Preparation of cobalt sandwich diphosphine ligand [(η5-C5H4iPr)Co(η4-C4(PPh2)2Ph2)] and its chelated palladium complex: Application of diphosphine ligand in the preparation of mono-substituted ferrocenylarenes

Article abstract of DOI:10.1016/j.ica.2009.11.010

The reaction of (η⁵-C₅H₄ⁱPr)Co(PPh₃)₂ with PhC{triple bond, long}CPPh₂ furnished two isomeric cyclobutadiene-substituted Cp′CoCb diphosphines, [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,2-(PPh₂)₂C₄Ph₂)] (5-cis) and [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,3-(PPh₂)₂C₄Ph₂)] (5-trans). Further reaction of 5-cis with one molar equivalent of Pd(COD)Cl₂ gave palladium complex [(η⁵-C₅H₄ⁱPr)Co(η⁴-1,2-(PPh₂)₂C₄Ph₂)-PdCl₂] (6) in good yield. Both of the molecular structures of 5-cis and 6 were determined by single-crystal X-ray diffraction methods. Unexpectedly, the palladium complex 6 was found to be more efficient than the combination of the commonly used Buchwald's ligand, biphenyl-2-yl-di-tert-butyl-phosphane, with Pd(OAc)₂ as the catalytic precursor in the Suzuki-Miyaura reaction between ferroceneboronic acid and 4-bromoaldehyde. The X-ray structural analysis and DFT study of several palladium complexes containing sandwich-type diphosphine chelating ligands revealed that the variations in bite angles are much larger than those in bite distances. The more energetically favorable conformation in the Pd(II) complexes is the one with bite angle close to 90°.

Full text of DOI:10.1016/j.ica.2009.11.010

Inorganica Chimica Acta 363 (2010) 412–417
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Preparation of cobalt sandwich diphosphine ligand
i
[(g
5-C5H4 Pr)Co(
g
4-C4(PPh2)2Ph2)] and its chelated palladium complex:
Application of diphosphine ligand in the preparation of mono-substituted
ferrocenylarenes
*
Chin-Pei Chang, Chia-Ming Weng, Fung-E Hong
Department of Chemistry, National Chung Hsing University, Taichung 40227, Taiwan
a r t i c l e i n f o
a b s t r a c t
i
Article history:
Received 29 October 2009
Received in revised form 5 November 2009
Accepted 9 November 2009
Available online 14 November 2009
The reaction of (
tuted Cp0CoCb diphosphines, [(
(PPh2)2C4Ph2)] (5-trans). Further reaction of 5-cis with one molar equivalent of Pd(COD)Cl2 gave
g
5-C5H4 Pr)Co(PPh3)2 with PhC„CPPh2 furnished two isomeric cyclobutadiene-substi-
i
i
g
5-C5H4 Pr)Co(
g g g
4-1,2-(PPh2)2C4Ph2)] (5-cis) and [( 5-C5H4 Pr)Co( 4-1,3-
i
palladium complex [(
g
5-C5H4 Pr)Co( 4-1,2-(PPh2)2C4Ph2)-PdCl2] (6) in good yield. Both of the molecular
g
structures of 5-cis and 6 were determined by single-crystal X-ray diffraction methods. Unexpectedly, the
palladium complex 6 was found to be more efficient than the combination of the commonly used
Buchwald’s ligand, biphenyl-2-yl-di-tert-butyl-phosphane, with Pd(OAc)2 as the catalytic precursor in
the Suzuki–Miyaura reaction between ferroceneboronic acid and 4-bromoaldehyde. The X-ray structural
analysis and DFT study of several palladium complexes containing sandwich-type diphosphine chelating
ligands revealed that the variations in bite angles are much larger than those in bite distances. The more
energetically favorable conformation in the Pd(II) complexes is the one with bite angle close to 90°.
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Suzuki–Miyaura reaction
Ferrocenylboronic acid
dppf
Cobalt-containing phosphine
DFT
1. Introduction
dppc (Diagram 1). The efficacy of these ligands in various cross-
coupling reactions has been examined [33,34]. These CpCoCb
One of the most celebrated achievements of modern synthetic
organic chemistry is the rapid development and extensive appli-
cations of ligand-assisted palladium-catalyzed cross-coupling
methodology. In spite of the emerging employment of N-hetero-
cyclic carbenes (NHC) in recent years as potentially effective
ligands in transition metal-catalyzed cross-coupling reactions
[1–8], organophosphines undoubtedly remain to be the ligands
of the most commonly used today [9–11]. Although numerous
kinds of organophosphines have been designed, prepared and
evaluated as ligands [12], examples of using organometallic phos-
phines (TM-phosphines) as ligands in cross-coupling reactions are
relatively limited in number and scope [13–22]. Bis(diphenyl-
phosphino)ferrocene (dppf) [23–27] and its numerous derivatives
(Diagram 1) are probably the most widely used organometallic
phosphine ligands [28,29]. One of the most admired characteris-
tics of dppf is its bite angle flexibility caused by free rotation of
two Cp rings [30–32].
diphosphines carrying the substituents on the same ring, such an
arrangement naturally leads to the bulkiness of this type of ligands,
which is obviously advantageous for the reductive elimination pro-
cess, the last step of the catalytic cycle [35–38]. Since the former,
dppc, contains a Cb ring, the new cobalt system could exhibit a
behavior different from that of the dppf in terms of the coordinat-
ing capacity toward palladium. Comparison between these two
systems is expected to provide useful information with respect to
the performance of an organometallic ligand upon variation in me-
tal and ring size.
One of the most frequently used methods of preparation of
arylferrocenes, ArFc, involves the direct reaction of ferrocene with
aryldiazonium salts [39–46]. However, the yields of desired prod-
ucts obtained by this method rarely exceed 50%, and in many cases
they are disappointedly low [40,47]. Due to the poor yields and
lack of characteristic generality of this method, a more feasible
route to arylferrocenes is obvious in need. The employment of
the renowned Suzuki–Miyaura reaction might provide a promising
alternative. The most commonly used organometallic compounds
in the Suzuki–Miyaura reaction are arylboronic acids. The arene
aromaticity of boronic acids is considered to be favoring the forma-
tion of the transition state during the oxidative addition process.
The cyclopentadienyl rings of the ferrocene are also regarded to
For the past few years, we had developed a new category of
dppf-analogous organocobalt phosphine ligands based on the
(g g
5-cyclopentadienyl)( 4-cyclobutadiene)cobalt framework, 1,2-
* Corresponding author. Fax: +886 4 22862547.
E-mail address: fehong@dragon.nchu.edu.tw (F.-E Hong).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.11.010

C.-P. Chang et al. / Inorganica Chimica Acta 363 (2010) 412–417
413
Me
Me
PPh2
PPh2
PPh2
PPh2
NMe2
PPh2
NMe2
PPh2
Co
Co
Fe
Fe
Fe
PPh2
PPh2
PPh2
ppfa
bppfa
dppf
1,2-dppc
1,1'-dppc
Diagram 1.
+ Na(η5-C5H4 Pr)
i
(η5-C5H4 Pr)Co(PPh3)2
2
i
CPPh2
PhC
+ 2
CoCl(PPh3)3
toluene, reflux
toluene, rt
1
3
iPr
iPr
iPr
R2
R1
+ Pd(COD)Cl2
R3
Ph
Δ
Co
Ph
Co
Co
R2
R4
Ph
2
P
Ph3P
R4
R3
Pd
Cl
R1
Ph2P
Cl
4a: R1,R3=PPh2; R2,R4=Ph
4b: R1,R4=PPh2; R2,R3=Ph
5-trans: R1,R3=PPh2; R2,R4=Ph
5-cis: R1,R4=PPh2; R2,R3=Ph
6
Scheme 1. Preparations of 5-trans and 5-cis and reaction of 5-cis with Pd(COD)Cl2
be aromatic. In principle, the Suzuki–Miyaura reaction between
ferroceneboronic acid, FcB(OH)2, and aryl halide, ArX, would yield
the desired product, ArFc. Unexpectedly, only a few articles con-
cerning this subject have been found in literature [48]. A system-
atic investigation of the synthesis of arylferrocenes using the
Suzuki–Miyaura reaction is highly desirable for improving the effi-
ciency of the method. In this report the preparation of 1,2-dppc as
well as its application in palladium-catalyzed Suzuki–Miyaura
reactions is presented.
the trans-isomer is concerned, its four cyclopentadienyl protons
are observed as two sets of triplets at 4.25 ppm (t, JH–H = 2.0 Hz,
2H, Cp) and 4.75 ppm (t, JH–H = 2.0 Hz, 2H, Cp) in the 1H NMR spec-
trum. The isopropyl group signals are at 2.08 (m, 1H, iPr) ppm and
i
0.87 ppm (d, JH–H = 6.8 Hz, 6H, Pr). The equivalence of two phos-
phorous atoms is also evidenced by a single signal at ꢀ15.8 ppm
in the 31P NMR. The molecular structure of 5-cis was determined
by X-ray diffraction methods, an ORTEP diagram being depicted
in Fig. 1. The two rings, cyclopentadienyl and cyclobutadiene, are
almost coplanar. The presence of two –PPh2 groups next to each
other makes it potentially a bidentate ligand.
2. Results and discussion
2.2. Synthesis of palladium complex 6
2.1. Syntheses of organocobalt diphosphine ligands 5-trans and 5-cis
Compound 5-cis was expected to act as an authentic diphos-
phine ligand towards the chelation of transition metals. Indeed,
further reaction of 5-cis with one molar equivalent of Pd(COD)Cl2
Two isomeric forms of cobalt sandwich diphosphine ligands, 5-
trans and 5-cis, were prepared as processes described in Section 3
(Scheme 1). As shown, the reaction of CoCl(PPh3)3 (1) with Na(g5
-
in toluene at 25 °C furnished palladium complex [(g5
-
i
C5H4 Pr) (2) at room temperature yielded an air-sensitive com-
C5H4(CHMe2))Co(g
4-1,2-(PPh2)2C4Ph2)-PdCl2] (6) in good yield
i
pound (
g
5-C5H4 Pr)Co(PPh3)2 (3). Further reaction of 3 with two
(Scheme 1). The binding mode of 5-cis is much more similar to
1,2-bis(diphenylphosphino)ethane (dppe) than of 1,10-dppf. Com-
pound 6 was characterized by spectroscopic methods. The spectro-
scopic data of 6 are not much different from that of 5-cis except for
the observed downfield shift in the 31P NMR (63 ppm) characteris-
tic of coordination. In 1H NMR, two sets of multiplets observed at
4.38 ppm (t, JH–H = 2.40) and 3.84 ppm (t, JH–H = 2.30) correspond
to four protons of the substituted cyclopentadienyl ring of 6. The
isopropyl group appears as a multiplet and a doublet at 1.52 ppm
(m, 1H, iPr) and 0.31 ppm (d, JH–H = 9.20, 6H, iPr), respectively.
The molecular structure of 6 was determined by X-ray diffraction
methods, the corresponding ORTEP diagram being depicted in
Fig. 2. It clearly shows a chelated palladium metal center and an
isopropyl group tilted away from it to prevent severe steric
hindrance.
molar equivalent of alkyne PhC„CPPh2 at refluxed toluene pre-
5-C5H4 Pr)-
i
sumably gave two isomeric forms of cobaltacycle (
g
Co(C4Ph2(PPh3)2), 4a and 4b. Finally, a mixture of trans- and 5-
cis in the ratio of 56:44 was observed from the 1H NMR. Previously
we have reported that only a Cp-unsubstituted analog of 5-trans
was isolated from a similar reaction of (g
5-C5H5)Co(PPh3)2 (3) with
PhC„CPPh2 at refluxed toluene. In contrast, only a cobaltacycle
analogous to 4a was isolated while 3 was reacted with HC„CPPh2
at the same reaction condition [33]. Apparently, it is the introduc-
tion of a bulky group, –iPr, on the Cp ring that caused a significant
change in the stereochemical outcome of reaction by exerting se-
vere steric hindrance on top of the molecule.
The mixture of 5-trans and 5-cis was characterized by 1H, 13C,
31P NMR, EA and MS. The 1H NMR spectrum of 5-cis shows two sets
of triplets at 4.60 ppm (t, JH–H = 2.4 Hz, 2H) and 4.63 ppm (t, JH–H
=
2.4 Hz, 2H) corresponding to four cyclopentadienyl protons in
two different environments. The isopropyl group signals are ob-
served at 1.82 ppm (m, 1H, iPr) and 0.77 ppm (d, JH–H = 7.2 Hz,
2.3. Application of 6 in palladium-catalyzed Suzuki–Miyaura reaction
i
6H, Pr). A single signal at ꢀ17.7 ppm in the 31P NMR spectrum
As is known, the catalytic performance of the palladium-cata-
lyzed Suzuki–Miyaura reaction is subjected to a variety of factors
indicates the equivalence of two phosphorous atoms. As far as

414
C.-P. Chang et al. / Inorganica Chimica Acta 363 (2010) 412–417
study the feasibility of employing 6 as the catalytic precursor in
Suzuki–Miyaura reaction, ferrocenylboronic acid and 4-bromoal-
dehyde were chosen (Scheme 2). The general procedure for the cat-
alytic reactions under investigation is as follows. A suitable
Schlenk tube was charged with 1.5 mmol of boronic acid, 1.0 mmol
of arylhalide, 1.0 mL of solvent, 3.0 mmol of base, 1.0 mol% of pal-
ladium source. The mixture was stirred at designated reaction tem-
perature and hours depending on the reactions executed. It was
then followed by a work-up. Several commonly bases were sur-
veyed since a well-chosen base is crucial to the success of the reac-
tion. The results are listed in Table 1 [51–53]. As shown, the best
result was obtained with K2CO3 (Entry 1). Unexpectedly, NaOtBu,
the base of choice in many Suzuki reactions, showed no conversion
at all (Entry 4).
The palladium source is one of the most influential factors in the
performance of Suzuki–Miyaura reaction. Two more catalytic pre-
cursor systems were screened here, the results are shown in Table
2. Unexpectedly, a rather poor yield was observed with a com-
monly used Buchwald’s ligand, biphenyl-2-yl-di-tert-butyl-phos-
phane P(tBu)biPh and palladium acetate (Entry 2) [54–57].
Furthermore, Pd(PPh)4 was even less efficient (Entry 3). In addition,
several arylbromides were examined. The procedures were the
same as previously (Table 1) except that K2CO3 and complex 6
were chosen as a base and a catalyst precursor, respectively. The
arylbromide with an electron-withdrawing group showed a better
conversion (Entries 1 versus 4 and 5), confirming the common
observation for the palladium-catalyzed Suzuki coupling reaction
[15]. No conversion was observed in the case of benzylbromide
(Entry 6).
Fig. 1. ORTEP drawing of 5-cis. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (°): P1–C6 1.804(4). P2–C9 1.816(4). C3–C46 1.507(5).
C7–C22 1.467(4). C8–C28 1.484(4). C7–C6–C9 89.9(2). C7–C8–C9 90.4(2). C6–C9–
C8 89.2(2). C8–C7–C6 90.5(2). C34–P2–C40 100.82(17). C16–P1–C10 101.89(16).
2.4. Computational studies on various palladium complexes
The bite angle (hP–M–P) and the bite distance (rP–M) are the two vi-
tal factors greatly affecting the catalytic efficiency of a bidentate
phosphine ligand-chelated metal complex [58,59]. The bite angles
(hP–M–P) and the bite distances (rP–M) of some complexes related to
t
6, namely, dppf_PdCl2 [60–62], Fc(P)4 Bu_PdCl2 [63], Josi-
phos_PdCl2 (R0 = tBu. R00 = Cy) [64], Josiphos_PdCl2 (R0 = Cy. R00 =
p-C6H4CF3) [65], ppfa_PdCl2 [66], dppm_PdCl2 [67], dppe_PdCl2
[68] and bppfa_PdCl2 [69], obtained from the X-ray data are listed
in Table 3. Since the state-of-the-art density functional theory
method (DFT) has proven to be a useful tool in the studies of transi-
tion metal-mediated catalytic reactions, it was employed to gain
information concerning the optimized geometries of these com-
plexes (Diagram 2). This method at the B3LYP level was utilized to
examine the effects of the bite angles (hP–M–P) and the bite distances
(rP–M) on the catalytic performance. For comparison, the data
obtained from the optimized geometries by DFT methods for several
complexes are listed in Table 3. By both methods the bite angles of
dppm_PdCl2 and dppe_PdCl2 are the smallest ones among all
complexes. It is understandable due to the rigidity of the carbon
backbone in both dppm and dppe. The bite angles of 6 and
Fig. 2. ORTEP drawing of 6. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (°): P2–C6 1.799(5). P1–C7 1.804(5). Pd1–P1 2.2418(13).
Pd1–P2 2.2628(14). Pd1–Cl2 2.3485(13). Pd1–Cl1 2.3570(15). P1–Pd–P2
101.89(16). Cl1–PdCl2 93.45(5). C22–P1–C28 108.9(2). C41–P1–C34 106.3(2). C7–
P1–Pd1 105.06(14). C6–P2–Pd1 105.60(15).
t
Fc(P)4 Bu_PdCl2, which are quite close, are the smallest ones among
such as temperature, solvent, base, the palladium salt, the type of
ligand, the ratio of ligand/palladium etc. [49,50]. The best catalytic
efficiency can be achieved by optimizing all the factors involved. To
the sandwich-type ligand complexes by both methods. The bite
angles of dppf_PdCl2 and bppfa_PdCl2 are relatively large due to
the coordination to substituents on both rings. Large bite angles
X
B(OH)2
[Pd]
Br
+
Fe
Fe
X
7a: X=C(O)H
7b: X=H
Scheme 2.

C.-P. Chang et al. / Inorganica Chimica Acta 363 (2010) 412–417
415
Table 1
distances between palladium and phosphorus are similar in all
cases suggesting that the bond strengths are of similar scope.
Suzuki coupling reactions with various bases.a
Entry
Base
Yield (%)b
2.5. Summary
1
2
3
4
K2CO3
KF
56
25 (33c)
46 (54d)
NR
K3PO4
A cobalt sandwich diphosphine ligand 5-cis and its chelated
palladium complex 6 were synthesized. The latter was successfully
applied in the preparation of ferrocenylarenes via the Suzuki–
Miyaura reaction. Compared with the previously reported method,
a better efficiency was observed. The DFT study showed that de-
spite of the wide variation of bite angles for different types of
bidentate ligands the bite distances between palladium and phos-
phorus are similar in all cases which suggest that the strength of
bonds are of similar scope.
NaOtBu
a
Reaction conditions: ArX:FcB(OH)2:base = 1:1:3. 1 mol% 6, 1 mL toluene, 100 °C,
24 h.
b
Isolated yield.
Dry KF.
Dry K3PO4.
c
d
Table 2
Suzuki coupling reactions with various catalyst precursors.a
3. Experimental
Entry
1
ArBr
Pd complex
Yield (%)b
56
3.1. General
6
O
Br
Br
Br
H
O
Most synthetic manipulations were carried out using standard
Schlenk techniques or operation in Dry Box under dry nitrogen
atmosphere. Moisture-free treated and freshly distilled solvents
were used in reaction. Separation was carried out by centrifugal
thin-layer chromatography (CTLC) on Chromatotron, Harrison mod-
el 8924. The plates were prepared using silica gel 60 PF254 contain-
ing gypsum (Merck). 1H and 31P{1H} NMR spectra were recorded on
a Varian Mercury-400 spectrometer operating at 400.44 and
162.10 MHz, respectively, and referenced to the residual resonance
of CHCl3 and external standard 85% H3PO4. 13C{1H} NMR spectra
were recorded either on a Varian Mercury-400 or 300 spectrometer
operating either at 100.70 or 75.43 MHz, respectively, and refer-
enced to the signal of deuterated chloroform. Coupling constants
are reported in Hz. Elemental analyses were obtained using a Herae-
us CHN–O–S-Rapid instrument. Mass spectra were recorded on JOEL
JMS-SX/SX 102A GC/MS/MS spectrometer.
2
3
BiPh(tBu)2/Pd(OAc)2
24
11
H
O
Pd(PPh)4
H
4
5
6
6
6
6
33
Br
Br
10.9c
NR
H C
Br
3
a
Reaction conditions: ArX:FcB(OH)2:K2CO3 = 1:1:3. 1 mol% palladium, 1 mL tol-
uene, 100 °C, 24 h.
b
Isolated yield.
c
NMR yield.
are also observed for Josiphos_PdCl2 (R0 = tBu. R00 = Cy), Josi-
phos_PdCl2 (R0 = Cy. R00 = p-C6H4CF3) and ppfa_PdCl2 probably due
to the formation of six-membered ring after chelation. It shows that
the bite angle is greatly affected by the ring size and attributed to
the original shape of the bidentate ligand. To contrast it, the bite
3.2. Syntheses
3.2.1. Synthesis and characterization of 5-cis and 5-trans
A 100 mL round-bottomed flask equipped with a magnetic stir-
bar and a rubber septum was charged with CoCl(PPh3)3 1 (0.44 g,
Table 3
Bite angles and bite distances of 6, dppf, Fc(P)4tBu, Josiphos, ppfa, dppm, dppe and bppfa chelated palladium complexes.
Complex
Methods
X-raya
DFTb
Bite angle (°)
89.87(5)
Bite distance (Å)
Bite angle (°)
89.12
Bite distance (Å)
6
2.241(13)
2.262(14)
2.277
2.277
2.240
2.246
2.305
2.282
2.237
2.397
2.396
2.376
2.362
2.288
2.284
–
dppf_PdCl2
Fc(P)4tBu_PdCl2
99.26
88.97
97.46
96.02
101.66
89.06
Josiphos_PdCl2
R0 = tBu. R00 = Cy
Josiphos_PdCl2
R0 = Cy.
R00 = p-C6H4CF3
ppfa_PdCl2
–
–
–
–
2.275
96.06
72.70
85.77
98.79
2.231 (P–Pd)
2.116 (N–Pd)
2.249
2.235
2.238
–
Dppm_PdCl2
Dppe_PdCl2
bppfa_PdCl2
74.49
87.46
–
2.301
2.301
2.300
2.318
–
2.238
2.298
2.302
a
Data from the X-ray crystal structures available.
Data from the optimized geometries obtained by the DFT method.
b

416
C.-P. Chang et al. / Inorganica Chimica Acta 363 (2010) 412–417
Me
Ph2
P
Ph2
P
tBu
tBu
R"2
P
Cl
Cl
P
Pd Cl
Cl
Ph2
Co
Pd
Ph2
PPh2
P
Cl
R2'
Fe
Pd
Fe
Ph
Ph
Fe
P
Cl
Cl
Pd
P
Ph2
PPh2
P
Cl
Ph2
t
dppf_PdCl2
Josiphos_PdCl2
6
Fc(P)4 Bu_PdCl2
Me
Me
NMe2
Pd
Ph2
P
Ph2
P
NMe2
Ph2
Cl
Cl
Cl
Cl
Pd
P
Ph2
Cl
Cl
Pd
P
Fe
Fe
Cl
Pd
P
Ph2
P
Ph2
P
Cl
Ph2
bppfa_PdCl2
ppfa_PdCl2
dppe_PdCl2
dppm_PdCl2
Diagram 2.
0.49 mmol) and sodium isopropylcyclopentadienide 2 (0.65 g,
0.44 mmol) before adding 10 mL toluene. After 0.5 h, a batch of
phenylethynyl diphenylphosphine (0.28 g, 1.00 mmol), dissolved
in toluene (5 mL), was added, and the solution was refluxed for
12 h. Subsequently, purification was carried out by using CTLC. A
yellow band containing both 5-cis and 5-trans in the ratio of 56/
44 was eluted out by mixed solvent CH2Cl2/hexane = 1:1. The total
yield of the resulted yellow solid is 34% (0.13 g, 0.17 mmol).
5-cis: 1H NMR (CDCl3/ppm): d 6.96–7.42 (m, 30H, Ph and PPh2),
4.60 (t, J = 2.0 Hz, 2H, Cp), 4.63 (t, J = 2.0 Hz, 2H, Cp), 1.82 (m, 1H,
iPr), 0.77 (d, J = 7.2 Hz, 6H, iPr). 13C{1H} NMR (CDCl3/ppm): d
126.0–136.8 (m, Ph and PPh2), 80.2 (Cp), 24.8 (iPr), 23.0 (iPr).
31P{1H} NMR (CDCl3/ppm): d ꢀ17.7. Anal. Calc. for C48H41CoP2: C,
78.072; H, 5.59. Found: C, 78.04; H, 5.59. LRMS: m/z = 738 (M+).
5-trans: 1H NMR (CDCl3/ppm): d 6.84–7.31 (m, 30H, Ph and
PPh2), 4.25 (t, J = 2.0 Hz, 2H, Cp), 4.75 (t, J = 2.0 Hz, 2H, Cp), 2.08
(m, 1H, iPr), 0.87 (d, J = 6.8 Hz, 6H, iPr). 13C{1H} NMR (CDCl3/
ppm): d 125.9–136.7 (m, Ph and PPh2), 87.8 (t, JC–P = 6.1 Hz, C(2)
and C(4) of Cb), 80.2 (Cp), 80.5 (Cp), 25.0 (iPr), 23.1 (iPr). 31P{1H}
NMR (CDCl3/ppm): d ꢀ15.8. LRMS: m/z = 738 (M+).
Table 4
Crystal data of 5-cis, and 6.
Compound
5-cis
6
Formula
C48H41CoP2
738.68
Monoclinic
P21/n
14.18(2)
17.89(2)
15.17(2)
–
93.79(3)
–
3839(10)
4
1.278
0.71073
0.563
1.10–24.40
7533
460
C48H41Cl2CoP2Pd
915.98
Monoclinic
P21/c
19.142(4)
10.991(2)
23.112(5)
–
110.14(3)
–
4564.8(16)
4
1.333
0.71073
0.975
1.83–26.05
8964
484
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (mg/m3)
k (Mo K
a
)
), Å
l
(mmꢀ1
h Range(°)
Observed reflections (F > 4r(F))
Number of refined parameters
R1 for significant reflectionsa
wR2 for significant reflectionsb
Goodness-of-fitc
0.0545
0.1365
0.981
0.0516
0.0966
1.006
3.2.2. Synthesis and characterization of 6
a
R1 = |
R
(|Fo| ꢀ |Fc|)/|
R
Fo||.
n
h
i.
h
io
The same size and set up of 100 mL flask was charged with di-
2
2
wR2
¼
R
wðF2o ꢀ F2c Þ
R
wðF2oÞ
1=2, w = 0.0934 and 0.0400 for 5-cis and 6,
b
chloro(1,5-cyclooctadiene)palladium (0.04 g, 0.15 mmol) and (g5
-
respectively.
C4H4-iPr)Co( 4-(PPh2)2C4Ph2) 5-cis (0.11 g, 0.15 mmol), and
g
h
i
1=2
2
GoF ¼
R
wðF2o ꢀ Fc2Þ =ðNrflns ꢀ Nparams
Þ
.
c
10 mL CH2Cl2. The solution was stirred at room temperature for
1 h before the solvent was removed in reduced pressure. Subse-
quently, purification was carried out by using CTLC. A yellow band
was eluted out by mixed solvent CH2Cl2/EA = 10:1. The yield of the
resulted yellow solid is 72% (0.10 g, 0.10 mmol).
temperature and then the crude material was purified by CTLC in a
CH2Cl2/hexane = 1:1 mixed solvent as a mobile phase. A red band
was eluted out and characterized latter as 7a in the yield of 56%
(0.164 g, 0.56 mmol) while 4-bromoaldehyde was used as the
arylhalide source. A lower yield, 33% (0.087 g, 0.33 mmol), was
calculated and identified latter as 7b for the case where bromoben-
zene was used as the starting bromide.
6: 1H NMR (CDCl3/ppm): d 7.14–8.10 (m, 30H, Ph and PPh2),
4.38 (t, JH–H = 2.4 Hz, 2H, Cp), 3.84 (t, JH–H = 2.3 Hz, 2H, Cp), 1.52
i
i
(m, 1H, Pr), 0.31 (d, JH–H = 9.2 Hz, 6H, Pr). 13C{1H} NMR (CDCl3/
ppm): d 127.5–132.9 (m, Ph), 135.6 (t, JC–P = 6.0, HC@C–PPh2),
82.0 (2C, Cp), 80.4 (2C, Cp), 24.3 (iPr), 22.0 (iPr). 31P{1H} NMR
(CDCl3/ppm): d 63.0. Anal. Calc. for C48H41Cl2CoP2Pd: C, 62.94; H,
4.51. Found: C, 60.93; H, 5.27. LRMS: m/z = 879 [MꢀCl]+.
3.3.1. Characterization of 7a and 7b
7a: 1H NMR (CDCl3/ppm): d 9.91 (s, 1H, CHO), 7.73 (d, 2H, JH–H
=
8.4 Hz, Ph), 7.54 (d, 2H, JH–H = 8.1 Hz, Ph), 4.69 (t, 2H, JH–H = 2.1 Hz,
Cp), 4.38 (t, 2H, JH–H = 2.1 Hz, Cp), 3.99 (s, 5H, Cp). 13C{1H} NMR
(CDCl3/ppm): d 191.66, 129.87, 126.01, 70.69, 69.81, 39.98 (m).
Anal. Calc. for C17H14FeO: C, 70.37; H: 4.86. Found: C, 69.83; H:
5.35. LRMS: m/z = 290 (M+).
3.3. General procedures for the Suzuki cross-coupling reactions
An oven-dried Schlenk tube was charged with 9.0 mg of 6
(0.01 mmol) and 3.0 mmol of base. The tube was evacuated and
backfilled with nitrogen followed by the addition of aryl bromide
(1.00 mmol), ferroceneboronic acid (0.229 g, 1.00 mmol) and tolu-
ene (2.0 mL). The tube was sealed with a Teflon screw cap, and the
mixture was stirred at 100 °C for 24 h then was filtered and con-
centrated in vacuo. The mixture was allowed to cool down to room
7b: 1H NMR (CDCl3/ppm): d 7.49 (m, 2H, Ph), 7.30 (m, 2H, Ph),
7.17 (m, 1H, Ph), 4.63 (t, 2H, JH–H = 1.6 Hz, Cp), 4.30 (t, 2H, JH–H
=
1.6 Hz, Cp), 4.04 (s, 5H, Cp). 13C{1H} NMR (CDCl3/ppm): d 128.29,
126.13, 125.89, 69.55, 68.84, 66.48. Anal. Calc. for C16H14Fe: C,
73.31; H: 5.38. Found: C, 72.93; H: 5.20. LRMS: m/z = 262 (M+).

C.-P. Chang et al. / Inorganica Chimica Acta 363 (2010) 412–417
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417
3.4. X-ray crystallographic studies
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Suitable crystals of 5-cis and 6 were sealed in thin-walled glass
capillaries under nitrogen atmosphere and mounted on a Bruker
AXS SMART 1000 diffractometer. Intensity data were collected in
1350 frames with increasing
x (width of 0.3° per frame). The space
group determination was based on a check of the Laue symmetry
and systematic absences, and was confirmed using the structure
solution. The structure was solved by direct methods using a SHEL-
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Fourier maps and hydrogen atoms were refined using a riding
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atoms, and fixed isotropic parameters were used for H atoms. Crys-
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