Highly active ferrocenylamine-derived palladacycles for carbon-carbon cross-coupling reactions

Article abstract of DOI:10.1016/j.poly.2007.04.030

{[(N-Methyl-N-p-R-benzyl)amino]benzyl}ferrocenes 4a-c (R = H(a), OCH₃(b), CH₃(c)) were synthesized by N-methylation of the corresponding sec-amines 3a-cwith the reagent CH₃I-t-BuOK. Treatment of 4a-c with Na₂PdCl₄ in the presence of NaOAc produced a pair of palladacycles σ-Pd[(η⁵-C₅H₅)Fe(η⁵- C₅H₃CH(C₆H₅)N(CH₃)CH₂-C₆H₄-R)]Cl(PPh₃) 5a-c (R = same as before) consisting of R_NR_P and S_NS_P configurations. The structure of 5a was determined by single crystal X-ray analysis. High catalytic activities of 5a-c for the Suzuki coupling of aryl chlorides with phenylboronic acid and the Heck reaction of bromobenzene with styrene were observed.

Full text of DOI:10.1016/j.poly.2007.04.030

Polyhedron 26 (2007) 3857–3864
www.elsevier.com/locate/poly
Highly active ferrocenylamine-derived palladacycles
for carbon–carbon cross-coupling reactions
*
Hong-Xing Wang , Hong-Fei Wu, Xiao-Li Yang, Nan Ma, Li Wan
Department of Chemistry, College of Sciences, Tianjin University, Tianjin 300072, PR China
Received 13 February 2007; accepted 13 April 2007
Available online 5 May 2007
Abstract
{[(N-Methyl-N-p-R-benzyl)amino]benzyl}ferrocenes 4a–c (R = H(a), OCH3(b), CH3(c)) were synthesized by N-methylation of the
corresponding sec-amines 3a–cwith the reagent CH3I-t-BuOK. Treatment of 4a–c with Na2PdCl4 in the presence of NaOAc produced
a pair of palladacycles r-Pd[(g5-C5H5)Fe(g5- C5H3CH(C6H5)N(CH3)CH2-C6H4-R)]Cl(PPh3) 5a–c (R = same as before) consisting of
RNRP and SNSP configurations. The structure of 5a was determined by single crystal X-ray analysis. High catalytic activities of 5a–c
for the Suzuki coupling of aryl chlorides with phenylboronic acid and the Heck reaction of bromobenzene with styrene were observed.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Ferrocene; Amine; Palladacycles; Crystal; Carbon–carbon cross-coupling
1. Introduction
Caryl–I bond, although several examples were also reported
to be efficient to the Caryl–Cl bond [5a,5c,5d,5h,5l]. To our
best knowledge, research on the Suzuki coupling catalyzed
by amine-derived palladacycles, particularly for activation
of the Caryl–Cl bond, are still scarce [5a,5i]. Thus it is essen-
tial to exploit the new type of amine-derived palladacycles
to activate aryl chlorides, because of the low costs and eas-
ily purchased substrates. Several years ago we initiated a
program, the synthesis of cyclometallated ferrocenylamines
and their applications in carbon–carbon bond formation.
It was observed that cyclopalladation or platination of
{[(N-methyl-N-benzyl or phenyl)amino]methyl} ferrocenes
always produced a pair of racemic metallocycles consisting
of RNRP and SNSP configurations [7]. Most importantly,
when a variety of phenyls are attached directly to the nitro-
gen in the ferrocenylamines, the corresponding palladacy-
cles are thermally unstable and thus cannot be used as
catalysts in carbon–carbon cross-coupling [7a]. In order
to evaluate the catalytic efficiency of amine-derived palla-
dacycles in this coupling, in this paper, we will present
herein the synthesis of three palladacycles derived
from {[(N-methyl-N-benzyl)amino]benzyl} ferrocenes and
their catalysis in the Suzuki coupling of aryl chlorides with
Functionalized biaryls are a class of important interme-
diates in the synthesis of natural products possessing bio-
logical activities [1]. These biaryls can be obtained by
Suzuki coupling of functionalized aryl halides and phen-
ylboronic acid, catalyzed by palladium–phosphine com-
plexes such as Pd(PPh3)4, Pd(PPh2)Cl2, Pd(OAc)2/PPh3,
etc. [2] or by the recently emerged N-heterocyclic carbene
(NHC)–palladium complexes [3]. However, cyclopalla-
dated complexes (also called palladacycles) as alternative
catalysts have also been proven to be efficient in such
couplings [4,5]. In addition, these palladacycles have
been already used successfully in the Heck reaction, which
gives a variety of olefins [4,6]. Previous researches on
Suzuki coupling catalyzed by palladacycles containing
nitrogen-donor atoms focused mainly on imines
[5a,5b,5c,5d,5e,5f,5l], oximes [5g,5h], etc., and most of the
palladacycles were found to be active to the Caryl–Br or
*
Corresponding author. Tel.: +86 022 27892355; fax: +86 022
27403475.
E-mail address: hongxing_wang@hotmail.com (H.-X. Wang).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.04.030

3858
H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
25
phenylboronic acid. In addition, the Heck reaction of
bromobenzene with styrene catalyzed by these pallada-
cycles, as mentioned above, will also be discussed.
23
21
R
19
18
Ph
11
N
3
4
2. Results and discussion
Pd Cl
PPh3
1
5 Fe
(ii)
(i)
4a-c
7
2.1. Synthesis of ferrocenylamines 4a–c and their
cyclopalladated complexes 5a–c
10
rac-5a-c
The preparation of tert-ferrocenylamines 4a–c is shown
in Scheme 1. Condensation of benzoylferrocene and
4 equiv. of benzylamine catalyzed by titanium tetrachloride
[8] in toluene produced the dark-red ferrocenylketimines
2a–c in good yields. Reduction of 2a–c with LiAlH4-AlCl3
[9] in THF gave sec-amines 3a–c, respectively in moderate
yields. An attempt at the synthesis of 4a–c from 3a–c by
our earlier used protocol, i.e. using aqueous HCHO, NaC-
NBH3 in HOAc, [10] was unsuccessful due to the easier
debenzylation of the former reactant [9,11] under such
reaction conditions. Thus, CH3I was chosen as the methyl-
ation reagent and t-BuOK as the base to synthesize 4a–c
from 3a–c (Scheme 1). 4a–c were finally obtained as orange
solids in yields of 50–65%.
The synthesis of palladacycles 5a–c is outlined in
Scheme 2. Treatment of 4a–c with 1 equiv. of Na2PdCl4–
PPh3 in methanol produced red-brown solids 5a–c in
70–80% yields after purification by column chromatogra-
phy (see Section 4). Similar to our earlier obtained pallada-
cycles [7a,7b,7c], 5a–c are very stable in air and easily
soluble in CH2Cl2, CHCl3, ethyl acetate, acetone and ben-
zene, but are insoluble in ethanol and hexane.
Scheme 2. (i) Na2PdCl4/NaOAc/CH3OH. (ii) PPh3/CH3OH. R = H (a),
4-OCH3 (b), 4-CH3 (c).
of the N atom and causes the d-values of N–CH3 to shift
downfield. In addition, the satellites of H20–H24 in the
phenyl ring all exhibit their unique AA0XX0 splitting pat-
terns (except 5a), indicating that palladacycles 5a–c are
formed via the activation of the CFerrocenyl–H bond rather
than the Cphenyl–H bond [13].
Since the nitrogen atom in 4a–c connects directly to three
different groups and a rapid N-inversion [14] exists, after the
coordination of the nitrogen atom with palladium, the forms
of the N–Pd coordinated intermediates (Fig. 1) can be sim-
plified as two kinds, i.e., one has a RN configuration, and
another has the opposite, regardless of the chirality of
C11. Accordingly, the following activation of the C–H bond
in the Cp ring will produce theoretically four isomeric palla-
dacycles (two pairs of racemes, i.e., RNRP and SNSP, SNRP
and RNSP). Similar to our earlier observations [7], only
one pair of raceme RNRP and SNSP was found to dominate
in these reactions, the other pair of raceme RNSP and SNRP
was observed in trace amounts and can be easily removed by
Compounds 2–5 were characterized by elemental analy-
1
sis, IR and H NMR. Elemental analyses of 2–5 are in
good agreement with their proposed formula. The IR and
1H NMR spectra of 2–4 are very similar to those observed
in imines, sec-amines and tert-amines derived from the
starting materials formylferrocene and benzylamines
[7b,7c]. The IR spectra of 5a–c show two medium absorp-
tion bands at m ꢀ 1100 and 1000 cmꢁ1, implying that each
of these palladacycles contains a free cyclopentadienyl (Cp)
ring [12]. The 1H NMR spectra of 5a–cclearly demonstrate
that the chemical shifts of N–CH3 are located downfield
(d ꢀ 2.80 ppm) compared to those of the free tert-amines
4a–c (d ꢀ 1.99 ppm). This change can be rationalized by
N–Pd coordination, which decreases the electron density
Pd
N
N
11
Pd
Ph
R
11
R
Ph
1
5
1
5
2
2
Fe
Fe
Fig. 1. The possible activation modes of C–H bonds in the Cp ring for
N–Pd coordinated intermediates (left: RN, right: SN).
23
R
R
R
19
19
19
18
18
18
Ph
Ph
Ph
Ph
11
11
11
O
N
NH
N
21
1
1
21
1
21
2
7
25
3
3
3
(i)
(ii)
(iii)
Fe
Fe
1
Fe
Fe
6
6
6
7
7
10
10
10
2a-c
3a-c
4a-c
Scheme 1. (i) RC6H4CH2NH2/TiCl4/toluene, reflux. R = H (a), 4-OCH3 (b), 4-CH3 (c). (ii) LiAlH4/AlCl3/THF. (iii) CH3I/t-BuOK, THF.

H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
3859
Table 2
chromatography. This stereoselective C–H bond activation
Selected bond lengths and angles for 5a
is probably attributed to the preferred N–Pd orientations in
the intermediates (Fig. 1), which allow the palladium atom
to approach preferably to the C2–H or C5–H bond and then
activate each of them. To some extent, the preferred N–Pd
orientations in these intermediates are relevant to the geom-
etries of the tert-ferrocenylamines [15]. In addition, zero
optical rotations of 5a–c measured at the given conditions
˚
Bond lengths (A)
Pd(1)–P(1)
Pd(1)–Cl(1)
C(2)–C(11)
2.2401(1)
2.3920(2)
1.520(4)
C(1)–C(2)
N(1)–C(11)
N(1)–C(19)
1.431(4)
1.524(4)
1.499(4)
Bond angles (ꢁ)
C(1)–Pd(1)–N(1)
N(1)–Pd(1)–Cl(1)
C(11)–N(1)–Pd(1)
C(19)–N(1)–C(11)
C(18)–N(1)–C(11)
82.18(1)
91.24(7)
109.92(2)
110.2(2)
112.1(2)
C(18)–N(1)–C(19)
C(1)–Pd(1)–P(1)
C(1)–Pd(1)–Cl(1)
P(1)–Pd(1)–Cl(1)
C(2)–C(1)–Pd(1)
107.5(2)
91.67(9)
173.25(8)
94.51(5)
˚
(k = 5893 A, CH2Cl2, 293 K) also indicate that these palla-
dacycles consist of racemes.
114.15(2)
The structure of 5a was determined by single crystal X-
ray analysis (Fig. 2, SNSP). Crystallographic data for 5a are
given in Table 1, selected bond lengths and angles are listed
in Table 2. X-ray diffraction studies demonstrates that
5a consists of the discrete molecule {Pd[(g5-C5H5)
Fe(g5-C5H3CHPhN(CH3)CH2C6H5)](PPh3)Cl} separated
by van der Waals contacts. The palladium atom is in a
slightly distorted square-planar environment, bonded to
Cl(1), P(1), N(1) and C(1). The deviation of each atom from
the mean plane is Pd(1), ꢁ0.1015; Cl(1), ꢁ0.0489; P(1),
˚
0.1071; N(1), 0.1149; C(1), ꢁ0.0716 A, respectively. 5a con-
tains a bicycle, which is formed by the substituted Cp ring of
the ferrocenyl fragment and a five-membered palladacycle
with an envelope-like conformation. The N(1)–Pd(1) bond
˚
length of 2.224(3) A is slightly longer than those observed
in cyclopalladated [(N,N-dimethylamino)methyl]ferrocene
˚
(FcN, 2.170 A) [16] and [({N-methyl-N-4-nitrobenzyl}-
˚
amino)methyl]ferrocene (BFcN, 2.195 A) [7c]. In addition,
the PPh3 moiety in 5a adopts a trans-configuration to N(1),
with a N(1)–Pd(1)–P(1) bond angle of 167.53(7)ꢁ, which
is slightly less than that in cyclopalladated BFcN
˚
(169.00(9)ꢁ). The Pd(1)–C(1) bond length of 2.002(3) A is
nearly the same as those observed in cyclopalladated FcN
˚
˚
(1.983(1) A) and BFcN (1.988(4) A). The average C–C bond
˚
length (1.418 A) in the ferrocenyl moiety is very close to the
Fig. 2. X-ray crystal structure of 5a (H atoms are all omitted for clarity).
reported values of other ferrocene derivatives [17]. The Fe–C
(Cp ring) bond lengths range from 2.036 to 2.082 A. The
˚
eclipsed two Cp rings are planar and nearly parallel (inter-
planar angle of 2.2ꢁ).
Table 1
Crystallographic data for 5a
Compound
5a
2.2. Suzuki coupling
Empirical formula
C
43H39ClFeNPPd
Formula weight
798.42
Before investigation of the Suzuki coupling for aryl
chlorides, the coupling of bromobenzene and phenylbo-
ronic acid catalyzed by 5a–c (under the conditions
K2CO3, THF) was studied. The coupling results showed
that 100% of biphenyl was obtained, indicating that palla-
dacycles 5a–c are excellent catalysts for activation of the
Crystal dimensions (mm)
Crystal system, space group
0.28 · 0.22 · 0.20
monoclinic, P2(1)/n
10.716(8)
17.638(1)
19.259(2)
90
94.153(1)
90
3631(5)
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Cphenyl–Br bond. To examine the catalytic efficiency of 5
3
for the coupling of aryl chlorides, a quick survey of sol-
vents including dioxane, toluene, THF and DMF/H2O
was made (Table 3). Table 3 revealed that using K2CO3
as the base and 0.1 mol% of 5a as the catalyst the coupling
reaction in dioxane gave the best results (Entry 1, 89%,
Table 3). We further investigated the effect of the bases,
e.g., K2CO3, Cs2CO3, K3PO4 and t-BuOK in the same
reaction (Table 3). It was found that K2CO3 was better
than the others (Entries 4–7). Therefore, K2CO3 was ulti-
mately chosen as the base for this system.
˚
V (A )
Z
4
qcalc (g cmꢁ3
)
1.461
1.044
l (mmꢁ1
)
h Range for data collection
Limiting indices
2.23 6 h 6 24.08ꢁ
ꢁ10 6 h 6 12,
ꢁ20 6 k 6 20, ꢁ21 6 l 6 22
19259/6383 [0.0375]
6383/0/434
0.0323, 0.0768
0.542 and ꢁ0.345
Reflections collected/unique [Rint
Data/restraints/parameters
Final R1, wR2
]
ꢁ3
˚
Largest difference in peak and hole (e A
)

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H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
Table 3
be highly efficient catalysts for the Suzuki coupling of
aryl chlorides with phenylboronic acid and the Heck
reaction of bromobenzene with styrene under the given
conditions.
Influence of solvents and bases on the Suzuki coupling of chlorobenzene
with phenyl-boronic acida
base
solvent
(HO)2B
+
Cl
Entry
Solvent
Base
Yield (%)b
4. Experimental
1
2
3
4
5
6
7
a
dioxane
toluene
THF
DMF/H2O
dioxane
dioxane
dioxane
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
K3PO4
t-BuOK
89.1
45.9
51.3
36.2
67.6
15.0
26.7
4.1. Materials and instruments
Benzoylferrocene, enzylamines, TiCl4, LiAlH4, AlCl3,
CH3I, t-BuOK, NaOAc, PPh3 were obtained commercially
and were used without further purification. Na2PdCl4 was
prepared in our laboratory. All of the solvents were puri-
fied with standard methods prior to use. Melting points
were obtained on a Yanaco micro melting point apparatus
and were uncorrected. Elemental analyses were measured
Reaction conditions: catalyst rac-5a (0.1 mol%), PhCl (1 mmol),
PhB(OH)2 (1.5 mmol), base (2 mmol), solvent (10 cm3), reflux, 10 h.
b
Determined by GC, based on PhCl, average of two runs.
1
on a Carlo Erba 1106 Elemental analyzer. H NMR spec-
tra were obtained with Bruker AV-400 spectrometer using
CDCl3 as the solvent and TMS as the internal standard. IR
spectra were recorded on a BIO-RAD 3000 spectropho-
tometer.
Under the optimized conditions as mentioned above,
the relative activities of 5a–c for the Suzuki coupling
of aryl chlorides and phenylboronic acid were studied
(Table 4). When the reactions were carried out at
100 ꢁC for 10 h, 5a–c all exhibited good activity with
the loading as low as 0.1 mol % (Entries 1–3). However,
when 0.01% of 5a was used, the coupling yield was lower
(Entry 4, 22.3%). Under the optimized reaction conditions
(K2CO3, dioxane, 100 ꢁC, 10 h) phenylboronic acid could
couple efficiently with the aryl chlorides ranging from
electron-donating to electron-withdrawing groups (Entries
5–10). In particular, for 4-CH3C6H5Cl the coupling yield
was up to 98.0% (Entry 6). Even for the bulky 2,4-dini-
trophenyl chloride, its coupling with phenylboronic acid
was also achieved and the resulting biaryl yield was
moderate.
4.2. Preparation of ferrocenylketimines (2)
General procedure: 2a–c were prepared according to the
literature method [8].
4.2.1. {(g5-C5H5)Fe(g5-C5H4C(C6H5)@NCH2C6H5)}
(2a)
Yield: (80%); a dark-red liquid; Anal. Calc. for
C24H21FeN: C, 76.00; H, 5.58; N, 3.69. Found, C, 76.08;
H, 5.69; N, 3.90%. FT-IR (KBr): 3084(w), 3027(w),
2856(w), 1614(vs), 1494(s), 1453(m), 1343(m), 1289(s),
1
1181(m), 1106(s), 1026(s), 1003(s), 822(s),703(s) cmꢁ1. H
NMR (CDCl3): d 3.81 (bs, 2H, H2, H5), 4.08 (bs, 2H,
H3, H4), 4.14 (s, 5H, g5-C5H5), 4.50 (s, 2H, H18), 7.45–
7.89 (m, 10H, Ph).
2.3. Heck reaction
We initially examined the Heck reaction of chloroben-
zene with styrene catalyzed by 5a–c. Unfortunately the
product yields were much lower (yield < 3%), and these
results were consistent with the another group’s observa-
tions [6]. Later we paid attention to the reaction of bromo-
benzene with styrene, and the results are summarized in
Table 5. It was found that using DMF as the solvent and
K2CO3 as the base at 140 ꢁC for 7 h, an excellent yield of
product could be obtained when the loading of palladacy-
cle 5b was as low as 0.1 mol% (Entry 6). Similar to the
Suzuki coupling, when 0.01% of catalyst was used, the cou-
pling yield was lower (Entry 8, 39%).
4.2.2. {(g5-C5H5)Fe(g5-C5H4C(C6H5)@NCH2C6H4-
OCH3-4)} (2b)
Yield: (76%); a dark-red liquid; Anal. Calc. for
C25H23FeNO: C, 73.36; H, 5.66; N, 3.42. Found, C,
73.25; H, 5.73; N, 3.19%. FT-IR (KBr): 3088(w),
3022(w), 2909(w), 1611(vs), 1511(vs), 1462(s), 1291(s),
1245(vs), 1173(m), 1101(s), 1035(s), 818(s), 702(s) cmꢁ1
.
1H NMR (CDCl3): d 3.82 (s, 3H, OCH3), 3.87 (bs, 2H,
H2, H5), 4.11 (bs, 2H, H3, H4), 4.17 (s, 5H, g5-C5H5),
4.55 (s, 2H, H18), 6.99–7.50 (m, 4H, H20, H21, H23,
H24), 7.25–7.38 (m, 5H, Ph).
3. Conclusions
4.2.3. {(g5-C5H5)Fe(g5-C5H4C(C6H5)@NCH2C6H4CH3-
4)} (2c)
tert-Ferrocenylamines were easily synthesized by N-
methylation of the corresponding sec-amines with
CH3I. Treatment of these tert-amines with Na2PdCl4
afforded racemic palladacycles with a r Pd–Csp2, Ferr-
ocenyl bond. These palladacycles have been proven to
Yield: (85%); a dark-red liquid; Anal. Calc. for
C25H23FeN: C, 76.35; H, 5.89; N, 3.56. Found: C,
76.21; H, 5.56; N, 3.81%. FT-IR (KBr): 3093(w),
3021(w), 2922(w), 1614(vs), 1515(s), 1480(s), 1290(vs),
1179(w), 1106(s), 1002(s), 820(vs), 703(vs) cmꢁ1
.
1H

H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
3861
Table 4
Palladacycles-catalyzed conversion of aryl chlorides to biarylsa
Entry
1
Aryl halide
Catalyst (mol%)
Product
Yield (%)b
89.1
rac-5a(0.1)
Cl
Cl
Cl
Cl
2
3
rac-5b(0.1)
rac-5c(0.1)
rac-5a(0.01)
rac-5a(0.1)
rac-5b(0.1)
rac-5c(0.1)
rac-5a(0.1)
rac-5b(0.1)
rac-5c(0.1)
rac-5c(0.1)
86.5
85.2
22.3
91.7
98.0
95.1
72.4
78.7
80.6
68.5
4
5
Cl
6
Cl
Cl
7
8
O2N
O2N
O2N
O2N
Cl
O2N
O2N
O2N
O2N
9
Cl
Cl
10
11
Cl
NO2
NO2
12
rac-5b(0.1)
45.3
NO2
NO2
Cl
NO2
NO2
a
Reaction conditions: ArCl (1 mmol), PhB(OH)2 (1.5 mmol), K2CO3 (2 mmol), dioxane (10 cm3), 100 ꢁC, 10 h.
Determined by GC, based on aryl chloride used, average of two runs.
b
NMR (CDCl3): d 2.15 (s, 3H, CH3), 3.85 (bs, 2H, H2,
tion conditions. In our experiment, 3% mmol of AlCl3 was
used as the catalyst and THF as the solvent.
H5), 4.10 (bs, 2H, H3, H4), 4.16 (s, 5H, g5-C5H5), 4.53
(s, 2H, H18), 7.13–7.25 (m, 4H, H20, H21, H23, H24),
7.43–7.55 (m, 5H, Ph).
4.3.1. {(g5-C5H5)Fe(g5-C5H4CH(C6H5)NHCH2C6H5)}
(3a)
4.3. Preparation of sec-ferrocenylamines (3)
Yield: (77%); an orange solid; m.p. 68–70 ꢁC. Anal.
Calc. for C24H23FeN: C, 75.60; H, 6.08; N, 3.67. Found:
C, 75.63; H, 6.25; N, 3.82%. FT-IR (KBr): 3328(s),
3084(m), 3022(m), 2948(m), 2857(m), 1598(m), 1493(vs),
General procedure: 3a–c were prepared with a modifica-
tion of the ‘Cais’ method [8]. The difference was the reduc-

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H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
Table 5
The Heck reaction of bromobenzene with styrenea
base
solvent
CH CH
CH CH2
+
Br
Entry
Solvent
Catalyst (mol%)
T (ꢁC)
Base
Yield (%)b
1
2
3
4
5
6
7
8
9
1,4-dioxane
1,4-dioxane
toluene
DMF
DMF
DMF
DMF
DMF
DMF
DMF
rac-5b(0.1)
rac-5b(1)
rac-5b(1)
rac-5b(0.1)
rac-5b(1)
rac-5b(0.1)
rac-5b(0.1)
rac-5b(0.01)
rac-5a(0.1)
rac-5c(0.1)
80
100
100
100
140
140
140
140
140
140
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
t-BuOK
K2CO3
K2CO3
K2CO3
3.0
5.0
3.0
22.0
100
100
87.0
39.0
96.0
98.0
10
a
All reactions were carried out with 1 mmol of PhBr, 1.5 mmol of styrene and 2 mmol of base in 10 cm3 of solvent for 7 h.
Determined by GC, based on PhBr, average of two runs.
b
1452(vs), 1283(m), 1197(m), 1105(vs), 1022(s), 996(s),
The solvent was removed under reduced pressure and
30 cm3 of water was then added. The mixture was
extracted with diethyl ether (3 · 20 cm3) and separated.
The extracts were combined, dried over Na2SO4 and
removed to give crude products which were purified by
column chromatography (silica gel, ethyl acetate/hex-
ane = 1:5, v/v) to afford 4a–c.
1
820(vs), 699(vs) cmꢁ1. H NMR (CDCl3): d 2.17 (s, 1H,
NH), 3.58–3.80 (q, 2H, H18) 4.06 (s, 1H, H11), 4.04 (s,
5H, g5-C5H5), 4.30 (bs, 2H, H2, H5), 4.48 (bs, 2H, H3,
H4), 7.23–7.43 (m, 10H, Ph).
4.3.2. {(g5-C5H5)Fe(g5-C5H4CH(C6H5)NHCH2C6H4-
OCH3-4)} (3b)
Yield: (72%); a yellow solid; m.p. 57–60 ꢁC. Anal. Calc.
for C25H25FeNO: C, 73.00; H, 6.13; N, 3.41. Found: C,
73.09; H, 6.31; N, 3.55%. FT-IR (KBr): 3324(m),
3083(m), 3022(m), 2954(s), 2827(m), 1610(vs), 1512(vs),
1452(s), 1300(m), 1247(vs), 1174(s), 1105(vs), 1036(s),
4.4.1. {(g5-C5H5)Fe(g5-C5H4CH(C6H5)N(CH3)CH2-
C6H5)} (4a)
Yield: (58%); an orange solid; m.p. 64–66 ꢁC. Anal.
Calc. for C25H25FeN: C, 75.96; H, 6.37; N, 3.54. Found:
C, 75.88; H, 6.60; N, 3.81%. FT-IR (KBr): 3081(s),
3019(s), 2957(s), 2783(s), 1596(s), 1493(vs), 1452(vs),
1
1001(s), 821(vs), 700(vs) cmꢁ1. H NMR (CDCl3): d 2.17
(s, 1H, NH), 3.51–3.74 (q, 2H, H18), 3.82 (s, 3H, OCH3),
4.04 (s, 5H, g5-C5H5), 4.05 (s, 1H, H11), 4.30 (bs, 2H,
H2, H5), 4.46 (bs, 2H, H3, H4), 6.90–7.41 (m, 4H, H20,
H21, H23, H24), 7.23–7.34 (m, 5H, Ph).
1366(m), 1286(m), 1106(vs), 1002(vs), 818(vs) cmꢁ1 1H
.
NMR (CDCl3): d 1.95 (s, 3H, H25), 3.22–3.51 (q, 2H,
H18), 3.79 (s, 5H, g5-C5H5), 4.13 (s, 1H, H11), 4.11 (bs,
2H, H2, H5), 4.34 (bs, 2H, H3, H4), 7.19–7.52 (m, 10H,
Ph).
4.3.3. {(g5-C5H5)Fe(g5-C5H4CH(C6H5)NHCH2C6H4-
CH3-4)} (3c)
Yield: (81%); a yellow solid; m.p. 93–94 ꢁC. Anal. Calc.
for C25H25FeN: C, 75.96; H, 6.37; N, 3.54. Found: C,
75.89; H, 6.15; N, 3.90%. FT-IR (KBr): 3324(m),
3073(m), 3013(m), 2924(m), 2821(m), 1597(m), 1508(vs),
1451(s), 1333(m), 1179(m), 1104(vs), 1021(s), 996(s),
4.4.2. {(g5-C5H5)Fe(g5-C5H4 CH(C6H5)N(CH3)CH2-
C6H4OCH3-4)} (4b)
Yield: (50%); an orange solid; m.p. 72–73 ꢁC. Anal.
Calc. for C26H27FeNO: C, 73.42; H, 6.40; N, 3.29. Found:
C, 73.37; H, 6.58; N, 3.36%. FT-IR (KBr): 3088(m),
3024(m), 2953(s), 2831(m), 2775(m), 1605(vs), 1510(vs),
1452(vs), 1296(m), 1242(vs), 1106(vs), 1002(vs), 818(vs)
1
817(vs), 699(vs) cmꢁ1. H NMR (CDCl3) d 2.17 (s, 1H,
NH), 2.14 (s, 3H, CH3), 3.54–3.76 (q, 2H, H18), 4.04 (s,
5H, g5-C5H5), 4.05 (s, 1H, H11), 4.30 (bs, 2H, H2, H5),
4.47 (bs, 2H, H3, H4), 7.12–7.21 (m, 4H, H20, H21, H23,
H24), 7.41–7.53 (m, 5H, Ph).
1
cmꢁ1. H NMR (CDCl3): d 1.98 (s, 3H, H25), 3.23–3.51
(q, 2H, H18), 3.85 (s, 3H, OCH3), 3.81 (s, 5H,g5-C5H5),
4.14 (s, 1H, H11), 4.13 (bs, 2H, H2, H5), 4.36 (bs, 2H,
H3, H4), 6.91–7.42 (m, 4H, H20, H21, H23, H24), 7.26–
7.35 (m, 5H, Ph).
4.4. Synthesis of tert-ferrocenylamines (4)
General procedure: To a stirred solution of 3 (2 mmol)
in 20 cm3 of THF was added CH3I (3 mmol) in 5 cm3
THF and t-BuOK (3 mmol). The mixture was kept in
the dark at room temperature and stirred for 48 h. TLC
monitored the reaction progress until it was complete.
4.4.3. {(g5-C5H5)Fe(g5-C5H4CH(C6H5)N(CH3)CH2-
C6H4CH3-4)} (4c)
Yield: (65%); an orange solid; m.p. 70–72 ꢁC. Anal.
Calc. for C26H27FeN: C, 76.29; H, 6.65; N, 3.42. Found:
C, 76.23; H, 6.43; N, 3.60%. FT-IR (KBr): 3091(m),

H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
3863
3023(m), 2956(s), 2776(m), 1600(m), 1513(vs), 1452(vs),
1286(m), 1106(vs), 1002(vs), 805(vs) cmꢁ1 1H NMR
1H, H3), 4.10 (m, 1H, H4), 7.13–7.22 (m, 4H, H20,
H21, H23, H24), 7.39–7.56 (m, 15H, PPh3), 7.70–7.85
(m, 5H, Ph).
.
(CDCl3): d 1.99 (s, 3H, H25), 2.35 (s, 3H, CH3), 3.24–
3.52 (q, 2H, H18), 3.83 (s, 5H, g5-C5H5), 4.16 (s, 1H,
H11), 4.15 (bs, 2H, H2, H5), 4.38 (bs, 2H, H3, H4),
7.13–7.22 (m, 4H, H20, H21, H23, H24), 7.44–7.55 (m,
5H, Ph).
4.6. General procedure for the Suzuki coupling
Palladacycles 5 (0.1 mmol%), aryl chlorides (1.0 mmol),
phenylboronic acid (1.5 mmol), K2CO3 (2 mmol), dioxane
(10 cm3) were added to a 25 cm3 round-bottomed flask
and the mixture was heated at 100 ꢁC for 10 h. Upon
cooling, the reaction mixture was poured into water and
extracted with CH2Cl2, concentrated and purified by flash
chromatography on silica gel. The purity of the com-
pounds was checked by GC and yields are based on aryl
chlorides.
4.5. Synthesis of cyclopalladated tert-ferrocenylamines (5)
General procedure: To a stirred solution of 4 (1 mmol),
sodium acetate (82 mg, 1 mmol) in 30 cm3 of methanol was
added dropwise a solution of Na2PdCl4 (0.29 g, 1 mmol) in
15 cm3 of methanol. The mixture was stirred for 4 h at
room temperature under argon and TLC monitored the
reaction’s progress. Then PPh3 (0.41 g, 1.5 mmol) was
added and the mixture was stirred for another 30 min.
The solvent was removed in vacuo, and the residues were
purified by column chromatography (silica gel, ethyl ace-
tate/hexane = 1:2, v/v) to give 5.
4.7. General procedure for the Heck reaction
Palladacycles
5
(0.1 mmol%), bromobenzene (1.0
mmol), styrene (1.5 mmol), K2CO3 (2 mmol), DMF
(10 cm3) were added to a 25 cm3 round-bottomed flask
and the mixture was heated at 140 ꢁC for 7 h. Upon cool-
ing, the reaction mixture was poured into water and
extracted with CH2Cl2, concentrated and purified by flash
chromatography on silica gel. The purity of the compounds
was checked by GC and yields are based on bromo-
benzene.
4.5.1. [PdCl(PPh3){(g5-C5H5)Fe(g5-C5H3CH(C6H5)N-
(CH3)CH2C6H5)}] (5a)
Yield: (72%); a red solid; m.p. > 193 ꢁC (dec.). Anal.
Calc. for C43H39ClFeNPPd: C, 64.68; H, 4.92; N, 1.75.
Found: C, 64.60; H, 4.89; N, 1.82%. FT-IR (KBr):
3054(w), 2955(w), 2922(w), 1486(m), 1450(m), 1435(vs),
1095(s), 999(s), 823(m), 752(s), 701(vs) cmꢁ1
.
1H
NMR(CDCl3): d 2.88 (m, 2H, H18), 3.21 (s, 3H, H25),
4.84 (s, 1H, H11), 3.85 (s, 5H, g5-C5H5), 3.76 (d, 1H,
H5), 4.08 (m, 1H, H4), 4.16 (d, 1H, H3), 7.73–7.82
(m,10H, 2Ph), 7.35–7.54 (m, 15H, PPh3).
4.8. X-ray crystallographic study of 5a
Crystals of 5a were grown at room temperature by slow
evaporation of a mixture of hexane and ethyl acetate over a
period of one week. A single crystal of this complex
was mounted on a Bruker SMART CCD diffractometer
equipped with monochromated graphite Mo Ka (k =
4.5.2. [PdCl(PPh3){(g5-C5H5)Fe(g5-C5H3CH(C6H5)N-
(CH3)CH2C6H4OCH3-4)}] (5b)
˚
0.71073 A) radiation at ambient temperature (T = 293 K)
Yield (80%); a red solid; m.p. > 189 ꢁC (dec.). Anal.
Calc. for C44H41ClFeNOPPd: C, 63.79; H, 4.99; N, 1.69.
Found: C, 63.72; H, 4.81; N, 1.96%. FT-IR (KBr):
3045(w), 2954(w), 1512(vs), 1454(m), 1435(vs), 1246(s),
using the x–2h multi-scans technique for data collection.
Semi-empirical absorption corrections were applied using
the SABABS program [18]. The structure was solved by direct
methods and refined by the full-matrix least-squares proce-
dure on F2 using the SHELX suite of programs [19]. The val-
ues of R1 were given based on Fo with a typical threshold of
F2 P 2r(F2). The weighted R-factors wR were based on F2
1
1178(s), 1100(s), 995(m), 816(s), 747(s), 702(vs) cmꢁ1. H
NMR (CDCl3): d 2.79 (s, 3H, H25), 3.24 (m, 2H, H18),
3.43 (s, 3H, OCH3), 3.73 (s, 5H, g5-C5H5), 3.74 (m, 1H,
H5), 3.80 (m, 1H, H4), 3.95 (d, 1H, H3), 4.96 (s, 1H,
H11), 6.90–7.05 (m, 4H, H20, H21, H23, H24), 7.39–7.66
(m, 15H, PPh3), 7.70–7.85 (m, 5H, Ph).
with calc. w = 1/[r2(Fo ) + (0.0000P)2 + 0.0827P] where
2
2
P = (Fo2 + 2Fc )/3 for 5a. Crystallographic data for 5a
are summarized in Table 1. Selected bond lengths and
4.5.3. [PdCl(PPh3){(g5-C5H5)Fe(g5-C5H3CH(C6H5)N-
(CH3)CH2C6H4 CH3-4)}] (5c)
angles for 5a are presented in Table 2.
Yield (70%);
a
red solid; m.p. > 172 ꢁC (dec.).
5. Supplementary material
Anal. Calc. for C44H41ClFeNPPd: C, 65.04; H, 5.09; N,
1.72. Found: C, 65.12; H, 4.85; N, 1.65%. FT-IR
(KBr): 3051(w), 2954(w), 2920(w), 1484(s), 1455(s),
1437(vs), 1185(m), 1103(s), 1002(m), 823(m), 751(s),
CCDC 603093 contains the supplementary crystallo-
graphic data for 5a. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
693(vs) cmꢁ1 1H NMR (CDCl3): d 2.43 (s, 3H, CH3),
.
2.79 (s, 3H, H25), 3.21 (m, 2H, H18), 3.50 (s, 5H, g5-
C5H5), 5.16 (s, 1H, H11), 3.73 (m, 1H, H5), 3.82 (d,

3864
H.-X. Wang et al. / Polyhedron 26 (2007) 3857–3864
(i) R.B. Bedford, C.S.J. Cazin, S.J. Coles, T. Gelbrich, M.B.
Acknowledgements
Hursthouse, V.J.M. Scordia, J. Chem. Soc., Dalton Trans. (2003)
3350;
We are indebted to the Natural Science Foundation of
Tianjin Metropolitan Council (Project No. 033609011)
and the State Key Laboratory of Elemento-organic Chem-
istry, Nankai University, People’s Republic of China for
financial support of this project.
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