Cationic arylpalladium complexes with chelating diamine ligands, [PdAr(N-N)(solv)]BF4 (N-N = N,N,N′,N′- tetramethylethylenediamine, 2,2′-bipyridine, 4,4′-dimethyl- 2,2′-bipyridine). Preparation, intermolecular coupling of the aryl ligands, and insertion of alkyne and allene into the Pd-C bond

Article abstract of DOI:10.1021/om0007466

Iodo(aryl)palladium complexes, [PdI{C₆H₃ (CF₃)₂-3,5}(N-N)] (N-N = tmeda, bpy, 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy)), react with AgBF₄ in CH₃CN, acetone, and THF to yield stable cationic arylpalladium complexes [Pd{C₆H₃ (CF₃)₂-3,5}(N-N)(solv)]BF₄. A similar reaction of AgBF₄ with [PdI(C₆H₃Me₂-3,5) (bpy)] in CH₃CN gives [Pd(C₆H₃Me₂- 3,5)(bpy)(CH₃CN)]BF₄. The complex does not change its NMR spectrum for 1 h at room temperature in CD₃CN but undergoes decomposition upon dissolution in acetone to release 3,3′,5,5′- tetramethylbiphenyl. Addition of AgBF₄ to acetone or THF solutions of [PdI(Ar)(bpy)] (Ar = Ph, C₆H₃Me₂-3,5) and of [PdI(Ar)(Me₂bpy)] (Ar = C₆H₄OMe-4, C₆H₃Me₂-3,5) does not lead to isolation of the cationic arylpalladium complexes and causes intermolecular coupling of the aryl ligands to yield the corresponding biaryls. The reaction of AgBF₄ with [PdI(C₆H₃Me₂-3,5)(bpy)] in the presence of an excess amount of dimethyl acetylenedicarboxylate (DMAD) in CH₃CN gives [Pd(CZ=CZ-CZ=CZ-C₆H₃Me₂-3,5)(bpy) (CH₃CN)]BF₄ (Z = COOMe) via insertion of two acetylene molecules into the Pd-aryl bond. A similar reaction in acetone or THF causes insertion of three DMAD molecules into the Pd-aryl bond and cyclization of the formed Pd-(CZ=CZ)₃-Ar group to give the product containing a cyclopentadiene structure in the ligand. [PdI(CZ=CZ-C₆H₃ Me₂-3,5)(bpy)] reacts with AgBF₄ in CH₃CN to form a cationic complex, [Pd(CZ=CZ-C₆H₃Me₂-3,5) (bpy)(CH₃CN)]BF₄. A series of cationic Pd complexes, formed through insertion of one, two, and three alkyne molecules into the Pd-aryl bond, are characterized by X-ray crystallography or NMR spectroscopy. Phenylallene reacts with [PdI(C₆H₃Me₂-3,5) (bpy)] in the presence of AgBF₄ to give [Pd{η³-CH₂C-(C₆H₃ Me₂-3,5)CHPh}(bpy)]BF₄ via insertion of the C=C double bond of the allene into the Pd-C bond of the cationic arylpalladium complex. The π-allylpalladium complex crystallizes exclusively in a form with a syn-oriented phenyl substituent but exists in solution as a mixture of the isomers with a syn or anti phenyl substituent.

Full text of DOI:10.1021/om0007466

Organometallics 2001, 20, 1087-1101
1087
Ca tion ic Ar ylp a lla d iu m Com p lexes w ith Ch ela tin g
Dia m in e Liga n d s, [P d Ar (N-N)(solv)]BF 4 (N-N )
N,N,N′,N′-tetr a m eth yleth ylen ed ia m in e, 2,2′-bip yr id in e,
4,4′-d im eth yl-2,2′-bip yr id in e). P r ep a r a tion ,
In ter m olecu la r Cou p lin g of th e Ar yl Liga n d s, a n d
In ser tion of Alk yn e a n d Allen e in to th e P d -C Bon d
Takeyoshi Yagyu, Makiko Hamada, Kohtaro Osakada,* and
Takakazu Yamamoto
Research Laboratory of Resources Utilization, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku, Yokohama 226-8503, J apan
Received August 28, 2000
Iodo(aryl)palladium complexes, [PdI{C6H3(CF3)2-3,5}(N-N)] (N-N ) tmeda, bpy, 4,4′-
dimethyl-2,2′-bipyridine (Me2bpy)), react with AgBF4 in CH3CN, acetone, and THF to yield
stable cationic arylpalladium complexes [Pd{C6H3(CF3)2-3,5}(N-N)(solv)]BF4. A similar
reaction of AgBF4 with [PdI(C6H3Me2-3,5)(bpy)] in CH3CN gives [Pd(C6H3Me2-3,5)(bpy)-
(CH3CN)]BF4. The complex does not change its NMR spectrum for 1 h at room temperature
in CD3CN but undergoes decomposition upon dissolution in acetone to release 3,3′,5,5′-
tetramethylbiphenyl. Addition of AgBF4 to acetone or THF solutions of [PdI(Ar)(bpy)] (Ar )
Ph, C6H3Me2-3,5) and of [PdI(Ar)(Me2bpy)] (Ar ) C6H4OMe-4, C6H3Me2-3,5) does not lead to
isolation of the cationic arylpalladium complexes and causes intermolecular coupling of the
aryl ligands to yield the corresponding biaryls. The reaction of AgBF4 with [PdI(C6H3Me2-
3,5)(bpy)] in the presence of an excess amount of dimethyl acetylenedicarboxylate (DMAD)
in CH3CN gives [Pd(CZdCZ-CZdCZ-C6H3Me2-3,5)(bpy)(CH3CN)]BF4 (Z ) COOMe) via
insertion of two acetylene molecules into the Pd-aryl bond. A similar reaction in acetone or
THF causes insertion of three DMAD molecules into the Pd-aryl bond and cyclization of
the formed Pd-(CZdCZ)3-Ar group to give the product containing a cyclopentadiene
structure in the ligand. [PdI(CZdCZ-C6H3Me2-3,5)(bpy)] reacts with AgBF4 in CH3CN to
form a cationic complex, [Pd(CZdCZ-C6H3Me2-3,5)(bpy)(CH3CN)]BF4. A series of cationic
Pd complexes, formed through insertion of one, two, and three alkyne molecules into the
Pd-aryl bond, are characterized by X-ray crystallography or NMR spectroscopy. Phenylal-
lene reacts with [PdI(C6H3Me2-3,5)(bpy)] in the presence of AgBF4 to give [Pd{η3-CH2C-
(C6H3Me2-3,5)CHPh}(bpy)]BF4 via insertion of the CdC double bond of the allene into the
Pd-C bond of the cationic arylpalladium complex. The π-allylpalladium complex crystallizes
exclusively in a form with a syn-oriented phenyl substituent but exists in solution as a
mixture of the isomers with a syn or anti phenyl substituent.
In tr od u ction
studies of such reactions have been carried out. Scheme
1(i) illustrates the associative insertion of CO into the
Pd-C bond of [PdBr(Ar)(PR3)2], which is generally
accepted as a plausible pathway in the Pd-catalyzed
carbonylation of bromoarene in the presence of amine
and alcohol to give carboxylic amides and esters.3 The
five-coordinate intermediates with a trigonal bipyrami-
dal structure have been proposed based on results of
kinetic studies of the overall carbonylation reactions.
A detailed NMR study of the reaction of CO or
CF2dCF2 with [PtMe(OMe)(dppe)] revealed the forma-
tion of the five-coordinate complex shown in Chart 1 at
low temperature and the migratory insertion of CO or
Palladium complex catalyzed carbonylation of aryl
halides1 and arylation of alkenes2 involve insertion of
small molecules such as CO and ethylene into the Pd-
aryl bond as a crucial step. A number of mechanistic
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10.1021/om0007466 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/16/2001

1088 Organometallics, Vol. 20, No. 6, 2001
Sch em e 1 . Tw o P a th w a ys P r op osed for In ser tion of CO in to th e P d -C Bon d
Yagyu et al.
Ch a r t 1
CO insertion (Scheme 2(i)). The cationic methylpalla-
dium complexes with chelating diphosphine or diamine
ligands undergo smooth migratory insertion of CO into
the Pd-Me bond with keeping the cis geometry of the
complexes throughout the reaction (Scheme 2(ii)). Thus,
these complexes with the cis structure imposed by the
chelating ligand have attracted recent attention not only
as the reaction intermediates of Pd-catalyzed carbony-
lation and related reactions but also as catalysts of
synthetic organic reactions and polymer synthesis in-
cluding insertion of CO and/or alkenes into the Pd-C
bond. Polymerization of alkenes7 and alternating copo-
lymerization of alkene and CO5,8-14 catalyzed by cationic
methylpalladium complexes have attracted recent at-
tention. The living polymerization found in these studies
afforded the polymers with regulated structures and
Ch a r t 2
CF2dCF2 into the Pt-OMe bond on warming the
solution of the complexes to room temperature.4 Re-
cently, several research groups suggested an alternative
pathway for CO and alkene insertion into the Pd-C
bond shown in Scheme 1(ii) based on the observation
that [PdR(solv)(L)2]+ type complexes undergo insertion
of the small molecules more easily than neutral [PdR-
(X)(L)2] (R ) Me, Ph, X ) Cl, Br, etc).5,6 For example,
trans-[PdPh(solv)(PMe3)2]BF4 reacts with methyl acry-
late at 5 °C to give methyl 2-phenylacrylate via insertion
of the CdC double bond into the Pd-Ph bond followed
by â-hydrogen elimination of the resulting alkylpalla-
dium intermediate, whereas a similar reaction of trans-
[PdCl(Ph)(PMe3)2] requires heating at 70 °C.6
Structures of typical cationic organopalladium com-
plexes with auxiliary phosphine or amine ligands are
shown in Chart 2. Cationic alkyl and arylpalladium
complexes with two monodentate phosphine ligands
tend to have a geometry with two trans phosphine
ligands but readily react with CO to cause insertion into
the Pd-C bond. Since CO is initially coordinated at the
trans position of the methyl or phenyl ligand, the
reaction probably involves isomerization of intermediate
trans-[PdR′(CO)(PR3)2]+ into the cis isomer prior to the
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Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1089
Sch em e 2 . In ser tion of CO in to th e P d -C Bon d of tr a n s- a n d cis-[P d R′(L)2(S)]+ Com p lexes
molecular weights. Although analogous cationic arylpal-
ladium complexes with chelating ligands would also
cause alkene or CO coordination and their smooth
migratory insertion into the Pd-C bond, there have
been only a few reports on preparation and detailed
chemical properties of such cationic arylpalladium
complexes with cis coordination.15,16 De Felice et al.
briefly reported preparation of [PdPh(bpy)(CH3CN)]BF4
and its reaction with unsaturated molecules.15
In this paper, we report the isolation of stable cationic
palladium complexes with an aryl group containing CF3
substituents and chelating diamine or bipyridine ligands.
The complexes with nonfluorinated aryl groups are un-
stable in acetone or THF and tend to undergo intermo-
lecular coupling of the aryl ligands in the solutions. This
unique reaction of the cationic cis arylpalladium com-
plexes and insertion of alkynes and allenes into the Pd-
aryl bond are described.
Resu lts
Ca tion ic Ar ylp a lla d iu m Com p lexes w ith Ch ela t-
in g Dia m in e or Bip yr id in e Liga n d s. Iodo(aryl)-
palladium(II) complexes [PdI(Ar)(N-N)] (N-N ) tme-
da, bpy, Me2bpy) were prepared by the oxidative addition
of iodoarene to Pd(dba)2 (dba ) dibenzylideneacetone)
in the presence of a bidentate ligand according to a
previously described method (eq 1).17,18
F igu r e 1. ORTEP drawing of 1c (a) and 2c (b) (50%
probability). Selected bond lengths (Å) and angles (deg) for
1c: Pd-I 2.583(1), Pd-N1 2.205(8), Pd-N2 2.134(9), Pd-
C1 1.98(1), I-Pd-N1 96.4(3), I-Pd-N2 177.1(3), I-Pd-
C1 88.4(3), N1-Pd-N2 83.5(4), N1-Pd-C1 172.8(4), N2-
Pd-C1 91.9(4). Selected bond lengths (Å) and angles (deg)
for 2c: Pd-I 2.5737(7), Pd-N1 2.133(4), Pd-N2 2.082(5),
Pd-C1 1.990(5), I-Pd-N1 98.6(1), I-Pd-N2 176.7(1),
I-Pd-C1 88.5(2), N1-Pd-N2 78.6(2), N1-Pd-C1 172.3-
(2), N2-Pd-C1 94.4(2).
of the square-planar complexes have Pd-C, Pd-N, and
Pd-I bonds whose lengths are similar to those of [PdI-
(16) Recently, the reaction of [Pd(dppp)(NCPh)2](BF4)2 (dppp ) 1,3-
bis(diphenylphosphino)propane) with B(C6F5)3 was reported to give
[Pd(dppp)(C6F5)(NCPh)]BF4. Isolation of the pure complex was not
feasible, although the complex obtained in situ catalyzes alternating
copolymerization of alkene and CO to give polyketones. See: Barlow,
G. K.; Boyle, J . D.; Cooley, N. A.; Ghaffar, T.; Wass, D. F. Organome-
tallics 2000, 19, 1470.
The new complexes, 1c, 2c, 2d , and 3b-3e, were
characterized by NMR spectroscopy and/or X-ray crys-
tallography. Figure 1 displays the molecular structures
of 1c and 2c determined by X-ray crystallography. Both
(17) 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.
(15) De Felice, V.; Cucciolito, M. E.; De Renzi, A.; Ruffo, F.; Tesauro,
D. J . Organomet. Chem. 1995, 443, 1.

1090 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
3,5}(N-N)(solv)]+BF4-, accompanied by separation of
AgI from the solution (eq 2).
Ta ble 1. Yield a n d An a lytica l Da ta of th e
Com p lexes
elemental analysis (%)a
yield (%)
51
C
H
N
I
1c
29.64
(29.89)
35.93
3.19
(3.40)
1.70
4.96
(4.98)
4.66
22.33
(22.56)
21.64
2c
59
52
66
62
70
74
75
96
51
94
84
46
(35.88)
43.32
(43.49)
38.21
(38.09)
45.95
(45.96)
40.56
(40.56)
33.70
(34.10)
39.55
(39.80)
48.26
(48.47)
42.23
(41.84)
48.88
(48.97)
48.98
(49.29)
56.63
(56.82)
(1.84)
3.89
(3.65)
2.56
(2.40)
4.23
(4.05)
2.88
(2.87)
3.86
(3.93)
2.35
(2.34)
4.32
(4.07)
3.14
(2.87)
4.00
(4.11)
4.33
(4.14)
4.52
(4.42)
(4.65)
5.32
(5.34)
4.57
(4.44)
5.23
(5.36)
4.96
(4.98)
7.58
(7.46)
6.67
(6.96)
8.43
(8.48)
7.28
(6.65)
6.64
(6.59)
5.68
(5.39)
4.67
(4.91)
(21.06)
24.75
(24.19)
19.73
(20.12)
24.02
(24.28)
22.06
3b
3c
3d
3e
(22.55)
Acetonitrile-coordinated complexes 4c-CH3CN, 5c-
CH3CN, and 6c-CH3CN are isolated as off-white solids
in 51-75% yields and characterized by NMR spectros-
copy and elemental analyses (Tables 1-3). The NMR
spectra of the complexes do not change for 24 h or longer
4c-CH3CN
5c-CH3CN
5d -CH3CN
6c-CH3CN
9-CH3CN
10-CH3CN
11
1
at room temperature. Figure 2b displays the H NMR
spectrum of 5c-CH3CN in CD3CN. The singlets at δ 7.72
and 7.94 are assigned to the para and ortho phenyl
protons. The former signal is shifted to a lower magnetic
field by approximately 0.2 ppm from the corresponding
neutral iodo(aryl)palladium complex 2c. Most of the
bipyridine hydrogen signals are observed at positions
similar to those of 2c; the multiplets due to H5, H5′, H4,
and H4′ are positioned at δ 7.41, 7.72, 8.16, and 8.20,
and a doublet of H6 and overlapped signals of H3 and
H3′ at δ 7.56 and 8.28, respectively. The H6′ signal
appears at a significantly higher magnetic field (δ 8.55)
than 2c (δ 9.51), suggesting that the low magnetic field
position of 2c is related to the H‚‚‚I electrostatic
interaction in solution. The position of the signal of
acetonitrile (δ 1.95) is almost the same as the free
solvent, which is due to a rapid exchange between the
coordinated and uncoordinated solvents and a much
smaller amount of coordinated CH3CN than coordinated
CD3CN.21
a
Calculated values are in parentheses.
(Ph)(tmeda)], [PdI(C6H4Me-4)(tmeda)], and [PdI(Ph)-
(bpy)].17,18 The distance between H6′, bonded to C9, and
I (2.982 Å) for 2c is shorter than the sum of the van der
Waals radii,19 which implies the presence of an electro-
static interaction. Such H‚‚‚I interaction has been found
also in several Pd(II) and Pt(II) complexes.20 Tables 1-3
summarize the yields and analytical values, as well as
the H and 13C{1H} NMR data of the complexes. The
1
1H NMR spectrum of 2c in CDCl3 gives rise to the
signals ofthe para and orthohydrogens of3,5-bis(trifluoro-
methyl)phenyl ligand at δ 7.42 and 7.88, which are at
a lower magnetic field than those of 2d (δ 6.52 and 6.99
in CDCl3) caused by the presence of electron-withdraw-
ing CF3 groups. Figure 2a shows the spectrum of 2c in
CD3CN, which exhibits the above signals at δ 7.53 and
7.93, respectively. The signals at δ 7.44, 7.64, 8.13, and
8.15 are assigned to the bpy hydrogens H5, H5′, H4, and
The reactions of AgBF4 with 1c in acetone and with
2c in acetone and THF also cause AgI formation. The
1H NMR spectra of the resulting solutions indicate
conversion of the complexes into the corresponding
cationic arylpalladium complexes, 4c-acetone, 5c-ace-
tone, and 5c-THF. Addition of hexane to the solutions
of the two latter complexes causes separation of the
H
4′ (Chart 3), respectively, while doublets at δ 7.49 and
1
complexes as off-white solids. The H NMR spectra of
9.51 are due to H6 and H6′ hydrogens. A much lower
magnetic field position of H6′ than H6 can be ascribed
to the electrostatic interaction between H6′ and I
mentioned above. The signals of H3 and H3′ hydrogens
are observed at δ 8.31 with severe overlapping. All these
assignments are based on their coupling patterns and
the solid products, however, show the signal of the
coordinated solvents (acetone or THF) in a weaker peak
intensity than expected from the formula (60% and 90%
for 5c-acetone and 5c-THF, respectively). These NMR
spectra as well as insufficient analytical results of the
complexes seem to suggest partial conversion of the
complexes into BF4-coordinated Pd complex [Pd{C6H3-
(CF3)2-3,5}(N-N)(BF4)] during the above procedure to
obtain the products as a solid.22
Although cationic palladium complexes with nonflu-
orinated aryl ligands show a much lower stability than
the complexes with a 3,5-bis(trifluoromethyl)phenyl lig-
and, it is possible to isolate the complexes in a CH3CN
the H-1H COSY spectrum.
1
The iodo(aryl)palladium(II) complexes are stable in
air and do not decompose below 50 °C in acetone.
Addition of AgBF4 to the Pd complexes with a 3,5-bis-
(trifluoromethyl)phenyl ligand, 1c, 2c, and 3c, in polar
solvents (CH3CN, acetone, and THF) converts them into
the cationic arylpalladium complexes, [Pd{C6H3(CF3)2-
(18) Osakada, K.; Sakata, R.; Yamamoto, T. Organometallics 1997,
16, 5354.
(19) Bondi, A. J . Phys. Chem. 1964, 68, 441.
(20) Alsters, P. L.; Engel, P. F.; Hogerheide, M. P.; Copijn, M.; Spek,
A. L.; van Koten, G. Organometallics 1993, 12, 1831. Connick, W. B.;
Gray, H. B. Acta Crystallogr. 1994, C50, 1040.
(21) The 1H NMR signals of free and coordinated CH3CN hydrogens
show differences in the chemical shifts (by approximately 0.3 ppm)
when the exchange of the molecule is slower than the NMR time scale.
See: Yagyu, T.; Aizawa, S.; Hatano, K.; Funahashi, S. Bull. Chem.
Soc. J pn. 1996, 69, 1961.

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1091
Ta ble 2. 1H NMR Da ta of th e Com p lexesa
b
tmeda
bpy or Me2bpy
Ar
N- CH3
-CH2-
H3
H3′
H4
H4′
H5
H5′
H6
H6′
4-CH3
4′-CH3
ortho
meta
para
solvent
1c
7.71(s)
7.23(s)
2.21(s)
2.63(s)
2.49(m)
2.66(m)
2c
7.88(s)
7.93(s)
6.99(s)
7.23*
7.42(s)
7.53(s)
6.52(s)
8.1*
8.04(m)
8.04(m)
8.13(m)
8.15(m)
7.96(m)
7.96(m)
7.39(m)
7.54(m)
7.44(m)
7.64(m)
7.32(m)
7.47(m)
7.47(d)
(5.4 Hz)
9.63(d)
(4.4 Hz)
7.49(d)
(5.9 Hz)
9.51(d)
(5.4 Hz)
7.65(d)
(5.9 Hz)
9.56(d)
(3.9 Hz)
7.53(d)
(5.4 Hz)
9.62(d)
(5.4 Hz)
7.16(d)
(5.4 Hz)
9.43(d)
(5.9 Hz)
7.52(d)
(5.9 Hz)
9.40(d)
(5.4 Hz)
7.42(d)
(5.4 Hz)
9.44(d)
(5.4 Hz)
8.1*
2cc
8.31*
8.31*
8.06*
8.06*
7.83(s)
7.83(s)
7.9*
2d d
3be
6.72(d)
(8.3 Hz)
7.09(d)
(5.9 Hz)
7.27(d)
(5.4 Hz)
7.3(m)
2.45(s)
2.50(s)
2.47(s)
2.53(s)
2.44(s)
2.50(s)
2.46(s)
2.52(s)
3c
7.88(s)
7.00(s)
7.41(s)
6.52(s)
7.9*
7.3(m)
3d f
7.82(s)
7.82(s)
7.85(s)
7.83(s)
7.11(d)
(6.4 Hz)
7.26(d)
(6.4 Hz)
7.14(d)
(4.9 Hz)
7.31(d)
(5.4 Hz)
3e
7.55(d)
(8.3 Hz)
7.25*
4c-CH3CNc
4c-acetoneg
5c-CH3CNc
5c-acetoneg
7.94(s)
8.05(s)
7.94(s)
8.11(s)
7.59(s)
7.47(s)
7.72(s)
7.67(s)
2.41(s)
2.66(s)
2.69(m)
2.87(m)
2.63(s)
2.65(s)
2.86(m)
3.08(m)
1.95(s)
2.07(s)
1.95(s)
2.08(s)
1.78(m)
8.28*
8.28*
8.66*
8.66*
8.62*
8.16(m)
8.20(m)
8.37(m)
8.39(m)
8.28(m)
7.41(m)
7.72(m)
7.64(m)
7.87(m)
7.48(m)
7.56(d)
(5.9 Hz)
8.55(d)
(4.9 Hz)
7.97(d)
(5.5 Hz)
8.48(d)
(4.9 Hz)
7.73(d)
(5.4 Hz)
8.6*
7.84(d)
(4.9 Hz)
8.62(d)
(4.9 Hz)
7.47(d)
(5.9 Hz)
8.47(d)
(5.4 Hz)
5c-THFh
8.13(s)
6.95(s)
7.68(s)
6.75(s)
8.58*
8.30*
8.26(m)
8.14(m)
7.79(m)
7.43(m)
3.62(m)
1.95(s)
5d -CH3CNc
8.32*
8.22(m)
7.73(m)
6c-CH3CNc
7.99(s)
7.73(s)
8.19(s)
8.21(s)
7.24(d)
(5.9 Hz)
7.57(d)
(5.4 Hz)
2.49(s)
2.57(s)
1.95(s)
a
b
400 MHz at 25 °C. In CDCl3 unless otherwise stated. Positions and splitting pattern of the peaks with asterisks are not determined
precisely due to severe overlapping with other signals. c In CD3CN. 2.19 (s, m-CH3). e 3.76 (s, p-OCH3). f 2.20 (s, m-CH3). In acetone-
d6. In THF-d8.
d
g
h
solvated form. Addition of AgBF4 to a CH3CN solution
1
of 2d causes a change in the H NMR signals, suggest-
ing the formation of the cationic arylpalladium com-
plex [Pd(C6H3Me2-3,5)(bpy)(CH3CN)]+BF4- (5d -CH3CN)
(eq 3).
The complex is stable at room temperature in the solid
state. The 1H NMR spectrum of a CD3CN solution of
5d -CH3CN does not change for 1 h at room temperature,
but it appears to gradually decompose on standing the

1092 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
F igu r e 2. 1H NMR spectra of (a) 2c and (b) 5c-CH3CN in
CD3CN (400 MHz).
Ch a r t 3
solution for a long period. Dissolution of 5d -CH3CN in
acetone causes rapid decomposition accompanied by the
release of 3,3′,5,5′-tetramethylbiphenyl in a 25% yield
as shown in eq 4.
To obtain further scope and insight into the intermo-
lecular coupling of the aryl ligands, the reactions of
AgBF4 with several iodo(aryl)palladium complexes were
carried out. As shown in eq 5, the complexes containing
bpy or Me2bpy ligands, 2a , 2d , 3b, and 3d , react with
AgBF4 in acetone or THF to give the corresponding
biaryls at room temperature. Characterization of the Pd-
containing products formed in the reaction was not
successful.

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1093
Ta ble 4. Yield s of Bia r yl in th e Rea ction of AgBF 4
w ith Ar ylp a lla d iu m Com p lexesa
Sch em e 3
yields of biaryl (%)
complex
solvent
1 h
6 h
24 h
1a
1a
1b
1c
1c
2a
2a
2a
2d
3b
3c
3c
3d
3e
CH3CN
acetone
CH3CN
CH3CN
acetone
CH3CN
acetone
THF
acetone
acetone
acetone
THF
0 (6 d)
0
0 (5 d)
0 (5 d)
0 (4 d)
0 (10 d)
55
3.9
87
56
68
28 (4 h)
95
63
83
96
0 (7 d)
0 (5 d)
acetone
acetone
79
0 (2 d, at 50 °C)
a
Reactions were carried out at room temperature unless
otherwise stated.
Table 4 summarizes the yields of the products and
their variation depending on the kind of chelating
ligand, aryl ligand, and solvent. Addition of AgBF4 to
acetone and THF solutions of 2a gives biphenyl in 63%
and 83% yields, respectively, after 24 h, whereas a
similar reaction in CH3CN does not give the coupling
product at all. Complexes 2d and 3d with a 3,5-
dimethylphenyl ligand react readily with AgBF4 to form
3,3′,5,5′-tetramethylbiphenyl in 87% and 79% yields,
respectively, after 1 h in acetone. The biaryl-forming
reaction 5 takes place via the initial formation of a
cationic intermediate, [PdAr(N-N)(solv)]+, and subse-
quent intermolecular coupling of the aryl ligands. The
stepwise pathway is demonstrated in reactions 3 and
4, which lead to the conversion of 2d to its cationic
derivative, 5d -CH3CN, and release of 3,3′,5,5′-tetra-
methylbiphenyl. The latter reaction involves an initial
exchange of the coordinated CH3CN with acetone to give
[Pd(C6H3Me2-3,5)(bpy)(acetone)]+ followed by the bimo-
lecular coupling of the aryl ligands.
Tmeda-coordinated complexes, 1a and 1c, react with
AgBF4 in acetone under similar conditions, probably
giving the corresponding cationic arylpalladium com-
plexes, but they do not produce the coupling products.
Complexes 3c and 3e with CF3 substituents on the aryl
ligand do not give the biaryl even after the reaction with
AgBF4 for several days. CF3 groups of the aryl ligand
stabilize the Pd-aryl bond and prevent the aryl ligand
transfer and/or their coupling reaction.
methylpalladium complexes, [PdCl(Me)(dppe)], [Pd-
(NO3)(Me)(dppe)], and [PdMe(thf)(dppe)]+, and found
more facile insertion of the alkyne into the Pd-Me bond
of the cationic complex than that of the neutral ones
having the same diphosphine ligand.25 More recent
studies by several research groups established the
reactions involving single and multiple insertion of
alkyne molecules into the Pd-C bond.26-28 Recently, we
reported that dimethyl acetylenedicarboxylate (DMAD)
reacts with 2d in the presence of AgBF4 in acetone or
THF, causing the insertion of three DMAD molecules
into the Pd-C bond, followed by the addition of the
Pd-C bond to a CdC double bond (Scheme 3).29 Maitlis,
Pfeffer, Vicente, and their respective co-workers also
found that similar Pd complexes promote cyclotrimer-
ization of alkynes to give the spirocyclic complexes.24,26,27
The reaction of DMAD with 2d takes place much more
slowly in the absence of AgBF4 to give the product PdI-
(CZdCZ-C6H3Me2-3,5) (bpy) (8) via the single insertion
of DMAD into the Pd-C bond, as reported previously.29
Figure 3 shows the molecular structure of 8 determined
by X-ray crystallography. The distances between H6′ and
I (2.917 and 2.955 Å) imply an electrostatic interaction
similar to that for 2c. Neither 7 nor 8 undergoes further
insertion of DMAD into the Pd-C bond at room tem-
perature. In this study, several reactions were con-
ducted in order to obtain more detailed insights into the
consecutive insertion of DMAD molecules into the Pd-C
bond.
In ser tion of Alk yn e in to th e P d -C Bon d of
Ar ylp a lla d iu m Com p lexes. Single and multiple in-
sertion of alkynes into the Pd-C bond affords various
organopalladium complexes depending on the alkyne
and the supporting ligand bonded to the metal center;
these have been studied in detail since the 1970s.23
Maitlis reported insertion of three alkyne molecules into
the Pd-C or Pd-Cl bond followed by cyclization of the
resulting linear alkyne trimer bonded to the Pd center.24
Clark et al. compared the reactions of alkynes with
The reaction of AgBF4 with 8 in CH3CN converts it
into [Pd(CZdCZ-C6H3Me2-3,5)(bpy)(CH3CN)]BF4 (9-
(25) Clark, H. C.; Milne, C. R. C.; Wong, C. S. J . Organomet. Chem.
1977, 136, 265.
(26) Dupont, J .; Pfeffer, M.; Daran, J .-C.; Gouteron, J . J . Chem. Soc.,
Dalton Trans. 1988, 2421. Maassarani, F.; Pfeffer, M.; Le Borgne, G.
Organometallics 1987, 6, 2043.
(27) Vicente, J .; Saura-Llamas, I.; de Arellano, M. C. R. J . Chem.
Soc., Dalton Trans. 1995, 2529. Vicente, J .; Saura-Llamas, I.; Palin,
M. G.; J ones, P. G. J . Chem. Soc., Dalton Trans. 1995, 2535. Vicente,
J .; Abad, J . A.; Ferna´ndez-de-Bobadilla, R.; J ones, P. G.; Ram´ırez de
Arellano, M. C. Organometallics 1996, 15, 24. Vicente, J .; Abad, J . A.;
Bergs, R.; J ones, P. G.; Ram´ırez de Arellano, M. C. Organometallics
1996, 15, 1422. Vicente, J .; Abad, J . A.; Shaw, K. F.; Gil-Rubio, J .;
Ram´ırez de Arellano, M. C.; J ones, P. G. Organometallics 1997, 16,
4557. Vicente, J .; Abad, J . A.; Mart´ınez-Viviente, E.; Ram´ırez de
Arellano, M. C.; J ones, P. G. Organometallics 2000, 19, 752
(28) LaPointe, A. M.; Brookhart, M. Organometallics 1998, 17, 1530.
(29) Yagyu, T.; Osakada, K.; Brookhart, M. Organometallics 2000,
19, 2125.
(22) Malachowski, M. R.; Carden, J .; Davidson, M. G.; Driessen, W.
L.; Reedijk, J . Inorg. Chim. Acta 1997, 257, 59. See also: Yamamoto,
A. Synlett 2000, 7, 925.
(23) Maitlis, P. M. Acc. Chem. Res. 1976, 9, 93. Maitlis, P. M. J .
Organomet. Chem. 1980, 200, 161. Schore, N. E. Chem. Rev. 1988, 88,
1081.
(24) Roe, D. M.; Calvo, C.; Krishnamachari, N.; Maitlis, P. M. J .
Chem. Soc., Dalton Trans. 1975, 125.

1094 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
to methyl, para, and ortho hydrogens of the 3,5-
dimethylphenyl ligand, respectively. Two OCH3 hydro-
gen signals are observed at δ 3.69 and 3.79. The
multiplets at δ 7.61, 7.68, 8.14, and 8.19 are assigned
to H5, H5′, overlapped signals of H3′ and H4′, and
overlapped signals of H3 and H4 of bpy, respectively. The
doublets due to the H6 and H6′ hydrogens of bpy are
close to each other (δ 8.48 and 8.65), whereas the cor-
responding signals of neutral and cationic aryl com-
plexes 2d and 5d -CH3CN exhibit much larger separa-
tions, approximately 2.0 and 1.0 ppm, respectively.
The 6:1 molar reaction of DMAD with 2d in the
presence of AgBF4 in CH3CN gives [Pd(CZdCZ-CZd
CZ-C6H3Me2-3,5)(bpy)(CH3CN)]BF4 (10-CH3CN) at
room temperature (eq 7). The reaction of DMAD with
F igu r e 3. ORTEP drawing of 8 (50% probability). One of
the two crystallographically independent molecules is
shown. Selected bond lengths (Å) and angles (deg):
Pd1-I1 2.583(1), Pd1-N1 2.10(1), Pd1-N2 2.06(1),
Pd1-C1 2.00(1), I1-Pd1-N1 97.1(3), I1-Pd1-N2
174.1(3), I1-Pd1-C1 88.1(3), N1-Pd1-N2 79.1(4),
N1-Pd1-C1 174.3(5), N2-Pd1-C1 95.5(5).
9-CH3CN in CH3CN gives the same product via the
insertion of a DMAD molecule into the Pd-vinyl bond.
These results suggest the stepwise insertion of DMAD
into the Pd-aryl bond of 5d -CH3CN, converting it into
9-CH3CN and further into 10-CH3CN. The reaction of
excess DMAD with 10-CH3CN does not cause any
further insertion of the alkynes into the Pd-vinyl bond
at room temperature.
The perspective view of 10-CH3CN is presented in
Figure 5. The molecule has a square-planar coordination
around the Pd center and two inserted DMAD units
between the aryl group and palladium center. The cis
geometry of the CdC double bonds of 8 and 10-CH3CN
indicates a cis addition of the Pd-C bond to the CtC
bond of DMAD in the insertion reaction. The aromatic
ring of the C6H3Me2-3,5 group and bpy ligand of 10-
CH3CN are essentially parallel, being separated by a
distance of 3.4 Å. The C13 atom on the aryl group is
located at an apical coordination site of the palladium-
(II) center with a Pd-C distance of 3.417 Å. These
structural parameters, including the interplane distance
which is similar to or shorter than the sum of van der
Waals radii,19 are ascribed to an attractive interaction
between the aryl group of the ligand and the Pd center
or to a π-π stacking between the aryl plane and
bipyridine ligand. The intramolecular interaction of an
organic ligand with the apical coordination site of the
Pd(II) center was suggested in molecular structures of
several organopalladium complexes, such as the di-
enylpalladium(II) complex shown in Chart 4.30 Both this
complex with an agostic interaction and 10-CH3CN in
this study have an organic ligand containing a -CZd
F igu r e 4. 1H NMR spectra of (a) 9-CH3CN and (b) 10-
CH3CN in CD3CN (400 MHz).
1
CH3CN) quantitatively (eq 6). Figure 4a shows the H
NMR spectrum of 9-CH3CN in CD3CN. All the signals
are at reasonable positions for the structure as described
below. The singlets at δ 2.07, 6.75, and 7.17 are assigned

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1095
(bpy)(acetone)]BF4 (10-acetone) and further insertion of
DMAD into the Pd-vinyl bond, but isolation of the
intermediate 10-acetone was prevented by a smooth
reaction of DMAD with the complex giving 7. In contrast
with the above results, a similar reaction of 9-CH3CN
leads to the isolation of 10-CH3CN, which does not
undergo further insertion of DMAD into the Pd-vinyl
bond.
The reaction of phenylallene with 2d in the presence
of AgBF4 in acetone leads to the insertion of a CdC
double bond into the Pd-aryl bond to give the π-al-
lylpalladium complex [Pd{η3-CH2C(C6H3Me2-3,5)CHPh}-
(bpy)]BF4 (11), as shown in eq 8. A single insertion of
F igu r e 5. ORTEP drawing of 10-CH3CN (50% prob-
-
ability). BF4 anion is omitted for clarity. Selected bond
lengths (Å) and angles (deg): Pd-N1 2.07(2), Pd-N2
2.01(2), Pd-N3 1.96(2), Pd-C1 2.05(2), N1-Pd-N2
81.3(7), N1-Pd-N3 94.4(8), N1-Pd-C1 173.1(7), N2-Pd-
N3 172.9(8), N2-Pd-C1 97.7(7), N3-Pd-C1 87.2(8).
Ch a r t 4
CZ-CZdCZ- moiety with a cis geometry of two CdC
double bonds and the single-bond cis structure. This
situation seems to make the intramolecular interaction
between the tethered organic ligand and the Pd center
easy.
allenes into the Pd-C bond has been reported to give
π-allylpalladium complexes,31 although several Pd com-
plexes catalyze the polymerization of allenes via mul-
tiple insertion of allenes into the Pd-C bond.32 Complex
11 does not undergo further insertion of allene into the
Pd-π-allyl bond.
Figure 6 depicts the crystallographically determined
molecular structure of 11 having a square-planar coor-
dination with bipyridine and π-allyl ligands bonded to
the Pd center.33 Both of the two crystallographically
independent molecules contain the syn-oriented phenyl
substituent on the π-allyl ligand. The 1H NMR spectrum
of 11 indicates the presence of two isomeric forms in
approximately 2:1 molar ratio in solution. The major
isomer exhibits the 1H NMR signals of π-allyl hydrogens
at δ 4.20, 4.48, and 5.17, while the corresponding signals
The 1H and 13C NMR spectra of 10-CH3CN in
CD3CN at room temperature indicate the presence of
1
four different OCH3 groups (Figure 4b). The H NMR
signal of the ortho phenyl hydrogens of 3,5-dimeth-
ylphenyl ligand is observed at δ 6.75, which is at a
higher magnetic field than 9-CH3CN (δ 7.17) by 0.4
ppm. The large shift of the signal can be ascribed to the
presence of interactions between the 3,5-dimethylphenyl
ligand and the Pd center or the bipyridine ligand in the
solution.
Scheme 4 summarizes insertion reactions of DMAD
into the Pd-aryl bond of neutral or cationic arylpalla-
dium complexes for forming various insertion products.
The iodo ligand of 8 and the CH3CN ligand of 10-
CH3CN block further migratory insertion of DMAD into
the Pd-C bond, while the reactions of DMAD with 2d
and with 9-CH3CN give the respective insertion prod-
ucts under similar conditions. An acetone-coordinated
vinylpalladium complex, [Pd(CZdCZ-C6H3Me2-3,5)-
(bpy)(acetone)]BF4 (9-acetone), was prepared from the
reaction of AgBF4 with 8 in acetone and characterized
by NMR spectroscopy.29 Addition of DMAD to 9-acetone
caused a smooth insertion of two alkyne molecules into
the Pd-C bond to give 7. The reaction probably involves
the formation of [Pd(CZdCZ-CZdCZ-C6H3Me2-3,5)-
(31) Powell, P. Synthesis of η3-Allyl Complexes. In The Chemistry
of the Metal-Carbon Bond; Hartley, F. R., Patai, S. Eds.; Wiley: New
York, 1982; pp 355-357. Deeming, A. J .; J ohnson, B. F. G.; Lewis, J .
J . Chem. Soc., D 1970, 598. Chisholm, M. H.; J ohns, W. S. Inorg. Chem.
1975, 14, 1189. Stevens, R. R.; Shier, G. D. J . Organomet. Chem. 1970,
21, 495. Hughes, R. P.; Powell, J . J . Organomet. Chem. 1972, 34, C51.
Hughes, R. P.; Powell, J . J . Organomet. Chem. 1973, 60, 409. May, C.
J .; Powell, J . J . Organomet. Chem. 1980, 184, 385.
(32) Ghalamkar-Moazzam, M.; J acobs, T. L. J . Polym. Sci., Polym.
Chem. Ed. 1978, 16, 615. Ru¨lke, R. E.; Kliphuis, D.; Elsevier: C. J .;
Fraanje, J .; Goubitz, K.; van Leeuwen, P. W. N. M.; Vrieze, K. J . Chem.
Soc., Chem. Commun. 1994, 1817. Tomita, I.; Kondo, Y.; Takagi, K.;
Endo, T. Macromolecules 1994, 27, 4413. Tomita, I.;. Kondo, Y.; Takagi,
K.; Endo, T. Acta Polym. 1995, 46, 432. Tomita, I.; Abe, T.; Takagi,
K.; Endo, T. J . Polym. Sci., Part A: Polym. Chem. 1995, 33, 2487. Delis,
J . G. P.; Groen, J . H.; Vrieze, K.; van Leeuwen, P. W. N. M.
Organometallics 1997, 16, 551. Takagi, K.; Tomita, I.; Nakamura, Y.;
Endo, T. Macromolecules 1998, 31, 2779.
(30) Roe, D. M.; Bailey, P. M.; Moseley, K.; Maitlis, P. M. J . Chem.
Soc., Chem. Commun. 1972, 1273. See also: Brookhart, M.; Green,
M. L. H. J . Organomet. Chem. 1983, 250, 395.
(33) Cationic π-allylpalladium complexes with a chelating py-
ridinepyrazole ligand have been reported recently. See: Satake, A.;
Nakata, T. J . Am. Chem. Soc. 1998, 120, 10391.

1096 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
Sch em e 4
Sch em e 5
oriented substituent is smaller than that observed in
most 1-substituted π-allylpalladium complexes which
exist in the form with the syn substituent exclusively
in solution.34 Steric repulsion between the Ph group at
the syn position and the 3,5-dimethylphenyl group at
the central carbon of the π-allyl ligand seems to desta-
bilize the syn isomer of 11 and makes differences in the
relative stability between the syn and anti isomers
small.
F igu r e 6. ORTEP drawing of 11 (50% probability). One
of the two crystallographically independent molecules is
-
shown. BF4 anion is omitted for clarity. Selected bond
lengths (Å) and angles (deg): Pd1-N1 2.11(2), Pd1-N2
2.13(2), Pd1-C1 2.05(3), Pd1-C2 2.17(3), Pd1-C3
2.14(3), N1-Pd1-N2 76(1), N1-Pd1-C1 173(1),
N1-Pd1-C2 138(1), N1-Pd1-C3 106(1), N2-Pd1-C1
109(1), N2-Pd1-C2 139(1), N2-Pd1-C3 174(1), C1-Pd1-
C2 39(1), C1-Pd1-C3 68(1), C2-Pd1-C3 42(1).
Discu ssion
The cationic arylpalladium complexes with chelating
2,2′-bipyridine or 4,4′-dimethyl-2,2′-bipyridine ligands
obtained in this study undergo intermolecular coupling
of the aryl ligands when a coordination site is occupied
by a labile acetone or THF ligand. On the other hand,
the neutral iodo(aryl)palladium complexes with the
bpy ligand and previously reported trans-[PdAr(PR3)2-
(solv)]+ 6 do not cause biaryl formation. Scheme 5 depicts
a plausible pathway for the above coupling reaction
involving intermolecular aryl ligand transfer to give
of the minor isomer are observed at δ 4.36, 4.87, and
6.83. The signals at δ 5.17 and 6.83 are at lower
magnetic field than the others and are assigned to the
CH-Ph hydrogen of the π-allyl ligand. The former
signal is at a higher position than the latter and is
assigned to the hydrogen at the anti position of the
isomer containing a syn-orientated Ph substituent. The
latter signal of the minor complex is due to the CHPh
hydrogen of the π-allyl ligand with an anti-orientated
phenyl substituent. Since dissolution of crystals of a
single isomer with a syn phenyl substituent of the
π-allyl ligand results in the existence of a mixture of
the isomers, the isomerization takes place rapidly in
solution via a η1-allylpalladium intermediate. The 2:1
ratio of the two isomers containing a syn- or anti-
(34) Isolation or observation of 1-aryl-η3-allylpalladium complex with
anti-orientated substituents of the allyl ligand is rare but found in
the literature. See: Ohta, T.; Hosokawa, T.; Murahashi, S.; Miki, K.;
Kasai, N. Organometallics 1985, 4, 2080. Osakada, K.; Chiba, T.;
Nakamura, Y.; Yamamoto, T.; Yamamoto, A. Organometallics 1989,
8, 2602.

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1097
Sch em e 6
complexes results in isolation of the one-electron oxida-
tion products containing Ni(I) and Ni(III) centers,
respectively.40 Ozawa and Yamamoto et al. observed
smooth aryl ligand transfer in the reaction of iodo(aryl)-
palladium with methyl(aryl)palladium complexes to give
the coupling products at room temperature (Scheme
6(ii)).41 The reaction probably involves initial dissocia-
tion of a phosphine ligand to give a three-coordinate Pd-
(II) complex which is susceptible to aryl ligand transfer
from the four-coordinate arylpalladium complex. Es-
pinet et al. designed Pd complexes having both polyha-
logeno aryl ligands and tht (tetrahydrothiophene) aux-
iliary ligands and achieved reversible conproportionation
and disproportionation shown in Scheme 6(iii).42 The Cl
and F substituents on the aryl ligands stabilize the
Pd-C bond and prevent intramolecular or intermolecu-
lar reductive elimination of biaryls during the reaction.
The aryl ligand transfer in Scheme 6(ii) and (iii) was
proposed to involve a dinuclear intermediate with a
bridging aryl ligand coordinated to two square-planar
Pd(II) centers. An initial dissociation of a neutral ligand
is requisite in the formation of such intermediate com-
plexes in aryl ligand transfer. Several transition metal
complexes with bridging aryl ligands were isolated and
structurally characterized.43 Very recently, Grushin
found that heating of [Pd(Ph)I(PPh3)2] caused formation
of biphenyl, but it is ascribed to the initial reductive
elimination of PPh4I and ensuing coupling of Ph groups
bonded to Pd and bonded to P centers (Scheme 6(iv)).44
AgBF4-promoted conversion of [PdI(Ar)(bpy)] to the
cationic complexes shown in this study triggers a new
type of transmetalation of the aryl ligand. A plausible
mechanism of the facile aryl ligand transfer of the
cationic complex is illustrated in Scheme 7. Mono-
nuclear cationic arylpalladium complexes dimerize eas-
ily to form dinuclear intermediate Pd complexes with
bridging aryl ligands accompanied by a loss of a solvent
ligand. Cleavage of a Pd-C bond of the bridging aryl
ligand leads to formation of the diarylpalladium complex
with a bpy ligand or regeneration of the initial cationic
arylpalladium complex. The transmetalation is pro-
moted by the subsequent irreversible reductive elimina-
tion of biaryl from the diarylpalladium complex with a
cis structure.
diarylpalladium complexes that is responsible for the
reductive elimination of the product. Results of previous
experimental and theoretical studies indicated that
reductive elimination of biaryl from cis diaryl complexes
of group 10 metals takes place much more easily than
the corresponding reductive elimination of alkanes from
similar dialkyl complexes.35 The disproportionation
shown in Scheme 5, therefore, induces smooth intramo-
lecular coupling of the aryl ligands of the resulting cis-
diarylpalladium complex. Based on this mechanism, the
rate-determining step of the reactions in Scheme 5
exists in the disproportionation via intermolecular aryl
ligand transfer. An alternative pathway involving direct
reductive elimination of biaryl from two arylpalladium
complex molecules is less plausible than the above
mechanism. Since coupling of two organic ligands
bonded to the two metal centers of dinuclear transition
metal complexes is quite rare36 and is unfavorable
according to results of the theoretical calculations,37 the
direct reductive elimination of biaryl from two aryl
complexes would be even slower.
Several neutral nickel and palladium complexes were
reported to undergo intermolecular aryl ligand transfer
as summarized in Scheme 6. Earlier work by Kochi et
al. established biaryl formation from monoarylnickel-
(II) complexes with PEt3 ligands via Ni(I) and Ni(III)
intermediates (Scheme 6(i)); the reaction of Ar-Br with
[NiAr(Br)(PEt3)2] at elevated temperature causes ex-
change of the aryl ligand and/or coupling of the aryl
groups. The initially formed five-coordinate Ni(III)
intermediate [NiArBr2(PEt3)2] undergoes aryl ligand
exchange with the Ni(II) complex [NiArBr(PEt3)2] to
give [NiAr2Br(PEt3)2], which readily causes reductive
elimination of biaryl.38 Amatore et al. reported the
electrochemical oxidation of arylnickel(II) complexes
leading to biaryl formation.39 Eventually, chemical and
electrochemical oxidation of several Ni(0) and Ni(II)
Similar disproportionation type transmetalation of
trans-[PdAr(PR3)2(solv)]+ appears to occur much less
(39) Amatore, C.; J utand, A. Organometallics 1988, 7, 2203. Ama-
tore, C.; J utand, A.; Mottier, L. J . Electroanal. Chem. 1991, 306, 125.
See also: Amatore, C.; J utand, A. J . Am. Chem. Soc. 1991, 113, 2819.
(40) Oguro, K.; Wada, M.; Sonoda, N. J . Organomet. Chem. 1979,
165, C10. Schiavon, G.; Bontempelli, G.; Corain, B. J . Chem. Soc.,
Dalton Trans. 1981, 1074. van de Kuil, L. A.; Grove, D. M.; Gossage,
R. A. Zwikker, J . W.; J enneskens, L. W.; Drenth, W.; van Koten, G.
Organometallics 1997, 16, 4985. Gossage, R. A.; van de Kuil, L. A.;
van Koten, G. Acc. Chem. Res. 1998, 31, 423.
(41) Ozawa, F.; Fujimori, M.; Yamamoto, T.; Yamamoto, A. Orga-
nometallics 1986, 5, 2144. Ozawa, F.; Hidaka, T.; Yamamoto, T.;
Yamamoto, A. J . Organomet. Chem. 1987, 330, 253. Ozawa, F.;
Kurihara, K.; Fujimori, M.; Hidaka, T.; Toyoshima, T.; Yamamoto, A.
Organometallics 1989, 8, 180.
(35) Braterman, P. S.; Cross, R. J .; Young, G. B. J . Chem. Soc.,
Dalton Trans. 1977, 1892. Komiya, S.; Abe, Y.; Yamamoto, A.;
Yamamoto, T. Organometallics 1983, 2, 1466. Low, J . J .; Goddard, W.
A., III. J . Am. Chem. Soc. 1984, 106, 6928 and 8321.
(36) Motyl, K. M.; Norton, J . R.; Schauer, C. K.; Anderson, O. P. J .
Am. Chem. Soc. 1982, 104, 7325. Chetcuti, M. J .; Chisholm, M. H.;
Folting, K.; Haitko, D. A.; Huffman, J . C. J . Am. Chem. Soc. 1982,
104, 2138.
(42) Casado, A. L.; Casares, J . A.; Espinet, P. Organometallics 1997,
16, 5730. Casado, A. L.; Espinet, P. Organometallics 1998, 17, 3677.
(43) Park, J . W.; Henling, L. M.; Schaefer, W. P.; Grubbs, R. H.
Organometallics 1991, 10, 171. Dickson, R. S.; Fallon, C. D.; Zhang,
Q.-Q. J . Chem. Soc., Dalton Trans. 2000, 1973. See also: Krueger, C.;
Sekutowski, J . C.; Berker, H.; Hoffmann, R. Z. Naturforsch. 1978, 33B
1110. Osakada, K.; Koizumi T.; Yamamoto, T. Angew. Chem., Int. Ed.
Engl. 1998, 37, 349. Koizumi, T.; Osakada K.; Yamamoto, T. Organo-
metallics 1998, 17, 5721.
(37) Trinquier, G.; Hoffmann, R. Organometallics 1984, 3, 370.
(38) Tsou, T. T.; Kochi, J . K. J . Am. Chem. Soc. 1979, 101, 7547.
(44) Grushin, V. V. Organometallics 2000, 19, 1888.

1098 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
Sch em e 7
Sch em e 8
Sch em e 9
smoothly than the bpy-coordinated complex. It may be
due to lower thermodynamic stability of the products
trans-[PdAr2(PR3)2] and [Pd(PR3)2(solv)2]2+ than the
starting monocationic complex or due to difficult direct
coupling of the aryl ligands of the resulting trans-[PdAr2-
(PR3)2]. The complexes with a tmeda ligand also form
no biaryls. Tmeda with a higher basicity than bpy and
Me2bpy may destabilize the bridging coordination of the
aryl ligand to the two Pd centers in the reaction.
Cationic methylpalladium complexes with bipyridine
or related diimine ligands are stable in solution, al-
though analogous arylpalladium complexes in this study
tend to cause intermolecular aryl ligand transfer. On
the other hand, neutral arylpalladium complexes, trans-
[PdAr(CtCPh)(PR3)2] and trans-[PdAr′(I)(PR′3)2], un-
dergo selective intermolecular alkynyl ligand transfer
without transmetalation of the aryl ligand.18,45 These
results seem to suggest the order of reactivity of the
metal-carbon bonds toward intermolecular transfer of
the organic ligands, M-CtCR > M-Ar > and M-R,
which is opposite of that expected from relative ther-
modynamic stability of transition metal-carbon bonds
in the order M-CtCR > M-Ar > and M-R.46
Scheme 8 illustrates plausible intermediate complexes
of transmetalation of aryl and methyl complexes of
transition metals schematically. The intermolecular aryl
ligand transfer involves the intermediate dinuclear
complex with a bridging aryl ligand. Since the bridging
coordination of the aryl group is partly stabilized by
π-orbitals of the ligand, it is more stable than the
bridging methyl coordination with a hypervalent carbon
center. Thus, the low stability of the intermediate
complex with a bridging methyl ligand hampers smooth
transmetalation of the cationic methylpalladium com-
plexes.
The mechanism of biaryl formation from monoarylpal-
ladium complexes shown in Scheme 7 is related to the
previously reported coupling of bromoarene promoted
by Ni(cod)2 in the presence of the bipyridine ligand in
DMF giving biaryls.47 Second-order kinetics of the
reaction with respect to the concentration of Ni(II)
complexes and negligible aryl ligand exchange with
bromoarene added to the reaction mixture indicate that
a pathway involving disproportionation of [NiBr(Ar)-
(bpy)] gives [NiAr2(bpy)], which releases biaryl product
as shown in Scheme 9. A similar reaction in toluene
occurs much more gradually and is accompanied by aryl
group migration between the Ni complex and bro-
moarene, indicating another mechanism probably in-
volving the Ni(I) and Ni(III) intermediates similarly to
the reactions reported by Kochi et al.38 The major role
of DMF in this reaction is to promote initial dissociation
of the bromo ligand to form a cationic arylnickel
intermediate, which induces subsequent intermolecular
aryl ligand transfer. Ishiguro et al. previously reported
that a Br ligand of [NiBr2(bpy)2] is dissociated in DMF
to form a stable cationic Ni complex in the solution on
the basis of calorimetric measurements.48 Aryl ligand
transmetalation of [PdI(Ar)(bpy)] requires addition of
AgBF4 to generate the dinuclear intermediate with a
bridging aryl ligand smoothly, while [NiAr(Br)(bpy)]
appears to undergo dissociation of the bromo ligand
upon dissolving it in DMF.
Milstein et al. reported the reaction of norbornene
with [PdCl(Ph)(P-P)] (P-P ) bis(diisopropylphosphi-
(45) Osakada, K.; Hamada, M.; Yamamoto, T. Organometallics 2000,
19, 458. Osakada, K.; Yamamoto, T. Rev. Heteroat. Chem. 1999, 21,
163.
(46) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw,
J . E. J . Am. Chem. Soc. 1987, 109, 1444.
(47) Yamamoto, T.; Wakabayashi, S.; Osakada, K. J . Organomet.
Chem. 1992, 428, 223. Osakada, K.; Sato, R.; Yamamoto, T. Organo-
metallics 1994, 13, 4645. Osakada, K.; Yamamoto, T. Coord. Chem.
Rev. 2000, 198, 379.
(48) Ishiguro, S.; Ozutsumi, K. Bull. Chem. Soc. J pn. 1989, 62, 2392.

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1099
Sch em e 10
no)propane) in DMF to give a mixture of phenylnorbor-
nane, [PdCl2(P-P)], and [Pd(norbornene)(P-P)].49 They
attributed the remarkable dependence of the reaction
on the solvents (DMF . dioxane) to the initial formation
of cationic species, [PdPh(P-P)(norbornene)]Cl, followed
by insertion of the CdC double bond into the Pd-Ph
bond. Formation of the two Pd complexes is due to
disproportionation type Cl ligand transfer from [PdCl-
(H)(P-P)]. In this case, intermolecular coupling of the
Ph ligand was preceded by the insertion of norbornene
to the Pd-Ph bond of the cationic phenylpalladium
complex.
Scheme 10 depicts a plausible pathway for the coor-
dination-insertion process of DMAD into the cationic
arylpalladium complex, involving rapid and reversible
exchange of the solvent molecule with DMAD to give
an intermediate with π-coordinated DMAD and the
insertion of the π-coordinated DMAD into the Pd-C
bond. The kind of solvent coordinated to the metal
center in the starting complex affects the equilibrium
between the starting and intermediate complexes. CH3-
CN is bonded to Pd firmly and is replaced with DMAD
to a much smaller degree than acetone or THF ligand.
Since the subsequent insertion process is not influenced
by the solvent, insertion of DMAD into the Pd-C bond
of the cationic arylpalladium complex with an acetone
ligand takes place more easily than the corresponding
CH3CN-coordinated complex. Eventually, insertion of
DMAD into the Pd-C bond of 10-CH3CN in CH3CN is
effectively suppressed, whereas the reaction of DMAD
with 9-acetone gives 7 via formation of [Pd(CZdCZ-
CZdCZ-Ar)(acetone)(bpy)]+ and the insertion of DMAD
into the Pd-C bond of it.
complexes (Scheme 10),50 lower reactivity of the inser-
tion of 8 than the cationic complexes could be ascribed
to thermodynamically unfavorable displacement of the
iodo ligand with π-coordinated DMAD. The degree of
donor properties in the order I > CH3CN > acetone is
directly related to the equilibrium between the starting
cationic complex and the intermediate with the π-coor-
dinated DMAD. Since complex 2d reacts with DMAD
to give the insertion product, 8, the reaction is controlled
not only by the ligand that will be replaced with DMAD
prior to insertion but also by the organic ligand attached
to the Pd center. The controlled insertion reactions of
DMAD into the Pd-C bond of various organopalladium
complexes in this study have been attained by choosing
a ligand that dominates the equilibrium to generate the
DMAD-coordinated intermediates prior to the insertion.
Con clu sion
Isolation of cationic arylpalladium complexes with a
cis coordination imposed by chelating bipyridine ligands
has long been of interest in this field because of its
relevance to synthetic organic reactions using Pd com-
plexes as a catalyst. Choosing a proper aryl group and
solvent ligand enabled isolation and characterization of
several [Pd(Ar)(N-N)(solv)]+ complexes. The intermo-
lecular coupling of the aryl ligand of the cationic
arylpalladium complexes with a chelating bpy ligand
is the main degradation pathway of the complexes and
provides the reason for their lower stability in solution
than the corresponding methylpalladium complexes.
The labile solvent ligand serves to facilitate the initial
intermolecular aryl ligand transfer to give cis-diarylpal-
ladium complexes which are ready to release coupling
products. The cationic arylpalladium complexes [Pd(Ar)-
(bpy)(solv)]+ also exhibit a high reactivity toward inser-
tion of alkynes into the Pd-aryl bond. The kind of
organic ligands bonded to the metal center and of
solvents used influence the reaction significantly. The
coupling and insertion reactions of organopalladium
complexes shown in this study are probably related not
only to synthetic organic reactions promoted by cationic
Pd complexes but also to those by noncationic Pd
complexes in polar solvents.
Complexes 5d -CH3CN and [Pd(C6H3Me2-3,5)(bpy)-
(acetone)]BF4, generated in situ from the addition of
AgBF4 to 2d in acetone, exhibit a significantly different
reactivity toward the disproportionation type trans-
metalation shown in Scheme 7. The former complex
keeps its purity for 1 h at room temperature in
CD3CN, but the reaction of AgBF4 with 2d in acetone
and dissolution of 5d -CH3CN in acetone cause rapid
decomposition of the complex accompanied by liberation
of the biaryl product once it is formed via [Pd(C6H3Me2-
3,5)(bpy)(acetone)]BF4. These complexes, however, react
readily with DMAD to give 10-CH3CN and 7, respec-
tively.
Exp er im en ta l Section
The insertion of alkynes into the Pd-C bond of neu-
tral iodo(aryl)palladium complexes is slower than that
of the corresponding cationic complexes. Complex 8 does
not undergo insertion of DMAD at all, whereas the
cationic complexes 9-CH3CN and 9-acetone are suscep-
tible to insertion. Provided that insertion of DMAD into
the Pd-C bond of the neutral complexes, [PdI(Ar)(bpy)],
would proceed in a similar pathway to the cationic
Gen er a l Con sid er a tion , Mea su r em en t, a n d Ma ter ia ls.
Manipulations of the palladium complexes were carried out
under nitrogen or argon using standard Schlenk techniques.
(50) A previous report that demonstrates isolation of a Pt complex
with a five-coordinate structure having π-coordinated DMAD to the
Pt center suggests a possible associative insertion via a stable five-
coordinate intermediate. See: De Felice, V.; De Renzi, A.; Giordano,
F.; Tesauro, D. J . Chem. Soc., Dalton Trans. 1993, 1927. The details
of exchange between the solvent and DMAD, however, are not directly
related to the different reactivity between the CH3CN-coordinated
complex and acetone or the THF-coordinated complexes toward alkyne
insertion into the Pd-C bond.
(49) Portnoy, M.; Ben-David, Y.; Rousso, I.; Milstein, D. Organo-
metallics 1994, 13, 3465.

1100 Organometallics, Vol. 20, No. 6, 2001
Yagyu et al.
Solvents were purified in usual manners and stored under
the cationic complex. The 1H NMR spectrum in dry THF-d8
indicated that it contained the complex partly free from the
coordinated solvent. Anal. Calcd for C22H19BF10N2OPd: C,
41.64; H, 3.02; N, 4.41. Found: C, 39.52; H, 3.47; N, 4.37.
Disagreement of the analyses may be ascribed to the partial
loss of the coordinated solvent during the purification proce-
dure.
P r epar ation of [P d(C6H3Me2-3,5)(bpy)(CH3CN)]BF4 (5d-
CH3CN). To a suspension of [PdI{C6H3Me2-3,5}(bpy)] (225 mg,
0.46 mmol) in dry CH3CN (10 mL) was added dropwise a CH3-
CN solution of AgBF4 (ca. 0.5 M) with stirring at 0 °C until no
formation of AgI was observed. After stirring for 1 min at 0
°C, the precipitated AgI was removed by filtration. Solvent was
evaporated under vacuum to give 5d -CH3CN (218 mg, 0.44
mmol, 96%) as an off-white solid. This complex is stable for 1
h in CD3CN at room temperature as monitored by the 1H NMR
spectrum.
argon. Pd(dba)2 and [PdI(Ar)(N-N)] (1a -3d )17,18 were pre-
51
pared as described before. The other chemicals were com-
mercially available. NMR spectra (1H, 13C{1H}, 1H-1H COSY,
and 1H-13C{1H} COSY) were recorded on J EOL EX-400 and
Varian MERCURY300 spectrometers. Elemental analyses
were carried out with a Yanaco MT-5 CHN autocorder.
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(tm ed a )(CH3CN)]-
BF 4 (4c-CH3CN). To a suspension of [PdI{C6H3(CF3)2-3,5}-
(tmeda)] (261 mg, 0.46 mmol) in dry CH3CN (1.5 mL) was
added dropwise a CH3CN solution of AgBF4 (ca. 0.5 M) with
stirring until no generation of AgI was observed. After further
stirring of the solution for 1 min at room temperature, the
precipitated AgI was removed by filtration. Addition of Et2O
(50 mL) to the filtrate caused separation of 4c-CH3CN as an
off-white air-stable solid, which was collected by filtration and
1
dried under vacuum (192 mg, 0.34 mmol, 74%). The H NMR
spectrum of the complex in CD3CN did not change for 5 days
at room temperature.
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(Me2bp y)(CH3CN)]-
BF 4 (6c-CH3CN). The cationic complex 6c-CH3CN was pre-
pared by a procedure similar to that for 4c-CH3CN, using
[PdI{C6H3(CF3)2-3,5}(Me2bpy)] (364 mg, 0.58 mmol) as the
starting material. The product (191 mg, 0.30 mmol, 51%) was
obtained as an off-white air-stable solid. This complex is stable
in CD3CN for a month at room temperature.
Rea ction of 5d -CH3CN in Aceton e-d 6. 5d -CH3CN (6.0
mg, 12 µmol) was placed into an NMR tube containing 0.60
mL of acetone-d6. As soon as the complex was dissolved, a black
solid precipitate was observed. Formation of 3,3′,5,5′-tetra-
methylbiphenyl was noted in the 1H NMR spectrum and
GC-MS. The yield of biaryl was estimated to be 25% (1.5 µmol)
based on the peak area of para and ortho phenyl protons of
biaryl compared with those of the complex.
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(tm ed a )(a ceton e)]-
BF 4 (4c-a ceton e). To a suspension of [PdI{C6H3(CF3)2-3,5}-
(tmeda)] (257 mg, 0.46 mmol) in dry acetone (4 mL) was added
dropwise an acetone solution of AgBF4 (ca. 0.8 M) with stirring
until no generation of AgI was observed. After further stirring
the mixture for 1 min at room temperature, the precipitated
AgI was removed by filtration. Solvent was evaporated under
vacuum to give 4c-acetone as a desiccated frothy off-white
solid. Although the 1H NMR spectrum of an acetone-d6 solution
of the complex indicated the proposed structure, its isolation
was not feasible due to the high deliquesency.
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(bp y)(CH3CN)]BF 4
(5c-CH3CN). The cationic complex 5c-CH3CN was prepared
by a procedure similar to that for 4c-CH3CN, using [PdI{C6H3-
(CF3)2-3,5}(bpy)] (573 mg, 0.95 mmol) as the starting material.
The product 5c-CH3CN was obtained as an off-white air-stable
solid (439 mg, 0.71 mmol, 75%) and did not change its 1H NMR
spectrum in CD3CN for 24 h at room temperature.
Rea ction s of AgBF 4 w ith [P d I(Ar )(N-N)]. A typical
procedure for the reactions of AgBF4 with [PdI(Ar)(N-N)] is
as follows. To a mixture of [PdI(Ar)(N-N)] (0.2-0.3 mmol) and
two times molar AgBF4 was added dry solvent (10 mL) with
stirring at room temperature. After stirring the mixture for
-
the prescribed time, excess NaI to BF4 anion (ca. 2:1) was
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(bp y)(a ceton e)]BF 4
(5c-a ceton e). To a suspension of [PdI{C6H3(CF3)2-3,5}(bpy)]
(784 mg, 1.3 mmol) in dry acetone (3 mL) was added dropwise
an acetone solution of AgBF4 (ca. 0.8 M) with stirring until no
generation of AgI was observed. After further stirring of the
solution for 1 min at room temperature, the precipitated AgI
was removed by filtration. Addition of hexane (50 mL) to the
filtrate caused separation of an off-white solid, which was
collected by filtration and dried under vacuum. The obtained
complex was kept for a few days at room temperature and then
dissolved in a minimum amount of acetone. After removing
insoluble Ag and Ag salts by filtration, hexane was added to
added to the solution to quench the cationic or coordinatively
unsaturated organopalladium complexes and stop the reaction.
The resulting insoluble solid was removed by filtration,
followed by extraction of the organic products with Et2O. The
products contained in the combined filtrate and extracts were
1
analyzed by H NMR and GC-MS spectra. The spectroscopic
data from the biaryl products were compared with the au-
thentic compounds, and their yields were estimated based on
1
the H NMR peak area relative to those of mesitylene added
to the solution as an internal standard. The results obtained
for the reactions conducted are summarized in Table 4.
P r epar ation of[P d{CZdCZ(C6H3Me2-3,5)}(bpy)(CH3CN)]-
BF 4 (9-CH3CN). A CH3CN solution of AgBF4 (ca. 0.5 M) was
added dropwise to a solution of 8 (102 mg, 0.16 mmol) in dry
CH3CN (6 mL) with stirring until no generation of AgI was
observed. The mixture was stirred for 5 min at room temper-
ature, and the precipitated AgI was removed by filtration.
Addition of Et2O (50 mL) to the filtrate yielded an off-white
solid, which was collected by filtration and dried under vacuum
to give 9-CH3CN (95 mg, 0.15 mmol, 94%). This complex is
stable in CD3CN for 5 days at room temperature. 1H NMR
(400 MHz, CD3CN): δ 1.95 (s, CH3CN), 2.07 (s, 6H, CH3C6H3),
3.69 (s, 3H, OCH3), 3.79 (s, 3H, OCH3), 6.75 (s, 1H, p-C6H2H),
7.17 (s, 2H, o-C6H2H), 7.61 (m, 1H, H5-bpy), 7.68 (m, 1H, H5′-
bpy), 8.14 (m, 2H, H3′, H4′-bpy), 8.19 (m, 2H, H3, H4-bpy), 8.48
(d, 1H, H6-bpy, J ) 5.4 Hz), 8.65 (d, 1H, H6′-bpy, J ) 5.4 Hz).
13C{1H} NMR (100 MHz, CD3CN): δ 21.2 (CH3C6H3), 52.6
(OCH3), 52.8 (OCH3), 124.3 (C3-bpy), 124.6 (C3′-bpy), 128.2 (o-
C6H3), 128.7 (C5, C5′-bpy), 130.1 (p-C6H3), 137.5, 138.6, 140.1,
142.4 (C4-bpy), 142.5 (C4′-bpy), 150.6 (C6-bpy), 153.9 (C6′-bpy),
154.5, 157.4, 164.6, 171.7.
1
the filtrate to give the cationic complex. The H NMR spectra
of the obtained complex in dry THF-d8 and acetone-d6 indi-
cated that it contained the complex free from the coordinated
solvent. Anal. Calcd for C21H17BF10N2OPd: C, 40.64; H, 2.76;
N, 4.51. Found: C, 39.52; H, 2.90; N, 4.59. Disagreement of
the analyses may be ascribed to the partial loss of the
coordinated solvent during the purification procedure.
P r ep a r a tion of [P d {C6H3(CF 3)2-3,5}(bp y)(th f)]BF 4 (5c-
THF ). To a suspension of [PdI{C6H3(CF3)2-3,5}(bpy)] (535 mg,
0.89 mmol) in dry THF (5 mL) was added dropwise a THF
solution of AgBF4 (ca. 0.6 M) with stirring until no generation
of AgI was observed. After further stirring of the solution for
1 min at room temperature, the precipitated AgI was removed
by filtration. Addition of hexane (50 mL) to the filtrate caused
separation of an off-white solid, which was collected by
filtration and dried in vacuo. The obtained complex was kept
for a few days at room temperature and then dissolved in a
minimum amount of THF. After removing insoluble Ag and
Ag salts by filtration, hexane was added to the filtrate to give
P r epar ation of [P d {CZdCZCZdCZ(C6H3Me2-3,5)}(bpy)-
(CH3CN)]BF 4 (10-CH3CN). To a dry CH3CN (10 mL) solution
(51) Ukai, T.; Kawazura, H.; Ishii, Y. Bonnet, J . J .; Ibers, J . A. J .
Organomet. Chem. 1974, 65, 253.

Cationic Arylpalladium Complexes
Organometallics, Vol. 20, No. 6, 2001 1101
Ta ble 5. Cr ysta llogr a p h ic Da ta of th e P a lla d iu m (II) Com p lexes
1c
2c
8
10-CH3CN
11
chemical formula
C
14H19N2PdF6I
C18H11N2PdF6I
C24H23O4N2PdI
•0.5C3H6O
665.80
C32H32O8N3PdBF4
C27H25N2PdBF4
fw
562.61
602.59
779.82
570.71
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21/c (No14)
15.439(4)
8.351(3)
15.991(4)
114.58(2)
1874.9(9)
4
monoclinic
P21/c (No14)
13.562(2)
8.785(1)
16.994(2)
109.732(8)
1905.9(5)
4
monoclinic
P21/n (No14)
16.058(2)
17.219(3)
19.315(3)
100.20(1)
5256(1)
monoclinic
P21/c (No14)
7.629(1)
22.120(7)
20.788(7)
91.77(2)
3506(1)
4
monoclinic
P21/c (No14)
10.809(2)
21.999(4)
26.211(3)
98.76(1)
6160(2)
8
â, deg
V, Å3
Z
8
µ, cm-1
F(000)
26.92
1080
1.993
26.57
1144
2.100
19.16
2624
1.683
6.03
1584
1.477
6.42
2304
1.231
D
calcd, g cm-3
cryst size, mm
2θ range, deg
no. of unique reflns
no. of reflns used
(I>3.0σ(I))
0.40 × 0.11 × 0.09
5.0-55.0
4601
0.50 × 0.38 × 0.06
5.0-55.0
4674
0.38 × 0.25 × 0.10
5.0-55.0
12 477
0.30 × 0.30 × 0.30
5.0-55.0
8241
0.75 × 0.20 × 0.13
5.0-55.0
11 332
2186
3038
3736
3386
3299
no. of variables
R
214
0.050
0.044
247
0.038
0.026
613
0.047
0.037
429
0.107
0.111
597
0.079
0.098
Rw
of [PdI(C6H3Me2-3,5)(bpy)] (469 mg, 0.95 mmol) and DMAD
(880 mg, 6.2 mmol) was added AgBF4 (290 mg, 1.5 mmol). The
mixture was stirred for 3 days at room temperature to
complete the separation of AgI, which was removed by filtra-
tion. Addition of Et2O (50 mL) to the concentrated filtrate gave
an off-white solid. Recrystallization from CH3CN-Et2O gave
10-CH3CN (624 mg, 84%). 1H NMR (400 MHz, CD3CN): δ 1.95
(s, CH3CN), 2.03 (s(br), 6H, CH3C6H3), 3.58 (s(br), 3H, OCH3),
3.66 (s(br), 3H, OCH3), 3.71 (s, 3H, OCH3), 3.73 (s, 3H, OCH3),
6.75 (s, 3H, o-, p-C6H3), 7.45 (m, 1H, H5-bpy), 7.75 (m, 1H, H5′-
bpy), 8.1 (m, 2H, H4, H6-bpy), 8.24 (d, 1H, H3-bpy, J ) 7.3 Hz),
8.28 (m, 1H, H4′-bpy), 8.32 (1H, H3′-bpy, J ) 8.2 Hz), 8.38 (d,
1H, H6′-bpy, J ) 5.4 Hz). 13C{1H} NMR (100 MHz, CD3CN): δ
21.2 (CH3C6H3), 52.6 (OCH3), 53.1 (OCH3), 53.2 (OCH3), 53.5
(OCH3), 124.3 (C3, C3′-bpy), 128.0, 128.7 (o-C6H3, C5, C5′-bpy),
132.4, 132.6 (p-C6H3), 136.1, 139.7, 142.2 (C4-bpy), 142.7 (C4′-
bpy), 150.5 (C6-bpy), 154.6 (C6′-bpy), 154.9, 157.3, 163.0, 167.6,
169.9, 171.8.
bpy), 8.66 (m, H3′-bpy), 8.71 (d, H3′-bpy, J ) 8.3 Hz), 9.16 (d,
H6′-bpy, J ) 5.4 Hz), 9.30 (d, H6-bpy, J ) 4.9 Hz), 9.61 (d, H6′′
bpy, J ) 4.9 Hz).
-
Cr ysta l Str u ctu r e Deter m in a tion . Crystals of 1c, 2c, 8,
10-CH3CN, and 11 suitable for X-ray diffraction study were
obtained by recrystallization from acetone-hexane, CH2Cl2-
Et2O, acetone-Et2O, CH3CN-Et2O, and acetone, respectively,
and mounted in glass capillary tubes. Intensities were collected
for Lorentz and polarization effects on a Rigaku AFC-5R
automated four-cycle diffractometer by using Mo KR radiation
(λ ) 0.71069 Å) and ω-2θ scan method, and an empirical
absorption correction (Ψ scan) was applied. Calculations were
carried out by using the program package TEXSAN for
Windows. Atomic scattering factors were obtained from the
literature.52 Three fluorine atoms of the CF3 group (1c), six
fluorine atoms of two CF3 groups (2c), three fluorine atoms of
-
the BF4 anion (10-CH3CN), and four fluorine atoms of two
BF4- anions (11) were assigned to the two disordered positions
with the occupancy of 1:1. A full matrix least-squares refine-
ment was used for non-hydrogen atoms with anisotropic
thermal parameters. Hydrogen atoms were located by assum-
ing the ideal geometry and included in the structure calcula-
tion without further refinement of the parameters. Crystal-
lographic data and details of refinement of the five complexes
are summarized in Table 5.
Rea ction of DMAD w ith 9-CH 3CN. To a CD3CN (0.5 mL)
solution containing 9-CH3CN (37 mg, 58 µmol) was added
DMAD (36 µL, 0.21 mmol) at room temperature. Change in
the 1H NMR spectrum of the solution was recorded at room
temperature.
P r ep a r a tion of [P d{η3-CH2C(C6H3Me2-3,5)CHP h }(bp y)]-
BF 4 (11). To a dry acetone (5 mL) solution containing a
mixture of 2d (104 mg, 0.21 mmol) and phenylallene (36.2 mg,
0.31 mmol) was added AgBF4 (72 mg, 0.37 mmol) in one
portion under argon. The mixture was stirred for 1 min at room
temperature to complete the separation of AgI. Removal of the
insoluble product by filtration and subsequent addition of
hexane (50 mL) to the filtrate gave an off-white solid. Recrys-
tallization from acetone-hexane gave 11 (55.5 mg, 0.097
mmol, 46%). The complex obtained contained only the isomer
with the syn-oriented phenyl substituent, but the NMR spectra
indicated the presence of isomers both with syn and anti
orientations of the phenyl substituents. 1H NMR (400 MHz,
acetone-d6): δ 2.19 (s, CH3, major), 2.30 (s, CH3, minor), 4.20
(m, Ha, major), 4.36 (d, Ha′, minor, J ) 2.0 Hz), 4.48 (d, Hb′,
major, J ) 1.5 Hz),), 4.87 (m, Hb′, minor), 5.17 (s, major, Hc),
6.83 (s, minor, Hc′), 6.92 (d, H6-bpy, J ) 4.9 Hz), 7.03 (s, major,
p-C6H3), 7.10, 7.12 (s, major, o-C6H3), 7.3-7.5 (m), 7.61 (m),
7.80 (m, H5′-bpy), 7.91 (m, H5-bpy), 7.95 (m, H5′′-bpy), 8.25 (m,
Ack n ow led gm en t . This work was supported by
the Grant-in-Aid for Scientific Research on Priority
Areas “Molecular Physical Chemistry” from the Ministry
of Education, Science, Culture, and Sports, J apan
(11166221). T.Y. is grateful for the fellowship from J SPS
(J apan Society for the Promotion of Science).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and isotropic thermal parameters, complete bond
lengths and distances, and thermal parameter of 1c, 2c, 8,
10-CH3CN, and 11. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM0007466
(52) International Tables for X-ray Crystallography; Kynoch: Bir-
H
4′′′-bpy), 8.36 (m, H4′-bpy), 8.44 (m, H4-bpy), 8.65 (m, H3′′′
-
mingham, England, 1974; Vol. 4.