Syntheses and characterization of thallium(I) complexes with 3-nitrophenoxide [Tl(3-np)], 4-nitrobenzoate [Tl(4-nb)] and 2,4-dinitrophenoxide [Tl(2,4-dnp)]: X-ray crystal structures of [Tl(3-np)]n and Tl(2,4-dnp) (two new polymeric compounds)

Article abstract of DOI:10.1016/S0277-5387(02)01230-5

Complexes thallium(I)3-nitrophenoxide [Tl(3-np)], thallium(I)2,4-dinitrophenoxide [Tl(2,4-dnp)] and thallium(I)4-nitrobenzoate [Tl(4-nb)] have been synthesized using a direct reaction between TlNO₃ and the appropriate ligand. The complexes have been isolated and characterized by IR spectra and CHN elemental analyses. The structures of [Tl(3-np)]_n and [Tl(2,4-dnp)] have been confirmed by X-ray crystallography. The single crystal X-ray crystallography of [Tl(3-np)]_n shows the complex to be a one-dimensional polymer as a result of bridging 3-nitrophenoxide ligands. The Tl atoms have an unsymmetrical three-coordinate, O₃ geometry (three oxygen atoms of the 3-nitrophenoxide ligand). The crystal structure of [Tl(2,4-dnp)] shows the complex to be a three-dimensional polymer as a result of bridging 2,4-dinitrophenoxide ligands. The Tl atoms have an unsymmetrical two-coordinate, 02 geometry (two oxygen atoms of the 2,4-dinitrophenoxide ligand). The arrangement of the 3-nitrophenoxide and 2,4-dinitrophenoxide ligands suggests a gap in coordination geometry around the Tl(I) ions, occupied possibly by a stereoactive lone pair of electrons on Tl(I). There is a π-π stacking interaction between the parallel aromatic rings belonging to adjacent chains in the compounds that may help to increase the 'gap' in coordination geometry around the Tl(I) ions.

Full text of DOI:10.1016/S0277-5387(02)01230-5

Polyhedron 21 (2002) 2555Á2560
/
www.elsevier.com/locate/poly
Syntheses and characterization of thallium(I) complexes with
3-nitrophenoxide [Tl(3-np)], 4-nitrobenzoate [Tl(4-nb)] and
2,4-dinitrophenoxide [Tl(2,4-dnp)]: X-ray crystal structures of
[Tl(3-np)]n and Tl(2,4-dnp) (two new polymeric compounds)
Ali R. Mahjoub *, Ali Morsali, Hossian Bagherzadeh
Department of Chemistry, School of Science, Tarbiat Modarres University, P.O. Box 14155-4838, Tehran, Iran
Received 21 March 2002; accepted 30 August 2002
Abstract
Complexes thallium(I)3-nitrophenoxide [Tl(3-np)], thallium(I)2,4-dinitrophenoxide [Tl(2,4-dnp)] and thallium(I)4-nitrobenzoate
[Tl(4-nb)] have been synthesized using a direct reaction between TlNO3 and the appropriate ligand. The complexes have been
isolated and characterized by IR spectra and CHN elemental analyses. The structures of [Tl(3-np)]n and [Tl(2,4-dnp)] have been
confirmed by X-ray crystallography. The single crystal X-ray crystallography of [Tl(3-np)]n shows the complex to be a one-
dimensional polymer as a result of bridging 3-nitrophenoxide ligands. The Tl atoms have an unsymmetrical three-coordinate, O3
geometry (three oxygen atoms of the 3-nitrophenoxide ligand). The crystal structure of [Tl(2,4-dnp)] shows the complex to be a
three-dimensional polymer as a result of bridging 2,4-dinitrophenoxide ligands. The Tl atoms have an unsymmetrical two-
coordinate, O2 geometry (two oxygen atoms of the 2,4-dinitrophenoxide ligand). The arrangement of the 3-nitrophenoxide and 2,4-
dinitrophenoxide ligands suggests a gap in coordination geometry around the Tl(I) ions, occupied possibly by a stereoactive lone
pair of electrons on Tl(I). There is a pÁp stacking interaction between the parallel aromatic rings belonging to adjacent chains in the
/
compounds that may help to increase the ‘gap’ in coordination geometry around the Tl(I) ions.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Thallium(I) complexes; Crystal structure; Nitrophenoxide complexes
1. Introduction
that seemingly minor differences in ligands or in the
crystal array can have quite marked effects upon the
coordination stereochemistry. Since the presence of a
lone pair is not directly detected but is inferred on the
basis of the spatial distribution of atoms assumed to be
donors to the central metal ion, the identification of
these donor atoms is fundamental to the analysis of any
particular system. Interestingly, this alone is not a
straightforward process. The lone pair activity can be
dependent on the following factors: (1) low and high
coordination number, (2) hard or soft ligands, (3)
attractive or repulsive interactions among ligands, (4)
lone pair has p or no p character, (5) fewer or more
electrons transferred from ligands to metal [14].
Thallium(I) complexes are interesting because of their
unique characteristics such as the potential ability to
form metalÁmetal bonds and the presence of a lone pair
/
in the valence shell [1,2]. An issue frequently discussed in
considering the coordination and stereoactivity of heavy
metals is that of the ‘‘stereochemical activity’’ of valence
shell lone electron pairs. It appears that in complexes of
Pb(II) [3Á
/
7], Tl(I) [8Á
/
10] and Bi(III) [11Á13], the nature
/
and form of the coordination sphere is generally
determined by a number of factors, possibly lone
pairÁbond pair repulsions of comparable influence, so
/
The salts of 2-,3-,4-nitrophenol, 2-npH, 3-npH and 4-
npH, have more recently been recognized as members of
a broad family of weak acid derivatives [15,16]. [Tl(2-
np)] and [Tl(4-np)] have been previously described [8]. In
* Corresponding author. Tel.: ꢀ
6544
E-mail address: mahjouba@net1cs.modares.ac.ir (A.R. Mahjoub).
/
98-21-801-1001; fax: ꢀ98-21-800-
/
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 2 3 0 - 5

2556
A.R. Mahjoub et al. / Polyhedron 21 (2002) 2555Á2560
/
the present paper, we want to show the nature of
adducts formed between thallium(I) nitrate and 3-
nitrophenoxide, 2,4-dinitrophenoxide and 4-nitrobenzo-
ate ligands.
2.4. Preparation of Tl(4-nb)
The complex Tl(4-nb) was prepared by dissolving
0.266 g (1 mmol) thallium(I) nitrate in distilled water
and adding an ethanolic solution of 3-nitrobenzoic acid
(0.167 g, 1 mmol) and potassium hydroxide (0.057 g, 1
mmol). The resulting solution was stirred for 2 h at
room temperature, and then it was allowed to stand for
2. Experimental
3Á4 days in a refrigerator. A white powder of the desired
/
2.1. Physical measurements
product precipitated, which was filtered off, washed
with acetone and ether and air dried (0.230 g, yield
55%), m.p. 208 8C.
IR spectra were recorded as Nujol mulls using
PerkinÁ
/
Elmer 597 and Nicolet 510P spectrophot-
Anal. Found: C, 22.15; H, 1.13; N, 3.82. Calc. for
C7H4NO4Tl: C, 22.67; H, 1.08; N, 3.78%.
IR(cmꢁ1) selected bands: 717(vs), 817(s), 1331(vs),
1375(vs), 1507(vs), 1544(s), 2980(w), 3045(w).
ometers. Microanalyses were carried out using a Her-
aeus CHN-O-Rapid analyzer.
2.2. Preparation of Tl(3-np)
2.5. Crystallography
The complex Tl(3-np) was prepared by dissolving
0.266 g (1 mmol) thallium(I) nitrate in distilled water
and adding a mixture of 3-nitrophenol (0.139 g, 1 mmol)
and potassium hydroxide (0.057 g, 1 mmol) in ethanol
(10 ml). The resulting solution was stirred for 1 h at
2.5.1. Crystal data and refinement details
[Tl(3-np)]. C12H8N2O6Tl2, M 684.94, triclinic, space
˚
¯
group P1, aꢂ
aꢂ85.159(8)8, bꢂ
347.8(2) A , Dcalc (Zꢂ
304. Specimen: 0.10ꢃ0.1ꢃ
/
3.7649(15), bꢂ
86.133(8)8, gꢂ
1 f.u.) 3.271 Mg mꢁ3, F(000)
0.20 mm; Tmax,min 0.761,
/
9.400(4), cꢂ
/
10.068(4) A,
/
/
/
78.749(7)8, Vꢂ
/
3
˚
/
room temperature, then it was allowed to stand for 2Á3
/
/
/
days in a refrigerator. Yellow crystals of the desired
product precipitated, were filtered off, washed with
acetone and ether and air dried (0.239 g, yield 70%),
m.p. 190 8C.
Anal. Found: C, 19.65; H, 1.29; N, 4.31. Calc. for
C12H8N2O6Tl2: C, 21.05; H, 1.17; N, 4.05%.
IR (cmꢁ1) selected bands: 720(s), 850(s), 1380(vs),
1590(s), 1612(s), 2980(w), 3140(w).
0.265, N 2891, N0 1359, R 0.0468, Rw 0.0835.
Tl(2,4-dnp)]. C6H3N2O5Tl, M 387.47, monoclinic,
space group P2(1)/c, aꢂ
/
5.7649(15), bꢂ
908, bꢂ91.857(11)8, gꢂ
4 f.u.) 3.208 Mg mꢁ3, F(000)
0.2ꢃ0.30 mm; Tmax,min 0.1553,
/
19.261(11),
˚
cꢂ
/
7.636(4) A, aꢂ
/
/
/
908, Vꢂ
/
3
˚
802.4(8) A , Dcalc (Zꢂ
/
696. Specimen: 0.05ꢃ
/
/
0.0294, N 9196, N0 2339, R 0.0500, Rw 0.1046.
2.5.2. Determination of the structures
2.3. Preparation of Tl(2,4-dnp)
Crystallographic measurements were made at 140(2)
K for [Tl(3-np)] and 120(2) K for [Tl(2,4-dnp)] using a
Siemens R3m/V diffractometer. The intensity data were
An ethanolic solution of 2,4-dinitrophenol (0.368 g, 2
mmol) and potassium hydroxide (0.114 g, 2 mmol) was
added to a solution of thallium(I) nitrate (0.532 g, 2
mmol) in water. The resulting solution was concentrated
on a water bath at 80 8C and cooled to room tempera-
collected within the range 2.0385
/
u 527.038 for [Tl(3-
/
np)] and 3.4185u 530.068 for [Tl(2,4-dnp)] using
/
/
graphite monochromated Mo Ka radiation (lꢂ
/
˚
0.71073 A). Accurate unit cell parameters and an
ture (ꢀ
/
25 8C), when a red microcrystalline compound
orientation matrix for data collection were obtained
from least-squares refinement. Intensities of 2891 and
9196 unique reflections were measured, from which 1359
was separated. The compound was filtered off, washed
with cold ethanol and dried over silica gel (0.387 g, yield
50%). The red single crystals were isolated by the
following branch tube method. The complex (0.3 g)
was placed in one arm of the branched tube. Methanol
was carefully added to fill both arms, then the tube was
sealed and the complex-containing arm immersed in a
bath at 60 8C while the other was at ambient tempera-
ture. After 10 days, red crystals (m.p. 240 8C) had
deposited in the cooler arm. Anal. Found: C, 18.3; H,
0.9; N, 7.3. Calc. for C6H3N2O5Tl: C, 18.59; H, 0.77; N,
7.23%.
and 2339 with I ꢁ2s(I) were used in the refinement for
/
[Tl(3-np)] and [Tl(2,4-dnp)], respectively. The structures
have been solved by direct methods and refined by full-
matrix least-squares techniques on F2.
The positions of hydrogen atoms were idealized and
included in the calculations of the structure factors as
fixed contributions. Each hydrogen atom was assigned
an isotropic thermal parameter. R, Rw, with goodness-
of-fit on F2 0.897 and 0.754 are 0.0468, 0.0835 and
00.0385, 0.0962 for [Tl(3-np)] and [Tl(2,4-dnp)], respec-
tively. The final difference density map showed a
IR(cmꢁ1) selected bands: 720(w), 850(w), 1180(s),
1350(vs), 1385(vs), 1560(s), 1590(s), 1640(vs), 3030(w).
ꢁ3
˚
1.495 e A
maximum peak and hole of 1.992, ꢁ
/
for

A.R. Mahjoub et al. / Polyhedron 21 (2002) 2555Á
/2560
2557
ꢁ3
˚
2.103 e A
[Tl(3-np)] and 2.507, ꢁ
/
for [Tl(2,4-dnp)].
Table 2
Crystal data and structure refinement for Tl(2,4-dnp)
Corrections for Lorentz and polarization effects as well
as the empirical correction for absorption using the
SADABS programs were applied. All structural calcula-
Empirical formula
Formula weight
Temperature (K)
C6H3N2O5Tl
387.47
120(2)
tions were carried out with a PDPÁ
/
11/23ꢀ computer
/
˚
Wavelength (A)
0.71073
monoclinic
P2(1)/c
using the SDP-PLUS program package [17,18].
Crystal system
Space group
Unit cell dimensions
Crystal data and structure refinement are given in
Tables 1 and 2. Selected bond lengths and angles are
given in Tables 3 and 4. Anisotropic thermal para-
meters, observed and calculated structure factors, full
lists of bond distances, bond angles and torsion angles
are given in the supplementary material. ORTEP dia-
grams and a perspective view of the packing in the unit
˚
a (A)
5.458(3)
19.261(11)
7.636(4)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
91.857(11)
90
3
˚
cells are shown in Figs. 1Á4.
/
V (A )
802.4(8)
4
3.208
Z
Dcalc (Mg mꢁ3
)
Absorption coefficient (mmꢁ1
F(000)
Crystal size (mm)
)
20.126
696
3. Discussion
0.05ꢃ0.2ꢃ0.3
Theta range for data collection (8) 3.41Á
/
30.06
3.1. Synthesis
Limiting indices
ꢁ75h 57, ꢁ275k 527,
ꢁ105l 510
9196/2339 [Rintꢂ0.0637]
99.3%
Reaction between 3-nitrophenoxide, 4-nitrobenzoate
and 2,4-dinitrophenoxide ligands provided powdered
Reflections collected/unique
Completeness to uꢂ30.068
Absorption correction
Max/min transmission
Refinement method
Semi-empirical from equivalents
0.1553, 0.0294
Full-matrix least-squares on F2
2339/0/127
0.754
Table 1
Crystal data and structure refinement for Tl(3-NO2C6H4O)
Data/restraints/parameters
Goodness-of-fit on F2
Identification code
Empirical formula
Formula weight
Temperature (K)
Tl(3-NO2C6H4O)
C12H8N2O6T12
684.94
Final R indices [for 1862 reflections R1ꢂ0.0385, wR2ꢂ0.0962
with 1.2s(I)]
140(2)
0.71073
triclinic
R indices (all data)
Largest difference peak and hole
R1ꢂ0.0500, wR2ꢂ0.1046
2.507 and ꢁ2.103
˚
Wavelength (A)
ꢁ3
˚
(e A
Crystal system
Space group
Unit cell dimensions
)
¯
P1
˚
a (A)
3.7649(15)
9.400(4)
10.068(4)
85.159(8)
86.133(8)
78.749(7)
347.8(2)
1
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Table 3
Selected bond lengths (A) and angles (8) for Tl(3-np)
˚
3
V (A )
˚
Z
Bond lengths
Bond angles
Dcalc (Mg mꢁ3
)
3.271
23.171
Absorption coefficient (mmꢁ1
F(000)
Crystal size (mm)
)
Tl(1)ÃO(1)
2.499(8)
2.562(7)
2.717(10)
3.005(8)
3.396(11)
3.515(10)
3.554(9)
O(1)ÃTl(1)ÃO(1)#1
O(1)ÃTl(1)ÃO(1)#2
O(1)#1ÃTl(1)ÃO(1)#2
O(1)ÃTl(1)ÃTl(1)#5
O(1)#1ÃTl(1)ÃTl(1)#5
O(1)#2ÃTl(1)ÃTl(1)#5
O(1)ÃTl(1)ÃTl(1)#6
73.0(3)
82.3(3)
90.9(3)
304
0.1ꢃ0.1ꢃ0.2
Tl(1)ÃO(1)#1
Tl(1)ÃO(1)#2
Tl(1)ÃO(2)#3
Tl(1)ÃO(1)#4
Tl(1)ÃO(3)#3
Tl(1)ÃO(2)#4
Tl(1)ÃTl(1)#2 3.9308(14) O(1)#1ÃTl(1)ÃTl(1)#6
Tl(1)ÃTl(1)#1 4.0696(14) O(1)#2ÃTl(1)ÃTl(1)#6
Tl(1)ÃTl(1)#5 3.7649(15) C(1)ÃO(1)ÃTl(1)
Tl(1)ÃTl(1)#6 3.7649(15) C(1)ÃO(1)ÃTl(1)#1
Theta range for data collection (8)
Index ranges
2.03Á27.03
/
95.88(19)
133.8(2)
42.88(16)
84.12(19)
46.2(2)
ꢁ45h 54, ꢁ125k 512,
ꢁ125l 512
2891
Reflections collected
Independent reflections
Completeness to thetaꢂ27.038
Absorption correction
Tmin/Tmax
1359 [Rintꢂ0.0708]
89.6%
137.12(16)
126.0(7)
123.7(7)
98.7(7)
SADABS program
0.265/0.761
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
full-matrix least-squares on F2
1359/0/100
0.897
O(1)ÃTl(1)#1
O(1)ÃTl(1)#2
2.562(7)
C(1)ÃO(1)ÃTl(1)#2
Tl(1)ÃO(1)ÃTl(1)#1
Tl(1)ÃO(1)ÃTl(1)#2
Tl(1)#1ÃO(1)ÃTl(1)#2
2.717(10)
107.0(3)
97.7(3)
90.9(3)
Final R indices [for 1008 reflections R1ꢂ0.0468, wR2ꢂ0.0835
with I ꢁ2s(I)]
R indices (all data)
Largest difference peak and hole
R1ꢂ0.0661, wR2ꢂ0.0877
1.992 and ꢁ1.495
Symmetry transformations used to generate equivalent atoms: #1
ꢁxꢀ1, yꢀ2, ꢁz, #2 ꢁx, ꢁyꢀ2, ꢁz, #3 ꢁxꢀ1, ꢁyꢀ1, ꢁz, #4
ꢁx, ꢁyꢀ1, ꢁz, #5 xꢀ1, y, z; #6 xꢁ1, y, z.
ꢁ3
˚
(e A
)

2558
A.R. Mahjoub et al. / Polyhedron 21 (2002) 2555Á2560
/
Table 4
˚
Selected bond lengths (A) and angles (8) for Tl (2,4-dnp)
Bond lengths
Bond angles
Tl(1)ÃO(1)
Tl(1)ÃO(1)#1
Tl(1)ÃTl(1)#2
2.601(5) O(1)ÃTl(1)ÃO(1)#1
2.626(5) O(1)ÃTl(1)ÃTl(1)#2
O(1)#ÃTl(1)ÃTl(1)#2
C(1)ÃO(1)ÃTl(1)
75.41(18)
127.69(11)
141.24(11)
124.6(4)
C(1)#ÃO(1)ÃTl(1)#1
Tl(1)ÃO(1)ÃTl(1)#1
130.6(4)
104.59(18)
Symmetry transformations used to generate equivalent atoms: #1
ꢁxꢀ1, ꢁyꢀ1, ꢁzꢀ2, #2 ꢁxꢀ1, ꢁyꢀ1, ꢁzꢀ1.
Fig. 2. A view perpendicular to a polymeric strand of the solid
showing the chelating and bridging functions of the 3-nitrophenoxide
ligand and the full donor atom environment of the Tl atoms in Tl(3-
np).
materials analyzing as [Tl(3-np)], [Tl(4-nb)] and [Tl(2,4-
dnp)], respectively. Attempts to isolate suitable single
crystals for X-ray crystallography for [Tl(4-nb)] were
not successful and each time the powdered compound
was isolated.
oxygen atoms of the 3-nitrophenoxide ligand with TlÃ
distances of Tl1Á Á ÁO1ꢂ2.499, Tl1Á Á ÁO1 (ꢁxꢀ1, ꢁ
2, ꢁz)ꢂ x, ꢁyꢀ2, ꢁz)ꢂ
2.562 and Tl1Á Á ÁO (ꢁ
/O
/
/
/
/y
ꢀ
/
/
/
/
/
/
/
/
˚
2.717 A), and the weak interaction of thallium(I) with
oxygen atoms of an adjacent molecule produces polymer
units in the solid state. In fact each Tl atom in this
structure alone with three normal bonds forms four
‘‘weak’’ TlÁ Á ÁO bonds and the exact distances are
3.2. Crystal structure of [Tl(3-np)]
Determination of the structure of [Tl(3-np] by X-ray
crystallography (Table 1) showed the complex in the
solid state (Fig. 2) to be a polymeric species with various
similarities to the polymeric structures of [Tl(2-np)] and
[Tl(4-np)], and it is really a novel one-dimensional
polymer. The thallium atoms are linked within a
classical ‘stair-polymer’ array by phenoxide oxygen
atoms, each Tl(m-O)2Tl unit having an inversion point
at its center, and a pair of them making up the unit b
component of the polymer.
Tl1Á Á ÁO2 (ꢁ
(ꢁx, ꢁyꢀ1, ꢁ
1, ꢁz)ꢂ
3.515 and Tl1Á Á ÁO2 (ꢁ
/
xꢀ
/
1,
ꢁ
/
yꢀ
/
1,
˚
ꢁ
/
z)ꢂ
3.396 A, Tl1Á Á ÁO3 (ꢁ
x, ꢁyꢀ1, ꢁ
/
3.005, Tl1Á Á ÁO3
xꢀ1, ꢁyꢀ
z)ꢂ3.554
/
/
/
/
z)ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
˚
A (Table 3). The presence of a lone pair of electron on
the thallium atom is apparently the reason that the
bridging interactions cannot come closer together. If the
stereochemically active lone pair was not present, it
might create more interaction between the bridging
atoms of thallium(I) with the neighboring oxygen atoms
Thus, each thallium atom can be considered to be
three-coordinate with an O3 donor atom array (three
Fig. 1. The ORTEP diagram of the Tl2O2 rhomb forming the basic link of the polymeric structure of [Tl(3-np)]2.

A.R. Mahjoub et al. / Polyhedron 21 (2002) 2555Á
/2560
2559
3.3. Crystal structure of [Tl(2,4-dnp)]
Determination of the structure of [Tl(2,4-dnp] by X-
ray crystallography (Table 2) showed the complex in the
solid state (Fig. 4) to be a polymeric species with various
similarities to the polymeric structures of [Tl(2-np)],
[Tl(4-dnp)] and [Tl(3-dnp)], and it is really a novel three-
dimensional polymer. The thallium atoms are linked
within a classical ‘stair-polymer’ array by phenoxide
oxygen atoms. Each thallium atom can be considered to
be two-coordinate with an O2 donor atom array (two
oxygen atoms of the 2,4-nitrophenoxide ligand) with
Fig. 3. The ORTEP diagram of Tl(2,4-dnp).
TlÃ
/
O distances of Tl1Á Á ÁO1ꢂ
/
2.601, and Tl1Á Á ÁO1
(ꢁxꢀ
/
/
1, ꢁyꢀ2, ꢁzꢀ2)ꢂ2.626, and the weak interac-
/
/
/
/
/
tion of thallium(I) with oxygen atoms of the nitro group
of an adjacent molecule produces polymer units in the
solid state (Table 4). There are ‘‘weak’’ TlÁ Á ÁTl bonds in
the polymeric state and the exact distances are Tl1Á Á ÁTl1
˚
3.740 A (Table 4). The
(ꢁ
/
xꢀ
/
1, ꢁ
/
yꢀ
/
1, ꢁ
/
zꢀ
/
1)ꢂ
/
presence of a lone pair of electrons on the thallium
atom is apparently the reason that the bridging interac-
tions cannot come closer together. The arrangement of
oxygen atoms of nitrophenoxide suggest a gap or hole in
the coordination geometry around the metal ion,
occupied possibly by a stereoactive lone pair of electrons
on thallium(I). If the stereochemically active lone pair
was not present, it might create more interaction
between the bridging atoms of thallium(I) with the
neighboring oxygen atoms of nitrophenoxide. Conse-
quently, this phenomenon could lead to more symmetry.
The strikingly similar feature of the [Tl(3-np)]n
complex with the [Tl(2,4-dnp)]n complex is that there
Fig. 4. A view perpendicular to a polymeric strand of the solid
showing the chelating and bridging functions of the 2,4-dinitrophen-
oxide ligand and the full donor atom environment of the Tl atoms in
Tl(2,4-dnp).
is a pÁ
aromatic rings belonging to adjacent chains in the two
compounds. The question is, does the pÁp stacking
between the parallel aromatic rings help to increase the
‘‘gap’’ in coordination geometry around the metal ion or
does the ‘gap’ arise from the ‘‘stereochemical activity’’
of valence shell lone electron pairs that then help to
/
p stacking [19,20] interaction between the parallel
/
of nitrophenoxide. Consequently, this phenomenon
could lead to more symmetry.
The arrangement of the oxygen atoms of nitrophen-
oxide suggest a gap or hole in the coordination geometry
around the metal ion, occupied possibly by a stereo-
active lone pair of electrons on thallium(I). The ob-
form pÁp stacking.
/
The strikingly different feature of the [Tl(3-np)]n
complex with the [Tl(2,4-dnp)]n complex is that the
[Tl(3-np)]n complex is a one-dimensional polymer
whereas the [Tl(2,4-dnp)]n complex is a three-dimen-
sional polymer. This point must relate to the additional
nitro group in the nitrophenoxide ligand. The [Tl(2-
np)]n and [Tl(4-np)]n complexes [8] are one-dimensional
polymers and support the presence of this feature.
Crystallographic data, selected bond lengths and
served shortening of the TlÃ
/
O bond on the side of the
Tl(I) ion opposite to the putative lone pair (2.499
˚
compared with 2.717 A adjacent to the lone pair)
supports the presence of this feature. There are some
‘‘weak’’ TlÁ Á ÁTl bonds in the polymeric state and the
/
exact distances are Tl1Á Á ÁTl1 (ꢁ
/
x, ꢁ
yꢀ2, ꢁz)ꢂ
3.7649 A and Tl1Á Á ÁTl1 (xꢁ
/
yꢀ
/
2, ꢁ
/
z)ꢂ
˚
˚
3.9308 A, Tl1Á Á ÁTl1 (ꢁ
/
xꢀ
/
1, ꢁ
/
/
/
/4.0696 A,
˚
Tl1Á Á ÁTl1 (xꢀ1, y, z)ꢂ
/
/
/1,
˚
y, z)ꢂ
/
3.7649 A (Table 3). The TlÁ Á ÁTl across the rhomb
angles are given in Tables 1Á4. Atomic coordinates,
/
˚
(3.7649 A) is appreciably shorter than the normal of
anisotropic thermal parameters, observed and calcu-
lated structure factors, full lists of bond distances, bond
angles and torsion angles are given in the supplementary
material. A perspective view of the ORTEP diagram and
˚
approximately 4.0696 A proposed as typical of TlÁ Á ÁTl
in Tl(m-O2)Tl rhomb. The nakedness of the resulting
thallium environment possibly suggests a stereochemi-
cally active lone pair.
the packing in the unit cell are shown in Figs. 1Á4.
/

2560
A.R. Mahjoub et al. / Polyhedron 21 (2002) 2555Á2560
/
A.H. White, Aust. J. Chem. 49 (1996) 1099;
(h) L.M. Engelhardt, J.M. Harrowfield, D.L. Kepert, H. Miya-
mae, J.M. Patrick, B.W. Skelton, A.A. Soudi, A.H. White, Aust.
J. Chem. 49 (1996) 111;
4. Supplementary material
Complete bond lengths and angles, co-ordinates and
displacement parameters have been deposited with the
Cambridge Crystallography Data Centre, CCDC Nos.
174597 for [Tl(3-np)] and 183434 for [Tl(2,4-dnp)].
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
(i) J.M. Harrowfield, H. Miyamae, B.W. Skelton, A.A. Soudi,
A.H. White, Aust. J. Chem. 49 (1996) 1121;
(j) J.M. Harrowfield, H. Miyamae, B.W. Skelton, A.A. Soudi,
A.H. White, Aust. J. Chem. 49 (1996) 1127;
(k) L.M. Engelhardt, J.M. Harrowfield, D.L. Kepert, H. Miya-
mae, J.M. Patrick, B.W. Skelton, A.A. Soudi, A.H. White, Aust.
J. Chem. 49 (1996) 1135;
Cambridge, CB2 1EZ, UK (fax: ꢀ44-1223-336033; e-
/
mail: deposit@cdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
(l) J.M. Harrowfield, D.L. Kepert, H. Miyamae, B.W. Skelton,
A.A. Soudi, A.H. White, Aust. J. Chem. 49 (1996) 1147;
(m) J.M. Harrowfield, H. Miyamae, B.W. Skelton, A.A. Soudi,
A.H. White, Aust. J. Chem. 49 (1996) 1157;
(n) J.M. Harrowfield, H. Miyamae, B.W. Skelton, J.M. Harrow-
field, H. Miyamae, B.W. Skelton, A.A. Soudi, A.H. White, Aust.
J. Chem. 49 (1996) 1165.
Acknowledgements
The Tarbiat Modarres University Research Council
supported this work. We thank the Institute of Orga-
noelement Compounds of the Russian Academy of
Science for determining the crystal structure by X-ray
crystallography.
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