Carbon-iodide bond activation by cyclometalated Pt (II) complexes bearing tricyclohexylphosphine ligand: A comparative kinetic study and theoretical elucidation

Article abstract of DOI:10.1002/aoc.4674

Cyclometalated Pt (II) complexes [PtMe(C^N)(L)], in which C^N?=?deprotonated 2,2′-bipyridine N-oxide (Obpy), 1, deprotonated 2-phenylpyridine (ppy), 2, deprotonated benzo [h] quinolone (bzq), 3, and L?=?tricyclohexylphosphine (PCy₃) were prepar

Full text of DOI:10.1002/aoc.4674

Received: 25 July 2018
DOI: 10.1002/aoc.4674
Revised: 28 September 2018
Accepted: 4 October 2018
F U L L P A P E R
Carbon‐iodide bond activation by cyclometalated Pt (II)
complexes bearing tricyclohexylphosphine ligand: A
comparative kinetic study and theoretical elucidation
1
1
2
Samira Chamyani | Hamid R. Shahsavari
| Sedigheh Abedanzadeh |
3
1
3
Mohsen Golbon Haghighi
| Sepideh Shabani | Behrouz Notash
1
Department of Chemistry, Institute for
Cyclometalated
Pt
(II)
complexes
[PtMe(C^N)(L)],
in
which
Advanced Studies in Basic Sciences
(
2
IASBS), Zanjan 45137‐66731, Iran
C^N = deprotonated 2,2′‐bipyridine N‐oxide (Obpy), 1, deprotonated 2‐
phenylpyridine (ppy), 2, deprotonated benzo [h] quinolone (bzq), 3, and
Institute of Biochemistry and Biophysics
IBB), University of Tehran, Tehran, Iran
(
3
L = tricyclohexylphosphine (PCy ) were prepared and fully characterized. By
3
Department of Chemistry, Shahid
Beheshti University, Evin, Tehran 19839‐
9411, Iran
treatment of 1–3 with excess MeI, the thermodynamically favored Pt (IV) com-
plexes cis‐[PtMe I(C^N)(PCy )] (C^N = Obpy, 1a; ppy, 2a; and bzq, 3a) were
6
2
3
obtained as the major products in which the incoming methyl and iodine
groups adopted cis positions relative to each other. All the complexes were
characterized by means of NMR spectroscopy while the absolute configuration
of 1a was further determined by X‐ray crystal structure analysis. The reaction
of methyl iodide with 1–3 were kinetically explored using UV–vis spectroscopy.
On the basis of the kinetic data together with the time‐resolved NMR investi-
gation, it was established that the oxidative addition reaction occurred through
Correspondence
Hamid R. Shahsavari, Department of
Chemistry, Institute for Advanced Studies
in Basic Sciences (IASBS), Zanjan 45137‐
66731, Iran.
Email: shahsavari@iasbs.ac.ir
Funding information
Institute for Advanced Studies in Basic
Sciences (IASBS) Research Council,
Grant/Award Number: G2018IASBS32629
the classical S 2 attack of Pt (II) center on the MeI reagent. Moreover, compar-
N
ative kinetic studies demonstrated that the electronic and steric nature of either
the cyclometalating ligands or the phosphine ligand influence the rate of reac-
tion. Surprisingly, by extending the oxidative addition reaction time, very sta-
ble iodine‐bridged Pt (IV)‐Pt (IV) complexes [Pt Me (C^N) (μ‐I) ]
2
4
2
2
(C^N = Obpy, 1b; ppy, 2b; and bzq, 3b) were obtained and isolated. In order
to find a reasonable explanation for the observation, a DFT (density functional
theory) computational analysis was undertaken and it was found that the
results were consistent with the experimental findings.
KEYWORDS
cyclometalated platinum complexes, DFT calculations, kinetic study, oxidative addition,
tricyclohexylphosphine ligand
[1–6]
1
| INTRODUCTION
and in transition metal mediated organic synthesis.
On‐going investigations continue to develop our under-
standing of the mechanism of the reaction with the
aim of obtaining better rationally designed catalysts in
the future.
The addition of alkyl halides to square planar metal
complexes, via oxidative addition reactions, is still of
great interest because of their important role in catalysis
Appl Organometal Chem. 2018;e4674.
wileyonlinelibrary.com/journal/aoc
© 2018 John Wiley & Sons, Ltd.
1 of 13
https://doi.org/10.1002/aoc.4674

2
of 13
CHAMYANI ET AL.
Platinum (II) complexes provide a useful platform for
reactivity compared. The major aim of this research was
to enhance our understanding of the effect of the ligand
system on the reactivity of cycloplatinated (II) complexes,
both from the synthetic and kinetico‐mechanistic points
of view.
kinetic and mechanistic studies of fundamental oxidative
addition reactions because of their relative inertness, high
[
7]
stability and availability of different oxidation states.
Oxidative addition of C–X bonds to platinum (II) com-
plexes is generally enthalpically favored and produces
the corresponding platinum (IV) products normally pro-
2
| RESULT AND DISCUSSION
.1 | Synthesis and characterization
ceeding through a S 2 type mechanism in which the Pt
N
2
[8,9]
(
II) center acts as a nucleophile via the filled d orbital.
z
2
However, a radical pathway as well as concerted three‐
center mechanisms have also been suggested for oxidative
[10–12]
The synthetic route for the preparation of cyclometalated
Pt (II) and Pt (IV) complexes is summarized in Scheme 1.
addition reactions.
Kinetic studies have revealed that the chemical reactiv-
ity of platinum complexes depends on the coordination
Methylplatinum (II) complexes [PtMe(C^N)(PCy )],
3
[
13]
C^N = deprotonated 2,2′‐bipyridine N‐oxide (Obpy),
environment around the central metal ions.
Π‐
[
30]
1,
deprotonated 2‐phenylpyridine (ppy), 2, and
extended cyclometalating ligands would be expected to
offer the metal ion, a strong ligand field and consequently
produce significant changes in the physical and chemical
deprotonated benzo [h] quinolone (bzq), 3, were synthe-
sized by the reaction of starting complexes [PtMe(C^N)
(SMe )], C^N = Obpy, A
with tricyclohexylphosphine (PCy3) ligand as the
monodentate P‐donor ligand. The dimethyl sulfide
(SMe ) ligands easily displaced with an equimolar quan-
tity of PCy at room temperature. The new synthesized
[
36];
[37];
[38]
[14]
ppy, B
and bzq, C,
properties. In particular, cyclometalated platinum com-
plexes have attracted long‐lasting interest due to their
potential applications in a wide range of research areas
2
[
15,16]
[17,18]
such as organometallic synthesis,
catalysis,
2
[
19,20]
organic light‐emitting diode (OLED)
and the design
3
[21,22]
complexes were characterized by NMR spectroscopy.
of antitumor agents.
The C^N‐cycloplatinated (II)
31
1
P{ H} NMR spectra display a sharp singlet signal with
complexes, where C^N = chelating carbon‐nitrogen donor
platinum satellites at 22.2, 23.4 and 24.2 ppm, for com-
plexes 1–3, respectively, confirming the presence of Pt
ligand, were found to be reactive substrates for oxidative
[23–25]
addition reactions.
(
II)‐bound PCy3 ligands. The coupling constants of
Accordingly, the nature of ancillary ligands can
strongly controls the lability of platinum complexes. With
regard to recent reports, the investigations based on the
oxidative addition of alkyl halides to platinum complexes,
were carried out using complexes with nitrogen donor
1
[30]
JPtP = 2162 Hz (1),
typical for the P‐trans‐C (sp ) geometry.
thy that this significant difference in the coupling values
1937 Hz (2) and 2052 Hz (3) are
2
[39]
It is notewor-
1
of J (about 120 Hz), is attributed to the trans influence
of coordinated carbon atom of the C^N‐cyclometalated
ligands (Obpy > bzq > ppy).
tra of these complexes contain a doublet resonance with a
PtP
[
26–28]
ligands,
and phosphine‐ligated platinum (II) ana-
[
40]
195
1
[29]
The Pt{ H} NMR spec-
logs have received less attention.
However, phosphine
ligands effectively provide a wide range of attractive fea-
tures for the platinum complexes, by inducing specific
electronic and steric properties. Therefore, there is still
great interest in synthesizing and evaluating the reactivity
of platinum phosphine complexes, due to their potential
[30,31]
applications in many active research areas.
Following our interest on the reaction kinetics of oxida-
[32–35]
tive addition of cycloplatinated (II) complexes,
in the
present study, a series of cyclometalated Pt (II) complexes
with general formula [PtMe(C^N)(L)], were designed to
be synthesized with different C^N‐cyclometalating ligands
[
30]
(C^N = deprotonated 2,2′‐bipyridine N‐oxide, 1,
deprotonated 2‐phenylpyridine, 2 and deprotonated benzo
[
(
h] quinolone, 3 while including tricyclohexylphosphine
PCy ) as the monodentate phosphine ligand (L). After-
3
wards, the oxidative addition reaction of MeI, one of the
promising haloalkanes, with the cyclometalated Pt (II)
complexes was investigated by a combination of experi-
mental and theoretical methods, and the differences in
SCHEME 1 Synthetic route for preparation of cyclometalated Pt
(II) complexes with the PCy ligand and their oxidative addition
3
reaction with MeI

CHAMYANI ET AL.
3 of 13
coupling constant value that is almost equal to that
to their Pt (II) parents. This observation is due to the
increasing in the oxidation state of the platinum center
from +2 to +4 during the oxidative addition reaction which
can be related to a formal change of hybridation state from
31
1
observed in the corresponding P{ H} NMR spectra. In
1
the H NMR spectra of these complexes, protons of Pt‐
coordinated methyl ligand appear as doublet resonances
with the Pt satellites at 0.83–1.07 ppm, which coupled
with both phosphorus and platinum nuclei. Additionally,
the characteristic protons of cyclohexyl substituents of
2
2
3 [33]
dsp to d sp .
The results confirm that the phosphine
ligand (PCy ) is placed in the mutual trans position relative
3
[34]
to the Me ligand, in any of the Pt (IV) products.
As a
the PCy were detected at 1.20–2.60 ppm, in the aliphatic
consequence, the complexes 1a‐3a were obtained almost
quantitatively as thermodynamically stable complexes
displaying cis disposition of Me and I ligands.
3
1
13
1
region of the H NMR spectra. Also, in the C{ H} NMR
spectra the carbon atom of the methyl group in 1–3
appears as a doublet signal (δ = −14.9 to −16.0 ppm)
due to coupling with the phosphorus atom and the Pt
As will be discussed later, density functional theory
(DFT) calculations highlighted the larger stabilization of
Pt (IV) complex with the cis arrangement of incoming
Me and I ligands, over the corresponding trans analogue.
In fact, the tricyclohexylphosphine ligand with large cone
2
1
[30]
center ( J = 6–7 Hz, J
= 752–763 Hz).
All the
PC
PtC
NMR spectra (Figures S1–S8) for the new Pt (II) com-
plexes together with the NMR labelling (Scheme S1) is
available in the Supporting Information. Furthermore,
the numerical NMR data are also reported with detail in
the Experimental section.
[
41]
angle value,
is considered to impose steric constraints
when located in an equatorial site of complex. Therefore,
the thermodynamically more stable product is preferen-
The methylplatinum (II) complexes, 1–3, were treated
with an excess of methyl iodide in CH Cl at room temper-
tially formed and the PCy ligand is situated in the axial
position, being introduced as the cis product.
3
2
2
ature to yield the corresponding Pt (IV) products with the
Complex 1a was structurally characterized by single
crystal X‐ray crystallography method. The appropriate
crystals were grown by slow diffusion of n‐hexane into
the CH Cl solution of complex. It was found to crystal-
general formula cis‐[PtMe I(C^N)(PCy )] (C^N = Obpy, 1a;
2
3
ppy, 2a; and bzq, 3a). The NMR spectra (Figures S9‐S20)
provide precise information about the reaction process. In
2
2
1
the H NMR spectra, a new doublet signal with platinum
lize in the monoclinic crystal system in space group
coupling was observed corresponding to the new incoming
P2 /c. The crystal data and structural refinement param-
1
Me group. Protons of cyclohexyl moieties in PCy , as well as
eters are summarized in Table S1. The ORTEP view of
1a is illustrated in Figure 1 which shows that the Pt
(IV) center adopts an octahedral coordination geometry
3
two Pt (IV)‐bound methyl groups (Me trans to N and
Me‐trans‐P) appeared as overlapping multiplets in the
1
31
1
aliphatic region of H NMR spectra. P{ H} NMR spectra
with the PCy ligand in an axial site. The X‐ray crystal
3
displayed a singlet resonance in shielded region, coupled
structure confirms the formation of thermodynamically
favored cis isomer for this complex. As shown in
Figure 1, Pt (IV) center adopts a slightly distorted octahe-
dral environment, surrounded by carbon‐nitrogen donor
atoms of the Obpy ligand (C1, N2), a carbon atom of
Me ligand (Cl2) and an iodine atom (I1) while the other
195
with Pt center which was related to the phosphorus atom
adjacent to the Pt (IV) center. These signals were observed
at −19.4 ppm (1a), −18.0 ppm (2a) and − 17.9 ppm (3a)
1
1
with J
coupling constants of J
= 955, 956 and
PtP
PtP
9
63 Hz, respectively, indicative of Pt (IV)‐bound phospho-
195
1
rus nuclei. The Pt{ H} NMR spectra of these complexes
possess a doublet at −3215.1 ppm with J
Me group (Cl1) besides the PCy moiety (P1) situated in
3
1
= 957 Hz
the axial positions. The dihedral angle between the aro-
matic rings of the cyclometalated Obpy ligand is 7.4°
PPt
1
(1a), −3175.7 ppm with J = 953 Hz (2a) and − 3201.6
PtP
1
[34,42]
with J = 968 Hz (3a), which are almost in conformance
with the coupling constant observed in the P{ H} NMR
spectra. As can be seen, the coupling constant values of Pt
which is in good agreement with previous reports.
PtP
31
1
The reaction mixtures were kept at room temperature
over time. After one day, very stable Pt (IV)–Pt (IV)
complexes of formula [Pt Me (C^N) (μ‐I) ], (C^N = Obpy,
(IV) products are almost the same while in the case of
2
4
2
2
[
43]
corresponding Pt (II) complexes 1–3 the values attained
1b; ppy, 2b; and bzq, 3b ) were detected along with the
equimolar amounts of [PCy Me]I
1
[32]
for JPtP, showed significant differences deriving from
(Scheme 1).
3
different trans influence of the bridgehead carbon atom in
Dinuclear cycloplatinated (IV) complexes with two iodine
atoms as bridging ligands have been generated by com-
plete removal of the monophosphine PCy3 ligands.
Similar observations have been reported in previous
13
1
each C^N ligand (Obpy, ppy, bzq). In the C{ H} NMR
spectra of Pt (IV) complexes, the carbon of both methyl
ligands (trans to N or trans to P) in 1a‐3a exhibit a doublet
[
35,43]
with a large coupling constant value to platinum center
studies.
NMR spectroscopy provided clear evidence
1
(
JPtC). Also, the aromatic regions in these spectra are
on the formation of complexes 1b‐3b (Figures S21‐S29).
almost similar to those of their Pt (II) derivatives with only
smaller coupling constants for the Pt (IV) center in relation
The characteristic signals related to the PCy ligands
disappeared in both the H and P{ H} NMR spectra. In
3
1
31
1

4
of 13
CHAMYANI ET AL.
FIGURE 1 ORTEP plot of the structure of 1a with its atom
labeling scheme. Selected bond lengths (Å) and angles (deg): Pt1‐
C1 1.994(8), Pt1‐C11 2.095(10), Pt1‐C12 2.103(8), Pt1‐N2 2.150(8),
Pt1‐I1 2.7694(10), Pt1‐P1 2.509(2), C11‐Pt1‐P1 177.2(3), C1‐Pt1‐I1
1
72.1(3), C12‐Pt1‐N2 168.3(3), C1‐Pt1‐N2 79.2(3), C1‐Pt1‐C11
5.8(4), C12‐Pt1‐I11 88.0(3). Ellipsoids are drawn at the 40%
8
probability level, and hydrogen atoms are eliminated for clarity
1
the H NMR spectra, two distinctive singlet resonances
flanked with Pt satellites at 1.10–1.20 and 1.40–170 ppm
which were assigned to the Me groups trans‐positioned
31
1
to I and N, respectively. Additionally, P{ H} NMR
spectroscopy revealed a sharp singlet signal at 33.7 ppm
1
for isolated [PCy Me] I while in the H NMR spectrum,
3
the aliphatic protons appeared as multiplets that over-
195
1
lapped with each other. The Pt{ H} NMR spectra of 1b‐
b contains a clear singlet which confirmed both platinum
centers in these complexes are equivalents. With regard to
3
13
1
the C{ H} NMR spectra for 1b‐3b, two sets of signals for
the methyl groups (trans to N or trans to I) appeared in
the aliphatic region. In order to provide a proper explana-
tion about the reaction route, DFT computational method
was applied and results are ascribed in later sections.
2.2 | Kinetic and mechanism study
The oxidative addition reaction of MeI with complexes 1–
were monitored in CH Cl using UV–vis spectroscopy.
3
2
2
An excess of MeI was added, so that its concentration
can be considered to be constant during each kinetic
run. The distinctive MLCT (metal to ligand charge trans-
fer) bands of the Pt (II) complexes gradually disappeared
with addition of excess MeI while oxidative addition reac-
tion occur. Figure 2 represents the changes in UV–vis
spectra of 1–3 at 298 K. In order to obtain pseudo‐first‐
order rate constants (kobs), the absorbance‐time profiles
FIGURE 2 Changes in the UV–vis spectrum of (a) 1, (b) 2 and (3)
with MeI in CH Cl at 25 °C (the inset shows the variation of the
2
2
absorbance at the corresponding wavelength over time)

CHAMYANI ET AL.
5 of 13
were fitted to a first‐order equation by nonlinear least‐
squares techniques. Figure 3 shows the linear plots of cal-
culated kobs values against the concentration of MeI with
no intercepts, providing information on the first‐order
dependence of the rate upon the MeI concentration.
The slope of each straight line is indicative of the
second‐order rate constant (k2).
aforementioned, the steric character of phosphine ligand
strongly controls the rate of the oxidative addition reac-
tion. Ligands with sterically bulk substituents enhance
the rate of the trans‐cis transformation that is generally
occurs to afford the thermodynamically stable product
in which incoming methyl and iodine groups occupy cis
positions relative to each other. Therefore, the rate of
oxidative addition reactions are greatly dependent on
the characteristics of coordinated ligands.
Based on the kinetically data, all of the reactions fol-
low second‐order rate law, first order in either the Pt
(
II) complex and the MeI reagent, following a classical
The proposed mechanism is depicted in Scheme 2. The
oxidative addition reaction initiated by the nucleophilic
attack of Pt (II) center to the methyl group of MeI. The
cationic intermediate is formed and subsequently
SN2 oxidative addition mechanism. Similar experiments
were carried out in different temperatures. All the
attained k values related to the Pt (II) complexes are col-
2
[44]
lected in Table 1. The activation parameters,
transform to the new intermediate by pseudo‐rotation.
#
#
ΔH = enthalpy and ΔS = entropy of activation, were
calculated using the Eyring equation (Figure 4) and are
also summarized in Table 1. The large negative value of
ΔS obtained for each reaction is the best evidence for
suggesting S 2 pathway.
Eventually, the corresponding thermodynamic Pt (IV)
complex is obtained by the coordination of iodine to the
cis vacant site of platinum center. It is believed that the
final product is more thermodynamically stable than
the experimentally non‐observed kinetic product.
#
N
The reaction rates of complexes 1–3 with MeI, pro-
ceed in the order 2 > 3 > > 1. For instance, the oxidative
addition of MeI to 2 was found to be faster than that of 1,
but the reaction rate of 3 is near to the reaction rate of 2.
This result is attributed to the relatively lower reactivity
of 1 when compared to 2 or 3. When the oxidative addi-
tion reaction of MeI to the Pt (II) complexes goes through
2.3 | NMR monitoring
In order to better understand about the details of the
reaction, NMR spectroscopy was applied to monitor the
process. Complex 1 was reacted with excess amounts of
CH I in CD Cl in the NMR tube and the reaction was
the S 2 mechanism, the Pt (II) center nucleophilically
N
3
2
2
1
31
1
attacks at the methyl group of MeI, confirming the asso-
ciative nature of reaction. Indeed, a more electron‐rich
metal center would react faster in this step. The different
electronic effects of the C^N ligands, evidently influences
the lability of the Pt (II) complex. Cyclometalating ligands
with electron‐withdrawing substituents lead the platinum
center to be less electron‐dense and consequently less
reactive toward the oxidative addition reaction. Thus,
the observed trend for the rate constant of complexes
followed up using H and P{ H} NMR spectroscopies
at room temperature (Figure 5). Addition of MeI immedi-
ately resulted in the formation of singlet signal with Pt
satellite at δ = −19.4 ppm, along with the disappearance
of the singlet resonance of Pt (II) complex, 1, at
δ = 22.2 ppm. The new signal, appeared in the shielded
region, was assigned to the thermodynamically stable
product 1a, with a cis arrangement of the Me and I
ligands. As stated previously, sterically‐hindered the
(
2 > 3 > > 1) is consistent with the trend of the
PCy ligand in the trans Pt (IV) product, caused the trans
3
donor ability of the supporting ligands as 2,2′‐bipyridine
N‐oxide (Obpy‐H) donates less electron density to the
platinum center when compared to 2‐phenylpyridine
isomer rapidly converts to the stable cis isomer. Thus, due
to the very fast interconversion process, the kinetic prod-
uct could not be detected in the NMR spectrum. Accord-
ing to the recorded NMR spectra, the intensity of the
resonance related to cis isomer gradually increased with
time. As the reaction progressed, the NMR monitoring
revealed the appearance of a new singlet signal at
δ = 33.7 ppm while the characteristic resonances of cis
isomer started to fade. On the basis of observations, the
(ppy‐H) or benzo [h] quinolone (bzq‐H). Notice that the
formation rate of kinetically favored trans isomers,
resulting from the trans addition of MeI to the Pt (II)
center, also shows the same trend. The more electron‐rich
metal center, certainly produces the related trans
product faster.
It should be noted that the kinetic product was
initially produced due to the intrinsic tendency of MeI
for mutual trans coordination but the large steric demand
growing signal was assigned to the [PCy Me] I species,
which has been formed by the reaction of dissociated
3
PCy with free MeI reagents during the reaction.
3
[41]
1
of PCy3
makes the kinetic product unstable enough to
Accordingly, the H NMR study provided the same
31
1
rapidly convert to the stable cis product. As a result, com-
plexes 1a‐3a having the Me and I in cis dispositions, were
synthesized, whereas no trans isomers were isolated. As
data which obtained from the P{ H} NMR spectra. The
distinctive signal at δ = 0.90 ppm (due to the coordinated
Me group in 1) was used to monitor the reaction.

6
of 13
CHAMYANI ET AL.
FIGURE 3 Plots of the first‐order rate
−
1
constants (kobs/s ) for the reaction of (a)
, (b) 2 and (3) with MeI in CH Cl at
1
2
2
different temperatures versus the MeI
concentration

CHAMYANI ET AL.
7 of 13
b
2 2
TABLE 1 Second‐order rate constants and activation parameters for the reaction of complexes 1–3 with MeI in CH Cl
2
−1 −1
1
0 k
2
/L mol
s
at
#
‐1
ΔS /JK mol‐1
#
−1
Complex
C^N
λ
max/nm
different temperatures
ΔH /kJ mol
1
0 °C
15 °C
1.11
1.92
1.79
20 °C
1.32
2.37
2.28
25 °C
1.55
2.81
2.66
30 °C
1.82
3.36
3.24
1
2
3
Obpy
ppy
396
375
391
0.9
39.2 ± 0.1
34.1 ± 0.2
35.6 ± 0.1
−96 ± 1
−109 ± 1
−102 ± 2
1.64
1.57
bzq
Estimated errors in k
2
values are ±3%.
b
2
Activation parameters were calculated from the temperature dependence of the second‐order rate constant in the usual way using Eyring equation (ln(k /
T) = ln (k /h) ‐ ΔH /RT + ΔS /R).
B
≠
≠
the stable dinuclear complex with the formula
Pt Me (Obpy) (μ‐I) ], 1b, was formed while two iodine
[
2
4
2
2
ligands join two Pt (IV) centers together. In addition, an
equimolar amount of [PCy Me] I species were simulta-
3
neously produced.
2.4 | Theoretical calculations
DFT calculations were utilized in order to gain further
insights into the reaction mechanism. Computed struc-
tures are depicted in Figure 6 with their respective rela-
−
1
tive energy values in kJ mol for the oxidative addition
reaction involving 1 with MeI. The result of the theoreti-
cal calculations are in close agreement with the experi-
mental observations.
According to the empirical kinetic studies, the oxida-
tive addition of MeI to Pt (II) complexes proceeded
FIGURE 4 Eyring plots for the reactions of 1–3 with MeI in
CH Cl
2
2
through the S 2 reaction pathway as can be observed in
N
However, new resonances started to appear when the
reaction was progressed. Based on the H NMR data, by
prolonging the reaction time, the phosphine ligand
started to leave the Pt (IV) trans product and ultimately,
Scheme 2. The nucleophilic attack of the Pt (II) center
on the carbon atom of the MeI reagent was proposed to
promote the reaction path resulting in the formation of
the initial product in which incoming methyl and iodine
1
N
SCHEME 2 Proposed S 2 mechanism for the oxidation of 1–3

8
of 13
CHAMYANI ET AL.
3
1
1
FIGURE 5 The reaction of 1 with an excess of MeI (30 folds) as monitored by P{ H} NMR spectroscopy in CD
2
Cl
2
at room temperature.
(
a) pure complex 1, (b) immediately, (c) 10 min, (d) 20 min, (e) 30 min, (f) 40 min, (g) 110 min, (h) 1 day, (i) 2 days after addition of excess
MeI and (j) pure [PCy Me]I. The signal assignments are depicted
3
−1
2 2
FIGURE 6 Relative energies (kJ mol ) for products and intermediates arising from the addition of MeI to 1 in CH Cl
groups occupy trans positions relative to each other.
Afterward, the kinetic product promptly converted to
the thermodynamic cis isomer, because of the significant
found to be more stable than related trans isomers. The
nucleophilic attack of 5dZ atomic orbital of Pt (II) center
2
on the σ* of Me‐I results in the formation of a transition
state entity (TS‐1a) in which the Pt‐C (Me)‐I angle is close
to 180° demonstrating a linear structure with a planar Me
at the center. In this structure, methyl is approaching the
metal center while the C‐I bond is gradually being broken
steric hindrance of the phosphine ligand (PCy ). Based on
3
the calculated energy profile which indicated in Figure 6,
the kinetically favored product is at higher energy by
comparison to the alternative thermodynamic isomer.
Therefore, DFT calculations parallel to experiments, dem-
onstrated that Pt (IV) products with cis geometry, were
which finally leads to the formation of cationic IM ‐1a
t
intermediate possessing a distorted square pyramidal

CHAMYANI ET AL.
9 of 13
geometry (incoming methyl is located on the apical
position). This intermediate can be converted to the trans
kinetic product (trans‐1a) or rearranged to cationic IMc‐
complexes
possessing
a
general
formula
of
cis‐[PtMe I(C^N)(PCy )] (C^N = Obpy, 1a; ppy, 2a; and
2
3
bzq, 3a) were exclusively obtained and isolated. As con-
firmed by DFT computational method, the primarily formed
kinetic product with trans arrangement of incoming Me and
I groups, prefers to transform to the more stable thermody-
namic product with cis geometry, certainly due to the steric
hindrance of tricyclohexylphosphine ligand. A close exami-
nation of NMR monitoring experiment, also indicated that
the isomerization process was so fast that the initial oxidative
addition of MeI to Pt (II) center, could not be detected. All
new complexes were spectroscopically characterized while
the six‐coordinate Pt (IV) structure of 1a was successfully
determined by X‐ray crystallography. Unexpectedly,
prolonging the reaction time to one day, caused to produce
Pt (IV)‐Pt (IV) complexes [Pt Me (C^N) (μ‐I) ](C^N=Obpy,
1
a intermediate which are theoretically more stable than
its IM ‐1a parent. It seems to be logical that the IM ‐1a
t
c
energy level is lower than that of IM ‐1a intermediate
t
because the IM ‐1a intermediate is eventually trans-
c
formed to the more stable cis product (cis‐1a) rather than
IM ‐1a intermediate.
t
By extending the reaction time, the stable iodine‐
bridged cycloplatinated complex 1b has been formed
accompanied with the equimolar quantities of [PCy Me]
3
I species. Interesting features were emerged by analyzing
the theoretical investigations. Activation barriers calcu-
lated revealed that the enthalpy value obtained for the
formation of dinuclear Pt (IV)‐Pt (IV) complex 1b
2
4
2
2
together with [PCy Me] I species, is significantly smaller
1b; ppy, 2b; and bzq, 3b) with bridging iodide ligands accom-
3
than that of Pt (IV) complex 1a. The greater stability of
panied by eqiumolar amount of [PCy Me]I. DFT computa-
3
1
b along with the formation of [PCy Me] I promotes the
tions fully supported the empirical results and interpreted
the reaction preference to progress over time due to the large
stabilization of iodine‐bridged complexes.
3
reaction over time. While, it appears that the intermedi-
ate (1b + 2MeI + 2PCy ) lies in levels above the reactants
3
(
1a + MeI), DFT studies clearly show that the thermody-
namic preference for 1b + [PCy Me]I. Hence, when the
3
4
4
| EXPERIMENTAL
reaction is in progress for a day, it is reasonable to
observe the formation of the dinuclear Pt (IV)‐Pt (IV)
complex 1b.
.1 | General procedures and materials
1
13
1
31
1
195
1
Multinuclear H, C{ H}, P{ H} and Pt{ H} NMR spec-
tra were recorded on a Bruker Avance DPX 400 MHz
instrument. All chemical shifts are reported in ppm (part
per million) relative to their corresponding external stan-
3
| CONCLUSION
This study presents an empirical and theoretical about the
oxidative addition reaction of methyl iodide to
cyclometalated Pt (II) complexes bearing phosphine ligands.
In summary, cyclometalated Pt (II) complexes [PtMe(C^N)
1
13
31
dards (SiMe for H and C, 85% H PO for P and
4
3
4
195
Na PtCl for Pt) and also all the coupling constants (J
2
6
values) are given in Hz. The microanalyses were performed
using a vario EL CHNS elemental analyzer. The UV–vis
absorption spectra were carried out using an Ultrospec
(PCy )], including tricyclohexylphosphine (PCy ) ligand,
3
3
for which C^N = deprotonated 2,2′‐bipyridine N‐oxide
Obpy, 1), deprotonated 2‐phenylpyridine (ppy, 2) and
3100 Pro UV–vis spectrometer with temperature controlling
(
system by a Pharmacia Biotech constant‐temperature bath.
All the reactions were performed using commercially avail-
able chemicals without any purification. 2‐Phenylpyridine
deprotonated benzo [h] quinolone (bzq, 3) were prepared
and readily characterized by multinuclear NMR techniques.
The reaction kinetics of excess MeI with the cyclometalated
Pt (II) phosphine complexes were accurately determined by
analyzing the UV–vis spectra. Kinetic results as well as calcu-
lated activation parameters, illustrated that the reactions
(Hppy), benzo [h] quinolone (Hbzq), 2,2′‐bipyridine N‐
oxide (HObpy), tricyclohexylphosphie (PCy ) and MeI were
3
purchased from Sigma‐Aldrich chemical. The starting
[
36]
[37]
complexes [PtMe(C^N)(SMe )], C^N = (Obpy,
ppy
2
goes through the S 2 pathway, following the second order
N
[38]
2
[30]
and bzq ), [PtMe(k N,C‐bipyO‐H)(PCy )] (1)
and
3
kinetic rate law. In addition, it was found that the rate‐
determining step of reaction processes is highly dependent
on the metal coordination architecture. The significantly
greater electron‐withdrawing character of the Obpy
cyclometalating ligand in comparison with ppy, makes the
Pt (II) center less electron rich toward the nucleophilic attack
and accordingly, decreases the rate of oxidative addition
reaction with MeI. As previously discussed, after the addition
of excess MeI to the solution of complexes 1–3, Pt (IV)
2
[43]
[
PtMe (k N,C‐bzq) (μ‐I) ] (3b)
were prepared according
4
2
2
to our previous reports.
4.2 | Synthesis of the Pt (II) complexes
Tricyclohexylphosphine, PCy , (0.1 mmol) was added to a
3
solution of starting complexes with general formula of
[
36];
[37];
[PtMe(C^N)(SMe )], C^N = Obpy, A
ppy, B
and
2

10 of 13
CHAMYANI ET AL.
[
38]
1
195
1
bzq, C,
(0.1 mmol) in acetone (15 mL), and the solu-
JPtP = 2052 Hz, 1P of PCy );
Pt{ H} NMR (86 MHz,
3
1
tion was stirred for 2 hr. Light yellow solids precipitated,
which were separated, washed with cold acetone, and
dried under vacuum.
CDCl ): δ = −4084.9 (s, J = 2049 Hz, 1Pt).
3
PtP
4
.3 | Reaction of Pt (II) complexes with
MeI
2
4
.2.1 | [PtMe(k N,C‐ppy)(PCy )] (2)
3
An excess amount of MeI (250 μL) was added to a solu-
tion of complexes 1–3 in CH Cl (15 ml). The reaction
2
2
Yield: 76%. Elem. anal. Calcd for C H NPPt (644.73); C,
30
44
mixture was stirred for 1 hr at room temperature and
then the solvent was evaporated under reduced pressure.
The precipitate was washed with diethyl ether and dried
under vacuum to give the product identified as 1a‐3a as
pure cis isomers.
5
5.89; H, 6.88; N, 2.17. Found: C, 55.76; H, 6.82; N, 2.26.
1
3
H NMR (400 MHz, CDCl ): δ = 1.07 (d, J = 5.3 Hz,
JPtH = 84.5 Hz, 3H, PtMe), 1.20–1.40 (m, 9H, Cy), 1.65
m, 6H, Cy), 1.70–1.90 (m, 9H, Cy), 1.97–2.14 (m, 6H,
3
PH
2
(
4
′
Cy), 2.36 (m, 3H, Cy), 7.09 (m, 1H, H ), 7.16 (t, 1H,
3
4
3
3
5′
3
JHH = 7.3 Hz, H ), 7.35 (td, 1H, JHH = 7.3 Hz,
JHH = 2.9 Hz, JPtH = 29.7 Hz, H ), 7.70 (bd, 1H,
JHH = 7.8, H ), 7.85 (m, 2H, H and H ), 7.95 (dd, 1H,
JHH = 6.3 Hz, J
4
5
2
4
.3.1 | cis‐[PtMe I(k N,C‐Obpy)(PCy )]
4
3
6′
2
3
(1a)
4
3
3′
= 1.1 Hz, J
= 46.8 Hz, H ),
HH
PtH
3
3
6
8
.84 (d, 1H, JHH = 5.6 Hz, JPtH = 18.3 Hz, H );
1
H NMR (400 MHz) in CDCl : δ = 0.86–2.11 (39H, ali-
3
1
1
3
3
1
2
C{ H} NMR (101 MHz, CDCl ): δ = −15.3 (d, J = 6 Hz,
3
PC
phatic region, overlapping multiplets of 2Me and 3Cy),
JPtC = 763 Hz, PtMe), 26.7 (s, C of PCy ), 28.1 (d,
JPC = 10 Hz, C of PCy ), 30.0 (s, J
3
4′
3
7
J
.21 (m, 1H, JHH = 6.6 Hz, H ), 7.50 (dd, 2H,
3
= 12 Hz, C of
PtC
3
4
4
5
3
= 6.5 Hz, J
= 2.1 Hz, J
= 53.1 Hz, H and
HH
3′
HH
3
PtH
3
1
2
PCy ), 32.9 (d, J = 21 Hz, J
= 19 Hz, C of PCy ),
4
3
PC
PtC
3
5
H ), 8.03 (m, 1H, J
= 7.9 Hz, J
= 7.8 Hz, H ),
HH
HH
3
3
3
1
1
19.1 (s, J
23.8 (s, C ), 124.9 (d, J = 5 Hz, J
= 17 Hz, C ), 121.8 (s, J
= 21 Hz, C ),
3
5′
3
PtC
5
PtC
8
.22 (d, 1H, J = 6.5 Hz, H ), 10.09 (d, J = 5.5 Hz,
HH
HH
′
4
3
6′
= 16 Hz, C ),
4
3
3
PC
3
PtC
JPtH = 16.1 Hz, 1H, H ), 10.26 (d, 1H, J
H, H ); C{ H} NMR (101 MHz, CDCl ): δ = −7.3 (d,
= 7.83 Hz,
HH
4
4′
1
J
29.8 (d, J = 6 Hz, J
= 24 Hz, C ), 132.2 (d,
6
13
1
PC
PtC
1
3
3
2
3′
4
= 11 Hz, J
= 81 Hz, C ), 136.9 (s, C ), 147.7 (s,
2
1
PC
′
PtC
JPC = 4 Hz, J
= 624 Hz, PtMe (Me trans to N)),
PtC
1
2
6
2
C ), 152.0 (s, J = 37 Hz, C ), 164.7 (d, J = 37 Hz,
C ), 167.4 (s, C );. P{ H} NMR (162 MHz, CDCl ):
δ = 23.4 (s, J = 1937 Hz, 1P of PCy ); Pt{ H} NMR
2
1
PtC
2
PC
1
0.7 (d, J = 106 Hz, J
to P)), 26.3 (s, C of PCy ), 27.7 (d, J = 9 Hz, C of
= 461 Hz, PtMe (Me trans
PC
PtC
2
′
31
1
3
3
3
PC
1
195
1
PtP
3
3
PCy ), 29.2 (s, JPtC = 8 Hz, C of PCy ), 35.7 (d,
3
3
1
(86 MHz, CDCl ): δ = −4043.3 (s, J = 1938 Hz, 1Pt).
1
2
3
2
3
PtP
JPC = 14 Hz, JPtC = 11 Hz, C of PCy ), 123.9 (s,
3
3′
3
5
JPtC = 72 Hz, C ), 126.3 (s, J
= 7 Hz, C ), 126.5 (s,
PtC
4′
2
6
J
= 12 Hz, C ), 127.1 (s, J = 14 Hz, C ), 136.8 (s,
PtC
4
PtC
2
4
.2.2 | [PtMe(k N,C‐bzq)(PCy )] (3)
3
3
1′
3
C ), 138.5 (s, C ), 144.2 (d, J = 6 Hz, C ), 148.5 (s,
PC
2
2
4
5′
J
= 26 Hz, C ), 153.7 (s, J
= 9 Hz, C ), 154.6 (s,
PtC
PtC
2′
Yield: 81%. Elem. anal. Calcd for C H NPPt (668.75); C,
31
1
32
44
C ); P{ H} NMR (162 MHz, CDCl ): δ = −19.4 (s,
JPtP = 955 Hz, 1P of PCy );
CDCl ): δ = −3215.1 (s, J = 957 Hz, 1Pt).
3
5
7.47; H, 6.63; N, 2.09. Found: C, 57.31; H, 6.69; N, 2.21.
1
195
1
Pt{ H} NMR (86 MHz,
3
1
H NMR (400 MHz, CDCl ): δ = 0.83–2.61 (3H of Me
1
3
3
PtP
3
3
and 33H of Cy), 7.46 (dd, 1H, J = 7.9 Hz, J = 7.8 Hz,
HH
HH
8
3
6
H ), 7.56 (d, 1H, JHH = 8.1 Hz, H ), 7.67 (d, 1H,
3
3
3
5
3
2
JHH = 8.1 Hz, H ), 7.74 (m, 1H, H ), 7.82 (d, 1H,
JHH = 8.7 Hz, H ), 8.23 (dd, 1H, JHH = 7.1 Hz,
JPtH = 45.5 Hz, H ), 8.34 (d, 1H, J
4.3.2 | cis‐[PtMe I(k N,C‐ppy)(PCy )] (2a)
2
3
7
3
9
3
4
1
= 8.3 Hz, H ),
H NMR (400 MHz) in CDCl : δ = 0.85–2.12 (39H, ali-
HH
3
3
4
3
9
.15 (d, 1H, J = 5.3 Hz, J = 1.1 Hz, J = 17.2 Hz,
phatic region, overlapping multiplets of 2Me and 3Cy),
HH
HH
PtH
2
13
1
3
3
4′
H ); C{ H} NMR (101 MHz, CDCl ): δ = −16.0 (d,
7.22 (dd, J
= 7.8 Hz, J
= 7.3 Hz, 1H, H ), 7.33
3
HH
5′
HH
2
1
6′
3
JPC = 7 Hz, J
= 754 Hz, PtMe), 26.6 (s, C of PCy ),
(m, 2H, H and H ), 7.50 (d, 2H,
JPtH = 48.9 Hz, H ), 7.71 (m, 1H, H ), 7.87 (ddd,
JHH = 7.5 Hz, J
7.96 (d, 1H,
JHH = 14.8 Hz, H ); C{ H} NMR (101 MHz, CDCl ):
δ = −7.3 (d, J = 3 Hz, J = 670 Hz, PtMe (Me trans
PC PtC
to N)), 10.4 (d, J = 109 Hz, J = 469 Hz, PtMe (Me
PC PtC
trans to P)), 26.4 (s, C of PCy ), 27.9 (d, J = 10 Hz, C of
3 PC
J
= 7.8 Hz,
HH
PtC
3
3
3
4
3′
4
2
8.2 (d, J = 10 Hz, C of PCy ), 30.1 (s, J = 11 Hz,
PC
3
PtC
1
2
3
3
4
5
C of PCy ), 32.5 (d, J = 20 Hz, J
PCy ), 121.1 (s, C ), 122.3 (s, C ), 122.9 (s, C ), 127.2
= 17 Hz, C of
= 8.0 Hz, J
= 1.3 Hz, 1H, H ),
3
PC
PtC
HH
HH
7
3
5/6
3
3
J
= 8.1 Hz, H ), 10.12 (d, 1H,
3
HH
6
14
4
4
9
3
13
1
(
(
(
s, C ), 129.5 (d, J = 5 Hz, C ), 129.9 (s, C ), 130.0
s, C ), 130.1 (s, C ), 134.3 (s, C ), 136.5 (s, C ), 144.3
PC
5/6
3
13
11
4
2
1
10
2
2
12
2
1
s, C ), 150.4 (s, JPtC = 28 Hz, C ), 163.7 (s, C );
31
1
3
P{ H} NMR (162 MHz, CDCl3):
δ
=
24.2 (s,

CHAMYANI ET AL.
11 of 13
3
1′
2
2
5′
PCy ), 29.1 (s, JPtC = 9 Hz, C of PCy ), 35.5 (d,
145.6 (s, C ), 148.7 (s, J
= 19 Hz, C ), 153.5 (s, C ),
3
3
PtC
1
3
3
2
2′
195
1
JPC = 13 Hz, JPtC = 10 Hz, C of PCy ), 119.5 (s,
154.1 (s, C );
δ = −3019.0 (s, 2Pt).
Pt{ H} NMR (86 MHz, CDCl ):
3
3
3
3
5
JPtC = 11 Hz, C ), 123.7 (s, J
= 10 Hz, C ), 124.2 (s,
= 15 Hz,
PtC
= 63 Hz, C ), 137.8 (s, C ), 141.1 (s,
PtC
5′
6′
3
J
= 8 Hz, C ), 125.1 (s, C ), 129.3 (s, J
PtC
′
4
2
3′
4
C ), 130.6 (s, J
C ), 152.9 (s, J
PtC
2
1
′
2
6
2
31
1
4.3.5 | [PtMe
4
(k N,C‐ppy)
2
(μ‐I) ] (2b)
2
= 18 Hz, C ), 161.8 (s, C ); P{ H}
PtC
1
NMR (162 MHz, CDCl ): δ = −18.0 (s, J = 956 Hz,
3
1
PtP
1
H NMR (400 MHz) in DMSO‐d : δ = 1.17 (s, 6H,
JPtH = 69.54 Hz, Me trans to I, PtMe), 1.47 (s, 6H,
JPtH = 69.64 Hz, Me trans to N, PtMe), 7.20–7.45 (6H,
overlapping multiplets of H and H and H ), 7.58 (t,
2H, JHH = 6.7 Hz, H ), 8.03 (m, 2H, H ), 8.15 (2H,
JHH = 8.3 Hz, H ), 8.39 (2H, J
(2H, JHH = 5.02 Hz, JPtH = 14.4 Hz, H ); C{ H} NMR
(101 MHz, CDCl ): δ = −5.3 (s, J
(Me trans to N)), −2.3 (s, J = 584 Hz, PtMe (Me trans
PtC
to I)), 120.7 (s, JPtC = 7 Hz, C ), 124.9 (s, C ), 125.5 (s,
C ), 126.1 (s, J = 17 Hz, C ), 127.5 (s, J = 10 Hz,
PtC PtC
C ), 130.9 (s, J
C ), 144.2 (s, C ), 151.3 (s, J
C ); Pt{ H} NMR (86 MHz, CDCl ): δ = −2985.3 (s, 2Pt).
3
1
95
6
1
P
of PCy3);
Pt{ H} NMR (86 MHz, CDCl3):
2
2
1
δ = −3175.7 (s, J = 953 Hz, 1Pt).
PtP
4
′
5′
6′
2
3
3′
4
4
.3.3 | cis‐[PtMe I(k N,C‐bzq)(PCy )] (3a)
2
3
3
5
3
3
= 8.1 Hz, H ), 9.79
HH
1
3
3
6
13
1
H NMR (400 MHz) in CDCl : δ = 0.80–2.27 (39H, ali-
phatic region, overlapping multiplets of 2Me and 3Cy),
.60–7.85 and 7.88 (m, 6H, aromatic region, overlapping
multiplets of bzq), 8.36 (d, 1H, J = 7.9 Hz, H ), 10.26
3
1
= 631 Hz, PtMe
3
PtC
1
7
3
4
3
3
5′
HH
3
3
2
13
1
5
3
4′
3
(m, 1H, J
= 5.3 Hz, J
= 15.5 Hz, H ); C{ H}
HH
PtH
2
6′
2
3′
4
NMR (101 MHz, CDCl ): δ = −7.7 (d, J = 4 Hz,
= 62 Hz, C ), 139.7 (s, C ), 141.7 (s,
3
PC
PtC
2′
1
2
1′
2
6
JPtC = 639 Hz, PtMe (Me trans to N)), 10.3 (d,
= 15 Hz, C ), 160.1 (s,
PtC
1
2
195
1
JPC = 104 Hz, JPtC = 476 Hz, PtMe (Me trans to P)),
3
2
6.3 (s, C of PCy ), 27.6 (d, J = 8 Hz, C of PCy ), 29.0
3
PC
3
3
1
(
s, J
= 8 Hz, C of PCy ), 35.6 (d, J = 15 Hz,
PtC 3 PC
JPtC = 13 Hz, C of PCy ), 122.7 (s, C ), 124.0 (s, C ),
26.6 (s, J = 47 Hz, C ), 127.5 (s, J = 12 Hz, C ),
PtC PtC
29.4 (s, C ), 129.5 (s, C ), 134.9 (s, J
2
2
7
5/6
4.3.6 | [PtMe
4
(k N,C‐bzq)
2
(μ‐I) ] (3b)
2
3
2
9
3
14
1
1
1
1
1
H NMR (400 MHz) in DMSO‐d : δ = 1.17 (s, 6H,
JPtH = 69.95 Hz, Me trans to I, PtMe), 1.65 (s, 6H,
JPtH = 70.43 Hz, Me trans to N, PtMe), 7.56 (d, 2H,
JHH = 7.2 Hz, J
.87–8.11 (8H, aromatic protons, overlapping multiplets
of 2bzq), 8.76 (d, 2H, J
JHH = 5.2 Hz, JPtH = 15.2 Hz, H ); C{ H} NMR
101 MHz, CDCl ): δ = −5.9 (s, J
Me trans to N)), −2.5 (s, J = 576 Hz, PtMe (Me trans
to I)), 124.0 (s, C ), 124.8 (s, C ), 122.3 (s, J = 16 Hz,
C ), 127.6 (s, J
JPtC = 63 Hz, C ), 134.6 (s, J
s, C ), 138.4 (s, C ), 142.7 (s, C ), 150.0 (s, J = 39 Hz,
C ), 150.5 (s, J = 11 Hz, C ); Pt{ H} NMR (86 MHz,
CDCl ): δ = −3008.4 (s, 2Pt).
4
3
3
13
6
= 10 Hz, C ),
PtC
4
2
2
3
5/6
11
10
36.6 (s, C ), 137.6 (s, C ), 141.2 (s, C ), 144.5 (s, C ),
2
2
12 31
1
51.3 (s, J
= 10 Hz, C ), 151.8 (s, C ); P{ H} NMR
PtC
3
9
3
= 47.5 Hz, H ), 7.76 (m, 1H, H ),
PtH
1
3 PtP
(
162 MHz, CDCl ): δ = −17.9 (s, J = 963 Hz, 1P of
7
195
1
PCy ); Pt{ H} NMR (86 MHz, CDCl ): δ = −3201.6 (s,
JPtP = 968 Hz, 1Pt).
Each reaction mixture containing Pt (II) complex with
excess of MeI, was further stirred for 1 day at room temper-
ature in CH Cl . A white solid precipitated in case 2b and
b, which were separated, washed with cold CH Cl , and
2 2
dried under vacuum. In case 1b, the solvent was removed
and the resulting residue was triturated with ether
3
3
3
4
= 8.2 Hz, H ), 9.98 (d, 1H,
1
HH
3
3
2
13
1
1
(
= 629 Hz, PtMe
3
PtC
1
(
PtC
5/6
2
2
7
3
PtC
4
3
3
3
14
= 9 Hz, C ), 128.9 (s, C ), 129.8 (s,
PtC
9
2
2
11
= 33 Hz, C ), 137.1
PtC
10
13
5/6
2
(
PtC
(
2 × 3 ml). Complexes 1b‐3b were obtained in the presence
of equimolar of [PCy Me] I while two components of the
mixture were completely separated and characterized (2b
12
2
2
195
1
PtC
3
3
and 3b). But for the mixture of 1b and [PCy Me] I, due
3
to high solubility of the complex 1b, all our attempts were
failed and we could not get 1b in the pure form.
4.3.7 | [PCy Me]I
3
1
H NMR (400 MHz) in CD Cl : δ = 1.23–2.52 (36H, ali-
2
2
phatic region, overlapping multiplets of Me and 3Cy);
2
4
.3.4 | [PtMe (k N,C‐Obpy) (μ‐I) ] (1b)
31
1
4
2
2
P{ H} NMR (162 MHz, CD Cl ): δ = 33.7 (s, 1P of PCy ).
2
2
3
1
H NMR (400 MHz) in CDCl : 0.83–2.70 (aliphatic region,
3
overlapping multiplets), 7.00–8.33 and 9.90–10.47 (aro-
matic region, overlapping multiplets of 2 Obpy); C{ H}
4.4 | Single‐crystal structure
13
1
determination
1
NMR (101 MHz, CDCl ): δ = −6.7 (s, J
= 639 Hz,
PtC
3
1
PtMe (Me trans to N)), 8.6 (s, J = 603 Hz, PtMe (Me
The X‐ray diffraction analysis was performed on a STOE
IPDS‐2/2 T diffractometer equipped using graphite‐
monochromated Mo Kα radiation. Suitable crystals were
PtC
2
3′
5
trans to I)), 123.5 (s, J
= 65 Hz, C ), 125.5 (s, C ),
PtC
6
4
′
4
3
1
26.6 (s, C ), 126.8 (s, C ), 136.1 (s, C ), 137.6 (s, C ),

12 of 13
CHAMYANI ET AL.
grown by diffusion method and mounted on a glass
fiber for further measurements. Diffraction data were col-
lected in a series of ω scans in 1° oscillations and inte-
4.7 | Computational details
All DFT calculations were employed using the Gauss-
[45]
[50]
grated using the Stoe X‐AREA
software package. A
ian09
program suite with the B3LYP level of theory.
[
51]
numerical absorption correction was applied using X‐
The LANL2DZ
basis set was selected to describe Pt
[
46]
[47]
RED
and X‐SHAPE
software. The structures were
and then refined on F by a
and I while the standard 6‐31G(d) basis set was utilized
[48]
2
solved by direct methods
for the other atoms. The geometric structures of com-
[
52,53]
full‐matrix least‐squares procedure using the X‐STEP32
plexes were optimized by PCM
model in acetone as
[49]
program.
All non‐hydrogen atoms were refined with
the high polar solvent. The vibrational frequency calcula-
tions were performed, in order to confirm the nature of
the optimized structures.
anisotropic displacement parameters. Hydrogen atoms
were positioned geometrically and constrained as riding
atoms with fixed thermal parameters. CCDC‐1840636
contains the supplementary crystallographic data for this
study.
ACKNOWLEDGMENTS
This work was supported by the Institute for Advanced
Studies in Basic Sciences (IASBS) Research Council
4.5 | Kinetic measurements
(
G2018IASBS32629). Technical support of the Chemistry
Computational Center at Shahid Beheshti University is
gratefully acknowledged.
In order to determine the kinetic rate constants of the oxi-
dative addition reaction of MeI with complexes 1–3, UV–
vis spectroscopy was used to follow the changes in the
absorbance in CH Cl . The absorbance‐time profiles were
2
2
ORCID
derived using pseudo first‐order methods. In all measure-
Hamid R. Shahsavari
2185
Mohsen Golbon Haghighi
http://orcid.org/0000-0002-2579-
http://orcid.org/0000-0002-
ments, the concentration of the Pt (II) complexes were
−
4
3
× 10 M in the presence of excess MeI reagent. The
collected kinetic data were fitted to the first‐order
equation (1) to give pseudo first‐order rate constants, kobs
2422-9075
.
Behrouz Notash http://orcid.org/0000-0003-4873-5770
Abs ¼ Abs
ðAbs − Abs Þ expð−kobstÞ
(1)
t
∞þ
0
∞
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SUPPORTING INFORMATION
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How to cite this article: Chamyani S, Shahsavari
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Notash B. Carbon‐iodide bond activation by
2
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