Synthesis, characterisation and optical properties of symmetrical and unsymmetrical Pt(II) and Pd(II) bis-acetylides. Crystal structure of trans-[Pt(PPh3)2(CC-C6H5)(CC-C 6H4NO2)]

Article abstract of DOI:10.1016/S0022-328X(00)00791-9

Symmetric trans-[Pt(PPh₃)₂(CCR)₂] and unsymmetrical trans-[Pt(PPh₃)₂Cl(CCR)], (R=C₆H₄-pNO₂, C₆H₄-pOCH₃), Pt(II) acetylides were prepar

Full text of DOI:10.1016/S0022-328X(00)00791-9

Journal of Organometallic Chemistry 627 (2001) 13–22
www.elsevier.nl/locate/jorganchem
Synthesis, characterisation and optical properties of symmetrical
and unsymmetrical Pt(II) and Pd(II) bis-acetylides. Crystal
structure of trans-[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4NO2)]
R. D’Amato a,*, A. Furlani a, M. Colapietro a, G. Portalone a, M. Casalboni b,
M. Falconieri c, M.V. Russo a
a Dipartimento di Chimica, Uni6ersita` di Roma ‘La Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy
b Dipartimento di Fisica ed Istituto Nazionale di Fisica della Materia, Uni6ersita` di Roma Tor Vergata, Via della Ricerca Scientifica,
1-00133 Rome, Italy
c ENEA, C.R. Casaccia, Via Anguillarese, 301-00060 Rome, Italy
Received 3 August 2000; received in revised form 3 September 2000; accepted 10 October 2000
Abstract
Symmetric trans-[Pt(PPh3)2(CꢀCR)2] and unsymmetrical trans-[Pt(PPh3)2Cl(CꢀCR)], (R=C6H4–pNO2, C6H4–pOCH3), Pt(II)
acetylides were prepared and characterised, as well as unsymmetrical Pt(II) bis-acetylides, trans-[Pt(PPh3)2(CꢀCR)(CꢀCR%)],
(R=C6H4–pNO2, R%=C6H5; R=C6H4–pOCH3, R%=C6H5; R=C6H4–pOCH3, R%=C6H4–pNO2; R=C6H4–pNO2, R%=
[(h5-C5H4)Fe(h5-C5H5)]). Also symmetric Pd(II) bis-acetylides, trans-[Pd(PPh3)2(CꢀCR)2] (R=C6H4–pNO2, C6H5) were synthe-
sised and characterised by IR, NMR, and UV–vis spectroscopies. The optical properties of the new complexes were compared
within a series of known Pt(II) complexes containing different phosphines and cis–trans configuration. The absorption and
photoluminescence spectra indicate that the emission is found in the range 355–600 nm, depending on the nature of the acetylide
ligand bound to Pt. Measurements of SHG for the unsymmetrical bis-acetylides dispersed in polymethylmethacrylate (PMMA)
show that the second-order nonlinear optical (NLO) properties depend on the strength of the donor–acceptor substituent of the
acetylide ligand. Third-order NLO properties (in particular the nonlinear absorption coefficient h2) were measured by the Z-scan
technique; strong push–push and pull–pull substituents on the Pt(II) symmetric bis-acetylides induce electronic delocalisation and
tuning of the NLO properties. The single crystal X-ray structure of trans-[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4NO2)] shows that the
unsymmetrical molecule crystallised in the Pbca centric space groups. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Pt, Pd acetylides; Optical properties; Crystal structures
and electron transfer between the metallic centres has
been confirmed [6–9]. Although a great number of
organometallic complexes have been studied, some ex-
amples have only recently been reported on complexes
in which electron withdrawing and electron donor frag-
ments had been combined in order to obtain high first
order hyperpolarisabilities [10–12]. New ferrocenyl het-
ero-bimetallic compounds have been recently synthe-
sised [13], for which large i values, as determined by
the hyper Rayleigh scattering method, have been found.
Preliminary investigations performed a few years ago
on unsymmetrical Pt acetylides evidentiated second or-
der NLO properties of these materials [3], but no
further studies were carried out. On the basis of our
experience in the synthesis of Pt acetylides [14–16], we
1. Introduction
A great deal of interest has been devoted to the
synthesis of new p-conjugated polymers, in view of
their third-order non-linear optical properties (NLO)
[1,2]. The most investigated systems have been metal
containing polyynes, showing high p-electron delocali-
sation, increased by the dp–pp* interactions between
the metal centres and the polyyne ligands [3–5]. Nu-
merous investigations have been also carried out on
acetylide complexes, mainly on dinuclear complexes,
* Corresponding author. Tel.: +39-06-49913347; fax: +39-06-
490324.
E-mail address: rosaria.damato@uniroma1.it (R. D’Amato).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00791-9

14
R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
2.2. Materials
have now prepared and characterised a series of sym-
metrical and unsymmetrical Pt and Pd complexes. We
hereby report on the synthesis of some of these com-
plexes, and the characterisation of their NLO proper-
ties. The unsymmetrical bis-acetylides were prepared in
order to investigate the influence of the electron attract-
ing and electron releasing substituents of the acetylenic
ligands on the second order NLO properties. The effect
of substituents on the third order NLO properties of
unsymmetrical and symmetrical complexes has been
also investigated by the Z-scan technique and a correla-
tion between chemical structure and NLO response is
proposed. The X-ray crystal structure of the unsymmet-
All the solvents and products (reagent-grade Carlo
Erba) were dried according to conventional methods
before use. The complexes cis-[Pt(PPh3)2Cl2] [20], cis-
[Pt(PTol3)2Cl2] (PTol3=tri para-tolylphosphine), cis-
[Pt(PMePh2)2Cl2] [21], and trans-[Pd(PPh3)2Cl2] [22]
were prepared following the procedures reported in the
literature. The synthesis of cis-[Pt(dppe)Cl2] (dppe=
1,2-diphenylphosphinoethane) reported by Westland
[23] was modified according to Leviston et al. [24].
Phenylacetylene (PA) (Fluka-purum) was distilled un-
der vacuum prior to use; p-nitrophenylacetylene
(pNPA) was prepared following a published method
[25]; ethynylferrocene (Efc) was obtained with modify-
ing the method reported by Doisneau et al. [26]; the
synthesis of p-methoxyphenylacetylene (pMOPA) was
performed with the literature procedure [27].
rical
bis-acetylide
[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–
C6H4NO2)] is also reported.
2. Experimental
2.3. Syntheses of the complexes
2.1. Instruments
The synthesis of the bis(acetylide) complexes trans-
[Pt(PMePh2)2(CꢀC–C6H5)2] (14) [28], trans-[Pt(PPh3)2-
IR and FIR spectra were recorded as Nujol mulls or
KBr mixture on a Fourier Transform Perkin–Elmer
1700 spectrometer. Laser Raman spectra were observed
on a Fourier Transform Perkin–Elmer 1700 spectrome-
ter, using Nd:YAG laser light, at 1064 nm. UV spectra
were recorded on a Perkin–Elmer Lambda 5 spectrom-
eter, using 1-cm optical fused quartz cells, and CHCl3
as the solvent. Photoluminescence measurements were
carried out using a fluorescence spectrophotometer
Perkin Elmer PL50 on CHCl3 solutions at room tem-
perature, using 1-cm optical fused quartz cells. 1H-, 13C-
and 31P-NMR spectra were run on a Varian XL300
instrument in CDCl3 solutions; the solvent was used as
a reference (l=7.24 and 77 ppm) for 1H and 13C
spectra; 85% H3PO4 was used as a reference (l=0) in
31P spectra. Elemental analyses were carried out at the
Laboratorio di Microanalisi, University of Pisa and at
Department of Chemistry, University of Rome ‘La
Sapienza’. Fast Atom Bombardment (FAB) analyses
were performed with a VG Quattro instruments, using
3-nitrobenzyl-alcohol as matrix and the reported molec-
ular weights. were determined by this technique. The
second order nonlinear optical measurements were per-
formed using the second harmonic generation technique
(SHG). The complexes were dispersed in polymethyl-
methacrilate (PMMA) and the films were poled by high
temperature corona-poling [17]. The third order
nonlinear optical properties of complexes have been
studied with the Z-scan set-up reported by M. Fal-
conieri et al. [18,19]. The laser source was a self-mode-
locked Ti-sapphire delivering 130 fs linearly polarised
pulses with 76 MHz repetition rate at laser wavelength
of 770 nm.
(CꢀC–C6H5)2]
(19)
[14],
trans-[Pt(PPh3)2(CꢀC–
C6H5)(CꢀC–{h5-C5H4}Fe{h5-C5H5})] (18) [29], and of
the monochloroacetylides trans-[Pt(PPh3)2(CꢀC–C6H5)-
Cl] [16] and trans-[Pt(PPh3)2(CꢀC–{h5-C5H4}Fe{h5-
C5H5})Cl] [29] were already reported. Also the reaction
procedures for the synthesis of some symmetric com-
plexes i.e. trans-[Pt(PTol3)2(CꢀC–C6H5)2] (12), trans-
[Pt(PTol3)2(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
(13),
trans - [Pt(PMePh2)2(CꢀC–{h5 - C5H4}Fe{h5 - C5H5})2]
(15), cis-[Pt(dppe)(CꢀC–C6H5)2] (16) and cis-[Pt-
(dppe)(CꢀC–{h5-C5H4}Fe{h5-C5H5})2] (17) were re-
ported elsewhere [30].
2.3.1. Symmetric bis(acetylide) bis(phosphine) Pt
complexes
Complexes 1 and 2 were prepared using the proper
Pt(II) precursors and acetylenic monomers, following a
well established reaction route. The basis for the assign-
ment of cis and trans structures of the complexes is
given in next session.
2.3.1.1. trans-[Pt(PPh3)2(CꢀC–C6H4NO2)2] (1). cis-
[Pt(PPh3)2Cl2] (0.500 g, 0.63×10−3 mol) was treated
with HCꢀC–C6H4NO2 (0.500 g, 3.4×10−3 mol) in
Et2NH (20 ml) in the presence of a catalytic amount of
CuI (5 mg) at reflux for 2 h. A crude material was
obtained, insoluble in the reaction solvent. After filtra-
tion and washing with Et2NH, H2O and EtOH a yellow
product was obtained that was crystallised from
CHCl3–EtOH (0.450 g, 70% yield). M.W. (a.m.u.)=
1012.
Elemental
analysis
(%):
Calc.
for
C52H38N2O4P2Pt: C, 61.72; H 3.79; N 2.77. Calc. for

R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
15
2.3.2. Monochloro(acetylide) bis(triphenylphosphine) Pt
complexes
C52H38N2O4P2Pt·1/3CHCl3: C, 59.71; H, 3.64; N, 2.66.
Found: C, 59.53; H, 3.59; N, 2.77. IR (cm−1): 2107
The novel monochloro-acetylides 4 and 5 were ob-
tained through similar procedures, reported in detail for
complex 4. The synthesis of complex 5 is reported
concisely in Table 1.
(wCꢀC).
2.3.1.2. trans and cis-[Pt(PPh3)2(CꢀC–C6H4OCH3)2] (2
and 3). The reaction procedures were the same reported
for complex 1. The crude product contained both trans
and cis-[Pt(PPh3)2(CꢀC–C6H4OCH3)2], as was evidenti-
ated from 31P-NMR spectrum, and they were separated
by crystallisation from CHCl3–EtOH. The first precipi-
tate is the trans product (0.300 g, 50% yield), while the
cis complex was obtained as yellow crystals by dry
evaporation of crystallisation solvents (0.060 g, 10%
yield). trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]: M.W.
(a.m.u.)=982. Elemental analysis (%): Calc. for
C54H44O2P2Pt: C, 66.05; H, 4.52. Calc. for
C54H44O2P2Pt·1/5CHCl3: C, 64.72; H, 4.43. Found: C,
64.66; H, 4.57. IR (cm−1): 2109 (wCꢀC). cis-
[Pt(PPh3)2(CꢀC–C6H4OCH3)2]: M.W. (a.m.u.)=982.
Elemental analysis (%): Found: C 65.84; H 4.70. IR
(cm−1): 2122 (wCꢀC).
2.3.2.1. trans-[Pt(PPh3)2(CꢀC–C6H4NO2)Cl] (4).
A
mixture of cis-[Pt(PPh3)2Cl2] (0.500 g, 0.63×10−3 mol)
and pNPA (0.670 g, 4.5×10−3 mol) in CHCl3 (40 ml)
with 0.8 ml of Et2NH was refluxed for 2 h. Upon
addition of absolute ethanol the yellow product precip-
itated. The pure, crystalline product was obtained by
recrystallisation from CHCl3–EtOH (0.230 g, 40%
yield). M.W. (a.m.u.)=901. Elemental analysis (%):
Calc. for C44H34ClNO2P2Pt: C, 58.64; H, 3.80; Cl, 3.93;
N, 1.55; Found: C, 58.55; H, 3.72; N, 1.53. IR (cm−1):
2118 (wCꢀC), 320, 280 (wPt–Cl).
2.3.2.2. trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl] (5).
0.400 g, 80% yield. M.W. (a.m.u.)=886. Elemental
analysis (%): Calc. for C45H37ClOP2Pt: C, 60.39; H,
Table 1
Comprehensive data for the synthesis of Pt and Pd complexes
No. Complex
Reference Reactions conditions
Cryst. solvent
Yield (%)
M.p. (°C)
1
2
3
4
5
6
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)2]
Et2NH–CuI, reflux, 2 h
Et2NH–CuI, reflux, 2 h
Et2NH–CuI, reflux, 2 h
CHCl3–EtOH
CHCl3–EtOH
CHCl3–EtOH
CHCl3–EtOH
CHCl3–EtOH
CHCl3–EtOH
70
50
10
40
80
55
\350(dec.)
247–248
\200(dec.)
235–238
214–215
234–236
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
cis-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)Cl]
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl]
trans-[Pt(PPh3)2(CꢀC–C6H5)-
(CꢀC–C6H4NO2)]
CHCl3–Et2NH, reflux, 2 h
CHCl3–Et2NH, reflux, 2 h
From Pt(PPh3)2(CꢀC–C6H5)Cl,
CHCl3–Et2NH, reflux, 3 h
From 4, CHCl3–Et2NH reflux, 3h
From 5, Et2NH, reflux, 2 h, chrom. CHCl3–EtOH
silica gel–toluene
From 5, Et2NH, reflux, 3 h, chrom. CHCl3–EtOH
silica gel–toluene
CHCl3–EtOH
85
60
234–236
225–226
7
8
9
trans-[Pt(PPh3)2(CꢀC–C6H5)-
(CꢀC–C6H4OCH3)]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)-
(CꢀC–C6H4OCH3)]
65
85
222–223
246–248
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)-
From
CHCl3–EtOH
C6H6–EtOH
Toluene–MeOH 93
C6H6–EtOH
(CꢀC–{h5-C5H4}Fe{h5-C5H5})]
Pt(CꢀC–{h5-C5H4}Fe{h5-C5H5})Cl,
CHCl3–Et2NH, reflux, 3 h
Et2NH–CuI, r.t., 1 h
10
trans-[Pd(PPh3)2(CꢀC–C6H5)2]
80
126–128
126–128
143–145
213–215
226–228
MeOH–NaOH–CuI, r.t., 24 h
Et2NH–CuI, r.t., 6 h
Et2NH–CuI, reflux, 18 h
Et2NH–CuI, reflux, 3 h
11
12
13
trans-[Pd(PPh3)2(CꢀC–C6H4NO2)2]
trans-[Pt(PTol3)2(CꢀC–C6H5)2]
trans-[Pt(PTol3)2-
86
90
90
[30]
[30]
Toluene–EtOH
CH2Cl2–EtOH
(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PMePh2)2(CꢀC–C6H5)2]
trans-[Pt(PMePh2)2-
14
15
[28]
[30]
Et2NH–CuI, reflux, 30 min
Et2NH–CuI, reflux, 1 h
CHCl3–EtOH
CHCl3–EtOH
55
85
193–194
\250(dec.)
(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
cis-[Pt(dppe)(CꢀC–C6H5)2]
cis-[Pt(dppe)-
16
17
[30]
[30]
Et2NH–CuI, reflux, 5 h
Et2NH–CuI, reflux, 5 h
CHCl3–hexane
C6H6–EtOH
85
25
\200(dec)
\250(dec.)
(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PPh3)2(CꢀC–C6H5)
(CꢀC–{h5-C5H4}Fe{h5-C5H5})]
18
19
[29]
[14]
From
C6H6–EtOH
70
85
210–212
220–222
Pt(CꢀC–{h5-C5H4}Fe{h5-C5H5})Cl,
CHCl3–Et2NH, reflux, 1 h
Et2NH–CuI, reflux, 2 h
trans-[Pt(PPh3)2(CꢀC–C6H5)2]
CHCl3–EtOH

16
R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
4.21. Found: C, 60.84; H, 4.70. IR (cm−1): 2125 (wCꢀC),
316, 280 (wPt–Cl).
2.3.4.1. trans-[Pd(PPh3)2(CꢀC–C6H5)2] (10). A mixture
of 0.200 g (0.3×10−3 mol) of trans-[Pd(PPh3)2Cl2] and
0.1 ml (0.093 g, 0.9×10−3 mol) of PA in 4 ml of a 0.2
M solution of NaOH in MeOH with 5 mg of CuI were
stirred magnetically for 18–20 h at T=20°C. We ob-
served formation of a snow-white powder that was
filtered, washed with H2O and MeOH and then crys-
tallised from C6H6–EtOH (0.240 g, yield 95%). Elemen-
tal analysis (%): Calc. for C52H40P2Pd: C, 74.96; H,
4.84. Found C, 75.79; H, 5.06. IR (cm−1): 2108 (wCꢀC).
2.3.3. Unsymmetrical bis(acetylide)
bis(triphenylphosphine) Pt complexes
The reaction route for the synthesis of the unsymmet-
rical complex 6 is reported in detail. Complexes 7, 8, 9
were prepared following the same procedure: the reac-
tion conditions are summarised in Table 1.
2.3.3.1. trans-[Pt(PPh3)2(CꢀC–C6H4NO2)(CꢀC–C6H5)]
(6). The unsymmetrical complex 6 was prepared in two
2.3.4.2. trans-[Pd(PPh3)2(CꢀC–C6H4NO2)2] (11). Yield
ways: (i) 0.170
g
(0.19×10−3 mol) of trans-
85%.
Elemental
analysis
(%):
Calc.
for
[Pt(PPh3)2(CꢀC–C6H4NO2)Cl] (4) were dissolved in 10
ml of CHCl3 with 0.1 ml (0.09 g, 1.0×10−3 mol) of PA
and 0.8 ml of Et2NH. The reaction mixture refluxed for
3 h and complex 6 was obtained as a yellow powder by
addition of EtOH and crystallised from CHCl3–EtOH
(0.160 g, 85% yield). (ii) trans-[Pt(PPh3)2(CꢀC–
C6H5)Cl] and pNPA (molar ratio 1:1) were dissolved in
CHCl3 following the procedure described in point (i).
The complex 6 was recrystallised from CHCl3–EtOH
(0.100 g, 55% yield). M.W. (a.m.u.)=967. Elemental
analysis (%): Calc. for C52H39NO2P2Pt: C, 64.59; H,
4.07; N, 1.45. Found: C, 64.18; H, 4.16; N, 1.61. IR
(cm−1): 2109 (wCꢀC).
C52H38N2O4P2Pd: C, 67.65; H, 3.03; N, 4.15. Anal.
Calc. for C52H38N2O4P2Pd·C6H6: C, 69.57; H, 4.39; N,
2.80. Found: C, 69.98; H, 4.42; N, 2.95. IR (cm−1):
2103 (wCꢀC).
3. Results and discussions
3.1. Synthesis of the complexes
In order to obtain new complexes with second and
third order nonlinear optical properties, a series of new
Pt(II) and Pd(II) acetylides were synthesised. A sum-
mary of all the experimental procedures is shown in
Table 1.
2.3.3.2.
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)(CꢀC–
C6H5)] (7). Complex 7 was obtained from PA and
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl] (5) (60% yield).
M.W. (a.m.u.)=952. Elemental analysis (%): Calc. for
C53H42OP2Pt: C, 66.87; H, 4.45. Found: C, 66.62; H,
4.26%. IR (cm−1): 2109 (wCꢀC).
The use of Et2NH as solvent, in the presence of CuI
as catalyst, and with an excess of the appropriate
acetylenes (ca. 1:5 ratio) led to the successful synthesis
of a wide range of symmetrical Pt(II) bis(acetylide)
complexes (see Refs. [14,30]). This result demonstrates
the wide applicability of this synthetic approach. It is
worth noting that, while we generally obtain the trans
isomer of the complexes, a small amount of cis form of
the p-methoxyphenylacetylide was also observed and
subsequently isolated as illustrated in Section 2. A
similar result was observed for the complex
[Pt(PPh3)2CꢀC–{h5-C5H4}Fe{h5-C5H5})2]. The insolu-
ble trans isomer was isolated by filtration, and the cis
form was crystallised from THF–EtOH [30].
2.3.3.3.
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)(CꢀC–
C6H4NO2)] (8). Complex 8 was obtained from pNPA
and trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl] (65% yield).
M.W. (a.m.u.)=997. Elemental analysis (%): Calc. for
C53H41NO3P2Pt: C, 63.85; H, 4.15; N, 1.40. Anal. Calc.
for C53H41NO3P2Pt·1/4CHCl3: C, 62.29; H, 4.05; N,
1.36. Found: C, 62.57; H, 3.99; N, 1.35. IR (cm−1):
2105 (wCꢀC).
In order to obtain the monochloro-acetylide species,
we used CHCl3 as the solvent and only a small amount
of Et2NH. This procedure avoided undesired formation
of significant amounts of the corresponding symmetric
bis(acetylide) complexes [16].
The unsymmetrical complexes were obtained reacting
the monochloro-acetylides trans-[Pt(PPh3)2(CꢀC–R)Cl]
with the related alkyne HCꢀC–R1 in Et2NH as solvent.
It is noteworthy that complexes 7, 8, 9, 18 can only be
obtained from the monochloro-acetylide containing the
OCH3 or ferrocene groups, as shown in Fig. 1. The
necessity for the presence of an electron-donating group
on the reacting acetylide can be interpreted in terms of
a charge repulsion effect towards the Cl ligand, and an
2.3.3.4.
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)(CꢀC–{p5-
C5H4}Fe{p5-C5H5})] (9). Complex 9 was obtained from
pNPA and trans-[Pt(PPh3)2(CꢀC–{p5-C5H4}Fe{h5-
C5H5})Cl] (85% yield). M.W. (a.m.u.)=1075. Elemen-
tal analysis (%): Calc. for C56H43FeNO2P2Pt: C, 62.58;
H, 4.03; N, 1.30. Found: C, 61.58; H, 4.05; N, 1.24. IR
(cm−1): 2106 (wCꢀC).
2.3.4. Symmetrical bis(acetylide) bis(triphenylphosphine)
Pd complexes
Complexes 10 and 11 were prepared according to the
reaction procedures reported for complex 1 (Table 1).
Complex 10 was also obtained using a new method:

R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
17
Fig. 1. Reaction scheme for the synthesis of asymmetric platinum complexes.
enhancement of the coordination of the entering
acetylenic ligand (i.e. –CꢀC–C6H4NO2, or –CꢀC–
C6H5). Only the bis-acetylide 6 could be prepared in
high yield either from complex 4 reacting with phenyl-
acetylene or from complex [Pt(PPh3)2(CꢀC–C6H5)Cl]
reacting with p-nitrophenylacetylene.
Pd(II) complexes were prepared at room temperature
from trans-[Pd(PPh3)2Cl2] and the alkyne. New reaction
conditions, with a solution of NaOH in MeOH as the
reaction solvent, led to the successful synthesis of
[Pd(PPh3)2(CꢀC–C6H5)2] (10). This method gave very
good results for the synthesis of Pd bis(acetylide)s,
while lower yields were observed for Pt complexes.
Palladium was more reactive and bis(acetylide) com-
plexes were obtained with almost quantitative yields in
milder conditions. However, this method required
longer reaction times than with Et2NH. Pd complexes
were generally unstable, and decomposed in solution at
temperature just higher than T=30°C.
In order to obtain pure products, the crude com-
plexes were chromatographed on a silica gel column
with benzene, toluene, or CHCl3 as the eluent. As
already observed in similar cases [31], elemental analy-
ses showed a tendency of some complexes to retain
solvents in the crystal molecular lattice. By changing
the crystallization solvents, different elemental analyses
are obtained.
tern due to the natural isotopic abundance of platinum.
The quasi-molecular ion [M+H]+ (m/z=1013) is
present together with peaks resulting from fragmenta-
tions that are typical of nitro-aromatic compounds
(elimination of one NO2 radical [M−NO2]+ m/z=966
and two NO radicals [M−2NO]+ m/z=952). The
typical fragmentation peaks of bis-acetilides are also
present. For example the peak due to loss of C6H4NO2
and
CꢀC–C6H4NO2
[M+1−C6H4NO2–CꢀC–
C6H4NO2]+ (m/z=745) is observed among the others.
The IR spectra of Pt and Pd complexes are character-
ised by the CꢀC stretching vibrations in the range
2103–2125 cm−1; the position of the band is shifted
towards higher frequencies in the mono-acetylides. A
band at 54095 cm−1, characteristic of cis-bis(tri-
phenylphosphine) acetylido–platinum complexes [32],
is observed in the spectrum of cis-[Pt(PPh3)2(CꢀC–
C6H4OCH3)2] (3). Its absence in the case of other Pt
and Pd complexes suggests a trans configuration.
The NMR parameters of the eleven new compounds
are listed in Table 2, and general trends are worth
mentioning. The 31P spectra of the platinum complexes
show the expected signal, which consists of three lines
in the ratio 17:66:17% because of the coupling with
1
195Pt. The magnitude of J (195Pt31P) is known to be
very sensitive to the nature of the ligands in square
planar platinum(II) complexes and can thus act as a
useful probe of the geometry of any present isomer [33].
1
3.2. Spectroscopic characterisation
The J (195Pt31P) values obtained for the compounds
here reported are in agreement with the values found in
other square planar platinum complexes, with the trans
isomers showing larger platinum–phosphorus coupling
constants than the cis analogues according to literature
results (see for example complexes 2 and 3 of Table 2)
[28,34,35].
The bis-triphenylphosphine ligand exhibits similar
13C-NMR pattern in all the investigated complexes
(Table 2). The resonance at 131.2 ppm is attributed to
the ipso carbon (directly linked to the P atom), and the
The full characterisation of the organometallic com-
pounds has been performed using traditional method-
1
ologies: elemental analysis, IR, UV–vis, H-, 13C- and
31P-NMR spectroscopy and mass spectrometry.
The FAB spectrum of the complex [Pt(PPh3)2(CꢀC–
C6H4NO2)2] (1) (M.W.=1011.91) in the m/z range
350–1100 is discussed in detail as an example. The
spectrum is characterised by platinum containing ions,
which are identified readily by their characteristic pat-

18
R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
resonances at 134.8, 130.4 and 127.9 ppm correspond to
the ortho, para and meta carbons, respectively. Some
minor shifts from these values are observed depending
on the different alkyne ligands. It is worth noting that
the coupling constant increases with decreasing C–P
distance, with the exception of the carbon in para
position, which appears as a singlet. The signals of the
benzene moiety of the alkyne ligand are detected in the
range 144.4–112.0 ppm and have been identified by
comparing the spectra of the new complexes of Table 2
with those of the precursors and of the free acetylenes.
The attribution of the quaternary carbons is more
difficult, because have low intensity and sometimes the
low solubility of the material does not allow for an easy
detection and assignment of these carbons. However,
the resonances of the CꢀC carbons are found around
100–113 ppm for the carbon bound to the metal, and
in the range 110–125 ppm for the carbon bound to the
aromatic ligand R of the CꢀC–R moiety. A doublet of
doublets at 101.0 ppm and a doublet at 110.0 ppm was
detected only in the case of the cis complex 3. These
two signals were unambiguously assigned to the C1 and
C2 atoms, respectively, of the ligand –C1ꢀC2–C6H4–
OCH3, as previously reported in the literature [30]. For
the other complexes, the poor resolution of the spectra
prevented a similar rigorous assignment.
The 1H chemical shifts of CꢀC–C6H4NO2, CꢀC–
C6H4OCH3, CꢀC–C6H5, and CꢀC–{h5-C5H4}Fe{h5-
C5H5} are independent of the nature of the phosphine,
but they are influenced by cis and trans complex
1
configuration; in fact the H-NMR signals are shifted
toward higher fields in the spectrum of the cis complex.
Further proof of the cis configuration is given by the
different pattern of phosphine signals for complex 3.
Table 2
NMR data for complexes 1–11 a
No. Complex
1H (ppm)
13C b (ppm)
31P (ppm) J
(Hz)
1
2
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)2]
7.73–7.38 (m, 34H, P(C6H5) and
C6H4NO2), 6.27 (d, 4H, C6H4NO2)
7.80–7.30 (m, 30H, P(C6H5)),
6.45–6.16 (dd, 8H, C6H4OMe), 3.65
(s, 6H, OCH3)
7.51–7.10 (m, 30H, P(C6H5)),
6.70–6.52 (dd, 8H C6H4OMe), 3.68 (s, (C6H4OCH3), 110.0 (d, ꢀC–Ph),
6H, OCH3)
144.3, 135.0, 131.0, 122.7
(C6H4NO2), 113.1, 97.4 (CꢀC)
131.9–112.6 (C6H4OMe), 55.0
(OCH3) c
19.5
(1JPtP=2592)
19.2
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
cis-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)Cl]
(1JPtP=2662)
3
157.1, 132.7, 120.9, 112.5
17.0
(1JPtP=2323)
101.0 (dd, ꢀC–Pt), 55.0 (OCH3)
144.3, 135.4, 131.0, 122.6
(C6H4NO2), 105.6, 98.3 (CꢀC)
157.2, 132.2, 121.0, 112.5
4
5
7.73–7.38 (m, 32H, P(C6H5) and
C6H4NO2), 6.11 (d, 2H, C6H4NO2)
20.3
(1JPtP=2617)
22.1
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl] 7.79–7.33 (m, 30H, P(C6H5)),
6.41–6.00 (dd, 4H C6H4OMe), 3.63 (s, (C6H4OMe), 115.9, 114.5 (CꢀC),
3H, OCH3)
(1JPtP=2664)
55.0 (OCH3)
6
7
8
9
trans-[Pt(PPh3)2(CꢀC–C6H5)
(CꢀC–C6H4NO2)]
7.78–7.37 (m, 32H, P(C6H5) and
C6H4NO2), 6.89–6.27 (m, 7H,
C6H4NO2 and C6H5).
144.1, 135.4, 131.0, 122.7
(C6H4NO2), 130.8, 128.2, 127.1,
124.8 (C6H5), 124.8, 112.2, 97.4
(CꢀC)
19.2
(1JPtP=2613)
trans-[Pt(PPh3)2(CꢀC–C6H5)
(CꢀC–C6H4OCH3)]
7.81–7.31 (m, 30H, P(C6H5)),
6.89–6.18 (m, 9H, C6H5 and
C6H4OMe), 3.65 (s, 3H, OCH3)
156.9, 132.0, 121.7, 112.6
(C6H4OCH3), 130.8, 128.6, 127.0,
124.5 (C6H5), 112.9, 112.8, 111.0,
108.0 (CꢀC), 55.0 (OCH3)
144.1, 135.8, 131.0, 122.7
(C6H4NO2), 157.1, 132.0, 122.4,
112.7 (C6H4OMe), 124.0, 121.0,
113.2, 112.4 (CꢀC), 55.0 (OCH3)
144.3, 135.0, 131.2, 122.7
19.2
(1JPtP=2656)
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)
(CꢀC–C6H4OCH3)]
7.75–7.26 (m, 32H, P(C6H5) and
C6H4NO2), 6.41–6.15 (td, 6H,
C6H4NO2 and C6H4OMe), 3.59 (s,
3H, OCH3)
7.80–7.37 (m, 32H, P(C6H5) and
C6H4NO2), 6.32–6.29 (d, 2H,
C6H4NO2), 3.68 (s, 5H, h5–C5H5),
3.74–3.35 (t, 4H, h5-C5H4)
7.81–7.33 (m, 30H, P(C6H5)),
6.90–6.31 (m, 10H, C6H5)
7.76–7.35 (m, 34H, P(C6H5) and
C6H4NO2), 6.33 (d, 4H, C6H4NO2)
19.2
(1JPtP=2619)
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)
(CꢀC-{h5-C5H4}Fe{h5-C5H5})]
19.0
(C6H4NO2), 108.2–99.8 (CꢀC), 70.1, (1JPtP=2638)
66.6 (h5-C5H4), 69.2 (h5-C5H5)
10
11
trans-[Pd(PPh3)2(CꢀC–C6H5)2]
130.7, 128.1, 127.1, 124.7 (C6H5),
115.0, 113.5 (CꢀC)
144.4, 130.8, 128.3, 122.8
(C6H4NO2), 125.0, 114.2 (CꢀC)
26.58
27.03
trans-[Pd(PPh3)2(CꢀC–C6H4NO2)2]
a The spectra were run in CDCl3 solutions.
b The 13C resonances of the P(C6H5) ligand are found at 134.8 (t, JPC=6.3Hz, ortho), 131.2 (t, JPC=27Hz, ipso), 130.4 (s, para), 127.9 (t,
JPC=5.3Hz, meta). These values are almost the same for the series of Pt and Pd complexes, with little differences (ca. 0.2 ppm) depending on
the bound acetylide ligands.
c Due to the low solubility, the quaternary carbon resonances could not be detected.

R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
19
Table 3
UV–vis data for complexes 1–19 a
No. Complexes
umax (nm) absorb.
m0 (l mol cm−1
)
umax (nm) emission
1
2
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)2]
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)Cl]
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)Cl]
trans-Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4NO2)
trans-Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4OCH3)
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)(CꢀC–C6H4NO2)]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2) (CꢀC–{h5-C5H4}Fe{h5-C5H5})]
trans-[Pd(PPh3)2(CꢀC–C6H5)2]
402
358
385
321
390
354
390
390
305
381
348
332, 368
343
331, 363
315
315, 363
340
49 000
24 700
26 600
12 610
32 200
22 600
25 600
24 700
36 870
39 470
26 600
14 200, 11 700
28 700
10 600, 8190
21 200
9200, 5160
16 500
29 700
475–600
400
515
355–429
500–600
425
510
510
385
490
413
410, 410
380
407, 407
387
400–428, 409–442
409
trans-[Pd(PPh3)2(CꢀC–C6H4NO2)2]
trans-[Pt(PTol3)2(CꢀC–C6H5)2]
trans-[Pt(PTol3)2(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PMePh2)2(CꢀC–C6H5)2]
trans-[Pt(PMePh2)2(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
cis-[Pt(dppe)(CꢀC–C6H5)2]
cis-[Pt(dppe)(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PPh3)2(CꢀC–C6H5) (CꢀC–{h5-C5H4}Fe{h5-C5H5})]
trans-[Pt(PPh3)2(CꢀC–C6H5)2]
350
421
a CHCl3 was used as the solvent.
Table 4
Absorption peak wavelength in films (umax PMMA), order parameter (b), SH coefficients (d33 and i)
No.
Chromophore
umax PMMA (nm)
b
d33 (10−9 esu)
i (10−30 esu)
DR1
490
387
354
391
384
341
0.30
0.07
0.12
0.08
0.18
0.10
20
7
1.5
5.5
11
22 [39]
16
3
12
16
6
7
8
9
18
trans-[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4NO2)]
trans-[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4OCH3)]
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3) (CꢀC–C6H4NO2)]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2) (CꢀC–{h5-C5H4}Fe{h5-C5H5})]
trans-[Pt(PPh3)2(CꢀC–C6H5) (CꢀC–{h5-C5H4}Fe{h5-C5H5})]
B0.1
B0.2
UV–vis characterisation was carried out on all the
complexes. The values of umax are reported in Table 3.
All the coordination compounds show no absorption
bands over 420 nm, so they are transparent in a very large
visible region, and this is a great advantage for optical
applications. The absorption bands are only slightly
influenced by the presence of the chromophore and by
the different environment (different phoshines). The
absorption peaks in the optical spectra are attributed to
metal“ligand charge transfer [3], and their position
moves to longer wavelengths due to coordination of
acetylide ligands. The highest red shift observed for our
acetylides is recorded for the bis(p-nitrophenylacetylide)
complex 1.
complex 1 exhibits emission at 475 nm (blue–green
emission colour) and another emission signal at 600 nm
(yellow–orange colour). Quite similar emission spectra
(blue region) were found recently for a copolymer
consisting of thiophene-based and uretane spacer units
[36] and similar features were observed in the photolu-
minescence spectra of platinum-containing polyynes with
aromatic and heteroaromatic spacers [4].
3.4. SHG measurements
A full discussion on the second order nonlinear char-
acteristics of organometallic platinum complexes has
been reported recently [17]. For purpose of completeness,
here we will briefly report on the optical characterisation
of the unsymmetrical bis(acetylides) bis(triphenylphos-
phine)Pt complexes 6–9, 18. The measurements were
carried out on PMMA films as the host matrix, by the
SHG technique. The molecular hyperpolarisability i and
the order parameter b could be determined and the
results are collected in Table 4. The most promising
molecule seems to be complex 9 containing both fer-
rocene (push) and nitro (pull) groups, as expected.
3.3. Photoluminescence
Preliminary measurements concerning the lumines-
cence properties were also performed. The photolumines-
cence spectra recorded for the solutions of the complexes
under excitation at the wavelength of the absorption
maximum (u=315–400 nm) show emission peaks in the
range 355–600 nm (Table 3). It is noteworthy that

20
R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
3.5. Third-order nonlinear optical measurements
give large nonlinearities. Different phosphines do not
seem to dramatically change the values of the nonlinear
optical constants. The central metal atom affects the h2
values as can be seen by comparing the values of
sample 1, where the metal centre is platinum, and
sample 11 which contains palladium. This is an interest-
ing effect which deserves, however, further
investigation.
Measurements on different Pt(II) and Pd(II) com-
plexes were carried out in order to relate their structure
(different phosphines and different acetylides) to their
third order nonlinear optical properties. The results
concerning 11 selected complexes are reported in Table
5.
These results are in agreement with studies reported
by Humphrey et al. on ruthenium bis-acetylene systems
[37]. Although being preliminary, our results show the
possibility of tailoring the molecular structure in order
to optimise a material for different nonlinear properties
and ultimately for different applications. Also, these
results could be used as a mean to study the electronic
polarisability, i.e. the delocalisation of the electrons in
coordination compounds.
The nonlinear refractive index n2 was in most cases
too low to be detectable (complexes 2, 10, 12, 14, 19).
An uncertainty of one order of magnitude affected the
determination of n2 in all the other cases. It can be seen
that the nonlinear absorption coefficient h2 is strictly
related to the presence of linear absorption feature
at/or near the half wavelength (u=380 nm) of the laser
light used for nonlinear measurements (u=770 nm). In
particular, all complexes showing detectable absorption
around 380920 nm also exhibit nonlinear absorption,
pointing out for a two-photon absorption mechanism.
The values of the nonlinear constants reported in
Table 5 are calculated for a single molecule, in order to
normalise the results obtained at different concentra-
tions. Non substituted bis(phenylacetylide)s do not
show measurable nonlinear optical constants. Appro-
priate substituents at the sides of the molecule are
needed to give large nonlinearities. The molecules con-
taining the donor ferrocene group show appreciable
nonlinearities confirming the high polarisability of this
group, in agreement with previous results reported in
the literature [3,13]. The highest value for h2, 1.2×
10−38 cm W−1, was found for [Pt(PPh3)2(CꢀC–
C6H4NO2)2] (1), which is a pull–pull (acceptor groups
at either sides) molecule, while the value for the push–
pull complex 8 is intermediate. The donor methoxy
group in [Pt(PPh3)2(CꢀC–C6H4OCH3)2] (2), does not
Table 6
Summary of crystal data, data collection a, structure solution and
refinement b
Crystal data
Empirical formula
Molar mass
PtP2C52H39NO2
966.923
Color, habit
Crystal size (mm)
Crystal system
Colorless, prismatic
0.3×0.2×0.2
Orthorombic
9.591(3)
3.036(15)
38.422(46)
8489(12)
Pbca
,
a (A)
,
b (A)
,
c (A)
3
,
V (A )
Space group
Z
4
F(0,0,0)
3856.0
1.513
34.235
Dcalc (g cm−3
)
v (cm−1
)
Data collection
Temperature (K)
298
Unit-cell reflections (q range (°))
Maximum value of q (°) for reflections
hkl range of reflections
Variation in three standard reflections
Reflections measured
10 (6–10)
25
0–11; 0–27; 0–45
B3%
9269
4879
Table 5
Third-order nonlinear optical coefficients for the complexes
a
No. Complex
h2 (cm W−1
u=770 nm
)
Unique reflections
Reflections with ꢀFo/\6|ꢀFoꢀ
3251
0.0527
1
2
8
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)2]
1.2×10−38
/
R of merged reflections
trans-[Pt(PPh3)2(CꢀC–C6H4OCH3)2]
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)
(CꢀC–C6H4OCH3)]
2.0×10−39
Structure solution and refinement
Refinement on
Solution method
Variables refine
Weighting scheme, 1ꢀ(a+bꢀFoꢀ+cꢀFoꢀ )
Fo
9
trans-[Pt(PPh3)2(CꢀC–C6H4NO2)
(CꢀC–{h5-C5H4}Fe{h5-C5H5})]
trans-[Pd(PPh3)2(CꢀC–C6H5)2]
trans-[Pd(PPh3)2(CꢀC–C6H4NO2)2]
trans-[Pt(PTol3)2(CꢀC–C6H5)2]
trans-[Pt(PTol3)2
6/ .8×10−39
Direct methods
523
54.34320, 1.00000,
0.00227
0.0560, 0.0790, 0.704
−1.72, 1.32 (16)
0.000
2
10
11
13
14
/
4.3×10−39
/
R, wR, GOF
Density range in final Z-map (e A
Final shift/error ratio
6.8×10−39
−3
,
)
(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PMePh2)2(CꢀC–C6H5)2]
trans-[Pt(PMePh2)2
15
16
/
1.1×10−38
a Data were collected using ꢀ scan. The intensities were corrected
for Lorentz-polarization effects, and for absorption.
(CꢀC–{h5-C5H4}Fe{h5-C5H5})2]
trans-[Pt(PPh3)2(CꢀC–C6H5)2]
b All calculations were done on a Pentium PC with SIR CAOS [40],
PARST [41], CRYSTALS [42], ORTEP-3 [43] packages. Atomic form
factors were taken from Ref. [44].
19
/
a The reported values are calculated for molecule.

R. D’Amato et al. / Journal of Organometallic Chemistry 627 (2001) 13–22
21
4. Conclusions
3.6. X-ray structure of trans-[Pt(PPh3)2(CꢀC–
C6H5)(CꢀC–C6H4NO2)]
A series of Pt(II) and Pd(II) bis-acetylides has been
prepared and characterised. The complexes show opti-
cal properties that can be finely modulated by the
choice of the acetylide ligand. The UV absorption and
emission spectra suggest that the complexes may be
considered as precursors or models of related
organometallic polymers with analogous properties.
Among the unsymmetrical molecules, the SHG mea-
surements indicate that the molecular hyperpolarisabil-
It is well known that p-electron conjugated molecules
with charge asymmetry are suitable for second-order
NLO properties. Moreover, for a bulk material, a non
centrosymmetric arrangement is also required. In order
to investigate the symmetry of complex 6 in its crystal
arrangement, the single crystal X-ray molecular struc-
ture was determined.
ity
i
is correlated with the strength of the
Crystals of complex 6 were grown by slow evapora-
tion from toluene–methanol. A suitable crystal was
mounted on Huber CS diffractometer [38] with graphite
donor/acceptor acetylide ligand and is alike that of a
typical azo-dye such as Disperse Red 1 (DR1) for
complexes 6 and 9.
,
monochromatized Mo–Ka radiation (u=0.71069 A).
Investigations on the third order nonlinear optical
properties show that a strong acceptor group like NO2
in the acetylide ligand s-bound to Pt(II) (complex 1)
induces the highest value of nonlinear absorption co-
efficient h2. A strong donor group (ferrocene in com-
plexes 13 and 15) also leads to appreciable values of h2,
suggesting that push–push or pull–pull substituents
modify the delocalisation of p electrons involving the
central Pt atom. The Pd complexes here investigated
show third-order properties to a lesser extent.
The results so far obtained for the reported series of
Pt and Pd bisacetylides suggest some general trends for
the implementation of materials with the desired NLO
properties.
Details of the crystal data, data collection, structure
solution and refinement are given in Table 6. All the
hydrogen atoms at calculated positions with thermal
parameters arbitrarily fixed at 1.2 times that of attached
C atoms were included in the final least-squares
refinement.
The structure consists of discrete molecules (Fig. 2) in
which phenylacetylene and p-nitrophenylacetylene moi-
eties are s-bonded to platinum in a trans configuration.
Coordination around the platinum atoms is square
planar, with small tetrahedral distortions (max 0.027(7)
,
A from the mean square plane passing through P(1),
P(2), C(1) and C(3) atoms). The mean planes through
phenylacetylene and p-nitrophenylacetylene form dihe-
dral angles of 9.54 and 2.64°, respectively, with the
coordination plane. The molecular geometry is that
normally expected for trans-(Ph3P)2Pt(II) compounds,
and no contacts other than those of van der Waals type
are observed in the crystal.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 147478 for compound 6.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336003;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
Acknowledgements
The authors wish to gratefully acknowledge MURST
(Italy) for financial support to this research.
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Fig. 2. Drawing of trans-[Pt(PPh3)2(CꢀC–C6H5)(CꢀC–C6H4NO2)]
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