Synthesis, characterization, and applications in Heck and Suzuki coupling reactions of amphiphilic cyclopalladated ferrocenylimines

Tetrahedron 63 (2007) 11475–11488

Synthesis, characterization, and applications in Heck and Suzuki

coupling reactions of amphiphilic cyclopalladated

ferrocenylimines

Bing Mu,^a,b,cTiesheng Li,^a,b,c,Wenjian Xu,^a,b,cGuoliang Zeng,^a,b,c

*

Pingping Liu^a,b,cand Yangjie Wu^a,b,c,

*

^aDepartment of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, PR China

^bThe Key and Open Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University,

Daxue road 75, Zhengzhou 450052, PR China

^cThe Key Lab of Advanced Nano-information Materials of Zhengzhou, Daxue road 75, Zhengzhou 450052, PR China

Received 7 March 2007; revised 1 August 2007; accepted 3 August 2007

Available online 7 August 2007

Abstract—A series of novel amphiphilic ferrocenylimines and their cyclopalladated complexes of general formula [Fe(h⁵-C₅H₅)(h⁵-

C₅H₄CR₁]NR₂)] (R₁¼H, R₂¼C₁₂H₂₅-n 4a, R₁¼H, R₂¼C₁₆H₃₃-n 4b, R₁¼CH₃, R₂¼C₁₂H₂₅-n 4c, R₁¼CH₃, R₂¼C₁₆H₃₃-n 4d),

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)CR₁]NR₂]}]₂(5a–d), [PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)–CR₁]NR₂]}(PPh₃)] (6a–d), were prepared and

1

characterized by H NMR, ¹³C NMR, ³¹P NMR, IR, HRMS, and elemental analysis. The crystal structures of 5c,d were determined by

X-ray crystallography. These amphiphilic cyclopalladated complexes are thermally stable and insensitive to oxygen and moisture. The redox

properties of 4a–d, 5a–d, 6a–d were also investigated using cyclic voltammetric technique. Compounds 5a–d, 6a–d displayed good activity in

the Heck reaction of a variety of aryl halides with ethyl acrylate or styrene and the Suzuki–Miyaura cross-coupling reaction of aryl bromides

with phenylboronic acid in bulk solution. They are also suitable for formation of Langmuir–Blodgett (LB) ﬁlms.

Ó 2007 Published by Elsevier Ltd.

1. Introduction

assortment including ferrocene derivatives in Heck reaction,

though under more harsh conditions, and excellent yields

and high TONs were recorded for the cyclopalladated com-

plexes.¹¹In our previous work, we have focused on the cy-

clometallation of ferrocenylimines and applications of

these systems (such as compounds 1, 2, 3 in Scheme 1).¹²

These cyclopalladated ferrocenylimines were effective

catalysts for the Heck reaction, the dimerizaton of aryl-

mercurials, and the Suzuki reaction.^13–16

Cyclopalladated compounds have been widely studied in re-

cent decades.¹They show important applications in organic

or organometallic synthesis, in the syntheses of polynuclear

organometallic complexes, in homogeneous catalysis, and in

chiral recognition or discrimination.^2–5In the past ten years,

a great effort has been made in order to achieve the synthesis

of palladacycles having [C, N, X]^ꢀ(X¼N, O, P, S) terdentate

groups,⁶mainly due to the potential hemilability of the s

(Pd–X) bond in these systems.⁷By far, ﬁve-membered

palladacycles with nitrogen donors have generated consider-

able interest because they are easily synthesized, thermally

stable, insensitive to air, and high activity for various cou-

pling reactions.⁸For example, it was reported that ortho-

palladated imines are highly reactive in Heck reaction to

afford quantitative yields and with very high TONs, and

the CN-palladacycles showed impressive efﬁciency in

Suzuki reaction by Milstein et al.^9,10Cyclopalladated ben-

zylamines were later studied in more detail and wider

In the recent years, amphiphilic transition metal catalysts on

solid substrates by Langmuir–Blodgett (LB) technique for

catalytic applications inspire much interest. For instance, it

was reported that amphiphilic manganese or iron porphyrins

as well as rhodium complexes of 4,4-diakylbipyridines had

been structured on a solid substrate leading to well-deﬁned,

supported catalytic systems by LB technique.^17–19These

results obtained with LB ﬁlms have demonstrated that the

catalysts’ activity and selectivity were inﬂuenced by mole-

cular order, and indicated that supporting transition metal

complexes on organized LB ﬁlms offered potential in the

design of tailor-made catalysts.²⁰

Keywords: Amphiphilic ferrocenylimines; Cyclopalladated complexes;

Cyclic voltammetric techniques; Heck reaction; Suzuki–Miyaura reaction;

Langmuir–Blodgett (LB) ﬁlms.

* Corresponding authors. Tel./fax: +86 371 67766667; e-mail addresses:

lts34@zzu.edu.cn; wyj@zzu.edu.cn

In the view of the facts and as a part of project directed to-

ward the synthesis of amphiphilic complexes, we have

now centered our attention on amphiphilic cyclopalladated

0040–4020/$ - see front matter Ó 2007 Published by Elsevier Ltd.

doi:10.1016/j.tet.2007.08.004

11476

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

CH₃

C

CH₃

C

CH₃

C

N

CH₃

N

Pd

Pd Cl

Fe

Cl

2

PPh₃

3

2

1

Scheme 1.

ferrocenylimines with long-chain hydrocarbon for further

LB ﬁlms formation.

precipitate, because they exhibited high solubility in metha-

nol. A solution of chloride-bridged palladacyclic dimer (5a–

d) were treated with 1.5 equiv of PPh₃per palladium in

CH₂Cl₂at room temperature for 0.5 h to afford the corre-

sponding monomeric compounds (6a–d) in 75–92% yields.

In this paper, we synthesized a series of novel long alkyl fer-

rocenylimines and their cyclopalladated complexes (4a–d,

5a–d, 6a–d), and undertake a broader investigation into

Heck and Suzuki–Miyaura cross-coupling reactions in

bulk solution as standard test reaction to probe the reactivity

of 5a–d, 6a–d and the inﬂuence of long-chain hydrocarbon

on catalytic activity. The study of their behavior at the air/

water interface also was reported. We investigated primarily

the catalytic application of the transferred 6d LB ﬁlms in

Heck reaction.

2.2. Characterization

All the amphiphilic complexes are thermally stable and not

sensitive to air and moisture. They are highly soluble in most

of the common solvents (chloroform, dichloromethane, ben-

zene, toluene, ethyl acetate, etc.), slightly soluble in petro-

leum ether, hexane and alcohols, and insoluble in water.

In addition, the electrochemical properties of ferrocene de-

rivatives^21,22have been widely studied because ferrocene

as an electrochemically active group is known to exchange

electrons very quickly between the ferrocene moiety and

electrode surface and behave as a reversible compound.²³

We thought it was interesting to elucidate the effect pro-

duced by the long-chain alkyl substituents at nitrogen on

the electronic environment of the iron(II).

The IR spectra of the free imines (4a–d) show an intense

sharp band in the range of 1628–1644 cm^ꢀ1assigned to the

stretching of the C]N bond. For the cyclopalladated com-

plexes this band appears at lower frequencies in both families

of complexes. This fact, which has been also reported for

other cyclopalladation of shiff bases,²⁴was attributed to a de-

crease in the bond order of the imine bond upon cyclopalla-

dation. The C]N absorption of the monomeric complexes

(1593–1601 cm^ꢀ1) is shifted to higher wave numbers in com-

parison to the dimeric complexes (1579–1585 cm^ꢀ1).

2. Results and discussion

The H NMR, ¹³C NMR spectra, HRMS, and elemental

1

2.1. Preparation of amphiphilic ferrocenylimines and

their cyclopalladated complexes 4a–d, 5a–d, 6a–d

analysis of 4a–d, 5a–d, 6a–d were consistent with the pro-

posed structures. For 6a–d, the appearance of only one sig-

nal around 38 ppm in ³¹P NMR spectra suggested the

formation of a single isomer.¹⁴

The synthesis of ferrocene derivatives is shown in Scheme 2.

The ferrocenylimines were synthesized by the condensation

of ferrocenecarbaldehyde or acetylferrocene with the corre-

sponding amines (n-dodecylamine, n-hexadecylamine), re-

The crystal structures of 6c and 6d were determined by X-ray

single crystal analysis. The molecules are illustrated in Fig-

ures 1 and 2, respectively. Crystal data are listed in Table 1.

˚

spectively, in the presence of molecular sieves (4 A). For

the syntheses of 4c, 4d, large excess of amines and molecular

sieves with long reaction time were needed to force the dis-

placement of the equilibria. The difﬁculties of preparing 4c,

4d might be ascribed to the bulkier methyl substituent at the

iminic carbon.²⁴

ꢁ

˚

Selected bond lengths (A) and angles ( ) are given in Table 2.

The Pd(II) atom in every complex is in a slightly distorted

square-planar environment bonded to the P, N, Cl, and C

(6) atoms of ferrocenyl moiety. The deviations of the palla-

˚

dium from the mean plane are 0.1155 and 0.1201 A for 6c

and 6d, respectively. The C₅H₃moiety and the ﬁve-mem-

bered palladacycle are approximately co-planar (dihedral

angles of 3.8 (6c) and 5.4^ꢁ(6d)). The two Cp rings are par-

allel, nearly eclipsed with tilt angles of 1.3 and 1.0^ꢁfor 6c

and 6d, respectively. The phosphine molecule and the imino

nitrogen adopt a trans arrangement with P1Pd1N1 angle of

169.95 and 170.17^ꢁfor 6c and 6d, respectively, possibly

due to the steric bulk of the long-chain hydrocarbon.

R₁

C=O

R₁

C

NR₂

R₂-NH₂

Li₂PdCl₄, NaOAc

CH₃OH

Fe

C₆H₅CH₃

4a-d

R₁

C

R₁

C

R₁

H

R₂

a

b

c

d

n-C₁₂H₂₅

NR₂

H

n-C₁₆H₃₃

NR₂

PPh₃

CH₂Cl₂

CH₃n-C_{12 25}

H

Fe

Fe Pd Cl

Pd Cl

CH₃n-C_{16 33}

PPh₃

6a-d

2

5a-d

2.3. Electrochemical behavior

Scheme 2.

To elucidate the effect produced by the long-chain alkyl sub-

stituents at nitrogen on the electronic environment of the

iron(II), we studied the electrochemical properties of ferro-

cene derivatives.

Compounds 5a–d were prepared according to the general

procedure.²⁵For ferrocenylimines with R¼H (4a, 4b), the

formation of the palladacycle was achieved without

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

11477

Figure 1. Molecular structure of complex 6c$0.25C₆H₁₂. C₆H₁₂and hydrogen atoms are omitted for clarity.

Figure 2. Molecular structure of complex 6d$0.5C₆H₁₂. C₆H₁₂and hydrogen atoms are omitted for clarity.

ꢁ

˚

Table 2. Selected bond lengths (A) and angles ( ) for 6c, 6d

Table 1. Crystallographic data and structure reﬁnement for 6c, 6d

Compound

6c$0.25C₆H₁₂

6d$0.5C₆H₁₂

Compound

6c$0.25C₆H₁₂

6d$0.5C₆H₁₂

Empirical formula

Formula weight

T (K)

C_43.50H₅₄ClFeNPPd C₄₉H₆₅ClFeNPPd

819.55

291(2)

Pd(1)–C(6)

Pd(1)–N(1)

Pd(1)–P(1)

Pd(1)–Cl(1)

N(1)–C(11)

N(1)–C(13)

C(6)–Pd(1)–N(1)

C(6)–Pd(1)–P(1)

N(1)–Pd(1)–P(1)

C(6)–Pd(1)–Cl(1)

N(1)–Pd(1)–Cl(1)

P(1)–Pd(1)–Cl(1)

C(11)–N(1)–Pd(1)

C(13)–N(1)–Pd(1)

1.988(5)

2.130(4)

2.2407(14)

2.3665(15)

1.295(6)

1.997(4)

2.134(4)

2.2432(13)

2.3779(13)

1.299(5)

896.69

291(2)

Crystal system

Space group

Monoclinic

P2(1)/c

25.712(5)

9.3761(19)

17.735(4)

90

Monoclinic

P2(1)/c

28.398(6)

9.2385(18)

17.775(4)

90

˚

a (A)

1.473(7)

1.472(6)

˚

b (A)

80.76(19)

92.98(16)

169.95(12)

169.76(16)

93.43(12)

93.87(6)

80.67(16)

93.13(13)

170.17(10)

169.38(13)

93.78(10)

93.51(5)

˚

c (A)

a (deg)

b (deg)

g (deg)

95.98(3)

90

93.32(3)

90

3

˚

V (A )

Z

4252.3(15)

4

1.280

4655.6(16)

4

1.279

114.4(4)

123.5(3)

114.8(3)

123.4(3)

D_calcd(Mg/m³)

Absorption coefﬁcient (mm^ꢀ1

F(000)

)

0.893

1704

0.822

1880

Crystal size (mm)

Completeness to 2q¼25.00

Data/restraints/parameters

GOF (on F²)

Final R indices R1, wR2[I>2s(I)] 0.0542, 0.1461

R indices (all data) R1, wR2 0.0711, 0.1565

0.20ꢂ0.17ꢂ0.16

0.20ꢂ0.18ꢂ0.17

Electrochemical parameters for 4a–d, 5a–d, 6a–d and re-

lated compounds were obtained one by one from cyclic vol-

tammetric studies of freshly prepared solutions (10^ꢀ4M) in

DMF using tetrabutylammonium perchlorate (0.1 M) as sup-

porting electrolyte. The most relevant electrochemical data

95.3%

7131/9/437

1.039

95.7%

8294/0/438

1.081

0.0530, 0.1427

0.0641, 0.1494

11478

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

in the equivalent environment. For 5a–d and 6a–d, the E⁰

values were also dependent on the nature of the substituents

(R₁). Moreover, the E⁰values were almost not affected by the

substituents (R₂), probably because their basicity of the nitro-

gen was nearly the same in both cases.²¹The E⁰values of im-

ines (4a–d) were more anodic than that of cyclopalladated

complexes (5a–d, 6a–d), thus indicating the binding of

Pd(II) to Fc facilitated the oxidation of Fe(II). Comparison

of the E⁰values for dimeric and monomeric compounds re-

vealed that dimeric complexes (5a–d) were less resistant to

oxidation. The above ﬁndings were in good agreement with

the results for related ferrocene derivations.²⁸Cyclic voltam-

mograms of di-m-chloro-bridged derivatives (5a–d) exhibited

only one wave thus suggesting that the two ferrocenyl units

are independent of each other.²⁹For the free ligand, di- and

mono- nuclear complexes, the corresponding E⁰values

were more cathodic than that reported for related ferrocene

derivatives with R₂¼phenyl group (1, 2, 3) in three families

of compounds, thus indicating that the alkyl long-chain sub-

stituents at nitrogen produced a greater enhancement of the

proclivity of the iron(II) to oxidation.

Table 3. Electrochemical data: anodic (E_pa) and cathodic potentials (E_pc),

half-wave potentials E⁰, and separation of the peaks (DE_p) for complexes

(4a–d, 5a–d, 6a–d) (in mV), at a scan speed y¼50 mV s^ꢀ1

Compound

E_pc

E_pa

E⁰

DE_p

Ferrocene

1

485

600

593

586

556

558

475

437

456

435

431

539

522

500

490

500

552

679

664

659

628

630

545

508

529

501

496

608

589

569

555

567

518.5

639.5

628.5

622.0

592.0

594.0

510

472.0

492.5

468.0

463.5

573.5

555.5

534.5

522.0

533.5

67

79

71

73

72

70

71

73

66

65

69

67

69

65

67

4a

4b

4c

4d

2

5a

5b

5c

5d

3

6a

6b

6c

6d

are summarized in Table 3. The cyclic voltammetric behav-

ior of all the compounds showed one pair of well-deﬁned and

stable redox waves in the potential range of 0–0.9 V at the

GC working electrode, which was attributed to the Fc/Fc⁺re-

dox process. These experiments were performed at different

scan rates, y {from10 to 300 mV s^ꢀ1}, and in all cases, the

I_pa/I_pcmolar ratio was close to 1 with a linear relationship be-

tween the I_paand y^1/2. All these ﬁndings were consistent with

those expected for a simple and reversible one-electron

transfer process.²⁶

2.4. Heck coupling reaction

Our initial survey of solvents, including toluene, dioxane,

DMA, and DMF with bromobenzene and ethyl acrylate as

the coupling partners (using 0.1 mol % of 5c, Et₃N as the

base and n-Bu₄NBr as cocatalyst) revealed that DMF was

much better than others (in Table 4, entries 1–5). The reac-

tion carried out in the absence of n-Bu₄NBr is in a very

low yield (entry 6). The role of n-Bu₄NBr probably strength-

ened the stabilizations of low coordinated Pd(0) species, and

was as the phase transfer catalyst for the inorganic base/polar

solvent/organic substrates/product phases.³⁰Then screening

a variety of bases (e.g., Et₃N, Na₂CO₃, K₂CO₃, Cs₂CO₃,

NaOAc, KF$2H₂O, and K₃PO₄), K₃PO₄was found to give

the best result (entries 5, 7–12). Increasing the loadings of

K₃PO₄from 0.5 mmol to 1 mmol could give 100% HPLC

yield (entry 13).

The half-wave potential E⁰of imines (4c, 4d) was more

cathodic than that of imines (4a, 4b), suggesting that the

replacement of an H by a CH₃facilitates the oxidation of the

iron(II). The variation could be related to the stronger elec-

tron donor ability of the CH₃group.²⁷For 4a and 4b or 4c

and 4d, thereplacement ofa–ⁿC₁₂H₂₅bya –ⁿC₁₆H₃₃hadalit-

tle inﬂuence on the E⁰values, which indicated that the two

long-chain alkyl substituents at nitrogen in both cases were

With the appropriate solvent (DMF), base (K₃PO₄) and

cocatalyst (n-Bu₄NBr) in hand, the relative activities of sev-

eral amphiphilic palladacycles 5a–d, 6a–d for bromoben-

zene and ethyl acrylate were studied (in Table 5, entries

Table 4. Inﬂuence of base, solvent on the Heck coupling of bromobenzene

and ethyl acrylate^a

cat 5c / base

(E-only)

Br +

COOEt

n-Bu₄NBr / solvent

Entry

Base

Solvent

Yield^b(%)

T (^ꢁC)

Table 5. The relative activities of several palladacycles (5a–d, 6a–d) on the

Heck coupling of bromobenzene and ethyl acrylate^a

1

2

3

4

Et₃N

Na₂CO₃

K₂CO₃

Cs₂CO₃

NaOAc

KF$2H₂O

K₃PO₄

Dioxane

Toluene

DMA

DMF

28

62

19

78

82

29

55

65

89

56

59

91

100

101

115

140

160

140

cat / base

n-Bu₄NBr / DMF

(E-only)

Br +

COOEt

5

6^c

7

Entry

Catalyst (0.1 mol %)

Yield^b(%)

8

9

10

11

12

13^d

1

2

3

4

5

6

7

8

5a

5b

5c

5d

6a

6b

6c

6d

96

99

>99

94

>99

K₃PO₄

a

Reaction conditions: PhBr (0.5 mmol), ethyl acrylate (2 mmol), catalyst

5c (0.1 mol %), base (0.5 mmol), n-Bu₄NBr (0.5 mmol), solvent

(1.5 mL), 12 h.

Yield determined by HPLC, based on the product.

n-Bu₄NBr (0 mmol).

K₃PO₄(1 mmol).

a

Reaction conditions: PhBr (0.5 mmol), ethyl acrylate (2 mmol), catalyst

(0.1 mol %), n-Bu₄NBr (0.5 mmol), K₃PO₄(1 mmol), DMF (1.5 mL),

12 h, 140 ^ꢁC.

b

c

d

b

Isolated yield (average of two runs).

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

Table 6. Heck coupling of aryl halides with ethyl acrylate^a

11479

cat 5c / K₃PO₄

(E-only)

COOEt

+

X

n-Bu₄NBr / DMF

R

7

Entry

ArX

Catalyst (mol %)

t (h)

Base (mmol)

Product

Yield^b(%)

No.

1

0.0001

0.01

0.1

12

24

12

1

7a

99

>99

91

I

COOEt

2

1

7a

7b

7c

7d

7e

7f

Br

COOEt

H₃C

H₃CO

F₃C

3

1

H₃C

H₃CO

F₃C

Br

COOEt

4

0.1

1

95

Br

COOEt

5

0.1

1

75

Br

H₃COC

O₂N

NC

6

0.1

1

84

H₃COC

O₂N

NC

Br

7

0.1

1

90

Br

8

0.01

0.1

0.5

1

7f

>99

88

9

7g

7h

7i

N

10

11

12

0.1

1

80

N

Br

0.1

1

90

N

S

COOEt

N

Br

0.1

1

7j

47

S

COOEt

13

14

15

0.1

12

24

1

7k

7l

96

93

CH₃

Br

CH₃

COOEt

CH₃

Br

0.1

12

1

7m

7a

57

COOEt

16

17

Trace

Cl

O₂N

0.1

12

1

7f

Trace

99

O₂N

Cl

COOEt

18

0.03

0.5

COOEt

a

Reaction conditions: aryl halide (0.5 mmol), ethyl acrylate (2.0 mmol), catalyst 5c, n-Bu₄NBr (0.5 mmol), base (K₃PO₄) and DMF (1.5 mL), at 140 ^ꢁC.

Isolated yields (average of two experiments).

b

11480

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

1–8). We found that 5c and 6a–d all exhibited higher activity

with 0.1 mol % catalyst loading. However, phosphine-free

cyclopalladated ferrocenylimine 5c was more friendly to en-

vironment than others, so a wide range of electronically and

structurally diverse aryl halides could be cross-coupled efﬁ-

ciently with ethyl acrylate or styrene by complex 5c under

these optimized reaction conditions (K₃PO₄, DMF,

n-Bu₄NBr, 140 ^ꢁC). The results are listed in Tables 6 and 7.

These data suggest that styrene with aryl halides required

the longer reaction time than ethyl acrylate with aryl halides.

Using 10^ꢀ4mol % of catalyst 5c to catalyze oleﬁnation of

iodobenzene with ethyl acrylate, the high turnover number

of 1 million was obtained in a ten-fold larger scale reaction

(in Table 6, entry 1). The reaction of 4-methoxybromoben-

zene with a strongly electron-donating group and ethyl acry-

late or styrene gave 95% and 91% isolated yields,

respectively (in Table 6, entry 4 and in Table 7, entry 4). 3-

Bromopyridine and bromonaphthalene could also proceed

the cross-coupling reaction smoothly under the same reac-

tion conditions to afford the cross-coupling products in

high yields (in Table 6, entries 11, 13 and in Table 7, entries

11, 13). The sterically hindered 2-bromotoluene gave the

cross-coupled product in only modest yields (in Table 6, en-

try 15 and in Table 7, entry 15). However, for 2-methylbro-

monaphthalene, prolonging the reaction time resulted in

good yields (in Table 6, entry 14 and in Table 7, entry 14).

For bromobenzene with ethyl acrylate or styrene, the catalyst

loading could be also lowered to 10^ꢀ2mol % with high activ-

ity (in Table 6, entry 2 and in Table 7, entry 2). Interestingly,

when the loading of K₃PO₄was reduced, we unexpectedly

found that the aryl halides with nitro group gave excellent re-

sults with catalyst loading as low as 0.01 mol % (in Table 6,

entries 8, 18 and in Table 7, entries 8, 18). As for non-acti-

vated chlorobenzene, complex 5c was nearly inactive under

the similar reaction conditions. As observed above, amphi-

philic cyclopalladated ferrocenylimines were efﬁcient cata-

lysts for the Heck coupling of aryl iodides, bromides, and

electron deﬁcient chlorides. Finally, it was worthy to note

that all of these reactions studied showed high regioselectiv-

ity for trans-coupling, and no cis-product was found.

Table 7. Heck coupling of aryl halides with styrene^a

cat 5c / K₃PO₄

n-Bu₄NBr / DMF

+

X

(E-only)

R

8

Entry

ArX

Catalyst (mol %)

t (h)

Base (mmol)

Product

Yield^b(%)

No.

1

2

3

4

5

6

7

8

9

10

0.0001

0.01

0.1

24

28

1

8a

61

91

75

91

90

54

94

90

65

I

1

8a

8b

8c

8d

8e

8f

Br

H₃C

H₃CO

F₃C

1

H₃C

H₃CO

F₃C

Br

0.1

1

Br

0.1

1

Br

H₃COC

O₂N

NC

0.1

1

H₃COC

O₂N

NC

Br

0.1

1

Br

0.01

0.1

0.5

1

8f

8g

8h

N

0.1

1

N

(continued)

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

11481

Table 7. (continued)

Entry

ArX

Catalyst (mol %)

t (h)

Base (mmol)

Product

Yield^b(%)

No.

Br

11

12

0.1

24

1

8i

87

58

N

8j

S

Br

13

14

15

0.1

24

28

24

1

8k

92

97

61

CH₃

Br

CH₃

8l

CH₃

Br

8m

16

17

0.1

24

1

8a

8f

Trace

68

Cl

O₂N

0.1

1

O₂N

Cl

O₂N

18

0.01

0.5

O₂N

a

Reaction conditions: aryl halide (0.5 mmol), styrene (1.5 mmol), catalyst 5c, n-Bu₄NBr (0.5 mmol), base (K₃PO₄) and DMF (1.5 mL), at 140 ^ꢁC.

Isolated yields (average of two experiments).

b

2.5. Suzuki–Miyaura cross-coupling reaction

smoothly in toluene. Among the tested bases, K₃PO₄$7H₂O

was found to be the most effective base.

Afterwards, the Suzuki–Miyaura cross-coupling reactions of

4-bromotoluene and phenylboronic acid were carried out

with various bases and solvents in the presence of

0.001 mol % of 6c without the protection of inert gas (Table

8). It can be seen from Table 8, the reaction proceeded

With the appropriate solvent (toluene) and base (K₃PO₄$

7H₂O) in hand with 0.001 mol % catalyst loading, the relative

activity of several palladacycles 5a–d, 6c and 6d for the

same model reaction was then studied. As shown in Table 9,

Table 9. Suzuki–Miyaura reaction: catalyst study^a

Table 8. Investigation of the Suzuki–Miyaura reaction conditions^a

Cat. 6c, base

Catalysts

.

K₃PO₄7H₂O

+

Br

H₃C

B(OH)₂

+

Br

H₃C

B(OH)₂

Solvent, T

Toluene, 110 °C

45 min

Entry

Base

Solvent

T (^ꢁC)

Yield^b(%)

Entry

Catalyst

Yield^b(%)

1

2

3

4

5

6

7

8

9

K₃PO₄$7H₂O

K₃PO₄

KF$2H₂O

K₂CO₃

NaOH

Dioxane

DMF

100

140

110

24

29

98

64

46

76

73

2

1

2

3

4

5

6

7

8

5a

5b

5c

5d

6a

6b

6c

6d

69

77

48

62

83

78

98

68

Toluene

NaOAc

NaO^tBu

6

a

Reaction conditions: 4-bromotoluene 0.5 mmol, PhB(OH)₂0.6 mmol,

base 1.0 mmol, solvent 2.5 mL, 5.0ꢂ10^ꢀ6mmol of Pd of catalyst 6c,

reaction time is 45 min.

Reaction conditions: 4-bromotoluene 0.5 mmol, PhB(OH)₂0.6 mmol,

K₃PO₄$7H₂O 1.0 mmol, Solvent 2.5 mL, 5.0ꢂ10^ꢀ6mmol of Pd of cata-

lyst, reaction time is 45 min.

b

Isolated yields based on 4-bromotoluene in two runs.

11482

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

60

50

40

30

20

10

0

monomeric complexes 6c, 6d showed higher activity toward

this reaction than dimeric complexes 5a–d. In contrast,

6c displayed the good activity between that of 5a–d, 6a–d

(entry 7).

Under the optimized reaction conditions (K₃PO₄$7H₂O,

toluene, 110 ^ꢁC), a variety of aryl bromides by using

0.001 mol % of 6c could be coupled efﬁciently with phenyl-

boronic acid. The results are shown in Table 10. For acti-

vated and inactivated aryl bromides, excellent yields were

obtained (entries 1, 3, 4, 5). However, 4-bromotoluene

with an electro-donating group also provided the biaryl

product in 98% isolated yield (entry 6). For 2-bromotoluene

only 40% isolated yield was obtained under the same reac-

tion conditions (entry 8). When the catalyst loading was

reduced to 0.0001 mol % for 4-nitro-bromobenzene and 4-

bromotoluene, only 63% and 30% isolated yields were

obtained, respectively (entries 2, 7). In a word, amphiphilic

cyclopalladated ferrocenylimines were efﬁcient catalysts for

aryl bromides with phenylboronic acid.

5b

6d

6c

5d

5a

6a

6b

5c

0

50

100

150

Finally, in comparison with similar catalyst like di-m-chloro-

bridged cyclopalladated ferrocenylimine 2,¹³and cyclopal-

ladated ferrocenylimine triphenylphosphine complexes,³¹

amphiphilic complexes 5c and 6c were more active for the

Heck and Suzuki coupling, respectively. This could be ac-

credited with two reasons: one was that long-chain alkyl sub-

stituents at nitrogen promoted oxidative addition of aryl

Area Per Molecular (Å²)

Figure 3. p–A isotherms for 5a–d, 6a–d on pure water subphase (compres-

sion rate: 10 mN/m).

halides to the Pd intermediate by making palladium more

electron rich and increased the activity consequently, the

other was that alkyl substituents improved the solubility of

the catalysts in organic solvent.

Table 10. Suzuki coupling of aryl bromides with phenylboronic acid^a

Cat. 6c

.

K₃PO₄7H₂O

2.6. The study on catalytic application of 6d LB ﬁlms in

Heck reaction

+

ArBr

Ar

B(OH)₂

Toluene, 110 °C

45 min

Compounds 5a–d, 6a–d were spread, respectively, on the

water surface at room temperature to measure surface pres-

sure (p)–area (A) isotherms (Fig. 3). The isotherms show

a gradual transition, indicating a slight structure alteration

in the molecules. Obviously, all the p–A isotherms have

high collapse pressure, suggesting the formation of the con-

densed monolayers on the subphase. Take 6d as an example,

monolayer of 6d could be transferred onto hydrophilic or

hydrophobic glass slides as a Y-type ﬁlms with a transfer

ratio of almost unity under a surface pressure of 25 mN/m,

using Langmuir–Blodgett technique. The LB ﬁlms were

stable, uniform and close packing of molecules.³²We investi-

gated primarily the catalytic activity of the transferred 6d LB

ﬁlms in Heck reaction. The results indicated that 6d LB ﬁlms

could not exhibit good catalytic activity, because the desorp-

tion of the ﬁlms was observed when glass slides were placed

in organic solvents or under heating conditions. Further ex-

periments are currently in progress to explore milder reac-

tion conditions in aqueous media at room temperature for

the catalytic application of LB ﬁlms.

Entry

ArBr

Mol %

of Pd

Product

No.Yield^b(%)

1

2

3

4

0.001

0.0001

0.001

9a 97

O₂N

Br

O₂N

9a 63

9b >99

9c >99

H₃COC

Br

H₃COC

Br

5

0.001

9d >99

6

7

8

0.001

0.0001

0.001

9e 98

9e 30

9f 39

H₃C

Br

H₃C

Br

3. Conclusions

9

0.001

9g 72

N

Br

N

We have synthesized a series of novel amphiphilic ferroce-

nylimines and their cyclopalladated complexes. The pallada-

cycles are thermally stable and insensitive to oxygen and

moisture. Electrochemical studies for ferrocene derivatives

a

Reaction conditions: aryl bromides 0.5 mmol, PhB(OH)₂0.6 mmol,

K₃PO₄$7H₂O 1.0 mmol, Solvent 2.5 mL.

Isolated yields.

b

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

11483

indicated a simple and reversible one-electron transfer pro-

cess, and the long-chain alkyl substituents at nitrogen pro-

duced a greater enhancement of the proclivity of the

iron(II) to oxidation than phenyl substituents at nitrogen.

Cyclopalladated complexes (5a–d, 6a–d) are efﬁcient cata-

lysts for the Heck reaction of aryl halides with ethyl acrylate

or styrene in bulk solution. Furthermore, they were also

found to be very efﬁcient for Suzuki–Miyaura cross-

coupling reaction of aryl bromides with phenylboronic

acid. They are suitable for formation of Langmuir–Blodgett

(LB) ﬁlms.

68.3, 62.0, 31.9, 30.9, 29.65, 29.63, 29.61, 29.5, 29.3,

27.3, 22.7, 14.1; HRMS (positive ESI) calcd for

C₂₃H₃₅FeN [M+1]⁺: 382.2197, found: 382.2190. Anal.

Calcd for C₂₃H₃₅FeN: C, 72.43; H, 9.25; N, 3.67. Found:

C, 72.21; H, 9.22; N, 3.67%.

4.2.1.2. [Fe(h⁵-C₅H₅)(h⁵-C₅H₄CH]NC₁₆H₃₃)] 4b.

Yield 97%, yellow solid, mp 69–70 ^ꢁC; IR (KBr): 2916,

1

2851, 1104, 1004, 1641, 823 cm^ꢀ1; H NMR (400 MHz,

CDCl₃) d 8.09 (1H, s, H–C]N), 4.62 (2H, t, J¼1.9 Hz,

C₅H₄), 4.34 (2H, t, J¼1.9 Hz, C₅H₄), 4.17 (5H, s, C₅H₅),

3.44 (2H, t, J¼7.4 Hz, CH₂), 1.66–1.62 (2H, m, CH₂),

1.32–1.25 (26H, m, C₁₃H₂₆), 0.88 (3H, t, J¼6.8 Hz, CH₃);

¹³C NMR (100 MHz, CDCl₃) d 160.4, 80.8, 70.2, 69.0,

68.3, 62.0, 31.9, 30.9, 29.7, 29.65, 29.64, 29.61, 29.5,

29.3, 27.3, 22.7, 14.1; HRMS (positive ESI) calcd for

C₂₇H₄₃FeN [M+1]⁺: 438.2823, found: 438.2817. Anal.

Calcd for C₂₇H₄₃FeN: C, 74.13; H, 9.91; N, 3.20. Found:

C, 74.30; H, 9.98; N, 3.44%.

4. Experimental

4.1. General

Melting points were measured using a WC-1 microscopic

apparatus and were uncorrected. Infrared spectra were re-

corded on a Bruker VECTOR22 spectrophotometer in KBr

1

pellets. H, ¹³C, and ³¹P {¹H} NMR spectra were recorded

4.2.1.3. [Fe(h⁵-C₅H₅)(h⁵-C₅H₄CMe]NC₁₂H₂₅)] 4c.

on a Bruker DPX-400 spectrometer in CDCl₃or DMSO-d₆

Yield 85%, yellow solid, mp 62–64 ^ꢁC; IR (KBr): 2916,

1

with TMS as an internal standard for H NMR, ¹³C NMR

2849, 1108, 1014, 1628, 818 cm^ꢀ1; H NMR (400 MHz,

and 85% H₃PO₄as external standard for ³¹P {¹H} NMR.

High-resolution mass spectra were measured on a Waters

Q-Tof MicroÔ spectrometer. HPLC was conducted on a

Waters 600 liquid chromatograph. Electrochemical experi-

ments were carried out in DMF (HPLC grade) with

CHI650A electrochemical analyzer. Solvents were dried

and freshly distilled prior to use. All other chemicals were

used as purchased. Elemental analyses were determined

with Elementar Analysensystem GmbH (varioELIII). Mea-

surement of surface pressure (p)–surface area (A) isotherms

and the deposition of monolayer were carried out with a com-

puter controlled Langmuir trough (KSV 5000-3). All the

Heck and Suzuki reactions were accomplished without the

protection of inert gas.

CDCl₃) d 4.65 (2H, s, C₅H₄), 4.30 (2H, s, C₅H₄), 4.13 (5H,

s, C₅H₅), 3.36 (2H, t, J¼7.2 Hz, CH₂), 2.12 (3H, s, CH₃–

C]N), 1.66–1.63 (2H, m, CH₂), 1.39–1.26 (18H, m,

C₉H₁₈), 0.88 (3H, t, J¼6.8 Hz, CH₃); ¹³C NMR (100 MHz,

CDCl₃) d 165.3, 85.9, 69.9, 69.1, 67.6, 51.8, 31.9, 30.9,

30.8, 29.72, 29.71, 29.69, 29.67, 29.63, 29.4, 27.7, 22.7,

15.9, 14.1; HRMS (positive ESI) calcd for C₂₄H₃₇FeN

[M+1]⁺: 396.2353, found: 396.2362. Anal. Calcd for

C₂₄H₃₇FeN: C, 72.90; H, 9.43; N, 3.54. Found: C, 73.13;

H, 9.34; N, 3.14%.

4.2.1.4. [Fe(h⁵-C₅H₅)(h⁵-C₅H₄CMe]NC₁₆H₃₃)] 4d.

Yield 83%, yellow solid, mp 76–78 ^ꢁC; IR (KBr): 2916,

1

2849, 1108, 1015, 1628, 817 cm^ꢀ1; H NMR (400 MHz,

CDCl₃) d 4.65 (2H, s, C₅H₄), 4.31 (2H, t, J¼1.4 Hz, C₅H₄),

4.13 (5H, s, C₅H₅), 3.37 (2H, t, J¼7.2 Hz, CH₂), 2.12 (3H,

s, CH₃–C]N), 1.66–1.63 (2H, m, CH₂), 1.37–1.26 (26H, m,

C₁₃H₂₆), 0.88 (3H, t, J¼6.8 Hz, CH₃); ¹³C NMR (100 MHz,

CDCl₃) d 165.3, 85.8, 70.0, 69.1, 67.7, 51.7, 31.9, 30.8, 29.7,

29.69, 29.68, 29.63, 29.4, 27.7, 22.7, 15.9, 14.1; HRMS (pos-

itive ESI) calcd for C₂₈H₄₅FeN [M+1]⁺: 452.2979, found:

452.2989. Anal. Calcd for C₂₈H₄₅FeN: C, 74.48; H, 10.05;

N, 3.10. Found: C, 74.46; H, 10.18; N, 3.49%.

4.2. Preparation of the compounds

4.2.1. Preparation of [Fe(h⁵-C₅H₅)(h⁵-C₅H₄CR₁]NR₂)]

(4a–d). A mixture of ferrocenecarbaldehyde or acetylferro-

cene (5.0 mmol) and the corresponding amine (5.01 mmol)

(n-dodecylamine or n-hexadecylamine) was dissolved in

80 mL of dry toluene and reﬂuxed on an oil bath under nitro-

˚

gen atmosphere in the presence of molecular sieves (4 A,

4.0 g). After 4–6 h, the reaction mixture was carefully ﬁl-

tered and the ﬁltrate was reduced to dryness. For the synthe-

ses of complexes (4c, 4d), the reaction mixture was reﬂuxed

for two days and for every 12 h amines (0.01 mmol) and

molecular sieves (0.8 g) were added (0.8 g) to force the

displacement of the equilibria. Molecular sieves (4 A) were

removed by ﬁltration, and the ﬁltrate was reduced to dryness.

All the solids were recrystallized from cold CH₃CN.

4.2.2. Preparation of [PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-

C₅H₃)CR₁]NR₂]}]₂(5a–d). A solution of lithium tetra-

chloropalladated (II) in 10 mL of methanol (Li₂PdCl₄,

1 mmol) was added to a solution of mole equivalents of

NaOAc and ferrocenylimine (4a–d) in 10 mL of methanol

or methanol/ethyl ether¼1:1, and the resulting red solution

was stirred at room temperature for about 24 h. The solution

(4a or 4b) was reduced to dryness, and then was puriﬁed via

column chromatography (CH₂Cl₂/CH₃CH₂OH¼40:1 as elu-

ent). The red oil formed was quenched by adding n-hexane.

Evaporation of the solvent gave the remaining solid as the

products. The solution (4c or 4d) was carefully ﬁltered,

and then the deep red solid obtained was puriﬁed via column

chromatography (CH₂Cl₂/CH₃CH₂OH¼120:1 as eluent).

The oil formed was quenched by adding of n-hexane fol-

lowed by vigorous stirring produced the precipitation of

˚

4.2.1.1. [Fe(h⁵-C₅H₅)(h⁵-C₅H₄CH]NC₁₂H₂₅)] 4a.

Yield 96%, yellow solid, mp 53–54 ^ꢁC; IR (KBr): 2924,

1

2853, 1106, 1009, 1644, 820 cm^ꢀ1; H NMR (400 MHz,

CDCl₃) d 8.09 (1H, s, H–C]N), 4.63 (2H, t, J¼1.8 Hz,

C₅H₄), 4.34 (2H, t, J¼1.8 Hz, C₅H₄), 4.17 (5H, s, C₅H₅),

3.44 (2H, t, J¼7.0 Hz, CH₂), 1.66–1.62 (2H, m, CH₂),

1.33–1.25 (18H, m, C₉H₁₈), 0.88 (3H, t, J¼6.8 Hz, CH₃);

¹³C NMR (100 MHz, CDCl₃) d 160.4, 80.8, 70.2, 69.0,

11484

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

the dimeric compounds. The solvent was evaporated to give

the products.

4.2.3. Preparation of [PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)-

CR₁]NR₂]}(PPh₃)] (6a–d). The solution of chloride-

bridged cyclopalladated dimer (5a–d) (0.1 mmol) and

PPh₃(0.3 mmol) in 10 mL of CH₂Cl₂was stirred at room

temperature for 1 h. The solution was concentrated in vacuo

and was puriﬁed via column chromatography (CH₂Cl₂/

CH₃CH₂OH¼120:1 as eluent). The red oil (6a, 6b) was

recrystallized from CH₂Cl₂/MeOH and (6c, 6d) was recrys-

tallized from CH₂Cl₂/petroleum ether.

4.2.2.1.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)CH]

NC₁₂H₂₅]}]₂5a. Yield 44%, red solid, mp 80–82 ^ꢁC; IR

(KBr): 2923, 2852, 1105, 1002, 1579, 817 cm^ꢀ1; H NMR

1

(400 MHz, CDCl₃) d 7.80 (1H, s, H–C]N), 4.79–4.77

(1H, m, C₅H₃), 4.38–4.27 (7H, m, C₅H₅, C₅H₃), 3.47–3.36

(2H, m, CH₂), 1.83–1.74 (2H, m, CH₂), 1.33–1.26 (18H, m,

C₉H₁₈), 0.88 (3H, t, J¼6.8 Hz, CH₃); ¹³C NMR (100 MHz,

CDCl₃) d 172.1, 102.3, 86.9, 73.7, 70.7, 67.6, 65.7, 60.0,

59.1, 31.9, 30.9, 30.5, 29.64, 29.60, 29.4, 29.3, 26.8, 22.7,

14.1; HRMS (positive ESI) calcd for C₄₆H₆₈Cl₂Fe₂N₂Pd₂

[MꢀCl]⁺: 1007.1839, found: 1007.1835. Anal. Calcd for

C₄₆H₆₈Cl₂Fe₂N₂Pd₂$0.5C₂H₅OC₂H₅: C, 53.30; H, 6.80; N,

2.59. Found: C, 53.78; H, 6.51; N, 2.42%.

4.2.3.1.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)CH]

NC₁₂H₂₅]}(PPh₃)] 6a. Yield 76%, red soild, mp 54–56 ^ꢁC;

IR (KBr): 2922, 2851, 1101, 1000, 1601, 818, 747,

696 cm^ꢀ^{1 1}H NMR (400 MHz, CDCl₃) d 8.05 (1H, d,

;

J¼8.3 Hz, H–C]N), 7.79–7.74 (6H, m, PPh₃), 7.45–7.36

(9H, m, PPh₃), 4.36 (1H, d, J¼2.4 Hz, C₅H₃), 4.02 (1H, t,

J¼2.2 Hz, C₅H₃), 3.96–3.89 (1H, m, CH₂), 3.86 (5H, s,

C₅H₅), 3.61–3.53 (1H, m, CH₂), 3.29 (1H, d, J¼2.1 Hz,

C₅H₃), 1.98–1.92 (1H, m, CH₂), 1.71–1.60 (1H, m, CH₂),

1.41–1.25 (18H, m, C₉H₁₈), 0.87 (3H, t, J¼6.8 Hz, CH₃);

¹³C NMR (100 MHz, CDCl₃) d 171.1, 135.0, 132.2, 131.7,

130.4, 128.1, 102.5, 87.7, 76.4, 70.0, 69.0, 66.2, 58.3,

31.9, 31.6, 29.8, 29.7, 29.68, 29.67, 29.65, 29.5, 29.4,

27.1, 22.7, 14.1; ³¹P {¹H} NMR (162 MHz, CDCl₃)

d 38.06; HRMS (positive ESI) calcd for C₄₁H₄₉ClFeNPPd

[MꢀCl]⁺: 748.1987, found: 748.1992. Anal. Calcd for

C₄₁H₄₉ClFeNPPd: C, 62.77; H, 6.30; N, 1.79. Found: C,

62.72; H, 6.33; N, 1.81%.

4.2.2.2.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)CH]

NC₁₆H₃₃]}]₂5b. Yield 65%, red solid, mp 102–103 ^ꢁC; IR

(KBr): 2922, 2851, 1105, 1001, 1585, 814 cm^ꢀ1; H NMR

1

(400 MHz, DMSO-d₆) d 8.26 (1H, s, H–C]N), 5.03 (1H, s,

C₅H₃), 4.55 (1H, d, J¼1.6 Hz, C₅H₃), 4.40 (1H, d, J¼2.0 Hz,

C₅H₃), 4.29 (5H, s, C₅H₅), 3.57–3.54 (1H, m, CH₂), 3.48–

3.43 (1H, m, CH₂), 1.68–1.60 (2H, m, CH₂), 1.28–1.23

(26H, m, C₁₃H₂₆), 0.85 (3H, t, J¼6.8 Hz, CH₃); ¹³C NMR

(100 MHz, CDCl₃) d 172.3, 103.0, 87.1, 74.0, 71.0, 67.8,

65.9, 60.0, 59.2, 31.9, 31.0, 30.5, 29.7, 29.4, 26.8, 22.7,

14.1; HRMS (positive ESI) calcd for C₅₄H₈₄Cl₂Fe₂N₂Pd₂

[MꢀCl]⁺: 1119.3091, found: 1119.3085. Anal. Calcd for

C₅₄H₈₄Cl₂Fe₂N₂Pd₂$0.5C₂H₅OC₂H₅: C, 56.34; H, 7.51; N,

2.35. Found: C, 56.66; H, 7.11; N, 2.01%.

4.2.3.2.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)CH]

NC₁₆H₃₃]}(PPh₃)] 6b. Yield 84%, red solid, mp 75–76 ^ꢁC;

IR (KBr): 2925, 2854, 1098, 999, 1601, 817, 747,

4.2.2.3.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)C(CH₃)]

696 cm^ꢀ^{1 1}H NMR (400 MHz, CDCl₃) d 8.05 (1H, d,

;

NC₁₂H₂₅]}]₂5c. Yield 78%, red solid, mp 144–146 ^ꢁC; IR

J¼8.3 Hz, H–C]N), 7.79–7.74 (6H, m, PPh₃), 7.42–7.35

(9H, m, PPh₃), 4.36 (1H, d, J¼2.2 Hz, C₅H₃), 4.02 (1H, t,

J¼2.2 Hz, C₅H₃), 3.95–3.89 (1H, m, CH₂), 3.85 (5H, s,

C₅H₅), 3.59–3.55 (1H, m, CH₂), 3.29 (1H, d, J¼1.9 Hz,

C₅H₃), 1.97–1.92 (1H, m, CH₂), 1.71–1.64 (1H, m, CH₂),

1.38–1.25 (26H, m, C₁₃H₂₆), 0.87 (3H, t, J¼6.8 Hz, CH₃);

¹³C NMR (100 MHz, CDCl₃) d 171.2, 134.9, 134.8, 132.1,

131.6, 130.3, 128.0, 102.5, 87.7, 76.4, 70.0, 69.0, 66.2,

58.2, 31.9, 31.5, 29.73, 29.71, 29.67, 29.65, 29.64, 29.62,

29.5, 29.3, 27.1, 22.7, 14.1; ³¹P {¹H} NMR (162 MHz,

(KBr): 2923, 2852, 1103, 1002, 1581, 812 cm^ꢀ1; H NMR

1

(400 MHz, DMSO-d₆) d 4.99 (1H, t, J¼0.9 Hz C₅H₃), 4.60

(1H, t, J¼1.1 Hz, C₅H₃), 4.33 (1H, d, J¼2.1 Hz, C₅H₃),

4.24 (5H, s, C₅H₅), 3.63–3.60 (1H, m, CH₂), 3.52–3.46

(1H, m, CH₂), 2.23 (3H, s, CH₃–C]N), 1.60–1.52 (2H, m,

CH₂), 1.30–1.24 (18H, m, C₉H₁₈), 0.85 (3H, t, J¼6.5 Hz,

CH₃); ¹³C NMR (100 MHz, CDCl₃) d 180.6, 101.2, 91.5,

73.8, 71.3, 66.4, 65.9, 53.2, 52.4, 31.9, 31.0, 29.7, 29.69,

29.63, 29.60, 29.4, 29.37, 27.2, 22.7, 14.4, 14.1; HRMS

(positive ESI) calcd for C₄₈H₇₂Cl₂Fe₂N₂Pd₂[MꢀCl]⁺:

1035.2152, found: 1035.2174. Anal. Calcd for

C₄₈H₇₂Cl₂Fe₂N₂Pd₂$0.25C₆H₁₂: C, 54.37; H, 6.91; N,

2.56. Found: C, 54.49; H, 6.65; N, 2.35%.

CDCl₃)

d 37.70; HRMS (positive ESI) calcd for

C₄₅H₅₇ClFeNPPd [MꢀCl]⁺: 804.2612, found: 804.2650.

Anal. Calcd for C₄₅H₅₇ClFeNPPd$CH₃OH: C, 63.31; H,

7.05; N, 1.61. Found: C, 63.31; H, 6.59; N, 1.77%.

4.2.2.4.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)C(CH₃)]

4.2.3.3.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)C(CH₃)]

NC₁₂H₂₅]}(PPh₃)] 6c. Yield 86%, red solid, mp 157–

NC₁₆H₃₃]}]₂5d. Yield 82%, red solid, mp 139–141 ^ꢁC; IR

(KBr): 2921, 2850, 1103, 1001, 1579, 812 cm^ꢀ1; H NMR

160 ^ꢁC; IR (KBr): 2922, 2852, 1097, 1000, 1594, 818,

1

(400 MHz, DMSO-d₆) d 4.99 (1H, d, J¼1.4 Hz, C₅H₃),

4.61 (1H, d, J¼1.5 Hz, C₅H₃), 4.33 (1H, t, J¼2.3 Hz,

C₅H₃), 4.25 (5H, s, C₅H₅), 3.62–3.58 (1H, m, CH₂), 3.52–

3.46 (1H, m, CH₂), 2.23 (3H, s, CH₃–C]N), 1.61–1.50

(2H, m, CH₂), 1.29–1.23 (26H, m, C₁₃H₂₆), 0.86 (3H, t,

J¼6.5 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃) d 180.6,

101.2, 91.4, 73.7, 71.2, 66.3, 65.8, 53.3, 52.3, 31.9, 30.9,

29.7, 29.68, 29.63, 29.60, 29.4, 27.2, 22.7, 14.4, 14.1;

HRMS (positive ESI) calcd for C₅₆H₈₈Cl₂Fe₂N₂Pd₂

[MꢀCl]⁺: 1147.3404, found: 1147.3406. Anal. Calcd for

C₅₆H₈₈Cl₂Fe₂N₂Pd₂: C, 56.77; H, 7.49; N, 2.36. Found: C,

57.07; H, 7.28; N, 2.16%.

748, 697 cm^ꢀ1; H NMR (400 MHz, CDCl₃) d 7.75–7.70

(6H, m, PPh₃), 7.38–7.34 (9H, m, PPh₃), 4.28 (1H, d, J¼

2.4 Hz, C₅H₃), 4.00–3.93 (2H, m, C₅H₃, CH₂), 3.77 (5H, s,

C₅H₅), 3.61–3.56 (1H, m, CH₂), 3.22 (1H, d, J¼2.2 Hz,

C₅H₃), 2.16 (3H, s, CH₃–C]N), 1.83–1.82 (1H, m, CH₂),

1.51–1.21 (19H, m, CH₂, C₉H₁₈), 0.83 (3H, t, J¼6.8 Hz,

CH₃); ¹³C NMR (100 MHz, CDCl₃) d 179.4, 135.0, 132.4,

131.9, 130.3, 128.0, 127.9, 101.3, 92.0, 76.2, 70.3, 67.8,

66.2, 51.2, 31.9, 30.3, 29.8, 29.7, 29.66, 29.63, 29.3, 27.3,

22.7, 14.5, 14.1; ³¹P {¹H} NMR (162 MHz, CDCl₃)

d 37.41; HRMS (positive ESI) calcd for C₄₂H₅₁ClFeNPPd

[MꢀCl]⁺: 762.2143, found: 762.2163. Anal. Calcd for

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

11485

C₄₂H₅₁ClFeNPPd: C, 63.17; H, 6.44; N, 1.75. Found: C,

63.15; H, 6.73; N, 2.22%.

round-bottom ﬂask. The catalyst was introduced as a toluene

solution (0.000005 mmol mL^ꢀ1), and additional toluene was

added to obtain a total volume of 2.5 mL. The reaction mix-

ture was stirred at 110 ^ꢁC for 45 min, and then quenched

with water. The organic layer was separated and the aqueous

layer was extracted with ethyl acetate for three times. The

combined organic phase was dried with MgSO₄, ﬁltered,

and the solvent was removed on a rotary evaporator, the

product was isolated by thin layer chromatography. The pu-

riﬁed products were identiﬁed by ¹H NMR, ¹³C NMR spec-

troscopy and melting points with the literature data.

4.2.3.4.

[PdCl{[(h⁵-C₅H₅)]Fe[(h⁵-C₅H₃)C(CH₃)]

NC₁₆H₃₃]}(PPh₃)] 6d. Yield 92%, red solid, mp 110–

113 ^ꢁC; IR (KBr): 2920, 2851, 1098, 1000, 1593, 819, 748,

697 cm^ꢀ1; ¹H NMR (400 MHz, CDCl₃) d 7.79–7.74 (6H, m,

PPh₃), 7.44–7.36 (9H, m, PPh₃), 4.33 (1H, s, C₅H₃), 4.03–

3.99 (2H, m, C₅H₃, CH₂), 3.82 (5H, s, C₅H₅), 3.66–3.58 (1H,

m, CH₂), 3.26 (1H, s, C₅H₃), 2.19 (3H, s, CH₃–C]N), 1.86–

1.85 (1H, m, CH₂), 1.54–1.25 (27H, m, CH₂, C₁₃H₂₆), 0.88

(3H, t, J¼6.2 Hz, CH₃); ¹³C NMR (100 MHz, CDCl₃) d

179.4, 135.0, 132.4, 131.9, 128.0, 101.5, 92.1, 76.3, 70.3,

67.8, 66.2, 51.2, 31.9, 30.9, 30.3, 29.9, 29.7, 29.69, 29.68,

29.64, 29.63, 29.4, 29.38, 27.4, 22.7, 14.5, 14.1; ³¹P {¹H}

NMR (162 MHz, CDCl₃) d 37.80; HRMS (positive ESI)

calcd for C₄₆H₅₉ClFeNPPd [MꢀCl]⁺: 818.2769, found:

818.2772. Anal. Calcd for C₄₆H₅₉ClFeNPPd$0.25C₆H₁₂: C,

65.15; H, 7.14; N, 1.60. Found: C, 65.46; H, 7.33; N, 1.54%.

4.5.1. Compound 7a.³³Light yellow liquid; ¹H NMR

(400 MHz, CDCl₃) d 7.68 (1H, d, J¼16.0 Hz), 7.51–7.49

(2H, m), 7.37–7.35 (3H, m), 6.43 (1H, d, J¼16.0 Hz), 4.26

(2H, q, J¼7.1 Hz), 1.33 (3H, t, J¼7.1 Hz); ¹³C NMR

(100 MHz, CDCl₃) d 167.0, 144.6, 134.5, 130.2, 128.9,

128.1, 118.3, 60.5, 14.3.

4.5.2. Compound 7b.³³Light yellow liquid; ¹H NMR

(400 MHz, CDCl₃) d 7.65 (1H, d, J¼16.0 Hz), 7.38 (2H, d,

J¼8.0 Hz), 7.15 (2H, d, J¼7.8 Hz), 6.37 (1H, d, J¼16.0 Hz),

4.24 (2H, q, J¼7.1 Hz), 2.33 (3H, s, OCH₃) 1.32 (3H, t,

J¼7.2 Hz); ¹³C NMR (100 MHz, CDCl₃) d 166.9, 144.4,

140.4, 131.5, 129.4, 127.8, 117.0, 60.1, 21.2, 14.1.

4.3. Electrochemical studies

Electrochemical data for compounds under study and related

compounds were obtained by cyclic voltammetry under N₂

at 20 ^ꢁC using DMF (HPLC grade) as solvent, and 0.1 M tet-

rabutylammonium perchlorate as supporting electrolyte, and

CHI650A electrochemical analyzer using a conventional

three-electrode system. The traditional three-electrode sys-

tem consists of a saturated calomel reference electrode

(SCE), a platinum wire auxiliary electrode, and a GC work-

ing electrode in 0.1 M tetrabutylammonium perchlorate

DMF. All E⁰values reported were estimated from cyclic vol-

tammetry as the average of the oxidative and reductive peak

potentials (E_pa+E_pc)/2. Cyclic voltammograms of 10^ꢀ4M

solutions of complexes (4a–d, 5a–d, 5a–d) in DMF were

run. In these experimental conditions the standard error of

the measured potentials is ꢃ5 mV. In all experiments, the cy-

clic voltammograms were registered using scan rate varying

4.5.3. Compound 7c.³³Light yellow liquid; ¹H NMR

(400 MHz, CDCl₃) d 7.64 (1H, d, J¼16.0 Hz), 7.47 (2H,

d, J¼8.6 Hz), 6.89 (2H, d, J¼8.6 Hz), 6.30 (1H, d,

J¼16.0 Hz), 4.25 (2H, q, J¼7.1 Hz), 3.82 (3H, s), 1.33

(3H, t, J¼7.1 Hz); ¹³C NMR (100 MHz, CDCl₃) d 167.2,

161.3, 144.2, 129.6, 127.1, 115.7, 114.5, 60.2, 55.3, 14.3.

4.5.4. Compound 7d. Light yellow solid; mp 33–34 ^ꢁC

1

(lit.³⁴31–33 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.69 (1H,

d, J¼16.1 Hz), 7.65–7.60 (4H, m), 6.50 (1H, d, J¼

16.1 Hz), 4.28 (2H, q, J¼7.1 Hz), 1.35 (3H, t, J¼7.1 Hz);

¹³C NMR (100 MHz, CDCl₃) d 166.8, 143.1, 138.3, 132.3,

131.9, 128.6, 126.3, 121.3, 61.2, 14.7.

from y¼10 to 300 mV s^ꢀ1

.

4.4. General procedure for the Heck reaction of aryl

halides with ethyl acrylate or styrene

4.5.5. Compound 7e. White solid; mp 42–44 ^ꢁC (lit.³⁴42–

44 ^ꢁC); ¹H NMR (400 MHz, CDCl₃) d 7.96 (2H, d,

J¼7.1 Hz), 7.69 (1H, d, J¼16.1 Hz), 7.61 (2H, d, J¼

7.3 Hz), 6.52 (1H, d, J¼16.1 Hz), 4.28 (2H, q, J¼7.1 Hz),

2.61 (3H, s), 1.35 (3H, t, J¼7.2 Hz); ¹³C NMR (100 MHz,

CDCl₃) d 197.3, 166.5, 143.0, 138.8, 138.0, 128.9, 128.1,

120.8, 60.8, 26.7, 14.3.

Aryl halide (0.5 mmol), ethyl acrylate (2.0 mmol) or styrene

(1.5 mmol) were combined with K₃PO₄(1 mmol) and

n-Bu₄NBr (0.5 mmol) in a small round-bottom ﬂask.

The catalyst was introduced as

a DMF solution

(0.0005 mmol mL^ꢀ1), and additional DMF was added to

obtain a total volume of 1.5 mL. The reaction mixture was

stirred at 140 ^ꢁC for 12 h or 24 h, and then quenched with

water. The organic layer was separated and the aqueous layer

was extracted with ethyl acetate for three times. The com-

bined organic phase was dried with MgSO₄, ﬁltered, and

the solvent was removed on a rotary evaporator, the product

was isolated by thin layer chromatography. The puriﬁed

4.5.6. Compound 7f. Yellow solid; mp 133–136 ^ꢁC (lit.³⁵

134–136 ^ꢁC); ¹H NMR (400 MHz, CDCl₃) d 8.26–8.23

(2H, m), 7.73–7.66 (3H, m), 6.56 (1H, d, J¼15.9 Hz), 4.30

(2H, q, J¼7.1 Hz), 1.36 (3H, t, J¼7.1 Hz); ¹³C NMR

(100 MHz, CDCl₃) d 166.4, 148.9, 142.0, 141.0, 129.0,

124.6, 123.0, 61.4, 14.7.

products were identiﬁed by H NMR, ¹³C NMR spectros-

4.5.7. Compound 7g. White solid; mp 67–69 ^ꢁC (lit.³⁶69–

1

copy and melting points with the literature data.

69.3 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.69–7.60 (5H,

m), 6.52 (1H, d, J¼16.0 Hz), 4.29 (2H, q, J¼7.1 Hz), 1.35

(3H, t, J¼7.1 Hz); ¹³C NMR (100 MHz, CDCl₃) d 166.1,

142.1, 138.8, 132.6, 128.4, 121.9, 118.4, 113.4, 60.9, 14.3.

4.5. General procedure for the Suzuki–Miyaura cross-

coupling reaction of aryl halide with phenylboronic acid

Aryl halide (0.5 mmol) and phenylboronic acid (0.6 mmol)

were combined with K₃PO₄$7H₂O (1 mmol) in a small

4.5.8. Compound 7h. Red solid; mp 72–73 ^ꢁC (lit.³³77–

78 ^ꢁC); ¹H NMR (400 MHz, CDCl₃) d 7.62 (1H, d,

11486

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

J¼15.8 Hz), 7.41 (2H, d, J¼8.8 Hz), 6.66 (2H, d, J¼8.8 Hz),

6.21 (1H, d, J¼15.8 Hz), 4.24 (2H, q, J¼7.2 Hz), 3.00 (6H,

s), 1.32 (3H, t, J¼7.1 Hz); ¹³C NMR (100 MHz, CDCl₃)

d 167.9, 151.7, 145.1, 129.7, 122.4, 112.6, 111.9, 60.1,

40.2, 14.4.

8.7 Hz), 3.81 (3H, s); ¹³C NMR (100 MHz, CDCl₃)

d 159.4, 137.7, 130.2, 128.7, 128.3, 127.8, 127.3, 126.7,

126.3, 114.2, 55.4.

4.5.17. Compound 8d. White solid; mp 132–134 ^ꢁC (lit.³⁴

1

132–134 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.59 (4H, s),

1

4.5.9. Compound 7i.³⁷Red liquid; H NMR (400 MHz,

7.52 (2H, d, J¼7.4 Hz), 7.38 (2H, t, J¼7.5 Hz), 7.30 (1H,

t, J¼7.3 Hz), 7.18 (1H, d, J¼16.2 Hz), 7.10 (1H, d,

J¼16.2 Hz); ¹³C NMR (100 MHz, CDCl₃) d 140.8, 136.6,

131.2, 129.1, 128.8, 128.3, 127.1, 126.8, 126.6, 125.7, 122.9.

CDCl₃) d 8.75 (1H, s), 8.60 (1H, d, J¼4.5 Hz), 7.85 (1H,

d, J¼7.8 Hz), 7.68 (1H, d, J¼16.1 Hz), 7.35–7.32 (1H, m),

6.52 (1H, d, J¼16.1 Hz), 4.28 (2H, q, J¼7.1 Hz), 1.35

(3H, t, J¼7.0 Hz); ¹³C NMR (100 MHz, CDCl₃) d 166.1,

150.7, 149.5, 140.6, 134.0, 130.1, 123.6, 120.3, 60.6, 14.1.

4.5.18. Compound 8e. Light yellow solid; mp 141–144 ^ꢁC

(lit.⁴²139.5–141.5 ^ꢁC); ¹H NMR (400 MHz, CDCl₃)

d 7.95 (2H, d, J¼8.3 Hz), 7.59–7.53 (4H, m), 7.38 (2H, t,

J¼7.5 Hz), 7.30 (1H, t, J¼7.3 Hz), 7.23 (1H, d,

J¼16.5 Hz), 7.13 (1H, d, J¼16.5 Hz), 2.60 (3H, s); ¹³C

NMR (100 MHz, CDCl₃) d 197.5, 142.0, 136.7, 136.0,

131.5, 128.9, 128.8, 128.3, 127.5, 126.9, 126.5, 26.6.

4.5.10. Compound 7j.³⁸Light yellow liquid; ¹H NMR

(400 MHz, CDCl₃) d 7.67 (1H, d, J¼15.9 Hz), 7.49–7.48

(1H, m), 7.34–7.27 (2H, m), 6.26 (1H, d, J¼15.9 Hz), 4.25

(2H, q, J¼7.1 Hz), 1.33 (3H, t, J¼7.2 Hz); ¹³C NMR

(100 MHz, CDCl₃) d 167.2, 138.1, 137.6, 128.0, 127.0,

125.2, 117.9, 60.5, 14.4.

4.5.19. Compound 8f. Light yellow solid; mp 155–157 ^ꢁC

1

4.5.11. Compound 7k.³⁹Light yellow liquid; H NMR

(lit.⁴³156–157 ^ꢁC); H NMR (400 MHz, CDCl₃) d 8.21

(400 MHz, CDCl₃) d 8.51 (1H, d, J¼15.8 Hz), 8.17 (1H, d,

J¼8.4 Hz), 7.84 (2H, t, J¼6.6 Hz), 7.71 (1H, d, J¼7.2 Hz),

7.54–7.41 (3H, m), 6.51 (1H, d, J¼15.7 Hz), 4.30 (2H, q,

J¼7.2 Hz), 1.36 (3H, t, J¼7.1 Hz); ¹³C NMR (100 MHz,

CDCl₃) d 166.9, 141.6, 133.7, 131.8, 131.4, 130.5, 128.8,

126.9, 126.2, 125.5, 125.0, 123.4, 121.0, 60.6, 14.4.

(2H, d, J¼8.7 Hz), 7.63 (2H, d, J¼8.7 Hz), 7.55 (2H, d,

J¼7.4 Hz), 7.42–7.31 (3H, m), 7.27 (1H, d, J¼16.3 Hz),

7.14 (1H, d, J¼16.3 Hz); ¹³C NMR (100 MHz, CDCl₃)

d 146.8, 143.9, 136.2, 133.3, 128.9, 128.85, 127.0, 126.9,

126.3, 124.1.

4.5.20. Compound 8g. Light yellow solid; mp 114–116 ^ꢁC

4.5.12. Compound 7l.⁴⁰Light yellow liquid; ¹H NMR

(400 MHz, CDCl₃) d 8.18 (1H, d, J¼16.3 Hz), 8.03 (1H,

d, J¼8.4 Hz), 7.79 (1H, d, J¼7.8 Hz), 7.71 (1H, d, J¼

8.4 Hz), 7.47–7.42 (2H, m), 7.31 (1H, d, J¼8.4 Hz), 6.22

(1H, d, J¼16.3 Hz), 4.32 (2H, q, J¼7.1 Hz), 2.49 (3H, s),

1.37 (3H, t, J¼7.1 Hz); ¹³C NMR (100 MHz, CDCl₃)

d 166.7, 142.6, 134.1, 132.1, 131.5, 130.8, 128.9, 128.6,

128.3, 126.6, 125.7, 125.2, 124.7, 60.7, 21.0, 14.4.

(lit.³⁴117–119 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.64–

1

7.52 (6H, m), 7.39 (2H, t, J¼7.4 Hz), 7.32 (1H, t,

J¼7.2 Hz), 7.21 (1H, d, J¼16.3 Hz), 7.08 (1H, d, J¼

16.3 Hz); ¹³C NMR (100 MHz, CDCl₃) d 141.9, 136.3,

132.5, 132.4, 128.9, 128.7, 127.0, 126.9, 126.8, 119.1, 110.6.

4.5.21. Compound 8h. Red solid; mp 145–147 ^ꢁC (lit.⁴⁴

1

144–146 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.47 (2H, d,

J¼7.5 Hz), 7.41 (2H, d, J¼8.7 Hz), 7.32 (2H, t, J¼

7.6 Hz), 7.19 (1H, t, J¼7.3 Hz), 7.05 (1H, d, J¼16.3 Hz),

6.91 (1H, d, J¼16.3 Hz), 6.72 (2H, d, J¼8.2 Hz), 2.97

(6H, s); ¹³C NMR (100 MHz, CDCl₃) d 150.5, 138.6,

129.2, 129.0, 128.0, 127.1, 126.4, 124.9, 112.9, 41.0.

1

4.5.13. Compound 7m.³³Light yellow liquid; H NMR

(400 MHz, CDCl₃) d 7.96 (1H, d, J¼15.9 Hz), 7.52 (2H, d,

J¼7.5 Hz), 7.24–7.15 (3H, m), 6.34 (1H, d, J¼15.9 Hz),

4.25 (2H, q, J¼7.1 Hz), 2.40 (3H, s), 1.32 (3H, t, J¼

7.1 Hz); ¹³C NMR (100 MHz, CDCl₃) d 167.0, 142.2, 137.6,

133.4, 130.8, 130.0, 126.4, 126.3, 119.2, 60.5, 19.8, 14.3.

4.5.22. Compound 8i. Light yellow solid; mp 78–80 ^ꢁC

1

(lit.⁴⁴81–82 ^ꢁC); H NMR (400 MHz, CDCl₃) d 8.72 (1H,

4.5.14. Compound 8a. White solid; mp 122–124 ^ꢁC (lit.³⁴

s), 8.48 (1H, d, J¼4.7 Hz), 7.82 (1H, d, J¼8.0 Hz), 7.52

(2H, d, J¼7.4 Hz), 7.39–7.26 (4H, m), 7.18 (1H, d, J¼

16.4 Hz), 7.06 (1H, d, J¼16.4 Hz); ¹³C NMR (100 MHz,

CDCl₃) d 148.9, 137.1, 133.4, 133.1, 131.3, 129.2, 128.6,

127.1, 125.3, 124.0.

1

120–122 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.52 (4H, d,

J¼7.4 Hz), 7.36 (4H, t, J¼7.6 Hz), 7.26 (2H, t, J¼7.3 Hz),

7.11 (2H, s); ¹³C NMR (100 MHz, CDCl₃) d 137.3,

128.71, 128.70, 127.6, 126.5.

4.5.15. Compound 8b. White solid; mp 117–119 ^ꢁC (lit.³⁴

4.5.23. Compound 8j. Light red solid; mp 118–121 ^ꢁC

1

121–122 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.49 (2H, d,

(lit.⁴⁵126–128 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.47

J¼7.5 Hz), 7.40 (2H, d, J¼8.0 Hz), 7.34 (2H, t, J¼

7.6 Hz), 7.23 (1H, t, J¼7.2 Hz), 7.15 (2H, d, J¼7.9 Hz),

7.09 (1H, d, J¼16.4 Hz), 7.04 (1H, d, J¼16.4 Hz), 2.35

(3H, s, CH₃); ¹³C NMR (100 MHz, CDCl₃) d 137.6, 134.6,

129.5, 128.7, 127.8, 127.5, 126.49, 126.46, 21.3.

(2H, d, J¼7.5 Hz), 7.36–7.30 (4H, m), 7.26–7.22 (2H, m),

7.12 (1H, d, J¼16.3 Hz), 6.95 (1H, d, J¼16.3 Hz); ¹³C

NMR (100 MHz, CDCl₃) d 140.2, 137.4, 128.7, 127.5,

126.3, 126.2, 125.0, 122.9, 122.4.

4.5.24. Compound 8k. White solid; mp 68–69 ^ꢁC (lit.⁴⁴71–

72 ^ꢁC); ¹H NMR (400 MHz, CDCl₃) d 8.21 (1H, d,

J¼8.0 Hz), 7.89–7.72 (4H, m), 7.60–7.28 (8H, m), 7.14

(1H, d, J¼16.0 Hz); ¹³C NMR (100 MHz, CDCl₃) d 137.7,

135.1, 133.8, 131.8, 131.5, 128.8, 128.7, 128.1, 127.9,

126.8, 126.2, 125.9, 125.8, 123.8, 123.7.

4.5.16. Compound 8c. Light yellow solid; mp 131–134 ^ꢁC

1

(lit.⁴¹132–133 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.48

(2H, d, J₁¼7.5 Hz), 7.44 (2H, d, J₁¼8.6 Hz), 7.33 (2H, t,

J¼7.6 Hz), 7.22 (1H, t, J¼7.3 Hz), 7.06 (1H, d, J¼

16.3 Hz), 6.96 (1H, d, J¼16.3 Hz), 6.89 (2H, d, J¼

B. Mu et al. / Tetrahedron 63 (2007) 11475–11488

11487

4.5.25. Compound 8l.⁴⁶Light yellow solid; mp 74–76 ^ꢁC;

¹H NMR (400 MHz, CDCl₃) d 8.15 (1H, d, J¼8.7 Hz),

7.79 (1H, d, J¼7.2 Hz), 7.68 (1H, d, J¼8.4 Hz), 7.57 (2H,

d, J¼7.4 Hz), 7.46–7.27 (7H, m), 6.75 (1H, d, J¼16.6 Hz);

¹³C NMR (100 MHz, CDCl₃) d 137.5, 135.6, 133.7, 133.3,

132.3, 132.2, 128.9, 128.8, 128.1, 127.8, 127.0, 126.4,

125.9, 125.8, 125.3, 124.9, 21.0.

corrected using uꢀ2q scan technique and corrected for

Lorenz and polarization factors. The structures were solved

by direct methods⁵²and expanded using Fourier techniques

and reﬁned by full-matrix least-squares methods. All non-

hydrogen atoms were described anisotropically, and hydro-

gen atoms were included but not reﬁned. All calculations

were performed using the TEXSAN²⁸crystallographic soft-

ware package of Molecular Structure Corporation. Crystal

data and detailed results of reﬁnement are summarized in

Table 1.

1

4.5.26. Compound 8m.⁴⁴Light yellow liquid; H NMR

(400 MHz, CDCl₃) d 7.56 (1H, d, J¼7.1 Hz), 7.49 (2H, d,

J¼7.6 Hz), 7.35–7.12 (7H, m), 6.97 (1H, d, J¼16.1 Hz),

2.40 (3H, s); ¹³C NMR (100 MHz, CDCl₃) d 137.6, 136.3,

135.7, 130.4, 130.0, 128.6, 127.54, 127.51, 126.5, 126.2,

125.3, 19.9.

Acknowledgements

We are grateful to the National Natural Science Foundation

of China (No. 20472074), the Innovation Fund for Outstand-

ing Scholar of Henan Province (No. 0621001100), the Fund

for Outstanding Younger Scholar of Henan Province for

their ﬁnancial support. We thank Professor Baoxian Ye for

comments on this paper.

4.5.27. Compound 9a. Light yellow solid; mp 111–113 ^ꢁC

1

(lit.⁴⁸111–112 ^ꢁC); H NMR (400 MHz, CDCl₃) d 8.30

(2H, d, J¼8.8 Hz), 7.74 (2H, d, J¼8.8 Hz), 7.63 (2H, d, J¼

7.0 Hz), 7.52–7.45 (3H, m); ¹³C NMR (100 MHz, CDCl₃)

d 147.6, 147.1, 138.8, 129.2, 128.9, 127.8, 127.4, 124.1.

4.5.28. Compound 9b. White solid; mp 117–118 ^ꢁC (lit.⁴⁹

1

116–118 ^ꢁC); H NMR (400 MHz, CDCl₃) d 8.04 (2H, d,

References and notes

J¼8.3 Hz), 7.69–7.62 (4H, m), 7.49–7.40 (3H, m), 2.64

(3H, s); ¹³C NMR (100 MHz, CDCl₃) d 197.8, 145.8,

139.8, 135.8, 128.9, 128.89, 128.21, 127.25, 127.20, 26.7.

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4.5.29. Compound 9c. White solid; mp 69–70 ^ꢁC (lit.⁴⁷68–

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71 ^ꢁC); H NMR (400 MHz, CDCl₃) d 7.60–7.58 (4H, m),

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7.49 (2H, d, J¼8.1 Hz), 7.42 (2H, t, J¼7.5 Hz), 7.33–7.30

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Article Doi

Synthesis, characterization, and applications in Heck and Suzuki coupling reactions of amphiphilic cyclopalladated ferrocenylimines

DOI: 10.1016/j.tet.2007.08.004

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Article abstract of DOI:10.1016/j.tet.2007.08.004

Full text of DOI:10.1016/j.tet.2007.08.004

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