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Suzuki cross-coupling of aryl bromides catalyzed by cyrhetrenylphosphine complexes of palladium (II)
Inorganic Chemistry Communications 14 (2011) 961–963
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
Suzuki cross-coupling of aryl bromides catalyzed by cyrhetrenylphosphine complexes of palladium (II) Diego Sierra a, César Zuñiga a, Gonzalo E. Buono-Core a, Fernando Godoy b, A. Hugo Klahn a,⁎ a b
Instituto de Química, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Valparaíso, Chile Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Santiago, Chile
a r t i c l e
i n f o
Article history: Received 21 October 2010 Accepted 18 March 2011 Available online 26 March 2011 Keywords: Cyrhetrenylphosphine ligand Heterobimetallic catalyst Suzuki reaction
a b s t r a c t The heterobimetallic Re–Pd complex (CO)3Re(η5-C5H4PPh2)PdCl2(NCMe) I and the chelated complexes (η5C5H4PPh2)(CO)2PR3Re–PdCl2 (R = Me, II and R = OMe, III) were used as precatalyst for the Suzuki reaction. Complexes II and III containing a metal–metal bond were shown to be more efficient precatalyst for crosscoupling reaction of a wide range of aryl bromides electronically activated, unactivated and sterically hindered. © 2011 Elsevier B.V. All rights reserved.
Over the last twenty years, the palladium catalyzed Suzuki crosscoupling reaction has become one of the most commonly used reactions in organic chemistry (Scheme 1) [1,2]. During this time, numerous efforts have been aimed on optimizing the catalytic systems used in this reaction, with most of them involving the electronic and steric properties of the ligands, improving the activity and selectivity of the catalytic system. An important part of these studies have been focused in the use of organometallic phosphines, mainly ferrocenylphosphines as a ligands, because the electron-rich metallocene helps to provide the electronic and steric characteristics that are often required to form a highly active catalyst [3–5]. Although they have been studied to a much lesser extent than their ferrocene analogs, cyrhetrenylphosphine ligands such as (η5C5H4PR2)Re(CO)3 (R = Ph, t-Bu) and (η5-C5H4PR2)Re(NO)(CH3) (PPh3) (R = Ph, t-Bu) [6], have also received attention, and have been shown to be competent components of Pd(II) systems for the Suzuki Cross-coupling reaction. These catalytic systems presented very similar activities to those based upon organic phosphines. However, the easiness of exchanging ligands coordinated to the rhenium center in these species, offers exciting possibilities to include a diversity of structural and electronic modifications in the organometallic ligand, which would improve the catalytic properties of this species.
⁎ Corresponding author. E-mail address: [email protected] (A.H. Klahn). 1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2011.03.042
These results have motivated us to carry on the study of three complexes of palladium (II), derived from cyrhetrenylphosphine ligands [7,8], as precatalysts for the Suzuki cross-coupling of aryl bromides (Fig. 1). As summarized in Scheme 2, the coupling of bromobenzene and phenylboronic acid was studied using 1 mol% of the palladium complexes. Phenylboronic acid was used in excess over bromobenzene (1.5:1), because some homocoupling can occur under Suzuki conditions. Table 1 summarize the results obtained from these assays. We have also included in Table 1, data reported by Gladysz for the same coupling reaction but with a catalytic system formed in situ by mixing Pd(OAc)2 and four equivalents of (η5-C5H4PPh2)Re(CO)3 [6]. A comparison of bromobenzene conversion of this system with I (96 (Entry 3) vs. 37% (Entry 2), under the same experimental conditions) remarkably differences can be observed. This may be attributed to a part of the phosphine ligand being consumed in the reduction of Pd(II) to Pd(0) species [(η5-C5H4PPh2)Re(CO)3]2Pd and/or [(η5-C5H4PPh2) Re(CO)3]Pd, which should be the active catalytic species [9–11]. The relatively lower activity of I (Table 1, Entries 1 and 2) could be due to the properties of the ligand NCCH3, which is significantly less bulky and basic than phosphines, which should decrease the ease of reductive elimination and oxidative addition, probably by the stabilization of some intermediate species [11,12]. Furthermore, using complex I as precatalyst, the rhenium center is not involved in any process of the catalytic cycle, behaves like a “spectator” metal. There are numerous examples of such ligands, where the metal is not involved in any process of rupture or bond formation [13,14]. However, in complexes II and III (Table 1, Entries 4–7) the rhenium center acts as a ligand coordinating to the palladium atom, forming a chelate type complex [8]. The use of chelate complexes from bi or
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D. Sierra et al. / Inorganic Chemistry Communications 14 (2011) 961–963
Pd Catalyst + (HO)2 B
X
Base Solvent
R
R
X= Cl, Br, I, OTf.... R= Aryl, Vinyl, Alkyl Scheme 1. Biphenyl synthesis by Suzuki cross-coupling of aryl halides.
PPh2 Pd
Re CO
OC
PPh2
Cl Re
Cl
NCMe
CO I
R2P
Pd
Cl
CO CO
Cl
R= Me II, OMe III
Fig. 1. Heterobimetallic complexes used as precatalyst.
multidentate ligands as catalysts for Suzuki cross-coupling reactions is currently being investigated, due to the excellent activity obtained when this type of species is used as precatalysts. However, there is not a final conclusion about the characteristics of the active catalytic species derived from these ligands [15,16]. Cs2CO3 proved to be a more effective base than K3PO4 for the initially tested aryl bromides, so it was used preferentially in subsequent reactions. Finally, a test conducted at lower temperatures (Table 1, Entry 6) produces poorer conversion rates, mainly due to a decrease in the solubility of the base. After determining the optimal experimental conditions, we proceeded to perform the cross-coupling of a wide range of aryl bromides; electronically activated, unactivated and sterically hindered substrates. The results of these studies are presented in Table 2. Electronically activated aryl bromides such as 4-bromoacetophenone (Entries 4, 5 and 6), 4-bromonitrobenzene (Entries 7, 8 and 9) and 1,4dichloro-2-bromobenzene (Entries 16, 17 and 18), were easily coupled using the three precatalyst complexes. More electron rich substrates like 4-bromotoluene are electronically unactivated (Entries 1, 2 and 3), but this aryl bromide was effectively coupled under the same reaction conditions. On the other hand, sterically hindered substrates like 2bromo-1,3-dimethylbenzene (Entries 13, 14 and 15) led to a decrease in the conversion rate, due to the steric demand and electronic inactivation by both methyl groups. On the other hand, the rate of coupling of 4-bromoaniline (Entries 10, 11 and 12) was severely diminished, which may be due to the basic properties of this substrate, which could coordinate to the catalytically active species, interfering with the catalytic cycle. All experiments were carried out under nitrogen atmosphere. Gas chromatography was performed on Shimadzu GCMS-QP5050 equipment. Toluene was dried and freshly distilled before using [17]. The reagents used in coupling reactions were purchased commercially and used without prior purification. A Schlenk flask ambiented with N2 and equipped with a magnetic stir bar, was charged with 3.4 mg (0.0046 mmol; 1 mol%) of the palladium complex, then were added 10 ml of dry toluene and
83.6 mg (0.686 mmol; 1.5 eq.) of phenylboronic acid. To this reaction mixture was added the corresponding aryl bromide (0.457 mmol, 1 eq.) and finally the appropriate base (2 eq.). This mixture was vigorously agitated at 100 °C. Complexes I, II and III were prepared according to the procedures reported by our laboratory [7,8]. In this report we determined the catalytic properties of three, air and moisture stable, cyrhetrenylphosphine of palladium (II) complexes and have established that these species are effective precatalysts of the Suzuki cross-coupling reaction of aryl bromides. A wide range of substrates (electronically activated, unactivated and sterically hindered) afford high conversions and good rates. Furthermore, the presence of the two metal centers bonding by a metal–metal double bond improve the catalytic properties of the complexes. In view of the ease of making structural changes in phosphinocyrhetrene type ligands, we anticipate further improvements in the activity of the catalytic systems, based on these types of complexes. This may even allow the coupling of aryl chlorides.
Acknowledgments The authors thank Fondecyt-Chile (project nos. 3090035 and 1060487). We also acknowledge the Dirección de Investigación of Pontificia Universidad Católica de Valparaíso for financial support. D. S. acknowledges MECESUP and CONICYT for his doctoral scholarship. We also thank Professor John Gladysz for proof reading and helpful comments.
Table 1 Data for Suzuki coupling of bromobenzene and phenylboronic acid under the conditions of Scheme 2. Entry
Complex
Temperature (°C)
Base
Conversion (%) after 2 ha
1 2 3b 4 5 6 7
I I CpPPh2Re(CO)3 + Pd(OAc)2 II II II III
100 100 100 100 100 50 100
Cs2CO3 K3PO4 K3PO4 Cs2CO3 K3PO4 Cs2CO3 Cs2CO3
68 37 96 96 78 32 94
a Average of two runs. 83.6 mg of phenylboronic acid (0.686 mmol; 1.5 eq.), 56.5 μL of bromobenzene (0.45 mmol; 1.0 eq.), Base (0.914 mmol; 2.0 eq.), 0.0045 mmol of Pd precatalyst complex (1 mol%) and dry toluene. b Data reported by Gladysz et al. [6].
Pd Catalyst 1 mol%
Br + (HO)2 B R
Base 2.0 eq. Toluene Temperature
R
Scheme 2. Standard screening conditions for Suzuki cross-coupling.
D. Sierra et al. / Inorganic Chemistry Communications 14 (2011) 961–963
963
Table 2 Suzuki cross-coupling of aryl bromides and phenylboronic acid. Entry
Complex
1
I
2
II
3
III
4
I
5
II
6
III
7
I
8
II
9
III
10
I
Aryl bromides
Conversion (%) 2 ha
Product
63
Br
H3C
H3C
94 84
O
O
100 100
Br
100 100
Br
O2N
O2N
100 100 4
Br
H2N
H2N
11
II
50
12
III
33
13
I
23
14
II
15
III
16
I
17
II
18
III
Br
72 40
Cl
100
Cl
100
Br
85
Cl
Cl
a Average of two runs. 0.686 mmol of phenylboronic acid (1.5 eq.), 0.450 mmol of the aryl bromide (1.0 eq.), 298 mg of Cs2CO3 (0.914 mmol; 2.0 eq.), 0.0045 mmol of Pd precatalyst complex (1 mol%) and dry toluene.
References [1] R.C. Smith, C.R. Bodner, M.J. Earl, N.C. Sears, N.E. Hill, L.M. Bishop, N. Sizemore, D.T. Hehemann, J.J. Bohn, J.D. Protasiewicz, J. Organomet. Chem. 690 (2005) 477. [2] M. Joshaghani, E. Faramarzi, E. Rafiee, M. Daryanavard, J. Xiao, J. Baillie, J. Mol. Catal. A Chem. 259 (2006) 35. [3] M.D. Sliger, G.A. Broker, S.T. Griffin, R.D. Rogers, K.H. Shaughnessy, J. Organomet. Chem. 690 (2005) 1478. [4] T.E. Pickett, C.J. Richards, Tetrahedron Lett. 42 (2001) 3767. [5] S.Y. Liu, M.J. Choi, G.C. Fu, Chem. Commun. (2001) 2408. [6] S. Eichenseher, O. Delacroix, K. Kromm, F. Hampel, J.A. Gladysz, Organometallics 24 (2005) 245. [7] D. Sierra, A. Muñoz, F. Godoy, A.H. Klahn, A. Ibañez, M.T. Garland, M. Fuentealba, Polyhedron 28 (2009) 322.
[8] D. Sierra, F. Godoy, A.H. Klahn, R. Ramirez, R. Arratia, M. Fuentealba, M.T. Garland, Dalton Trans. 39 (2010) 6295. [9] C. Baillie, L. Zhang, J. Xiao, J. Org. Chem. 69 (2004) 7779. [10] C. Amatore, E. Carré, A. Jutand, M.A. M'Barki, Organometallics 14 (1995) 1818. [11] A.F. Littke, C. Dai, G.C. Fu, J. Am. Chem. Soc. 122 (2000) 4020. [12] N.T.S. Phan, M. Van Der Sluys, C.W. Jones, Adv. Synth. Catal. 348 (2006) 609. [13] J. Giner Planas, J.A. Gladysz, Inorg. Chem. 41 (2002) 6947. [14] O. Delacroix, J.A. Gladysz, Chem. Commun. (2003) 665. [15] C.A. Fleckenstein, H. Plenio, Organometallics 27 (2008) 3924. [16] R.V. Smaliy, M. Beaupérin, H. Cattey, P. Meunier, J. Hierso, J. Roger, H. Doucet, Y. Coppel, Organometallics 28 (2009) 3152. [17] D.D. Perrin, L.F. Armarego, Purification of Laboratory Chemicals, 3rd ed., Pergamon Press, 1988.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
Suzuki cross-coupling of aryl bromides catalyzed by cyrhetrenylphosphine complexes of palladium (II) Diego Sierra a, César Zuñiga a, Gonzalo E. Buono-Core a, Fernando Godoy b, A. Hugo Klahn a,⁎ a b
Instituto de Química, Pontificia Universidad Católica de Valparaíso, Av. Universidad 330, Curauma, Valparaíso, Chile Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Santiago, Chile
a r t i c l e
i n f o
Article history: Received 21 October 2010 Accepted 18 March 2011 Available online 26 March 2011 Keywords: Cyrhetrenylphosphine ligand Heterobimetallic catalyst Suzuki reaction
a b s t r a c t The heterobimetallic Re–Pd complex (CO)3Re(η5-C5H4PPh2)PdCl2(NCMe) I and the chelated complexes (η5C5H4PPh2)(CO)2PR3Re–PdCl2 (R = Me, II and R = OMe, III) were used as precatalyst for the Suzuki reaction. Complexes II and III containing a metal–metal bond were shown to be more efficient precatalyst for crosscoupling reaction of a wide range of aryl bromides electronically activated, unactivated and sterically hindered. © 2011 Elsevier B.V. All rights reserved.
Over the last twenty years, the palladium catalyzed Suzuki crosscoupling reaction has become one of the most commonly used reactions in organic chemistry (Scheme 1) [1,2]. During this time, numerous efforts have been aimed on optimizing the catalytic systems used in this reaction, with most of them involving the electronic and steric properties of the ligands, improving the activity and selectivity of the catalytic system. An important part of these studies have been focused in the use of organometallic phosphines, mainly ferrocenylphosphines as a ligands, because the electron-rich metallocene helps to provide the electronic and steric characteristics that are often required to form a highly active catalyst [3–5]. Although they have been studied to a much lesser extent than their ferrocene analogs, cyrhetrenylphosphine ligands such as (η5C5H4PR2)Re(CO)3 (R = Ph, t-Bu) and (η5-C5H4PR2)Re(NO)(CH3) (PPh3) (R = Ph, t-Bu) [6], have also received attention, and have been shown to be competent components of Pd(II) systems for the Suzuki Cross-coupling reaction. These catalytic systems presented very similar activities to those based upon organic phosphines. However, the easiness of exchanging ligands coordinated to the rhenium center in these species, offers exciting possibilities to include a diversity of structural and electronic modifications in the organometallic ligand, which would improve the catalytic properties of this species.
⁎ Corresponding author. E-mail address: [email protected] (A.H. Klahn). 1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2011.03.042
These results have motivated us to carry on the study of three complexes of palladium (II), derived from cyrhetrenylphosphine ligands [7,8], as precatalysts for the Suzuki cross-coupling of aryl bromides (Fig. 1). As summarized in Scheme 2, the coupling of bromobenzene and phenylboronic acid was studied using 1 mol% of the palladium complexes. Phenylboronic acid was used in excess over bromobenzene (1.5:1), because some homocoupling can occur under Suzuki conditions. Table 1 summarize the results obtained from these assays. We have also included in Table 1, data reported by Gladysz for the same coupling reaction but with a catalytic system formed in situ by mixing Pd(OAc)2 and four equivalents of (η5-C5H4PPh2)Re(CO)3 [6]. A comparison of bromobenzene conversion of this system with I (96 (Entry 3) vs. 37% (Entry 2), under the same experimental conditions) remarkably differences can be observed. This may be attributed to a part of the phosphine ligand being consumed in the reduction of Pd(II) to Pd(0) species [(η5-C5H4PPh2)Re(CO)3]2Pd and/or [(η5-C5H4PPh2) Re(CO)3]Pd, which should be the active catalytic species [9–11]. The relatively lower activity of I (Table 1, Entries 1 and 2) could be due to the properties of the ligand NCCH3, which is significantly less bulky and basic than phosphines, which should decrease the ease of reductive elimination and oxidative addition, probably by the stabilization of some intermediate species [11,12]. Furthermore, using complex I as precatalyst, the rhenium center is not involved in any process of the catalytic cycle, behaves like a “spectator” metal. There are numerous examples of such ligands, where the metal is not involved in any process of rupture or bond formation [13,14]. However, in complexes II and III (Table 1, Entries 4–7) the rhenium center acts as a ligand coordinating to the palladium atom, forming a chelate type complex [8]. The use of chelate complexes from bi or
962
D. Sierra et al. / Inorganic Chemistry Communications 14 (2011) 961–963
Pd Catalyst + (HO)2 B
X
Base Solvent
R
R
X= Cl, Br, I, OTf.... R= Aryl, Vinyl, Alkyl Scheme 1. Biphenyl synthesis by Suzuki cross-coupling of aryl halides.
PPh2 Pd
Re CO
OC
PPh2
Cl Re
Cl
NCMe
CO I
R2P
Pd
Cl
CO CO
Cl
R= Me II, OMe III
Fig. 1. Heterobimetallic complexes used as precatalyst.
multidentate ligands as catalysts for Suzuki cross-coupling reactions is currently being investigated, due to the excellent activity obtained when this type of species is used as precatalysts. However, there is not a final conclusion about the characteristics of the active catalytic species derived from these ligands [15,16]. Cs2CO3 proved to be a more effective base than K3PO4 for the initially tested aryl bromides, so it was used preferentially in subsequent reactions. Finally, a test conducted at lower temperatures (Table 1, Entry 6) produces poorer conversion rates, mainly due to a decrease in the solubility of the base. After determining the optimal experimental conditions, we proceeded to perform the cross-coupling of a wide range of aryl bromides; electronically activated, unactivated and sterically hindered substrates. The results of these studies are presented in Table 2. Electronically activated aryl bromides such as 4-bromoacetophenone (Entries 4, 5 and 6), 4-bromonitrobenzene (Entries 7, 8 and 9) and 1,4dichloro-2-bromobenzene (Entries 16, 17 and 18), were easily coupled using the three precatalyst complexes. More electron rich substrates like 4-bromotoluene are electronically unactivated (Entries 1, 2 and 3), but this aryl bromide was effectively coupled under the same reaction conditions. On the other hand, sterically hindered substrates like 2bromo-1,3-dimethylbenzene (Entries 13, 14 and 15) led to a decrease in the conversion rate, due to the steric demand and electronic inactivation by both methyl groups. On the other hand, the rate of coupling of 4-bromoaniline (Entries 10, 11 and 12) was severely diminished, which may be due to the basic properties of this substrate, which could coordinate to the catalytically active species, interfering with the catalytic cycle. All experiments were carried out under nitrogen atmosphere. Gas chromatography was performed on Shimadzu GCMS-QP5050 equipment. Toluene was dried and freshly distilled before using [17]. The reagents used in coupling reactions were purchased commercially and used without prior purification. A Schlenk flask ambiented with N2 and equipped with a magnetic stir bar, was charged with 3.4 mg (0.0046 mmol; 1 mol%) of the palladium complex, then were added 10 ml of dry toluene and
83.6 mg (0.686 mmol; 1.5 eq.) of phenylboronic acid. To this reaction mixture was added the corresponding aryl bromide (0.457 mmol, 1 eq.) and finally the appropriate base (2 eq.). This mixture was vigorously agitated at 100 °C. Complexes I, II and III were prepared according to the procedures reported by our laboratory [7,8]. In this report we determined the catalytic properties of three, air and moisture stable, cyrhetrenylphosphine of palladium (II) complexes and have established that these species are effective precatalysts of the Suzuki cross-coupling reaction of aryl bromides. A wide range of substrates (electronically activated, unactivated and sterically hindered) afford high conversions and good rates. Furthermore, the presence of the two metal centers bonding by a metal–metal double bond improve the catalytic properties of the complexes. In view of the ease of making structural changes in phosphinocyrhetrene type ligands, we anticipate further improvements in the activity of the catalytic systems, based on these types of complexes. This may even allow the coupling of aryl chlorides.
Acknowledgments The authors thank Fondecyt-Chile (project nos. 3090035 and 1060487). We also acknowledge the Dirección de Investigación of Pontificia Universidad Católica de Valparaíso for financial support. D. S. acknowledges MECESUP and CONICYT for his doctoral scholarship. We also thank Professor John Gladysz for proof reading and helpful comments.
Table 1 Data for Suzuki coupling of bromobenzene and phenylboronic acid under the conditions of Scheme 2. Entry
Complex
Temperature (°C)
Base
Conversion (%) after 2 ha
1 2 3b 4 5 6 7
I I CpPPh2Re(CO)3 + Pd(OAc)2 II II II III
100 100 100 100 100 50 100
Cs2CO3 K3PO4 K3PO4 Cs2CO3 K3PO4 Cs2CO3 Cs2CO3
68 37 96 96 78 32 94
a Average of two runs. 83.6 mg of phenylboronic acid (0.686 mmol; 1.5 eq.), 56.5 μL of bromobenzene (0.45 mmol; 1.0 eq.), Base (0.914 mmol; 2.0 eq.), 0.0045 mmol of Pd precatalyst complex (1 mol%) and dry toluene. b Data reported by Gladysz et al. [6].
Pd Catalyst 1 mol%
Br + (HO)2 B R
Base 2.0 eq. Toluene Temperature
R
Scheme 2. Standard screening conditions for Suzuki cross-coupling.
D. Sierra et al. / Inorganic Chemistry Communications 14 (2011) 961–963
963
Table 2 Suzuki cross-coupling of aryl bromides and phenylboronic acid. Entry
Complex
1
I
2
II
3
III
4
I
5
II
6
III
7
I
8
II
9
III
10
I
Aryl bromides
Conversion (%) 2 ha
Product
63
Br
H3C
H3C
94 84
O
O
100 100
Br
100 100
Br
O2N
O2N
100 100 4
Br
H2N
H2N
11
II
50
12
III
33
13
I
23
14
II
15
III
16
I
17
II
18
III
Br
72 40
Cl
100
Cl
100
Br
85
Cl
Cl
a Average of two runs. 0.686 mmol of phenylboronic acid (1.5 eq.), 0.450 mmol of the aryl bromide (1.0 eq.), 298 mg of Cs2CO3 (0.914 mmol; 2.0 eq.), 0.0045 mmol of Pd precatalyst complex (1 mol%) and dry toluene.
References [1] R.C. Smith, C.R. Bodner, M.J. Earl, N.C. Sears, N.E. Hill, L.M. Bishop, N. Sizemore, D.T. Hehemann, J.J. Bohn, J.D. Protasiewicz, J. Organomet. Chem. 690 (2005) 477. [2] M. Joshaghani, E. Faramarzi, E. Rafiee, M. Daryanavard, J. Xiao, J. Baillie, J. Mol. Catal. A Chem. 259 (2006) 35. [3] M.D. Sliger, G.A. Broker, S.T. Griffin, R.D. Rogers, K.H. Shaughnessy, J. Organomet. Chem. 690 (2005) 1478. [4] T.E. Pickett, C.J. Richards, Tetrahedron Lett. 42 (2001) 3767. [5] S.Y. Liu, M.J. Choi, G.C. Fu, Chem. Commun. (2001) 2408. [6] S. Eichenseher, O. Delacroix, K. Kromm, F. Hampel, J.A. Gladysz, Organometallics 24 (2005) 245. [7] D. Sierra, A. Muñoz, F. Godoy, A.H. Klahn, A. Ibañez, M.T. Garland, M. Fuentealba, Polyhedron 28 (2009) 322.
[8] D. Sierra, F. Godoy, A.H. Klahn, R. Ramirez, R. Arratia, M. Fuentealba, M.T. Garland, Dalton Trans. 39 (2010) 6295. [9] C. Baillie, L. Zhang, J. Xiao, J. Org. Chem. 69 (2004) 7779. [10] C. Amatore, E. Carré, A. Jutand, M.A. M'Barki, Organometallics 14 (1995) 1818. [11] A.F. Littke, C. Dai, G.C. Fu, J. Am. Chem. Soc. 122 (2000) 4020. [12] N.T.S. Phan, M. Van Der Sluys, C.W. Jones, Adv. Synth. Catal. 348 (2006) 609. [13] J. Giner Planas, J.A. Gladysz, Inorg. Chem. 41 (2002) 6947. [14] O. Delacroix, J.A. Gladysz, Chem. Commun. (2003) 665. [15] C.A. Fleckenstein, H. Plenio, Organometallics 27 (2008) 3924. [16] R.V. Smaliy, M. Beaupérin, H. Cattey, P. Meunier, J. Hierso, J. Roger, H. Doucet, Y. Coppel, Organometallics 28 (2009) 3152. [17] D.D. Perrin, L.F. Armarego, Purification of Laboratory Chemicals, 3rd ed., Pergamon Press, 1988.