Toward an understanding of the anion effect in CpRu-based diels-alder catalysts via PGSE-NMR measurements

Article abstract of DOI:10.1021/om049559o

The rate dependence of the [Ru(η⁵-C₅H ₅)(BIPHOP-F)(acetone)][Y] -catalyzed Diels-Alder reaction of cyclopentadiene with methacrolein on the anion, Y, is shown to be due to selective ion pairing. Pulsed gradient spin-echo (

Full text of DOI:10.1021/om049559o

5410
Organometallics 2004, 23, 5410-5418
Toward an Understanding of the Anion Effect in
CpRu-Based Diels-Alder Catalysts via PGSE-NMR
Measurements
P. G. Anil Kumar and P. S. Pregosin*
Laboratory of Inorganic Chemistry, ETHZ, Ho¨nggerberg, CH-8093 Zu¨rich, Switzerland
M. Vallet, G. Bernardinelli, R. F. Jazzar, F. Viton, and E. P. Ku¨ndig*
Department of Organic Chemistry, University of Geneva, 30 Quai Ernest Ansermet,
CH-1211 Geneva 4, Switzerland
Received June 16, 2004
The rate dependence of the [Ru(η5-C5H5)(BIPHOP-F)(acetone)][Y]-catalyzed Diels-Alder
reaction of cyclopentadiene with methacrolein on the anion, Y, is shown to be due to selective
ion pairing. Pulsed gradient spin-echo (PGSE) diffusion measurements on the model Cp
and indenyl complexes [Ru(η5-C5H5)(CH2dCH-CN)(BIPHOP-F)][Y], Y ) BF4 and BArF, and
[Ru(η5-C9H7)(CH2dCH-CN)(BIPHOP-F)][Y], Y ) BF4 and BArF, respectively, combined with
1H-19F HOESY NMR data can be used to understand how the ion pairing for the BF4 anion
differs relative to that of the BArF anion. Solid-state structures for [Ru(η5-C5H5)(CH2dCH-
CN)(BIPHOP-F)][BF4] and [Ru(η5-C5H5)(CH2dCH-CN)(BIPHOP-F)][BArF] are reported and
support the NMR solution data. The model carbonyl complexes [Ru(η5-C5H5)(BIPHOP-F)-
(CO)][Y], 8 (Y ) BF4, SbF6, and BArF) have been synthesized. The IR CO stretching
frequencies for 8 showed little variation with anion, thereby proving that the anions do not
affect the Lewis acidity of the salts.
Introduction
ordinating; however, recent evidence shows that even
these anions are capable of coordination to the cation,
either directly or via hydrogen bonding.7 A number of
reports show that the presence of the counterion BArF-
(tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) acceler-
Although cationic transition metal complexes are
important catalysts and reagents in organic synthesis,1-5
the role of the anion is not often investigated in these
reactions. This despite the fact that anion/cation inter-
actions can dramatically affect solubility of the catalyst,
accelerate or decelerate reactions, improve reaction
selectivity, or even change its course.6 Anions such as
-
ates selected reactions when compared to PF6 or
BF4
of anions, e.g., PF6
.
- 6a,8,9 Moreover, cations can assist in the hydrolysis
.
- 10 Thus, while it is well known that
the counteranion (e.g., BF4-, PF6-, SbF6-, and BArF-)
influences not only the solubility of the salt but also its
reactivity, the precise role of the anion is not often
established.
-
BF4-, PF6-, and SbF6 are often thought to be nonco-
(1) (a) Geneˆt, J. P. Acros Org. Acta 1995, 1, 4. (b) Wiles, J. A.;
Bergens, S. H.; Young, V. G. J. Am. Chem. Soc. 1997, 119, 2940. (c)
Ohkuma, T.; Ishii, D.; Takeno, H.; Noyori, R. J. Am. Chem. Soc. 2000,
122, 6510.
Recently, it was found that the rate of the enantiose-
lective Diels-Alder reaction of cyclopentadiene with
methacrolein, catalyzed by [Ru(η5-C5H5)(BIPHOP-F)-
(acetone)][Y] (1), depends on the nature of the anion, Y
(Scheme 1).2 A similar, though less pronounced, trend
was found for the indenyl analogue [Ru(η5-C9H7)-
(BIPHOP-F)(acetone)][Y] (2).11
(2) (a) Ku¨ndig, E. P.; Saudan, C. M.; Bernardinelli, G. Angew. Chem.,
Int. Ed. 1999, 38, 1220. (b) Davenport, A. J.; Davies, D. L.; Fawcett,
J.; Garratt, S. A.; Russell, D. R. J. Chem. Soc., Dalton Trans. 2000,
4432. (c) Faller, J. W.; Lavoie, A. R.; Grimmond, B. J. Organometallics
2002, 21, 1662. (d) Viton, F.; Bernardinelli, G.; Ku¨ndig, E. P. J. Am.
Chem. Soc. 2002, 124, 4968. (e) Carmona, D.; Lamata, M. P.; Viguri,
F.; Rodriguez, R.; Oro, L. A.; Balana, A. I.; Lahoz, F. J.; Tejero, T.;
Merino, P.; Franco, S.; Montesa, I. J. Am. Chem. Soc. 2004, 126, 2716.
(3) Pregosin, P. S.; Salzmann, R. Coord. Chem. Rev. 1996, 155, 35.
(4) (a) Trost, B. M.; Van Vranken, D. L. Chem. Rev. 1996, 96, 395.
(b) Trost, B. M.; Toste, F. D. J. Am. Chem. Soc. 2002, 124, 5025. (c)
Trost, B. M.; Shen, H. C.; Schulz, T.; Koradin, C.; Schirok, H. Org.
Lett. 2003, 5, 4149. (d) Trost, B. M.; Rudd, M. T. Org. Lett. 2003, 5,
4599.
(7) (a) Romeo, R.; Nastasi, N.; Scolaro, L. M.; Plutino, M. R.; Albinati,
A.; Macchioni, A. Inorg. Chem. 1998, 37, 5460. (b) Song, J.-S.; Szalda,
D. J.; Bullock, R. M. Organometallics 2001, 20, 3337.
(8) Pfaltz, A.; Blankenstein, J.; Hilgraf, R.; Hormann, E.; McIntyre,
S.; Menges, F.; Schonleber, M.; Smidt, S. P.; Wustenberg, B.; Zimmer-
mann, N. Adv. Synth. Catal. 2003, 345, 33.
(5) Fagnou, K.; Lautens, M. Angew. Chem., Int. Ed. 2002, 41, 26.
(6) (a) Evans, D. A.; Murry, J. A.; von Matt, P.; Norcross, R. D.;
Miller, S. J. Angew. Chem., Int. Ed. Engl. 1995, 34, 798. (b) Trost, B.
M.; Bunt, R. C. J. Am. Chem. Soc. 1998, 120, 70. (c) Macchioni, A.;
Bellachioma, G.; Cardaci, G.; Travaglia, M.; Zuccaccia, C.; Milani, B.;
Corso, G.; Zangrando, E.; Mestroni, G.; Carfagna, C.; Formica, M.
Organometallics 1999, 18, 3061. (d) Ludwig, M.; Stroemberg, S.;
Svensson, M.; Akermark, B. Organometallics 1999, 18, 970. (e) Rifat,
A.; Patmore, N. J.; Mahon, M. F.; Weller, A. S. Organometallics 2002,
21, 2856. (f) Takenaka, N.; Huang, Y.; Rawal, V. H. Tetrahedron 2002,
58, 8299.
(9) (a) Carmona, D.; Elipe, S.; Lahoz, F. J.; Oro, L. A.; Cativiela, C.;
Pilar Lopez-Ram de Viu, M.; Pilar Lamata, M.; Vega, C.; Viguri, F.
Chem. Commun. 1997, 2351. (b) Ku¨ndig, E. P.; Saudan, C. M.; Viton,
F. Adv. Synth. Catal. 2001, 343, 51.
(10) (a) Connelly, N. G.; Einig, T.; Herbosa, G. G.; Hopkins, P. M.;
Mealli, C.; Orpen, A. G.; Rosair, G. M.; Viguri, F. J. Chem. Soc., Dalton
Trans. 1994, 2025. (b) Kitagawa, S.; Kondo, M.; Kawata, S.; Wada, S.;
Maekawa, M.; Munakata, M. Inorg. Chem. 1995, 34, 1455. (c) Drago,
D.; Pregosin, P. S. Organometallics 2002, 21, 1208.
(11) Ku¨ndig, E. P.; Saudan, C. M.; Alezra, V.; Viton, F.; Bernar-
dinelli, G. Angew. Chem., Int. Ed. 2001, 40, 4481.
10.1021/om049559o CCC: $27.50 © 2004 American Chemical Society
Publication on Web 10/08/2004

Anion Effect in CpRu-Based Diels-Alder Catalysts
Organometallics, Vol. 23, No. 23, 2004 5411
Scheme 1
The reactions are fastest with the counterion BArF-,
readily recognizes ion pairing,16 we turned to this
technique to analyze the Ru-cation/anion interactions.
When a large transition metal cation containing a bulky
-
and rates decreased in the order BArF- > SbF6- > PF6
> BF4-. The X-ray crystal structure2a of [Ru(η5-C5H5)-
(BIPHOP-F)(methacrolein)][SbF6] showed a close prox-
imity of the anion/cation with distances between F and
the H atoms of the aldehyde and Cp ligand below the
sum of van der Waals radii. Preliminary HOESY NMR
studies of the corresponding PF6- complex showed these
interactions to exist also in solution. In this paper we
wish to report the results of more detailed studies
carried out in order to delineate the origins of the anion
effect in this family of compounds. The primary tech-
nique used for this investigation is pulsed gradient
spin-echo (PGSE) NMR.12
PGSE NMR diffusion studies provide information on
the size of species in solution and on intermolecular or
interionic interactions.12 Measuring translational prop-
erties of the molecules, this technique is directly re-
sponsive to molecular size and shape and has found
widespread application.13-16 As diffusion methodology
(13) (a) Mo, H. P.; Pochapsky, T. C. J. Phys. Chem. B 1997, 101,
4485. (b) Harris, R. K.; Kinnear, K. A.; Morris, G. A.; Stchedroff, M.
J.; Samadi-Maybodi, A.; Azizi, N. Chem. Commun. 2001, 2422. (c)
Dvinskikh, S. V.; Furo, I.; Sandstroem, D.; Maliniak, A.; Zimmermann,
H. J. Magn. Reson. 2001, 153, 83. (d) Deaton, K. R.; Feyen, E. A.;
Nkulabi, H. J.; Morris, K. F. Magn. Reson. Chem. 2001, 39, 276. (e)
Wan, Y.; Angleson, J. K.; Kutateladze, A. G. J. Am. Chem. Soc. 2002,
124, 5610. (f) Schlorer, N. E.; Cabrita, E. J.; Berger, S. Angew. Chem.
2002, 41, 107.
(14) (a) Zuccaccia, D.; Sabatini, S.; Bellachioma, G.; Cardaci, G.; Clot,
E.; Macchioni, A. Inorg. Chem. 2003, 42, 5465. (b) Stahl, N. G.;
Zuccaccia, C.; Jensen, T. R.; Marks, T. J. J. Am. Chem. Soc. 2003, 125,
5256.
(15) (a) Beck, S.; Geyer, A.; Brintzinger, H.-H. Chem. Commun.
1999, 2477. (b) Olenyuk, B.; Levin, M. D.; Whiteford, J. A.; Shield, J.
E.; Stang, P. J. J. Am. Chem. Soc. 1999, 121, 10434. (c) Gorman, C.
B.; Smith, J. C.; Hager, M. W.; Parkhurst, B. L.; Sierzputowska-Gracz,
H.; Haney, C. A. J. Am. Chem. Soc. 1999, 121, 9958. (d) Stoop, R. M.;
Bachmann, S.; Valentini, M.; Mezzetti, A. Organometallics 2000, 19,
4117. (e) Burini, A.; Fackler, J. P., Jr.; Galassi, R.; Macchioni, A.;
Omary, M. A.; Rawashdeh-Omary, M. A.; Pietroni, B. R.; Sabatini, S.;
Zuccaccia, C. J. Am. Chem. Soc. 2002, 124, 4570.
(16) (a) Martinez-Viviente, E.; Rueegger, H.; Pregosin, P. S.; Lopez-
Serrano, J. Organometallics 2002, 21, 5841. (b) Pregosin, P. S.;
Martinez-Viviente, E.; Kumar, P. G. A. Dalton Trans. 2003, 4007. (c)
Martinez-Viviente, E.; Pregosin, P. S. Inorg. Chem. 2003, 42, 2209.
(d) Kumar, P. G. A.; Pregosin, P. S.; Goicoechea, J. M.; Whittlesey, M.
K. Organometallics 2003, 22, 2956.
(12) (a) Stilbs, P. Prog. NMR Spectrosc. 1987, 19, 1. (b) Price, W. S.
Ann. Rep. NMR Spectrosc. 1996, 32, 51. (c) Price, W. S. Concepts Magn.
Reson. 1997, 9, 299. (d) Price, W. S. Concepts Magn. Reson. 1998, 10,
197. (e) Price, W. S.; Stilbs, P.; Soderman, O. J. Magn. Reson. 2003,
160, 139.

5412 Organometallics, Vol. 23, No. 23, 2004
Kumar et al.
Scheme 2. Synthesis of
Scheme 3
[Ru(η5-C5H5)(BIPHOP-F)(CO)][Y] Complexes
Table 1. Diffusion Valuesa and Hydrodynamic
Radii for 9a-d and 10
CD2Cl2
rh (Å)
CDCl3
rh (Å)
(CD3)2CO
rh (Å)
compound
cation {1H} 9a, BF4
anion {19F}
D
D
D
chelating ligand, such as BIPHOP-F (3) or BINAP (7),
forms strong ion pairs (or hydrogen bonds) with a
smaller anion, e.g., BF4-, the diffusion constant (D
value) for the latter is markedly reduced. Consequently,
8.26 6.5 6.07 6.8 10.73 6.8
12.33 4.3 6.14 6.8 26.84 2.7
cation {1H} 9b, CF3SO3 8.16 6.6 6.00 6.9 10.51 6.9
anion {19F}
12.16 4.4 6.14 6.8 24.63 2.9
8.36 6.4 6.13 6.8 10.64 6.8
12.30 4.4 6.52 6.4 26.89 2.7
7.76 6.9 4.78 8.6 10.31 7.0
7.93 6.8 4.97 8.5 11.47 6.3
8.51 6.3 6.53 6.4
1
if one uses both H and 19F NMR methods to monitor
cation {1H} 9c, PF6
anion {19F}
the individual cation and anion D values (and more
importantly, the changes in these), ion pairing can be
explored in a direct fashion. We report here new PGSE
diffusion, X-ray crystallographic, and preparative stud-
ies for a number of cationic half-sandwich complexes of
ruthenium and suggest an explanation for the observed
anion effect.
cation {1H} 9d, BArF
anion {1H}
neutral {1H} 10
a Measured at 400 MHz, 2 mM; D values, 10-10 m2 s-1
.
by treating the known complex [Ru(η5-C5H5)(PPh3)2Cl]
with BINAP, 7, followed by abstraction of the halide
using a variety of silver salts in the presence of aceto-
nitrile to afford the complexes [Ru(η5-C5H5)(BINAP)(CH3-
CN)][Y] (Y ) BF4 9a, CF3SO3 9b, PF6 9c, and BArF 9d).
Table 1 shows the measured D values in chloroform,
acetone, and dichloromethane together with the hydro-
dynamic radii, rh, which were calculated using the
Stokes-Einstein equation.
Results and Discussion
Infrared Measurements. The increase in the cata-
-
lytic reactivity of the complexes upon going from BF4
to BArF- could possibly be attributed to an electronic
contribution of the counteranion to the Lewis acidity of
the transition metal center. To evaluate this hypothesis,
we examined the IR carbonyl stretching frequencies of
the complexes [Ru(η5-C5H5)(BIPHOP-F)(CO)][Y] (Y )
BF4 8a, SbF6 8b, and BArF 8c). IR νCO shifts are very
sensitive to the metal electron density, and they are
generally taken as a reliable measure for the extent of
π-back-donation in metal carbonyl complexes.17
D ) kT/6πηrh
(1)
where k ) Boltzmann constant, T ) absolute temper-
ature, η ) viscosity, and rh ) hydrodynamic radius.
Data from the neutral complex [Ru(η5-C5H5)(BINAP)-
Cl] (10) have also been obtained and provide an indica-
tion as to the correct D value and hydrodynamic radius
for this class (ca. 6.3-6.4 Å) in the absence of strong
solvation and/or ion-pairing effects.
The requisite carbonyl complexes, 8a-c, were readily
obtained in quantitative yield upon bubbling CO gas
through a CH2Cl2 solution of the corresponding acetone
complex2 at room temperature. As shown in Scheme 2,
the stretching frequencies showed little variation. If at
all, the anion has only a very small influence on the
withdrawing properties of the cation. Moreover, we have
established that for the CpRu catalyst precursor 1b the
rate-determining step is not the Diels-Alder reaction
but the product/adduct exchange. This follows from the
observation that the reaction rate remains unchanged
upon increasing 5-fold the amount of diene.9b
As we have now come to expect,16 the chloroform data
reveal tight ion pairing, i.e, close to equivalent transla-
tion rates for both cation and anion. Due to the ion
pairing the calculated rh values are larger in chloroform
than, for example, dichloromethane, especially for the
BArF- salt. The acetone rh values for the cations are
all on the large side. We have no obvious explanation
for this, although we have observed this effect pre-
viously.16b Further, in acetone, the BF4-, CF3SO3-, and
1
PGSE and H-19F HOESY Measurements. Prior
to investigating the Ru-BIPHOP-F complexes, we es-
tablished PGSE data for the closely related complexes
[Ru(η5-C5H5)(BINAP)(CH3CN)][Y], 9 (see Scheme 3),
derived from [Ru(η5-C5H5)(BINAP)Cl], 10. Very little
diffusion data are known for η5-C5H5 complexes, and a
comparison of complexes differing in the nature of the
chiral phosphorus ligand is valuable. In addition, the
new complexes offered an interesting comparison with
our previously measured [Ru(η6-p-cymene)(BINAP)Cl]-
[Y], 11, complexes.16d The complexes 9 were prepared
-
PF6 all give relatively small rh values, ca. 2.7-2.9 Å.
-
In dichloromethane, the rh values for the BF4
,
CF3SO3-, and PF6 anions 9a-c, respectively, are all
-
relatively large and suggest a significant ion pairing.
To support this idea, 1H-19F HOESY spectra in dichlo-
romethane have been measured for the BF4-, CF3SO3
,
-
and BArF- salts. Figure 1 shows NOE contacts from
-
the CF3SO3 anion to the bound acetonitrile, the η5-
C5H5 ligand, and some of the aromatic protons. The
-
analogous BF4 spectrum shows the same contacts as
the CF3SO3 anion; however, the BArF- anion shows
-
(17) (a) Tolman, C. A. J. Am. Chem. Soc. 1970, 92, 2953. (b) Tolman,
C. A. Chem. Rev. 1977, 77, 313. (c) Ku¨ndig, E. P.; Dupre, C.; Bourdin,
B.; Cunningham, A., Jr.; Pons, D. Helv. Chim. Acta 1994, 77, 421.
no signals in the 1H-19F HOESY spectrum. The strong
CH3CN contact in dichloromethane suggests that the

Anion Effect in CpRu-Based Diels-Alder Catalysts
Organometallics, Vol. 23, No. 23, 2004 5413
Table 2. Diffusion Values and Hydrodynamic
Radii for 15a,b-17a,ba
CD2Cl2
(CD3)2CO
compound
D
rh (Å)
D
rh (Å)
cation {1H}
anion {19F}
cation {1H}
anion {1H}
cation {1H}
anion {19F}
cation {1H}
anion {1H}
cation {1H}
anion {19F}
cation {1H}
anion {1H}
RR-15a, BF4
7.84
9.67
7.28
7.84
7.80
9.79
7.20
7.90
7.95
8.96
7.39
7.99
6.8
5.5
7.4
6.8
6.9
5.5
7.4
6.8
6.7
6.0
7.2
6.7
9.72
27.36
9.44
11.85
9.17
24.45
9.16
11.44
9.82
7.5
2.6
7.7
6.1
7.9
3.0
7.9
6.3
7.4
3.0
7.6
6.1
RR-15b, BArF
16a, BF4
16b, BArF
17a, BF4
24.19
9.58
11.85
17b, BArF
a Measured at 400 MHz, 2 mM; D values, 10-10 m2 s-1
.
Figure 1. 1H-19F HOESY spectrum of complex [Ru(η5-
C5H5)(CH3CN)(BINAP)][CF3SO3], 9b. The small additional
Cp resonance at ca. 4.4 ppm arises from the Cp signal for
18 (OTf) in which the BINAP is a 6e- donor (see Experi-
mental Section).
Scheme 4. Variation of the Labile Ligand L in the
Cationic Cp and Indenyl Ru Complexes
Figure 2. 1H-19F HOESY spectrum of complex [Ru(η5-
C5H5)(CH2dCHCN)(BIPHOP-F)][BF4], 15a. Note that only
one of the CHO backbone resonances, at ca. 5.3 ppm, shows
a cross-peak and that there is selectivity to one of the
phenyl rings. The second methine CHO signal appears to
low frequency of the η5-C5H5 resonance.
anion approaches the positive metal center via the
bound nitrile.
In dichloromethane solutions the calculated rh values
(5.5 Å) for the BF4- anion in both RR-15a and 16a are
The present diffusion data reveal that the Cp com-
plexes 9 and the p-cymene complexes 11 behave simi-
larly, but that, perhaps, the p-cymene complexes16d for
Y ) BF4 and CF3SO3 possess slightly larger volumes
(smaller D values) than the η5-C5H5 complexes.
With this background we turned our attention to the
BIPHOP-F complexes. Attempts to use the methacrolein
complex [Ru(η5-C5H5)(BIPHOP-F)(CH2CH(Me)CHO)]-
[Y], 12, met with difficulties because of the presence of
small amounts of the aquo complex [Ru(η5-C5H5)-
(BIPHOP-F)(H2O)][Y], 13. The same difficulty was
encountered with the indenyl complexes where [Ru(η5-
C9H7)(BIPHOP-F)(H2O)][Y], 14, was present as an
impurity. The catalytic system was closely mimicked
through the synthesis of the acrylonitrile complexes [Ru-
(η5-C5H5)(CH2dCHCN)(BIPHOP-F)][Y], 15, and [Ru(η5-
C9H7)(CH2dCHCN)(BIPHOP-F)][Y], 16 (see Scheme 4).
The complexes 15 and 16 containing the same anions
were readily obtained in quantitative yield from the
reaction of the corresponding acetone complexes with
excess acrylonitrile in CH2Cl2 at room temperature.
Results from the 1H and 19F PGSE measurements for
the model Ru-BIPHOP-F derivatives, [Ru(η5-C5H5)-
(CH2dCHCN)(BIPHOP-F)][Y], 15, and [Ru(η5-C9H7)(CH2-
CHCN)(BIPHOP-F)][Y], 16, with Y ) BF4 and BArF,
in dichloromethane and acetone are given in Table 2.
-
clearly too large to arise from a simple solvate of BF4
and suggest surprisingly strong ion pairing. In solvents
not promoting strong ion pairing, e.g., acetone or
-
methanol, the rh value for the BF4 anion is normally
ca. 2.6-3.0 Å. The 5.5 Å value was the largest rh we
have yet found for this anion in this solvent. However,
the cation rh values for RR-15a and 16a, ca. 6.8-6.9 Å,
are reasonable enough. To further explore the observed
solvent dependence of the ion pairing, the 1H-19F
HOESY spectra of RR-15a and 16a were measured.
These spectra show selective contacts to one of the CHO
backbone signals, the vinyl protons of the acrylonitrile,
the η5-ligand, and additional contacts to the ortho
protons of one of the phenyl groups (see Figure 2). In
the case of the BArF salts, in dichloromethane solution,
RR-15b and 16b both afford rh values for the anion of
6.8 Å. These radii are close to what we find for the
BINAP compound 9d and other salts that we have
reported.16d A typical rh value for BArF salts in acetone
or methanol is ca. 6.1-6.3 Å; therefore a 6.8 Å value is
consistent with some interactions, but would not be
considered as predominant ion pairing.
X-ray Studies on RR-15a and RR-15b. For both
RR-15a and RR-15b, the above-mentioned NMR obser-
vations are in good agreement with the full molecular

5414 Organometallics, Vol. 23, No. 23, 2004
Kumar et al.
Figure 3. Perspective view of the cationic moiety of the crystal structure of [Ru(C46H20NO2F20P2)][BF4], RR-15a, with
atom numbering (the numbering scheme for RR-15b is identical). Ellipsoids are represented with 30% probability.
Table 3. Selected Geometrical Parameters for
RR-15a and RR-15b
RR-15a
RR-15a′
RR-15b
Bond Lengths (Å)
Ru(1)-P(1)
Ru(1)-P(2)
Ru(1)-N(1)
Ru(1)-C(1)
Ru(1)-C(2)
Ru(1)-C(3)
Ru(1)-C(4)
Ru(1)-C(5)
N(1)-C(44)
C(44)-C(45)
C(45)-C(46)
Ru(1)-Cp(mean plane)
2.249(4)
2.260(3)
2.02(1)
2.23(2)
2.24(1)
2.18(1)
2.16(1)
2.25(1)
1.14(2)
1.45(2)
1.29(3)
1.867(1)
2.258(4)
2.268(2)
2.257(2)
2.050(5)
2.234(7)
2.256(7)
2.248(7)
2.210(6)
2.218(6)
1.150(8)
1.42(1)
2.256(3)
2.04(1)
2.24(2)
2.20(2)
2.18(1)
2.17(1)
2.21(2)
1.11(2)
1.48(2)
1.30(3)
1.859(2)
1.09(2)
1.880(1)
Bond Angles (deg)
P(1)-Ru(1)-P(2)
P(1)-Ru(1)-N(1)
P(2)-Ru(1)-N(1)
Ru(1)-P(1)-O(1)
Ru(1)-P(2)-O(2)
89.6(1)
95.8(3)
87.1(3)
115.8(3)
117.2(3)
90.3(1)
89.34(6)
86.2(1)
94.8(3)
85.9(3)
116.9(3)
117.9(4)
97.2(2)
115.9(2)
115.6(2)
Figure 4. Perspective view of the cationic moiety of the
crystal structure of [Ru(C46H20NO2P2F20)][C32H12F24B], RR-
15b with atom numbering and showing the large displace-
ment parameters affecting the terminal carbon atom (C46)
of the acrylonitrile ligand. Ellipsoids are represented with
30% probability.
The Ru-N bond lengths in RR-15a (2.02(1) and 2.04-
(1) Å) and RR-15b (2.050(5) Å) are in line with other
Ru-NC-R complexes (e.g., 2.041 Å for [Ru(η5-C5H5)(CH3-
CN)(PPh3)2][BF4]).18 As observed previously in the case
of [Ru(η5-C5H5)(BIPHOP-F)(CH2dC(CH3)CHO)][SbF6],2
the fluorine atoms of the BF4 anions are involved in H‚
‚‚F interactions with both the hydrogen atoms of the
Cp and acrylonitrile ligands (H‚‚‚F distances smaller
than 3.0 Å), thereby shielding the chiral binding site
(see Table 4). Interestingly, one finds a single orienta-
tion of the acrylonitrile vinyl group with respect to the
Cp ligand.
geometry of these complexes, which was elucidated by
crystallographic measurements as shown in Figure 3
and Figure 4, respectively. Selected bond distances and
bond angles are given in Table 3. Both RR-15a and RR-
15b exhibit distorted piano-stool geometries with the
coordinated acrylonitrile ligand embedded within the
chiral pocket. In the case of RR-15a the asymmetric unit
contains two complexes of the same absolute configu-
ration, RR-15a and RR-15a′, which adopt almost identi-
cal conformations.
The solid-state structure of the BArF- complex RR-
-
15b presents interesting differences relative to the BF4
(18) Carreon, O. Y.; Leyva, M. A.; Fernandez-G., J. M.; Penicaud,
A. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1997, 53, 301.

Anion Effect in CpRu-Based Diels-Alder Catalysts
Organometallics, Vol. 23, No. 23, 2004 5415
Table 4. C-H‚‚‚F Hydrogen Bond Interactions
Involved between the Acrylonitrile and the
Counterions
C‚‚‚F (Å)
H‚‚‚F (Å)
C-H‚‚‚F (deg)
RR-15aa (BF4)
C45-H45‚‚‚F3c
3.32(2)
3.16(2)
3.13(2)
3.49(3)
2.72
2.59
2.45
2.59
119
117
126
154
C45-H45‚‚‚F4c
C46 H462‚‚‚F1d
C46-H462‚‚‚F4d
RR-15a′a (BF4)
C45-H45‚‚‚F1c(i)b
C45-H45‚‚‚F2c(i)b
C46-H462‚‚‚F2d(ii)b
C46-H462‚‚‚F4d(ii)b
RR-15b (BArF)
3.45(2)
3.21(2)
3.44(2)
3.30(3)
2.70
2.63
2.50
2.50
134
118
156
137
C45-H45‚‚‚F4a(iii)b
C46-H462‚‚‚F8a(iv)b
3.41(1)
3.59(2)
2.98
2.60
107
171
Figure 6. 1H-19F HOESY spectrum of the complex [Ru-
(η5-C5H5)(CH3CN)(BIPHOP-F)][BF4], 17a.
a The interactions with the other disordered fluorine atoms have
been omitted for clarity. b Equivalent positions for the fluorine
atoms: (i): x, y, z + 1; (ii): 1 - x, y - 1/2, 2 - z; (iii): x + 1, y, z
+ 1; (iv): 2 - x, 1/2 + y, 1 - z.
detailed 1H-19F HOESY results, Macchioni and co-
workers19 have recently suggested strong interionic
-
contacts of the BF4 anion in a [Pt(alkene)(Me)(di-
imine)][BF4] salt in dichloromethane. Consequently, this
ion pairing appears to have some generality.
The aquo complexes [Ru(η5-C5H5)(BIPHOP-F)(H2O)]-
[BF4], 13a, and [Ru(η5-C9H7)(BIPHOP-F)(H2O)][BF4],
14a, are observed when the acetone analogues, e.g., [Ru-
(η5-C5H5)(acetone)(BIPHOP-F)][BF4], 1a, were dissolved
in wet acetone-d6.
For 13a, the complexed water shows a two-proton
resonance at ca. δ 3.5. Interestingly, the D values/rh (Å)
in dichloromethane for the BF4- anion (8.30/6.4 Å), the
complexed water (7.86/6.8 Å), and the Ru cation (7.88/
6.8 Å) are all similar. This is understandable since
HOESY spectroscopy shows a strong NOE between the
BF4- and the water signal, suggesting H-bonding as the
source of this reduced BF4- translation. Phase-sensitive
1H-1H NOE studies show that the water signal is in
slow exchange with free water, and we estimate the
exchange rate, based on magnetization transfer studies,
to be ca. 7 s-1 in CD2Cl2 and 20-30 s-1 in CD3COCD3.
This observation is not relevant for the Diels-Alder
chemistry since the reaction solvent is dry, and this
brings us to a possible explanation for the BF4-/BArF-
anion effect.
Figure 5. Diffusion data for the complex [Ru(η5-C5H5)(CH3-
CN)(BIPHOP-F)][BF4], 17a, in dichloromethane. The white
circles depict the translation of the cation, while the black
ones are those for the anion. The inset shows the diffusion
for the anion in acetone-d6.
complex. Once again the anion is placed so that one
finds relatively short contacts between the BArF- anion
and both the Cp ring and the acrylonitrile ligand, via
H‚‚‚F interactions, but these are less numerous and
weaker as shown in Table 4. The moderate interaction
of the BArF- anion with the acrylonitrile results in more
freedom for the vinyl moiety, as indicated by the large
displacement parameters (see Figures 3 and 4) observed
in the acrylonitrile fragment with respect to RR-15a.
Although not directly related to the solution structure,
this difference hints at the higher catalytic activity
observed in the case of the BArF- anion.
Comments and Conclusion. In the Diels-Alder
reactions, catalyzed by the Ru-Lewis acids 1 and 2, in
dichloromethane, no significant difference in the values
of product ee as a function of anion is observed.
However, the reaction rates are quite different. This
suggests that substrate/product coordination as a func-
Solution Studies on [Ru(η5-C5H5)(CH3CN)-
(BIPHOP-F)][BF4], 17a. Returning to the solu-
tion data, the 5.5 Å rh value observed in both RR-15a
and 16a was sufficiently unexpected for us to study
the parent acetonitrile complex [Ru(η5-C5H5)(CH3CN)-
(BIPHOP-F)][BF4], 17a (see Table 2). In this case the
rh value for the BF4- anion in dichloromethane of 6.0 Å
is now so large that ion pairing has to be invoked as a
major contributor to the total structure (see Figure 5).
The size of the cation remains unchanged, as attaching
-
tion of anion may be important. If the BF4 anion ion
pairs strongly, it might well interfere with the complex-
ation of the dienophile oxygen donor, slow the aldehyde
exchange, or hinder the approach of the diene. Any of
the above would be sufficient to slow the reaction. The
BArF- anion is not so strongly ion paired, and HOESY
and X-ray measurements reveal little or no contacts
between the CF3 groups (or ortho aryl protons) and the
cation. The increased distance of this anion from the
reactive site would provide a rationale for the higher
turnover frequency of the catalyst. Clearly the PGSE/
HOESY NMR combination provides a powerful meth-
odology for recognizing the source of unexpected cation-
anion interactions.
-
BF4 does not significantly change its volume. Once
again, the 1H-19F HOESY (see Figure 6) confirms
selective contacts. The selectivity concerns the CHO
methine resonances, in that the resonance at δ 4.9 ppm
does not show a contact, whereas that at δ 5.5 ppm does.
The BArF analogue, 17b, affords D and rh values that
are similar to those for 16. We note that on the basis of
(19) Zuccaccia, C.; Macchioni, A.; Orabona, I.; Ruffo, F. Organome-
tallics 1999, 18, 4367.

5416 Organometallics, Vol. 23, No. 23, 2004
Kumar et al.
formed with XTAL system22 and ORTEP23 programs. Both
independent molecules of the asymmetric unit of RR-15a are
similar. CD spectra of both crystals used for the structure
determination confirm the reported values below.
Table 5. Summary of Crystal Data, Intensity
Measurement, and Structure Refinement for
RR-15a and RR-15b
RR-15a
RR-15b
CCDC-240176 and CCDC-240177 contain the supple-
mentary crystallographic data in cif format for RR-15a and
RR-15b. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+ 44) 1223-336-033; or deposit@
ccdc.cam.ac.uk).
Diffusion. All the measurements were performed on Bruk-
er AVANCE spectrometers (300, 400, and 500 MHz) equipped
with a microprocessor-controlled gradient unit and a multi-
nuclear probe (normal or inverse) with an actively shielded
Z-gradient coil. The shape of the gradient pulse was rectan-
gular, their length was 1.75 ms, and its strength varied
automatically in the course of the experiment. The time
between midpoints of the gradients (∆) was chosen as 167.75
ms. The measurements were carried out without sample
spinning and in the absence of external airflow. The experi-
ments were carried out at 299 K for our RT measurements,
which were controlled by a digital BVT 3000 variable-temper-
ature unit.
formula
[Ru(C46H20F20NO2- [Ru(C46H20F20NO2-
P2)]2(BF4)2(CH2Cl2) P2)](C32H12F24B)
MW
2581.9
2024.9
cryst syst
space group
a (Å)
monoclinic
P21
monoclinic
P21
11.5543(7)
23.1672(9)
20.9274(15)
96.751(8)
5563.0(6)
2, 2
12.1877(8)
17.2400(8)
18.6316(13)
96.268(8)
3891.4(4)
2, 1
b (Å)
c (Å)
â (deg)
V (Å3)
Z, Z′
Dcalc (g cm-3
)
1.541
1,728
cryst size (mm)
cryst color
0.09 × 0.13 × 0.31
0.10 × 0.29 × 0.32
yellow
yellow
radiation
Mo KR
Mo KR
µ (mm-1
)
0.504
0.398
Tmin, Tmax
0.9208, 0.9563
0.615
0.9042, 0.9673
0.638
((sin θ)/λ)max (Å-1
temperature (K)
)
200
200
no. measured reflns
no. indep reflns
no. obsd reflns
Rint
64 413
54 465
21 032
16 910
12 526
10 903
The diffusion values for the Cp and indenyl complexes are
measured in the solvents indicated in the tables. The concen-
tration of all the samples was maintained at 2 mM. The
diffusion of the cation was measured using the 1H signal from
the Cp, indenyl, or hydrocarbon backbone, whereas the anion
diffusion was obtained using the 19F signal.
0.057
0.046
criterion for obsd
refinement (on F)
no. params
|Fo| > 4σ(Fo)
full-matrix
1462
|Fo| > 4σ(Fo)
full-matrix
1189
weighting scheme Pa 0.00025
0.00015
-0.02(1)
0.033
Flack parameter, x
max. ∆/σ
0.01(4)
0.036
-0.59, 0.93
The error coefficients for the D values based on our experi-
ence is (0.06.
min. and max.
-1.25, 0.55
∆F (e Å-3
S
)
The viscosities used in the Stokes-Einstein relation are
those of pure solvents: CH2Cl2, 0.405; CHCl3, 0.529; (CH3)2-
CO, 0.303.24
Synthesis. All reactions involving air-sensitive compounds
were carried out in an atmosphere of purified nitrogen using
an inert gas/vacuum double manifold and standard Schlenk
or glovebox techniques.
1.94(2)
0.045, 0.047
1.26(1)
0.031, 0.030
R, Rw
a w ) 1/[σ2(Fo) + P(Fo)2].
Experimental Section
General Procedures. 1H, 31P, and 19F spectra were re-
corded on Bruker Avance 250, 300, or 400 spectrometers.
Chemical shifts are quoted in parts per million (ppm) down-
field of tetramethylsilane. 31P NMR chemical shifts were
referenced externally to 85% H3PO4 (δ 0.0). 19F NMR chemical
shifts were referenced externally to CFCl3 (δ 0.0). Coupling
constants J are quoted in Hz. 13C NMR and DEPT-135 spectra
were recorded with a broad band probe. IR spectra were
recorded on a Perkin-Elmer 1600 FT-IR spectrometer using a
Golden Gate accessory. Elemental analysis was performed by
the EA-Service of the Laboratory of Organic Chemistry
(ETHZ). Mass-spectra were obtained by the MS-Service of the
Laboratory of Organic Chemistry (ETHZ, MALDI, matrix 2,5-
dihydroxybenzoic acid (DHB)). The exact mass measurement
in TOF mode was obtained by electrospray using a quadrupole
time-of-flight Q STAR XL (Applied Biosystems/MDS Sciex)
mass spectrometer.
Unless otherwise stated, conventional (but not deuterated)
solvents were purified, degassed, and dried by standard
methods (distillation). [Ru(η5-C5H5)(CH3CN)3][PF6] was pre-
pared according to the literature.20
X-ray Crystal Structures. A summary of crystal data,
intensity measurement, and structure refinement for RR-15a
and RR-15b is reported in Table 5. Cell dimensions and
intensities were measured at 200 K on a Stoe-IPDS diffrac-
tometer. Data were corrected for Lorentz and polarization
effects and for absorption. The crystal structures were solved
by direct methods using Sir-97.21 All calculations were per-
Synthesis of RuCl(η5-C5H5)(BINAP) (10). In a typical
experiment, RuCl(η5-C5H5)(PPh3)2 (866 mg, 1.20 mmol), BI-
NAP (733 mg, 1.20 mmol), and 50 mL of toluene were placed
in a Schlenk tube fitted with a magnetic stirrer. The mixture
was then stirred at 120 °C for 5 days, during which time the
formation of red crystals was observed. The precipitate was
collected and washed twice with pentane and then dried, in
vitro, to afford 670 mg (0.80 mmol, 68%) of pure product. Anal.
Calcd for C49H37ClP2Ru: C, 71.36; H, 4.61. Found: C, 71.40;
H, 4.52. 1H NMR (400 MHz, CD2Cl2): δ 7.89-7.82 (m, 2H,
ArH), 7.60-7.44 (m, 6H, ArH), 7.38-7.22 (m, 11H, ArH), 7.15-
7.05 (m, 3H, ArH), 7.01-6.88 (m, 4H, ArH), 6.80-6.74 (m, 2H,
ArH), 6.65-6.59 (m, 2H, ArH), 6.38 (d, J ) 9 Hz, 1H, ArH),
6.28 (d, J ) 9 Hz, 1H, ArH), 4.22 (s, 5H, η5-C5H5). 31P{1H}
NMR (161.9 MHz, CD2Cl2): δ 54.4 (d, JPP ) 64 Hz), 44.8 (d,
JPP ) 64 Hz). MS (MALDI): 789 (M+ - Cl) (100).
Synthesis of [Ru(η5-C5H5)(CH3CN)(BINAP)][BF4] (9a).
In a typical experiment, a Schlenk tube was loaded with RuCl-
(η5-C5H5)(BINAP) (119 mg, 0.15 mmol), AgBF4 (28 mg, 0.15
mmol), and 3 mL of dry acetonitrile. The solution was then
stirred in the dark overnight, after which time the solvent was
evaporated and 2 mL of dichloromethane was added. The
resulting solution was then filtered through a plug of Celite
and evaporated. Crystallization of the crude product from
dichloromethane/ether, washing with ether, and drying under
vacuum afforded 84 mg (0.09 mmol, 62%) of a product mixture.
(22) Hall, S. R.; Flack, H. D.; Stewart, J. M. XTAL3.2 User’s Manual;
Universities of Western Australia and Maryland, 1992.
(23) Johnson, C. K. ORTEP II; Report ORNL-5138; Oak Ridge
National Laboratory: Oak Ridge, TN, 1976.
(24) Chemical Properties Handbook; McGraw-Hill: New York, 1999
(http://www.Knovel.com).
(20) Gill, T. P.; Mann, K. R. Organometallics 1982, 1, 485.
(21) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R.
J. Appl. Crystallogr. 1999, 32, 115-119.

Anion Effect in CpRu-Based Diels-Alder Catalysts
Organometallics, Vol. 23, No. 23, 2004 5417
The second component, which appears in all of these halide
extraction experiments, is the known [Ru(η5-C5H5)(BINAP)]-
[BF4]25 (18(BF4)), which results from dissociation of the nitrile
and complexation of a naphthyl backbone double bond. This
crude product was used for the NMR measurements without
further purification. The major product is 9a (90% by NMR).
1H NMR (300 MHz, CD2Cl2): the aromatic protons are found
in the range δ 7.85-6.31 (32H, ArH), 4.50 (s, 5H, η5-C5H5),
1.15 (s, 3H, CH3CN). 31P{1H} NMR (121.4 MHz, CD2Cl2): δ
54.5 (d, JPP ) 46 Hz), 47.1 (d, JPP ) 46 Hz). Minor component
[Ru(η5-C5H5)(BINAP)][BF4], (18(BF4)): 1H NMR (300 MHz,
CD2Cl2): δ 8.10-8.00 (m, 2H, ArH), 7.90-7.00 (m, 24H, ArH),
6.90-6.70 (m, 1H, ArH), 6.29 (m, 1H, ArH), 6.15-5.90 (m, 4H,
ArH), 4.45 (s, 5H, η5-C5H5). 31P{1H} NMR (121.4 MHz, CD2-
Cl2): 74.3 (d, JPP ) 44 Hz), 14.2 (d, JPP ) 44 Hz).
Synthesis of [Ru(η5-C5H5)(CH3CN)(BINAP)][CF3SO3]
(9b). In a typical experiment a Schlenk was loaded with [Ru-
(η5-C5H5)(Cl)(BINAP)] (50 mg, 0.06 mmol), NaSO3CF3 (10 mg,
0.06 mmol), and 2 mL of dry acetonitrile. The solution was
then stirred at 80 °C overnight. At the end of the reaction the
solvent was evaporated and 2 mL of dichloromethane was
added. Subsequent filtration through a plug of Celite, recrys-
tallization from dichloromethane/ether, washing twice with
ether, and drying under vacuum afforded 46 mg (0.05 mmol,
83%) of the final product mixture. The mixture could not be
further purified and was used as such. Major product (89%
by NMR) [Ru(η5-C5H5)(CH3CN)(BINAP)][CF3SO3] (9b): 1H
NMR (250 MHz, CD2Cl2): the aromatic protons are found in
the range δ 7.85-6.28 (32H, ArH), 4.48 (s, 5H, η5-C5H5), 1.11
(s, 3H, CH3CN). 31P{1H} NMR (101.2 MHz, CD2Cl2): δ 54.5
(d, JPP ) 46 Hz), 47.1 (d, JPP ) 46 Hz). One finds ca. 11% of
18(OTf).
room temperature for 5 min. After removing volatiles under
vacuum, two more cycles of acrylonitrile-addition/stirring/
evaporation were performed. Finally, removal of the solvent
afforded the product as a yellow powder in quantitative yield.
Crystals suitable for X-ray measurements were obtained from
CH2Cl2/hexane.
[Ru(η5-C5H5)(acrylonitrile)(BIPHOP-F)][BF4] (RR-15a).
1H NMR (300 MHz, CDCl3): δ 7.23-6.91 (m, 6H, ArH), 6.83
(brs, 2H, ArH), 6.64-6.42 (m, 3H, CHOP, ArH), 6.24 (d, J )
18.0 Hz, 1H, CH2), 6.10 (d, J ) 12.0 Hz, 1H, CH2), 5.75-5.65
(dd, J ) 18.0 Hz, J ) 12 Hz, 1H, NCCH), 5.07-5.02 (dd, J )
15.0 Hz, J ) 8.0 Hz, 1H, CHOP), 5.03 (s, 5H, η5-C5H5). 31P-
{1H} NMR (121.5 MHz, CDCl3): δ 129.0 (d, Jpp ) 65 Hz), 124.0
(d, Jpp ) 65 Hz). 19F{1H} NMR (282 MHz, CDCl3): δ -142.2
(br, 4F, o-C6F5), -143.7 (br, 4F, o-C6F5), -147.0 (m, 2F, p-C6F5),
-147.9 (m, 2F, p-C6F5), -152.3 (s, BF4), -158.2 (br, 8F,
m-C6F5). HRMS: calcd for C46H20O2NF20P2Ru 1155.972, found
1155.975. [R]20 +74.54 (CH2Cl2, c 0.5). CD (CH2Cl2, C ) 1 ×
D
10-4 M, 20 °C): λ(∆ꢀ) 353 (+4.21), 286 (-19.38), 250 (-16.49).
[Ru(η5-C5H5)(acrylonitrile)(BIPHOP-F)][BArF] (RR-
1
15b). H NMR (300 MHz, CDCl3): δ 7.71 (s, 8H, BArF), 7.52
(s, 4H, BArF), 7.16-7.06 (m, 6H, ArH), 6.43 (d, J ) 18.0 Hz,
1H, CH2), 6.30 (d, J ) 12.0 Hz, 1H, CH2), 6.24-5.97 (m, 5H,
CHOP, ArH), 5.64 (dd, J ) 18.0 Hz, J ) 12.0 Hz, 1H, NCCH),
4.94 (br, 1H, CHOP), 4.82 (s, 5H, η5-C5H5). 31P{1H} NMR (121.5
MHz, CDCl3): δ 129.2 (d, Jpp ) 61 Hz), 124.2 (d, Jpp ) 61 Hz).
19F{1H} NMR (282 MHz, CDCl3): δ -62.9 (s, CF3), -140.6 (br,
4F, o-C6F5), -142.00 (br, 4F, o-C6F5), -145.2 (m, 2F, p-C6F5),
-146.1 (m, 2F, p-C6F5), -157.5 (m, 8F, m-C6F5). HRMS: calcd
for C46H20O2NF20P2Ru 1155.972, found 1155.973. [R]20D +80.62
(CH2Cl2, c 0.5). CD (CH2Cl2, C ) 1 × 10-4 M, 20 °C): λ(∆ꢀ)
351 (+5.30), 285 (-26.11), 248 (-20.48).
[Ru(η5-C9H7)(acrylonitrile)(BIPHOP-F)][BF4] (16a).
Yield: 88%. 1H NMR (300 MHz, acetone-d6): δ 7.66-7.56 (m,
2H, ArH, η5-C9H7), 7.51-7.45 (m, 2H, ArH, η5-C9H7), 6.73-
6.64 (m, 2H, ArH, η5-C9H7), 7.36-6.94 (m, 12H, ArH, η5-C9H7,
CHOP), 6.60 (dd, J ) 18.0 Hz, J ) 12.0 Hz, 1H, NCCH), 6.41
(d, J ) 12 Hz, 1H, CH2), 6.37 (d, J ) 18.0 Hz, 1H, CH2), 5.53
(q, J ) 9.0 Hz, 1H, CHOP), 5.21 (s, 1H, η5-C9H7), 4.83 (t, J )
9.0 Hz, 1H, η5-C9H7), 4.42 (s, 1H, η5-C9H7). 31P{1H} NMR (121.5
MHz, CDCl3): δ 132.4 (d, Jpp ) 56 Hz), 127.3 (d, Jpp ) 56 Hz).
19F{1H} NMR (282 MHz, CDCl3): δ -141.2 (br, 4F, o-C6F5),
-142.0 (br, 4F, o-C6F5), -145.9 (m, 2F, p-C6F5), -146.3 (m,
2F, p-C6F5), -152.0 (s, BF4), -158.5 (br, 8F, m-C6F5). HRMS:
calcd for C50H22O2NF20P2 Ru 1205.9877, found 1205.986.
[Ru(η5-C9H7)(acrylonitrile)(BIPHOP-F)][BArF] (16b).
Yield: 90%. 1H NMR (300 MHz, acetone-d6): δ 7.75 (s, 8H,
BArF), 7.55 (s, 4H, BArF), 6.73-6.64 (m, 2H, ArH, η5-C9H7),
7.49-7.40 (m, 2H, ArH, η5-C9H7), 7.21-7.14 (m, 3H, ArH, η5-
C9H7) 7.08-6.03 (m, 4H, ArH, η5-C9H7), 6.73-6.674 (m, 3H,
ArH, η5-C9H7) 7.36-6.94 (m, 12 H, ArH, η5-C9H7), 6.50 (br,
2H), 6.30 (d, J ) 18.0 Hz, 1H, CH2), 6.20 (d, J ) 12.0 Hz, 1H,
CH2), 5.60 (dd, J ) 18.0 Hz, J ) 12.0 Hz, 1H, NCCH), 5.33 (s,
1H), 5.02 (s, 1H, η5-C9H7), 4.94 (t, J ) 9.0 Hz, 1H, η5-C9H7),
4.79 (q, J ) 6.0 Hz, 1H, CHOP), 4.51 (s, 1H, η5-C9H7). 31P{1H}
NMR (121.5 MHz, CDCl3): δ 133.2 (d, Jpp ) 53 Hz), 128.6 (d,
Jpp ) 53 Hz). 19F{1H} NMR (282 MHz, CDCl3): δ -62.4 (s,
CF3), -139.4 (m, 4F, o-C6F5), -140.8 (m, 4F, o-C6F5), -143.5
(m, 2F, p-C6F5), -144.4 (m, 2F, p-C6F5), -156.3 (br, 8F,
m-C6F5). HRMS: calcd for C50H22O2NF20P2Ru 1205.9877, found
1205.9906.
Synthesis of [Ru(η5-C5H5)(CH3CN)(BINAP)][PF6] (9c).
In a typical experiment a Schlenk was loaded with RuCl(η5-
C5H5)(BINAP) (133 mg, 0.16 mmol), AgPF6 (41 mg, 0.16 mmol),
and 2 mL of dry acetonitrile. The solution was then stirred
overnight in the dark. At the end of the reaction the solvent
was evaporated and 2 mL of dichloromethane was added.
Subsequent filtration through a plug of Celite, recrystallization
from dichloromethane/ether, washing twice with ether, and
drying under vacuum afforded 66 mg (0.07 mmol, 44%) of the
final product. The major product (90%) is [Ru(η5-C5H5)(CH3-
CN)(BINAP)][PF6] (9b). 1H NMR (250 MHz, CD2Cl2): the
aromatic protons are found in the range δ 7.85-6.33 (32H,
ArH), 4.51 (s, 5H, η5-C5H5), 1.14 (s, 3H, CH3CN). 31P{1H}
NMR (101.2 MHz, CD2Cl2): δ 54.5 (d, JPP ) 46 Hz), 47.1 (d,
JPP ) 46 Hz). One finds ca. 10% of 18(PF6).
Synthesis of [Ru(η5-C5H5)(CH3CN)(BINAP)][BArF] (9d).
A Schlenk tube was loaded with [RuCl(η5-C5H5)(BINAP)] (50
mg 0.06 mmol), NaBArF (54 mg, 0.06 mmol), and 2 mL of
acetonitrile. The solution was then stirred overnight at 80 °C,
after which time the solvent was evaporated and 2 mL of
dichloromethane was added. The resulting solution was fil-
tered through a plug of Celite and evaporated. The crude
product was washed twice with pentane and dried under
vacuum to give 49 mg (0.03 mmol, 62%) of the final product
[Ru(η5-C5H5)(CH3CN)(BINAP)][BArF] (9d). 1H NMR: (250
MHz, CD2Cl2) δ 7.90-6.29 (44H, ArH), 4.47 (s, 5H, η5-C5H5),
1.15 (s, 3H, CH3CN). 31P{1H} NMR (101.2 MHz, CD2Cl2): δ
55.2 (d, JPP ) 46 Hz), 47.0 (d, JPP ) 46 Hz).
Synthesis of the Acrylonitrile Complexes [Ru(η5-C5H5)-
(acrylonitrile)(BIPHOP-F)][Y] and [Ru(η5-C9H7)(acrylo-
nitrile)(BIPHOP-F)][Y]: General Procedure. The appro-
priate complex [Ru(η5-C5H5)(acetone)(BIPHOP-F)][Y] or [Ru-
(η5-C9H7)(acetone)(BIPHOP-F)][Y]9 was dissolved in CH2Cl2
and degassed by three freeze-pump-thaw cycles. Then acrylo-
nitrile (20 equiv) was added, and the solution was stirred at
Synthesis of [Ru(η5-C5H5)(BIPHOP-F)(CH3CN)][BF4]
(17a). A 10 mM solution (ca. 2 mg in 0.6 mL of CD2Cl2) of
[Ru(η5-C5H5)(acetone or water)(BIPHOP-F)][Y] (Y ) BF4 or
BArF) was placed in an NMR tube. Dry acetonitrile (1 µL) was
added, thereby generating the complex quantitatively in situ.
The volatile materials were removed, and a fresh equivalent
of acetonitrile was added. 1H NMR (400 MHz, CD2Cl2): δ 7.20-
6.71 (10H, ArH), 5.48 (m, 1H, CH), 4.88 (m, 1H, CH), 4.86 (s,
5H, η5-C5H5), 2.70 (s, 3H, Ru-CH3CN), 2.06 (s, 3H, free
acetone), 1.91 (s, free CH3CN). 31P{1H} NMR (161.9 MHz, CD2-
(25) (a) den Reijer, C. J.; Dotta, P.; Pregosin, P. S.; Albinati, A. Can.
J. Chem. 2001, 79, 693. (b) Geldbach, T. J.; Pregosin, P. S. Eur. J.
Inorg. Chem. 2002, 1907.

5418 Organometallics, Vol. 23, No. 23, 2004
Kumar et al.
Cl2): δ 124.8 (d, Jpp ) 65 Hz), 129.6 (d, Jpp ) 65 Hz). 19F{1H}
NMR (376 MHz, CD2Cl2): δ -141.2 (br, 4F, o-C6F5), -142.0
(br, 4F, o-C6F5), -145.9 (m, 2F, p-C6F5), -146.3 (m, 2F, p-C6F5),
-152.0 (s, BF4), -158.5 (br, 8F, m-C6F5).
5.28 (q, J ) 8.0 Hz,1H, CHOP), 5.19 (s, 5H, η5-C5H5), 4.94 (t,
J ) 8.0 Hz 1H, CHOP). 1H NMR (300 MHz, acetone-d6): δ
7.79 (s, 8H, BArF), 7.67 (s, 4H, BArF), 7.27-7.18 (m, 6H, ArH),
7.09 (br, 4H, ArH), 5.90-5.87 (m, 1H, CHOP), 5.83 (s, 5H, η5-
C5H5), 5.76 (t, J ) 8.0 Hz 1H, CHOP). 31P{1H} NMR (121.5
MHz, CDCl3): δ 127.6 (d, Jpp ) 42 Hz), 117.7 (d, Jpp ) 42 Hz).
31P NMR (121.5 MHz, acetone-d6): δ 127.6 (d, Jpp ) 51 Hz),
119.4 (d, Jpp ) 51 Hz). 19F{1H} NMR (282 MHz, CDCl3): δ
-62.6 (s, CF3), -136.6 (br, 4F, o-C6F5), -137.9 (br, 4F, o-C6F5),
-141.0 (m, 2F, p-C6F5), -142.3 (m, 2F, p-C6F5), -155.1 (m,
8F, m-C6F5). 19F NMR (282 MHz, acetone-d6): δ -63.2 (s, CF3),
-144.0 (br, 4F, o-C6F5), -145.4 (br, 4F, o-C6F5), -148.0 (m,
2F, p-C6F5), -149.0 (m, 2F, p-C6F5), -159.6 (m, 8F, m-C6F5).
HRMS: calcd for C44H17O3F20P2 Ru 1130.9404, found 1130.9398.
Synthesis of the CO Complexes [Ru(η5-C5H5)-
(BIPHOP-F)(CO)][Y] (8): General Procedure. The ap-
propriate [(η5-C5H5)Ru(BIPHOP-F)(acetone)][Y] complex was
dissolved in CH2Cl2 and degassed using three freeze-pump-
thaw cycles. One atmosphere of CO was then allowed into the
reaction vessel, and the reaction mixture was stirred while
bubbling CO through the solution for 15 min. Volatiles were
removed under vacuum, yielding the pale yellow carbonyl
complexes quantitatively.
[Ru(η5-C5H5)(CO)(BIPHOP-F)][BF4] (7a). IR (neat, cm-1):
2028 (νCO). 1H NMR (300 MHz, acetone-d6): δ 7.48-7.643 (m,
14H, ArH), 6.21-5.89 (m, 1H, CHOP), 5.82 (s, 5H, η5-C5H5),
5.77 (t, J ) 8.0 Hz, 1H, CHOP). 31P{1H} NMR (121.5 MHz,
CDCl3): δ 128.6 (d, Jpp ) 46 Hz), 119.9 (d, Jpp ) 46 Hz). 31P-
{1H} NMR (121.5 MHz, acetone-d6): δ 127.6 (d, Jpp ) 45 Hz),
119.6 (d, Jpp ) 45 Hz). 19F{1H} NMR (282 MHz, CDCl3): δ
-139.1 (br, 4F, o-C6F5), -140.0 (br, 4F, o-C6F5), -142.9 (m,
2F, p-C6F5), -144.0 (m, 2F, p-C6F5), -153.3 (s, BF4), -157.4
Acknowledgment. E.P.K. thanks G. Hopfgartner
for the TOF-MS measurements. Special thanks are due
to H. Ru¨egger and M. Valentini for both experimental
assistance and timely advice. E.P.K. and P.S.P. thank
the Swiss National Science Foundation for financial
support. P.S.P. thanks the BBW and the ETH Zu¨rich
for financial support and Johnson Matthey for the loan
of precious metal compounds.
(br, 8F, m-C6F5). 19F{1H} NMR (282 MHz, acetone-d6):
δ
-144.0 (br, 4F, o-C6F5), -145.5 (br, 4F, o-C6F5), -148.0 (m,
2F, p-C6F5), -148.9 (m, 2F, p-C6F5), -151.9 (s, BF4), -160.8
(br, 8F, m-C6F5). HRMS: calcd for C44H17O3F20P2 Ru 1130.9404,
found 1130.9457.
Supporting Information Available: X-ray crystallo-
graphic data, including cif files, and tables of bond lengths and
angles for compounds RR-15a and RR-15b. This material is
available free of charge via the Internet at http://pubs.acs.org.
[Ru(η5-C5H5)(CO)(BIPHOP-F)][BArF] (7b). IR (neat,
cm-1): 2033 (νCO). 1H NMR (300 MHz, CDCl3): δ 7.75 (s, 8H,
BArF), 7.53 (s, 4H, BArF), 7.26-7.19 (m, 4H, ArH), 7.17 (br,
2H, ArH), 6.93 (d, J ) 7.0 Hz, 2H, ArH), 6.66 (br, 2H, ArH),
OM049559O