Thiocyanato-bridged platinum heterocycles: Structure and properties of disc-like metallomesogens

Article abstract of DOI:10.1016/S0022-328X(00)00782-8

The synthesis and liquid crystalline properties of novel disc-like di- and tetra-platinum organyls have been described recently. Here, the synthesis and mesomorphic properties of the first thiocyanato-bridged, sheet-shaped di- and tetra-platinum complexes are described. Structural features of these sheet-shaped thiocyanato-bridged di- and tetra-platinum organyls based on various methods (e.g. ¹H-, ¹³C-, ¹⁹⁵Pt-NMR) are discussed and related to the mesomorphic properties of these compounds. In addition, the molecular structure of a new thiocyanato-bridged diplatinum organyl carrying eight hexyl chains has been elucidated by single crystal X-ray diffraction analysis.

Full text of DOI:10.1016/S0022-328X(00)00782-8

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 620 (2001) 249–255
Thiocyanato-bridged platinum heterocycles: structure and
properties of disc-like metallomesogensꢀ
Belkız Bilgin Eran a,*, Dirk Singer b, Joachim Pickardt c, Klaus Praefcke d
a
8
Department of Chemistry, Yıldız Teknik Uni6ersitesi, TR-34210 Istanbul, Turkey
b Department of Chemistry, Howard Uni6ersity, Washington, DC 20059, USA
c Faculty of Chemistry, Technische Uni6ersita¨t Berlin, D-10623 Berlin, Germany
d Technische Uni6ersita¨t Berlin, J4, D-10623 Berlin, Germany
Received 7 June 2000; received in revised form 16 October 2000
Abstract
The synthesis and liquid crystalline properties of novel disc-like di- and tetra-platinum organyls have been described recently.
Here, the synthesis and mesomorphic properties of the first thiocyanato-bridged, sheet-shaped di- and tetra-platinum complexes
are described. Structural features of these sheet-shaped thiocyanato-bridged di- and tetra-platinum organyls based on various
1
methods (e.g. H-, 13C-, 195Pt-NMR) are discussed and related to the mesomorphic properties of these compounds. In addition,
the molecular structure of a new thiocyanato-bridged diplatinum organyl carrying eight hexyl chains has been elucidated by single
crystal X-ray diffraction analysis. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Cycloplatination; Liquid crystals; Metallomesogens; Thiocyanato-bridged platinum organyls; X-ray structure analysis
1. Introduction
matic-discotic (ND) type of mesophase [2]. Moreover,
tetranuclear palladium(II) complexes derived from or-
tho-palladated Schiff bases of p-phenylene diamine car-
rying 12 peripheral chains form columnar Colob,d
mesophases with an oblique two-dimensional arrange-
ment of the columns and a highly disordered intra-
columnar stacking [2–4].
In principle, structurally related halogeno-bridged
platinum organyls [5,6] show the same mesomorphic
behavior as their palladium analogues. In particular,
dinuclear platinum complexes with halogeno bridges
and eight aliphatic chains form, if any, the ND type of
mesophase, whereas the tetranuclear platinum organyls
with 12 peripheral chains exhibit Colob,d mesophases.
Here, the synthesis and characterization of the meso-
genic properties of the first thiocyanato-bridged ortho-
platinated compounds 1–4, derived from imines and
bisimines, are described.
Cyclometallated compounds have been a particularly
fertile area of research in recent times, with many
different examples from different groups, especially
within the field of liquid crystals [1]. Palladium(II) and
platinum(II) complexes of this type are stable in air, of
sufficient thermal stability, and allow the design and
realization of unusual molecular geometries owing to
the square-planar coordination of these metals.
H-shaped mesogenic dinuclear ortho-metallated pal-
ladium(II) complexes, mainly derived from aromatic
Schiff bases or azines, first attracted attention and were
shown to form nematic and smectic phases [1]. More
recently, our group has shown that just by increasing
the number of peripheral aliphatic chains to eight such
dinuclear palladium organyls have a more elliptical or
sheet-like shape, resulting in the formation of the ne-
ꢀ This paper is number 127 on liquid-crystalline compounds of the
Berlin Research Group; paper 126: B. Bilgin Eran, D. Singer, K.
Praefcke, J. Inorg. Chem. in press.
2. Results and discussion
* Corresponding author. Tel.: +90-212-4491750; fax: +90-212-
4491514.
The thiocyanato bridged platinum organyls 1–4 were
E-mail address: bilgin@yildiz.edu.tr (B. Bilgin Eran).
prepared from their chloro-bridged analogues [5–7] by
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00782-8

250
B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
simple exchange reactions with potassium thiocyanate
in dichloromethane–acetone under argon at room tem-
perature (see Section 4).
dinuclear halogeno-bridged platinum organyls [5,7] ex-
ist as mixtures (17:83) of the isomers with parallel (syn)
and anti-parallel (anti) orientation of their imine lig-
ands; attempts to separate these two isomers were
The new compounds presented here were character-
1
1
ized by various spectroscopic methods, e.g. H-, 13C-
unsuccessful. The H-NMR spectra of the thiocyanato-
NMR, IR, and (in part) also 195Pt-NMR (CDCl3). The
proposed structures are in full agreement with these
spectroscopic data and with elemental analyses. In ad-
dition, for the dinuclear thiocyanato-bridged platinum
organyl 2 the molecular structure was determined by
single crystal X-ray diffraction.
bridged dinuclear platinum organyls 1 and 2, however,
show neither the syn/anti isomerism of their previously
described halogeno-bridged diplatinum analogues [5,7],
nor isomerism resulting from parallel or anti-parallel
orientation of the thiocyanato bridging groups to each
other, as observed for sheet-like and calamitic thio-
cyanato-bridged dipalladium organyls [2,9]. Even more
important, the X-ray single crystal structure analysis of
the new platinum organyl 2, having eight flexible hexyl
chains, shows clearly the anti-parallel orientation of the
thiocyanato bridging groups. The sulfur atoms of the
thiocyanato bridges are trans to the imine nitrogen
atoms of the two ligands.
The 1H- and 13C-NMR data for the platinum or-
ganyls 1–4 are similar to those of the analogous multi-
nuclear platinum(II) complexes with halogeno bridges
[5–7] (Fig. 1). In particular, the l(195Pt) value of
−3599.5 ppm for the methoxy-substituted compound 1
is well within the range expected for organoplatinu-
m(II) compounds with ortho-metallated nitrogen donor
ligands [6–8].
In principle, for dinuclear ortho-metallated palla-
dium and platinum complexes of the type investigated
here, two isomers are possible based on the parallel or
anti-parallel orientation of the two imine ligands to
each other. In addition, asymmetric bridging groups
like the SCN-moieties used here can introduce further
isomerism: these bridging groups can be oriented paral-
lel or anti-parallel to each other. In addition, in the case
of anti-parallel orientations of both the ligands and
SCN bridging group, two isomeric forms of the square-
planar coordination sphere of the platinum atoms can
be distinguished: one in which the sulfur atoms are
trans to the imine nitrogen atoms and one in which
they are trans to the coordinating carbon atom. Unlike
the analogous halogeno-bridged dipalladium organyls
[2], which show no isomerism, the previously described
Crystals suitable for X-ray analysis were grown by
slow evaporation of a solution of 2 in methanol–ace-
tone. The platinum compound 2 crystallizes in the
(
triclinic space group P1 with Z=1 molecule per unit
cell. Fig. 2 shows a DIAMOND [10] plot of the molecule.
The molecule is centrosymmetric; its inversion center
lies on an inversion center of the unit cell. The carbon
chains exhibit a slightly increasing distortion at the
periphery. The non-bonding PtꢀPt distance is
564.0(2) pm. The thiocyanato groups act as m2 bridging
ligands. The ‘core’ is almost planar, only the ring
C9···C14 is turned out of the plane of the molecular
core by approximately 49°. The bridging thiocyanato
group forces the molecule into a completely coplanar
geometry of the two square-planar platinum centers.
The PtꢀC distance, at 199. (5) pm, is slightly larger than
that in the analogous chloro-bridged platinum organyl
Fig. 1. Structural formulas of the new multi-nuclear platinum organyls 1–4 showing their thiocyanato bridges in anti-parallel arrangement; see
discussion (Section 2) about the NMR spectra of the macrocycles 3 and 4.

B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
251
molecules; specifically, there are no significant attractive
interactions perpendicular to the molecular plane.
Therefore, the formation of this type of mesophase is
very sensitive to small changes in the interaction profile
of the constituent molecules. Here, either a small differ-
ence in the electron density distribution resulting from
the replacement of palladium with platinum or lack of
a second isomer with a different interaction profile
suppresses the formation of an ND phase.
However, the dinuclear platinum organyl 2 shows
induced/stabilized mesomorphism with the strong elec-
tron acceptor 2,4,7-trinitro-fluorenone (TNF). Contact
mixtures of the non-liquid-crystalline thiocyanato-
bridged complex 2 with TNF shows a fluid mesophase
with Schlieren texture and visible thermal fluctuations
typical for a nematic phase. The maximum of the
clearing temperature is 98°C, which is 14°C lower than
that of the charge transfer complex of the correspond-
ing palladium compound with TNF [11a]. Thus, the
Fig. 2. Crystal structure of 2. For clarity the carbon atoms of the side
chains are represented by open circles with an arbitrary radius, as the
outer C atoms have increasing and comparatively large thermal
parameters. See Table 3 concerning the symmetry code for equivalent
atoms.
Table 1
Crystal and data collection parameters for 2a
Formula
Formula weight 1636.02
C76H116N4O6Pt2S2
[5]. Relevant X-ray data of the structure analysis of 2
are given in Tables 1–3.
Crystal size
(mm)
Crystal system
Space group
Z
0.1×0.25×0.6
The 1H-NMR spectra of the thiocyanato-bridged
tetraplatinum organyls 3 and 4 show no isomerism.
Based on the NMR data, see Section 4, two isomers are
possible. The first isomer is centrosymmetric, as de-
picted in Fig. 2, with an antiparallel orientation not
only of the two SCN bridges within each Pt(SCN)2Pt
unit, but also of those moieties to each other. In the
second isomer the two Pt(SCN)2Pt substructures are
parallel to each other and, therefore, only a C2 axis
exists. However, which one of these conceivable anti-
parallel thiocyanato-bridged isomers has been formed
in the ortho-metallation reaction cannot be deduced
from these NMR data. The only way to elucidate this
problem is a single crystal X-ray analysis of these two
dimeric macrocyclic molecules. Unfortunately, this pos-
sibility is hampered by the unsatisfactory crystallization
of both compounds.
triclinic
(
P1 (no. 2)
1
,
a (A)
9.625(2)
12.017(3)
18.329(5)
73.79(2)
78.41(2)
76.32(2)
1957.2(8)
1.39
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
dc (g cm−3
)
Radiation, u
Mo–Ka, 0.710 69
,
(A)
v (cm−1
)
36.7
50.0
2qmax (°)
hkl range
Scan type
Scan speed
05h511, −135k514, −215l521
ꢀ-scan
min 1.0, max 29.3
(° min−1
No. of data
measured
No. of unique
data
)
7343
6892
5856
406
In contrast to their palladium analogues [2], the
thiocyanato-bridged dinuclear compounds 1 and 2
show no liquid crystalline behavior; no mesophase
could be detected even with a cooling rate as high as
100 K min−1. In general, the effect of the metal atom
(Pd or Pt) on the mesomorphism of such dinuclear
metal organyls is usually small. Thus, a possible reason
for the non-existence of a liquid crystalline phase could
be that the di-platinum organyl 2, in contrast to the
palladium analogue, does not exist as an isomeric mix-
ture. However, the melting temperature of 2 is also
about 10 K lower than that of the analogue palladium
complex, cf. Table 4 and Ref. [2]. In ND phases no
strong attractive interactions exist between the mesogen
No. of data
with I\2|(I)
No. of
parameters
R
0.067
0.055
Rw (on F2)
w
1/[|2(Fo)2+(0.1311P)2+3.18P], where
P=(Max(F2o, 0)+2F2c)/3
−3.67/5.69
Res. electron
density
−3
(e−
)
,
A
a Estimated standard deviations are given in parentheses.

252
B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
Table 2
only be observed for thiocyanato-bridged di-palladium
and di-platinum compounds. In all the other examples
of mesophase induction/stabilization between disc-
shaped electron donors (including dinuclear palladium
and platinum complexes [11]) and strong electron ac-
ceptors the formation of columnar aggregates occurs,
Atom positions and Ueq values for 2a
b
2
,
Atom
x
y
z
Ueq (A )
Pt
S
0.0449(1)
0.3137(1)
0.4947(3)
0.3651(8)
0.1450(7)
0.3265(6)
0.1156(6)
0.4273(1)
0.3851(2)
0.5174(5)
0.4499(4)
0.1623(4)
0.1579(4)
0.2750(4)
0.4416(6)
0.3385(5)
0.3364(5)
0.2769(5)
0.2175(5)
0.2221(5)
0.2802(5)
0.3992(5)
0.5156(5)
0.5559(6)
0.6170(7)
0.6367(6)
0.5947(7)
0.5346(6)
0.1596(6)
0.0888(6)
0.0138(7)
0.052(1)
0.081(1)
0.072(2)
0.053(2)
0.068(2)
0.066(2)
0.070(2)
0.063(3)
0.055(2)
0.053(2)
0.059(2)
0.055(2)
0.055(2)
0.058(2)
0.054(2)
0.055(2)
0.063(2)
0.076(3)
0.076(3)
0.081(3)
0.068(3)
0.071(3)
0.074(3)
0.075(3)
0.080(3)
0.112(5)
0.144(8)
0.079(3)
0.080(3)
0.091(4)
0.098(4)
−0.1001(4)
0.0827(11)
0.1667(9)
−0.1546(8)
0.0017(8)
N(1)
N(2)
O(1)
O(2)
O(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
either
arranged
into
nematic-columnar
(NC)
mesophases or forming columnar phases with a two-di-
mensional lattice, most commonly a hexagonal one
(Colh phase) [11,12].
The methoxy-substituted platinum organyl 1 shows
no induced or stabilized mesomorphism with TNF
owing to its high melting temperature and rapid decom-
position in the isotropic state (see Table 4).
The tetranuclear thiocyanato-bridged platinum com-
pounds 3 and 4 both exhibit enantiotropic mesophases.
On heating each of the tetraplatinum organyls 3 and 4
above their melting temperatures, highly viscous and
birefringent mesophases can be observed under a polar-
izing microscope between crossed polarizers up to very
high clearing temperatures. In their isotropic phases a
rapid and strong decomposition takes place; therefore,
only on rapid cooling of samples of the platinomesogen
4 are typical textures developed. They resemble those of
columnar hexagonal (Colh) mesophases. However, mis-
cibility studies (contact method) with the mesophases of
analogous tetrapalladium organyls [4a] seem to indicate
complete miscibility; thus, the mesophase of 4 appears
to be of the same type, i.e. Colob.
0.1675(9)
−0.0130(6)
0.5761(9)
0.2625(8)
0.1466(8)
0.0972(8)
0.1600(9)
0.2726(8)
0.3235(9)
0.0880(8)
0.0853(9)
0.0906(12)
0.0134(11)
0.0885(10)
0.0873(12)
0.0037(11)
−0.0748(10)
−0.0729(11)
0.1673(11)
0.2398(11)
0.2265(11) −0.0273(10)
0.3048(14) −0.0859(11)
0.3967(12) −0.0311(12)
0.4121(13)
0.3331(12)
0.0815(12)
0.1390(10)
0.4445(10)
0.4800(12)
0.4845(12)
C(15) −0.2371(13)
C(16) −0.3112(12)
C(17) −0.2124(13)
C(18) −0.2832(14)
C(19) −0.1958(18)
C(20) −0.2740(20)
0.5104(12) −0.0562(7)
0.5169(19) −0.1309(9)
0.5360(20) −0.1980(9)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
0.0969(14)
0.0596(15)
0.1375(16)
0.1046(19)
0.1660(30)
0.3080(30)
0.1617(12)
0.1380(12)
0.1989(13) −0.0547(8)
0.1766(14) −0.1248(7)
0.2520(20) −0.2013(11) 0.145(8)
0.2490(30) −0.2147(15) 0.190(13)
0.0888(7)
0.0211(6)
0.0882(18) −0.1014(14)
0.1780(30) −0.2216(14)
0.2670(30) −0.2659(19)
0.3370(50) −0.3940(30)
0.4380(50) −0.4600(40)
0.4980(30) −0.5830(20)
0.4827(16) −0.0933(16)
0.3932(15) −0.0990(14)
0.4777(16) −0.1401(14)
0.3879(17) −0.1424(16)
0.4620(20) −0.1770(20)
0.3730(20) −0.1761(19)
0.2831(14) 0.133(8)
0.2957(14) 0.155(10)
0.3550(15) 0.154(9)
0.3600(20) 0.250(20)
0.3880(30) 0.310(30)
0.3914(18) 0.205(15)
Table 3
a,b
,
Selected bond distances (A) and angles (°) for 2
PtꢀC(2)
PtꢀN(1)
PtꢀN(2)
PtꢀS
1.991(9)
2.040(9)
2.064(8)
2.309(3)
C(2)ꢀPtꢀN(1)
C(2)ꢀPtꢀN(2)
N(1)ꢀPtꢀN(2)
C(2)ꢀPtꢀS
N(1)ꢀPtꢀS
N(2)ꢀPtꢀS
178.6(4)
81.1(4)
98.0(3)
89.6(3)
91.3(3)
170.7(2)
105.9(4)
179.5(11)
162.4(8)
113.0(6)
127.7(6)
0.7040(7)
0.7817(7)
0.8479(7)
0.9267(8)
0.9939(9)
1.0699(9)
0.105(5)
0.089(4)
0.095(4)
0.106(5)
0.130(7)
0.132(6)
SꢀC(1)
1.637(10)
1.190(14)
1.416(13)
1.414(13)
1.384(13)
1.429(13)
1.417(14)
1.401(14)
1.375(13)
1.298(12)
1.442(12)
1.371(14)
1.369(14)
1.401(16)
1.372(19)
1.383(18)
1.391(15)
C(1)ꢀN(1)i
C(2)ꢀC(3)
C(2)ꢀC(7)
C(3)ꢀC(4)
C(3)ꢀC(8)
C(4)ꢀC(5)
C(5)ꢀC(6)
C(6)ꢀC(7)
C(8)ꢀN(2)
C(9)ꢀN(2)
C(9)ꢀC(10)
C(9)ꢀC(14)
C(10)ꢀC(11)
C(11)ꢀC(12)
C(12)ꢀC(13)
C(13)ꢀC(14)
C(1)ꢀSꢀPt
N(1)iꢀC(1)ꢀS
C(1)iꢀN(1)ꢀPt
C(8)ꢀN(2)ꢀPt
C(9)ꢀN(2)ꢀPt
a Estimated standard deviations are given in parentheses.
b Ueq=(1/3)ꢀiꢀj Uij a*a*aiaj.
i
j
stability of the deeply monotropic and unobserved ND
phase is increased through the charge transfer interac-
tions of the electron donor 2 with the electron acceptor
TNF — a similar behavior has already been observed
in the thiocyanato-bridged palladium analogues [11].
However, this stabilized/induced ND phase of the sys-
tem 2/TNF mirrors the lower stability of the mesophase
of neat 2 compared with that of the analogous palla-
dium mesogen.
a Estimated standard deviations are given in parentheses.
b Symmetry transformations used to generate equivalent atoms:
i, −x+1, −y+1, −z+1.
Interestingly, the exclusive stabilization of the ND
phase by charge-transfer interactions up to now has

B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
253
The thermal phase-transition data of these new thio-
cyanato-bridged metallocyclic compounds are summa-
rized in Table 4. The clearing temperature of 4 is, at
286°C, nearly identical to that of the respective tetra-
pallado mesogen (290°C) [2].
The extremely high viscosity and clearing tempera-
ture prevented a detailed study of the thermotropic
mesophase of the hexyloxy-substituted platinum com-
pound 3. In particular, no identifiable textures were
obtained; the nature of the mesophase of 3, therefore,
remains unknown.
(Bruker WH-400 or AM-270 spectrometers respec-
tively, CDCl3 solutions), 195Pt-NMR (in part) (Bruker
ARX 400 spectrometer (86.02 MHz) in CDCl3 solutions
using a separate reference sample (0.5 g Na2PtCl6 in
2 ml D2O)), IR (Beckmann 9, CCl4 solutions) and MS
(Varian MAT 711). Only structurally relevant reso-
nances are given; see below.
Phase-transition data were determined by differential
scanning calorimetry (Mettler TA 3000/DSC-30 S with
TA 72.5 software) and by polarizing microscopy (Leitz
Laborlux 12 Pol with a Mettler FP 82 hot-stage or
using the Linkam THMS 600 system) with heating rates
of 5 or 20 K min−1 in both methods.
3. Conclusions
4.1. Single-crystal X-ray diffraction analysis
Thiocyanato-bridged di- and tetra-nuclear platinum
complexes are easily accessible by simple exchange reac-
tions from their chloro-bridged analogues. Single-crys-
tal X-ray diffraction proves the coplanar arrangement
of the two square-planar platinum(II) coordination
polyhedral in 2. The dinuclear compound 2 shows none
of the possible forms of isomerism and is not mesomor-
phic, in contrast to the respective di-palladium organyl.
However, with TNF as a strong electron acceptor the
induction/stabilization of an ND mesophase is ob-
served. The mesomorphic properties of the new tetranu-
clear platinum organyl 4 strongly resemble those of the
analogous pallado-mesogen. Thus, here the exchange of
platinum for palladium has a significant impact and
results in the absence of an ND mesophase in 2. How-
ever, for the tetranuclear platinum mesogen 4 the
switch from palladium to platinum has nearly no im-
pact on the type and stability of the exhibited
mesophase.
Data were collected on a Syntex P21 diffractometer
,
using Mo–Ka radiation (u=0.710 69 A). The structure
was solved after Lp correction by Patterson methods
using SHELXS [13] and refined with anisotropic thermal
parameters for the non-hydrogen atoms with SHELXL
[14]. Hydrogen positions were calculated and refined
with a riding model; the methyl groups were refined as
rigid groups.
4.2. Preparation of the compounds 1–4
The thiocyanato-bridged platinum organyls 1–4 were
prepared from the corresponding chloro-bridged pre-
cursors [5–7] by the usual exchange reactions with
potassium thiocyanate in methylene chloride–acetone
under argon at room temperature. The crude products
were purified by crystallization.
4.2.1. Synthesis of the dinuclear platinum organyls 1
and 2
4. Experimental
The exchange reaction (Cl“SCN) was carried out
by stirring either 0.1 mmol (0.12 g) of the methoxy-sub-
stituted chloro-bridged platinum organyl [7] or
0.1 mmol (0.16 g) of the hexyloxy-substituted chloro-
bridged platinum organyl [5] with 3 mmol (0.29 g) of
The characterizations of the compounds 1–4 pre-
sented here are based on correct elementary analyses
and on various spectroscopic data, e.g. H-, 13C-NMR
1
Table 4
Phase transition temperaturesa T and enthalpies DH of 1–4
b
Platinum organyl
Crystalline
Colob
Mb
Ib
T (°C)
DH (kJ mol−1
)
T (°C)
DH (kJ mol−1
)
T (°C)
DH (kJ mol−1
)
T (°C)
dec.
1
2
3
4
172.6
86.2
69.0
17.2
42.5
20.7
11.9
56.9
–
–
–
–
–
c
308.2
–
–
dec.
dec.
c
286.1
–
a Mettler TA 3000/DSC-30 S with TA 72.5 software. Heating rates 5 K min−1 for the melting and 20 K min−1 for the clearing processes.
b Colob: columnar oblique; M: a highly viscous phase of unknown type; I: isotropic.
c Here, the clearing process is strongly interfered with by decomposition; therefore, the DH value obtained of less than 1 kJ mol−1 is to be
considered with caution.

254
B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
KSCN in a mixture of 40 ml CH2Cl2, and 20 ml of
acetone for 6 days under argon. The crude products
were purified by removing the solvent under reduced
pressure followed by recrystallization from methanol–
acetone. The melting points of 1 and 2 are given in
Table 4.
HCꢁN), 7.34, 7.19 (2d, J:8 Hz each; 4 arom. Hs of the
4,4%-di-N-substituted phenyl rings), 6.78, 6.37 (2s; 4
arom. Hs of the benzylidene rings), 4.20–4.11 (m; 6
OCH2 groups), 4.07, 3.89, 3.86 (3t, J:6.5 Hz each; 6
OCH2 groups). 13C-NMR: l=176.40, 172.82 (2d; 4
HCꢁN), 160.02, 158.42, 154.03, 153.76, 148.87, 148.26,
145.94, 137.98, 136.88, 136.76, 132.96, 130.29, 126.20,
121.70 (14s; 24 arom. Cs and 4 SCN groups), 124.12,
123.74, 112.24, 111.00 (4d; 12 arom. CH situations),
74.55, 73.52, 68.96, 68.70 (4t; 12 OCH2 groups). IR
(CCl4): w=2176 and 2147 cm−1 (SCN). Anal. Found:
C, 50.03; H, 6.43; N, 3.88. Calc. for C116H172N8O12Pt4S4
(2779.3): C, 50.13; H, 6.24; N, 4.03%.
Bis[m - (thiocyanato - N:S)]bis[3,4,5 - tris(methoxy) - 2-
{[(4-hexylphenyl)imino]methyl}phenyl-C,N]diplatinum-
(II) (1). Yield: 87 mg (72%) of yellow crystals. 1H-NMR:
l=8.41 (s; 2 HCꢁN), 7.27, 7.22 (2d, J:8 Hz each; 4
arom. Hs of the N-substituted phenyl rings), 6.35 (s; 2
arom. Hs of the Pt-substituted phenyl rings), 3.95, 3.89,
3.77 (3s; 6 OCH3 groups), 2.68 (t, J:7.5 Hz; 2 a-CH2
groups). 13C-NMR: l=172.03 (d; 2HCꢁN), 157.82,
153.84, 147.58, 142.75, 137.71, 137.53, 132.76 (7s; 14
arom. Cs and 2 SCN groups), 128.57, 123.09, 110.05
(3d; 4, 4 and 2 arom. CH respectively), 61.71, 60.71,
56.00 (3q; 6 OCH3 groups), 35.49 (t; 2 a-CH2 groups).
195Pt-NMR: l= −3599.5 (s). IR (CCl4): w=2162 cm−
Bis{m - [1,4 - phenylenbis[nitrilomethylidyn(3,4,5 - tris-
(dodecyloxy)-2,1-phenylen)]]}tetrakis-[m-(thiocyanato-
N:S)]tetraplatinum(II) (4). Yield: 241 mg (64%) of
1
sticky yellow-brown crystals. H-NMR: l=8.35, 8.19
(2s; 4 HCꢁN), 7.34, 7.19 (2d, J:8 Hz each; 4 arom. Hs
of the 4,4%-di-N-substituted phenyl rings), 6.78, 6.37 (2s;
4 arom. Hs of the benzylidene rings), 4.20–4.11 (m; 6
OCH2 groups), 4.07, 3.89, 3.86 (3t, J:6.5 Hz each; 6
OCH2 groups). 13C-NMR: l=176.37, 172.79 (2d; 4
HCꢁN), 160.03, 158.42, 154.03, 153.75, 148.86, 148.26,
145.98, 138.01, 136.85, 136.73, 132.95, 130.28, 126.21,
121.76 (14s; 24 arom. Cs and 4 SCN groups), 124.13,
123.75, 112.25, 110.98 (4d; 12 arom. CH situations),
74.55, 73.53, 68.94, 68.71 (4t; 12 OCH2 groups). IR
(CCl4): w=2176 and 2148 cm−1 (SCN). Anal. Found C,
59.35; H, 8.12; N, 2.64. Calc. for C188H316N8O12Pt4S4
(3789.2): C, 59.59; H, 8.41; N, 2.96%.
1
(SCN). Anal. Found: C, 45.41; H, 4.63; N, 4.42. Calc.
for C46H56N4O6Pt2S2 (1215.3): C, 45.46; H, 4.64; N,
4.61%.
Bis[m - (thiocyanato - N:S)]bis[3,4,5 - tris(hexyloxy) - 2-
{[(4-hexylphenyl)imino]methyl}phenyl-C,N]diplatinum-
(II) (2). Yield: 125 mg (76%) of yellow crystals. 1H-
NMR: l=8.38 (s; 2 HCꢁN), 7.26, 7.22 (2d, J:8 Hz
each; 4 arom. Hs of the N-substituted phenyl rings),
6.31 (s; 2 arom. Hs of the Pt-substituted phenyl rings),
4.12, 4.01, 3.85 (3t; J:6.5 Hz each; 3 types of OCH2
group), 2.68 (t, J:8 Hz; 2 a-CH2 groups). 13C-NMR:
l=172.24 (d; 2 HCꢁN), 157.79, 153.65, 147.75, 142.66,
137.20, 137.01,133.07 (7s; 14 arom. Cs and 2 SCN
groups), 128.60, 123.12, 110.89 (3d; 4, 4 and 2 arom. CH
respectively), 74.56, 73.50, 68.62 (3 t; 6 OCH2 groups),
35.52 (t; 2 a-CH2 groups). MS: m/z (%)=1634.8 (15)
[M+]. IR (CCl4): w=2161 cm−1 (SCN). Anal. Found:
C, 55.09; H, 7.56; N, 3.79. Calc. for C76H116N4O6Pt2S2
(1636.1): C, 55.79; H, 7.15; N, 3.42%.
5. Supplementary material
Crystallographic data have been deposited at the
Cambridge Data Center and may be obtained without
charge on quoting the depository number CCDC
143811 from CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-336033, e-mail deposit@
ccdc.cam.ac.uk).
4.2.2. Synthesis of the tetranuclear platinum organyls 3
and 4
The exchange reaction (Cl“SCN) was carried out by
stirring 0.1 mmol (0.27 g) of the hexyloxy-substituted
chloro-bridged tetra-platinum organyl [6] or 0.1 mmol
(0.37 g) of the respective dodeclyoxy-substituted chloro-
bridged platinum complex [6] with 10 mmol (0.97 g) of
KSCN in a mixture of 60 ml CH2Cl2 with 30 ml acetone
for 6 days under argon. The crude products were
purified by removing the solvent under reduced pressure
and recrystallization from methylene chloride–acetone.
The melting and clearing temperatures of 3 and 4 are
given in Table 4.
Acknowledgements
B. Bilgin Eran wishes to thank Yıldız Teknik
Universitesi Research Fond and Devlet Planlama
8
Tes¸kilatı (DPT) (State Planning Organization Turkey)
for the supply of a polarizing microscope. K. Praefcke
is grateful to the Deutsche Forschungsgemeinschaft,
Bonn (Sonderforschungsbereich Sfb 335 ‘Anisotrope
Fluide’, project C 3), the Fonds der Chemischen Indu-
strie, Frankfurt/Main, the Gesellschaft von Freunden
der Technischen Universita¨t Berlin, and to the Tech-
nische Universita¨t Berlin, Germany, for financial sup-
port of his liquid crystal work as well as to Degussa
AG., Hanau, Germany, for the supply of palladium and
platinum precursors.
Bis{m - [1,4 - phenylenbis[nitrilomethylidyn(3,4,5 - tris-
(hexyloxy) - 2,1 - phenylen)]]}tetrakis - [m - (thiocyanato-
N:S)]tetraplatinum(II) (3). Yield: 132 mg (47%) of
1
sticky yellow crystals. H-NMR: l=8.34, 8.18 (2s; 4

B. Bilgin Eran et al. / Journal of Organometallic Chemistry 620 (2001) 249–255
255
Palladiums und Platins, Verlag Dr Ko¨ster, Berlin, 1996, ISBN
3-89574-155-8.
References
[6] K. Praefcke, B. Bilgin, N. Usol’tseva, B. Heinrich, D. Guillon, J.
Mater. Chem. 5 (1995) 2257.
[7] K. Praefcke, B. Bilgin, J. Pickardt, M. Borowski, J. Organomet.
Chem. 592 (1999) 155.
[1] (a) J.L. Serrano (Ed.), Metallomesogens, Synthesis, Properties,
and Applications, VCH, Weinheim, 1996. (b) A.M. Giroud-
Godquin, in: D. Demus, J. Goodby, G.W. Gray, H.-W. Spiess,
V. Vill (Eds.), Handbook of Liquid Crystals, vol. IIB, Wiley–
VCH, Weinheim, 1998, p. 901.
[8] P.S. Pregosin, Coord. Chem. Rev. 44 (1982) 247.
[9] (a) J. Barbera, P. Espinet, E. Lalinde, M. Marcos, J.L. Serrano,
Liq. Cryst. 2 (1987) 833. (b) M.A. Ciriano, P. Espinet, E.
Lalinde, M.B. Ros, J.L. Serrano, J. Mol. Struct. 196 (1989) 327.
[10] G. Bergerhoff, K. Brandenburg, M. Berndt, DIAMOND, Visuelles
Informationssystem fu¨r Kristallstrukturen, Bonn, 1996.
[11] (a) D. Singer, A. Liebmann, K. Praefcke, J.H. Wendorff, Liq.
Cryst. 14 (1993) 785. (b) K. Praefcke, D. Singer, Mol. Mater. 3
(1994) 265.
[12] (a) K. Praefcke, D. Singer, in: D. Demus, J. Goodby, G.W.
Gray, H.-W. Spiess, V. Vill (Eds.), Handbook of Liquid Crys-
tals, vol. IIB, Wiley–VCH, Weinheim, 1998, p. 945. (b) S.
Zamir, D. Singer, N. Spielberg, E.J. Wachtel, H. Zimmermann,
R. Poupko, Z. Luz, Liq. Cryst. 21 (1996) 39.
[2] K. Praefcke, D. Singer, B. Gu¨ndog˘an, Mol. Cryst. Liq. Cryst.
223 (1992) 181.
[3] (a) B. Gu¨ndog˘an, K. Praefcke, Chem. Ber. 126 (1993) 1253. (b)
K. Praefcke, D. Singer, B. Gu¨ndog˘an, K. Gutbier, M. Langner,
Ber. Bunsenges. Phys. Chem. 98 (1994) 118. (c) N. Usol‘tseva, K.
Praefcke, D. Singer, B. Gu¨ndog˘an, Liq. Cryst. 16 (1994) 601.
[4] (a) K. Praefcke, S. Diele, J. Pickardt, B. Gu¨ndog˘an, U. Nu¨tz, D.
Singer, Liq. Cryst. 18 (1995) 857. (b) K. Praefcke, J.D. Holbrey,
N. Usol%tseva, Mol. Cryst. Liq. Cryst. 288 (1996) 189. (c) N.
Usol’tseva, G. Hauck, H.D. Koswig, K. Praefcke, B. Heinrich,
Liq. Cryst. 20 (1996) 731. (d) K. Praefcke, J.D. Holbrey, N.
Usol’tseva, D. Blunk, Mol. Cryst. Liq. Cryst. 292 (1997) 123. (e)
B. Heinrich, K. Praefcke, D. Guillon, J. Mater. Chem. 7 (1997)
1363.
[13] G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Solu-
tion, Go¨ttingen, 1997.
[5] (a) K. Praefcke, B. Bilgin, J. Pickardt, M. Borowski, Chem. Ber.
127 (1994) 1543. (b) B. Bilgin, Neue fla¨chige Mesogene des
[14] G.M. Sheldrick, SHELXL-97, Program for Refinement of Crystal
Structures, Go¨ttingen, 1997.
.