Bis(diphenylphosphino)acetylene as bifunctional ligand in cycloplatinated complexes: Synthesis, characterization, crystal structures and mechanism of MeI oxidative addition Dedicated to Prof. Mehdi Rashidi, a great teacher, in friendship and appreciation.

Article abstract of DOI:10.1016/j.jorganchem.2013.07.032

Binuclear cycloplatinated(II) complexes with general formula of [Pt ₂Me₂(?N)₂(μ-dppac)], (1, ?N = deprotonated 2-phenylpyridine (ppy); 2, ?N = deprotonated benzo{h}quinoline (bhq)) in which dppac = 1,1′-bis(diphenylphosphino) acetylene, are synthesized by the reaction of [PtMe(SMe₂)(?N)] with 0.5 equiv of dppac at room temperature. The complexes are fully characterized using multinuclear (¹H, ³¹P and ¹⁹⁵Pt) NMR spectroscopy and complex 2 is further identified by single crystal X-ray structure determination. Kinetics of the reaction of complexes 1 and 2 with MeI are investigated in CHCl₃ and based on the UV-vis and ³¹P NMR data, a mechanism involving a double MeI oxidative addition is suggested. The classical S_N2 mechanism is proposed for both steps and the involved intermediates are suggested. Although MeI in each step was trans oxidatively added to one of the platinum(II) centers, further trans to cis isomerizations of methyl and iodide ligands were also identified. The rates are almost four times slower in the second step as compared to the first step due to the electronic effects transmitted through the dppac ligand. Reaction rates concerning complex 2, having bhq ligand, are almost 1.3 times slower than those involving the related ppy complex 1. This is attributed to the stronger donor ability of the ppy ligand, as compared to that bhq ligand and is in agreement with the values of ¹J_PtP observed in the ³¹P NMR spectra of the complexes 1 and 2. The structure of the Pt(IV)-Pt(IV) dimeric complex [Pt₂I₂Me₄(ppy)₂(μ-dppac) ], 3, produced by oxidative addition of complex 1 to MeI, is also determined using X-ray diffraction which is the first X-ray structural determination of a diplatinum complex containing two Pt(IV) centers bridged by one dppac ligand.

Full text of DOI:10.1016/j.jorganchem.2013.07.032

Journal of Organometallic Chemistry 745-746 (2013) 148e157
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Bis(diphenylphosphino)acetylene as bifunctional ligand in
cycloplatinated complexes: Synthesis, characterization, crystal
structures and mechanism of MeI oxidative addition
,
a
b,
S. Masoud Nabavizadeh a , Hajar Sepehrpour , Reza Kia c, Arnold L. Rheingold d
*
a Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
b Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran
c Deutsches Elektronen-Synchrotron (DESY), Division Structural Dynamics of (Bio)chemical Systems, Photon Science at DESY, Notkestr,
85, 22607 Hamburg, Germany
d Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Binuclear cycloplatinated(II) complexes with general formula of [Pt2Me2(C^N)2(
m
-dppac)], (1, C^N ¼
Received 30 May 2013
Received in revised form
9 July 2013
deprotonated 2-phenylpyridine (ppy); 2, C^N
¼
deprotonated benzo{h}quinoline (bhq)) in which
dppac ¼ 1,10-bis(diphenylphosphino)acetylene, are synthesized by the reaction of [PtMe(SMe2)(C^N)]
with 0.5 equiv of dppac at room temperature. The complexes are fully characterized using multinuclear
(1H, 31P and 195Pt) NMR spectroscopy and complex 2 is further identified by single crystal X-ray structure
determination. Kinetics of the reaction of complexes 1 and 2 with MeI are investigated in CHCl3 and
based on the UVevis and 31P NMR data, a mechanism involving a double MeI oxidative addition is
suggested. The classical SN2 mechanism is proposed for both steps and the involved intermediates are
suggested. Although MeI in each step was trans oxidatively added to one of the platinum(II) centers,
further trans to cis isomerizations of methyl and iodide ligands were also identified. The rates are almost
four times slower in the second step as compared to the first step due to the electronic effects trans-
mitted through the dppac ligand. Reaction rates concerning complex 2, having bhq ligand, are almost 1.3
times slower than those involving the related ppy complex 1. This is attributed to the stronger donor
Accepted 10 July 2013
Dedicated to Prof. Mehdi Rashidi, a great
teacher, in friendship and appreciation.
Keywords:
Organoplatinum
Kinetic and mechanism
Crystal structure
1
ability of the ppy ligand, as compared to that bhq ligand and is in agreement with the values of JPtP
observed in the 31P NMR spectra of the complexes 1 and 2. The structure of the Pt(IV)ePt(IV) dimeric
complex [Pt2I2Me4(ppy)2(m-dppac)], 3, produced by oxidative addition of complex 1 to MeI, is also
determined using X-ray diffraction which is the first X-ray structural determination of a diplatinum
complex containing two Pt(IV) centers bridged by one dppac ligand.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
also received much attention due to their potential applications in
catalysis, molecular recognition and photoactive devices [10e12]. A
Binucleartransition metal complexes that showligand-mediated
metal-to-metal electronic communications are extensively investi-
gated due to their potential application to molecular-scale elec-
tronics and devices [1,2]. Additionally, these complexes are
attractive because they provide interesting mixed-valence species
that are regarded as prototypes for molecular switches and wires
[1e9]. The binuclear complexes containing bridging ligands have
key to synthesize the related two-centered metal-based material is
the selection of bridging ligands capable of mediating electronic
communications. The spacers used are, in most cases, either C-donor
or N-/O-donor ligands connected by sp or sp2 carbon chains [13e20].
Like the conjugated N- or C-donor ligands, the rodlike P-donor
spacers also display some characteristics such as photostability,
conjugation and rigidity. These P-donor ligands have molecular or-
bitals with suitable energies to overlap with those of the attached
metal centers. The capacity of bis(diphenylphosphino)acetylene
(Ph2PC^CPPh2, abbreviated as dppac) to act as a bifunctional ligand
to transition metals has been examined [21e28]. This ligand has a
* Corresponding author. Tel.: þ98 711 613 7110; fax: þ98 711 646 0788.
E-mail
addresses:
nabavi@chem.susc.ac.ir,
nabavizadeh@yahoo.com
(S.M. Nabavizadeh).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.07.032

S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
149
linear geometry with two terminal phosphine moieties and one
acetylene moiety able to coordinate to metal ions [29,30]. The
dominant coordination modes, which leave the ligand intact, are
end-on terminal [31,32] and end-on bridging [33e36] coordination
through the phosphorus atoms.
formula of the C^N ligands with the carbon atoms numbered to
clarify the following chemical shift assignments.
2.1. [Pt2Me2(ppy)2(m-dppac)], 1
On the other hand, transition metal cyclometalated complexes,
in particular those involving platinum and 2-phenylpyridyine are of
interest due to their potential applications as chemosensors [37],
photocatalysts [38] and luminescence [39e50]. Square planar
cyclometalated platinum complexes have also been used as
“building blocks” for complex systems such as self-assembly [51]
and dendrimers [52,53].
To a solution of [PtMe(ppy)(SMe2)] (100 mg, 0.23 mmol) in
acetone (15 mL) was added 0.5 equiv bis(diphenylphosphino)acet-
ylene (46 mg, 0.12 mmol) at room temperature. The mixture was
stirred for 3 h. The solvent was removed under reduced pressure,
and the residue was washed with diethyl ether (2 ꢀ 3 mL) and dried
under vacuum. Yield 100 mg; 76%, mp. 230 ꢁC (decomp). Anal. Calcd.
for C50H42N2P2Pt2: C, 53.5; H, 3.8; N, 2.5; Found: C, 53.8; H, 3.6; N,
We have recently studied the synthesis and reactivity of
some cyclometalated organoplatinum complexes aiming to prepare
more complex structures for potential applications as molecular
materials. Our previous works describe the preparation of some
types of complexes with bidentate phosphine ligand, including
bis(diphenylphosphino)methane, dppm, bis(diphenylphosphino)
ethane, dppe and 1,10-bis(diphenylphosphino)ferrocene, dppf
[54,55]. For the purpose of designing new complexes potentially
suitable for molecular wires based on platinum complexes, we have
examined to the construction of novel dimers of cyclometalated
platinum(II) complexes linked by the conjugated rigid diphosphine
spacer, bis(diphenylphosphino)acetylene (dppac). The precursors
used for this purpose are [PtMe(C^N)(SMe2)] (C^N ¼ deprotonated 2-
phenylpyridine (ppy) or deprotonated benzo{h}quinoline (bhq)). In
this paper, we describe the preparation, structural and spectro-
scopic characterization of binuclear cyclometalated platinum
complexes connected by conjugated diphosphine, dppac. We also
describe here the kinetic and mechanism of the reaction of Pt(II)e
Pt(II) complexes with MeI to form new Pt(IV)ePt(IV) complexes,
the first binuclear cyclometalated Pt(IV) complexes containing
dppac as bridging ligand.
2.3. NMR data:
d
(1H) 0.70 [d, 3JPH ¼ 8.9 Hz, 2JPtH ¼ 82.5 Hz, 6H, Me
0
0
0
0
0
0
ligands], 6.40 [ddd, 3J3HH4 ¼ 5.8 Hz, 3J4H5H ¼ 8.6 Hz, 5JP4H ¼1.3 Hz, 2H, H4
of ppy], 7.10e7.37 (overlapping hydrogens), 7.42 [t,
0
0
0
3J5H6H z 3J5H4H ¼ 8.2 Hz, 2H, H5 of ppy], 7.81 [td, 3JH3 H4 z 4JP3H z 6.0 Hz,
4 3050
0
0
J
¼ 1.4 Hz, 3J3PtH ¼ 54.1 Hz, 2H, H3 of ppy], 8.30 [d, 3JH5 6H ¼ 5.9 Hz,
HH
3 6
J
¼ 14.8 Hz, 2H, H6 of ppy],
d(
31P) 12.6 [s, 1JPtP ¼ 2049 Hz, 2P of
PtH
dppac];
d
(
195Pt) ꢂ2594 [d, 1JPtP ¼ 2047 Hz, 2Pt].
2.2. [Pt2Me2(bhq)2(m-dppac)], 2
This was prepared by the method as described above for
preparation of complex 1 using the starting materials [PtMe
(bhq)(SMe2)] and dppac. Yield: 74%, mp. 250 ꢁC (decomp). Anal.
Calcd. for C54H42N2P2Pt2: C, 55.4; H, 3.6; N, 2.4; Found:C, 55.6; H, 3.5;
N, 2.2. NMR data:
d
(1H) 0.88 [d, 2JPtH ¼ 82.7 Hz, 3JPH ¼ 9.0 Hz, 6H, Me
0
0
0
0
0
ligands], 6.60 [dd, 3JH3 H4 ¼ 6.1 Hz, 3JH4 H5 ¼ 8.0 Hz, 2H, H4 of bhq], 7.25e
3 3040
4 30
7.76 (overlapping hydrogens), 8.10 [td,
J
z
J
z 6.1 Hz,
HH
PH
0
0
3 3050
J
¼ 1.4 Hz, 3J3PtH ¼ 51.8 Hz, 2H, H3 of bhq], 8.50 [dt, 3JH6 5H ¼ 5.3 Hz,
HH
4J6HP z 4J6H4H z 1.4 Hz, 3JP6tH ¼ 14.7 Hz, 2H, H6 of bhq];
d(
31P) 12.3 [s,
1JPtP ¼ 2102 Hz, 2P of dppac];
d(
195Pt) ꢂ2590 [d, 1JPtP ¼ 2104 Hz, 2Pt].
2.3. [Pt2I2Me4(ppy)2(m-dppac)], 3
2. Experimental section
To a solution of [Pt2Me2(ppy)2(m-dppac)], 1, (50 mg in 25 mL
CH2Cl2) was added an excess of MeI (550
m
L) at room temperature
The 1H, 13C, 31P and 195Pt NMR spectra were recorded on a
Bruker Avance DRX 500 MHz spectrometer in CDCl3 as solvent. The
operating frequencies and references, respectively, are shown in
parentheses as follows: 1H (500 MHz, TMS), 13C (125 MHz, TMS),
31P (202 MHz, 85% H3PO4), and 195Pt (107 MHz, aqueous Na2PtCl4).
The chemical shifts and coupling constants are in ppm and Hz,
respectively. Kinetic studies were carried out by using a Perkine
Elmer Lambda 25 spectrophotometer with temperature control
using an EYELA NCB-3100 constant temperature bath. Benzo{h}
quinoline, 2-phenylpyridine and bis(diphenylphosphino)acetylene
were commercially available and the precursor compounds
[PtMe(C^N)(SMe2)] (C^N ¼ deprotonated 2-phenypyridine (ppy) or
deprotonated benzo{h}quinoline (bhq)) were prepared according
to reported procedures [54,56,57]. Scheme 1 shows the structural
and the mixture was stirred for 2 h. The solvent was removed under
reduced pressure, and the residue was washed with diethyl ether
(2 ꢀ 3 mL). The product was dried under vacuum. Yield 40 mg; 64%,
mp. 175 ꢁC (decomp.). Anal. Calcd. for C52H48I2N2P2Pt2: C, 44.4; H,
3.4; N, 2.0; Found: C, 44.2; H, 3.2; N, 1.7. NMR data: d
(1H) 1.16 (d,
2
3JPH ¼ 7.9 Hz, JPtH ¼ 62.1 Hz, 3H, 1 Me group trans to P), 1.17 (d,
2
3JPH ¼ 7.9 Hz, JPtH ¼ 62.0 Hz, 3H, 1 Me groups trans to P), 1.50 (d,
2
3JPH ¼ 8.7 Hz, JPtH ¼ 70.1 Hz, 3H, 1 Me group trans to N), 1.52 (d,
3JPH ¼ 8.9 Hz, 2JPtH ¼ 70.3 Hz, 3H, 1 Me group trans to N), (aromatic
3
protons): 6.8e7.9 (overlapping multiplets), 9.42 (d, JHH ¼ 5.2 Hz,
3JPtH ¼ 9 Hz, 1H, CH group adjacent to coordinated N atom), 9.47 (d,
3JHH ¼ 5.2 Hz, 3JPtH ¼ 9 Hz, 1H, CH group adjacent to coordinated N
atom);
d
(
13C) ꢂ5.9 (d, 1JPtC ¼ 628 Hz, 2JPC ¼ 23.6 Hz, 1C, Me trans to
N), ꢂ5.7 (d, 1JPtC ¼ 628 Hz, 2JPC ¼ 23.7 Hz, 1C, Me trans to N), 6.9 (d,
1JPtC ¼ 509 Hz, 2JPC ¼ 116 Hz, 1C, Me trans to P), 7.1 (d, 1JPtC ¼ 509 Hz,
2JPC ¼ 116 Hz, 1C, Me trans to P), 101.7 (d, with 1JPC ¼ 66.2 Hz, 1C, e
C^C), 101.9 (d, with 1JPC ¼ 66.2 Hz, 1C, eC^C), 147.0, 147.1 (each a
doublet, with 2JPC ¼ 13.6 Hz, 1JPtC ¼ 888 Hz, 2C, C atoms of the ppy
ligands connected to Pt atoms), other aromatic Cs were not
4'
4'
5'
3'
3'
5'
6'
R
R
assigned;
d
(
31P) ꢂ23.9 (s, 1JPtP ¼ 976 Hz,1P), ꢂ23.7 (s, 1JPtP ¼ 977 Hz,
Pt
Pt
1P);
d
(
195Pt) ꢂ1797 and ꢂ1806 (2 overlapping d, each with
P
1JPtP ¼ 975 Hz, 2 Pt).
P
N
3
4
N
6
2.4. [Pt2I2Me4(bhq)2(m-dppac)], 4
4
6
5
5
This was prepared by the method as described above for prep-
aration of complex 3 using the starting material [Pt2Me2(bhq)2(
dppac)], 2. Yield: 64%, mp. 190 ꢁC (decomp.). Anal. Calcd. for
m-
Scheme 1. Representation of C^N ligands [ppy (left) and bhq (right)] with position
labeling.

150
S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
Table 1
2.5. Reaction of [Pt2Me2(ppy)2(m-dppac)], 1, with MeI
Crystal data, data collection, and structure refinement details for complexes 2 and 3.
This reaction was monitored by 31P NMR spectroscopy at room
temperature in an NMR tube. To a solution of [Pt2Me2(ppy)2(
dppac)], 1, (10 mg) in CDCl3 (0.7 mL), an excess of MeI (3 L) was
added. The NMR spectra were recorded several times at during
about 2 h until the mixture was gradually converted to complex 3 in
solution.
Complex 2
Complex 3
m
-
Formula
C54H42N2P2Pt2
1171.02
291(2)
Triclinic
P-1
9.6765(10)
9.8839(10)
23.624(3)
2235.8(4)
2
1.739
6.361
0.884/1.000
1132
15,489
C52H48I2N2P2Pt2
1406.84
100(2)
Monoclinic
P2(1)/c
14.7189(4)
16.7379(5)
19.4066(6)
4725.2(2)
4
1.978
7.326
0.234/0.322
2664
43,031
m
Formula weight
Temperature/K
Crystal system
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
vol/A
2.6. Kinetic study
3
ꢀ
Z
D(calc)/Mg mꢂ3
In a typical experiment, a solution of complex 1 in CHCl3
(3 mL, 1.06 ꢀ 10ꢂ4 M) in a cuvette was thermostated at 25 ꢁC and
a known excess of MeI was added using a micro syringe. After
m
/mmꢂ1
Tmin/Tmax
F(000)
No. of reflns
No. of independent reflns
No. of observed reflns
rapid stirring, the absorbance at
time.
l
¼ 352 nm was monitored with
8049 [R(int) ¼ 0.0542]
9667 [R(int) ¼ 0.0603]
5143
7771
[I > 2
GooF (F2)
R1, wR2 [I > 2
R1, wR2 (all data)
s(I)]
2.7. Crystallography
0.75
0.0285, 0.0475
0.0589, 0.0509
1.122
0.0373, 0.0592
0.0556, 0.0631
s
(I)]
Single crystal of [Pt2Me2(bhq)2(m-dppac)], 2, was grown from
a concentrated CH2Cl2 solution by slow diffusion of n-pentane.
Single crystal X-ray data for complex 2 were collected at 296(1) K
C56H48I2N2P2Pt2: C, 46.2; H, 3.3; N, 1.9; Found: C, 46.5; H, 3.2; N, 1.7.
ꢀ
on STOE IPDS 2T diffractometer (Mo K
a
¼ 0.71073 A). The cell
2
3
NMR data:
d
(1H) 1.14 (d, JPtH ¼ 62.2 Hz, JPH ¼ 7.9 Hz, 3H, 1 Me
parameters were retrieved using X-AREA [58] software and
refined using X-AREA on all observed reflections. Data reduction
and correction for Lp (Lorentz-polarization) and decay were
performed using X-AREA software. Absorption corrections were
applied using MULABS [59,60]. All structures were solved by
direct methods and refined by full-matrix least squares on F2 for
all data using SHELXTL software [61]. All calculations were per-
formed by PLATON. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were positioned geometrically
and refined with a riding model approximation with their pa-
rameters constrained to the parent atom with Uiso (H) ¼ 1.2 or 1.5
3
2
group trans to P), 1.16 (d, JPH ¼ 7.9 Hz, JPtH ¼ 62.6 Hz, 3H, 1 Me
3
2
groups trans to P), 1.65 (d, JPH ¼ 8.7 Hz, JPtH ¼ 70.1 Hz, 3H, 1 Me
3
2
group trans to N), 1.67 (d, JPH ¼ 8.7 Hz, JPtH ¼ 70.0 Hz, 3H, 1 Me
group trans to N), (aromatic protons): 6.9e8.1 (overlapping multi-
plets), 9.50 (d, 3JHH ¼ 5.1 Hz, 3JPtH ¼ 11 Hz, 1H, CH group adjacent to
3
3
coordinated N atom), 9.60 (d, JHH ¼ 5.3 Hz, JPtH ¼ 11 Hz, 1H, CH
1
group adjacent to coordinated N atom);
d
(
13C) ꢂ6.7 (d, JPtC
¼
2
1
622 Hz, JPC z 3 Hz, 1C, Me trans to N), ꢂ6.5 (d, JPtC ¼ 624 Hz,
2JPC ¼ 3.7 Hz, 1C, Me trans to N), 6.2 (d, 1JPtC ¼ 505 Hz, 2JPC ¼ 115 Hz,
1C, Me trans to P), 6.5 (d, 1JPtC ¼ 504 Hz, 2JPC ¼ 115 Hz, 1C, Me trans
1
to P), 101.3 (d, with JPC ¼ 66 Hz, 1C, eC^C), 101.8 (d, with
Ueq (C). Single crystal of [Pt2I2Me4(ppy)2(m-dppac)], 3, was grown
1JPC ¼ 66 Hz, 1C, eC^C), other aromatic C’s were not assigned;
from a concentrated CH2Cl2 solution by slow diffusion of n-
pentane. The single crystal X-ray diffraction study of 3 was car-
ried out on a Bruker Platform D8 CCD diffractometer equipped
1
1
d(
(
31P) ꢂ23.9 (s, JPtP ¼ 975 Hz, 1P), ꢂ23.6 (s, JPtP ¼ 976 Hz, 1P);
d
195Pt) ꢂ1832 and ꢂ1823 (2 overlapping d, each with
1JPtP ¼ 978 Hz, 2Pt).
with Mo Ka radiation (
l
¼ 0.71073). A 0.28 ꢀ 0.24 ꢀ 0.20 mm
Me
N
Ph2PC
CPPh2
C
N
Me
Ph2
Ph2
2
Pt
C
Pt
P
C
C
P
Pt
C
- SMe2
SMe2
N
Me
C
1
N
ppy
bhq
ppy
bhq
2
-
N
N
C
=
N
+ Excess MeI
-
I
C
Me
N
C
N
Ph2
Ph2
Me
Pt
C
P
C
C
P
Pt
I
Me
3
ppy
bhq
4
Me
N
Scheme 2. Reactions studied in this work.

S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
151
Fig. 1. The 1H NMR spectrum of complex 2.
crystal was mounted on a Cryo-loop with Paratone-N. The Bruker
3. Results and discussion
program packages, APEX-II and SAINT were used for data
collection, integration and corrections. Solution and refinement
proceeded as described for complex 2. At both Pt(IV) sites of
complex 3, there was iodide/methyl group disorder; the minority
component is designated with a prime. The major configuration
at Pt1 is 71% occupied, and at Pt2, 88% occupied. The occupancies
were refined with a unit occupancy constraint. Crystal data, data
collection, and structure refinement details are listed in Table 1.
3.1. Synthesis and characterization of the Pt(II)ePt(II) complexes
The synthetic procedures are summarized in Scheme 2.
The starting complexes [PtMe(C^N)(SMe2)], in which C^N ¼ ppy
or bhq, reacted with bis(diphenylphosphino)acetylene (dppac) in
a 1:0.5 molar ratio to give the organodiplatinum(II) complexes
[PtMe2(C^N)2(
m-dppac)], 1e2. They were isolated as stable solids
ꢀ
Fig. 2. (a) The molecular structure of complex [Pt2Me2(bhq)2(
m
-dppac)], 2, showing 40% probability ellipsoids. The H atoms omitted for clarity. Selected bond distances (A) and
angles (ꢁ): Pt(1)eC(1) 2.059(7); Pt(1)eC(14) 2.069(6); Pt(1)eN(1) 2.130(5); Pt(1)eP(1) 2.2672(17); Pt(2)eC(15) 2.053(7); Pt(2)eC(28) 2.066(6); Pt(2)eN(2) 2.144(5); Pt(2)eP(2)
2.2750(18); P(2)eC(54) 1.783(7); P(2)eC(47) 1.824(7); P(2)eC(41) 1.840(6); P(1)eC(53) 1.779(7); P(1)eC(29) 1.836(6); P(1)eC(35) 1.839(6); C(1)ePt(1)eC(14) 89.6(3); C(1)ePt(1)e
N(1) 80.3(2); C(14)ePt(1)eN(1) 169.7(2); C(1)ePt(1)eP(1) 173.85(19); C(14)ePt(1)eP(1) 85.81(19); N(1)ePt(1)eP(1) 104.44(15); C(15)ePt(2)eC(28) 91.2(3); C(15)ePt(2)eN(2)
80.6(3); C(28)ePt(2)eN(2) 171.8(3); C(15)ePt(2)eP(2) 176.7(2); C(28)ePt(2)eP(2) 91.2(2).

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S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
0
4 3050
which were characterized by their 1H, 31P and 195Pt NMR spectra and
elementary analysis and the structure of complex 2 was further
determined by X-ray crystallography. Typically, in the 1H NMR
J
¼ 1.4 Hz and 3JH3 Pt ¼ 51.8 Hz. In the room temperature 31P NMR
HH
spectrum of the binuclear complex 2, the observation of a sharp
singlet signal for each of the analogs at a chemical shift of 12.3 ppm,
which is accompanied by Pt satellites, 1JPtP ¼ 2102 Hz, confirm that
the two PtMe(bhq) moieties, joined together by the dppac spacer
ligand, are equivalent. Consistent with this, in the 195Pt NMR spec-
spectrum of [Pt2Me2(bhq)2(
m-dppac)], 2, in CDCl3 at room temper-
ature (see Fig. 1), the methylplatinum resonance appeared at
d
¼ 0.88 as a doublet due to coupling to phosphorus (with
3JPH ¼ 9.0 Hz) which is further coupled to 195Pt (with 2JPtH ¼ 82.7 Hz)
confirming that the methyl ligands are located trans to aromatic N
atoms, which is characteristic values for PteMe trans to N [62e64].
The hydrogen related to the CH group adjacent to ligating N atom of
trum of 2, a doublet at
d
ꢂ2590 with 1JPtP ¼ 2104 Hz was observed.
This 1JPtP value is consistent with P trans to a ligand with high trans
influence like carbon; trans to N would give a larger coupling con-
stant [64e66]. These data suggest that dppac is acting as a spacer
ligand between the two PtMe(bhq) moieties and each P atom is
coordinated to a Pt atom in a trans disposition to coordinating C
atom of the phenyl ring of bhq ligand. Each Me ligand is thus located
trans to the coordinated N atom of bhq ligand.
the C^N ligand appeared as a doublet of triplet at
d
¼ 8.50 with
3 6 5
J
HH
¼ 5.3 Hz, 4J6HP z 4JH6 4H z1.4 Hz and 3JH6 Pt ¼ 14.7 Hz. The hydrogen
related to the CH group adjacent to ligating C atom of the C^N ligand
0
0
4 30
appeared as a triplet of doublet at
d
¼ 8.10 with 3JH3 H4 z JHP z 6.1 Hz,
Fig. 3. The NMR spectra of complex 3. (A): 1H in the Me region; (B): 31P NMR and (C) 13C NMR in the Me region. The peak labeled * in 1H NMR is due to water of CDCl3 solvent.

S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
153
connected by P atoms of dppac ligand. The fragment PeCeCeP is
almost linear [P1eC53eC54 174.4(5)ꢁ] and the Pt1eP1, P1eC53 and
ꢀ
Pt1eN1 distances are 2.2672(17), 1.779(7) and 2.130(5) A, respec-
tively. The terminal Me ligands are in a transoidal disposition; the
ꢀ
unique C^C distance is 1.199(7) A. The square-planar environment
for both platinum centers is completed by the aromatic N atom and
the ortho C of the bhq ligand forming cycloplatinated complex.
Mono m-dppac complexes which a dppac molecule acts as a unique
bridging ligand between two metal fragments are not very com-
mon [31].
3.2. Synthesis and characterization of Pt(IV)ePt(IV) complexes
The methylplatinum(II) complexes, 1 and 2, were reacted
cleanly with an excess of MeI in CH2Cl2 at room temperature to give
air-stable solid products having the general formula [Pt2I2
-
Me4(C^N)2(
m
-dppac)] (C^N ¼ ppy, 3; bhq, 4). The synthesized Pt(IV)
complexes were fully characterized using 1H, 13C, 31P and 195Pt NMR
spectroscopy and elemental analysis. Complex 3 was further
identified by single crystal X-ray structure determination. Full data
Fig. 4. (a) The molecular structures of complex [Pt2I2Me4(ppy)2(m-dppac)], 3. Selected
ꢁ
ꢀ
bond distances (A) and angles ( ): Pt1eC38 2.074(6); Pt1eC50 2.102(6); Pt1eC52
2.089(14); Pt1eN1 2.112(6); Pt1eI1 2.7343(7); Pt1eP1 2.3886(14); Pt2eC49 2.037(5);
Pt2eC51 2.102(5); Pt2eC53 2.051(9); Pt2eN2 2.133(5); Pt2eI2 2.7378(5); Pt2eP2
2.4146(14); C38ePt1eC52 92.4(4); C50ePt1eC52 92.0(4); C38ePt1eN1 80.3(2); C50e
Pt1eN1 89.2(3); C52ePt1eN1 172.5(4); C38ePt1eP1 92.41(16); C50ePt1eP1 176.7(2);
N1ePt1eP1 87.57(13); C38ePt1eI1 175.12(17); N1ePt1eI1 97.47(15); P1ePt1eI1
91.82(4); C49ePt2eC51 87.5(2); C49ePt2eN2 79.8(2); C53ePt2eN2 170.3(3); C51e
Pt2eN2 88.7(2); C49ePt2eP2 92.63(15); C51ePt2eP2 175.36(18); N2ePt2eP2
86.80(12); C49ePt2eI2 175.90(15); C53ePt2eI2 90.6(2); N2ePt2eI2 98.08(13); P2e
Pt2eI2 90.72(4).
are collected in the Experimental section. On the base of 1H and 13
C
NMR spectra of complex [Pt2I2Me4(ppy)2(m-dppac)], 3, (see Fig. 3),
two different Me groups being trans to P and two different Me
groups locating trans to N ligating atoms were assigned. Thus, in the
1H NMR spectrum of complex 3 (see Fig. 3A), the Me groups trans to
P were observed at
62.0 Hz, respectively, while Me groups locating trans to N ligating
d
1.16 and 1.17 as doublets with, 2JPtH ¼ 62.1 and
atoms were appeared at d 1.50 and 1.52, with a considerably higher
2JPtH values of 70.1 and 70.3, respectively, due to lower trans in-
fluence of N atom as compared with that of P atom [66,67]. The
hydrogen related to the CH groups adjacent to ligating N atom of
When more than 0.5 equiv of dppac (e.g., [PtMe(C^N)
(SMe2)]:dppac ¼ 1:1) is used in the related reaction, on the basis of
the 1H and 31P NMR spectra, only the corresponding dimer was
formed as a mixture with free dppac.
the ppy ligands appeared as a doublet at
d
¼ 9.40 and 9.50 each
with 3JHH ¼ 5.2 Hz and 3JPtH ¼ 9.0 Hz. Consistently, in the 13C NMR
spectrum of 3, in the Me region (see Fig. 3C), two doublets were
The structure of complex [Pt2Me2(bhq)2(m-dppac)], 2, was
appeared at
groups trans to P; each doublet further coupled to platinum to give
d
6.9 and 7.1 with a 2JPC value close to 116 Hz for the Me
further determined by X-ray crystallography and is shown in Fig. 2;
the selected bond lengths and bond angles are also shown. The
geometry around the Pt(II) atoms in complex 2 is slightly-distorted
a
1JPtC value close to 509 Hz. Two other doublets were appeared
further high field at
to 23.6 Hz, indicating that they are located cis to P atom and thus
must be trans to N atom; the JPtC value of 628 Hz for each of the
d
ꢂ5.9 and ꢂ5.7 each with a 2JPC value of close
ꢀ
square-planar with mean deviation of 0.026(3) A for Pt1 [C1/N1/
1
ꢀ
C14/P1 plane] and ꢂ0.021(3) A for Pt2 [C15/N2/C28/P2 plane]. The
complex 2 is formed by two identical moieties “PtMe(bhq)”
signals is also significantly higher than the value of 508 Hz found
+
Me
Pt
Me
Me
Pt
I
Me
Ph2
Me
N
C
N
_
Ph2
P
Ph2
P
Me
N
C
Ph2
P
Me
Ph2
P
Ph2
P
Me
+ MeI
I
C
Pt
C
C
C
Pt
P
C
C
C
C
Pt
C
C
Pt
k
2
N
N
N
(A)
1
trans-cis isomerization
of Pt(IV) center
+
+
I
C
Me
C
Me
C
Pt
I
Me
Me
N
N
Me
_
N
Me
_
Ph2
Ph2
P
Me
Ph2
P
Ph2
Ph2
P
Ph2
P
Me
+ MeI
k'
Me
Pt
C
Pt
P
C
C
C
Pt
C
C
C
P
Pt
I
I
C
Pt
C
C
2
N
N
Me
N
(B)
trans-cis isomerization of
the second Pt(IV) center
+
Me
C
I
Me
C
Me
C
Pt
I
N
Me
Ph2
N
Me
Ph2
Ph2
N
Me
Ph2
Ph2
_
Ph2
C
Pt
P
C
C
P
Pt Me
Me Pt
N
P
C
C
P
Pt
I
I
Me Pt
N
P
C
P
N
Me
Me
I
Me
I
C
3
C
(C)
Scheme 3. Suggested mechanism for reaction of complexes 1 and 2 with MeI.

154
S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
for Me groups trans to P atoms. In the 31P NMR spectrum of
the formation of a statistical 1:1 mixture of two stereoisomers may
be a reasonable explanation.
[Pt2I2Me4(ppy)2(m-dppac)], 3, (see Fig. 3B) two different P signals at
d
ꢂ23.7 and ꢂ23.9 with 1JPtP ¼ 977 and 976 Hz, respectively, which
Complex 3 was also characterized by single-crystal X-ray
diffraction analysis as illustrated in Fig. 4. It confirms the charac-
terization of 3 as an octahedral diplatinum(IV) complex formed by
oxidative addition of MeI to complex 1. The coordination geometry
around each platinum atom is octahedral with the Me group, the
nitrogen atom and the ortho C of the ppy ligand, iodide and one P
atom of the dppac. The three carbon atoms have fac geometry. The
as expected is much lower than the corresponding value of 2049 Hz
found for the starting Pt(II) complex 1, were observed and these are
consistent with the observation of two signals in the 195Pt NMR
spectrum of complex 3 at
d
ꢂ1797 and ꢂ1806 (two almost over-
lapping doublets each with 1JPtP ¼ 975 Hz). These data would well
establish the relative disposition of the different ligands on each Pt
center as shown in Scheme 1 (with chirality at each Pt center), but it
is not possible to use the present data to actually propose any
“frozen” conformer(s) for complexes 3 and 4 resulting from rota-
tion around one or two of the PteP bonds. As twice the “expected”
number of signals was observed in the NMR spectra of complex 3,
ꢀ
bond distances between platinum and carbon atom is 2.089(14) A
for Pt1eC52. This value is considerably shorter than Pt1eC14 bond
ꢀ
in the complex 2 (here the bond length is 2.069(6) A), indicating the
conversion of Pt(II) to Pt(IV) product upon oxidative addition re-
action. The iodide atom is located trans to the C atom of the ppy
Fig. 5. The reaction of complex 1 with excess MeI as monitored by 31P NMR spectroscopy in CDCl3 at room temperatures. Top: Pt(II) region. Bottom: Pt(IV) region. (a) pure 1, (b)
immediately after addition of excess MeI, (c) 8 min after addition of excess MeI, (d) 16 min after addition of excess MeI, (e) 36 min after addition of excess MeI, (f) 1 h after addition
of excess MeI and (g) 100 min after addition of excess MeI. The peak assignments are shown.

S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
155
ligand. The bond length of Pt1eC50 (trans to P1) and Pt1eC52
(trans to N1) are 2.102(6) and 2.089(14), respectively. The trend is in
agreement with the observed 2JPtH values in 1H NMR of complex 3,
showing lower trans influence of N atom as compared with that of P
atom. The two methyl groups are cis disposed to one another (C50e
Pt1eC52 92.0(4)ꢁ), indicating that the angles around the Pt center
are rather close to the ideal angle of 90ꢁ. The aromatic N atom is
coordinated to platinum center, which is in accord to the usual
preference of the ppy ligand to form cyclometalated complexes,
and is positioned trans to a Me group. The Pt1eP1 distance of
ꢀ
2.3886(14) A in complex 3 is significantly longer than the Pt1eP1
ꢀ
distance of 2.2672(17) A in complex 2, consistent with the oxidation
states of þ4 and þ2 for Pt atoms in complexes 3 and 2, respectively.
To the best of our knowledge this is the first Xeray structural
determination of a diplatinum(IV) complex having dppac as
bridging ligand.
3.3. Kinetic and mechanism of the reaction of complexes 1 and 2
with MeI
Fig. 7. Plots of first-order rate constants [(a) first step, kobs/sꢂ1, and (b) second step,
k0obs=sꢂ1] for the reaction of complex 1 with MeI at 30 ꢁC versus [MeI] in CHCl3.
On the basis of the NMR and UVevis spectroscopic studies,
described below, a mechanism for reaction of complexes 1 and 2
with MeI is suggested as shown in Scheme 3.
is probably due to higher trans influence of Me as compared to that
of the ppy-C ligand. For intermediate B, two singlet signals, one at
d
11.4 (with 1JPtP ¼ 1838 Hz, located in the Pt(II) region) and another
3.3.1. Monitoring the reaction of complex 1 with MeI by 31P NMR
spectroscopy
To investigate the details of mechanism of addition of MeI to
diplatinum(II) complexes containing dppac as spacer ligand, the
one at
d
ꢂ26.9, located in the Pt(IV) region with 1JPtP ¼ 988 Hz, were
observed. As the time was passing on, the signals due to the starting
material 1, and intermediates A and B were disappearing while
those due to the intermediate C and final product 3 were growing.
For the intermediate C, two signals in the Pt(IV) regions with ex-
pected JPtP values (one signal at
another signal at
reaction of complex [Pt2Me2(ppy)2(m-dppac)], 1, with excess MeI in
CDCl3 was monitored by 31P NMR spectroscopy at room tempera-
ture. The spectra are shown in Fig. 5. Based on the results obtained
from 31P NMR spectroscopy (and UVevis spectroscopy, see next
section), the complexes and intermediates suggested for the reac-
tion sequence, described in Scheme 3, were assigned. The com-
plexes 1 and 3 are characterized as described in the main text and
Experimental section. Therefore the characteristic 31P NMR data for
these complexes were used to indicate the complexes in the reac-
tion sequence. Immediately after the addition of MeI at room
temperature, apart from complex 1, two Pt(II)ePt(IV) species
d
ꢂ24.2, with JPtP ¼ 971 Hz,
1
1
d
ꢂ24.3, with 1JPtP ¼ 980 Hz) were observed. After
100 min, all the signals were completely disappeared and the final
Pt(IV)ePt(IV) product 7 was purely obtained.
3.3.2. Kinetic studies using UVevis spectroscopy
The kinetics of oxidative addition of MeI in CHCl3 to binuclear
complexes 1 and 2 was studied by using UVevis spectroscopy. In
each case, an excess of MeI was used and disappearance of the
MLCT band was followed to monitor the reaction. The change in the
spectrum during a typical run is shown in Fig. 6. The absorbancee
time curves monitored at 360 nm for the reaction of complex 1 (or
400 nm for complex 2) with MeI in CHCl3 solution were obtained in
the presence of large excesses of MeI, such that its concentration
remained effectively constant in each experiment. The kinetic data
were in accord with the occurrence of two sequential first-order
assigned as intermediates A and B, were detected. For intermediate
1
A, two singlet signals, one at
d
14.0 (with JPtP ¼ 2047 Hz close to
that of the Pt(II)ePt(II) starting complex 1) and another one at
1
d
ꢂ24.0 with JPtP ¼ 639 Hz, were observed. The latter value is
typical for Pt(IV)eP coupling, but is higher than the corresponding
value found for Pt(IV)ePt(IV) complex 3 (with 1JPtP ¼ 628 Hz); this
Fig. 6. Changes in the UVevis spectrum during the reaction of complexes 1 (left) and 2 (right) with MeI in CHCl3; successive spectra were recorded at intervals of 30 s.

156
S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
Table 2
Rate constantsa and activation parametersb for reaction of complexes 1 and 2 with MeI in CHCl3.
Rate constants at different temperatures
10 ꢁC
20 ꢁC
25 ꢁC
30 ꢁC
35 ꢁC
40 ꢁC
D
Hz/kJ molꢂ1
D
Sz/J Kꢂ1 molꢂ1
Complex 1
102k2/(L molꢂ1 sꢂ1
)
)
0.36
0.10
0.70
0.19
0.89
0.24
1.22
0.32
1.61
0.43
2.24
0.56
41.9 ꢃ 0.9
38.9 ꢃ 0.8
ꢂ143 ꢃ 3
ꢂ164 ꢃ 3
102k02/(L molꢂ1 sꢂ1
Complex 2
102k2/(L molꢂ1 sꢂ1
102k02/(L molꢂ1 sꢂ1
)
)
0.29
0.09
0.59
0.15
0.67
0.18
1.00
0.24
1.24
0.28
1.45
0.37
37.4 ꢃ 2.2
31.1 ꢃ 1.1
ꢂ160 ꢃ 8
ꢂ192 ꢃ 4
a
Estimated error in k values are ꢃ5%.
b
Obtained from the Eyring equation.
reactions. Thus, the pseudo-first-order rate constants, kobs(1) and
kobs(2), for the two steps of the reaction were evaluated by nonlinear
least-square fitting of the absorbanceetime profiles to the biphasic
first order equation (Eq. (1) and Fig. 1S).
the Pt(II) center of a Pt(II)ePt(II) complex, 1, while in step 2, MeI
reacts with the Pt(II) center of a Pt(II)ePt(IV) species (complex B).
As such the reaction should be slower in the second step since in
contrast to complex 1, in species 2, the adjacent Pt(IV) moiety re-
duces the nucleophilicity of the Pt(II) center through the bridging
biphosphine group, dppac.
h
ꢀ
ꢁi
h
ꢀ
ꢁi
Abst
¼
a
exp ꢂ kobsð1Þ
t
þ
b
exp ꢂ kobsð2Þ
t
þ AbsN (1)
Both of the pseudo-first-order rate constants kobs(1) and kobs(2)
show a variation with [MeI] that is linear with no intercepts (Fig. 7),
showing a first-order dependence of the rate on the concentration
of MeI in each step. Least-squares analysis gives the second-order
rate constants (k2 for the first step and k02 for the second step)
and the results are given in Table 2. The findings are consistent with
3.4. Effect of C^N ligand on the rate of oxidative addition reaction
As is clear from Table 2, the reaction rates of complex
[Pt2Me2(bhq)2(
peratures for both steps, are at least 1.2e1.3 times slower than the
corresponding reaction of complex [Pt2Me2(ppy)2( -dppac)], 1. For
m-dppac)], 2, with MeI in CHCl3 at different tem-
m
the two-step sequence indicated in the last section based on the 31
P
example, in step 1, MeI at 25 ꢁC reacted nearly 1.3 times faster with
NMR data (see Fig. 5) for the reaction of complex 1 with MeI.
Therefore, each step of the reaction (see Scheme 3) obeys a simple
second-order rate law (Eq. (2) for step 1 and Eq. (3) for step 2); note
that k2 > k0 and the reproducibility of the data were remarkable
(ꢃ4%). The2 same method was used at other temperatures and
activation parameters were obtained from the Eyring equation (see
Eq. (4) and Fig. 2S). The data are shown in Table 2.
[Pt2Me2(ppy)2(
m
-dppac)] (k2 ¼ 5.36 ꢀ 10ꢂ1 Lmolꢂ1 sꢂ1) than with 2
(k2 ¼ 4.01 ꢀ 10ꢂ1 Lmolꢂ1
s
ꢂ1). This confirms the stronger donor
ability of the ppy ligand as compared to that of the bhq ligand and
shows that the platinum center in the ppy complex 1 is more
electron rich than the platinum center in complex 2 toward elec-
1
trophilic attacks. This is consistent with the trends found for JPtP
values in the 31P NMR spectra of the analogous complexes 1
(2049 Hz) and 2 (2102 Hz). Therefore it may be concluded that the
trans influence of metalated C atom of ppy ligand is greater than
that of bhq ligand [57,69].
ꢂd½1ꢄ=dt ¼ k2½1ꢄ½Meꢄ
(2)
(3)
ꢂd½Bꢄ=dt ¼ k’2½Bꢄ½MeIꢄ ꢂ k2½1ꢄ½MeIꢄ
ꢂ ꢃ
ꢂ
ꢃ
4. Conclusions
k
T
kB
h
D
R
Sz
D
Hz
ln
¼ ln
þ
ꢂ
RT
k ¼ k2 or k02
(4)
Two new binuclear complexes, [Pt2Me2(C^N)2(m-dppac)], in
The values of the entropy of activation were large and negative
which C^N ¼ deprotonated 2-phenylpyridine (1) or benzo{h}quin-
oline (2) and dppac ¼ bis(diphenylphosphino)acetylene, were
synthesized. The related two-step reactions of complexes 1 and 2
with MeI were investigated by UVevis spectrophotometry; the
reaction of complex 1 with MeI was also monitored by 31P NMR
spectroscopy. On the basis of the results, both steps of MeI oxidative
addition proceed by the classical SN2 type mechanism [70,71], as
for both steps, which are in favor of a classical SN2 type mechanism.
Based on these NMR and kinetic data, we suggest that as shown in
Scheme 3, at the first step MeI attacks (via an electrophilic addition)
on one of the electron rich Pt(II) centers of dimer complex 1 with an
SN2 type mechanism with the rate constant k2 and the mix valence
Pt(II)ePt(IV) binuclear intermediate A is formed. The intermediate
A would then quickly performs a facile trans to cis isomerization of
the Pt(IV) center having Me and I in trans disposition to form the
intermediate B. Intermediate B was then reacted with MeI in the
second step again by an SN2 type mechanism, with the rate con-
stant k02 which is nearly 4 times smaller than the corresponding
value for the rate constant of first step (k2, see Table 2) to form
intermediate C (Scheme 3). Then, a rapid transecis isomerization of
the resulting Pt(IV) center was occurred to form the final product 3.
As is clear from Table 2, in the two-step oxidative addition re-
actions studied in this work based on the qualitative 31P NMR in-
vestigations and UVevis calculation (see Supporting information
for rate constants assignment using the Espenson’s approach [68]),
the step 2 appears to be slower than the step 1. In step 1, MeI attacks
shown in Scheme 3, with large negative D
Sz values. In the first step,
the electron rich platinum center of the Pt(II)ePt(II) starting com-
plex 1 attacks the methyl carbon of MeI to form the intermediate B
which is suggested to be a Pt(II)ePt(IV) complex. The rate of the
reaction of the platinum(II) center in complex B with MeI was
considerably slower (by a factor of 4) than that for the platinum(II)
center in the starting complex 1, which is consistent with a sig-
nificant electronic effect transmitted through the dppac bridging
ligand. The PteP bond length for P atom trans to the C atom of ppy
ligand is rather longer than that of the P atom trans to the C atom of
bhq ligand. The difference, although modest, indicates that ppy
ligand probably exerts a higher trans influence than the bhq ligand.
1
This is in agreement with the values of JPtP (observed in the 31P

S.M. Nabavizadeh et al. / Journal of Organometallic Chemistry 745-746 (2013) 148e157
157
[28] D. Xu, H.J. Murfee, W.E. van der Veer, B. Hong, J. Organomet. Chem. 596 (2000)
53e63.
NMR spectra) and rates of MeI oxidative addition of the related
complexes.
[29] V.K. Jain, L. Jain, Coord. Chem. Rev. 249 (2005) 3075e3197.
[30] K.S. Shin, D.Y. Noh, Bull. Korean Chem. Soc. 25 (2004) 130e132.
[31] L.R. Falvello, J. Forniés, J. Gómez, E. Lalinde, A. Martín, F. Martínez,
M.T. Moreno, J. Chem. Soc. Dalton Trans. (2001) 2132e2140.
[32] J.R. Galsworthy, C.E. Housecroft, A.L. Rheingold, J. Chem. Soc. Dalton Trans.
(1996) 2917e2922.
[33] S.L. James, E. Lozano, M. Nieuwenhuyzen, Chem. Commun. (2000) 617e618.
[34] O. Orama, J. Organomet. Chem. 314 (1986) 273e279.
[35] E. Louattani, J. Suades, K. Urtiaga, M. Arriortua, X. Solans, Organometallics 15
(1996) 468e471.
[36] G. Hogarth, T. Norman, J. Chem. Soc. Dalton Trans. (1996) 1077e1085.
[37] M. Albrecht, R.A. Gossage, U. Frey, A.W. Ehlers, E.J. Baerends, A.E. Merbach,
G. Van Koten, Inorg. Chem. 40 (2001) 850e855.
[38] M. Hissler, J.E. McGarrah, W.B. Connick, D.K. Geiger, S.D. Cummings,
R. Eisenberg, Coord. Chem. Rev. 208 (2000) 115e137.
Acknowledgments
This work has been supported by Shiraz University and the Iran
National Science Foundation (Grant No. 90005392). We are grateful
to M. Golbon Haghighi for valuable suggestions and Dr. H. R.
Shahsavari for helpful assistance. We thank University of Isfahan,
for the diffractometer facility.
Appendix A. Supplementary material
[39] S.W. Lai, T.C. Cheung, M.C.W. Chan, K.K. Cheung, S.M. Peng, C.M. Che, Inorg.
Chem. 39 (2000) 255e262.
[40] H. Jude, J.A.K. Bauer, W.B. Connick, Inorg. Chem. 44 (2005) 1211e1220.
[41] H. Yersin, Highly Efficient OLEDs with Phosphorescent Materials, Wiley-VCH,
2008.
CCDC 928600 and 930544 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
[42] R.C. Evans, P. Douglas, C.J. Winscom, Coord. Chem. Rev. 250 (2006) 2093e
2126.
[43] D.N. Kozhevnikov, V.N. Kozhevnikov, M.M. Ustinova, A. Santoro, D.W. Bruce,
B. Koenig, R. Czerwieniec, T. Fischer, M. Zabel, H. Yersin, Inorg. Chem. 48
(2009) 4179e4189.
[44] J. Schneider, P. Du, X. Wang, W.W. Brennessel, R. Eisenberg, Inorg. Chem. 48
(2009) 1498e1506.
[45] A.F. Rausch, U.V. Monkowius, M. Zabel, H. Yersin, Inorg. Chem. 49 (2010)
7818e7825.
[46] M. Ghedini, T. Pugliese, M. La Deda, N. Godbert, I. Aiello, M. Amati, S. Belviso,
F. Lelj, G. Accorsi, F. Barigelletti, Dalton Trans. (2008) 4303e4318.
[47] T. Calvet, M. Crespo, M. Font-Bardia, K. Gómez, G. González, M. Martínez,
Organometallics 28 (2009) 5096e5106.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.07.032.
References
[1] S.N. Semenov, O. Blacque, T. Fox, K. Venkatesan, H. Berke, J. Am. Chem. Soc.
132 (2010) 3115e3127.
[48] C.K. Koo, K.L. Wong, K.C. Lau, W.Y. Wong, M.H.W. Lam, Chem. Eur. J. 15 (2009)
7689e7697.
[49] A.A. Rachford, F.N. Castellano, Inorg. Chem. 48 (2009) 10865e10867.
[50] S.K. Yen, D.J. Young, H.V. Huynh, L.L. Koh, T.S.A. Hor, Chem. Commun. (2009)
6831e6833.
[2] K.-J. Wei, J. Ni, Y. Liu, Inorg. Chem. 49 (2010) 1834e1848.
[3] B. Xi, I.P.-C. Liu, G.-L. Xu, M.M. Choudhuri, M.C. DeRosa, R.J. Crutchley, T. Ren,
J. Am. Chem. Soc. 133 (2011) 15094e15104.
[4] J.L. Chen, L.Y. Zhang, Z.N. Chen, L.B. Gao, M. Abe, Y. Sasaki, Inorg. Chem. 43
(2004) 1481e1490.
[51] M. Lopez-Torres, A. Fernandez, J.J. Fernandez, A. Suarez, S. Castro-Juiz,
J.M. Vila, M.T. Pereira, Organometallics 20 (2001) 1350e1353.
[52] P.A. Chase, R.J.M. Gebbink, G. van Koten, J. Organomet. Chem. 689 (2004)
4016e4054.
[53] H.P. Dijkstra, C.A. Kruithof, N. Ronde, R. van de Coevering, D.J. Ramón, D. Vogt,
G.P.M. van Klink, G. van Koten, J. Org. Chem. 68 (2003) 675e685.
[54] M.G. Haghighi, M. Rashidi, S.M. Nabavizadeh, S. Jamali, R.J. Puddephatt, Dalton
Trans. 39 (2010) 11396e11402.
[5] K.D. Demadis, C.M. Hartshorn, T.J. Meyer, Chem. Rev. 101 (2001) 2655e2686.
[6] F.A. Cotton, C. Lin, C.A. Murillo, Acc. Chem. Res. 34 (2001) 759e771.
[7] F. Barigelletti, L. Flamigni, Chem. Soc. Rev. 29 (2000) 1e12.
[8] W. Kaim, A. Klein, M. Glockle, Acc. Chem. Res. 33 (2000) 755e763.
[9] R.L. Carroll, C.B. Gorman, Angew. Chem. Int. Ed. 41 (2002) 4378e4400.
[10] P.J. Steel, Acc. Chem. Res. 38 (2005) 243e250.
[11] Y.C. Liu, C.I. Li, W.Y. Yeh, G.H. Lee, S.M. Peng, Inorg. Chim. Acta 359 (2006)
2361e2368.
[55] S. Jamali, Z. Mazloomi, S.M. Nabavizadeh, D. Milic, R. Kia, M. Rashidi, Inorg.
Chem. 49 (2010) 2721e2726.
[12] M. Ruben, J. Rojo, F.J. Romero-Salguero, L.H. Uppadine, J.M. Lehn, Angew.
Chem. Int. Ed. 43 (2004) 3644e3662.
[56] S.M. Nabavizadeh, M.G. Haghighi, A.R. Esmaeilbeig, F. Raoof, Z. Mandegani,
S. Jamali, M. Rashidi, R.J. Puddephatt, Organometallics 29 (2010) 4893e4899.
[57] S.M. Nabavizadeh, H. Amini, H.R. Shahsavari, M. Namdar, M. Rashidi, R. Kia,
B. Hemmateenejad, M. Nekoeinia, A. Ariafard, F.N. Hosseini, Organometallics
30 (2011) 1466e1477.
[13] Y. Hoshino, S. Higuchi, J. Fiedler, C.Y. Su, A. Knodler, B. Schwederski, B. Sarkar,
H. Hartmann, W. Kaim, Angew. Chem. Int. Ed. 42 (2003) 674e677.
[14] P.J. Mosher, G.P.A. Yap, R.J. Crutchley, Inorg. Chem. 40 (2001) 1189e1195.
[15] R. Dembinski, T. Bartik, B. Bartik, M. Jaeger, J. Gladysz, J. Am. Chem. Soc. 122
(2000) 810e822.
[58] X-AREA Stoe & Cie, Version 1.52: Program for the Acquisition and Data
Analysis, Stoe & Cie GmbH, Darmstadt, Germany, 2009.
[16] F. Paul, W.E. Meyer, L. Toupet, H. Jiao, J.A. Gladysz, C. Lapinte, J. Am. Chem. Soc.
122 (2000) 9405e9414.
[59] R.H. Blessing, Acta Crystallogr. Sect. A Found Crystallogr. 51 (1995) 33e38.
[60] A.L. Spek, Acta Crystallogr. Sect. D Biol. Crystallogr. 65 (2009) 148e155.
[61] G.M. Sheldrick, Acta Crystallogr. Sect. A Found Crystallogr. 64 (2008) 112.
[62] J.D. Scott, R.J. Puddephatt, Organometallics 2 (1983) 1643e1648.
[63] P.K. Monaghan, R.J. Puddephatt, Organometallics 3 (1984) 444e449.
[64] S. Jamali, S.M. Nabavizadeh, M. Rashidi, Inorg. Chem. 44 (2005) 8594e8601.
[65] S.J. Hoseini, S.M. Nabavizadeh, S. Jamali, M. Rashidi, Eur. J. Inorg. Chem. 2008
(2008) 5099e5105.
[17] T. Ren, G. Zou, J.C. Alvarez, Chem. Commun. (2000) 1197e1198.
[18] K.T. Wong, J.M. Lehn, S.M. Peng, G.H. Lee, Chem. Commun. (2000) 2259e2260.
[19] J. Bear, B. Han, Z. Wu, E. Van Caemelbecke, K. Kadish, Inorg. Chem. 40 (2001)
2275e2281.
[20] F.A. Cotton, J.P. Donahue, C.A. Murillo, J. Am. Chem. Soc. 125 (2003) 5436e
5450.
[21] S. Bhargava, K. Kitadai, T. Masashi, D.W. Drumm, S.P. Russo, V.W.-W. Yam,
T.K.-M. Lee, J. Wagler, N. Mirzadeh, Dalton Trans. 41 (2012) 4789e4798.
[22] A. Fazal, B.E. Ali, L. Ouahab, M. Fettouhi, Polyhedron 49 (2013) 7e11.
[23] M.A. Bennett, J. Castro, A.J. Edwards, M.R. Kopp, E. Wenger, A.C. Willis,
Organometallics 20 (2001) 980e989.
[66] S. Jamali, S.M. Nabavizadeh, M. Rashidi, Inorg. Chem. 47 (2008) 5441e5452.
[67] T.G. Appleton, M.A. Bennett, I.B. Tomkins, J. Chem. Soc. Dalton Trans. (1976)
439e446.
[68] M. Shimura, J.H. Espenson, Inorg. Chem. 23 (1984) 4069e4071.
[69] S.M. Nabavizadeh, M.D. Aseman, B. Ghaffari, M. Rashidi, F.N. Hosseini,
G. Azimi, J. Organomet. Chem. 715 (2012) 73e81.
[70] M. Werner, C. Bruhn, D. Steinborn, Trans. Met. Chem. 34 (2009) 61e74.
[71] T. Calvet, M. Crespo, M. Font-Bardía, S. Jansat, M. Martínez, Organometallics 31
(2012) 4367e4373.
[24] K.S. Shin, K.I. Son, J.I. Kim, C.S. Hong, M. Suh, D.Y. Noh, Dalton Trans. (2009)
1767e1775.
[25] A.K. Powell, M.J. Went, J. Chem. Soc. Dalton Trans. (1992) 439e445.
[26] J.-C. Daran, E. Cabrera, M.I. Bruce, M.L. Williams, J. Organomet. Chem. 319
(1987) 239e246.
[27] G. Hogarth, T. Norman, Polyhedron 15 (1996) 2859e2867.