Catalytic hydrodefluorination of aromatic fluorocarbons by ruthenium N-heterocyclic carbene complexes

Article abstract of DOI:10.1021/ja806545e

The catalytic hydrodefluorination (HDF) of hexafluorobenzene, pentafluorobenzene, and pen- tafluoropyridine with alkylsilanes is catalyzed by the ruthenium N-heterocyclic carbene (NHC) complexes Ru(NHC)(PPh ₃)2(CO)H₂ (NHC = SIMes (1,3-bis(2,4,6-trimethylphenyl) imidazolin-2-ylidene) 13, SIPr (1,3- bis(2,6-diisopropylphenyl)imidazolin-2- ylidene) 14, IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) 15, IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) 16). Catalytic activity follows the order 15 > 13 > 16 > 14, with 15 able to catalyze the HDF of C₆F₅H with Et₃SiH with a turnover number of up to 200 and a turnover frequency of up to 0.86 h^-1. The catalytic reactions reveal (i) a novel selectivity for substitution at the 2-position in C₆F₅H and C₅F₅N, (ii) formation of deuterated fluoroarene products when reactions are performed in C ₆D_6, or C₆D₅CD₃, and (iii) a first-order dependence on [fluoroarene] and zero-order relationship with respect to [R₃SiH]. Mechanisms are proposed for HDF of C ₆F₆ and C₆F₅H, the principal difference being that the latter occurs by initial C-H rather than C-F activation.

Full text of DOI:10.1021/ja806545e

Published on Web 01/21/2009
Catalytic Hydrodefluorination of Aromatic Fluorocarbons by
Ruthenium N-Heterocyclic Carbene Complexes
Steven P. Reade, Mary F. Mahon, and Michael K. Whittlesey*
Department of Chemistry, UniVersity of Bath, ClaVerton Down, Bath BA2 7AY, U.K.
Received August 18, 2008; E-mail: chsmkw@bath.ac.uk
Abstract: The catalytic hydrodefluorination (HDF) of hexafluorobenzene, pentafluorobenzene, and pen-
tafluoropyridine with alkylsilanes is catalyzed by the ruthenium N-heterocyclic carbene (NHC) complexes
Ru(NHC)(PPh ) (CO)H (NHC ) SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) 13, SIPr (1,3-
3 2 2
bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) 14, IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) 15,
IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) 16). Catalytic activity follows the order 15 > 13 >
1
6 > 14, with 15 able to catalyze the HDF of C
6
F
5
H with Et
a turnover frequency of up to 0.86 h . The catalytic reactions reveal (i) a novel selectivity for substitution
at the 2-position in C H and C N, (ii) formation of deuterated fluoroarene products when reactions are
performed in C or C CD , and (iii) a first-order dependence on [fluoroarene] and zero-order relationship
with respect to [R SiH]. Mechanisms are proposed for HDF of C and C H, the principal difference
being that the latter occurs by initial C-H rather than C-F activation.
3
SiH with a turnover number of up to 200 and
-
1
F
6 5
5 5
F
D
6 6
D
6 5
3
3
F
6 6
6 5
F
Introduction
6 6
Aizenberg reported that hydrodefluorination (HDF) of C F and
C
6
F
5
H in the presence of R′
3
SiH (R′ ) Ph, OEt) was catalyzed
The activation and functionalization of fluorocarbons represents
by the Rh-silyl complex Rh(PMe
SiPhMe2). A year later, the same group showed that the
pentafluorophenyl complex Rh(PMe ) (C F ) would also per-
form catalytic HDF in the presence of H2. In both cases, the
driving force for reaction involves the formation of a strong
element-fluoride (E-F) bond, either R Si-F or HF, as sum-
marized in Scheme 1a.
More recently, Holland and co-workers have reported the use
of a ꢀ-diketiminate iron(II) fluoride species to catalyze HDF of
perfluoroaromatics, as well as perfluoroalkenes, also in the
3
)
3
(SiR ) (SiR ) SiPh ,
3
3
3
a significant challenge due to the great strength of the C-F
2
0
1,2
interaction. While there has been considerable progress in the
3
-10
8,11-13
3
3
6 5
stoichiometric cleavage of fluoroarenes,
fluoroalkenes,
2
1
8,14,15
and even fluoroalkanes,
C-F bonds remain relatively scarce.
metal catalyzed transformations of
1
6-19
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3
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10.1021/ja806545e CCC: $40.75

2009 American Chemical Society
J. AM. CHEM. SOC. 2009, 131, 1847–1861 9 1847

A R T I C L E S
Reade et al.
Scheme 1
Scheme 2
2
2
presence of silanes as the reductant (Scheme 1b). Intriguingly,
and in contrast to the rhodium chemistry, the iron hydride
absence of silane, a factor which has prevented the mechanism
of catalysis being fully elucidated. In practical terms, both the
Rh and Fe systems suffer disadvantages, in the need for either
forcing conditions (Rh(PMe ) (C F ) required the presence of
species furnished by reaction of the iron fluoride with R
showed no evidence for direct C-F bond activation in the
3
SiH
3
3
6 5
2 3
ca. 6 atm of H and 10 equiv of Et N (as a trap for released
(
17) (a) Ishii, Y.; Chatani, N.; Yorimitsu, S.; Murai, S. Chem. Lett. 1998,
HF) at 373 K) or high catalyst loadings (20 mol% in the case
of the Fe system). Both of these factors, along with higher
catalytic activity, need to be addressed if more viable catalytic
C-F functionalization is to be realized.
We recently reported the synthesis and reactivity of a series
of N-heterocyclic carbene (NHC) ruthenium fluoride complexes
1
57–158. (b) Young, R. J., Jr.; Grushin, V. V. Organometallics 1999,
1
8, 294–296. (c) B o¨ hm, V. P. W.; Weskamp, T.; Gst o¨ ttmayr, C. W. K.;
Herrmann, W. A. Angew. Chem., Int. Ed. 2001, 40, 3387–3389. (d)
Braun, T.; Perutz, R. N.; Sladek, M. I. Chem. Commun. 2001, 2254–
2
255. (e) Desmarets, C.; Kuhl, S.; Schneider, R.; Fort, Y. Organo-
metallics 2002, 21, 1554–1559. (f) Kuhl, S.; Schneider, R.; Fort, Y.
AdV. Synth. Catal. 2003, 345, 341–344. (g) Renkema, K. B.; Werner-
Zwanziger, U.; Pagel, M. D.; Caulton, K. G. J. Mol. Catal. A: Chem.
Ru(NHC)(PPh
3 2
) (CO)HF containing the N-alkyl substituted
2004, 224, 125–131. (h) Fuchibe, K.; Akiyama, T. J. Am. Chem. Soc.
2006, 128, 1434–1435. (i) Peterson, A. A.; McNeil, K. Organome-
i
NHCs IMe , IEt Me , ICy, and I Pr Me (complexes 1-4,
4
2
2 2 2 2
3
tallics 2006, 25, 4938–4940. (j) Braun, T.; Wehmeier, F.; Altenh o¨ ner,
K. Angew. Chem., Int. Ed. 2007, 46, 5321–5324. (k) Fuchibe, K.;
Ohshima, Y.; Mitomi, K.; Akiyama, T. J. Fluorine Chem. 2007, 128,
Scheme 2). These complexes, which can be formed quite
easily and in good yield by addition of the free carbenes to
3 3
Ru(PPh ) (CO)HF, proved to be unstable in solution, isomer-
1
158–1167.
(
(
18) Schaub, T.; Backes, M.; Radius, U. J. Am. Chem. Soc. 2006, 128,
izing to the corresponding cis-phosphine isomers over a period
of days at room temperature. In the case of 4, isomerization
was also accompanied by disproportionation.
1
5964–15965.
19) For other catalytic transformations involving C-F cleavage, see: (a)
Terao, J.; Ikumi, A.; Kuniyasu, H.; Kambe, N. J. Am. Chem. Soc.
2
003, 125, 5646–5647. (b) Terao, J.; Watabe, H.; Kambe, N. J. Am.
While reactivity studies on 1-4 were largely precluded by
their willingness to isomerize/disproportionate, we found that
for the most stable of them, the N-methyl species 1, the addition
Chem. Soc. 2005, 127, 3656–3657. (c) Scott, V. J.; C¸ elenigil- C¸ etin,
R.; Ozerov, O. V. J. Am. Chem. Soc. 2005, 127, 2852–2853. (d)
Panisch, R.; Bolte, M.; M u¨ ller, T. J. Am. Chem. Soc. 2006, 128, 9676–
9
682. (e) Klahn, M.; Fischer, C.; Spannenberg, A.; Rosenthal, U.;
of Et
Ru(IMe
SiH at room temperature afforded the dihydride complex
)(PPh (CO)H and Et SiF. Given that Ru(II) hydride
3
Krossing, I. Tetrahedron Lett. 2007, 48, 8900–8903. (f) Douvris, C.;
Ozerov, O. V. Science 2008, 321, 1188–1190.
4
)
3 2
2
3
(
(
(
20) Aizenberg, M.; Milstein, D. Science 1994, 265, 359–361.
21) Aizenberg, M.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 8674–8675.
22) Vela, J.; Smith, J. M.; Yu, Y.; Ketterer, N. A.; Flaschenriem, C. J.;
Lachicotte, R. J.; Holland, P. L. J. Am. Chem. Soc. 2005, 127, 7857–
complexes have been shown to activate C-F bonds under very
(23) Reade, S. P.; Nama, D.; Mahon, M. F.; Pregosin, P. S.; Whittlesey,
7
870.
M. K. Organometallics 2007, 26, 3484–3491.
1
848 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
Scheme 3
1
2,24
mild conditions,
disproportionation could be prevented, the facile interconversion
of Ru(NHC)(PPh (CO)HF/Ru(NHC)(PPh (CO)H (x ) 1, 2)
this suggested to us that if isomerization/
resolved upon addition of Me
3
SiCF
3
or CsF or upon redissolving
crystalline 5, suggesting that the broadening results from traces
3
0
3
)
x
)
3 x
2
of adventitious moisture. Both 6 and 7 proved to be highly
complexes might allow the design of a new catalytic system
for C-F functionalization.
hexane soluble and thus could not be completely separated from
31,32
the PPh
their room temperature H, P, and F spectra displayed Ru-H,
PPh , and Ru-F resonances which appeared (at best) as only
3
produced in the substitution reaction.
Consequently,
1
31
19
We now report that the use of N-aryl substituted NHCs
affords a ruthenium system which catalyzes HDF of aromatic
fluorocarbons. The isolation of both Ru hydride fluoride and
dihydride complexes has allowed a mechanistic investigation
of the reaction to be undertaken and revealed a number of unique
features, particularly an unusual regioselectivity in the HDF
products.
3
poorly resolved doublets, suggestive of some interaction between
the metal center and the residual phosphine. Upon cooling
toluene solutions of both complexes to 214 K, a new set of
hydride signals (with doublet of doublet multiplicity) appeared
in each case at ca. δ -6 in a 1:2.2 (6) and 1:0.2 (7) ratio with
the starting material. A new, broad, low frequency F signal
was also apparent at ca. δ -360 in each sample. The spectra
are consistent with the appearance of the 18-electron bis-
19
Results and Discussion
Synthesis and Characterization of Ru(NHC)(PPh
1, 2). The coordinatively unsaturated complexes
Ru(NHC)(PPh )(CO)HF (NHC ) SIMes 5, SIPr 6, IPr 7; see
Scheme 3 for structures of NHCs) were formed upon reaction
of Ru(PPh (CO)HF with the pentafluorobenzene adducts
SIMes(C )H and SIPr(C )H, or the free carbene IPr, at
elevated temperatures. While the formation of the saturated
3 x
) (CO)HF
(x
)
phosphine complexes Ru(SIPr)(PPh
Ru(IPr)(PPh (CO)HF (10). NMR spectra recorded at 200 K
upon the addition of further PPh (total of 2.6 equiv present in
3 2
) (CO)HF (9) and
3
3 2
)
3
)
3 3
solution) revealed complete conversion of the IPr complex 7 to
10, while, in the case of the SIPr species, a 1:1 mixture of 6
and 9 was produced. Dissolution of a crystallized sample of 5
F
6 5
6 5
F
25,26
carbene complex 5 was complete within 2.5 h at 343 K, more
forcing conditions were needed for reaction of the bulkier 2,6-
diisopropylphenyl substituted ligands (6: 393 K, 16 h; 7: 363
K, 6 h).
The SIMes complex 5 was isolated from benzene/hexane and
displayed NMR features expected for a five-coordinate
in the presence of 2.6 equiv of PPh
3
also resulted in the complete
formation to Ru(SIMes)(PPh (CO)HF (8) at 200 K.
3 2
)
The N-mesityl carbene complex Ru(IMes)(PPh )(CO)HF (11)
3
(IMes ) 1,3-bis(2,4,6-trimethyl)phenylimidazol-2-ylidene) was
formed by reaction of IMes with Ru(PPh ) (CO)HF, although
3
3
2
5b
both Ru(IMes) (CO)HF
2
3 3 2
and Ru(PPh ) (CO)H were also
3
Ru(NHC)(PPh )(CO)HF structure, with a low frequency doublet
hydride signal (δ -23.4, JHP ) 24 Hz) and a doublet phosphorus
(
28) Poulton, J. T.; Sigalas, M. P.; Folting, K.; Streib, W. E.; Eisenstein,
resonance (JPF ) 27 Hz). The Ru-F signal appeared as a broad
O.; Caulton, K. G. Inorg. Chem. 1994, 33, 1476–1485.
2
7-29
(29) Poulton, J. T.; Sigalas, M. P.; Eisenstein, O.; Caulton, K. G. Inorg.
Chem. 1993, 32, 5490–5501.
singlet at δ -215.8,
although the 27 Hz JFP splitting was
(
30) There is no suggestion of any reaction between 5 and Me
3 3
SiCF to
(
24) Whittlesey, M. K.; Perutz, R. N.; Moore, M. F. Chem. Commun. 1996,
give a Ru-CF
3
complex. See: (a) Huang, D. J.; Koren, P. R.; Folting,
K.; Davidson, E. R.; Caulton, K. G. J. Am. Chem. Soc. 2000, 122,
7
87–788.
(
25) There are relatively few examples of NHC metal fluoride complexes
known. See refs 10, 18, and 23 along with:(a) Laitar, D. S.; M u¨ ller,
P.; Gray, T. G.; Sadighi, J. P. Organometallics 2005, 24, 4503–4505.
8916–8931.
3
(31) The inability to completely remove PPh from samples of 6, 7, and
11 prevented us from attaining accurate elemental analysis on these
compounds (see Experimental Section). To prove their integrity, they
were trapped (along with 5) by CO to give the corresponding
(
b) Chatwin, S. L.; Davidson, M. G.; Doherty, C.; Donald, S. M.;
Jazzar, R. F. R.; Macgregor, S. A.; McIntyre, G. J.; Mahon, M. F.;
Whittlesey, M. K. Organometallics 2006, 25, 99–110. (c) Nikiforov,
G. B.; Roesky, H. W.; Jones, P. G.; Magull, J.; Ringe, A.; Oswald,
R. B. Inorg. Chem. 2008, 47, 2171–2179. (d) Schaub, T.; Backes,
M.; Radius, U. Eur. J. Inorg. Chem. 2008, 17, 2680–2690.
26) Schaub, T.; Fischer, P.; Steffen, A.; Braun, T.; Radius, U.; Mix, A.
J. Am. Chem. Soc. 2008, 130, 9304–9317.
3 2
dicarbonyl complexes Ru(NHC)(PPh )(CO) HF (NHC ) SIMes 17,
SIPr 18, IPr 19, IMes 20), which were analytically and structurally
characterized (CCDC 697992-697995). See Supporting Information
for details.
(
(
3 2 2
(32) Efforts to use the phosphine sponge Pd(CH CN) Cl to isolate clean
samples of 6 and 7 proved unsuccessful, as the addition of 1 equiv of
the Pd complex turned yellow solutions of both Ru complexes brown
(to black after 12 h at room temperature) and generated a mixture of
four new hydride containing species.
27) We see no H-F coupling on either the hydride or fluoride resonances.
As any coupling would be <10 Hz, we assume it may be lost in the
line width of the signals.
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1849

A R T I C L E S
Reade et al.
3
Figure 1. X-ray crystal structure of Ru(SIMes)(PPh )(CO)HF 5. Thermal
Figure 2. X-ray crystal structure of Ru(IMes)(PPh
3
)(CO)HF 11. Thermal
ellipsoids are shown at the 30% level. All hydrogen atoms (except the NHC
backbone hydrogens and Ru-H) are omitted for clarity. Selected bond
lengths (Å) and angles (deg): Ru(1)-C(1) 1.800(2), Ru(1)-C(2) 2.071(2),
Ru(1)-F(1) 2.0172(13), Ru(1)-P(1) 2.3494(5), C(2)-Ru(1)-P(1) 168.44(6),
F(1)-Ru(1)-C(1) 174.64(8), N(1)-C(2)-N(2) 108.25(18).
ellipsoids are shown at the 30% level. All hydrogen atoms (except the NHC
back bone hydrogens and Ru-H) and the solvent molecule are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru(1)-C(1) 1.820(3),
Ru(1)-C(2) 2.077(2), Ru(1)-F(1) 2.0315(13), Ru(1)-P(1) 2.3403(6),
C(2)-Ru(1)-P(1) 173.28(6), F(1)-Ru(1)-C(1) 174.13(16), N(1)-C(2)-N(2)
1
03.61(18).
produced. A much cleaner synthetic pathway to 11 involved
Scheme 4
treatment of the dihydride complex Ru(IMes)(PPh
3
)
2
(CO)H
N·3HF (Scheme 3). The compound
showed analogous solution behavior to 6 and 7 with low
3 2
temperature coordination of PPh to give Ru(IMes)(PPh ) -
2
3
3
(
16) with 1 equiv of Et
3
3
3
4
(
CO)HF (12).
X-ray Crystal Structures of Ru(SIMes)(PPh
Ru(IMes)(PPh
3
)(CO)HF and
3
)(CO)HF. The molecular structures of the five
coordinate N-mesityl substituted products 5 and (more fortu-
itously) 11 are shown in Figures 1 and 2. As expected, both
compounds display square pyramidal geometries at the ruthe-
nium centers with the hydride ligand in the apical site trans to
a vacant coordination site and fluoride trans to CO. While the
OC-Ru-F angle in 5 is similar to that for the major disordered
component in 11, the CNHC-Ru-PPh
3
angle is ca. 5° wider in
1. Although no significant difference is seen in the two
1
Ru-CNHC bond lengths, the Ru-F distance in 5 is significantly
shorter than that measured in 11 (2.0172(13) and 2.0315(13)
3
5
Å, respectively). On the basis that this implies greater
π-donation in the former, the expected shorter Ru-CO and
longer C-O distances are found.
Ru(NHC)(PPh ) (CO)H (NHC ) SIMes 13, SIPr 14, IPr 15,
3
2
2
IMes 16). Compounds 13-15 (16 was reported by us some time
3
6,37
Characterization of Ru(NHC)(PPh
with C-F Bonds. Due to the difficulty noted earlier in completely
separating complexes 6, 7, and 11 from PPh , reactivity studies
3
)
2
(CO)H
2
and Reactions
ago upon heating Ru(PPh
3 3
) (CO)H
2
with IMes
) were fully
characterized by a combination of NMR and IR spectroscopies,
elemental analysis, and X-ray crystallography. Each complex
displayed two multiplet hydride resonances at δ -6.3 to δ -6.6
and δ -8.1 to δ -8.4, with coupling constants consistent with
3
of these compounds, along with 5, were performed with samples
in which free phosphine was present. Thus, at room temperature,
5
-7 and 11 reacted with Et
3
3
SiH within minutes to generate
a geometry in which the hydrides are trans to CO and PPh
the NHC ligands are trans to one of the phosphines (Scheme
). It is worth noting that, in contrast to 16, we had not
previously been able to prepare 13-15 in even moderate yields
upon heating Ru(PPh (CO)H with SIMes, SIPr, or IPr. It is
3
and
Et SiF and afford the bis-phosphine dihydride compounds
4
(
(
33) Complexes 5-7 could also be formed the same way starting with
complexes 13-15.
)
3 3
2
34) The solution IR spectra of 6, 7, and 11 all showed two carbonyl
unclear why these three carbenes behave differently to IMes in
not fully substituting one of the phosphine ligands.
The X-ray crystal structures of 13-15 are shown in Figure
3, with pertinent bond angles and distances reported in Table
-1
absorption bands at 1922/1907, 1919/1906, and 1913/1903 cm
respectively, consistent with the presence of both Ru(NHC)(PPh
,
3
)-
(
CO)HF and Ru(NHC)(PPh
3
)
2
(CO)HF. Upon addition of excess
phosphine to each of the solutions, the higher frequency bands
disappeared leaving single carbonyl stretches at 1907, 1905, and 1902
cm . See ref 28 for a comparison of other 16- and 18e ruthenium
monocarbonyl complexes.
-1
(36) Jazzar, R. F. R.; Macgregor, S. A.; Mahon, M. F.; Richards, S. P.;
Whittlesey, M. K. J. Am. Chem. Soc. 2002, 124, 4944–4945.
(37) Jazzar, R. F. R. PhD Thesis, University of Bath, 2003.
(
2
35) X-ray and neutron structures of Ru(IMes) (CO)HF yielded Ru-F
distances of 2.0326(15) and 2.042(6) Å, respectively. See ref 25b.
1
850 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
Figure 3. X-ray crystal structures of Ru(SIMes)(PPh
3 2
) (CO)H
2
13, Ru(SIPr)(PPh
3 2
) (CO)H
2
14, and Ru(IPr)(PPh
3 2
) (CO)H
2
15. Thermal ellipsoids are shown
at the 30% level. All hydrogen atoms (except the NHC backbone hydrogens and Ru-H) are omitted for clarity, as are the solvent molecules present in 14
and 15.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
other cases now reported, the M-NHC bond lengths are the
Ru(NHC)(PPh
6)
3
)
2
(CO)H
2
(NHC ) SIMes 13, SIPr 14, IPr 15, IMes
40
same for both unsaturated and saturated carbene ligands.
1
When complexes 13-15 were heated at 343 K for 15 h in
the presence of 10 equiv of C F in THF-d , C-F bond
6 6 8
a
13
14
15
16
Ru-NHC
2.097(3)
1.910(3)
2.3058(8)
2.3622(10)
2.085(3)
1.889(4)
2.3473(9)
2.3850(9)
2.087(4)
1.897(5)
2.0956(17)
1.9145(17)
2.2985(5)
2.3628(4)
Ru-CO
(
38) (a) Burling, S.; Mahon, M. F.; Paine, B. M.; Whittlesey, M. K.;
Ru-Ptrans to NHC
Ru-Ptrans to H
trans-NHC-Ru-P 145.49(9)
cis-NHC-Ru-P 106.30(10)
OC-Ru-Ptrans to NHC 97.71(10)
OC-Ru-Pcis to NHC 100.36(11)
N-C-N
2.3333(12)
2.3832(11)
152.83(11)
104.11(11)
92.13(14)
98.65(14)
101.5(3)
Williams, J. M. J. Organometallics 2004, 23, 4537–4539. (b) Burling,
S.; Kociok-K o¨ hn, G.; Mahon, M. F.; Whittlesey, M. K.; Williams,
J. M. J. Organometallics 2005, 24, 5868–5878.
151.97(9)
146.33(5)
104.94(5)
94.76(5)
100.65(5)
101.55(14)
104.69(9)
93.27(11)
97.63(11)
102.1(3)
(
(
39) Burling, S.; Paine, B. M.; Nama, D.; Brown, V. S.; Mahon, M. F.;
Prior, T. J.; Pregosin, P. S.; Whittlesey, M. K.; Williams, J. M. J.
J. Am. Chem. Soc. 2007, 129, 1987–1995.
105.3(3)
40) (a) Hillier, A. C.; Sommer, W. J.; Yong, B. S.; Petersen, J. L.; Cavallo,
L.; Nolan, S. P. Organometallics 2003, 22, 4322–4326. (b) Viciu,
M. S.; Navarro, O.; Germaneau, R. F.; Kelly, R. A.; Sommer, W. J.;
Marion, N.; Stevens, E. D.; Cavallo, L.; Nolan, S. P. Organometallics
a
Data taken from ref 37.
3
7
1
.
In line with the structures of 16
and other
2
004, 23, 1629–1635. (c) Kelly, R. A.; Scott, N. M.; D ´ı ez-Gonz a´ lez,
S.; Stevens, E. D.; Nolan, S. P. Organometallics 2005, 24, 3442–
447. (d) Dorta, R.; Stevens, E. D.; Scott, N. M.; Costabile, C.;
Cavallo, L.; Hoff, C. D.; Nolan, S. P. J. Am. Chem. Soc. 2005, 127,
485–2495. (e) de Fr e´ mont, P.; Scott, N. M.; Stevens, E. D.; Nolan,
S. P. Organometallics 2005, 24, 2411–2418.
3
8,39
Ru(NHC)(PPh
3 2
) (CO)H
2
compounds,
all three compounds
3
show distorted octahedral geometries with trans-CNHC-Ru-P
angles of 145.49(9)° (13), 151.97(9)° (14), and 152.83(11)° (15)
2
3
7
(
cf. 146.33(5)° in 16). As in 5 and 11, and in a number of
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1851

A R T I C L E S
Reade et al.
Table 2. Catalytic Hydrodefluorination (HDF) of C
6
F
6
(Entries 1–4)
(CO)H
to be catalytically inactive showing that the NHC ligands play
a key role in the behavior of these ruthenium systems. A series
of kinetic experiments were performed (with only 1 equiv of
silane added and at a slightly lower temperature of 339 K) in
and C
6
F
5
H (Entries 5–8) with Et
3
SiH by Ru(NHC)(PPh
)
3 2
2
a
(
NHC ) SIMes 13, SIPr 14, IPr 15, IMes 16)
b
d
product
distribution (%)
selectivity
(%)
TOF
-1
c
entry
catalyst
TON
(h
)
which the initial rates of formation of C
by F NMR for the different ruthenium precursors (Figure
6
F
4
H
2
were monitored
1
13
C
(
6
F
5
H (44.9), 1,2-C
6
F
4
H
2
2
2
–
6.1
0.31
0.09
0.37
0.20
0.32
0.14
0.36
0.07
19
45,46
7.6), 1,4-C
F H
6 4 2
(0.5)
4
).
Linear behavior was observed with the kinetic activity
2
3
4
5
6
7
8
14
15
16
13
14
15
16
C
6
F
5
H (14.2), 1,2-C
6
F
4
H
–
1.8
7.4
3.9
6.3
2.7
7.0
1.3
also in the order 15 > 13 > 16 > 14.
For all of the ruthenium catalysts, HDF of C F gave C F H
6 6 6 5
(
1.6), 1,4-C
F H
6 4 2
(0.1)
C
6
F
5
H (32.2), 1,2-C
6
F
4
H
–
(
19.9), 1,4-C
F H
6 4 2
(0.9)
as the major product. Of most interest, however, was the fact
that the C that was formed was mostly the 1,2-isomer
rather than the 1,4-isomer (this was established by comparison
C
6
F
5
H (18.0), 1,2-C
6
F
H
4 2
–
6 4 2
F H
(
10.3), 1,4-C
F H
6 4 2
(0.3)
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
6
F
6
4
H
2
(61.2),
(1.1)
(24.8),
(1.0)
(67.7),
(1.6)
(10.9),
(0.9)
98.2
96.2
97.7
92.2
19
1
4
F H
2
to F NMR spectra of authentic samples of both compounds).
This was investigated further using C H as the starting
fluoroarene, and selectivities of 92-98% for 1,2-C were
found, with turnover numbers about the same as those with
. Consideration of the data in Table 2 shows that, in terms
of activity, both 13 and 15 prove to be more efficient HDF
catalysts toward C and C H than Holland’s iron diketimi-
nate based system, which gave a maximum TON of 2.5 (TOF
F
6 4
H
2
6 5
F
1
6
4
F H
2
6 4 2
F H
F
6 4
H
2
1
3
1
6
4
F H
2
F
6 4
H
2
6 6
C F
1
6
4
F H
2
F
6 6
6 5
F
a
Reaction conditions: 0.01
M
Ru(NHC)(PPh
3
)
2
(CO)H
2
,
THF
3
solution, 0.1 M fluoroarene, 0.2 M Et SiH, 343 K for 19.45 h.
-
1
22
b
)
0.026 h at 318 K) with Et
combination of Rh(PMe (C ) and (EtO)
to give TONs of 30-40 (TOF ) 0.68-0.79 h at 367 K) for
3
SiH as the reductant. The
Selectivity is given as the % of main HDF product/total % of HDF
c
products. TON ) (moles of fluoroaromatic product(s) multiplied by the
no. of HDF steps)/moles of catalyst. TOF ) TON/h.
)
3 3
F
6 5
SiH was reported
3
d
-1
2
0
both substrates. Prompted by the good activity and high
stability of 15 noted above, HDF of C H with Et SiH was
activation of the fluoroarene took place to give the hydride
fluoride complexes 5-7 (Scheme 4) and 1 equiv of the HDF
6 5
product C F H (characterized by the appearance of H and F
F
6 5
3
performed at a lower catalyst loading (0.21 mol%, no solvent)
in a catalytic run lasting 400 h and resulted in a turnover number
of 202, corresponding to a turnover frequency (TOF) of 0.51
1
19
4
1
NMR resonances at δ 6.8, and δ -142, -158, and -166).
While C-F cleavage also proceeded when 16 was heated with
, the ruthenium containing products consisted of the
corresponding hydride fluoride complex 11 in a 3:2 ratio with
the carbene loss product Ru(PPh (CO)HF. Further studies with
the IPr complex 15 showed that C-F activation also occurred
with C H, resulting again in the formation of 7 and now 1,2-
(vide infra). In contrast to previous reports involving
-
1
47
-1
h . The TOF was raised to 0.86 h upon increasing the
temperature to 363 K (TON of 62.2 after 72 h of reaction),
although a further temperature rise to 393 K had an adverse
6 6
C F
-1
)
3 3
effect on the rate of reaction (TOF ) 0.16 h with TON of
1.6 after 72 h), presumably due to catalyst instability.
Further studies on the HDF of C H by 15 revealed a drop
in activity by a factor of 2 upon changing the solvent from THF
to C (Table 3, entries 1 and 3). While this may simply reflect
1
6 5
F
C F H
6 4 2
6 5
F
the reactions of Ru-H complexes with C-F bonds, there was
6 6
H
no evidence by NMR for the formation of any ruthenium
22
the influence of solvent polarity on the catalysis, an additional
contributing factor may be a side reaction involving C-H
activation which was observed when deuterated aromatic
solvents were used. Thus, reactions of both C
in either C or C CD gave both C D and C
with C H and 1,2-C . The deuterated compounds made
2
4,42
fluoroaryl hydride products.
Catalytic Hydrodefluorination of C
of the interconversion of complexes 5-7 and 11 with 13-16
by reaction with Et SiH and C or C H, catalytic HDF of
6 6 6 5
F and C F H. In light
4
8
F
6 6
and C
6 5
F H
3
F
6 6
6 5
F
D
6 6
D
6 5
6
F
F D along
6 4 2
3
5
aromatic fluorocarbons was attempted. The activity of the
F
6 5
6 4 2
F H
dihydride complexes 13-16 was screened at 10 mol% catalyst
up 6-15% of the total product distribution and were identified
by the appearance of their 19F resonances at slightly lower
frequency than the protio isotopomers. None of the deuterated
6 6 3
loading with C F in the presence of 2 equiv of Et SiH in THF
4
3
at 343 K for ca. 20 h. The results are summarized in Table 2.
All four complexes catalyzed HDF of C to give a mixture
of C H and C (entries 1-4). The IPr complex 15 proved
to be the most effective catalyst, giving 7.4 turnovers, followed
4
9
6 6
F
8
products were observed in THF-d .
F
6 5
6 4 2
F H
4
4
(45) Espenson, J. H. Chemical Kinetics and Reaction Mechanisms, 2nd
ed; McGraw-Hill: New York, 1995.
(46) Kinetic experiments were run in THF at 339 K, the boiling point of
the solvent.
by 13 (SIMes) > 16 (IMes) > 14 (SIPr). NMR spectra
recorded at the end of the catalytic reactions revealed, however,
that only 15 remained intact, with the other three precatalysts
having eliminated their carbene ligands over the course of the
(
47) Turnover numbers of up to 90 have been recorded by Braun and co-
workers for the conversion of hexafluoropropene into 3,3-trifluoro-
propylsilanes. See ref 17j.
2
0 h reaction time to leave Ru(PPh
3 3 2
) (CO)H as the major
identifiable metal containing species. This complex was found
(48) We and others have shown previously that Ru-NHC complexes can
bring about bond activation of aromatic solvents. Thus, in ref 36 we
reported that thermolysis of 16 in C
6
D
6
led to a mixture of products
)(CO)H , Ru(IMes) (PPh )(CO)HD,
(CO)HD. Leitner and co-workers
(
(
(
41) The reaction was slowed considerably in the presence of 3 equiv of
PPh or upon changing the solvent to pyridine-d
including 16-HD, Ru(IMes)
2
(PPh
3
2
2
3
3
5
.
Ru(PPh (CO)H , and Ru(PPh
3
)
3
2
3
)
3
42) Jasim, N. A.; Perutz, R. N.; Foxon, S. P.; Walton, P. H. J. Chem.
Soc., Dalton Trans. 2001, 1676–1685.
subsequentlyshowedthatthedihydrogendihydridecomplexRu(IMes)(P-
2
Cy
3 2 2 2 6 5 3
)(η -H ) H was able to induce H/D exchange of C D CD at room
43) The rapid room temperature reactions of 5-7 and 11 with alkysilanes
temperature. The resulting organometallic complex, which was now
labeled Ru-D, Ru(η -D ) and at the ortho-mesityl groups, was
2
2
prevented us from using the Ru(NHC)(PPh
3
)(CO)HF complexes as
catalytic precursors as they were simply transformed into complexes
subsequently used to introduce deuterium into a range of aromatic
substrates including benzene, aniline, and anisole. Giunta, D.; H o¨ lscher,
M.; Lehmann, C. W.; Mynott, R.; Wirtz, C.; Leitner, W. AdV. Synth.
Catal. 2003, 345, 1139–1145.
1
3-16 under the reaction conditions.
(
44) TON is defined as (the number of moles of fluoroaromatic product(s)
multiplied by no. of HDF steps)/number of moles of catalyst.
1
852 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
Figure 4. Time course plot of the catalytic HDF of C
showing changes in the rates upon variation of the Ru-NHC precursor ([Et
6
F
5
H (THF, 339 K) by Ru(NHC)(PPh
3
)
2
(CO)H
2
(NHC ) SIMes 13, SIPr 14, IPr 15, and IMes 16)
3
SiH] ) [C
6 5
F H] ) 0.1 M, [Ru] ) 0.01 M).
a
Table 3. Catalytic Hydrodefluorination (HDF) of Fluoroarenes by Ru(IPr)(PPh ) (CO)H (15)
3 2 2
b
f
selectivity
(%)
TOF
-1
c
entry
substrate
solvent
silane
product distribution (%)
TON
(h )
1
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CF
THF
Et
Et
Et
Et
3
3
3
3
SiH
SiH
SiH
SiH
1,2-C
,2-C
1,2-C
,2-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
1,2-C
,4-C
2,3,4,5-C
6
F
6
4
H
2
(67.7),
(1.6)
(86.0),
(1.8)
(31.7),
(0.5)
(62.6),
(2.4)
(60.7),
(1.2)
(35.8),
(6.5)
(45.8),
(2.4)
(2.5),
(0.3)
(66.4),
(1.2)
(5.0),
(1.3)
(2.9),
(0.4)
(57.5),
(1.6)
(56.3),
(1.7)
(54.7),
(1.3)
97.7
97.9
98.4
96.3
98.1
84.6
95.0
88.7
98.2
79.1
87.8
97.3
97.0
97.6
–
7.0
8.9
3.3
6.5
6.2
4.3
4.9
0.3
6.8
0.7
0.4
6.0
5.8
5.6
2.6
0.36
0.19
0.17
0.33
0.32
0.22
0.25
0.02
0.35
0.04
0.02
0.31
0.30
0.29
–
1
4
F H
2
d
2
THF
benzene
toluene
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
F
6 4
H
2
1
6
4
F H
2
3
F
6 4
H
2
1
6
4
F H
2
e
4
F
6 4
H
2
1
6
4
F H
2
5
6
7
8
9
iPr
Ph
Ph
3
SiH
6 4 2
F H
F H
6 4 2
1
2
MeSiH
SiH
F
6 4
H
2
1
6
4
F H
2
3
F
6 4
H
2
1
6
4
F H
2
(EtO)
3
SiH
F
6 4
H
2
1
6
4
F H
2
Et
Et
Et
Et
Et
Et
Et
3
3
3
3
3
3
3
SiH/1 atm H
2
2
F
6 4
H
2
1
6
4
F H
2
1
1
1
1
1
1
0
1
2
3
4
5
SiH/1 atm O
F
6 4
H
2
1
6
4
F H
2
SiH/0.03 M PPh
3
F
6 4
H
2
1
6
4
F H
2
SiH/0.03 M Et
3
N
F
6 4
H
2
1
6
4
F H
2
SiH/0.03 M DHA
SiH/0.03 M CsF
SiH
F
6 4
H
2
1
6
4
F H
2
F
6 4
H
2
1
6
4
F H
2
3
6
F
4
HCF
3
(3.1),
(14.1),
(3.3)
HN (23.8),
HN (15.9),
2
2
,3,5,6-C
6 3 2 3
,3,6-C F H CF
6
F HCF
4 3
1
6
C
5
F
5
N
THF
Et
3
SiH
2,3,4,5-C
5
F
4
–
13.6
–
2
2
3
3
,3,5,6-C
5
F
4
,3,5-C
,4,5-C
5
F
F
3
H
H
2
N (8.2),
5
3
2
N (35.1),
5 2 3
,4-C F H N (3.2)
a
b
Reaction conditions: 0.01 M 15, 0.1 M fluoroarene, 0.2 M silane, 343 K for 19.45 h unless otherwise stated. Selectivity is given as the % of main
c
d
HDF product/total % of HDF products. TON ) (moles of fluoroaromatic product(s) multiplied by the no. of HDF steps)/moles of catalyst. Reaction
run at 343 K for 48 h. Reaction run at 393 K for 19.45 h. TOF ) TON/h.
e
f
Table 3 shows that triethylsilane proved to be the most effective
reductant as increasing the bulk of the R substituent on the silane led
6: Ph
2
MeSiH: TON ) 4.3, selectivity 84.6%) or shut it down
SiH: TON ) 0.3).
altogether (entry 8: (EtO)
3
to a decrease in both the activity and selectivity of C
6
F
5
H hydrode-
SiH: TON ) 6.2, selectivity
SiH: TON ) 4.9, selectivity 95.0%). Similarly, changes
to the electronic structure at silicon reduced activity even further (entry
Catalytic HDF of Other Perfluoroarenes. Attempts to conduct
hydrodefluorination on other fluoroaromatic substrates met with
mixed success (Table 3, entries 15-16). After 20 h of reaction,
i
fluorination (Table 3, entries 5 and 7: Pr
8.1%; Ph
3
9
3
6 5 3 6 4 3
C F CF gave a mixture of three products, 2,3,5,6-C F HCF
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1853

A R T I C L E S
Reade et al.
Figure 5. Time course plot of the catalytic HDF of C
6 5
F H by Ru(IPr)(PPh
3 2
) (CO)H
2
15 (THF, 339 K) showing changes in the initial rates upon varying
the concentrations of C
6 5
F H, Et
3
SiH and 15 versus a standard experiment ([Et
3
SiH] ) [C F H] ) 0.1 M, [15] ) 0.01 M).
6 5
Table 4. Initial Rates for the Catalytic Hydrodefluorination of
8
H with Et SiH Using Ru(IPr)(PPh (CO)H (15) (THF-d , 339
(
(
2
14.1%), 2,3,4,5-C
6
F
4
HCF
3.3%). Fluorocarbons with a lower fluorine content (C
,3,4,5,6-pentafluorobiphenyl and both 1,2- and 1,4-C
3
(3.1%), and 2,3,6-C
6
F
6
3
H
2
CF
3
3
50
C
6
K)
F
5
3
3
)
2
2
5
F CH
,
6
F
4 2
H )
[C
6
F
5
H]
0
[Et SiH]
3
(M)
0
[15]
(M)
0
initial rate
M
were unreactive. Pentafluoropyridine proved to be highly active
TON ) 13.6) although the hydrodefluorination was also the
entry
-
7
-1 -1
(M)
(10
s )
(
1
2
3
4
5
0.1
0.2
0.4
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.4
0.1
0.1
0.1
0.1
0.1
0.01
0.01
0.01
0.01
0.005
0.01
3.34 ( 0.11
6.16 ( 0.17
9.25 ( 0.29
3.27 ( 0.13
2.23 ( 0.66
3.95 ( 0.12
3.53 ( 0.15
1.94 ( 0.08
1.35 ( 0.05
most unselective, with products resulting from one, two, and
three HDF steps formed. The regioselectivity of the monode-
a
fluorination reaction followed that of C
substitution mostly at the 2-position, with more 2,3,4,5-C
23.8%) formed than 2,3,5,6-C HN (15.9%). Unlike C
however, further HDF of 2,3,4,5-C HN occurred at both the
- and 4-positions to give 3,4,5-C N (35.1%) and 2,3,5-
N (8.2%). Over a longer time, 3,4,5-C N reacted
F
6 6
and C
6 5
F
H in giving
HN
H,
b
5 4
F
c
6
7
8
(
F
5 4
6 5
F
c
0.01 + 0.0015 M PPh
0.01 + 0.003 M PPh
0.01 + 0.006 M PPh
3
5 4
F
c
3
2
C
F H
5 3 2
c
9
3
F H
5 3 2
5 3 2
F H
5
1
a
SiH] ) 0.02 M, an initial rate of (3.44 ( 0.13) × 10 M-1
-7
further to afford small amounts of 3,4-C
Mechanistic Studies of Catalytic HDF. A kinetic study of the
HDF of C H in the presence of Et SiH with 15 is summarized
by the time course plots shown in Figure 5. In a series of
experiments in which the formation of 1,2-C was moni-
tored by 19F NMR in the presence of R,R,R-trifluorotoluene as
a standard, the initial concentrations of C H, Et SiH and 15
were varied while the other two were kept constant and the
5 2 3
F H N.
At [Et
3
s- was found. A kinetic run with [15] ) 0.2 M proved unreliable for
1
b
kinetic analysis due to the incomplete solubility of the complex at this
F
6 5
3
c
concentration. Experiments run at 342 K.
6 4 2
F H
and ruthenium precursor and a zero-order dependence on the
concentration of silane (Table 4). These results suggest that the
rate-limiting step in the catalytic cycle involves activation of
the fluoroarene, in contrast to Holland’s results on the ꢀ-diketim-
inate iron(II) system which showed that reaction with silane
was rate-determining. It is worth reiterating an earlier point that
whereas our Ru system will directly activate a C-F bond, the
iron complex only performed C-F activation when silane was
present.
F
6 5
3
4
6
initial rates measured. The plots indicate a first-order depen-
dence with respect to the concentrations of both fluoroarene
5
(49) This contrasts with an earlier report (ref 16) employing (η -C
5
H
5
2
) ZrCl
2
/
Mg/HgCl in which deuterium could be extracted from THF-d .
2
8
1
(
50) Analysis of the H NMR spectrum at longer times (ca. 85 h) showed
the presence of a new ruthenium species assigned as the fluoroaryl
HDF of C
equiv of PPh
11). Compared to a standard reference experiment (Table 3,
entry 1), we found that the addition of Et N or CsF (3 equiv in
6 5
F H was shut down when either 1 atm of O
2
or 3
hydride complex Ru(IPr)(PPh
3 6 4 3
)(CO)(C F CF )H. This displayed a
3
(see below) were added (Table 3, entries 10 and
hydride resonance at δ-25.83 (JHP ) 24.01, JHF ) 5.95 Hz) with a
3
1
doublet of triplets multiplicity and a singlet P signal at δ 55.0. The
1
9
1
presence of a 2,3,5,6-C
6
F
4
CF
3
ligand was inferred from a F- H
3
HMBC experiment which showed a correlation from the hydride signal
each case) somewhat reduced the efficiency of the catalysis
to two 19F signals at δ-111.1 (dd, J ) 34.10, J ) 15.62 Hz) and
1
9
19
δ-117.6 (multiplet). F- F COSY confirmed the presence of a
further three 19F resonances, two multiplets at δ-146.3 and-148.6,
and a triplet at δ-57.6 (JFF ) 21.68 Hz). The proton spectrum also
1
(51) Similarly, analysis of the H NMR spectrum at the end of the catalytic
reaction with pentafluoropyridine showed a broad doublet hydride
2
displayed the presence of free H
2
in solution, suggesting that
signal at δ-25.62 ( JHP ) 23.50 Hz), which showed an HMQC
31
coordination of the benzotrifluoride ligand occurs via activation of
the C-H bond. This was confirmed by reaction of 15 with 5 equiv of
correlation to a broad P resonance at δ 47.0. We assign these signals
as arising from Ru(IPr)(PPh
3
)(CO)(C
5 4
F N)H on the grounds that the
1
9
2
(
,3,5,6-C
CO)(C
Heating the solution to 343 K gave the product in a ratio of 1:1.5
with Ru(IPr)(PPh (CO)H
6
F
F
4
HCF
3 3
which generated a small amount of Ru(IPr)(PPh )-
F NMR showed four signals in a 1:1:1:1 ratio, which was correlated
1
9
19
6
4
CF
3
)H at room temperature within 30 min of addition.
by F- F COSY. The appearance of a singlet at δ 4.3 in the proton
spectrum for H is consistent with formation of the 2,3,5,6-tetrafluo-
ropyridyl ligand by C-H activation of 2,3,5,6-tetrafluoropyridine.
2
3
)
2
2
.
1
854 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
Figure 6. Time course plot of the catalytic HDF of C
6 5
F H by Ru(IPr)(PPh
3
)
2
(CO)H
2
15 (339 K, THF) showing changes in the initial rates upon addition
of Et
3
N, CsF, and dihydroanthracene (DHA) versus a standard experiment ([Et
3 6 5
SiH] ) [C F H] ) 0.1 M, [15] ) 0.01 M).
(
Table 3, entries 12 and 14), although time course plots for each
Mechanistic cycles to explain both the inorganic and
organic products formed under stoichiometric and catalytic
conditions are proposed in Schemes 5and 6 and involve
oxidative addition/metathesis reactions of C-F and C-H
bonds. A reaction pathway for fully fluorinated substrates
of these two additives showed no significant change to the
5
2
kinetics (Figure 6). No change in TON or selectivity was
observed when HDF of C H with Et SiH was performed under
atm of H rather than 1 atm of argon (Table 3, entry 9),
F
6 5
3
1
2
showing that, at least at this pressure, dihydrogen is not a
competent reductant. This was substantiated further by the
(e.g., C
was supported by a series of kinetic experiments at variable
[PPh ] (Table 4, entries 6-9) which revealed a close to
inverse first-order dependence of catalytic activity on phos-
phine concentration. As these experiments were conducted
6 6 3
F ) is shown in Scheme 5. Facile dissociation of PPh
complete removal of all silane and the attempted HDF of C
with H alone, which failed to give any C even under 3
atm of H
6 5
F H
3
2
F H
6 4 2
2
.
with 0.15-0.6 equiv PPh
3
per Ru, this suggests that trapping
to reform the 18e bis-
The most commonly accepted pathways for C-F bond
of I (see Schemes 5 and 6) by PPh
3
activation involve oxidative addition, nucleophilic substitution,
2
phosphine dihydride precursor must be very fast. Phosphine
dissociation has also previously been reported by us for the
or electron transfer. Neither of the latter two mechanisms is
consistent with the regioselectivity of the HDF products as both
pathways would favor activation of a C-F bond para to an
6 5
electron-withdrawing group; thus HDF of C F H should yield
3 2
analogous N-alkyl substituted complexes Ru(NHC)(PPh ) -
3
9
(
CO)H
absence of R
species (I) could then “interact” with C
a formal oxidative addition reaction to Ru(II) seems un-
2
.
Under stoichiometric conditions (i.e., in the
SiH), the resulting 16-electron five-coordinate
(species II). As
1
,4-C
6 4 2
F H rather than the 1,2-isomer which is observed.
3
5
3
6 6
F
Similarly, as seen for a number of Rh and Pd/Pt phosphine
5
4
complexes, nucleophilic substitution or electron transfer
pathways would lead to activation of the para-C-F bond in
pentafluoropyridine, whereas attack at the 2-position, as seen
5
6
likely, we assume that coordination would involve one of
2
4,26,57
thetwoacceptedbindingmodes,eitheranη -C
6
F
6
complex
5
8
5
,55
or a σ-aryl-F-M species. In either case, subsequent
here and also for a number of Ni phosphine species,
is more
5
9
metathesis would lead to the formation of a new C-H bond,
affording C H and the final ruthenium containing species
Under catalytic conditions in which R SiH is present, 7
consistent with an oxidative addition process. Holland has also
noted that, for electron transfer, catalytic conversion should
correlate with the electron affinity of the perfluoroarene
6 5
F
6
0
7
.
3
2
2
substrate, again something we do not observe. A common
tool used for probing electron transfer involves addition of
a radical trap, such as dihydroanthracene (DHA). In our case,
we observe a negligible effect on the rate of HDF activity
(56) While Ru(IV) di-, tri-, and indeed polyhydride complexes are known
i
(
e.g., Ru(P Pr
3 2 2 2
) H Cl (Wolf, J.; St u¨ er, W.;Gr u¨ nwald, C.; Gevert, O.;
Laubender, M.; Werner, H. Eur. J. Inorg. Chem. 1998, 1827-1834)
5
and (η -C
5 5 3 3
Me )Ru(PR )H (Rodriguez, V.; Donnadieu, B.; Sabo-
(
Figure 6, Table 3).
Etienne, S.; Chaudret, B. Organometallics 1998, 17, 3809-3814),
2
2
Kubas has noted that σ-coordination vs oxidation (e.g., M(η -H ) vs
H-M-H) is highly ligand dependent and that CO ligands tend to
(
52) Thus, there is no evidence to suggest that fluoride promotes activation
favor σ-complexes. For this reason, we feel that σ-coordination of,
5
2
reactions, as seen by Edelbach and Jones (ref 6) with (η -
for example, C
)H
nium(IV) intermediate Ru(NHC)(PPh
F
6 6
to afford the Ru(II) species Ru(NHC)(PPh
3
)(CO)(η -
5 5 3 2
C Me )Rh(PMe )H .
C F
6 6
2
is more likely than oxidative addition to give the ruthe-
)(CO)(C )FH . Kubas, G. J.
(
53) Noveski, D.; Braun, T.; Neumann, B.; Stammler, A.; Stammler, H.-
G. Dalton Trans. 2004, 4106–4119.
3
6
F
5
2
Metal Dihydrogen and σ-Bond Complexes: Kuwer Academic: New
York, 2001.
(
54) Jasim, N. A.; Perutz, R. N.; Whitwood, A. C.; Braun, T.; Izundu, J.;
Neumann, B.; Rothfeld, S.; Stammler, H.-G. Organometallics 2004,
(57) (a) Belt, S. T.; Duckett, S. B.; Helliwell, M.; Perutz, R. N. J. Chem.
Soc., Chem. Commun. 1989, 928–929. (b) Braun, T.; Cronin, L.;
Higgitt, C. L.; McGrady, J. E.; Perutz, R. N.; Reinhold, M. New
J. Chem. 2001, 25, 19–21.
2
3, 6140–6149.
(
55) Archibald, S. J.; Braun, T.; Gaunt, J. A.; Hobson, J. E.; Perutz, R. N.
J. Chem. Soc., Dalton Trans. 2000, 2013–2018.
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1855

A R T I C L E S
Reade et al.
Scheme 5
Scheme 6
2
could form a σ-complex (III) with R
3
SiH, which upon silyl
in such a way (e.g., an η -C
6
F
5
H complex) to give IV in which
6
1
group transfer would eliminate R
to detect III proved unsuccessful, as addition of Et
at low temperature led to the formation of Et SiF even at
3
SiF and reform I. Efforts
the C-H bond (rather than C-F bond) is primed for reaction.
Subsequent metathesis and elimination of H would leave the
fluoroaryl complex Ru(IPr)(PPh )(CO)(C )H, which we then
3
SiH to 7
2
3
3
6 5
F
2
04 K.
postulate could undergo a ꢀ-F transfer from the ring to the metal
to give the tetrafluorobenzyne hydride fluoride species V.
Subsequent hydrogen transfer from Ru to the ring would yield
6 4 2 6 5
The formation of 1,2-C F H from C F H is consistent with
a mechanism proposed in Scheme 6, in which I initially interacts
1
856 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
an o-C
6
F
4
H complex (VI). Recoordination of H
2
and metathesis
Efforts to support the intermediacy of a tetrafluorobenzyne
species proved less successful. Jones and co-workers have
6
6
would lead to the elimination of 1,2-C
F H
6 4 2
and leave 7, which
5
5
shown that the decomposition of (η -C
Zr(C )F and tetrafluorobenzyne (“C
be trapped as a Diels-Alder adduct with 2,3,5,6-tetramethyl-
5
H
5
)
2
Zr(C
F
6 4
6 5 2
F ) gives (η -
then reacts with silane as in Scheme 5 to restart the catalytic
cycle. At this time, we can only speculate on how the proposed
catalytic cycle relates back to the kinetic experiments in, for
example, explaining the first-order dependence on the concen-
tration of fluoroarene. It also worth remembering that while
varying the concentration of silane has no effect on the kinetics,
both TON and selectivity were affected by different R groups
on the silane, perhaps reflecting the ability of different silanes
to form σ-silane complexes.
C
5
H )
5 2
F
6 5
”), which could
6
7
benzene (durene). However, later work showed that an
intermediate Zr-C species proposed on the decomposition
6 4
F
5
5
5 5 2 6
pathway of (η -C Me ) Zr(o-C FH
4 5 5 2 6 5
)H to (η -C Me ) Zr(C H )F
could not be trapped, possibly due to the tetrafluobenzyne
15
remaining coordinated at all times to the Zr center. This may
then also explain our lack of success in the trapping experiments
68
with durene.
While problems of H/D exchange prevented us from measur-
6
2
Conclusions
ing a kinetic isotope effect for the HDF reaction, a range of
other experiments were performed in an effort to support the
proposed mechanisms. Conclusive evidence for activation of
the C-H rather than a C-F bond in partially fluorinated arenes
The N-aryl substituted N-heterocyclic carbene complexes
Ru(NHC)(PPh ) (CO)H have been shown to be precursors for
the catalytic hydrodefluorination (HDF) of aromatic fluorocar-
bons in the presence of alkyl silanes. Stoichiometric experiments
have shown that the activity of these ruthenium dihydride species
is based on their ability to abstract fluoride to give the
coordinatively unsaturated species Ru(NHC)(PPh )(CO)HF,
which undergo F/H exchange in the presence of a silane.
The most unusual aspect of the HDF chemistry is the high
regioselectivity for formation of 1,2-partially fluorinated prod-
ucts starting from C F H. This substitution pattern contrasts with
6 5
the 1,4-products reported by both Milstein and Holland for the
Rh and Fe catalyzed reactions. Deuterium labeling experiments
suggest that the selectivity in our Ru experiments arises out of
a preference for C-H over C-F activation under catalytic
conditions and may involve a fluorinated benzyne intermediate.
Together with the recent reports of C-F activation and C-C
bond formation from the Radius group, our results suggest
that interesting future developments on the functionalization of
fluorocarbons may arise from metal-NHC complexes.
3
2
2
was found upon reaction of Ru(IPr)(PPh
10 equiv) at room temperature (THF-d ) which generated C
together with Ru(IPr)(PPh (CO)HD and Ru(IPr)(PPh
Many of the early studies on C-F bond activation
also reported a preference for C-H over C-F activation in the
3 2
) (CO)D
2
6 5
with C F H
(
8
6 5
F D
3
)
2
3 2
) -
6
3
3
(
2
CO)H .
4,64
6 5
reactions of C F H and other partially fluorinated substrates.
More recently, calculations have been used to show that this
6
5
preference is largely kinetic in origin. For example, while for
both of the coordinatively unsaturated fragments M(H PCH
CH PH ) (M ) Ni, Pt) C-F activation is the more thermody-
2
2
-
2
2
namically favorable reaction, C-H activation (at least for Pt)
7
is a more kinetically accessible process.
1
8
(
58) (a) Bouwkamp, M. W.; De Wolf, J.; Del Heirro Morales, I.; Gercama,
J.; Meetsma, A.; Troyanov, S. I.; Hessen, B.; Teuben, J. H. J. Am.
Chem. Soc. 2002, 124, 12956–12957. (b) Bouwkamp, M. W.;
Budzelaar, P. H. M.; Gercama, J.; Del Heirro Morales, I.; De Wolf,
J.; Meetsma, A.; Troyanov, S. I.; Teuben, J. H.; Hessen, B. J. Am.
Chem. Soc. 2005, 127, 14310–14319.
Experimental Section
(
59) Perutz, R. N.; Sabo-Etienne, S. Angew. Chem., Int. Ed. 2007, 46, 2578–
General Comments. All manipulations were carried out under
argon using standard Schlenk, high vacuum, or glovebox techniques
under an atmosphere of argon. Solvents were purified using an
MBraun SPS solvent system (hexane, Et
gies solvent system (THF) or under a nitrogen atmosphere from
sodium benzophenone ketyl (benzene, toluene) or Mg/I (ethanol).
NMR solvents (Fluorochem) were vacuum transferred from potas-
2
592.
(
60) Deuterium labelling studies indicate that the mechanism is not
altogether this simple since reaction of Ru(IPr)(PPh (CO)D with
0 equiv of C in THF-d not only yields the expected C D but
also gives some C H. The protio source appears to involve
orthometallation of the PPh ligands. See ref 62.
61) An alternative catalytic pathway could involve the initial reaction of
5 with R SiH rather than fluoroarene. Although no reaction was
apparent when 15 was heated with 10 equiv of Et SiH at 343 K in
, the formation of both Ru(IPr)(PPh (CO)HD and Et SiH was
seen at room temperature within 5 min of mixing when 15 was treated
with Et SiD. Thus, reaction of 15 does occur with Si-H bonds at
room temperature, although the formation of a RuH rather than a
Ru(SiR )H product implies that any initial reaction with silane would
only serve to generate the catalytic intermediate I.
62) Measurement of a kinetic isotope effect using Ru(IPr)(PPh
was thwarted by D/H exchange. While the dideuteride can be prepared
by simply placing Ru(IPr)(PPh (CO)H under 1 atm of D , we
observed that efforts to maximize the level of D-incorporation by
continually replenishing the D atmosphere and leaving the reaction
for longer led to broadening of the P NMR signals, suggestive of
H/D exchange into the ortho-phenyl positions of the PPh ligands.
Thus a sample of Ru(IPr)(PPh (CO)D (ca. 78% RuD ) was prepared
from a single cycle of D + Ru(IPr)(PPh (CO)H , isolated, and then
)
3 2
2
2
O), Innovative Technolo-
1
F
6 6
8
6 5
F
6 5
F
3
2
(
(
69
1
3
sium(C
6
D
,
6
,C
6
D
5
CD
3
,THF-d
8
).Ru(PPh
3 3 2 3 2
) (CO)H , Ru(IMes)(PPh ) -
3
37
70
71
72 73
(
CO)H
2
IMes, IPr, SIMes(C )H, and SIPr(C F )H were
F
6 5
6 5
C
D
6 6
3
)
2
3
prepared via literature methods. Fluorocarbons and silanes were
dried over activated 3 Å molecular sieves and subsequently stored
under argon.
3
2
3
1H NMR spectra were recorded on Bruker Avance 400 and 500
MHz NMR spectrometers, at 298 K unless otherwise stated, and
3 2 2
) (CO)D
3
)
2
2
2
(65) Bosque, R.; Clot, E.; Fantacci, S.; Maseras, F.; Eisenstein, O.; Perutz,
R. N.; Renkema, K. B.; Caulton, K. G. J. Am. Chem. Soc. 1998, 120,
2
12634–12640.
3
1
2
(66) The first stable M(η -C
6
F
4
) complexes were prepared relatively recently
3
by Hughes and co-workers. (a) Hughes, R. P.; Williamson, A.;
Sommer, R. D.; Rheingold, A. L. J. Am. Chem. Soc. 2001, 123, 7443–
7444. (b) Hughes, R. P.; Laritchev, R. B.; Williamson, A.; Incarvito,
C. D.; Zakharov, L. N.; Rheingold, A. L. Organometallics 2002, 21,
4873–4885.
3
)
2
2
2
2
)
3 2
2
1
31
heated at 322 K for 1.5 h and followed by H and P NMR; we
observed clear H/D exchange into the ortho-phenyl protons leaving a
mixture of the RuD
2
, RuHD, and RuH
2
species. As this scrambling
(67) (a) Edelbach, B. L.; Kraft, B. M.; Jones, W. D. J. Am. Chem. Soc.
1999, 121, 10327–10331. (b) Kraft, B. M.; Lachicotte, R. J.; Jones,
W. D. Organometallics 2002, 21, 727–731.
occurs some 20 K lower than the temperature used for catalysis (343
K), clearly RuD
determined.
2
would be exchanged before any KIE could be
(68) Coordinated or trapped fluorobenzynes have also been described in
the following cases: (a) Reference 9. (b) Keen, A. L.; Johnson, S. A.
J. Am. Chem. Soc. 2006, 128, 1806–1807. (c) Werkema, E. L.;
Andersen, R. A. J. Am. Chem. Soc. 2008, 130, 7153–7165.
(
(
63) See refs 50 and 51.
64) Selmeczy, A. D.; Jones, W. D.; Partridge, M. G.; Perutz, R. N.
Organometallics 1994, 13, 522–532.
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1857

A R T I C L E S
referenced to benzene at δ 7.15 ( C, δ 128.0), toluene at δ 2.04,
Reade et al.
1
3
redissolved in a minimum of C
6
D
6
, and transferred to a J. Youngs
1
3
1
or THF at δ 3.58. No effort was made to assign C signals for the
resealable NMR tube for characterization. H NMR (C
MHz, 298 K):* δ 3.83 (sept, JHH ) 6.72 Hz, 2H, CH(CH )
3 2
6
D
6
, 500
), 3.66
(s, 4H, NCH ), 3.57 (sept, J ) 6.72 Hz, 2H, CH(CH ) ), 1.61
1
PPh
referenced externally to 85% H
referenced to CFCl (δ 0.0). 2D experiments ( H COSY, H-X
X ) C, P, F) HMQC/HMBC) were performed using standard
3
ligands unless specified. 31P{ H} NMR chemical shifts were
19
3
PO (δ 0.0), while F spectra were
4
2
HH
3 2
1 1
3
(d, JHH ) 6.72 Hz, 6H, CH(CH ) ), 1.40 (d, J ) 6.72 Hz, 6H,
3 2
HH
13
31
19
(
CH(CH ) ), 1.24 (d, J ) 6.72 Hz, 6H, CH(CH ) ), 1.18 (d, J
3
2
HH
3 2
HH
Bruker pulse sequences. IR spectra were recorded on a Nicolet
Nexus FTIR spectrometer. Elemental analyses were conducted by
Elemental Microanalysis Ltd., Okehampton, Devon, UK.
) 6.72 Hz, 6H, CH(CH ) ), -23.05 (d, J ) 23.80 Hz, 1H,
3
2
HP
Ru-H). *The presence of free PPh prevented assignment of the
3
1
31
1
aromatic region of the H spectrum. P{ H}: δ 38.3 (d, J ) 26.1
PF
1
9
13
1
Ru(SIMes)(PPh
mmol) and SIMes(C
3
)(CO)HF (5). Ru(PPh
3
)
3
(CO)HF (500 mg, 0.52
Hz). F: δ -217.1 (br d, J ) 24.8 Hz). C{ H}: δ 219.9 (d, J
FP
CP
6
F
5
)H (760 mg, 1.60 mmol) were dissolved in
) 97.6 Hz, NCN), 204.9 (br d, J ) 75.8 Hz, Ru-CO), 149.0 (s,
CF
i
i
i
benzene (20 mL) in an ampule fitted with a PTFE tap and heated
at 343 K for 2.5 h. The resultant green solution was pumped to
dryness, washed with hexane (50 mL), and dried in Vacuo to yield
C Pr H ), 149.2 (s, C Pr H ) 137.4 (N-C ), 125.3 (s, C Pr H ),
6
2
3
6
2
3
ipso
6
2
3
i
125.2 (s, C Pr H ), 54.6 (s, NCH ), 54.5 (s, NCH ), 29.7 (s,
6
2
3
2
2
CH(CH ) ), 29.5 (s, CH(CH ) ), 27.3 (s, CH(CH ) ), 27.1 (s,
CH(CH ) ), 24.9 (s, CH(CH ) ), 24.7 (s, CH(CH ) ). IR (C D ,
3 2 3 2 3 2 6 6
3
2
3 2
3 2
Ru(SIMes)(PPh
product could be obtained by treatment of a benzene solution (20
mL) of Ru(SIMes)(PPh (CO)H (13: 100 mg, 0.010 mmol) with
Et N·3HF (18 mg, 0.011mmol) and subsequent stirring at room
3
)(CO)HF. Yield (310 mg, 81%). A higher purity
-
1
cm ): 1922 (νCO, 6), 1907 (νCO, 9).
Ru(SIPr)(PPh (CO)HF (9). In the presence of a total of 2.6
equiv of PPh (5 mg, 0.019 mmol mmol), a solution of 6 (6 mg,
.007 mmol) was transformed into a 50:50 mixture of 6 and
Ru(SIPr)(PPh (CO)HF (9) as shown by low temperature NMR
spectroscopy. Selected NMR data. H (400 MHz, C
K): δ -5.71 (dd, JHP ) 121.45, JHP ) 24.91 Hz, Ru-H). P{ H}:
3
)
2
2
3 2
)
3
3
temperature for 2 h. The resultant yellow solution was stirred with
CsF (84 mg, 0.055 mmol) for 1 h, the solution filtered, and the
filtrate reduced to dryness. The residue was washed with hexane
0
3 2
)
1
6
D
5
CD
3
, 201
(
(
2 × 10 mL) to afford 5 as a yellow microcrystalline solid. Yield
31
-1
1
60 mg, 75%). Crystals suitable for X-ray crystallography were
19
δ 30.8 (m), 15.5 (m). F: δ -367.0 (br s). IR (C
6
D
6
, cm ): 1907
obtained by layering a benzene solution with hexane. Analysis for
OFPRu·0.5C [found (calculated)]: C, 68.24 (68.21);
H, 5.99 (6.11); N, 3.70 (3.64). H NMR (C
(
νCO).
C
43
H
45
N
2
6 6
H
3
Ru(IPr)(PPh )(CO)HF (7). A toluene (20 mL) solution of
Ru(PPh ) (CO)HF (100 mg, 0.10 mmol) was heated with IPr (110
3 3
mg, 0.29 mmol) at 363 K for 6 h to give 100% conversion to 7 by
NMR spectroscopy. An alternative route to the complex involved
) (CO)H (50 mg, 0.05 mmol) with
3 2 2
Et N·3HF (10 mg, 0.06 mmol) in benzene (10 mL) at ambient
temperature for 1 h, followed by addition of CsF (40 mg, 0.29
mmol), continued stirring at room temperature for 1 h, and finally
filtration by cannula. The filtrate was reduced to dryness, redissolved
1
6
D
6
, 400 MHz, 298 K):
), 6.85 (s, 2H, C Me ),
), 2.65 (s, 6H, C-CH
) -23.37 (d, JHP ) 24.11
δ 7.40 (m, 6H, PC
6
H
5
), 6.97 (m, 9H, PC
), 3.28 (s, 4H, NCH
6
H
5
6
3 2
H
6
.77 (s, 2H, C
6
Me
3
H
2
2
3
)
2.48 (s, 6H, C-CH3
3
1
), 2.10 (s, 6H, C-CH
3
the reaction of Ru(IPr)(PPh
3
1
Hz, 1H, Ru-H). P{ H}: δ 38.8 (br d, JPF ) 18.0 Hz) [upon
addition of Me SiCF , this becomes a sharper doublet with a
resolved JFP coupling of 26.7 Hz)]. F: δ 215.8 (br s), [upon
addition of Me SiCF , this becomes a sharper doublet with a
resolved JFP coupling of 26.7 Hz)]. C{ H}: δ 217.0 (d, JCP
3
3
1
9
3
3
1
3
1
)
2
in a minimum amount of C
tube for spectroscopic analysis. H NMR (C
K):* δ 6.62 (s, 2H, NCH), 3.30 (sept, JHH ) 6.86 Hz, 2H,
6 6
D , and transferred to a J. Youngs NMR
9
1
9.3 Hz, NCN), 205.4 (br s, Ru-CO), 138.5 (s, o-/p-C
38.3 (s, o-/p-C Me ), 137.0 (s, N-Cipso), 136.3 (d, JCP ) 39.0
), 135.3 (d, JCP ) 12.1 Hz, PC ), 130.3 (s,
), 130.3 (s, m-C Me ), 129.9 (br s, PC ), 128.8 (s,
) 51.5 (s, NCH ), 51.5 (s, N-CH ), 21.8 (s, CCH ), 19.3 (s,
), 19.2 (s, CCH
Ru(SIMes)(PPh
5 mg, 0.018 mmol) to a solution of 5 (5 mg, 0.007 mmol) showed
6
Me
3
H
),
1
6
6
D , 500 MHz, 298
6
3 2
H
Hz, PC
m-C Me
PC
CCH
6
H
H
5
6 5
H
H
6 5
CH(CH
3
)
2
), 3.10 (sept, JHH ) 6.66 Hz, 2H, CH(CH
), 1.28 (d, JHH ) 6.66 Hz, 6H,
), 1.12 (d, JHH ) 6.86 Hz, 6H, CH(CH ), 1.08 (d, JHH
), -22.83 (d, JHP ) 23.78 Hz, 1H,
Ru-H). *The presence of free PPh prevented assignment of the
3 2
) ), 1.54 (d,
6
3
2
6
3
H
2
J
HH ) 6.66 Hz, 6H, CH(CH
3
)
2
6
H
5
2
2
3
CH(CH
3
)
2
3 2
)
-
1
3
3
). IR (C
6 6
D , cm ): 1916 (νCO).
)
3 2
6.86 Hz, 6H, CH(CH )
3
)
2
(CO)HF (8). Addition of 2.6 equiv of PPh
3
3
31
(
1
1
aromatic region of the H spectrum. P{ H}: δ 40.0 (d, JPF ) 26.9
1
by low temperature NMR full conversion to 8. Selected H NMR
19
13
1
Hz). F: δ -209.9 (br s). C{ H}: δ 205.3 (dd, JCF ) 75.6, JCP
)
(
(
(
C
6
D
5
CD
br s, 3H, CH
br s, 3H, CH
3
, 400 MHz, 201 K): δ 3.28-2.98 (br s, 3H, CH
3
), 2.91
), 1.57
1
C
1
1.0 Hz, Ru-CO), 194.7 (d, JCP ) 104.1 Hz, NCN), 148.0 (s,
3
), 2.80 (br s, 3H, CH ), 2.32 (br s, 6H, CH
3
3
i
i
i
6
Pr
2
H
3
), 147.8 (s, C
6
Pr
), 124.2 (s, NCH), 29.7 (s, CH(CH
), 27.0 (s, CH(CH ), 26.7 (s, CH(CH
), 23.8 (s, CH(CH
2
H
3
), 137.2 (N-Cipso), 124.7 (s, C
), 29.6 (s,
), 24.0 (s,
, cm ): 1919 (νCO, 7),
6 2 3
Pr H ),
3
) -5.67 (dd, JHP ) 118.02, JHP ) 28.00 Hz, 1H,
i
24.6 (s, C
6
Pr
2
H
3
3 2
)
3
1
1
19
Ru-H. P{ H}: δ 34.4 (br s), 15.7 (m). F: δ -360.7 (br s).
CH(CH
CH(CH
3
)
)
2
3
)
2
3 2
)
1
3
1
C{ H}: δ 218.3 (br d, JCP ) 93 Hz, NCN), 204.0 (br d, JCF ) 70
-
1
3
2
3 2 6 6
) ). IR (C D
-
1
Hz, Ru-CO). IR (C
Ru(SIPr)(PPh )(CO)HF (6). A toluene (20 mL) solution of
Ru(PPh (CO)HF (100 mg, 0.1 mmol) was heated with
SIPr(C )H (160 mg, 0.29 mmol) in an ampule fitted with a PTFE
tap at 393 K for 16 h. NMR spectroscopy showed full conversion
to 6. An alternative route involved addition of Et N·3HF (10 mg,
.06mmol) to a solution of Ru(SIPr)(PPh (CO)H (50 mg, 0.05
6 6
D , cm ): 1902 (νCO).
1
906 (νCO, 10).
Ru(IPr)(PPh
equiv of PPh (5 mg, 0.020 mmol), low temperature NMR revealed
3
complete conversion of 7 (6 mg, 0.008 mmol) to 10. H (C ,
3
3 2
) (CO)HF (10). In the presence of a total of 2.6
3 3
)
F
6 5
3
1
D
6 5
CD
00 MHz, 201 K): δ 6.68 (s, 1H, NCH), 6.67 (s, 1H, NCH) 4.06
m, 1H, CH(CH ), 3.74 (m, 1H, CH(CH ), 3.56 (m, 1H,
), 2.86 (m, 1H, CH(CH ), 1.80 (br m, 3H, CH(CH ),
), 1.24 (br m, 3H, CH(CH ), 1.18 (br
), 0.97 (br m, 3H, CH(CH ), -0.17 (br m, 3H,
), -5.53 (dd, JHP ) 124.48, JHP ) 25.97 Hz, 1H, Ru-H).
The presence of free PPh prevented assignment of the aromatic
4
3
(
3
)
2
3 2
)
0
3
)
2
2
CH(CH
3
)
2
3
)
2
3 2
)
mmol) in benzene (10 mL). The solution was agitated at ambient
temperature for 1 h before addition of CsF (40 mg, 0.29 mmol)
and filtration by cannula. The solution was then reduced in Vacuo,
1
.62 (br m, 3H, CH(CH
m, 9H, CH(CH
CH(CH
3
)
2
3 2
)
3
)
2
3 2
)
3 2
)
*
3
(
69) Ahmad, N.; Levison, J. J.; Robinson, S. D.; Uttley, M. F. Inorg. Synth.
1
31
1
19
region of the H spectrum. P { H}: δ 32.8 (m), 14.9 (m). F: δ
1
974, 15, 45–64.
-1
-
369.1 (br s). IR (C
Ru(IMes)(PPh )(CO)HF (11). Ru(IMes)(PPh
0.05 mmol) was dissolved in benzene (10 mL) and Et
3
6 6
D , cm ): 1905 (νCO).
(
70) Arduengo, A. J., III.; Krafczyk, R.; Schmutzler, R.; Craig, H. A.;
Goerlich, J. R.; Marshall, W. J.; Unverzagt, M. Tetrahedron 1999,
3
3
)
2
2
(CO)H (50 mg,
5
5, 14523–14534.
N·3HF (13
(
(
(
71) Jafarpour, L.; Stevens, E. D.; Nolan, S. P. J. Organomet. Chem. 2000,
mg, 0.08 mmol) added via syringe. The solution was agitated at
ambient temperature for 1 h before addition of CsF (40 mg, 0.23
mmol) and filtration by cannula. The solution was then reduced to
6
06, 49–54.
72) Nyce, G. W.; Csihony, S.; Waymouth, R. M.; Hedrick, J. L.
Chem.sEur. J. 2004, 10, 4073–4079.
dryness, redissolved in a minimum amount of C
6
D
6
, and transferred
to a J. Youngs NMR tube for analysis. H NMR (C , 500 MHz,
298 K):* δ 6.82 (s, 2H, C Me ), 6.75 (s, 2H, C Me ), 6.23 (s,
73) Bedford, R. B.; Betham, M.; Blake, M. E.; Frost, R. M.; Horton, P. N.;
Hursthouse, M. B.; L o´ pez-Nicol a´ s, R.-M. Dalton Trans. 2005, 2774–
1
6
D
6
2
779.
6
3
H
2
6
3 2
H
1
858 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
3
1
1
2
H, NCH), 2.46 (s, 6H, CH
3
), 2.31 (s, 6H, CH
3
), 2.10 (s, 6H, CH
23.10 (br s, 1H, Ru-H). P{ H}: δ 39.5 (br d, JPH ) 24.6 Hz).
9
3
),
) 4.80 Hz, 1H, Ru-H). P{ H}: δ 55.2 (d, JPP ) 16.0 Hz), 44.5
13 1
3
1
1
-
(d, JPP ) 16.0 Hz). C{ H}: δ 231.3 (dd, JCP ) 72.2, JCP ) 5.9
Hz, NCN), 205.7 (dd, JCP ) 8.6, JCP ) 7.9 Hz, Ru-CO), 149.2 (s,
1
3
F: δ -207.5 (br s). *The presence of free PPh prevented
1
13
1
i
i
i
i
assignment of the aromatic region of the H spectrum. C{ H}: δ
o-C
o-C
6
Pr
Pr
2
2
6
6
6
H
H
H
H
H
3
3
5
5
5
6 2 3 6 2 3
), 148.6 (s, o-C Pr H ), 148.5 (s, o-C Pr H ), 148.2 (s,
2
1
1
1
05.5 (dd, JCF ) 74.0, JCP ) 12.7 Hz, Ru-CO), 191.4 (d, JCP
03.9 Hz, NCN), 139.0 (s, CCH ), 137.6 (s, CCH ), 137.5 (s, N-C),
37.4 (s, CCH ), 129.9 (s, o-/p-C Me ), 129.8 (s, o-/p-C Me ),
22.9 (s, NCH), 21.9 (s, CH ), 19.2 (s, CH ), 19.1 (s, CH ). IR
, cm ): 1913 (νCO, 11), 1903 (νCO, 12).
Ru(IMes)(PPh (CO)HF (12). In the presence of a total of 2.6
equiv of PPh (8 mg, 0.029 mmol), a solution of 11 (7 mg, 0.010
mmol) was found by low temperature NMR spectroscopy to have
)
6
), 143.9 (s, N-C) 141.7 (s, N-C), 141.6 (d, JCP ) 24.3
Hz, PC
Hz, PC
Hz, PC
Hz, PC
Hz, PC
), 139.5 (d, JCP ) 31.4 Hz, PC
), 136.4 (d, JCP ) 11.3 Hz, PC
), 134.6 (d, JCP ) 11.9 Hz, PC
6
6
6
H
H
H
5
5
5
), 136.4 (d, JCP ) 12.7
), 135.3 (d, JCP ) 11.1
), 129.8 (d, JCP ) 11.9
H ), 127.9 (d, JCP ) 8.5
), 126.1 (s, C
3
3
3
6
H
3 2
6
3 2
H
3
3
3
-
1
(
C
6
D
6
6
H
H
5
), 128.2 (d, JCP ) 8.9 Hz, PC
6 5
i
3
)
2
6
5
), 127.5 (d, JCP ) 9.0 Hz, PC
6
H
5
6
Pr
), 55.5
), 29.9 (s, CH(CH ),
), 27.6 (s, CH ), 27.3 (s,
), 25.4 (s, CH ), 24.3 (s, CH ),
). IR (nujol, cm ): 1953 (νCO).
(15). Ru(PPh (CO)HF (400 mg, 0.43
2 3
H ),
i
i
i
125.8 (s, C
(s, NCH ), 54.5 (s, NCH
29.6 (s, CH(CH ), 29.5 (s, CH(CH
CH ), 27.2 (s, CH ), 27.0 (s, CH
24.1 (s, CH ), 23.4 (s, CH
Ru(IPr)(PPh (CO)H
6
Pr
2
H
3
), 125.6 (s, C
6 2 3 6 2 3
Pr H ), 125.1 (s, C Pr H
3
2
2
), 30.0 (s, CH(CH
)
3 2
3 2
)
1
undergone complete conversion to 12. H NMR (C
MHz, 201 K):* δ 6.00 (s, 1H, NCH), 5.85 (s, 1H, NCH) 2.70 (s,
6
D
5
CD
3
, 400
3
)
2
3
)
2
3
3
3
3
3
3
-
1
3
2
)
H, CH
.12 (s, 3H, CH
28.01 Hz, 1H, Ru-H). *The presence of free PPh
3
), 2.54 (s, 3H, CH
3
), 2.32 (s, 3H, CH
), -5.54 (dd, JHP ) 123.47, JHP
prevented
3
), 2.24 (s, 3H, CH
3
),
3
3
), 1.35 (s, 3H, CH
3
3
)
2
2
3 3
)
3
mmol) and IPr (250 mg, 0.64 mmol) were dissolved in toluene (30
mL) in an ampule fitted with a PTFE valve. The reaction mixture
was heated at 363 K for 6 h, cooled to room temperature, and then
concentrated. Hexane was added to the yellow solid, and the
3
31
1
1
assignment of the aromatic region of the H spectrum. P{ H}: δ
3
5.5 (m), 14.3 (m). 19F: δ -362.1 (br s). IR (C
D , cm ): 1902
-1
6 6
(
ν
CO).
Ru(SIMes)(PPh
3
)
2
(CO)H
2
(13). Ru(PPh
3
)
3
(CO)HF (300 mg,
3
solution was filtered through a filter cannula. Et SiH (0.3 mL, 1.88
0
.032 mmol) and SIMes(C
6
F
5
)H (450 mg, 0.096 mmol) were
mmol) was added to the filtrate, which was then stirred for 1 h to
afford a white precipitate. The mixture was filtered, and the solid
was washed with EtOH (20 mL) and hexane (20 mL) and dried
combined in an ampule fitted with a PTFE tap, dissolved in benzene
30 mL), and heated at 343 K for 2.5 h. The solution was filtered
by cannula, Et SiH (0.25 mL, 0.157 mmol) was added to the filtrate,
(
under vacuum to give Ru(IPr)(PPh
Yield 140 mg (31%). Analysis for C64
lated)]: C, 73.61 (73.22); H, 6.56 (6.87); N, 2.68 (2.53). H NMR
3
)
2
(CO)H
2
as a white powder.
Ru [found (calcu-
3
and the resulting solution was stirred at room temperature for 1 h.
The resulting solution was reduced in volume, and EtOH (30 mL)
was added with stirring to afford a red suspension of a white solid.
The solid was isolated by cannula filtration, washed with hexane
H
68
N
2
OP
2
1
(
C
6
D
6
, 500 MHz, 298 K): δ 7.66-7.29 (m, 11H, PC
6
H
5
), 7.29-7.19
), 7.06-6.83 (m,
), 6.81 (d, JHH ) 1.78 Hz, 1H, NCH), 6.77 (d, JHH
.78 Hz, 1H, NCH), 6.76-6.58 (br m, 3H, PC ), 3.50 (sept, JHH
i
i
(
m, 4H, C
6
Pr
2
H
3
6 2 3
), 7.14-7.07 (m, 2H, C Pr H
1
1
6H, PC
6
H
5
)
(
2 × 30 mL), and dried under vacuum to give 152 mg of product
6
H
5
(
Yield: 49%) Analysis for C58 OP Ru [found (calculated)]:
.
H
58
N
2
2
1
) 6.80 Hz, 1H, CH(CH ) ), 3.44 (sept, J ) 6.80 Hz, 1H,
C, 72.41 (72.15); H, 6.08 (6.48); N, 2.91 (2.65). H NMR (C
6
D
6
,
3 2
HH
CH(CH
3
)
2
), 3.37 (sept, JHH ) 6.80 Hz, 1H, CH(CH
HH ) 6.80 Hz, 1H, CH(CH ), 1.66 (d, JHH ) 6.80 Hz, 3H, CH
.14 (d, JHH ) 6.80 Hz, 3H, CH ),1.10 (d, JHH ) 6.80 Hz, 3H,
), 1.04 (d, JHH ) 6.80 Hz, 3H, CH ), 1.02 (d, JHH ) 6.80 Hz,
H, CH ), 0.96 (d, JHH ) 6.80 Hz, 3H, CH
Hz, 3H, CH ), 0.25 (d, J ) 6.80 Hz, 3H, CH ), -6.27 (dt, J
3
)
2
), 2.95 (sept,
5
2
4
00 MHz, 298 K): 7.50-7.27 (m, 12H, PC
6
H
5
), 7.05-6.97 (m,
Me ), 3.27 (br s,
), 2.34 (s, 6H, CH ), 2.21 (br s, 6H,
), -6.63 (ddd, JHP ) 24.39, JHP ) 22.81,
HH ) 5.63 Hz, 1H, Ru-H), -8.20 (ddd, JHP ) 77.41, JHP ) 33.28,
J
1
CH
3
3
)
2
3
),
0H, PC
H NCH
6
H
5
+ C
6
Me
3
H
2
), 6.84 (br s, 2H, C
6
3 2
H
), 2.61 (br s, 3H, CH
3
3
3
2
3 3
CH ), 1.51 (br s, 3H, CH
3
3
3
3
), 0.80 (d, JHH ) 6.80
J
J
4
6
3
1
1
)
HH ) 5.63 Hz, 1H, Ru-H). P{ H}: δ 57.4 (d, JPP ) 15.8 Hz),
3
HH
3
HP
1
3
1
23.65, JHP ) 23.59, JHH ) 5.60 Hz, 1H, Ru-H), -8.14 (ddd, J
)
4
(
)
(
7.6 (d, JPP ) 15.8 Hz). C{ H}: δ 224.9 (dd, JCP ) 72.1, JCP
.5 Hz, NCN), 205.7 (dd, JCP ) 8.7, JCP ) 8.5 Hz, Ru-CO), 142.6
), 142.2 (s, NCipso), 138.8 (s, C Me ),
38.7 (d, JCP ) 13.7 Hz, PC ), 135.2 (s, C Me ), 135.3 (d,
), 133.1 (d, JCP ) 9.6 Hz, PC ), 132.1 (d,
), 131.8 (s, C Me ), 129.5 (d, JCP ) 2.0 Hz,
), 128.1 (d, JCP ) 8.6 Hz, PC ), 127.8 (d, JCP ) 9.0 Hz,
), 51.8 (s, NCH ) 21.8 (CH ). IR (nujol, cm ): 1941 (νCO).
(CO)H (14). Ru(PPh (CO)HF (130 mg, 0.14
)H (230 mg, 0.41 mmol) were dissolved in
)
HP
31 1
82.85, JHP ) 31.16, JHH ) 5.60 Hz, 1H, Ru-H). P{ H}: δ
13 1
4.6 (d, JPP ) 13.7 Hz), 57.6 (d, JPP ) 13.7 Hz). C{ H}: δ 205.6
dd, JCP ) 8.7, JCP ) 8.4 Hz, Ru-CO), 202.8 (dd, JCP ) 75.8, JCP
(
1
d, JCP ) 13.7 Hz, PC
6
H
5
6
3 2
H
6
H
5
6
3 2
H
i
iPr
H ), 146.8
6 2 3
7.6 Hz, NCN), 149.1 (s, o-C
6
Pr
H
2 3
), 149.0 (s, o-C
), 141.9 (d, JCP ) 36.1 Hz,
), 142.2 (d, JCP ) 36.4 Hz, PC ), 140.1 (s, N-C), 135.3
J
CP ) 3.1 Hz, PC
6
H
5
6 5
H
i
i
6 2 3 6 2 3
s, o-C Pr H ), 146.5 (s, o-C Pr H
JCP ) 2.9 Hz, PC
6
H
5
6
3 2
H
PC
6
H
5
6 5
H
PC
PC
6
H
H
5
6 5
H
-
1
(d, JCP ) 11.5 Hz, PC H ), 130.7 (s, PC H ), 129.6 (s, PC H ),
1
1
C
6
5
6
5
6
5
6
5
2
3
29.0 (s, PC
26.3 (s, C
6
H
5
), 128.6 (s, PC
6
H
5
), 127.9 (d, JCP ) 9.4 Hz, PC
H
6 5
),
), 125.3 (s,
), 125.1 (s,
),
), 26.9 (s,
), 23.6 (s, CH ),
). IR (nujol, cm ): 1947 (νCO). ESI-
Ru(SIPr)(PPh
3
)
F
6 5
2
2
3 3
)
i
i
6
2 3 6 2 3
Pr H ), 125.6 (s, NCH), 125.6 (s, C Pr H
mmol) and SIPr(C
i
i
i
6
Pr
Pr
2
H
3
), 125.2 (s, C
6
Pr
2
H
3
6 2 3
), 125.2 (s, C Pr H
toluene (20 mL) in an ampule fitted with a PTFE tap, and the
solution was refluxed at 393 K for 16 h. The reaction mixture was
subsequently reduced to dryness, and hexane (20 mL) was added.
i
C
6
2
H
3
), 125.1 (s, NCH), 30.3 (s, CH(CH
), 29.5 (s, CH(CH ), 27.1 (s, CH
), 26.7 (s, CH ), 24.3 (s, CH
), 22.8 (s, CH
3 2 3 2
) ), 29.8 (s, CH(CH )
2
9.6 (s, CH(CH
CH ), 26.8 (s, CH
2.9 (s, CH
TOF MS: [M-PPh
81.2868).
Kinetic Experiments. A THF solution of 15 (0.01 M), fluoro-
arene (0.1 M), Et SiH (0.1 M), and R,R,R-trifluorotoluene (0.08
3
)
2
3
)
2
3
3
3
3
3
3
3
The solution was subjected to cannula filtration, and Et SiH (0.10
-
1
2
3
3
mL, 0.63 mmol) was added to the filtrate. After stirring for 1 h at
room temperature, the mixture was filtered and the light green solid
was washed with EtOH (20 mL) and hexane (20 mL). Upon drying,
+
3
-H +H] m/z ) 781.2882 (theoretical m/z )
2
7
Ru(SIPr)(PPh
)
3 2
(CO)H
27%). Analysis for C64
73.16); H, 6.73 (6.97); N, 2.68 (2.47). H NMR (C
6 5
98 K): δ 7.80 (m, 2H, PC ), 7.46-7.20 (m, 13H, PC H +
2
was isolated as a white solid. Yield 39 mg
3
(
(
2
H N
70 2
OP Ru [found (calculated)]: C, 73.47
2
1
M) as standard were added to an NMR tube fitted with a J. Youngs
resealable valve in the glovebox. The tube was placed into the
preheated (339 K) probe of a 400 MHz NMR spectrometer, and
6
6
D , 500 MHz,
6
H
5
i
i
C
6
Pr
3H, PC
.00 (sept, JHH ) 6.73 Hz, 1H, CH(CH
+ NCH ), 2.99 (sept, JHH ) 6.73 Hz, 1H, CH(CH
), 1.26 (d, JHH ) 6.73 Hz, 3H,
), 1.21 (d, JHH ) 6.73 Hz, 3H, CH ), 1.17 (d, JHH ) 6.73 Hz,
), 1.15 (d, JHH ) 6.73 Hz, 3H, CH
Hz, 3H, CH ), 0.69 (d, JHH ) 6.73 Hz, 3H, CH
.73 Hz, 3H, CH ), -6.47 (ddd, JHP ) 25.43, JHP ) 20.36, JHH
2
H
3
), 7.13-7.00 (m, 4H, PC
6
H
5
+ C
6
6
Pr
), 6.61 (m, 2H, PC
), 3.95-3.64 (m, 6H,
),
2
H
3
), 6.99-6.78 (m,
1
9
i
F spectra were recorded periodically for a total of 12 h (relaxation
1
4
6
H
5
+ C
6
Pr
2
H
3
) 6.72 (m, 2H, PC
H
5
6 5
H ),
74
times of 20 s were employed to ensure correct integrations).
3 2
)
CH(CH
1
3
)
2
2
3
)
2
HDF Experiments for Determination of Turnover Numbers.
An NMR tube fitted with a J. Youngs resealable valve was loaded
with a ruthenium complex (0.01 M), fluoroarene (0.1 M), and
alkysilane (0.2 M) in THF, benzene, or toluene in the glovebox,
and a standardized capillary tube of R,R,R-trifluorotoluene was
.72 (d, JHH ) 6.73 Hz, 3H, CH
3
3
CH
3
3
H, CH
3
3
), 0.97 (d, JHH ) 6.73
3
3
), 0.32 (d, JHH
)
)
1
9
6
4
3
inserted. An initial F spectrum was recorded at room temper-
ature, the capillary was removed from the NMR tube, and the
.80 Hz, 1H, Ru-H), -8.40 (ddd, JHP ) 77.20, JHP ) 32.27, JHH
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1859

A R T I C L E S
Reade et al.
Table 5. Data Collection and Refinement Details for Compounds 5, 11, 13, 14, and 15
compound
5
11
13
14
15
empirical formula
formula weight
T/K
crystal system
space group
a/Å
C
40
H
42FN
2
OPRu
C
44
H
48FN
2
O
2
PRu
C
58
H
58
N
2
OP
2
Ru
C
68
H
78
N
2
O
2
P
2
Ru
68 76 2 2 2
C H N O P Ru
1116.32
150(2)
717.80
150(2)
monoclinic
P2 /a
15.1040(2)
14.1360(2)
16.7450(3)
90
99.633(1)
90
3524.82(9)
4
1.353
0.529
1488
787.88
150(2)
monoclinic
P2 /a
13.7310(1)
13.6060(1)
21.7640(3)
90
105.746(4)
90
3913.46(7)
4
1.337
0.485
1640
962.07
150(2)
triclinic
1118.33
150(2)
orthorhombic
P2 cn
11.7530(1)
12.4800(1)
39.0720(4)
90
orthorhombic
P2 cn
j
1
1
P1
1
1
11.3050(2)
11.8970(3)
20.7740(6)
96.212(1)
96.477(1)
118.000(2)
2409.50(10)
2
11.6010(1)
12.6060(2)
39.3500(6)
90
90
90
5754.63(14)
4
1.288
0.375
2352
b/Å
c/Å
R/deg
ꢀ/deg
90
90
γ/deg
U/Å3
Z
5730.98(9)
4
1.296
0.377
2360
-3
D
c
/g cm
1.326
0.435
1004
-1
µ/mm
F(000)
crystal size/mm3
θ min., max for
data collection
index ranges
0.25 × 0.20 × 0.12
0.25 × 0.25 × 0.10
0.25 × 0.13 × 0.10
0.15 × 0.07 × 0.07
0.15 × 0.07 × 0.07
3.70, 27.47
4.77, 30.04
3.62, 27.45
3.53, 27.45
3.52, 25.00
-18 e h e 19;
-19 e h e 19;
-19 e k e 19;
-30 e l e 30
79 321
-14 e h e 14;
-15 e k e 15;
-25 e l e 26
24 476
-15 e h e 15;
-16 e k e 16;
-50 e l e 50
83 489
-13 e h e 13;
-14 e k e 14;
-45 e l e 46
60 542
-
-
56 161
18 e k e 18;
21 e l e 21
reflections
collected
independent
reflections, Rint
reflections observed (>2σ)
data
8060, 0.0564
11 386, 0.0600
10 596, 0.0441
12 837, 0.0933
10 099, 0.0914
6642
0.996
8514
0.993
8742
0.961
9950
0.997
7990
0.996
completeness
absorption
correction
max., min.
multiscan
0.94, 0.89
8060/2/430
multiscan
multiscan
multiscan
multiscan
0.95, 0.89
11 386/3/493
0.96, 0.92
10 596/2/601
0.97, 0.92
0.96, 0.93
transmission
data/restraints/
parameters
12 837/30/711
10 099/15/689
goodness-of-fit on F2
final R1, wR2
1.071
0.0318, 0.0729
1.054
0.0396, 0.0945
1.146
0.0504, 0.1100
1.048
0.0472, 0.0757
1.062
0.0470, 0.0792
[
I > 2σ(I)]
final R1, wR2
all data)
largest diff. peak,
hole/eÅ
Flack parameter
0.0443, 0.0787
0.677, -0.547
-
0.0646, 0.1059
0.741, -0.561
-
0.0670, 0.1168
0.961, -0.845
-
0.0778, 0.0843
0.521, -0.508
0.01(2)
0.0730, 0.0874
0.528, -0.461
-0.03(3)
(
-3
reaction mixture was then heated in an oil bath at 343 K for a
set period of time. The NMR tube was removed from the oil
bath and cooled, and the capillary was reinserted before further
component was readily located, it was refined at full occupancy
(as there was no credible possibility of locating 0.3 of a hydrogen
atom!). The asymmetric unit in this structure was also seen to
contain one molecule of THF, also disordered over two sites in
a similar ratio to that for the carbonyl. The minor component
partial atoms in the solvent were treated isotropically in the final
stages of refinement. C3 and C4 of the NHC ring in 13 were
disordered in a 60:40 ratio over two sites. Analysis of 14 showed
that one molecule of THF was also present in the asymmetric
unit, in which two carbons were disordered in a 45:55 ratio.
These disordered atomic fragment atoms were refined subject
to distance and ADP restraints. A very small crystal was chosen
for 15, in order to ensure the sample was “single”. Consequently,
data cutoff is at a Bragg angle of 25°. The asymmetric unit was
seen to contain one molecule of THF in which the carbon atoms
were disordered. This disorder was modeled over two sites in a
40:60 ratio, with O-C and C-C bond distances therein
restrained to being similar.
1
9
74
F spectra were periodically recorded. HDF products were
integrated relative to the standard and identified by comparison
to authentic samples purchased from Fluorochem, Aldrich, or
Apollo Scientific.
X-ray Crystallography. Single crystals of compounds 5, 11,
3, 14, and 15 were analyzed using a Nonius Kappa CCD
1
diffractometer. Details of the data collections, solutions, and
refinements are given in Table 5. The structures were solved
7
5
using SHELXS-97 and refined using full-matrix least-squares
7
5
in SHELXL-97. Where hydrides were located, they were
universally refined at a distance of 1.6 Å from the central metal.
Refinements were generally straightforward. Nonetheless, the
following points are noteworthy. In 5, the hydride was located
and modeled over two positions in 50:50 ratio, based on maxima
in the penultimate difference Fourier map. Carbonyl disorder in
a 70:30 ratio evident in 11 necessarily means that the hydride
must be similarly disordered. However, as the major hydride
Crystallographic data for compounds 5, 11, 13, 14, and 15 have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publications CCDC 697987-697991. Copies of
the data can be obtained free of charge on application to CCDC,
(
74) Kaspi, A. W.; Yahav-Levi, A.; Goldberg, I.; Vigalok, A. Inorg. Chem.
2
008, 47, 5–7.
(
75) Sheldrick, G. M. Acta Crystallogr. 1990, 46-47B, A46. Sheldrick,
G. M. SHELXL-97, a computer program for crystal structure refine-
ment, University of G o¨ ttingen, 1997.
1
2 Union Road, Cambridge CB2 1EZ, UK [fax: (+44) 1223
336033, e-mail: deposit@ccdc.cam.ac.uk].
1
860 J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009

Catalytic Hydrodefluorination of Aromatic Fluorocarbons
A R T I C L E S
Acknowledgment. We acknowledge Johnson Matthey plc for
Supporting Information Available: X-ray crystallographic
files in CIF format for complexes 5, 11, 13, 14, and 15.
3
the loan of RuCl . Financial support was provided via a Doctoral
Analytical and structural data for Ru(NHC)
2 3 2
(PPh )(CO) HF
Training Award to S.P.R. We thank Dr. John Lowe for help with
NMR experiments, Profs. Stuart Macgregor and Robin Perutz for
invaluable discussions, and Prof. Andrew Weller for the loan of
high pressure NMR tubes.
(17-20). This material is available free of charge via the Internet
at http://pubs.acs.org.
JA806545E
J. AM. CHEM. SOC. 9 VOL. 131, NO. 5, 2009 1861