Binuclear fluorovinyl complexes of iridium: Transformation of an iridium-bound trifluorovinyl group into a trans-[Ir-C(F)=C(F)CH3] moiety

Article abstract of DOI:10.1021/om020295k

The fluorovinyl complexes [Ir₂(CF=CF₂)(CH₃)(CO)₂(μ-Cl)(dppm )₂][CF₃SO₃] (2) and [Ir₂-(C(H)=CF₂)(CH₃)(CO)₂(μ-Br)(d ppm)₂][CF₃SO₃] (3) are prepared by the oxidative addition of ClFC=CF₂ and BrHC=CF₂, respectively, to [Ir₂(CH₃)(CO)₂(dppm)₂] [CF₃SO₃] (1). Both compounds have the methyl and fluorovinyl groups on different metals essentially opposite the metal-metal bond. Protonation of 2 occurs at the Ir-Ir bond to give [Ir₂(CF=CF₂)(CH₃)-(CO)₂(μ-Cl)( μ-H)(dppm)₂] [CF₃SO₃]₂ (4). Attempts to remove the chloride ligand from 2 or to replace it with hydride or methyl groups failed. Instead, the reaction of 2 with methyllithium resulted in replacement of one fluoride substituent on the trifluorovinyl group by a methyl group to give [Ir₂(CF=CFCH₃)(CH₃)(CO)₂(μ-Cl)(dp pm)₂][CF₃SO₃] (5). The X-ray structural determination of 5 indicates that replacement of a fluoride trans to the Ir-C₂F₃ bond has occurred and that migration of the resulting methyldifluorovinyl group to the metal bearing the methyl ligand has occurred. A proposal is put forth to rationalize these observations.

Full text of DOI:10.1021/om020295k

5172
Organometallics 2002, 21, 5172-5181
Bin u clea r F lu or ovin yl Com p lexes of Ir id iu m :
Tr a n sfor m a tion of a n Ir id iu m -Bou n d Tr iflu or ovin yl
Gr ou p in to a tr a n s-[Ir -C(F )dC(F )CH3] Moiety
Dusan Ristic-Petrovic, Meitian Wang,‡ Robert McDonald,‡ and Martin Cowie*,§
Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2
Received April 16, 2002
The fluorovinyl complexes [Ir2(CFdCF2)(CH3)(CO)2(µ-Cl)(dppm)2][CF3SO3] (2) and [Ir2-
(C(H)dCF2)(CH3)(CO)2(µ-Br)(dppm)2][CF3SO3] (3) are prepared by the oxidative addition of
ClFCdCF2 and BrHCdCF2, respectively, to [Ir2(CH3)(CO)2(dppm)2][CF3SO3] (1). Both
compounds have the methyl and fluorovinyl groups on different metals essentially opposite
the metal-metal bond. Protonation of 2 occurs at the Ir-Ir bond to give [Ir2(CFdCF2)(CH3)-
(CO)2(µ-Cl)(µ-H)(dppm)2][CF3SO3]2 (4). Attempts to remove the chloride ligand from 2 or to
replace it with hydride or methyl groups failed. Instead, the reaction of 2 with methyllithium
resulted in replacement of one fluoride substituent on the trifluorovinyl group by a methyl
group to give [Ir2(CFdCFCH3)(CH3)(CO)2(µ-Cl)(dppm)2][CF3SO3] (5). The X-ray structural
determination of 5 indicates that replacement of a fluoride trans to the Ir-C2F3 bond has
occurred and that migration of the resulting methyldifluorovinyl group to the metal bearing
the methyl ligand has occurred. A proposal is put forth to rationalize these observations.
In tr od u ction
a period of days at ambient temperature and was only
observed on one occasion) and the increasing difficulty
of obtaining trifluoroethylene or its synthons, have to
date prevented us from studying this transformation
further. Two questions that we had hoped to address
in this apparent double-activation process was whether
C-H or C-F activation occurred first, and what the
functions of the adjacent metals might be in such a
transformation. Compound 1 had previously been dem-
onstrated to undergo double C-H activation of 1,3-
butadiene,7 suggesting a role for adjacent metals in
olefin activation.
Our inability to obtain the desired information di-
rectly from the reaction of 2 with trifluoroethylene
encouraged us to seek this information indirectly. If
C-H activation was the first activation step, the first
species produced would be a trifluorovinyl complex,
whereas initial C-F activation would yield a 2,2-
difluorovinyl group. We therefore sought routes to
complexes containing these fluorovinyl ligands. Several
fluorovinyl complexes of transition metals are known,
including a few of iridium.8 However, we are unaware
of any binuclear complexes of iridium containing fluo-
rovinyl groups. Our interest in binuclear complexes of
fluorovinyl ligands relates to the functions of the
adjacent metals in the activation of fluorocarbon ligandss
a topic that seems to have been only briefly addressed
in the past.9 Vinyl fluorides are normally quite inert;
The activation of carbon-fluorine bonds is of impor-
tance from a number of perspectives. Fluorocarbons are
global-warming gases,1 having long atmospheric life-
times,2 so methods for transforming them to more
innocuous substances are being sought. In addition,
fluorocarbons are finding applications as agrochemicals
and pharmaceuticals,3 necessitating new methods for
selectively transforming or creating C-F bonds in
relevant synthons. The challenges in achieving the goals
of C-F activation result, in a large measure, from the
strength of the C-F bond, which is the strongest single
bond involving carbon.4 The paucity of nucleophilic
substitutions of alkyl fluorides highlights the dimin-
ished reactivity of the C-F bond relative to other C-X
bonds; this reaction is more than 2 orders of magnitude
slower for alkyl fluorides than for alkyl chlorides.5
In a recent study we observed the apparent C-H and
C-F activation of trifluoroethylene by the diiridium
complex [Ir2(CH3)(CO)2(dppm)2][CF3SO3] (1; dppm )
µ-Ph2PCH2PPh2) to yield a difluorovinylidene-bridged
product.6 However, a number of factors, including the
capricious nature of the reaction (which took place over
* Corresponding author. E-mail: martin.cowie@ualberta.ca.
‡ X-ray Crystallography Laboratory.
§ Killam Annual Professor 2000/01.
(1) (a) Intergovernmental Panel on Climate Change. Climate Change-
The IPCC Scientific Assessment; Cambridge University Press: Cam-
bridge, 1990. (b) Zurer, P. Chem. Eng. News 1993, 71, 16.
(2) Ravishankara, A. R.; Soloman, S.; Turnipseed, A. A.; Warren,
R. F. Science 1993, 259, 194.
(3) (a) Biochemistry Involving the Carbon-Fluorine Bond; Filler, R.,
Ed.; American Chemical Society: Washington, DC, 1976. (b) Selective
Fluorination in Organic and Bioorganic Chemistry; Welch, J . T., Ed.;
American Chemical Society: Washington, DC, 1991.
(4) (a) Smart, B. E. Mol. Struct. Eng. 1986, 3, 141. (b) McMillen, D.
F.; Golden, D. M. Annu. Rev. Phys. Chem. 1982, 33, 493.
(5) Satai, P., Ed. The Chemistry of the Carbon-Halogen Bond, Part
1; J . Wiley and Sons: New York, 1973; p 416.
(6) (a) Ristic-Petrovic, D.; Cowie, M. Unpublished results. (b)
Although an X-ray structure determination of the product from our
initial attempt clearly indicated a bridging difluorovinylidene group,
we have been unable to duplicate this result subsequently.
(7) Ristic-Petrovic, D.; Torkelson, J . R.; Hilts, R. W.; McDonald, R.;
Cowie, M. Organometallics 2000, 19, 1432.
(8) (a) Hughes, R. P.; Kovacik, I.; Lindner, D. C.; Smith, J . M.;
Willemsen, S.; Zhang, D.; Guzei, I. A.; Rheingold, A. L. Organometallics
2001, 20, 3190. (b) Siedle, A. R.; Newmark, R. A. Organometallics 1989,
8, 1442.
10.1021/om020295k CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/29/2002

Binuclear Fluorovinyl Complexes of Ir
Organometallics, Vol. 21, No. 24, 2002 5173
Ta ble 1. Sp ectr oscop ic Da ta for th e Com p ou n d s
NMRa,b
δ(19F)f
g,h
compound
δ(31P{1H})c
δ(1H)d,e
δ(13C{1H})d
IR, cm-1
2
[Ir2(C2F3)(CH3)(CO)2(µ-Cl)-
(dppm)2][CF3SO3] (2)i
-6.9 (m), 5.80 (m, 2H), 4.35 (m,
-78.8 (s, 3F), -92.8 (ddt,
172.5 (t, J C-P ) 9 Hz), 2024(s), 1709 (w)
3
4
2
2
-11.3(m) 2H), 1.17 (t, 3H, J P-H
1F, J P-3 F ) 5 Hz, J F-F
)
170.8 (t, J C-P ) 11 Hz),
) 5 Hz))
89 Hz, J F-F ) 37 Hz),
-24.0 (m)
2
-126.9 (dd, 1F, J F-F ) 89
3
Hz, J F-F ) 110 Hz), -139.1
3
(dd, 1F, J F-F ) 110, 37 Hz)
2
[Ir2(C2F2H)(CH3)(CO)2(µ-Br)- -6.8 (m), 4.93 (m, 2H), 3.76 (m,
(dppm)2][CF3SO3] (3)
-79.1 (s, 3F), -65.9 (ddt, 1F, 174.4 (t, J C-P ) 9 Hz), 2021 (s), 1672 (w)
3
3
2
-10.3 (m) 2H), 4.62 (ddt, J H-F
)
2J F-F ) 59 Hz, J H-F ) 12
169.5 (t, J C-P ) 11 Hz),
3
4
42 Hz, J H-F ) 12 Hz,
Hz, J P-F ) 5 Hz), -84.9 (ddt, -24.4 (m)
3J P-H)5 Hz), 0.88 (t, 3H, 1F, J H4-F ) 42 Hz, J F-F
3J P-H ) 5 Hz)
59 Hz, J P-F ) 5 Hz)
-12.9 (m), 5.26 (m, 2H), 5.13 (m, 2H), -78.8 (s, 3F), -92.5 (dd, 1F,
)
3
2
[Ir2(C2F3)(CH3)(CO)2(µ-H)-
(dppm)2][CF3SO3]2 (4)
2021 (s), 1706 (w)
-20.8 (m) 1.40 (t, 3H, J P-H ) 6 Hz) 3J F-F ) 110 Hz, J F-F ) 86
3
2
-13.00 (b, 1H) Hz), -122.1 (pt, 1F, J ) 100
3
Hz), -133.6 (dd, J F-F
)
3
110 Hz, J F-F ) 43 Hz)
[Ir2(C2F2CH3)(CH3)(CO)2-
(µ-Cl)(dppm)2][CF3SO3] (5)
1.2 (m), 4.08 (m, 2H), 3.44 (m, 2H), -78.8 (s, 3F), -126 (b, 2F)
196.8 (b), 174.0 (b), 20.2 2019 (s), 1676
(m) -24.8 (m)
-15.7 (m) 1.22 (t, 3H, J F-F ) 12 Hz),
(w, ν(CdC))
3
1.07 (t, 3H, J P-H) 7 Hz)
a
b
NMR abbreviations: s ) singlet, d ) doublet, t ) triplet, pt ) psueudotriplet, m ) multiplet, b ) broad. NMR data at 298 K in
CD2Cl2 unless otherwise stated. 31P{1H} chemical shifts are referenced vs external 85% H3PO4. 1H and 13C chemical shifts are referenced
c
d
vs external TMS. e Chemical shifts for the phenyl hydrogens are not given in the 1H data. 19F chemical shifts are referenced vs external
f
g
h
i
CFCl3. IR abbreviations (ν(CO) unless otherwise stated): s ) strong, w ) weak. CH2Cl2 solution unless otherwise stated. NMR data
in acetone-d6 solution.
obtained on a Bio-Rad RTS-60 Fourier transform infrared
however, examples of C-F bond cleavage reactions in
the presence of nucleophiles have been reported.10-12 In
spectrometer as solutions in KCl cells with 0.5-mm-window
path lengths or as solids using a Nicolet Magna 750 with a
this paper we outline our preliminary results on the
Nic-Plan infrared microscope. Carbonyl stretches reported are
preparation of fluorovinyl complexes of diiridium and
for non-isotopically enriched samples. Mass spectrometric
on some subsequent transformations.
analyses were performed by positive ion electrospray ionization
on
a Micromass ZabSpec Hybrid Sector-TOF. Elemental
Exp er im en ta l Section
analyses were performed by the microanalytical service within
the department. Spectroscopic data for all compounds are given
in Table 1.
Gen er a l Com m en ts. All solvents were dried (using ap-
propriate drying agents), distilled before use, and stored under
dinitrogen. Deuterated solvents used for NMR experiments
were freeze-pump-thaw degassed (three cycles) and stored
under nitrogen or argon over molecular sieves. Reactions were
carried out at ambient temperature under argon using stan-
dard Schlenk techniques, and compounds that were used as
solids were purified by recrystallization. Prepurified argon and
nitrogen were purchased from Linde, carbon-13 enriched CO
(99%) was supplied by Isotec Inc., and fluoroolefins (chloro-
trifluoroethylene, iodotrifluoroethylene, and 1-bromo-2,2-dif-
luoroethylene) were supplied by Lancaster. All gases were used
as received, and all other reagents were purchased from
Aldrich and were used as received. The compound [Ir2(CH3)-
(CO)(µ-CO)(dppm)2][CF3SO3] (1) was prepared as previously
reported.13
Proton NMR spectra were recorded on Varian Unity 400,
500, or 600 spectrometers or on a Bruker AM400 spectrometer.
Carbon-13 NMR spectra were recorded on Varian Unity 400
or Bruker AM300 spectrometers. Phosphorus and fluorine
spectra were recorded on Varian Unity 400 or Bruker AM400
spectrometers. Two-dimensional NMR experiments (GCOSY,
TROESY, GTOCSY, and 13C-1H HMQC) were obtained on
Varian Unity 400 or 500 spectrometers. Infrared spectra were
P r ep a r a tion of Com p ou n d s. (a ) [Ir 2(C2F 3)(CH3)(CO)2-
(µ-Cl)(d p p m )2][CF 3SO3] (2). A brick-red solution of [Ir2(CH3)-
(CO)(µ-CO)(dppm)2][CF3SO3] (1) (93 mg, 0.066 mmol) dissolved
in 15 mL of dichloromethane was cooled to -78 °C using a
dry ice/acetone bath. Excess chlorotrifluoroethylene gas was
condensed onto the stirred solution, which was stirred at this
temperature for 30 min, at which time the cooling bath was
removed and the vessel allowed to warm to room temperature
(ca. 4 h). After stirring at room temperature overnight, the
yellow solution was reduced in vacuo to ca. 3 mL. Slow addition
of 10 mL of Et2O afforded a bright yellow powder. The product
was washed twice with 10 mL of Et2O, the supernatant
decanted, and then the solid dried briefly under a stream of
argon and then in vacuo (89% yield). Anal. Calcd for Ir2-
SCIP4F6O5C56H14: C, 44.74; H, 3.18; Cl, 2.38. Found: C, 45.15;
H, 3.15; 2.69. MS(ESI)P+ ) 1341.1.
(b) [Ir 2(C2F 2H)(CH3)(CO)2(µ-Br )(d p p m )2][CF 3SO3] (3).
The procedure was the same as that described for 2 except
that 1-bromo-2,2-difluoroethylene was used instead of chlo-
rotrifluoroethylene. The yield of the orange powder was 78%.
Anal. Calcd for Ir2BrSP4F5O5C56H48
: C, 44.36, H, 3.19.
Found: C, 44.15; H, 3.06. MS(ESI)P+ ) 1367.
(c) Rea ction of 1 w ith Iod otr iflu or oeth ylen e. In an
NMR tube, 25 mg (0.018 mmol) of 1 was dissolved in 0.7 mL
of CD2Cl2 and cooled to -78 °C, giving a brick-red solution.
Iodotrifluoroethylene (18 µL, 0.018 mmol) was added by
syringe. The NMR spectra were recorded at -78 °C and at 20
deg intervals until approximately ambient temperature was
reached, by which time the solution had become bright red
and complete conversion to the known compound, [Ir2(CO)2-
(µ-CH2)(µ-I)(dppm)2][CF3SO3] (6),14 was indicated by the 1H
and 31P NMR spectra. Throughout the NMR monitoring of this
(9) (a) Booth, R. L.; Haszeldine, R. N.; Mitchell, R. R.; Cox, J . J . J .
Chem. Soc., Chem. Commun. 1967, 529. (b) Bonnet, J . J .; Mathieu,
R.; Poilblanc, R.; Ibers, J . A. J . Am. Chem. Soc. 1979, 101, 7487.
(10) Tamborski, C.; Soloski, E. J .; de Pasquale, R. J . J . Organomet.
Chem. 1968, 15, 494.
(11) (a) Seyferth, D.; Wada, T. Inorg. Chem. 1962, 1, 78. (b) Martin,
S.; Sauvetre, R.; Normant, J .-F. Tetrahedron Lett. 1983, 24, 5615.
(12) (a) de Cadenet, K. G.; Rumin, R.; Pe´tillon, F. Y.; Yufit, D. S.;
Muir, K. W. Eur. J . Inorg. Chem. 2002, 639. (b) Peterson, T. H.; Golden,
J . T.; Bergman, R. G. Organometallics 1999, 18, 2005. (c) Fujiwara,
M.; Ichikawa, J .; Okauchi, T.; Minami, T. Tetrahedron Lett. 1999, 40,
7261. (d) de Cadenet, K. G.; Rumin, R.; Pe´tillon, F. Y. Organometallics
2000, 19, 1912.
(13) Torkelson, J . R.; Antwi-Nsiah, F. H.; McDonald, R.; Cowie, M.;
Pruis, J . G.; J alkanen, K. J .; DeKock, R. L. J . Am. Chem. Soc. 1999,
121, 3666.
(14) (a) Torkelson, J . R. Ph.D. Thesis, University of Alberta, 1998,
Chapter 5. (b) Torkelson, J . R.; Oke, O.; Muritu, J .; McDonald, R.;
Cowie, M. Organometallics 2000, 19, 854.

5174 Organometallics, Vol. 21, No. 24, 2002
Ristic-Petrovic et al.
reaction the NMR spectra (1H, 19F, 31P) showed only this
compound, unreacted 1, and iodotrifluoroethylene.
from the data collection. The space group was determined to
be P21/n (an alternate setting of P21/c [No. 14]). The data were
corrected for absorption through use of the SADABS procedure.
See Table 2 for a summary of crystal data and X-ray data
collection information.
Colorless crystals of [Ir2(CFdCF2)(Me)(CO)2(µ-Cl)(µ-H)-
(dppm)2][CF3SO3]2 (4) were obtained via slow diffusion of
diethyl ether into a dichloromethane solution of the compound.
Data were collected and corrected for absorption as for 2 above.
Unit cell parameters were obtained from a least-squares
refinement of the setting angles of 5118 reflections from the
data collection, and the space group was determined to be P21/c
(No. 14).
(d ) [Ir 2(C2F 3)(CH 3)(CO)2(µ-H)(µ-Cl)(d p p m )2][CF 3SO3]2
(4). Compound 2 (48 mg, 0.032 mmol) was dissolved in 10 mL
of dichloromethane, forming a yellow solution. To this was
added trifluoromethanesulfonic acid (3 µL 0.034 mmol), caus-
ing the solution to lighten in color and become slightly cloudy.
The mixture was stirred for 15 min and then reduced in vacuo
to 5 mL. The supernatant liquid was decanted and the
remaining powder washed twice with 10 mL volumes of Et2O,
leaving 37 mg (70%) of a pale yellow powder. Anal. Calcd for
Ir2ClS2P4F9O8C57H48: C, 41.75; H, 3.01. Found: C, 41.92; H,
2.82.
Yellow crystals of [Ir2(CFdCFMe)Me(CO)(µ-Cl)(µ-CO)-
(dppm)2][CF3SO3]‚0.5Et2O‚0.5Me2CO (5) were obtained via
slow diffusion of diethyl ether into an acetone solution of a
mixture of compounds 2 and 5. A crystal of 5 was hand picked
from a mixture of crystals of the two compounds. Redissolving
the crystals afterward gave compounds 2 and 5 in the same
ratio as before crystallization. Data were collected and cor-
rected for absorption as for 2 above. Unit cell parameters were
obtained from a least-squares refinement of the setting angles
of 5438 reflections from the data collection, and the space
group was determined to be C2/c (No. 15).
(e) [Ir 2(C2F 2CH3)(CH3)(CO)2(µ-Cl)(d p p m )2][CF 3SO3] (5).
Compound 2 (29 mg, 0.020 mmol) was dissolved in 20 mL of
THF, and the yellow solution was cooled in a dry ice/acetone
bath to -78 °C, at which time 0.1 mL of a 1.4 M solution of
methyllithium in Et2O (Aldrich) was added. The solution was
stirred at this temperature for 10 min and then allowed to
warm to room temperature. Stirring was continued at room
temperature for a further hour, at which time the cloudy
solution was transferred into another vessel that had been
charged with approximately 5 g of dry Florisil. The solution
was stirred over Florisil for 5 min, during which time the
yellow color of the solution was discharged and the Florisil
became bright yellow. The colorless supernatant was decanted,
and the Florisil with adsorbed compound 5 was extracted with
10 mL of acetonitrile. The yellow extract was filtered through
Celite and then reduced in vacuo to a pale yellow powder,
which was found by 31P NMR spectroscopy to consist of
approximately 60% of 5, with the remainder being unreacted
2. The labeled product, [Ir2(C2F2CH3)(13CH3)(13CO)2(µ-Cl)-
(dppm)2][CF3SO3] (5), was obtained by the same procedure
except that [Ir2(13CH3)(13CO)(µ-13CO)(dppm)2][CF3SO3] (1*) was
used as the precursor. The percent of 13CH3 enrichment in
Str u ctu r e Solu tion a n d Refin em en t. The structure of 2
was solved using automated Patterson location of the heavy
metal atoms and structure expansion via the DIRDIF-96
program system.16 Refinement was completed using the pro-
gram SHELXL-93.17 Hydrogen atoms were assigned positions
based on the geometries of their attached carbon atoms and
were given thermal parameters 20% greater than those of the
attached carbons. An idealized geometry was imposed upon
the inversion-disordered half-occupancy solvent acetone mol-
ecule using the following restraints: d(C(4S)-C(5S) ) d(C(5S)-
C(6S)) ) 1.47 Å; d(O(2S)-C(5S)) ) 1.23 Å; d(C(4S)‚‚‚C(6S)) )
2.55 Å; d(O(2S)‚‚‚C(4S)) ) d(O(2S)‚‚‚C(6S)) ) 2.34 Å. The final
model for 2 refined to values of R1(F) ) 0.0386 (for 9911 data
1
compounds 1 and 5 is essentially 100% as judged from H NMR
spectroscopy. All attempts to separate 5 from unreacted 2
failed, as did attempts to effect complete transformation of 2
to 5, so elemental analyses were not obtained.
with Fo g 2σ(Fo2)) and wR2(F2) ) 0.0860 (for all 12165
2
independent data).
The structure of 4 was solved using direct methods (SHELXS-
8618), and refinement was completed using the program
SHELXL-93. Hydrogen atoms were treated as for 2 except for
the hydrido ligand, which was assigned a fixed isotropic
displacement parameter and idealized interatomic distances
(Ir-H(1) ) Ir′-H(1) ) 1.85 Å; P(1)‚‚‚H(1) ) P(2′)‚‚‚H(1) to
within 0.002 Å). The final model for 4 refined to values of R1-
(f) Rea ction of 2 w ith Hyd r id e Sou r ces a n d Lew is
Acid s. In a typical experiment, 40 mg of 2 was dissolved in
20 mL of THF (for reactions with hydride sources) or benzene
(for reactions with Lewis acids). To this was added a solution
of the test reagent (10 mg of NaBH4 (10 equiv) in 35 mL of
THF or 100 µL of 1.0 M KHB(sec-Bu)3 (4 equiv) in 20 mL of
THF). In the case of the reaction of KH, a solution of 2 as above
was added to a suspension of 2 mg of KH suspended in 15 mL
of THF. In the case of the Lewis acids 40 mg of 2 in 20 mL of
benzene was reacted with the test reagents (15 µL of a 2.0 M
toluene solution of trimethylaluminum (1 equiv), or 3.5 µL of
methyl triflate (1 equiv), or 5 µL of trimethylsilyl triflate (1
equiv), each in 20 mL of benzene, or with 10 mg of silver
triflate (1 equiv) in 20 mL of acetonitrile). In all cases, progress
of the reaction was assessed by pumping the mixture to
(F) ) 0.0387 (for 5217 data with Fo g 2σ(Fo2)) and wR2(F2) )
2
0.0935 (for all 5980 independent data).
The structure of 5 was solved using the DIRDIF-96 program
system in the same manner as for 2 above. Refinement was
completed using the program SHELXL-93, during which the
hydrogen atoms were treated as for 2. Idealized geometries
were imposed upon one of the half-occupancy triflate ion
positions and upon the half-occupancy solvent diethyl ether
and acetone molecules through use of intramolecular distance
restraints (fully detailed in the Supporting Information). The
final model for 5 refined to values of R1(F) ) 0.0479 (for 9444
1
dryness after 1 h and observing the 31P, H, and 19F NMR in
CD2Cl2 solution and, in a replicate experiment, pumping the
mixture to dryness after 24 h and again running the NMR.
Partial conversion to the dication 4 was observed after 1 h in
the reactions with Lewis acids. From the hydride-source
reactions, unreacted 2 was recovered after 24 h, accompanied
by variable amounts of unidentified decomposition products.
X-r a y Da ta Collection . Yellow crystals of [Ir2(CFdCF2)-
(Me)(CO)2(µ-Cl)(dppm)2][CF3SO3]‚1.5Me2CO (2) were obtained
via slow diffusion of n-pentane into an acetone solution of the
data with Fo g 2σ(Fo2)) and wR2(F2) ) 0.1398 (for all 12 952
2
independent data).
Resu lts a n d Com p ou n d Ch a r a cter iza tion
The trifluorovinyl compound [Ir2(CFdCF2)(CH3)(CO)2-
(µ-Cl)(dppm)2][CF3SO3] (2) is readily obtained by the
complex. Data were collected on
a Bruker PLATFORM/
SMART 1000 CCD diffractometer15 using Mo KR radiation at
-80 °C. Unit cell parameters were obtained from a least-
squares refinement of the setting angles of 5737 reflections
(16) Beurskens, P. T.; Beurskens, G.; Bosman, W. P.; deGelder, R.;
Garcia Granda, S.; Gould, R. O.; Israel, R.; Smits, J . M. M. The
DIRDIF-96 program system; Crystallography Laboratory, University
of Nijmegen: The Netherlands, 1996.
(17) Sheldrick, G. M. SHELXL-93, Program for crystal structure
determination; University of Go¨ttingen: Germany, 1993.
(18) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(15) Programs for diffractometer operation, data collection, data
reduction, and absorption correction were those supplied by Bruker.

Binuclear Fluorovinyl Complexes of Ir
Organometallics, Vol. 21, No. 24, 2002 5175
Ta ble 2. Cr ysta llogr a p h ic Exp er im en ta l Deta ils for Com p ou n d s 2, 4, a n d 5
A. Crystal Data
formula
C
60.5H56ClF6Ir2O6.5P4S
C57H48ClF9Ir2O8P4S2
C60.5H58ClF5Ir2O6P4S
fw
1576.84
1639.80
1551.86
cryst dimens (mm)
cryst syst
space group
0.30 × 0.10 × 0.09
0.24 × 0.15 × 0.12
0.36 × 0.19 × 0.09
monoclinic
monoclinic
monoclinic
P21/n (an alternate setting
of P21/c [No. 14])
P21/c (No. 14)
C2/c (No. 15)
unit cell paramsa
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
12.2660 (8)
32.721 (2)
15.4317 (10)
106.1367 (12)
5949.6 (7)
4
11.3860 (7)
11.8677 (8)
21.8526 (14)
97.5621 (12)
2927.2 (3)
2
29.974 (2)
15.2663 (10)
27.8913 (19)
95.9674 (14)
12693.6 (15)
8
Fcalcd (g cm-3
µ (mm-1
)
1.760
4.726
1.860
4.850
1.624
4.426
)
B. Data Collection and Refinement Conditions
diffractometer
Bruker PLATFORM/SMART
1000 CCD
Bruker PLATFORM/SMART
1000 CCD
Bruker PLATFORM/SMART
1000 CCD
radiation (λ [Å])
graphite-monochromated
Mo KR (0.71073)
-80
graphite-monochromated
Mo KR (0.71073)
-80
graphite-monochromated
Mo KR (0.71073)
-80
temperature (°C)
scan type
data collection 2θ limit (deg)
total no. of data collected
ω scans (0.2°) (30 s exposures)
52.80
ω scans (0.2°) (25 s exposures)
52.78
ω scans (0.2°) (30 s exposures)
52.78
28714 (-15 e h e 14,
15804 (-14 e h e 14,
30695 (-37 e h e 27,
-33 e k e 40,
-14 e k e 14,
-19 e k e 18,
-19 e l e 16)
-24 e l e 27)
-34 l e 34)
no. of ind reflns
no. of obsd reflns
structure solution method
12 165 (Rint ) 0.0434)
5980 (Rint ) 0.0313)
12 952 (Rint ) 0.0424)
2
2
2
9911 [Fo g 2σ(Fo2)]
5217 [Fo g 2σ(Fo2)]
9444 [Fo g 2σ(Fo2)]
Patterson search/structure
expansion (DIRDIF-96)
full-matrix least-squares on
F2 (SHELXL-93)
direct methods (SHELXS-86)
Patterson search/structure
expansion (DIRDIF-96)
full-matrix least-squares on
F2 (SHELXL-93)
refinement methodb
full-matrix least-squares on
F2 (SHELXL-93)
abs corr method
empirical (SADABS)
0.6757-0.3313
empirical (SADABS)
0.5937-0.3890
empirical (SADABS)
0.6914-0.2987
range of transmn factors
no. of data/restraints/params
goodness-of-fit (S)f
2
2
2
12 165 [Fo g -3σ(Fo2)]/6c/710
5980 [Fo g -3σ(Fo2)]/3d/384
12 952 [Fo g -3σ(Fo2)]/32e/695
2
2
2
1.044 [Fo g -3σ( Fo2)]
1.108 [Fo g -3σ( Fo2)]
1.051 [Fo g -3σ( Fo2)]
final R indicesg
2
R1 [Fo g 2σ(Fo2)]
0.0386
0.0860
2.115 and -1.114
0.0387
0.0935
1.721 and -1.411
0.0479
0.1398
3.319 and -1.071
2
wR2 [Fo g -3σ( Fo2)]
largest diff peak and
hole (e Å-3
)
a
Obtained from least-squares refinement of 5737 centered reflections for compound 2, 5118 reflections for 4, and 5438 reflections for
5. Refinement on Fo for all reflections (all of these having Fo g -3σ(Fo2)). Weighted R-factors wR2 and all goodnesses of fit S are based
b
2
2
on Fo2; conventional R-factors R1 are based on Fo, with Fo set to zero for negative Fo2. The observed criterion of Fo > 2σ(Fo2) is used only
2
2
for calculating R1 and is not relevant to the choice of reflections for refinement. R-factors based on Fo are statistically about twice as
large as those based on Fo, and R-factors based on ALL data will be even larger. c An idealized geometry was imposed upon the inversion-
disordered half-occupancy solvent acetone molecule using the following restraints: d(C(4S)-C(5S)) ) d(C(5S)-C(6S)) ) 1.47 Å; d(O(2S)-
d
C(5S)) ) 1.23 Å; d(C(4S)‚‚‚C(6S)) ) 2.55 Å; d(O(2S)‚‚‚C(4S)) ) d(O(2S)‚‚‚C(6S)) ) 2.34 Å. An idealized geometry was imposed upon the
hydrido ligand by fixing the Ir-H(1) and Ir′-H(1) distances to equal 1.85 Å and by constraining the P(1)‚‚‚H(1) and P(2′)‚‚‚H(1) distances
to be equal (to within 0.002 Å). e One of the half-occupancy triflate ion positions was found to be disordered about a crystallographic
2-fold axis, leading to employment of the following restraints: d(S(2)-C(92)) ) 1.80 Å; d(S(2)-O(94)) ) d(S(2)-O(95)) ) d(S(2)-O(96))
) 1.45 Å; d(F(94)-C(92)) ) d(F(95)-C(92)) ) d(F(96)-C(92)) ) 1.35 Å; d(F(94)‚‚‚F(95)) ) d(F(94)‚‚‚F(96)) ) d(F(95)‚‚‚F(96)) ) 2.20 Å;
d(O(94)‚‚‚O(95)) ) d(O(94)‚‚‚O(96)) ) d(O(95)‚‚‚O(96)) ) 2.37 Å; d(F(94)‚‚‚O(95)) ) d(F(94)‚‚‚O(96)) ) d(F(95)‚‚‚O(94)) ) d(F(95)‚‚‚O(96))
) d(F(96)...O(94)) ) d(F(96)‚‚‚O(95)) ) 3.04 Å. Distances were also assigned idealized values for the half-occupancy solvent diethyl ether
(d(O(1S)-C(1S)) ) d(O(1S)-C(3S)) ) 1.43 Å; d(C(1S)-C(2S)) ) d(C(3S)-C(4S)) ) 1.54 Å; d(O(1S)‚‚‚C(2S)) ) d(O(1S)‚‚‚C(4S)) ) 2.43 Å;
d(C(1S)‚‚‚C(3S)) ) 2.34 Å) and acetone (d(O(2S)-C(6S)) ) 1.20 Å; d(C(5S)-C(6S)) ) d(C(6S)-C(7S)) ) 1.54 Å; d(O(2S)‚‚‚C(5S)) )
2
d(O(2S)‚‚‚C(7S)) ) 2.38 Å; d(C(5S)‚‚‚C(7S)) ) 2.67 Å) molecules. f S ) [∑w(Fo - Fc2)2/(n - p)]1/2 (n ) number of data; p ) number of
parameters varied; w ) [σ2(Fo2) + (AP)2 + BP]-1 where P ) [Max(Fo2,0) + 2Fc2]/3). For compound 2, A ) 0.0381, B ) 6.2180; for 4, A )
0.0378, B ) 13.5695; for 5, A ) 0.0670, B ) 151.3170. R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑w(Fo4)]1/2
.
g
2
oxidative addition of the C-Cl bond of chlorotrifluoro-
ethylene to [Ir2(CH3)(CO)(µ-CO)(dppm)2][CF3SO3] (1), as
shown in Scheme 1. Attempts to detect intermediates
in this transformation, such as a chlorotrifluoroethylene
adduct, were not successful. At -80 °C no reaction
between 1 and ClFCdCF2 was observed over a 2 h
period by NMR, whereas warming to ambient temper-
ature resulted in the slow but complete conversion to 2
overnight (ca. 18 h). At intermediate temperatures the
only species observed were the reactants and product
in varying amounts.
belonging to an AA′BB′ spin system. In the 1H NMR
spectrum the methylene protons of the dppm ligands
appear normal and the methyl group appears as a
triplet at 1.17 ppm, with coupling of 5 Hz to the two
adjacent 31P nuclei on one iridium. The 13C{1H} NMR
spectrum of the 13C-enriched [Ir2(C2F3)(13CH3)(13CO)2-
(µ-Cl)(dppm)2][CF3SO3] (2*) displays resonances typical
of terminally bound Ir-carbonyls (172.5, 170.8 ppm) and
a high-field resonance at -24.0 ppm corresponding to
the methyl group. In the 19F NMR spectrum the three
trifluorovinyl fluorines appear at -92.8, -126.9, and
-139.1 ppm, in the normal range for fluorines attached
to sp2-hybridized carbon atoms.19 The assignment of the
The 31P{1H} NMR spectrum of 2 shows the charac-
teristic, second-order multiplets at -6.9 and -11.3 ppm,

5176 Organometallics, Vol. 21, No. 24, 2002
Ristic-Petrovic et al.
Sch em e 1
19F spectrum is aided by comparisons to other trifluo-
rovinyl groups in which the coupling between geminal
fluorines (2J FF) is found in the range 75-107 Hz. For
example, in trifluoroethylene and chlorotrifluoroethyl-
2
ene J FF ) 87 and 76 Hz, respectively, while in a series
of trifluorovinyl complexes [M(X)(Y)(PEt3)2] (M ) Ni, Pd,
Pt; X ) C2F3; Y ) C2F3, Br),20 cis-[Pt(CFdCF2)2(PPh3)2],
and cis-[PtCl(CFdCF2)(PBu3)2]21 values near 100 Hz
have been reported. For the aforementioned compounds
cis coupling (3J FF
)
is in the range 32-40 Hz, whereas
trans
cis
trans coupling (3J FF
)
between 101 and 120 Hz is
observed. On the basis of the coupling constants, the
two 19F resonances of 2 at -92.8 and -126.9 ppm are
assigned to the geminal fluorines on the â-carbon,
having a mutual coupling of 89 Hz. The former signal
appears as a doublet of doublets of triplets and is
assigned as cis to the lone fluorine on the R carbon (at
-139.1 ppm) on the basis of the 37 Hz coupling between
the two. The triplet coupling (5 Hz) of this â-fluorine
results from four-bond coupling with the 31P nuclei that
are bound to the same metal as the C2F3 ligand. Neither
of the other two fluorines shows coupling to the 31P
nuclei. The two mutually trans fluorines show mutual
coupling of 110 Hz.
The structure proposed for 2 has been confirmed by
an X-ray structure determination, as shown for the
complex cation in Figure 1. Selected bond lengths and
angles are given in Table 3. Compound 2 has an
unsymmetrical A-frame structure in which the chloro
ligand bridges the metals in an essentially symmetrical
manner. One carbonyl on each metal lies approximately
F igu r e 1. Perspective view of the [Ir2(CFdCF2)(CH3)(CO)2-
(µ-Cl)(dppm)2]+ cation of complex 2 showing the atom-
labeling scheme. Non-hydrogen atoms are represented by
Gaussian ellipsoids at the 20% probability level. The
methylene and methyl hydrogens are shown with arbi-
trarily small thermal parameters, while the phenyl hydro-
gens are not shown.
opposite the Ir-Cl bonds, while the methyl and trifluo-
rovinyl groups occupy positions on each metal opposite
the metal-metal bond, but bent slightly toward the
bridging chloride ligand (Ir(1)-Ir(2)-C(3) ) 156.8(2)°,
Ir(2)-Ir(1)-C(4) ) 165.7(2)°). The Ir-Ir separation
(2.8116(3) Å) is consistent with a single bond and is
noticeably shorter than the intraligand P-P separations
(P(1)-P(2) ) 3.026(2) Å, P(3)-P(4) ) 3.033(2) Å),
consistent with a bonding interaction between the two
metals. Both C-F distances on the â-carbon (C(5)-F(2)
(19) Dungan, C. H.; van Wazer, J . R. Compilation of Reported F19
NMR Chemical Shifts; Wiley-Interscience: New York, 1970.
(20) Rest, A. J .; Rosevear, D. T.; Stone, F. G. A. J . Chem. Soc. (A)
1967, 66.
(21) Banger, K. K.; Brisdon, A. K.; Gupta, A. Chem. Commun. 1997,
139.

Binuclear Fluorovinyl Complexes of Ir
Organometallics, Vol. 21, No. 24, 2002 5177
Ta ble 3. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 2
with a CdC double bond, although is somewhat shorter
than for nonfluorinated olefins.27
(a) Distances (Å)
An analogous 2,2-difluorovinyl complex, [Ir2(CHd
CF2)(CH3)(CO)2(µ-Br)(dppm)2][CF3SO3] (3), is prepared,
much as is 2, by the oxidative addition of 1-bromo-2,2-
difluoroethylene to 1 (see Scheme 1). This reaction
occurs more readily than that involving 1 and chloro-
trifluoroethylene, with small amounts of 3 being de-
tected by NMR even at -80 °C, and the reaction
proceeding to completion within 1 h at ambient tem-
perature. This is in accord with the expectation of more
facile C-Br oxidative addition to an electron-rich tran-
sition metal compared to addition of a C-Cl bond.28
Spectroscopically, compound 3 is quite comparable to
2; in particular, their 31P{1H} NMR spectra are very
similar (see Table 1). The methyl protons of 3 again
appear as a triplet (3J PH ) 5 Hz) at typically high field
(0.88 ppm), and the hydrogen of the difluorovinyl ligand,
at 4.62 ppm, shows 42 Hz coupling to the trans fluorine
(at -84.9 ppm) and 12 Hz to the cis fluorine (at -65.9
ppm). This vinyl hydrogen also displays coupling (5 Hz)
to the adjacent pair of 31P nuclei. In the 19F NMR
spectrum, both fluorines display coupling of 59 Hz,
significantly less than the geminal coupling observed
in 2. Smaller geminal coupling has previously been
observed when a fluorine on the adjacent R-carbon has
been replaced by a less electronegative group.29 At-
tempts to prepare the fluoro-bridged analogue of 3,
which would be related to a presumed C-F bond-
activation product of trifluoroethylene, by bromide
replacement in 3 using KF/18-crown-6 in THF gave no
reaction overnight. Similarly, the reaction of 3 with AgF
in THF gave only decomposition products.
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
P(1)
Ir(2)
Cl
2.8116(3)
2.416(1)
2.350(1)
2.353(1)
1.863(7)
2.090(6)
2.449(1)
2.353(1)
2.346(1)
1.809(6)
2.182(6)
3.026(2)a
P(1)
P(2)
P(3)
P(3)
P(4)
F(1)
F(2)
F(3)
O(1)
O(2)
C(4)
C(6)
C(6)
C(7)
P(4)
C(7)
C(4)
C(5)
C(5)
C(1)
C(2)
C(5)
1.822(5)
1.821(5)
1.817(5)
3.033(2)a
1.823(5)
1.376(7)
1.351(8)
1.337(8)
1.143(7)
1.142(7)
1.298(9)
P(1)
P(3)
C(1)
C(4)
Cl
P(2)
P(4)
C(2)
C(3)
P(2)
(b) Angles (deg)
55.24(3) Cl
92.95(3) P(2) Ir(2) P(4) 174.66(5)
Ir(2) Ir(1) Cl
Ir(2) Ir(1) P(1)
Ir(2) Ir(1) P(3)
Ir(2) Ir(1) C(1)
Ir(2) C(3) 102.7(2)
92.60(3) P(2) Ir(2) C(2)
87.6(2)
89.6(2)
89.1(2)
86.6(2)
94.9(3)
70.62(4)
96.7(2)
P(2) Ir(2) C(4)
P(4) Ir(2) C(2)
Ir(2) Ir(1) C(4) 165.7(2)
Cl
Cl
Cl
Cl
Ir(1) P(1)
Ir(1) P(3)
90.69(5) P(4) Ir(2) C(3)
91.23(5) C(2) Ir(2) C(3)
Ir(1) C(1) 151.9(2)
Ir(1) C(4) 110.6(2)
Ir(1) Cl
Ir(1) P(1) C(6) 110.0(2)
Ir(2)
P(1) Ir(1) P(3) 174.25(5) Ir(2) P(2) C(6) 112.1(2)
P(1) Ir(1) C(1)
P(1) Ir(1) C(4)
P(3) Ir(1) C(1)
P(3) Ir(1) C(4)
C(1) Ir(1) C(4)
Ir(1) Ir(2) Cl
88.9(2)
88.6(2)
92.0(2)
85.7(2)
97.5(3)
Ir(1) P(3) C(7) 111.8(17)
Ir(2) P(4) C(7) 111.6(2)
Ir(1) C(1) O(1) 177.0(6)
Ir(2) C(2) O(2) 174.9(7)
Ir(1) C(4) F(1) 121.4(4)
54.14(3) Ir(1) C(4) C(5) 127.7(5)
92.19(3) F(1) C(4) C(5) 110.7(5)
92.80(3) F(2) C(5) F(3) 106.8(6)
Ir(1) Ir(2) P(2)
Ir(1) Ir(2) P(4)
Ir(1) Ir(2) C(2) 108.2(2)
Ir(1) Ir(2) C(3) 156.8(2)
F(2) C(5) C(4) 127.5(7)
F(3) C(5) C(4) 125.5(6)
Cl
Cl
Cl
Ir(2) P(2)
Ir(2) P(4)
93.42(5) P(1) C(6) P(2) 112.4(3)
91.06(5) P(3) C(7) P(4) 112.8(3)
Ir(2) C(2) 162.3(2)
a
In an attempt to generate the iodo-bridged, trifluo-
rovinyl analogue of 2, the reaction between 1 and
iodotrifluoroethylene was attempted. However, instead
of a simple oxidative-addition reaction paralleling the
formation of 2 and 3, the only product obtained is the
iodo- and methylene-bridged product [Ir2(CO)2(µ-I)(µ-
CH2)(dppm)2][CF3SO3] (6), shown in Scheme 1. This
product, previously prepared by a different route and
characterized in this group,14 displays a singlet at -7.9
ppm in the 31P{1H} NMR spectrum and a quintet (3J PH
) 8.3 Hz) for the protons of the bridging methylene
Nonbonded distance.
) 1.351(8) Å, C(5)-F(3) ) 1.337(8) Å) are somewhat
shorter than C(4)-F(1) of 1.376(7) Å; the shortening of
C-F bonds as the number of fluorines on a carbon is
increased has previously been noted.22 Metal-fluoro-
carbon bonds are also generally observed to be shorter
and stronger than those involving nonfluorinated hy-
drocarbons,23 and the same is observed in 2, in which
the Ir(1)-C(4) bond (2.090(6) Å) is significantly shorter
than Ir(2)-C(3) (2.182(6) Å). Although some of this
difference results from the different hybridizations of
the trifluorovinyl and methyl carbons (r(sp2) ) 0.74 Å;
r(sp3) ) 0.77 Å), some shortening certainly must be due
to fluorine substituents on the former. However, the
Ir(1)-C2F3 bond is not substantially different than
related Rh-vinyl distances in the isopropenyl and
trimethylvinyl compounds [RhOs(C(CH3)dCH2)(CO)3-
(dppm)2]and [RhOs(C(CH3)dC(CH3)2)(CH3)(CO)3(dppm)2]-
[CF3SO3] (2.04(2) and 1.955(5) Å, respectively)24 and is
also comparable to the Ir-vinyl distances (2.0(2)-2.13-
(1) Å) in [Ir2Cl2(CRdCHR)2(CO)2(dppm)2]25 and Ir2ClH-
(CRdCHR)(CO)2(µ-H)(dppm)2][BF4]26 (R ) CO2Me). The
olefinic C(4)-C(5) separation (1.298(9) Å) is consistent
1
group at 10.0 ppm in the H NMR spectrum. The other
presumed product in the reaction, trifluoroethylene, was
not detected by 19F NMR spectroscopy. The bridging
methylene group of this product is established as
originating from the methyl group of 1 by labeling
experiments. Therefore, starting with 13CH3-labeled 1
gives a product having a µ-13CH2 group; no trace of
unlabeled product is detected by 1H NMR spectroscopy.
Attempts to replace the bridging chloro ligand in 2
with either hydride or alkyl groups have met with
failure. Compound 2 was unreactive to NaBH4, KH, or
KHB(sec-Bu)3 in THF at ambient temperature and was
also unreactive to the Lewis acids trimethylaluminum,
methyltriflate, and trimethylsilyl triflate. In all cases
2 was recovered, as the sole or major product, although
(22) Peters, D. Chem. Phys. 1963, 38, 561.
(23) (a) Kiplinger, J . L.; Richmond, T. G.; Osterberg, C. E. Chem.
Rev. 1994, 94, 373. (b) Brothers, P. J .; Roper, W. R. Chem. Rev. 1988,
88, 1293.
(24) Sterenberg, B. T.; McDonald, R.; Cowie, M. Organometallics
1997, 16, 2297.
(25) Sutherland, B. R.; Cowie, M. Organometallics 1985, 4, 1801.
(26) Vaartstra, B. A.; Cowie, M. Organometallics 1990, 9, 1594.
(27) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 1987, 51.
(28) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G. In
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Section 5.5.
(29) Manatt, S. L.; Bowers, M. T. J . Am. Chem. Soc. 1969, 91, 4381.

5178 Organometallics, Vol. 21, No. 24, 2002
Ristic-Petrovic et al.
Sch em e 2
in the attempted reactions of the Lewis acids, varying
amounts of a hydride species was recovered. This
hydride product, the complex cation of which was
identified as [Ir2(CFdCF2)(CH3)(CO)2(µ-H)(µ-Cl)(d-
ppm)2]+2, presumably results from hydrolysis of the
Lewis acid by adventitious water and subsequent pro-
tonation of 2; this species was subsequently generated
quantitatively by reaction of 2 with triflic acid to give
[Ir2(CFdCF2)(CH3)(CO)2(µ-H)(µ-Cl)(dppm)2][CF3SO3]2 (4)
(see Scheme 2). Spectroscopically, compound 4 bears a
strong resemblance to 2, and in particular the 19F NMR
spectrum displays similar chemical shifts and coupling
constants for the trifluorovinyl group in both compounds
1
(see Table 1). The H NMR spectrum shows the methyl
group as a triplet at 1.40 ppm (3J PH ) 6 Hz), and the
hydride ligand appears as a broad unresolved resonance
at -13.00 ppm; the breadth of the hydride resonance
presumably results from coupling to all four phosphorus
nuclei, suggesting a bridging arrangement, which has
been confirmed by 31P-decoupling experiments. This
structural assignment has been confirmed by an X-ray
determination, and the final structure of the cation is
shown in Figure 2, with selected bond lengths and
angles given in Table 4. The molecule was found to be
disordered about an inversion center, meaning that the
trifluorovinyl group and C(2)O(2) are superimposed at
50% occupancy, as are the methyl group and C(1)O(1)
as well as Cl and H(1); nevertheless, the non-hydrogen
atoms are readily resolved, and least-squares refine-
ment proceeded satisfactorily. Although, the disorder
precludes unambiguous location of the hydride ligand,
its position bridging the metals is supported by the
substantial lengthening of the Ir-Ir bond from 2.8116(3)
Å in 2 to 3.0315(5) Å in 4. Also consistent with the
bridging location of the hydride ligand is the opening
up of the pocket between the carbonyls on protonation.
As a consequence, the Ir-Ir-CO angles in 2 (96.7(2)°,
108.2(2)°) have increased substantially to 124.7(5)° and
128.7(5)° in 4. Both effects are well documented in
hydride-bridged metal-carbonyl clusters.30 Although
the observed disorder would normally preclude a discus-
sion of bond lengths, the parameters involving the
trifluorovinyl group give us confidence that our disor-
dered model accounts accurately for the atom positions.
F igu r e 2. Perspective view of the [Ir2(CFdCF2)(CH3)(CO)2-
(µ-H)(µ-Cl)(dppm)2]2+ cation of complex 4 showing the
atom-labeling scheme. The bridging hydride ligand was not
located in the X-ray study. Thermal parameters are as
described for Figure 1. Only one of the disordered molecules
is shown. For an explanation of the disorder see the text.
The C-F bond lengths in compound 4 agree well with
those of 2 and show the same trend (CR-F > Câ-F). In
the geometry shown, both the trifluorovinyl and methyl
groups are opposite the bridging hydride ligand and
might be expected to show somewhat elongated metal-
carbon bonds owing to the high trans influence of the
hydride ligand.31 However, both of these bonds in 4 (Ir-
C(3) ) 2.02(1) Å, Ir′-C(5) ) 2.15(1) Å) are actually
somewhat shorter than the corresponding distances in
2 (2.090(6), 2.182(6) Å). It should be recalled however
that metal-metal bonds can also display a significant
trans influence,32 which in these compounds appears to
exceed that of the bridging hydride ligand. It may also
be that the methyl and trifluorovinyl ligands in 2 are
exerting a trans influence on each other via the metal-
(31) Huheey, J . E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry,
Principles of Structure and Reactivity, 4th ed.; Harper Collins: New
York, 1993; Chapter 13.
(32) (a) Sutherland, B. R.; Cowie, M. Organometallics 1984, 3, 1869.
(b) Cowie, M.; Dwight, S. K. Inorg. Chem. 1980, 19, 209. (c) Cowie,
M.; Gibson, J . A. E. Organometallics 1984, 3, 984. (d) Farr, J . P.;
Olmstead, M. M.; Balch, A. L. Inorg. Chem. 1983, 22, 1229.
(30) (a) Churchill, M. R.; deBoer, B. G.; Rotella, F. J . Inorg. Chem.
1976, 15, 1843. (b) Teller, R. G.; Bau, R. Struct. Bonding 1981, 44, 1.

Binuclear Fluorovinyl Complexes of Ir
Organometallics, Vol. 21, No. 24, 2002 5179
Ta ble 4. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 4
(a) Distances (Å)
Ir
Ir′
3.0315(5)a
2.318(3)
2.372(1)
2.381(1)
1.90(1)
2.02(1)
1.85b
Ir′
H(1)
P(2)
C(6)
C(6)
C(3)
C(4)
C(4)
C(1)
C(2)
C(4)
1.85b
Ir
Cl
P(1)
P(1)
P(2)
F(1)
F(2)
F(3)
O(1)
O(2)
C(3)
3.051(2)c
1.818(6)
1.834(6)
1.39(2)
1.29(2)
1.34(2)
1.11(2)
1.09(2)
1.33(2)
Ir
Ir
Ir
Ir
P(1)
P(2′)
C(1)
C(3)
H(1)
Cl
Ir
Ir′
Ir′
Ir′
2.369(3)
1.89(2)
2.15(1)
C(2)
C(5)
(b) Angles (deg)
50.45(8) Cl
89.48(4) Cl
90.98(4) Cl
Ir′
Ir′
Ir′
Ir′
Ir′
Ir′
Cl
Cl
Ir
Cl
Ir′
Ir′
Ir′
Ir′
P(2)
C(2) 177.6(5)
89.65(8)
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
Ir
P(1)
P(2′)
C(1)
C(3)
H(1)
P(1)
P(2′)
C(1)
C(3)
H(1)
C(5)
H(1)
C(2)
C(5)
H(1)
C(2)
C(5)
H(1)
C(5)
H(1)
94.8(4)
124.7(5)
145.9(4)
35.0d
Cl
84.0d
P(1′) Ir′
P(1′) Ir′
88.1(4)
88.9(4)
88.6d
91.1(4)
91.1(4)
91.4d
88.20(8) P(1′) Ir′
91.64(8) P(2)
Ir′
Ir′
Ir′
Ir′
Ir′
Ir′
Cl
Cl
Cl
Cl
175.1(5)
95.4(4)
85.4d
P(2)
P(2)
C(2)
F igu r e 3. Perspective view of the [Ir2(CFdC(F)CH3)(CH3)-
(CO)2(µ-Cl)(dppm)2]+ cation of complex 5 showing the atom-
labeling scheme. Thermal parameters are as described for
Figure 1.
87.5(6)
P(1)
P(1)
P(1)
P(1)
P(2′) Ir
P(2′) Ir
P(2′) Ir
C(1)
C(1)
C(3)
Ir
P(2′) 179.25(5) C(2)
93.7d
C(1)
C(3)
H(1)
C(1)
C(3)
H(1)
C(3)
H(1)
91.7(4)
89.5(4)
90.5d
C(5)
Ir
Ir
H(1) 110.0d
Ir′
80.58(9)
P(1) C(6) 111.5(2)
P(2) C(6) 109.4(2)
C(1) O(1) 177(1)
C(2) O(2) 166(2)
C(3) F(1) 116(1)
C(3) C(4) 137(1)
C(3) C(4) 106(1)
C(4) F(3) 110(1)
C(4) C(3) 130(2)
C(4) C(3) 120(1)
C(6) P(2) 113.3(3)
88.6(4)
89.8(4)
90.2d
Ir′
Ir
Ir′
Ir
Ir
F(1)
two chemically inequivalent fluorine atoms of the meth-
yl difluorovinyl group resonate at approximately the
same chemical shift as a broad unresolved signal at
-126 ppm, and this signal integrates well compared to
that of the triflate anion. The 13C{1H} NMR and the IR
spectra are consistent with one terminal and one
bridging carbonyl ligand. To establish which methyl
group in 5 results from the Ir-bound methyl group in
the precursor and which is obtained from methyl-
lithium, the 13C-enriched precursor [Ir2(CFdCF2)(13CH3)-
(13CO)2(µ-Cl)(dppm)2][CF3SO3] was reacted with unen-
riched MeLi. The product had the 13CH3 group exclu-
sively on iridium, with no significant 13CH3 enrichment
of the methyldifluorovinyl group. Clearly, the iridium-
bound methyl group remains on the metals, while
replacement of a fluoride is effected by MeLi. In the 13C-
{1H} NMR spectrum of this 13CH3-enriched sample the
iridium-bound methyl signal appears at -24.8 ppm,
while that for the vinylic methyl group is at lower field
(20.2 ppm) and is very weak since no enrichment
occurred at this site (observation of the 13C signal for
the vinyl-substituted methyl group required overnight
data acquisition). Both signals are broad and unre-
solved, so coupling to 31P or 19F nuclei cannot be
determined.
Although spectroscopy clearly establishes the forma-
tion of a methyldifluorovinyl group in 5, it did not enable
us to establish the geometry of this group or the relative
positions of the methyl and vinyl ligands. However,
these details were established by an X-ray structural
determination of 5, which is shown for the cation in
Figure 3. Relevant bond lengths and angles are given
in Table 5. Two details immediately stand out in the
structure of 5; first, the methyl and methyldifluorovinyl
groups are mutually cis on the same metal, and second,
fluoride substitution has occurred trans to the Ir-vinyl
bond to give the trans isomer of the methyldifluorovinyl
group. The Ir-Ir distance (2.9603(4) Å) is substantially
longer than a normal single bond (cf. 2.8116(3) Å in 2),
Ir
Ir
Ir
89.5(6)
89.7d
H(1) 179.2d
Ir′ Cl
Ir′ C(2)
Ir′ C(5)
Ir′ H(1)
Ir′ P(1′)
48.97(7) F(2)
Ir
Ir
Ir
Cl
128.7(5)
143.7(4)
35.0d
F(2)
F(3)
P(1)
91.10(8) Ir
H(1) Ir′
110.0d
a
Primed atoms are related to unprimed ones via the crystal-
b
lographic inversion center (0, 0, 0). Distance fixed during refine-
ment. c Nonbonded distance. Angle includes Ir-H distances fixed
d
during refinement.
metal bond. The transmission of electronic effects from
one metal to another in binuclear complexes has been
observed.33 All other parameters within the complex are
as expected.
Attempts to replace the chloro ligand in 2 by a methyl
group by reaction with methyllithium also did not
succeed, although in this case a reaction did occur. In
the presence of a 7-fold excess of methyllithium, 65%
conversion to a new product, 5, occurred (Scheme 2).
However, NMR studies demonstrated that chloride
replacement did not occur; instead, replacement of one
fluorine on the trifluorovinyl group by a methyl group
occurred, yielding [Ir2(CFdCFMe)(CH3)(CO)(µ-Cl)(µ-
1
CO)(dppm)2][CF3SO3] (5). The H NMR spectrum of 5
shows two methyl resonances. The signal at 1.22 ppm
appears as a pseudo triplet and is assigned to the
methyl group on the vinyl ligand, in which the coupling
to both fluorine nuclei is essentially the same (J FH
=
12 Hz), whereas the higher-field resonance at 1.07 ppm
is due to the methyl that is bound to one metal, showing
coupling to two adjacent 31P nuclei. Surprisingly, the
(33) (a) Cowie, M.; Vasapollo, G.; Sutherland, B. R.; Ennett, J . P.
Inorg. Chem. 1986, 25, 2648. (b) Sola, E.; Torres, F.; J imenez, M. V.;
Lo´pez, J . A.; Ruiz, S. E.; Lahoz, F. J .; Elduque, A.; Oro, L. A. J . Am.
Chem. Soc. 2001, 123, 11925. (c) Rowsell, B. D.; Trepanier, S. J .; Lam,
R.; McDonald, R.; Cowie, M. Organometallics 2002, 21, 3228.

5180 Organometallics, Vol. 21, No. 24, 2002
Ristic-Petrovic et al.
Ta ble 5. Selected In ter a tom ic Dista n ces a n d
An gles for Com p ou n d 5
Both the Ir-vinyl and Ir-methyl bonds in 5 (2.066(8),
2.099(8) Å, respectively) are shorter than the analogous
distances in 2 (2.090(6), 2.182(6) Å), probably reflecting
the movement of these groups away from their locations
in 2 opposite the Ir-Ir bond (recall our argument earlier
about the high trans influence of this bond). In 5 the
trans influence of the methyl group appears responsible
for the significantly longer Ir(2)-Cl(1) bond compared
to Ir(1)-Cl(1) (2.552(2) vs 2.401(2) Å). Within the
methyldifluorovinyl group, both C-F bonds are es-
sentially identical, and consistent with earlier argu-
ments, removal of a fluorine substituent from 2 has
resulted in a lengthening of the remaining C-F bond
on the â-carbon.
(a) Distances (Å)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(1)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
Ir(2)
Cl(1)
P(1)
P(3)
C(1)
C(2)
Cl(1)
P(2)
P(4)
C(2)
C(3)
C(4)
2.9603(4)
2.401(2)
2.358(2)
2.349(2)
1.834(8)
2.116(8)
2.552(2)
2.358(2)
2.361(2)
2.083(8)
2.099(8)
2.066(8)
P(1)
P(1)
P(2)
P(3)
P(3)
P(4)
F(1)
F(2)
O(1)
O(2)
C(4)
C(5)
P(2)
C(7)
C(7)
P(4)
C(8)
C(8)
C(4)
C(5)
C(1)
C(2)
C(5)
C(6)
3.057(3)a
1.828(8)
1.840(9)
3.133(3)a
1.818(8)
1.829(8)
1.40(1)
1.39(1)
1.14(1)
1.158(9)
1.30(1)
1.48(1)
(b) Angles (deg)
Ir(2) Ir(1) Cl(1)
Ir(2) Ir(1) P(1)
Ir(2) Ir(1) P(3)
Ir(2) Ir(1) C(1) 147.8(2)
Ir(2) Ir(1) C(2)
Cl(1) Ir(1) P(1)
Cl(1) Ir(1) P(3)
Cl(1) Ir(1) C(1) 156.5(3)
Cl(1) Ir(1) C(2) 100.0(2)
55.68(5) P(2) Ir(2) C(2)
91.05(5) P(2) Ir(2) C(3)
92.19(5) P(2) Ir(2) C(4)
92.8(2)
89.2(2)
89.0(2)
88.3(2)
88.7(2)
89.6(2)
86.8(3)
Discu ssion
P(4) Ir(2) C(2)
P(4) Ir(2) C(3)
As noted earlier, our one-time observation that gemi-
nal C-H and C-F activation of trifluoroethylene by the
diiridium complex 1 yielded a difluorovinylidene group6
prompted us to investigate related trifluorovinyl and
2,2-difluorovinyl complexes in order to gain information
on the order of C-H vs C-F activation in partially
fluorinated olefins. If C-H activation of trifluoroethyl-
ene occurred first, we were interested in determining
how the adjacent metals effected subsequent C-F
activation of the resulting trifluorovinyl group. Simi-
larly, if C-F activation was first, the resulting 2,2-
difluorovinyl group would yield a difluorovinylidene
group by subsequent C-H activation.
44.7(2)
84.70(7) P(4) Ir(2) C(4)
87.25(7) C(2) Ir(2) C(3)
C(2) Ir(2) C(4) 174.1(3)
C(3) Ir(2) C(4)
167.60(7) Ir(1) Cl(1) Ir(2)
87.6(3)
73.33(5)
P(1)
P(1)
P(1)
P(3)
P(3)
Ir(1) P(3)
Ir(1) C(1)
Ir(1) C(2) 101.6(2)
Ir(1) C(1)
Ir(1) C(2)
92.6(3)
Ir(1) P(1)
Ir(2) P(2)
Ir(1) P(3)
Ir(2) P(4)
C(7) 112.9(3)
C(7) 108.4(3)
C(8) 111.2(3)
C(8) 111.1(3)
91.0(3)
89.1(2)
C(1) Ir(1) C(2) 103.4(3)
Ir(1) C(1) O(1) 177.6(7)
50.99(4) Ir(1) C(2) Ir(2) 89.7(3)
90.36(5) Ir(1) C(2) O(2) 128.5(6)
92.02(5) Ir(2) C(2) O(2) 141.5(7)
Ir(1) Ir(2) Cl(1)
Ir(1) Ir(2) P(2)
Ir(1) Ir(2) P(4)
Ir(1) Ir(2) C(2)
Ir(1) Ir(2) C(3) 132.4(2)
Ir(1) Ir(2) C(4) 140.0(2)
45.6(2)
Ir(2) C(4) F(1) 115.7(6)
Ir(2) C(4) C(5) 132.3(7)
F(1) C(4) C(5) 111.6(7)
The targeted trifluorovinyl and 2,2-difluorovinyl com-
plexes [Ir2(R)(CH3)(CO)2(µ-X)(dppm)2][CF3SO3] (R )
FCdCF2, X ) Cl (2); R ) HCdCF2, X ) Br (3)) were
readily prepared by the oxidative addition of ClFCdCF2
and BrHCdCF2, respectively, to [Ir2(CH3)(CO)(µ-CO)-
(dppm)2][CF3SO3] (1). The structure of both species has
the fluorovinyl and the methyl groups on the outside of
the complex, essentially opposite the metal-metal bond.
Unfortunately, this is not a suitable position for activa-
tion of the fluorovinyl substrates by the adjacent metal,
and attempts to induce such activation in these halide-
bridged species, under refluxing conditions (CH2Cl2 or
THF solvent), failed. Attempts to substitute the bridging
chloride ligand in 2 by hydride, to give a species
analogous to that proposed in an initial C-H activation
of trifluoroethylene, failed with a number of hydride
sources. Furthermore, attempts to remove the chloride
ligand using Lewis acids such as (CH3)3SiOSO2CF3 also
failed. The only reaction observed in these cases was
protonation of 2, by the acids derived from hydrolysis
of the Lewis acid by adventitious water. It is noteworthy
that protonation of 2 did not result in subsequent
reductive elimination of either methane or trifluoroet-
hylene. However, protonation at the metal-metal bond,
as observed, leaves the hydride trans to both organic
ligands and unable to readily eliminate. Given the facile
protonation of 2, it is perhaps surprising that analogous
methylation by methyl triflate did not occur, although
we have previously observed that similar cationic spe-
cies can be basic enough to be protonated, yet remain
unreactive to the weaker electrophile, methyl triflate.
Attempts to effect removal of the chloride ion in 2 by
reaction with silver triflate resulted in decomposition.
In an attempt to replace the bridging chloride ligand
in 2 by a methyl group using methyllithium, one of the
Cl(1) Ir(2) P(2)
Cl(4) Ir(2) P(4)
Cl(1) Ir(2) C(2)
Cl(1) Ir(2) C(3) 175.5(2)
Cl(1) Ir(2) C(4)
93.87(7) F(2) C(5) C(4) 117.1(7)
88.17(6) F(2) C(5) C(6) 111.4(8)
96.3(2)
C(4) C(5) C(6) 131.4(9)
P(1) C(7) P(2) 113.0(4)
P(3) C(8) P(4) 118.4(4)
89.2(2)
P(2)
Ir(2) P(4)
177.52(7)
a
Nonbonded distance.
but is compressed compared to nonbonded distances in
comparable compounds, for which separations are usu-
ally substantially greater than 3 Å. This Ir(1)-Ir(2)
separation is also less than the nonbonded intraligand
P(1)-P(2) and P(3)-P(4) separations of 3.057(3) and
3.133(3), respectively, indicating some compression
along the metal-metal axis. The bonding can therefore
be considered in terms of two extremes. In the first
scenario the metals are nonbonded and the bridging
carbonyl is semibridging, in which it is primarily bound
to Ir(2) while simultaneously functioning as a π-acceptor
from Ir(1). This view is consistent with the long Ir(1)-
Ir(2) separation noted and with the unsymmetrical
geometry of the bridging carbonyl (Ir(2)-C(2) ) 2.083(8)
Å, Ir(1)-C(2) ) 2.116(8) Å; Ir(2)-C(2)-O(2) ) 141.5(7)°,
Ir(1)-C(2)-O(2) ) 128.5(6)°), which is more linear with
respect to the metal to which it is more strongly bound.
In the second extreme a symmetrically bridging carbo-
nyl would be accompanied by an Ir-Ir bond. The
observed structure is probably best described as lying
somewhere between the two extremes. In the former
description the geometry about Ir(2) is octahedral, while
that about Ir(1) is tetragonal pyramidal, having the
weaker π-interaction to the semibridging carbonyl in the
apical site.

Binuclear Fluorovinyl Complexes of Ir
Organometallics, Vol. 21, No. 24, 2002 5181
Sch em e 3
mation of 2 to 5. This scheme does not explain the trans
arrangement of substituents on the vinyl group; how-
ever, we note that other related substitutions on fluo-
rovinyl groups also gave trans products.10,11,12b This may
result from steric factors favoring a trans arrangement
of the bulkier methyl and metal substituents. It is also
possible that the transformation of 2 to 5 occurs by
migration of the methyl group to the metal bearing the
fluorovinyl ligand, rather than by the mechanism
described above. However, we rule this out since such
a product would have the positions of these two groups
reversed in the final product.
The mutually cis arrangement of methyl and vinyl
ligands on the same metal suggests the possibility of
reductive elimination of trans-2,3-difluoro-2-butene gen-
erating the known36 A-frame complex cation [Ir2(CO)2-
(µ-Cl)(dppm)2]+. Certainly, the reductive elimination
involving unsaturated substrates is known to be more
facile than that involving saturated substrates.37 This
has not been achieved under relatively mild conditions
(refluxing CH2Cl2), presumably reflecting the strong Ir-
fluorovinyl bond,23 but attempts will be made to promote
reductive elimination through the use of oxidizing
agents.38
fluorines on the trifluorovinyl group was instead re-
placed. We were initially surprised that replacement of
an olefin-bound fluorine was preferred to replacement
of the metal-bound chloride and were also subsequently
surprised by the stereoselective replacement of the
fluorine trans to iridium and by the final geometry of
the complex in which both the methyldifluorovinyl
group and the methyl ligand are mutually cis on the
same metal. Clearly transfer of either the methyl or the
vinyl group from one metal to the other has occurred.
Substitution on vinyl fluorides by strong nucleophiles
has been reported to proceed by an addition-elimina-
tion sequence to give the substituted vinyl derivative.34
It is reasonable to expect nucleophilic attack to occur
at the â-carbon, which should be more electrophilic as
a consequence of the two fluorine substituents. The
transfer of the vinyl group in 2 to the metal bearing
the methyl group in 5 suggests a bridging arrangement
for this vinylic group at some stage. We therefore
suggest that nucleophilic attack is accompanied by
movement of the resulting fragment to the bridging site,
yielding a trifluoroalkylidene-bridged species (B) as
shown in Scheme 3 (dppm ligands are omitted for
clarity). Analogous fluoroalkylidene-bridged species have
been reported.9 Subsequent loss of fluoride ion as LiF
(evidenced by the cloudy solution), with movement of
the new methyl-substituted vinyl group to the second
metal, would yield the observed product (5) as shown.
Alternately, nucleophilic attack on a putative trifluo-
rovinyl-bridged intermediate (A) would yield the same
fluoroalkylidene-bridged species (B). Although bridging
vinyl groups have not been observed in the chemistry
reported herein, binuclear complexes containing such
groups are well documented.35 Consequently, an inter-
mediate such as A cannot be ruled out in the transfor-
Con clu sion s
Although binuclear complexes containing the trifluo-
rovinyl and 2,2-difluorovinyl ligands have been synthe-
sized, attempts to activate the C-F and C-H bonds on
the R-carbons of these ligands by the adjacent metal
have failed. Certainly one factor inhibiting the targeted
activation steps is the location of the fluorovinyl groups
on the outside of the respective complexes, in a position
remote from the adjacent metal. Attempts to replace or
remove the bridging chloride ligand in 2 in attempts to
bring the trifluorovinyl group toward the bridging site
have failed. Subsequent studies will be aimed at related
complexes in which halide removal or replacement can
be achieved in order to probe the functions of adjacent
metals in the activation of fluorocarbyl groups.
We have discovered that the fluorine atom trans to
Ir in the trifluorovinyl complex 2 can be selectively
replaced by a methyl group, and we propose that this
occurs via a fluoroalkylidene-bridged intermediate.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada (NSERC)
and the University of Alberta for financial support of
this research and NSERC for funding the PLATFORM/
SMART 1000 CCD diffractometer. M.C. thanks the
University of Alberta and the Killam Trusts for a Killam
Annual Research Professorship and acknowledges Pro-
fessor J eff Stryker for helpful discussions.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
experimental details, atomic coordinates, interatomic distances
and angles, anisotropic thermal parameters, and hydrogen
parameters for compounds 2, 4, and 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
(34) March, J . In Advanced Organic Chemistry; J ohn Wiley &
Sons: New York, 1985; p 671.
(35) See for example: (a) Knox, S. A. R. J . Organomet. Chem. 1990,
400, 255, and references therein. (b) Akita, M.; Hua, R.; Knox, S. A.
R.; Moro-oka, Y.; Nakanishi, S.; Yates, M. I., Chem. Commun. 1997,
51. (c) Nubel, P. O.; Brown, T. L. J . Am. Chem. Soc. 1984, 106, 3474.
(d) Casey, C. P.; Meszaros, M. W.; Fagan, P. J .; Bly, R. K.; Colborn, R.
E. J . Am. Chem. Soc. 1986, 108, 4053. (e) Casey, C. P.; Austin, E. A.;
Rheingold, A. L. Organometallics 1987, 6, 2157. (f) Casey, C. P.; Austin,
E. A. J . Am. Chem. Soc. 1988, 110, 7106. (g) Cao, D. H.; Stang, P. J .;
Arif, A. M. Organometallics 1995, 14, 2733. (h) Ting, C.; Messerle, L.
J . Am. Chem. Soc. 1987, 109, 6506. (i) Suzuki, H.; Omori, H.; Lee, D.
H.; Yoshida, Y.; Fukushima, M.; Tanaka, M.; Moro-oka, Y. Organo-
metallics 1984, 13, 1129.
OM020295K
(36) Sutherland, B. R.; Cowie, M. Inorg. Chem. 1984, 23, 2324.
(37) Calhorda, M. J .; Brown, J . M.; Cooley, N. A. Organometallics
1991, 10, 1431.
(38) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G. In
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; p 324.