Carbon-fluorine bond activation coupled with carbon-carbon bond formation at iridium. Confirmation of complete kinetic diastereoselectivity at the new carbon stereocenter by intramolecular trapping using vinyl as the migrating group

Article abstract of DOI:10.1021/ja042345d

The iridium(perfluoropropyl)(vinyl) complex Cp*Ir(PMe ₃)(n-C₃F₇)(CH=CH₂) (5) has been prepared. It has been characterized by X-ray crystallography, and its ground state conformation in solution has been determined by ¹⁹F{ ¹H} HOESY NMR studies. It reacts with the weak acid lutidinium iodide to afford the η¹-allylic complex Cp*Ir(PMe ₃)((Z)-CH₂CH=CFC₂F₅)I (6), which has also been characterized crystallographically. The mechanism of C-F bond activation and C-C bond formation leading to 6 has been elucidated in detail by studying the reaction of 5 with lutidinium tetrakis[3,5-bis(trifluoromethyl) phenyl]borate [LUtH⁺B(ArF)₄^-], containing a weakly coordinating counteranion. The main kinetic product of this reaction, determined by ¹⁹F{¹H} HOESY studies at -50 °C, is the endo-Cp*Ir(PMe₃)(anti-η³-CH ₂CHCFCF₂CF₃)-[B(ArF)₄] diastereomer 9, along with a small amount of the exo-syn-isomer 8. Isomer 9 rearranges at -20 °C to its exo-anti isomer 7, and subsequently to the thermodynamically favored exo-syn-isomer 8, which has been isolated and crystallographically characterized. Complex 8 reacts with iodide to afford complex 6. On the basis of the unambiguously defined kinetically controlled stereochemistry of 9 and 8, a detailed mechanism for the C-F activation/C-C coupling reaction is proposed, the principal conclusion of which is that C-F activation is completely diastereoselective.

Full text of DOI:10.1021/ja042345d

Published on Web 04/05/2005
Carbon-Fluorine Bond Activation Coupled with
Carbon-Carbon Bond Formation at Iridium. Confirmation of
Complete Kinetic Diastereoselectivity at the New Carbon
Stereocenter by Intramolecular Trapping Using Vinyl as the
Migrating Group
Russell P. Hughes,*,† Roman B. Laritchev,† Lev N. Zakharov,‡ and
Arnold L. Rheingold‡
Contribution from the Departments of Chemistry, 6128 Burke Laboratory, Dartmouth College,
HanoVer, New Hampshire 03755, and UniVersity of California,
San Diego, California 92093-0358
Received December 20, 2004; E-mail: rph@dartmouth.edu
Abstract: The iridium(perfluoropropyl)(vinyl) complex Cp*Ir(PMe3)(n-C3F7)(CHdCH2) (5) has been prepared.
It has been characterized by X-ray crystallography, and its ground state conformation in solution has been
determined by 19F{1H} HOESY NMR studies. It reacts with the weak acid lutidinium iodide to afford the
η1-allylic complex Cp*Ir(PMe3)((Z)-CH2CHdCFC2F5)I (6), which has also been characterized crystallo-
graphically. The mechanism of C-F bond activation and C-C bond formation leading to 6 has been
elucidated in detail by studying the reaction of 5 with lutidinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate
[LutH+B(ArF)4-], containing a weakly coordinating counteranion. The main kinetic product of this reaction,
determined by 19F{1H} HOESY studies at -50 °C, is the endo-Cp*Ir(PMe3)(anti-η3-CH2CHCFCF2CF3)-
[B(ArF)4] diastereomer 9, along with a small amount of the exo-syn-isomer 8. Isomer 9 rearranges at -20
°C to its exo-anti isomer 7, and subsequently to the thermodynamically favored exo-syn-isomer 8, which
has been isolated and crystallographically characterized. Complex 8 reacts with iodide to afford complex
6. On the basis of the unambiguously defined kinetically controlled stereochemistry of 9 and 8, a detailed
mechanism for the C-F activation/C-C coupling reaction is proposed, the principal conclusion of which is
that C-F activation is completely diastereoselective.
Introduction
have been employed. The roots of this interest are many,
including perhaps most prominently the conversion of environ-
The activation of aliphatic carbon-fluorine bonds using
transition metal complexes has been a topic of long-standing
interest. A variety of methods, including strongly reducing
conditions1-9 and radical-based transition metal chemistry,10-13
mentally harmful chlorofluorocarbons (CFCs) and perfluoro-
carbons (PFCs) to more friendly and useful fluorocarbon
compounds,14,15 coupled with the intellectual challenge of
activating the strongest single bond to carbon16 in molecules
originally designed to be chemically inert.17
Almost all successful attempts to generate fluorinated ste-
reocenters in organic molecules rely on C-F bond formation
approaches, in some cases with the assistance of transition metal
complexes.18-29 The asymmetric synthesis of carbon stereo-
† Dartmouth College.
‡ University of California, San Diego.
(1) Richmond, T. G. Top. Organomet. Chem. 1999, 3, 243-269.
(2) McAlexander, L. H.; Beck, C. M.; Burdeniuc, J. J.; Crabtree, R. H. J. Fluor.
Chem. 1999, 99, 67-72.
(3) Burdeniuc, J.; Siegbahn, P. E. M.; Crabtree, R. H. New J. Chem. 1998, 22,
503-510.
(4) Burdeniuc, J.; Jedlicka, B.; Crabtree, R. H. Chem. Ber./Recl. 1997, 130,
145-154.
(14) Manzer, L. E. Chem. Ind. 1994, 53, 411-418.
(15) Manzer, L. E. Science 1990, 249, 31-35.
(5) Kiplinger, J. L.; Richmond, T. G. J. Am. Chem. Soc. 1996, 118, 1805-
1806.
(16) Smart, B. E. Fluorocarbons. In Chemistry of Functional Groups, Supplement
D; Patai, S., Rappoport, Z., Eds.; Wiley, New York: 1983; Chapter 14, pp
603-655.
(6) Bennett, B. K.; Harrison, R. G.; Richmond, T. G. J. Am. Chem. Soc. 1994,
116, 11165-11166.
(17) Lemal, D. M. J. Org. Chem. 2004, 69, 1-11.
(18) Baudequin, C.; Loubassou, J.-F.; Plaquevent, J.-C.; Cahard, D. J. Fluor.
Chem. 2002, 122, 189-193.
(7) Harrison, R. G.; Richmond, T. G. J. Am. Chem. Soc. 1993, 115, 5303-
5304.
(8) Kiplinger, J. L.; Richmond, T. G. Chem. Commun. 1996, 1115-1116.
(9) Hughes, R. P.; Laritchev, R. B.; Zakharov, L. N.; Rheingold, A. L. J. Am.
Chem. Soc. 2004, 126, 2308-2309.
(19) Ma, J.-A.; Cahard, D. Chem. ReV. 2004, 104, 6119-6146.
(20) Gouverneur, V.; Greedy, B. Chem. Eur. J. 2002, 8, 766-771.
(21) Mohar, B.; Baudoux, J.; Plaquevent, J.-C.; Cahard, D. Angew. Chem., Int.
Ed. 2001, 40, 4214-4216.
(10) Jones, W. D. Dalton Trans. 2003, 3991-3995.
(11) Kraft, B. M.; Lachicotte, R. J.; Jones, W. D. J. Am. Chem. Soc. 2000, 122,
8559-8560.
(22) Piana, S.; Devillers, I.; Togni, A.; Rothlisberger, U. Angew. Chem., Int.
Ed. 2002, 41, 979-982.
(12) Kraft, B. M.; Lachicotte, R. J.; Jones, W. D. J. Am. Chem. Soc. 2001, 123,
10973-10979.
(23) Prakesch, M.; Gre´e, D.; Gre´e, R. Acc. Chem. Res. 2002, 35, 175-181.
(24) Muniz, K. Angew. Chem., Int. Ed. 2001, 40, 1653-1656.
(25) Shibata, N.; Suzuki, E.; Asahi, T.; Shiro, M. J. Am. Chem. Soc. 2001, 123,
7001-7009.
(13) Clot, E.; Me´gret, C.; Kraft, B. M.; Eisenstein, O.; Jones, W. D. J. Am.
Chem. Soc. 2004, 126, 5647-5653.
9
10.1021/ja042345d CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 6325-6334
6325

A R T I C L E S
Scheme 1
Hughes et al.
centers bearing fluorine has been of particular interest due to
their potential biological applications.19,30,31 We have sought
methodology for the complementary approach, in which C-H
and C-C bonds can be generated by substitution at a C-F
bond.32-35 Clearly, the strength of the C-F bond allows
synthetic methodology for its production via C-F bond forma-
tion chemistry, whether it be via F- addition to electrophilic
carbon or by electrophilic “F+” addition to nucleophilic carbon
centers, to be straightforward, while providing a thermodynamic
impediment to the complementary approach involving breaking
the C-F bond, which must be compensated for by formation
of a strong bond from fluorine to another element.
The question of whether the σ* orbitals of C-F bonds R to
transition metals are capable of acting as π-acceptors, thereby
weakening the C-F bond and activating it toward reaction, has
long intrigued chemists and is an idea whose appeal has waxed
and waned over the years,36-39 as has its organic equivalent of
negative hyperconjugation.40-43 However, while there are few
pieces of evidence for such weakening in spectroscopic or
ground state structural studies, it has long been clear that
aliphatic C-F bonds are labile toward external Lewis acids
when they are R to certain transition metal centers and that C-F
bond activation by various exogenous protic acids44-47 and
Lewis acids48-52 can be achieved quite easily. The recent
discovery in our group that the source of the exogenous acid
could be heterolytically activated H2, with resulting hydro-
genolysis of R-C-F bonds of fluoroalkyl ligands to liberate
environmentally friendly hydrofluorocarbons (HFCs), provided
considerable stimulation for more detailed studies of this type
of reaction.32,34
Even more recently we reported the first apparently diaste-
reoselective R-C-F bond activation, coupled with formation
of a C-C bond.35 Remarkably, instead of undergoing proto-
nation at the metal or at the Ir-CH3 bond to give methane, the
iridium complex 1 reacts with HCl in the form of lutidinium
chloride at the R-CF2 group to give HF in the form of lutidinium
fluoride; migration of the methyl group from iridium to the
R-carbon generates a new C-C bond and a carbon stereocenter,
and subsequent trapping at the metal with the chloride coun-
teranion affords product 2a (Scheme 1). The diastereoselectivity
of this reaction was 100%, and the relative configurations at
the R-carbon and at Ir were shown unambiguously to be (RC,RIr)
or (SC,SIr) by X-ray crystallography.35
When this reaction was carried out using lutidinium trifluo-
roacetate, the product was 3, formed as a 4:1 mixture of
diastereomers. Monitoring the reaction by NMR indicated that
the initially formed product was indeed 2b, which then
isomerized to 3. In this case, it was proposed that trifluoroacetate
trapped the metal reversibly compared to chloride, allowing
eventual â-H elimination from the intermediate cation 4 to occur,
with resultant rearrangement as shown in Scheme 1.35 Clearly
the final overall outcome of this reaction, and thus the
preservation or destruction of the newly formed carbon stereo-
center, depends on the nature of the trapping counteranion.
Moreover, even when the migrating group is one incapable of
further rearrangement, such as hydride or phenyl, loss of
diastereoselectivity in the final product can occur by inversion
at iridium if the 16-electron species 4 (or its analogue) has a
significant lifetime, by virtue either of slow trapping or of anion
dissociation after initial trapping. As a consequence, the clarity
of any conclusion whether diastereoselectivity of C-F activation
(26) Togni, A.; Mezzetti, A.; Barthazy, P.; Becker, C.; Devillers, I.; Frantz, R.;
Hintermann, L.; Perseghini, M.; Sanna, M. Chimia 2001, 55, 801-805.
(27) Shibata, N.; Suzuki, E.; Takeuchi, Y. J. Am. Chem. Soc. 2000, 122, 10728-
10729.
(28) Differding, E.; Lang, R. W. Tetrahedron Lett. 1988, 29, 6087-6090.
(29) Iseki, K. Tetrahedron 1998, 54, 13887-13914.
(30) Ramachandran, P. V. ACS Symp. Ser. 2001, 746, 310.
(31) Filler, R. ACS Symp. Ser. 2001, 746, 1-20.
(32) Hughes, R. P.; Smith, J. M. J. Am. Chem. Soc. 1999, 121, 6084-6085.
(33) Hughes, R. P.; Lindner, D. C.; Rheingold, A. L.; Liable-Sands, L. M. J.
Am. Chem. Soc. 1997, 119, 11544-11545.
(34) Hughes, R. P.; Willemsen, S.; Williamson, A.; Zhang, D. Organometallics
2002, 21, 3085-3087.
(35) Hughes, R. P.; Zhang, D.; Zakharov, L. N.; Rheingold, A. L. Organome-
tallics 2002, 21, 4902-4904.
(36) Graham, W. A. G. Inorg. Chem. 1968, 7, 315-321.
(37) King, R. B.; Bisnette, M. B. J. Organomet. Chem. 1964, 2, 15-37.
(38) Cotton, F. A.; McCleverty, J. A. J. Organomet. Chem. 1965, 4, 490.
(39) Cotton, F. A.; Wing, R. M. J. Organomet. Chem. 1967, 9, 511-517.
(40) Saunders, W. H. J. Org. Chem. 1999, 64, 861-865.
(41) Farnham, W. B.; Dixon, D. A.; Calabrese, J. C. J. Am. Chem. Soc. 1988,
110, 2607-2611.
(42) Dixon, D. A.; Fukunaga, T.; Smart, B. E. J. Am. Chem. Soc. 1986, 108,
4027-4031.
(43) Dawson, W. H.; Hunter, D. H.; Willis, C. J. Chem. Soc., Chem. Commun.
1980, 874-875.
(47) Michelin, R. A.; Ros, R.; Guadalupi, G.; Bombieri, G.; Benetollo, F.;
Chapuis, G. Inorg. Chem. 1989, 28, 840-846.
(44) Appleton, T. G.; Berry, R. D.; Hall, J. R.; Neale, D. W. J. Organomet.
Chem. 1989, 364, 249-273.
(48) Koola, J. D.; Roddick, D. M. Organometallics 1991, 10, 591-597.
(49) Crespi, A. M.; Shriver, D. F. Organometallics 1985, 4, 1830-1835.
(50) Richmond, T. G.; Crespi, A. M.; Shriver, D. F. Organometallics 1984, 3,
314-319.
(45) Clark, G. R.; Hoskins, S. V.; Roper, W. R. J. Organomet. Chem. 1982,
234, C9-C12.
(46) Burrell, A. K.; Clark, G. R.; Rickard, C. E. F.; Roper, W. R. J. Organomet.
Chem. 1994, 482, 261-269.
(51) Richmond, T. G.; Shriver, D. F. Organometallics 1984, 3, 305-314.
(52) Reger, D. L.; Dukes, M. D. J. Organomet. Chem. 1978, 153, 67-72.
9
6326 J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005

Carbon−Fluorine Bond Activation
A R T I C L E S
Scheme 2
at carbon is itself 100% in all cases can be muddied by
subsequent inversion or ligand rearrangement chemistry involv-
ing the metal center.
indistinguishable pathways, three of which must proceed with
net inversion at iridium.
To eliminate those pathways involving inversion at iridium,
it was decided to design a reaction in which the migrating group
could act as an intramolecular trap at the metal immediately
after formation of the new C-C bond and new carbon
stereocenter, thereby effectively guaranteeing that it would trap
at the metal from the same side as it attacked the R-carbon;
that is, the reaction would have to proceed with retention at the
metal. The vinyl derivative 5 was deemed a likely prospect,
and to this end its synthesis and chemistry were examined and
are described herein.
As mentioned, the relative configurations of the Ir and C
stereocenters of 2a have been firmly established as (RC,RIr) or
(SC,SIr) by X-ray crystallography.35 Unhappily, this relative
stereochemistry in the product can be afforded via six stereo-
chemically distinct pathways for the sequence of C-F bond
activation and C-C bond formation, followed by counterion
trapping with either retention or inversion at the iridium
stereocenter. These are shown in Scheme 2 as evolving from
the three staggered conformations of the S-enantiomer of 1, each
of which is viewed as a Newman projection down the C-Ir
bond. The observed ground state conformation of 1, in the solid
state and in solution, is that shown as 1a in Scheme 2. For
example, completely diastereoselective protonation of FA from
conformation (S)-1a, followed by (or concomitant with) migra-
tion of the methyl with retention at carbon, followed in turn by
trapping by chloride with retention at iridium, affords the correct
(SC,SIr) configuration. Likewise, completely diastereoselective
protonation of FB from conformation (S)-1a, methyl migration
with retention at carbon, and chloride trapping with inversion
at iridium affords the indistinguishable (RC,RIr) enantiomer. Two
analogous pathways from conformer (S)-1b, both of which
generate the observed relative (SC,SIr) stereochemistry, are shown
in Scheme 2. An additional pathway is also available from
conformation (S)-1c, but this must lead to the (RC,RIr) enanti-
omer of the product, as shown in Scheme 2. Unfortunately,
therefore, the information available regarding the relative
stereochemistries at C and Ir cannot address the question of
individual diastereoselectivities at either atom, as the observed
relative stereochemistry in the product can be obtained via six
Results and Discussion
The desired vinyl complex 5 was prepared by addition of an
ethereal solution of vinyllithium53 to a suspension of Cp*Ir-
(PMe3)(CF2CF2CF3)OTf35 in ether at -78 °C. Crystals of 5
suitable for X-ray diffraction were obtained by slow evaporation
of a hexane solution in the absence of air. Details of this crystal-
lographic determination, and of others described later in this
paper, are given in Table 1. An ORTEP diagram of 5 is shown
in Figure 1. In the solid state, the vinyl group is positioned
(53) Seyferth, D.; Weiner, M. A. J. Am. Chem. Soc. 1961, 83, 3583-3586.
9
J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005 6327

A R T I C L E S
Hughes et al.
Table 1. Crystal, Data Collection, and Refinement Parameters for Compounds 5, 6, and 8
5
6
8
formula
fw
C18H27F7IrP
599.57
C18H27F6IIrP
707.47
C50H38BF30IrP
1442.78
space group
a, Å
b, Å
P2(1)/n
8.7408(5)
25.7847(14)
9.2802(5)
90
103.9830(10)
90
2029.58(19)
4
P2(1)/c
14.8066(11)
9.0186(7)
16.9374(12)
P1h
12.1256(9)
12.5665(9)
18.2649(13)
84.3880(10)
73.3670(10)
84.6180(10)
2647.6(3)
2
c, Å
R, deg
90
â, deg
103.5590(10)
90
2198.7(3)
4
γ, deg
V, Å3
Z
cryst color, habit
D(calcd), g/cm3
µ(Mo KR), mm-1
temp, K
diffractometer
radiation
measd reflns
indep reflns
R(F) [I > 2σ(I)], %a
R(wF2) [I > 2σ(I)], %a
yellow, plate
1.962
6.719
orange, block
2.137
7.600
100(2)
Bruker Smart Apex CCD
Mo KR (λ ) 0.71073 Å)
13214
4950 [Rint ) 0.0331]
2.59
colorless, block
1.810
2.694
12526
22728
11 762 [Rint ) 0.0215]
5.27
4612 [Rint ) 0.0227]
2.25
5.34
5.64
11.83
a R ) ∑||Fo| - |Fc||/∑|Fo|; R(wF2) ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2; w ) 1/[σ2(Fo ) + (aP)2 + bP], P ) [2Fc + max(Fo,0)]/3.
2
2
2
2
2
its use in organometallic analogues of 2 and 5, in which the
solution state conformations can be deduced from the NOE
interactions between fluorine atoms of the perfluoroalkyl ligand
and the protons of Cp*, PMe3, and other ligands.54 The 19F-
{1H} HOESY spectrum of 5 is shown in Figure 2; the only
solution conformation consistent with the observed cross-peaks
is illustrated in the same figure as a Newman projection viewed
along the CF2-Ir bond. The preferred solution conformation is
clearly the same as that found in the solid state (vide supra).
It was initially anticipated that reaction of compound 5 with
HI in the form of 2,6-lutidinium iodide would result in R-C-F
bond activation followed by vinyl group migration to give an
η1-allyl intermediate, followed by rapid intramolecular closure
to give an η3-allylic ligand, thereby freezing the stereochemistry
at the fluorinated carbon. Instead, the reaction afforded the
rearranged η1-allyl complex 6 (Scheme 3), which was isolated
and fully characterized by X-ray crystallography and spectros-
copy. An ORTEP representation of the structure is shown in
Figure 3. In addition to characteristic Cp* and PMe3 peaks, the
1H NMR spectrum of 6 shows the two diastereotopic R-hydro-
gens as multiplets at 2.36 and 3.11 ppm, with the â-hydrogen
appearing at 5.76 ppm as a doublet of doublets of doublets from
coupling to two hydrogens and the trans-fluorine atom. The
19F NMR spectrum shows the CF3 as a doublet of triplets, an
AB quartet due to the diastereotopic fluorine atoms of the CF2
group, and a broad multiplet due to the single vinylic fluorine.
When the reaction was monitored by 1H NMR spectroscopy,
a complex mixture of intermediates was observed, which
evolved over a period of several hours at room temperature to
give clean signals for the final product 6. Unfortunately the
spectra of these intermediate species have proven difficult to
decipher, and all the desired information about diastereoselec-
Figure 1. ORTEP diagram for 5 with ellipsoids drawn at the 30%
probability level. Hydrogen atoms are excluded, with the exception of those
on the vinyl ligand. Selected bond lengths (Å) and angles (deg): Ir(1)-
C(11), 2.067(3); Ir(1)-C(13), 2.062(3); Ir(1)-P(1), 2.2627(9); Ir(1)-Cp-
(cent), 1.920(5); C(11)-C(12), 1.322(5); C(13)-F(1), 1.406(4); C(13)-
F(2), 1.398(4); C(13)-Ir(1)-C(11), 83.59(13); C(13)-Ir(1)-P(1), 93.06(10);
C(11)-Ir(1)-P(1), 86.51(10); C(12)-C(11)-Ir(1), 127.9(3); F(2)-C(13)-
F(1), 101.6(2); F(3)-C(14)-F(4), 107.0(3).
conveniently for migration as the vinylic CH2 terminus is
oriented away from the perfluoropropyl group. To examine the
preferred conformation of 5 in solution, 19F{1H} HOESY (het-
eronuclear Overhauser effect spectroscopy) techniques were em-
ployed.54 For molecules containing 1H and 19F nuclei this
methodology can provide information about the relative spatial
orientation of groups containing these nuclei in solution, with
a cross-peak observed if two nuclei are close in space (e5 Å).55
It has been extensively used in studying transition metal ion-
pair interactions in solution,56-64 and we have recently reported
(54) Hughes, R. P.; Zhang, D.; Ward, A. J.; Zakharov, L. N.; Rheingold, A. L.
J. Am. Chem. Soc. 2004, 126, 6169-6178.
(55) Neuhaus, D.; Williamson, M. P. The Nuclear OVerhauser Effect in
Structural and Conformational Analysis; Wiley-VCH: New York, 2000.
(56) Macchioni, A.; Romani, A.; Zuccaccia, C. Organometallics 2003, 22, 1526-
1533.
(57) Macchioni, A. Eur. J. Inorg. Chem. 2003, 195-205.
(58) Kumar, P. G. A.; Pregosin, P. S.; Goicoechea, J. M.; Whittlesey, M. K.
Organometallics 2003, 22, 2956-2960.
(59) Burini, A.; Fackler, J. P.; Galassi, R.; Macchioni, A.; Omary, M. A.;
Rawashdeh-Omary, M. A.; Pietroni, B. R.; Sabatini, S.; Zuccaccia, C. J.
Am. Chem. Soc. 2002, 124, 4570-4571.
(60) Zuccaccia, C.; Bellachioma, G.; Cardaci, G.; Macchioni, A. J. Am. Chem.
Soc. 2001, 123, 11020-11028.
(61) Macchioni, A.; Zuccaccia, C.; Clot, E.; Gruet, K.; Crabtree, R. H.
Organometallics 2001, 20, 2367-2373.
(62) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Valentini, F.; Zuccaccia, C.;
Foresti, E.; Sabatino, P. Organometallics 2000, 19, 4320-4326.
(63) Zuccaccia, C.; Macchioni, A.; Orabona, I.; Ruffo, F. Organometallics 1999,
18, 4367-4372.
(64) Macchioni, A.; Bellachioma, G.; Cardaci, G.; Gramlich, V.; Rueegger, H.;
Terenzi, S.; Venanzi, L. M. Organometallics 1997, 16, 2139-2145.
9
6328 J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005

Carbon−Fluorine Bond Activation
A R T I C L E S
Figure 2. 19F{1H} HOESY spectrum for 5 in C6D6 (mixing time 3.0 s) and the solution conformation of 5 deduced from this spectrum. (The curved lines
show the observed NOE interactions.)
Figure 4. ORTEP diagram for cation of 8 with ellipsoids drawn at the
30% probability level. All hydrogen atoms are excluded. Selected bond
lengths (Å) and angles (deg): Ir(1)-P(1), 2.3180(16); Ir(1)-C(1), 2.191-
(7); Ir(1)-C(2), 2.106(7); Ir(1)-C(3), 2.144(7); Ir(1)-Cp(cent), 1.854(5);
C(1)-C(2), 1.415(11); C(2)-C(3), 1.436(10); C(3)-F(1), 1.378(11); C(1)-
C(2)-C(3), 115.5(7); C(2)-C(3)-C(4), 119.6(6); C(2)-C(3)-F(1), 116.6-
(6).
Figure 3. ORTEP diagram for 6 with ellipsoids drawn at the 30%
probability level. Selected hydrogen atoms are excluded. Selected bond
lengths (Å): Ir(1)-C(1), 2.147(4); Ir(1)-P(1), 2.2591(11); Ir(1)-I(1),
2.7112(3); Ir(1)-Cp(cent), 1.861(5); C(1)-C(2), 1.485(6); C(2)-C(3),
1.319(6); C(3)-F(1), 1.368(5). C(1)-Ir(1)-P(1), 90.97(12); C(1)-Ir(1)-
I(1), 86.05(11); P(1)-Ir(1)-I(1), 87.52(3).
tivity of the vinyl migration is lost via allylic rearrangement
and coordination of iodide. In an attempt to circumvent these
problems, the reaction was repeated using lutidinium tetrakis-
isomer. We note that the preferred exo-orientation of this η3-
allylic ligand is quite unusual; in similar rhodium66 and iridium67
systems containing the parent η3-allyl ligand, the endo-orienta-
tion is thermodynamically preferred. As expected, reaction of
compound 8 with iodide affords the previously characterized
compound 6.
[3,5-bis(trifluoromethyl)phenyl]borate [LutH+B(ArF)4
]
- 65 con-
taining a weakly coordinating counteranion.
Reaction of 5 with [LutH+B(ArF)4-] in CD2Cl2 at room
temperature was complete within seconds to give a mixture of
η3-allylic complexes, shown to be the exo-anti isomer 7 and
exo-syn-isomer 8 in a ratio of 5.7:1 (Scheme 4). On standing in
solution at room temperature for several hours exo-anti-7
completely rearranged into exo-syn-8, which is clearly and
unambiguously the thermodynamically preferred η3-allylic
The thermodynamic isomer 8 was isolated as pale yellow
1
crystals and was completely characterized by H, 19F, and 31P
NMR spectroscopy, microanalysis, and X-ray crystallography.
The crystal structure of the cationic portion of 8, along with
selected bond lengths and angles, is shown in Figure 4. The
(66) Periana, R. A.; Bergman, R. G. J. Am. Chem. Soc. 1986, 108, 7346-7355.
(67) McGhee, W. D.; Bergman, R. G. J. Am. Chem. Soc. 1988, 110, 4246-
4262.
(65) Yandulov, D. V.; Schrock, R. R. J. Am. Chem. Soc. 2002, 124, 6252-
6253.
9
J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005 6329

A R T I C L E S
Hughes et al.
Figure 5. 19F{1H} HOESY spectrum for 8 in CD2Cl2 (mixing time 3.0 s) and the solution conformation of 8 deduced from the spectrum. (The curved lines
1
show the observed NOE interactions; additional H/1H NOE interactions are described in the text.)
Scheme 3
Scheme 4
solution structure of 8 was shown to be exo-syn, consistent with
that in the solid state, using 19F{1H} HOESY (Figure 5) and
1D 1H,1H NOESY experiments. The latter experiment showed
that the Ha proton has an NOE interaction with Cp* but not
with PMe3. No attempts were made to use this technique to
measure specific distances as others have done.57,60 Here we
are concerned only with determining relative proximities to
afford a rapid, yet unambiguous, determination of solution
conformation and configuration. The structure of 7 was likewise
unequivocally established by the results of 19F{1H} HOESY
9
6330 J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005

Carbon−Fluorine Bond Activation
A R T I C L E S
Figure 6. 19F{1H} HOESY spectrum for 7 in CD2Cl2 (mixing time 3.0 s) and the solution conformation of 7 deduced from the spectrum. (The curved lines
1
show the observed NOE interactions; additional H/1H NOE interactions are described in the text.)
Figure 7. 19F{1H} HOESY spectrum for 9 in CD2Cl2 (mixing time 3.0 s) and the solution conformation of 9 deduced from the spectrum. (The curved lines
1
show the observed NOE interactions; additional H/1H NOE interactions are described in the text.)
(Figure 6) and 1D 1H,1H NOESY experiments. Once again the
latter experiment showed that the Ha proton has an NOE
interaction with Cp* but not with PMe3.
However, compounds 7 and 8 observed and isolated at room
temperature are not the true kinetic products of the C-F
activation/vinyl migration reaction, which are revealed by the
reaction of 5 with [LutH+B(ArF)4-] at -50 °C. At this
temperature the only two products observed by 1H and 19F NMR
spectroscopy are 8 and the previously unobserved endo-anti-
isomer 9, in a ratio of 1:8 (Scheme 4). As with its previously
described isomers, structural characterization of 9 was firmly
established by 19F{1H} HOESY (Figure 7) and 1D 1H,1H
9
J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005 6331

A R T I C L E S
Scheme 5
Hughes et al.
NOESY experiments at low temperature. The anti arrangement
of the C2F5 substituent on the allyl ligand is evident from the
observed HOESY cross-peaks between FA of the CF2 unit and
both terminal hydrogens of the allyl ligand and a strong
interaction between the allylic C-F fluorine and Ha. The endo
orientation of the allyl ligand is suggested by the observed
HOESY interactions of both CF2 fluorines with Cp* hydrogens
and the allylic C-F fluorine with the PMe3 hydrogens and
structures must be accommodated by the mechanism, are exo-
syn-8 and endo-anti-9, with the latter being by far the dominant
product. The small amount of 8 formed kinetically at -50 °C
cannot arise via intermediate 7, which is stable to isomerization
at this temperature. Consequently the kinetic reaction pathway
must be one that generates 9 as the principal kinetic product,
but also accounts for the formation of small amounts of 8
without the intermediacy of 7.
Scheme 5 illustrates two pathways emanating from the ground
state conformation of 5, shown as 5a. Diastereoselective loss
of FA and vinyl migration affords η1-allylic intermediate 10,
rapid closure of which affords the observed major diastereomer
9. Rotation within the η1-allyl bond in 10 before closure can
afford 11, which in turn generates the observed small amount
of diastereomer 8. We cannot discount that 10 and 11 are formed
directly by competitive migration from two different conforma-
tions of the vinyl ligand itself, with concerted formation of the
η3-allyl species, and indeed there is some support for avoidance
of coordinatively unsaturated intermediates when a concerted
reaction is possible.72 However, this does not affect any
arguments concerning the stereochemistry of C-F bond activa-
tion. At higher temperatures 9 evolves to 7 and eventually to 8
as shown in Scheme 5. Notably diastereomer 12 is the only
η3-allyl isomer not observed spectroscopically. Formation of 8
1
confirmed by a 1D H,1H NOESY experiment, which showed
an interaction of Ha with the PMe3 but not with Cp*.
On warming the solution to -20 °C, the resonances of 9
rapidly evolve into those of 7 and, on warming to 20 °C,
eventually into those of the thermodynamic isomer 8. Thus,
compound 7 does not arise directly from migration of the vinyl
group in compound 5, but is formed by rearrangement of endo-
anti-isomer 9 presumably by rotation around the Ir-allyl bond
or an η3fη1fη3 rearrangement of the allylic ligand.68-71 This
transformation is sufficiently rapid so that 9 is not observed at
-20 °C or above.
As a result, the products that truly reveal the stereochemistry
of the C-F-activation/vinyl-migration reaction, and whose
(68) Faller, J. W.; Incorvia, M. J. J. Organomet. Chem. 1969, 19, P13-P16.
(69) Blom, R.; Swang, O. Eur. J. Inorg. Chem. 2002, 411-415.
(70) Guerrero, A.; Jalon, F. A.; Manzano, B. R.; Rodriguez, A.; Claramunt, R.
M.; Cornago, P.; Milata, V.; Elguero, J. Eur. J. Inorg. Chem. 2004, 549-
556.
(71) Xue, P.; Bi, S.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G.
Organometallics 2004, 23, 4735-4743.
(72) Casey, C. P.; Vosejpka, P. C.; Underiner, T. L.; Slough, G. A.; Gavney, J.
A., Jr. J. Am. Chem. Soc. 1993, 115, 6680-6688.
9
6332 J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005

Carbon−Fluorine Bond Activation
A R T I C L E S
Scheme 6
and dried over Aquasorb, or in an MBraun drybox. Methylene chloride,
hexanes, diethyl ether, tetrahydrofuran, and toluene were dried over
an alumina column under nitrogen.73 NMR spectra were recorded on a
Varian Unity Plus 300 or 500 FT spectrometer. 1H NMR spectra were
referenced to the protio impurity in the solvent: C6D6 (7.15 ppm), CD2-
Cl2 (5.32 ppm). 19F NMR spectra were referenced to external CFCl3
(0.00 ppm). 31P{1H} NMR spectra were referenced to 85% H3PO4 (0.00
ppm). Coupling constants are reported in units of hertz. Elemental
analyses were performed by Schwartzkopf (Woodside, NY). Cp*Ir-
(PMe3)(CF2CF2CF3)OTf35 and LiCHdCH253 were prepared according
to literature procedures.
1
Monitoring by H NMR Spectroscopy. The migration reactions
were monitored in the probe of a Varian Unity Plus 500 spectrometer
at temperatures in the range -60 to 35 °C. Each starting compound
was dissolved to 0.65-0.75 mL of solution, and a sample was
transferred to a J. Young’s NMR tube and placed in the NMR probe.
For reactions carried out at low temperature, the reaction mixture was
prepared in an NMR tube on a Schlenk line in a -78 °C cold bath and
then placed in the NMR probe at the appropriate temperature. 1,3,5-
Trimethoxybenzene was used as an internal integration standard.
Cp*Ir(PMe3)(n-C3F7)(CHdCH2) (5). To a suspension of Cp*Ir-
(PMe3)(n-C3F7)OTf (100 mg, 0.138 mmol) in dry ether (∼10 mL) was
added a 0.1 M solution of CH2dCHLi in ether (2 mL, 0.2 mmol) all
at once at -78 °C. The resultant yellow solution was stirred for 20
min at -78 °C and warmed to room temperature. The solvent was
removed in vacuo, the product extracted with hexanes at room
temperature, and the hexanes solution filtered through Celite under an
atmosphere of nitrogen. Removal of the hexanes afforded a colorless
oil, which crystallized within an hour to give pure product (60 mg,
72%).
from 7 either requires 7 to revert to 9 before conversion to 8,
or it must pass through 12 en route to 8. If the latter pathway
pertains, since conversion of 9 f 7 is fast at -20 °C, and since
7 converts to 8 only slowly at room temperature, it seems
consistent that the allylic rotation or η3fη1fη3 rearrangement
that converts 12 f 8 is considerably faster than formation of
12 from 7, so that no significant observable concentration of
12 is formed above -20 °C. Notably, while loss of FA from 5a
affords the observed kinetic diastereomers, diastereoselective
activation of FB from this conformation must lead to formation
of 12 and 7, neither of which is observed as a kinetic product
at -50 °C. Similarly, activation of either FA or FB from
conformation 5c cannot afford the observed kinetic products.
In contrast, activation of either FA or FB from conformation 5b
can afford the observed kinetic products.
Given that this reaction precludes formation of products
arising from inversion at iridium, at least under conditions of
true kinetic control, the options for the selectivity of C-F bond
activation are narrowed to those three pathways shown in
Scheme 5 that afford 9 and 8. Provided that these conclusions
pertain to other analogous migrating groups such methyl, and
thus excluding all pathways leading to the observed diastere-
omers that require inversion at iridium, the six pathways shown
in Scheme 2 are reduced to the three illustrated in Scheme 6,
which originate from only two possible conformations of the
fluoroalkyl ligand. It would be a remarkable coincidence if more
than one of these three pathways is operative, since each appears
to have quite different steric requirements for approach of the
acid to the R-fluorine and for methyl migration. We conclude,
therefore, that C-F activation by exogenous acid and formation
of the new carbon stereocenter in these systems involve a
completely diastereoselective pathway, a conclusion also re-
quired by application of Occam’s razor.
Anal. Calcd for C18H27F7IrP: C, 36.06; H, 4.54. Found: C, 35.95;
H, 4.91. 1H NMR (C6D6 300 MHz, 22 °C): δ 1.09 (d, 2JHP ) 10.2 Hz,
4
4
9H, PMe3), 1.50 (d, JHP ) 1.8 Hz, 15H, Cp*), 5.37 (ddd, JHP ) 2.1
2
3
Hz, Jgem-HH) 2.1 Hz, Jtrans-HH ) 18.0 Hz, 1H, CH2, cis to Ir-C),
6.53 (ddd, JHP ) 2.1 Hz, Jgem-HH ) 2.1 Hz, Jcis-HH ) 10.2 Hz, 1H,
4
2
3
3
3
CH2, trans to Ir-C), 8.09 (ddd, JHP ) 2.1 Hz, Jcis-HH ) 10.2 Hz,
3Jtrans-HH ) 18.0 Hz, 1H, CH). 19F NMR (C6D6 282 MHz, 22 °C): δ
2
3
-76.16 (br d, JFF ) 292 Hz, 1F, R-CF2), -78.85 (t, JFF ) 12.4 Hz,
3F, CF3) -82.50 (br d, 2JFF ) 292 Hz, 1F, R-CF2), -114.25 (d, 2JFF
)
273 Hz, 1F, â-CF2), -115.55 (d, JFF ) 273 Hz, 1F, â-CF2). 31P{1H}
2
3
NMR (C6D6, 121.4 MHz, 22 °C): δ -36.75 (t, JPF ) 8.4 Hz, 1P,
PMe3).
Cp*Ir(PMe3)((Z)-CH2CHdCFC2F5)I (6). Cp*Ir(PMe3)(n-C3F7)-
(CHdCH2) (5) (50 mg, 0.083 mmol) and lutidinium iodide (19.6 mg,
0.083 mmol) were dissolved in CH2Cl2 (∼5 mL) in a Schlenk flask.
After 10 h of stirring at room temperature the solution became yellow.
The solvent was removed in vacuo, and the product extracted with
hexanes. The solution was filtered, and upon slow removal of hexanes
by static evaporation orange crystals suitable for X-ray analysis were
obtained, (55.7 mg, 95%).
Anal. Calcd for C18H27F6IIrP: C, 30.56; H, 3.85. Found: C, 30.86;
H, 3.91. 1H NMR (CD2Cl2 500 MHz, 21 °C): δ 1.635 (d, 2JPH ) 10.0
2
3
Hz, 9H, PMe3), 1.80 (d, JPH ) 2.0 Hz, 15H, Cp*), 2.36 (dddqd, JHH
) 7.5 Hz, 3JPH ) 7.3 Hz, 2JHH ) 7.0 Hz, 6JFH ) 3.3 Hz, 4JFH ) 2.7 Hz,
1H, CH2), 3.11 (dddm, 3JHH) 10.5 Hz, 2JHH ) 7.0 Hz, 3JPH ) 4.1 Hz,
1H, CH2), 5.76 (ddd, 3JFH ) 36.5 Hz, 3JHH ) 10.5 Hz, 3JHH ) 7.5 Hz,
4
1H, CH). 19F NMR (CD2Cl2, 470.3 MHz, 21 °C): δ -84.23 (dt, JFF
3
2
) 7.4 Hz, JFF ) 3.3 Hz, 3F, CF3), -119.26 (dm, JF(AB) ) 278 Hz,
Further studies are underway with a view to establishing
enantioselective transformations based on this chemistry and
to better understanding of the mechanistic details of this unusual
reaction type.
1F, CF2), -119.40 (dm, 2JF(AB) ) 278 Hz, 1F, CF2), -144.78 (dddqdd,
3JHF ) 36.5 Hz, JFF ) 17.6 Hz, JFF ) 17.6 Hz, JFF ) 7.4 Hz, JHF
) 2.7 Hz, 4JHF ) 1.0 Hz, 1F, CF). 31P{1H} NMR (CD2Cl2, 202.3 MHz,
21 °C): δ -40.67 (s, PMe3).
3
3
4
4
[exo-Cp*Ir(PMe3)(anti-η3-CH2CHCFCF2CF3)][B(ArF)4] (7) and
[exo-Cp*Ir(PMe3)(syn-η3-CH2CHCFCF2CF3)][B(ArF)4] (8). Cp*Ir-
Experimental Section
General Considerations. Air-sensitive reactions were performed in
oven-dried glassware, using standard Schlenk techniques, under an
atmosphere of nitrogen, which was deoxygenated over BASF catalyst
(73) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.; Timmers,
F. J. Organometallics 1996, 15, 1518-1520.
9
J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005 6333

A R T I C L E S
Hughes et al.
(PMe3)(n-C3F7)(CHdCH2) (5) (9.5 mg, 0.0158 mmol) and lutidinium
tetrakis(3,5-trifluoromethylphenyl)borate (15.4 mg, 0.0158 mmol) were
placed in a J. Young’s tube, and CD2Cl2 (0.7 mL) was added to dissolve
the solids. At room temperature the reaction was complete within
seconds. Compound 7 was formed along with compound 8 in a ratio
∼6:1 and was identified by its NMR spectra.
tube and stoppered with a septum. The tube was cooled in an acetone/
dry ice bath, and a solution of lutidinium tetrakis(3,5-trifluorometh-
ylphenyl)borate (15.4 mg, 0.0158 mmol) in CD2Cl2 (0.3 mL) was added
dropwise by the side of the tube. The two layers were mixed while the
sides of the tube were cooled by liquid nitrogen to avoid warming the
sample. The tube was transferred to the NMR probe, which had been
precooled to -50 °C. The product was observed by NMR spectroscopy
at temperatures below -30 °C.
2
1H NMR (CD2Cl2, 500 MHz, 21 °C): δ 1.68 (dd, JPH ) 10.3 Hz,
4
4JFH ) 1.2 Hz, 9H, PMe3), 1.93 (d, JPH ) 1.9 Hz, 15H, Cp*), 2.54
3
2
3
(ddd, JHH ) 10.0 Hz, JHH ) 2.5 Hz, JPH ) 16.5 Hz, 1H, syn-CH2),
1H NMR (CD2Cl2, 500 MHz, -50 °C): δ 1.52 (d, 2JPH ) 10.7 Hz,
3
2
3
4
3
3.22 (ddd, JHH ) 8.0 Hz, JHH ) 2.5 Hz, JPH ) 3.0 Hz, 1H, anti-
9H, PMe3), 1.91 (d, JPH ) 1.8 Hz, 15H, Cp*), 3.25 (bd, JHH ) 12.0
3
3
3
3
2
CH2), 4.40 (ddddd, JHH ) 10.0 Hz, JHH ) 8.0 Hz, JFH ) 13.5 Hz,
Hz, 1H, syn-CH2), 4.00 (dd, JHH ) 7.9 Hz, JHH ) 3.9 Hz, 1H, anti-
4JFH ) 5.0 Hz, JPH ) 2.53 Hz, 1H, CH). 19F NMR (CD2Cl2, 470.3
CH2), 4.72 (m, 1H, CH). 19F NMR (CD2Cl2, 470.3 MHz, -50 °C): δ
3
4
4
2
MHz, 21 °C): δ -82.59 (d, JFF ) 14.3 Hz, 3F, CF3), -111.88 (dd,
-80.66 (d, JFF ) 12.2 Hz, 3F, CF3), -112.89 (dd, JF(AB) ) 279 Hz,
2JF(AB) ) 274 Hz, JFF ) 15.0 Hz, 1F, CF2), -118.99 (dd, JF(AB)
)
3JFF ) 17.4 Hz, 1F, CF2), -120.75 (d, JF(AB) ) 279 Hz, 1F, CF2),
3
2
2
274 Hz, 4JHF ) 5.0 Hz, 1F, CF2), -153.97 (dqdd, 3JFF ) 15.0 Hz, 4JFF
-158.23 (bs, 1F, CF). 31P{1H} NMR (CD2Cl2, 202.4 MHz, -50 °C):
) 14.3 Hz, JHF ) 13.5 Hz, JPF ) 7.5 Hz, 1F, CF). 31P{1H} NMR
(CD2Cl2, 202.4 MHz, 21 °C): δ -48.30 (d, 3JPF ) 7.5 Hz, 1P, PMe3).
On standing for several hours at room temperature the resonances
of 7 evolve into those of the thermodynamic product 8. The solvent
was removed in vacuo and the product extracted with ether. Removal
of the ether afforded a pale yellow crystalline material, which was
recrystallized from ether/hexanes to give X-ray quality crystals (22.8
mg, 99%).
δ -37.88 (d, JPF ) 21.3 Hz, 1P, PMe3).
3
3
3
X-ray Crystal Structure Determinations. Diffraction intensity data
were collected at 100 K with a Bruker Smart Apex CCD diffractometer.
The structures were solved using the Patterson function, completed by
subsequent difference Fourier syntheses, and refined by full matrix least-
squares procedures on F2. SADABS absorption corrections were applied
(Tmin/Tmax ) 0.706). Non-hydrogen atoms were refined with anisotropic
displacement coefficients except the F atoms in disordered CF3 groups,
which were refined with isotropic thermal parameters. The hydrogen
atoms were treated as idealized contributions. It was found that in the
crystal structure of 8 the Ir atom, CH2CCFCF2CF3, and PMe3 groups
in the cation are disordered in a ratio 74/26 over two positions
approximately related by a mirror plane. Two CF3 groups in the anion
are disordered as well. All software and sources of scattering factors
are contained in the SHELXTL (5.10) program package (G. Sheldrick,
Bruker XRD, Madison, WI).
Anal. Calcd for C50H39BF30IrP: C, 41.59; H, 2.72. Found: C, 41.66;
H, 2.84. 1H NMR (CD2Cl2, 500 MHz, 21 °C): δ 1.59 (dd, 2JPH ) 10.7
Hz, 5JFH ) 1.3 Hz, 9H, PMe3), 1.92 (dd, 4JPH ) 1.8 Hz, 5JFH ) 0.5 Hz,
15H, Cp*), 2.94 (ddddd, 3JHH ) 10.0 Hz, 2JHH ) 2.85 Hz, 3JPH ) 13.6
Hz, 5JFH ) 0.8 Hz, 5JFH ) 0.8 Hz, 1H, syn-CH2), 3.20 (ddddd, 3JHH
)
7.4 Hz, 2JHH ) 2.85 Hz, 3JPH ) 0.9 Hz, 4JFH ) 1.05 Hz, 5JFH ) 1.8 Hz,
3
3
3
1H, anti-CH2), 4.09 (dddddd, JHH ) 10.0 Hz, JHH ) 7.4 Hz, JPH
)
1.9 Hz, 3JFH ) 9.0 Hz, JFH ) 2.25 Hz, JFH ) 2.25 Hz, 1H, CH). 19F
NMR (CD2Cl2, 282.2 MHz, 21 °C): δ -82.41 (d, 4JFF ) 13.6 Hz, 3F,
CF3), -115.43 (dd, 2JF(AB) ) 282 Hz, 3JFF ) 17.0 Hz, 1F, CF2), -120.36
4
4
Acknowledgment. R.P.H. is grateful to the National Science
Foundation for generous financial support of this research.
2
3
3
(dd, JF(AB) ) 282 Hz, JFF ) 7.5 Hz, 1F, CF2), -181.79 (bd, JPF
)
70.5 Hz, 1F, CF). 31P{1H} NMR (CD2Cl2, 121.4 MHz, 21 °C): δ
Supporting Information Available: Crystallographic infor-
mation files (CIF) for compounds 5, 6, and 8. This material is
available free of charge via the Internet at http://pubs.acs.org.
3
-36.08 (d, JPF ) 70.5 Hz, 1P, PMe3).
endo-Cp*Ir(PMe3)(anti-η3-CH2CHCFCF2CF3)[B(ArF)4] (9). Cp*Ir-
(PMe3)(n-C3F7)(CHdCH2) (9.5 mg, 0.158 mmol) was dissolved in CD2-
Cl2 (0.5 mL), and the resultant solution was placed in a J. Young’s
JA042345D
9
6334 J. AM. CHEM. SOC. VOL. 127, NO. 17, 2005