Unexpected H2O-induced Ar-X activation with trifluoromethylpalladium(II) aryls

Article abstract of DOI:10.1021/ja0602389

A series of new complexes [(L-L)Pd(Ar)(CF₃)] (L-L = dppe, dppp, tmeda; Ar = Ph, p-Tol, C₆D₅) have been synthesized and fully characterized in solution and in the solid state. Remarkable Ph-X activation (X = I, Cl) by [(dppe)Pd(Ph)(CF₃)] (1) has been found to come about to cleanly produce biphenyl and [(dppe)Pd(Ph)(X)]. This reaction does not take place under rigorously anhydrous conditions but in the presence of traces of water it readily occurs, exhibiting an induction period and being zero order in PhI. As shown by mechanistic studies, the role of water is to promote reduction of small quantities of the Pd(II) complex to Pd(0) which activates the Ph-X bond. Subsequent transmetalation to give diphenyl Pd complexes, followed by Ph-Ph reductive elimination give rise to the observed products. The water-induced reduction to catalytically active Pd(0) has been demonstrated to proceed via both the Pd(II)/P(III) to Pd(0)/P(V) redox mechanism and α-F transfer, followed by facile hydrolysis of the difluorocarbene to carbonyl, migratory insertion, and reductive elimination of PhC(X)O (X = F, OH, or OOCPh). In the absence of H₂O and ArX, the diphosphine-stabilized trifluoromethyl Pd phenyl complexes undergo slow Ph-CF₃ reductive elimination under reinforcing conditions (xylenes, 145 °C).

Full text of DOI:10.1021/ja0602389

Published on Web 03/18/2006
Unexpected H2O-Induced Ar-X Activation with
Trifluoromethylpalladium(II) Aryls†
Vladimir V. Grushin* and William J. Marshall
Contribution from the Central Research and DeVelopment, E.I. DuPont de Nemours & Co., Inc.,
Experimental Station, Wilmington, Delaware 19880-0328
Received January 19, 2006; E-mail: vlad.grushin-1@usa.dupont.com
Abstract: A series of new complexes [(L-L)Pd(Ar)(CF3)] (L-L ) dppe, dppp, tmeda; Ar ) Ph, p-Tol, C6D5)
have been synthesized and fully characterized in solution and in the solid state. Remarkable Ph-X activation
(X ) I, Cl) by [(dppe)Pd(Ph)(CF3)] (1) has been found to come about to cleanly produce biphenyl and
[(dppe)Pd(Ph)(X)]. This reaction does not take place under rigorously anhydrous conditions but in the
presence of traces of water it readily occurs, exhibiting an induction period and being zero order in PhI. As
shown by mechanistic studies, the role of water is to promote reduction of small quantities of the Pd(II)
complex to Pd(0) which activates the Ph-X bond. Subsequent transmetalation to give diphenyl Pd
complexes, followed by Ph-Ph reductive elimination give rise to the observed products. The water-induced
reduction to catalytically active Pd(0) has been demonstrated to proceed via both the Pd(II)/P(III) to
Pd(0)/P(V) redox mechanism and R-F transfer, followed by facile hydrolysis of the difluorocarbene to
carbonyl, migratory insertion, and reductive elimination of PhC(X)O (X ) F, OH, or OOCPh). In the absence
of H2O and ArX, the diphosphine-stabilized trifluoromethyl Pd phenyl complexes undergo slow Ph-CF3
reductive elimination under reinforcing conditions (xylenes, 145 °C).
Introduction
“CuCF3”. The only reported catalytic reductive coupling reaction
of this type utilizes iodoarenes, perfluoroalkyl iodides (Rf I),
Selectively fluorinated organic compounds commonly exhibit
biological activity.1,2 “At present, up to 30-40% of agrochemi-
cals and 20-30% of pharmaceuticals contain at least one
fluorine atom”.3 Aromatics containing a CF3 group constitute
one of the most important classes of such compounds, including
the highly commercially successful antidepressant Prozac and
herbicide Fusilade.4 There are, however, only a limited number
of methods for the introduction of a perfluoroalkyl group into
the aromatic ring.
Zn metal, and a Pd catalyst under sonication (eq 1).8
Pd cat.
Rf-I + Ar-I + Zn ultrasound8 Rf-Ar + ZnI2
(1)
Perfluoroalkyl palladium aryls are likely to mediate reaction
1, undergoing Ar-Rf reductive elimination from the metal
center.8 Considering the importance of aromatic perfluoroalky-
lation, it is surprising that the chemistry of complexes containing
both a σ-aryl and a perfluoroalkyl on Pd remains largely
unexplored. Among several Pd perfluoroalkyls reported9-14 there
is only one such species, [(dppbz)Pd(CF3)(o-Tol)], where dppbz
) 1,2-bis(diphenylphosphino)benzene, which is reluctant to
undergo C-C reductive elimination for days at 130 °C.13 Herein,
we describe the synthesis, full characterization, and unexpected
striking reactivity of the new complexes [LnPd(Ar)(CF3)].
Some progress has been made in the development of
alternatives to the classical Swarts reaction,5 such as metal-
mediated Ar-CF3 coupling1,2,6,7 which commonly employs ArI
and stoichiometric amounts of in situ generated, reactive
(6) For reviews, see: Dolbier, W. R., Jr. Chim. Oggi 2003, 21, 66. Furin, G.
G. Russ. Chem. ReV. 2000, 69, 491.
(7) Very recently, an efficient procedure for this type of coupling in ionic liquids
was reported: Xiao, J.-C.; Ye, C.; Shreeve, J. M. Org. Lett. 2005, 7, 1963.
(8) Kitazume, T.; Ishikawa, N. Chem. Lett. 1982, 137.
(9) For reviews of perfluoroorganometallic compounds, see: (a) Hughes, R.
P. AdV. Organomet. Chem. 1990, 31, 183. (b) Morrison, J. A. AdV.
Organomet. Chem. 1993, 35, 211. (c) Stone, F. G. A. J. Fluorine Chem.
1999, 100, 227.
(10) Galiotos, J. K.; Morrison, J. A. Organometallics 2000, 19, 2603.
(11) Hughes, R. P.; Overby, J. S.; Williamson, A.; Lam, K.-C.; Concolino, T.
E.; Rheingold, A. L. Organometallics 2000, 19, 5190.
(12) Hughes, R. P.; Meyer, M. A.; Tawa, M. D.; Ward, A. J.; Williamson, A.;
Rheingold, A. L.; Zakharov, L. N. Inorg. Chem. 2004, 43, 747.
(13) Culkin, D. A.; Hartwig, J. F. Organometallics 2004, 23, 3398.
(14) Naumann, D.; Kirij, N. V.; Maggiarosa, N.; Tyrra, W.; Yagupolskii, Y.
L.; Wickleder, M. S. Z. Anorg. Allg. Chem. 2004, 630, 746.
† Contribution No. 8662.
(1) For a recent monograph, see: Kirsch, P Modern Fluoroorganic Chemistry;
Wiley-VCH: Weinheim, 2004.
(2) For a monograph on fluorinated aromatic compounds, see: Clark, J. H.;
Wails, D.; Bastock, T. W. Aromatic Fluorination; CRC Press: Boca Raton,
FL, 1996.
(3) Large, S.; Roques, N.; Langlois, B. R. J. Org. Chem. 2000, 65, 8848.
(4) Quadbeck-Seeger, H.-J.; Faust, R.; Knaus, G.; Siemeling, U. World Records
in Chemistry; Wiley-VCH: Weinheim, 1999.
(5) The Swarts reaction (displacement of aliphatic Cl with F in the presence
of antimony fluorides) has been known for over a century: Swarts, F. Acad.
R. Belg. 1892, 24, 309.
9
4632
J. AM. CHEM. SOC. 2006, 128, 4632-4641
10.1021/ja0602389 CCC: $33.50 © 2006 American Chemical Society

H2O-Induced Ar−X Activation
A R T I C L E S
Figure 1. ORTEP drawings of 1 (left) and 4 (right) with thermal ellipsoids shown at the 50% probability level.
Scheme 1
New complexes 1-10 were characterized by elemental
analysis and 1H, 19F, and 31P NMR data (see the Experimental
Section). Complexes 1, 4, 6, 9, and 10 were also studied by
single-crystal X-ray diffraction (e.g., Figure 1). Selected ge-
ometry parameters for these structures and for [(dppe)Pd(CF3)I]
(11) and [(dppe)Pd(CF3)Cl] (12) (see below) are presented in
Table 1.
The data in Table 1 complement the recent detailed structural
studies of a series of RfPd complexes by Hughes’ group and
Rheingold and Zakharov.11,12 Our structural data confirms the
conclusion11,12 that a CF3 group has a much stronger trans
influence than I and Cl, as can be judged by the Pd-P bond
distances in complexes 11 and 12 (Table 1). This difference is
particularly significant for the chloro complex 12, in which the
Pd-P bond trans to CF3 is 0.10 Å longer than the one trans to
Cl. Considering the fact that the trans influence might be
governed exclusively by inductive/field effects16 and that the
field parameters for Cl and CF3 are very similar,17 the difference
of 0.10 Å is remarkable. Indeed, the values17 of σm (Hammett),
F (Swain-Lupton, modified), and σF (Taft) for Cl vs CF3 are
σm ) 0.37 vs 0.43, F ) 0.42 vs 0.38, and σF ) 0.43 vs 0.46.
Even more astounding is the fact that in the nonfluorinated
analogue of 12, [(dppe)Pd(CH3)Cl], the Pd-P bond distances18
of 2.339(1) Å (trans to C) and 2.231(1) Å (trans to Cl) are
approximately the same as those in 12 (Tables 1 and 2). Unlike
the strongly electron-withdrawing CF3 (see above), a methyl
group is almost electroneutral (σm ) -0.07; F ) 0.01; σF )
0.01).17
The previously obtained data on the trans influence of
perfluoroalkyl groups vs methyl are not without controversy.11,12
Nonetheless, the almost identical coordination geometry in the
structures of [(dppe)Pd(CF3)Cl] (12) and [(dppe)Pd(CH3)Cl]
(Table 2; Figure 2) is unexpected. The chlorine/methyl disorder
of 8% was determined from the refined occupancies and is too
small to affect substantially the real values for the geometry
parameters. Furthermore, the structure of [(dcpe)Pd(CH3)Cl]18
(dcpe ) 1,2-bis(dicyclohexylphosphino)ethane) that is devoid
of disorder, displays essentially the same parameters (Table 2).
Therefore, we conclude that for this series of complexes, the
trans and cis influence of the electronically and sterically
different CH3 and CF3 groups are strikingly similar.19 In contrast,
Results and Discussion
Synthesis and Characterization. New trifluoromethyl pal-
ladium aryls were prepared using Ruppert’s reagent, Me3SiCF3,
in the presence of CsF (Scheme 1). The Me3SiCF3/F- system
has been widely used to make CF3-derivatives of various metals,
including Pd.13,14 The reaction of [(dppe)Pd(I)Ph] with excess
Me3SiCF3/CsF cleanly produced [(dppe)Pd(CF3)Ph] (1) which
was isolated spectroscopically and analytically pure in 69%
yield. Similarly, [(tmeda)Pd(CF3)Ph] (6) was prepared in 91%
yield from [(tmeda)Pd(I)Ph].15 An alternative route was devel-
oped to 1 by reacting 6 with dppe in the presence of KHSO4 as
a scavenger for the tmeda released upon P,P/N,N ligand
exchange. Such ligand exchange could also be performed in
situ, i.e., by running the reaction of [(tmeda)Pd(I)Ph] with Me3-
SiCF3/CsF in the presence of a bidentate phosphine. This
technique was found most convenient for the preparation of
[(dppp)Pd(CF3)Ph] (4). The aforementioned methods were also
used for the synthesis of analogous complexes containing σ-p-
Tol and σ-C6D5 ligands (Scheme 1). An attempt to prepare
[(tmeda)Pd(CF3)2] from [(tmeda)PdCl2] failed due to the poor
solubility of the latter. However, more easily soluble [(teeda)-
PdCl2] (teeda ) tetraethylethylenediamine) and [(dippp)PdCl2]
(dippp ) bis(1,3-diisopropylphosphinopropane) were readily
converted to [(teeda)Pd(CF3)2] (9) and [(dippp)Pd(CF3)2] (10),
respectively, upon treatment with Me3SiCF3/CsF.
(15) The reaction of [(Ph3P)2Pd(I)Ph] with Me3SiCF3/CsF was poorly selective,
leading to inseparable reaction mixtures due to facile phosphine displace-
ment. The formation of a mixture of trans-[(Ph3P)2Pd(CF3)Ph], cis- and
trans-[(Ph3P)Pd(CF3)2Ph]-, and free PPh3 was observed by 19F and 31P
NMR even at <50% conversion. This result is consistent with the recent
report14 demonstrating facile displacement of PPh3 on Pd and Pt with CF3
upon treatment with Me3SiCF3/[Me4N]F.
(16) Landis, C. R.; Firman, T. K.; Root, D. M.; Cleveland, T. J. Am. Chem.
Soc. 1998, 120, 1842.
(17) Hansch, H.; Leo, A.; Taft, R. W. Chem. ReV. 1991, 97, 165.
(18) Calabrese, J. C. Unpublished results (DuPont Crystallographic Database,
1996).
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J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006 4633

A R T I C L E S
Grushin and Marshall
[(dppe)-
Table 1. Selected Geometry Parameters for 1, 4, 6, and 9-12
complex
[(dppe)-
Pd(Ph)CF3]
hexane 1
[(dppp)-
[(tmeda)-
Pd(Ph)CF3]
6
[(teeda)-
Pd(CF3)2]
9
[(dippp)-
Pd(CF3)2]
10
[(dppe)-
Pd(CF3)I]
11a
geometry params
(Å or deg)
‚
Pd(Ph)CF3]
‚
4
Pd(CF3)Cl]‚
1/2PhCl 12
1/2CH2Cl2
Pd-Ph
2.056(2)
2.067(2)
2.055(2)
2.071(2)
1.996(1)
1.993(1)
Pd-CF3
2.025(1)
2.070(4)
2.090(4)
2.157(8)
2.646(1)
2.255(1)
2.302(1)
2.084(3)
Pd-I
Pd-Cl
Pd-P
(trans to Ph or X)
Pd-P
(trans to CF3)
Pd-N
(trans to Ph)
Pd-N
(trans to CF3)
2.354(1)
2.246(1)
2.341(1)
2.298(1)
2.356(1)
2.310(1)
2.342(1)
2.343(1)
2.345(1)
2.198(1)
2.169(1)
85.28(6)
2.193(1)
85.90(7)
CF3-Pd-Ph (or X)
86.73(6)
84.85(7)
92.0(2)
88.71(8)
CF3-Pd-CF3
86.1(2)
Ph-Pd-P (cis)
CF3-Pd-P (cis)
89.04(5)
99.14(5)
85.57(5)
96.21(5)
89.6(1)
90.1(1)
93.9(2)
91.01(8)
85.37(3)
P-Pd-P
N-Pd-N
Ph-Pd-N (cis)
CF3-Pd-N (cis)
X-Pd-P (cis)
85.10(2)
93.36(2)
84.42(5)
82.77(5)
93.76(6)
98.27(6)
83.06(5)
95.54(5)
89.68(4)
94.77(3)
a The iodine and CF3 groups are disordered (0.87/0.13), and hence the presented Pd-CF3 bond distance for 11 may be artificially lengthened.
Table 2. Selected Geometry Parameters for [(dppe)Pd(CF3)Cl], [(dppe)Pd(CH3)Cl], and [(dcpe)Pd(CH3)Cl]
geometry parameter
(Å or deg)
[(dppe)Pd(CF3)Cl] (12)
[(dppe)Pd(CH3)Cl]a
(ref 18)
[(dcpe)Pd(CH3)Cl]
(ref 18)
(this work)
Pd-C
2.084(3)
2.354(1)
2.345(1)
2.246(1)
88.71(8)
85.37(3)
91.01(8); 176.06(8)
94.77(3); 175.36(3)
2.135(4)
2.376(1)
2.339(1)
2.231(1)
87.0(2)
86.26(4)
91.1(2); 177.4(2)
95.68(4); 174.86(5)
2.130(6)
2.381(2)
2.320(2)
2.222(2)
89.22(2)
87.74(6)
91.0(2); 175.8(2)
92.38(6); 175.08(6)
Pd-Cl
Pd-P (trans to C)
Pd-P (trans to Cl)
C-Pd-Cl
P-Pd-P
C-Pd-P
Cl-Pd-P
a There is a minor 8% chlorine/methyl disorder as determined from the refined occupancies.
P(N) bond distances trans to the Ph ligands are less than 0.05
Å longer than those trans to the CF3 groups (Table 1), despite
the fact that a phenyl group is a much weaker acceptor (σm
)
0.06; F ) 0.12; σF ) 0.14).17 The Pd-Ph and Pd-CF3 bond
distances are almost the same within the molecules of 1
(2.056(2) and 2.067(2) Å), 4 (2.055(2) and 2.071(2) Å), and 6
(1.996(1) and 1.993(1) Å).
Ar-X Activation. To model catalytic formation of PhCF3,
reductive elimination from 1 was studied in the presence of PhI.
It was reasoned that, if the Ph-CF3 bond formed, the resulting
Pd(0) would be trapped by in situ Ph-I oxidative addition to
give [(dppe)Pd(I)Ph]. Against this expectation, however, the
reaction took a completely different path, leading cleanly to
[(dppe)Pd(CF3)I] (11) and biphenyl (eq 2). Similarly, heating
1 in neat PhCl for 2 h at 135 °C did not produce PhCF3, but
full conversion of 1 was observed to Ph2 and [(dppe)Pd(CF3)-
Figure 2. Superimposed molecules of [(dppe)Pd(CF3)Cl] (12) and its
nonfluorinated congener [(dppe)Pd(CH3)Cl], showing essentially identical
coordination geometry around Pd.
(19) (a) As early as 1972, Clark and co-workers19b reported that the trans
influence of a CF3 group in a series of Pt complexes is almost as strong as
that of a methyl group. Bennett et al.19c have observed both smaller and
larger trans influence for CF3 as compared to that for CH3. For a detailed
discussion, see refs 11 and 12. (b) Appleton, T. G.; Chisholm, M. H.; Clark,
H. C.; Manzer, L. E. Inorg. Chem. 1972, 11, 1786. (c) Bennett, M. A.;
Chee, H.-K.; Robertson, G. B. Inorg. Chem. 1979, 18, 1061. Bennett, M.
A.; Chee, H.-K.; Jeffery, J. C.; Robertson, G. B. Inorg. Chem. 1979, 18,
1071.
the Pd-N bond distances trans to C in [(tmeda)Pd(i-C3F7)I]
and [(tmeda)Pd(CH3)I] have been measured11 at 2.137(18) and
2.204(7) Å, respectively, clearly indicating that CH3 is a stronger
trans influencing ligand than perfluoroalkyl (i-C3F7). The Pd-
9
4634 J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006

H2O-Induced Ar−X Activation
A R T I C L E S
Figure 3. ORTEP drawings of 11 (left) and 12 (right) with thermal ellipsoids shown at the 50% probability level.
Cl] (12) at ca. 90% selectivity. Both 11 and 1220 were fully
characterized, including X-ray diffraction (Figure 3).
The reactivity of 1 toward PhCl and PhI (eq 2) was striking.
Although PhX oxidative addition to the Pd(II) center, followed
by Ph-Ph reductive elimination from Pd(IV) would rationalize
the observed results, this path is highly unlikely,21 especially
given the particular inertness of the Ph-Cl bond.22 To gain
insight into the mechanism of this remarkable ArX activation
with a Pd(II) complex, a series of experiments were carried out
and observations made, as follows.
[(dppe)Pd(CF3)(C6D5)] (3) at 115 °C in toluene in the presence
or absence of H2O for 6 h.
(5) Complex 4, the dppp analogue of 1, reacted with PhI
similarly, except that faster kinetics and lower selectivities were
observed.
(6) The iodo congener of 1, [(dppe)Pd(Ph)(I)], appeared
unreactive toward PhI under similar conditions.
(1) A free radical mechanism proposed23 for the formally
similar reactivity of a PCP Pd pincer complex can be ruled out
since reaction 2 in toluene did not produce bibenzyl (GC-MS).
(2) Reaction 2 is promoted by adventitious water. No reaction
was observed under rigorously anhydrous conditions commonly
used in our laboratories.24 Upon deliberate addition of minute
quantities of water, an induction period (0.5-1 h) was observed,
after which the reaction proceeded with acceleration, displaying
complex kinetics and being zero order in PhI.
(3) The H2O-induced reaction of [(dppe)Pd(CF3)(p-Tol)] (2)
with C6D5I gave rise (GC-MS) to p-Tol-C6D5 (ca. 60%), Ph-
C6D5 (ca. 20%), and smaller quantities of (C6D5)2, p-Tol-Ph,
Ph2 and p-Tol2 (eq 3). The aryl scrambling was also observed
by 19F NMR, especially toward the end of the reaction.
(4) No aryl-aryl exchange was detected (NMR) after heating
[(dppe)Pd(CF3)(p-Tol)] (2), [(dppp)Pd(CF3)(p-Tol)] (5), or
(7) Reaction 2 shares some features with the arylation of PhI
with [L2PdPh2] (L ) Et2PPh) to give Ph2 and [L2Pd(I)Ph].25a
Both exhibit an induction period and are zero order in PhI.
Unlike the reaction of [L2PdPh2] with PhI, which is catalyzed
by its product, [L2Pd(I)Ph],25a reaction 2 is not autocatalytic in
11. However, reaction 2 was found to be catalyzed by [(dppe)-
Pd(Ph)(I)] (7 mol %) under anhydrous conditions.26 Even in
the presence of catalytic quantities of [(dppe)Pd(Ph)(I)], reaction
2 was slow at the beginning, accelerating upon formation of
11, with the conversion being ca. 1% and 30% after 2 and 4 h
at 115 °C, respectively.
On the basis of the above data, a mechanism is presented
(Scheme 2) that involves an in situ transformation of a small
quantity of 1 to a reactive, phosphine-stabilized Pd(0) species
which undergoes facile oxidative addition of PhI. The resulting
[LPd(I)Ph] then reacts with 1 via transmetalation,25,27 with the
iodo ligand providing critical nucleophilic assistance to the SE-
Ar-type process.28 The promoting but not catalytic effect of the
(20) Strukul, G.; Ros, R.; Michelin, R. A. Inorg. Chem. 1982, 21, 495.
(21) See, for example: Bo¨hm, V. P. W.; Herrmann, W. A. Chem. Eur. J. 2001,
7, 4191. Canty, A. J.; Patel, J.; Rodemann, T.; Ryan, J. H.; Skelton, B.
W.; White, A. H. Organometallics 2004, 23, 3466. Consorti, C. S.; Flores,
F. R.; Dupont, J. J. Am. Chem. Soc. 2005, 127, 12054 and references therein.
(22) Grushin, V. V.; Alper, H. Chem. ReV. 1994, 94, 1047.
(23) Kraatz, H.-B.; Van der Boom, M. E.; Ben-David, Y.; Milstein, D. Isr. J.
Chem. 2001, 41, 163.
(25) (a) Ozawa, F.; Hidaka, T.; Yamamoto, T.; Yamamoto, A. J. Organomet.
Chem. 1987, 330, 253. (b) Ozawa, F.; Fujimori, M.; Yamamoto, T.;
Yamamoto, A. Organometallics 1986, 5, 2144.
(26) Insufficiently purified samples of 1-3 were found to react with PhI in the
absence of added water, likely due to contamination with small quantities
of the catalytically active starting materials [(dppe)Pd(Ar)(I)].
(27) For a recent report, see: Albeniz, A. C.; Espinet, P.; Lo´pez-Cimas, O.;
Mart´ın-Ruiz, B. Chem. Eur. J. 2005, 11, 242 and references therein.
(24) Macgregor, S. A.; Roe, D. C.; Marshall, W. J.; Bloch, K. M.; Bakhmutov,
V. I.; Grushin, V. V. J. Am. Chem. Soc. 2005, 127, 15304 and references
therein.
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A R T I C L E S
Scheme 2
Grushin and Marshall
carbonyl,31 migratory insertion to Pd benzoyl, and reductive
elimination of PhC(X)O, where X ) F34 or OOCPh35 if the
Pd-F bond is hydrolyzed.
The Key First Step: Pd(II) Reduction. To elucidate the
reduction mechanism, 1 was decomposed with water in toluene
in a sealed high-pressure NMR sapphire tube at 115 °C. After
ca. 1 h the solution turned light tan, and several hours later
Pd(0) was produced in the form of palladium metal, along with
reddish-brown viscous oil, poorly soluble in toluene. After 24
h, full conversion of 1 was observed. The 19F NMR spectrum
displayed several resonances from the decomposition products,
of which two were reliably identified by their characteristic
chemical shifts and coupling constant, PhC(F)O (+16 ppm, s)
and CF3H (-79.8 ppm, d, JF-H ) 80 Hz). Only few signals of
very low intensity were found in the 31P NMR spectrum of the
same sample, indicating that almost all P-containing species
were located in the red-brown oily precipitate, rather than in
the toluene phase. The tube was then unsealed under N2 in a
drybox, and the toluene solution was decanted off the brown
oil. GC-MS analysis of the toluene fraction confirmed the
formation of PhC(F)O and revealed the presence of benzene,
biphenyl, benzophenone, and benzoic anhydride, among other
products. The toluene-insoluble red-brown oil was dissolved in
MeCN and analyzed by 31P NMR. A number of broad
resonances were observed, along with two sharp lines from
[(dppe)2Pd]2+ (58.0 ppm) and dppeO2 (30.8 ppm). To release
all P-ligands coordinated to palladium, the solution was treated
with excess [Bu4N]+ CN-. After this treatment, 31P NMR
analysis of the sample indicated the presence of free dppe
(singlet, -12.8 ppm), dppeO (two doublets, -12.0 and 29.5
ppm, JP-P ) 48.3 Hz),29 and dppeO2 (singlet, 30.8 ppm), in a
ca. 6:3:2 ratio.
product (11) might deal with extra nucleophilic assistance from
its I ligand, i.e. [LPd(I)Ph] interacts with 1 only via Ph, with
iodide for coordination to 1 provided by 11.28b Reductive
elimination of biphenyl completes the catalytic cycle (Scheme
2).
The catalytic loop presented in Scheme 2 is similar to the
Ozawa-Yamamoto mechanism,25 although the origin of the Pd-
(0) is unclear. There are at least a few pathways that might
produce Pd(0) from 1 and H2O. The water-induced Pd(II)/P(III)
to Pd(0)/P(V) process would conceivably lead to “[(dppeO)-
Pd]”.29,30 Stoichiometry considerations suggest that the reaction
of 1 with water should give “[(dppeO)Pd]”, PhH, and CF3H. In
fact, monitoring reaction 2 by 31P NMR often revealed the
presence of a small amount (1-5%) of a species exhibiting two
doublets at 43.4 and 58.3 ppm (JP-P ) 26.7 Hz) which is
consistent with a Pd-dppeO moiety (but not free dppeO29).
Alternatively, Pd(0) might be generated from 1 via R-F
transfer,31,32 followed by coupling of the (F)PddCF2 with the
Ph ligand33 or facile hydrolysis of the difluorocarbene to
Apart from the Pd(0) produced, all of the identified products
of the reaction of 1 with H2O in toluene can be divided into
two groups, A and B (eq 4). The A group products, dppe and
(28) (a) Reutov, O. A.; Beletskaya, I. P. Reaction Mechanisms of Organometallic
Compounds; Wiley-Interscience: New York, 1968. (b) A reviewer proposed
that the transmetalation step (Scheme 2) might involve more reactive28c
Pd species produced upon ionization of the Pd-I bond. Such Pd-I
ionization is certainly a possibility, which would give rise to a cationic Pd
species of enhanced electrophilicity. The critical28a nucleophilic assistance
might then come from the I- formed upon Pd-I bond ionization or be
provided by 11. (c) See, for example: Kawataka, F.; Kayaki, Y.; Shimizu,
I.; Yamamoto, A. Organometallics 1994, 13, 3517. Yamamoto, A. J.
Organomet. Chem. 1995, 500, 337. Kayaki, Y.; Shimizu, I.; Yamamoto,
A. Bull. Chem. Soc. Jpn. 1997, 70, 917.
(29) For a recent review, see: Grushin, V. V. Chem. ReV. 2004, 104, 1629.
(30) For original research papers reporting the Pd(II)/P(III) to Pd(0)/P(V) redox
transformation, induced by hard nucelophiles, such as F-, AcO-, OH-,
and H2O, see: (a) Mason, M. R.; Verkade, J. G. Organometallics 1990, 9,
864 and 1992, 11, 2212. (b) Ioele, M.; Ortaggi, G.; Scarsella, M.; Sleiter,
G. Polyhedron 1991, 10, 2475. (c) Amatore, C.; Jutand, A.; M’Barki, M.
A. Organometallics 1992, 11, 3009. (d) Ozawa, F.; Kubo, A.; Hayashi, T.
Chem. Lett. 1992, 2177. (e) Grushin, V. V.; Alper, H. Organometallics
1993, 12, 1890. (f) Mandai, T.; Matsumoto, T.; Tsuji, J.; Saito, S.
Tetrahedron Lett. 1993, 34, 2513. (g) Ozawa, F.; Kubo, A.; Matsumoto,
Y.; Hayashi, T.; Nishioka, E.; Yanagi, K.; Moriguchi, K. Organometallics
1993, 12, 4188. (h) Grushin, V. V.; Bensimon, C.; Alper, H. Inorg. Chem.
1994, 33, 4804. (i) Monteil, F.; Kalck, P. J. Organomet. Chem. 1994, 482,
45. (j) Amatore, C.; Carre´, E.; Jutand, A.; M’Barki, M. A. Organometallics
1995, 14, 1818. (k) Amatore, C.; Blart, E.; Geneˆt, J. P.; Jutand, A.; Lemaire-
Audoire, S.; Savignac, M. J. Org. Chem. 1995, 60, 6929. (l) Papadogianakis,
G.; Peters, J. A.; Maat, L.; Sheldon, R. A. J. Chem. Soc., Chem. Commun.
1995, 1105.
aromatic carbonyl compounds, point to the Pd reduction path
involving R-F transfer31,32 leading to a fluoro difluorocarbene
σ-phenyl palladium complex. At this point, the dppe ligand may
be coordinated to the metal in a monodentate fashion. The
difluorocarbene ligand is fully expected31 to be highly suscep-
tible to hydrolysis leading to a carbonyl species. The latter
undergoes facile migratory insertion to produce a Pd benzoyl,
followed by reductive elimination (Scheme 3). If the Pd-F bond
is hydrolyzed prior to that, benzoic anhydride rather than PhC-
(31) For a review, see: Brothers, P. J.; Roper, W. R. Chem. ReV. 1988, 88,
1293.
(32) Huang, D.; Caulton, K. G. J. Am. Chem. Soc. 1997, 119, 3185. Huang, D.;
Koren, P. R.; Folting, K.; Davidson, E. R.; Caulton, K. G. J. Am. Chem.
Soc. 2000, 122, 8916.
(34) Fraser, S. L.; Antipin, M. Yu.; Khroustalyov, V. N.; Grushin, V. V. J. Am.
Chem. Soc. 1997, 119, 4769.
(35) Grushin, V. V.; Alper, H. J. Am. Chem. Soc. 1995, 117, 4305.
(33) van der Boom, M. E.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1999,
121, 6652.
9
4636 J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006

H2O-Induced Ar−X Activation
A R T I C L E S
Scheme 3
might proceed via a metallophosphorane, as has been recently
demonstrated by Macgregor.24,36
The two reduction mechanisms may be symbiotic. For
instance, the HF produced upon hydrolysis of the CF2 ligand
(Scheme 3) might facilitate protonolysis of the Pd-Ph bond
(Scheme 4). It is also conceivable that the formation of dppeO
(Scheme 4) may accelerate the hydrolysis of the C-F bonds
(Scheme 3) due to the basicity of the oxygen center of dppeO.
The overall mechanism (Scheme 2) is fully consistent with
the lack of reactivity of [(dippp)Pd(CF3)2] (10) that is devoid
of a σ-aryl ligand, toward PhI and PhCl in the temperature range
of 115-145 °C.
The Ar/Ar exchange accompanying the reaction (e.g., eq 3)
likely occurs via reversible P-C reductive elimination,39-45
although a metallophosphorane path24,36 cannot be completely
ruled out. Commonly, P-C reductive elimination from a σ-aryl
Pd(II) tertiary phosphine complex requires coordinative un-
saturation,39-43 whereas the metallophosphorane path does not,24
and sometimes both can be observed simultaneously.24,43 The
complexity of the water-induced reduction of 1 to zero-valent
palladium (Schemes 3 and 4) prevents a conclusive study of
the Ar/Ar exchange during the reaction (eq 3). Nonetheless,
the fact that the Ar/Ar exchange does occur during the reaction
(eqs 2 and 3) but not upon heating four-coordinate 2, 3, or 5 at
the same temperature (see above) supports the P-C reductive
elimination path which involves coordinatiVely unsaturated Pd
aryls.
Scheme 4
The lack of reactivity of [(dppe)Pd(I)Ph] toward PhI under
conditions employed for reaction 2 indicates that the CF3 group
in 1 facilitates the transmetalation, apparently by lowering the
accessible LUMO on Pd and thus increasing the efficiency of
nucleophilic assistance to SEAr via (CF3)Pd‚‚‚I-Pd interaction.
In accord with the mechanism shown in Scheme 2, [(dippp)-
Pd(CF3)2] and [(teeda)Pd(CF3)2] remained unreactive toward ArI
under the standard conditions (eq 2).
(F)O is the final product. The formation of (PhCO)2O upon
reaction of [(Ph3P)2Pd2(Ph)2(OH)2] with CO has been demon-
strated35 to occur via initial reductive elimination of PhCOOH.
The acid reacts instantaneously with the as yet unreacted
hydroxo complex to produce a Pd benzoyl benzoate which
reductively eliminates the anhydride.35 As for the formation of
benzophenone, it would take place via transmetalation giving
rise to a σ-phenyl Pd benzoyl.
The B-group products come from the reduction of Pd(II) to
Pd(0) at the expense of dppe oxidation29,30 (Scheme 4). The
first step likely involves coordination of H2O to the metal center
and protonolysis of the Pd-Ph bond. Intramolecular nucleophilic
attack of the OH ligand on a phosphorus atom24 followed by H
transfer36 and H-CF3 reductive elimination should lead to
Pd(0) stabilized by only one dppeO ligand. Disproportionation
of the “(dppeO)Pd” then gives rise to Pd metal and
[(dppeO)nPd].37 P-ligand exchange between the dppeO Pd(0)
species produced and the starting complex 1 would yield
[(dppeO)2Pd(Ph)CF3] which can also undergo the Pd(II)/P(III)
to Pd(0)/P(V) transformation, to give dppeO2 (Scheme 4).
Although the sequence of events is not precisely known, it is
clear that the formation of Pd(0) from 1 is due to at least two
well-documented reactions, R-F transfer31,32 (Scheme 3) and the
Pd(II)/P(III) to Pd(0)/P(V) redox process29,30 (Scheme 4) which
Although a detailed study of Ar-CF3 reductive elimination
is beyond the scope of this work, we would like to disclose
some of our preliminary results in this article. Like [(dppbz)-
Pd(CF3)(o-Tol)],13 our trifluoromethyl palladium aryls did not
undergo Ar-CF3 reductive elimination at 130 °C. The formation
(37) We attempted the synthesis and isolation of [(dppeO)Pd(Ph)I] to demonstrate
that this complex, like [(dppe)Pd(Ph)I], can catalyze reaction 2. For that,
a 1:2 mixture of [Pd2(dba)3] and dppeO in benzene was treated with excess
PhI. In this way we had earlier prepared and successfully isolated [(dppmO)-
Pd(Ph)I].29 Unlike the latter, however, its dppeO congener was not isolable,
probably due to poor stability. We believe that the weak dppeO chelation
(seven-membered ring) makes the complex more prone to oligomerization38
and/or P-C reductive elimination (see below), as compared to the much
more stable six-membered dppmO chelate.29 Nonetheless, the in situ
generated [(dppeO)Pd(Ph)I], a stronger electrophile than [(dppe)Pd(Ph)I],
is expected (Scheme 2) to contribute to the catalysis of reaction 2.
(38) Coyle, R. J.; Slovokhotov, Yu. L.; Antipin, M. Yu.; Grushin, V. V.
Polyhedron 1998, 17, 3059.
(39) Kong, K.-C.; Cheng, C.-H. J. Am. Chem. Soc. 1991, 113, 6313.
(40) Sakamoto, M.; Shimizu, I.; Yamamoto, A. Chem. Lett. 1995, 1101.
(41) Segelstein, B. E.; Butler, T. W.; Chenard, B. L. J. Org. Chem. 1995, 60,
12.
(42) Goodson, F. E.; Wallow, T. I.; Novak, B. M. J. Am. Chem. Soc. 1997,
119, 12441.
(43) Grushin, V. V. Organometallics 2000, 19, 1888.
(44) For Ar/Ar exchange in dppe Pd aryls, see, for example: Baranano, D.;
Hartwig, J. F. J. Am. Chem. Soc. 1995, 117, 2937. Mann, G.; Baranano,
D.; Hartwig, J. F.; Rheingold, A. L.; Guzei, I. A. J. Am. Chem. Soc. 1998,
120, 9205.
(45) For examples of facile P-C reductive elimination from cyclopalladated
complexes, see: (a) Vicente, J.; Arcas, A.; Bautista, D.; Tiripicchio, A.;
Tiripicchio-Camellini, M. New J. Chem. 1996, 20, 345. (b) Vicente, J.;
Arcas, A.; Bautista, D.; Jones, P. G. Organometallics 1997, 16, 2127. (c)
Vicente, J.; Abad, J.-A.; Frankland, A. D.; Ram´ırez de Arellano, M. C.
Chem. Eur. J. 1999, 5, 3066.
(36) Macgregor, S. A.; Neave, G. W. Organometallics 2004, 23, 891.
9
J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006 4637

A R T I C L E S
Grushin and Marshall
separated from the almost colorless mother liquor, washed with hexanes,
and dried under vacuum. The yield of >95% pure (31P NMR) [(dppe)-
Pd(Ph)I] was 0.49 g (99%).
of PhCF3, however, was observed after heating 1 or 4 in the
presence of dppe and dppp, respectively, in xylenes at 145 °C
(oil bath). The reaction of 1 was very sluggish and poorly
selective, producing PhCF3 in only ca. 10% yield (19F NMR)
after 64 h. The decomposition of 4 in the presence of dppp
under similar conditions was at least an order of magnitude
faster, with the selectivity toward PhCF3 being ca. 60%.
Complex 6 produced only traces of PhCF3 under such condi-
tions.
[(dppp)Pd(Ph)I]. A mixture of [(tmeda)Pd(Ph)I] (0.30 g; 0.70
mmol), dppp (0.33 g; 0.80 mmol), and toluene (5 mL) was stirred under
N2 at room temperature for 4 h. The originally formed amorphous-
looking precipitate first turned oily, and then a crystalline solid formed.
Ether (12 mL) was added, and the mixture was stirred overnight. The
yellow solid was separated from the purple mother liquor, washed with
ether, and recrystallized from 1,2-dichloroethane-ether to produce
orange crystalline [(dppp)Pd(Ph)I] in 0.41 g (81%) yield.
Conclusions
[(tmeda)Pd(Ph)CF3]. In a glovebox, a 25-mL round-bottom flask
with a magnetic stir-bar was charged with [(tmeda)Pd(Ph)I] (0.62 g;
1.45 mmol), freshly dried, finely ground CsF (0.66 g; 4.34 mmol), and
THF (10 mL). The flask was capped with a rubber septum and brought
out. At stirring, CF3SiMe3 (0.40 mL; 2.71 mmol) was syringed in, and
the mixture was vigorously stirred at room temperature until decolori-
zation (2 h) and then for an additional 0.5 h. The product was isolated
in air. The solution was evaporated and the residue extracted with CH2-
Cl2 (10 mL, then 3 × 3 mL). The combined extracts were filtered
through Celite, evaporated to ca. 1 mL, and treated with ether (40 mL).
After standing at +5 °C overnight, the white crystals were collected,
washed with ether, and dried under vacuum. The yield was 0.47 g.
Evaporation of the combined mother liquor and the washings produced
a residue which gave additional 0.02 g of the pure product upon washing
with ether and drying. Total yield: 0.49 g (91%). Anal. Calcd for
C13H21F3N2Pd, %: C, 42.3; H, 5.7; N, 7.6. Found, %: C, 42.1; H, 5.6;
We have conducted the first systematic study of trifluoro-
methylpalladium aryls, including high-yield synthesis and full
characterization of a series of new complexes of that type. Some
of these complexes can undergo Ar-CF3 reductive elimination
under reinforcing conditions. It has been found that the new
CF3Pd(II) aryl complexes are surprisingly capable of activating
the inert Ar-X (X ) I, Cl) bonds of nonactivated haloarenes.
This reaction is induced by traces of water and involves the
formation of minute quantities of Pd(0) species which serve as
a catalyst for the process. The reaction then involves Ar-X
oxidative addition to the Pd(0) catalyst, followed by trans-
metalation to give biaryl Pd complexes and their Ar-Ar
reductive elimination reaction. The water-induced reduction to
catalytically active Pd(0) has been demonstrated to occur via
both the Pd(II)/P(III) to Pd(0)/P(V) redox process and R-F
transfer, followed by facile hydrolysis of the difluorocarbene
to carbonyl, migratory insertion, and reductive elimination of
PhC(X)O, where X ) F, OH, or OOCPh.
The Ar-X activation chemistry described in this article
points, once again, to the inability of Pd(II) species to oxidatively
add the C-X bond of nonactivated haloarenes.21 The new
“hidden” pathway (Schemes 2-4), as elucidated by mechanistic
studies, involves H2O-induced reduction of the Pd(II) complex
to a small quantity of Pd(0) which, in tandem with the initial
Pd(II) aryl, provides an easy path for activation and coupling
of the ArX substrate.
1
N, 7.4. H NMR (CD2Cl2, 20 °C), δ: 2.2 (s, 6H, CH3), 2.6 (br, 4H,
CH2), 2.7 (s, 6H, CH3), 6.9 (m, 1H, p-Ph), 7.0 (m, 2H, m-Ph), 7.5 (m,
2H, o-Ph). 19F NMR (CD2Cl2, 20 °C), δ: -21.2 (s).
[(tmeda)Pd(Tol)CF3]. In a glovebox, a 50-mL flask with a magnetic
stir-bar was charged with [(tmeda)Pd(Tol)I] (1.00 g; 2.34 mmol), freshly
dried, finely ground CsF (0.95 g; 6.25 mmol), and THF (20 mL). The
flask was capped with a rubber septum and brought out. At stirring,
CF3SiMe3 (0.70 mL; 4.74 mmol) was syringed in, and the mixture was
vigorously stirred at room temperature for 1.5 h, until the original orange
color was gone. The product was isolated in air. The solution was
evaporated and the residue extracted with CH2Cl2 (20 mL, then 3 × 5
mL). The combined extracts were filtered through Celite, evaporated
to ca. 2 mL, and treated with ether (30 mL). After standing at +5 °C
for 6 h, the white crystals were collected, washed with ether, and dried
under vacuum. The yield was 0.785 g (90%). Anal. Calcd for
C14H23F3N2Pd, %: C, 43.9; H, 6.1; N, 7.3. Found, %: C, 43.6; H, 5.9;
Experimental Section
1
All chemicals were purchased from Aldrich and Strem chemical
companies and used as received. The solvents were thoroughly dried
using standard techniques and stored over freshly calcined molecular
sieves (4 Å) in a glovebox. dppeO,46 [(tmeda)Pd(Ar)I],47 and [(dippp)-
PdCl2],48 were prepared as described in the literature. All manipulations
were carried out under nitrogen in a glovebox, unless otherwise noted.
NMR spectra were obtained with a Bruker Avance DRX400 spectrom-
eter. A Bruker-CCD instrument was used for single-crystal X-ray
diffraction studies. Microanalyses were performed by Micro-Analysis,
Inc., Wilmington, Delaware.
[(dppe)Pd(Ph)I]. A mixture of [(tmeda)Pd(Ph)I] (0.30 g; 0.70
mmol), dppe (0.305 g; 0.77 mmol), and toluene (10 mL) was stirred
under N2 at room temperature for 3 h. The pale-yellow precipitate was
separated, washed with hexanes, and dried under vacuum. The product
was recrystallized by dissolving in ca. 8 mL of 1,2-dichloroethane
(note: CH2Cl2 seemed to slowly decompose the complex) and adding
hexanes (ca. 60 mL). After 1.5 h at +5 °C, the yellow crystals were
N, 7.0. H NMR (CD2Cl2, 20 °C), δ: 2.2 (s, 6H, NCH3), 2.3 (s, 3H,
CCH3), 2.6 (m, 4H, CH2), 2.7 (s, 6H, NCH3), 6.8 (d, 2H, J ) 7.9 Hz,
C6H4), 7.3 (d, 2H, J ) 7.9 Hz, C6H4). 19F NMR (CD2Cl2, 20 °C), δ:
-21.2 (s).
[(dppe)Pd(Ph)CF3]. (a) In a glovebox, a 25-mL round-bottom flask
with a magnetic stir-bar was charged with [(dppe)Pd(Ph)I] (0.30 g;
0.42 mmol), freshly dried, finely ground CsF (0.20 g; 1.32 mmol), and
THF (8 mL). The flask was capped with a rubber septum and brought
out. At stirring, CF3SiMe3 (0.12 mL; 0.81 mmol) was syringed in, and
the mixture was vigorously stirred at room temperature until the yellow
color was gone (1 h). Stirring the milky-white suspension for an
additional 10 min resulted in the appearance of a light tan color. The
reaction mixture was worked up in air. After all volatiles were removed
under vacuum, the solid residue was extracted with CH2Cl2 (first 5
mL, then 3 × 2 mL). The combined extracts were filtered through
Celite, evaporated to ca. 1 mL, and treated with 10 mL of MeOH
(portion-wise). After 24 h at +5 °C, the solid was separated, washed
with MeOH, and recrystallized by dissolving in boiling benzene (ca. 3
mL), cooling to room temperature, and adding ether (3 mL). After 12
h, the white crystals were separated, washed with ether, and dried under
vacuum. The yield of [(dppe)Pd(Ph)CF3]‚0.5C6H6 was 0.20 g (69%).
Anal. Calcd for C33H29F3P2Pd, %: C, 62.7; H, 4.7. Found, %: C, 62.5;
H, 4.7. 1H NMR (CD2Cl2, 20 °C), δ: 2.3 (m, 4H, CH2), 6.8-7.8
(46) Grushin, V. V. J. Am. Chem. Soc. 1999, 121, 5831; U.S. Patent 5,919,984,
1999; Organometallics 2001, 20, 3950.
(47) Markies, B. A.; Canty, A. J.; de Graaf, W.; Boersma, J.; Janssen, M. D.;
Hogerheide, M. P.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. J.
Organomet. Chem. 1994, 482, 191.
(48) Portnoy, M.; Ben-David, Y.; Rousso, I.; Milstein, D. Organometallics 1994,
13, 3465.
9
4638 J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006

H2O-Induced Ar−X Activation
A R T I C L E S
(multiplets, 25H, Ph). 19F NMR (toluene, 20 °C), δ: -18.0 (dd, cis-
JF-P ) 19.5 Hz, trans-JF-P ) 52.8 Hz). 31P NMR (toluene, 20 °C), δ:
40.1 (dq, 1P, cis-JP-P ) 15.8 Hz, trans-JF-P ) 52.8 Hz, P trans to
CF3); 41.8 (dq, 1P, cis-JP-P ) 15.8 Hz, cis-JF-P ) 19.5 Hz, P cis to
CF3).
2H, arom. Tol), 6.9-7.3 (multiplets, 16H, Ph), 7.5 (t-looking dd, JH-H
) 7.8 Hz, JH-P ) ca. 7.8 Hz, 2H, arom Tol), 7.8 (m, 4H, Ph). 19F
NMR (toluene-d8, 20 °C), δ: -16.2 (dd, cis-JF-P ) 19.5 Hz, trans-
JF-P ) 52.3 Hz). 31P NMR (toluene-d8, 20 °C), δ: 38.6 (dq, JP-P
)
15.8 Hz, JF-P ) 19.5 Hz, 1P, P cis to CF3), 40.3 (dq, JP-P ) 15.8 Hz,
JF-P ) 52.3 Hz, 1P, P trans to CF3).
(b) A mixture of [(tmeda)Pd(Ph)CF3] (0.10 g; 0.27 mmol), dppe
(0.115 g; 0.29 mmol), CH2Cl2 (3 mL), and KHSO4 (0.20 g) was
vigorously stirred under N2 for 3 days. Isolation of the product was
performed in air. 19F NMR analysis of the reaction mixture indicated
>99% conversion. The reaction mixture was filtered through cotton
wool, evaporated to ca. 1 mL, and treated with MeOH (5 mL). After
standing at +5 °C overnight, the white crystals of [(dppe)Pd(Ph)CF3]
were separated, washed with MeOH and ether, dried, and then
recrystallized from benzene-ether. The yield was 0.155 g (85%).
[(dppe)Pd(Ph-d5)CF3]. This complex was prepared from [(tmeda)-
Pd(Ph-d5)CF3] and dppe, as described above.
[(dppp)Pd(Tol)CF3]. A mixture of [(tmeda)Pd(Tol)CF3] (0.21 g;
0.55 mmol), dppp (0.30 g; 0.73 mmol), CH2Cl2 (8 mL), and KHSO4
(0.7 g) was vigorously stirred under N2 for 18 h. 19F NMR analysis of
the reaction mixture indicated 99% conversion. Isolation of the product
was performed in air. The reaction mixture was filtered through cotton
wool, evaporated to ca. 2 mL, and treated with MeOH (5 mL). A few
oily droplets formed, which quickly crystallized on gentle swirling.
After 20 min, more MeOH (20 mL) was added. After 1 h at room
temperature and then 3 h at +5 °C the white crystals were separated,
thoroughly washed with MeOH and ether, and dried under vacuum.
The yield of [(dppe)Pd(Tol)CF3] was 0.325 g (87%). Anal. Calcd for
C35H33F3P2Pd, %: C, 61.9; H, 4.9. Found, %: C, 61.4; H, 5.0. 1H NMR
(CD2Cl2, 20 °C), δ: 1.8 (m, 2H, central CH2), 2.1 (s, 3H, CH3), 2.45
(m, 4H, side CH2), 6.45 (d, JH-H ) 7.3 Hz, 2H, arom Tol), 6.9 (t-
looking dd, JH-H ) 7.3 Hz, JH-P ) ca. 7.3 Hz, 2H, arom Tol), 7.1-
7.8 (multiplets, 20H, Ph). 19F NMR (CD2Cl2, 20 °C), δ: -19.3 (dd,
cis-JF-P ) 17.2 Hz, trans-JF-P ) 48.2 Hz). 31P NMR (CD2Cl2, 20 °C),
δ: 1.1 (dq, JP-P ) 41.5 Hz, JF-P ) 17.2 Hz, 1P, P cis to CF3), 8.8 (dq,
JP-P ) 41.5 Hz, JF-P ) 48.2 Hz, 1P, P trans to CF3). 1H NMR (toluene-
d8, 20 °C), δ: 1.3 (m, 2H, central CH2), 1.9 (m, 4H, side CH2), 2.1 (s,
3H, CH3), 6.6 (dd, JH-H ) 7.9 Hz, 2H, arom Tol), 6.8-7.2 (multiplets,
16H, Ph), 7.75 (t-looking dd, JH-H ) 7.9 Hz, JH-P ) ca. 7.9 Hz, 2H,
arom Tol), 7.75 (m, 4H, Ph). 19F NMR (toluene-d8, 20 °C), δ: -17.5
(dd, cis-JF-P ) 18.0 Hz, trans-JF-P ) 50.0 Hz). 31P NMR (toluene-d8,
20 °C), δ: 0.8 (dq, JP-P ) 39.5 Hz, JF-P ) 18.0 Hz, 1P, P cis to CF3),
8.7 (dq, JP-P ) 39.5 Hz, JF-P ) 50.0 Hz, 1P, P trans to CF3).
Reaction of [(dppe)Pd(Ph)CF3] with PhI. A mixture of [(dppe)-
Pd(Ph)CF3] (90 mg), PhI (0.2 mL), and N2-saturated (but not anhydrous)
toluene (3 mL) was sealed under nitrogen and heated at 115 °C (oil
bath). The starting complex had quickly dissolved, and yellow crystals
were noticed after 2.5 h. The heating was continued for additional 2.5
h, after which the mixture was allowed to cool to room temperature
and then kept at +5 °C overnight. The yellow crystals were separated,
washed with ether, and dried under vacuum. The yield of [(dppe)Pd-
[(dppp)Pd(Ph)CF3]. In a glovebox, a 15-mL round-bottom flask
with a magnetic stir-bar was charged with [(tmeda)Pd(Ph)I] (0.17 g;
0.40 mmol), dppp (0.17 g; 0.41 mmol), freshly dried, finely ground
CsF (0.18 g; 1.18 mmol), and THF (6 mL). The flask was capped with
a rubber septum and brought out; the mixture was stirred for 1-2 min
until all solids, except CsF had dissolved. At stirring, CF3SiMe3 (0.10
mL; 0.68 mmol) was syringed in, and the mixture was vigorously stirred
at room temperature for 1.5 h. More CF3SiMe3 (0.10 mL; 0.68 mmol)
was added, and stirring continued for another 1 h and 20 min until the
orange-yellow color was gone and a light tan color of the liquid phase
developed. The reaction mixture was worked up in air. After all volatiles
were removed under vacuum, the oily residue was extracted with CH2-
Cl2 (3 × 3 mL). The combined extracts were filtered through cotton
wool and evaporated to give an oil. After drying under vacuum and
stirring with 2 mL of ether for a minute, the oil solidified. After
evaporation of the ether, the residue was dried under vacuum and
dissolved in 3 mL of warm benzene. The benzene solution was filtered
warm through Celite, evaporated to ca. 1 mL, and treated with 10 mL
of ether. Briefly scratching the inner glass wall under the cloudy solution
with a spatula prompted crystallization. After 1 h, the slightly yellow
crystals were separated, washed with ether, and dried. The complex
was recrystallized once again by adding ether (15 mL) to its solution
in ca. 1 mL of benzene. The yield of [(dppp)Pd(Ph)CF3]‚0.5Et2O as
pale-yellow crystals was 0.20 g (71%). Anal. Calcd for C36H36F3O0.5P2-
Pd, %: C, 61.6; H, 5.2. Found, %: C, 61.3; H, 5.3. 1H NMR (CD2Cl2,
20 °C), δ: 1.2 (t, 3H, CH3 of Et2O), 1.8 (m, 2H, CH2), 2.45 (m, 4H,
CH2), 3.5 (q, 2H, CH2 of Et2O), 6.6-7.8 (multiplets, 25H, Ph). 19F
NMR (toluene, 20 °C), δ: -19.3 (dd, cis-JF-P ) 17.8 Hz, trans-JF-P
1
(I)CF3] was 80 mg (82%). H NMR (CD2Cl2, 20 °C), δ: 2.3 (m, 4H,
CH2), 7.5-8.0 (multiplets, 20H, Ph). 19F NMR (CD2Cl2, 20 °C), δ:
-11.9 (dd, cis-JF-P ) 26.4 Hz, trans-JF-P ) 64.2 Hz). 31P NMR (CD2-
Cl2, 20 °C), δ: 46.2 (dq, 1P, trans-JF-P ) 64.2 Hz, JP-P ) 21.7 Hz, P
trans to CF3); 56.2 (br m, 1P, P cis to CF3). The mother liquor was
filtered through silica gel and analyzed by GC-MS. The analysis
indicated the formation of biphenyl and no bibenzyl.
) 49.9 Hz). 31P NMR (toluene, 20 °C), δ: 1.1 (dq, 1P, cis-JP-P
37.5 Hz, trans-JF-P ) 49.9 Hz, P trans to CF3); 9.1 (dq, 1P, cis-JP-P
37.5 Hz, cis-JF-P ) 17.8 Hz, P cis to CF3).
)
)
Reaction of [(dppe)Pd(Ph)CF3] with PhCl. A 5-mm NMR tube
was charged with [(dppe)Pd(Ph)CF3] (20 mg) and N2-saturated (but
not anhydrous) PhCl (0.6 mL), sealed under N2, and heated at 140 °C
(oil bath) for 2 h to produce [(dppe)Pd(Cl)CF3] in ca. 90% yield at
100% conversion. The reaction mixture remained colorless and solid-
free during the reaction. Layering the solution with hexanes resulted
in crystal formation, some of which were of X-ray quality. 19F NMR
(CD2Cl2, 20 °C), δ: -19.8 (dd, cis-JF-P ) 27.0 Hz, trans-JF-P ) 67.1
Hz). 31P NMR (CD2Cl2, 20 °C), δ: 42.3 (dq, 1P, trans-JF-P ) 67.1
Hz, JP-P ) 27.7 Hz, P trans to CF3); 58.5 (m, 1P, P cis to CF3). The
mother liquor was filtered through silica gel and analyzed by GC-MS
to indicate the formation of biphenyl.
[(dppe)Pd(Tol)CF3]. A mixture of [(tmeda)Pd(Tol)CF3] (0.15 g; 0.39
mmol), dppe (0.20 g; 0.50 mmol), CH2Cl2 (5 mL), and KHSO4 (0.5 g)
was vigorously stirred under N2 for 5 h. 19F NMR analysis of the
reaction mixture indicated >99% conversion. Isolation of the product
was performed in air. The reaction mixture was filtered through cotton
wool, evaporated to ca. 2 mL, and treated with MeOH (first 1 mL,
after 30 min 5 more mL). The white crystals were separated, thoroughly
washed with MeOH and ether, and dried under vacuum. After
recrystallization from CH2Cl2-ether and drying under vacuum, the yield
of [(dppe)Pd(Tol)CF3] was 0.25 g (96%). Anal. Calcd for C34H31F3P2-
Pd, %: C, 61.4; H, 4.7. Found, %: C, 60.0; H, 4.8. 1H NMR (CD2Cl2,
20 °C), δ: 2.2 (s, 3H, CH3), 2.3 (m, 4H, CH2), 6.7 (dd, JH-H ) 7.6
Hz, JH-P ) 1.5 Hz, 2H, arom Tol), 7.05 (t-looking dd, JH-H ) 7.6 Hz,
JH-P ) ca. 7.6 Hz, 2H, arom Tol), 7.3-7.9 (multiplets, 20H, Ph). 19F
NMR (CD2Cl2, 20 °C), δ: -18.0 (dd, cis-JF-P ) 18.9 Hz, trans-JF-P
) 51.1 Hz). 31P NMR (CD2Cl2, 20 °C), δ: 40.0 (dq, JP-P ) 15.8 Hz,
Reaction of [(dppe)Pd(Tol)CF3] with C6D5I in toluene. In a
glovebox, two 5-mm NMR tubes were charged with [(dppe)Pd(Tol)-
CF3] (13 mg), C6D5I (5 µL), and anhydrous toluene-d8 (0.8 mL), and
sealed with rubber septa. Both tubes were brought out. Degassed H2O
(0.2 µL) was microsyringed in one of the tubes, and both samples were
placed in an oil bath at 115 °C. The H2O-free sample remained colorless,
and no reaction was observed (NMR) after 6 h. The H2O containing
JF-P ) 18.9 Hz, 1P, P cis to CF3), 41.4 (dq, JP-P ) 15.8 Hz, JF-P
)
51.1 Hz, 1P, P trans to CF3). 1H NMR (toluene-d8, 20 °C), δ: 1.85 (m,
4H, CH2), 2.2 (s, 3H, CH3), 6.8 (dd, JH-H ) 7.8 Hz, JH-P ) 1.5 Hz,
9
J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006 4639

A R T I C L E S
Grushin and Marshall
Table 3. Selected Crystallographic Data for 1, 4, 6, and 9-12
1
4
6
9
empirical formula
FW
C36H36F3P2Pd
693.99
C34H31F3P2Pd
664.93
C13H21F3N2Pd
368.72
C12H24F6N2Pd
416.73
cryst color, form
cryst system
space group
a (Å)
colorless, irreg. block
monoclinic
P2(1)/n
12.214(5)
colorless, irreg. block
monoclinic
P2(1)/c
11.265(4)
colorless, irreg. block
monoclinic
P2(1)/n
8.361(3)
colorless, prism
monoclinic
Cc
15.702(5)
b (Å)
15.812(7)
22.727(9)
16.466(6)
8.550(3)
c (Å)
16.782(7)
13.333(5)
11.389(4)
11.809(3)
R (deg)
90
98.318(6)
90
3207(2)
90
90
90
94.882(5)
90
1579.6(8)
â (deg)
111.946(7)
90
3166(2)
110.163(5)
90
1471.8(9)
γ (deg)
V (Å3)
Z
4
4
4
4
density (g/cm3)
1.437
0.72
1420
1.395
0.726
1352
1.664
1.282
744
1.752
1.231
840
abs. µ(mm-1
F(000)
)
cryst size (mm)
temp (°C)
0.34 × 0.22 × 0.22
0.38 × 0.32 × 0.32
0.28 × 0.28 × 0.19
0.18 × 0.18 × 0.16
-100
-100
-100
-100
scan mode
detector
ω
ω
ω
ω
Bruker-CCD
Bruker-CCD
Bruker-CCD
Bruker-CCD
θ
max (deg)
28.3
27962
7956
0.0322
28.29
31729
7843
0.0323
29.22
27438
3973
0.0278
28.31
13683
1952
0.0299
no. obsrvd reflns
no. unique reflns
Rmerge
no. params
352
361
176
98
R indices [I > 2σ(I)]a
R indices (all data)a
Sb
wR2)0.059, R1)0.025
wR2)0.061, R1)0.029
1.075
wR2)0.073, R1)0.027
wR2)0.076, R1)0.031
1.06
wR2)0.047, R1)0.018
wR2)0.047, R1)0.019
1.068
wR2)0.035, R1)0.014
wR2)0.036, R1)0.014
1.066
max diff peak, hole (e/Å3)
0.40,-0.36
0.61,-0.48
0.72,-0.52
0.31,-0.40
10
11
12
empirical formula
FW
C17H34F6P2Pd
520.78
C27H24F3IP2 Pd
700.7
C30H29Cl1.5F3P2Pd
668.05
cryst.color, form
cryst system
space group
a (Å)
colorless, rod
monoclinic
P2(1)
8.0634(6)
gold, prism
orthorhombic
P2(1)2(1)2(1)
8.625(4)
colorless, irreg. block
monoclinic
P2(1)/n
9.215(2)
b (Å)
14.7398(12)
13.616(6)
26.278(7)
c (Å)
19.8663(14)
22.834(10)
12.097(3)
R (deg)
90
90
90
90
2682(2)
90
â (deg)
110.509(3)
90
2211.5(3)
101.897(4)
90
2866.3(13)
γ (deg)
V (Å3)
Z
4
4
4
density (g/cm3)
1.564
1.032
1064
1.736
1.997
1368
1.548
0.937
1350
abs. µ(mm-1
F(000)
)
cryst size(mm)
temp (°C)
scan mode
detector
0.48 × 0.18 × 0.15
0.37 × 0.13 × 0.10
0.26 × 0.18 × 0.13
-100
-100
-100
ω
ω
ω
Bruker-CCD
Bruker-CCD
Bruker-CCD
θ
max (deg)
28.49
17164
5576
0.0316
28.32
47171
6646
0.0557
28.33
26290
7102
0.0401
no. obsrvd reflns
no. unique reflns
Rmerge
no. params
243
314
361
R indices [I > 2σ(I)]a
R indices (all data)a
Sb
wR2)0.105, R1)0.043
wR2)0.113, R1)0.056
1.037
wR2)0.081, R1)0.028
wR2)0.082, R1)0.030
1.091
wR2)0.087, R1)0.035
wR2)0.094, R1)0.047
1.035
max diff peak, hole (e/Å3)
1.50,-1.20
1.02,-0.57
0.77,-0.44
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) {∑ [w(Fo - Fc )2]/∑ [w(Fo )2]}1/2 (sometimes denoted as Rw2). b GooF ) S ) {∑ [w(Fo - Fc )2]/(n - p)}1/2
where n is the number of reflections, and p is the total number of refined parameters.
,
2
2
2
2
2
sample turned yellow after 3 h. After 5 and 8 h since the beginning of
the reaction, 19F NMR analysis indicated 50% and ca. 100% conversion,
respectively. The 19F NMR spectra recorded during the reaction
indicated partial Ar/Ar scrambling in both the starting material and
the product. After cooling the sample to room temperature, the pale-
yellow liquid phase was separated and filtered through a short silica
plug; the colorless filtrate was analyzed by GC-MS to indicate the
formation of Tol-C6D5 (ca. 60%), Ph-C6D5 (ca. 20%), and smaller
quantities of (C6D5)2, p-Tol-Ph, Ph2 and p-Tol2.
[(teeda)PdCl2]. In air, PdCl2 (1.0 g) was dissolved in 100 mL of
boiling MeCN. To the hot solution, teeda (3 mL) was added at stirring.
Yellow crystals of the product began to precipitate. After cooling to
room temperature and keeping the mixture at +5 °C overnight, the
yellow crystalline product was separated by filtration, washed with ether
(4 × 30 mL), and dried under vacuum. The yield was 1.85 g (94%).
[(teeda)Pd(CF3)2]. In a glovebox, a 10-mL round-bottom flask with
a magnetic stir-bar was charged with [(teeda)PdCl2] (0.10 g; 0.29
mmol), freshly dried, finely ground CsF (0.46 g; 3.03 mmol), and CH2-
9
4640 J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006

H2O-Induced Ar−X Activation
A R T I C L E S
Cl2 (5 mL). The flask was capped with a rubber septum and brought
out. At stirring, CF3SiMe3 (0.25 mL; 1.70 mmol) was syringed in, and
the mixture was vigorously stirred at room temperature for 68 h, at
which point the starting yellow complex had disappeared. The product
was isolated in air. The solution was filtered through Celite, evaporated
to ca. 2 mL, treated with ether (10 mL), and kept at +5 °C for 2 h.
The precipitate was recrystallized by adding 12 mL of ether to its warm
solution in ca. 2 mL of boiling CH2Cl2 and then keeping the mixture
at +5 °C for 2 h. The yield was 0.07 g (59%). Anal. Calcd for
C12H24F6N2Pd, %: C, 34.6; H, 5.8; N, 6.7. Found, %: C, 34.7; H, 5.6;
N, 6.7. 1H NMR (CD2Cl2, 20 °C), δ: 1.4 (t, 12H, J ) 7 Hz, CH3), 2.7
(s, 4H, CH2), 2.85 (m, 4H, CH2), 3.15 (m, 4H, CH2). 19F NMR (CD2-
Cl2, 20 °C), δ: -26.5 (s).
[(dippp)Pd(CF3)2]. In a glovebox, a 30-mL round-bottom flask with
a magnetic stir-bar was charged with [(dippp)PdCl2] (0.30 g; 0.66
mmol), freshly dried, finely ground CsF (1.10 g; 7.24 mmol), and
CH2Cl2 (10 mL). The flask was capped with a rubber septum and
brought out. At stirring, CF3SiMe3 (0.75 mL; 5.08 mmol) was syringed
in, and the mixture was vigorously stirred at room temperature for 40
h. 19F NMR analysis of the brown liquid phase indicated 100%
conversion to [(dippp)Pd(CF3)2]. The mixture was evaporated, and the
residue was extracted with benzene (4 × 5 mL). The combined extracts
were filtered through Celite, evaporated to ca. 2 mL, and treated with
hexanes (20 mL). The product (0.32 g; 94% yield) was recrystallized
from CH2Cl2-hexanes three times without losses and appeared pure
by NMR, although was tannish in color. To obtain the complex as a
white solid it was recrystallized by adding ether (7 mL) to its solution
in a minimal volume of CH2Cl2 and keeping the mixture at +5 °C
overnight. The white crystals were separated cold, washed with cold
ether, and dried under vacuum. The yield was 0.29 g (85%). Anal.
Calcd for C17H34F6P2Pd, %: C, 39.2; H, 6.6. Found, %: C, 39.1; H,
6.3. 1H NMR (CD2Cl2, 20 °C), δ: 1.2 (dd, 12H, J ) 7.1 and 11.6 Hz,
CH3), 1.35 (dd, 12H, J ) 7.4 and 18.6 Hz, CH3), 1.6 (m, 4H, CH2),
1.9 (m, 2H, CH2), 2.4 (m, 4H, CH). 19F NMR (CD2Cl2, 20 °C), δ:
-20.5 (m). 31P NMR (CD2Cl2, 20 °C), δ: 23.3 (m).
µL), sealed, and heated at 115 °C. After ca. 1 h the solution turned
light tan, and several hours later precipitation of palladium metal and
reddish-brown viscous oil was observed. After 24 h, full conversion
of 1 was detected. The 19F NMR spectrum displayed several resonances
from the decomposition products. Two of them were identified as
PhC(F)O (+16 ppm, s) and CF3H (-79.8 ppm, d, JF-H ) 80 Hz). A
few resonances of very low intensity were found in the 31P NMR
spectrum of the sample, indicating that almost all P-containing species
were located in the red-brown oily precipitate, rather than in the toluene
phase. The tube was then unsealed under N2 in a glovebox, and the
toluene solution was decanted off the brown oil. GC-MS analysis of
the toluene fraction confirmed the formation of PhC(F)O and revealed
the presence of benzene, biphenyl, benzophenone, and benzoic anhy-
dride, among other products. The toluene-insoluble red-brown oil was
dissolved in MeCN and analyzed by 31P NMR. A number of broad
resonances were observed, along with two sharp lines from [(dppe)2Pd]2+
(58.0 ppm) and dppeO2 (30.8 ppm). To release all coordinated P-ligands,
the solution was treated with [Bu4N]+ CN- (65 mg). After this
treatment, 31P NMR analysis of the sample indicated the presence of
free dppe (s, -12.8 ppm), dppeO (d, -12.0; d, 29.5 ppm; JP-P ) 48.3
Hz),29 and dppeO2 (s, 30.8 ppm) in a 6:3:2 molar ratio.
X-ray Crystallographic studies. A summary of crystallographic
data for new complexes 1, 4, 6, and 9-12 is presented in Table 3. The
CIF files for these complexes and also for [(dppe)Pd(Cl)CH3]18 and
[(dcpe)Pd(Cl)CH3]18 are presented in the Supporting Information.
Acknowledgment. We thank Drs. Viacheslav A. Petrov,
David L. Thorn, Kenneth G. Moloy, and Stuart A. Macgregor
for discussions.
Supporting Information Available: Full details of the
crystallographic data (CIF) for new complexes 1, 4, 6, 9-12
and for previously analyzed18 [(dppe)Pd(Cl)CH3] and [(dcpe)-
Pd(Cl)CH3]. This material is available free of charge via the
Internet at http://pubs.acs.org.
Water-Induced Decomposition of 1. A high-pressure NMR sap-
phire tube was charged with 1 (40 mg), toluene (0.4 mL), and water (5
JA0602389
9
J. AM. CHEM. SOC. VOL. 128, NO. 14, 2006 4641