Mononuclear cycloplatinated complexes derived from 2-tolylpyridine with N-donor ligands: Reactivity and structural characterization

Article abstract of DOI:10.1016/j.poly.2011.11.055

The cycloplatinated dichloro-bridged complex [(2-Tolpy)Pt(μ-Cl)] ₂ (1), obtained by treatment of 2-tolylpyridine with K ₂PtCl₄, reacts with different N-donor ligands in a 1:2 molar ratio in chloroform to give the correspon

Full text of DOI:10.1016/j.poly.2011.11.055

Polyhedron 33 (2012) 13–18
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Mononuclear cycloplatinated complexes derived from 2-tolylpyridine with
N-donor ligands: Reactivity and structural characterization
a
a
a
Antonio Rodríguez-Castro a, , Alberto Fernández , Margarita López-Torres , Digna Vázquez-García ,
⇑
Leticia Naya a, José Manuel Vila b,1, Jesús J. Fernández a,
⇑
a Departamento de Química Fundamental, Universidade da Coruña, E-15008 La Coruña, Spain
b Departamento de Química Inorgánica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 July 2011
Accepted 2 November 2011
Available online 9 December 2011
The cycloplatinated dichloro-bridged complex [(2-Tolpy)Pt(l-Cl)]2 (1), obtained by treatment of 2-tolyl-
pyridine with K2PtCl4, reacts with different N-donor ligands in a 1:2 molar ratio in chloroform to give the
corresponding mononuclear complexes [(2-Tolpy)Pt(L)Cl] [L = pyridine (2), 2-trifluoromethylpyridine (3),
3-trifluoromethylpyridine (4), 4-trifluoromethylpyridine (5), 2,6-dibromopyridine (6), 2-tolylpyridine (7)
and morpholine (8)]. Compounds 2–5 and 8 exist as a single isomer in solution which show a trans-C,Cl
geometry. In the case of compounds 6 and 7 a mixture of two isomers (trans-C,Cl and trans-C,L) was
obtained and its relative ratio depends on the temperature. The crystal and molecular structures of com-
pounds 5 and 7 were determined by X-ray crystallography.
Keywords:
Cyclometallation
Platinum
N-donor ligands
Isomerization
Ó 2011 Published by Elsevier Ltd.
1. Introduction
as solubility and stability. Furthermore, a number of sensors for
biomolecules [6], gases and organic vapours have been obtained
The tendency of transition metal salts to give cyclometallated
complexes with heteroaromatic ligands is well documented. Most
of these complexes are halogen-bridged dimers. However, mono-
nuclear complexes with the general formula [M(C^N)LX] (M = Pd,
Pt; C^N = orthometallated ligand; L = neutral monodentate ligand;
X = halide ligand) have also been reported [1]. Pt(II) derivatives
have been the most widely studied in recent years, one of the rea-
sons is the interesting range of properties that platinum complexes
exhibit, such as the efficient emission from triplet excited states
which is extremely useful in order to incorporate these systems
into organic light emitting devices (OLEDs) [2,3]. Another reason
is that square-planar Pt(II) compounds may coordinate different
substrates through covalent interactions and undergo inner-sphere
interactions and atom transfer reactions.
It has been reported that heteroleptic complexes with a cyclo-
metallated ligand and a non-cyclometallated ancillary chelate offer
a number of advantages over the corresponding homoleptic com-
plexes [4]. Moreover, the synthesis of heteroleptic complexes re-
quires milder reaction conditions and the yields are generally
higher than for homoleptic complexes [5]. The appropriate choice
of ligands is also a means to achieve interesting properties such
using these materials [7].
The photophysical properties of the corresponding complexes
depend to a large extent on the withdrawing or donating character
of the ligand [8]. This is due to the influence of the ligand on the
relative electron density at the metal centre, which modifies the
quantity of metal-to-ligand charge transfer (MLCT) character in
the lowest energy transition state and, as a result, may alter the
relative energy and lifetime of the excited state [5,9]. These aspects
can therefore be used to tune the complexes in order to achieve the
desired characteristics [8,10], and phosphorescent N,C,N-coordi-
nated Pt(II) complexes [11] have proven to be excellent emitters
for OLEDs [12]. An efficient method to enhance the luminescence
quantum yields by preventing non-radioactive decay is the use of
ligands with a very strong ligand-field, e.g. with a metallated aro-
matic carbon bonded to the platinum centre [13]; thus, wide
ranges of emission wavelengths, decay times and quantum yields
have been reported [14]. Furthermore, cycloplatinated complexes
have become the focus of scientific interest because of their poten-
tial antitumoral activity [15].
In this paper we present the synthesis and characterization of
several platinum complexes derived from 2-tolylpyridine and dif-
ferent monodentate N-donor ligands. The influence of the steric
requirements on the structure is also described and some com-
pounds show dynamic behaviour in solution that involves two dif-
ferent isomers. The molecular structures of some of the complexes
are also reported.
⇑
Corresponding authors. Fax: +34 981 167065.
E-mail address: lujjfs@udc.es (J.J. Fernández).
Fax: +34 981 597525.
1
0277-5387/$ - see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.poly.2011.11.055

14
A. Rodríguez-Castro et al. / Polyhedron 33 (2012) 13–18
The IR spectra of the compounds showed a characteristic band
at 1605–1609 cmꢀ1 assigned to
C@N, similar to that found in plat-
2. Results and discussion
m
inum complexes containing heterocyclic cyclometallated ligands
[18,19]; for compounds 2–7 an additional band was observed at
1587–1591 cmꢀ1 assigned to the C@N group of the coordinated
pyridine ligands [20], which was shifted as a consequence of the
Pt–N bond formation [21,22]. The IR spectrum of complex 8
showed a band at 3185 cmꢀ1 assigned to the N–H stretching vibra-
2.1. Mononuclear cycloplatinated complexes
For the convenience of the reader the compounds and reactions
are shown in Scheme 1. The compounds described in this paper
were characterized by elemental analysis (C, H, N), mass spectrom-
etry, and IR and 1H, 13C–{1H}, 19F and 195Pt NMR spectroscopy
(data in Section 3).
tion of the morpholine ligand (cf. m
N–H 3500–3310 cmꢀ1 for second-
ary amines) consistent with Nmorpholine–Pt bond formation.
The signals in the 1H NMR spectra were assigned on the basis of
the chemical shifts observed for similar complexes [24–26]. The
resonances attributed to the protons adjacent to the five-mem-
bered metallacylce (H2 and H11) showed the satellites due to the
coupling with 195Pt [3J(Pt–H) = 19–24 Hz].
The H11 resonance for complexes 2, 4, 5 and 8 was high-field
shifted (6.08–6.14 ppm, 2, 4 and 5; 6.97 ppm, 8). The greater shift
observed for 2, 4 and 5 was attributed to the shielding effect of the
aromatic ring of the pyridine ring situated cis to the metallated C12
carbon [25,27,28]. The spectra of complexes 2, 4, 5 and 8 showed
the H2 signal at 9.51–9.67 ppm low-field shifted due to the proxim-
ity of the pyridine nitrogen atom. The 1H NOESY spectra showed
close contacts between the hydrogen atoms of the pyridine coli-
gand and the H11 hydrogen atom of the cycloplatinated ligand
(e.g. in the spectrum for 4 a weak correlation between H24-CF3py
and H11 could be distinguished). These data confirm the isolation
of the compound with a pyridine coligand trans to nitrogen
The dichloro-bridged dinuclear complex [(2-Tolpy)Pt(l-Cl)]2 (1)
was obtained by heating 2-tolylpyridine with potassium tetrachlo-
roplatinate(II) at 65 °C for 8 h in water/ethanol (see data in Section
3). Related cycloplatinated compounds derived from different het-
erocyclic systems including phenylpyridine have been obtained
using K2PtCl4 but with ethylene glycol or a mixture of 2-ethoxyeth-
anol/water as solvent [16].
Treatment of the cycloplatinated dichloro-bridged dinuclear
complex[(2-Tolpy)Pt(l-Cl)]2 (1)with N-donorligands ina 1:2 molar
ratio in chloroform gave the corresponding mononuclear complexes
[(2-Tolpy)Pt(L)Cl] [L = pyridine (2), 2-trifluoromethylpyridine (3),
3-trifluoromethylpyridine (4), 4-trifluoromethylpyridine (5),
2,6-dibromopyridine (6), 2-tolylpyridine (7) and morpholine (8)].
The microanalytical data were consistent with the empirical
formula (see Section 3). The MS-FAB spectra showed the character-
istic clusters of isotopic peaks due to the presence of the numerous
platinum isotopes, and they were assigned to [M]+, [(2-Tol-
py)Pt(L)]+ and [(2-Tolpy)Pt]+ ions [17].
R2
R1
N
2: R1 = R2 = H
4: R1 = CF3, R2 =H
5: R1 = H, R2 =CF3
Cl
N
Pt
CF3
Pt
Cl
N
N
ii
3
iii
Me
10
O
11
12
9
8
Cl
N
i
iv
7
Pt
H
6
2
Pt
5
4
N
N
Cl
N
2
1
3
8
v
10'
7'
R1
11'
9'
N
8'
12' Cl
Pt
R2
Pt
R2
6'
Cl
N
5'
4'
N
N
R1
2'
3'
6: R1 = R2 = Br
7: R1 = H, R2 = p-MeC6H4
Scheme 1. (i) K2PtCl4, EtOH/H2O, 65 °C, 8 h; (ii) L, CHCl3, r.t., 2 h; (iii) 2-CF3Py, CHCl3, reflux, 24 h; (iv) HN(CH2CH2)2O, CHCl3, r.t., 2 h; (v) 2,6-Br2Py, CHCl3, reflux, 24 h (6);
2-TolPy, CH2Cl2, r.t., 2 h (7).

A. Rodríguez-Castro et al. / Polyhedron 33 (2012) 13–18
15
disposition, in agreement with the trans-choice model [29] accord-
ing to which in square planar Pd(II) complexes the ligand with the
hardest donor atom choose as ancillary ligand in trans position the
ligand with the softer one.
with a trans-N,N geometry for compound 7 could be determined
by X-ray single-crystal diffraction (vide infra).
2.2. X-ray diffraction analysis
The 13C NMR resonances, including the Pt satellites, were in
accordance with the proposed structures (see Section 3) with the
C2 and C12 carbons showing the most noticeable low field shifts.
In the case of complex 5 the expected quadruplet for the –CF3
group [J(CF) = 3.53 Hz] was observed [23]. The 19F NMR spectra
of compounds 4 and 5 showed a singlet resonance which was
assigned to the CF3 groups (ꢀ62.99, 4 and ꢀ65.41, 5, ppm). The
chemical shifts in the 195Pt NMR spectra of the complexes
appeared between ꢀ3266 and ꢀ3200 ppm.
Suitable crystals of compounds 5 and 7 were obtained by
recrystallization from dichloromethane/hexane. Both crystals con-
sisted of discrete molecules separated by typical van der Waals dis-
tances. The molecular structures of the complexes together with
the labelling schemes used are given in Figs. 1 and 2, respectively.
Selected bond distances and angles are given in Table 1. Crystallo-
graphic data are listed in Table 2.
The crystal structures of complexes [(2-Tolpy)Pt(4-CF3py)Cl] (5)
However, the 1H NMR spectrum of compound 3 showed the H2
and H11 resonances, at 8.88 [3J(PtH2) = 22.71 Hz] and 7.66 ppm,
respectively; we suggest these data are in accordance with the pyr-
idine ligand in a cis to nitrogen disposition. The 1H NOESY spec-
trum showed a weak correlation between H62-CF3py and H2,
which is in agreement with the proposed structure. The 19F NMR
spectrum showed a singlet at ꢀ100.29 for the CF3 group; the
195Pt NMR spectrum showed a signal at ꢀ3540 ppm. The 1H NMR
spectra for complexes 2–5 and 8 recorded at high temperature
showed no substantial changes.
and [(2-Tolpy)Pt(TolpyH-j
1N)Cl] (7) consist of one and two mono-
nuclear molecules per asymmetric unit, respectively. In both cases
the platinum atom is in a slightly distorted square-planar coordi-
nation environment and is bonded to an adjacent ortho-carbon
atom and to the nitrogen atom of the 2-tolylpyridine ligand, a
nitrogen atom (trans to N, from the 4-CF3-pyridine ring in 5 and
from the 2-tolylpyridine coligand in 7) and to a chlorine atom
(trans to C). The sum of the angles around the metal centre is very
close to 360°, with the most noticeable distortion in the somewhat
reduced ‘‘bite’’ angle upon chelation. The requirements of the five-
membered chelate ring force the C(1)–Pt(1)–N(1) bond angle to
80.5(3)° (5) and to 81.51(12)° and 81.48(12)° [7, for Pt(1) and
Pt(2), respectively].
In all of the molecules the phenyl and the pyridine rings of the
cyclometallated ligand are almost coplanar, with a dihedral angle
of 4.62° (5) and 3.20° and 2.86° (7). In complex 5 the platinum
atom, the metallated carbon atom and both nitrogen atoms are
almost coplanar, and the chlorine atom is located 0.448 Å above
the plane defined by aforementioned atoms. In complex 7 the dis-
placement is smaller (0.205 and 0.07 Å), i.e. in one of the molecules
the chlorine atom is almost coplanar with the aforementioned
atoms.
In complex 5 the 4-CF3py ring is tilted with respect to the cyclo-
metallated 2-Tolpy moiety, with an angle between these planes of
60.34°. In complex 7 the values for the dihedral angles described
by the two rings of the non-cyclometallated 2-tolylpyridine ligand
and the cyclometallated ring are 44.25° and 43.28°.
The Pt–C bond lengths are 2.004(8) Å for 5 and 1.985(3) and
1.982(3) Å for 7 and these are within the range of values obtained
for analogous complexes in which a trans-C,Cl geometry is present
[1c,d,25,30,31]. These values are consistent with a reinforced bond
For 6 and 7 the 1H and 13C NMR spectra showed two sets of sig-
nals attributable to the presence of two isomers in solution (see
Section 3). For the convenience of the reader, the protons of one
isomer are denoted as Hx and Hxpy (for the protons corresponding
to the cyclometallated moiety and to the pyridine ligand, respec-
0
tively) whereas for the other isomer they are denoted as Hx and
0
H
x py, (also, respectively). The most noticeable difference between
0
0
the two sets of signals was for the H2/H2 and H11/H11 resonances.
The signals corresponding to H2 and H11 protons in one of the sets
appeared at similar chemical shifts to those observed for 2, 4 and 5
(vide supra) and consequently are consistent with a N-trans-N
arrangement.
In the other set of signals the resonance coupled to the 195Pt nu-
0
cleus, assigned to the H2 proton was only slightly high-field shifted
0
(ca. 0.3 ppm), but the singlet assigned to H11 appeared low-field
shifted by more than 1 ppm as compared to H11 (at 7.26 and
7.59 ppm for 6 and 7, respectively) and did not show coupling to
the platinum nucleus. These results are in agreement with a
N-cis-N arrangement, in which the shielding effect of the pyridine
0
ring does not affect the H11 proton. The cis/trans molar ratio was
1:1 for both complexes, as calculated from the integrals in the 1H
NMR spectra.
through
p back donation.
The high temperature 1H NMR spectrum of 6 was unchanged in
comparison to the room temperature one. However, in the case of
complex 7, the high temperature 1H NMR spectrum showed in-
crease in the amount of the trans isomer (a 1:2 cis/trans ratio
was determined). When the solution of complex 7 was cooled to
room temperature the high temperature spectrum did not change.
Different condition reactions, e.g., increasing the reaction time or
refluxing the corresponding mixtures, were tested, but substantial
changes were not observed.
These results were in contradiction with the trans-choice model
(vide supra). In the case of complexes 6 and 7 the trans disposition
is only partially achieved and the two theoretical isomers were
observed in solution and, in the case of 3, only the cis isomer
was detected. It has been reported that the steric effects may play
an essential role in the geometry of pyridine complexes [20] and
consequently we suggest that this behaviour may be attributable
to steric requirements of pyridine coligands in which the substitu-
ents are adjacent to the coordinated nitrogen (CF3, 3; Br, 6;
p-MeC6H4, 7). The cis arrangement may ease the steric repulsion
between this substituent and the methyl group of the p-tolyl-
cyclometallated ring [20]. The molecular structure of the isomer
Fig. 1. Crystal structure of [(2-Tolpy)Pt(4-CF3py)Cl] (5), with labelling scheme.
Hydrogen atoms have been omitted for clarity.

16
A. Rodríguez-Castro et al. / Polyhedron 33 (2012) 13–18
Table 2
Crystal data and structure refinement data for complexes 5 and 7.
Complex
5
7
Empirical formula
Formula mass
Crystal system
Space group
Unit cell dimensions
a (Å)
C
18H14ClF3N2Pt
C24H21ClN2Pt
567.97
545.85
monoclinic
P2(1)
triclinic
ꢀ
P1
4.7616(3)
13.5232(8)
13.1212(8)
90
96.248(4)
90
839.88(9)
2
2.158
11.0507(4)
14.1465(5)
14.3145(5)
67.520(2)
79.671(2)
89.157(2)
2030.65(12)
4
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg mꢀ3
)
1.858
7.053
l
(Mo K
a
) (mmꢀ1
)
8.546
F(000)
516
1096
Crystal size (mm)
T (K)
0.20 ꢁ 0.07 ꢁ 0.03
100(2)
11123
4047
0.993
0.0365
0.0789
0.30 ꢁ 0.16 ꢁ 0.08
100(2)
No. of reflections collected
No. of independent reflections
Goodness of fit (GOF) on F2
Ra
36506
10013
1.097
0.0186
Fig. 2. Crystal structure of [(2-Tolpy)Pt(TolpyH-j
1N)Cl] (7), with labelling scheme.
Hydrogen atoms have been omitted for clarity.
b
wR2
0.0499
a
R1
wR2 = [
=
R
||Fo|-|Fc||/
R
R
|Fo|, [F >4
r(F)].
b
[w(Fo2-Fc2)2/
R
w(Fo2)2]1/2], all data.
Table 1
Selected bond lengths (Å) and angles (°) for complexes [(2-Tolpy)Pt(4-CF3py)Cl] (5)
and [(2-Tolpy)Pt(TolpyH-j
1N)Cl] (7).
spectrometer with a Cs ion-gun and 3-NBA matrix. NMR spectra
were obtained as CDCl3 or CD3CN solutions and were recorded
on a Bruker AC-200F spectrometer (200.0 MHz for 1H, 50.3 MHz
for 13C–{1H}, 188.3 MHz for 19F). 195Pt NMR spectra were recorded
on a Bruker DRX-500 spectrometer (107.5 MHz, using a saturated
solution of K2PtCl4 in D2O as internal standard).
5
7
C(1)–Pt(1)
N(1)–Pt(1)
N(2)–Pt(1)
Cl(1)–Pt(1)
C(25)–Pt(2)
N(3)–Pt(2)
N(4)–Pt(2)
Cl(2)–Pt(2)
C(1)–Pt(1)–N(1)
C(1)–Pt(1)–N(2)
N(1)–Pt(1)–N(2)
C(1)–Pt(1)–Cl(1)
N(1)–Pt(1)–Cl(1)
N(2)–Pt(1)–Cl(1)
C(25)–Pt(2)–N(3)
C(25)–Pt(2)–N(4)
N(3)–Pt(2)–N(4)
C(25)–Pt(2)–Cl(2)
N(3)–Pt(2)–Cl(2)
N(4)–Pt(2)–Cl(2)
2.004(8)
2.012(7)
2.020(7)
2.413(2)
1.985(3)
2.016(3)
2.038(3)
2.4091(8)
1.982(3)
2.017(3)
2.036(3)
2.4104(8)
81.51(12)
96.07(12)
173.41(10)
176.77(9)
95.50(8)
87.04(8)
81.48(12)
98.93(12)
177.22(10)
176.13(9)
95.53(8)
87.01(8)
3.2. Synthesis of the complexes
80.5(3)
95.9(3)
173.2(2)
172.1(2)
96.60(17)
87.68(18)
3.2.1. [(2-Tolpy)Pt(l-Cl)]2 (1)
K2PtCl4 (1.226 g, 2.95 mmol) was dissolved in the minimum
amount of warm water in a Schlenk vessel and 2-tolylpyridine
(500 mg, 2.95 mmol, 520 lL) in ethanol (40 ml) was added. The
resultant pink suspension was heated at 65 °C for 8 h under
Schlenk conditions and the resulting green-yellow suspension
was filtered off and the solid washed with hexane and Et2O. Yield:
975 mg (41.4%). Anal. Calc. for (C12H10NPtCl)2: C, 36.1; H, 2.5; N,
3.5. Found: C, 36.4; H, 2.3; N, 3.5%. FAB-Mass: 797 [M+]; 532 [(2-
Tolpy)2Pt]; 362 [(2-Tolpy)Pt]. IR (KBr, cmꢀ1): 3029 (w), 1608 (m).
The Pt–N bond lengths (see Table 1) of 2.012(7) and 2.020(7) Å
are in agreement with the expected values in complexes with an
N-trans-N arrangement [1d,c,5,25].
The Pt–Cl bond length, 2.413(2) Å, is in accordance with the
strong trans effect of the carbon atom [1d,c,25,30,31] and it is long-
er than the corresponding distance found in compounds with
N-donor atoms [18,32–34] or chlorine atoms [35] in a trans
disposition.
3.2.2. [2-(p-tolpy)PtPyCl] (2)
Complex 1 (100 mg, 0.125 mmol) was suspended in chloroform
and pyridine (21.82 mg, 0.276 mmol, 22.32 lL) was added. The ini-
tial suspension became a yellow solution immediately and the
mixture was stirred at room temperature for 2 h. The solvent
was removed under reduced pressure, the resulting yellow solid
was washed with Et2O and recrystallized from dichloromethane/
n-hexane. Yield: 66 mg (55.0%). Anal. Calc. for C17H15N2PtCl: C,
42.7; N, 5.8; H, 3.2. Found: C, 42.6; N, 5.7; H, 3.2%. FAB-Mass:
478 [M+]; 442 [(2-Tolpy)PtPy]; 363 [(2-Tolpy)Pt]. IR (KBr, cmꢀ1):
3024 (w), 1606 (s), 1587 (s). 1H NMR (CDCl3): d(ppm) = 9.67 (dd;
1H, H2; 3J(H2H3) = 5.8 Hz; 4J(H2H4) = 0.5 Hz; 3J(PtH2) = 21.7 Hz);
3. Experimental
3.1. General remarks
9.01 (dd with Pt; 2H; H2,6-py; 3J(H2,6-pyH3,5-py) = 6.5 Hz; 4J(H2,6-pyH4py
= 1.4 Hz; 3J(PtH2,6-py) = 21.4 Hz); 7.99 (d, 1H; H5; 3J(H5H4) =
)
Solvents were distilled prior use from appropriate drying agents
[36]. All chemicals were used as supplied from commercial sources
and were used without further purification. Elemental analyses (C,
H, N) were carried out on a Carlo-Erba 1108 elemental analyser. IR
spectra were recorded as KBr pellets on a Perkin-Elmer 1330 spec-
trophotometer. Mass spectra were obtained on a QUATRO mass
7.8 Hz); 7.91 (tt, 1H; H4-py;
3J(H4-pyH3,5-py) = 1.0 Hz); 7.78 (dd, 1H;
H4; 3J(H4H3) = 1.5 Hz); 7.44 (dd, 2H; H3,5-py); 7.37 (d, 1H; H9;
3J(H9H8) = 7.8 Hz;); 7.24 (dd, 1H; H3); 6.92 (d, 1H; H8); 6.14 (s,
broad; 1H, H11
d(ppm) = 154.08 (s,
;
3J(PtH11) = 23.9 Hz); 2.19 (s, CH3). 13C–{1H} NMR:
C
2,6-py); 151.29 (s, C2); 125.95 (s, C12;

A. Rodríguez-Castro et al. / Polyhedron 33 (2012) 13–18
17
J(PtC12) = 22.1 Hz); 21.80 (s, CH3); rest of aromatic carbons:
142.10–117.87 ppm. 195Pt NMR: d(ppm) = ꢀ3266.
J(CF) = 3.5 Hz); rest of aromatic carbons: 142.04–117.98; 21.81
(CH3). 19F NMR (CDCl3): d = ꢀ65.41 ppm. 195Pt NMR: d(ppm)
ꢀ3257. Crystals suitable for X-ray diffraction studies were ob-
tained by recrystallization from a CH2Cl2/hexane solution.
3.2.3. [(2-Tolpy)Pt(2-CF3py)Cl] (3)
2-Trifluoromethylpyridine (36.7 mg, 0.125 mmol, 29.7 lL) was
added to a suspension of 1 (100 mg, 0.125 mmol) in chloroform.
The mixture was stirred and heated under reflux for 24 h. The
resulting solid was filtered off and washed with Et2O and hexane.
Yield: 59 mg (43.2%). Anal. Calc. for C18H14F3N2PtCl: C, 39.6; N,
5.1; H, 2.6. Found: C, 39.9; N, 5.3; H, 2.4%. FAB-Mass: 544 [M+].
IR (KBr, cmꢀ1): 3027 (w), 1651 (s), 1607 (s), 1588 (s). 1H NMR
(CD3CN): d(ppm) = 9.48 (broad, 1H, H6py), 8.80 (dd; 1H, H2;
3J(H2H3) = 5.5 Hz; 3J(PtH2) = 22.7 Hz); 8.00 (dd, 1H; H4;
3J(H4H5) = 7.8 Hz; 3J(H4H3) = 1.2 Hz); 7.90 (broad, 1H, H3py), 7.77
(d, 1H; H5); 7.66 (s, 1H; H11); 7.55 (broad, 2H, H3py, H4py), 7.40
(d, 1H; H9; 3J(H9H8) = 7.9 Hz); 7.18 (dd, 1H; H3); 6.94 (d, 1H; H8);
3.2.6. [(2-Tolpy)Pt(2,6-Br2py)Cl] (6)
A suspension of 1 (100 mg, 0.125 mol) in CHCl3 was treated
with 2,6-dibromopyridine (59.22 mg, 0.250 mmol) and this mix-
ture was stirred and heated under reflux for 24 h to give a yellow
solution. The solvent was removed under reduced pressure and the
resulting yellow oil triturated with Et2O and hexane to give an
olive green solid. Yield: 61 mg (38.4%). Anal.
Calc. for
C17H13N2Br2PtCl: C, 32.1; N, 4.4; H, 2.0. Found: C, 32.4; N, 4.7; H,
2.2%. FAB-Mass: 592 [(2-Tolpy)Pt(2,6-Br2py)]; 532 [(2-Tolpy)2Pt];
363 [(2-Tolpy)Pt]. IR (KBr, cmꢀ1): 3028 (w), 1605 (s), 1588 (s). 1H
NMR:
d(ppm) = 9.59
(dd;
1H,
H2;
3J(H2H3) = 5.8 Hz;
13C–{1H} NMR (CD3CN): d(ppm) = 168.69 (C2); 150.82 (s, C2py
2J(PtC2py) = 9.8 Hz); 133.59 (s; C12; J(PtC12) = 32.4 Hz); 124.59 (s;
C3py
3J(PtC3py) = 20.8 Hz); 122.68 (s; C6py 2J(PtC6py) = 19.4 Hz);
119.44 (s; C5py
;
4J(H2H4) = 0.8 Hz; 3J(PtH2) = 19.7 Hz); 9.23 (dd; 1H, H2 ;
0
3
3
3
0
0
0
0
0
J(H2 H3 ) = 5.9 Hz; J(H2 H4 ) = 0.9 Hz; J(PtH2 ) = 22.6 Hz); 7.99 (d,
;
;
2H; H3,5-py;
3J(H3,5-pyH4-py) = 8.0 Hz); 7.69 (t, 1H; H4-py); 7.91 (dd,
;
4J(PtC5py) = 22.2 Hz); rest of aromatic carbons:
broad; 1H, H4; 3J(H4H3) = 1.5 Hz); 7.46 (d, broad; 1H, H9;
143.79–125.71; 21.77 (CH3). 19F NMR (CD3CN): d = ꢀ100.29 ppm.
3J(H9H8) = 7.9 Hz); 7.33 (d, broad; 1H, H3); 7.26 (s, 1H, H11 ); 7.21
0
195Pt NMR: d(ppm) ꢀ3540.
(d, broad; 1H, H5; 3J(H5H4) = 7.2 Hz); 7.13 (d, 2H; H3,5-py
;
0
3J(H3,5-py H4py ) = 7.0 Hz); 7.01 (t, 1H; H4py ); 6.80 (d, broad; 1H,
H8); 6.00 (s; 1H, H11
3J(PtH11) = 24.2 Hz); 2.26 (s, 3H, CH3); 2.15
0
0
0
3.2.4. [(2-Tolpy)Pt(3-CF3py)Cl] (4)
;
3-Trifluoromethylpyridine (36.7 mg, 0.250 mmol, 29.71
l
L) was
(s, 3H, CH3). 13C–{1H} NMR: d(ppm) = 167.25 and 162.36 (C2,6-py);
154.34 and 151.12 (C2); 141.54–117.62 (rest of aromatic carbons);
21.82 and 21.41 (CH3). The 1H NMR spectrum at high temperature
in CDCl3 was also recorded and no changes were observed. 195Pt
NMR: d(ppm) ꢀ3201.
added to a suspension of 1 (100 mg, 0.125 mmol) in chloroform.
The initial green suspension became a yellow solution which was
stirred for 2 h at room temperature. The solvent was removed un-
der reduced pressure and the resulting green-yellow solid was
washed with Et2O and hexane. Yield: 99 mg (72.6%). Anal. Calc.
for C18H14F3N2PtCl: C, 39.6; N, 5.1; H, 2.6. Found: C, 39.4; N, 5.0;
H, 2.9%. FAB-Mass: 1054 [(2-Tolpy)2Pt2(3-CF3py)2Cl]; 545 [M+];
510 [(2-Tolpy)Pt(3-CF3py)]; 363 [(2-Tolpy)Pt]. IR (KBr, cmꢀ1):
3077 (w), 1609 (s), 1590 (s). 1H NMR (CDCl3): d(ppm) = 9.62 (dd;
1H; H2; 3J(H2H3) = 5.8 Hz; 4J(H2H4) = 0.7 Hz; 3J(PtH2) = 19.7 Hz);
3.2.7. [(2-Tolpy)Pt(TolpyH-
2-Tolylpyridine (42.50 mg, 0.250 mmol, 42.88
j
1N)Cl] (7)
lL) was added to
a suspension of 1 (100 mg, 0.125 mmol) was in dichloromethane.
The initial suspension became a yellow solution immediately
which was stirred at room temperature for 2 h. The mixture was
filtered and the solvent was removed under reduced pressure.
The resulting brown oil which was triturated with Et2O and hexane
to five a brown solid which was filtered off. Yield: 68.3 mg (48.1%).
Anal. Calc. for C24H21N2PtCl: C, 50.7; N, 4.9; H, 3.7. Found: C, 51.0;
N, 4.8; H, 3.8%. FAB-Mass: 567 [M+], 532 [(2-Tolpy)Pt(TolpyH-
9.34 (s, broad; 1H, H2py
H6py
3J(H6pyH5py) = 5.0 Hz; 3J(PtH6py) = 22.1 Hz); 8.17 (d, broad;
1H; H4py
3J(H4pyH3py) = 8.1 Hz; 5J(PtH4py) = 53.7 Hz); 7.79 (dd,
;
3J(PtH2py) = 23.3 Hz); 9.26 (d, broad; 1H;
;
;
1H; H5py); 7.62–7.59 (complicated multiplet; 2H, H3 and H4);
7.37 (d, 1H; H9; 3J(H9H8) = 7.9 Hz); 7.11 (d, 1H; H5;
3J(H5H4) = 6.6 Hz; 4J(H5H3) = 1.3 Hz); 6.92 (d, 1H; H8); 6.08 (s; 1H,
j
1N)]; 363[(2-Tolpy)Pt]. IR (KBr, cmꢀ1): 3031 (w), 1606 (s), 1591
H11
;
3J(PtH11) = 23.1 Hz); 2.19 (s, 3H; CH3). 13C–{1H} NMR (CDCl3)
(s). 1H NMR: d(ppm) = 9.58 (dd; 1H, H2; 3J(H2H3) = 5.9 Hz;
3
3J(PtH2) = 19.0 Hz); 9.23, (dd; 1H, H2 ;
J(H2 H3 ) = 5.9 Hz;
0
0
0
d(ppm) = 167.31 (C2py); 157.18 (C2); 121.50 (C12
;
J(PtC12) =
4
3
0
0
0
0
83.5 Hz); rest of the aromatic carbons: 151.50–118.00; 21.77
(CH3). 19F NMR (CDCl3): d = ꢀ62.99 ppm. 195Pt NMR: d(ppm)
ꢀ3260.
J(H2 H4 ) = 1.0 Hz; J(PtH2 ) = 10.9 Hz); 9.14; (m; 1H, H6py
;
3J(H6py H5py ) = 5.9 Hz; 4J(H6py H4py = 1.5 Hz; 5J(H6py H3py ) = 0.6 Hz;
0
0
0
0
0
0
3J(PtH6py ) = 18.5 Hz); 8.77 (s, broad; 1H, H6py); 7.59 (s, H11 ); 6.00
(s; 1H, H11; 3J(PtH11) = 23.9 Hz); 2.44, 2.41, 2.26, 2.15 (s, CH3). Rest
of aromatic protons: 8.13–6.63 ppm. 13C–{1H} NMR: d = 167.26–
117.62 (aromatic carbons); 21.81–20.27 (methyl groups). 195Pt
NMR: d(ppm) -3200 ppm. Crystals suitable for X-ray diffraction
studies were obtained by recrystallization from a CH2Cl2/hexane
solution.
0
0
3.2.5. [(2-Tolpy)Pt(4-CF3py)Cl] (5)
A suspension of 1 (100 mg, 0.125 mmol) in chloroform was
treated with 4-trifluoromethylpyridine (36.7 mg, 0.250 mmol,
29.85 lL). The resultant yellow solution was stirred for 2 h at room
temperature. The solvent was removed under reduced pressure to
give a green oil which was triturated with Et2O and hexane to give
a green-yellow solid, which was filtered off and dried in vacuo.
Yield: 48.5 mg (35.5%). Anal. Calc. for C18H14F3N2PtCl: C, 39.6; N,
5.1; H, 2.6. Found: C, 39.4; N, 5.1; H, 2.9%. FAB-Mass: 1054 [(2-Tol-
py)2Pt2(4-CF3py)2Cl]; 545 [M+]; 510 [(2-Tolpy)Pt(4-CF3py)]; 363
[(2-Tolpy)Pt]. IR (KBr, cmꢀ1): 3028 (w), 1609 (s), 1590 (s). 1H
NMR: d = 9.62 (d, broad; 1H, H2; 3J(H2H3) = 5.9 Hz; 3J(PtH2) =
19.7 Hz); 9.26 (d, 2H; H2,6-py 3J(H2,6pyH3,5-py) = 6.5 Hz;
3J(PtH2,6-py) = 22.3 Hz); 7.82 (dd, 1H; H4; 3J(H4H5) = 7.4 Hz;
3J(H4H3) = 1.5 Hz; 7.71 (d, 2H; H3,5-py); 7.60 (d, 1H; H5); 7.37 (d,
1H; H9; 3J(H9H8) = 7.9 Hz); 7.11 (dd, 1H; H3); 3J(H3H2) = 1.4 Hz;
3.2.8. [(2-Tolpy)Pt(morpholine-
The dimeric complex 1 (100 mg, 0.125 mmol) was suspended in
chloroform and morpholine (21.78 mg, 0.250 mmol, 21.86 L) was
j
1N)Cl] (8)
l
added. The initial suspension became an olive green solution,
which was stirred at room temperature for 2. The solvent was re-
moved under reduced pressure to give a green-yellow solid. Yield:
47 mg (38.7%). Anal. Calc. for C16H19N2PtClO: C, 39.53; N, 5.76; H,
3.91. Found: C, 36.80; N, 5.12; H, 3.64%. FAB-Mass 486 [M+]; 451
[(2-Tolpy)Pt(morpholine-j
1N)]; 363 [(2-Tolpy)Pt]. IR (KBr, cmꢀ1):
3185 (m), 2845 (m), 1605 (s), 1587 (s). 1H NMR: d = 9.57 (dd; 1H,
H2; 3J(H2H3) = 6.4 Hz; 4J(H2H4) = 0.8 Hz; 3J(PtH2) = 19.4 Hz); 7.74
(dd, 1H; H4; 3J(H4H5) = 7.2 Hz; 3J(H4H3) = 1.5 Hz); 7.56 (d, 1H; H9;
2J(H9H8) = 8.0 Hz); 7.39 (d, 1H, H8); 7.04 (dd, 1H; H3); 6.98 (d,
6.93 (d, 1H; H8); 6.11 (s; 1H, H11
NMR: d = 167.25 (s, C2); 155.24 (s; C3,5-py
151.30 (s; C2,6-py
2J(PtC2,6-py) = 9.8 Hz); 121.93 (q, CF3;
;
3J(PtH11) = 23.2 Hz). 13C–{1H}
3J(PtC3,5-py) = 6.2 Hz);
;
;

18
A. Rodríguez-Castro et al. / Polyhedron 33 (2012) 13–18
[9] (a) K. Zhang, J. Hu, K.C. Chan, K.Y. Wong, J.H.K. Yip, Eur. J. Inorg. Chem. (2007)
1H; H5); 6.97 (s; 1H, H11;
3J(PtH11) = 21.5 Hz); 4.77 (s, broad; 1H,
384;
NH; 2J(PtHNH) = 81.7 Hz); 3.97–3.19 (m, 8H, morpholine
(b) Y. You, J. Seo, S.H. Kim, K.W. Kim, T.K. Ahn, D. Kim, S.Y. Park, Inorg. Chem.
47 (2008) 1476.
protons); 2.43 (s, 3H; CH3). 13C NMR–{1H}: d(ppm) = 166.75 (s,
[10] H. Yersin, K. Donges, W. Humbs, J. Strasser, Inorg. Chem. 41 (2002) 4915.
[11] J.A.G. Williams, Top. Curr. Chem. 281 (2007) 205.
[12] (a) M. Cocchi, D. Virgili, V. Fattori, D.L. Rochester, J.A.G. Williams, Adv. Funct.
Mater. 17 (2007) 285;
C2); 117.89 (s; C12
;
J(PtC12) = 21.5 Hz); 68.54 (s; C3,5-morphol
;
2J(PtC3,5-morphol) = 24.8 Hz); 51.82 (s; C2,6-morphol
;
3J(PtC2,6-morphol
)
= 7.1 Hz); 22.13 (s, CH3); rest of aromatic carbons: 151.42–
124.49 ppm. 195Pt NMR: d(ppm) ꢀ3222 ppm.
(b) M. Cocchi, J. Kalinowsky, D. Virgili, V. Fattori, S. Develay, J.A.G. Williams,
Appl. Phys. Lett. 90 (2007) 163508;
(c) M. Cocchi, D. Virgili, V. Fattori, J.A.G. Williams, J. Kalinowski, Appl. Phys.
Lett. 90 (2007) 023506.
[13] (a) T.K. Aldridge, E.M. Stacy, D.R. McMillin, Inorg. Chem. 23 (1984) 4249;
(b) F. Niedermair, O. Kwon, K. Zojer, S. Kappaun, G. Trimmel, K. Mereiter, C.
Slugovc, Dalton Trans. (2008) 4006.
3.2.9. X-ray crystallographic study
Three dimensional X-ray data were collected on Bruker Smart
1 K and Bruker AXS CCD diffractometers using graphite-monochro-
mated Mo Ka radiation. All the measured reflections were cor-
[14] (a) W. Lu, M.C. W Cham, K.-K. Cheung, C.-M. Che, Organometallics 20 (2001)
2477;
rected for Lorentz and polarization effects and for absorption by
semi-empirical methods based on symmetry-equivalent and re-
peated reflections. The structures were solved by direct methods
and refined by full matrix least-squares on F2.
Hydrogen atoms were included in calculated positions and re-
fined in riding mode. All non-hydrogen atoms were refined aniso-
tropically. The structure solution and refinement were carried out
using the program package SHELX-97 [37].
(b) J.F. Michaelec, S.A. Bejune, D.G. Cuttell, G.C. Summerton, J.A. Gertenbach,
J.S. Field, R.J. Haines, R.D. McMillin, Inorg. Chem. 40 (2001) 2193;
(c) H. Yersin, D. Donges, Top. Curr. Chem. 214 (2001) 81.
[15] (a) M.D. Hall, R.W. Humbley, Coord. Chem. Rev. 232 (2002) 46;
(b) T. Kostova, Recent Pat. Anti-Cancer Drug Discovery 1 (2006) 1.
[16] (a) J. Brooks, Y. Babayan, S. Lamanskym, P.I. Djurovich, I. Tsyba, R. Bau, M.E.
Thompson, Inorg. Chem. 41 (2002) 3055;
(b) H. Fukuda, Y. Yamada, D. Hashimuze, T. Takayama, M. Watabe, Appl.
Organomet. Chem. 23 (2009) 154.
[17] (a) L. Tusek-Bozic, M. Curic, P. Traldi, Inorg. Chim. Acta 254 (1997) 49;
(b) L. Tusek-Bozic, M. Komac, M. Curic, A. Lycka, M. Dálpaos, V. Scarcia, A.
Furlani, Polyhedron 19 (2000) 937.
Acknowledgements
[18] A. Zucca, S. Stoccoro, M.A. Cinellu, G. Minghetti, M. Manassero, M. Sansoni, Eur.
J. Inorg. Chem. (2002) 3336.
[19] K.-W. Tan, F. Liu, Y. Li, G.-K. Tan, P.-H. Leung, J. Organomet. Chem. 691 (2006)
4753.
[20] F.D. Rochon, M. Fakhfakh, Inorg. Chim. Acta 362 (2009) 1455.
[21] R.C. Paul, H.S. Makhni, P. Singh, S.L. Chadha, Z. Anorg. Allg. Chem. 37 (1970)
108.
We thank the Ministerio de Educación y Ciencia (Projects
CTQ2006-15621-C02-02/BQU, UDC, and CTQ2006-15621-C02-01/
BQU, USC) and the Xunta de Galicia (Ref. PGIDIT04PXI10301IF
and INCITE07PXI103083ES) for financial support.
[22] R.D. Kross, V.A. Fassel, M. Hargoshes, J. Am. Chem. Soc. 78 (1956) 1332.
[23] (a) A. Rodríguez, A. Sousa-Pedrares, J.A. García-Vázquez, J. Romero, A. Sousa,
Eur. J. Inorg. Chem. (2005) 2242;
Appendix Appendix. A. Supplementary data
(b) A. Rodríguez, A. Sousa-Pedrares, J.A. García-Vázquez, J. Romero, A. Sousa,
U. Russo, Eur. J. Inorg. Chem. (2007) 1444.
[24] P.-I. Kvam, J. Songstad, Acta Chem. Scand. 49 (1995) 313.
[25] M.M. Mdleleni, J.S. Bridgewater, R.J. Watts, P.C. Ford, Inorg. Chem. 34 (1995)
2334.
[26] S. Fernández, J. Forniés, B. Gil, J. Gómez, E. Lalinde, J. Chem. Soc., Dalton Trans.
(2003) 822.
[27] (a) G.L. Edwards, D.S.C. Black, G.B. Deacon, L.P.G. Wakelin, Can. J. Chem. 83
(2005) 980;
CCDC 791986 and 791987 contain the supplementary crystallo-
graphic data for 5 and 7. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
(b) G. Minghetti, S. Stoccoro, M.A. Cinellu, G.L. Petretto, A. Zucca,
Organometallics 27 (2008) 3415;
(c) A. Zucca, G.L. Petretto, S. Stoccoro, M.A. Cinellu, G. Minghetti,
Organometallics 25 (2006) 2253;
References
[1] (a) J.M. Vila, M. Gayoso, M.T. Pereira, A. Romar, J.J. Fernández, M. Thornton-
Pett, J. Organomet. Chem. 401 (1991) 385;
(d) P. Shao, W. Sun, Inorg. Chem. 46 (2007) 8603.
[28] (a) C. López, A. Caubet, S. Pérez, X. Soláns, M. Font-Bardía, J. Organomet. Chem.
681 (2003) 82;
(b) F. Niedermair, K. Waich, S. Kappaun, T. Mayr, G. Trimmel, K. Mereiter, C.
Slugovc, Inorg. Chim. Acta 360 (2007) 2767;
(b) A. Fernández, D. Vázquez-García, J.J. Fernández, M. López-Torres, A. Suárez,
S. Castro-Juiz, J.M. Vila, New J. Chem. 26 (2002) 398.
[29] J.V. Cuevas, G. García Herbosa, D. Miguel, A. Muñoz, Inorg. Chem. Commun. 5
(2002) 340.
[30] R. Martín, M. Crespo, M. Font-Bardia, T. Calvet, Organometallics 28 (2009) 587.
[31] A. Zucca, G.L. Petretto, S. Stoccoro, M.A. Cinellu, M. Manissero, C. Manissero, G.
Minghetti, Organometallics 28 (2009) 2150.
[32] C.-K. Koo, Y.-M. Ho, C.-F. Chow, M.H.-W. Lam, T.-C. Lau, W.-Y. Wong, Inorg.
Chem. 46 (2007) 3603.
[33] R. McGuire Jr., M.H. Wilson, J.J. Nash, P.E. Fanwick, D.R. McMillin, Inorg. Chem.
47 (2008) 2946.
(c) C.P. Newman, K. Casey-Green, G.J. Clarkson, G.W.V. Cave, W. Errington, J.P.
Rourke, Dalton Trans. (2007) 3170;
(d) N. Godbert, T. Pugliese, I. Aiello, A. Bellusci, A. Crispini, M. Ghedini, Eur. J.
Inorg. Chem. (2007) 5105.
[2] (a) E. Polikarpov, M.E. Thompson, Mater. Matters 2 (2007) 21;
(b) R.C. Evans, P. Douglas, C. Winscom, Coord. Chem. Rev. 250 (2006) 2093.
[3] H. Yersin (Ed.), Highly Efficient OLEDs with Phosphorescent Materials, Wiley-
VCH, Weinheim, 2008.
[4] J. Brooks, Y. Babayan, S. Lamansky, P.I. Djurovich, I. Tsyba, R. Bau, M.E.
Thompson, Inorg. Chem. 41 (2002) 3055.
[5] S.-Y. Chang, Y.-M. Cheng, Y. Chi, Y.-C. Lin, C.-M. Jiang, G.H. Lee, P.-T. Chou,
Dalton Trans. (2008) 6901.
[6] (a) W.D. McFadyen, L.P.G. Wakelin, I.A.G. Roos, B.L. Hillcoat, Biochem. J. 242
(1987) 177;
(b) H.Q. Liu, S.M. Peng, C.M. Che, J. Chem. Soc., Chem. Commun. (1995) 509;
(c) L. Monsú Scolaro, A. Romeo, A. Terracina, Chem. Commun. (1997) 1451.
[7] (a) Y. Kunigi, K.R. Mann, L.L. Miller, C.L. Exstrom, J. Am. Chem. Soc. 120 (1998)
589;
(b) W.W.W. Lee, K.Y. Wong, X.M. Li, Anal. Chem. 65 (1993) 255.
[8] F.-M. Hwang, H.-Y. Chen, P.-S. Chen, C.-S. Liu, Y. Chi, C.-F. Shu, F.I. Wu, P.-T.
Chou, S.-M. Peng, F.-H. Lee, Inorg. Chem. 44 (2005) 1344.
[34] T.V. Segapelo, I.A. Guzei, L.C. Spencer, W.E. Van Zyl, J. Darkwa, Inorg. Chim.
Acta 362 (2009) 3314.
[35] G.M. Rakic´, S. Grguric´-Šipka, G.N. Kaluderovic´, S. Gómez Ruiz, S.K. Bjelogrlic´,
ˇ
S.S. Radulovic´, Z.L. Tešic´, Eur. J. Med. Chem. 44 (2009) 1921.
[36] W.L.F. Armarego, C.L.L. Chai, Purification of Laboratory Chemicals, fifth ed.,
Butterworth–Heinemann, Bodmin, 2003.
[37] A short history of SHELX G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008)
112.