Tandem C-F and C-H bond activation in fluoroolefins promoted by a bis(diethylphosphino)methane-bridged diiridium complex: Role of water in the activation processes

Article abstract of DOI:10.1021/om2011968

The diiridium complex [Ir₂(CO)₃(μ-H)(depm) ₂]⁺ (1) reacts with vinyl fluoride, 1,1-difluoroethylene, trifluoroethylene, and tetrafluoroethylene, undergoing C-F bond activation in all cases, in addition to C-H activation in the incompletely substituted fluoroolefins. Reaction of 1 with vinyl fluoride readily undergoes geminal C-F/C-H activation, resulting in the bridging vinylidene product, [Ir ₂(H)(CO)₃(μ-C=CH₂)(depm)₂] ⁺ (2). Compound 1 reacts with 1,1-difluoroethylene at subambient temperature to give minor amounts of [Ir₂(CO)₃(κ ¹:η²-C≡CH)(depm)₂]⁺ (4), resulting from the loss of 2 equiv of HF from the fluoroolefin complex, along with a mixture of two isomers of [Ir₂(C(F)=CH₂)(CO) ₃(μ-CF₂CH₂)(depm)₂]⁺ (5a/5b), in which 2 equiv of the olefin has been incorporated. Compound 1 also reacts with trifluoroethylene at -30 °C, giving a 1:1 mix of isomers of the trifluoroethylene-bridged species [Ir₂(H)(CO)₃(μ- CFHCF₂)(depm)₂]⁺ (7a/7b), and warming this mixture above -15 °C converts both isomers to two products, [Ir ₂(H)(CO)₃(μ-C=CF₂)(depm)₂] ⁺ (8), in which the geminal C-F and C-H bonds in the fluoroolefin have been activated, and [Ir₂(H)(CO)₃(μ-CHCF ₃)(depm)₂]⁺ (9), the result of a [1,2]-fluoride shift to give the bridging 2,2,2-trifluoroethylidene moiety. Compound 9 reacts further with a second equivalent of trifluoroethylene over 12 h to produce the 2,2,2-trifluoroethylidene/cis-difluorovinyl complex, [Ir₂(C(F)=CFH) (CO)₃(μ-CHCF₃)(depm)₂]⁺ (10). Finally, tetrafluoroethylene reacts with 1 to produce the bridged adduct, [Ir₂(H)(CO)₃(μ-CF₂CF₂)(depm) ₂]⁺ (11), followed by a single C-F activation to give [Ir₂(C(F)=CF₂)(CO)₃(depm)₂] ⁺ (12). The roles of the hydride ligand and exogenous water in the C-F activation processes are discussed.

Full text of DOI:10.1021/om2011968

Article
pubs.acs.org/Organometallics
Tandem C−F and C−H Bond Activation in Fluoroolefins Promoted by
a Bis(diethylphosphino)methane-Bridged Diiridium Complex: Role of
Water in the Activation Processes
Michael E. Slaney,† Michael J. Ferguson,†,‡ Robert McDonald,†,‡ and Martin Cowie*,†
‡
†Department of Chemistry and X-ray Crystallography Laboratory, University of Alberta, Edmonton, AB T6G 2G2, Canada
S
* Supporting Information
ABSTRACT: The diiridium complex [Ir2(CO)3(μ-H)-
(depm)2]+ (1) reacts with vinyl fluoride, 1,1-difluoroethylene,
trifluoroethylene, and tetrafluoroethylene, undergoing C−F
bond activation in all cases, in addition to C−H activation in
the incompletely substituted fluoroolefins. Reaction of 1 with
vinyl fluoride readily undergoes geminal C−F/C−H activa-
tion, resulting in the bridging vinylidene product, [Ir2(H)-
(CO)3(μ-CCH2)(depm)2]+ (2). Compound 1 reacts with
1,1-difluoroethylene at subambient temperature to give minor
amounts of [Ir2(CO)3(κ1:η2-CCH)(depm)2]+ (4), resulting
from the loss of 2 equiv of HF from the fluoroolefin complex,
along with a mixture of two isomers of [Ir2(C(F)CH2)(CO)3(μ-CF2CH2)(depm)2]+ (5a/5b), in which 2 equiv of the olefin
has been incorporated. Compound 1 also reacts with trifluoroethylene at −30 °C, giving a 1:1 mix of isomers of the
trifluoroethylene-bridged species [Ir2(H)(CO)3(μ-CFHCF2)(depm)2]+ (7a/7b), and warming this mixture above −15 °C
converts both isomers to two products, [Ir2(H)(CO)3(μ-CCF2)(depm)2]+ (8), in which the geminal C−F and C−H bonds in
the fluoroolefin have been activated, and [Ir2(H)(CO)3(μ-CHCF3)(depm)2]+ (9), the result of a [1,2]-fluoride shift to give the
bridging 2,2,2-trifluoroethylidene moiety. Compound 9 reacts further with a second equivalent of trifluoroethylene over 12 h to
produce the 2,2,2-trifluoroethylidene/cis-difluorovinyl complex, [Ir2(C(F)CFH)(CO)3(μ-CHCF3)(depm)2]+ (10). Finally,
tetrafluoroethylene reacts with 1 to produce the bridged adduct, [Ir2(H)(CO)3(μ-CF2CF2)(depm)2]+ (11), followed by a single
C−F activation to give [Ir2(C(F)CF2)(CO)3(depm)2]+ (12). The roles of the hydride ligand and exogenous water in the C−F
activation processes are discussed.
demonstrated the efficacy of [Cp*2ZrH2] in the hydro-
defluorination of 1,1-difluoroethylene, 1,1-difluoromethylene-
cyclohexane, and perfluoropropene to ethylene, methylcyclo-
hexane, and propane, respectively,18,21,23 while Whittlesey and
co-workers have shown conversion of hexafluoropropene to
mixtures of (Z)- and (E)-1,2,3,3,3-pentafluoropropene and
2,3,3,3-tetrafluoropropene by cis-[Ru(dmpe)2H2].19 In the
reactions of [Rh(H)(PEt3)3] with hexafluoropropene, Braun
et al. found that only the olefinic C−F bonds are activated,
producing 1,1,1-trifluoropropane under a hydrogen atmos-
phere.20,24,30 Also with late metals, Caulton and co-workers
reported that the osmium−hydride complex, [Os(H)3Cl-
(PiPr3)2] reacts with vinyl fluoride and 1,1-difluoroethylene to
produce a variety of condition-specific products, including the
carbyne complex, [Os(H)(F)(Cl)(CCH3)(PiPr3)2],22 while
a similar complex, namely, [Os(H)2(CO)(PtBu2Me)2], con-
verts vinylfluoride to ethylene in the presence of a tertiary
silane.25
A. INTRODUCTION
The activation of C−F bonds in fluorocarbons represents an
important ongoing challenge in organometallic chemistry as
new, more effective routes are sought for the removal of
persistent fluorine-containing atmospheric pollutants,1,2 and for
the synthesis of fluorine-containing compounds, having
applications as surfactants,3−5 polymers,6,7 pharmaceuticals,8−12
and agrochemicals.13,14 Transition-metal hydride complexes
have been successfully utilized to effect carbon−fluorine bond
activation in a range of fluorine-containing organic sub-
strates,15−35 often under very mild conditions, and in a few
cases, these reactions have been shown to be catalytic.31−35 In
all of these transformations, the hydride ligands have been
shown or proposed to fulfill a number of different roles,
including elimination of HF once C−F bond activation has
occurred and functionalization of the activated fragment to give
a new carbon−hydrogen bond.15−35
Although the majority of C−F bond activation studies have
focused on the cleavage of aromatic C−F bonds,36−47 there has
been growing interest in the activation of olefinic C−F
bonds.18−25,30,48−66 Varying degrees of selectivity have been
observed in the hydrodefluorination of fluoroolefins using
metal−hydride complexes. For example, Jones et al. have
Special Issue: Fluorine in Organometallic Chemistry
Received: November 30, 2011
Published: February 1, 2012
© 2012 American Chemical Society
1384
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
Scheme 1
Our approach in bringing about C−F activation in
fluoroolefins has involved the use of pairs of metals for the
cooperative and selective activation of these substrates. The
bridging fluoroolefins in [Ir2(CH3)(CO)2(μ-olefin)(dppm)2]+
(dppm = μ-Ph2PCH2PPh2; olefin = C2F4, C2F3H, or 1,1-
C2F2H2) undergo facile fluoride-ion abstraction by Lewis or
Brønsted acids, including water,67−69 and in one exceptional
case, the activation of 1,1-difluoroethylene was promoted under
a CO atmosphere, leading to complete dehydrofluorination of
this group.69 Following C−F bond activation in these
fluoroolefins, a series of C−C and C−H bond-forming
reactions have allowed the conversion of tetrafluoroethylene
to trifluoroethylene; the conversion of trifluoroethylene into cis-
difluoroethylene, 1,2-difluoropropene, 2,3-difluoropropene, and
1,1,1-trifluoroethane; and the conversion of 1,1-difluoro-
ethylene to 2-fluoropropene.68,69
noted in the Experimental Section, even with this anion, we
were often unsuccessful in obtaining solid samples; our inability
to obtain crystalline samples remains one of the disadvantages
of depm in this study.
Compound 2 displays two multiplets (appearing as
pseudotriplets) in the 31P{1H} NMR spectrum at δ −8.1 and
−16.9, consistent with the chemical inequivalence of the metal
centers and the resulting inequivalence of the different ends of
1
the bridging diphosphines. The H NMR spectrum shows two
vinylidene protons as singlets at δ 6.33 and 6.29, two multiplets
corresponding to the methylene groups linking the two PEt2
moieties of each depm ligand at δ 2.71 and 2.09, an upfield
triplet at δ −11.95 with coupling to the pair of neighboring
phosphines (2JHP = 16.2 Hz), and the ethyl resonances in their
expected positions (all having the appropriate integrations).
1
The H NMR spectrum also displays a broad singlet at δ 12.0,
In an attempt to extend the scope of cooperative C−F
activation by binuclear complexes, we have made two key
modifications. First, we have replaced the bridging dppm
groups by the smaller, more basic depm (bis-
(diethylphosphino)methane, Et2PCH2PEt2), in order to
improve access of the fluoroolefins to the metals and to utilize
the ligand basicity as an aid in stabilizing the cationic products
of fluoride-ion removal. In addition, we have replaced the
methyl ligand in the above complex by a hydride ligand in order
to determine what role this ligand might play in the C−F
activation process and in the replacement of fluorines in
fluoroolefin substrates. The initial results of this study are
reported herein.
indicating the formation of solvated HF as a byproduct, which
also appears in the 19F NMR spectrum as a broad singlet at δ
−160; both signals are sufficiently broad (ca. 220 Hz at half
height) to mask the H−F coupling, which can vary between
120 and 520 Hz, depending upon the solution species
present.70−72 The 13C{1H} NMR spectrum of 2 displays
three equal intensity carbonyl resonances at δ 179.3, 179.0, and
164.8, all appearing as triplets owing to coupling to the adjacent
pairs of 31P nuclei, and selective 31P decoupling experiments
establish that the hydride and the carbonyl at δ 179.0 are on
one metal with the remaining pair of carbonyls bound to the
other metal.
An X-ray structure determination of compound 2, shown for
the complex cation in Figure 1, is fully consistent with the
structure proposed based upon NMR spectroscopy. The Ir(1)−
Ir(2) separation of 2.7960(4) Å confirms a metal−metal
interaction, while the bridging vinylidene displays a C(4)−C(5)
distance (1.330(4) Å) consistent with a double bond, and is
unsymmetrically bridged, being closer to Ir(1) than to Ir(2)
(2.031(3) versus 2.126(3) Å), presumably a result of greater
crowding at the metal having two carbonyls attached (Ir(2)).
Attempts to investigate the possible role of the hydride
ligand in the C−F activation of vinyl fluoride by substituting
the hydride ligand by deuterium (1-D) proved to be
challenging owing to the propensity of 1 to undergo H/D
exchange with adventitious water. However, labeling was
achieved by the deliberate addition of 15 equiv of D2O to a
solution of 1, forming a 4:1 mixture of 1-D and 1 within 24 h.
This mixture of isotopologues reacts with vinyl fluoride to
produce a protonated version of 2, in which the deuterium label
is lost, indicating that the terminal hydride in the product
originates from vinyl fluoride, and not from the original hydride
or water. The substantial acceleration of the reaction upon the
addition of water identifies that it plays a key role in the C−F
activation process, but the role of the hydride ligand is not
clear. The mechanism of C−F activation and the role of water
B. RESULTS
i. Activation of Vinyl Fluoride. The reaction of
[Ir2(CO)3(μ-H)(depm)2][BArF ] (BArF ¯ = [B(3,5-
4
4
(CF3)2C6H3)4]¯) (1) with vinyl fluoride at ambient temper-
ature results in the formation of [Ir2(H)(CO)3(μ-CCH2)-
(depm)2][BArF ] (2) and [Ir2(H)2(CO)2(μ-H)(μ-CCHF)-
(depm)2][BArF4] (3) in an approximate 20:1 ratio after 30 min,
4
as shown in Scheme 1. The major product, compound 2, a
vinylidene-bridged compound, is the apparent result of
simultaneous C−F and C−H activation of the geminal
hydrogen/fluorine pair in vinyl fluoride, while the minor
product 3, a fluorovinylidene compound, is the result of double
C−H activation of the geminal hydrogens, accompanied by CO
loss. Repeating the reaction of 1 with vinyl fluoride in the
presence of trimethylamine-N-oxide (TMNO) results in the
exclusive formation of 3 after 10 min, indicating that CO loss is
the rate-determining step in the double geminal C−H bond
activation process, whereas performing the reaction in the
presence of added water (ca. 5 equiv) results in the exclusive
formation of 2, again in only 10 min, indicating that water is
involved in the C−F activation pathway. Much of the chemistry
reported herein was carried out using the [BArF ]¯ anion since
4
it gave the best results for obtaining solid samples. However, as
1385
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
ii. Activation of 1,1-Difluoroethylene. The reaction of 1
with 1,1-difluoroethylene at −10 °C over 6 h gives three
products in an approximate 1:2:1 ratio, and as noted above,
water is again found to enhance the rate of reaction, in which all
three products are formed within minutes when the reaction is
repeated with the deliberate addition of ca. 15 equiv of water.
One product, [Ir2(CO)3(κ1:η2-CCH)(depm)2][BArF ] (4),
4
results from the apparent elimination of 2 equiv of HF from a
1,1-difluoroethylene adduct, while the remaining 2:1 mixture
consists of two isomers of [Ir2(C(F)CH2)(CO)3(μ-
CF2CH2)(depm)2][BArF ] (5a and 5b), differing only in the
4
orientation of the fluorovinyl group, as shown in Scheme 2.
Compounds 5a and 5b contain two fluorocarbyl units, and
although we were unable to observe the stepwise incorporation
of the two difluoroethylene molecules, we have successfully
achieved this with trifluoroethylene, as will be discussed in what
follows.
The acetylide-bridged product (4) is highly reminiscent of
the propynyl-bridged analogue, observed in the activation of
1,1-difluoroethylene by a dppm-bridged methyl complex.69
Complex 4 displays a broad singlet in the 31P{1H} NMR
spectrum, which changes little upon cooling to −80 °C, while
the quintet at δ 181.6 (2JCP = 5.6 Hz) in the 13C{1H} NMR
spectrum of a 13CO-enriched sample broadens slightly upon
cooling. The static structure proposed should display two 31P
resonances, owing to the chemical inequivalence of both
metals, and should also display three carbonyl resonances. We
propose a fluxional process whereby the bridging acetylide
group is undergoing a “windshield-wiper” process in which it
migrates between the two metals as observed in other alkynyl-
bridged compounds.69,74−78 The acetylide proton appears at δ
5.04, typical for such a group,75 and in the presence of D2O
undergoes H/D exchange to produce the deutero-acetylide
analogue, indicative of the acidic nature of acetylides.
Unfortunately, this rapid H/D exchange does not allow us to
obtain information regarding the role of the hydride ligand in
the formation of 4 by use of deuterium labeling of 1.
Figure 1. Perspective view of the complex cation of [Ir2(H)(CO)3(μ-
CCH2)(depm)2][BArF ] (2) showing the atom labeling scheme.
4
Non-hydrogen atoms are represented by Gaussian ellipsoids at the
20% probability level. Hydrogen atoms are shown with arbitrarily small
thermal parameters except for depm ethyl hydrogens, which are not
shown. Relevant bond distances (Å) and angles (deg): Ir(1)−Ir(2) =
2.7960(4); Ir(1)−C(4) = 2.031(3); Ir(2)−C(4) = 2.126(3); C(4)−
C(5) = 1.330(4); C(1)−Ir(1)−C(4) = 158.0(1); C(2)−Ir(2)−C(4) =
136.0(1); Ir(1)−C(4)−Ir(2) = 84.5(1); C(2)−Ir(2)−C(3) =
116.1(1); C(3)−Ir(2)−C(4) = 107.8(1); Ir(1)−C(4)−C(5) =
143.6(2); Ir(2)−C(4)−C(5) = 131.9(2).
in these processes will be addressed for this and other
fluoroolefins later in the article.
The fluorovinylidene-bridged trihydride compound (3), the
product of double C−H activation, displays two equal intensity
multiplets at δ −7.1 and 9.1 in the 31P{1H} NMR spectrum,
again indicating the chemical inequivalence of each end of the
1
diphosphines. A doublet at δ 6.61 in the H NMR spectrum,
representing the vinylidene proton, displays geminal fluorine
coupling of 108.2 Hz. Three upfield signals are observed at δ
−12.54, −13.09, and −15.48 (all as multiplets), in which the
first two correspond to the terminal hydrides, while the upfield
signal corresponds to the bridging hydride. The 13C{1H} NMR
spectrum of a 13CO-enriched sample displays only a single
broad resonance at δ 171.1; however, integration relative to
compound 2 indicates that this broad signal results from the
coincidental overlap of two carbonyls. The lone vinylidene
fluorine appears as a doublet at δ −72.1 in the 19F NMR
spectrum, displaying the same geminal coupling as observed in
the fluorovinylidene proton signal. The process of double C−H
activation, promoted by CO loss, will not be discussed in this
report since it has been addressed in a separate report dealing
specifically with this topic.73
Compound 5a, the major product formed, displays a broad
multiplet at δ −23.1 and a pseudotriplet at δ −26.9 in the
31P{1H} NMR spectrum. The breadth of the downfield signal
results from additional 19F coupling involving the μ-CF2CH2
group, as verified by 31P{1H, 19F} NMR experiments. In the 1H
NMR spectrum, the two fluorovinyl protons appear at δ 5.55
and 4.45, with cis (3JHF = 28.1 Hz) and trans coupling (3JHF
=
62.1 Hz), respectively, to the single fluoro substituent, which
appears in the 19F NMR spectrum as a doublet of doublets at δ
−53.4 (31P coupling is not observed for this signal), as shown in
Figure 2. Selective 31P decoupling experiments show minor,
unresolved coupling between the fluorovinyl protons and the
upfield phosphorus signal, indicating that the fluorovinyl
moiety is bound to the same metal as the “CH2” end of the
Scheme 2
1386
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
Figure 2. The 19F{31P} NMR spectrum of a mixture of compounds 5a and 5b. The bridging olefin appears as a pair of overlapping triplets for 5a and
5b, with the latter slightly offset, resulting in the upfield shoulder feature at δ −28.6. Integrations are shown underneath.
μ-C2F2H2 group. Similarly, the methylene protons of the
bridging C2F2H2 group appear as a multiplet in the H NMR
are observed in the 13C{1H} NMR spectrum at similar shifts to
those of 5a. The similarities in all spectral parameters of 5a and
5b, except for the chemical shifts of the vinyl fluorines, which
indicates significantly different environments for these sub-
stituents, suggest that their difference is a result of rotation of
this fluorovinyl group around the Ir−C bond. Presumably, the
crowded octahedral environment at Ir results in a significant
barrier to rotation. Consistent with this interpretation, a spin-
saturation transfer experiment at 0 °C, in which saturation of
the vinyl proton signal at δ 5.01 of compound 5b results in the
disappearance of the corresponding signal at δ 5.55 for
compound 5a, demonstrates exchange between these isomers.
Increasing the temperature above 0 °C results in the
conversion of both 5a and 5b to an initial vinylidene-bridged
product, which slowly converts to a second vinylidene-bridged
product after 12 h; both products are the result of C−F
activation of the fluorovinyl moiety and accompanying loss of
difluoroethylene. The only signals evident in the 19F NMR
spectrum after these transformations are those of the free
1
spectrum, which, upon selective decoupling of the upfield 31P
signal, collapses to a pseudotriplet at δ 1.58 due to coupling to
the adjacent CF2 fluorines (21.1 Hz). The single resonance for
the bridging difluoroethylene unit at δ −28.6 in the 19F NMR is
consistent with ″top/bottom″ mirror symmetry about the
equatorial plane of the metals and displays coupling to the pair
of olefin protons. Three carbonyl resonances appear in the
13C{1H} NMR spectrum at δ 177.1, 174.6, and 151.6 (the
downfield signal as a multiplet, while the other signals are broad
singlets), and selective 31P decoupling experiments confirm that
the upfield and downfield carbonyls are found on one metal,
while also defining the orientation of the fluoroolefin as having
the pair of fluorines adjacent to these carbonyls, as shown by
the collapse of the signal at δ 177.1 to a triplet (3JCF = 17.7 Hz)
upon 31P decoupling, displaying residual coupling to the pair of
fluorines.
The minor isomer 5b displays similar spectroscopic
parameters to 5a, with two signals in the 31P{1H} NMR
spectrum at δ −24.2 and −28.7; the former is again broad,
owing to coupling to the adjacent “CF2” fragment of the
bridging C2F2H2 unit, while the latter appears as a
pseudotriplet. The 1H NMR spectrum displays two vinyl
protons, each as doublets at δ 5.01 and 3.77, cis (3JHF = 29.8
Hz) and trans (3JHF = 64.1 Hz) coupling, respectively, to the
vinylic fluorine, together with minor unresolved coupling to the
upfield 31P signal, indicating that the fluorovinyl group is again
adjacent to the “CH2” portion of the bridging 1,1-difluoro-
ethylene unit, as for compound 5a. The methylene protons of
the bridging C2F2H2 unit appear as a multiplet at δ 1.31, which,
upon 31P decoupling (either broadband or selective at δ
−28.7), collapses to a pseudotriplet (3JHF = 21.2 Hz) in which
coupling to the adjacent fluorines remains. The 19F NMR
spectrum displays two signals (Figure 2), a doublet of doublets
at δ −14.6 due to the vinylic fluorine, with couplings matching
those observed in with the vinylic proton resonances, while the
“CF2” unit of the bridging olefin overlaps with the equivalent
signal from 5a. Phosphorus decoupling simplifies the over-
lapping signals to triplets, with the resonance from 5b
appearing as a slightly upfield-shifted shoulder on the signal
for 5a; integration confirms that the CF2 resonance for 5b is
overlapping with the signal for 5a. Three carbonyl resonances
olefin, BArF ¯, and solvated HF. This transformation is the
4
result of adventitious water, as confirmed by the rate
enhancement upon the deliberate addition of water. Both
products appear to have the formulation [Ir(OH)(CO)3(μ-
CCH2)(depm)2]+ (6a and 6b; possibly also having
coordinated H2O), as confirmed by three distinct carbonyl
resonances in the 13C NMR spectrum; however, our inability to
identify the coordination modes of the presumed hydroxido
ligands owing to our inability to identify the 1H NMR
resonances of this group (in the presence of H2O) and our
inability to separate these species, does not allow their
structural characterization. Identification of the vinylidene
1
ligands is unambiguous in the H NMR spectrum, with 6a
displaying two doublets at δ 6.32 and 5.81 (2JHH = 3.8 Hz),
whereas 6b shows two resonances at δ 6.05 and 6.00 (2JHH
=
4.6 Hz).
iii. Activation of Trifluoroethylene. Compound 1 reacts
with trifluoroethylene (ca. 5 equiv) over 2 h at −30 °C to give a
1:1 mixture of two isomers of [Ir2(H)(CO)3(μ-CFHCF2)-
(depm)2][BArF ] (7a and 7b), both the result of trifluoro-
4
ethylene coordination in the position bridging the two metal
centers; these isomers differ only in the orientation of this
bridging trifluoroethylene group (Scheme 3), as explained
below.
1387
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
Scheme 3
The 31P{1H} spectrum for 7a shows two broad multiplets at
δ −13.8 (2P) and −15.9 (2P), whereas 7b displays three broad
signals at δ −13.1 (1P), −14.6 (1P), and −15.9 (2P). Although,
for each isomer, all four phosphorus nuclei are chemically
inequivalent and are expected to produce four signals each, as a
result of the top/bottom asymmetry and the inequivalence of
both metals, the slight top/bottom asymmetry resulting from
the orientation of the C2F3H ligand leads to coincidental
overlaps in some resonances, as previously reported for the
trifluoroethylene-bridged complex [Ir2(CH3)(CO)2(μ-C2F3H)-
Warming the mixture of the trifluoroethylene-bridged
isomers (7a and 7b) to −20 °C results in the conversion of
7a to a 1:1 mixture of [Ir2(H)(CO)3(μ-CCF2)(depm)2]-
[BArF ] (8) and [Ir2(H)(CO)3(μ-CHCF3)(depm)2][BArF ]
(9) after 5 h, while leaving 7b intact at this temperature.
Warming slightly to −15 °C results in the disappearance of 7b
after 5 h and a corresponding increase in the concentrations of
8 and 9, which remain in a 1:1 ratio, as shown in Scheme 4.
4
4
Scheme 4
68
(dppm)2]+. However, the H NMR spectrum confirms the
loss of both ″top/bottom″ and ″front/back″ symmetry with the
appearance of eight unique signals corresponding to the
methylene protons for the depm backbone of both isomers.
The bridging trifluoroethylene proton for 7a appears at δ 5.50,
showing geminal fluorine coupling (2JHF = 65.6 Hz), whereas
for 7b, this signal appears at δ 5.13 (2JHF = 64.5 Hz); however,
the breadth of both signals masks other fluorine couplings. The
terminal hydride resonances for 7a and 7b appear as
pseudotriplets at δ −8.77 and −8.42, respectively, displaying
coupling to the adjacent 31P nuclei. TROSEY NMR experi-
ments79 confirm the bridging orientation of trifluoroethylene,
with the olefinic proton showing correlation to one methylene
resonance of the depm backbone for each compound. The 19F
NMR spectrum of 7a and 7b displays six fluorine signals: three
belonging to the bridging fluoroolefins of each isomer (7a: δ
−108.7, −118.7, and −195.9) (7b: δ −93.5, −104.2, and
−216.5). The distinct geminal F−F couplings for 7a and 7b
(2JFF = 198.3, 155.3 Hz, respectively) confirms rehybridization
of the bridging group toward sp3, with the large geminal
coupling exceeding that of sp2-hybridized fluoroolefins.80,81 The
13C{1H} NMR spectrum displays three terminal carbonyl
resonances for each compound (7a: δ 188.1, 183.7, and 182.2)
(7b: δ 187.6, 185.8, and 182.3). In the case of 7a, the upfield
and downfield carbonyl signals show mutual trans coupling
(2JCC = 42.9 Hz), while the remaining signal appears as a broad
doublet (3JCF = 15.8 Hz), confirming its location opposite the
“CFH” end of the olefin. For compound 7b, a mutual trans
carbonyl coupling (2JCC = 41.8 Hz) is again evident, this time
between two downfield resonances, while the remaining signal
appears as a broad triplet (3JCF = 12.4 Hz), indicating its
location trans to the “CF2” end of the olefin. Further support
for the proposed ligand arrangement in 7a and 7b is evident in
the HMBC NMR spectrum, in which exclusive correlation
between the hydride ligand and the two mutually trans
carbonyls is observed for each compound. Interestingly,
compounds 7a and 7b are the only ones in this study to
assume the geometries in which one metal is square-planar and
coordinatively unsaturated, while the other is octahedral and
saturated. Most others have a pseudosymmetrical ligand
arrangement having two terminal and one bridging ligand
(omitting depm) at each metal.
1
Compound 8, the difluorovinylidene analogue to 2, results
from geminal C−H/C−F activation of the bridging trifluoro-
ethylene ligand, while the 2,2,2-trifluoroethylidene-bridged
compound 9 is a result of a [1,2]-fluoride shift within the
bridging trifluoroethylene units of 7a and 7b. Performing this
reaction in the presence of added water greatly enhances the
rate of conversion to both products (1 h vs 5 h), again
suggesting that water is playing a pivotal role in the activation
processes. The possible effect of added fluoride ion in the
transformation to 9 was not investigated.
Compound 8 displays NMR parameters nearly identical to
those of 2, with the exception of two mutually coupled doublets
in the 19F NMR spectrum at δ −68.4 and −77.2 (2JFF = 98.6
Hz). The terminal hydride appears at δ −12.46 in the 1H NMR
spectrum as a triplet of doublets, the doublet resulting from
long-range coupling to a fluorine of the bridging difluor-
ovinylidene unit (4JHF = 7.7 Hz).
An X-ray structure determination of 8 confirms the
formulation noted above, revealing a bridged difluorovinylidene
group adjacent to the hydride ligand, as shown in Figure 3. The
iridium/iridium separation (Ir(1)−Ir(2) = 2.7914(5) Å) is
consistent with a metal/metal interaction, and much like
compound 2, the vinylidene unit is bound more strongly to the
hydride-containing iridium (Ir(1)−C(4) = 2.08(1) Å, Ir(2)−
C(4) = 2.03(1) Å), presumably a consequence of less crowding
at this metal. All other crystallographic parameters are as
expected and are in close agreement to those of compound 2.
Deuterium labeling of the terminal hydride of 7a and 7b (by
starting with 1-D), in conjunction with the differing reaction
rates of 7a and 7b, enables us to obtain some mechanistic
1388
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
diphosphines at both metals. The proton of the bridging
2,2,2-trifluoroethylidene group appears as a broad multiplet at δ
4.94 in the 1H NMR spectrum, resulting from coupling to four
phosphorus and three fluorine nuclei, and broad-band 31P
decoupling results in collapse of this signal to a quartet (3JHF
=
17.0 Hz), while the hydride signal appears at δ −10.52 as a
broad multiplet. Three terminal carbonyl signals were found in
the 13C{1H} NMR, all appearing as multiplets, whereas the 19
F
NMR spectrum displays a doublet at δ −46.6 (3JFH = 17.0 Hz),
a shift typical for a bridging trifluoroethylidene group.49,50,68
Interestingly, in the presence of excess trifluoroethylene,
compound 9 converts to [Ir2(C(F)CFH)(CO)3(μ-CHCF3)-
(depm)2][BArF ] (10) overnight at ambient temperatures, the
4
result of C−F bond activation of a second equivalent of
trifluoroethylene, as outlined in Scheme 6. Again, the deliberate
Scheme 6
Figure 3. Perspective view of the complex cation of [Ir2(H)(CO)3(μ-
CCF2)(depm)2][BArF ] (8) showing the atom labeling scheme.
4
Thermal parameters are as described in Figure 1. Relevant bond
distances (Å) and angles (deg): Ir(1)−Ir(2) = 2.7914(5); Ir(1)−C(4)
= 2.08(1); Ir(2)−C(4) = 2.03(1); C(4)−C(5) = 1.28(2); C(1)−
Ir(1)−C(2) = 114.9(5); C(1)−Ir(1)−C(4) = 108.4(5); C(2)−Ir(1)−
C(4) = 136.7(5); C(3)−Ir(2)−C(4) = 158.7(7); Ir(1)−C(4)−Ir(2) =
85.5(5), F(1)−C(5)−F(2) = 106(1).
addition of water results in an order-of-magnitude rate increase.
The NMR spectral parameters for 10 are similar to those of 9,
apart from the additional resonances of the cis-difluorovinyl
group and the disappearance of the hydride resonance. The
difluorovinyl proton appears as a doublet of doublets at δ 5.75
information regarding their conversion to compound 8.
Compound 9 forms from a [1,2]-fluoride shift with the
deuterium incorporation found exclusively at the terminal
hydride position, with no deuterium incorporation into the
trifluoroethylidene unit. As shown in Scheme 5, reaction of
1
in the H NMR spectrum with geminal (81.6 Hz) and trans
(24.1 Hz) fluorine coupling, while the two additional fluorine
resonances at δ −84.4 and −138.1 each appear as doublets in
the 19F NMR spectrum, with the former showing trans proton
coupling and the latter displaying geminal proton coupling.
Surprisingly, no cis coupling is observed between the two
Scheme 5
fluorine resonances; however, the chemical shifts of the two 19
F
signals, in conjunction with the coupling values observed with
the vinylic proton, lead us to assign the cis arrangement. The
stepwise transformations of 1 through 9, followed by the
conversion of 9 to 10, are reminiscent of the reaction of 1 with
1,1-difluoroethylene, in which 2 equiv of fluoroolefin was again
incorporated, except that incorporation of the second
equivalent of trifluoroethylene did not occur until after
isomerization of the first equivalent to a bridging trifluor-
oethylidene group (9). Although, for 1,1-difluoroethylene, we
were unable to observe intermediates involving the first
equivalent of C2F2H2, the reaction of 1 with trifluoroethylene
demonstrates the stepwise C−F activation of two fluoroolefins
units. It is curious that the structurally similar difluorovinyli-
dene-bridged species does not also incorporate a second C2F3H
unit.
either 7a or its deutero analogue (7a-D) with D2O yields 8, in
which the terminal hydride position is completely protonated,
indicating that trifluoroethylene is the source of this hydride
ligand. However, compound 7b or 7b-D reacts with D2O to
produce 8-D, in which the hydride is completely deuterated,
and, therefore, originating from D2O. The significance of this
study will be addressed later.
The 2,2,2-trifluoroethylidene-bridged species (9) displays
four signals in the 31P{1H} spectrum, indicative of four
inequivalent phosphorus environments, with pairs of signals
displaying a large mutual coupling of 351.9 and 302.9 Hz,
consistent with a mutually trans arrangement of the
iv. Activation of Tetrafluoroethylene. Compound 1
reacts with tetrafluoroethylene at 0 °C over 1 h to produce the
tetrafluoroethylene-bridged complex, [Ir2(H)(CO)3(μ-
CF2CF2)(depm)2][BArF ] (11), in ∼60% yield based upon
4
31P{1H} NMR integrations (Scheme 7) together with
unidentified decomposition products. Compound 11 has
resulted from C2F4 coordination in the bridging site,
accompanied by movement of the hydride ligand from a
bridging to a terminal position. As such, compound 11 very
much resembles the trifluoroethylidene-bridged species (9),
1389
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
Scheme 7
2
while having a surprisingly different structure from those of the
trifluoroethylene adducts 7a and 7b. This product gives rise to
two broad resonances in the 31P{1H} NMR spectrum, the
breadth of which is a consequence of 19F coupling from the
adjacent “CF2” units of the bridging tetrafluoroethylene ligand.
−132.4, showing mutual coupling (3JFFtrans = 110.8 Hz, JFF
=
3
92.9 Hz, JFFcis = 33.4 Hz), identifying the trifluorovinyl group.
C. DISCUSSION
We initiated our current investigation into the C−F bond
activation in fluoroolefins, promoted by a pair of adjacent
metals, using depm (bis(diethylphosphino)methane) as an
ancillary bridging ligand, on the assumption that this smaller
and more basic diphosphine would result in enhanced reactivity
over our previously studied dppm-bridged complexes. This has
certainly proven to be the case in a number of ways. First, a
comparison of [Ir2(CO)3(μ-H)(depm)2]+ (1) and its dppm
analogue has shown that, while the latter is unreactive to all
fluoroolefins studied in this report, the depm compound (1)
reacts readily with all of them. Second, although we had
observed water-promoted C−F activation in some of the
previous dppm chemistry,68,69 this involvement was not nearly
as extensive as it has proven to be in the current depm system,
as will be discussed. Furthermore, in much of the chemistry
reported herein, the smaller size of depm (and possibly its
greater basicity) has allowed the incorporation of two
fluoroolefin-derived fragments, whereas with dppm, only a
single fluorocarbyl unit was incorporated. The facile incorpo-
ration of two fluoroolefins was most prevalent with 1,1-
difluoroethylene, occurring readily, even at low temperature.
i. Trifluoroethylene Activation. Of the four fluoroolefins
investigated (vinyl fluoride, 1,1-difluoroethylene, trifluoro-
ethylene, and tetrafluoroethylene) we initiate our discussion
with trifluoroethylene, since this fluoroolefin is the best
behaved, in the sense that the stepwise transformations could
be easily followed in which the reactions first yielded an olefin
adduct, followed by its C−F activation, and (for one C−F
activation product) the incorporation of a second fluoroolefin,
accompanied by its C−F activation.
As shown earlier in Scheme 3, reaction of 1 with
trifluoroethylene yields two isomeric adducts in which the
fluoroolefin unit bridges the pair of metals, differing only in its
orientation with respect to the chemically inequivalent metal
centers. Both isomers react further to yield the same two final
products (8 and 9; see Scheme 4), although the isomer having
the “CHF” end of the olefin adjacent to the Ir(I) center (7a)
reacts at slightly lower temperature than the isomer having this
end of the olefin adjacent to the Ir(III) center (7b). It appears
that the slower conversion of 7b to subsequent products cannot
be rationalized on the basis of its prior isomerization to 7a,
since spin-saturation transfer experiments failed to detect
isomerization between these isomers at −20 °C. Furthermore,
the conversion of 7a to 8 and 9 at −20 °C is sufficiently slow (1
h) that the isomerization of 7b to 7a should be visible upon
warming, which is not observed. Finally, the different H/D-
labeling studies for the two isomers indicate that 7a cannot be a
common intermediate.
1
The terminal hydride appears in the H NMR spectrum at δ
−12.63 as a triplet of triplets, displaying coupling to the
adjacent pair of 31P nuclei and to two fluorines from one end of
the bridging tetrafluoroethylene moiety (2JHP = 17.3 Hz, 3JHF
=
17.3 Hz). The 19F NMR spectrum displays a triplet at δ −74.4
and a doublet of triplets at δ −80.7, with each displaying
coupling to different pairs of phosphorus nuclei as well as
coupling to the terminal hydride (3JFH = 17.3 Hz) for the
second signal. Surprisingly, no F−F coupling was observed in
either signal.
Monitoring the reaction for longer periods (>5 h) shows the
formation of two other products, namely, [Ir2(C(F)CF2)-
(CO)3(depm)2][BArF ] (12) (ca. 20%), the result of C−F
4
activation of the bridging tetrafluoroethylene unit with
concomitant loss of the hydride ligand, and [Ir2(C2F3)-
(CO)x(μ-C2F4)(depm)2][BArF ] (13) (<5%) containing an
4
intact tetrafluoroethylene and a trifluorovinyl group. The
incomplete characterization of this minor species has not
allowed us to determine its origin. The rate of this
transformation is again enhanced upon the addition of 5
equiv of water, increasing the yield of 12 to ca. 40% after 2 h,
but with no appreciable change in the quantity of 13 produced.
Attempts to favor the formation of 13 by increasing the
temperature to 40 °C or increasing the pressure of tetrafluoro-
ethylene had no result.
Compound 12 displays two resonances in the 31P{1H} NMR
spectrum, indicating the inequivalence of the two metals. In the
1H NMR spectrum, only depm resonances appear, with the
bridging methylene protons of the depm backbone appearing as
a single resonance, indicative of front/back symmetry about the
Ir2P4 plane. The 19F NMR spectrum displays three signals for
the trifluorovinyl moiety at δ −93.8, −123.9, and −136.1, each
2
appearing as a doublet of doublets (3JFFtrans = 111.6 Hz, JFF
=
3
93.0 Hz, and JFFcis = 39.7 Hz). The 2:1 ratio of carbonyl
resonances in the 13C{1H} NMR spectrum and the apparent
″front/back″ symmetry lead us to suggest the structure shown
in Scheme 7, with a terminal trifluorovinyl group on the metal
containing two carbonyls, while the other metal has the
remaining carbonyl.
As noted above, compound 13 is never obtained in an
appreciable yield, even after extended periods (2 days) or upon
heating (40 °C) and has only been identified by 19F NMR
spectra owing to our inability to locate its 31P{1H} and 13C{1H}
resonances. Nevertheless, the five signals in a 2:2:1:1:1 ratio in
the 19F NMR identifies that two fluorocarbyl groups are
present; two signals appear for each set of olefinic CF2 units (δ
−76.3 and −80.4), with three signals at δ −94.3, −121.3, and
1390
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
Both products in the conversion of 7a and 7b are the result
of fluoride-ion loss; in one case, fluoride-ion recoordination at
the β-carbon of the resulting 2,2-difluorovinyl group occurs
(formally a 1,2-fluoride shift) to give a 2,2,2-trifluoroethylidene-
bridged product (9), while in the second case, the fluoride ion
is eliminated as HF, accompanied by subsequent C−H
activation, yielding the difluorovinylidene-bridged product
(8). Formation of 9 is not surprising, having been previously
observed in the dppm system,68 and being favored by the
increase in C−F bond strengths that occurs upon increasing the
fluorine substitution at carbon.27,82,83 The acceleration of this
1,2-fluoride shift in the presence of water leads us to suggest
that fluoride-ion transfer is water-assisted. Given that this 1,2-
shift involves loss of fluoride ion from the “CHF” end of the
olefin and recoordination at the “CF2” end, the somewhat more
facile transfer involving 7a can be rationalized by greater π-
back-donation from the Ir(I) center into the adjacent C−F σ*
orbital in this isomer. In isomer 7b, the “CHF” end is bound to
the Ir(III) center from which π-back-donation and the resulting
labilization of the fluoride ion should be less (see Scheme 3 for
the structures of 7a and 7b).
In the transformation of isomers 7a and 7b to 8, formally by
HF loss, water again plays a role, as seen by acceleration upon
H2O addition. Labeling studies have proved useful in allowing
us to propose a mechanism for the C−F and C−H activation
steps in converting the trifluoroethylene ligand in 7a to the
difluorovinylidene ligand in 8. In the reactions of 7a and the
deuteride analogue (7a-D), carried out in the presence of D2O,
compound 8 is observed exclusively as the hydride, with no
deuterium incorporation. This hydride can only come from the
trifluoroethylene ligand. We propose that HF loss occurs first
through protonation by water, yielding the 2,2-difluorovinyl
group, as shown in Scheme 8. Presumably, H2O coordination at
fluorovinyl C−H bond to give the observed cis arrangement of
difluorovinylidene and hydride ligands.
The mechanism for C−F and C−H activation in the isomer
7b is not so easily rationalized since the same deuterium-
labeling experiments with this isomer give the deuteride (8-D)
exclusively. We assume that, since the rates of reactions of 7a
and 7b, although not identical, are very similar, the mechanisms
differ only slightly, giving an isomer of 8 in which the hydride
ligand migrates to its final location in 8 by a water-assisted
deprotonation/reprotonation sequence, as has been observed
in related dppm chemistry.69 Proton transfer in the presence of
D2O would give predominately the deuteride (8-D). Activation
of the C−F bond of the “CHF” end of the olefin is favored over
those at the “CF2” end owing to the greater C−F bond
strengths involving the more substituted carbon.27,82,83
Certainly, the isomerization of 7b to the 2,2,2-trifluoroethyli-
dene-bridged complex (8), noted above, already demonstrates
the lability of this isolated fluorine.
Although the difluorovinylidene-bridged product (8) is
unreactive toward additional trifluoroethylene, the related
2,2,2-trifluoroethylidene-bridged product (9) reacts with this
olefin, resulting in HF loss and replacement of the hydride
ligand by a cis-difluorovinyl group in the product (10; see
Scheme 9). Acceleration of this reaction by added water again
Scheme 9
Scheme 8
suggests water-assisted fluoride-ion loss, which would give a
dicationic vinyl/hydride species, which, upon deprotonation,
yields 10. In Scheme 9, we show the trifluoroethylene group as
η2-bound to one metal since it seems improbable that it could
attain a bridging geometry in a structure already having the
trifluoroethylidene group bridging on one face of the complex.
However, we cannot rule out the possibility of reversible CO
loss in this transformation. The exclusive formation of the cis-
difluorovinyl group is consistent with the stability gained in this
cis geometry through hyperconjugation,83,86 although it is
surprising that fluoride-ion loss has not occurred from the
“CHF” end of the olefin.
ii. 1,1-Difluoroethylene Activation. Although, as noted
earlier, no intermediates are observed in the reaction of 1 with
1,1-difluoroethylene, the formation of two of the products
(isomers 5a and 5b; see Scheme 2) is reminiscent of compound
10, in which 2 equiv of the fluoroolefin has been incorporated.
It is tempting, therefore, to rationalize the formation of 5a and
the vacant site on the unsaturated metal adjacent to the “CHF”
end of the olefin increases its acidity, allowing protonation of
the nearby fluorine substituent, much as observed in a previous
study on trifluoroethylene.68 Water-assisted fluoride-ion
abstraction involving the α-fluorines of fluoroalkyl groups has
been well documented by Hughes and co-workers.29,54,84,85
Subsequent deprotonation of the acidic Ir−H in the dicationic
intermediate can then give rise to oxidative addition of the
1391
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
5b as occurring in a sequence paralleling that shown for 10 in
Scheme 9, whereby fluorovinyl-group formation occurred as the
last step. However, we feel that this is unlikely, because we have
previously shown that fluoroolefins are more susceptible to
fluoride-ion loss when bridging than when terminally bound.
Consistent with this idea, activation of the bridging trifluoro-
ethylene ligand in 7 first occurs to give the trifluoroethylidene-
bridged product (9), which subsequently reacts with the second
equivalent of the olefin at a slower rate. Although we have no
data to support our proposal beyond the acceleration of the
reaction by water, we propose water-promoted fluoride-ion loss
from a 1,1-difluoroethylene-bridged intermediate, followed by
deprotonation of the hydrido ligand to yield a 1-fluorovinyl
complex, which subsequently coordinates the additional
difluoroethylene ligand. Consistent with the idea that the
second difluoroethylene ligand in 5a and 5b coordinates after
conversion of the first to the fluorovinyl group, warming a
mixture of these isomers to above 0 °C results in loss of the
fluoroolefin, confirming that it is weakly bound. Fluoroolefin
loss is accompanied by removal of the remaining fluorine
substituent on the fluorovinyl group, yielding the two
incompletely characterized vinylidene products (6a, 6b) as
described earlier. This is the only example in this study in which
sequential activation of a pair of geminal C−F bonds occurs; for
the more highly substituted fluoroolefins (C2F3H and C2F4),
their stronger C−F bonds presumably inhibit loss of a second
fluoride.27,82,83 In any case, for the trifluoroethylene adducts
(7a and 7b), the geminal C−F/C−H activation is more
favorable. We have previously observed geminal C−F activation
in tri- and tetrafluoroethylene;68,69 however, fluoride-ion
removal in these cases required the very strong fluorophile,
Me3Si+ (as the triflate salt).
Possibly the most fascinating transformation in the chemistry
reported herein is the complete loss of both equivalents of HF
from the presumed 1,1-difluoroethylene adduct of 1 to yield the
acetylide-bridged product [Ir2(CO)3(μ-CCH)(depm)2]+
(4). As noted earlier, this reactivity parallels that of the
dppm-bridged species, [Ir2(CH3)(CO)2(μ-C2F2H2)(dppm)2]+,
which, in the presence of CO, slowly yielded the propynyl-
bridged product [Ir(CO)3(μ-CCCH3)(dppm)2]+, again by
loss of both equivalents of HF.69 In this previous case, the
source of the propynyl methyl group was clearly the methyl
ligand in the precursor. However, in the present case, neither
the source of the acetylide hydrogen nor the role of the hydrido
ligand in the precursor could be ascertained, owing to facile H/
D scrambling. How the loss of both equivalents of HF occurs
remains a mystery. We considered the possibility that loss of a
second fluoride ion could be catalyzed by HF generated in the
first abstraction, as has already been shown by Caulton and co-
workers;22 however, the addition of triethylamine, in attempts
to trap the HF produced, has no effect on the product
distribution shown in Scheme 2.
As with all previous olefin adducts in this study, fluoride-ion
removal from the tetrafluoroethylene-bridged 11 is accelerated
by the addition of water. The failure of a related C2F4-bridged
complex of dppm, namely, [Ir2(CH3)(CO)2(μ-C2F4)-
(dppm)2]+, to react with water is certainly a further reflection
of the influence of the more basic depm ligand on the reactivity.
However, the absence of a vacant site on the saturated metals in
11, which does not allow coordination of water, combined with
the accompanying loss of the hydrido ligand, suggests a possible
role of this ligand in the overall dehydrofluorination of 11, in
which water could be simultaneously involved in hydrogen
bonding with a fluorine substituent and the hydrido ligand, as
shown in Chart 1, leading to loss of HF. Therefore, although
Chart 1
the hydrido ligand is not directly involved in fluoride-ion
abstraction from the fluoroolefin, this proposed hydrogen-
bonding interaction should increase water’s acidity, promoting
HF loss.
iv. Vinyl Fluoride Activation. Finally, the fluoroolefin
activation, about which we have the least information, involves
vinyl fluoride, for which no olefin adduct is observed. On the
basis of our previous work and the observations discussed
above, we suggest that this olefin also binds in the bridging site
between the metals. As for the trifluoroethylene adduct 7a,
deuterium-labeling studies indicate that the hydrido ligand in
the C−H/C−F activation product originates from the
fluoroolefin, so we suggest a stepwise series of transformations
consisting of HF loss upon protonation by water and H+ loss
from the resulting dicationic hydrido intermediate, followed by
C−H bond activation of the resulting vinyl group by the
adjacent metal, much as outlined in Scheme 8.
In summary, the depm complex [Ir2(CO)3(μ-H)(depm)2]+
has proven to be much more active toward C−F bond
activation than either its dppm analogue or the related species
[Ir2(CH3)(CO)2(dppm)2]+. In all of the chemistry described
herein, water plays a pivotal role, being involved in protonation
of the coordinated fluoroolefin, resulting in subsequent HF loss
and, in one case, in the water-assisted 1,2-fluoride migration in
trifluoroethylene, yielding a bridging 2,2,2-trifluoroethylidene
group. In the two fluoroolefins investigated having a geminal
arrangement of H and F substituents (vinyl fluoride and
trifluoroethylene), activation of both of these bonds occurred in
a stepwise manner in which, as described above, water-assisted
fluoride-ion loss (as HF) is followed by oxidative addition of
the α-C−H bond of the resulting vinyl or 2,2-difluorovinyl
group at the adjacent metal. The hydride ligand in the
precursor complex (1) appears to play no direct role in the
activation processes and, instead, appears to be lost as H+
during the subsequent transformations, replacing the proton
lost by water in protonation of a fluorine substituent.
iii. Tetrafluoroethylene Activation. The sequence,
proposed above, for the reaction of 1 with 1,1-difluoroethylene
finds support in the reactivity of compound 1 with tetrafluoro-
ethylene, in which the tetrafluoroethylene-bridged complex
(11) is initially formed, followed by the subsequent C−F
activation of the bridging unit to produce a trifluorovinyl
complex 12 (refer to Scheme 7). Although there is evidence for
a bridging-tetrafluoroethylene/trifluorovinyl complex (13) that
is analogous to the 1,1-difluoroethylene adducts 5a and 5b, its
origin is uncertain, owing to its low abundance and consequent
incomplete characterization.
D. EXPERIMENTAL SECTION
i. General Comments. All solvents were dried (using appropriate
drying agents), distilled before use, and stored under dinitrogen.
1392
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
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 under argon using
standard Schlenk techniques, and compounds that were obtained as
solids were purified by recrystallization. Prepurified argon and nitrogen
were purchased from Praxair, carbon-13-enriched CO (99%) was
supplied by Isotec Inc., vinyl fluoride and 1,1-difluoroethylene were
supplied by Aldrich, and trifluoroethylene and tetrafluoroethylene
were supplied by SynQuest Fluorochemicals. All purchased gases were
used as received. All other reagents were obtained from Aldrich and
were used as received (unless otherwise stated). Compound 1 was
prepared as described.73 Trimethylamine-N-oxide dihydrate was dried
by azeotropic distillation as described in literature.87 All other reagents
were obtained from Aldrich and were used as received (unless
otherwise stated).
b. Reaction of Compound 1 with 1,1-Difluoroethylene. An NMR
tube charged with compound 1 (84 mg, 0.049 mmol) was dissolved in
0.8 mL of CD2Cl2 and cooled to −80 °C via a dry ice/acetone bath.
1,1-Difluoroethylene (5 mL, 0.219 mmol) was added via a gastight
syringe, and the reaction was monitored by variable-temperature,
multinuclear NMR spectroscopy. Leaving the mixture at −10 °C for 5
h resulted in the mixture of [Ir2(CO)3(μ-κ1:η2-CCH)(depm)2]-
[BArF ] (4), and two isomers of [Ir2(κ1-C(F)CH2)(CO)3(μ-
4
C2F2H2)(depm)2][BArF ] (5a and 5b) in a 1:2:1 ratio, respectively.
4
Warming both 5a and 5b to 27 °C resulted in the conversion to
[Ir2(OH)(CO)3(μ-CCH2)(depm)2][BArF ] (6a), and leaving the
4
mixture at this temperature for 12 h converts 6a to a second
vinylidene-bridged product (6b). Attempts to isolate any product prior
to the formation of 6b were unsuccessful due to the high solubility in
polar and nonpolar solvents. (76% yield of compound 6b).
1
Proton NMR spectra were recorded on Varian Unity 400 or 500
spectrometers, or on a Bruker AM400 spectrometer. Carbon-13 NMR
spectra were recorded on Varian Unity 400 or 500 or Bruker AM300
spectrometers. Phosphorus-31 and fluorine-19 NMR spectra were
recorded on Varian Unity 400 or 500 or Bruker AM400 spectrometers.
Compound 4: H NMR (498 MHz, CD2Cl2, 27 °C): δ 5.04 (s,
1H,−CCH), 1.99 (m, 2H, depm), 1.72 (m, 2H, depm). 13C{1H}
NMR (125 MHz, CD2Cl2, 27 °C): δ 181.6 (quin, 3C, 2JCP = 5.6 Hz).
31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ −6.1 (s, 4P). HRMS m/
z calcd for [193Ir]2P4O3C23H45 [M*]+: 879.1586. Found: 879.1572.
Compound 5a: 1H NMR (400 MHz, CD2Cl2, −10 °C): δ 5.55 (d,
1
Two-dimensional NMR experiments (COSY, NOESY and H−13C
3
3
HMQC) were obtained on Varian Unity 400 or 500 spectrometers. All
ethyl resonances corresponding to depm appeared as expected in the
1H NMR spectrum (δ 1.00−2.50) with the appropriate integrations. In
1H, JHFcis = 28.1 Hz, C(F)CHH), 4.45 (d, 1H, JHFtrans = 62.1 Hz,
C(F)CHH), 3.38 (m, 2H, depm), 2.49 (m, 2H, depm), 1.58 (m,
3
2H, JHF = 21.1 Hz, μ-C2H2F2). 13C{1H} NMR (101 MHz, CD2Cl2,
3
cases when these resonances interfered with relevant ligand resonances
that were important for compound characterization, depm-D20 was
used.88,89
−10 °C): δ 177.1 (m, 1C, JCF = 17.7 Hz), 174.6 (bs, 1C), 151.6 (bs,
1C). 19F NMR (376 MHz, CD2Cl2, −10 °C): δ −28.6 (m, 2F), −53.4
(dd, 1F, JHFtrans = 62.1 Hz, JHFcis = 28.1 Hz). 31P{1H} NMR (162
3
3
2
a. Preparation of Compounds. Reaction of Compound 1
with Vinylfluoride. Method i: To an NMR tube charged with
compound 1 (54 mg, 0.031 mmol) was added 0.8 mL of
CD2Cl2, resulting in a clear, orange solution. Vinylfluoride gas
was then added via a gastight syringe (5 mL, 0.219 mmol) to
the headspace, and the tube was mixed vigorously. After 30
min, NMR spectroscopy showed complete conversion to a
MHz, CD2Cl2, −10 °C): δ −23.1 (bm, 2P), −26.9 (t, 2P, JPP = 38.5
Hz).
Compound 5b: 1H NMR (400 MHz, CD2Cl2, −10 °C): δ 5.01 (d,
3
3
1H, JHFcis = 29.8 Hz, C(F)CHH), 3.77 (d, 1H, JHFtrans = 64.1 Hz,
C(F)CHH), 3.36 (m, 2H, depm), 2.48 (m, 2H, depm), 1.31 (m,
2H, JHF = 21.2 Hz, μ-C2F2H2). 13C{1H} NMR (101 MHz, CD2Cl2,
3
3
−10 °C): δ 177.6 (m, 1C, JCF = 16.3 Hz), 174.6 (bs, 1C), 151.5 (bs,
mixture of [Ir2(H)(CO)3(μ-CCH2)(depm)2][BArF ] (2) and
1C). 19F NMR (376 MHz, CD2Cl2, −10 °C): δ −14.6 (dd, 1F, 3JHFtrans
4
[Ir2(H)2(CO)2(μ-H)(μ-CCHF)(depm)2][BArF ] (3) in a
= 64.1 Hz, JHFcis = 29.8 Hz), −28.6 (m, 2F). 31P{1H} NMR (162
3
4
2
20:1 ratio. The solution was transferred to a Schlenk tube,
and the solvent was removed under vacuum. The mixture was
redissolved in 2 mL of diethyl ether, and 25 mL of pentane was
added to induce precipitation of a yellow solid. (94% yield of
compound 2). Method ii: A round-bottom flask containing
compound 1 (78 mg, 0.045 mmol) dissolved in 10 mL of
CH2Cl2 was cooled to −80 °C via a dry ice/acetone bath. In a
separate round-bottom flask, trimethylamine-N-oxide (4 mg,
0.053 mmol) was dissolved in 5 mL of CH2Cl2 and cooled to
−80 °C. The TMNO solution was transferred, via a cannula, to
the solution of 1, followed by the addition of vinyl fluoride via a
gastight syringe (10 mL, 0.438 mmol). The solution was slowly
warmed to ambient temperature and left to stir for 1 h. The
solvent was then removed, leaving a yellow/orange residue.
NMR of the residue revealed exclusive formation of compound
3. Attempts to recrystallize the mixture were unsuccessful due
to the high solubility of the product (83% yield of compound
3).
MHz, CD2Cl2, −10 °C): δ −24.2 (bm, 2P), −28.7 (t, 2P, JPP = 38.5
Hz).
1
Compound 6a: H NMR (498 MHz, CD2Cl2, 27 °C): δ 6.32 (d,
2
2
1H, JHH = 3.8 Hz, −CCHH), 5.81 (d, 1H, JHH = 3.8 Hz, −C
CHH), 2.89 (m, 2H, depm), 1.95 (m, 2H, depm). 13C{1H} NMR
(125 MHz, CD2Cl2, 27 °C): δ 180.0 (t, 1C, 3JCP = 10.2 Hz), 172.1 (b,
1C), 157.7 (b, 1C). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ
−19.3 (bs, 4P).
1
Compound 6b: H NMR (498 MHz, CD2Cl2, 27 °C): δ 6.05 (d,
2
2
1H, JHH = 4.6 Hz, −CCHH), 6.00 (d, 1H, JHH = 4.6 Hz, −C
CHH), 2.91 (m, 2H, depm), 2.54 (m, 2H, depm). 13C{1H} NMR
(125 MHz, CD2Cl2, 27 °C): δ 174.0 (m, 1C), 170.9 (m, 1C), 164.1
(m, 1C). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ −14.7 (t, 2P,
2JPP = 35.5 Hz), −21.8 (t, 2P, JPP = 35.5 Hz).
2
c. Reaction of Compound 1 with Trifluoroethylene. In an NMR
tube containing compound 1 (64 mg, 0.037 mmol) dissolved in 0.8
mL of CD2Cl2, cooled to −80 °C in a dry ice/acetone bath, was added
trifluoroethylene (5 mL, 0.219 mmol) via a gastight syringe. The
mixture was monitored by variable-temperature, multinuclear NMR
spectroscopy. Keeping the mixture at −30 °C for 2 h resulted in the
Compound 2: 1H NMR (498 MHz, CD2Cl2, 27 °C): δ 6.33 (s, 1H,
μ-CCH2), 6.29 (s, 1H, μ-CCH2), 2.71 (m, 2H, depm), 2.09 (m,
2H, depm), −11.95 (t, 1H, 2JHP = 16.2 Hz, Ir-H). 13C{1H} NMR (125
formation of [Ir2(H)(CO)3(μ-CFHCF2)(depm)2][BArF ] (7a) and
4
2
[Ir2(H)(CO)3(μ-CF2CHF)(depm)2][BArF ] (7b) in a 1:1 ratio.
MHz, CD2Cl2, 27 °C): δ 179.3 (t, 1C, JCP = 7.6 Hz), 179.0 (t, 1C,
4
2
2JCP = 9.2 Hz), 164.8 (t, 1C, JCP = 11.5 Hz). 31P{1H} NMR (202
Warming to −20 °C shows the conversion of 7a to a 1:1 mixture of
2
[Ir2(H)(CO)3(μ-CCF2)(depm)2][BArF ] (8) and [Ir2(H)(CO)3(μ-
MHz, CD2Cl2, 27 °C): δ −8.1 (t, 2P, JPP = 34.3 Hz), −16.9 (t, 2P,
4
2JPP = 34.3 Hz). Elemental analysis calcd (%) for Ir2P4F24O3C55H59
(1743.2): C, 37.90; H, 3.41. Found: C, 38.06; H, 3.68.
CHCF3)(depm)2][BArF ] (9), while warming to −15 °C leads to the
4
conversion of 7b to compounds 8 and 9, again in a 1:1 ratio. Leaving
the mixture of 8 and 9 overnight under an atmosphere of
trifluoroethylene at ambient temperature leads to the conversion of
Compound 3: 1H NMR (498 MHz, CD2Cl2, 27 °C): δ 6.61 (d, 1H,
2JHF = 108.2 Hz, μ-CCHF), 2.77 (m, 2H, depm), 1.67 (m, 2H,
depm), −12.54 (m, 1H, Ir-H), −13.09 (m, 1H, Ir-H), −15.48 (m, 1H,
9 to [Ir2(κ1-C(F)CFH)(CO)3(μ-CHCF3)(depm)2][BArF ] (10),
4
Ir-H-Ir). 13C{1H} NMR (125 MHz, CD2Cl2, 27 °C): δ 171.1 (bm,
with compound 8 remaining in solution. The mixture was transferred
to a Schlenk tube and the solvent was removed under vacuum, giving a
yellow resin. The resin was redissolved in 2 mL of diethyl ether, and 25
mL of pentane was added to induce precipitation of a yellow solid. The
2
2C). 19F NMR (469 MHz, CD2Cl2, 27 °C): δ −72.1 (d, 1F, JHF
=
108.2 Hz). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ −7.1 (m,
2P), −9.1 (m, 2P).
1393
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
solid was further washed with 2 × 10 mL of pentane and dried to
produce a fine, yellow solid (73% yield of compound 8).
17.3 Hz, 3JFP = 13.4 Hz). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ
2
2
−15.0 (bt, 2P, JPP = 48.1 Hz), −21.9 (bt, 2P, JPP = 48.1 Hz).
1
Compound 7a: 1H NMR (400 MHz, CD2Cl2, −30 °C): δ 5.50 (bd,
Compound 12: H NMR (498 MHz, CD2Cl2, 27 °C): δ 2.96 (m,
4H, depm). 13C{1H} NMR (125 MHz, CD2Cl2, 27 °C): δ 185.6 (t,
1H, 2JHFgem = 65.6 Hz, μ-CF2CFH), 4.07 (m, 1H, depm), 3.72 (m, 1H,
2
2
2C, JCP = 13.3 Hz), 185.2 (bt, 1C, JCP = 10.4 Hz). 19F NMR (498
depm), 2.03 (m, 1H, depm), 1.71 (m, 1H, depm), −8.77 (t, 1H, 2JHP
=
2
3
12.9 Hz, Ir-H). 13C{1H} NMR (101 MHz, CD2Cl2, −30 °C): δ 188.1
(dm, 1C, 2JCC = 42.9 Hz), 183.7 (bd, 1C, 3JCF = 15.8 Hz), 182.2 (dm,
MHz, CD2Cl2, 27 °C): δ −93.8 (dd, 1F, JFF = 93.0 Hz, JFFcis = 39.7
Hz), −123.9 (dd, 1F, 3JFFtrans = 111.6 Hz, 2JFF = 93.0 Hz), −136.1 (dd,
3JFFtrans = 111.6 Hz, JFFcis = 39.7 Hz). 31P{1H} NMR (202 MHz,
3
2
1C, JCC = 42.9 Hz). 19F NMR (376 MHz, CD2Cl2, −30 °C): δ
CD2Cl2, 27 °C): δ −17.4 (t, 2P, 2JPP = 24.9 Hz), −20.5 (bt, 2P, 2JPP
=
−108.7 (dd, 1F, 2JFFgem = 198.3 Hz, 3JFFtrans = 46.9 Hz), −118.7 (d, 1F,
2JFFgem = 198.3 Hz), −195.9 (dd, 1F, 2JFHgem = 65.6 Hz, 3JFFtrans = 46.9
Hz). 31P{1H} NMR (162 MHz, CD2Cl2, −30 °C): δ −13.8 (bm, 2P),
−15.9 (bm, 2P).
24.9 Hz).
Compound 13: 19F NMR (498 MHz, CD2Cl2, 27 °C): δ −76.3 (bs,
2F), −80.4 (bs, 2F), −94.3 (dd, 1F, 2JFF2 = 92.9 Hz, 3JFFcis = 33.4 Hz),
3
Compound 7b: 1H NMR (400 MHz, CD2Cl2, −30 °C): δ 5.13 (bd,
−121.3 (dd, 1F, JFF3trans = 110.8 Hz, JFF = 92.9 Hz), −132.4 (dd,
3JFFtrans = 110.8 Hz, JFFcis = 33.4 Hz).
1H, 2JHFgem = 64.5 Hz, μ-CHFCF2), 4.20 (m, 1H, depm), 3.68 (m, 1H,
depm), 1.95 (m, 1H, depm), 1.86 (m, 1H, depm), −8.42 (t, 1H, 2JHP
=
a. X-ray Structure Determinations. General. Crystals were
grown via slow diffusion of n-pentane into a diethyl ether
solution of the compound. Data were collected using a Bruker
APEX II CCD detector/D8 diffractometer90 with the crystals
cooled to −100 °C; all data were collected using Mo Kα
radiation (λ = 0.71073 Å). The data were corrected for
absorption through Gaussian integration from indexing of the
crystal faces. Structures were solved using Patterson search/
structure expansion (DIRDIF-200891 for 2) or direct methods
(SHELXS-9792 for 8). Refinements were completed using the
program SHELXL-97.92 Nonhydridic hydrogen atoms were
assigned positions based on the sp2 or sp3 hybridization
geometries of their attached carbon atoms and were given
isotropic displacement parameters 20% greater than those of
their parent atoms. See the Supporting Information for a listing
of crystallographic experimental data.
i. Special Refinement Conditions. 2. The Ir(1)−H(1) distance
was constrained to be 1.55(1) Å during refinement. F−C
distances within two disordered trifluoromethyl groups (of the
[B{C6H3-3.5-(CF3)2}4]− ion) were constrained to be equal
(within 0.03 Å) to a common value during refinement:
d(F(71A)−C(77)) = d(F(72A)−C(77)) = d(F(73A)−C(77))
= d(F(71B)−C(77)) = d(F(72B)−C(77)) = d(F(73B)−
C(77)) = d(F(74A)−C(78)) = d(F(75A)−C(78)) = d(F-
(76A)−C(78)) = d(F(74B)−C(78)) = d(F(75B)−C(78)) =
d(F(76B)−C(78)).
12.7 Hz, Ir-H). 13C{1H} NMR (101 MHz, CD2Cl2, −30 °C): δ 187.6
(dm, 1C, 2JCC = 41.8 Hz), 185.8 (dm, 1C, 2JCC = 41.8 Hz), 182.3 (bt,
1C, 3JCF = 12.4 Hz). 19F NMR (376 MHz, CD2Cl2, −30 °C): δ −93.5
(dd, 1F, 2JFFgem = 155.3 Hz, 3JFF2trans = 49.7 Hz), −104.3 (d, 1F, 2JFFgem
3
= 155.3 Hz), −216.5 (dd, 1F, JFHgem = 64.5 Hz, JFFtrans = 49.7 Hz).
31P{1H} NMR (162 MHz, CD2Cl2, −30 °C): δ −13.1 (bm, 1P), −14.6
(bm, 1P), −15.9 (bm, 2P).
1
Compound 8: H NMR (498 MHz, CD2Cl2, 27 °C): δ 2.67 (m,
2H, depm), 1.95 (m, 2H, depm), −12.46 (td, 1H, 2JHP = 15.7 Hz, 4JHF
= 7.7 Hz, Ir-H). 13C{1H} NMR (125 MHz, CD2Cl2, 27 °C): δ 177.2
(bm, 1C), 169.4 (bm, 1C), 159.7 (bm, 1C). 19F NMR (469 MHz,
CD2Cl2, 27 °C): δ −68.4 (d, 1F, 2JFF = 98.6 Hz), −77.2 (d, 1F, 2JFF
=
98.6 Hz). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ −6.7 (t, 2P,
2
2JPP = 28.5 Hz), −16.2 (t, 2P, JPP = 28.5 Hz). HRMS m/z calcd for
[
193Ir]2P4O3C23H451F2 [M*]+: 917.1540. Found: 917.1543.
Compound 9: H NMR (498 MHz, CD2Cl2, 27 °C): δ 4.94 (m,
3
1H, JHF = 17.0 Hz, −C(H)CF3), 2.53 (m, 1H, depm), 2.51 (m, 1H,
depm), 1.95 (m, 1H, depm), 1.91 (m, 1H, depm), −10.52 (bm, 1H, Ir-
H). 13C{1H} NMR (125 MHz, CD2Cl2, 27 °C): δ 177.3 (m, 1C),
176.8 (m, 1C), 159.3 (m, 1C). 19F NMR (469 MHz, CD2Cl2, 27 °C):
δ −46.4 (d, 3F, JFH = 17.0 Hz). 31P{1H} NMR (202 MHz, CD2Cl2,
3
2
2
27 °C): δ −11.0 (dm, 1P, JPP = 351.9 Hz), −17.9 (dm, 1P, JPP
=
=
2
2
351.9 Hz), −18.0 (dm, 1P, JPP = 302.9 Hz), −31.2 (dm, 1P, JPP
302.9 Hz).
1
ii. 8. The Ir(2)−H(1) distance was fixed at 1.79 Å during
refinement. The C−F and F···F distances within the disordered CF3
groups (centered by carbon atoms C(58A), C(58B), and C(87)) of
the anion were restrained to be 1.35(1) and 2.20(1) Å, respectively.
Additionally, the C(43A)−C(44A) distance was restrained to be
1.50(1) Å.
Compound 10: H NMR (498 MHz, CD2Cl2, 27 °C): δ 5.75 (dd,
1H, 2JHF = 81.6 Hz, 3JHF = 24.1 Hz, −C(F)CFH), 4.89 (m, 1H, 3JHF
= 17.4 Hz, −C(H)CF3), 3.23 (m, 1H, depm), 3.11 (m, 1H, depm),
2.95 (m, 1H, depm), 2.14 (m, 1H, depm). 13C{1H} NMR (125 MHz,
CD2Cl2, 27 °C): δ 174.7 (m, 1C), 165.3 (m, 1C), 157.1 (m, 1C). 19F
3
NMR (469 MHz, CD2Cl2, 27 °C): δ −47.1 (d, 3F, JFH = 17.4 Hz),
3
2
−84.6 (d, 1F, JFH = 24.1 Hz), −138.1 (dm, 1F, JFH = 81.6 Hz).
31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δ −18.8 (dm, 1P, JPP
=
=
2
ASSOCIATED CONTENT
* Supporting Information
■
2
2
S
356.2 Hz), −22.5 (dm, 1P, JPP = 285.7 Hz), −28.7 (dm, 1P, JPP
2
356.2 Hz), −32.3 (dm, 1P, JPP = 285.7 Hz). HRMS m/z calcd for
Tables of crystallographic experimental details for 2 and 8;
ORTEP diagrams for the complex cation of 8, showing the
disorder in the depm groups; and atomic coordinates,
interatomic distances and angles, anisotropic thermal parame-
ters, and hydrogen parameters for 2 and 8 in a CIF file. This
material is available free of charge via the Internet at http://
pubs.acs.org.
[
193Ir]2P4O3C25H46F5 [M*]+: 999.1571. Found: 999.1571.
d. Reaction of Compound 1 with Tetrafluoroethylene. In an
NMR tube containing compound 1 (91 mg, 0.053 mmol) dissolved in
0.8 mL of CD2Cl2 was added tetrafluoroethylene (5 mL, 0.219 mmol)
via a gastight syringe. The solution was mixed and left at 0 °C for 1 h.
The reaction was verified by multinuclear NMR spectroscopy,
confirming the formation of [Ir2(H)(CO)3(μ-CF2CF2)(depm)2]-
[BArF ] (11) (63% yield). Leaving the mixture at ambient temperature
4
AUTHOR INFORMATION
Corresponding Author
*E-mail: martin.cowie@ualberta.ca. Fax: 01 7804928231. Tel:
01 7804925581.
■
for 5 h results in the formation of minor amounts of [Ir2(C(F)
CF2)(CO)3(depm)2][BArF ] (12) (22% yield) and [Ir2(C(F)
4
CF2)(CO)3(μ-CF2CF2)(depm)2][BArF ] (13) (<5% yield), as
4
observed in the 19F NMR spectrum. Leaving the mixture for longer
periods of time (2 days) or heating to 40 °C results in the
decomposition to numerous unidentified products.
Notes
The authors declare no competing financial interest.
1
Compound 11: H NMR (498 MHz, CD2Cl2, 27 °C): δ 3.28 (m,
2H, depm), 2.86 (m, 2H, depm), −12.63 (tt, 1H, 2JHP = 17.3 Hz, 3JHF
= 17.3 Hz, Ir-H). 13C{1H} NMR (125 MHz, CD2Cl2, 27 °C): δ 174.4
(bm, 1C), 164.6 (bm, 1C), 153.9 (bm, 1C). 19F NMR (469 MHz,
ACKNOWLEDGMENTS
We thank the Natural Sciences and Engineering Research
Council of Canada (NSERC) and the University of Alberta for
■
CD2Cl2, 27 °C): δ −74.4 (t, 2F, 3JFP = 17.0 Hz), −80.7 (dt, 2F, 2JFH
=
1394
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
(33) Young, R. J.; Grushin, V. V. Organometallics 1999, 18, 294.
financial support for this research and NSERC for funding the
Bruker D8/APEX II CCD diffractometer. We thank the
Chemistry Department’s NMR Spectroscopy and Analytical
and Instrumentation Laboratories. Finally, we thank NSERC
and Alberta Innovates−Technology (formerly Alberta Ingen-
uity Fund) for scholarships to M.E.S.
(34) Braun, T.; Wehmeier, F.; Altenhoner, K. Angew. Chem., Int. Ed.
̈
2007, 46, 5321.
(35) Jager-Fiedler, U.; Klahn, M.; Arndt, P.; Baumann, W.;
̈
Spannenberg, A.; Burlakov, V. V.; Rosenthal, U. J. Mol. Catal. A:
Chem. 2007, 261, 184.
(36) Edelbach, B. L.; Jones, W. D. J. Am. Chem. Soc. 1997, 119, 7734.
(37) Schaub, T.; Backes, M.; Radius, U. J. Am. Chem. Soc. 2006, 128,
15964.
(38) Camadanli, S.; Beck, R.; Florke, U.; Klein, H. F. Dalton Trans.
2008, 5701.
(39) Nova, A.; Erhardt, S.; Jasim, N. A.; Perutz, R. N.; Macgregor, S.
A.; McGrady, J. E.; Whitwood, A. C. J. Am. Chem. Soc. 2008, 130,
15499.
(40) Buckley, H. L.; Wang, T. E.; Tran, O.; Love, J. A.
Organometallics 2009, 28, 2356.
REFERENCES
■
(1) Wallington, T. J.; Schneider, W. F.; Worsnop, D. R.; Nielsen, O.
J.; Sehested, J.; Debruyn, W. J.; Shorter, J. A. Environ. Sci. Technol.
1994, 28, A320.
(2) Metz, B., Kuijpers, L., Solomon, S., Andersen, S. O., Davidson,
O., Pons, J., de Jager, D., Kestin, T., Manning, M., Meyer, L., Eds.
Safeguarding the Ozone Layer and the Global Climate System: Issues
Related to Hydrofluorocarbons and Perfluorocarbons; Cambridge
University Press: Cambridge, U.K., 2005.
(3) Giesy, J. P.; Kannan, K. Environ. Sci. Technol. 2002, 36, 146A.
(4) Kennedy, G. L.; Butenhoff, J. L.; Olsen, G. W.; O’Connor, J. C.;
Seacat, A. M.; Perkins, R. G.; Biegel, L. B.; Murphy, S. R.; Farrar, D. G.
Crit. Rev. Toxicol. 2004, 34, 351.
(5) Sweetman, A. J.; Paul, A. G.; Jones, K. C. Environ. Sci. Technol.
2009, 43, 386.
(6) Ellis, D. A.; Mabury, S. A.; Martin, J. W.; Muir, D. C. G. Nature
2001, 412, 321.
(7) Narita, T. Polym. J. 2011, 43, 497.
(41) Johnson, S. A.; Taylor, E. T.; Cruise, S. J. Organometallics 2009,
28, 3842.
(42) Reade, S. P.; Mahon, M. F.; Whittlesey, M. K. J. Am. Chem. Soc.
2009, 131, 1847.
(43) Zheng, T. T.; Sun, H. J.; Chen, Y.; Li, X. Y.; Durr, S.; Radius, U.;
Harms, K. Organometallics 2009, 28, 5771.
(44) Clot, E.; Eisenstein, O.; Jasim, N.; Macgregor, S. A.; McGrady, J.
E.; Perutz, T. Acc. Chem. Res. 2011, 44, 333.
(45) Doster, M. E.; Johnson, S. A. Angew. Chem., Int. Ed. 2009, 48,
2185.
(46) Johnson, S. A.; Huff, C. W.; Mustafa, F.; Saliba, M. J. Am. Chem.
Soc. 2008, 130, 17278.
(47) Johnson, S. A.; Mroz, N. M.; Valdizon, R.; Murray, S.
Organometallics 2011, 30, 441.
(48) Bonnet, J. J.; Mathieu, R.; Poilblanc, R.; Ibers, J. A. J. Am. Chem.
Soc. 1979, 101, 7487.
(49) Booth, B. L.; Haszeldine, R. N.; Mitchell, P. R.; Cox, J. J. Chem.
Commun. 1967, 529.
(50) Green, M.; Laguna, A.; Spencer, J. L.; Stone, F. G. A. J. Chem.
Soc., Dalton Trans. 1977, 1010.
(51) Hacker, M. J.; Littlecott, G. W.; Kemmitt, R. D. W. J. Organomet.
Chem. 1973, 47, 189.
(52) Hudlicky, M. J. Fluorine Chem. 1989, 44, 345.
(53) Hughes, R. P.; Laritchev, R. B.; Zakharov, L. N.; Rheingold, A.
L. J. Am. Chem. Soc. 2004, 126, 2308.
(8) Park, B. K.; Kitteringham, N. R.; O’Neill, P. M. Annu. Rev.
Pharmacol. Toxicol. 2001, 41, 443.
(9) Ismail, F. M. D. J. Fluorine Chem. 2002, 118, 27.
(10) Isanbor, C.; O’Hagan, D. J. Fluorine Chem. 2006, 127, 303.
(11) Kirk, K. L. J. Fluorine Chem. 2006, 127, 1013.
(12) O’Hagan, D. J. Fluorine Chem. 2010, 131, 1071.
(13) Key, B. D.; Howell, R. D.; Criddle, C. S. Environ. Sci. Technol.
1997, 31, 2445.
(14) Theodoridis, G. In Advances in Fluorine Science; Alain, T., Ed.;
Elsevier, 2006; Vol. 2, p 121.
(15) Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Chem. Rev.
1994, 94, 373.
(16) Burdeniuc, J.; Jedlicka, B.; Crabtree, R. H. Chem. Ber./Recl.
1997, 130, 145.
(17) Richmond, T. In Activation of Unreactive Bonds and Organic
Synthesis; Murai, S., Alper, H., Gossage, R., Grushin, V., Hidai, M., Ito,
Y., Jones, W., Kakiuchi, F., van Koten, G., Lin, Y. S., Mizobe, Y., Murai,
S., Murakami, M., Richmond, T., Sen, A., Suginome, M., Yamamoto,
A., Eds.; Springer: Berlin, 1999; Vol. 3, p 243.
(18) Kraft, B. M.; Lachicotte, R. J.; Jones, W. D. J. Am. Chem. Soc.
2000, 122, 8559.
(19) Kirkham, M. S.; Mahon, M. F.; Whittlesey, M. K. Chem.
Commun. 2001, 813.
(54) Hughes, R. P.; Rose, P. R.; Rheingold, A. L. Organometallics
1993, 12, 3109.
(55) Jones, M. T.; McDonald, R. N. Organometallics 1988, 7, 1221.
(56) Kemmitt, R. D. W.; Nichols, D. I. J. Chem. Soc. A 1969, 1577.
(57) Kuhnel, M. F.; Lentz, D. Angew. Chem., Int. Ed. 2010, 49, 2933.
(58) Lentz, D.; Kuhnel, M. F. Angew. Chem., Int. Ed. 2010, 49, 2933.
(59) Maples, P. K.; Green, M.; Stone, F. G. A. J. Chem. Soc., Dalton
Trans. 1973, 2069.
(60) Ohashi, M.; Kambara, T.; Hatanaka, T.; Saijo, H.; Doi, R.;
Ogoshi, S. J. Am. Chem. Soc. 2011, 133, 3256.
(61) Peterson, A. A.; McNeill, K. Organometallics 2006, 25, 4938.
(62) Peterson, A. A.; Thoreson, K. A.; McNeill, K. Organometallics
2009, 28, 5982.
(63) Rieth, R. D.; Brennessel, W. W.; Jones, W. D. Eur. J. Inorg. Chem.
2007, 2839.
(20) Braun, T.; Noveski, D.; Neumann, B.; Stammler, H. G. Angew.
Chem., Int. Ed. 2002, 41, 2745.
(21) Kraft, B. M.; Jones, W. D. J. Am. Chem. Soc. 2002, 124, 8681.
(22) Ferrando-Miguel, G.; Gerard, H.; Eisenstein, O.; Caulton, K. G.
Inorg. Chem. 2002, 41, 6440.
(23) Jones, W. D. Dalton Trans. 2003, 3991.
(24) Noveski, D.; Braun, T.; Schulte, M.; Neumann, B.; Stammler, H.
(64) Ristic-Petrovic, D.; Wang, M.; McDonald, R.; Cowie, M.
Organometallics 2002, 21, 5172.
(65) Roundhill, D. M.; Lawson, D. N.; Wilkinson, G. J. Chem. Soc. A
G. Dalton Trans. 2003, 4075.
(25) Renkema, A.; Werner-Zwanziger, U.; Pagel, M. D.; Caulton, K.
G. J. Mol. Catal. A: Chem. 2004, 224, 125.
(26) Torrens, H. Coord. Chem. Rev. 2005, 249, 1957.
(27) Perutz, R. N.; Braun, T. In Comprehensive Organometallic
Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.; Elsevier Science,
2007; Vol. 1, p 725.
1968, 845.
(66) Roundhill, D. M.; Wilkinson, G. J. Chem. Soc. A 1968, 506.
(67) Anderson, D. J.; McDonald, R.; Cowie, M. Angew. Chem., Int.
Ed. 2007, 46, 3741.
(68) Slaney, M. E.; Anderson, D. J.; Ferguson, M. J.; McDonald, R.;
Cowie, M. J. Am. Chem. Soc. 2010, 132, 16544.
(69) Slaney, M. E.; Anderson, D. J.; Ristic-Petrovic, D.; McDonald,
R.; Cowie, M. Chem.Eur. J., in press.
(28) Amii, H.; Uneyama, K. Chem. Rev. 2009, 109, 2119.
(29) Hughes, R. P. Eur. J. Inorg. Chem. 2009, 2009, 4591.
(30) Braun, T.; Salomon, M. A.; Altenhoner, K.; Teltewskoi, M.;
Hinze, S. Angew. Chem., Int. Ed. 2009, 48, 1818.
(31) Aizenberg, M.; Milstein, D. Science 1994, 265, 359.
(32) Aizenberg, M.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 8674.
(70) Soriano, J.; Shamir, J.; Netzer, A.; Marcus, Y. Inorg. Nucl. Chem.
Lett. 1969, 5, 209.
1395
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396

Organometallics
Article
(71) Gouin, L.; Cousseau, J.; Smith, J. A. S. J. Chem. Soc., Faraday
Trans. 1977, 73, 1878.
(72) Giguere, P. A.; Turrell, S. J. Am. Chem. Soc. 1980, 102, 5473.
(73) Slaney, M. E.; Anderson, D. J.; Ferguson, M. J.; McDonald, R.;
Cowie, M. Submitted for publication in Organometallics, Dec 2011.
(74) Cowie, M.; Loeb, S. J. Organometallics 1985, 4, 852.
(75) Deraniyagala, S. P.; Grundy, K. R. Organometallics 1985, 4, 424.
(76) Yam, V. W. W.; Yeung, P. K. Y.; Chan, L. P.; Kwok, W. M.;
Phillips, D. L.; Yu, K. L.; Wong, R. W. K.; Yan, H.; Meng, Q. J.
Organometallics 1998, 17, 2590.
(77) Wong, K. M. C.; Hui, C. K.; Yu, K. L.; Yam, V. W. W. Coord.
Chem. Rev. 2002, 229, 123.
(78) Lam, W. H.; Yam, V. W. W. Inorg. Chem. 2010, 49, 10930.
(79) Wuthrich, K.; Wider, G. Magn. Reson. Chem. 2003, 41, S80.
(80) Ihrig, A. M.; Smith, S. L. J. Am. Chem. Soc. 1970, 94, 34.
(81) Foris, A. Magn. Reson. Chem. 2004, 42, 534.
(82) Shi, J.; He, J. A.; Wang, H. J. J. Phys. Org. Chem. 2011, 24, 65.
(83) O’Hagan, D. Chem. Soc. Rev. 2008, 37, 308.
(84) Hughes, R. P.; Lindner, D. C.; Rheingold, A. L.; LiableSands, L.
M. J. Am. Chem. Soc. 1997, 119, 11544.
(85) Hughes, R. P.; Lindner, D. C.; Smith, J. M.; Zhang, D. H.;
Incarvito, C. D.; Lam, K. C.; Liable-Sands, L. M.; Sommer, R. D.;
Rheingold, A. L. Dalton Trans. 2001, 2270.
(86) Goodman, L.; Gu, H. B.; Pophristic, V. J. Phys. Chem. A 2005,
109, 1223.
(87) Soderquist, J. A.; Anderson, C. L. Tetrahedron Lett. 1986, 27,
3961.
(88) Novikova, Z. S.; Prishchenko, A. A.; Lutsenko, I. F. Zh. Obshch.
Khim. 1977, 47, 775.
(89) Prishchenko, A. A.; Nifantex, N. E.; Novikova, Z. S.; Lutsenko, I.
F. Zh. Obshch. Khim. 1980, 50, 1881.
(90) Programs for diffractometer operation, unit cell indexing, data
collection, data reduction, and absorption correction were those
supplied by Bruker.
(91) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits, J. M. M.;
Garcia-Granda, S.; Gould, R. O. The DIRDIF-2008 Program System;
Crystallography Laboratory, Radboud University Nijmegen: Heyen-
daal, The Netherlands, 2008.
(92) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
1396
dx.doi.org/10.1021/om2011968 | Organometallics 2012, 31, 1384−1396