactive toward 1 and do not react in a manner similar
to give the [2+2+2] addition products. It is interesting to note
that the barriers for the two separated steps in the coupling
reactions of CH2dCdCH2 and CH2dCH2 are similar, but the
overall barriers are significantly different in these two cases.
Apparently, the high stability of IN1-allene-a helps to lower
the overall barrier for the addition reaction of allene with NBD.
Due to the higher overall barrier and unfavorable thermody-
namics for the formation of the precursor to the addition product,
the reactions of [Cp*Ru(H2O)(NBD)]+ with olefins do not lead
to [2+2+2] addition products, but to other compounds. The
barrier of the first step of the reaction of [Cp*Ru(H2O)(NBD)]+
with CH2dCH2 is not that unusually high (Figure 6b), but is
close to that of allene. Thus it is still possible for the reaction
of [Cp*Ru(H2O)(NBD)]+ with olefin to proceed through met-
allacyclopentane by oxidative coupling. Once formed, metal-
lacyclopentane can undergo other side reactions. In the reaction
Figure 6. Energy profiles for the [2+2+2] addition reactions of
the ruthenium cationic complexes [CpRu(NBD)(HCtCH)]+ (a) and
[CpRu(NBD)(CH2dCH2)]+ (b). The relative energies and free
energies (in parentheses) are given in kcal/mol.
The energy profiles for [2+2+2] addition reactions of [CpRu-
(L)(NBD)]+ (L ) H2, Me3SiH, CH2dCdCH2) are shown in
Figures 1 and 5. The energy profiles of the corresponding
addition reactions of [CpRu(L)(NBD)]+ (L ) CH2dCH2, HCt
CH) have been briefly described in our preliminary report. To
aid the following discussion, these profiles are reproduced in
Figure 6.
In the reaction of H2, the first hydrogen transfer leads to the
formation of a hydride intermediate (IN-H2) containing an
agostic interaction (Figure 1a). In the reaction of Me3SiH, the
first hydrogen transfer leads to the formation of a silyl
intermediate (IN1-silane-a) also containing an agostic interac-
tion (Figure 1b). In the reaction of CH2dCdCH2, the interme-
diate formed after the first C-C bond formation corresponds
to an η3-allyl structure (IN1-allene-a) (Figure 5). In the reaction
of HCtCH, the intermediate formed after the first C-C bond
formation corresponds to an η2-alkenyl structure (IN-yne)
(Figure 6a). The intermediates IN-H2, IN1-allene-a, and IN-
yne are more stable than the corresponding parent model
complexes. However, the corresponding intermediates IN-ene
formed from the reaction of H2CdCH2 and IN1-silane-a formed
from the reaction of HSiMe3 are found to be significantly
unstable. The stabilities of IN-H2, IN1-allene-a, and IN-yne
are apparently related to the additional C-H agostic bond and
metal-π interaction in the Ru-η3-allyl and Ru-η2-alkenyl units,
respectively. The presence of these interactions makes these
intermediates formally 18e complexes. IN1-silane-a is also an
18e species. Its instability is likely related to the weaker Ru-
Si bond. It is understandable that IN-ene is less stable, because
it is formally a 16e species. Although there are â-H’s in IN-
ene, no agostic interaction is possible because of the five-
(29) Ziegler, T.; Folga, E.; Berces, A. J. Am. Chem. Soc. 1993, 115,
636, and references therein.

2352 Organometallics, Vol. 25, No. 9, 2006
Xue et al.
CD2Cl2, 298 K): δ 2.08 (s, 15 H, Cp*), 5.78 (s, 6 H, C6H6). 13C{1H}
NMR (75.48 MHz, CD2Cl2, 298 K): δ 12.8 (s, Cp*), 89.2 (s, C6H6),
99.1 (s, Cp*).
of styrene, the intermediate undergoes â-H elimination followed
by reductive elimination to give complex 5 (Scheme 4). The
proposition is supported by calculations. As shown in Figure
6b, the barrier for the formation of the model complex PR-
ene-a via TS2-ene-a is indeed quite low compared to the second
step of the addition reaction via TS2-ene. In the case of reaction
of NBD, the intermediate can undergo C-C bond cleavage
reaction to give an allyl intermediate, which further evolves to
complex 8. â-H elimination does not occur in this case because
the â-H’s are oriented away from the ruthenium center.
Summary. We have demonstrated that reactions of [Cp*Ru-
(H2O)(NBD)]+ with H2 Ph3SiH, MeCtCPh, and ArCHdCd
CH2 lead to formal [2+2+2] addition between the substrates
and the coordinated NBD, while similar reactions are not
observed for the reactions with styrene or NBD. Theoretical
calculations suggest that [Cp*Ru(substrate)(NBD)]+ is the active
species in the observed reactions. The facile reactions of H2
and Ph3SiH can be attributed to the sperical nature of the H 1s
orbital, which can lower the reaction barriers and the ability of
the formed C-H bond to interact with the metal center
agostically, which can stabilize the intermediate. The easy
reactions of alkynes can be attributed to the extra π -bond of
alkynes. The extra π -bond has been found to play a key role
in stabilizing the relevant reaction intermediate by forming 18e
η2-vinyl species, as well as lowering the reaction barriers. The
easy reactions of allenes can also be attributed to the extra
π-bond of allenes. The extra π-bond helps to stabilize the
relevant reaction intermediate by forming 18e η3-allyl species
and lower the overall reaction barrier. The olefin reaction has
a very high overall reaction barrier for the [2+2+2] addition
reaction. Thus the metallacyclopane intermediate formed after
oxidative coupling evolves to other products through C-H or
C-C bond cleavage reactions.
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with Ph3SiH; Prepara-
tion of [Cp*Ru(η6-C6H5-SiPh2OH)]BF4 (4OH). To a stirred
solution of [Cp*Ru(H2O)(NBD)]BF4 (1) (168 mg, 0.388 mmol) in
acetone (8 mL) was added dropwise a solution of Ph3SiH (106 mg,
0.407 mmol) in acetone (18 mL). After the addition was completed,
the mixture was stirred for a further 2 h, and then it was filtered.
The volume of the filtrate was reduced to ca. 3 mL, and then hexane
(3 mL) was added along the flask wall to give a two-layer mixture.
A brown oil was formed at the bottom of the flask after standing
for 2 h. This oily material was separated, and the solution was
concentrated to dryness. The residue was washed with hexane (5
mL), diethyl ether (4 mL × 3), and a mixture of CH2Cl2/hexane (1
mL/5 mL) to give an oil, which changed to a yellow solid when
1
completely dried under vacuum. The H NMR spectrum showed
that the solid is mainly 4OH. Yield: 187 mg, 86%. 1H NMR (300
MHz, CDCl3, 298 K): δ 1.82 (s, 15 H, Cp*), 5.68-5.82 (m, 4 H,
SiOH and η6-Ph), 5.97 (d, J(HH) ) 5.4 Hz, 2 H, η6-Ph), 7.34-
7.46 (m, 6 H, Ph), 7.63 (d, J(HH) ) 6.5 Hz, 4 H, Ph). MS (FAB,
m/z): 527.1 (M - BF4).
Preparation of [Cp*Ru(η6-C6H5-SiPh2OCH3)]BPh4 (4). A
solution of NaBPh4 (450 mg, 1.31 mmol) in MeOH (1 mL) was
added dropwise to a stirred solution of [Cp*Ru(η6-C6H5-SiPh2OH)]-
BF4 (4OH) (200 mg, 0.357 mmol) in MeOH (5 mL) to give an
off-white precipitate. The mixture was stirred for a further 1 h.
The precipitate was collected by filtration, washed with MeOH (1
mL) and diethyl ether (2 mL), and dried under vacuum. The product
is further purified by column chromatography on silica (deactivated
by 5% H2O, v/v) with CH2Cl2 as the eluent to afford 4 as a white
solid. Yield: 196 mg, 65%. MS (TOF, m/z): 527.1135 (M - BPh4).
Anal. Calcd for C53H53BORuSi: C, 75.25; H, 6.31. Found: C,
75.10; H, 6.53. 1H NMR (300 MHz, CDCl3, 298 K): δ 1.67 (s, 15
H, Cp*), 3.67 (s, 3 H, OCH3), 4.91 (t, J(HH) ) 5.7 Hz, 1 H, η6-
Ph), 4.98 (t, J(HH) ) 5.7 Hz, 2 H, η6-Ph), 5.48 (d, J(HH) ) 5.7
Hz, 2 H, Ph), 6.89 (t, J(HH) ) 7.1 Hz, 4 H, Ph), 7.03 (t, J(HH) )
7.3 Hz, 8 H, Ph), 7.38-7.58 (m, 18 H, Ph). Single crystals of 4
were grown by layering diethyl ether on top of a solution of 4 in
CDCl3.
Experimental Section
All manipulations were carried out at room temperature under a
nitrogen atmosphere using standard Schlenk techniques, unless
otherwise stated. Solvents were distilled under nitrogen from
sodium-benzophenone (hexane, diethyl ether, THF, benzene) or
calcium hydride (dichloromethane, CHCl3). The starting materials
[Cp*Ru(H2O)(NBD)]BF4,11 phenylallene, and p-tolylallene30 were
prepared following the procedures described in the literature.
Microanalyses were performed by M-H-W Laboratories (Phoenix,
Identification of Nortricyclene (3) in the Reaction of [Cp*Ru-
(H2O)(NBD)]BF4 with Ph3SiH. A mixture of [Cp*Ru(H2O)(NBD)]-
BF4 (37 mg, 0.085 mmol) and Ph3SiH (24 mg, 0.092 mmol) in
CD2Cl2 (1 mL, freshly distilled by vacuum-transfer) was stirred
for 1 h. The volatile portion was then collected by vacuum transfer.
The 1H NMR spectrum shows that the vacuum-transferred portion
1
AZ). H, 13C{1H}, and 31P{1H} NMR spectra were collected on a
1
Bruker ARX-300 spectrometer (300 MHz). 1H and 13C NMR
chemical shifts are relative to TMS, and 31P NMR chemical shifts
are relative to 85% H3PO4. Mass spectra were obtained on a
Finnigan LCQ MAT mass spectrometer.
contains nortricyclene. H NMR (300 MHz, CD2Cl2, 298 K): δ
0.92 (br s, 3 H, CH), 1.11 (br d, J(HH) ) 1.2 Hz, 6H, CH2), 1.83-
1.86 (m, 1 H, CH).
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with Styrene. Isolation
6
6
of [Cp*Ru(η -C6H5-CHdCH-C7H9)]BPh4 (5BPh4), [Cp*Ru(η -
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with H2; Identification
of Nortricyclene (3) and [Cp*Ru(η6-C6H6)]BF4 (2). To an NMR
tube charged with [Cp*Ru(H2O)(NBD)]BF4 (40 mg, 0.092 mmol)
were added CD3COCD3 (1.0 mL) and C6D6 (0.2 mL). The reaction
mixture was allowed to stand for 15 h under H2. The volatile portion
of the reaction mixture was then collected by vacuum transfer. The
1H NMR spectrum shows that the vacuum-transferred portion
contains nortricyclene.13 1H NMR (300 MHz, acetone-d6, 298 K):
δ 1.09 (br s, 3 H, CH), 1.27 (br s, 6H, CH2), 2.00 (m, 1 H, CH).
13C NMR (CD2Cl2, 75.5 MHz): δ 9.4 (s), 29.2 (s), 32.6 (s). To
identify [Cp*Ru(η6-C6H6)]BF4 (2), the reaction was carried out with
C6H6 instead of C6D6. After the volatile portion of the reaction
mixture was removed under vacuum, the NMR data showed that
the residue contains [Cp*Ru(η6-C6H6)]BF4.20 1H NMR (300 MHz,
C6H5-CHdCH2)]BF4 (6BF4), C6H5-CHdCH-C7H9 (7), and
Cp*Ru(η5-C5H4-C9H11) (8). A mixture of [Cp*Ru(H2O)(NBD)]-
BF4 (1.30 g, 3.00 mmol) and styrene (1.00 mL, 10.6 mmol) in
acetone (25 mL) was stirred at RT for 2 days. Hexane (20 mL)
was added, and the mixture was stirred for 10 min to give a pale
yellow solid. The solid was collected by filtration, washed with
hexane, and dried under vacuum. 1H, 13C, COSY, HC-COSY NMR
and MS data indicate that the solid is 6BF4, which was obtained
previously from the reaction of [Cp*Ru(CH3CN)3]+ with styrene.
Yield: 0.40 g, 31%. The solvents of the filtrate were removed
completely under vacuum to give a brown oil. The brown oil was
extracted with hexane (30 mL). The residue was redissolved in
methanol (30 mL), and then NaBPh4 (1.30 g, 3.80 mmol) was
added. The mixture was stirred for 1 h to give a pale yellow solid,
which was collected by filtration, washed with methanol and diethyl
ether in turn, and dried under vacuum overnight to give 5BPh4.
(30) Brandsma, L.; Verkruijsse, H. D. Synthesis of Acetylenes, Allenes
and Cumulenes; Elsevier: Amsterdam, 1981.

Reactions of [Cp*Ru(H2O)(NBD)]+
Organometallics, Vol. 25, No. 9, 2006 2353
Yield: 0.86 g, 38%. The volume of hexane extraction obtained
above was reduced to ca. 2 mL. The residue was subjected to
column chromatography (silica gel) and eluted by hexane to give
7 (yield: 0.053 g, 9%) and the known compound 821 (yield: 0.14
g, 11%). The colorless single crystals of 5BPh4 were grown by
layering hexane on top of a CH2Cl2 solution of 5BPh4. Character-
ization data for 5BPh4: Anal. Calcd for C49H51BRu‚H2O: C, 76.45;
H, 6.94. Found: C, 76.88; H, 6.63. 1H NMR (300.13 MHz,
CD2Cl2): δ 1.00 (m, 1 H, CH2), 1.48 (d, 1 H, J(HH) ) 8.3 Hz,
CH2), 1.61 (d, br, 1 H, J(HH) ) 6.7 Hz, CH2), 1.93 (s, 15 H, Cp*),
2.19 (m, 1 H, CH2), 3.03 (br, 3 H, CH), 5.44 (m, 5 H, Ph), 5.89 (d,
1 H, J(HH) ) 15.8 Hz, dCH), 6.10 (m, 2 H, dCH), 6.41 (dd, 1 H,
J(HH) ) 5.8, 3.1 Hz, dCH), 7.00-7.44 (m, 20 H, BPh4). 13C{1H}
NMR (75.48 MHz, CD2Cl2): δ 10.21 (s, Cp*), 32.74 (s, CH2),
42.69 (s, CH), 42.93 (s, CH), 48.28 (s, CH), 49.70 (s, CH2), 83.84
(s, η6-Ph), 86.27 (s, η6-Ph), 86.62 (s, η6-Ph), 96.02 (s, Cp*), 98.61
(s, η6-Ph), 121.7 (s, dCH), 121.8 (s, BPh4), 125.6 (s, BPh4), 132.1
(s, dCH), 135.9 (s, BPh4), 138.3 (s, BPh4), 144.2 (s, dCH), 163.9
(q, BPh4). Characterization data for 7: 1H NMR (300.13 MHz,
CD2Cl2): δ 0.93 (m, 1 H, CH2), 1.30 (m, 1 H, CH2), 1.48 (m, 1 H,
CH2), 2.26 (m, 1 H, CH2), 2.90 (br, 3 H, CH), 5.88 (dd, 1 H,
J(HH) ) 15.8, 8.6 Hz, dCH), 6.05 (dd, 1 H, J(HH) ) 5.8, 2.5 Hz,
dCH), 6.24 (dd, 1 H, J(HH) ) 5.8, 3.0 Hz, dCH), 6.40 (d, 1 H,
J(HH) ) 15.7 Hz, dCH), 7.27-7.36 (m, 5 H, Ph). MS(FAB,
m/z): 197 [M + 1]+.
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with PhCtCPh; Prepa-
ration of [Cp*Ru(η6-Ph2C2(C7H8))]BF4 (10BF4). A mixture of
[Cp*Ru(H2O)(NBD)]BF4 (0.35 g, 0.80 mmol) and diphenylacet-
ylene (0.15 g, 0.84 mmol) in acetone (20 mL) was stirred for 20
min. The volume of the reaction mixture was reduced under
vacuum, and diethyl ether was added to give an off-white solid.
The solid was collected by filtration, washed with diethyl ether,
and dried under vacuum overnight. Yield: 0.42 g, 82%. Anal. Calcd
for C31H33BF4Ru: C, 62.74; H, 5.60. Found: C, 62.63; H, 5.56.
1
MS(FAB, m/z): 593 [M - BPh4]. H NMR (300.13 MHz, CD3-
COCD3): δ 1.64 (m, 1 H, CH), 1.7-1.9 (m, 3 H, CH), 1.95 (m, 1
H, CH), 2.10 (s, 15 H, Cp*), 2.48 (m, 1 H, CH), 3.11 (m, 1 H,
CH), 3.17 (m, 1H, CH), 5.64 (d, J(HH) ) 6.0 Hz, 1 H, dCH),
5.88 (t, J(HH) ) 6.0 Hz, 1 H, dCH), 6.03 (t, J(HH) ) 6.0 Hz, 1
H, dCH), 6.17 (t, J(HH) ) 6.0 Hz, 1 H, dCH), 6.27 (d, J(HH) )
6.0 Hz, 1 H, dCH), 7.30-7.50 (m, 5 H, Ph). 13C{H} NMR (75.48
MHz, CD3COCD3): δ 11.05 (s, Cp*), 23.94 (s, CH), 26.52 (s, CH),
33.36 (s, CH2), 53.98 (s, CH), 56.07 (s, CH), 57.81 (s, CH), 85.7-
87.5 (m, o,p,m-η6-Ph), 88.58 (s, ipso-η6-Ph), 97.55 (s, Cp*), 102.6-
131.0 (m, o,m,p-Ph), 136.83 (s, CdC), 137.97 (s, CdC), 152.89
(s, ipso-Ph).
Preparation of [Cp*Ru(η6-Ph2C2(C7H8))]BPh4 (10BPh4). A
mixture of [Cp*Ru(η6-Ph2C2(C7H8))]BF4 (0.59 g, 1.0 mmol) and
NaBPh4 (0.51 g, 1.5 mmol) in methanol (30 mL) was stirred for
30 min to give a white solid. The solid was collected by filtration,
washed with methanol and diethyl ether, and dried under vacuum
overnight. Yield: 0.76 g, 92%. Anal. Calcd for C55H53BRu: C,
79.99, H, 6.47. Found: C, 80.16, H, 6.52. The NMR data are
essentially the same as those of [Cp*Ru(η6-Ph2C2(C7H8))]BF4,
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with NBD; Preparation
of Cp*Ru(η5-C5H4-C9H11) (8). A mixture of [Cp*Ru(H2O)(NBD)]-
BF4 (11.7 mg, 0.027 mmol) and NBD (0.0100 mL, 0.0927 mmol)
in acetone-d6 (0.35 mL) was allowed to stand overnight at room
temperature. The 1H NMR spectrum showed that compound 820 is
formed as the sole product. Column chromatography on silica gel
with hexane as the eluent gave a colorless solid of 8 after removal
1
-
except the additional H and 13C signals of BPh4
.
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with PhCHdCdCH2;
Preparation of [Cp*Ru(η6-C6H5-C10H11)]BF4 (11BF4) and
[Cp*Ru(η6-C6H5-C10H11)] BPh4 (11BPh4). To a solution of
[Cp*Ru(H2O)(NBD)]BF4 (436 mg, 1.01 mmol) in acetone (10 mL)
was slowly added (in 1 h) a solution of phenylallene (367 mg, 3.16
mmol) in pentane (1 mL). The resulting solution was stirred for a
further 0.5 h. The mixture was then concentrated to dryness. The
residue was purified by column chromatography on silica gel
(deactivated by 5% H2O, v/v), by first eluting with CH2Cl2 to
remove a mixture of some unidentified organic products, and then
with a mixture of Me2CO/CH2Cl2 (4-8:100, v/v) to give an orange-
red band, from which compound 11BF4 was isolated (with a small
amount of unknown species as indicated by 1H NMR) as a
brownish-yellow solid. Yield: 169 mg, 31%. Characterization data
of 11BF4: 1H NMR (300 MHz, CDCl3, 298 K): δ 0.49 (br t,
J(HH) ) 4.8 Hz, 1 H, CH, ∆-C3H3), 1.10 (br t, J(HH) ) 4.5 Hz,
1 H, CH, ∆-C3H3), 1.21 (br t, J(HH) ) 4.3 Hz, 1 H, CH, ∆-C3H3),
1.54-1.58 (br m, 1 H, CH), 1.97 (s, 15 H, CH3, Cp*), 2.00-2.04
(br s, 2 H, CH2), 2.39 (br s, 1 H, CH), 2.57 (br t, 1 H, CH), 3.57
(br s, 1 H, CH), 4.79 (br s, 1 H, dCH2), 5.26 (br s, 1 H, CH2d),
5.74-5.82 (m, 2 H, η6-Ph), 5.86 (t, J(HH) ) 5.7 Hz, 1 H, η6-Ph),
5.94 (t, J(HH) ) 5.9 Hz, 1 H, η6-Ph), 6.00 (d, J(HH) ) 5.9 Hz, 1
H, η6-Ph). To further purify the compound, the BF4- counteranion
was changed to BPh4- to give 11BPh4. A solution of NaBPh4 (71.9
mg, 0.210 mmol) in MeOH (0.8 mL) was added to a stirred solution
of 11BF4 (92 mg, 0.173 mmol) in MeOH (1.5 mL) to give a pale
yellow precipitate. The mixture was stirred for 0.5 h. The precipitate
formed was collected by filtration, washed with MeOH (0.8 mL)
and diethyl ether (2 mL), and dried under vacuum. Yield: 73 mg,
54%. Single crystals of 11BPh4 were grown by layering MeOH
on the top of a solution of 11BPh4 in CH2Cl2, followed by layering
of hexane on top of MeOH. Characterization data of 11BPh4: Anal.
Calcd for C50H51BRu: C, 78.62; H, 6.73. Found: C, 78.69; H, 6.96.
1H NMR (300 MHz, CDCl3, 298 K): δ 0.42 (br t, J(HH) ) 5.7
Hz, 1 H, CH, ∆-C3H3), 0.99 (br t, J(HH) ) 6.0 Hz, 1 H, CH,
∆-C3H3), 1.22 (br t, J(HH) ) 6.0 Hz, 1 H, CH, ∆-C3H3), 1.48-
1.72 (m, 2 H, CH2), 1.76 (s, 15 H, CH3, Cp*), 1.98 (br s, 1 H,
1
of the solvent. Yield: 6 mg, 53%. H NMR (300 MHz, CDCl3,
298 K): δ 1.24-1.34 (m, 1 H, CH), 1.59 (s, 2 H, CH2-bridge),
1.62-1.68 (m, 1 H, CH), 1.70-1.88 (m, 2 H, CH2), 1.92 (s, 15 H,
CH3, Cp*), 2.16-2.24 (m, 1 H, CH), 2.63 (br s, 1 H, CH-
bridgehead), 2.69 (br s, 1 H, CH-bridgehead), 4.04-4.12 (m, 4 H,
C5H4), 5.92-5.99 (m, 2 H, CHd).
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with MeCtCPh; Prepa-
ration of [Cp*Ru(η6-PhCH3C2(C7H8))]BF4 (9BF4). A mixture of
[Cp*Ru(H2O)(NBD)]BF4 (0.50 g, 1.15 mmol) and methylphenyl-
acetylene (0.14 g, 1.20 mmol) in acetone (40 mL) was stirred for
20 min. The volume of the reaction mixture was reduced to 5 mL
under vacuum, and diethyl ether was added to give an off-white
solid. The solid was collected by filtration, washed with diethyl
ether, and dried under vacuum overnight. Yield: 0.53 g, 87%. Anal.
Calcd for C26H31BF4Ru: C, 58.77; H, 5.88. Found: C, 58.67; H,
1
6.18. H NMR (300.13 MHz, CD3COCD3): δ 1.6-1.9 (m, 4 H,
CH), 2.09 (s, 15 H, Cp*), 2.16 (s, 3 H, CH3), 2.19 (m, 2 H, CH),
2.80 (m, 1 H, CH), 2.94 (m, 1 H, CH), 6.00-6.21 (m, 5 H, Ph).
13C{1H} NMR (75.48 MHz, CD3COCD3): δ 10.83 (s, Cp*), 16.00
(s, CH3), 24.07 (s, CH), 24.20 (s, CH), 25.96 (s, CH), 33.04 (s,
CH2), 52.93 (s, CH), 55.11 (s, CH), 57.60 (s, CH), 85.10-88.21
(m, η6-Ph), 97.11 (s, Cp*), 105.2 (s, Ph), 132.9(s, CdC), 149.8 (s,
CdC).
[Cp*Ru(η6-PhCH3C2(C7H8))]BPh4 (9BPh4). A mixture of
[Cp*Ru(η6-PhCH3C2(C7H8))]BF4 (0.53 g, 1 mmol) and NaBPh4
(0.51 g, 1.5 mmol) in methanol (30 mL) was stirred for 30 min to
give a white solid. The solid was collected by filtration, washed
with methanol and diethyl ether in turn, and dried under vacuum
overnight. Yield: 0.70 g, 82%. Anal. Calcd for C50H51BRu: C,
78.62; H, 6.73. Found: C, 78.79; H, 6.85. 1H NMR (300.13 MHz,
CD2Cl2): δ 1.50 (br, 2 H, CH), 1.61 (br, 2 H, CH), 1.94 (s, 3 H,
CH3), 1.97 (s, 15 H, Cp*), 2.14 (br, 2 H, CH), 2.73 (br, 1 H, CH),
2.83 (br, 1 H, CH), 5.36-5.67 (m, 5 H, η6-Ph), 7.02 (t, 4 H,
J(HH) ) 7.1 Hz, BPh4), 7.16 (t, 8 H, J(HH) ) 7.2 Hz, BPh4), 7.46
(br, 8 H, BPh4).

2354 Organometallics, Vol. 25, No. 9, 2006
Xue et al.
CH), 2.17 (br s, 1 H, CH), 2.57 (br t, 1 H, CH), 3.33 (br s, 1 H,
CH), 4.69 (br s, 1 H, CHd), 4.78-4.90 (m, 2 H, η6-Ph), 5.00 (t,
J(HH) ) 5.4 Hz, 1 H, η6-Ph), 5.07 (d, J(HH) ) 5.2 Hz, 1 H, η6-
Ph), 5.25 (br s, 1 H, CHd), 5.69 (d, J(HH) ) 6.0 Hz, 1 H, η6-Ph),
6.92 (t, J(HH) ) 7.2 Hz, 4 H, Ph), 7.05 (t, J(HH) ) 7.2 Hz, 8 H,
Ph), 7.38-7.62 (m, 8 H, Ph).
atoms were refined anisotropically, and all hydrogen atoms were
positioned geometrically and refined using a riding model. Further
details on crystal data, data collection, and refinements are
summarized in Table 1.
Computational Study. All structures were optimized at the
B3LYP level of density functional theory.31 Frequency calculations
were also performed to confirm the characteristics of the calculated
structures as minima or transition states. In the B3LYP calculations,
the effective core potentials (ECPs) of Hay and Wadt with a
double-ú valence basis set (LanL2DZ)32 were used to describe Ru
and Si atoms, while the standard 6-31g basis set was used for C
and H. Polarization functions33 were added for the η2-H2 ligand
(ú(p) ) 1.1), Si (ú(d) ) 0.262), and the carbon atoms (ú(d) ) 0.6)
of the HSiMe3, H2CdCH2, CH2dCdCH2, and HCtCH substrates.
Calculations of intrinsic reaction coordinates (IRC)34 were also
performed on transition states to confirm that such structures are
indeed connecting two minima. All the calculations were performed
with the Gaussian 03 software package.35
Reaction of [Cp*Ru(H2O)(NBD)]BF4 with p-CH3C6H4CHd
CdCH2; Preparation of [Cp*Ru(η6-p-CH3C6H4-C10H11)]BF4
(12BF4) and [Cp*Ru(η6-p-CH3C6H4-C10H11)]BPh4 (12BPh4).
These complexes were prepared following the same procedures as
for 11BF4 and 11BPh4, respectively. From the reaction of [Cp*Ru-
(H2O)(NBD)]BF4 (593 mg, 1.37 mmol) with p-tolylallene (525 mg,
4.05 mmol) in acetone (15 mL), 12BF4 was isolated as a brownish-
yellow solid after purification by column chromatography. Yield:
247 mg, 33%. Counterion transformation of 12BF4 (178 mg, 0.327
mmol) with NaBPh4 (135 mg, 0.393 mmol) gave compound 12BPh4
as a pale yellow solid. Single crystals of 12BPh4 were grown from
a three-layer solvent system similar to that for 11BPh4. Yield: 112
mg, 44%. Found: C, 78.90; H, 7.00. Anal. Calcd for C51H53BRu:
C, 78.75; H, 6.87. Found: C, 78.90; H, 7.00. 1H NMR (300 MHz,
CDCl3, 298 K): δ 0.50 (br t, J(HH) ) 4.7 Hz, 1 H, CH, ∆-C3H3),
1.01 (br t, J(HH) ) 3.4 Hz, 1 H, CH, ∆-C3H3), 1.29 (br t, 1 H,
CH, ∆-C3H3), 1.54-1.68 (m, 2 H), 1.83 (s, 15 H, CH3, Cp*), 1.95
(s, 3 H, CH3, tolyl), 2.04 (br s, 1 H, CH), 2.44 (br s, 1 H, CH),
2.62 (br s, 1 H, CH), 3.41 (br s, 1 H, CH), 4.76 (br s, 1 H, CHd),
5.14 (d, J(HH) ) 6.0 Hz, 1 H, η6-C6H4), 5.22 (d, J(HH) ) 6.0 Hz,
1 H, η6-C6H4), 5.30 (d + s, 2 H, CHd, η6-C6H4), 5.80 (d, J(HH)
) 6.0 Hz, 1 H, C6H4), 6.99 (t, J(HH) ) 7.2 Hz, 4 H, Ph), 7.12 (t,
J(HH) ) 7.2 Hz, 8 H, Ph), 7.46-7.62 (m, 8 H, Ph).
Acknowledgment. This work was supported by the Hong
Kong Research Grant Council (Project Nos. HKUST602304,
HKUST601804, DAG05/06.SC19) and the National Natural
Science Foundation of China through the Outstanding Young
Investigator Award Fund (Project No. 20429201).
Supporting Information Available: Crystallographic data for
4, 11BPh4, and 12BPh4 in CIF format. Cartesian coordinates for
all the calculated structures and references for citations with more
than 10 authors. The materials are available free of charge via the
Internet at http://pubs.acs.org.
Crystallographic Analysis. Selected yellow crystals of 4,
11BPh4, and 12BPh4, with crystal sizes of 0.40 × 0.25 × 0.15,
0.35 × 0.15 × 0.10, and 0.40 × 0.15 × 0.10 mm3, respectively,
were mounted on top of glass fiber and transferred into the cold
stream of nitrogen. Data collections were performed on a Bruker
Apex CCD area detector, by using graphite-monochromated Mo
KR radiation (λ ) 0.71073 Å) at 100(2) K. Multiscan absorption
corrections (SADABS) were applied. All structures were solved
by direct methods, expanded by difference Fourier syntheses, and
refined by full matrix least-squares on F2 using the Bruker
SHELXTL (Version 6.10) program package. All non-hydrogen
OM0600285
(31) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Miehlich, B.;
Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200. (c) Lee,
C.; Yang, W.; Parr, G. Phys. ReV. B 1988, 37, 785.
(32) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299
(33) Huzinaga, S. Gaussian Basis Sets for Molecular Calculations;
Elsevier Science Pub. Co.: Amsterdam, 1984.
(34) (a) Fukui, K.; J. Phys. Chem. 1970, 74, 4161. (b) Fukui, K. Acc.
Chem. Res. 1981, 14, 363.
(35) Frisch, M. J.; et al. Gaussian 03, revision B05; Gaussian, Inc.:
Pittsburgh, PA, 2003.