Synthesis and solution structure of palladium tris(o-tolyl)phosphine mono(amine) complexes

Article abstract of DOI:10.1021/om9509599

The complex(es) resulting from a 1:4 mixture Of Pd₂(DBA)₃ and P(o-tol)₃ react with aryl bromides or aryl iodides p-XC₆H₄R (X = Br, I; R = Me, t-Bu, OMe) to generate the corresponding halide dimers {Pd[P(o-tol)₃](p-C₆H₄R)(μ-X)}₂ (X = Br, R = t-Bu (1), Me (2), OMe (3); X = I, R = t-Bu (4), Me (5), OMe (6)) in 46-76% yield. Iodide dimer 5 reacts with AgOTf in acetonitrile to form the cationic bis(acetonitrile) complex {Pd[P(o-tol)₃](p-C₆H₄-Me)(CH ₃CN)₂]}⁺OTf^- (8) which was treated in situ with LiCl to form the chloride dimer {Pd[P(o-tol)₃](p-C₆H₄Me)(μ-Cl)}₂ (9) in 93% yield. The p-tolyl halide dimers 2, 5, and 9 react with N-benzylmethylamine to generate the corresponding 1:1 palladium amine adducts Pd[P(o-tol)₃](p-C₆H₄Me)[HN(Me)Bn]X (X - Cl (12), 85%; X = Br (13), 72%; X = I (14), 77%). Reaction of a mixture of Pd₂(DBA)₃ and P(o-tol)₃ with the haloamines 2-IC₆H₄(CH₂)₂N(H)Bn, 2-BrC₆H₄CH₂N(H)(p-tolyl), and 2-BrC₆H₄(CH₂)₃N(H)Bn gave the chelated palladium amine complexes Pd[P(o-tol)₃](2-C₆H₄(CH₂) ₂N(H)Bn]I (18, 71%), Pd[P(o-tol)₃][2-C₆H₄CH ₂N(H)(p-tolyl)]Br (19, 77%), and Pd[P(o-tol)₃](2-C₆H₄(CH₂) ₃N(H)Bn]Br (21, 24%), respectively. Variable-temperature ¹H and ³¹P NMR analysis of 12-14 and related complexes was consistent with hindered rotation about the P-C bonds, with predominant formation of the exo₂-P(o-tol) conformer, and hindered rotation about the Pd-P bond with formation of three unequally populated rotamers.

Full text of DOI:10.1021/om9509599

Organometallics 1996, 15, 2745-2754
2745
Syn th esis a n d Solu tion Str u ctu r e of P a lla d iu m
Tr is(o-tolyl)p h osp h in e Mon o(a m in e) Com p lexes
Ross A. Widenhoefer, H. Annita Zhong, and Stephen L. Buchwald*
Department of Chemistry, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139
Received December 14, 1995X
The complex(es) resulting from a 1:4 mixture of Pd2(DBA)3 and P(o-tol)3 react with aryl
bromides or aryl iodides p-XC6H4R (X ) Br, I; R ) Me, t-Bu, OMe) to generate the
corresponding halide dimers {Pd[P(o-tol)3](p-C6H4R)(µ-X)}2 (X ) Br, R ) t-Bu (1), Me (2),
OMe (3); X ) I, R ) t-Bu (4), Me (5), OMe (6)) in 46-76% yield. Iodide dimer 5 reacts with
AgOTf in acetonitrile to form the cationic bis(acetonitrile) complex {Pd[P(o-tol)3](p-C6H4-
Me)(CH3CN)2]}+OTf- (8) which was treated in situ with LiCl to form the chloride dimer
{Pd[P(o-tol)3](p-C6H4Me)(µ-Cl)}2 (9) in 93% yield. The p-tolyl halide dimers 2, 5, and 9 react
with N-benzylmethylamine to generate the corresponding 1:1 palladium amine adducts Pd-
[P(o-tol)3](p-C6H4Me)[HN(Me)Bn]X (X ) Cl (12), 85%; X ) Br (13), 72%; X ) I (14), 77%).
Reaction of a mixture of Pd2(DBA)3 and P(o-tol)3 with the haloamines 2-IC6H4(CH2)2N(H)Bn,
2-BrC6H4CH2N(H)(p-tolyl), and 2-BrC6H4(CH2)3N(H)Bn gave the chelated palladium amine
complexes Pd[P(o-tol)3](2-C6H4(CH2)2N(H)Bn]I (18, 71%), Pd[P(o-tol)3][2-C6H4CH2N(H)(p-
tolyl)]Br (19, 77%), and Pd[P(o-tol)3](2-C6H4(CH2)3N(H)Bn]Br (21, 24%), respectively. Vari-
1
able-temperature H and 31P NMR analysis of 12-14 and related complexes was consistent
with hindered rotation about the P-C bonds, with predominant formation of the exo2-P(o-
tol) conformer, and hindered rotation about the Pd-P bond with formation of three unequally
populated rotamers.
Sch em e 1
In tr od u ction
In 1983 Migita reported that Pd[P(o-tol)3]2Cl2 (o-tol
) o-tolyl) served as an effective catalyst for the cross-
coupling of aryl bromides with (diethylamino)stannane
in toluene at 100 °C.1 Despite the importance of
aromatic amines in areas such as pharmaceuticals2 and
conductive polymers,3 and due to limitations in tradi-
tional methods for the synthesis of anilines,4 Pd-
catalyzed C-N bond formation remained undeveloped
for over a decade. However, recent work5 has led to the
development of a tin-free Pd-catalyzed procedure for the
conversion of aryl bromides6 to the corresponding
anilines via reaction with free amine and sodium tert-
butoxide. For example, reaction of 5-bromo-m-xylene,
N-benzylmethylamine (1.2 equiv), and sodium tert-
butoxide (1.4 equiv) with 2 mol % of Pd(DBA)2 (DBA )
dibenzylideneacetone) and 4 mol % of P(o-tol)3 in toluene
at 65 °C formed N-benzyl-N-methyl-3,5-xylidine in 84%
yield (Scheme 1).6a The corresponding reaction of aryl
iodides7 and amines required higher temperatures and
produced slightly lower yields of cross-coupled product
than did aryl bromides.
The proposed catalytic cycle for the palladium-
catalyzed amination of aryl halides, based on Hartwig’s
mechanism for the cross-coupling of aminostannanes
with aryl bromides,5b,c is shown in Scheme 2. The key
steps include the cleavage of the aryl halide dimer A
(X ) Br, I) by free amine to form the corresponding
palladium amine monomer B followed by deprotonation
to generate the requisite three-coordinate palladium
amide complex C. Due to the central role of the 1:1
palladium amine adducts B in the overall catalytic cycle,
we have been interested in the factors which influence
both the formation and reactivity of these complexes.
Here we report on the synthesis and solution structure
of a series of cyclic and acyclic palladium tris(o-tolyl)-
phosphine mono(amine) complexes.8
X Abstract published in Advance ACS Abstracts, April 15, 1996.
(1) Kosugi, M.; Kameyama, M.; Migita, T. Chem. Lett. 1983, 927.
(2) Negwer, M. Organic-Chemical Drugs and Their Synonyms (an
International Survey), 7th ed.; Akademie Verlag: Berlin, 1994.
(3) D’Aproano, G.; Schiavon, G.; Zotti, G.; Leclerc, M. Chem. Mater.
1995, 7, 33.
(4) (a) March, J . Advanced Organic Chemistry, 4th ed.; Wiley: New
York, 1992; pp 641-676. (b) Mitchell, H.; Leblanc, Y. J . Org. Chem.
1994, 59, 682. (c) ten Hoeve, W.; Kruse, C. G.; Luteyn, J . M.; Thiecke,
J . R. G.; Wynberg, H. J . Org. Chem. 1993, 58, 5101. (d) Banfi, A.;
Bartoletti, M.; Bellora, E.; Bignotti, M.; Turconi, M. Synthesis 1994,
777. (e) Finet, J . P.; Khamsi, J .; Barton, D. H. R. Tetrahedron Lett.
1986, 27, 3615.
(5) (a) Guram, A. S.; Buchwald, S. L. J . Am. Chem. Soc. 1994, 116,
7901. (b) Paul, F.; Patt, J .; Hartwig, J . F. J . Am. Chem. Soc. 1994,
116, 5969. (c) Hartwig, J . F.; Paul, F. J . Am. Chem. Soc. 1995, 117,
5373.
(6) (a) Guram, A. S.; Rennels, R. A.; Buchwald, S. L. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1348. (b) Louie, J .; Hartwig, J . F. Tetrahedron
Lett. 1995, 36, 3609.
(7) Wolfe, J . P.; Buchwald, S. L. J . Org. Chem. 1996, 61, 1133.
(8) While this work was in progress, Hartwig and co-workers
reported the syntheses of some palladium tris(o-tolyl)phosphine amine
adducts: Paul, F.; Patt, J .; Hartwig, J . F. Organometallics 1995, 14,
3030.
S0276-7333(95)00959-9 CCC: $12.00 © 1996 American Chemical Society

2746 Organometallics, Vol. 15, No. 12, 1996
Widenhoefer et al.
Sch em e 2
Sch em e 4
24 h produced a ∼1:1 mixture of 3:7.10 31P NMR
analysis of the crude reaction mixtures in the syntheses
of aryl iodide dimers 4-6 showed no evidence for
formation of the diiodide mono(phosphine) dimer {Pd-
[P(o-tol)3]I(µ-I)}2.11
Sch em e 3
Syn th esis of P a lla d iu m Ar yl Ch lor id e Dim er s.
Due to the low cost and wide availability of aryl
chlorides, the palladium-catalyzed cross-coupling of
amines with aryl chlorides represents a significant and
as yet unrealized transformation.12 Because the pal-
ladium aryl chloride dimers {Pd[P(o-tol)3](Ar)(µ-Cl)}2
are the potential intermediates in these transforma-
tions, we have also investigated their coordination
chemistry. However, because the direct oxidative ad-
dition of aryl chlorides to Pd2(DBA)3/P(o-tol)3-derived
catalysts has not yet been demonstrated, palladium
chloride dimers were generated via silver-mediated
halide exchange from the corresponding bromide or
iodide dimers. For example, when a suspension of
iodide dimer 5 and AgOTf in CH3CN was stirred for 2
min, a yellow solution of Pd[P(o-tol)3](p-C6H4Me)(CH3-
CN)2]+OTf- (8) was formed and treated with LiCl
without isolation (Scheme 4). The resulting cream-
colored suspension was evaporated, extracted with
toluene, and precipitated with hexane to give the aryl
Resu lts a n d Discu ssion
Syn th esis of th e P a lla d iu m Ar yl Br om id e a n d
Iod id e Dim er s {P d [P (o-tol)3](Ar )(µ-X)}2. Hartwig
has previously reported the synthesis of the aryl bro-
mide dimers {Pd[P(o-tol)3](p-C6H4R)(µ-Br)}2 (R ) t-Bu
(1), Me (2), n-Bu) from the reaction of Pd[P(o-tol)3]2 with
the corresponding aryl bromide.5b,c,8 However, we sought
a synthesis of the aryl bromide dimers which did not
require isolation of the bis(phosphine) complex Pd[P(o-
tol)3]2. To this end, reaction of Pd2(DBA)3, P(o-tol)3 (8
equiv), and 1-bromo-4-tert-butylbenzene (10 equiv) in
benzene for 1 h led to the isolation of the palladium
bromide dimer 1 in 69% yield (Scheme 3). A similar
procedure was employed to synthesize the bromide
dimers 2‚1/4OEt2 (76%) and {Pd[P(o-tol)3](p-C6H4OMe)-
(µ-Br)}2 (3; 46%) and also the aryl iodide dimers {Pd-
[P(o-tol)3](p-C6H4CMe3)(µ-I)}2 (4; 52%), {Pd[P(o-tol)3](p-
C6H4Me)(µ-I)}2 (5; 60%), and {Pd[P(o-tol)3](p-C6H4OMe)(µ-
I)}2 (6; 51%).
chloride dimer {Pd[P(o-tol)3](p-C6H4Me)(µ-Cl)}2 (9) in
1
93% yield. Dimer 9 was characterized by H NMR, 31
P
NMR, and elemental analysis. By a similar procedure,
the chloride dimer {Pd[P(o-tol)3](p-C6H4CMe3)(µ-Cl)}2
(10) was formed from bromide dimer 1 via the bis-
(acetonitrile) adduct Pd[P(o-tol)3](p-C6H4CMe3)(CH3-
CN)2]+OTf- (11).
Attempts to isolate the bis(acetonitrile) adducts 8 and
11 by concentration of solvent or by precipitation with
ether led to rapid decomposition. However, the corre-
sponding cations Pd[P(o-tol)3](p-C6H4Me)(CD3CN)2]+OTf-
(8-(CD3CN)2) and Pd[P(o-tol)3](p-C6H4CMe3)(CD3CN)2]+-
(10) The origin of dibromide complex 7 is not clear. The reaction of
p-bromoanisole with Pd2(DBA)3 and P(o-tol)3 in C6D6 did not produce
detectable quantities of the palladium bis(p-anisole) complex Pd[P(o-
tol)3]2(p-anisole)2 (as determined by 1H NMR) or its reductive-elimina-
tion product 4,4′-dimethoxybiphenyl (as determined by GCMS analy-
sis), which suggests that 7 is not formed by disproportionation of 3.
Similarly, products derived from insertion of DBA into a palladium-
anisyl bond followed by â-hydrogen elimination, such as PhCHCHC-
(O)C(p-anisyl)CHPh or PhCHCHC(O)CHC(p-anisyl)Ph, were not de-
tected. Such a process would presumably lead to the formation of free
HBr via reductive elimination from the initially formed palladium
bromide hydride complex. However, GC-MS analysis of the reaction
mixture indicated the presence of significant quantities of anisole,
which may suggest the presence of an electron transfer process. We
thank a reviewer for suggesting this mechanism.
In the syntheses of palladium bromide dimers 1-3,
reaction times of >1 h led to contamination of the
desired aryl bromide dimer with the bis(phosphine)
dibromide complex Pd[P(o-tol)3]2Br2 (7),9 although the
extent of contamination was dependent on the aryl
bromide. For example, reaction of Pd2(DBA)3, P(o-tol)3,
and 1-bromo-4-tert-butylbenzene in benzene for 48 h
1
formed only a trace (e5%) of 7, as determined by H
and 31P NMR analysis of the crude reaction mixtures.
The analogous reaction of Pd2(DBA)3, P(o-tol)3, and
p-bromotoluene for 24 h gave a ∼5:1 ratio of 1:7, while
reaction of Pd2(DBA)3, P(o-tol)3, and p-bromoanisole for
(11) Reaction of PdI2 and excess P(o-tol)3 (2 equiv) forms only the
mono(phosphine) diiodide complex {Pd[P(o-tol)3]I(µ-I)}2 and none of the
corresponding bis(phosphine) monomer (see Experimental Section).
(12) Grushin, V. V.; Alper, H. Chem. Rev. 1994, 94, 1047.
(9) Bennett, M. A.; Longstaff, P. A. J . Am. Chem. Soc. 1969, 91,
6266.

Pd Tris(o-tolyl)phosphine Mono(amine) Complexes
Organometallics, Vol. 15, No. 12, 1996 2747
Sch em e 5
Sch em e 6
spectrum of 14 revealed an equilibrium mixture of 14
and 5 (∼80:20) and HN(Me)Bn.14 An excess of N-
benzylmethylamine (0.03 M) was required to effect
complete conversion (>95% by H NMR) of 5 to 14 in
solution at room temperature.
OTf- (11-(CD3CN)2) were generated in CD3CN and were
analyzed without isolation by 1H, 31P, and 19F NMR
1
spectroscopy. The H NMR spectrum of 8-(CD3CN)2 at
1
75 °C displayed a singlet at δ 2.25 for the time-averaged
P(o-tol)3 methyl groups and a peak at δ 2.09 for the
p-tolyl methyl group. As the temperature was lowered,
the signals for the P(o-tol)3 methyl groups broadened
and split into three resonances at δ 3.11, 2.13, and 1.53
at -47 °C. In the 19F NMR spectrum of 8-(CD3CN)2 no
resonances were observed which could be assigned to
coordinated OTf. Similar bis(acetonitrile) or bis(solvent)
palladium complexes have been generated via reaction
of palladium halide complexes with silver salts.13
Syn t h esis of P a lla d iu m Am in e Com p lexes.
Amines reacted rapidly (<1 min) with palladium halide
dimers via cleavage of the halide bridge to produce
monomeric palladium amine complexes (Scheme 5).8 For
example, addition of N-benzylmethylamine (5 equiv) to
a yellow benzene solution of the chloride dimer 9 gave
a clear solution from which the 1:1 palladium amine
adduct Pd[P(o-tol)3](p-C6H4Me)[HN(Me)Bn]Cl (12) pre-
cipitated in 85% yield as a white microcrystalline solid.
Amine adduct 12 was characterized by spectroscopy and
by elemental analysis, and a trans orientation of the
amine and phosphine ligands is inferred by analogy to
the corresponding benzylamine derivative (see below).
Palladium amine adducts 13 and 14 were also formed
as the exclusive products in the reaction of N-benzyl-
methylamine, Pd2(DBA)3, P(o-tol)3, and p-bromotoluene
or p-iodotoluene, respectively, in C6D6. Isolation of 13
or 14 from the corresponding preparative-scale reactions
was complicated by the comparable solubility of free
DBA. However, the related amine adduct Pd[P(o-tol)3]-
(p-C6H4OMe)[HN(CH3)Bn]Br (15) was isolated in 51%
yield from reaction of p-bromoanisole, N-benzylmethyl-
amine, Pd2(DBA)3, and P(o-tol)3. The formation of the
1:1 palladium amine adducts 13-15 from mixtures of
Pd2(DBA)3 and P(o-tol)3 is consistent with the interme-
diacy of the 1:1 amine adducts in the Pd2(DBA)3/P(o-
tol)3-catalyzed cross-coupling of aryl halides and amines.
Although the chloride adduct 12 was thermodynami-
cally stable, the coordinated N-benzylmethylamine was
kinetically labile and was readily displaced by free
amine. For example, addition of benzylamine to a
1
solution of 12 in CDCl3 revealed resonances in the H
NMR spectrum after <1 min corresponding to benzyl-
amine, N-benzylmethylamine, 12, and Pd[P(o-tol)3](p-
C6H4Me)[H2NBn]Cl (16), where K ) [16][HN(Me)Bn]/
1
The H NMR spectrum of 12 (CDCl3, 55 °C) displayed
1
[12][benzylamine] ≈ 4 at 25 °C (Scheme 6).14 The H
a resonance at δ 2.07 for the methyl group of the p-tolyl
ligand and a broad peak at δ 2.3 (ω1/2 ) 70 Hz) for the
methyl groups of the P(o-tol)3 ligand. Coordination of
amine to palladium was confirmed by resonances for the
diastereotopic benzyl protons at δ 4.39 (br t, J ) 12.4
Hz) and 3.47 (dd, J ) 7.0, 12.5 Hz). The presence of an
NMR spectrum obtained after 15 min was identical with
that obtained directly after addition of benzylamine,
consistent with rapid approach to equilibrium. Like-
wise, addition of HN(Me)Bn to a CDCl3 solution of 16
generated an equilibrium mixture of 12, 16, HN(Me)-
Bn, and benzylamine. Pure 16 was isolated in 70% yield
from reaction of benzylamine with 9, although the
synthesis was complicated by formation of the bis-
(benzylamine) complex Pd(p-C6H4Me)[H2NBn]2Cl.15
The stereochemistry of the 1:1 palladium amine
adducts was determined from the 31P NMR spectra of
the 15N-labeled benzylamine adducts Pd[P(o-tol)3](p-
C6H4Me)[H215NBn]Cl (16-15N) and Pd[P(o-tol)3](p-C6H4-
Me)[H215NBn]Br (17-15N). 16-15N displayed a doublet
in the 31P{1H} NMR spectrum at δ 28.3 (J PN ) 40.0 Hz),
while the bromide derivative 17-15N displayed a doublet
at δ 27.7 (J PN ) 40.1 Hz). The J PN values observed for
16-15N and 17-15N are consistent with trans-phosphine
1
NH proton was confirmed by a H NMR resonance at δ
3.22, which diminished in intensity upon addition of
D2O.
The related 1:1 palladium bromide and iodide N-
benzylmethylamine adducts were more soluble than
complex 12 and were synthesized by a modified proce-
dure. Addition of N-benzylmethylamine to a yellow
methylene chloride solution of bromide dimer 2 gave a
clear solution. Concentration of the solution and addi-
tion of hexane gave the 1:1 palladium amine adduct Pd-
[P(o-tol)3](p-C6H4Me)[HN(Me)Bn]Br (13) in 83% yield.
Likewise, reaction of N-benzylmethylamine with the
palladium iodide dimer led to the isolation of the amine
adduct Pd[P(o-tol)3](p-C6H4Me)[HN(Me)Bn]I (14) in 71%
yield. Unlike the corresponding chloride (12) and
(14) The equilibrium constant for the formation of palladium amine
adducts from the corresponding halide dimers is dependent on both
the halide ligand and the amine: Widenhoefer, R. A.; Buchwald, S. L.
Organometallics 1996, 15, 2755.
1
bromide adducts (13), the room-temperature H NMR
(15) The rate and extent of formation of bis(amine) complexes was
dependent on both the amine and the halide ligand. We are currently
investigating the formation of palladium bis(amine) complexes in detail
as a potential chain-limiting step in the catalytic cross-coupling of aryl
bromides and primary amines.
(13) (a) Valk, J . M.; Maassarani, F.; van der Sluis, P.; Spek, A. L.;
Boersma, J .; van Koten, G. Organometallics 1994, 13, 2320. (b) Vicente,
J .; Saura-Llamas, I.; J ones, P. G. J . Chem. Soc., Dalton Trans. 1993,
3619.

2748 Organometallics, Vol. 15, No. 12, 1996
Widenhoefer et al.
and amine ligands.16 For example, in a series of
rhodium complexes containing amine and phosphine
ligands, trans-J PN ranged from 35 to 45 Hz, while cis-
J PN was consistently <5 Hz.16a
Con for m a tion s a n d In ter ch a n ge Mech a n ism s of
M[P (o-tol)3] Com p lexes. In his initial report, Migita
noted that the P(o-tol)3 ligand was crucial to the success
of the palladium-catalyzed cross-coupling of aryl bro-
mides and aminostannanes.1 The use of P(o-tol)3 has
also been shown to produce higher reaction rates than
PPh3 in both the palladium-catalyzed Heck arylation
reaction17 and Stille reaction.18 The enhanced activity
of P(o-tol)3 has typically been attributed to the steric
bulk of the P(o-tol)3 ligand, which promotes both phos-
phine lability and coordinative unsaturation of the
metal.18 In addition, P(o-tol)3 can also undergo cyclo-
metalation of the o-methyl group with electrophilic
transition metals17,19 to generate catalysts of unusually
high activity. For example, Herrmann and Beller have
recently shown that P(o-tol)3 reacts with Pd(OAc)2 to
F igu r e 1. The two-ring-flip mechanism for interconversion
of the exo3 and exo2 conformations of the P(o-tol)3 ligand,
as viewed down the M-P axis.
from space-filling CPK models with a M-P bond dis-
tance of 2.28 Å,26 while a cone angle of 198° was
determined from the crystal structure of the mercury
perchlorate dimer {Hg[ClO4][P(o-tol)3](µ-Cl)}2.27 Con-
versely, a cone angle of 160° was calculated from the
crystal structure of the exo2-P(o-tol)3 chromium dicar-
bonyl complex (p-xylene)Cr(CO)2P(o-tol)3.28 Both the
exo3 and exo2 P(o-tol)3 conformers are chiral due to the
screw axis generated by the propeller-like arrangement
of the o-tolyl rings.
form the acetate-bridged cyclometalated dimer {Pd[P(o-
Because of the steric congestion about the o-tolyl
rings, rotation about a single P-ipso-C bond requires
correlated rotation about the other two P-ipso-C bonds.
These rotations are often of sufficient energy to generate
configurationally stable conformers and enantiomers on
the NMR time scale. The mechanisms for the correlated
rotation of sterically hindered triaryl systems were
originally proposed by Kruland.29 The lowest energy
process for P-C bond rotation in P(o-tol)3 complexes
involves rotation of one ring (Figure 1, ring a) through
the plane perpendicular to the M-P-ipso-C plane with
correlated rotation of the other two rings (Figure 1, rings
b and c) through the corresponding M-P-ipso-C
planes.30 This two-ring-flip mechanism29 interconverts
the exo2 and exo3 isomers and necessarily inverts the
helicity of the phosphine; consecutive two-ring flips then
leads to complete interchange of the o-tolyl rings.
F lu xion a l Beh a vior a n d Solu tion Str u ctu r e of
13. The 1H NMR spectrum of bromide adduct 13 in
CD2Cl2 at -42 °C displayed a 1:1:1 ratio of three sets
of P(o-tol)3 methyl resonances at δ 3.30, 3.50, 3.27 (∼8:
2:1), δ 2.39, 2.14, 2.26 (∼8:2:1), and δ 1.54, 1.61, 1.58
tol)2-o-C6H4CH2](µ-OAc)}2, which was an extremely
active catalyst for both the Heck arylation reaction20 and
the Suzuki cross-coupling reaction.21
Of the potential conformations available to rotation-
ally restricted triaryl systems,22 two conformations of
P(o-tol)3 are accessible and have been observed in
structurally characterized metal complexes. The exo3
conformation23 orients the three o-methyl groups toward
the metal atom (exo), with each o-tolyl ring rotated
approximately 60° off the M-P-ipso-C plane (Figure
1). The exo2 conformation24 possesses two exo o-tolyl
groups in an orientation similar to those in the exo3
conformer, while the third o-methyl group is directed
away from the metal atom (endo) with the o-tolyl ring
rotated only slightly off the M-P-ipso-C plane (∼15°).
The exo2 conformation decreases the phosphine cone
angle ∼35° relative to the exo3 conformation at the
expense of approximately 9 kcal mol-1 increased strain
energy between the o-tolyl groups.25 For example,
Tolman calculated a cone angle for exo3-P(o-tol)3 of 195°
(16) (a) Carlton, L.; De Sousa, G. Polyhedron 1993, 12, 1377. (b)
Mason, J . Chem. Rev. 1981, 81, 205. (c) von Philipsborn, W.; Muller,
R. Angew. Chem., Int. Ed. Engl. 1986, 25, 383.
(24) (a) Ooi, S.; Matsushita, T.; Nishimoto, K.; Okeya, S.; Nakamura,
Y.; Kawaguchi, S. Bull. Chem. Soc. J pn. 1983, 56, 3297. (b) Howell, J .
A. S.; Palin, M. G.; Tirvengadum, M. C.; Cunningham, D.; McArdle,
P.; Goldschmidt, Z.; Gottlieb, H. E. J . Organomet. Chem. 1991, 413,
269. (c) Wierda, D. A.; Barron, A. R. Polyhedron 1989, 8, 831. (d) Alyea,
E. C.; Dias, S. A.; Ferguson, G.; Roberts, P. J . J . Chem. Soc., Dalton
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D. R.; Parnell, D. R. J . Am. Chem. Soc. 1970, 92, 1511. (h) Okeya, S.;
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1744.

Pd Tris(o-tolyl)phosphine Mono(amine) Complexes
Organometallics, Vol. 15, No. 12, 1996 2749
F igu r e 3. Pd-P bond rotamers of the exo2-P(o-tol)3 ligand
in 13 relative to the p-tolyl and bromide ligands, as viewed
down the N-Pd-P axis (amine not shown).
observed for the H-6 proton of the endo-P(o-tol)3 ring in
the 1H NMR spectrum of the palladium complex Pd-
[P(o-tol)3][hfac]2 (hfac ) 1,1,1,5,5,5-hexafluoro-2,4-pen-
tanedionate).33 Similarly, the bis(phosphine)palladium
complex Pd[P(t-Bu2Ph)]2 displayed a resonance at δ 9.33
for the deshielded ortho phenyl protons.34
The formation of a 1:1:1 ratio of P(o-tol)3 methyl
resonances at δ 3.30, 2.39, and 1.54 (major isomer) is
expected for a static exo2-P(o-tol)3 ligand. One o-methyl
group is distinguished by its endo orientation; the two
exo-o-methyl groups are inequivalent due to the helicity
of the phosphine, which orients one o-methyl group
toward an endo-o-tolyl ring and one o-methyl group
toward an exo-o-tolyl ring (Figure 1). The failure to
detect p-tolyl or P(o-tol)3 methyl resonances which did
not correlate with a high-field resonance indicates that
the concentration of the exo3 isomer (which would
display p-tolyl and P(o-tol)3 methyl resonances but no
high-field resonance) must be small (<10%).
The 2:1:8 multiplicity of both the 1:1:1 P(o-tol)3 methyl
groups and the high-field H-6 endo-o-tolyl resonance of
13 in the 1H NMR spectrum at -42 °C is consistent with
hindered rotation about the Pd-P bond with the forma-
tion of three unequally populated rotamers. Three
gauche rotamers of the P(o-tol)3 ligand which differ in
the relative orientation of the endo-P(o-tol)3 ring to the
cis-bromide and p-tolyl ligands are depicted in Figure
3. Presumably, the highest frequency H-6 endo-P(o-tol)3
resonance (δ 9.36) corresponds to rotamer 13a , in which
1
F igu r e 2. Variable-temperature H NMR spectrum of the
H-6 resonance of the endo-P(o-tol)3 ring of 13 in CD2Cl2.
Temperatures are given in °C.
(∼8:2:1).31 As the temperature was raised, the P(o-tol)3
methyl resonances broadened and coalesced at 24 °C,
forming a single broad resonance at δ 2.30 (ω1/2 ) 95
Hz) at 55 °C (CDCl3). In addition, the -42 °C spectrum
displayed a ∼2:1:8 ratio of high-frequency peaks at δ
9.36 (dd, J ) 7.33, 18.7 Hz), 8.71 (dd, J ) 8.2, 18.1 Hz),
and 8.36 (dd, J ) 8.0, 17.6 Hz) (Figure 2), which
integrated to one proton. As the temperature was
raised, these resonances broadened and coalesced at
∼15 °C (Figure 2), eventually forming a broad three-
proton resonance at δ 7.5-8.0 at 55 °C (CDCl3). The
p-tolyl methyl resonance, which was observed as a sharp
singlet at δ 2.05 at 55 °C in CDCl3, broadened slightly
but did not split upon cooling to -50 °C (CD2Cl2).
Resonances corresponding to the coordinated amine
were broadened and uninformative at low temperatures.
2
the endo ring is in closest proximity to the dz orbital.
However, halide ligands have also been shown to induce
downfield shifts in proximal aromatic resonances.35
Hindered rotation of M-P bonds with formation of
rotamers in metal complexes possessing bulky phos-
phine ligands has been observed. For example, the bis-
(phosphine) carbonyl chloride complexes M[P(t-Bu)2Et]2-
(CO)Cl (M ) Ir,36 Rh37 ) displayed resonances corre-
sponding to three rotamers in the low-temperature 31P
NMR spectrum.
The presence of a single P(o-tol)3 resonance at δ 2.33
1
in the H NMR spectrum of 13 at 55 °C is consistent
1
The H NMR spectrum of 13 at -42 °C is consistent
with rapid rotation about both the Pd-C and Pd-P
bonds. Although P-C rotation in P(o-tol)3 complexes
is typically of higher energy than M-P rotation, the
with two processes: (1) hindered rotation about the
P-ipso-C bonds with predominant formation of the exo2-
P(o-tol)3 conformer and (2) hindered rotation about the
Pd-P bond with formation of three unequally populated
rotamers (see below). The high-frequency resonance at
δ 8.36 (dd, J ) 8.0, 17.6 Hz, major isomer) is indicative
of the exo2-P(o-tol)3 conformation as the H-6 proton of
the endo-P(o-tol)3 ring is forced into close proximity to
(33) (a) Okeya, S.; Miyamoto, T.; Ooi, S.; Nakamura, Y.; Kawaguchi,
S. Bull. Chem. Soc. J pn. 1984, 57, 395. (b) Ooi, S.; Matsushita, T.;
Nishimoto, K.; Nakamura, Y.; Kawaguchi, S.; Okeya, S. Inorg. Chim.
Acta 1983, 76, L55.
(34) Matsumoto, M.; Yoshioka, H.; Nakatsu, K.; Yoshida, T.; Otsuka,
S. J . Am. Chem. Soc. 1974, 96, 3322.
(35) (a) Byers, P. K.; Canty, A. J . Organometallics 1990, 9, 210. (b)
Cusares, J . A.; Coco, S.; Espinet, P.; Liu, Y. S. Organometallics 1995,
14, 3058.
(36) (a) Bright, A.; Mann, B. E.; Masters, C.; Shaw, B. L.; Slade, R.
M.; Stainbank, R. E. J . Chem. Soc. A 1971, 1826. (b) Rithner, C. D.;
Bushweller, C. H. J . Phys. Chem. 1986, 90, 5023. (c) DiMeglio, C. M.;
Luck, L. A.; Rithner, C. D.; Rheingold, A. L.; Elcesser, W. L.; Hubbard,
J . L.; Bushweller, C. H. J . Phys. Chem. 1990, 94, 6255. (d) Bushweller,
C. H.; Rithner, C. D.; Butcher, D. J . Inorg. Chem. 1986, 25, 1610.
(37) Mann, B. E.; Masters, C.; Shaw, B. L.; Stainbank, R. E. J . Chem.
Soc. D 1971, 1103.
2
the palladium dz orbital. The H-6 proton then experi-
ences a downfield shift due to the paramagnetic ani-
sotropy of the palladium atom.32 A similar chemical
shift and J PH value (δ 9.27 (d, J PH ) 16 Hz)) was
(31) Similar results were obtained in CDCl3.
(32) (a) Miller, R. G.; Stauffer, R. D.; Fahey, D. R.; Parnell, D. R. J .
Am. Chem. Soc. 1970, 92, 1511. (b) Deeming, A. J .; Rothwell, I. P.;
Hursthouse, M. B.; New, L. J . Chem. Soc., Dalton Trans. 1978, 1490.

2750 Organometallics, Vol. 15, No. 12, 1996
Widenhoefer et al.
Amine adducts 12 and 14 displayed temperature-
dependent 1H NMR behavior analogous to that dis-
played by bromide derivative 13; at -42 °C, each
complex displayed three high-frequency H-6 endo-P(o-
tol)3 resonances (Table 1) along with the corresponding
P(o-tol)3 methyl resonances. Because the chemical
shifts for the P(o-tol)3 methyl groups were similar for
each complex, the coalescence temperature (Tc; Table
1) is directly related to the rotational barrier for each
complex. Comparison of Tc values (Table 1) reveals that
Tc increased in the order 12 < 13 < 14, which corre-
sponds to the van der Waals radius of the cis-halide
ligand (Cl (1.75 Å) < Br (1.85 Å) < I (1.96 Å)],38
presumably due to increased steric interaction of the
P(o-tol)3 ligand with increasing halide size. The steric
bulk of ancillary ligands has been shown to increase the
rotational barriers of P-C and M-P bonds of PPh3 and
P(o-tol)3 complexes.39
Ch ela ted P a lla d iu m Am in e Com p lexes. Palla-
dacyclic amine complexes are of interest as potential
intermediates in the Pd-catalyzed intramolecular ami-
nation of haloamines.40 A series of chelating palladium
amine complexes was synthesized in a one-pot proce-
dure analogous to that employed in the synthesis of 17.
For example, reaction of Pd2(DBA)3, P(o-tol)3, and
N-benzyl-o-iodophenethylamine in benzene for 24 h at
F igu r e 4. Potential diastereomers of 13 as viewed down
the N-Pd-P bond. Diastereomers are related horizontally
by inversion of phosphine helicity and vertically by amine
inversion; enantiomers are related diagonally.
simultaneous coalescence of all nine P(o-tol)3 methyl
resonances indicates that the two processes possess
comparable rotational barriers. The simultaneous coa-
lescence of the P(o-tol)3 methyl resonances may result
from correlated P-C and Pd-P rotation due to inter-
meshing of the phosphine o-tolyl rings with the p-tolyl
ligand. The presence of diastereotopic benzyl protons
of the coordinated HN(Me)Bn ligand at 55 °C requires
that chirality of the amine be static on the NMR time
scale.
room
tem-
perature led to the isolation of the six-membered palla-
dacycle Pd[P(o-tol)3][2-C6H4(CH2)N(H)Bn]I (18) in 71%
yield. By a similar procedure, the five-membered palla-
Although hindered Pd-P bond rotation has prece-
dence and adequately accounts for the 2:1:8 isomer ratio
observed in the low-temperature H NMR spectrum of
dacyles Pd[P(o-tol)3][2-C6H4(CH2)N(H)p-tolyl]Br (19)
and Pd[P(o-tol)3][2-C6H4(CH2)15N(H)Ph]Br (20) and the
1
seven-membered palladacycle Pd[P(o-tol)3][2-C6H4(CH2)3-
13, hindered Pd-P bond rotation is not required to
produce the observed isomers. For example, because
both the phosphine and the amine are chiral on the
NMR time scale, two sets of diastereomers of 13 are
possible (Figure 4). In addition, three geometric iso-
mers, two of which possess cis-amine and phosphine
ligands, are also possible (Figure 5). As a result, a
combination of diastereomers and geometric isomers
could account for the observed 2:1:8 ratio of isomers in
13. In an effort to probe for the presence of these
potential isomers, we investigated the variable-temper-
ature 31P{1H} NMR spectrum of 16-15N, which possesses
an achiral, 15N-labeled amine.
N(H)Bn]Br (21) were also isolated.
1
The H NMR spectra of the five-membered pallada-
cycles were similar to those of the corresponding acyclic
derivatives. For example, 20 displayed a 1:2.6:2.6 ratio
of high-field resonances at δ 9.54 (br d, J ) 17.2 Hz),
8.78 (dd, J ) 7.05, 15.5 Hz), and 8.28 (dd J ) 8.6, 17.5
1
Hz) in the low-temperature H NMR spectrum (Figure
7, Table 1), and a 2.6:2.6:1 ratio of doublets at δ 36.8
(J PN ) 36.3 Hz), 34.1 (J PN ) 37.0 Hz), and 28.7 (J PN
)
36.3 Hz) in the low-temperature 31P{1H} NMR spectrum
(Figure 7, Table 1). Complexes 18 and 21 were some-
what unusual, as only a single isomer was detected by
low-temperature 1H and 31P NMR spectroscopy. As was
anticipated, chelation promotes coordination of amine
to the palladium atom. For example, the 1H NMR
spectrum of iodide complex 18 at 55 °C showed no
evidence for amine dissociation and formation of a
palladium iodide dimer, in contrast to the acyclic iodide
derivative 14, which was ∼35% dissociated at room
temperature.
The 31P{1H} NMR spectrum of 16-15N at -42 °C
displayed a ∼2:1.3:1 ratio of doublets at δ 27.6 (J PN
)
36.8 Hz), 26.9 (J PN ) 35.6 Hz), and 23.9 (J PN ) 37.4
Hz), consistent with trans phosphine and amine ligands
(Figure 6). As the temperature was raised, these
doublets collapsed and eventually formed a doublet at
δ 26.4 (J PN ) 40.1 Hz) at 35 °C. In addition, a small
doublet at δ 27.1 (J PN ) 36.6 Hz) was observed at -33
°C which accounted for <10% of the total isomers and
may correspond to a small amount of an exo3-P(o-tol)3
isomer. The presence of multiple isomers which all
possess trans-phosphine and amine ligands in the low-
temperature 31P NMR spectrum of 16-15N suggests that
the low-temperature isomers of 13 also correspond to
neither geometric isomers nor diastereomers. The
failure to observe diastereomers in 13 as a result of
amine chirality indicates that either one set of diaster-
eomers is highly favored relative to the second set or
that chirality at nitrogen does not significantly perturb
the chemical shifts of the P(o-tol)3 proton resonances.
The chelated amine complexes 18-20 displayed higher
coalescence temperatures (Tc) for the P(o-tol)3 methyl
resonances than did the corresponding acyclic deriva-
tives (Table 1). In the chelated amine complexes, the
(38) Porterfield, W. W. Inorganic Chemistry: A Unified Approach;
Addison-Wesley: Reading, MA, 1984; p 168.
(39) (a) Chudek, J . A.; Hunter, G.; MacKay, R. L.; Kremminger, P.;
Scho¨gl, K.; Weissensteiner, W. J . Chem. Soc., Dalton Trans. 1990, 2001.
(b) Hunter, G.; Weakley, T. R. J .; Weissensteiner, W. J . Chem. Soc.,
Dalton Trans. 1987, 1545.
(40) Wolfe, J . N.; Rennels, R. A.; Buchwald, S. L. Tetrahedron, in
press.

Pd Tris(o-tolyl)phosphine Mono(amine) Complexes
Organometallics, Vol. 15, No. 12, 1996 2751
F igu r e 5. Potential geometric isomers of 13.
generate gram quantities of the corresponding pal-
ladium halide dimers in a single step as pure material.
These halide dimers undergo a rapid bridge cleavage
reaction with amines to form the corresponding 1:1
palladium amine adducts which possess trans phos-
phine and amine ligands. The amine complexes are also
formed as the exclusive product in the reaction of Pd2-
(DBA)3 and P(o-tol)3 with aryl halide and amine. Vari-
able-temperature 1H and 31P NMR analysis of the
palladium amine adducts was consistent with hindered
rotation about the P-C bonds, with predominant for-
mation of the exo2-P(o-tol)3 conformer and hindered
rotation about the Pd-P bond. The barriers for rotation
about the P-C and Pd-P bonds were sensitive to the
steric bulk of the ligands cis to the phosphine ligand.
We are currently investigating the effect of both the
halide ligand and the amine on the equilibrium forma-
tion and reactivity of the 1:1 palladium amine adducts
and the relevance of these processes on the Pd-catalyzed
cross-coupling of amines and aryl halides. In addition,
we are investigating the formation of palladium bis-
(amine) complexes as a potential chain-limiting step in
the catalytic process.
F igu r e 6. Variable-temperature 31P{1H} NMR spectra of
16-15N in CDCl3. Temperatures are given in °C.
Exp er im en ta l Section
Gen er a l Meth od s. Palladium halides, Pd2(DBA)3, aryl
halides, amines, and phosphines were manipulated in air. All
other manipulations and all reactions were performed under
an atmosphere of nitrogen or argon in an inert-atmosphere
glovebox or by standard Schlenk techniques. Preparative-scale
reactions were performed in flame or oven-dried Schlenk tubes
equipped with a stirbar, side-arm joint, and a septum. NMR
spectra were obtained on a Varian XL-300 spectrometer in
CDCl3 at ambient temperature unless otherwise noted. 1H and
13C{1H} (75.6 MHz) spectra were referenced relative to the
residual solvent peak. Room-temperature 31P NMR (96 MHz)
spectra were referenced relative to external 85% H3PO4; low-
temperature 31P NMR spectra were referenced relative to
external PPh3 in CDCl3 (δ -4.69). Probe temperatures were
calibrated with a 0.3% solution of HCl in methanol. IR spectra
were recorded on a Perkin-Elmer Model 6000 FTIR spectrom-
eter. Elemental analyses were performed by E+R Analytical
Laboratories (Corona, NY).
Diethyl ether, hexane, pentane, benzene, and benzene-d6
were distilled from purple solutions of sodium and benzophe-
none under argon or nitrogen. THF-d8 and dioxane-d8 were
distilled from Na/K alloy, methylene chloride and methylene
chloride-d2 were distilled from CaH2, and CDCl3 was distilled
from P2O5. Pd2(DBA)3 (Strem),43 P(o-tol)3 (Strem), 1-bromo-
4-tert-butylbenzene (Fluka), 1-iodo-4-tert-butylbenzene (Lan-
caster), p-bromotoluene (Aldrich), p-iodotoluene (Lancaster),
p-bromoanisole (Aldrich), and p-iodoanisole (Aldrich) were
used as received. LiI (Aldrich), LiCl (Mallinckrodt), and LiBr
(Aldrich) were dried at 80 °C under vacuum prior to use.
N-Benzylmethylamine and benzylamine were purchased from
Aldrich and were distilled from CaH2 under N2 prior to use.
aryl ring is forced to lie in or near the coordination
plane.41 Although this orientation may not produce
excessive ground-state interaction between the H-6
proton of the palladium-bound aryl ligand and the
phosphine-bound o-tolyl groups due to potential inter-
meshing, rotation about the Pd-P or P-C bonds will
clearly produce a high-energy interaction. Conversely,
the palladium: bound p-tolyl ligand of the corresponding
acyclic amine complexes is able to rotate about the P-C
bond and adopt an orientation perpendicular to the
coordination plane either in the ground state or as a
transition state for Pd-P and/or P-C rotation.42 The
very high coalescence temperature (85 °C) of 18 appar-
ently results from the combination of the large iodide
ligand and the chelated aryl ring.
Con clu sion s
Reaction of aryl bromides or aryl iodides with a
mixture of Pd2(DBA)3 and P(o-tol)3 can be employed to
(41) (a) Albert, J .; Granell, J .; Sales, J .; Font-Bardia, M.; Solans, X.
Organometallics 1995, 14, 1393. (b) Albert, J .; Gomez, M.; Granell, J .;
Sales, J .; Solans, X. Organometallics 1990, 9, 1405. (c) Fuchita, Y.;
Tsuchiya, H. Inorg. Chim. Acta 1993, 209, 229. (d) Vila, J . M.; Gayoso,
M.; Pereira, M. T.; Ortigueira, J . M.; Fernandez, A.; Bailey, N. A.;
Adams, H. Polyhedron 1993, 12, 171. (e) Barro, J .; Granell, J .; Sainz,
D.; Sales, J .; Font-Bardia, M.; Solans, X. J . Organomet. Chem. 1993,
456, 147. (f) Vila, J . M.; Gayoso, M.; Pereira, M. T.; Romar, A.;
Fernandez, J . J .; Thornton-Pett, M. J . Organomet. Chem. 1991, 401,
385. (g) Fuchita, Y.; Tsuchiya, H. Polyhedron 1993, 12, 2079.
(42) (a) Pregosin, P. S.; Wombacher, F.; Albinati, A.; Lianza, F. J .
Organomet. Chem. 1991, 418, 249. (b) Markies, B. A.; Canty, A. J .; de
Graaf, W.; Boersma, J .; J anssen, M. D.; Hogerheide, M. P.; Smeets,
W. J . J .; Spek, A. L.; van Koten, G. J . Organomet. Chem. 1994, 482,
191.
(43) The stoichiometry and purity of Pd2(DBA)3 was confirmed by
elemental analysis. Anal. Calcd (found) for C51H42O3Pd: C, 66.9 (67.16);
H, 4.6 (4.75); Pd, 23.2 (23.08).

2752 Organometallics, Vol. 15, No. 12, 1996
Ta ble 1. Low -Tem p er a tu r e 1H NMR Da ta for Com p lexes 12-14 a n d 18-21
Widenhoefer et al.
cmpd
12
temp (°C)
H-6 endo-P(o-tol)3 resonance (δ)
P(o-tol)3 methyl resonances (δ)
isomer ratio
Tc ((5 °C)a
-42b
9.33 (dd, J ) 8.3, 17.6 Hz)
8.71 (dd, J ) 7.8, 18.0 Hz)
8.34 (dd, J ) 7.9, 17.0 Hz)
3.35, 2.00, 1.42
3.12, 2.11, 1.41
3.15, 2.24, 1.43
1.5
1
10
0b
13
14
-42b
-16b
9.36 (dd, J ) 7.2, 18.6 Hz)
8.71 (dd, J ) 7.1, 18.1 Hz)
8.36 (dd, J ) 7.8, 17.6 Hz)
3.50, 2.14, 1.61
3.27, 2.26, 1.58
3.30, 2.39, 1.54
2.5
1
8.4
25b
55c
9.46 (dd, J ) 8, 18 Hz)
8.7 br
8.42 (dd, J ) 8, 18 Hz)
3.32, 1.93, 1.37
5
1
5
3.48, 2.03, 1.48
3.17, 1.51, 0.83
18
19
-42b
-42b
9.49 (dd, J ) 8.2, 18.1 Hz)
65d
65d
9.54 (br d, J ) 18 Hz)
8.78 (dd, J ) 8.4, 17.7 Hz)
8.38 (dd, J ) 7.8, 17.7 Hz)
2.85, 1.32, 1.53
3.12, 1.82, 1.58
2.73, 1.94, 1.55
1
2.6
2.6
20
8c
9.54 (br d, J ) 17.2 Hz)
8.73 (dd, J ) 7.1, 15.5 Hz)
8.28 (dd, J ) 8.6, 17.5 Hz)
2.82, 1.30, 1.52
3.11, 1.92, 1.57
2.66, 1.79, 1.55
1
2.6
2.6
85d
21
8c
9.50 (dd, J ) 7.8, 16.5 Hz)
3.18, 1.98, 0.92
a
b
d
Coalescence temperature for P(o-tol)3 methyl resonances. CD2Cl2. c CDCl3. Toluene-d8.
Sch em e 7
Calcd (found) for C62H68Br2P2Pd2: C, 59.68 (59.78); H, 5.49
(5.51); Br, 12.81 (12.62).
{P d [P (o-tol)3](p-C6H4Me)(µ-Br )}2 (2).8 Reaction of Pd2-
(DBA)3 (500 mg, 0.55 mmol), P(o-tol)3 (700 mg, 2.3 mmol), and
4-bromotoluene (1.4 g, 8.2 mmol) using a procedure analogous
to that used to prepare 1 led to the isolation of 2 (480 mg,
76%) as a bright yellow powder which contained 0.4 Et2O/Pd
1
by H NMR analysis. 1H NMR (55 °C): δ 7.65 (br), 7.26 (m),
7.07 (br), 6.58 (br), 6.30 (d, J ) 7.71 Hz), 2.18 [br, 9 H, P(o-
tol)3], 1.98 (C6H4Me). 31P{1H} NMR: δ 28.4 (br).
{P d [P (o-tol)3](p-C6H4OMe)(µ-Br )}2 (3). Reaction of Pd2-
(DBA)3 (250 mg, 0.27 mmol), P(o-tol)3 (330 mg, 1.1 mmol), and
4-bromoanisole (510 mg, 2.7 mmol) using a procedure analo-
gous to that used to prepare 1 led to the isolation of 3 (152
mg, 46%) as a bright yellow powder which contained traces
1
(<5%) of Et2O by H NMR analysis. 1H NMR (55 °C): δ 7.55
(br), 7.29 (m), 7.06 (br), 6.59 (br), 6.15 (d, J ) 7.95 Hz), 3.53
(C6H4OMe), 2.19 [br, 9 H, P(o-tol)3]. 31P{1H} NMR: δ 28.2.
Anal. Calcd (found) for C56H56Br2O2P2Pd2: C, 56.26 (56.53);
H, 4.72 (4.96); Br, 13.37 (13.58).
F igu r e 7. H-6 resonance of the endo-P(o-tol)3 ring in the
1H NMR spectrum (top) and 31P{1H} NMR spectrum
(bottom) of 20 at -42 °C in CD2Cl2.
Benzylamine-15N (Isotech) and aniline-15N (Cambridge Isotope
Laboratories) were used as received. N-benzyl-o-iodophen-
ethylamine and N-benzyl-3-(o-bromophenyl)propylamine were
synthesized by published procedures.7a
{P d [P (o-tol)3](p-C6H4CMe3)(µ-I)}2 (4). A solution of Pd2-
(DBA)3 (250 mg, 0.27 mmol), P(o-tol)3 (330 mg, 1.1 mmol), and
p-tert-butyliodobenzene (700 mg, 2.7 mmol) in 15 mL of
benzene was stirred at room temperature for 30 min. The
resulting green-brown solution was filtered through Celite, and
the solution was concentrated to 10 mL under vacuum.
Addition of Et2O (50 mL) formed an orange precipitate over 4
h, which was collected, washed with Et2O, and dried under
{P d [P (o-tol)3](p-C6H4CMe3)(µ-Br )}2 (1).8 A purple solu-
tion of Pd2(DBA)3 (1.5 g, 1.6 mmol), P(o-tol)3 (2.0 g, 6.6 mmol),
and p-tert-butyl bromobenzene (3.2 g, 14.7 mmol) in 80 mL of
benzene was stirred at room temperature for 1 h. The
resulting green-brown solution was filtered through Celite, and
benzene was evaporated under vacuum. Addition of Et2O (100
mL) to the oily residue formed a precipitate over 4 h, which
was filtered, washed with Et2O, and dried under vacuum to
give 1 (1.4 g, 69%) as a yellow powder. 1H NMR (55 °C): δ
7.24, 7.11, 7.03, 6.68, 6.48 (d, J ) 8.2 Hz), 2.14 [br, 9 H, P(o-
tol)3], 1.08 (C6H4CMe3). 31P{1H} NMR: δ 28.7 (br). Anal.
1
vacuum to give 4 (190 mg, 52%) as a pale orange powder. H
NMR (55 °C): δ 7.24, 7.10 (br), 6.88 (br), 6.50 (d, J ) 8.33
Hz), 2.10 [br, 9 H, P(o-tol)3], 1.08 (C6H4CMe3). 31P{1H} NMR:
δ 25.8 (br). Anal. Calcd (found) for C62H68I2P2Pd2: C, 55.50
(55.32); H, 5.11 (5.14); I, 18.92 (19.08).
{P d [P (o-tol)3](p-C6H4Me)(µ-I)}2 (5).8 Reaction of Pd2-
(DBA)3 (250 mg, 0.27 mmol), P(o-tol)3 (330 mg, 1.1 mmol), and

Pd Tris(o-tolyl)phosphine Mono(amine) Complexes
Organometallics, Vol. 15, No. 12, 1996 2753
p-iodotoluene (0.6 g, 2.7 mmol) using a procedure analogous
to that used to prepare 4 led to the isolation of 5 (207 mg,
60%) as a pale orange powder which contained traces (<5%)
analogous to that used to generate 8-(CD3CN)2 formed 11-(CD3-
CN)2, which was analyzed without isolation by NMR. 1H NMR
(CD3CN, 50 °C): δ 7.64 (m), 7.49 (t, J ) 7.5 Hz), 7.28 (m),
6.75, 6.72, 6.67 (m), 2.16 [br s, 9 H, P(o-tol)3], 1.32 (s, 3 H,
C6H4CMe3). 31P{1H} NMR (CD3CN, 50 °C): δ 25.2.
1
of Et2O by H NMR analysis. 1H NMR (55 °C): δ 7.34, 7.07
(br), 6.73 (br), 6.32 (d, J ) 6.38 Hz), 2.11 [br, 9 H, P(o-tol)3],
1.98 (C6H4Me). 31P{1H} NMR: δ 25.5 (br). Anal. Calcd
(found) for C56H56I2P2Pd2: C, 53.48 (53.45); H, 4.49 (4.65); I,
20.18 (20.19).
P d [P (o-tol)3](p-C6H4Me)[HN(CH3)Bn ]Cl (12). N-Benzyl-
methylamine (263 mg, 2.2 mmol) was added to a yellow
solution of 9 (200 mg, 0.19 mmol) in 10 mL of C6H6 and stirred
at room temperature for 15 min, and the resulting clear
solution was allowed to stand at room temperature. A white
precipitate formed over 2 h, which was filtered, washed with
ether, and dried under vacuum to give 12 (207 mg, 85%) as a
white microcrystalline solid. 1H NMR (55 °C): δ 7.63 (br), 7.51
(d, J ) 3.4 Hz), 7.38 (m), 7.34, 7.29 (t, J ) 7.5 Hz), 7.09 (m),
6.36 (m), 4.39 [br t, J ) 12.4 Hz, 1 H, HN(CH3)CH2Ph], 3.47
[dt, J ) 12.5, 7 Hz, HN(CH3)CH2Ph], 3.22 [br s, 1 H, HN(CH3)-
Bn], 2.46 [d, J ) 6.0 Hz, 3 H, HN(CH3)Bn], 2.22 [br, 9 H, P(o-
tol)3], 2.03 (s, C6H4Me). 31P{1H} NMR: δ 27.9. IR (Nujol):
3261 cm-1. Anal. Calcd (found) for C36H39ClNPPd: C, 65.66
(65.92); H, 5.97 (6.07); N, 2.13 (2.10).
{P d [P (o-tol)3](p-C6H4OMe)(µ-I)}2 (6). Reaction of Pd2-
(DBA)3 (250 mg, 0.27 mmol), P(o-tol)3 (330 mg, 1.1 mmol), and
p-iodoanisole (900 mg, 3.8 mmol) using a procedure analogous
to that used to prepare 4 led to the isolation of 6 (180 mg,
51%) as a pale orange powder which contained traces (<5%)
of Et2O by 1H NMR analysis. 1H NMR (55 °C): δ 7.25 (m),
7.08 (br), 6.75 (br), 6.17 (d, J ) 7.46 Hz), 3.53 (s, 3 H,
C6H4OMe), 2.14 [br, 9 H, P(o-tol)3]. 31P{1H} NMR: δ 25 (br).
Anal. Calcd (found) for C56H56I2O2P2Pd2: C, 52.16 (52.01); H,
4.38 (4.54); I, 19.68 (19.97).
{P d [P (o-tol)3]I(µ-I)}2. A solution of PdI2 (200 mg, 0.55
mmol), LiI (162 mg, 1.21 mmol), and P(o-tol)3 (380 mg, 1.25
mmol) in MeOH (7 mL) was heated at reflux for 30 min. The
resulting brown suspension was cooled to room temperature,
filtered in air, washed with methanol (20 mL) and Et2O (20
mL), and dried under vacuum to give {Pd[P(o-tol)3]I2}2 (357
mg, 97%) as a dark brown powder. 1H NMR: δ 9.21, 7.47,
7.14, 3.26, 1.90, 1.55. 31P{1H} NMR: δ 30.6 (br). Anal. Calcd
(found) for C42H42I4P2Pd2: C, 37.95 (37.65); H, 3.26 (3.11); I,
38.19 (38.09).
P d [P (o-tol)3](p-C6H4Me)[HN(CH 3)Bn ]Br (13). N-Ben-
zylmethylamine (160 mg, 1.32 mmol) was added to a yellow
solution of 2 (150 mg, 0.13 mmol) in 5 mL of CH2Cl2 and stirred
at room temperature for 10 min. The resulting colorless
solution was concentrated to 1 mL under vacuum and diluted
with 20 mL of hexane. Cooling the solution via concentration
to 10 mL under vacuum formed a white precipitate, which was
filtered, washed with hexane, and dried under vacuum to give
13 (148 mg, 83%) as a pale yellow microcrystalline solid. 1H
NMR (55 °C): δ 7.84, 7.37, 7.29 (t, J ) 7 Hz), 7.10, 6.38, 4.40
[br s, 1 H, HN(CH3)CH2Ph], 4.35 [br s, 1 H, HN(CH3)Bn], 3.42
[br s, 1 H, HN(CH3)CH2Ph], 2.46 [br s, 3 H, HN(CH3)Bn], 2.18
[br, 9 H, P(o-tol)3], 2.05 (s, 3 H, C6H4Me). 31P{1H} NMR: δ
P d [P (o-tol)3]2Br 2 (7).9 Reaction of PdBr2 (200 mg, 0.75
mmol), LiBr (140 mg, 1.61 mmol), and P(o-tol)3 (514 mg, 1.70
mmol) using a procedure analogous to that used to prepare
{Pd[P(o-tol)3]I2}2 led to the isolation of 7 (623 mg, 100%) as
an orange powder. 1H NMR: δ 9.21, 8.85, 7.22, 7.10, 2.97 (br),
1.95 (br), 1.60. 31P{1H} NMR: δ 20.2, 19.4 (∼1:1).
27.9. IR (Nujol): 3257 cm-1. Anal. Calcd (found) for C36H39
BrNPPd: C, 61.51 (61.63); H, 5.59 (5.83); N, 1.99 (2.06).
-
{P d [P (o-tol)3](p-C6H4Me)[CD3CN]2}+OTf- (8-(CD3CN)2).
Silver triflate (3 mg, 1 × 10-2 mmol) was added to a suspension
of 5 (5 mg, 4 × 10-3 mmol) in CD3CN (0.75 mL), and the
mixture was shaken for 1 min. The resulting yellow solution
of 8-(CD3CN)2 was filtered into an NMR tube and analyzed
without isolation. 1H NMR (CD3CN, 75 °C): δ 7.68 (m), 7.48
(t, J ) 7.5 Hz), 7.33 (t, J ) 7.5 Hz), 7.28 (t, J ) 7.5 Hz), 6.56
(t, J ) 7.5 Hz), 2.34 [br s, 9 H, P(o-tol)3], 2.10 (s, 3 H, C6H4Me).
31P{1H} NMR (CD3CN, 50 °C): δ 25.2.
P d [P (o-tol)3](p-C6H4Me)[HN(CH3)Bn ]I (14). Reaction of
5 (220 mg, 0.18 mmol), and N-benzylmethylamine (212 mg,
1.75 mmol) using a procedure analogous to that used to
prepare 13 led to the isolation of 14 (186 mg, 71%) as a pale
yellow microcrystalline solid. 1H NMR (∼80:20 ratio of 14:5):
δ 7.37, 7.29, 7.05, 6.4, 4.48 [br, 1 H, HN(CH3)CH2Ph], 3.47
[br, 1 H, HN(CH3)CH2Ph], 3.22, [br, 6 H, P(o-tol)3], 2.48 [br, 3
H, HN(CH3)Bn], 2.04 (s, 3 H, C6H4Me), 1.50 [br s, 3 H, P(o-
tol)3], HN(CH3)Bn not observed. 31P{1H} NMR {CDCl3 [0.05
M HN(Me)Bn]}: δ 28.1. IR (Nujol): 3253 cm-1. Anal. Calcd
(found) for C36H39ClNPPd: C, 57.65 (57.53); H, 5.24 (5.48); N,
1.87 (2.14).
{P d [P (o-tol)3](p-C6H4Me)(µ-Cl)}2 (9). A suspension of 5
(220 mg, 0.17 mmol) and AgOTf (94 mg, 0.37 mmol) in 5 mL
of CH3CN was stirred at room temperature for 5 min. The
resulting yellow solution was decanted from the gray precipi-
tate, which was extracted with an additional 5 mL of CH3CN.
LiCl (500 mg, 12.7 mmol) was added to the combined extracts,
and the resulting suspension was stirred at room temperature
for 2 days. Acetonitrile was evaporated under vacuum, and
the residue was extracted with toluene and filtered through
Celite. Evaporation of toluene and addition of Et2O (5 mL)
gave a pale yellow solution. Dropwise addition of pentane (10
mL) formed a yellow precipitate, which was washed with Et2O
and pentane and dried under vacuum to give 9 (175 mg, 93%)
as a pale yellow powder. 1H NMR: δ 7.68 (br, 3 H), 7.27 (t, J
) 7.05 Hz, 3 H), 7.08 (m, 6 H), 6.48 (br, 2 H), 6.30 (d, J ) 7.72
Hz, 2 H), 2.22 [s, 9 H, P(o-tol)3], 1.98 (s, 3 H, C6H4Me). 31P-
{1H} NMR: δ 28.8. Anal. Calcd (found) for C56H56Cl2P2Pd2:
C, 62.59 (62.34); H, 5.25 (5.53); Cl, 6.60 (6.71).
{P d [P (o-tol)3](p-C6H4CMe3)(µ-Cl)}2 (10). Reaction of 1
(410 mg, 0.33 mmol) and AgOTf (169 mg, 0.66 mmol), followed
by treatment with LiCl (750 mg, 17.8 mmol) using a procedure
analogous to that used to prepare 9, led to the isolation of 10
(216 mg, 57%) as a yellow powder. 1H NMR (55 °C): δ 7.70
(br, 3 H), 7.25 (m, 3 H), 7.08 (br, 6 H), 6.59 (br), 6.47 (d, J )
7.76 Hz), 2.17 [br, 9 H, P(o-tol)3], 1.07 (C6H4CMe3). 31P{1H}
NMR: δ 28.2. Anal. Calcd (found) for C62H68Cl2P2Pd2: C,
64.26 (64.48); H, 5.91 (6.17); Cl, 6.12 (6.11).
P d[P (o-tol)3](p-C6H4OMe)[HN(CH3)Bn ]Br (15). A purple
solution of Pd2(DBA)3 (150 mg, 0.16 mmol), P(o-tol)3 (250 mg,
0.82 mmol), p-bromoanisole (313.1 mg, 1.6 mmol), and benzyl-
(methyl)amine (235 mg, 1.9 mmol) in 5 mL of benzene was
stirred at room temperature for 2 days. The resulting green-
brown suspension was filtered through Celite, and the residue
was extracted with CH2Cl2 (50 mL) and evaporated under
vacuum. Addition of Et2O (20 mL) to the resulting oily residue
formed a yellow precipitate, which was filtered, washed with
Et2O and pentane, and dried under vacuum to give 15 (120
mg, 51%) as a pale yellow powder. 1H NMR (C6D6, 75 °C): δ
7.80, 7.20, 7.05, 6.88, 6.36, 4.55 [br, HN(Me)CH2Ph], 3.50 [br,
HN(Me)CH2Ph], 3.29 (s, C6H4OMe), 3.18 [br, HN(Me)CH2Ph],
2.33 [br, P(o-tol)3], 2.25 [br, HN(Me)Bn]. 31P{1H} NMR: δ 27.9
(br). IR (Nujol): 3258 cm-1. Anal. Calcd (found) for C36H39
BrNOPPd: C, 60.14 (60.35); H, 5.47 (5.79); N, 1.95 (1.95).
-
P d [P (o-tol)3](p-C6H4Me)[H2NBn ]Cl (16). Reaction of 9
(150 mg, 0.14 mmol) and benzylamine (74 mg, 0.7 mmol) using
a procedure analogous to that used to prepare 13 led to the
isolation of 16 (127 mg, 70%) as a pale yellow microcrystalline
solid, which contained traces (e5%) of hexane by 1H NMR
analysis. 1H NMR (50 °C): δ 7.74 (br, 3 H), 7.28 (t, J ) 6.4
Hz, 3 H) 7.21 (m, 3 H), 7.11 (m, 7 H), 6.58 (br s, 2 H), 6.46 (d,
J ) 7.3 Hz, 2 H), 3.75 (br, 2 H, H2NCH2Ph), 2.91 (br, 2 H,
H2NCH2Ph), 2.21 [br s, 9 H, P(o-tol)3], 2.07 (s, 3 H, C6H4Me).
{P d [P (o-tol)3](p-C6H4CMe3)[CD3CN]2}+OTf- (11-(CD3-
CN)2). Reaction of silver triflate (5 mg, 2 × 10-2 mmol) and
1 (7 mg, 6 × 10-3 mmol) in CD3CN (0.80 mL) using a procedure

2754 Organometallics, Vol. 15, No. 12, 1996
Widenhoefer et al.
31P{1H} NMR: δ 28.3. Anal. Calcd (found) for C35H37
-
19 (260 mg, 77%). 1H NMR (-42 °C): δ 9.54 (br d, J ) 17
Hz), 8.78 (dd, J ) 7.92, 17.6 Hz), and 8.38 (dd, J ) 7.72, 17.6
Hz) (1:2.6:2.6, 1 H), 7.50-6.80 (m, 17 H), 6.2-6.5 (m, 3 H),
5.26 (dd, J ) 6.3, 15.0 Hz), 5.16 (dd, J ) 5.6, 14.6 Hz), and
4.94 (dd, J ) 6.6, 15.3 Hz) (1:2.6:2.6, 1 H), 4.20 (br d, J ) 15.3
Hz, 1 H), 3.12, 2.85, and 2.73 [2.6:1:2.6, 3 H, P(o-tol)3], 2.26,
2.20, and 2.17 [2.6:2.6:1, 3 H, p-tolyl], 1.94, 1.82, and 1.32 [2.6:
2.6:1, 3 H, P(o-tol)3], 1.58, 1.55, 1.53 [2.6:2.6:1, 3 H, P(o-tol)3].
ClNPPd: C, 65.23 (65.03); H, 5.78 (5.93); N, 2.17 (2.31).
P d [P (o-t ol)3](p -C6H 4Me)[H 215NBn ]Cl (16-15N). Small
amounts (<0.5 mL) of benzylamine-15N were added via syringe
to a solution of 9 (7 mg, 6 × 10-3 mmol) in CDCl3 (0.75 mL)
1
and monitored after each addition by H NMR spectroscopy.
Addition of 1.4 mL of benzylamine-15N generated 16-15N, which
contained ∼5% 9 by 1H NMR analysis. 31P{1H} NMR (50 °C):
δ 28.1 (d, J PN ) 40.0 Hz).
IR (Nujol): 3187 cm-1
.
31P{1H} NMR (96 MHz, CDCl3, -42
P d [P (o-tol)3](p-C6H4Me)[H2NBn ]Br (17). Reaction of 2
(100 mg, 0.09 mmol), and benzylamine (19 mg, 0.18 mmol)
using a procedure analogous to that used to prepare 13 led to
the isolation of 17 (82 mg, 69%) as a pale yellow microcrys-
talline solid which contained traces (e5%) of hexane by 1H
NMR analysis. 1H NMR (50 °C): δ 7.80 (br s, 3 H), 7.31 (t, J
) 7.9 Hz, 3 H), 7.24 (s, 5 H), 7.12 (br s, 6 H), 6.63 (br s, 2 H),
6.51 (br s, 2 H), 3.79 (br, 2 H, H2NCH2Ph), 2.98 (br, 2 H, H2-
NCH2Ph), 2.20 [br s, 9 H, P(o-tol)3], 2.09 (s, 3 H, C6H4Me). 31P-
{1H} NMR: δ 28.9. Anal. Calcd (found) for C35H37BrNPPd:
C, 61.02 (61.25); H, 5.41 (5.32).
°C): δ 37.3, 35.1, and 29.4 (2.6:2.6:1). Anal. Calcd (found)
for C35H35BrNPPd: C, 61.20 (61.22); H, 5.14 (5.37); N, 2.04
(1.95).
P d [P (o-tol)3][2-C6H4(CH2)15N(H)P h ]Br (20). A suspen-
sion of 2-bromobenzyl bromide (0.6 g, 2.4 mmol), aniline-15N
(1 g, 11 mmol), and K2CO3 (1.4 g, 10 mmol) in 5 mL of THF
was refluxed for 2 h. After the suspension was cooled to room
temperature, water (5 mL) and Et2O (5 mL) were added and
the layers were separated. The aqueous layer was extracted
with Et2O (3 × 5 mL), and the combined Et2O fractions were
dried (MgSO4) and concentrated under vacuum to give a
mixture of 15N-phenyl-o-bromobenzylamine-15N44 and aniline-
15N. The resulting oil was diluted to 5 mL with C6H6, and 1.5
mL of this solution was added via syringe to a solution of Pd2-
(DBA)3 (150 mg, 0.16 mmol) and P(o-tol)3 (200 mg, 0.66 mmol)
in C6H6 (10 mL). The resulting mixture was stirred for 2 h to
form a brown solution, which was filtered through Celite and
concentrated to 1 mL under vacuum. Addition of Et2O (20 mL)
formed a tan precipitate over 4 h, which was filtered, washed
with Et2O, and dried under vacuum to give 20 (113 mg, 51%
based on Pd) as a yellow powder which contained ∼5% Et2O
by 1H NMR analysis. 1H NMR (0 °C): δ 9.54 (dd, J ) 6.8,
17.2 Hz), 8.73 (dd, J ) 7.05, 15.5 Hz), and 8.28 (dd J ) 8.6,
17.5 Hz) (1:2.6:2.6, 1 H), 7.5-6.8 (m, 12 H), 6.6-5.8 (m, HN +
aromatic, 3 H), 5.26 (dd, J ) 7.2, 13.8 Hz), 5.17 (dd, J ) 7.1,
14.2 Hz), and 4.95 (dd, J ) 7.4, 13.7 Hz) (1:2.6:2.6, 1 H), 4.25
(d, J ) 13.9 Hz, 1 H), 3.11, 2.82, and 2.66 [2.6:1:2.6, 3 H, P(o-
tol)3], 1.92, 1.79, and 1.30 [2.6:2.6:1, 3 H, P(o-tol)3], 1.57, 1.55,
and 1.52 [2.6:2.6:1, 3 H, P(o-tol)3]. 31P{1H} NMR (-42 °C): δ
36.8 (d, J PN ) 36.3 Hz), 34.1 (d, J PN ) 37.0 Hz), and 28.7 (d,
J PN ) 36.3 Hz) (2.6:2.6:1).
P d [P (o-tol)3](p-C6H4Me)[H215NBn ]Br (17-15N). Reaction
of benzylamine-15N and 2 (7 mg, 6 × 10-3 mmol) in CDCl3 (0.75
mL) using the procedure employed in the synthesis of 16-15N
formed 17-15N. 31P{1H} NMR: δ 28.9 (d, J PN ) 40.1 Hz).
P d [P (o-tol)3][2-C6H4(CH2)2N(H)Bn ]I (18). A purple sus-
pension of Pd2(DBA)3 (200 mg, 0.21 mmol), P(o-tol)3 (370 mg,
1.1 mmol), and 2-IC6H4(CH2)2N(H)Bn (535 mg, 0.57 mmol) in
20 mL of benzene was stirred at room temperature for 24 h.
The resulting green-brown suspension was filtered through
Celite, and benzene was evaporated under vacuum. Addition
of Et2O (10 mL) to the oily residue formed a white precipitate,
which was filtered, washed with Et2O, and dried under
vacuum to give 18 (368 mg, 71%) as a yellow powder which
was g95% pure by 1H NMR analysis. 18 was further purified
by recrystallization from CH2Cl2/hexane. 1H NMR (0 °C): 9.49
(dd, J ) 8.2, 18.1 Hz), 7.4-6.3 (m, aromatic), 5.49 (br s, 1 H,
NH, identified by D2O exchange), 3.93 (dd, 1 H, J ) 4.2, 13.8
Hz), 3.53 (dt, 1 H, J ) 6.4, 13.2 Hz), 3.17 [s, 3 H, P(o-tol)3],
2.81 (m, 2 H), 2.05 (br t, J ) 9.3 Hz), 1.51 [s, 3 H, P(o-tol)3],
0.83 [s, 3 H, P(o-tol)3]. 31P NMR: δ 29.1. IR (Nujol): 3241
cm-1. Anal. Calcd (found) for C36H37INPPd: C, 57.81 (57.63);
H, 4.99 (4.84); N, 1.87 (1.80).
N-(p-tolyl)-o-br om oben zyla m in e. A suspension of 2-bro-
mobenzyl bromide (5 g, 20.1 mmol), p-toluidine (10.7 g, 100
mmol), and K2CO3 (14 g, 100 mmol) in 20 mL of THF was
refluxed for 18 h. After the suspension was cooled to room
temperature, water (50 mL) and Et2O were added and the
layers were separated. The aqueous layer was extracted with
Et2O (3 × 75 mL), and the combined Et2O fractions were dried
(MgSO4) and concentrated using a rotary evaporator. The
residue was chromatographed (SiO2, hexane/ethylacetate, (2/
1) with 1% Et3N), and the first band to elute was collected to
give N-(p-tolyl)-o-bromobenzylamine (4.7 g, 85%) as a yellow
oil which solidified upon standing. 1H NMR: δ 7.55 (dd, J )
2.2, 8.2 Hz, 1 H), 7.39 (dd, J ) 2.0, 7.7 Hz, 1 H), 7.23 (dt, J )
2.0, 7.7 Hz, 1 H), 7.10 (dt, J ) 1.8, 7.4 Hz, 1 H), 6.97 (d, J )
8.3 Hz, 2 H), 6.52 (d, J ) 8.2 Hz, 2 H), 4.36 (s, 2 H), 4.05 (br
s, 1 H), 2.22 (s, 3 H). 13C{1H} NMR: δ 145.6, 138.5, 132.9,
129.9, 129.3, 128.7, 127.6, 127.0, 123.4, 113.2, 48.8, 20.5. Anal.
Calcd (found) for C14H14BrN: C, 60.89 (60.98); H, 5.11 (5.21).
P d [P (o-tol)3](2-C6H4(CH2)3N(H)Bn ]Br (21). Reaction of
Pd2(DBA)3 (410 mg, 0.88 mmol), P(o-tol)3 (530 mg, 1.74 mmol),
and 2-BrC6H4(CH2)3N(H)Bn (570 mg, 1.90 mmol) using a
procedure analogous to that used to prepare 18 led to the
isolation of 21 (150 mg, 24%) as a white powder. 1H NMR: δ
9.6 (br, 1 H), 7.6-7.0, 6.8-6.2 (m, 8 H), 4.14 (s, 1 H), 4.01 (s,
2 H), 3.18 (s, 3 H), 3.10 (s, 2 H), 2.96 (s, 1 H), 3.36 (s, 1 H),
1.98 (s, 1 H), 1.77 (s, 1 H), 1.53 (s, 1 H), 0.92 (s, 3 H). 31P{1H}
NMR (50 °C): δ 28.5 (br). IR (Nujol): 3227 cm-1. Anal. Calcd
(found) for C37H39BrNPPd: C, 62.15 (61.87); H, 5.50 (5.43); N,
1.96 (2.13).
Ack n ow led gm en t. We thank the National Science
Foundation, the National Institutes of Health, Dow
Chemical, and Pfizer for their support of this work.
R.A.W. is an NCI Postdoctoral Trainee supported by
NIH Cancer Training Grant CI T32CA09112. We thank
Dr. R. A. Rennels for supplying N-benzyl-o-iodophen-
ethylamine and N-benzyl-3-(o-bromophenyl)propylamine.
P d [P (o-tol)3][2-C6H4CH2N(H)(p-tolyl)]Br (19). Reaction
of Pd2(DBA)3 (200 mg, 0.44 mmol), P(o-tol)3 (290 mg, 0.95
mmol), and 2-Br-C6H4CH2N(H)(p-tolyl) (345 mg, 1.25 mmol)
using a procedure analogous to that used to prepare 18 gave
OM9509599
(44) Park, Y. T.; Lee, I. H.; Kim, Y. H. J . Heterocycl. Chem. 1994,
31, 1625.