Trans-cis isomerization of [(C6H5)3P]2PtCl2 complex in dimethylformamide solutions

Article abstract of DOI:10.1016/j.molstruc.2014.06.082

The kinetics of the trans-cis isomerization reactions of the [(C₆H₅)₃P]₂PtCl₂ neutral complex catalyzed by four different metal ions: Be²⁺, Mg²⁺, Ca²⁺ and Sr²⁺ has been studied. The isomerization reactions were investigated in dimethylformamide (DMF) solutions at five temperatures in the range of 278-298 K keeping a constant concentration of metal ions c = 0.5 M. The rates of the isomerization reactions were determined spectrophotometrically by monitoring the absorbance changes at the 277 nm wavelength. The spectral measurements were carried out in the UV-Vis region using the Perkin-Elmer Lambda 650 instrument with the scan accuracy of 1 nm and 1 nm slit width at the 120 scanning rate. The observable rate constants were computed using the Glint program based on the global analysis. The activation energies were determined using the Arrhenius equation. The differences in the structures of the obtained cis and trans geometric isomers were confirmed on the basis of their IR spectra.

Full text of DOI:10.1016/j.molstruc.2014.06.082

Journal of Molecular Structure 1075 (2014) 620–624
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Trans–cis isomerization of [(C H ) P] PtCl complex in
6
q
5 3
2
2
dimethylformamide solutions
⇑
_
Dagmara Jacewicz , Joanna Pranczk, Dariusz Wyrzykowski, Krzysztof Zamoj c´ , Lech Chmurzy n´ ski
Faculty of Chemistry, University of Gda n´ sk, Wita Stwosza 63, 80-308 Gda n´ sk, Poland
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
ꢀ
The isomerization reaction of
(C P] PtCl is catalyzed
by metal ions.
The rates of the isomerization
reaction were determined
spectrophotometrically.
The reaction proceeds in a single step
according to the dissociative
mechanism.
[
6 5
H )
3
2
2
The kinetics of the isomerization
reaction was monitored in DMF
solution.
a r t i c l e i n f o
a b s t r a c t
Article history:
The kinetics of the trans–cis isomerization reactions of the [(C H ) P] PtCl neutral complex catalyzed by
6
5 3
2
2
Received 29 November 2013
Received in revised form 15 May 2014
Accepted 25 June 2014
2+
2+
2+
2+
four different metal ions: Be , Mg , Ca and Sr has been studied. The isomerization reactions were
investigated in dimethylformamide (DMF) solutions at five temperatures in the range of 278–298 K keep-
ing a constant concentration of metal ions c = 0.5 M. The rates of the isomerization reactions were deter-
mined spectrophotometrically by monitoring the absorbance changes at the 277 nm wavelength. The
spectral measurements were carried out in the UV–Vis region using the Perkin–Elmer Lambda 650 instru-
ment with the scan accuracy of 1 nm and 1 nm slit width at the 120 scanning rate. The observable rate
constants were computed using the ‘‘Glint’’ program based on the global analysis. The activation energies
were determined using the Arrhenius equation. The differences in the structures of the obtained cis and
trans geometric isomers were confirmed on the basis of their IR spectra.
Available online 2 July 2014
Keywords:
Platinum complexes
Isomerization reaction
Kinetics and mechanism
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
effect is the synthesis of cisplatin. Starting from potassium tetra-
chloroplatinate(II), K
any of four equivalent positions but the second NH
2
[PtCl
4
], the first NH
3
ligand can be added to
molecule
The trans effect in square complexes can be explained in terms
of an addition/elimination mechanism that goes through a trigonal
bipyramidal intermediate [1]. The classic example of the trans
3
could be added in the cis or trans position to the bound ammine
ꢁ
ligand. Since the Cl ion has a larger trans effect than the NH
3
mol-
ecule, the second ammine ligand preferentially substitutes trans to
the chloride ligand, and therefore cis to the first ammine molecule.
ꢁ
ꢁ
ꢁ
The trans effect of the halides follows the order I > Br > Cl ,
q
Selected paper presented at XIIth International Conference on Molecular
2ꢁ
therefore the synthesis is conducted using [PtI
4
]
to ensure a high
spectroscopy, Kraków – Białka Tatrza n´ ska, Poland, September 8–12, 2013.
⇑
yield and purity of the cis isomer, followed by the conversion of
PtI (NH into PtCl (NH [2].
Corresponding author. Tel.: +48 58 523 50 60; fax: +48 58 523 54 72.
E-mail address: dagmara.jacewicz@ug.edu.pl (D. Jacewicz).
2
3
)
2
2
3 2
)
http://dx.doi.org/10.1016/j.molstruc.2014.06.082
022-2860/Ó 2014 Elsevier B.V. All rights reserved.
0

D. Jacewicz et al. / Journal of Molecular Structure 1075 (2014) 620–624
621
Structure–activity relationships for a class of platinum coordi-
nation compounds confirm that only these with the cis geometry
block a cell growth. The better understanding of both the chemical
properties and the pharmacological action of cisplatin has guided
the development of analogs having always the cis geometry but
differing from cisplatin either for the ammine carrier ligands or
for the leaving chlorides [3,4]. In general, a modification of the
chloride leaving groups of cisplatin results in compounds with dif-
ferent pharmacokinetic properties, whereas a modification of the
carrier ligands alters the efficacy and/or the spectrum of activity
of the resulting complex. Platinum complexes effective as cyto-
static agents have been introduced into a medicinal practice by
the end of seventieths of the twentieth century [5,6]. Cisplatin, or
cis-diamminedichloroplatinum(II), is the first of a series of square
planar platinum(II)-containing chemotherapy drugs, including car-
boplatin and oxaliplatin [7,8]. The interaction of DNA and cisplatin
results in 35–45° bend in the large groove in the direction of the
spot within the cis-Pt-GG-N7, N7 chain adduct [9–12]. Moreover,
many other complex compounds of platinum(II) and palladium(II)
were studied in terms of the human cell lines and the ovarian
fibroma hamster. These studies confirmed that the complex com-
2
+
2+
pounds of both Pd and Pt affected the cell apoptosis, however,
the compounds of platinum(II) showed a much more potent and
higher activity [13–15].
There are two main reasons to be interested in the isomeriza-
tion reactions of the platinum complexes. Firstly, as mentioned
above, the platinum complexes play very important roles in our
body and our life. Therefore the knowledge of the kinetics of isom-
erization reactions of this class of compounds is of big importance.
The ability to isomerize of the compounds, especially in the pres-
ence of other individuals (such as metal ions) that are capable to
catalyze the processes of structure transformation has a great
impact on their biological properties. Furthermore, due to the
dependence of the pharmacokinetics of platinum compounds on
the substituted ligand type it seems to be reasonable to perform
the kinetic stability study of interesting class of platinum coordina-
6 5 3 2 2 6 5 3 2 2
Fig. 1. Structures of the trans-[(C H ) P] PtCl and cis- [(C H ) P] PtCl .
complexes is 790.56. The melting point equals to 300 °C. Elemental
analysis data for the isomers are as follows: cis-[(C P] PtCl : C,
4.51, H, 38.02; for trans-[(C P] PtCl : C, 54.62, H, 38.14, whereas
the theoretical composition for both isomers is as follows: C, 54.71, H,
H )
6 5 3
2
2
5
H )
6 5 3
2
2
3
8.23.
Fig.
1
6 5 3 2 2
shows the structures of trans-[(C H ) P] PtCl and
cis-[(C
6
5
H )
3
P] PtCl complex compounds.
2
2
The solubility of tested complex compounds is inversely
proportional to the increasing value of the dielectric constant of
the solvent. Thus, the compounds studied are insoluble in water,
slightly soluble in DMSO, and completely soluble in DMF.
6 5 3 2 2
tion compounds which are trans-/cis-[(C H ) P] PtCl isomers.
Secondly, in the literature one can find insufficient data concerning
this type of reactions in both aqueous, and especially, non-aqueous
solutions. Consequently, it is possible to find only few kinetic
studies concerning the trans–cis isomerization reactions of metal
complex compounds in non-aqueous solvents [16,17] such as
tetrahydrofuran, dimethyl sulfoxide or dimethylformamide. More-
over, there is a lack of consistent data on the influence of metal
ions as catalysts on the kinetics of the trans–cis isomerization reac-
tions in solutions. Thus, the present work is needed to supplement
the information on the kinetic stability of platinum(II) complexes
in non-aqueous solutions in the presence of different metal
cations. Besse and Johnson [18] have stated that the racemization
of tris(oxalate)chromate(III) is dependent upon a large number of
different cations, including magnesium, whereas Schlafer and
co-workers [19] have reported that the rate of the trans–cis
isomerization is independent on the added magnesium ion.
Due to the lack of data and the described discrepancies in the
findings it seemed worthwhile to investigate the catalytic effect
Kinetic measurements
The isomerization reactions were investigated in dimethylform-
amide (DMF) solutions at five temperatures: 278 K, 283 K, 288 K,
93 K and 298 K. The stock solutions containing the metal cations
2
used as catalysts were prepared using the nitrate salts of the cat-
ions which were soluble in dimethylformamide (DMF) – all metals
of the second group of the periodic table except for the salt of
2
+
2+
2+
2+
barium, namely Be , Mg , Ca and Sr . The stock solutions of
cations were 0.5 M. 2 ml of such solution was placed in a cuvette,
which was thermostated at the snap of temperature control
(
Peltier system) with the option of mixing and water circulation.
Then the solution was added to the cuvette with the pure, finely
grounded complex, trans-[(C P] PtCl stirred until the
6
5
H )
3
2
2
,
dissolution of the sample.. Subsequently, the trans–cis isomeriza-
tion reaction of the complex studied was monitored spectrophoto-
metrically. The rates of reactions studied were measured at the
wavelength equal to 277 nm.
of metal ions such: Be2 , Mg , Ca and Sr on the trans–cis
isomerization of [(C P] PtCl in the dimethylformamide
DMF) solutions. The non-aqueous solvent had to be used owing
+
2+
2+
2+
H
6 5
)
3
2
2
(
IR spectra
to the fact that the both isomers studied were not soluble in water.
IR spectra were recorded as the Nujol mulls using the Bruker IFS
66 spectrophotometer.
Experimental section
Reagents
Potentiometric measurements
The cis- and trans-dichlorobis(triphenylophosphine)platinum(II)
were bought from Sigma Aldrich. The molecular weight of both
The potentiometric measurements were carried out using an
ion-selective electrode (SCHOTT Instruments Ag 6280). The

6
22
D. Jacewicz et al. / Journal of Molecular Structure 1075 (2014) 620–624
temperature of the reaction cell was kept at 298.15 K by means of
Lauda E100 circulation thermostat.
whereas the trans isomer at 315 cmꢁ1. The remaining bands are
very similar for both isomers. The C@C stretch in aromatics can
ꢁ1
be observed at 1481 cm
for cis-[(C
PtCl , respectively [24,25]. Further-
more, for both complexes there exists the band characteristic for
6
H
5
)
3
P]
2
PtCl
2
and at
ꢁ
1
Instrumentation and simulations
1463 cm for trans-[(C
6
5
H )
3
P]
2
2
ꢁ1
The spectral measurements were carried out in the UV–Vis
region using the Perkin–Elmer Lambda 650 instrument with the
scan accuracy of 1 nm and 1 nm slit width at the scanning rate of
Pt–P stretching vibrations – at about 700 cm [25].
Kinetic studies
1
20. The observable rate constants were computed using the
‘
‘Glint’’ program based on a global analysis [20–23].
The isomerization reaction of the [(C
be presented as follows (Scheme 1):
6 5 3 2 2
H ) P] PtCl complex can
As mentioned, the progress of the isomerization reaction of the
P] PtCl complex catalyzed by four different metal ions
Results and discussion
[
(C
6
5
H )
3
2
2
was monitored spectrophotometrically. Fig. 4 shows the changes
in the absorbance caused by the isomerization reaction of the
IR spectra
trans-/cis-[(C
ion. As seen on the electronic spectra (Fig. 4), the trans-/cis-
(C P] PtCl complexes have the absorption maxima at almost
the same positions. However, the molar absorption coefficient of
the cis isomer is much lower than that for the trans isomer. This
allows the application of the spectrophotometric technique in
investigations on the kinetics of the isomerization reaction.
Carrying out the spectrophotometric measurements of isomer-
6 5 3 2 2
H ) P] PtCl complex catalyzed by the magnesium
The IR spectra obtained in the solid-state were merely carried
out to confirm different geometric conformations of the two
isomers of [(C H ) P] PtCl complex. Thus, the differences in the
6 5 3 2 2
structures of the obtained cis and trans geometric isomers were
found on their basis. Figs. 2 and 3 show the infrared spectra for
[
6
5
H )
3
2
2
the trans-[(C
respectively. The IR spectrum of trans-[(C
stretching vibrations v(@CAH) in aromatics with minima at
6
5
H )
3
P]
2
PtCl
2
and cis-[(C
6
H
)
5 3
P]
2
PtCl
2
complexes,
6
H
)
5 3
P]
2
PtCl shows
2
ꢁ
1
6 5 3 2 2
ization reaction of the trans-[(C H ) P] PtCl complex catalyzed by
3
PtCl
080.1 and 3065.8 cm , whereas for the cis form of cis-[(C
6 5
H )
3
P]
2
ꢁ1
four different metal ions of the second group of the periodic table,
it can be noted that for all probes the approximated curves decay
monoexponentially and, consequently, the reaction studied pro-
2
these bands are shifted to 3058.8 and 3085.8 cm wavenum-
bers, respectively. The cis isomer exhibits PtACl bonds at 293 cm
ꢁ1
,
1
ceeds in one step. A linear function of ln(A –A) versus time (t)
(Fig. 5) is consistent with the following kinetic equation:
-
dtrans-½ðC
6
H
5
Þ Pꢂ PtCl
2
=dt ¼ ktrans-½ðC
6
H
5
Þ Pꢂ PtCl
2
ð1Þ
3
2
3
2
Scheme 1. The isomerization reaction of trans-/cis-[(C
6
H
5 3
) P]
2 2
PtCl complex.
6 5 3 2 2
Fig. 2. The IR spectrum for the trans-[(C H ) P] PtCl .
Fig. 4. Absorbance changes for isomerization reaction of trans/cis-[(C
complex ([Mg2 ] = 0.5 M, T = 293 K).
6 5 3 2 2
H ) P] PtCl
+
6 5 3 2 2
Fig. 3. The IR spectrum for the cis-[(C H ) P] PtCl .

D. Jacewicz et al. / Journal of Molecular Structure 1075 (2014) 620–624
623
Fig. 5. The linear function of ln(A
1
–A) versus time (t) for the isomerization reaction
of [(C P] PtCl complex catalyzed by magnesium ion.
6
H
)
5 3
2
2
In order to determine the values of rate constants two methods,
namely the singular value decomposition analysis (SVD) and global
analysis (GA) based on A ? B reaction model, were used. It should
be highlighted that by using both methods almost the same results
were obtained. The rate constants and activation energies for the
6 5 3 2 2
isomerization reaction of the trans-/cis-[(C H ) P] PtCl complex
catalyzed by metal ions are collected in Table 1. The determined
ꢁ3
ꢁ4 ꢁ1
reaction rate constants values are the order of 10 or 10
s ,
which indicates that the exchange of ligands in these complexes
takes place relatively slowly, despite the presence of the catalysts.
This means that the trans-/cis- [(C H ) P] PtCl complexes may be
6 5 3 2 2
Scheme 2. The proposed mechanism of the trans–cis isomerization of
[
6 5 3 2 2
(C H ) P] PtCl .
classified as inert. Based on the obtained low values of activation
energy it can be concluded that the reaction rate slightly depends
on the temperature, which is consistent with the Arrhenius equa-
tion. A rise in temperature speeds up the reaction of the
isomerization.
Pt–Cl = 2.2997 Å, P–Pt–Cl = 87.88° for the cis isomer and 92.12°
for the trans isomer [26]. Since Pt–P and Pt–P bonds have almost
the same lengths it was crucial to check the presence of chloride
ions in the solution. Thus, the dissociative mechanism in DMF solu-
tion was confirmed conductometrically by checking the conductiv-
ity changes in the solution caused by the presence of chloride ions.
In the first phase of the isomerization reaction the chloride
As seen, reaction rate constants determined have comparable
values for all four catalysts applied. The observed differences in
DMF solutions are within the limits of experimental error. Thus,
the unequivocal conclusion regarding the dependence of the reac-
tion rates on the ionic radius of the catalyst cannot be explicit for-
6 5 3 2 2
anion is separated from the rest of the trans-[(C H ) P] PtCl mol-
ecule (Scheme 2a). The presence of chloride ions in the solution
during isomerization was confirmed potentiometrically by using
a chloride-selective electrode. The complex compound with the
reduced coordination number changes the bond angle between
central atoms. (Scheme 2b). Ligands change their position to some
extent as a result of the turnover. The new structure also has a
coordination number equals 3 and a flat triangular structure. In
the next step of the process the chloride anion is coordinated to
platinum which adopts the coordination number 4. Ligands are
in the cis position (Scheme 2d). During the whole process bonds
mulated. However, it can be concluded that the Be2 , Ca and Sr
+
2+
2+
cations cause that the values of reaction rate constants become
similar with the temperature increase. In contrast, in the case of
2
+
Mg the reaction rate constants are approximately 1.5 times lower
than for the other cations.
Furthermore, the activation energy values, being very low, are
approximately equal (1.31–1.35 kJ/mol) for all catalysts except
the calcium ion. For the latter this value (1.08 kJ/mol) differs from
the remaining ones.
Based on the kinetic data obtained, the dissociative mechanism
for the studied coordination compound has been proposed
between platinum and P(C
The obtained results of kinetic studies on the trans–cis isomer-
ization reactions of the [(C P] PtCl complex in non-aqueous
medium in the presence of Be , Mg , Ca and Sr ions as
6 5 3
H ) molecules remain indissoluble.
(Scheme 2). To formulate the mechanism some geometrical
6
5
H )
3
2
+
2
2+
2
2+
2+
parameters were taken into account: Pt–P = 2.3163 Å,
Table 1
The rate constants (k, (sꢁ1)) for isomerization reaction of trans-/cis-Pt[P(C
Cl
6 5
H )
3
2
] complex (Cmetalions = 0.5 M).
Metal ion
Temperature (K)
78
a
E (kJ/mol)
2
283
288
293
298
Be2
Mg
+
3.14ꢃ10 (±0.01ꢃ10
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
)
)
)
)
5.85ꢃ10 (±0.03ꢃ10
ꢁ4
ꢁ4
)
)
)
)
6.53ꢃ10 (±0.02ꢃ10
ꢁ4
ꢁ4
)
1.26ꢃ10 (±0.03ꢃ10
ꢁ3
ꢁ3
ꢁ4
)
)
)
)
1.31ꢃ10 (±0.07ꢃ10
ꢁ3
ꢁ3
ꢁ4
ꢁ3
ꢁ3
)
)
)
)
1.31 (±0.02)
1.35 (±0.02)
1.08 (±0.02)
1.34 (±0.02)
2+
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
2.51ꢃ10 (±0.07ꢃ10
2.73ꢃ10 (±0.10ꢃ10
3.22ꢃ10 (±0.05ꢃ10
)
)
)
5.74ꢃ10 (±0.11ꢃ10
9.22ꢃ10 (±0.15ꢃ10
2+
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ3
Ca
2.21ꢃ10 (±0.01ꢃ10
5.37ꢃ10 (±0.17ꢃ10
9.75ꢃ10 (±0.20ꢃ10
7.72ꢃ10 (±0.13ꢃ10
1.12ꢃ10 (±0.08ꢃ10
2
+
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ4
ꢁ3
Sr
3.08ꢃ10 (±0.01ꢃ10
3.17ꢃ10 (±0.14ꢃ10
6.42ꢃ10 (±0.08ꢃ10
8.03ꢃ10 (±0.01ꢃ10
1.11ꢃ10 (±0.01ꢃ10

6
24
D. Jacewicz et al. / Journal of Molecular Structure 1075 (2014) 620–624
catalysts provide some conclusions and allow to find differences in
the kinetics in aqueous [27] and non-aqueous environments. In
non-aqueous medium (DMF) the dependence of reaction rate on
the activation energies in DMF solutions were determined and
compared with those characteristic for aqueous solutions.
the type of the metal ion (Be2 , Mg , Ca or Sr ) used as the cat-
+
2+
2+
2+
Acknowledgements
alyst is not observed, whereas in aqueous medium in the presence
2
+
2+
2+
2+
of Be , Mg , Ca and Sr ions as catalysts a weak dependence of
reaction rate on ionic radius of the catalyst has been found [27].
The observed different behavior can be explained in terms of solva-
tion differences in water and non-aqueous media [28–31]. The sol-
vation effects resulting from the different polarity of water and
DMF molecules are also responsible for the different activation
energies observed in both media considered. In the DMF medium
a weak solvation is present due to the low polarity and, conse-
quently, the activation energies are low. In the case of aqueous
environment the solvation effects are large and the activation
energies are much higher. Thus the activation energies for the
trans–cis isomerization reactions running in DMF are of the order
of 1.3 kJ/mol, whereas in water they are as high as 75–76 kJ/mol.
It should be noted that in literature one can find other examples
of complex compounds of this type undergoing the cis–trans isom-
This work was financially supported by Polish Ministry of Sci-
ence and Higher Education under grant 2012/07/B/ST5/00753.
References
[
[
[
[
[
[
1] A. von Zelewsky, Stereochemistry of coordination compounds, John Wiley &
Sons, New York, 1996.
2] D.U. Miodragovi c´ , J.A. Quentzel, J.W. Kurutz, C.L. Stern, R.W. Ahn, I. Kandela, A.
Mazar, T.V. O’Halloran, Angew. Chem. Int. Ed. 52 (2013) 10749–10752.
3] A.A. Batista, S.L. Queiroz, M.P. de Araujo, K.S. MacFarlne, B.R. James, J. Chem. Ed.
78 (2001) 89–90.
4] A.A. Batista, S.L. Queiroz, M.P. de Araujo, K.S. MacFarlne, B.R. James, J. Chem.
Educ. 78 (2001) 87–88.
5] M.J. Bloemink, H. Engelking, S. Karentzopoulos, B. Krebs, J. Reedijk, Inorg.
Chem. 35 (1996) 619–627.
6] F. Collin, I. Sasaki, H. Eury, P. Faller, C. Hureau, Commun. 49 (2013) 2130–2132.
[7] Y. Chen, Z. Guo, S. Parsons, P.J. Sadler, Chem. Eur. J. 4 (1998) 672–676.
[8] L. Pereira Franco, E. Pereira de Góis, B. Santoni Codonho, A.L. Raymundo Pavan,
I. de Oliveira Pereira, M.J. Marques, E. Tonon de Almeida, Palladium(II) imine
ligands cyclometallated complexes with a potential leishmanicidal activity on
Leishmania (L.) amazonensis 22 (2013) 1049–1056.
erization. For example the reaction of C
rotrifluorophenyl) with Pd(PPh (a very common catalyst
precursor) produces cis-[Pd(C Cl )I(PPh ] complex [32], which
slowly isomerizes to trans-[Pd(C )I(PPh ]. It has been found
that for all cases described the trans forms are more stable than cis
isomers, inversely than is the case of the Pt[P(C Cl ] complex
studied in this work. Furthermore, all reactions of isomerization
run according to the associative mechanism, in the contrast to
6 5 3 2
Pt[P(C H ) Cl ] studied for which the isomerization reaction pro-
6 2 3 6 2 3
Cl F (C Cl F = 3,5-dichlo-
3 4
)
[9] M.J. Bloemink, J.J.M. Diederen, J.P. Dorenbos, et al., Eur. J. Inorg. Chem. (1999)
6
2
F
3
3
)
2
1655–1657.
6
Cl
2
F
3
3 2
)
[
10] D. Colangelo, A. Ghiglia, I. Viano, H. Mahboobi, A. Ghezzi, C. Cassino, D. Osella, J.
Inorg. Biochem. 98 (2004) 61–67.
H
6 5
)
3
2
[11] G. Repetto, A. del Peso, J. Zurita, Nat. Protocols 3 (2008) 1125–1131.
[
12] L. Giovagnini, L. Ronconi, D. Aldinucci, D. Lorenzon, S. Sitran, D. Fregona, J.
Med. Chem. 48 (2005) 1588–1595.
[
13] F.K. Keter, Pyrazole and pyrazolyl palladium(II) and platinum(II) complexes:
synthesis and in vitro evaluation as anticancer agents. A thesis submitted in
partial fulfillment of the reqiurments for the degree of masters in science in
the Department of Chemistry. University of the Western Cape. November,
ceeds in a single step according to the dissociative mechanism.
2004.
Conclusions
[14] R. Duncan, M.J. Vicent, F. Greco, R.I. Nicholson, Endocr. Relat. Cancer 12 (2005)
S189–S199.
[
[
15] R. Haag, F. Kratz, Angew. Chem. Int. Ed. Engl. 45 (2006) 1198–1215.
16] M. van Beusichem, N. Farrell, Inorg. Chem. 31 (1992) 634–639.
The kinetics of the trans–cis isomerization reaction of the
[
(
(C
6
H
5
)
3
P]
2
PtCl
2
complex catalyzed by four different metal ions
[17] M.A.A. Batista, E.E. Castellano, G.V. Poelhsitz, J. Ellena, R.C.L. Zampieri, J. Inorg.
Biochem. 92 (2002) 82–88.
2
+
2+
2+
2+
Be , Mg , Ca and Sr ) in DMF solution was studied. It turned
[
[
18] N.W.D. Besse, C.H. Johnson, Trans. Faraday Soc. 31 (1935) 1632–1642.
19] H.I. Schlafer, H. Gausmann, W. Tausch, Z. Physik. Chem. 34 (1962) 113–372.
out that the two studied isomers are kinetic stable in DMF solu-
tions and that metal cations of second group are effective catalysts
in the trans–cis isomerization reaction in the case of coordination
compounds of studied type. Furthermore, it has been found that
in the case of the isomerization reaction studied converting of
the trans compound to cis isomer was observed in contrary to
the literature most observed cases that the conversion of cis isomer
to trans compound took place. Moreover, on the basis of kinetic
studies in dimethylformamide solutions it has been found that
reaction rate does not depend, in contrast to aqueous solutions,
on the ionic radius of the catalyst. The mechanism of isomerization
[20] M.L. Johanson, J.J. Correira, D.A. Yphantis, H.R. Halvorson, J. Biophys. 36 (1981)
75–588.
5
[
[
21] J.F. Nagel, L.A. Parodi, R.H. Lozier, J. Biophys. 38 (1982) 161–174.
22] J.R. Knutson, J.M. Beechem, L. Brand, Chem. Phys. Lett. 102 (1983) 501–507.
[23] M. Maeder, A. Zuberbuchler, Anal. Chem. 64 (1990) 2220–2224.
[
24] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, Part B: Application in Coordination, Organometallic and
Bioorganic Chemistry, John Wiley & Sons, New York, 1997.
[25] R.D. Gillard, M.F. Pilbrow, Adducts of Coordination Compounds. Part IX.
Isomerism and Salvation of Dichlorobis(Triphenylophosphine)Platinum(II),
John Wiley & Sons, New York, 1974.
[
26] M.H. Johansson, S. Otto, Acta Cryst. C56 (2000) e12–e15.
[27] D. Jacewicz, D. Wyrzykowski, K. Z_ amoj c´ , D. Czerwi n´ ska, P. Czaja, L.
reaction of the [(C
6
5
H )
P]
3 2
PtCl
2
complex has been proposed on the
Chmurzy n´ ski, Struct. Chem. 23 (2012) 333–340.
[
[
28] J. Barthel, H.J. Gores, G. Schneeer, R. Wachter, Non-aqueous electrolyte
solutions in chemistry and modern technology, Top. Curr. Chem. 111 (1983).
29] L. Chmurzy n´ ski, Z. Warnke, Aust. J. Chem. 46 (1993) 185–194.
basis of the kinetic data as well as potentiometric and conducto-
metric measurements. It assumes that the isomerization reaction
proceeds in a single step according to the dissociative mechanism.
The temperature dependence shows that with increasing temper-
ature the rate of isomerization reaction increases. Furthermore,
[30] U. Mayer, Coord. Chem. Rev. 21 (1976) 159–179.
[
[
31] L. Chmurzy n´ ski, Anal. Chim. Acta 326 (1996) 267–274.
32] A.L. Casado, P. Espinet, Organometallics 17 (1998) 954–959.