Pt(II) and Pd(II)-assisted coupling of nitriles and 1,3-diiminoisoindoline: Synthesis and luminescence properties of (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) and Pd(II) complexes

Article abstract of DOI:10.1016/j.poly.2017.05.036

Treatment of trans-[PtCl₂(NCR)₂] 1 (R?=?Me (1a), Et (1b), o-ClC₆H₄ (1c), p-ClC₆H₄ (1d), p-(HC[dbnd]O)C₆H₄ (1e), p-O₂NC₆H₄CH₂ (1f)) with 1,3-diiminoisoindoline HN[dbnd]CC₆H₄C(NH)[dbnd]NH 2 gives access to the corresponding (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes [PtCl{NH[dbnd]C(R)N[dbnd]C(C₆H₄)NC[dbnd]NC(R)[dbnd]NH}] 3a–f, in good yields (65–70%). The reaction of trans-[PdCl₂(NCMe)₂] 4a with 2 furnishes (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II) complex [PdCl{NH[dbnd]C(Me)N[dbnd]C(C₆H₄)NC[dbnd]NC(Me)[dbnd]NH}] 5a, in good yield (65%). However, the reaction of trans-[PdCl₂(NCR)₂] 4 (R?=?Ph (4b), p-MeC₆H₄CH₂ (4c), p-(HC[dbnd]O)C₆H₄ (4d), p-O₂NC₆H₄CH₂ (4e)) with 2 gives a number of unidentified products. The compounds 3a–f and 5a were characterized by IR,¹H,¹³C and DEPT-135 NMR spectroscopies, elemental analyses and, in the case of the Pt(II) complex [PtCl{NH[dbnd]C(Me)N[dbnd]C(C₆H₄)NC[dbnd]NC(Me)[dbnd]NH}] 3a, also by X-ray diffraction analysis. Compounds 3a and 3b were also characterized by UV–Vis absorption and luminescence emission spectroscopies. Emission quantum yields of ca. 3?×?10^?3 were obtained in dichloromethane solution, and luminescence lifetimes are in the order of the tens of nanoseconds. Both compounds also exhibited luminescence in solid state (polystyrene matrix), with luminescence lifetimes in the order of hundreds of nanoseconds.

Full text of DOI:10.1016/j.poly.2017.05.036

Polyhedron 133 (2017) 195–202
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Pt(II) and Pd(II)-assisted coupling of nitriles and 1,3-diiminoisoindoline:
Synthesis and luminescence properties of (1,3,5,7,9-pentaazanona-
1,3,6,8-tetraenato)Pt(II) and Pd(II) complexes
b
c
b
Jamal Lasri a, , Bruno Pedras , Matti Haukka , Mário N. Berberan-Santos
⇑
a Department of Chemistry, Rabigh College of Science and Arts, P.O. Box 344, King Abdulaziz University, Jeddah, Saudi Arabia
b Centro de Química-Física Molecular, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal
c University of Jyväskylä, Department of Chemistry, University of Jyväskylä, P.O. Box 35, FI-40014, Finland
a r t i c l e i n f o
a b s t r a c t
Article history:
Treatment of trans-[PtCl2(NCR)2] 1 (R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HC@O)C6H4 (1e),
p-O2NC6H4CH2 (1f)) with 1,3-diiminoisoindoline HN@CC6H4C(NH)@NH 2 gives access to the correspond-
ing (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes [PtCl{NH@C(R)N@C(C6H4)NC@NC(R)@
Received 24 January 2017
Accepted 20 May 2017
Available online 29 May 2017
NH}] 3a–f, in good yields (65–70%). The reaction of trans-[PdCl2(NCMe)2] 4a with
2 furnishes
(1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II) complex [PdCl{NH@C(Me)N@C(C6H4)NC@NC(Me)@
NH}] 5a, in good yield (65%). However, the reaction of trans-[PdCl2(NCR)2] 4 (R = Ph (4b), p-MeC6H4CH2
(4c), p-(HC@O)C6H4 (4d), p-O2NC6H4CH2 (4e)) with 2 gives a number of unidentified products. The com-
pounds 3a–f and 5a were characterized by IR, 1H, 13C and DEPT-135 NMR spectroscopies, elemental anal-
yses and, in the case of the Pt(II) complex [PtCl{NH@C(Me)N@C(C6H4)NC@NC(Me)@NH}] 3a, also by X-ray
diffraction analysis. Compounds 3a and 3b were also characterized by UV–Vis absorption and lumines-
cence emission spectroscopies. Emission quantum yields of ca. 3 Â 10À3 were obtained in dichloro-
methane solution, and luminescence lifetimes are in the order of the tens of nanoseconds. Both
compounds also exhibited luminescence in solid state (polystyrene matrix), with luminescence lifetimes
in the order of hundreds of nanoseconds.
Keywords:
Metal-assisted additions
Nitriles
1,3-Diiminoisoindoline
Pentaazanonatetraene complexes
Luminescence
Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction
and DFT [8] show that they have a greater capacity of coordination
to metal ions than b-diimines. Nevertheless, the coordination
Several methods to prepare coordination compounds by nucle-
ophilic additions to nitrile ligands have been developed during the
last two decades [1]. Various types of nucleophiles [2,3] or 1,3-
dipoles [4] have been used for the preparation of compounds con-
taining C–N and/or C–O bonds. 1,3-Diiminoisoindoline has been
used for the synthesis of pthalocyanines [5] and hemiporphyrazine
[6], which have a wide range of industrial applications. The imi-
noisoindoline-1-one, bearing a nucleophilic sp2-imino group, has
been used as a nucleophile in reaction with various metal-bound
isonitriles and nitriles to furnish iminocarbene or triazapentadien-
ato complexes, respectively [7]. However, 1,3-diiminoisoindoline
contains two sp2-nitrogen centres which can use both imine moi-
eties for additions to metal-coordinated nitriles, thus furnishing
symmetrical triazapentadienate complexes. In contrast to b-diimi-
nes, ligands such as triazapentadienes have one extra N donor site,
chemistry of triazapendiene species is less reported, due to the
instability of triazapentadiene complexes, particularly the unsub-
stituted ones [9]. A single-pot synthesis with electron-deficient
nitriles has been used to synthetize triazapentadiene complexes
[10]. Ni(II)-complexes bearing imidoylamidine ligands have been
prepared using oximes and nitriles in the presence of Ni(II) ions
[11], and this methodology has been used to synthetize a variety
of (1,3,5-triazapentadienato)Pd(II) complexes [12]. Recently, we
have also reported the synthesis of (alkoxy-1,3,5-triazapentadien-
ato)Cu(II) complexes using a template synthesis [13].
On the other hand, Pt(II)-based imidoylamidinate compounds
are emissive both in solid state and in solution, at room tempera-
ture. UV–Vis and luminescence spectroscopies indicate that the
lowest excited state of these complexes is 3MLCT or 3IL with signif-
icant MLCT character, with emission lifetimes of a few ms [14].
In continuation of our research program on the additions to
metal-bound nitriles [15], we decided to extend the addition of a
sp2-nitrogen nucleophile, 1,3-diiminoisoindoline HN@CC6H4C
⇑
Corresponding author.
E-mail address: jlasri@kau.edu.sa (J. Lasri).
http://dx.doi.org/10.1016/j.poly.2017.05.036
0277-5387/Ó 2017 Elsevier Ltd. All rights reserved.

196
J. Lasri et al. / Polyhedron 133 (2017) 195–202
(NH)@NH 2, (i) to various Pt(II)-bound nitriles trans-[PtCl2(NCR)2]
1 (R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HC@O)
C6H4 (1e), p-O2NC6H4CH2 (1f)); and (ii) to another type of metal
complex such as Pd(II)-bound acetonitrile trans-[PdCl2(NCMe)2]
4a; and also (iii) to investigate the UV–Vis absorption and the
luminescence emission spectra of some of those complexes. We
have thus observed the formation of (1,3,5,7,9-pentaazanona-
1,3,6,8-tetraenato)Pt(II) and Pd(II) complexes, 3a–f and 5a, respec-
tively. The photophysical characterization of compounds 3a and 3b
permitted the assessment of parameters which, by correlation with
other Pt(II) emissive complexes [14], enabled further insight into
their electronic structure, namely in terms of optical transitions.
air to give trans-[PtCl2(NCMe)2] 1a or trans-[PtCl2(NCEt)2] 1b,
respectively, in excellent yields (ca. 90%).
2.2.2. Reaction of PtCl2 with solid nitriles
PtCl2 (200 mg, 0.752 mmol) was added at room temperature to
o-chlorobenzonitrile (1034 mg, 7.52 mmol), p-chlorobenzonitrile
(1034 mg, 7.52 mmol), p-cyanobenzaldehyde (986 mg, 7.52 mmol)
or p-nitrophenylacetonitrile (1218 mg, 7.52 mmol), and the mix-
ture was heated at the melting point of each nitrile (46, 93, 102
or 115 °C, respectively) in a sealed glass vial for 12 h. Also in this
case, during the course of the reaction, the green gray PtCl2 powder
dissolved in the melted nitrile, forming a homogeneous light yel-
low solution. The excess of nitrile was then removed by washing
the reaction mixture with three 10 mL portions of diethyl ether
or chloroform (depending on the solubility of the nitrile used)
and dried under air to give trans-[PtCl2(NC(o-ClC6H4))2] 1c, trans-
[PtCl2(NC(p-ClC6H4))2] 1d, trans-[PtCl2(NC(p-(HC@O)C6H4))2] 1e
or trans-[PtCl2(NC(p-O2NC6H4CH2))2] 1f, respectively, in excellent
yields (ca. 87%).
2. Experimental
2.1. General methods
1H, 13C and DEPT-135 NMR spectra (in CDCl3 or DMSO-d6) were
measured on Bruker Avance III HD 600 MHz (AscendTM Magnet)
spectrometer at ambient temperature. 1H, 13C and DEPT-135
chemical shifts (d) are expressed in ppm relative to TMS. Infrared
spectra (400–4000 cmÀ1) were recorded on an Alpha Bruker FT-
IR instrument in KBr pellets. C, H and N elemental analyses were
carried out by the Microanalytical Service of the King Abdulaziz
University.
The solvents used for photophysical characterization were all of
spectroscopic grade. Dichloromethane (99.5% for spectroscopy,
Acros Organics), chloroform (ꢀ99.8% ACS spectrometric grade,
Sigma–Aldrich), ethanol (95%, UV HPLC spectroscopic, Sigma–
Aldrich). Deionized water was obtained from a Millipore system
To confirm the formation of those Pt(II) complexes, the new
compounds e.g. 1c and 1e were characterized by 1H, 13C and
DEPT-135 NMR spectroscopy, then the NMR data were compared
with their respective starting materials (o-chlorobenzonitrile and
p-cyanobenzaldehyde).
2.2.2.1. o-Chlorobenzonitrile N„C(o-ClC6H4). 1H NMR (CDCl3), d:
7.40 (t, JHH 7.5 Hz, 1H, CHaromatic), 7.53–7.58 (m, 2H, CHaromatic),
7.69 (d, JHH 7.7 Hz, 1H, CHaromatic). 13C NMR (CDCl3), d: 113.4
(C„N), 115.9 (Cl-Caromatic), 127.1, 130.1, 133.9, 134.0, 136.9 (Caro-
matic). DEPT-135 NMR (CDCl3), d: 127.1, 130.1, 133.9, 134.0
(CHaromatic).
Milli-Q ꢀ 18 MX cm. Polystyrene beads (average Mw 35,000,
Sigma–Aldrich) was used to prepare solid films of compounds 3a
and 3b, by dissolving 1 mg of the respective compound in a solu-
tion of ca. 80 mg of polystyrene in 1 mL chloroform, which was
subsequently deposited over a quartz plate, allowing the solvent
to evaporate. Luminescence quantum yields were calculated by
using Ru(bpy)3 as reference quantum yield standard for com-
pounds 3a and 3b. The electronic absorption spectra were recorded
using a Jasco V-660 spectrophotometer. Fluorescence measure-
ments were carried out in a Horiba-Jobin Yvon Fluorolog-3 spec-
trofluorimeter. All spectra were recorded with samples in 1 cm
optical path length quartz cells, except for the solid films, where
the film was placed directly in the optical path, in a 45° angle
between the excitation source and the detector. Luminescence life-
time measurements were performed using the single-photon tim-
ing method with laser excitation and microchannel plate detection,
with the set-up already described [16]. Excitation wavelength used
was 335 nm for solution and 304 nm for solid state and the emis-
sion wavelength was 605 nm. The timescale was 438.2 ps/channel
for solution measurements, 679.2 ps/channel for solid state 3a and
786.7 ps/channel for solid state 3b.
2.2.2.2. Trans-[PtCl2(NC(o-ClC6H4))2] (1c). Yield: 87%. 1H NMR
(CDCl3), d: 7.49 (t, JHH 7.7 Hz, 2H, CHaromatic), 7.60 (d, JHH 8.2 Hz,
2H, CHaromatic), 7.70 (t, JHH 7.7 Hz, 2H, CHaromatic), 7.80 (d, JHH
7.8 Hz, 2H, CHaromatic). 13C NMR (CDCl3), d: 110.5 (Cl-Caromatic),
114.1 (C„N), 127.4, 130.5, 135.5, 136.3, 138.9 (Caromatic). DEPT-
135 NMR (CDCl3), d: 127.4, 130.5, 135.5, 136.3 (CHaromatic).
2.2.2.3. p-Cyanobenzaldehyde N„C(p-(HC@O)C6H4). 1H NMR
(CDCl3), d: 7.86 (d, JHH 8.3 Hz, 2H, CHaromatic), 8.00 (d, JHH 8.3 Hz,
2H, CHaromatic), 10.10 (s, 1H, HC@O). 13C NMR (CDCl3), d: 117.6
and 117.7 (C„N), 129.9, 132.9, 138.7 (Caromatic), 190.6 (HC@O).
DEPT-135 NMR (CDCl3), d: 129.9, 132.9 (CHaromatic), 190.6 (HC@O).
2.2.2.4. Trans-[PtCl2(NC(p-(HC=O)C6H4))2] (1e). Yield: 85%. 1H NMR
(CDCl3), d: 8.04 (d, JHH 8.4 Hz, 4H, CHaromatic), 8.10 (d, JHH 8.4 Hz,
4H, CHaromatic), 10.16 (s, 2H, HC@O). 13C NMR (CDCl3), d: 113.9
and 115.8 (C„N), 129.9, 134.6, 140.3 (Caromatic), 190.0 (HC@O).
DEPT-135 NMR (CDCl3), d: 129.9, 134.6 (CHaromatic), 190.0 (HC@O).
2.2.3. Reactions of the nitrile Pt(II) complexes trans-[PtCl2(NCR)2] 1
(R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HC@O)C6H4
(1e), p-O2NC6H4CH2 (1f)) with 1,3-diiminoisoindoline 2
To a solution of 1a, 1b, 1c, 1d, 1e or 1f (0.532 mmol) in chloro-
form (5 mL) was added at room temperature to 1,3-diiminoisoin-
doline 2 (77.2 mg, 0.532 mmol), and the mixture was refluxed for
2 h whereupon the solvent was removed in vacuo. The crude resi-
due was purified by column chromatography on silica (chloroform
as the eluent), followed by evaporation of the solvent in vacuo to
give the final 3a, 3b, 3c, 3d, 3e or 3f products, respectively.
2.2. Preparation of the nitrile Pt(II) complexes trans-[PtCl2(NCR)2] 1
(R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HC@O)C6H4
(1e), p-O2NC6H4CH2 (1f)) and their reactions with 1,3-
diiminoisoindoline 2
2.2.1. Reaction of PtCl2 with liquid nitriles
PtCl2 (200 mg, 0.752 mmol) was added at room temperature to
acetonitrile or propionitrile (5 mL), and the mixture was heated
under stirring at 70 °C for 8 h. During the course of the reaction,
the green gray PtCl2 powder dissolved, forming a homogeneous
light yellow solution. The reaction mixture was then dried in vacuo,
washed with three 5 mL portions of diethyl ether and dried under
2.2.3.1. [PtCl{NH=C(Me)N=C(C6H4)NC=NC(Me)=NH}] (3a). Yield:
67%. IR (cmÀ1): 3441 (NH), 1628 (C@N). 1H NMR (CDCl3), d: 2.55
(s, 6H, CH3), 7.75 (dd, JHH 3.0 and 5.5 Hz, 2H, CHaromatic), 8.24 (dd,
JHH 3.0 and 5.5 Hz, 2H, CHaromatic), 9.80 (s, br, 2H, NH). 13C NMR

J. Lasri et al. / Polyhedron 133 (2017) 195–202
197
(CDCl3), d: 28.8 (CH3), 123.2, 132.2, 137.9 (Caromatic), 153.1, 159.8
(C@N). DEPT-135 NMR (CDCl3), d: 28.8 (CH3), 123.2, 132.2 (CHaro-
matic). Anal. Calc. for C12H12N5ClPt (456.79): C, 31.55; H, 2.65; N,
15.33. Found: C, 31.67; H, 2.74; N, 15.28.
2.3. Preparation of the nitrile Pd(II) complexes trans-[PdCl2(NCR)2] 4
(R = Me (4a), Ph (4b), p-MeC6H4CH2 (4c), p-(HC@O)C6H4 (4d), p-O2NC6
H4CH2 (4e)) and their reactions with 1,3-diiminoisoindoline 2
2.3.1. Reaction of PdCl2 with liquid nitriles
2.2.3.2.
[PtCl{NH@C(Et)N@C(C6H4)NC@NC(Et)@NH}]
(3b)
PdCl2 (200 mg, 1.127 mmol) was added at room temperature to
acetonitrile, benzonitrile or p-tolylacetonitrile (5 mL), and the
mixture was heated under stirring at 70 °C for 8 h. During the
course of the reaction, the brown PdCl2 powder dissolved, forming
[15]. Yield: 65%. IR (cmÀ1): 3443 (NH), 1615 (C@N). 1H NMR
(CDCl3), d: 1.47 (t, JHH 7.5 Hz, 6H, CH3CH2), 2.82 (q, JHH 7.5 Hz,
4H, CH3CH2), 7.75 (dd, JHH 3.0 and 5.4 Hz, 2H, CHaromatic), 8.26
(dd, JHH 3.0 and 5.4 Hz, 2H, CHaromatic), 9.77 (s, br, 2H, NH). 13C
NMR (CDCl3), d: 11.0 (CH3), 35.1 (CH2), 123.2, 132.1, 137.9
(Caromatic), 153.2 and 163.8 (C@N). DEPT-135 NMR (CDCl3), d:
11.0 (CH3), 35.1 (CH2), 123.2, 132.1 (CHaromatic). Anal. Calc. for
C14H16N5ClPt (484.84): C, 34.68; H, 3.33; N, 14.44. Found: C,
34.74; H, 3.25; N, 14.33.
a
homogeneous light yellow solution. The reaction mixture
was then dried in vacuo, washed with three 5 mL portions of
diethyl ether and dried under air to give yellow solid com-
pounds trans-[PdCl2(NCMe)2] 4a, trans-[PdCl2(NCPh)2] 4b or trans-
[PdCl2(NC(p-MeC6H4CH2))2] 4c, respectively.
The Pd(II) complexes 4a, 4b and 4c were used without further
characterization.
2.2.3.3.
[PtCl{NH@C(o-ClC6H4)N@C(C6H4)NC@NC(o-ClC6H4)@NH}]
(3c). Yield: 68%. IR (cmÀ1): 2926 (NH), 1678 (C@N). 1H NMR
(CDCl3), d: 7.48 (t, JHH 7.7 Hz, 2H, CHaromatic), 7.53–7.61 (m, 4H,
CHaromatic), 7.70 (t, JHH 7.7 Hz, 2H, CHaromatic), 7.80 (m, 2H, CHaro-
matic), 8.04 (d, JHH 7.6 Hz, 1H, CHaromatic), 8.36 (dd, JHH 3.0 and
5.5 Hz, 1H, CHaromatic), 10.80 (s, br, 2H, NH). 13C NMR (CDCl3), d:
110.5 (Cl-Caromatic), 123.6, 127.3, 127.4, 130.5, 130.7, 131.0, 131.6,
132.4, 135.5, 136.3, 138.9 (Caromatic), 153.7 and 155.9 (C@N).
DEPT-135 NMR (CDCl3), d: 123.6, 127.3, 127.4, 130.5, 130.7,
2.3.2. Reaction of PdCl2 with solid nitriles
PdCl2 (200 mg, 1.127 mmol) was added at room temperature to
p-cyanobenzaldehyde (1477 mg, 11.27 mmol) or p-nitropheny-
lacetonitrile (1825 mg, 11.27 mmol), and the mixture was heated
at the melting point of each nitrile (102 or 115 °C, respectively)
in a sealed glass vial for 12 h. Also in this case, during the course
of the reaction, the brown PdCl2 powder dissolved in the melted
nitrile, forming a homogeneous light yellow solution. The excess
of nitrile was then removed by washing the reaction mixture with
three 10 mL portions of chloroform and dried under air to give yel-
low solid compounds trans-[PdCl2(NC(p-(HC@O)C6H4))2] 4d or
trans-[PdCl2(NC(p-O2NC6H4CH2))2] 4e, respectively.
131.0, 131.6, 132.4, 135.5, 136.3 (CHaromatic). Anal. Calc. for C22H14
N5Cl3Pt (649.82): C, 40.66; H, 2.17; N, 10.78. Found: C, 40.78; H,
2.55; N, 10.21.
-
The Pd(II) complexes 4d and 4e were used without further
characterization.
2.2.3.4.
[PtCl{NH@C(p-ClC6H4)N@C(C6H4)NC@NC(p-ClC6H4)@NH}]
(3d). Yield: 69%. IR (cmÀ1): 3196 (NH), 1677 (C@N). 1H NMR
(CDCl3), d: 7.58 (d, JHH 8.6 Hz, 6H, CHaromatic), 7.77 (d, JHH 8.6 Hz,
4H, CHaromatic), 8.24 (d, JHH 8.6 Hz, 1H, CHaromatic), 8.36 (dd, JHH
3.0 and 5.4 Hz, 1H, CHaromatic), 10.36 (s, br, 2H, NH). 13C NMR
(CDCl3), d: 107.2 (Cl-Caromatic), 123.5, 128.8, 129.5, 130.2, 132.4,
134.9, 142.7 (Caromatic), 153.9 and 155.3 (C@N). DEPT-135 NMR
(CDCl3), d: 123.5, 128.8, 129.5, 130.2, 132.4, 134.9 (CHaromatic). Anal.
Calc. for C22H14N5Cl3Pt (649.82): C, 40.66; H, 2.17; N, 10.78. Found:
C, 40.53; H, 2.45; N, 10.61.
2.3.3. Reactions of the nitrile Pd(II) complexes trans-[PdCl2(NCR)2] 4
(R = Me (4a), Ph (4b), p-MeC6H4CH2 (4c)) with 1,3-diiminoisoindoline
2
A solution of 4a, 4b or 4c (0.532 mmol) in acetonitrile, benzoni-
trile or p-tolylacetonitrile (5 mL), respectively, was added at room
temperature to 1,3-diiminoisoindoline 2 (77.2 mg, 0.532 mmol),
and the mixture was refluxed for 2 h whereupon the solvent was
removed in vacuo. The crude residue was washed with three
5 mL portions of diethyl ether and dried under air.
After a careful IR and NMR analyses of each compound, it was
observed that only the Pd(II) complex [PdCl{NH@C(Me)N@C
(C6H4)NC@NC(Me)@NH}] (5a) was formed.
2.2.3.5.
[PtCl{NH@C(p-(HC@O)C6H4)N@C(C6H4)NC@NC(p-(HC@O)
C6H4)@NH}] (3e). Yield: 67%. IR (cmÀ1): 3424 (NH), 1607 (C@N),
1702 (C@O). 1H NMR (CDCl3), d: 7.87 (dd, JHH 3.0 and 5.4 Hz, 2H,
CHaromatic), 8.11 (d, JHH 8.4 Hz, 4H, CHaromatic), 8.44 (dd, JHH 3.0
and 5.4 Hz, 2H, CHaromatic), 8.48 (d, JHH 8.4 Hz, 4H, CHaromatic),
10.20 (s, 2H, HC@O), 10.61 (s, br, 2H, NH). 13C NMR (CDCl3), d:
123.7, 128.2, 129.9, 130.4, 132.7, 132.9, 137.9, 138.1, 141.7 (Caro-
matic), 154.2 and 155.3 (C@N), 191.5 (HC@O). DEPT-135 NMR
(CDCl3), d: 123.7, 128.2, 129.9, 130.4, 132.7, 132.9 (CHaromatic),
191.5 (HC@O). Anal. Calc. for C24H16N5ClO2Pt (636.95): C, 45.26;
H, 2.53; N, 11.00. Found: C, 45.37; H, 2.19; N, 11.25.
2.3.3.1. [PdCl{NH@C(Me)N@C(C6H4)NC@NC(Me)@NH}] (5a). Yield:
65%. IR (cmÀ1): 3440 (NH), 1639 (C@N). 1H NMR (DMSO-d6), d:
2.57 (s, 6H, CH3), 7.75 (m, 2H, CHaromatic), 8.20 (m, 2H, CHaromatic),
10.20 (s, br, 1H, NH), 10.33 (s, br, 1H, NH). 13C NMR (DMSO-d6),
d: 27.1 (CH3), 123.3, 124.1, 133.8, 133.9, 134.8, 137.9 (Caromatic),
156.3, 164.8 (C@N).
Anal. Calc. for C12H12N5ClPd (368.13): C, 39.15; H, 3.29; N,
19.02. Found: C, 39.46; H, 3.53; N, 19.27.
2.2.3.6. [PtCl{NH@C(p-O2NC6H4CH2)N@C(C6H4)NC@NC(p-O2NC6H4-
CH2)@NH}] (3f). Yield: 64%. IR (cmÀ1): 3270 (NH), 1605 (C@N).
1H NMR (CDCl3), d: 4.22 (s, 4H, CH2) 7.60 (d, JHH 8.8 Hz, 4H, CHaro-
matic), 7.77 (dd, JHH 3.1 and 5.4 Hz, 2H, CHaromatic), 8.18 (dd, JHH 3.1
and 5.4 Hz, 2H, CHaromatic), 8.25 (d, JHH 8.8 Hz, 4H, CHaromatic), 9.96
(s, br, 2H, NH). 13C NMR (CDCl3), d: 47.7 (CH2), 123.5, 124.1, 124.4,
128.9, 130.4, 132.6, 134.3, 137.6, 141.7, 147.5 (Caromatic), 153.9 and
159.6 (C@N). DEPT-135 NMR (CDCl3), d: 47.7 (CH2), 123.5, 124.1,
2.3.4. Reactions of the nitrile Pd(II) complexes trans-[PdCl2(NCR)2] 4
(R = p-(HC@O)C6H4 (4d), p-O2NC6H4CH2 (4e)) with 1,3-diiminoisoin-
doline 2
A solution of 4d or 4e (0.532 mmol) in acetone (5 mL) was
added at room temperature to 1,3-diiminoisoindoline 2 (77.2 mg,
0.532 mmol), and the mixture was refluxed for 2 h whereupon
the solvent was removed in vacuo. The crude residue was washed
with three 5 mL portions of diethyl ether and dried under air.
After a careful IR and NMR analyses of each reaction product, it
was observed the absence of the products of the addition of 1,3-
diiminoisoindoline to nitrile group (N„C), the resulting mixtures
124.4, 128.9, 130.4, 132.6, 134.3 (CHaromatic). Anal. Calc. for C24H18
-
N7ClO4Pt (698.98): C, 41.24; H, 2.60; N, 14.03. Found: C, 41.55; H,
2.73; N, 14.15.

198
J. Lasri et al. / Polyhedron 133 (2017) 195–202
contain a number of unidentified products. Additionally, the reac-
tion of 4e with 2 affords also p-nitrophenylacetonitrile (resulting
from the decomposition of complex 4e).
Herein, we describe the selective synthesis of new symmetrical
(1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes by
using various aliphatic and aromatic nitriles as starting bis(nitrile)
Pt(II) complexes and 1,3-diiminoisoindoline as the reacting sp2-
nitrogen nucleophile.
2.4. X-ray structure determinations
The starting Pt(II)-bound nitrile complexes trans-[PtCl2(NCR)2]
1 (R = Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HC@O)
C6H4 (1e), p-O2NC6H4CH2 (1f)) were prepared, in excellent yields
(ca. 90%), by reaction of PtCl2 with the respective nitrile under
heating. Treatment of complexes 1a-f with one equivalent of 1,3-
diiminoisoindoline HN@CC6H4C(NH)@NH 2, in refluxing chloro-
form for 2 h, gives access to the corresponding symmetrical
(1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes [PtCl
{NH@C(R)N@C(C6H4)NC@NC(R)@NH}] 3a–f in good yields (65–
70%) (Scheme 1).
In a blank experiment, a prolonged reflux (24 h) of a mixture of
one equivalent of acetonitrile and two equivalents of 1,3-diimi-
noisoindoline in chloroform showed no addition to cyanocarbon
of acetonitrile and only the starting materials were recovered, indi-
cating the Pt(II)-assisted character of the coupling.
For the X-ray structure determination; X-ray-quality single
crystal of Pt(II) complex [PtCl{NH@C(Me)N@C(C6H4)NC@NC
(Me)@NH}] 3a was obtained by slow evaporation from chloroform.
The crystals of 3a were immersed in cryo-oil, mounted in a MiTe-
Gen loop and measured at 120 K. The X-ray diffraction data were
collected on a Bruker KappaApex II or an Agilent Technologies
Supernova using Mo Ka radiation (k = 0.70173 Å). The CrysAlisPro
[17] program packages were used for cell refinements and data
reductions. The structure was solved by charge flipping method
using the SUPERFLIP [18] program. A multi-scan absorption correc-
tion based on equivalent reflections (CrysAlisPro) was applied to
the data. Structural refinement was carried out using SHELXL2014
[19]. The N–H hydrogen atom (H1) was located from the difference
Fourier map and refined isotropically. Other hydrogen atoms were
positioned geometrically and constrained to ride on their parent
atoms, with CÁ Á ÁH = 0.95–0.98 Å and Uiso = 1.2–1.5 Ueq (parent
atom).
The obtained Pt(II) complexes 3a–f were characterized by IR,
1H, 13C and DEPT-135 NMR spectroscopies, elemental analyses
and also by X-ray diffraction (in the case of 3a). The IR spectra of
complexes 3a-f do not exhibit the typical
m
m
(N„C) values (2350–
(NH) and (N@C) are
The crystallographic details are summarized in Table 1. Detailed
structural parameters are given in Supplementary material.
2300 cmÀ1 range), while new bands due to
m
observed at ca. 3255 and ca. 1648 cmÀ1, respectively. For example,
in the 1H NMR spectrum of the complex [PtCl{NH@C(Me)N@C
(C6H4)NC@NC(Me)@NH}] 3a, the signal of the two methyl groups
appears as a singlet at d 2.55, and the NH protons are exhibited
at d 9.80. The 13C NMR spectrum of 3a shows the characteristic sig-
nals of the imine N@C groups at d 153.1 and 159.8, and the absence
of the nitrile N„C resonance at ca. 116 ppm confirms that the
nucleophilic addition of 1,3-diiminoisoindoline 2 occurs to both
acetonitrile ligands in 1a (see Section 2 for more details).
3. Results and discussion
3.1. Reactions of bis(nitrile) Pt(II) complexes 1 with 1,3-
diiminoisoindoline 2
We have recently found [15] that 1,3-diiminoisoindoline, which
represents a family of aromatic diimines, exhibits nucleophilic
properties toward Pt(II)-bound nitriles (propionitrile and benzoni-
trile). The stability of the 1,3-diiminoisoindoline and of the prod-
ucts of its addition to nitrile ligands encouraged us to expand
this type of reaction to other Pt(II) and Pd(II)-bound nitriles. 1,3-
Diiminoisoindoline bears two nucleophilic sp2-nitrogen centres
and one endocyclic amine group, which upon deprotonation might
coordinate to Pt(II) or Pd(II) metal centre forming stable chelated
fused metallacycles (Fig. 1).
3.2. X-ray structure crystallography
Complex 3a has a relatively simple molecular structure. The
crystal data and structure refinement are given in Table 1, repre-
sentative diagram is given in Fig. 2 and selected bond distances
and angles are provided in Table 2. Other relevant features of the
structure of 3a are given as Supplementary Material. The geometry
around the Pt ion in 3a is of square planar type, comprising two
fused six-membered metallacycles. Atoms Cl1, Pt1, and N3 are
placed on a twofold rotation axis. Practically planar molecules
Table 1
Crystal data and structure refinement for complex 3a.
are forming stacks with metal–
crystallographic c-axis (Fig. 3). The shortest atom–atom distances
between the adjacent planes are Pt1-C5#1: 3.3575(3) Å, C1–C4#2
p and p–p interactions along the
3ª
Empirical formula
Fw
T (K)
k (Å)
Cryst syst
Space group
a (Å)
b (Å)
c (Å)
C12H12ClN5Pt
456.81
120(2)
:
3.3890(4) Å and C3–C3#1: 3.3639(4) Å (#1: Àx, 1Ày, Àz, #2: x,
1 À y, À1/2 + z). The stacks are further supported by weak H-bonds
between the NH group and Cl as well as CH3 group and Cl (Fig. 3).
In the previously published structure 3b, the metal compounds are
also stacked with shortest C–C distances ranging from 3.344 Å to
3.369 Å. In this structure the stacks are supported both by weak
CH2–Cl H-bonds and much stronger H-bonds involving water of
crystallization [15].
1.54184
Monoclinic
C2/c
11.8678(5)
19.6347(2)
7.7596(3)
135.018(7)
1278.13(14)
4
2.374
22.405
13958
1356
b (°)
V (Å3)
Z
qcalc (mg/m3)
l
(K
a
) (mmÀ1
)
3.3. Reactions of bis(nitrile) Pd(II) complexes 4 with 1,3-
diiminoisoindoline 2
No. reflns.
Unique reflns.
Goodness-of-fit (GOF) on F2
1.139
Rint
0.0747
0.0313
0.0823
Here, we report the selective synthesis of new symmetrical
a
R1 (I ꢀ 2
r
)
r
(1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II)
complex
by
b
wR2 (I ꢀ 2
)
using trans-[PdCl2(NCMe)2] as the starting bis(nitrile) Pd(II) com-
plex and 1,3-diiminoisoindoline as the reacting sp2-nitrogen
nucleophile.
a
R1
wR2 = [
=
R
||Fo| À |Fc||/
R|Fo|.
b
R
[w(F2o À F2c)2]/
R .
[w(F2o)2]]1/2

J. Lasri et al. / Polyhedron 133 (2017) 195–202
199
Auxiliary amine
H
N
H
N
Nucleophilic
center
Nucleophilic
center
R
R
M
N
H
N
N
N
NH
NH
Symmetrical 1,3,5,7,9-pentaazanona-
1,3,6,8-tetraenato complex
1,3-diiminoisoindoline
M = Pt, Pd
R = alkyl, aryl
Fig. 1. Left: 1,3-Diiminoisoindoline. Right: Symmetrical 1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato complex (M = Pt, Pd).
R
NH
NH
NH
Cl
N
Pt
+
N
Cl
R
2
1a: R = Me
1b: R = Et
CHCl3, reflux, 2 h
- HCl
1c: R = o-ClC6H4
1d: R = p-ClC6H4
1e: R = p-(HC=O)C6H4
1f: R = p-O2NC6H4CH2
Cl
H
N
H
N
R
3a: R = Me
R
Pt
N
3b: R = Et
N
N
3c: R = o-ClC6H4
3d: R = p-ClC6H4
3e: R = p-(HC=O)C6H4
3f: R = p-O2NC6H4CH2
Scheme 1. Synthesis of (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes 3a–f.
The starting Pd(II)-bound acetonitrile complex trans-[PdCl2(-
NCMe)2] 4a was prepared, in excellent yield (89%), by reaction of
PdCl2 with acetonitrile under heating. Treatment of complex 4a
with one equivalent of 1,3-diiminoisoindoline 2, in refluxing ace-
tonitrile for 2 h, gives access to the symmetrical (1,3,5,7,9-pen-
taazanona-1,3,6,8-tetraenato)Pd(II) complex [PdCl{NH@C(Me)
N@C(C6H4)NC@NC(Me)@NH}] 5a in good yield (65%) (Scheme 2,
reaction a).
ited at d 10.20 and 10.33. The 13C NMR spectrum shows the char-
acteristic signals of the imine N@C groups at d 156.3 and 164.8, and
the absence of the nitrile N„C resonance at ca. 116 ppm confirms
that the nucleophilic addition of 1,3-diiminoisoindoline 2 occurs to
both acetonitrile ligands in 4a.
We have also studied the reaction of 1,3-diiminoisoindoline
with other bis(nitrile) complexes trans-[PdCl2(NCR)2]. Hence, the
careful NMR analysis of the products of the reaction of trans-
[PdCl2(NCR)2] 4 (R = Ph (4b), p-MeC6H4CH2 (4c), p-(HC@O)C6H4
(4d), p-O2NC6H4CH2 (4e)) with 2 shows the formation of a number
of unidentified products (in the case of 4b and 4d), or the free
nitriles p-tolylacetonitrile and p-nitrophenylacetonitrile (resulting
from the decomposition of the complexes 4c and 4e, respectively)
The IR spectrum of complex 5a do not exhibit the typical
m
(N„C) values (2350–2300 cmÀ1 range), while new bands due to
t
(NH) and m
(N@C) are detected at 3440 and 1639 cmÀ1, respec-
tively. In the 1H NMR spectrum of 5a, the signal of the two methyl
groups appears as a singlet at d 2.57, and the NH protons are exhib-

200
J. Lasri et al. / Polyhedron 133 (2017) 195–202
complexes. The bands located around 330 nm are more ligand-cen-
tered and, due to the solvent cut-off, it was not possible to observe
the highest energy absorption bands, which should be located
below 250 nm for this type of complexes [14], and correspond to
1
(p–
p⁄) IL (intraligand) transitions.
The absorption data (maximum absorption wavelengths and
corresponding molar absorption coefficients) are summarized in
Table 3.
3.5. Luminescence emission spectra
Both compounds are emissive in dichloromethane solution, and
exhibit very similar emission spectra, luminescence quantum
yields and lifetimes. This might be due to the structural similarity
between the two compounds, which only differ by one carbon
atom in two of the imine substituents. The emission data are col-
lected in Table 3. Absorption, emission and excitation spectra of
both complexes are represented in Figs. 4 and 5.
By comparison of the luminescence lifetimes assessed for these
compounds with those collected for Pt(II) imidoylamidinates [14],
it is possible to observe that the former are several orders of mag-
nitude lower. This might be due to the fact that Pt(II) complexes 3a
and 3b exhibit a smaller degree of electronic delocalization, which
ultimately governs the lifetime of the emissive triplet state. It is
worth mentioning that degassing produced no effect on their life-
times and quantum yields.
Fig. 2. Crystal structure of complex 3a.
Table 2
Selected bond lengths [Å] and angles [°] for complex 3a.
3.6. Solid state luminescence
Pt1–N(3)
Pt1–N(1)#
Pt1–N(1)
Pt1–Cl1
1.961(6)
1 1.972(5)
1.972(5)
Compounds 3a and 3b also exhibited luminescence in solid
state. The characterization was performed following the procedure
described in Section 2.1, and the resulting emission spectra are
depicted in Fig. 6.
The spectra are very similar to the ones obtained in solution for
both compounds, except for the slight elevation of the baseline,
which is common for solid samples, owing to scattering. Regarding
luminescence lifetimes, a significant increase occurs in the solid
state, a common lifetime of 160 ns being measured for both 3a
and 3b. Immobilization of the compounds in the solid matrix sig-
nificantly reduces collisional quenching, hence increasing the
excited state lifetime.
2.3178(16)
N(3)–Pt1–N(1)
N(1)#1–Pt1–N(1)
N(3)–Pt1–Cl1
N(1)–Pt1–Cl1
89.34(11)
178.7(2)
180.0
90.66(11)
Symmetry transformations used to generate equivalent atoms: #1 Àx, y, Àz + 1/2.
together with a number of uncharacterized products (Scheme 2,
reaction b). The 13C NMR spectra show the absence of the charac-
teristic signals of the imine N@C groups at d 153 and 165.
3.4. UV–Vis absorption spectra
4. Conclusions
The absorption spectra of the Pt(II) complexes 3a and 3b exhibit
a band at 400–430 nm typical of a metal-to-ligand charge transfer
(MLCT) low energy transition, and intrinsic of the d8 platinum
The results of this work can be summarized under four
perspectives. First, the reaction between trans-[PtCl2(NCR)2] 1 and
1,3-diiminoisoindoline 2 affords (1,3,5,7,9-pentaazanona-1,3,6,8-
Fig. 3. Left: Packing of 3a along the crystallographic c-axis. Right: H-Bonds in 3a. N1–H1: 0.83(9) Å, H1Á Á ÁCl1#3: 2.69(9) Å, N1Á Á ÁCl1#3: 3.403(5), N1-H1Á Á ÁCl1#3: 145(7)°, C2–
H2: 0.98 Å, H1Á Á ÁCl1#3: 2.87, C2Á Á ÁCl1#3: 3.643 Å, C2–H2Á Á ÁCl1#3: 137° (#3: Àx + 1/2, Ày + 1/2, Àz + 1).

J. Lasri et al. / Polyhedron 133 (2017) 195–202
201
Cl
H
N
H
N
Me
Me
Pd
N
R
4a: R = Me
Cl
N
N
N
acetonitrile, reflux, 2 h
Pd
N
- HCl
(a)
Cl
R
4
5a
+
4b: R = Ph
4c: R = p-MeC6H4CH2
4d: R = p-(HC=O)C6H4
4e: R = p-O2NC6H4CH2
NH
NH
NH
Unidentified products
reflux, 2 h
2
(b)
Scheme 2. Synthesis of (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II) complex 5a.
Table 3
Wavelengths of the absorption maxima, respective molar absorption coefficients, luminescence quantum yields and lifetimes for Pt(II) complexes 3a and 3b.
kmax/nm (
e
/MÀ1 cmÀ1), CH2Cl2
kem/nm, CH2Cl2
/L/Â10À3, CH2Cl2
3.1
s
70a
/ns
3a
3b
334 (8930)
404 (4225)
428 (3995)
607
318 (8215)
330 (8587)
401 (4355)
426 (4375)
605
3.6
82a (95)b
a
In chloroform.
In dichloromethane.
b
Fig. 4. Normalized absorption, emission (solid lines) and excitation (dashed line)
spectra of compound 3a in CH2Cl2. kexc = 428 nm.
Fig. 5. Normalized absorption, emission (solid lines) and excitation (dashed line)
spectra of compound 3b in CH2Cl2. kexc = 426 nm.
tetraenato)Pt(II) complexes 3. Second, we achieved the selective
synthesis of new symmetrical (1,3,5,7,9-pentaazanona-1,3,6,8-
tetraenato)Pd(II) complex 5a by using trans-[PdCl2(NCMe)2] 4a
and 1,3-diiminoisoindoline 2, and the system represents a novel
reactivity mode which has never been reported so far. Third, the
developed synthetic methods operate under mild conditions
(reflux, 2 h), furnish pure symmetrical (1,3,5,7,9-pentaazanona-
1,3,6,8-tetraenato)Pt(II) and Pd(II) complexes, and, in contrast to
the preparation of (1,3,5-triazapentadienato)Ni(II) complexes
[7a], does not need the use of a base. Fourth, the emissive Pt(II)
complexes 3a and 3b exhibited significantly lower luminescent
lifetimes in solution when compared to their Pt(II)
imidoylamidinate analogues [14], which is a consequence of a

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J. Lasri et al. / Polyhedron 133 (2017) 195–202
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This project was funded by the Deanship of Scientific Research
(DSR) at King Abdulaziz University, Jeddah, under grant no. (G-
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