Pentafluorophenyl imidato palladium(II) complexes: Catalysts for Suzuki cross-coupling reactions

Article abstract of DOI:10.1039/b503101j

Novel N-bonded imidato complexes of general formula [Pd(N-N)(C ₆F₅)(imidate)] (imidate = maleimidate, succinimidate or phthalimidate; N-N = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2, 2′-bipyridine (Me₂bipy) or N,N,N′,N′- tet

Full text of DOI:10.1039/b503101j

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
Pentafluorophenyl imidato palladium(II) complexes: catalysts for
Suzuki cross-coupling reactions
Jose´ Ruiz,*a Consuelo Vicente,a Natalia Cutillasa and Jose´ Pe´rezb
a Departamento de Qu´ımica Inorga´nica, Universidad de Murcia, 30071, Murcia, Spain.
E-mail: jruiz@um.es; Fax: (+34) 968 36 41 48
b
´
Departamento de Ingenier´ıa Minera, Geolo´gica y Cartogra´fica. Area de Qu´ımica Inorga´nica,
Universidad Polite´cnica de Cartagena, E-30203, Cartagena, Spain
Received 2nd March 2005, Accepted 19th April 2005
First published as an Advance Article on the web 4th May 2005
Novel N-bonded imidato complexes of general formula [Pd(N–N)(C6F5)(imidate)] (imidate = maleimidate,
succinimidate or phthalimidate; N–N = 2,2ꢀ-bipyridine (bipy), 4,4ꢀ-dimethyl-2,2ꢀ-bipyridine (Me2bipy) or
N,N,Nꢀ,Nꢀ-tetramethylethylenediamine (tmeda)), [NBu4][Pd(C6F5)(H2O)(succinimidate)2] and [NBu4]-
[Pd(C6F5)(L)(succinimidate)2] (L = PPh3 or t-BuNC) have been synthesised. These complexes are air-, light- and
moisture-stable. The crystal structures of [Pd(tmeda)(C6F5)(maleimidate)]·H2O·0.5CHCl3, [NBu4][Pd(C6F5)-
(H2O)(succinimidate)2]·H2O and [NBu4][Pd(C6F5)(t-BuNC)(succinimidate)2]·2H2O have been determined by X-ray
diffraction. Many of these new complexes are shown to be active phosphine-free palladium catalysts/precatalysts for
the Suzuki cross-coupling reactions of aryl bromides and aryl chlorides with phenylboronic acid.
In view of these catalytic results we report here the preparation
of novel pentafluorophenyl imidate complexes of the types
Introduction
Over the last twenty-five years great advances in the development
of palladium-catalysed carbon–carbon and carbon–heteroatom
[Pd(N–N)(C6F5)(imidate)] (imidate = maleimidate, succini-
midate or phthalimidate; N–N
=
2,2ꢀ-bipyridine (bipy),
bond forming processes have been made.1–5 Palladium-catalysed
cross-coupling utilizing organoboron compounds (the Suzuki
reaction) is a powerful tool for the formation of carbon–carbon
bonds.6,7 The practical advantages of this reaction are mainly
related to the wide range of functionalized substrates that can
be used under mild conditions. The search for appropriate
ancillary ligands that facilitate the generation of highly active
catalyst precursors is of current interest. Significant progress
has been made recently with the employment of ligands such
as electron-rich, sterically hindered phosphines8–12 and N-
heterocyclic carbenes.13–18 The use of cyclometallated Pd(II)
complexes as precatalysts, has in part, led the advances seen
in the last decade.19–27 Bedford et al.20,21 have also observed
the important role played by the anionic ligand in the overall
performance of catalysts. On the other hand, Fairlamb et al.28–33
have recently reported the successful catalytic application of
some new imidato palladium complexes of the types [Pd(C∧N)-
(imidate)(PR3)], [Pd(imidate)(PPh3)2(Br)], [Pd(imidate)2(PPh3)2]
and [NBu4][Pd{C4(COOMe)4}(imidate)(PR3)] (imidate = suc-
cinimidate, maleimidate or phthalimidate) in Stille, Sonogashira
and Suzuki cross-coupling reactions. The conversions appear28
to be dependent, to some extent, on the type of imidate ligand,
suggesting a role for these pseudohalides in the catalytic cycle
in these cross-coupling processes. The hemilability of imidate
ligands derives from their ability to act as either monodentate
or bidentate ligands. Generally four coordination modes to
transition metals are considered possible (I–IV, Fig. 1).
4,4ꢀ-dimethyl-2,2ꢀ-bipyridine (Me2bipy) or N,N,Nꢀ,Nꢀ-tetra-
methylethylenediamine (tmeda)), [NBu4][Pd(C6F5)(H2O)-
(succinimidate)2] and [NBu4][Pd(C6F5)(L)(succinimidate)2]
(L = PPh3 or t-BuNC). We also report the application of many
of these new complexes as catalysts for Suzuki coupling of aryl
bromides and aryl chlorides with boronic acid.
Results and discussion
Synthesis and characterisation of complexes 1–9
We have recently described34,35 the synthesis of monomeric
hydroxo palladium(II) complexes of the type [Pd(N–
N)(C6F5)(OH)] (N–N = bipy, Me2bipy, phen or tmeda) and their
reactions with CO or SO2 in methanol at room temperature to
yield the corresponding methoxy carbonyl or alkylsulfito com-
plexes [Pd(N–N)(C6F5)(X)] (X = CO2Me or SO3Me)]. We have
also shown36 the reactions of the monomeric hydroxo complexes
[Pd(N–N)(C6F5)(OH)] with some active methyl (CH3COR or
CH3NO2) and methylene (CH2X2) (X = CO2Et or CN) to yield
the corresponding C-bound enolate palladium complexes.
The reaction of the monomeric hydroxo palladium complex
of the type [Pd(N–N)(C6F5)(OH)] (N–N = bipy, Me2bipy
or tmeda) with maleimide, succinimide or phthalimide in
toluene gives the corresponding imidate complex [Pd(N–
N)(C6F5)(imiditate)] 1–9 (Scheme 1) in 76–95% yield. The acidic
proton of the imide is abstracted by the corresponding hydroxo-
complex generating the anionic ligand imidate which is subse-
quently trapped by the organometallic moiety [Pd(N–N)(C6F5)]+
to form complexes 1–9 and the concomitant release of water.
The structures were assigned on the basis of microanalytical,
IR and 1H and 19F NMR data. Complexes 1–9 are all air-stable
solids and the thermal analysis shows that they decompose above
◦
181 C in a dynamic N2 atmosphere. The IR spectra show the
characteristic absorptions of the C6F5 group37 at 1630, 1490,
1450, 1050, 950 and a single band at ca. 800 cm−1 which is
derived from the so-called X-sensitive mode38 in C6F5 halogen
molecules, as expected for the presence of only one C6F5 group
in the coordination sphere of the palladium atom and behaves
like a m(M–C) band.39–41 The IR spectra also show one strong
Fig. 1 Possible coordination modes of succinimide ligands to metal
centres.
These interesting modes of coordination might offer unique
stabilizing properties for key catalytic intermediates.
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6
1 9 9 9
©

View Article Online
Table 1 Selected bond lengths (A) and angles (◦) for complex
3·H2O·0.5CHCl3
˚
Molecule 1
Pd(1)–C(1)
Pd(1)–N(1)
2.008(6)
2.020(5)
Pd(1)–N(2)
Pd(1)–N(3)
2.081(5)
2.132(5)
C(1)–Pd(1)–N(1)
C(1)–Pd(1)–N(2)
N(1)–Pd(1)–N(2)
88.6(2)
93.7(2)
177.6(2)
C(1)–Pd(1)–N(3)
N(1)–Pd(1)–N(3)
N(2)–Pd(1)–N(3)
178.0(2)
92.59(19)
85.21(19)
Molecule 2
Pd(2)–C(17)
Pd(2)–N(4)
2.019(6)
2.016(5)
Pd(2)–N(5)
Pd(2)–N(6)
2.127(5)
2.084(5)
C(17)–Pd(2)–N(6)
C(17)– Pd(2)–N(4)
N(4)–Pd(2)–N(5)
92.8(2)
89.5(2)
92.2(2)
C(17)–Pd(2)–N(5)
N(4)–Pd(2)–N(6)
N(6)–Pd(2)–N(5)
178.1(2)
177.0(2)
85.6(2)
◦
˚
Table 2 Hydrogen bonds for complex 3·H2O·0.5CHCl3 (A and
)
D–H · · · A d(D–H) d(H · · · A) d(D · · · A) ∠(DHA)
O(5)–H(5A) · · · O(3) 0.84(6)
O(5)–H(5B) · · · O(4)a 0.84(6)
O(6)–H(6A) · · · O(2) 0.81(6)
O(6)–H(6B) · · · O(1)b 0.81(6)
2.10(6)
2.07(7)
2.22(7)
2.00(6)
2.942(7)
2.870(7)
2.960(7)
2.772(7)
177(8)
160(11)
154(10)
160(8)
Scheme 1
Symmetry transformations used to generate equivalent atoms:a −x + 1,
carbonyl band around 1640 cm−1 that is characteristic of the
imidate group.28 The characteristic resonances of the neutral
ligands35,42–44 were observed in the 1H NMR spectra. The
expected resonances of the imidate ligands are also seen.32 The
19F NMR spectra of complexes 1–9 reveal the presence of a freely
rotating pentafluorophenyl ring which gives three resonances (in
the ratio 2 : 2 : 1) at ca. −118.0, −163.0 and −160.0 for the o-,
m- and p-fluorine atoms, respectively.
Fig. 2 shows the X-ray structure of complex 3·H2O·0.5CHCl3,
with selected bond lengths and angles listed in Table 1. The
crystal structure of compound 3·H2O·0.5CHCl3 shows two
independent molecules in the asymmetric unit with the pal-
ladium atom in a slightly distorted square planar geometry.
The imidate ligand is approximately perpendicular to the
coordination plane, with angles between planes of 85.4(2)◦ in
molecule 1 and 86.9(2)◦ in molecule 2. The Pd–N maleim-
y − 1/2, −z + 1/2. b −x, y + 1/2, −z + 1/2.
˚
˚
and Pd(2)–N(6) 2.084(5) A, Pd(2)–N(5) 2.127(5) A in molecule
2) are in agreement with the higher trans influence of the C6F5
group compared to maleimidate. The Pd–C6F5 bond length
˚
˚
(2.008(6) A in molecule 1 and 2.019(6) A in molecule 2) is in the
range found in the literature for pentafluorophenyl–palladium
complexes.45 As can be seen in Fig. 3 and Table 2 in the crystal
˚
there are OH · · · O hydrogen bonds (2.772–2.960 A) involving
the maleimidate ligand and the water molecule of crystallization
leading to zigzag one-dimensional hydrogen-bonded chains.
Synthesis and characterisation of complexes 10–12
The bisimidate palladium complexes [NBu4][Pd(C6F5)(H2O)-
(succinimidate)2] 10 and [NBu4][Pd(C6F5)(L)(succinimidate)2]
11, 12 have been prepared by reaction in methanol or
˚
idate distance (Pd(1)–N(1) 2.020(5) A in molecule 1 and
Pd(2)–N(4) 2.016(5) A in molecule 2) is a bit shorter than
˚
dichloromethane of the halo-complexes [NBu4]2[{Pd(C6F5)(Br)-
that observed in [NBu4][Pd{C4(COOMe)4}(maleimidate)(P(p-
(l-Br)}2]46 or [{Pd(C6F5)(L)(l-Cl)}2] [L = t-BuNC,47 PPh3
]
48
32
˚
C6H4F)3)] (2.077(3) A). The different Pd–N tmeda distances
with [NBu4]OH and succinimide in the molar ratio 1 : 6 : 6,
as shown in Schemes 2 and 3. The preparations of complexes
10–12 have been optimised. When less than 6 equivalents of
succinimide were used no pure compounds were obtained. The
new complexes 10–12 have been characterized by elemental
analysis and spectroscopic data. The IR spectra of complexes
10–12 show one strong carbonyl band around 1620 cm−1 that
is characteristic of the imidate group.28 The IR spectrum of
complex 11 shows also an absorption assigned to m(C≡N) of the
˚
˚
(Pd(1)–N(2) 2.081(5) A, Pd(1)–N(3) 2.132(5) A in molecule 1
t-BuNC group49–51 at ca. 2220 cm−1. The H NMR spectrum
1
of complex 10 exhibits an unique resonance at d 2.28 ppm
for the succinimidate groups which suggests a trans isomer
in CDCl3 solution. No isomerization process was observed
when a solution of 10 was kept in solution in CDCl3 for a
prolonged period. A trans structure of 10 was confirmed by
X-ray diffraction (vide infra). On the other hand, the 1H NMR
spectra of complexes 11 and 12 suggest a cis isomer in CDCl3
solution showing two distinct resonances for the protons of
the succinimidate groups indicating the presence of two type
of imidate ligands, one trans to C6F5 and the other trans to L
(L = PPh3 or t-BuNC). A cis structure of 11 was revealed by X-
ray diffraction (vide infra). The 1H NMR spectrum of complex
Fig. 2 ORTEP of complex 3·H2O·0.5CHCl3 showing the atom num-
bering scheme. Displacement ellipsoids are drawn at the 50% probability
level.
2 0 0 0
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6

View Article Online
Fig. 3 Schematic showing the zigzag chain formed by hydrogen bonding in complex 3·H2O·0.5CHCl3.
Scheme 2
Fig. 4 ORTEP of complex 10·H2O showing the atom numbering
scheme. Displacement ellipsoids are drawn at the 50% probability level.
of [Pd(C6F5)(H2O)(succinimidate)2]2·2H2O (Fig. 5). Thus the
water molecule coordinated to the Pd1 atom is a hydrogen bond
donor to O6 and O9 of the succinimides ligands of molecule 2
(Table 4) and the water molecule coordinated to the Pd2 atom
is a hydrogen bond donor to O2 and O3 of molecule 1. The
molecules of non-coordinated water are also involved in the
formation of the dimeric units. There are also intermolecular
p-stacking interactions involving the carbonyl groups,31 thus
Scheme 3
11 shows also a singlet resonance for the t-BuNC group at d
1.37 ppm. The 31P MNR spectrum of complex 12 shows a unique
resonance for the phosphine ligand at d25.5 ppm. The 19F NMR
spectra of 10–12 exhibit three resonances with relative intensities
of 2 : 1 : 2 (2Fortho : 1Fpara : 2Fmeta) corresponding to only one type
of pentafluorophenyl ring.
The crystal structure of compound 10·H2O shows three
independent molecules in the asymmetric unit. The structure
of the first molecule of the unit cell is shown in Fig. 4 and
selected bond lengths and angles of the three molecules are in
Table 3. A trans-geometry around the Pd-centre is observed.
For example, in the first molecule of the unit cell the angle
N(1)–Pd(1)–N(2) is 179.4(2)◦. The crystal structure of the related
bisimidato complex trans-[Pd(PPh3)2(succinimidate)2] has been
recently reported.31 The Pd–OH2 distances are similar to those
found in [Pd(C6F5)(AsPh3)(H2O)2][CF3SO3].52 An interesting
feature of the crystal structure is the presence of dimeric units
˚
relatively short intermolecular contacts O3 · · · C28 (3.091 A)
˚
and O9 · · · C11 (2.985 A) are observed.
The structure of 11·2H2O is shown in Fig. 6 and selected
bond lengths and angles in Table 5. The geometry around the
palladium atom is approximately square planar. A cis structure
was revealed with an angle N(1)–Pd–N(2) of 89.25(11)◦. The
Pd(1)–N(2) bond distance (trans to the C6F5 group) is longer
than the Pd(1)–N(1) bond (trans to the t-BuNC ligand). Two
˚
relatively short intramolecular contacts N2 · · · O1 (2.988 A) and
˚
N1 · · · O4 (3.038 A) are observed, which suggest a significant
extra stabilization of the arrangement due to intramolecular
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6
2 0 0 1

View Article Online
◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for complex 10·H2O
Molecule 1
Pd(1)–C(5)
Pd(1)–N(1)
1.985(6)
2.039(5)
Pd(1)–N(2)
Pd(1)–O(5)
2.016(4)
2.122(4)
C(5)–Pd(1)–N(2)
C(5)–Pd(1)–N(1)
N(2)–Pd(1)–N(1)
89.6(2)
89.9(2)
179.4(2)
C(5)–Pd(1)–O(5)
N(2)–Pd(1)–O(5)
N(1)–Pd(1)–O(5)
177.3(2)
87.73(17)
92.72(18)
Molecule 2
Pd(2)–C(19)
Pd(2)–N(4)
1.977(6)
2.008(5)
Pd(2)–N(3)
Pd(2)–O(10)
2.015(5)
2.109(4)
C(19)–Pd(2)–N(4)
C(19)–Pd(2)–N(3)
N(4)–Pd(2)–N(3)
90.3(2)
89.1(2)
177.61(19)
C(19)–Pd(2)–O(10)
N(4)–Pd(2)–O(10)
N(3)–Pd(2)–O(10)
176.7(2)
88.83(19)
91.92(18)
Fig. 6 ORTEP of complex 11·2H2O showing the atom numbering
Molecule 3
scheme. Displacement ellipsoids are drawn at the 50% probability level.
Pd(3)–C(33)
Pd(3)–N(5)
1.988(6)
2.014(4)
Pd(3)–N(6)
Pd(3)–O(15)
2.018(4)
2.112(4)
◦
˚
Table 5 Selected bond lengths (A) and angles ( ) for complex 11·2H2O
C(33)–Pd(3)–N(5)
C(33)–Pd(3)–N(6)
N(5)–Pd(3)–N(6)
89.4(2)
89.5(2)
178.2(2)
C(33)–Pd(3)–O(15)
N(5)–Pd(3)–O(15)
N(6)–Pd(3)–O(15)
177.9(2)
90.34(18)
90.75(18)
Pd(1)–C(15)
Pd(1)–C(1)
1.935(4)
2.008(3)
Pd(1)–N(1)
Pd(1)–N(2)
2.041(3)
2.083(3)
C(15)–Pd(1)–C(1)
C(15)–Pd(1)–N(1)
C(1)–Pd(1)–N(1)
89.75(14)
173.94(13)
90.16(12)
C(15)–Pd(1)–N(2)
C(1)–Pd(1)–N(2)
N(1)–Pd(1)–N(2)
90.90(13)
179.14(12)
89.25(11)
p-stacking interactions involving the carbonyl groups.31
Another relatively short intramolecular contact O3 · · · C15
˚
(2.993 A) is also observed. Furthermore, as can be seen in
Fig. 7 and Table 6 in the crystal there are OH · · · O hydrogen
˚
bonds (2.782–2.919 A) involving O4 and O1 of the maleimidate
ligands and the water molecules of crystallization leading to the
formation of channels along the b-axis.
Fig. 5 The dimeric structure of [Pd(C6F5)(H2O)(succinimidate)2]2·
Fig. 7 View of the channels created along the b-axis by the hydro-
gen-bonding interactions in complex 11·2H2O.
2H2O showing the hydrogen bonds.
◦
˚
Table 4 Hydrogen bonds for complex 10·H2O (A and
)
D–H · · · A
d(D–H)
d(H · · · A)
d(D · · · A)
∠(DHA)
166(6)
O(5)–H(5A) · · · O(6)a
O(5)–H(5B) · · · O(9)a
O(10)–H(10A) · · · O(2)b
O(10)–H(10B) · · · O(3)b
O(15)–H(15A) · · · O(14)c
O(15)–H(15B) · · · O(11)c
O(16)–H(161) · · · O(8)
O(16)–H(162) · · · O(7)
O(18)–H(18A) · · · O(12)
O(18)–H(18B) · · · O(13)
0.84(7)
0.79(7)
0.77(7)
0.72(8)
0.75(8)
0.78(9)
0.67
0.90
0.67
0.86
1.91(7)
1.96(8)
1.96(8)
2.05(8)
1.98(8)
1.99(10)
2.26
1.92
2.26
1.98
2.729(6)
2.750(6)
2.727(6)
2.760(6)
2.713(6)
2.759(6)
2.871(6)
2.819(5)
2.859(7)
2.806(6)
174(7)
176(7)
171(8)
168(7)
171(9)
153.4
174.0
149.4
161.1
Symmetry transformations used to generate equivalent atoms:a x, y, z + 1. b x, y, z − 1. c −x + 2, −y, −z + 1.
2 0 0 2
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6

View Article Online
◦
˚
Table 6 Hydrogen bonds for complex 11·2H2O (A and
D–H · · · A d(D–H) d(H · · · A) d(D · · · A) ∠(DHA)
2.65(12) 2.919(7) 104(10)
)
reaction conditions were not optimised, but rather toluene was
used as solvent and K2CO3 as base in order to allow comparison
with previous studies in the literature21,25 (complexes 1, 2, 4, 5, 7
and 8 could not tested due to their low solubility in toluene).
Given that these Pd sources do not possess a phosphine
ligand (except complex 12), the catalytic activity and yields
are promising. Thus although it has been recently reported53
that the Pd(OAc)2/1,4-diazabicyclo[2,2,2]octane system is a
highly efficient phosphine-free palladium catalyst for the Suzuki
cross-coupling, when the electronically deactivated substrate
4-bromoanisole is used (a good indicator of optimal catalyst
performance) only a TON (turnover number) of 420 is achieved
after 48 h. In our case, using complex 9 a TON of 55000 with
4-bromoanisole is achieved after 18 h (Table 7, entry 16). It can
also be observed that the conversions appear to be dependent
on the type of imidate ligand.
O(6)–H(61) · · · O(6)a 0.75(2)
O(6)–H(62) · · · O(4)b 0.748(19) 2.06(2)
2.805(14) 174(5)
2.840(5)
2.782(4)
O(5)–H(51) · · · O(6)c 0.74(2)
2.16(6)
153(12)
172(6)
O(5)–H(52) · · · O(1)b 0.738(19) 2.05(2)
Symmetry transformations used to generate equivalent atoms:a −x, −y,
−z. b −x + 1, −y + 1, −z + 1. c −x, −y + 1, −z.
Application of the imidato-Pd-complexes as
catalysts/precatalysts in Suzuki cross-coupling
The Pd-complexes were screened for catalytic activity in the
cross-coupling of aryl bromides or aryl chlorides with phenyl-
boronic acid (Scheme 4).
We have also tested the catalytic activity of complexes 9, 10
and 12 in the Suzuki cross-coupling of aryl chloride substrates
with phenylboronic acid, and the results are summarized in
Table 8. The activity shown is moderate. These yields are,
however, improved by the addition of phosphine (Table 9).54 Pre-
sumably the active specie is not the same when PCy3 is presented.
Conclusion
Scheme 4
The acid–base reaction between [Pd(N–N)(C6F5)(OH)] and
imides is a convenient method for the preparation of N-bonded
imidato-palladium complexes of the general formula [Pd(N–
N)(C6F5)(imidate)] which are air-, light- and moisture-stable.
We first tested the catalytic activity of complexes 3, 6, 9–11 and
12 in the Suzuki cross-coupling of aryl bromides with phenyl-
boronic acid, and the results are summarized in Table 7. The
Table 7 Suzuki cross-coupling of aryl bromides with phenylboronic acida
Entry
Aryl bromide
Catalyst
Catalyst loading (mol% Pd)
Conversion (%)
TON (mol product/mol cat)
1
2
3
4
5
6
7
8
9
3
0.1
0.01
0.001
0.01
0.001
0.01
0.001
0.01
0.001
0.001
0.0001
83
100
85
100
96
100
40
100
47
830
10000
85000
10000
96000
10000
40000
10000
47000
100000
190000
6
6
9
9
10
10
11
11
12
12
10
11
100
19
12
13
14
9
0.01
0.001
0.001
100
69
84
10000
69000
84000
9
12
15
16
17
9
0.01
0.001
0.001
100
55
10
10000
55000
10000
9
12
a Conditions: aryl bromide (2.5 mmol), phenylboronic acid (3.75 mmol), K2CO3 (5 mmol), toluene (7.5 mL), 110 ◦C, 18 h.
Table 8 Suzuki cross-coupling of aryl chlorides with phenylboronic acid by complex 9, 10 or 12 a
Entry
Aryl chloride
Catalyst
Catalyst loading (mol% Pd)
Conversion (%)
TON (mol product/mol cat)
1
2
3
9
10
12
1
1
1
52
40
19
52
40
19
4
9
9
1
15
15
5
1
4
4
a Conditions: aryl chloride (2.5 mmol), phenylboronic acid (3.75 mmol), K3PO4 (5 mmol), toluene (7.5 mL), 110 ◦C, 18 h.
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6
2 0 0 3

View Article Online
a
Table 9 Suzuki cross-coupling of aryl chlorides with phenylboronic acid by mixtures of complex 9, 10 or 12 and PCy3
Entry
Aryl chloride
Catalyst
Catalyst loading mol% Pd)
Added PCy3 (mol%)
Conversion (%)
100
96
100
69
40
50
100
72
22
TON
1
2
3
4
5
6
7
8
9
9
1
2
1
0.5
0.05
2
1
1
0.2
0.1
100
192
200
1380
40
9
0.5
0.5
0.05
1
9
9
10
10
12
12
12
1
50
0.5
0.1
0.1
200
720
220
10
11
12
13
14
9
1
1
0.5
0.5
0.5
2
1
0.5
1
0.5
68
100
78
34
3
68
100
156
68
9
9
12
12
6
15
16
17
18
9
1
1
0.5
0.5
2
1
1
0.5
32
90
32
2
32
90
64
4
9
12
12
a Conditions: aryl chloride (2.5 mmol), phenylboronic acid (3.75 mmol), K3PO4 (5 mmol), toluene (7.5 mL), 110 ◦C, 18 h.
1
=
The bisimidato [NBu4][Pd(C6F5)(H2O)(succinimidate)2] and
[NBu4][Pd(C6F5)(L)(succinimidate)2] (L = PPh3 or t-BuNC)
have also been synthesised. The crystal structures of [Pd(tmeda)-
m(C O) 1660, m(Pd–C6F5) 785. H NMR (CDCl3) d 8.33 (d,
ꢀ
ꢀ
1 H, Ha, J(HaHb) = 5.1 Hz), 8.12 (m, 4 H, Hc + Hc + Hd + Hd ),
ꢀ
ꢀ
ꢀ
7.98 (d, 1 H, Ha , J(Ha Hb ) = 5.1 Hz), 7.52 (m, 1 H, Hb), 7.40
(m, 1 H, Hb ), 6.58 (s, 2 H, mal). 19F NMR (CDCl3) d −118.8 (d,
ꢀ
(C6F5)(maleimide)]·H2O·0.5CHCl3,
[NBu4][Pd(C6F5)(H2O)-
(succinimidate)2]·H2O and [NBu4][Pd(C6F5)(t-BuNC)(succini-
midate)2]·2H2O show OH · · · O hydrogen bonds involving the
imidate ligands and the water molecules of crystallization. Many
of these new complexes are shown to be active phosphine-free
palladium catalysts/precatalysts for the Suzuki cross-coupling
reactions of aryl bromides with phenylboronic acid.
2Fo, J(FoFm) = 20.9 Hz), −159.5 (t, 1 Fp, J(FmFp) = 19.9 Hz),
−162.4 (m, 2 Fm). 2: Yield 89% (Found: C, 47.4; H, 2.6; N, 7.7.
C22H14N3F5O2Pd requires C, 47.7; H, 2.6; N, 7.6%). Mp 288 ◦C
−1
1
=
(decomp.). IR (Nujol, cm ) m(C O) 1658, m(Pd–C6F5) 792. H
NMR (CDCl3) d 8.07 (d, 1 H, Ha, J(HaHb) = 5.6 Hz), 7.79 (s,
ꢀ
ꢀ
ꢀ
ꢀ
2 H, Hd + Hd ), 7.72 (d, 1 H, Ha , J(Ha Hb ) = 5.8 Hz), 7.21
ꢀ
ꢀ
ꢀ
(d, 1 H, Hb, J(HaHb) = 5.6 Hz), 7.08 (d, 1 H, Hb , J(Ha Hb ) =
5.8 Hz), 6.49 (s, 2 H, mal), 2.47 (s, 3 H, Me2bipy), 2.46 (s,
3 H, Me2bipy). 19F NMR (CDCl3) d −118.8 (d, 2Fo, J(FoFm) =
21.2 Hz), −160.1 (t, 1 Fp, J(FmFp) = 19.8 Hz), −162.9 (m, 2 Fm).
3: Yield 92% (Found: C, 39.3; H, 3.6; N, 8.7. C16H18N3F5O2Pd
requires C, 39.6; H, 3.7; N, 8.7%). Mp 233 ◦C (decomp.). IR
Experimental
Instrumental measurements
C, H, N analyses were performed with a Carlo Erba model
EA 1108 microanalyzer. Decomposition temperatures were
determine◦d with a Mettler TG-50 thermobalance at a heating
rate of 5 C min−1 and the solid sample under nitrogen flow
−1
1
=
(Nujol, cm ) m(C O) 1652, m(Pd–C6F5) 810. H NMR (CDCl3)
d 6.32 (s, 2 H, mal), 2.67 (m, 4 H, CH2), 2.59 (s, 6 H, CH3), 2.55
(s, 6 H, CH3). 19F NMR (CDCl3) d −118.9 (d, 2Fo, J(FoFm) =
21.7 Hz), −160.3 (t, 1 Fp, J(FmFp) = 19.8 Hz), −162.9 (m, 2 Fm).
4: Yield 76% (Found: C, 45.2; H, 2.5; N, 7.8.◦C20H12N3F5O2Pd
requires C, 45.5; H, 2.3; N, 8.0%). Mp: 292 C (decomp.). IR
1
(100 mL min−1). The H and 19F NMR spectra were recorded
on a Bruker AC 200E, Bruker AC 300E or Bruker AV-400
spectrometer, using SiMe4 or CFCl3 as standards respectively.
Infrared spectra were recorded on a Perkin-Elmer 16F PC FT-
IR spectrophotometer using Nujol mulls between polyethylene
sheets. GC analyses were performed on a CE instruments GC
8000TP fitted with a 30 m SPB column.
−1
1
=
(Nujol, cm ) m(C O) 1630, m(Pd–C6F5) 792. H NMR (CDCl3)
ꢀ
d 8.29 (d, 1 H, Ha, J(HaHb) = 5.2 Hz), 8.11 (m, 4 H, Hc + Hc +
ꢀ
ꢀ
ꢀ
ꢀ
Hd + Hd ), 7.96 (d, 1 H, Ha , J(Ha Hb ) = 5.0 Hz), 7.52 (m, 1 H,
Hb), 7.39 (m, 1 H, Hb ), 2.66 (s, 4 H, suc). 19F NMR (CDCl3) d
ꢀ
Materials
−118.6 (d, 2Fo, J(FoFm) = 20.5 Hz), −159.6 (t, 1 Fp, J(FmFp) =
20.3 Hz), −162.4 (m, 2 Fm). 5: Yield 88% (Found: C, 47.8; H, 3.2;
N, 7.8. C22H16N3F5O2Pd requires C, 47.5; H, 2.9; N, 7.6%). Mp
The starting complexes [Pd(N–N)(C6F5)(OH)] [(N–N
=
2,2ꢀ-bipyridine (bipy), 4,4ꢀ-dimethyl-2,2ꢀ-bipyridine (Me2bipy)
or N,N,Nꢀ,Nꢀ-tetramethylethylenediamine (tmeda)],34 [NBu4]2-
[{Pd(C6F5)(Br)(l-Br)}2],46 and [{Pd(C6F5)(L)(l-Cl)}2] (L =
t-BuNC,47 PPh348) were prepared by procedures described
elsewhere. The commercially available chemicals were purchased
from Aldrich Chemical Co. and were used without further
purification. Solvents were dried by the usual methods.
◦
−1
=
181 C (decomp.). IR (Nujol, cm ) m(C O) 1625, m(Pd–C6F5)
790. 1H NMR (CDCl3) d 8.05 (d, 1 H, Ha, J(HaHb) = 5.6 Hz),
ꢀ
ꢀ
ꢀ
ꢀ
7.78 (s, 2 H, Hd + Hd ), 7.71 (d, 1 H, Ha , J(Ha Hb ) = 5.7 Hz), 7.23
ꢀ
ꢀ
ꢀ
(d, 1 H, Hb, J(HaHb) = 5.6 Hz), 7.08 (d, 1 H, Hb , J(Ha Hb ) =
5.7 Hz), 2.70 (s, 6 H, Me2bipy), 2.47 (s, 4 H, suc). 19F NMR
(CDCl3) d −118.6 (d, 2Fo, J(FoFm) = 20.9 Hz), −160.2 (t, 1 Fp,
J(FmFp) = 20.6 Hz), −162.9 (m, 2 Fm). 6: Yield 87% (Found: C,
39.1; H, 4.1; N, 8.4. C16H20N3F5O2Pd requires C, 39.4; H, 4.1;
Preparation of complexes [Pd(N–N)(C6F5)(imidate)] (1–9).
To a solution or suspension of the corresponding hydroxo
complex [Pd(N–N)(C6F5)(OH)] (0.24 mmol) in toluene (15 mL)
was added the imide (0,24 mmol). The resulting mixture was
stirred for 90 min. The solvent was partially evaporated under
reduced pressure. On addition of hexane the white complexes
1–9 precipitated and were filtered off and air-dried. 1: Yield 76%
(Found: C, 46.0; H, 2.1; N, 7.8. C20H10N3F5O2Pd requires C,
45.7; H, 1.9; N, 8.0%). Mp 253 ◦C (decomp.). IR (Nujol, cm−1)
◦
−1
=
N, 8.6%). Mp 244 C (decomp.). IR (Nujol, cm ) m(C O) 1644,
m(Pd–C6F5) 784. 1H NMR (CDCl3) d 2.74 (m, 4 H, CH2 tmeda),
2.67 (s, 6 H, CH3), 2.61 (s, 6 H, CH3), 2.44 (s, 4 H, suc). 19F
NMR (CDCl3) d −118.3 (d, 2Fo, J(FoFm) = 21.7 Hz), −160.4
(t, 1 Fp, J(FmFp) = 19.8 Hz), −162.9 (m, 2 Fm). 7: Yield 77%
(Found: C, 44.9; H, 2.1; N, 6.4. C24H12N3F5O2Pd requires C,
45.2; H, 1.9; N, 6.6%). Mp 295 ◦C (decomp.). IR (Nujol, cm−1)
1
=
m(C O) 1662, m(Pd–C6F5) 794. H NMR (CDCl3) d 8.32 (d, 1 H,
2 0 0 4
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6

View Article Online
−1
=
ꢀ
ꢀ
Ha, J(HaHb) = 5.2 Hz), 8.12 (m, 4 H, Hc + Hc + Hd + Hd ), 7.97
(decomp.). IR (Nujol, cm ) 2214 m(CN), m(C O) 1622, m(Pd–
C6F5) 786. 1H NMR (CDCl3) d 2.46 (s, 4 H, suc), 2.33 (s,
4 H, suc), 1.37 (s, 9H, t-Bu). 19F NMR (CDCl3) d −116.0 (d,
2Fo, J(FoFm) = 23.0 Hz), −162.2 (t, 1 Fp, J(FmFp) = 23 Hz),
−164.9 (m, 2 Fm). 12: Yield 83% (Found: C, 58.9; H, 6.3; N, 4.5.
C48H59N3F5PO4Pd requires C, 59.2; H, 6.1; N, 4.3%). Mp 213 ◦C
ꢀ
ꢀ
ꢀ
(d, 1 H, Ha , J(Ha Hb ) = 5.3 Hz), 7.65 (m, 4 H, pht), 7.41 (m,
2 H, Hb + Hb ). 19F NMR (CDCl3) d −118.5 (d, 2Fo, J(FoFm) =
ꢀ
21.7 Hz), −159.6 (t, 1 Fp, J(FmFp) = 19.8 Hz), −162.4 (m, 2 Fm).
8: Yield 86% (Found: C, 51.5; H, 2.9; N, 6.7. C26H16N3F5O2Pd
requires C, 51.7; H, 2.7; N, 7.0%). Mp 269 ◦C (decomp.). IR
−1
1
−1
1
=
=
(Nujol, cm ) m(C O) 1664, m(Pd–C6F5) 792. H NMR (CDCl3)
(decomp.). IR (Nujol, cm ) m(C O) 1615, m(Pd–C6F5) 787. H
NMR (CDCl3) d 7.63 (m, 6 H, Ph), 7.30 (m, 9 H, Ph), 2.28 (s,
4 H, suc), 1.85 (s, 4 H, suc). 19F NMR (CDCl3) d −114.2 (d,
2Fo, J(FoFm) = 30.0 Hz), −163.3 (t, 1 Fp, J(FmFp) = 18.8 Hz),
−164.9 (m, 2 Fm). 31P NMR (CDCl3) d 25.5 (s).
ꢀ
d 8.17 (d, 1 H, Ha, J(HaHb) = 5.4 Hz), 7.89 (s, 2 H, Hd + Hd ),
ꢀ
ꢀ
ꢀ
7.82 (d, 1 H, Ha , J(Ha Hb ) = 5.4 Hz), 7.65 (m, 4 H, pht), 7.22
ꢀ
ꢀ
ꢀ
(d, 1 H, Hb, J(HaHb) = 5.4 Hz), 7.17 (d, 1 H, Hb , J(Ha Hb ) =
5.4 Hz), 2.54 (s, 3 H, Me2bipy), 2.52 (s, 3 H, Me2bipy). 19F NMR
(CDCl3) d −118.4 (d, 2Fo, J(FoFm) = 20.6 Hz), −160.1 (t, 1 Fp,
J(FmFp) = 20.9 Hz), −162.7 (m, 2 Fm). 9: Yield 95% (Found: C,
44.5; H, 3.8; N, 7.5. C20H20N3F5O2Pd requires C, 44.8; H, 3.8;
General method for the Suzuki coupling of aryl halides with
phenylboronic acid
◦
−1
=
N, 7.8%). Mp 250 C (decomp.). IR (Nujol, cm ) m(C O) 1660,
All reactions were performed in a Radley’s carousel adapted
for rigorous inert atmosphere reactions. To a mixture of the
appropriate aryl halide (2.5 mmol), aryl boronic acid (471.4 mg,
3.75 mmol), the appropriate base (5 mmol), toluene (7.5 mL)
and hexadecane (0.102 mmol, internal standard) was added the
Pd catalyst as a toluene solution made up to the correct concen-
tration by multiple volumetric dilutions of a stock solution (for
the aryl bromides) or as solid (for the aryl chlorides). In some
cases tricyclohexylphosphine (P : Pd ratio 2 : 1 or 1 : 1) was also
added. The resultant mixture was then heated at 110 ◦C for 18 h,
cooled in an ice bath, and an aliquot of 0.2 mL was extracted to
which HCl(aq) (2 M, 0.5 mL) was added to quench the reaction.
The aqueous layer was extracted with toluene (3 × 1 mL).
The organic extract was dried over MgSO4. The conversion to
product was determined by GC.
1
m(Pd–C6F5) 786. H NMR (CDCl3) d 7.52 (m, 4 H, pht), 2.78
(m, 4 H, CH2 tmeda), 2.69 (s, 6 H, CH3), 2.65 (s, 6 H, CH3). 19
F
NMR (CDCl3) d −118.5 (d, 2Fo, J(FoFm) = 25.0 Hz), −160.4
(t, 1 Fp, J(FmFp) = 21.4 Hz), −162.8 (m, 2 Fm).
Preparation of complex [NBu4][Pd(C6F5)(succinimidate)2(OH2)]
(10). To a solution of succinimide (66.7 mg, 0.666 mmol) in
methanol (5 mL) was added 20% [NBu4]OH (aq) (873 lL,
0.666 mmol). To the resulting solution was added a solution
of [NBu4]2[{Pd(C6F5)(Br)(l-Br)}2] (150 mg, 0.111 mmol) in
methanol (10 mL). The mixture was stirred at room temperature
for 12 h and then solvent was partially evaporated under reduced
pressure. On addition of water the white complex 10 precipitated
and was filtered off and air-dried. 10: Yield 92% (Found: C,
49.1; H, 6.6; N, 5.6. C30H46N3F5O5Pd requires C, 49.4; H, 6.4;
N, 5.8%). Mp: 190 ◦C (decomp.). IR (Nujol, cm−1) 3450 m(O–H,
X-Ray crystal structure analysis
1
=
H2O), m(C O) 1632, m(Pd–C6F5) 793. H NMR (CDCl3) d 2.28
(s, 8 H, suc). 19F NMR (CDCl3) d −116.1 (d, 2Fo, J(FoFm) =
26.4 Hz), −164.2 (t, 1 Fp, J(FmFp) = 20.7 Hz), −166.3 (m, 2 Fm).
Suitable crystals of 3·H2O·0.5CHCl3, 10·H2O and 11·2H2O were
grown from chloroform–hexane. Data collection for 10·H2O and
11·2H2O was performed at −173 ◦C on a Bruker smart CCD
diffractometer with a nominal crystal to detector distance of
4.5 cm. Diffraction data were collected based on a x scan run. A
total of 2524 frames were collected at 0.3◦ intervals and 10 s per
frame. The diffraction frames were integrated using the SAINT
package55 and corrected for absorption with SADABS.56 Data
collection for 3·H2O·0.5CHCl3 was performed at −100 ◦C on a
Siemens P4 diffractometer. The structures were solved by direct
methods and refined by full-matrix least-squares techniques
using anisotropic thermal parameters for non-H atoms.57
Crystallographic data for the compounds are listed in
Table 10.
Preparation of complexes [NBu4][Pd(C6F5)(succinimidate)2(L)]
(L = t-BuNC 11, PPh3 12). To a solution of succinimide
(78.1 mg, 0.78 mmol) in methanol (5 mL) was added 20%
[NBu4]OH (aq) (1.02 mL, 0.78 mmol). To the resulting solution
was added a solution of [{Pd(C6F5)(L)(l-Cl)}2] (L = t-BuNC
or PPh3) (0.13 mmol) in dichloromethane (15 mL). The mixture
was stirred at room temperature for 12 h and then solvent was
removed under reduced pressure and the residue was treated
with dichloromethane/hexane. The white solid was filtered off
and air-dried. 11: Yield 78% (Found: C, 52.7; H, 6.6; N, 6.9.
C35H53N4F5O4Pd requires C, 52.9; H, 6.7; N, 7.1%). Mp 187 ◦C
Table 10 Crystal structure determination details
3·H2O·0.5CHCl3
10·H2O
11·2H2O
Formula
M
C32H36F10N6O4Pd2·2H2O·CHCl3
C30H46F5N3O5Pd·H2O
C35H53F5N4O4Pd·2H2O
1126.87
Monoclinic
15.2880(10)
14.3170(10)
20.7880(10)
90
747.4
831.25
Crystal system
Monoclinic
10.3563(5)
41.9620(18)
24.4230(11)
90
97.77(1)
90
10516.1(8)
100(2)
P21/c
12
0.599
122099
24434
0.0378
0.0853
0.1796
Triclinic
˚
a/A
10.1604(5)
10.3459(5)
20.5010(10)
82.1130(10)
80.4260(10)
69.3144(8)
1980.81(17)
100(2)
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
V/A
T/K
107.000(10)
90
4351.2(5)
173(2)
P21/c
4
1.102
10391
7639
3
˚
¯
Space group
Z
P1
2
l/mm−1
0.538
23353
8933
0.0412
0.0488
0.1238
Reflections collected
Independent reflections
Rint
0.0346
0.0450
0.1309
R1 [I > 2r(I)]a
wR2(all data)b
2
2
a R1 = RꢁFo| − |Fcꢁ/R|Fo|, wR2 = [R[w(Fo − Fc2)2]/Rw(Fo2)2]0.5
.
b w = 1/[r2((Fo2) + (aP)2 + bP], where P = (2Fc + Fo2)/3 and a and b are
constants set by the program.
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6
2 0 0 5

View Article Online
CCDC reference numbers 265321–265323.
See http://www.rsc.org/suppdata/dt/b5/b503101j/ for cry-
stallographic data in CIF or other electronic format.
26 D. Alonso, C. Na´jera and M. C. Pacheco, J. Org. Chem., 2002, 67,
5588.
27 L. Botella and C. Na´jera, Angew. Chem., Int. Ed., 2002, 41, 179.
28 I. J. S. Fairlamb, A. R. Kapdi, A. F. Lee, G. Sa´nchez, G. Lo´pez, J. L.
Serrano, L. Garc´ıa, J. Pe´rez and E. Pe´rez, Dalton Trans., 2004, 3970.
29 I. J. S. Fairlamb, R. J. K. Taylor and A. C. Whitwood, Chem.
Commun., 2003, 2194.
Acknowledgements
This work was supported by the Direccio´n General de Inves-
tigacio´n del Ministerio de Ciencia y Tecnolog´ıa (Project No.
BQU2001-0979-C02-01), Spain, and the Fundacio´n Se´neca de
la Comunidad Auto´noma de la Regio´n de Murcia (Project No.
00448/PI/04).
30 C. M. Crawforth, I. J. S. Fairlamb and R. J. K. Taylor, Tetrahedron
Lett., 2004, 45, 461.
31 I. J. S. Fairlamb, A. R. Kapdi, J. M. Lynam, R. J. K. Taylor and A. C.
Whitwood, Tetrahedron, 2004, 60, 5711.
32 J. L. Serrano, I. J. S. Fairlamb, G. Sa´nchez, L. Garc´ıa, J. Pe´rez, J.
Vives, G. Lo´pez, C. M. Crawforth and R. J. K. Taylor, Eur. J. Inorg.
Chem., 2004, 2706.
33 N. M. Chaignon, I. J. S. Fairlamb, A. R. Kapdi, R. J. K. Taylor and
A. C. Whitwood, J. Mol. Catal. A.: Chem., 2004, 219, 191.
34 J. Ruiz, M. T. Mart´ınez, F. Florenciano, V. Rodr´ıguez, G. Lo´pez, J.
References
1 Metal-catalyzed Cross-coupling Reactions, ed. A. de Meijere and
F. Diederich, Wiley-VCH, Weinheim, 2nd edn., 2004.
2 M. Beller and A. C. Frisch, Angew. Chem., Int. Ed., 2005, 44, 674.
3 U. Christmann and R. Vilar, Angew. Chem., Int. Ed., 2005, 44, 366.
4 A. Zapf and M. Beller, Chem. Commun., 2005, 431.
5 L.-C. Liang, P.-S. Chien and M.-H. Huang, Organometallics, 2005,
24, 353.
6 A. Suzuki and N. Miyaura, Chem. Rev., 1995, 95, 2457.
7 A. Suzuki, J. Organomet. Chem., 1999, 576, 147.
8 A. F. Littke, C. Y. Dai and G. C. Fu, J. Am. Chem. Soc., 2000, 122,
4020.
9 S. Y. Liu, M. J. Choi and G. C. Fu, Chem. Commun., 2001, 2408.
10 D. W. Old, J. P. Wolfe and S. L. Buchwald, J. Am. Chem. Soc., 1998,
120, 9722.
11 S. D. Walker, T. E. Barder, J. R. Martinelli and S. L. Buchwald,
Angew. Chem., Int. Ed., 2004, 43, 1871.
P
3650.
e´rez, P. A. Chaloner and P. B. Hitchcock, Inorg. Chem., 2003, 42,
35 J. Ruiz, M. T. Mart
´ınez, F. Florenciano, V. Rodr´ıguez, G. Lo´pez, J.
Pe´rez, P. A. Chaloner and P. B. Hitchcock, Dalton Trans., 2004, 929.
36 J. Ruiz, M. T. Mart´ınez, V. Rodr´ıguez, G. Lo´pez, J. Pe´rez, P. A.
Chaloner and P. B. Hitchcock, Dalton Trans., 2004, 3521.
37 D. A. Long and D. Steele, Spectrochim. Acta, 1963, 19, 1955.
38 E. Maslowski, Vibrational Spectra of Organometallic Compounds,
Wiley, New York, 1977, p. 437.
39 E. Alonso, J. Fornie´s, C. Fortun˜o and M. Toma´s, J. Chem. Soc.,
Dalton Trans., 1995, 3777.
40 G. L
o´pez, J. Ruiz, C. Vicente, J. M. Mart´ı, G. Garc´ıa, P. A. Chaloner
and P. B. Hitchcock, Organometallics, 1992, 11, 4091.
41 J. Ruiz, M. T. Mart
´ınez, C. Vicente, G. Garc´ıa, G. Lo´pez, P. A.
Chaloner and P. B. Hitchcock, Organometallics, 1993, 12, 4321.
42 P. K. Byers and A. J. Canty, Organometallics, 1990, 9, 210.
43 Y. Fuchita and Y. Harada, Inorg. Chim. Acta, 1993, 208, 43.
44 G. D. Smith, B. E. Hanson, J. S. Merola and F. J. Waller,
Organometallics, 1993, 12, 568.
12 J. J. Yin, M. P. Rainka, X. X. Zhang and S. L. Buchwald, J. Am.
Chem. Soc., 2002, 124, 1162.
13 C. M. Zhang, J. K. Huang, M. L. Trudell and S. P. Nolan, J. Org.
Chem., 1999, 64, 3804.
45 J. Fornie´s, F. Mart´ınez, R. Navarro and E. P. Urriolabeitia,
J. Organomet. Chem., 1995, 495, 185.
46 R. Uso´n, J. Fornie´s, J. A. Nalda, M. J. Lozano, P. Espinet and A. C.
Albe´niz, Inorg. Chim. Acta, 1989, 156, 251.
47 R. Uso´n, J. Fornie´s, P. Espinet and E. Lalinde, J. Organomet. Chem.,
1983, 254, 371.
14 W. A. Herrmann, C. P. Reisinger and M. Spiegler, J. Organomet.
Chem., 1998, 557, 93.
15 T. Weskamp, V. P. Bohm and W. A. Herrmann, J. Organomet. Chem.,
1999, 585, 348.
16 S. B. Biakey and D. W. C. MacMillan, J. Am. Chem. Soc., 2003, 125,
6046.
48 R. Uso´n, J. Fornie´s, R. Navarro and M. P. Garc´ıa, Inorg. Chim. Acta,
1979, 33, 69.
17 O. Navarro, R. A. Kelly and S. P. Nolan, J. Am. Chem. Soc., 2003,
125, 16194.
18 O. Navarro, H. Kaur, P. Mahjoor and S. P. Nolan, J. Org. Chem.,
2004, 69, 3173.
49 J. Ruiz, V. Rodr´ıguez, N. Cutillas, F. Florenciano, J. Pe´rez and G.
L
o´pez, Inorg. Chem. Commun., 2001, 4, 23.
50 J. Ruiz, M. T. Mart´ınez, C. Vicente, G. Garc´ıa, G. Lo´pez, P. A.
Chaloner and P. B. Hitchcock, Organometallics, 1993, 30, 1594.
51 J. Ruiz, J. F. J. Lo´pez, V. Rodr´ıguez, J. Pe´rez, M. C. Ram´ırez de
Arellano and G. Lo´pez, J. Chem. Soc., Dalton Trans., 2001, 2683.
52 J. Ruiz, F. Florenciano, C. Vicente, M. C. Ram´ırez de Arellano and
G. Lopez, Inorg. Chem. Commun., 2000, 3, 73.
19 D. A. Albisson, R. B. Bedford and P. N. Scully, Tetrahedron Lett.,
1998, 39, 9793.
20 R. B. Bedford, C. S. J. Cazin, S. J. Coles, T. Gelbrich, P. N. Horton,
M. B. Hursthouse and M. E. Light, Organometallics, 2003, 22, 987.
21 R. B. Bedford, C. S. J. Cazin, S. J. Coles, T. Gelbrich, M. B.
Hursthouse and V. J. M. Scordia, Dalton Trans., 2003, 3350.
22 S. Iyer and C. Ramesh, Tetrahedron Lett., 2000, 41, 8981.
23 P. Beletskaya, A. N. Kashin, N. B. Karlstedt, A. V. Mitin, A. V.
Cheprakov and G. M. Kazankov, J. Organomet. Chem., 2001, 622,
89.
53 J.-H. Li and W.-J. Liu, Org. Lett., 2004, 6, 2809.
54 R. B. Bedford, C. S. J. Cazin, M. B. Hursthouse, M. E. Light and
V. J. M. Scordia, Dalton Trans., 2004, 3864.
55 SAINT, Version 6.22, Bruker AXS Inc.
24 F. Yang, Y. Zhang, R. Zheng, J. Tie and M. He, J. Organomet. Chem.,
56 G. M. Sheldrick, SADABS; University of Gottingen, 1996.
57 G. M. Sheldrick, SHELX-97. Programs for Crystal Structure Analysis
2002, 651, 146.
25 H. Weissman and D. Milstein, Chem. Commun., 1999, 1901.
(Release 97-2), University of G
o¨ttingen, Germany, 1998.
2 0 0 6
D a l t o n T r a n s . , 2 0 0 5 , 1 9 9 9 – 2 0 0 6