Kinetics of complex formation between palladium(II) acetate and bis(diphenylphosphino)ferrocene

Article abstract of DOI:10.1016/j.poly.2008.11.038

The kinetics of complex formation between palladium(II) acetate, and 1,1'-bis(diphenylphosphino)ferrocene, dppf, in two different deuterated solvents CDCl₃ and DMSO-d₆ were investigated using ³¹P NMR spectroscopy. The mole

Full text of DOI:10.1016/j.poly.2008.11.038

Polyhedron 28 (2009) 609–613
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Kinetics of complex formation between palladium(II) acetate
and bis(diphenylphosphino)ferrocene
*
Mahbubeh Pourshahbaz, Mohsen Irandoust, Ezzat Rafiee, Mohammad Joshaghani
Chemistry Department, Razi University, Kermanshah 67149, Iran
Kermanshah Oil Refining Company, Kermanshah, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The kinetics of complex formation between palladium(II) acetate, and 1,1’-bis(diphenylphosphino)ferro-
cene, dppf, in two different deuterated solvents CDCl3 and DMSO-d6 were investigated using 31P NMR
spectroscopy. The mole ratio and the 31P-chemical shifts in DMSO-d6 solution revealed the formation
of an intermediate, which is gradually converted into the more stable [Pd(dppf)OAc)2] species with a dppf
acting as a chelate ligand. In the chloroform solution however, the interaction of metal ion and the ligand
resulted directly in the formation of [Pd(dppf)OAc)2] species with a chelating dppf. The rate constant for
the complexation reaction was evaluated from computer fitting of the corresponding integration-time
data.
Received 27 October 2008
Accepted 27 November 2008
Available online 31 December 2008
Keywords:
Phosphine
Palladium
Kinetics
Ferrocene
dppf
Ó 2008 Elsevier Ltd. All rights reserved.
NMR
1. Introduction
complexes and to gain some useful information about the mecha-
nism of complex formation.
Since the time of the synthesis of 1,1’-bis(diphenylphosphino)
ferrocene [1], dppf, this ligand is probably the most intensively
studied ferrocenyl phosphines compounds to date and a variety
of transition-metal complexes stabilized by dppf have been charac-
terized [2–12]. Among them, the Pd-dppf complexes have richer
chemistry and have been widely used as catalysts especially for
carbon-carbon bond forming reactions [13–27]. It is well known
that the bidentate dppf shows a versatile coordination ability
adapting its steric bite angle as well as electronic properties to
the geometric and electronic requirements of the metal through
the appropriate coordination [28–30]. Although the chelating coor-
dination mode is the predominant character of dppf, multinuclear
complexes containing bridging dppf are also known [31–60].
While very high efficiency of Pd-dppf catalysts is due to a com-
bination of electronic and steric parameters of these precursors, no
comprehensive study on the rate of the formation of dppf com-
plexes has been carried out, albeit to the best of our knowledge.
We have recently reported the application of Pd-phosphine cata-
lysts in the Suzuki cross coupling reactions [61]. Our interest in
the physicochemical properties of the dppf [62], encouraged us
to determine the rate constants for formation of the Pd-dppf
2. Experimental
CDCl3 and DMSO-d6 were commercially available from the Al-
drich and used as received. The ligand dppf was prepared as previ-
ously described [62]. An authentic sample of Pd(dppf)(OAc)2 was
synthesized by the reaction of equimolar amounts of palladium(II)
acetate and dppf according to literature procedure for preparation
of Pd(dppf)Cl2 [63] and characterized by multi-nuclear NMR spec-
troscopy as well as ICP elemental analysis. Anal. calc. for
C38H34FeO4P2Pd, C, 58.29%, H, 4.92%, Fe, 7.13%, P, 7.91%, Pd,
13.59%. Found C, 58.87, H, 4.65, Fe, 7.52, P, 7.75, Pd, 13.91%. 1H
NMR (200 MHz, CDCl3): d 2.15 (s, 6, CH3 of acetate ions), 4.00–
4.45 (m, 8), 7.15–7.90 (m, 20); 31P{1H} NMR (81.014 MHz, CDCl3):
d 28.05 (s). 31P{1H} NMR (81.014 MHz, DMSO-d6): d 24.58 (s).
All NMR measurements were made on a Bruker Avance (DPX)
200FT- NMR spectrometer with a field strength of 4.7 T (47 KG)
equipped with a temperature controller, ( 0.1 °C). At this field,
31P resonates at 81.014 MHz. In 31P NMR experiments, the stan-
dard was %85 H3PO4. All chemical shift measurements were carried
out at a temperature of 25.0 0.1 °C.
One milliliter of stock solution of the ligand (0.0554 g in 1 mL,
0.1 M) in each solvent was placed in a NMR tube and then, 50 lL
of the stock metal solution of Pd(OAc)2 dissolved in the same sol-
* Corresponding author. Fax: +98 831 4274559.
E-mail
addresses:
MJoshaghani@razi.ac.ir,
joshaghanim@yahoo.com
vent (0.0673 g in 0.3 mL, 1 M, calculated for monomeric form)
(M. Joshaghani).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.11.038

610
M. Pourshahbaz et al. / Polyhedron 28 (2009) 609–613
was added. The 31P NMR spectrum of the resulting solution was
measured at different times.
0.06
0.05
0.04
0.03
0.02
0.01
0
3. Results and discussion
In the solid state, palladium(II) acetate exists as a trimer and has
a maximum at 370–450 nm in its UV–Vis spectrum [64,65]. In con-
trast, the UV–Vis spectra of this salt in both solvents CDCl3 and
DMSO-d6 do not have such typical signal (Fig. 1). In addition, the
trimer–monomer equilibrium strongly depends on the addition
of ligand; led to formation of monomeric form of palladium(II) ace-
tate in solution. Therefore, it could be possible to consider it as
monomer in kinetic calculations.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
[M]/[L]
NMR spectroscopy has been widely used for the investigation of
the kinetics and mechanisms of inorganic reactions. The chemical
shifts, line broadening, and the integral of the signals are quantita-
tive factors used for this purposes. In the cases where the changes
in the chemical shifts and line broadening are negligible, the inte-
gral of the signals could be used as a very sensitive measure of the
concentration of a particular species. This tool has been particu-
larly used for consecutive reactions.
Fig. 2. The product formation as a measure of the rate of reaction vs. the metal to
ligand mole ratio. All concentrations were determined by the integration of their 31P
NMR signals at the same times.
The ICP elemental analysis confirms the formation of
[Pd(OAc)2(dppf)] (Scheme 1).
Therefore, the reaction may be considered as a simple second-
order reaction either reversible Eq. (1) or irreversible reactions
Eq. (2)
The kinetics of the complexation between palladium(II) acetate
and dppf were sufficiently slow to lead us monitor all species
formed during the complexation.
k1
Initial investigation of reaction rates was carried out using dif-
ferent metal to ligand mole ratio. It was observed that the concen-
tration of the product as a measure of the rate of reaction, increases
with increasing the concentration of palladium(II) acetate linearly.
This evidence led us to conclude that the reaction is first-order
with respect to the palladium source (Fig. 2).
½Pdꢁ þ dppf ꢀ ½PdðdppfÞꢁ
ð1Þ
ð2Þ
k
ꢀ1
k1
½Pdꢁ þ dppf !½PdðdppfÞꢁ
where [Pd] represents the starting palladium(II) acetate.
The best intensity changes in the 31P NMR lines were observed
at 0.5 metals to ligand mole ratio. In addition, many reports have
been published in where, the catalytic reactions were carried out
using this mole ratio [66]. Therefore, the kinetic studies were
investigated using this mole ratio.
3.2. Kinetic studies in chloroform solution
The concentration of the free dppf and its Pd complex are deter-
mined by the integration of their 31P NMR signals. The stack dia-
gram for the 31P NMR spectra is shown in Fig. 4.
At the first stage, calculations were carried out using the sec-
ond-order reversible Eq. (1). The resulted rate constants show that
the forward rate constant is much greater than the backward rate
constant (Table 1). In addition, careful monitoring of the 31P NMR
spectra rules out any dissociation of dppf and reaction reversibility.
Therefore, the overall reaction may be considered as irreversible
Eq. (2) which involves the following rate law Eq. (3):
3.1. Investigation of the species involved in the CDCl3 solution
In CDCl3 solution, 1,1’-bis(diphenylphosphino)ferrocene, dppf,
has two chemically and magnetically equivalent phosphorus
atoms, which appear as a singlet at ꢀ18.90 ppm, with respectto
an internal standard solution of H3PO4 (Fig. 3). During the com-
plexation at 25 °C, the intensity of this signal is gradually
decreased and simultaneously, a signal at 28.05 ppm downfield-
shifted from the ligand appears which corresponds to
[Pd(dppf)(OAc)2] [67].
1
½Pdꢁ0½dppfꢁt
Ln
½dppfꢁ0 ꢀ ½Pdꢁ0 ½dppfꢁ0½Pdꢁt
¼ k1t
ð3Þ
with subscripts t and 0 representing time t and 0, respectively. A
plot of the left term of Eq. (3) versus time should be a straight line
with a positive slope equal to k (Fig. 5). The overall rate constant of
the reaction is listed in Table 1.
3
2.5
2
It is reported that even if one reagent (here [Pd]) be maintained
in only a two-fold excess over another reagent (here [dppf]), the er-
ror in the computed second-order rate constant is 62% for 60% con-
version and as the reaction proceeds toward the end of the
reaction, pseudo first-order conditions certain hold [68,69]. Similar
re-computation of our kinetics data for pseudo first-order irrevers-
ible reaction was carried out and the resulted rate constant con-
firmed this hypothesis (Table 1, entry 3). Other re-computations
of the kinetic data for other kinetic models such as third-order re-
sulted poor regressions.
1.5
b
1
a
0.5
0
300
350
400
450
500
3.3. Investigation of the species involved in the DMSO-d6 solution
Wave le ngth (nm)
Fig. 1. Spectra of Pd(II) acetate (4.5 ꢂ 10ꢀ4 M, calculated for the monomeric form)
at 25 °C in CDCl3 (a) and DMSO-d6 (b).
In the DMSO-d6 solution, the free ligand appears at ꢀ19.27 ppm.
This signal is gradually decreased during the complexation and a

M. Pourshahbaz et al. / Polyhedron 28 (2009) 609–613
611
Fig. 3. 31P NMR spectrum of reaction mixture of Pd(II) acetate/dppf in CDCl3 at 25 °C.
100
Ph2
P
OAc
OAc
80
60
40
20
0
Fe
Pd
PPh2
Scheme 1. Structure of [Pd(dppf)(OAc)2] complex.
0
20
40
60
80
100
120
Time (min)
Fig. 5. Second-order irreversible plot for reaction of Pd(II) acetate:dppf in CDCl3 at
25 °C.
Table 1
Rate and stability constants of reaction of Pd(II) acetate:dppf in CDCl3 at 25 °C.
Entry
Type of reaction
k1 (sꢀ1 Mꢀ1
)
k
ꢀ1(sꢀ1) ꢂ 104
Ke (Mꢀ1
1000 90
)
1
2
3
Reversible second-order
Irreversible second-order
Pseudo first-order
0.52 0.03
0.50 0.02
0.53 0.03
5.2ꢂ 0.2
Fig. 4. The change in the 31P NMR spectra vs. time in CDCl3 at 25 °C.
Fig. 6. 31P NMR spectrum of Pd(II) acetate/dppf in DMSO-d6 and at 25 °C.
8
<
k1
k2
1
2
Pd þ dppf ! ½Pd2ð
l
ꢀ dppfÞ2ꢁ !½PdðdppfÞꢁ
signal appears at 29.70 ppm, which may be due to the formation of
a M2L2 di-palladium intermediate (Fig. 6) [70–72]. The observation
of this intermediate is probably due to the coordinating ability of
DMSO, which probably makes the coordination of dppf slower
and allows the formation of the intermediate.
ð4Þ
k3
:
Pd þ dppf !½PdðdppfÞꢁ
3.4. Kinetic studies in DMSO-d6 solution
The relative intensities of both signals are decreased on going to
continue the reaction and an additional signal appears at
24.58 ppm corresponding to the ML species involved chelating
dppf [67]. The ICP elemental analysis confirms the formation of
[Pd(OAc)2(dppf)]. The pattern of relative intensity changes indi-
cates that the ML is produced possibly from two paths; directly
from the starting reactants via a consecutive reaction as a main
path [73,74] together with a simple second-order reaction Eq. (4)
The concentration of the free dppf and its Pd complexes are
determined by the integration of their characteristic 31P NMR sig-
nals. Distribution of all species versus time is shown in Fig. 7. It
should be noticed that the concentration of the free ligand could
not exponentially decay to zero since it is used in two-fold excess.
Initial calculation based on Eq. (5) was carried out by simulta-
neously solving of three equations for the change of concentration

612
M. Pourshahbaz et al. / Polyhedron 28 (2009) 609–613
center [75]. The better solubility of the reactants in CDCl3 also
0.10
0.08
0.06
0.04
0.02
0.00
plays an important role. The difference in the reaction rates make
such kinetic studies very important in the catalytic reactions in
where, a mixture of metal and ligand are used as catalyst. For
example, it is reported that using methanol as solvent, no meth-
oxycarbonylation of 2-bromoaniline was observed. Changing to a
solvent mixture of toluene-methanol increased remarkable the
conversion [76]. This feature is of greater importance particularly
whenever the complex formation between metal and ligand is
the rate determining step and/or one of previous catalytic cycle.
Another noteworthy of such kinetics studies outcome on com-
paring the rate of catalytic reactions using a ML catalyst with
in situ prepared catalyst by addition of metal and ligand. The sim-
ilarity between the rates of both reactions may be an excellent evi-
dence for the presence of a similar mechanism.
[L]
[ML]
60
[M2L2]
50
0
10
20
30
40
70
Time (min)
Fig. 7. Distribution diagram for involving species in the reaction of Pd(II) acetate
and dppf in DMSO-d6 at 25 °C. The solid lines are the best trendlines obtained by
Excel program.
Acknowledgments
The authors thank the Razi University Research Council and
Kermanshah Oil Refining Company for support of this work.
Table 2
Rate constants of the reaction of Pd(II) acetate:dppf (1:2) in DMSO-d6 at 25 °C.
References
Entry Type of reaction
kobs
k2
(sꢀ1 Mꢀ1) ꢂ 102
(sꢀ1) ꢂ 10
[1] J.J. Bishop, A. Davison, M.L. Katcher, D.W. Lichtenberg, R.E. Merrill, J.C. Smart, J.
Organomet. Chem. 27 (1971) 241.
[2] K.-S. Gan, T.S.A. Hor, in: A. Togni, T. Hayashi (Eds.), Ferrocenes-Homogeneous
Catalysis Organic Synthesis Materials Science, VCH, Weinheim, Germany,
1995.
Parallel consecutive and irreversible
reactions
1.0 0.1
1.0 0.1
[3] A.W. Rudie, D.W. Lichtenberg, M.L. Katcher, A. Davison, Inorg. Chem. 17 (1978)
2859.
of the ligand, [L]; the intermediate, [M2L2]; and the final chelating
[4] W.R. Cullen, J.D. Woollins, Coord. Chem. Rev. 39 (1981) 1.
[5] T. Hayashi, M. Kumada, Acc. Chem. Res. 15 (1982) 395.
[6] D.A. Clemente, G. Pilloni, B. Corain, B. Longato, M. Tiripicchino- Camellini,
Inorg. Chim. Acta 115 (1986) L9.
[7] L.-T. Phang, S.C.F. Au-Yeung, T.S.A. Hor, S.B. Khoo, Z.-Y. Zhou, T.C.W. Mak, J.
Chem, Soc. Dalton Trans. 1 (1993) 165.
complex; [ML], with time Eq. (5)
8
ꢀkobs
t
>
½Lꢁ ¼ ½L0ꢁe
½M2L2ꢁ ¼
>
>
<
kobs½Lꢁ
obst
2t
feꢀk ꢀ eꢀk
g
k2ꢀkobs
ð5Þ
n
o
>
>
>
:
1
obst
2t
½MLꢁ ¼ ½Lꢁ 1 ꢀ k
ðk2eꢀk ꢀ kobseꢀk
[8] G.M. deLima, C.A.L. Filgueiras, M.T.S. Giotto, Y.P. Mascarenhas, Transition Met.
Chem. 20 (1995) 380.
2ꢀkobs
[9] S. Otto, A. Roodt, Acta Crystallogr. Sect. C c53 (1997) 1414.
[10] S.A. Bodolosky, S. Schreiner, Synthesis, characterization and reactivity of
platinum -bis(diphenylphosphino) ferrocene complexes: Book of Abstracts, in:
213th ACS National Meeting, San Francisco, 1997, p. 13.
[11] T.A. Peganova, N.V. Vologdin, P.V. Petrovskii, I.D. Nesterov, K.A. Lyssenko, O.V.
Gusev, Russ. Chem. Bull. 55 (2006) 683.
[12] X.L. Lu, S.Y. Ng, J.J. Vittal, G.K. Tan, L.Y. Goh, T.S.A. Hor, J. Organomet. Chem. 688
(2003) 100.
[13] T.J. Colacot, Platinum Met. Rev. 45 (2001) 22.
[14] T. Hayashi, M. Konishi, Y. Kobori, M. Kumada, T. Higuchi, K. Hirotsu, J. Am.
Chem. Soc. 106 (1984) 158.
[15] B.E. Bosch, I. Brümmer, K. Kunz, G. Erker, R. Frölich, S. Kotila, Organometallics
19 (2000) 1255.
The corresponding rate constants are calculated by Excel-fitting
of the experimental points (Fig. 7) and are given in Table 2.
As Eq. (5) shows, determination of individual amounts of k1 and
k3 is impossible and a summation of them as kobs could be obtained
in this way. An approximate value for these rate constants could be
easily calculated by considering two extremes of Eq. (5)
ꢀ
aÞk1 >> k3 ) kobs ꢃ k1
bÞk1 << k3 ) kobs ꢃ k3
The first extreme was arisen if the consecutive reaction is the
major contributor of the overall rate constant while the second ex-
treme could be obtained if the second-order path is the major
contributor.
The relative magnitude of the kobs [Pd] (sꢀ1) and k2 (sꢀ1) rate
constants shows that the consecutive reaction is the major contrib-
utor of the overall reaction rate. Therefore, the first extreme is
more logic.
Interestingly, the intermediate was observed only in metal to li-
gand mole ratios near 0.5. This may be because both rate of forma-
tion (k1) and consumption (k2) of the intermediate depend on the
concentrations of metal and ligand as a same way (steady state
approximation).
[16] M. Ogasawara, K. Yoshida, T. Hayashi, Organometallics 19 (2000) 1567.
[17] A.L. Boyes, I.R. Butler, S.C. Quayle, Tetrahedron Lett. 39 (1998) 7763.
[18] W. Mägerlein, A.F. Indolese, M. Beller, Angew. Chem. Int. Ed. Engl. 40 (2001)
2856.
[19] M.S. Driver, J.F. Hartwig, J. Am. Chem. Soc. 118 (1996) 7217.
[20] T.E. Müller, M. Berger, M. Grosche, E. Herdtweck, F.P. Schmidtchen,
Organometallics 20 (2001) 4384.
[21] K. Mikami, K. Aikawa, Org. Lett. 4 (2002) 99.
[22] V. Cadierno, P. Crochet, J. Diez, S.E. Garcia-Garrido, J. Gimeno, S. Garcia-
Garrido, Organometallics 22 (2003) 5226.
[23] V. Cadierno, P. Crochet, J. Diez, S.E. Garcia-Garrido, J. Gimeno, Organometallics
23 (2004) 4836.
[24] T. Ohe, N. Miyaura, A. Suzuki, J. Org. Chem. 58 (1993) 2201.
[25] M. Sato, A. Miyaura, A. Suzuki, Chem. Lett. (1989) 1408.
[26] W.J. Thompson, J. Gaudino, J. Org. Chem. 49 (1984) 5237.
[27] O.R. Hughes, J.D. Unruh, J. Mol. Catal. 12 (1981) 71.
[28] B. Therrien, L. Vieille-Petit, J. Jeanneret-Gris, P. Stepnicka, G. Suess-Fink, J.
Organomet. Chem. 689 (2004) 2456.
[29] T. Sixt, J. Fiedler, W. Kaim, Inorg. Chem. Commun. 3 (2000) 80.
[30] P.J. Stang, B. Olenyuk, J. Fan, A.M. Arif, Organometallics 15 (1996) 904.
[31] T.S.A. Hor, S.P. Neo, C.S. Tan, T.C.W. Mak, K.W.P. Leung, R.J. Wang, Inorg. Chem.
31 (1992) 4510.
[32] S.P. Neo, T.S.A. Hor, J. Organomet. Chem. 464 (1994) 113.
[33] S.P. Neo, Z.-Y. Zhou, T.C.W. Mak, T.S.A. Hor, J. Chem. Soc., Dalton Trans. (1994)
3458.
[34] S.G. Bott, K. Yang, M.G. Richmond, J. Chem. Cryst. 25 (1995) 263.
[35] L.T. Phang, T.S.A. Hor, Z.Y. Zhou, T.C.W. Mak, J. Organomet. Chem. 469 (1994)
253.
4. Conclusion
In comparison, the complex formation is faster in CDCl3 than
DMSO, which may be due to the coordinating ability of DMSO. This
coordination probably makes the coordination of dppf slower and
allows the formation of the intermediate. It also decreases the elec-
trophilicity of metal as well as the steric crowding at the metal

M. Pourshahbaz et al. / Polyhedron 28 (2009) 609–613
613
[36] I.D. Salter, V. Sik, S.A. William, T. Adatia, J. Chem. Soc., Dalton Trans. (1996)
652.
[55] C. Jiang, Y.-S. Wen, L.-K. Liu, T.S.A. Hor, Y.K. Yan, Organometallics 17 (1998)
173.
[37] V.W.-W. Yam, S.W.-K. Choi, K.-K. Cheung, J. Chem. Soc., Dalton Trans. (1996)
3415.
[56] T.J. Kim, S.C. Kwon, Y.H. Kim, N.H. Heo, M.M. Teeter, A. Yamano, J. Organomet.
Chem. 426 (1992) 71.
[38] P.M.N. Low, A.L. Tan, T.S.A. Hor, Y.-S. Wen, L.-K. Liu, Organometallics 15 (1996)
2595.
[57] Z.-G. Fang, Y.-S. Wen, R.K.L. Wong, S.-C. Ng, L.-K. Liu, T.S.A. Hor, J. Cluster Sci. 5
(1994) 327.
[39] F. Canales, M.C. Gimeno, A. Laguna, P.G. Jones, Organometallics 15 (1996)
3412.
[40] G. Pilloni, R. Graziani, B. Longato, B. Corain, Inorg. Chim. Acta 190 (1991) 165.
[41] U. Caselato, R. Graziani, G. Pilloni, J. Crystallogr. Spectrosc. Res. 23 (1993) 571.
[42] B.H. Aw, K.K. Looh, H.S.O. Chan, K.L. Tan, T.S.A. Hor, J. Chem. Soc., Dalton Trans.
(1994) 3182.
[58] S.M. Draper, C.E. Housecroft, A.L. Rheingold, J. Organomet. Chem. 435 (1992) 9.
[59] T.S.A. Hor, L.T. Phang, L.-K. Liu, Y.-S. Wen, J. Organomet. Chem. 397 (1990) 29.
[60] W.-Y. Yeh, S.-B. Chen, S.-M. Peng, G.-H. Lee, J. Organomet. Chem. 481 (1994)
183.
[61] M. Joshaghani, M. Daryanavard, E. Rafiee, J. Xiao, C. Baillie, Tetrahedron Lett. 48
(2007) 2025.
[43] I.D. Salater, S.A. Williams, T. Adatia, Polyhedron 14 (1995) 2803.
[44] S. Onaka, T. Moriya, S. Takagi, A. Mizuno, H. Furuta, Bull. Chem. Soc. Jpn. 65
(1992) 1415.
[45] S. Onaka, A. Mizuno, S. Takagi, Chem. Lett. (1989) 2040.
[46] W.H. Watson, A. Nelg, S. Hwang, M.G. Richmond, J. Organomet. Chem. 445
(1993) 170.
[47] S. Onaka, M. Otsuka, A. Mizuno, S. Takagi, K. Sako, M. Otomo, Chem. Lett.
(1994) 48.
[48] S.T. Chacon, W.R. Cullen, M.I. Bruce, O.B. Shawkataly, F.W.B. Einstein, R.H.
Jones, A.C. Willis, Can. J. Chem. 68 (1990) 2001.
[62] M.B. Gholivand, A. Babakhanian, M. Joshaghani, Anal. Chim. Acta 584 (2007)
302.
[63] T. Hayashi, M. Konishi, Y. Kobori, M. Kumada, T. Higuchi, K. Hirotsuf, J. Am.
Chem. Soc. 106 (1984) 158.
[64] A.C. Skapski, M.L. Smart, J. Chem. Soc. D, Chem. Commun. (1970) 659.
[65] J. Evans, L. O’Neill, V.L. Kambhampati, G. Rayner, S. Turin, A. Genge, A.J. Dent, T.
Neisius, J. Chem. Soc., Dalton Trans. (2002) 2212.
[66] For example B. Wei, T.S.A. Hor, J. Mol. Catal. A 132 (1998) 229.
[67] B. Corain, B. Longato, G. Favero, D. Ajò, G. Pilloni, U. Russo, F.R. Kreissl, Inorg.
Chim. Acta 157 (1989) 266.
[49] M.I. Bruce, P.A. Humphrey, O.B. Shawkataly, M.R. Snow, E.R.T. Tiekink, W.R.
Cullen, Organometallics 9 (1990) 2910.
[50] G. Rheinwald, H. Stoeckli-Evans, G. Suess-Fink, J. Organomet. Chem. 512
(1996) 27.
[68] J. Rawlings, S. Wherland, H.B. Gray, J. Am. Chem. Soc. 99 (1977) 1968.
[69] J.L. Jensen, R.C. Kanner, G.R. Shaw, Int. J. Chem. Kinetics 22 (1990) 1211.
[70] M. López-Torres, A. Fernández, J.J. Fernández, A. Suárez, S. Castro-Juíz, J.M. Vila,
M.T. Pereira, Organometallics 20 (2001) 1350.
[51] A.J. Blake, A. Harrison, B.F.G. Johnson, E.J.L. McInnes, S. Parsons, D.S. Shephard,
L.J. Yellowless, Organometallics 14 (1995) 3160.
[71] A. Fernández, D. Vázquez-Garcıá, J.J. Fernández, M. López- Torres, A. Suárez, S.
Castro-Juíz, J.M. Vila, New J. Chem. 26 (2002) 404.
[52] L.K. Liu, Y.S. Wen, T.S.A. Hor, H.S.O. Chan, K.-L. Tan, L-T. Phang, Y.K. Yan,
Polyhedron 10 (1991) 2437.
[53] Y.K. Yan, H.S.O. Chan, T.S.A. Hor, K.-L. Tan, L.-K. Liu, Y.-S. Wen, J. Chem. Soc.,
Dalton Trans. (1992) 426.
[54] Y.K. Yan, T.S.A. Hor, S.-L. Lam, Y.-X. Cui, C.C.F. Au-Yeung, Inorg. Chem. 33
(1994) 2407.
[72] S.R. Ananias, A.E. Mauro, V.A. De Lucca Neto, Trans. Met. Chem. 26 (2001) 570.
[73] P. Hendry, A.M. Sargeson, Inorg. Chem. 25 (1986) 865.
[74] E.T. Gray Jr., R.W. Taylor, D.W. Margerum, Inorg. Chem. 16 (1977) 3047.
[75] B.A. Steinhoff, S.R. Fix, S.S. Stahl, J. Am. Chem. Soc. 124 (2002) 766.
[76] I.J.S. Fairlamb, S. Grant, P. McCormack, J. Whittall, J. Chem. Soc., Dalton Trans.
(2007) 865.