Mechanistic studies on oxidative addition of aryl halides and triflates to Pd(BINAP)2 and structural characterization of the product from aryl triflate addition in the presence of amine

Article abstract of DOI:10.1021/om0108088

Kinetic studies of the oxidative addition of phenyl iodide and phenyl triflate to Pd(BINAP)₂ (1) are reported. The products of the oxidative addition of phenyl trifluoromethanesulfonate to 1 in the presence of the primary amines n-octylamine and isoamylamine are the cationic aryl palladium(II) complexes [(BINAP)Pd(Ph)(H₂NR)]OTf (2a,b), and the product of the oxidative addition of phenyl iodide to 1 is the phenylpalladium iodide {(BINAP)Pd(Ph)I} (3). Structural characterization of the rare, stable σ-aryl Pd(II) triflate complex (2b), in this case coordinated by isoamylamine, is reported. Initial mechanistic studies focused on measuring the rates of reactions containing concentrations of aryl electrophile ranging from 8.94 × 10^-7 to 0.2 M. Under these conditions, the oxidative addition of PhOTf and Phi to 1 was inverse first-order in added BINAP ligand when the concentration of ArX was low. The oxidative addition reaction was first-order in ArX when the concentration of ArX was low and was zero order in ArX when the concentration of ArX was high. At these high concentrations, the reaction rate depended solely on the rate for dissociation of BINAP from 1. However, additional experiments using concentrations of aryl iodide and aryl bromide up to 4.0 M led to a measurable increase in observed rate constants and detection of a second concurrent reaction mechanism. This effect was not observed with phenyl triflate. The relevance of this phenomenon to catalytic coupling and oxidative addition of aryl bromides is discussed. Reactions of triflate complex 2a with several bases to form N-octylaniline are also reported.

Full text of DOI:10.1021/om0108088

Organometallics 2002, 21, 491-502
491
Mech a n istic Stu d ies on Oxid a tive Ad d ition of Ar yl
Ha lid es a n d Tr ifla tes to P d (BINAP )2 a n d Str u ctu r a l
Ch a r a cter iza tion of th e P r od u ct fr om Ar yl Tr ifla te
Ad d ition in th e P r esen ce of Am in e
Luis M. Alcazar-Roman and J ohn F. Hartwig*
Department of Chemistry, Yale University, P.O. Box 208107,
New Haven, Connecticut 06520-8107
Received September 10, 2001
Kinetic studies of the oxidative addition of phenyl iodide and phenyl triflate to Pd(BINAP)2
(1) are reported. The products of the oxidative addition of phenyl trifluoromethanesulfonate
to 1 in the presence of the primary amines n-octylamine and isoamylamine are the cationic
aryl palladium(II) complexes [(BINAP)Pd(Ph)(H2NR)]OTf (2a ,b), and the product of the
oxidative addition of phenyl iodide to 1 is the phenylpalladium iodide {(BINAP)Pd(Ph)I}
(3). Structural characterization of the rare, stable σ-aryl Pd(II) triflate complex (2b), in this
case coordinated by isoamylamine, is reported. Initial mechanistic studies focused on
measuring the rates of reactions containing concentrations of aryl electrophile ranging from
8.94 × 10-7 to 0.2 M. Under these conditions, the oxidative addition of PhOTf and PhI to 1
was inverse first-order in added BINAP ligand when the concentration of ArX was low. The
oxidative addition reaction was first-order in ArX when the concentration of ArX was low
and was zero order in ArX when the concentration of ArX was high. At these high
concentrations, the reaction rate depended solely on the rate for dissociation of BINAP from
1. However, additional experiments using concentrations of aryl iodide and aryl bromide up
to 4.0 M led to a measurable increase in observed rate constants and detection of a second
concurrent reaction mechanism. This effect was not observed with phenyl triflate. The
relevance of this phenomenon to catalytic coupling and oxidative addition of aryl bromides
is discussed. Reactions of triflate complex 2a with several bases to form N-octylaniline are
also reported.
In tr od u ction
imines,36-40 azoles,39 alcohols,41-46 phenols47,48), as
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10.1021/om0108088 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 01/09/2002

492 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
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Aryl Triflate Addition
Organometallics, Vol. 21, No. 3, 2002 493
Sch em e 1
The reactivity of aryl halide electrophiles toward
Pd(0) is typically ArI > ArBr ≈ ArOTf . ArCl.1 The
difference in the reactivity of ArX has been linked to
the difference in C-X bond strengths, a factor that
would affect the rate of oxidative addition when the
rate-limiting step of this process is C-X bond scission.
However, we have shown recently that ligand dissocia-
tion and not C-X bond cleavage is the rate-limiting step
of aryl bromide oxidative addition to Pd(0) when the
concentration of aryl bromide is high. Therefore, the
turnover-limiting step of a catalytic cycle can be ligand
dissociation.99 In these cases, the reactivity of the aryl
halide does not control the rate of oxidative addition.
The products from oxidative addition of aryl triflates
are generally unstable, and few have been isolated in
pure form.109-111 J utand and Mosleh reported that the
product from oxidative addition of phenyl triflate to Pd-
(PPh3)4 is a cationic (σ-aryl)palladium complex that is
stabilized by coordination of the DMF solvent used in
these reactions.109 Most aryl triflato complexes of pal-
ladium ligated by chelating phosphines are also less
stable than aryl halide complexes.112 Brown reported
the in situ generation and characterization of [(BINAP)-
Pd(Ph)(THF)]OTf at -78 °C.111 J utand has observed
clean reactions of aryl triflates with (DPPF)Pd(η2-
methylacrylate), but only in the presence of coordinating
anions, such as iodide and acetate.102
The absence of these addition products has hampered
detailed studies on the oxidative addition of aryl triflates
to Pd(0). Studies with platinum model complexes have
been reported, but these studies do not address directly
the relative rates for different elementary reactions in
the multistep addition process with palladium.113 Jutand
and Mosleh described the mechanism for oxidative
addition of aryl triflates to Pd(PPh3)4109 and showed that
a mechanism similar to that for the previously studied
oxidative addition of aryl iodides to Pd(PPh3)4 was
followed.106 J utand and Brown reported the mechanism
of oxidative addition of aryl triflates to the zerovalent
(DPPF)Pd(η2-methylacrylate) in DMF.102 These studies
revealed mechanistic aspects of the aryl triflate activa-
tion in highly polar, coordinating solvents and in the
presence of added coordinating anions. However, these
studies did not show how aryl triflates add in nonpolar
solvents. Additions of aryl triflates in nonpolar solvents
initiate the reactions between aryl triflates and many
heteroatom and carbon nucleophiles developed recently
in our lab and others.94,114-116
These reactions typically occurred at 70 °C over the
course of about 2 h.99 These results implied that the
same maximum rate would be observed for reactions of
aryl halides or triflates using BINAP-ligated palladium
as catalyst. However, room-temperature amination
reactions have been reported with aryl iodides.117 The
rates for catalytic amination of aryl triflates, relative
to bromides and iodides, vary with metal complex,100
but the amination of aryl triflates occurred with rates
similar to the amination of aryl bromides when cata-
lyzed by Pd(0) ligated by DPPF or BINAP.115,116 Al-
though the Pd(0) species in reactions catalyzed by
the combination of Pd2(dba)3 and BINAP and by Pd-
(BINAP)2 may be different we also considered that aryl
iodides could react by a different mechanism than do
aryl bromides. To investigate the mechanistic origin of
the faster rates for catalytic reactions of aryl iodides,
we studied the mechanism for oxidative addition of aryl
iodides and triflates to Pd(BINAP)2.
Here we report distinct mechanistic features for
oxidative addition of aryl iodides and triflates vs aryl
bromides. The isolation and full characterization of the
amine-ligated product from addition of aryl triflate,
[(BINAP)Pd(Ar)(H2NR)]OTf, allowed for a detailed ki-
netic study of the oxidative addition of ArOTf to Pd-
(BINAP)2. Because this amine-ligated species is a crucial
intermediate in the amination of aryl triflates, its
reactivity with bases to form free amine products was
also studied. Moreover, we report its structural deter-
mination by single-crystal X-ray diffraction, which
provides an unusual example of a structurally charac-
terized product from aryl triflate oxidative addition.
Resu lts
Oxid a tive Ad d ition of Ar OTf to P d (BINAP )2 a n d
Syn th esis of [(BINAP )P d (Ar )(H2NR)]OTf (2). Reac-
tion of phenyl triflate alone with 1 at 50 °C led to the
formation of several reaction products. To determine the
spectroscopic features of the addition product, [(BINAP)-
Ph(Ph)Br] was treated with silver trifluoromethane-
sulfonate in THF or acetonitrile at room temperature.
However, this reaction, again, generated a mixture of
several phosphine-containing complexes, none of which
displayed in the 31P{1H} NMR spectrum the appro-
priate AB pattern for [(BINAP)Pd(Ph)OTf]. Finally,
we attempted to trap the oxidative addition product
[(BINAP)Pd(Ph)OTf] with amine, which would generate
an intermediate important in the amination of aryl
triflates.
We have previously studied the oxidative addition of
aryl bromides to Pd(BINAP)2 (1).99 Ligand dissociation
from 1 was the rate-limiting step of the oxidative
addition of ArBr to 1 and in the catalytic reaction of
aryl bromides with primary amines catalyzed by 1.
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To do so, we conducted the reaction between phenyl
trifluoromethanesulfonate and Pd(BINAP)2 in the pres-
ence of 5 equiv of n-octylamine (Scheme 1). At 50 °C
the reaction proceeded smoothly to generate a single AB
(113) Stang, P. J .; Kowalski, M. H.; Schiavelli, M. D.; Longford, D.
J . Am. Chem. Soc. 1989, 111, 3347-3346.
(114) Ozawa, F.; Kubo, A.; Hayashi, T. J . Am. Chem. Soc. 1991, 113,
1414-1419.
(115) Wolfe, J . P.; Buchwald, S. L. J . Org. Chem. 1997, 62, 1264-
1267.
(116) Louie, J .; Driver, M. S.; Hamann, B. C.; Hartwig, J . F. J . Org.
Chem. 1997, 62, 1268-1273.
(117) Wolfe, J . P.; Buchwald, S. L. J . Org. Chem. 1997, 62, 6066-
6068.

494 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
Pd is 360.1°. The phenyl group bound to palladium
describes a 101° dihedral angle with the plane defined
by N1, Pd1, and C1. Although the hydrogen atoms of
the NH2 group were not located, 2.266 Å was found to
be the closest distance between the oxygens of the
triflate counterion and the NH2 hydrogens placed at
idealized positions. This distance suggests the possibil-
ity of hydrogen bonding between the triflate and the NH
protons of the coordinated amine ligand. The Pd-P bond
lengths differ by 0.142 Å (P1-Pd1 2.401 Å; P2-Pd1
2.259 Å). The longer bond is trans to the phenyl ligand.
The Pd1-P2 bond distance is within the range of
distances reported for monocationic BINAP complexes
of palladium(II) (2.183-2.332 Å).121,122,124-126,128,129 The
Pd1-P1 bond distance is longer than the Pd-P bond
lengths measured in the reports above, but it is shorter
than the longest Pd-P distance found in [(R)-p-Tol-
BINAP]Pd(p-C6H4-CN)(Br), also corresponding to phos-
phorus trans to the aryl ligand.120
Mech a n ism of Oxid a tive Ad d ition of Ar yl Tr i-
fla tes a n d Ar yl Iod id es to P d (BINAP )2. Ar yl Tr i-
fla te Ad d ition s. Rate constants for oxidative addition
of PhOTf to Pd(BINAP)2 were determined from plots of
the disappearance of the absorbance band at 519 nm
corresponding to Pd(BINAP)2. Rate constants were
obtained at 45 °C in the presence of amine to trap the
triflate addition product. The reaction solutions con-
tained 2.25 × 10-5 M Pd(BINAP)2, 2.26 × 10-4 to 1.36
M PhOTf, 1.70 × 10-4 to 6.78 × 10-4 M BINAP, and
1.13 × 10-4 M of n-octylamine. A typical plot for the
decay of Pd(BINAP)2 vs time is shown in Figure 2. There
was no dependence of kobs on the concentration of added
n-octylamine: reactions with a concentration of PhOTf
equal to 2.26 × 10-4 M and amine concentrations
ranging from 1.13 × 10-4 to 1.13 × 10-3 M gave rate
constants within 15% of each other. Although Pd-
(BINAP)2 is consumed by reaction with PhOTf with or
without added amine, we were not able to obtain
reproducible rate constants for the disappearance of
Pd(BINAP)2 in the absence of n-octylamine. Many
F igu r e 1. ORTEP drawing of [(BINAP)Ph(Ph)(H2N(CH2)2-
CH(CH3)2]OSO2CF3, 2b. Hydrogen atoms and triflate coun-
terion omitted for clarity.
Sch em e 2
pattern in the 31P{1H} NMR spectrum without the
detection of any intermediates. The compound formed
from the oxidative addition of aryl triflate in the
presence of n-octylamine was assigned as [(BINAP)Pd-
(Ph)(H2N(CH2)7CH3)]OSO2CF3 (2a ) based on spectro-
scopic data. Diastereotopic amine NH2 resonances were
observed at 3.24 and 3.44 ppm in the 1H NMR spectrum,
and the triflate counterion displayed νSO bands at 816
and 1284 cm-1 corresponding to a free triflate.118 This
material was synthesized independently by treating a
suspension of (BINAP)Pd(Ph)Br in toluene with n-
octylamine and 1 equiv of silver trifluoromethane-
sulfonate (Scheme 2). Single crystals suitable for an
X-ray diffraction study were obtained by recrystallizing
this material from toluene and pentane. However, the
n-octyl chain of the primary amine ligand was severely
disordered, and a final refinement of the structure was
not achieved. {(BINAP)Pd(Ph)[H2N(CH2)2CH(CH3)2]}-
OTf (2b) was synthesized by treating a CH2Cl2 solution
of (BINAP)Pd(Ph)Br and isoamylamine with silver
trifluoromethanesulfonate. Crystallization of the result-
ing CH2Cl2 solution by addition of toluene and heptane
produced single crystals of 2b suitable for X-ray dif-
fraction. An ORTEP plot of 2b is shown in Figure 1.
The P1-Pd1-P2 angle is 90.8°, which is the smallest
bite angle known for BINAP complexes of the nickel
triad (91.3-95.8°).94,119-130 The sum of the angles around
1
unidentified H and 31P{1H} resonances were observed,
and the reaction turned a dark orange-brown color.
Thus, it was unclear what reaction corresponded to the
rate being measured in the absence of added amine.
The dependence of the reaction rate constant on
[BINAP] was measured with a 2.26 × 10-4 M concen-
tration of PhOTf and a 1.13 × 10-4 M concentration of
amine. A plot of 1/kobs vs [BINAP], shown in Figure 3,
(121) Kuwano, R.; Ito, Y. J . Am. Chem. Soc. 1999, 121, 3236-3237.
(122) Fujii, A.; Hagiwara, E.; Sodeoka, M. J . Am. Chem. Soc. 1999,
121, 5450-5458.
(123) Alcock, N. W.; Brown, J . M.; Perez-Torrente, J . J . Tetrahedron
Lett. 1992, 33, 389-392.
(124) Pregosin, P. S.; Ruegger, H.; Salzmann, R.; Albinati, A.;
Lianza, F.; Kunz, R. W. Organometallics 1994, 13, 83-90.
(125) Sodeoka, M.; Tukunoh, R.; Miyazaki, F.; Hagiwara, E.; Shiba-
saki, M. Synlett 1997, 5, 463.
(126) Drommi, D.; Nesper, R.; Pregosin, P. S.; Trabesinger, G.;
Zurcher, F. Organometallics 1997, 16, 4268-4275.
(127) Wicht, D. K.; Zhuravel, M. A.; Gregush, R. V.; Glueck, D. S.;
Guzei, I. A.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics
1998, 17, 1412-1419.
(128) Yamaguchi, M.; Yabuki, M.; Yamaishi, T.; Sakai, T.; Tsubo-
mura, T. Chem. Lett. 1996, 3, 241-242.
(129) Pregosin, P. S.; Ruegger, H.; Salzmann, R.; Albinati, A.;
Lianza, F.; Kunz, R. W. Organometallics 1994, 13, 5040-5048.
(130) 3D Search and Research Using the Cambridge Structural
Database Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993,
8, 31-37.
(118) Lawrance, G. A. Chem. Rev. 1986, 86, 17-33.
(119) Tominaga, H.; Sakai, K.; Tsubomura, T. J . Chem. Soc., Chem.
Commun. 1995, 2273-2274.
(120) Drago, D.; Pregosin, P. S.; Tschoerner, M.; Albinati, A. J .
Chem. Soc., Dalton Trans. 1999, 2279-2280.

Aryl Triflate Addition
Organometallics, Vol. 21, No. 3, 2002 495
nium bromide. No difference between the 31P{1H}
resonances of the reaction product and those of 2a were
observed when the reactions were run in the presence
of added tetrabutylammonium triflate or hexafluoro-
phosphate.
Ar yl Iod id e Ad d ition s. The oxidative addition of
aryl iodides to Pd(0) usually proceeds faster than the
oxidative addition of aryl bromides and chlorides.
Indeed, qualitative studies on the oxidative addition of
iodobenzene to Pd(BINAP)2 showed that the reaction
did proceed faster than the addition of bromobenzene.
This result appeared to contradict our results, presented
in the Introduction, regarding the zero-order depen-
dence on aryl bromide concentration for the oxidative
addition of ArBr to 1.117 Naturally, reaction rates that
are zero-order in substrate should also be independent
of the identity of the substrate.
To understand this apparent contradiction, we con-
ducted quantitative kinetic studies on the addition of
aryl iodides to 1. Rate constants for oxidative addition
of PhI to Pd(BINAP)2 were measured by UV-vis
spectroscopy. The reactions were performed at 40 °C.
Typically, reaction mixtures contained 8.55 × 10-7 to
2.25 × 10-5 M Pd(BINAP)2. Concentrations of ArI
ranged from 8.94 × 10-7 to 4.20 M, and concentrations
of BINAP ranged from 3.39 × 10-6 to 1.70 × 10-4 M. A
typical plot of the decay of Pd(BINAP)2 vs time is shown
in Figure 5. The dependence of the reaction rate
constant on [BINAP] was measured using a concentra-
tion of phenyl iodide (1.79 × 10-6 M) that lies within
the range of concentrations that produced a first-order
dependence on PhI (see below). A plot of 1/kobs vs
[BINAP], presented in Figure 6, shows a linear relation-
ship between these quantities. The dependence of the
reaction rate on [PhI] was measured with [BINAP]
equal to 1.70 × 10-4 M. Figure 7 shows that for the
F igu r e 2. Typical decay of 1 during the reaction of phenyl
triflate with 1 at 45 °C in benzene solvent.
concentration range of 3.35 × 10-6 to 2.00 × 10-2
M
the rate constant displayed saturation behavior.
F igu r e 3. Order in [BINAP] for the reaction of phenyl
trifluoromethanesulfonate with 1.
However, kobs was not completely independent of
[PhI], as revealed by increasing the concentration of
phenyl iodide far beyond 2.50 × 10-2 M. Rate constants
as a function of [PhI] at high concentrations of PhI are
shown in Figure 8. NMR spectroscopic studies showed
that reactions occurred in high yield at these high
concentrations of aryl iodide; the decay of Pd(BINAP)2
was not accelerated by a side reaction that also con-
sumed Pd(BINAP)2. No biaryl side products were de-
tected by analyzing reactions containing high concen-
trations of PhI by GC/MS. These data argue against an
electron transfer mechanism that generates freely dif-
fusing σ-phenyl radicals. Reactions conducted with
iodobenzene that was freshly distilled from sodium
bisulfite, CaH2, and KOH to remove H2O, HI, and I2
impurities occurred with the same rate constants as
those conducted with PhI that was used directly from a
commercial supplier. No measurable accumulation of an
adduct of the ArI with the starting Pd(BINAP)2 was
indicates a linear relationship between rate constant
and free ligand concentration. The dependence of the
reaction rate on [PhOTf] was measured at a constant
1.70 × 10-4 M concentration of added BINAP. Figure 4
shows that the reaction is first-order in [PhOTf] at low
[PhOTf], but that the reaction rate is independent of
[PhOTf] at high [PhOTf]. Increasing the concentration
of PhOTf beyond 0.2 M had no further effect on the rate
of the reaction. To probe for solvent effects, reactions
were performed with [PhOTf] of 2.26 × 10-4 M in THF,
2,5-dimethyl THF, and mesitylene solvent. These data
are summarized in Table 3. The rate constants obtained
in these solvents were nearly identical to each other and
to the rate constant for reaction in benzene. Rate
constants for reactions conducted in the presence of
tetraoctylammonium chloride, tetraoctadecylammonium
bromide, tetrabutylammonium triflate, or tetrabutyl-
ammonium hexafluorophosphate were within experi-
mental error of rate constants obtained for reactions
conducted in the absence of these additives (Table 3).
31P{1H} NMR analysis of these reactions indicated that
(BINAP)Pd(Ph)X (X ) Cl, Br) complexes were formed
instead of 2a when the reaction was conducted with
tetraoctylammonium chloride and tetraoctadecylammo-
1
detected by H or 31P{1H} NMR spectroscopy.
To probe for a medium effect that may result from
changes in solvent polarity at these high concentrations
of PhI, reactions were performed with [PhI] of 3.50 ×
10-3 M and increasing amounts of added chlorobenzene.
Chlorobenzene is more polar than PhI and does not
react with 1. Reactions with concentrations of PhCl as

496 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
F igu r e 4. Order in [PhOTf] for the reaction of phenyl trifluoromethanesulfonate with 1.
Ta ble 1. In tr a m olecu la r Bon d Dista n ces (Å) a n d
An gles (d eg) for 2b
Pd(1)-P(1)
Pd(1)-N(1)
2.401(1)
2.09(1)
Pd(1)-P(2)
Pd(1)-C(1)
2.259(4)
2.00(2)
P(1)-Pd(1)-P(2)
P(2)-Pd(1)-C(1)
P(1)-Pd(1)-C(1)
90.8(1)
91.8(4)
175.1(6)
P(1)-Pd(1)-N(1)
N(1)-Pd(1)-C(1)
P(2)-Pd(1)-N(1)
92.7(3)
84.8(5)
176.4(3)
Ta ble 2. Da ta Collection a n d Refin em en t
P a r a m eter s for th e X-r a y Str u ctu r e of
[(BINAP )P d (P h )(H2N(CH2)2CH(CH3)2]OTf (2b)
empirical formula
fw
C56H50NO3F3P2SPd‚0.75(C7H16
1117.57
)
cryst color, habit
cryst dimens
cryst syst
colorless, plate
0.08 × 0.10 × 0.13 mm
monoclinic
lattice type
lattice params
primitive
a ) 11.013(1) Å
b ) 16.361(1) Å
c ) 15.481(1) Å
â ) 94.024(4)°
2782.5(3) Å3
F igu r e 5. Typical decay of 1 during the reaction of phenyl
iodide with 1 at 45 °C in benzene solvent.
volume
space group
Z value
P21 (#4)
2
diffractometer
radiation
Nonius KappaCCD
Mo KR (λ ) 0.71069 Å)
graphite monochromated
-90.0 °C
T
residuals
R; Rw
0.055; 0.050
goodness-of-fit indicator
1.59
Ta ble 3. Effect of Solven t a n d Ad d itives on th e
Oxid a tive Ad d ition of P h OTf to 1
kobs
additive
(THF solvent)
kobs
solvent
benzene
THF
× 105 s-1
× 105 s-1
4.3 ((0.3)a N(n-Bu)4OTf
4.21
2,5-dimethyl- 2.44
THF
4.58
4.41
4.38
N[n-(CH2)7(CH3)]4Cl
N[n-(CH2)17(CH3)]4Br
mesitylene
2.61
N(n-Bu)4PF6
4.68
a
The relative errors in rate constants were similar in all cases
and were estimated from duplicate and in some cases triplicate
runs under identical conditions.
F igu r e 6. Order in [BINAP] for the reaction of 1 with
phenyl iodide.
high as 4.00 M showed only a modest increase in rate
constant (filled circles in Figure 8). In addition, there
was no dependence of kobs in THF solvent on added
NBu4PF6 (Table 4), which would also change solvent
polarity. The reaction rate constant also did not change
appreciably with a complete change in medium. At 4.15
× 10-6 M [PhI] and 6.24 × 10-6 [BINAP], the rate
constants were within a factor of 4 when obtained in
benzene, THF, and 2,5-dimethyl THF solvent (Table 4).

Aryl Triflate Addition
Organometallics, Vol. 21, No. 3, 2002 497
F igu r e 7. Order in [PhI] for the reaction of 1 with phenyl
iodide for [PhI] < 2.0 × 10-4 M.
F igu r e 9. Dependence of kobs on [PhBr] for the reaction
of 1 with phenyl bromide for [PhBr] 0.50-3.20 M (circles)
and 1.78 × 10-3 to 89.5 × 10-3 M (triangles, inset).
beyond that measured at concentrations where kobs is
nearly zero-order in [PhBr]. These data stand in con-
trast to the large increase in kobs for reactions with the
high concentrations of iodobenzene.
R ea ct ivit y of [(BINAP )P d (Ar )(H 2NR )]OTf (2a ).
To test the competence of the amine-ligated aryl triflate
complex [(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OSO2CF3 as
an intermediate in the catalytic amination of aryl
triflates, we treated solutions of 2a in C6D6 or C7D8
containing 2 equiv of free BINAP with several bases.
Addition of NaO-t-Bu to 2a generated N-octylaniline
and Pd(BINAP)2 in quantitative yield at room temper-
ature. Addition of cesium carbonate or potassium phos-
phate, which have been reported to be superior bases
for the amination of aryl triflates,115 to a suspension of
2a in toluene-d8 at room temperature led to no reaction.
However, heating and vigorously stirring the suspension
of Cs2CO3 in a toluene-d8 solution of 2a for 7 h at 50 °C
generated N-octylaniline in 97% yield. Reaction of 2a
with K3PO4 was slower and occurred only after heating
for 18 h at 50 °C (94% yield of N-octylaniline). For
comparison, Cs2CO3 was suspended and stirred in a
C6D6 solution of (BINAP)Pd(Ph)Br, n-octylamine, and
2 equiv of BINAP. No reaction was observed after 2 h
at room temperature. Prolonged heating of the reaction
mixture at 50 °C generated free PPh3 and no N-
octylaniline, indicating that cleavage of the P-C bond
of the BINAP ligand backbone99 is faster than the
formation of an aryl amido complex from (BINAP)Pd-
(Ph)Br, n-octylamine, and Cs2CO3 under these condi-
tions.
F igu r e 8. Dependence of kobs on [PhI] for the reaction of
1 with phenyl iodide for [PhI] < 4.0 M (triangles). Depen-
dence of kobs on increasing [PhCl] at [PhI] of 3.50 × 10-3
M (circles).
Ta ble 4. Effect of Solven t a n d Ad d itives on th e
Oxid a tive Ad d ition of P h I to 1
kobs
kobs
solvent
benzene
THF
2,5-dimethyl-THF 0.43
× 104 s-1
additive
× 104 s-1
1.63 ((0.1) n-octylamine
1.83
0.45 (benzene solvent)
N(n-Bu)4PF6
0.27
(THF solvent)
Finally, there was no dependence on added amine (Table
4) that would be present in catalytic aryl halide ami-
nation.
Ad d ition of Ar yl Br om id es a t High [P h Br ]. Hav-
ing observed an effect of [ArI] on reaction rate at high
concentrations of aryl iodide, we measured rate con-
stants for the addition of PhBr to Pd(BINAP)2 at
concentrations up to 3.20 M. Rate constants were
obtained at 45 °C by UV-vis spectroscopy. The reactions
Complexes of the formula (BINAP)Pd(Ar)Br have
been shown to undergo P-C bond cleavage to form 4a
(Scheme 3).99 In contrast, 2a was stable for greater than
8 h at 60 °C. Heating of 2a at 80 °C for 3 h did lead to
the onset of decomposition. This thermolysis generated
several products, but none of the products could be
assigned to a cationic, amine-ligated P-C cleaved
complex 4b (Scheme 3). Moreover, addition of DMPE
(1,2-bis(dimethylphosphino)ethane) to the reaction mix-
ture did not liberate PPh3 as it did after thermolysis of
BINAP-ligated arylpalladium halide complexes. Thus,
P-C cleavage did not occur during the thermal decom-
contained 2.25 × 10-5 M Pd(BINAP)2, 1.70 × 10-4
M
BINAP, and concentrations of PhBr ranging from 0.50
to 3.20 M. Figure 9 shows these new data along with
those published previously.99 These results showed that
there is again an increase in rate with these large
increases in ArX concentration. However, there was only
a modest increase in the rate of oxidative addition

498 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
Sch em e 4
Sch em e 3
position of 2a . No N-octylaniline was detected by GC/
MS analysis of the reaction mixture.
cleanly with bases in the presence of added BINAP to
afford N-octylaniline and Pd(BINAP)2. Although 2a
reacted with weak, insoluble bases only upon heating,
it did react faster than [(BINAP)Pd(Ar)(Br) with amine
and Cs2CO3 under identical conditions.115,132
Discu ssion
P r ep a r a tion a n d Rea ctivity of [(BINAP )P d (Ar )-
(H2NR)](OTf). Studies on the oxidative addition of aryl
triflates to Pd(0) ligated by chelating bisphosphines
have been hampered by the instability of the resulting
[LPdArY]+OTf- complexes. In the past, the oxidative
addition product has been trapped by added anions such
as Cl-, I-, or AcO- to form stable (DPPF)Pd(Ar)X
complexes.102 Ludwig and Åkermark reported the prepa-
ration of several arylpalladium triflate complexes li-
gated by dppp, dppe, dcpe, and dppet (1,3-bis(diphen-
ylphosphino)propane, 1,2-bis(diphenylphosphino)ethane,
1,2-bis(dicyclohexylphosphino)ethane, and (Z)-1,2-bis-
(diphenylphosphino)ethylene).110 In this report, the
complexes were generated in situ by reaction of the
corresponding iodo complexes with silver triflate, but
the triflate complexes were not isolated. J utand and
Mosleh reported the oxidative addition of aryl triflates
to Pd(PPh3)4.109 They monitored by electrochemical
techniques the decay of Pd(0) and the appearance in
DMF of a new conducting complex. They also reported
the synthesis and isolation of two PPh3-ligated arylpal-
ladium trifluoromethanesulfonate complexes. These
complexes contained coordinated CH2Cl2 and were
handled in solutions of strongly coordinating solvents
such as acetone and DMF. While these studies provide
information on catalytic reactions that are commonly
run in DMF solvent or in the presence of added
coordinating anions, such as the Heck reaction, they are
less informative about the oxidative addition in the
amination chemistry that is conducted in noncoordinat-
ing, less polar solvents. In general, the amination
chemistry does not occur in polar solvents such as NMP
or DMF,131 and the addition of halide salts inhibits the
reaction of aryl triflates with amines when bisphos-
phines are used.115,116
Mech a n ism of Oxid a tive Ad d ition of Ar X to P d -
(BINAP )2. Potential mechanisms for the oxidative
addition of aryl halides and sulfonates to Pd(BINAP)2
are shown in Scheme 4. Path A involves the reversible
associative displacement of an arm of the bisphosphine
by the aryl halide or sulfonate electrophile, followed by
rate-limiting C-X bond scission by the resulting coor-
dinatively saturated 18-electron Pd(0) complex. The rate
law for this mechanism predicts a reaction that is first-
order in Ar-X and zero-order in added ligand (eq 1).
Path B depicts a mechanism in which one arm of the
coordinated BINAP undergoes reversible dissociation to
create an open coordination site. Irreversible coordina-
tion of Ar-X and cleavage of the C-X bond follows this
preequilibrium. This path would show a zero-order
dependence of rate on free ligand concentration and a
variable dependence of kobs on [ArX]. The rate law
derived from this mechanism (eq 2) shows that the
reaction can display zero-order behavior in [ArX] at high
concentration of aryl halide or sulfonate. This zero-order
behavior arises when the k2[ArX] term in the denomi-
nator becomes much larger than k-1. Path C is similar
to the mechanism in path B, except that coordination
of aryl halide or triflate is reversible. This mechanism
would reversibly generate a Pd(0) complex containing
both a chelating BINAP and an intact, coordinated
Ar-X through a combination of dissociative and as-
sociative steps. The rate law for this mechanism (eq 3)
predicts reaction orders similar to those predicted by
Reaction of PhOTf with a toluene solution of Pd-
(BINAP)2 containing 5 equiv of n-octylamine or reaction
of (BINAP)Pd(Ph)Br with silver trifluoromethane-
sulfonate in toluene in the presence of n-octylamine
resulted in the clean formation of the likely catalytic
intermediate [(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OTf (2a ).
Indeed, [(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OTf reacted
(131) Louie, J .; Paul, F.; Hartwig, J . F. Organometallics 1996, 15,
2794-2805.
(132) Wolfe, J . P.; Buchwald, S. L. Tetrahedron Lett. 1997, 38, 6359-
6362.

Aryl Triflate Addition
Organometallics, Vol. 21, No. 3, 2002 499
could be due to solvent polarities or reagent impurities
rather than the onset of a second, concurrent mecha-
nism. At the highest concentrations of iodobenzene, this
reagent accounted for more than 50% of the sample
volume. However, replacing the iodobenzene with chlo-
robenzene, which is an unreactive haloarene with a
greater dielectric constant, provided only modest in-
creases in kobs. Extraneous consumption of Pd(BINAP)2
by contaminants in the PhI, such as I2, HI, or H2O, was
ruled out by observing similar rates for oxidative
addition when using commercial PhI as received and
when using purified PhI. Thus, solvent polarity or
reagent impurities do not account for the increase in
rate at high concentrations of ArX.
path D. Path D involves the full, reversible dissociation
of a chelating ligand to generate the 14-electron inter-
mediate (BINAP)Pd, which undergoes irreversible oxi-
dative addition of aryl halide or triflate. The rate law
corresponding to path D is shown in eq 4. This rate
Instead, we propose that a second mechanism, which
is faster for iodides than bromides and does not occur
at all when using aryl triflates, operates at high
concentrations of ArX. The dependence of kobs at high
[PhI] is clearly positive, but is not strictly linear.
Nonideal solution behavior of substrate may lead to this
curvature at the highest concentrations of aryl halide.
This second mechanism must involve reaction of the
metal with ArX before the irreversible step. This mech-
anism cannot involve full dissociation of ligand because
full dissociation of ligand is slower than the overall
reaction at high [ArI]. This reaction could involve
coordination or addition of the ArX to the 16-electron
palladium metal center formed by partial ligand dis-
sociation, as shown in pathway B or C of Scheme 4. At
the concentrations of ArX that approach those of solvent,
coordination of ArX may compete with reassociation of
an arm of the partially dissociated BINAP. Alterna-
tively, an electron transfer mechanism may begin to
operate at high ArX. This mechanism may involve an
electron transfer that is first-order in both palladium
and ArX reagent and that occurs prior to dissociation
of ligand from the metal center. If this mechanism does
operate, then it must not form arene or biaryl com-
pounds because the reaction yields are equally high at
low or high concentrations of ArX.
Our data do not firmly support addition of the aryl
bromide to the 16-electron species over the electron
transfer pathway, but we do favor nonradical mecha-
nism B or C. The absence of biphenyl formed at high
concentrations of ArX suggests the absence of freely
diffusing Ar• intermediates. Moreover, the trend in
importance of this second mechanism at high ArX as a
function of X tracks well with the coordinating ability
of the aryl electrophile and less with its electrophilicity.
Halocarbon coordination to low-valent late metals is
known to be more favorable for iodides than bro-
mides,133-139 and complexes of intact alkyl or aryl
triflates are unknown. Iodobenzene is a better ligand
equation predicts an inverse first-order dependence of
reaction rate on free ligand concentration and a first-
order dependence on [ArX] when the ratio of [ArX] to
[L] (L ) BINAP) is low. However, this rate law predicts
zero-order behavior in both [ArX] and [L] at high ratios
of [ArX] to [L]. For our reactions of aryl triflates in the
presence of amine, all four paths involve fast trapping
of the (BINAP)Pd(Ar)OTf intermediate by amine. This
trapping of the aryl triflate addition product would have
no effect on the rate of oxidative addition. Indeed, the
reaction rates were zero-order in the concentration of
added amine.
No single mechanism accounts for all of our data.
Instead, a combination of mechanism D and either
mechanism B or C is consistent with our rate measure-
ments. Our data rule out paths A and B as the
mechanism for addition of aryl triflates and as the
mechanism for addition of aryl iodides and bromides at
modest concentrations of the aryl halides. Path A is
inconsistent with the zero-order dependence of kobs
observed at high [ArX]. Moreover, both paths A and B
are inconsistent with the inverse first-order dependence
on ligand concentration observed for reactions run at
modest concentrations of ArX.
Paths C and D are most consistent with the observed
first-order rate dependence on [ArX] at low concentra-
tions, zero-order rate dependence at high [ArOTf], zero-
order rate dependence on [ArX] for reactions of aryl
bromides and iodides up to about 0.1 M, and inverse
first-order dependence on [BINAP] at modest ArX
concentrations. We favor path D over path C for reac-
tions of aryl triflates and for reactions of aryl halides
at modest concentrations of [ArX]. It seems likely that,
at these concentrations of aryl halide or triflate, the
recoordination of a ligand arm would be faster than
intermolecular coordination of the weakly donating aryl
electrophile. Yet, reaction by exclusively path C or D at
all concentrations of aryl halide is inconsistent with the
increase in kobs observed when the concentration of ArI
and ArBr was above 1 M.
(133) Kulawiec, R. J .; Crabtree, R. H. Coord. Chem. Rev. 1990, 99,
89-115.
(134) Crabtree, R. H.; Mellea, M. F.; Mihelcic, J . M. Inorg. Synth.
1990, 28 (Reagents Transition Met. Complex Organomet. Synth.), 56-
60.
(135) Crabtree, R. H.; Mellea, M. F.; Mihelcic, J . M. Inorg. Synth.
1989, 26, 122-126.
(136) Crabtree, R. H.; Faller, J . W.; Mellea, M. F.; Quirk, J . M.
Organometallics 1982, 1, 1361-1366.
(137) Kulawiec, R. J .; Faller, J . W.; Crabtree, R. H. Organometallics
1990, 9, 745-755.
(138) Winter, C. H.; Arif, A. M.; Gladysz, J . A. J . Am. Chem. Soc.
1987, 109, 7560-7561.
Thus, we probed whether the increase in rate constant
with such high concentrations of aryl halide substrate
(139) Butts, M. D.; Scott, B. L.; Kubas, G. J . J . Am. Chem. Soc. 1996,
118, 11831-11843.

500 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
Ta ble 5. Ra tio of k2/k-1 for th e Oxid a tive Ad d ition
rate at very high [PhBr] is moderate, and only a
doubling of the rate constant for oxidative addition is
observed with large increases in aryl bromide concen-
tration. No effect of increasing aryl triflate concentra-
tions was observed on the rate for oxidative addition of
this substrate. The increase in reactivity for aryl iodides
uncovered in this study may be attributed to the
coordinating ability or the X group of the aryl electro-
phile and is consistent with reports on the coordination
ability of haloarenes to low-valent late metals.133,136,137,139
This increase in reactivity at very high [ArX] suggests
that the initial phases of catalytic reactions conducted
on a synthetic scale may occur, in part, by a mechanism
that operates in parallel to the one identified in our
recent study.
of Ar X to 1
ArX
(k2/k-1) × 103
k2 rel
PhOTf
PhBr
PhI
85.2
97.2
31600.0
1.0
1.1
370.9
than bromobenzene because of the higher polarizability
of the iodide lone pairs. Phenyl triflate is a poorer donor
than aryl halides is to Pd(0) because of the hardness of
the triflate oxygens.
R ela t ive R ea ct ivit y of Ar I, Ar Br , a n d Ar OTf.
When kobs for oxidative addition of aryl halides to 1
reaches saturation with respect to the concentration of
ArX, the rate of the oxidative addition is solely con-
trolled by the rate of ligand dissociation from 1. In path
D, k1 (eq 4) represents the rate of ligand dissociation
from 1. The different reactivity of the aryl electrophile
toward the unsaturated intermediate (BINAP)Pd can
be inferred from the relative magnitudes of the rate
constant for the bond-breaking step of the mechanism,
k2. We cannot directly measure k2, but we can determine
the ratio of k2/k-1 from plots of the dependence of kobs
on the concentration of aryl halide or sulfonate using
all concentrations of PhOTf, concentrations of PhBr up
to 90 mM, and concentrations of PhI up to 0.2 mM. We
can compare these ratios for different aryl electrophiles
because the rate constant for re-coordination of BINAP
to (BINAP)Pd, k-1, is independent of the identity of the
aryl electrophile. The more reactive the electrophile, the
larger the magnitude of k2/k-1. Table 5 contains the
values of k2/k-1 determined from the data in Figures 4,
7, and the inset of 9. Comparison of the values of k2/k-1
reveals that phenyl triflate is almost exactly as reactive
as phenyl bromide, while phenyl iodide is nearly 400
times more reactive than either PhBr or PhOTf. This
information further supports our preference for reaction
of aryl triflates and aryl halides at modest concentra-
tions by path D, in which the aryl electrophile oxida-
tively adds to the 14-electron (BINAP)Pd intermediate
without prior reversible coordination. Bromobenzene
would be expected to compete with an arm of the BINAP
ligand for a coordination site more effectively than
would phenyl triflate, and reaction of the aryl bromide
would, thereby, produce a significantly higher ratio of
k2/k-1 than would reaction of PhOTf.140
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Unless otherwise noted, all
manipulations were conducted using standard Schlenk tech-
1
niques or in an inert atmosphere glovebox. H NMR spectra
were obtained on a Bruker Advance DPX-400 MHz, GE QE
300 MHz, GE Ω 500 MHz, or GE Ω 300 MHz Fourier
transform NMR spectrometer. 31P{1H} NMR spectra were
obtained on the Ω 300 and 500 MHz spectrometers operating
at the corresponding frequencies. 19F{1H} NMR spectra were
recorded on a Bruker Advance DPX-400 MHz Fourier trans-
form NMR spectrometer and referenced to both an external
and an internal fluorobenzene standard. 1H NMR spectra were
recorded relative to residual protiated solvent. 31P{1H} NMR
spectra were recorded in units of parts per million relative to
85% H3PO4 as external standard. 19F{1H} spectra were re-
corded in units of parts per million relative to 1 × 10-2
M
fluorobenzene in C6D6 as an external standard. UV-vis spectra
were collected on a Varian Cary 3E spectrophotometer equipped
with a thermostated multicell block. IR spectra were collected
on a Midac M-Series FT-IR spectrophotometer. Elemental
analyses were performed by Robertson Microlit Laboratories,
Inc., Madison, NJ .
All reagents were purchased from commercial suppliers and
used without further purification. Pd(BINAP)299 and (BINAP)-
Pd(Ph)Br99 were prepared using literature procedures, unless
otherwise noted. n-Octylamine was heated at reflux over CaH2
and KOH, distilled under nitrogen, and stored in an inert
atmosphere glovebox. Iodobenzene and bromobenzene were
heated over sodium sulfite, CaH2, and KOH under N2, distilled
under vacuum, and stored in an inert atmosphere glovebox.
Protiated solvents were heated to reflux and distilled from
purple solutions containing sodium benzophenone ketyl under
N2. Deuterated solvents were dried similarly but were collected
by vacuum transfer.
Oxid a tive Ad d ition of P h OTf to P d (BINAP )2 in th e
P r esen ce of Am in e. Pd(BINAP)2 (7 mg, 5.2 µmol) was
dissolved in 0.6 mL of THF. The solution was then transferred
to a screw-capped NMR tube containing a PTFE-lined septum
cap. Prior to sealing the tube, PhOTf (4.2 µL, 5.9 mg, 26.1
µmol) and n-octylamine (4.3 µL, 3.3 mg, 25.5 µmol) were added
to the solution. An initial 31P{1H} spectrum was taken, and
the solution was heated at 65 °C in an oil bath. Intermediate
spectra were recorded at 15 and 30 min, and at 3, 14, and 17
h of reaction time.
Oxid a tive Ad d ition of P h OTf to P d (BINAP )2 in th e
Absen ce of Am in e. Pd(BINAP)2 (7 mg, 5.2 µmol) was dis-
solved in 0.6 mL of THF. The solution was then transferred
to a screw-capped NMR tube containing a PTFE-lined septum
cap. Prior to sealing the tube, PhOTf (4.2 µL, 5.9 mg, 26.1
µmol) was added to the solution. An initial 31P{1H} NMR
spectrum was taken, and the solution was heated at 65 °C in
an oil bath. Spectra were recorded at 15, 30, and 60 min of
reaction time.
Con clu sion
We have shown that the oxidative additions of aryl
iodides, bromides, and triflates follow the same mech-
anism at moderate ArX concentrations. However, a
second mechanism, which occurs more readily for ArI
than for ArBr and not at all for ArOTf, appears to
operate at high concentrations of ArX electrophile. In
the case of ArI, this mechanism accounts for more than
an 8-fold increase in the rate of oxidative addition
relative to the rate of ligand dissociation from Pd(0).
This phenomenon is likely to account for the ability to
conduct aryl iodide aminations at lower temperatures
than aryl bromide aminations when using a Pd catalyst
ligated by BINAP. For aryl bromides, the increase in
(140) The relevant ratio corresponding to path C is actually more
complicated and not a ratio but a constant. From eq 3, the proper
expression would be k-1/k1k2 + (1 + k2[L]/k3).

Aryl Triflate Addition
Organometallics, Vol. 21, No. 3, 2002 501
P r ep a r a t ion of [(BINAP )P d (P h )(H2N(CH2)7CH 3)]OTf
(2a ). (BINAP)Pd(Ph)Br (300 mg, 0.34 mmol) was suspended
in 10 mL of toluene. While stirring, n-octylamine (45.9 mg,
0.36 mmol) was added to the reaction mixture, followed by
silver trifluoromethanesulfonate (91.3 mg, 0.36 mmol). A fine
white precipitate formed immediately upon addition of AgOTf,
and the color of the solution changed from pale yellow to
almost colorless. After stirring at room temperature for 5 min,
the solution was carefully decanted and filtered through a plug
of Celite. The precipitate was extracted with 2 mL of toluene,
and the extract was added to the supernatant after filtration
through a plug of Celite. The resulting solution was evaporated
to 1/10th of the original volume. The toluene solution was
layered with pentane and allowed to rest at -34 °C overnight.
The white powdered product was isolated by filtration through
room temperature for 5 min, the solution was carefully
decanted and filtered through a plug of Celite. The precipitate
was extracted with 2 mL of toluene, and the extract was added
to the supernatant after filtration through a plug of Celite.
The resulting solution was added dropwise to a solution of
tetraoctylammonium chloride (142.0 mg, 0.284 mmol) in
toluene with stirring. The resulting pale yellow solution was
concentrated to 1/10th its original volume, layered with
pentane, and placed in a freezer at -34 °C. A pale cream-
colored solid was recovered (196.1 mg, 83% yield). 1H NMR
(400 MHz, CD2Cl2): δ 6.508 (broad, 2H), 6.58 (d, J ) 8.8 Hz,
1H), 6.697 (multiplet, 3H), 6.75-6.82 (multiplet, 2H), 6.84-
6.93 (multiplet, 3H), 6.94-7.10 (multiplet, 6H), 7.15-7.27
(multiplet, 3H), 7.29-7.47 (multiplet, 7H), 7.49-7.63 (mul-
tiplet, 6H), 7.72-7.84 (multiplet, 3H), 7.966 (dd, J 1 ) 9.0 Hz,
J 2 ) 1.6 Hz, 1H). 31P{1H} (C6D6): δ 13.69 (d, J pp ) 39 Hz),
30.54 (d, J pp ) 39 Hz). Anal. Calcd for C50H37P2PdCl: C, 71.35;
H, 4.43. Found: C, 71.02; H, 4.45.
1
a medium-porosity fritted funnel (319.4 mg, 87.1% yield). H
NMR (400 MHz, C6D6): δ 0.747 (m, 4H), 0.862 (t, J ) 7.2 Hz,
4H), 0.962 (m, 2H), 1.064 (m, 2H), 1.205 (m, 3H), 1.869 (br,
1H), 2.101 (br, 1H), 3.235 (br, 1H), 3.438 (b, 1H), 6.406 (m,
2H), 6.557 (m, 6H), 6.704 (m, 2H), 6.841 (m, 4H), 6.988 (m,
2H), 7.069 (app t, 2H), 7.18-7.27 (m, 4H), 7.409 (m, 6H), 7.619
(app t, 2H), 7.743 (br, 2H), 7.95-8.15 (m, 5H). 31P{1H} (C6D6):
δ 15.04 (d, J pp ) 38 Hz), 28.84 (d, J pp ) 37 Hz). 19F{1H} (C6D6):
-77.21 (s). IR (C6H6): 3310 w, 3216 w, 2924 w, 2857 w, 1576
m, 1437 m, 1284 s, 1259 m, 1224 m, 1099m, 816 w, 748 w.
Anal. Calcd for C59H56F3NO3P2PdS: C, 65.34; H, 5.20; N, 1.29.
Found: C, 65.08; H, 5.35; N, 1.19.
P r ep a r a tion of (BINAP )P d (P h )I. (BINAP)Pd(Ph)Br (250
mg, 0.28 mmol) was suspended in 10 mL of toluene. While
stirring, n-octylamine (36.5 mg, 0.28 mmol) was added to the
reaction mixture, followed by silver trifluoromethanesulfonate
(76.1 mg, 0.30 mmol). A fine white precipitate formed im-
mediately upon addition of AgOTf, and the color of the solution
changed from pale yellow to almost colorless. After stirring at
room temperature for 5 min, the solution was carefully
decanted and filtered through a plug of Celite. The precipitate
was extracted with 2 mL of toluene, and the extract was added
to the supernatant after filtration through a plug of Celite.
The resulting solution was added dropwise to a suspension of
tetraheptylammonium iodide (166.9 mg, 0.31 mmol) in toluene
with stirring. The resulting pale yellow suspension was
concentrated to 1/10th its original volume, layered with
pentane, and placed in a freezer at -34 °C. A pale yellow solid
was recovered (105.1 mg, 39.9% yield). 1H NMR (400 MHz,
CD2Cl2): δ 6.478 (broad, 2H), 6.52 (d, J ) 8.8 Hz, 1H), 6.72
(multiplet, 3H), 6.76-6.80 (multiplet, 2H), 6.82-6.89 (mul-
tiplet, 3H), 6.94-7.25 (multiplet, 9H), 7.33-7.48 (multiplet,
7H), 7.50-7.68 (multiplet, 6H), 7.74-7.90 (multiplet, 3H), 7.85
(dd, J 1 ) 8.9 Hz, J 2 ) 1.6 Hz, 1H). 31P{1H} (C6D6): δ 9.29 (d,
J pp ) 41 Hz), 21.20 (d, J pp ) 39 Hz). Anal. Calcd for C50H37P2-
PdI: C, 64.36; H, 4.00. Found: C, 64.69; H, 4.00.
P r ep a r a tion of [(BINAP )P d (P h )(H 2N(CH2)2CH(CH3)2]-
OTf (2b). (BINAP)Pd(Ph)Br (300 mg, 0.34 mmol) was dis-
solved in 5 mL of CH2Cl2. While stirring, isoamylamine (45.9
mg, 0.36 mmol) was added to the reaction mixture, followed
by silver trifluoromethanesulfonate (91.3 mg, 0.36 mmol). A
fine white precipitate formed immediately upon addition of
AgOTf, and the color of the solution changed from pale yellow
to almost colorless. After stirring at room temperature for 5
min, the solution was carefully decanted and filtered through
a plug of Celite. The precipitate was extracted with 1 mL of
CH2Cl2, and the extract was added to the supernatant after
filtration through a plug of Celite. The resulting solution was
evaporated to approximately 1/10th of the original volume. The
solution was layered with toluene and allowed to rest at -34
°C for 1 h. Heptane was then carefully layered on the solution.
The mixture was allowed to rest at -34 °C overnight. The
product was isolated as colorless crystals suitable for X-ray
diffraction, which included ∼3/4 molecule of heptane per
molecule of complex in the crystal lattice. To obtain satisfactory
combustion analysis, this material was further recrystallized
by allowing a concentrated toluene solution of 2b to rest at
-34 °C overnight. The product was isolated by filtration as a
white microcrystalline powder that retained 1/2 molecule of
toluene per molecule of complex (319.4 mg, 87.1% yield). 1H
NMR (400 MHz, C6D6): δ 0.387 (dd, J 1 ) 6.6 Hz, J 2 ) 2.1 Hz,
6H), 0.60 (multiplet, 2H), 0.904 (h, J ) 6.7 Hz, 1H), 1.894 (br,
1H), 2.023 (br, 1H), 3.187 (br, 1H), 3.398 (br, 1H), 6.37-6.45
(multiplet, 2H), 6.48-6.64 (multiplet, 6H), 6.66-6.74 (mul-
tiplet, 2H), 6.78-6.92 (multiplet, 4H), 6.95-7.10 (multiplet,
4H), 7.13-7.28 (multiplet, 6H), 7.33-7.50 (multiplet, 5H),
7.599 (td, J 1 ) 7.7 Hz, J 2 ) 2.8 Hz, 2H), 7.742 (br, 2H), 7.94-
8.14 (multiplet, 4H). 31P{1H} (C6D6): δ 15.12 (d, J pp ) 39 Hz),
27.81 (d, J pp ) 35 Hz). 19F{1H} (C6D6): -77.21 (s). IR (C6H6):
3310 w, 3216 w, 2924 w, 2857 w, 1576 m, 1437 m, 1284 s,
1259 m, 1224 m, 1099m, 816 w, 748 w. Anal. Calcd for
Th er m olyisis of [(BINAP )P d (P h )(H 2N(CH2)7CH3)]OTf.
[(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OTf (10 mg, 9.2 µmol) was
dissolved in 0.6 mL of toluene. The solution was transferred
to a screw-capped NMR tube equipped with a PTFE-lined
septum cap. An initial 31P{1H} NMR spectrum was recorded,
and the solution was heated at 60 °C in an oil bath. After 6 h
of heating, no color change was observed, and 31P{1H} NMR
spectrometry showed that no change had occurred. The sample
was then returned to an oil bath and heated at 80 °C. After
30 min of reaction time the color had changed to light orange.
31P{1H} NMR spectroscopy showed that ca. 70% of the starting
material had reacted. Further heating (6 h) showed complete
conversion of 2a and the formation of several unidentified
31P{1H} resonances. DMPE (4.6 µL, 4.2 mg, 27.1 µmol) was
then added to the sample, and a 31P{1H} spectrum was re-
corded. A resonance due to Pd(DMPE)2 was observed, but no
resonances for free PPh3 or free BINAP were observed. No
N-octylaniline was detected by GC/MS analysis of the reaction
solution.
C
56H50F3NO3P2PdS‚1/2C7H8: C, 65.65; H, 5.00; N, 1.29.
Rea ction of [(BINAP )P d (P h )(H2N(CH2)7CH3)]OTf w ith
Na O-t-Bu . [(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OTf (10 mg, 9.2
µmol) and 1,3,5-trimethoxybenzene (0.7 mg, 4.2 µmol) were
Found: C, 65.75; H, 4.94; N, 1.01.
P r ep a r a tion of (BINAP )P d (P h )Cl. (BINAP)Pd(Ph)Br
(250 mg, 0.28 mmol) was suspended in 10 mL of toluene. While
stirring, n-octylamine (36.5 mg, 0.28 mmol) was added to the
reaction mixture, followed by silver trifluoromethanesulfonate
(76.1 mg, 0.30 mmol). A fine white precipitate formed im-
mediately upon addition of AgOTf, and the color of the solution
changed from pale yellow to almost colorless. After stirring at
1
dissolved in benzene-d6. A H NMR spectrum was recorded.
NaO-t-Bu (1.8 mg, 18.7 µmol) was added to the tube, followed
by BINAP (11.5 mg, 18.5 µmol). The tube was resealed and
shaken. The immediate appearance of a dark red color, due
to Pd(BINAP)2, was observed. A 1H NMR spectrum was
recorded, and the yield of N-octylaniline was determined by

502 Organometallics, Vol. 21, No. 3, 2002
Alcazar-Roman and Hartwig
integrating the R-CH2 resonances of the amine complex and
N-octylaniline vs resonances of the internal standard.
Rea ction of [(BINAP )P d (P h )(H2N(CH2)7CH3)]OTf w ith
Cs2CO3 a n d K3P O4. [(BINAP)Pd(Ph)(H2N(CH2)7CH3)]OTf (25
mg, 23.1 µmol), BINAP (28.7 mg, 46.1 µmol), and 1,3,5-
trimethoxybenzene (3.9 mg, 25.1 µmol, internal standard) were
that was fixed at 1.80 × 10-6 M, a Pd(BINAP)2 concentration
that was set to 8.55 × 10-7 M, and a concentration of BINAP
that was varied from 1.70 × 10-4 to 1.08 × 10-3 M. For
experiments to determine the reaction order in PhI, [Pd-
(BINAP)2] was fixed at 4.27 × 10-7, 8.55 × 10-7, 2.26 × 10-5
,
1.35 × 10-6, 5.62 × 10-6, and 2.25 × 10-5 M. The concentration
of BINAP was held constant at 1.70 × 10-4 M, and the
concentration of PhI was varied from 8.94 × 10-7 to 4.20 M.
For the determination of the effect of varying solvent and
additives the concentrations of Pd(BINAP)2, BINAP, and PhI
were fixed at 8.55 × 10-7, 1.70 × 10-4, and 1.80 × 10-6 M,
respectively. When obtaining kobs values for the addition of
PhOTf, experiments to determine the reaction order in BINAP
contained a PhOTf concentration that was fixed at 2.26 × 10-4
M, a Pd(BINAP)2 concentration that was 2.25 × 10-5 M, an
n-octylamine concentration that was 1.13 × 10-4 M, and a
concentration of BINAP that was varied from 170 × 10-4 to
6.78 × 10-4 M. For experiments to determine the reaction order
in PhOTf, [Pd(BINAP)2] was fixed at 2.25 × 10-5 M, the
n-octylamine concentration was fixed at 1.13 × 10-4 M,
[BINAP] was held constant at 1.70 × 10-4 M, and [PhOTf]
was varied between 2.26 × 10-4 and 1.36 M. For the deter-
mination of solvent, amine, and additive effects the concentra-
tions of Pd(BINAP)2, BINAP, n-octylamine, and PhOTf were
fixed at 2.25 × 10-5, 1.70 × 10-4, 1.13 × 10-4, and 2.26 × 10-4
M, respectively. When obtaining kobs values for addition of
PhBr, experiments to determine the reaction order in PhBr
contained [Pd(BINAP)2] that was fixed at 2.25 × 10-5 M,
[BINAP] that was held constant at 1.70 × 10-4 M, and [PhBr]
that was varied between 0.50 and 4.00 M.
1
dissolved in 4 mL of toluene-d8. A H NMR spectrum of this
solution was recorded. Cs2CO3 (9.0 mg, 27.6 µmol) or K3PO4
(6.0 mg, 36.6 µmol) were weighed into two separate screw-
capped vials. A 1.2 mL portion of the solution described above
was transferred into each vial. A magnetic stir bar was added,
and the vials were sealed with PTFE-lined septum screw-caps.
The suspensions were allowed to stand at room temperature
with vigorous stirring for 2 h. In both cases, only a very faint
pink color developed due to the formation of small amounts of
Pd(BINAP)2. A 1H NMR spectrum revealed that the conversion
of the starting material was negligible. The vials were then
removed from the glovebox and placed in an oil bath heated
to 50 °C. After 7 h 1H NMR spectra of both reactions were
recorded, and after 18 h a 1H NMR spectrum for the reaction
with K3PO4 was recorded. The yields of N-octylaniline were
determined by integrating the R-CH2 resonances of the amine
complex and products vs resonances of the internal standard.
Complete conversion of the starting material for reaction with
Cs2CO3 after 7 h and for reaction with K3PO4 after 18 h was
confirmed by 31P{1H} NMR spectroscopy.
Rea ction of (BINAP )P d (P h )(Br ) w ith n -Octyla m in e
a n d Cs2CO3. (BINAP)Pd(Ph)(Br) (4.0 mg, 4.5 µmol), BINAP
(5.6 mg, 9.0 µmol), and 1,3,5-trimethoxybenzene (1.0 mg, 6.4
µmol, internal standard) were dissolved in 1 mL of benzene-
d6. A 1H NMR spectrum of this solution was recorded. Cs2CO3
(9.0 mg, 27.6 µmol) was weighed into a screw-capped vial and
then added to the solution described above. A magnetic stir
bar was added, and the vial was sealed with a PTFE-lined
septum screw-cap. The suspension was allowed to stand at
room temperature with vigorous stirring for 1 h. Only a very
faint pink color developed due to the formation of small
X-r a y Cr yst a l St r u ct u r e of [(BINAP )P d (P h )(H 2N-
(CH2)2CH(CH3)2]OTf (2b). A colorless plate crystal of C56H50
-
NO3F3P2PdSPd‚0.75(C7H16) was mounted on a glass fiber, and
all measurements were made on an Nonius KappaCCD
diffractometer with graphite-monochromated Mo KR radiation.
The data were collected at a temperature of -90 ( 1 °C to a
maximum 2θ value of 50.1°. Of the 9399 reflections that were
collected, 5096 were unique (Rint ) 0.102). The structure was
solved by the Patterson method and expanded using Fourier
techniques.141 The final cycle of full-matrix least-squares
refinement142 was based on 2565 observed reflections (I >
3.00σ(I)) and 632 variable parameters and converged (largest
parameter shift was 0.06 times its esd) with unweighted and
weighted agreement factors of R ) 0.055 and Rw ) 0.050. For
details on data acquisition and structure solution, see the
Supporting Information.
1
amounts of Pd(BINAP)2. A H NMR spectrum revealed that
the conversion of the starting material was negligible. The vial
was then removed from the glovebox and placed in an oil bath
heated to 50 °C. After 1, 3, and 12 h 1H NMR spectra were
recorded. No N-octylaniline was detected. A 31P{1H} NMR
spectrum of the reaction mixture revealed that the (BINAP)-
Pd(Ph)Br starting material had been completely consumed.
GC/MS analysis of the reaction mixture revealed PPh3 had
been produced but showed no N-octylaniline.
Deter m in a tion of Ra te Con sta n ts for th e Oxid a tive
Ad d ition of P h I, P h OTf, a n d P h Br to P d (BINAP )2.
Separate stock solutions of Pd(BINAP)2, BINAP, PhI, PhOTf,
PhBr, and n-octylamine in benzene were prepared. Similar
stock solutions were prepared in THF and 2,5-dimethyl-THF.
The stock solutions were stored at -35 °C in a freezer. Samples
were prepared by adding stock solutions into 5 mL volumetric
flasks. Each flask was then filled to the 5 mL mark with the
appropriate solvent. The resulting solutions were shaken and
transferred (∼3 mL) to quartz cuvettes that were fitted with
airtight Teflon valves. The UV-visible spectrometer cell block
was warmed to 40 °C for reactions of PhI and to 45 °C for
reactions of PhOTf and PhBr. The absorbance of Pd(BINAP)2
was monitored at λ ) 519 nm over at least three half-lives,
with a 1 s signal averaging time and 30 s between acquisitions.
Kinetic data were fit to the expression A519 ) B e-kt + c, in
which k is the pseudo-first-order rate constant kobs. When
obtaining kobs for addition of PhI, experiments to determine
the reaction order in BINAP contained a PhI concentration
Ack n ow led gm en t. We are grateful to the NIH
(R01GM55382-02-04) for support of this work.
Su p p or tin g In for m a tion Ava ila ble: Tables of positional
parameters and Beq, U values, intramolecular distances,
intramolecular bond angles, and torsion or conformational
angles for hydrogen and non-hydrogen atoms for 2b (PDF).
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM0108088
(141) Beurskens, P. T., Admiraal, G., Beurskens, G., Bosman, W.
P., de Gelder, R., Israel, R., Smits, J . M. M. DIRDIF94, The DIRDIF-
94 program System; Technical Report of the Crystallography Labora-
tory; University of Nijmegen: The Netherlands, 1994.
(142) Least-squares function minimized: ∑w(|Fo| - |Fc|)2, where w
2
2
) 4Fo2/σ2(Fo2) ) [σ2(Fo) + (pFo/2)2]-1, Fo ) ∑(C - RB)/Lp, and σ2(Fo
)
) [∑2(C + R2B) + (pFo2)2]/Lp2, S ) scan rate, C ) total integrated
peak count, R ) ratio of scan time to background counting time, B )
total background count, Lp ) Lorentz-polarization factor, p ) p-factor.