New platinum(II) and palladium(II) quinoline-imine-pyridine, quinoline-imine-thiazole and quinoline-imine-imidazole complexes by metal-assisted condensation reactions

Article abstract of DOI:10.1016/j.jorganchem.2011.03.046

Pt(II) and Pd(II) methyl- and chloro-complexes with the tridentate N-donor ligands ((pyridin-2-yl)methylene)quinolin-8-amine (NNPy), ((pyridin-2-yl) ethylidene)quinolin-8-yl-amine (NNMePy), (phenyl(pyridin-2-yl)methylene) quinolin-8-yl-amine (NNPhPy), ((thiazol-2-yl)methylene)quinolin-8-amine (NNTh) and ((imidazol-4-yl)methylene)quinolin-8-amine (NNImH) were prepared by metal-assisted condensation of 8-aminoquinoline and an ortho-substituted aldehydo- or keto- N-heterocycle. Preliminary reactivity studies involving the coordinated tridentate N-donors, the chloro-ligand and the M-CH₃ bond were carried out, leading to the synthesis of several new complexes. During these studies, the formation of a novel five-coordinate Pt(II) carbonyl-complex was observed.

Full text of DOI:10.1016/j.jorganchem.2011.03.046

Journal of Organometallic Chemistry 696 (2011) 2565e2575
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
New platinum(II) and palladium(II) quinoline-imine-pyridine,
quinoline-imine-thiazole and quinoline-imine-imidazole complexes
by metal-assisted condensation reactions
,
a
,
a
b
c
Marco Bortoluzzi a , Gino Paolucci
, Bruno Pitteri , Piero Zennaro , Valerio Bertolasi
*
**
a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
b Dipartimento di Scienze Ambientali, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
c Dipartimento di Chimica e Centro di Strutturistica Diffrattometrica, Università di Ferrara, Via L. Borsari 46, 44100 Ferrara, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Pt(II) and Pd(II) methyl- and chloro-complexes with the tridentate N-donor ligands ((pyridin-2-yl)
methylene)quinolin-8-amine (NNPy), ((pyridin-2-yl)ethylidene)quinolin-8-yl-amine (NNMePy), (phe-
nyl(pyridin-2-yl)methylene)quinolin-8-yl-amine (NNPhPy), ((thiazol-2-yl)methylene)quinolin-8-amine
(NNTh) and ((imidazol-4-yl)methylene)quinolin-8-amine (NNImH) were prepared by metal-assisted
condensation of 8-aminoquinoline and an ortho-substituted aldehydo- or keto- N-heterocycle. Prelimi-
nary reactivity studies involving the coordinated tridentate N-donors, the chloro-ligand and the M-CH3
bond were carried out, leading to the synthesis of several new complexes. During these studies, the
formation of a novel five-coordinate Pt(II) carbonyl-complex was observed.
Received 27 January 2011
Received in revised form
22 March 2011
Accepted 29 March 2011
Keywords:
Platinum
Palladium
N-Donor ligands
Metal-assisted syntheses
Methyl-complexes
Five-coordinate complexes
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
The synthesis and reactivity of complexes with this kind of
chelates and similar ligands have been reported with various metal
Transition metal complexes with pyridine-based polydentate
ligands such as 2,20:60,200-terpyridine (terpy) are a deeply investi-
gated field of research in coordination chemistry [1]. Terpy forms
stable complexes with d8 transition metal centres such as plati-
num(II) and palladium(II), which have been applied in the last years
in the fields of bioinorganic chemistry [2], analytical chemistry [3]
and supramolecular chemistry [4]. Among all, the chloro and
methyl terpy-derivatives of the type [ML(terpy)]þ {L ¼ CH3, Cl;
M ¼ Pd, Pt} are useful precursors for the synthesis of a wide range
of other complexes [5,6].
centres, such as iron(II), cobalt(II), cobalt(III), nickel(II) and
platinum(IV) [9]. Chloro-complexes of Pd(II) and Pt(II) and methyl-
complexes of Pd(II) with [N,N,N]-donor ligands formed by
metal-assisted condensation of 8-aminoquinoline with pyridine-2-
carboxaldehyde, 2-acetyl-pyridine and 2-benzoyl-pyridine were
prepared some years ago by our research group [10].
In the present work we extended the metal-assisted approach to
the synthesis of new platinum(II) cationic methyl-complexes.
Moreover, pyridine-2-carboxaldehyde was replaced with other
N-heterocycle aldehydes, such as thiazole-2-carboxaldehyde and
imidazole-4-carboxaldehyde, to give insight into the effects of
different heterocycles on the reactivity of the corresponding palla-
dium and platinum complexes. The reaction of the methyl-
complexes with CO allowed highlighting the effects induced by the
different heterocycles on the electronic structure of the complexes.
Besides terpy, other polydentate N-donor ligands acting as tri-
dentate towards a d8 metal centre and having a delocalised
p
-system have been studied in the last years. Some examples of
these ligands are the 2,3,5,6-tetrakis(2-pyridinyl)pyrazine [7] and
the isomers of 2,6-di(pyrazolyl)-pyridine [8].
Other ligands having electronic and steric features similar to
terpy are imine ligands derived from the condensation of 8-ami-
noquinoline and ortho-substituted aldehydo- or keto-pyridines.
2. Experimental section
2.1. Materials
* Corresponding author. Tel.: þ39 0412348651; fax: þ39 0412348517.
** Corresponding author. Tel.: þ39 0412348653; fax: þ39 0412348517.
E-mail addresses: markos@unive.it (M. Bortoluzzi), paolucci@unive.it
(G. Paolucci).
The nitrogen heterocycles, 1,5-cyclooctadiene (COD), dime-
thylsulfide, tetramethyltin, palladium chloride and the inorganic
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.03.046

2566
M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
salts were purchased from Aldrich and used without further puri-
fications. Carbon monoxide was purchased form SIAD. K2[PtCl4]
was prepared from metallic platinum (Chimet) using a two-steps
procedure: (1) the oxidation of metallic platinum to [PtCl6]2- with
aqua regia and the isolation of the Pt(IV) complex as potassium salt;
(2) the slow reduction of [PtCl6]2- to [PtCl4]2- by dropwise addition
of a hydrazine hydrochloride solution.
standard programs. NMR spectra were elaborated with the MestRe-
C software package [17].
Conductivity measurements were carried out at 298 K on
10ꢁ3 M solutions of the complexes in dimethylformamide or
nitromethane, using a Radiometer Copenhagen CDM 83 instru-
ment. Molar conductivity values were compared with data repor-
ted in the literature [18].
The organic solvents and the triethylamine were purified
following common procedures [11]. Deuterated solvents were
Euriso-Top products, with the exception of deuterated nitro-
methane (Aldrich).
Cis/trans-PtCl2(SMe2)2 [12], PtCl2(COD) [13], PtClMe(COD) [14],
PdCl2(COD) [15], and PdClMe(COD) [16] were synthesized on the
basis of reported procedures. The synthesis of the palladium
methyl-complex [PdMe(NNPy)](SO3CF3) (2Py) was reported in
a previous paper [10].
Safety notes: Nitromethane is a potentially explosive solvent and
must be handled with care. Perchlorate salts of transition metal
complexes with organic ligands are also potentially explosive, but
in the experimental conditions described all the products were
stable both in solution and in the solid state.
2.3. Ligands
The polydentate ligands coordinated to the metal centres in the
complexes described in this paper are sketched in Scheme 1.
NNPy ¼ ((pyridin-2-yl)methylene)quinolin-8-amine; NNMePy ¼
((pyridin-2-yl)ethylidene)quinolin-8-yl-amine; NNPhPy ¼ (phe-
nyl(pyridin-2-yl)methylene)quinolin-8-yl-amine; NNTh ¼ ((thia-
zol-2-yl)methylene)quinolin-8-amine; NNImH ¼ ((imidazol-4-yl)
methylene)quinolin-8-amine; NNIm ¼ ((imidazolate-4-yl)methy-
lene)quinolin-8-amine. Heterocycle rings were numbered
following common conventions.
2.4. Synthesis of [PtMe(NNPy)](ClO4) (1NNPy), [PtMe(NNMePy)]X
(X ¼ ClO4 or SO3CF3) (1NNMePy), [PtMe(NNPhPy)](ClO4) (1NNPhPy),
[PtMe(NNTh)]X (X ¼ ClO4 or SO3CF3) (1NNTh) and
2.2. Instruments
[PtMe(NNImH)](ClO4) (1NNImH
)
Elemental analyses (C, H, N, Cl) were carried out at the “Istituto di
Chimica Inorganica e delle Superfici”, C.N.R., Padua. The purification
of the stable products before the elemental analyses was carried out
by slowly cooling (from þ30 ꢀC to ꢁ25 ꢀC during a week) clear
solutions of the complexes dissolved in mixtures of solvents such as
dimethylformamide, nitromethane and diethylether. The vials or
glass tubes containing the solutions were cooled in a jacketed glass
vessel connected to a programmable Thermo Scientific C25P cryo-
stat having a Phoenix II controlling unit.
A suspension of PtClMe(COD) (0.202 g, 0.57 mmol) in 30 mL of
methanol was heated to 50 ꢀC until the complete dissolution of the
complex. Keeping the temperature constant, a solution containing
8-aminoquinoline (0.082 g, 0.57 mmol) and an equimolar amount
of the proper aldehyde or ketone in 10 mL of methanol was added
dropwise (pyridine-2-carboxaldehyde, 54
pyridine, 63
L, for 1NNMePy; 2-benzoyl-pyridine, 0.104 g, for
1NNPhPy; thiazol-2-carboxaldehyde, 50 L, for 1NNTh; imidazol-4-
m
L, for 1NNPy; 2-acetyl-
m
m
IR spectra were recorded in the range 4000 cmꢁ1e450 cmꢁ1 on
a PerkineElmer Spectrum One spectrophotometer. Solid samples
were dispersed in nujol or KBr. IR spectra in solution were recorded
in the range 2350 cmꢁ1e1650 cmꢁ1 on 10ꢁ2 M solutions of the
complexes in nitromethane, using cells with KBr windows.
GCeMS experiments were carried out with a Finnegan Trace
GCeMS. The assignments were done by comparison between
theoretical and experimental isotopic clusters.
NMR spectra were recorded on a Bruker AC 200 and Bruker
Avance 300 spectrometers. The NMR spectra of the complexes were
collected at temperatures ranging from 298 K to 370 K, using
CD3NO2 and/or (CD3)2SO as solvents. The spectra of mixtures of
8-aminoquinoline with N-heterocycle aldehydes or ketones were
recorded at 298 K in CD3OD. 1H and 13C chemical shift values were
attributed using tetramethylsilane as internal reference. COSY,
NOESY, HSQC and HMBC experiments were carried out using their
carboxaldehyde, 0.054 g, for 1NNImH). The resulting solution was
stirred at room temperature for 3 h. Subsequently, a 5:1 excess of
lithium triflate (0.455 g, 2.85 mmol) or lithium perchlorate (0.303 g,
2.85 mmol) was added. A yellow or red solid started to precipitate
slowly. After keeping the reaction mixture at ꢁ25 ꢀC for one night,
the product was filtered, washed with 5 mL of methanol and 10 mL
of diethylether. Slow diffusion of diethylether into dime-
thylformamide/nitromethane solutions purified all the complexes
as microcrystalline solids. The yields were all >85% for the
perchlorate salts and >60% for the triflate salts.
2.4.1. Characterization of 1NNPy
Elemental analysis for C16H14ClN3O4Pt: calcd. C 35.4, H 2.60,
N 7.74, Cl 6.53; found C 35.3, H 2.61, N 7.71, Cl 6.50. LM (dmf,
298 K) ¼ 71 Uꢁ1 molꢁ1 cm2. No melting or decomposition at
T ꢂ 260 ꢀC. 1H NMR {DMSO-d6, 346 K, ppm}: 10.06 (s, 1H,
Scheme 1. Polydentate ligands considered in this paper.

M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2567
3
3
3JPtH ¼ 38 Hz, imine-CH); 8.96 (d, 1H, JHH ¼ 4.9 Hz, JPtH ¼ 56 Hz,
298 K) ¼ 63 Uꢁ1 molꢁ1 cm2. No melting or decomposition at
T ꢂ 260 ꢀC. 1H NMR {DMSO-d6, 298 K, ppm}: 13.81 (s, br, 1H,
quinoline-H2); 8.83 (d, 1H, 3JHH ¼ 8.1 Hz, quinoline-H4); 8.74 (d, 1H,
3JHH ¼ 4.9 Hz, 3JPtH ¼ 50 Hz, pyridine-H6’); 8.48 (d, 1H, 3JHH ¼ 7.5 Hz,
3
imidazole-NH); 9.53 (s, 1H, JPtH ¼ 32 Hz, imine-CH); 8.75 (d, 1H,
3
quinoline-H7); 8.35 (t, 1H, JHH ¼ 7.5 Hz, pyridine-H4’); 8.22 (d, 1H,
3JPtH ¼ 57 Hz, 3JHH ¼ 5.1 Hz, quinoline-H2); 8.69 (d, 1H, 3JHH ¼ 8.3 Hz,
quinoline-H4); 8.28 (s, 1H, imidazole-H2’); 8.25 (d, 1H,
3JHH ¼ 8.1 Hz, quinoline-H7); 8.24 (s, 1H, imidazole-H5’); 7.98 (d, 1H,
3JHH ¼ 8.1 Hz, quinoline-H5); 7.68 (t, 1H, 3JHH ¼ 8.0 Hz, quinoline-H6);
7.53 (dd, 1H, 3JHH ¼ 5.1 Hz, 3JHH ¼ 8.3 Hz, quinoline-H3); 0.82 (s, 3H,
2JPtH ¼ 75 Hz, Pt-CH3). 13C {1H} NMR {DMSO-d6, 298 K, ppm}: 148.9
quinoline-C2, 148.7 imine-C, 139.2 imidazole-C2’, 137.8 quinoline-C4,
129.0 quinoline-C5, 128.6 quinoline-C6, 126.9 imidazole-C5’, 123.9
quinoline-C3, 119.8 quinoline-C7, -16.7 (1JPtC ¼ 760 Hz) Pt-CH3, 150.4,
147.0, 139.7, 130.8 ancillary ligand not H-bonded carbons.
3JHH ¼ 7.5 Hz, quinoline-H5); 8.09 (d, 1H, 3JHH ¼ 7.5 Hz, pyridine-H3’);
7.97e7.77 (m, 2H, quinoline-H6, pyridine-H5’); 7.68 (dd, 1H,
3JHH ¼ 4.9 Hz, 3JHH ¼ 8.1 Hz, quinoline-H3); 1.10 (s, 3H, 2JPtH ¼ 75 Hz,
Pt-CH3). 13C {1H} NMR {DMSO-d6, 298 K, HSQC projection, ppm}:
156.8 imine-C, 151.2 pyridine-C6’, 150.4 quinoline-C2, 141.2 pyridine-
C4’, 139.0 quinoline-C4, 131.1 quinoline-C5, 130.7 pyridine-C3’, 130.1
pyridine-C5’, 129.3 quinoline-C6, 124.5 quinoline-C3, 121.1 quinoline-
C7, -7.70 Pt-CH3.
2.4.2. Characterization of 1NNMePy
Elemental analysis for C18H16F3N3O3PtS: calcd. C 35.7, H 2.66, N
2.5. Synthesis of [PdMe(NNTh)](X) (X ¼ SO3CF3 or ClO4) (2NNTh
)
6.93; found
C
35.6,
H
2.67,
N
6.91. LM (dmf, 298 K)
¼
and [PdMe(NNImH)](ClO4) (2NNImH
)
68
U
ꢁ1 molꢁ1 cm2. No melting or decomposition at T ꢂ 260 ꢀC. 1H
3
NMR {DMSO-d6, 298 K, ppm: 8.59 (d, 1H, JHH
¼
5.4 Hz,
The synthetic procedure for the preparation of 2NNTh and 2NNImH
was the same as previously described for the Pt(II) complexes 1NNTh
and INNImH, using PdClMe(COD) (0.151 g, 0.57 mmol) as starting
reagent. The yields were >90% for all the perchlorate salts and
>65% for the triflate salt.
4JHH ¼ 1.0 Hz, quinoline-H2); 8.55 (d, 1H, JHH ¼ 8.5 Hz, quinoline-
3
3
H4); 8.34 (d, 1H, JHH ¼ 5.7 Hz, pyridine-H6’); 8.21e8.12 (m, 2H,
3
quinoline-H7 and pyridine-H4’); 8.05 (d, 1H, JHH ¼ 7.8 Hz, pyridine-
3
H3’); 7.92 (d, 1H, JHH ¼ 8.2 Hz, quinoline-H5); 7.64e7.53 (m, 2H,
3
quinoline-H6 and pyridine-H5’); 7.42 (dd, 1H, JHH ¼ 5.4 Hz,
3JHH ¼ 8.5 Hz, quinoline-H3); 2.50 (s, 3H, imine-CH3); 0.57 (s, 3H,
2JPtH ¼ 72 Hz, Pt-CH3). 13C {1H} NMR {DMSO-d6, 298 K, ppm}: 149.5
pyridine-C6’, 148.9 quinoline-C2, 140.3 pyridine-C4’, 138.6 quinoline-
C4, 130.8, 130.2, 130.1, 129.8 quinoline-C5, pyridine-C3’, quinoline-C6,
pyridine-C5’, 126.3 quinoline-C7, 124.0 quinoline-C3, 19.5 imine-CH3,
-6.6 Pt-CH3 (1JPtC ¼ 805 Hz), 168.3, 162.5, 151.8, 139.3, 129.0 ancillary
ligand not H-bonded carbons.
2.5.1. Characterization of 2NNTh
Elemental analysis of C15H12F3N3O3PdS2: calcd. C 35.3, H 2.37,
N
8.24; found
C 35.2, H 2.36, N 8.21. LM (nitromethane,
298 K) ¼ 84
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 240 ꢀC. 1H NMR
{CD3NO2, 336 K, ppm}: 9.30 (s, 1H, imine-CH); 8.74 (dd, 1H,
3JHH ¼ 5.2 Hz, JHH
¼
1.3 Hz, quinoline-H2); 8.65 (dd, 1H,
4
3JHH ¼ 8.4 Hz, 4JHH ¼ 1.3 Hz, quinoline-H4); 8.33 (d, 1H, 3JHH ¼ 7.9 Hz,
3
quinoline-H7); 8.28 (d, 1H, JHH ¼ 3.2 Hz, thiazole-H5’); 8.20 (d, 1H,
2.4.3. Characterization of 1NNPhPy
3JHH ¼ 7.9 Hz, quinoline-H5); 8.06 (d, 1H, 3JHH ¼ 3.2 Hz, thiazole-H4’);
7.87 (t, 1H, 3JHH ¼ 7.9 Hz, quinoline-H6); 7.74 (dd, 1H, 3JHH ¼ 5.2 Hz,
3JHH ¼ 8.4 Hz, quinoline-H3); 1.08 (s, 3H, Pd-CH3). 13C {1H} NMR
{CD3NO2, 336 K, ppm}: 153.1, 148.1, 144.2, 141.3, 133.6, 130.7, 130.2,
125.2, 122.3 ancillary ligand CH carbons; 170.4, 151.5, 139.1, 132.9
ancillary ligand not H-bonded carbons; 1.9 Pd-CH3.
Elemental analysis for C22H18ClN3O4Pt: calcd. C 42.7, H 2.93,
N 6.79, Cl 5.73; found C 42.6, H 2.94, N 6.77, Cl 5.72. LM (dmf,
298 K) ¼ 61 Uꢁ1 molꢁ1 cm2. No melting or decomposition at
T ꢂ 260 ꢀC. 1H NMR {DMSO-d6, 298 K, ppm}: 9.12 (d, 1H,
3JHH ¼ 5.3 Hz, 3JPtH ¼ 53 Hz, quinoline-H2); 9.00 (d,1H, 3JHH ¼ 5.3 Hz,
3
pyridine-H6’); 8.90 (d, 1H, JHH ¼ 8.2 Hz, quinoline-H4); 8.30 (t, 1H,
3JHH ¼ 7.8 Hz, pyridine-H4’); 8.21 (d, 1H, 3JHH ¼ 8.0 Hz, quinoline-H7);
7.92 (m, 1H, pyridine-H53’); 7.88e7.77 (m, 5H, imine-phenyl); 7.75
2.5.2. Characterization of 2NNImH
Elemental analysis of C14H13ClN4O4Pd: calcd. C 37.9, H 2.96,
N 12.6, Cl 8.00; found C 37.7, H 2.97, N 12.5, Cl 7.97. LM (dmf,
3
(dd, 1H, JHH ¼ 5.3 Hz, JHH ¼ 8.2 Hz, quinoline-H3); 7.56 (t, 1H,
3JHH ¼ 8.0 Hz, quinoline-H6); 7.34 (d, 1H, 3JHH ¼ 7.8 Hz, pyridine-H3’);
6.94 (d,1H, 3JHH ¼ 8.0 Hz, quinoline-H5); 1.21 (s, 3H, 2JPtH ¼ 74 Hz, Pt-
CH3). 13C {1H} NMR {DMSO-d6, 298 K, ppm}: 167.2 imine-C,
163.4e124.1 ancillary ligand carbons, ꢁ6.2 Pt-CH3.
298 K) ¼ 77
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 240 ꢀC. 1H NMR
{DMSO-d6, 298 K, ppm}: 13.71 (s, very br,1H, imidazole-NH); 9.12 (s,
1H, imine-CH); 8.61 (d, 1H, 3JHH ¼ 8.3 Hz, quinoline-H4); 8.53 (d, 1H,
3JHH ¼ 5.0 Hz, quinoline-H2); 8.23 (s, 1H, imidazole-H2’); 8.20 (d,
1H, 3JHH ¼ 7.7 Hz, quinoline-H7); 8.14 (s, 1H, imidazole-H5’); 8.00 (d,
1H, 3JHH ¼ 7.7 Hz, quinoline-H5); 7.72 (t, 1H, 3JHH ¼ 7.7 Hz, quinoline-
H6); 7.63 (dd, 1H, 3JHH ¼ 5.0 Hz, 3JHH ¼ 8.3 Hz, quinoline-H3); 0.62 (s,
3H, Pd-CH3). 13C {1H} NMR {DMSO-d6, 298 K, ppm}: 151.0 quinoline-
C2, 149.3 imine-C, 139.4 imidazole-C2’, 139.2 quinoline-C4, 129.2
quinoline-C5,128.1 quinoline-C6,125.7 imidazole-C5’,123.3 quinoline-
C3, 119.5 quinoline-C7, -3.7 Pd-CH3, 148.2, 144.9, 138.1, 130.3 ancillary
ligand not H-bonded carbons.
2.4.4. Characterization of 1NNTh
Elemental analysis for C15H12F3N3O3PtS2: calcd. C 30.1, H 2.02,
N
7.02; found C 30.0, H 2.02, N 7.00. LM (nitromethane,
298 K) ¼ 71 Uꢁ1 molꢁ1 cm2. No melting or decomposition at
T ꢂ 260 ꢀC. 1H NMR {CD3NO2, 298 K, ppm}: 9.77 (s,1H, 3JPtH ¼ 37 Hz,
3
3
imine-CH); 8.78 (d, 1H, JHH ¼ 5.0 Hz, JPtH ¼ 59 Hz, quinoline-H2);
8.66 (d, 1H, 3JHH ¼ 8.5 Hz, quinoline-H4); 8.31 (d, 1H, 3JHH ¼ 8.0 Hz,
3
quinoline-H7); 8.29 (d, 1H, JHH ¼ 3.2 Hz, thiazole-H5’); 8.12 (d, 1H,
3JHH ¼ 8.0 Hz, quinoline-H5); 7.99 (d, 1H, 3JHH ¼ 3.2 Hz, 3JPtH ¼ 20 Hz,
3
thiazole-H4’); 7.74 (t, 1H, JHH ¼ 8.0 Hz, quinoline-H6); 7.56 (dd, 1H,
2.6. Synthesis of [PtCl(NNTh)](SO3CF3) (3NNTh) and
3JHH ¼ 5.0 Hz, 3JHH ¼ 8.5 Hz, quinoline-H3); 1.22 (s, 3H, 2JPtH ¼ 77 Hz,
Pt-CH3). 13C {1H} NMR {CD3NO2, 298 K, HSQC projection, ppm}:
150.6 quinoline-C2, 148.6 imine-C, 143.4 thiazole-C4’, 139.9 quinoline-
C4, 132.8 quinoline-C5, 131.8 thiazole-C5’, 131.0 quinoline-C6, 126.0
quinoline-C3, 122.1 quinoline-C7, -11.1 Pt-CH3.
[PtCl(NNImH)](X) (X ¼ SO3CF3 or ClO4) (3NNImH
)
The synthetic procedure for the preparation of chloro-
complexes 3NNTh and 3NNImH was the same previously described
for the methyl-complexes 1NNTh and 1NNImH, starting from 0.222 g
(0.57 mmol) of cis/trans-PtCl2(SMe2)2. The yields were >80% for the
perchlorate salt and >70% for the triflate salts. Slow cooling of
dimethylformamide/nitromethane/diethylether solutions purified
all the complexes as microcrystalline solids.
2.4.5. Characterization of 1NNImH
Elemental analysis for C14H13ClN4O4Pt: calcd. C 31.6, H 2.46,
N 10.5, Cl 6.67; found C 31.5, H 2.45, N 10.5, Cl 6.65. LM (dmf,

2568
M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2.6.1. Characterization of 3NNTh
Elemental analysis for C14H9ClF3N3O3PtS2: calcd. C 27.2, H 1.47,
N 6.79, Cl 5.73; found C 27.1, H 1.47, N 6.76, Cl 5.71. LM (nitro-
quinoline-H6); 7.87 (dd, 1H, 3JHH ¼ 5.2 Hz, 3JHH ¼ 8.2 Hz, quinoline-
H3). 13C {1H} NMR {DMSO-d6, 298 K, HSQC projection, ppm}: 155.5
imine-C, 151.9 quinoline-C2, 140.7 imidazole-C5’, 140.4 quinoline-C4,
129.5 quinoline-C5, 128.7 quinoline-C6, 128.1 imidazole-C2’, 123.8
quinoline-C3, 120.5 quinoline-C7.
methane, 298 K) ¼ 74
U
ꢁ1 molꢁ1 cm2. No melting or decomposition
at T ꢂ 260 ꢀC. 1H NMR {CD3NO2, 298 K, ppm}: 9.77 (s, 1H,
3JPtH ¼ 98 Hz, imine-CH); 9.0 (d, 1H, JHH ¼ 5.0 Hz, JPtH ¼ 42 Hz,
quinoline-H2); 8.76 (d, 1H, 3JHH ¼ 8.3 Hz, quinoline-H4); 8.54 (d, 1H,
3JHH ¼ 3.2 Hz, thiazole-H5’); 8.50 (d, 1H, 3JHH ¼ 8.0 Hz, quinoline-H7);
8.25 (d, 1H, 3JHH ¼ 8.0 Hz, quinoline-H5); 8.07 (d, 1H, 3JHH ¼ 3.2 Hz,
3
3
2.8. Synthesis of [Pt(OSO2CH3)(NNImH)](SO3CF3) (5NNImH
)
thiazole-H4’); 7.88 (t, 1H, JHH ¼ 8.0 Hz, quinoline-H6); 7.69 (dd, 1H,
To a solution of 3NNImH (triflate salt, 0.162 g, 0.27 mmol) in 20 mL
of nitromethane a stoichiometric amount of silver methanesulfo-
nate (0.055 g, 0.27 mmol) was added. The reaction mixture was left
overnight under stirring in the dark at room temperature. The AgCl
formed was then removed by filtration and the solution was
concentrated under reduced pressure to about 3 mL. Diethylether
was then added drop by drop until a dark yellow solid started to
separate. After one night at ꢁ25 ꢀC the product was collected by
filtration, washed with diethylether (20 mL) and dried at reduced
pressure. Yield > 75%.
3
3JHH ¼ 5.0 Hz, 3JHH ¼ 8.3 Hz, quinoline-H3). 13C {1H} NMR {CD3NO2,
298 K, HSQC projection, ppm}: 153.7 imine-C, 151.4 quinoline-C2,
144.0 thiazole-C4’, 141.5 quinoline-C4, 133.5 quinoline-C5, 133.0 thia-
zole-C5’, 131.2 quinoline-C6, 125.9 quinoline-C3, 122.5 quinoline-C7.
2.6.2. Characterization of 3NNImH
Elemental analysis for C13H10Cl2N4O4Pt: calcd. C 28.3, H 1.83,
N 10.2, Cl 12.8; found C 28.2, H 1.82, N 10.1, Cl 12.79. LM (dmf,
298 K) ¼ 54 Uꢁ1 molꢁ1 cm2. No melting or decomposition at
T ꢂ 260 ꢀC. 1H NMR {DMSO-d6, 298 K, ppm}: 14.5 (s, very br, 1H,
2.8.1. Characterization of 5NNImH
3
imidazole-NH); 9.74 (s, 1H, JPtH ¼ 96 Hz, imine-CH); 9.21 (d, 1H,
Elemental analysis for C15H13F3N4O6PtS2: calcd. C 27.2, H 1.98,
N 8.47; found C 27.3, H 2.00, N 8.44. LM (nitromethane, 298 K) ¼
54 Uꢁ1 molꢁ1 cm2; LM (DMSO, 298 K) ¼ 32 Uꢁ1 molꢁ1 cm2. No
melting or decomposition at T ꢂ 260 ꢀC. 1H NMR {DMSO-d6, 298 K,
ppm}: 9.76 (s, 1H, imine-CH); 9.50 (s, br, 1H, imidazole-NH); 9.05
(d, 1H, 3JHH ¼ 8.6 Hz, quinoline-H4); 8.91 (s, 1H, imidazole-H2’); 8.84
(s, 1H, imidazole-H5’); 8.74 (d, 1H, 3JHH ¼ 8.2 Hz, quinoline-H7); 8.65
3JHH ¼ 5.0 Hz, quinoline-H2); 8.97 (d, 1H, JHH ¼ 8.5 Hz, quinoline-
3
H4); 8.65 (d, 1H, 3JHH ¼ 8.0 Hz, quinoline-H7); 8.62 (s, 1H, imidazole);
8.52 (s, 1H, imidazole); 8.25 (d, 1H, 3JHH ¼ 8.0 Hz, quinoline-H5); 7.94
3
3
(t, 1H, JHH ¼ 8.0 Hz, quinoline-H6); 7.88 (dd, 1H, JHH ¼ 5.0 Hz,
3JHH ¼ 8.5 Hz, quinoline-H3). 13C {1H} NMR {DMSO-d6, 298 K, HSQC
projection, ppm}: 155.6 imine-C, 150.9 quinoline-C2, 141.9 imidazole,
140.9 quinoline-C4, 130.5 imidazole, 130.4 quinoline-C5, 130.1 quin-
oline-C6, 125.0 quinoline-C3, 121.4 quinoline-C7.
3
3
(d, 1H, JHH ¼ 5.3 Hz, quinoline-H2); 8.31 (d, 1H, JHH ¼ 8.2 Hz,
quinoline-H5); 8.01 (t, 1H, 3JHH ¼ 8.2 Hz, quinoline-H6); 7.87 (dd, 1H,
3JHH ¼ 5.3 Hz, 3JHH ¼ 8.6 Hz, quinoline-H3); 2.35 (s, 3H, CH3SO3). 13
C
{1H} NMR {DMSO-d6, 298 K, ppm}: 155.9 imine-CH, 151.2 quinoline-
C2, 149.6 imidazole-C2’, 141.4 quinoline-C4, 141.2 imidazole-C5’, 130.5
quinoline-C7, 130.2 quinoline-C6, 125.2 quinoline-C3, 121.1 quinoline-
C5, 148.5, 146.1, 141.5, 130.8 ancillary ligand not H-bonded carbons,
40.6 CH3SO3 (HSQC projection).
2.7. Synthesis of [PdCl(NNTh)](SO3CF3) (4NNTh) and
[PdCl(NNImH)](SO3CF3) (4NNImH
)
The synthetic procedure for the preparation of 4NNTh and 4NNImH
was the same as previously described for the Pt(II) chloro-
complexes 3NNTh and 3NNImH
, using PdCl2(COD) (0.163 g,
0.57 mmol) as starting reagent. The yield was >70% for both the
complexes.
2.9. Synthesis of [Pd(OSO2CH3)(NNImH)](SO3CF3) (6NNImH
)
The synthetic procedure for the preparation of 6 was the same
previously described for the Pt(II) complexes 5NNImH, using 4NNImH
(0.139 g, 0.27 mmol) as starting reagent. Yield > 75%.
2.7.1. Characterization of 4NNTh
Elemental analysis for C14H9ClF3N3O3PdS2: calcd. C 31.7, H 1.71,
N 7.92, Cl 6.69; found C 31.6, H 1.70, N 7.89, Cl 6.67. LM (nitro-
methane, 298 K) ¼ 59
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 220 ꢀC.
2.9.1. Characterization of 6NNImH
1H NMR {CD3NO2, 298 K, ppm}: 9.24 (s, 1H, imine-CH); 8.93 (d, 1H,
Elemental analysis for C15H13F3N4O6PdS2: calcd. C 31.5, H 2.29,
N 9.78; found C 31.4, H 2.28, N 9.75. LM (nitromethane, 298 K) ¼
57 Uꢁ1 molꢁ1 cm2; LM (DMSO, 298 K) ¼ 32 Uꢁ1 molꢁ1 cm2.
Decomposition at T > 220 ꢀC. 1H NMR {CD3NO2, 336 K, ppm}: 9.04
3JHH ¼ 5.3 Hz, quinoline-H2); 8.74 (d, 1H, JHH ¼ 8.4 Hz, quinoline-
3
3
H4); 8.45 (d, 1H, JHH ¼ 7.8 Hz, quinoline-H7); 8.42 (d, 1H,
3JHH ¼ 3.3 Hz, thiazole-H5’); 8.27 (d, 1H, 3JHH ¼ 7.8 Hz, quinoline-H5);
3
3
8.13 (d, 1H, JHH ¼ 3.3 Hz, thiazole-H4’); 7.94 (t, 1H, JHH ¼ 7.8 Hz,
quinoline-H6); 7.79 (dd, 1H, 3JHH ¼ 5.3 Hz, 3JHH ¼ 8.4 Hz, quinoline-
H3). 13C {1H} NMR {CD3NO2, 298 K, HSQC projection, ppm}: 154.3
quinoline-C2, 153.9 imine-C, 145.1 thiazole-C4’, 142.5 quinoline-C4,
134.1 quinoline-C5, 132.2 thiazole-C5’, 130.7 quinoline-C6, 125.5
quinoline-H3, 122.8 quinoline-C7.
3
(s, 1H, imine-CH); 8.75 (d, 1H, JHH ¼ 8.3 Hz, quinoline-H4); 8.47
(s, 1H, imidazole-H2’); 8.42 (d, 1H, 3JHH ¼ 5.2 Hz, quinoline-H2); 8.38
(d, 1H, 3JHH ¼ 7.8 Hz, quinoline-H7); 8.31 (s, 1H, imidazole-H5’); 8.11
3
3
(d, 1H, JHH ¼ 7.8 Hz, quinoline-H5); 7.89 (t, 1H, JHH ¼ 7.8 Hz,
quinoline-H6); 7.78 (dd, 1H, 3JHH ¼ 5.2 Hz, 3JHH ¼ 8.3 Hz, quinoline-
H3); 2.10 (s, 3H, CH3SO3). 1H NMR {DMSO-d6, 298 K, ppm}: 9.46 (s,
1H, imine-CH); 9.44 (s, br, 1H, imidazole-NH); 8.96 (d, 1H,
3JHH ¼ 8.4 Hz, quinoline-H4); 8.70 (s, 1H, imidazole-H2’); 8.65 (s, 1H,
imidazole-H5’); 8.63 (d, 1H, 3JHH ¼ 7.8 Hz, quinoline-H7); 8.37 (d, 1H,
2.7.2. Characterization of 4NNImH
Elemental analysis for C14H10ClF3N4O3PdS: calcd. C 32.8, H 1.96,
N 10.9, Cl 6.91; found C 32.7, H 1.95, N 10.9, Cl 6.89. LM (dmf,
3
3JHH ¼ 5.2 Hz, quinoline-H2); 8.26 (d, 1H, JHH ¼ 7.8 Hz, quinoline-
3
298 K) ¼ 57
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 220 ꢀC. 1H NMR
H5); 8.00 (t, 1H, JHH ¼ 7.8 Hz, quinoline-H6); 7.87 (dd, 1H,
{DMSO-d6, 298 K, ppm}: 14.22 (s, very br, 1H, imidazole-NH); 9.34
3JHH ¼ 5.2 Hz, 3JHH ¼ 8.4 Hz, quinoline-H3); 2.37 (s, 3H, CH3SO3). 13
C
(s, 1H, imine-CH); 8.93 (d, 1H, 3JHH ¼ 5.2 Hz, quinoline-H2); 8.88 (d,
{1H} NMR {CD3NO2, 317 K, ppm}: 155.9e120.6 ancillary ligand CH
carbons, 40.2 CH3SO3. 13C {1H} NMR {DMSO-d6, 298 K, ppm}: 156.0,
152.6,148.9,147.1,144.2,141.1,140.7,139.0,130.5,129.2, 128.9, 123.9,
119.8 ancillary ligand carbons.
3
3
1H, JHH ¼ 8.2 Hz, quinoline-H4); 8.56 (d, 1H, JHH ¼ 7.9 Hz, quino-
line-H7); 8.51 (s, 1H, imidazole-H2’); 8.43 (s, 1H, imidazole-H5’); 8.22
3
3
(d, 1H, JHH ¼ 7.9 Hz, quinoline-H5); 7.93 (t, 1H, JHH ¼ 7.9 Hz,

M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2569
2.10. Synthesis of [PtMe(NNIm)] (7NNIm
)
n
¼ 1689 cmꢁ1
[
n
(CO)]. 1H NMR {CD3NO2, 298 K, ppm}: 9.16 (s, 1H,
3
imine-CH); 8.55 (d, 1H, JHH ¼ 8.3 Hz, quinoline-H4); 8.53 (d, 1H,
In an NMR tube 1NNImH (38 mg, 71
m
mol) was dissolved in 1 mL
3JHH ¼ 5.0 Hz, quinoline-H2); 8.26 (d, 1H, 3JHH ¼ 3.3 Hz, thiazole-H5’);
3
3
of DMSO-d6. An equimolar amount of triethylamine (10 L, 71 L)
m
m
8.19 (d, 1H, JHH ¼ 7.8 Hz, quinoline-H7); 8.11 (d, 1H, JHH ¼ 7.8 Hz,
was then added with a microsyringe and the 1H NMR spectrum was
recorded. After the addition of the base the 1H NMR spectrum
showed only signals attributable to the products formed. The
complex was separated from the by-product [NHEt3](ClO4) by slow
addition of diethylether followed by fractional crystallization. The
complex was then washed several times with diethylether to
remove the traces of DMSO and dried under vacuum.
quinoline-H5); 7.99 (d, 1H, JHH ¼ 3.3 Hz, thiazole-H4’); 7.79 (t, 1H,
3
3JHH
¼
7.8 Hz, quinoline-H6); 7.67 (dd, 1H, JHH
¼
5.0 Hz,
3
3JHH ¼ 8.3 Hz, quinoline-H3); 2.67 (s, 3H, Pd-COCH3). 13C {1H} NMR
{CD3NO2, 298 K, ppm}: 229.9 Pd-COCH3, 169.0, 153.0, 137.9, 132.4
ancillary ligand not H-bonded carbons, 154.16 quinoline-C2, 149.2
imine-C, 146.2 quinoline-C4, 141.6 thiazole-C4’, 133.6 quinoline-C5,
130.6 thiazole-C5’, 129.9 quinoline-C6, 125.0 quinoline-C3, 121.6
quinoline-C7, 32.9 Pd-COCH3.
2.10.1. Characterization of 7NNIm
Elemental analysis for C14H12N4Pt: calcd. C 39.0, H 2.80, N 13.0;
2.12.2. Characterization of 9NNPy
found C 39.2, H 2.81, N 13.1. 1H NMR {DMSO-d6, 298 K, ppm}: 9.38
Elemental analysis for C18H14F3N3O4PdS: calcd. C 40.7, H 2.65,
3
3
(s, 1H, JPtH ¼ 36 Hz, imine-CH); 8.99 (d, 1H, JHH ¼ 4.9 Hz,
N
7.90; found
C
40.5,
ꢁ1 molꢁ1 cm2. Decomposition at T > 220 ꢀC. IR (KBr):
(CO)]. 1H NMR {CD3NO2, 298 K, ppm}: 9.16 (s, 1H,
H 2.64, N 7.88. LM (nitromethane,
3JPtH ¼ 52 Hz, quinoline-H2); 8.77 (d, 1H, JHH ¼ 8.4 Hz, quinoline-
298 K) ¼ 81
U
3
3
H4); 8.27 (d, 1H, JHH ¼ 7.5 Hz, quinoline-H7); 7.95 (d, 1H,
n
¼ 1677 cmꢁ1
[n
3JHH ¼ 7.5 Hz, quinoline-H5); 7.91 (s, 1H, imidazolate); 7.72 (t,
imine-CH); 8.59 (dd, 1H, 3JHH ¼ 8.5 Hz, 4JHH ¼ 1.5 Hz, quinoline-H4);
8.53 (dd, 1H, 3JHH ¼ 4.8 Hz, 4JHH ¼ 1.5 Hz, quinoline-H2); 8.30e7.72
(m, 7H, aromatic protons); 7.70 (d, 1H, 3JHH ¼ 8.5 Hz, 3JHH ¼ 4.8 Hz,
quinoline-H3); 2.67 (s, 3H, Pd-COCH3). 13C {1H} NMR {CD3NO2, 298 K,
ppm}: 235.9 Pd-COCH3, 157.0 imine-C, 155.2 quinoline-C2, 141.7
quinoline-C4, 125.1 quinoline-C3, 154.1, 142.6, 133.4, 131.5, 131.3,
129.9, 121.6 aromatic rings CH carbons, 158.4, 148.9, 138.0, 122.1
aromatic rings not H-bonded carbons, 32.8 Pd-COCH3.
3
3
1H, JHH ¼ 7.5 Hz, quinoline-H6); 7.57 (dd, 1H, JHH ¼ 4.9 Hz,
3JHH ¼ 8.4 Hz, quinoline-H3); 7.54 (s, 1H, imidazolate); 0.99 (s, 3H,
2JPtH ¼ 78 Hz, Pt-CH3).
2.11. Synthesis of [PtMe(CO)(NNTh)](SO3CF3) (8NNTh
)
A solution of 1NNTh (0.148 g, 0.25 mmol) in 25 mL of nitro-
methane was kept under stirring at room temperature under CO
atmosphere. The evolution of the reaction was followed by IR
spectroscopy. The reaction ends after about 9 h. The product can be
isolated by addition of diethylether to the reaction mixture, but the
2.12.3. Characterization of 9NNImH
Elemental analysis for C15H13ClN4O5Pd: calcd. C 38.2, H 2.74,
N 11.9, Cl 7.52; found C 38.1, H 2.73, N 11.9, Cl 7.50. LM (dmf,
final complex slowly loses CO with the formation of 1NNTh
.
298 K) ¼ 66
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 210 ꢀC. IR (nujol):
A solution of pure complex for NMR characterization was prepared
by carrying out the same reaction in 1 mL of deuterated nitro-
methane, using 15 mg (0.025 mmol) of 1NNTh as reactant.
n
¼ 1666 cmꢁ1
[n
(CO)]. 1H NMR {CD3NO2, 298 K, ppm}: 11.21 (s,
very br, 1H, imidazole-NH); 8.85 (s, 1H, imine-CH); 8.65 (dd, 1H,
3JHH
¼
5.1 Hz, JHH
¼
1.5 Hz, quinoline-H2); 8.52 (dd, 1H,
4
3JHH ¼ 8.4 Hz, JHH ¼ 1.5 Hz, quinoline-H4); 8.08 (s, 1H, imidazole-
4
2.11.1. Characterization of 8NNTh
H2’); 8.04 (d, 1H, JHH ¼ 7.8 Hz, quinoline-H7); 7.98 (d, 1H,
3
LM (nitromethane, 298 K) ¼ 80 Uꢁ1 molꢁ1 cm2. IR (KBr):
3JHH ¼ 7.8 Hz, quinoline-H5); 7.96 (s, 1H, imidazole-H5’); 7.73 (t,
3
3
n
n
¼ 2095 cmꢁ1
¼ 2060 cmꢁ1
[n
n
(CO)], IR (nitromethane):
n
¼ 2106 cmꢁ1
[
n(
12CO)],
1H, JHH ¼ 7.8 Hz, quinoline-H6); 7.67 (dd, 1H, JHH ¼ 5.1 Hz,
3JHH ¼ 8.4 Hz, quinoline-H3); 2.60 (s, 3H, Pd-COCH3). 13C {1H} NMR
{CD3NO2, 298 K, ppm}: 229.4 Pd-COCH3, 153.5, 150.3, 142.3, 141.3,
131.3, 129.5, 126.5, 124.4, 119.3 ancillary ligand CH carbons, 148.4,
145.3, 138.7, 132.2 ancillary ligand not H-bonded carbons, 34.9 Pd-
COCH3.
[
(
13CO)]. 1H NMR {CD3NO2, 298 K, ppm}: 9.79 (s, 1H,
3
3
3JPtH ¼ 43 Hz, imine-CH); 9.22 (d, 1H, JHH ¼ 4.7 Hz, JPtH ¼ 46 Hz,
quinoline-H2); 8.91 (d, 1H, 3JHH ¼ 8.1 Hz, quinoline-H4); 8.46 (d, 1H,
3JHH ¼ 8.0 Hz, quinoline-H7); 8.35 (d, 1H, 3JHH ¼ 3.1 Hz, thiazole-H5’);
3
8.27 (d, 1H, JHH ¼ 8.0 Hz, quinoline-H5); 8.15e7.92 (m, 2H, quino-
line-H6 and thiazole-H4’); 7.84 (dd, 1H, 3JHH ¼ 4.7 Hz, 3JHH ¼ 8.1 Hz,
2
quinoline-H3); 1.42 (s, 3H, JPtH ¼ 71 Hz, Pt-CH3).
2.13. Theoretical calculations
2.12. Synthesis of [Pd(COMe)(NNTh)](SO3CF3) (9NNTh),
Restricted DFT calculations were applied for the geometry
optimisation of the Pt(II) and Pd(II) methyl-complexes and their
adducts with CO. The calculations were carried out using the EDF2
and M06 hybrid functionals [19] in combination with the LACVP**
basis set [20]. The stationary points were characterized as true
minima by IR simulation. The energy differences between reactants
and products were corrected for the zero-point vibrational energy
and the basis set superposition error. Charge distributions were
derived from Mulliken population analysis [21]. All the calculations
were performed with an Intel Core I7-based x86-64 workstation
using the Spartan ’08 software package [22].
[Pd(COMe)(NNPy)](SO3CF3) (9NNpy) and [Pd(COMe)(NNImH)](ClO4)
(9NNImH
)
A solution of 2NNTh (0.102 g, 0.20 mmol), 2NNPy (triflate salt,
0.101 g, 0.20 mmol) or 2NNImH (0.089 g, 0.20 mmol) in 20 mL of
nitromethane was put under a CO atm and allowed to stir at room
temperature. The evolution of the reaction was followed by IR
spectroscopy. After a variable time (48 h using 2NNTh, 8 h using
2NNPy, 2.5 h using 2NNImH) the solution was concentrated at reduced
pressure to about 5 mL. Slow addition of diethylether caused the
separation of a dark yellow solid, which was filtered, washed with
diethylether (20 mL) and dried under vacuum. Yields >95% in all
the cases.
3. Results and discussion
3.1. Metal-assisted synthesis of Pd(II) and Pt(II) complexes
2.12.1. Characterization of 9NNTh
Elemental analysis for C16H12F3N3O4PdS2: calcd. C 35.7, H 2.25,
The metal-assisted condensation between pyridine-2-
carboxaldehyde or 2-keto-pyridines and 8-aminoquinoline,
affording the formation of quinoline-imine-pyridine complexes
N
7.81; found
C 35.6, H 2.24, N 7.78. LM (nitromethane,
298 K) ¼ 60
U
ꢁ1 molꢁ1 cm2. Decomposition at T > 210 ꢀC. IR (nujol):

2570
M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2
having d8 metal centres, was already reported in the literature
[9,10]. In particular, we published the synthesis and characteriza-
tion of [PtCl(NNPy)](OTf), [PdCl(NNPy)](OTf), [PdMe(NNPy)](OTf)
(2NNPy), [PdMe(NNMePy)](OTf) and [PdMe(NNPhPy)](OTf).
complexes as singlet in the low-frequency region with a JPtH
coupling constant ranging from 73 to 77 Hz. The signals corre-
sponding to the aromatic protons of the N-heterocycles have been
assigned on the basis of COSY and NOESY spectra. In the case of
complex 1NNImH a broad signal at 13.81 ppm indicates the presence
of the NH proton and the NOESY spectrum highlights its chemical
exchange with water traces on the NMR timescale. 13C {1H} NMR
spectra are in agreement with the proposed formulations and the
carbon atoms have been correlated to their bonded hydrogen atoms
on the basis of HSQC spectra. Imine carbon atoms give 13C NMR
signals in the range 167.2e148.6 ppm, while the coordinated methyl
groups are observable between ꢁ16.7 and ꢁ6.2 ppm.
The reaction of the starting precursor PtClMe(COD) with stoi-
chiometic amounts of 8-aminoquinoline and aldehydes such
as pyridine-2-carboxaldehyde, thiazole-2-carboxaldehyde and
imidazole-4-carboxaldehyde leads to the formation of the new
cationic Pt(II) methyl-complexes [PtMe(NNPy)]þ (1NNPy),
PtMe(NNTh)]þ (1NNTh
)
and [PtMe(NNImH)]þ (1NNImH). The
replacement of the aldehydes with ketones such as 2-acetyl-pyri-
dine and 2-benzoyl-pyridine leads to the metal-assisted conden-
sation products [PtMe(NNMePy)]þ (1NNMepy) and [PtMe(NNPhPy)]þ
(1NNPhPy) (see Scheme 2). All these compounds have been isolated
as triflate and/or perchlorate salts and characterized. Triflate salts
are slightly more soluble in methanol than the corresponding
perchlorates. The elemental analyses of the Pt(II) methyl-complexes
are in agreement with the proposed formulations. Conductivity
data show that these complexes behave as 1:1 electrolytes in
nitromethane or dimethylformamide solutions. IR spectra do not
show any signal attributable to the C]O stretching. In the 1H NMR
spectra of the aldehyde derivatives 1NNPy, 1NNTh and 1NNImH a sharp
singlet is observable in the high-frequency region, attributable to
the imine proton. Experiments at variable temperature
(298e346 K) carried out on 1NNPy have highlighted no meaningful
The methyl-complexes of palladium(II) [PdMe(NNTh)]þ (2NNTh
)
and [PdMe(NNImH)]þ (2NNImH) have been obtained on the basis of
the same procedure described for 1NNTh and 1NNImH
,
using
PdClMe(COD) as precursor (see Scheme 2). The complex
[PdMe(NNPy)](OTf) (2NNPy), already described in a previous paper
[10], has been synthesized again to compare its reactivity with that
of 2NNTh and 2NNImH. The formulations proposed for 2NNTh and
2NNImH, isolated as perchlorate or triflate salts, are in agreement
with the elemental analyses and the conductivity data. The solu-
bility of 2NNTh is lower using perchlorate as counter-anion. As for
the Pt(II) complexes, the 1H NMR spectra of 2NNTh and 2NNImH show
singlets at 9.30 ppm (2NNTh) and 9.12 (2NNImH) attributable to the
imine protons, while the coordinated CH3 resonates at 1.08 ppm
(2NNTh) and 0.62 ppm (2NNImH). Experiments at variable tempera-
ture (298e336 K) carried out on 2NNTh have shown no meaningful
change on the 1H NMR spectrum. As for 1NNImH, also in the NOESY
spectrum of 2NNImH cross-peaks attributable to the chemical
3
influence of temperature on the 1H NMR spectrum. The JPtH
coupling constants are in the range 32e38 Hz. In the case of 1NNMePy
the methyl substituent on the imine group corresponds to a singlet
at 2.50 ppm. The coordinated methyl ligand is observable in all the
Scheme 2. Synthesis of complexes 1e4.

M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2571
exchange between the NH (13.71 ppm) and water traces are
observable. The aromatic regions of the 1H NMR spectra are
comparable with those of the corresponding Pt(II) derivatives, with
the obvious absence of the 195Pt satellites. Also the 13C {1H} NMR
spectra of 2NNTh and 2NNImH are strictly similar to those of the Pt(II)
derivatives.
8-aminoquinoline and thiazole-2-carboxaldehyde leads to the
presence in solution of a complex mixture of different species.
In the presence of an appropriate transition metal precursor we
have observed in all the cases the formation of the condensation
products coordinated to the metal centre. These results allow
supposing that the reaction pathway leading to the final complexes
is scarcely dependent upon possible equilibrium reactions between
the organic ligands. The ability of the transition metal precursor to
coordinate the 8-aminoquinoline and the other N-heterocycle is,
instead, of primary importance. The metal-assisted condensation
does not happen, for example, using PtCl2(COD), which is less
reactive than cis/trans-PtCl2(SMe)2 [23]. Moreover, in our previous
studies we have observed in some cases that the metal-assisted
condensation happens only by removing a coordinated chloro-
ligand from the transition metal precursor using a silver salt [10].
Probably, the key step of the metal-assisted condensation
reactions is the formation of an intermediate species where both
the 8-aminoquinolne and the other N-heterocycle are coordinated
with a suitable geometry. This intermediate could be stabilized by
an intramolecular hydrogen bond between the 8-aminoquinoline
NH2 group and the carbonyl oxygen atom. An increase of acidity of
the NH protons caused by coordination is expectable, and a proton
transfer from NH2 to the carbonyl oxygen atom probably happens
before the electrophilic attack of the carbonyl C atom on the
coordinated sp3 N atom of 8-aminoquinoline. After the formation of
the hydroxy-amine species, the successive elimination of water
Chloro-complexes of Pt(II) and Pd(II), indicated as [PtCl(NNTh)]þ
(3NNTh), [PtCl(NNImH)]þ (3NNImH), [PdCl(NNTh)]þ (4NNTh
) and
[PdCl(NNImH)]þ (4NNImH) have been obtained as perchlorate and/
or triflate salts by metal-assisted condensation of thiazole-2-
carboxaldehyde or imidazole-4-carboxaldehyde with 8-amino-
quinoline, using as precursors cis/trans-PtCl2(SMe2)2 and
PdCl2(COD) (see Scheme 2). Chloro-complexes of Pt(II) and Pd(II)
containing a pyridine ring in the tridentate ligand have been
already prepared on the basis of the same synthetic approach [10].
Preliminary studies have shown that the complex PtCl2(COD) is not
a suitable precursor for the metal-assisted condensations con-
sidered in this work, having a lower reactivity as compared to
cis/trans-PtCl2(SMe2)2 [23]. The formation of tridentate cationic
complexes has been confirmed by their elemental analyses (C, H, N,
Cl), the conductivity of their solutions in polar solvents and their
NMR spectra. The high-frequency regions of the 1H NMR and
13C {1H} spectra are similar to those of the already described
3
methyl-complexes. The JPtH coupling constant between the metal
centre and the imine CH proton in 3NNTh and 3NNImH is around
96e98 Hz, meaningfully higher than those observed for the cor-
responding methyl-complexes, 32e37 Hz. This result highlights the
greater trans-influence of the methyl ligand with respect to the
chloro-ligand and the consequent elongation of the Pt-N(imine)
bond [24].
should be favoured by the formation a
p-extended system. The
supposed reaction mechanism is depicted in Scheme 3.
3.3. Preliminary reactivity studies: reactions with silver salts and
bases
The methyl- and chloro-complexes 1e4 have been obtained in
very pure form by slow diffusion of diethylether in concentrated
dimethylformamide or dimethylformamide/nitromethane solution
of the complexes. Small crystals of these products have been also
isolated by slowly cooling (from þ30 ꢀC to ꢁ25 ꢀC during a week)
clear solutions of these complexes in mixtures of dimethylforma-
mide, nitromethane and diethylether. Other solvents, such as
dimethylsulfoxide, dichloromethane, methanol and 2,2,2-tri-
fluoroethanol have been used in various proportions, but we have
never obtained crystals of the products using these last solvents.
Even if several small crystals obtained were apparently suitable for
X-Ray diffraction, all the measurements carried out using a Nonius
The preliminary reactivity studies have been focused on the new
imidazole-based complexes. The chloro-complexes 3NNImH and
4NNImH have been used as precursors for the preparation of Pt(II)
and Pd(II) square-planar complexes having weak O-donor ligands
in their coordination sphere [26]. In our previous work we obtained
[Pd(h1eOSO2CH3)(NNMePy)](OTf) by reacting [PdCl(NNMe-
Py)](OTf) with
a
stoichiometric amount of AgCH3SO3 in
Kappa CCD diffractometer with graphite-monochromated Mo-K
a
radiation haven’t led to any resolved structure, because all the
crystals displayed high mosaicity and very poor diffraction figures.
3.2. Factors influencing the reaction mechanism
The reaction between 8-aminoquinoline and the various alde-
hydes and ketones considered in this paper has been studied by
NMR spectroscopy in CD3OD at room temperature. 8-amino-
quinoline readily reacts with pyridine-2-carboxaldehyde with the
formation of the corresponding emiaminal [10]. GS-MS measure-
ments on a freshly prepared solution of 8-aminoquinoline and
pyridine-2-carboxaldehyde in methanol showed a signal attribut-
able to the imine-ligand NNPy (m/z ¼ 233), but the elimination of
a water molecule from the corresponding emiaminal is attributable
to the temperature required for this experiment, above 100 ꢀC. No
reaction has been observed by NMR spectroscopy between
8-aminoquinoline and 2-acetyl-pyridine, 2-benzoyl-pyridine and
imidazole-4-carboxaldehyde in the same experimental conditions
used for the metal-assisted condensations, even if the formation of
condensation products is possible in the presence of catalysts or
using harsh conditions [9,25]. Finally, the reaction between
Scheme 3. Proposed reaction mechanism for the metal-assisted condensation.

2572
M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
Table 1
nitromethane at room temperature [10]. The same reaction, carried
Selected coupling constants in 1NNImH and 7NNIm
.
out on the chloro-complexes 3NNImH and 4NNImH, leads to the
h
1-methanesulphonato-complexes [Pt(O-
Coupling constant
Fragment
1NNImH (Hz)
7NNIm (Hz)
formation of the
SO2CH3)(NNImH)](SO3CF3)
(5NNImH
)
and
[Pt(O-
2JPtH
3JPtH
3JPtH
Pt-CH3
Pt-imine
Pt-quinoline
75
36
52
78
32
57
SO2CH3)(NNImH)](SO3CF3) (6NNImH), as depicted in Scheme 4.
The elemental analyses are in agreement with the proposed
formulations. The complexes 5NNImH and 6NNImH behave as 1:1
electrolytes both in nitromethane solution and in dimethylsulfoxide
solution. This last result allows concluding that the weak meth-
anesulfonato ligand is not easily displaced by the soft ligand DMSO
at room temperature either in the Pt(II) or in the Pd(II) complex.
1H and 13C {1H} NMR spectra are comparable with those of
the other imidazole-based complexes described in this work.
The most important signals are the singlets corresponding to the
methanesulfonato-ligand, which fall around 2.3e2.4 ppm in the
1H NMR spectra and around 40e41 ppm in the 13C {1H} NMR spectra.
The presence of NH protons in the imidazole-based complexes,
which resonate in the high-frequency region and give chemical
exchange with water traces on the NMR timescale, has prompted us
to study the deprotonation of the coordinated NNImH ligand. This
reaction has been carried out in an NMR tube using DMSO-d6 as
solvent and triethylamine as base. The addition of a stoichiometric
amount of NEt3 to the methyl-complex 1NNImH causes the imme-
diate formation of the neutral complex PtMe(NNIm) (7NNIm). The
elemental analysis on the isolated product agrees with the
formulation and solutions of compound 7NNIm in DMSO are not
conductive. The same reaction carried out on 2NNImH or on the
chloro-complexes 3NNImH and 4NNImH leads instead to the
progressive formation of mixtures of products in solution, probably
because of the higher reactivity of Pd(II) as compared to Pt(II) and
the displacement of chloride by DMSO.
and the quinoline-H2 are 32 Hz and 57 Hz, respectively. These
values are compared in Table 1 for clarity.
The comparison of the coupling constants between 7NNIm and
1NNImH shows that the removal of the positive charge from complex
1NNImH causes a very limited variation of the bonds between the
metal centre and the ligands, a result in agreement with the
expected capability of charge delocalising of the polydentate
ligands considered in this work. The reaction leading to the
formation of 7NNIm is sketched in Scheme 4.
3.4. Reactivity with CO
The preliminary reactivity studies have been prosecuted on the
Pt(II) and Pd(II) methyl-complexes, using carbon monoxide as
reactant. The reaction with CO at 1 atm in nitromethane at room
temperature with the platinum derivatives 1NNTh, 1NNPy and 1NNImH
has been followed by IR spectroscopy. In these experimental
conditions the only complex that reacts with CO is the thiazole-
derivative [PtMe(NNTh)]þ (1NNTh), leading to the carbonyl-
complex 8NNTh. During about 9 h the progressive appearing of an
IR signal at 2106 cmꢁ1 has been observed, which has been attrib-
uted to the 12CO carbonyl stretching. A weak signal at 2060 cmꢁ1
corresponds to the isotopic band
experimental
theoretical value for a single carbonyl-complex using the harmonic
approximation.
n(
13CO), as observable in Fig. 1. The
Complex 7NNIm is scarcely soluble in most of the common
organic solvents, with the exception of dimethylsulfoxide. The
1H NMR spectrum shows a singlet for the coordinated methyl group
n
(
12CO)/ 13CO) ratio is 1.022, which agrees with the
n(
2
at 0.99 ppm, with a JPtH coupling constant of 78 Hz. Besides the
In nitromethane solution complex 8NNTh behaves as 1:1 elec-
trolyte. This species can be isolated as solid, but a partial lose of CO
during the work-up has been always observed, leading to the
formation of the reactant 1NNTh. The 1H NMR spectrum of a pure
sample of 8NNTh has been obtained by carrying out the reaction
between 1NNTh and CO in deuterated nitromethane. The 1H NMR
spectrum shows in the high-frequency region the signals of the
NNTh ligand, whose pattern is similar to that observed in the
1H NMR spectrum of 1NNTh. The coupling of the quinoline-H2 and
imine-CH protons with 195Pt are clearly observable. In the low-
aromatic protons, in the high-frequency region a singlet for the
imine CH at 9.38 ppm is observable, with a 3JPtH coupling constant
3
of 36 Hz. The JPtH coupling constant between Pt(II) and the quin-
2
oline-H2 is 52 Hz. In the charged precursor 1NNImH the JPtH
coupling constant corresponding to the Pt-CH3 bond is 75 Hz, while
3
the JPtH coupling constants between Pt(II) and the imine proton
frequency region
a singlet at 1.42 ppm attributable to the
Fig. 1. IR spectra (nitromethane solution) of the reaction between 1NNTh and CO taken
at different times.
Scheme 4. Synthesis of 5NNImH, 6NNImH and 7NNIm
.

M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2573
Table 2
Table 3
Selected coupling constants in 1NNTh and 8NNTh
.
Selected bond lengths (Å) and angles (ꢀ) calculated for complex 8NNTh with the M06
and EDF2 DFT functionals.
Coupling constant
Fragment
1NNTh (Hz)
8NNTh (Hz)
M06
EDF2
M06
EDF2
2JPtH
3JPtH
3JPtH
Pt-CH3
Pt-imine
Pt-quinoline
77
37
59
71
43
46
Pt-C(methyl)
Pt-C(CO)
Pt-N(thiazole)
Pt-N(imine)
2.098 2.102 C(CO)-Pt-C(methyl)
1.965 1.962 N(thiazole)-Pt-N(imine)
2.092 2.090 N(imine)-Pt-N(quinoline)
2.374 2.364 C(methyl)-Pt-N(imine)
158.5 158.3
76.0
77.0
84.9
76.1
77.2
83.8
Pt-N(quinoline) 2.084 2.084 C(CO)-Pt-N(imine)
116.5 117.9
coordinated methyl ligand is detectable, which couples with the
Pt(II) centre with a JPtH coupling constant of 71 Hz. This coupling
2
constant strongly supports the presence of a CH3 ligand coordi-
nated to the platinum centre. Selected coupling constants of 8NNTh
are compared with those of the precursor 1NNTh in Table 2.
mol in the case of NNTh, while is around 2 kcal/mol for the NNPy
and NNTh ligands.
The CO frequency of 8NNTh, 2106 cmꢁ1, indicates that carbon
All the spectroscopic data for 8NNTh are in agreement with the
simple coordination of CO to 1NNTh and the formation of a five-
coordinate Pt(II) complex having formula [PtMe(CO)(NNTh)](OTf).
Complexes of platinum(II) with a CO, an alkyl (or aryl) ligand and
a tridentate N-donor ligand in the coordination sphere are not
common and the most studied species are probably neutral
monoxide coordinates Pt(II) mainly through
s-interaction. The
lowest-energy unoccupied molecular orbital in the Pt(II) methyl-
complexes able to interact with an additional ligand is that
having Pt-6 pz character and its relative energy grows on replacing
the thiazole ring with pyridine or imidazole, as observable in
Table 4. The influence of the N-ligands on the energy of this metal-
centred unoccupied orbital is probably the reason of the coordi-
nation of CO only in the case of the thiazole derivative.
scorpionate-based
Pt(R)(Tp)(CO) [27].
complexes
having
general
formula
The formation of a five-coordinate species only in the presence
of the thiazole-based ligand NNTh is quite interesting. The geom-
etry of 8NNTh has been elucidated using DFT methods and is
reported in Fig. 2. Compound 8NNTh is referable neither to a square
pyramid nor to a trigonal bipyramid. The three coordinating
N atoms and the Pt atom lie on the same plane and the N(thiazole)-
Pt-N(imine) and N(imine)-Pt-N(quinoline) angles are around
76e77ꢀ. The CH3 ligand is almost perpendicular to this plane and
the C(methyl)-Pt-N(angle) angle is around 84e85ꢀ. The C atom of
the methyl ligand is instead on the same plane of the Pt and
N atoms in 1NNTh, giving a classical square-planar geometry dis-
torted by the coordination of tridentate ligand, which imposes the
N(thiazole)-Pt-N(imine) and N(imine)-Pt-N(quinoline) angles
lower than 90ꢀ. The coordinated CO in 8NNTh lies on the other side
of the plane defined by the tridentate ligand, respect to CH3. The
C(methyl)-Pt-C(CO) angle is 158ꢀ. This coordination mode can be
The reactivity studies on the new complexes have been prose-
cuted by reacting the Pd(II) methyl-complexes with CO. The
palladium derivatives 2NNTh, 2NNPy and 2NNImH react with CO at
1 atm in nitromethane with the formation of the corresponding
acyl-complexes [Pd(COMe)(NNTh)]þ (9NNTh), [Pd(COMe)(NNPy)]þ
(9NNPy) and [Pd(COMe)(NNImH)]þ (9NNImH) (see Scheme 5). The
C]O stretching, falling in the range 1689e1666 cmꢁ1, has been
used to follow the reactions by IR spectroscopy. During our
experiments we have never observed signals attributable to inter-
mediate carbonyl-complexes. Besides the IR spectra, the formation
of these acyl-complexes, isolated as triflate or perchlorate salts, has
been confirmed by their elemental analyses, conductivity
measurements and NMR spectroscopy. Unfortunately, we did not
obtain crystals suitable for X-Ray diffraction because of the lack of
stability of these complexes in solution for long time. Besides
the characteristic signals of the tridentate N-donor ligands, in the
1H NMR spectra the singlets attributable to the acyl ligands around
2.6e2.7 ppm are observable. Their 13C NMR signals have been
assigned on the basis of HSQC and HMBC experiments. The methyl
carbon of C(]O)CH3 resonates between 34.9 and 32.8, while the
carbonyl carbon is observable in the range 235.9e229.4 ppm. This
carbon atom gives a strong HMBC cross-peak not only with the
protons of the acyl ligand but, interestingly, also with the hydrogen
atom of the imine group, this confirming the presence of the C(]O)
CH3 ligand coordinated to the Pd(NNPy), Pd(NNTh) and Pd(NNImH)
fragments.
explained of considering that the
p-acceptor CO probably tends to
be in trans position to the methyl ligand, which is a strong
s
-donor
group. A selection of computed bond lengths and angles is reported
in Table 3.
The coordination of CO in the Pt(II) methyl-complexes happens
only using NNTh as ancillary ligand, i.e. that having the lower
basicity. DFT calculations on all the Pt(II) methyl-complexes predict
the formation of a weak Pt-CO bond only in the case of the NNTh
ligand, in agreement with the experimental results. In the case of
NNPy or NNImH the Pt(II) complexes keep their square-planar
geometry by addition of CO, and the calculated Pt-CO distances
are higher than 3.3 Å. The calculated energy for the reaction
between the square-planar Pt(II) methyl complex and CO is 13 kcal/
The rate of formation of the acyl-complex depends upon the
basicity of the N-donor ligand. The formation of the acyl complex is
in fact faster using [PdMe(NNImH)]þ (2NNImH) as reactant, while the
reaction is slower for [PdMe(NNPy)]þ (2NNPy) and it is still slower for
[PdMe(NNTh)]þ (2NNTh). It is to be remembered that the basicity of
the heterocycles follows the order imidazole (pKa ¼ 6.95) > pyridine
(pKa ¼ 5.25) > thiazole (pKa ¼ 2.44) [28] and that the basicity of
these N-donor heterocycles is usually a quite good parameter to
estimate their relative s
-donor behaviour towards d8 metal centres
[29]. Interestingly, ground-state DFT calculations carried out on the
Table 4
Energy of the lowest-energy unoccupied molecular orbital having Pt-6 pz character
in 1NNTh, 1NNPy and 1NNImH (EDF2 functional).
Complex
Orbital
Energy (eV)
1NNTh
1NNPy
1NNImH
LUMOþ8
LUMOþ7
LUMOþ7
ꢁ2.099
ꢁ2.062
ꢁ1.951
Fig. 2. DFT-optimised geometry (M06 functional) of complex 8NNTh
.

2574
M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
Scheme 5. Synthesis of the complexes 9NNTh, 9NNPy and 9NNImH
.
Pd(II) methyl-complexes show
a
very poor influence of the
faster. These considerations can explain the reactivity order
NNTh NNPy NNImH experimentally observed for the
CO insertion in the Pd-CH3 bond.
N-ligands on the Pd-CH3 bond. Moreover, these calculations predict
a behaviour of the Pd(II) methyl-complexes towards CO coordina-
tion which is about the same previously described for the analogous
Pt(II) complexes (see data reported in Table 5). This allows
concluding that the influence of the N-donor ligands on the rate of
CO insertion can not be explained on the basis of the ground-state
electronic properties of these complexes. The N-ligands probably
influence the transition state of the insertion reaction, which is
<
<
4. Conclusions
In this paper we have highlighted how the metal-assisted
approach could be applied for the synthesis of new Pd(II) and
Pt(II) complexes with several tridentate N-donor ligands containing
different heterocycles. We have observed that the reactivity of both
the palladium(II) and the platinum(II) methyl-complexes with CO is
strongly dependent upon the electronic features of the heterocycles
and this allows a fine-tune of the reactivity that could be of interest
in different application fields.
positively charged and contains a strong
p-acceptor ligand, CO.
A more -donor N-ligand can lead to the relative stabilization of
s
the five-coordinate transition state, making the insertion reaction
Table 5
Selected ground-state properties of the Pd(II) methyl-complexes 2NNTh
2NNImH and their adducts with CO (EDF2 functional).
, ,
2NNPy
Acknowledgements
Complex Pd-CH3 CH3 Mulliken Pd Mulliken
E Pd-5 pz MO Pd-CO
Charge (a.u.) (eV) (Å)
2.040
(Å)
Charge (a.u.)
The Ca’ Foscari University of Venice is gratefully acknowledged
for financial support (Ateneo fund 2009). We acknowledge the
CINECA Award N. HP10CI3CHF, 2010 for the availability of high
performance computing resources and support.
2NNTh
2NNPy
2NNImH
2.026
2.029
2.029
ꢁ0.059
ꢁ0.073
ꢁ0.072
0.481
0.485
0.475
ꢁ2.049
ꢁ2.021
ꢁ1.928
> 3.1
> 3.1

M. Bortoluzzi et al. / Journal of Organometallic Chemistry 696 (2011) 2565e2575
2575
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