Synthesis of Cp′Ru(CO)(L)(η2-olefin)+ complexes and kinetic studies of Olefin substitution

Article abstract of DOI:10.1021/om061096u

The ruthenium(II)-olefin complexes [Cp′Ru(CO)(L)(η²- olefin)]⁺ (Cp′ = Cp, Cp* L = CO, PPh₃; olefin = methyl oleate, cw-3-hexene, trans-3-hexene, 1,4-pentadiene) have been synthesized and characterized by IR and ¹H and ¹³C NMR spectroscopy. An X-ray structure of [CpRu(CO)(PPh₃) (η²-cis-3-hexene)]⁺ shows that the olefinic bond is nearly parallel to the plane of the Cp ligand. The olefins in [CpRu(CO) ₂(η²-trans-3-hexene)]⁺ and [Cp′Ru(CO)2(η²-trans-3-hexene)]⁺ rotate rapidly about the Ruolefin bond, even at -30°C, as established by the presence of a single methyl signal for the olefin in the ¹H NMR spectrum, whereas olefin rotation in [CpRu(CO)(PPh₃)(η²-trans,-3-hexene) ]⁺ is slow on the ¹H NMR time scale at -25°C. The [CpRu(CO)(PPh₃)]⁺ unit exhibits a unique diastereoselectivity by binding to only one face of trans-3-hexene, due to steric repulsion between the ethyl groups of the trans-3-hexene and the bulky Cp and PPh₃ ligands. Kinetic studies of the substitution of the olefin in [Cp'Ru-(CO)₂(η²-olefin)]⁺ by PPh ₃ show that the lability of the large methyl oleate is similar to that of the smaller cis-3-hexene. Replacement of Cp by Cp* and of cis-3-hexene by trans-3-hexene increases substantially the rate of olefin substitution, due to an increase in steric repulsion.

Full text of DOI:10.1021/om061096u

Organometallics 2007, 26, 1665-1673
1665
Synthesis of Cp′Ru(CO)(L)(η2-olefin)+ Complexes and Kinetic
Studies of Olefin Substitution
Kevin M. McWilliams, Arkady Ellern,† and Robert J. Angelici*
Department of Chemistry, Iowa State UniVersity, Ames, Iowa 50011-3111
ReceiVed December 1, 2006
The ruthenium(II)-olefin complexes [Cp′Ru(CO)(L)(η2-olefin)]+ (Cp′ ) Cp, Cp*; L ) CO, PPh3;
olefin ) methyl oleate, cis-3-hexene, trans-3-hexene, 1,4-pentadiene) have been synthesized and
1
characterized by IR and H and 13C NMR spectroscopy. An X-ray structure of [CpRu(CO)(PPh3)(η2-
cis-3-hexene)]+ shows that the olefinic bond is nearly parallel to the plane of the Cp ligand. The olefins
in [CpRu(CO)2(η2-trans-3-hexene)]+ and [Cp′Ru(CO)2(η2-trans-3-hexene)]+ rotate rapidly about the Ru-
olefin bond, even at -30 °C, as established by the presence of a single methyl signal for the olefin in the
1H NMR spectrum, whereas olefin rotation in [CpRu(CO)(PPh3)(η2-trans-3-hexene)]+ is slow on the 1H
NMR time scale at -25 °C. The [CpRu(CO)(PPh3)]+ unit exhibits a unique diastereoselectivity by binding
to only one face of trans-3-hexene, due to steric repulsion between the ethyl groups of the trans-3-
hexene and the bulky Cp and PPh3 ligands. Kinetic studies of the substitution of the olefin in [Cp’Ru-
(CO)2(η2-olefin)]+ by PPh3 show that the lability of the large methyl oleate is similar to that of the
smaller cis-3-hexene. Replacement of Cp by Cp* and of cis-3-hexene by trans-3-hexene increases
substantially the rate of olefin substitution, due to an increase in steric repulsion.
(methyl oleate (18:1), methyl linoleate (18:2), and methyl
linoleneate (18:3)) and smaller olefins (cis-3-hexene and 1,4-
pentadiene) in [CpPd(PR3)(η2-olefin)]+ complexes.9 None of
the complexes of the unsaturated fatty esters were sufficiently
stable to be isolated. On the basis of previous reports of [CpRu-
(CO)2(η2-olefin)]+ complexes, it appeared that it may be possible
to isolate analogous complexes of the unsaturated fatty esters
and compare the kinetic lability of η2-methyl oleate (18:1, cis-
CH3(CH2)7CHdCH(CH2)7CO2Me) with smaller olefins in a
series of [CpRu(CO)2(η2-olefin)]+ complexes. The ability of
ruthenium to successfully bind large olefins has been detailed
in a recent study, in which Ph3C[PF6] was used to abstract a
hydride from CpRu(CO)2(η1-C16H33) to yield [CpRu(CO)2(η2-
CH2dCH(CH2)13CH3)]+.10
Introduction
Transition-metal-olefin complexes of the type [CpFe(CO)2-
(η2-olefin)]+ (Cp ) C5H5) can be prepared by a number of
methods such as alkene exchange,1 displacement of water from
[CpFe(CO)2(OH2)]+,2 oxidation of [CpFe(CO)2]2,3 and halide
abstraction from CpFe(CO)2I.4 These complexes are useful as
models for catalytic intermediates as well as reagents in organic
synthesis.5 The ruthenium analogues are not nearly as well
studied in either the number of compounds or investigations of
their reactivity.6 Known compounds of the type [CpRu(CO)2-
(η2-olefin)]+ (olefin ) ethylene, propene, cyclohexene, 1-pen-
tene, 1-hexadecene)7 are relatively few, which may be attributed
to the limited synthetic techniques that have been employed,
almost all of which center on using a Lewis acid in the presence
of excess olefin.8
Herein we report the synthesis and characterization of a series
of ruthenium-olefin complexes of the type [Cp′Ru(CO)(L)-
(η2-olefin)]+, where Cp′ ) Cp, Cp* and L ) CO, PPh3, with a
focus on defining the orientation and rotational fluxionality of
the olefin and diastereoselectivity of the [CpRu(CO)(PPh3)]+
unit for binding one face of the olefin. Kinetic studies of the
displacement of the olefin in the [Cp′Ru(CO)2(η2-olefin)]+
complexes by PPh3 were performed in an effort to determine
the structural effects of the olefin and Cp′ ligand on the lability
of the olefin.
Recently our group reported equilibrium constants for η2
coordination of several unsaturated fatty acid methyl esters
* To whom correspondence should be addressed. E-mail: angelici@
iastate.edu. Tel: 515-294-2603. Fax: 515-294-0105.
† Molecular Structure Laboratory, Iowa State University, Ames, IA
50011-3111.
(1) (a) Ishii, Y.; Kagayana, T.; Inada, A.; Ogawa, M. Bull. Soc. Chem.
Jpn. 1983, 56, 2861. (b) Marsi, M.; Rosenblum, M. J. Am. Chem. Soc.
1984, 106, 7264. (c) Rosenblum, M.; Turnbull, M. M.; Foxman, B. M.
Organometallics 1986, 5, 1062.
(2) Tahiri, A.; Guerchais, V.; Toupet, L.; Lapinte, C. J. Organomet.
Chem. 1990, 381, C47.
(3) Krivykh, V. V.; Gusev, O. V.; Peterleitner, M. G.; Denisovitch, L.
I.; Rybinskaya, M. I. Chem. Abstr. 1987, 106, 120.
Results and Discussion
(4) Reger, D. L.; Belmore, K. A.; Mintz, E.; Charles, N. G.; Griffith, E.
A. H.; Amma, E. L. Organometallics 1983, 2, 101.
(5) Davies, S. G. Organotransition Metal Chemistry: Applications to
Organic Synthesis; Pergamon Press: Oxford, England, 1982.
(6) Bennett, M. A.; Bruce, M. I.; Matheson, T. W. In ComprehensiVe
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W.,
Eds.; Pergamon Press: Oxford, England, 1982; Vol. 4.
Synthesis and Structural Characterization of the [Cp′Ru-
(CO)(L)(η2-olefin)]+Y- Complexes. These complexes were all
prepared by the abstraction of Cl- from Cp′Ru(CO)(L)Cl, where
L ) CO, PPh3 and Cp′ ) Cp (η5-C5H5), Cp* (η5-C5Me5), in
the presence of the desired olefin (Scheme 1).
(7) (a) Jungbauer, A.; Behrens, H.; Z. Naturforsch., B 1978, 33, 1083.
(b) Fischer, E. O.; Vogler, A. Z. Naturforsch., B 1962, 17, 421.
(8) Bennett, M. A.; Khan, K.; Wenger, E. In ComprehensiVe Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Shriver,
D. F., Bruce, M. I., Eds.; Pergamon Press: Oxford, England, 1995; Vol. 7.
(9) Ghebreyessus, K. Y.; Ellern, A.; Angelici, R. J. Organometallics 2005,
24, 1725.
(10) Clayton, H. S.; Moss, J. R.; Dry, M. E. J. Organomet. Chem. 2003,
688, 181.
10.1021/om061096u CCC: $37.00 © 2007 American Chemical Society
Publication on Web 03/03/2007

1666 Organometallics, Vol. 26, No. 7, 2007
McWilliams et al.
Å) of free ethylene.13 The olefinic CdC distance in 10 is shorter
than that (1.416(13) Å) in [Cp*Ru(CO)(PMeiPr2)(η2-ethene)]+
(13), presumably because the higher electron density provided
by the Cp* and phosphine ligands increases π back-bonding to
the olefin in 13.14 The tilt angle (θ) is slightly larger (99.2°)
for 13 in comparison to the angle (94.6°) in 10. In both
compounds, the olefins tilt away from the PR3 ligand, with the
larger tilt in 13 being attributed to the lack of R groups on the
olefin, permitting the ethylene to rotate closer to the Cp ring.
The P(1)-Ru(1)-C(26) angle (85.50(15)°) is greater than the
C(30)-Ru-C(27) angle (78.34(2)°) in 10. This difference may
be attributed to the larger size of the PPh3 ligand forcing the
olefin toward the smaller carbonyl ligand, as was also suggested
for 13. The torsion angles C(25)-C(26)-C(27)-H(27a) (140°)
and C(28)-C(27)-C(26)-H(26a) (-143°) in 10 are smaller
than that predicted for the free olefin (180°), which indicates
that the substituents on the olefinic carbons are bent out of the
π nodal plane upon binding to the metal fragment.
Scheme 1
Cp′Ru(CO)(L)Cl +
AgY, CH2Cl2
2
+
-
olefin
8
[Cp′Ru(CO)(L)(η -olefin)] Y
1-12
-AgCl
For Cp′ ) Cp, L ) CO, Y ) BF4: olefin ) 18:1 (1), c3hx
(2), t3hx (3), 1,4ptd (4)
For Cp′ ) Cp*, L ) CO, Y ) PF6: olefin ) 18:1
(5), c3hx (6), t3hx (7), 1,4ptd (8)
For Cp′ ) Cp, L ) PPh3, Y ) PF6: olefin )18:1 (9), c3hx
(10), t3hx (11), 1,4ptd (12)
18:1 ) cis-CH3(CH2)7CHdCH(CH2)7CO2Me; c3hx )
cis-3-hexene; t3hx ) trans-3-hexene; 1,4ptd )
1,4-pentadiene
Previous studies of [Cp′M(CO)2(olefin)]+ (M ) Fe, Ru) by
Faller and Johnson showed the preferred orientation of the
olefins in these systems to be approximately parallel to the Cp
ring.15 This assignment was based on low-temperature NMR
studies of the complexes where Cp′ was an indenyl group. For
the propene complex, estimated shifts for the olefinic protons
Ha, Hb, and Hc were calculated on the basis of a geometric model
and shielding effects caused by ring currents. It was found that
both propene and trans-2-butene in their iron complexes likely
assume an approximate tilt angle of 100° to reduce the steric
interaction of the methyl groups with the indenyl ligand. For
cis-2-butene, the NMR data suggested a tilt angle of 90° in
which both methyl groups are directed toward the less bulky
carbonyl ligands. At 94.6° the tilt angle of cis-3-hexene in 10
is similar to those in the aforementioned complexes. Therefore,
in 10, the cis-3-hexene is approximately parallel to the Cp ring,
as is the case for the cis-2-butene in Faller’s studies, but the
ethyl groups in 10 point toward the Cp ring rather than away
from it in the [Cp′Fe(CO)2(η2-olefin)]+ complexes, owing to
the bulkiness of the PPh3 in 10.
The general structures of the synthesized compounds are
shown in Figure 1. With the exception of 5 and 9, all products
were isolated as either light tan or light yellow solids. Complexes
5 and 9 were isolated as a dark brown oil and a dark yellow
oil, respectively. All of the solid compounds, with the exception
of 8, are stable indefinitely as solids and stable for several days
if left in solution open to air.
In the ν(CO) region of their IR spectra, complexes 1-3 have
two peaks that appear at ∼2077 and ∼2034 cm-1; these
absorptions occur at slightly higher values of 2083 and 2040
cm-1 in the 1,4ptd complex 4. Complexes 5-8 exhibit ν(CO)
values (∼2062 and ∼2018 cm-1) that are about 15 cm-1 lower
than those in the analogous Cp complexes 1-4, due to the
stronger electron-donating ability of the Cp* ligand.11 The PPh3-
substituted complexes 9-11 give one ν(CO) peak at ∼2003
cm-1, whereas the 1,4ptd complex 12 is again slightly higher
at 2006 cm-1. In the compounds 1, 5, and 9 of 18:1, the ν(Cd
O) value of the ester group is the same as that (1732 cm-1) in
free methyl oleate, which indicates that the Ru does not bind
to the ester group. The preference for ruthenium binding to an
olefin in the presence of an ester group has been shown
previously in the [CpRu{Ph2PCH(CH3)CH(CH3)PPh2}(η2-
H2CdCH(CO2Me)]+ complex.12
An X-ray structure determination of 10 shows that the crystal
diffraction data were consistent with the space groups P1 and
P1h (Table 1). The E statistics strongly suggested the centrosym-
metric space group P1, which yielded chemically reasonable
and computationally stable refinement results. Two molecules
of 10, two counterions, and one molecule of CH2Cl2 solvent
were found in an asymmetric unit of the triclinic cell, showing
the existence of both enantiomers in the crystal lattice. The
ORTEP drawing for one of them is shown in Figure 2. Both
enantiomers assume a three-legged piano-stool geometry. The
double bond of the cis-3-hexene ligand is approximately parallel
to the Cp ring, having a tilt angle (θ) of 94.6°, which is defined
by the angle between the Ru(1)-C(26)dC(27) plane and the
plane defined by the Cp centroid, Ru(1), and the C(26)dC(27)
centroid (Figure 3A). Both ethyl groups in 10 point up toward
but away from the cyclopentadienyl ring. The Ru(1)-C(26) and
Ru(1)-C(27) bond lengths (2.285(5) and 2.304(5) Å, respec-
tively) are the same within experimental error. The C26-C27
bond distance (1.367(8) Å) is slightly longer than that (1.337
Results of studies of [CpRe(NO)(PPh3)(η2-olefin)]+ (14) with
monosubstituted (CH2dCHR) and disubstituted olefins (CHRd
CHR′) have led to the proposal that the double bond of the olefin
prefers to align with the Re-P vector to maximize π back-
bonding to the olefin.16 The tilt angle (θ) in an idealized structure
would be 45° (Figure 3B). From X-ray diffraction studies of
the complexes with styrene, cis-2-butene, and trans-2-butene,
the tilt angles were found to be 65, 64.2, and 71.8°, respec-
tively.17 Deviations from the ideal angle of 45° were attributed
to minimizing the steric interactions between the olefin R groups
and both the PPh3 and Cp ligands. The tilt angle of 94.6° in 10
as compared to 64.2° in [CpRe(NO)(PPh3)(cis-2-butene)]+
suggests that steric interactions play a more important role than
electronic factors in 10, as π back-bonding in both the Ru and
Re systems would be maximized at an angle of 45°. The greater
importance of steric repulsions in 10 may be attributed to the
smaller size of the Ru atom, as indicated by the shorter Ru-P
bond (2.336(2) Å) in comparison to the Re-P bond (2.426(1)
Å), resulting in a more congested environment around Ru
(13) Bartell, L. S.; Roth, E. A.; Hollowell, C. D.; Kuchitsu, K.; Young,
J. E., Jr. J. Chem. Phys. 1965, 42, 2683.
(14) Jimenez-Tenorio, M.; Palacies, M. D.; Puerta, M. C.; Valerga, P.
Organometallics 2004, 23, 504.
(15) Faller, J. W.; Johnson, B. V. J. Organomet. Chem. 1975, 88, 101.
(16) Peng, T.; Gladysz, J. A. J. Am. Chem. Soc. 1992, 114, 4174.
(17) (a) Bocher, G. S.; Peng, T.; Arif, A. M.; Gladysz, J. A. Organo-
metallics 1990, 9, 1191. (b) Pu, J.; Peng, T.; Mayne, C. L.; Arif, A. M.;
Gladysz, J. A. Organometallics 1993, 12, 2686.
(11) Friedrich, H. B.; Makhesha, P. A.; Moss, J. R.; Williamson, B. K.
J. Organomet. Chem. 1990, 384, 325.
(12) Consiglio, G.; Pregosin, P.; Morandini, F. J. Organomet. Chem.
1986, 308, 345.

Cp′Ru(CO)(L)(η2-olefin)+ Complexes
Organometallics, Vol. 26, No. 7, 2007 1667
Figure 1. Structures of compounds 1-12. Carbon and hydrogen labels correspond to NMR assignments given in the Experimental Section.
Table 1. Crystal Data and Structure Refinement Details for
[(η5-C5H5)Ru(CO)(PPh3)(η2-c3hx)][PF6] (10)
empirical formula
fw
cryst syst
space group
C30H32OP2F6Ru‚0.5CH2Cl2
728.03
triclinic
P1h
unit cell dimens
a
9.522(2) Å
b
c
17.427(4) Å
19.654(4) Å
83.043(4)°
R
â
83.922(4)°
γ
78.551(3)°
V
Z
3161.8(11) Å3
4
density (calcd)
abs coeff
F(000)
1.529 Mg/m3
0.740 mm-1
1476
no. of rflns collected
max, min transmissn
no. of data/restraints/params
goodness of fit on F2
final Ra indices (I > 2σ(I))
Ra indices (all data)
largest diff peak, hole
24 803
1, 0.79
12 791/0/748
1.027
R1 ) 0.0574, wR2 ) 0.1529
R1 ) 0.0925, wR2 ) 0.1741
2.018, -1.253 e Å-3
a R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) {∑[w(Fo2 - Fc2)2 ]/∑[w(Fo2)2]}1/2
.
Figure 2. ORTEP drawing of one of the independent [CpRu(CO)-
(PPh3)(c3hx)]+ enantiomers in 10, showing the atom-numbering
scheme (50% probability thermal ellipsoids). Hydrogen atoms are
omitted for clarity. Selected bond lengths (Å): Ru(1)-C(26), 2.285-
(5); Ru(1)-C(27), 2.304(5); Ru(1)-P(1), 2.336(2); Ru(1)-C(30),
1.871(6); C(26)-C(27), 1.367(8). Selected bond angles (deg): Ru-
(1)-C(26)-C(27), 73.4(3); Ru(1)-C(27)-C(26), 71.9(3); C(26)-
Ru(1)-P(1), 85.50(15); C(27)-Ru(1)-C(30), 78.34(2); Ru(1)-
C(26)-C(25), 117.4(4); Ru(1)-C(27)-C(28), 116.0(4); P(1)-
Ru(1)-C(30), 88.68(17); C(26)-C(27)-C(28), 125.9(5); C(25)-
C(26)-C(27), 124.4(5).
leading to a greater tilt angle to relieve strain within the complex.
A notable difference between 14 and 10 is the orientation of
the R groups in the olefin. In the Re complex, the methyl groups
on the butene point away from the Cp ring (Figure 3B), whereas
the ethyl groups in 10 point toward the Cp (Figure 3A). As
described by Gladysz,17a electronic factors in the rhenium
complex primarily control the olefin orientation, while steric
interactions play a secondary role. Therefore, the cis-2-butene
methyl groups are directed away from both the Cp and PPh3
ligands in order to minimize steric congestion and allow for an
angle close to 45° to maximize back-bonding. On the other hand,
steric interactions are most important in 10, which lead to the
ethyl groups pointing up toward and away from the Cp to
minimize interactions with the PPh3 ligand, which has been
noted in previous work as being more sterically demanding than
a Cp ring.17b The similarity of the tilt angles in [Cp*Ru(CO)-
(PMeiPr2)(η2-ethene)]+ (13) (99.2°) and 10 (94.6°) suggests that
steric factors are more important in 13 also.
[CpRu(CO)2(C2H4)]+, [CpRu(CO)2(C3H6)]+, and [CpRu(CO)2-
1
(C6H10)]+.7 In the H NMR spectrum of 2, only one methyl
signal at 1.25 (t) ppm is observed for the bound olefin, but there
are two methylene multiplets at 2.28 and 2.08 ppm; the free
olefin exhibits a single multiplet at 2.05 ppm for the CH2
protons. Cooling a sample of 2 in acetone-d6 to -35 °C failed
to broaden the olefinic proton peaks. 1H-1H COSY experiments
show that the two hydrogens on the same methylene carbon
are different and are coupled to each other. This inequivalence
is consistent with the structure A (Figure 4), in which the CdC
olefin bond is parallel to the Cp ring, but it is not consistent
with the static perpendicular orientation B, in which all four
methylene protons would be inequivalent. The observation of
[Cp′Ru(CO)(L)(η2-c3hx)]Y Complexes (2, 6, and 10). In
the 1H NMR spectrum of 2, there is a modest shift upfield from
5.35 to 5.21 ppm for the olefinic protons in c3hx upon binding
to the [CpRu(CO)2]+ fragment. This is consistent with chemical
shifts of other known olefin complexes of ruthenium: e.g.,
1
two methylene H NMR signals is not only consistent with a

1668 Organometallics, Vol. 26, No. 7, 2007
McWilliams et al.
peak may be assigned to protons on the same carbon due to the
coupling with only one olefinic proton; the absence of a cross-
peak between the methylene peaks is presumably due to the
five-bond separation. Shifts of the methylene protons in 10 are
determined more by the neighboring ligands (CO or PPh3) than
1
by the direction the methylene protons are pointing. The H
NMR spectrum of 10 in solution is consistent with parallel
binding of the olefin, as shown in the structure determined by
X-ray diffraction.
[Cp′Ru(CO)(L)(η2-18:1)]Y Complexes (1, 5, and 9). As in
2, the bound olefin signals in 1 are observed upfield of free
methyl oleate (5.32 ppm) at 5.15 ppm. Larger shifts occur in
the 13C NMR spectrum, where the olefinic carbons (C9 and C10)
are shifted upfield from approximately 130 ppm in free methyl
oleate to 81.04 and 80.88 ppm in the bound form. Two discrete
13C peaks for the CO ligands appear at 195.15 and 195.08 ppm,
indicating the asymmetry of the methyl oleate ligand as well
as the absence of rapid dissociation and reassociation of the
olefin that would result in the CO groups becoming equivalent.
Complex 1 is stable with respect to air and moisture in solution
for several days; as a sticky solid, the compound did not degrade
noticeably over several months. The sticky composition is likely
due to the flexibility of the long hydrocarbon chain in the methyl
Figure 3. Structure of [CpRu(CO)(PPh3)(CHRdCHR)]+ (A),
depicting a tilt angle of 90°, and structure of [CpRe(NO)(PPh3)-
(CH2dCHR)]+ (B), showing the idealized 45° tilt angle.
1
oleate ligand. Low-temperature (-35 °C) H NMR studies of
1 in acetone-d6 did not show significant broadening of the olefin
peak. The long pendant groups of the methyl oleate pose a larger
steric problem to rotation than do the ethyl groups in cis-3-
hexene, but rotational fluxionality cannot be ruled out. To the
best of our knowledge, this is the first isolated and characterized
transition-metal complex of methyl oleate.
Figure 4. Parallel (A) and perpendicular (B) orientations of cis-
3-hexene with respect to the Cp ring, showing the different
methylene protons.
The influence of the Cp* ligand in 5 is clearly seen in the 1H
NMR spectrum, where the olefin signal (3.88 ppm) of the methyl
oleate is much further upfield than in 1 (5.15 ppm). Methylene
splitting occurs as in the previously discussed compounds with
resonances at 2.10 and 1.95 ppm, and two carbon signals for
the inequivalent CO ligands in the 13C NMR spectrum occur at
198.51 and 198.47 ppm, which is similar to those in 1 (195.15,
195.08 ppm).
The 1H NMR spectrum of 9 shows two olefinic protons (3.80
and 3.48 ppm) further upfield than those in 1. The upfield peak
at 3.48 ppm may be assigned to the olefinic proton nearest the
PPh3 ligand, whose phenyl rings would be expected to shield
this proton.17b
static parallel structure but would also be consistent with a
structure in which the olefin is rapidly rotating. Rotation occurs
in both 13 as well as in many of the [CpRe(NO)(PPh3)
(η2-olefin)]+ compounds, some of which must be cooled to
-100 °C in order to distinguish between diastereomers. On the
basis of the nearly parallel structures of 10 and 13 in the solid
state, it seems likely that the olefin in 2 is parallel to the Cp,
but unlike the structure of 10, the ethyl groups are probably
directed away from the Cp ring (A in Figure 4) because of the
absence of the bulky PPh3 ligand that is present in 10. However,
it is not possible to state whether structure A for 2 is static or
the olefin is rotating rapidly. This is also the situation for
complexes 1, 2, 4-6, 8-10, and 12. Only for the complexes
of t3hx (3, 7, 11) is it possible to conclude that the olefin is
rotating rapidly on the NMR time scale at room temperature.
At 3.86 ppm the olefinic protons of compound 6 are upfield
as compared with those (5.21 ppm) in 2, due to the greater
electron donation by the Cp* ligand. As in 2, 6 has only one
methyl signal for the cis-3-hexene at 1.22 ppm, but there are
again two methylene signals at 2.20 and 2.12 ppm that are
coupled to one another. In compound 10, the chiral ruthenium
gives rise to two distinct olefin multiplets at 3.88 and 3.49 ppm
for the cis-3-hexene ligand. There are again two methylene
resonances at 2.12 and 1.83 ppm, with the former being almost
resolved into two separate multiplets. The hydrogen atoms on
carbon 2 (Figure 1) located closer to the CO ligand are expected
to be different from those on carbon 5, which will be closer to
the PPh3 ligand. The methylene hydrogens on carbons 2 and 5
will also be different from one another, as observed in 2 and 6.
Therefore, one expects four separate resonances for the meth-
ylene hydrogen atoms in 10. The methylene peak at 2.12 ppm
shows only a cross-peak with the olefin proton at 3.88 ppm,
whereas the methylene peak at 1.83 ppm shows only a cross-
peak with the olefin proton at 3.49 ppm. Thus, each methylene
[Cp′Ru(CO)(L)(η2-t3hx)]Y Complexes (3, 7, and 11). In
the 1H NMR spectrum of 3, the methyl groups are observed as
a single triplet at 1.17 ppm, but two methylene resonances are
1
observed at 2.23 and 1.64 ppm. H-1H COSY spectra show
that these signals arise from two protons on the same methylene
carbon. The appearance of two CO peaks in the 13C NMR
spectrum at 197.02 and 192.58 ppm is in contrast to the case
for compound 2, which exhibits only a single CO peak at 194.85
ppm. If the t3hx were locked into a parallel orientation (A in
Figure 4), the methylene groups would be inequivalent and
therefore appear as two signals. The appearance of only one
methyl signal, combined with the sharpness of the peaks,
indicates a fast rotation of the olefin about the metal-olefin
bond. Fast rotation, in this case, would not make the two CO
peaks equivalent in the 13C NMR. The barrier to rotation must
be small, as 1H NMR experiments performed at -35 °C failed
to show any evidence for peak broadening.
Surprisingly, 7 is not soluble in CD2Cl2 at room temperature,
whereas the other ruthenium compounds are. In acetone-d6, the
olefinic protons appear upfield at 4.48 ppm, and the two
methylene peaks appear at 2.29 and 1.61 ppm. As in 3, a single

Cp′Ru(CO)(L)(η2-olefin)+ Complexes
Organometallics, Vol. 26, No. 7, 2007 1669
formation of 11 is very selective for coordination to one face
of the t3hx. The high selectivity of 11 for one face of the trans-
3-hexene is surprising, as the compounds [CpRe(NO)(PPh3)-
(trans-2-butene)]+ (15) and [CpRe(NO)(PPh3)(trans-3-hexene)]+
(16) both exhibit lower kinetic selectivity. At room temperature,
15 forms an 85:15 ratio of the RSS,SRR and RRR,SSS diaster-
eomers, whereas compound 16 exhibits a lower selectivity ratio
of 52:48. When the temperature is increased to 85 °C,
equilibrium values of >99:1 are obtained for both 15 and 16.
Thermodynamic equilibrium values for 11 could not be obtained,
as the compound begins to degrade at higher temperatures. The
selective binding of ruthenium to one face of an olefin has been
reported earlier for the series of (Pybox)RuCl2(η2-olefin)
complexes by Nishiyama and co-workers.18
Figure 5. Diastereomers of 11.
[Cp′Ru(CO)(L)(η2-1,4ptd)]Y Complexes (4, 8, and 12).
Although methyl oleate forms the isolable complexes 1, 5, and
9, attempts to prepare analogous complexes with methyl
linoleate (cis,cis-CH3(CH2)4CHdCHCH2CHdCH(CH2)7CO2-
Me), containing a 1,4-diene unit, yielded mixtures of oily
products that decomposed upon attempted purification. In order
to explore the possibility that the 1,4-diene unit in methyl
linoleate could bind to metal centers, complexes of 1,4-
pentadiene (1,4ptd) were prepared. The complex [CpRu(CO)2-
(1,4ptd)]BF4 (4) was obtained (Scheme 1) by using excess olefin
to ensure that only one of the double bonds of the 1,4-pentadiene
would bind to the metal, leaving the other double bond
Figure 6. Diastereomers of [CpRu(CO)(PPh3)(1,4ptd)]PF6 (12).
1H NMR methyl signal for the olefin is observed at 1.17 ppm,
and the inequivalent CO groups are observed at 201.27 and
196.23 ppm in the 13C NMR spectrum. These data show that
the olefin is rotating rapidly, as in 3.
At room temperature, the 1H NMR spectrum of 11 does not
exhibit any distinguishable peaks for the hydrogens on the olefin
bond. Broad phenyl peaks are observed downfield at ∼7.50 ppm
with a singlet Cp peak appearing at 5.75 ppm. No peaks are
observed further upfield, except for a large broad signal at 1.51
ppm. After the NMR tube is cooled to -25 °C, sharp peaks for
the olefinic protons are observed at 5.01 and 3.26 ppm. The
chemical shifts of these proton resonances are very different
from those in 10 at 3.88 and 3.49 ppm. Four distinct methylene
resonances are observed at 3.23, 2.38, 1.66, and 1.01 ppm, and
two methyl peaks appear at 1.23 and 0.67 ppm. Depending on
the face through which the olefin binds to the metal, two isomers
(Figure 5) of 11 can form. The ethyl groups on the olefin could
point toward the Cp and the CO, as in 11a, or toward the Cp
and the PPh3, as in 11b. In the X-ray structure of 10, the ethyl
groups of the cis-3-hexene both point up and away from the
PPh3 ligand. In the case of 11, one of the ethyl groups will
always be directed toward the Cp. The other ethyl group is then
either pointing toward the PPh3 or the CO. On the basis of the
structure of 10, it is likely that the ethyl group would point
toward the small CO ligand, as in 11a. The olefin resonance in
the 1H NMR spectrum of 11 at 3.26 ppm is similar to the signals
at 3.88 and 3.49 ppm for the olefin protons in 10 and may
therefore be assigned to the olefin proton in 11a that is pointing
away from the Cp ligand. The other olefin proton has a chemical
shift (5.01 ppm) that is similar to those in 1 (5.15 ppm) and 2
(5.21 ppm), in which the olefin protons are likely pointing
toward the Cp. Isomer 11a should give rise to four different
1
uncoordinated. In the H NMR spectrum of 4, peaks for the
bound olefinic group appear at 5.21, 4.05, and 3.69 ppm, with
the last two peaks appearing as doublets due to coupling (J )
8.4 and 14 Hz) with the peak at 5.21 ppm. The magnitudes of
the coupling constants indicate that the proton at 4.05 ppm is
cis to the proton at 5.21 ppm, while the proton at 3.69 ppm is
trans to the proton at 5.21 ppm. As in the complexes of 18:1,
c3hx, and t3hx (1-3, 5-7, 9-11), the internal methylene
protons, H4 and H5, appear as two separate multiplets at 3.07
and 2.66 ppm. In the 13C NMR spectrum, two CO peaks are
observed at 195.11 and 194.39 ppm because there is no plane
of symmetry in the complex. The unbound olefin carbons (C4
and C5) appear at 135.25 and 119.38 ppm, in contrast to the
bound olefin carbons, which appear much further upfield at
1
84.12 and 51.08 ppm. Low-temperature H NMR experiments
at -35 °C do not result in broadening.
1
The H NMR spectrum of 8 exhibits peaks for the bound
olefinic group at 4.10, 3.57, and 3.03 ppm with the last two
appearing as doublets with coupling constants of 14 and 8.4
Hz, respectively. Unbound olefin resonances appear downfield
at 5.98 and 5.29 ppm, and two methylene signals are observed
at 3.17 and 2.49 ppm. Unlike compounds 1-7 and 9-12, 8
decomposes rapidly in solution and even slowly in the solid
state. The decomposition appears to yield a discrete product
with new peaks appearing at 4.38, 3.67, 3.45, and 2.85 ppm.
1
An off-white compound with essentially the same H NMR
1
spectrum was obtained when 2 equiv of Cp*Ru(CO)2Cl was
reacted with 1 equiv of 1,4-pentadiene in the presence of AgPF6.
Therefore, the product of the decomposition of 8 was assigned
the structure [Cp*Ru(CO)2]2(1,4ptd)2+, in which a [Cp*Ru-
(CO)2]+ unit is coordinated to each double bond of the 1,4ptd
ligand. It should be noted that we previously reported the
isolation and X-ray characterization of the complex [CpPd-
(PMe3)]2(1,4ptd)2+, in which a [CpPd(PMe3)]+ unit was coor-
dinated to each of the double bonds in the 1,4ptd.9
methylene signals, as previously discussed for 10. In the H-
1H COSY spectrum of 11 at -25 °C, the peaks at 3.23 and
1.01 ppm are coupled to one another as well as to the olefin
peak at 3.26 ppm. These peaks may therefore be assigned to
the CH2 protons on the ethyl group that is pointing toward the
Cp plane. The remaining methylene proton signals at 2.38 and
1.66 ppm, which are coupled to one another and to the olefin
peak at 5.01 ppm, may therefore be assigned to the CH2 group
near the CO ligand. The chemical shifts (2.38 and 1.66 ppm)
are similar to those (2.12 and 1.83 ppm) of the methylene
protons of 10, providing support for structure 11a for compound
11. There is no evidence for isomer 11b, which means that the
(18) Motoyama, Y.; Murata, K.; Kurihara, O.; Naitoh, T.; Aoki, K.;
Nishiyama, H. Organometallics 1998, 17, 1251.

1670 Organometallics, Vol. 26, No. 7, 2007
McWilliams et al.
Table 2. Rate Constants for the Reaction (Eq 1) of
olefin bond or the stability of the transition state. A comparison
of k1 values for complexes 1 and 2 shows that c3hx dissociates
slightly faster than 18:1, but the difference between them is
small. Thus, the long and short alkyl groups on the cis olefinic
bond do not greatly affect the rate of the olefin dissociation. In
equilibrium studies9 of the substitution of the NCR′ ligand in
[CpPd(PR3)(NCR′)]+ by olefins, it was observed that K values
for 18:1 were only a factor of 2 less than those for c3hx. Thus,
in both the kinetic and equilibrium studies, the length of the
alkyl groups on the cis olefin exerts a relatively small influence
on olefin binding to the metal.
In contrast to the very similar values for complexes 1 and 2,
the rate of c3hx dissociation from [Cp*Ru(CO)2(c3hx)]+ (6) is
approximately 10 times faster than from [CpRu(CO)2(c3hx)]+
(2). Similarly, the dissociative pathway (k1) for the substitution
of the dibenzothiophene (DBT) in [Cp*Ru(CO)2(DBT)]+ by
phosphines is 29 times faster than that for the dissociation of
DBT from the Cp analogue, [CpRu(CO)2(DBT)]+.19 The large
difference in rates between 2 and 6 may be attributed to steric
repulsions between the c3hx and Cp* ligands in 6 being greater
than those between c3hx and Cp ligands in 2. Alternatively,
the Cp* ligand may better stabilize the electron-deficient metal
as the olefin dissociates. A comparison of k1 values for 6 and
7 shows that t3hx dissociates nearly 10 times faster than c3hx
from [Cp*Ru(CO)2]+. This difference in rates may be attributed
to the much smaller steric effect of the ethyl groups, which may
be directed away from the bulky Cp* ligand in 6, while an ethyl
group in the t3hx ligand is forced to interact with the Cp* in
all orientations of the t3hx ligand in 7 (Figure 1). Equilibrium
studies of the binding of cis and trans olefins to Ag(I), Cu(I),
Rh(I), and Pt(II) also show that cis olefins generally coordinate
more strongly than trans olefins.20
Observation of the same k2 values (Table 2) for compounds
1 and 2 is surprising, because a pathway involving nucleophilic
attack of PPh3 on the Ru should be slower for the larger 18:1
than for c3hx. The same rates for these reactions could mean
that either the PPh3 attack is from a side of the Ru away from
the olefin or the rate of this associative pathway is dominated
by breaking of the Ru-olefin bond rather than making of the
Ru-PPh3 bond. The similar k1 values for 1 and 2 suggest that
the strengths of the Ru-olefin bonds in these compounds are
similar.
A comparison of k2 values for 2 and 6 shows that k2 is slightly
smaller for the Cp* complex (6). Because the k1 values indicate
that the c3hx is less strongly bound in 6 than in 2, the slower
rate of c3hx substitution in 6 is probably due to the bulky Cp*,
which reduces the rate of PPh3 addition to 6 as compared with
that to 2. In the case of compound 7, the k1 value is so large
that it is not possible to measure a k2 value for this compound,
which indicates that t3hx dissociates so rapidly by the k1
pathway that an associative pathway is not competitive.
[Cp′Ru(CO)2(olefin)]+ with PPh3 in CDCl3 at 40.0 °C
compd
106k1, s-1
105k2, M-1 s-1
CpRu(CO)2(18:1)+ (1)
CpRu(CO)2(c3hx)+ (2)
Cp*Ru(CO)2(c3hx)+ (6)
Cp*Ru(CO)2(t3hx)+ (7)
1.28
1.96
21.8
6.08
6.08
3.04
0.0
208
Due to the asymmetry of the [CpRu(CO)(PPh3)]+ fragment,
12 exists as the two diastereomers 12a and 12b (Figure 6),
depending on the face of the olefin to which the metal is
coordinated. Peak assignments were made on the basis of 1H-
1
1H COSY and H-13C HETCOR experiments as well as peak
integrations. The diastereomers were differentiated by the
chemical shifts of H2, which can either be opposite the PPh3
ligand, as in 12a, or the CO ligand, as in 12b. The H2 peak of
the major isomer occurs at 4.06 ppm, whereas the peak of the
minor isomer occurs at 3.59 ppm. The more upfield peak at
3.59 ppm is assigned to H2 situated near the PPh3 ligand. Thus,
the major isomer with the more downfield 4.06 ppm value for
H2 is assigned structure 12a, in which the free olefin is situated
near the CO ligand; the minor diastereomer, 12b, has the free
olefin opposite the PPh3. Isolated complex 12 contains a 1.00:
0.65 ratio of 12a and 12b; due to the slow rate of olefin
dissociation (see below) it seems likely that the diastereomers
are not in equilibrium. During the formation of 12, 12a would
likely be the preferred structure, due to reduced steric interac-
tions between the bulky PPh3 ligand and the unbound olefinic
group. Unfortunately, the compound decomposes upon heating
to 50 °C in CD2Cl2, so that thermodynamic equilibrium ratios
could not be determined. The internal methylene in 12a at 2.70
ppm exists as a multiplet, whereas the methylene splitting is
larger in the minor isomer, with peaks appearing at 2.65 and
1.94 ppm, which may be due to greater shielding of one of the
methylene protons by the PPh3 ligand. The presence of the two
isomers is also evident in the 31P NMR spectrum of 12, which
shows a phosphine peak for 12a at 50.36 ppm and for 12b at
49.05 ppm. No noticeable broadening or changes in chemical
1
shifts were observed in the H NMR spectrum of a sample of
12 at -35 °C.
Kinetic Studies of Olefin Substitution in the [Cp′Ru(CO)2-
(η2-olefin)]+ Complexes. The [Cp′Ru(CO)2(η2-olefin)]+ com-
plexes react (eq 1) with PPh3 to give the free olefin and the
[Cp′Ru(CO)2(PPh3)]+ complexes. Kinetic studies of this reaction
[Cp′Ru(CO)2(olefin)]BF4 + PPh3 f
[Cp′Ru(CO)2(PPh3)]BF4 + olefin (1)
at 40.0 °C in CDCl3 solvent were performed under pseudo-
first-order conditions with at least a 10-fold excess of PPh3.
The compounds used in the kinetic studies were 1, 2, 6, and 7.
Unfortunately, the other complexes did not give useful kinetic
results for various reasons, including low solubility (3),
decomposition (4, 8, 9-12), and weighing problems due to oily
composition (5). The kobs values (see Table S1 in the Supporting
Information) obtained from slopes of first-order plots depend
upon the PPh3 concentration in the following way: kobs ) k1 +
k2[PPh3]. For complex 7, the k2 term is negligible, so that kobs
) k1. Rate constant values for each complex are given in Table
2. The PPh3-independent term (k1) is consistent with a mech-
anism in which the rate-determining step is the dissociation of
the olefin ligand. The PPh3-dependent term (k2) is consistent
with an associative mechanism involving rate-determining
addition of PPh3 to the complex.
Conclusions
The series of complexes [Cp′Ru(CO)(L)(η2-olefin)]+ (Cp′ )
Cp, Cp*; L ) CO, PPh3, olefin ) 18:1, c3hx, t3hx, 1,4ptd)
1
were prepared and characterized by their IR and H, 13C{1H},
(19) Vecchi, P. A.; Ellern, A.; Angelici, R. J. Organometallics 2005,
24, 2168.
(20) (a) Blytas, G. C. In Separation and Purification Technology; Li,
N. N., Calo, J. M., Eds.; Marcel Dekker: New York, 1992. (b) Hughes, R.
P. In ComprehensiVe Organometallic Chemistry; Wilkinson, G., Stone, F.
G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, England, 1982; Vol. 5.
(c) Young, G. B. ComprehensiVe Organometallic Chemistry; Wilkinson,
G., Stone, F. G. A., Abel, E. W., Puddephatt, R. J., Eds.; Pergamon Press:
Oxford, England, 1995; Vol. 9.
Since the k1 values describe the rate of olefin dissociation, it
is expected that these values will reflect the strength of the Ru-

Cp′Ru(CO)(L)(η2-olefin)+ Complexes
Organometallics, Vol. 26, No. 7, 2007 1671
and 31P{1H} NMR spectra. An X-ray structural study of 10
shows that the CdC bond of the olefin is approximately parallel
to the plane of the Cp ligand. Only for [CpRu(CO)(PPh3)(η2-
t3hx)]+ (11) was it possible to show conclusively that the olefin
ligand rotates slowly on the NMR time scale (at -25 °C). The
preparation of 11 gives only one diastereomer, demonstrating
that the [CpRu(CO)(PPh3)]+ unit is highly selective for coor-
dination to one face of the olefin. The synthesis of [CpRu(CO)-
(PPh3)(η2-1,4ptd)]+ gives a 1.0:0.65 ratio of the two possible
diastereomers. Selective binding of one face of an olefin to metal
complexes is important in catalytic reactions involving stereo-
centers, as in olefin polymerization catalyzed by R2TiCl2
compounds,21 enantioselective diboration of alkenes by LnM-
(BR2)2,22 and ring-closing olefin metathesis.23 Kinetic studies
of olefin substitution in the [Cp′Ru(CO)2(η2-olefin)]+ complexes
show that the rate of olefin dissociation is (1) very similar for
c3hx and 18:1, (2) much faster when Cp′ is Cp* rather than
Cp, and (3) much faster for t3hx than for c3hx. The difference
between the reactions of [CpRu(CO)2(c3hx)]+ (2) and [CpFe-
(CO)2(η2-H2CdCH2)]+ with PPh3 is worth noting. While the
PPh3 simply replaces the c3hx ligand in 2, the PPh3 adds to the
ethylene in the Fe complex to give [CpFe(CO)2(CH2CH2-
PPh3)]+.24 Steric and electronic differences between ethylene
and c3hx may account for this difference, because [CpRu(CO)2-
(η2-H2CdCH2)]+ also undergoes attack at the ethylene when
reacted with NH3.25
temperature for 4-6 h until the reaction was complete, as indicated
by the IR spectrum. The solution was then filtered to remove AgCl
and concentrated in vacuo to approximately 1 mL, and then 20
mL of hexanes was added to precipitate the product. The tan solid
products were isolated by filtration and washed with hexanes (3 ×
5 mL) to remove excess olefin. Isolated yields were typically 75-
85%. The products could be further purified by recrystallization
from CH2Cl2/ether. The 1H NMR and 13C NMR spectra were
obtained in either CDCl3 or CD2Cl2, depending on the compound
solubility.
Characterization of Compounds 1-4. [CpRu(CO)2(η2-18:1)]-
BF4 (1). 1H NMR (CDCl3, 400 MHz, 293 K): δ 5.89 (s, 5H, C5H5),
5.15 (m, 2H, H9,10), 3.66 (s, 3H, OMe), 2.31 (t, 3JHH ) 7.2 Hz, 3H,
H2), 2.19 (m, 2H, H8,11), 1.97 (m, 2H, H8,11), 1.27-1.65 (m, 22 H,
3
H3,12), 0.90 (t, JHH ) 6.4 Hz, 3H, H18). 13C{1H} NMR (CDCl3,
100 MHz, 293 K): δ 195.15, 195.08 (CtO), 174.47 (CdO), 91.21
(C5H5), 81.04 (C10), 80.88 (C9), 51.04 (OMe), 34.20 (C2), 32.00-
22.86 (C3,8,11,12), 14.31 (C18). IR (CH2Cl2; cm-1): ν(CO) 2076 (s),
2032 (s); ν(CdO) 1731 (s). Anal. Calcd for C26H41BF4O4Ru: C,
51.58; H, 6.83. Found: C, 51.09; H, 6.77.
1
[CpRu(CO)2(η2-c3hx)]BF4 (2). H NMR (CDCl3, 400 MHz,
293 K): δ 5.91 (s, 5H, C5H5), 5.21 (m, 2H, H3,4), 2.28 (m, 2H,
3
H
2,5), 2.08 (m, 2H, H2,5), 1.25 (t, JHH ) 7.2 Hz, 6H, H1,6). 13C-
{1H} NMR (CDCl3, 100 MHz, 293 K): δ 194.85 (CtO), 90.98
(C5H5), 82.15 (C3,4), 24.56 (C2,5), 15.55 (C1,6). IR (CH2Cl2; cm-1):
ν(CO) 2077 (s), 2033 (s). Anal. Calcd for C13H17BF4O2Ru: C,
39.71; H, 4.37. Found: C, 39.69; H, 4.46.
[CpRu(CO)2(η2-t3hx)]BF4 (3). H NMR (CD2Cl2, 400 MHz,
1
293 K): δ 5.87 (s, 5H, C5H5), 4.86 (m, 2H, H3,4), 2.23 (m, 2H,
Experimental Section
3
H
2,5), 1.64 (m, 2H, H2,5), 1.17 (t, JHH ) 7.6 Hz, 6H, H1,6).
Methods and Materials. All reactions were carried out under
an inert atmosphere of dry argon using standard Schlenk techniques.
Diethyl ether, methylene chloride, and hexanes were purified on
alumina using a Solv-Tek solvent purification system, similar to
that reported by Grubbs.26 The olefins methyl oleate (18:1), methyl
linoleate (18:2), trans-3-hexene (t3hx), 1,4-pentadiene (1,4ptd), and
styrene were purchased from Sigma-Aldrich Chemical Co. and used
as received. cis-3-Hexene (c3hx) was purchased from TCI Chemical
Co. and used as received. All deuterated solvents were purchased
from Cambridge Isotope Laboratories. Solution infrared spectra
were recorded on a Nicolet-560 spectrophotometer using NaCl cells
13C{1H} NMR (acetone-d6, 100 MHz, 293 K): δ 197.02
(CtO), 192.58 (CtO), 91.78 (C5H5), 85.15 (C3,4), 32.89 (C2,5),
18.12 (C1,6). IR (CH2Cl2; cm-1): ν(CO) 2078 (s), 2035 (s). Anal.
Calcd for C13H17BF4O2Ru: C, 39.71; H, 4.37. Found: C,
40.07; H, 4.77.
[CpRu(CO)2(η2-1,4ptd)]BF4 (4). 1H NMR (CD2Cl2, 400 MHz,
293 K): δ 5.89 (s, 5H, C5H5), 5.82 (m, 1H, H4), 5.21 (m, 3H,
H2,5), 4.05 (d, 3JHH ) 8.4 Hz, 1H, H1), 3.69 (d, 3JHH ) 14 Hz, 1H,
H1), 3.07 (m, 1H, H4 or H5), 2.66 (m, 1H, H4 or H5). 13C{1H} NMR
(CD2Cl2, 100 MHz, 293 K): δ 195.11 (CtO), 194.39 (CtO),
135.25 (C4), 119.38 (C5), 91.63 (C5H5), 84.12 (C2), 51.08 (C1), 40.60
(C3). IR (CH2Cl2; cm-1): ν(CO) 2083 (s), 2040 (s). Anal. Calcd
for C12H13BF4O2Ru: C, 38.21; H, 3.48. Found: C, 37.89;
H, 3.32.
General Procedure for Preparations of the [Cp*Ru(CO)2-
(η2-olefin)]PF6 Complexes (5-8). To a solution of dry CH2Cl2
(20 mL) containing AgPF6 (77.1 mg, 0.305 mmol) was added
Cp*Ru(CO)2Cl (100 mg, 0.305 mmol) and 0.915 mmol of olefin
(olefin ) 18:1, c3hx, t3hx, 1,4ptd). The solution was stirred for 4
h at room temperature until the reaction was complete, as indicated
by the IR spectrum. The solution, which contained AgCl precipitate,
was then filtered and concentrated in vacuo. Because the 18:1 salt
does not precipitate when hexane is added, the product could only
be partially purified by repeated washing with hexane to remove
unbound methyl oleate. The other olefin salts (6-8) were easily
precipitated by hexane, filtered, and washed with additional hexane
(3 × 5 mL). The 18:1 salt (5) was obtained as a dark brown oil,
whereas the other salts were obtained as light tan solids. Isolated
yields were typically 55-80%. The solid products could be
recrystallized from CH2Cl2/ether. Depending on their solubilities,
1H NMR and 13C NMR spectra of the compounds were taken in
CDCl3, CD2Cl2, or acetone-d6.
1
with a 0.1 mm path length. H, 13C, and 31P NMR spectra were
recorded on a Bruker DRX-400 spectrometer using the deuterated
solvents as internal references. Elemental analyses were performed
on a Perkin-Elmer 2400 Series II CHNS/O analyzer. The com-
pounds CpRu(CO)2Cl,27 Cp*Ru(CO)2Cl,28 and CpRu(CO)(PPh3)-
Cl29 were all prepared according to reported methods.
General Procedure for Preparations of the [CpRu(CO)2(η2-
olefin)]BF4 Complexes (1-4). To a mixture of dry CH2Cl2 (20
mL) containing AgBF4 (75.6 mg, 0.388 mmol) was added CpRu-
(CO)2Cl (100 mg, 0.388 mmol) and 1.2 mmol of olefin (olefin )
18:1, c3hx, t3hx, 1,4ptd). The solution was stirred at room
(21) Eisch, J. J.; Gitua, J. N. Organometallics 2003, 22, 4172.
(22) Trudeau, S.; Morgan, J. B.; Shrestha, M.; Morken, J. P. J. Org.
Chem. 2005, 70, 9538.
(23) Funk, T. W.; Berlin, J. M.; Grubbs, R. H. J. Am. Chem. Soc. 2006,
128, 1840.
(24) (a) Rosan, A.; Rosenblum, M.; Tancrede, J. J. Am. Chem. Soc. 1973,
95, 3062. (b) Nicholas, K. M.; Rosan, A. M. J. Organomet. Chem. 1975,
84, 351.
(25) Behrens, H.; Jungbauer, A. Z. Naturforsch., B 1979, 34, 1477.
(26) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.
(27) Eisenstadt, A.; Tannenbaum, R.; Efraty, A. J. Organomet. Chem.
1981, 221, 317.
Characterization of Compounds 5-8. [Cp*Ru(CO)2(η2-18:
1
(28) Nagashima, H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.;
Fukahori, T.; Suzuki, H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organometallics
1990, 9, 799.
(29) Davies, S. G.; Simpson, S. J. J. Chem. Soc., Dalton Trans. 1984,
993.
1)]PF6 (5). H NMR (CDCl3, 400 MHz, 293 K): δ 3.88 (m, 2H,
3
H9,10), 3.65 (s, 3H, OMe), 2.30 (t, JHH ) 7.6 Hz, 2H, H2), 2.10
(m, 2H H8,11), 1.98 (s, 15H, C5Me5), 1.95 (m, 2H, H8,11), 1.20-
3
1.65 (m, 22H, H3,12), 0.872 (t, JHH ) 6.8 Hz, 3H, CH3). 13C{1H}

1672 Organometallics, Vol. 26, No. 7, 2007
McWilliams et al.
NMR (CDCl3, 100 MHz, 293 K): δ 198.51 (CtO), 198.47
(CtO), 174.43 (CdO), 104.39 (C5Me5), 84.14 (C10), 83.99 (C9),
51.64 (OMe), 34.14 (C2), 31.93-22.80 (C3,8,11,12), 14.25 (C18), 9.74
(C5Me5). IR (CH2Cl2; cm-1): ν(CO) 2061 (s), 2016 (s); ν(CdO)
1732 (s).
293 K): δ 48.50 (s). IR (CH2Cl2; cm-1): ν(CO) 2000 (s). Anal.
Calcd for C30H32F6OP2Ru: C, 52.56; H, 4.70. Found: C, 52.79;
H, 4.72.
[CpRu(CO)(PPh3)(η2-t3hx)]PF6 (11). 1H NMR (acetone-d6,
400 MHz, 250 K): δ 7.65 (m, 9H, Phm,p), 7.43 (m, 6H, Pho), 5.75
(s, 5H, C5H5), 5.01 (m, 1H, H3), 3.26 (m, 1H, H4), 3.23 (m, 1H,
1
[Cp*Ru(CO)2(η2-c3hx)]PF6 (6). H NMR (CD2Cl2, 400 MHz,
293 K): δ 3.86 (m, 2H, H3,4), 2.20 (m, 2H, H2,5), 2.12 (m, 2H,
3
H5), 2.38 (m, 1H, H2), 1.66 (m, 1H, H2), 1.23 (t, JHH ) 7.2 Hz,
3
H
2,5), 2.02 (s, 15 H, C5Me5), 1.22 (t, JHH ) 7.2 Hz, 6 H, H1,6).
3
3H, H1), 1.01 (m, 1H, H5), 0.67 (t, JHH ) 7.2 Hz, 3H, H6). 13C-
13C{1H} NMR (CD2Cl2, 100 MHz, 293 K): δ 198.62 (CtO),
104.63 (C5Me5), 86.02 (C3,4), 25.09 (C2,5), 15.98 (C1,6), 10.12
(C5Me5). IR (CH2Cl2; cm-1): ν(CO) 2062 (s), 2018 (s). Anal.
Calcd for C18H27PF6O2Ru: C, 41.45; H, 5.23. Found: C, 41.58;
H, 5.39.
{1H} NMR (acetone-d6, 100 MHz, 250 K): δ 203.96 (CtO),
133.92 (Co), 132.39 (Cp), 130.19 (Ci), 130.08 (Cm), 92.97 (C5H5),
74.66 (C4), 71.19 (C3), 31.19 (C5), 30.92 (C2), 19.31 (C6), 18.62
(C1). 31P{1H} NMR (acetone-d6, 162 MHz, 250 K): δ 49.52 (PPh3).
IR (CH2Cl2; cm-1): ν(CO) 2000 (s). Anal. Calcd for C30H32F6-
OP2Ru: C, 52.56; H, 4.70. Found: C, 52.79; H, 4.72.
[Cp*Ru(CO)2(η2-t3hx)]PF6 (7). 1H NMR (acetone-d6, 400 MHz,
293 K): δ 4.48 (m, 2H, H3,4), 2.29 (m, 2H, H2,5), 2.15 (s, 15H,
Synthesis of [CpRu(CO)(PPh3)(η2-14ptd)]PF6 (12). Major
3
C5Me5), 1.61 (m, 2H, H2,5), 1.17 (t, JHH ) 7.2 Hz, 6H, H1,6).
isomer (12a): 1H NMR (CDCl3, 400 MHz, 293 K) δ 5.89 (m, 1H,
13C NMR (acetone-d6, 400 MHz, 293 K): δ 201.27 (CtO), 196.23
(CtO), 105.393 (C5Me5), 88.75 (C3,4), 31.32 (C2,5), 18.51 (C1,6),
10.23 (C5Me5). IR (CH2Cl2; cm-1): ν(CO) 2063 (s), 2020 (s).
3
H6), 5.36 (s, 5H, C5H5), 5.14 (m, 2H, H7,8), 4.06 (d, JHH ) 13.6
Hz, 1H, H2), 3.74 (m, 1H, H3), 2.70 (m, 2H, H4,5), 2.60 (d, 3JHH
)
8.4 Hz, 1H, H1); 13C{1H} NMR (acetone-d6, 100 MHz, 293 K) δ
[Cp*Ru(CO)2(η2-1,4ptd)]PF6 (8). 1H NMR (CD2Cl2, 400 MHz,
293 K): δ 5.98 (m, 1H, H4), 5.29 (m, 2H, H5), 4.10 (m, 1H, H2),
2
3
205.32 (d, JCP ) 19.0 Hz, CtO), 138.50 (C2), 134.17 (d, JCP
)
10.3 Hz, Co), 133.33 (d, 1JCP ) 52.6 Hz, Ci), 132.87 (d, 5JCP ) 2.7
Hz, Cp), 130.34 (d, 4JCP ) 2.6 Hz, Cm), 117.06 (C1), 92.06 (d, 1JCP
) 1.1 Hz, C5Me5), 78.95 (C4), 49.22 (C5), 42.94 (C3); 31P{1H} NMR
(CD2Cl2, 162 MHz, 293 K) δ 50.36 (PPh3). Minor isomer (12b):
1H NMR (CDCl3, 400 MHz, 293 K) δ 5.72 (m, 1H, H6), 5.32 (s,
5H, C5H5), 5.02 (d, 3JHH ) 10.4 Hz, 1H, H7), 4.95 (d, 3JHH ) 16.8
3.57 (d, 3JHH ) 14 Hz, 1H, H1), 3.17 (m, 1H, H3), 3.03 (d, 3JHH
)
8.4 Hz, 1 H, H1), 2.49 (m, 1 H, H3), 2.02 (s, 15 H, C5Me5). 13C
NMR (CD2Cl2, 100 MHz, 293 K): δ 198.21 (CtO), 197.42 (Ct
O), 134.80 (C4), 118.02 (C5), 104.83 (C5Me5), 85.12 (C2), 56.38
(C1), 40.09 (C3), 9.98 (C5Me5). IR (CH2Cl2; cm-1): ν(CO) 2069
(s), 2026 (s).
3
Hz, 1H, H8), 4.69 (m, 1H, H3), 3.59 (d, JHH ) 8.4 Hz, 1H, H2),
General Procedure for Preparations of the [CpRu(CO)-
(PPh3)(η2-olefin)]PF6 Complexes (9-12). To a solution of dry
CH2Cl2 (20 mL) containing AgPF6 (51.4 mg, 0.203 mmol) was
added CpRu(CO)(PPh3)Cl (100 mg, 0.203 mmol) and 0.610 mmol
of olefin (olefin ) 18:1, c3hx, t3hx, 1,4ptd). The solution was stirred
at room temperature for 4-6 h until the reaction was complete
according to the IR spectrum. The solution was then filtered to
remove the AgCl precipitate and concentrated in vacuo. Because
the 18:1 salt does not precipitate when hexane is added, the product
could only be partially purified by repeated washing with hexane
to remove unbound methyl oleate. The other olefin salts were easily
precipitated by hexane, filtered, and washed with additional hexane
(3 × 5 mL). The 18:1 salt (9) was obtained as a viscous yellow
oil, whereas the other salts were obtained as light yellow solids.
Isolated yields were typically 70-80%. The solid products could
be recrystallized from CH2Cl2/ether. Depending on their solubilities,
1H NMR and 13C NMR spectra of the compounds were taken in
either CDCl3, CD2Cl2, or acetone-d6.
2.65 (m, 1H, H4), 2.58 (d, 3JHH ) 8 Hz, 1H, H1), 1.94 (m, 1H, H5);
13C{1H} NMR (acetone-d6, 100 MHz, 293 K) δ 204.13 (d, 2JCP
)
19.7 Hz, CtO), 139.06 (C4), 133.93 (d, 3JCP ) 10.5 Hz, Co), 132.80
5
1
(d, JCP ) 2.4 Hz, Cp), 132.08 (d, JCP ) 52.5 Hz, Ci), 130.45 (d,
4JCP ) 2.3 Hz, Cm), 116.82 (C5), 92.59 (C5Me5), 70.71 (C2), 48.64
(C1), 40.90 (C3); 31P{1H} NMR (CD2Cl2, 162 MHz, 293 K) δ 49.05
(PPh3); IR (CH2Cl2; cm-1) ν(CO) 2006 (s). Anal. Calcd for
C29H28F6OP2Ru: C, 52.02; H, 4.22. Found: C, 51.70;
H, 4.26.
General Procedure for Kinetic Studies. A 0.010 mmol sample
of the complex was placed in an NMR tube with an excess, weighed
amount of PPh3. The tube was evacuated, flushed with nitrogen,
and capped with a septum. A 0.70 mL aliquot of CDCl3 or CD2Cl2
was added, and the tube was placed in liquid nitrogen. The tube
was then flame-sealed under vacuum. After the solution thawed,
the tube was placed in a constant-temperature bath at 40.0 ( 0.1
°C. The tube was removed from the bath periodically, and the
spectrum was recorded on a Bruker DRX-400 spectrometer at room
temperature using the deuterated solvent as the internal lock and
standard. The tube was then returned to the bath within a 10 min
period. The products formed during the course of the kinetic
reactions were [Cp′Ru(CO)2(PPh3)]+ 7a,30 and the free olefins, which
were identified by their 1H NMR spectra. The Cp′ or olefin methyl
peaks were integrated using XWIN-NMR software. Rate constants,
Characterization of Compounds 9-12. [CpRu(CO)(PPh3)-
1
(η2-18:1)]PF6 (9). H NMR (CDCl3, 400 MHz, 293 K): δ 7.65
(m, 9H, Phm,p), 7.16 (m, 6H, Pho), 5.20 (s, 5H, C5H5), 3.80 (m,
1H, H10), 3.66 (s, 3H, OMe), 3.48 (m, 1H, H9), 2.30 (t, 3JHH ) 7.8
Hz, 2H, H2), 2.01 (m, 2H, H11), 1.77 (m, 2H, H8), 0.95-1.65 (m,
22H, H3,12), 0.87 (t, 3JHH ) 6.4 Hz, 3H, H18). 13C{1H} NMR (CDCl3,
2
100 MHz, 293 K): δ 204.27 (d, JPC ) 20.0 Hz, CtO), 174.45
(CdO), 132.65 (d, 2JPC ) 10.2 Hz, Co), 132.11 (d, 4JPC ) 2.0 Hz,
k
obs, were obtained from the slopes of first-order least-squares plots
1
3
Cp), 130.02 (d, JPC ) 24.1 Hz, Ci), 129.70 (d, JPC ) 10.6, Cm),
91.68 (C5H5), 77.11 (C10), 75.50 (C9), 51.58 (OMe), 34.14 (C2),
33.29-22.80 (C3,8,11,12), 14.27 (C18). IR (CH2Cl2; cm-1): ν(CO)
2003 (s); ν(CdO) 1732 (s).
of ln (1 + [product]/[reactant]) vs time.19
X-ray Structure Determination of 10. The crystal evaluations
and data collections were performed at 203 K on a Bruker CCD-
1000 diffractometer with Mo KR (λ ) 0.710 73 Å) radiation and
a detector-to-crystal distance of 5.03 cm. The data were collected
using the full-sphere routine and were corrected for Lorentz and
polarization effects. The absorption correction was based on fitting
a function to the empirical transmission surface, as sampled by
multiple equivalent measurements using SADABS software. The
1
[CpRu(CO)(PPh3)(η2-c3hx)]PF6 (10). H NMR (CD2Cl2, 400
MHz, 293 K): δ 7.57 (m, 9H, Phm,p), 7.21 (m, 6H, Pho), 5.21 (s,
5H, C5H5), 3.88 (m, 1H, H3), 3.49 (m, 1H, H4), 2.12 (m, 2H, H2),
1.83 (m, 2H, H5), 1.23 (t, 3JHH ) 7.2 Hz, 3H, H1), 0.88 (t, 3JHH
)
3.6 Hz, 3H, H6). 13C{1H} NMR (CD2Cl2, 100 MHz, 293 K): δ
204.75 (d, 2JCP ) 19.9 Hz, CtO), 133.04 (d, 2JCP ) 10.2 Hz, Co),
132.58 (d, 4JCP ) 2.4 Hz, Cp), 130.13 (Ci), 130.02 (Cm), 91.91 (d,
1JCP ) 1.4 Hz, C5H5), 79.63 (C3), 77.43 (C4), 26.85 (C2), 26.69
(C5), 17.60 (C1), 16.67 (C6). 31P{1H} NMR (CD2Cl2, 162 MHz,
(30) Bruce, M. I.; Zaitseva, N. N.; Skelton, B. W.; White, A. H. Aust. J.
Chem. 1998, 51, 433.

Cp′Ru(CO)(L)(η2-olefin)+ Complexes
Organometallics, Vol. 26, No. 7, 2007 1673
structure was solved by direct methods and refined by using a full-
matrix anisotropic approximation for non-hydrogen atoms. All
hydrogen atoms were placed in the structure factor calculations at
idealized positions and were allowed to ride on the neighboring
atoms with relative isotropic displacement coefficients.
Research, Education and Extension Service, Grant No. 2003-
35504-12846.
Supporting Information Available: Table giving kobs rate
constants for reactions in eq 1 and a CIF file containing X-ray
crystallographic data for complex 10. This material is available free
of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This project was supported by the
National Research Initiative of the USDA Cooperative State
OM061096U