A one-dimensional thallium(I) coordination polymer involving polyhapto-aromatic interactions

Article abstract of DOI:10.1002/hlca.200690029

A one-dimensional coordination polymer involving Tl...C interactions, [Tl(μ₄-dpa)]_n(Hdpa = diphenylacetic acid), was synthesized and characterized. The single-crystal X-ray data of the compound show that the coordination number of the Tl^I ions is five and that Tl centers have an irregular coordination sphere containing a 'configurationally active' lone pair/hexahapto (η⁶) interaction, thus resulting in a total hapticity of eleven for a TlC₆O₅ environment.

Full text of DOI:10.1002/hlca.200690029

Helvetica Chimica Acta – Vol. 89 (2006)
265
A One-Dimensional Thallium(I) Coordination Polymer Involving Polyhapto-
Aromatic Interactions
by Azadeh Askarinejad and Ali Morsali*
Department of Chemistry, School of Sciences, Tarbiat Modarres University, P. O. Box 14155-4838,
Tehran, Iran
(e-mail: morsali_a@yahoo.com)
A one-dimensional coordination polymer involving Tl···C interactions, [Tl(m4-dpa)]n(Hdpa=
diphenylacetic acid), was synthesized and characterized. The single-crystal X-ray data of the compound
show that the coordination number of the TlI ions is five and that Tl centers have an irregular coordina-
tion sphere containing a ‘configurationally active’ lone pair/hexahapto (h6) interaction, thus resulting in a
total hapticity of eleven for a TlC6O5 environment.
Introduction. – Thallium reagents, despite their inherent toxicity and cost, have
played a conspicuous role in the development of modern inorganic and organometallic
chemistry [1–5]. Thallium(I) chemistry is very interesting due to a variety of reasons: 1.
thallium salts or complexes are often anhydrous; 2. the lone pair present at the TlI atom
may or may not be ‘configurationally active’; 3. the ability to exhibit a high coordina-
tion number because of the large size of the TlI ion; 4. the ease with which TlI com-
plexes are able to form metal–metal bonds and also complexes with aromatic hydrocar-
bons [6–27]. In a recent structural study of TlI complexes of anthranilates and salicy-
lates [8], it has been argued that polyhapto-aromatic interactions also play an impor-
tant role in determining the solid-state lattices of such compounds. Thus it was antici-
pated that this might be true also for the TlI complex with the diphenylacetato ligand
(Hdpa=diphenylacetic acid). The diphenylacetate anion is an interesting ligand with
two aromatic groups, and because of its ability to form polyhapto complexes it may
also be a very good candidate for the investigation of the ‘configurational activity’ of
valence-shell electron lone pairs in polymeric and supramolecular compounds.
In the present study, the structure determination of the thallium(I) complex with
dpaÀ established the presence of a one-dimensional polymer which interestingly,
involves new short Tl···C interactions.
© 2006 Verlag Helvetica Chimica Acta AG, Zürich

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Results and Discussion. – The reaction between diphenylacetic acid (Hdpa) and TlI
(NO3) provided a crystalline material of the general formula [Tl(m4-dpa)]n (1). Deter-
mination of the structure of 1 by X-ray crystallography showed the complex to be a
novel one-dimensional polymer (Fig. 1,a). There are five (TlO5) coordinate Tl atoms,
and the Tl centers can be considered to be five-coordinate. The separation between
the Tl atoms is 4.223(7) Å, which is longer than the sum [8] of van der Waals radii of
ca. 3.92 Å [8] of two TlI atoms. Hence, no thallophilic TlÀTl interaction are considered
for this compound. Each dpaÀ ligand is pentadentate connecting four TlI ions. The
COOÀ group of the dpaÀ ligand acts as both a bidentate chelating group where the
two O-atoms of the COOÀ group coordinate to a TlI ion, and as a bridging group
where one of these O-atoms acts as a bridge to two other TlI atoms and the other O-
atom is a bridge to only one TlI atom, a very novel and interesting behavior of a
COOÀ group (Fig. 2).
In 1, the lone pair of TlI is ‘active’ in the solid state. However, the arrangement of
the O-atoms suggests a gap or hole in the coordination sphere around the TlI atom (Fig.
1), a gap possibly occupied by a ‘configurationally active’ electron lone pair. Hence, the
geometry of the coordination environment of every TlI atom is likely to be caused by
the geometrical constraints of coordinated O-atoms, and by the influence of a ‘config-
urationally active’ electron lone pair in a hybrid orbital of the metal. The observed
shortening of the TlÀO bond on the side of the TlI ion opposite to the putative lone
pair (TlÀO(1) 2.687(6) Å compared with TlÀO(2) 2.831(5) Å adjacent to the lone
pair) supports the presence of this feature [28].
To find any other potential donor center, it is necessary to extend the bonding limit.
A search was made generally for Tl···C approaches, and it appears that the Tl center in
1 may also be involved in an h6interaction with the Ph groups of neighboring molecules.
Thus, the TlI atoms are linked to 6 C-atoms of the Ph groups, with distances Tl···C(9)i,
Tl···C(10)i, Tl···C(11)i, Tl···C(9)iii, Tl···C(13)iii and Tl···C(14)iii (i: –y, x, –z; iii: –x, –y, z)
of 3.995(2), 3.561(2), 3.979(2), 3.824(3), 3.877(5), and 3.379(5) Å, respectively (Figs. 1,b
and 3). Hence, the TlI coordination sphere is completed, and rather than a TlO5 coor-
dination sphere, the complex can be considered to contain a hexahapto TlC6O5 center
with an irregular eleven coordination number. In recently studied Tl species [8][26],
the Tl···C separations range from 3.20 to 4.00 Å. Thus, the hexahapto-aromatic coordi-
nation of the TlI atom appears to be yet another factor which can make varying contri-
butions to the stability of the complexes of this metal ion. The obvious question then is
whether the lone pair at the TlI atom is or is not involved in donor bonding. Since some-
what surprisingly, the very recent report of polyhapto-aromatic interactions in a PbII
complex suggested that the active lone pair at the PbII atom may be involved in
donor bonding [29]. Comparison of the structure data of 1 with those reported for
the PbII compound suggests that the unusually high coordination number of 1 might
reflect the capacity of TlI to act as both a Lewis acid and a Lewis base, like PbII.
There are edge-to-edge p–p stacking [30][31] interactions between Ph groups of the
dpaÀ ligands belonging to adjacent chains of the coordination polymer in the network,
with the distance 4.140 Å.
In summary, the structure of [Tl(m4-dpa)]n (1) is interesting because it represents a
new, rarely observed one-dimensional framework with an unusual bridging of the
COOÀ group and with a hemisphere TlI coordination sphere. Moreover comparison

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Fig. 1. a) Fragment of the coordination polymer 1 showing the 1D pattern; b) bonding and polyhapto
interactions within a fragment of the coordination polymer 1 after extending the bonding limit.
Selected bond lengths [Å]: TlÀO(1)i 2.672(6), TlÀO(1) 2.687(6), TlÀO(1)ii 2.828(5), TlÀO(2)
2.831(5), and TlÀO(2)iii 2.874(5). Selected bond angles [8]: O(1)iÀTlÀO(1) 75.47(17), O(1)iÀTlÀ
O(1)ii 78.32(18), O(1)ÀTlÀO(1)ii 78.07(17), O(1)iÀTlÀO(2) 101.12(16), O(1)ÀTlÀO(2) 46.78(15),
O(1)iiÀTlÀO(2) 121.31(15), O(1)iÀTlÀO(2)iii 79.65(15), O(1)ÀTlÀO(2)iii 105.78(17), O(1)iiÀTlÀ
O(2)iii 155.84(16), and O(2)ÀTlÀO2iii 72.79(16). Superscripts i, ii, and iii indicate the symmetry (Ày,
x, Àz), (y, Àx, Àz), and (Àx, Ày, z), respectively
with other reported complexes with O-donor ligands suggests the presence of an
‘active’ lone pair at the TlI ester of 1 which might be capped by involvement in a
donor bonding and act as both a Lewis acid and a Lewis base.

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Fig. 2. Line diagram of the coordination mode of the dpaÀ anion in the
coordination polymer 1
Fig. 3. Tl···C Interactions within 1 after extending the bonding limit
Support of this work by the Tarbiat Modarres University is gratefully acknowledged.
Experimental Part
catena-Poly[thallium-m4(diphenylacetato-kO,kO’:kO:kO:kO’)]
(=(a-Phenylbenzeneacetato)thal-
lium Homopolymer; 1) The complex [Tl(m4-dpa)]n was prepared by dissolving thallium(I) nitrate
(0.266 g, 1 mmol) in distilled H2O and MeOH and adding a mixture of diphenylacetic acid (0.212 g, 1
mmol) and NaOH (0.04 g, 1 mmol) in MeOH. The resulting soln. was stirred and then allowed to
stand for some days at r.t. Slow evaporation of the solvent at r.t. yielded suitable crystals for X-ray anal-
ysis: 0.207g (50%) of 1. The crystals were washed with acetone and air dried. M.p. 1578. IR (selected
bands): 642m, 694s, 734s, 1361s, 1484m, 1532vs, 1563s, 1587s, 2885w, 3050w. Anal. calc. for C14H11O2Tl:
C 40.42, H 2.64, Tl 49.10; found: C 40.82, H 2.56, Tl 50.10.
X-Ray Crystal-Structure Analysis. Crystallographic measurements were made at 293(2) K with a
Bruker-Smart 1000-CCD area detector [32]. The structure was solved and refined with the program sys-
tem SHELXTL [33]. Intensity data were collected within the range 2.228ꢀqꢀ30.028 with graphite mon-
ochromated MoKa radiation for a crystal of the dimension 0.25×0.12×0.04 mm. Plots were prepared
with ORTEP III [34], and WinGX [35] was used as an interface during the structure-solution [36] pro-
cedure. Semiempirical absorption correction from equivalents was applied. Crystal data: formula,
C14H11O2Tl; Mr 415.60; tetragonal system, space group P-42(1)c; a=b=18.3594(11), c=7.3337(6) Å;
V=2472.0(3) Å3; Dc =2.233 Mg/m3 (Z=8); F(000)=1536; R(wR)=0.0353 (0.0803) for 3101 reflections,
with I>2s(I); R(wR)=0.0422 (0.0828) for all data. The absolute structure of the noncentrosymmetric
was determined by refinement of Flack’s parameter x=À0.040(18) [37].

Helvetica Chimica Acta – Vol. 89 (2006)
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CCDC-270822 contains the supplementary crystallographic data for 1. These data can be obtained
free of charge from the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_
request/cif.
REFERENCES
[1] P. Pyykko, Chem. Rev. 1997, 97, 597.
[2] H. M. Alvarez , P. A. Gillespie, C. D. Gause, Polyhedron 2004, 23, 617.
[3] C. Janiak, Coord. Chem. Rev. 1997, 163, 107.
[4] C. Janiak, Main Group Met. Chem. 1998, 21, 33.
[5] C. Janiak, J. Prakt. Chem. 1998, 340, 181.
[6] R. P. Sharma, R. Bala, J. Mol. Struct. 2005, 249, 738.
[7] A. R. Mahjoub, A. Morsali, H. Bagherzadeh, Polyhedron 2002, 21, 2555.
[8] F. Wiesbrock, H. Schmidbaur, J. Am. Chem. Soc. 2003, 125, 3622.
[9] H. Schumann, C. Janiak, J. Pickardt, U. Borner, Angew. Chem., Int. Ed. Engl. 1987, 26, 789.
[10] C. Janiak, R. Hofmann, J. Am. Chem. Soc. 1990, 112, 5924.
[11] C. Janiak, R. Hofmann. Angew. Chem., Int. Ed. Engl. 1989, 28, 1688.
[12] P. H. M. Budzelaar, J. Boersma, Recl. Trav. Chim. Pays-Bas 1990, 109, 187.
[13] P. Schwerdtfeger, Inorg. Chem. 1991, 30, 1660.
[14] H. Schumann, C. Janiak, H. Khani, J. Organomet. Chem. 1987, 330, 347.
[15] C. Janiak, J. Pickardt, U. Borner, Angew. Chem., Int. Ed. Engl. 1987, 26, 789.
[16] H. Schumann, C. Janiak, M. A. Khan, J. J. Zuckerman, J. Organomet. Chem. 1988, 354, 7.
[17] H. Schmidbaur, Angew. Chem., Int. Ed. Engl. 1985, 24, 893.
[18] H. Schmidbaur, W. Bublak, J. Riede, G. Muller, Angew. Chem., Int. Ed. Engl. 1985, 24, 414.
[19] W. Frank, G. Korrell, G. J. Reiss, Z. Anorg. Allg. Chem. 1995, 621, 765.
[20] W. Frank, G. Korrell, G. J. Reiss, J. Organomet. Chem. 1996, 506, 293.
[21] S. H. Strauss, M. D. Noirot, O. P. Anderson, Inorg. Chem. 1986, 25, 3850.
[22] M. D. Noirot, O. P. Anderson, S. H. Strauss, Inorg. Chem. 1987, 26, 2216.
[23] D. M. Schubert, M. A. Bandman, W. S. Rees, C. B. Knobler, P. Lu, W. Nam, M. F. Hawthorne, Orga-
nometallics 1990, 9, 2046.
[24] M. A. Bandman, C. B. Knobler, M. F. Hawthorne, Inorg. Chem. 1988, 27, 2399.
[25] H. Schmidbaur, W. Bublak, B. Huber, J. Hofmann, G. Muller, Chem. Ber. 1989, 122, 265.
[26] J. Beck, J. Strahle, Z. Naturforsch., B 1986, 41, 1381.
[27] S. D. Waezsada, T. Belgardt, M. Noltemeyer, H. W. Roesky, Angew. Chem., Int. Ed. Engl. 1994, 33,
1351.
[28] R. D. Hancock, M. S. Shaikjee, S. M. Dobson, J. C. A. Boeyens, Inorg. Chim. Acta 1988, 154, 229.
[29] J. M. Harrowfield, S. Maghaminia, A. A. Soudi, Inorg. Chem. 2004, 43, 1810.
[30] C. A. Hunter, J. K. M. Sanders, J. Am. Chem. Soc. 1990, 112, 5525.
[31] C. Janiak, J. Chem. Soc., Dalton Trans. 2000, 3885.
[32] ‘Smart, Bruker Molecular Analysis Tool’, Version 5.059, Bruker AXS, Madison, Wisconsin, USA,
1998.
[33] G. M. Sheldrick, ‘Structure Determination Software. SHLXTL,’ Version 5.10, Bruker AXS, Madi-
son, Wisconsin, USA, 1998.
[34] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
[35] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837.
[36] G. M. Sheldrick, ‘SADABS’ Version 2.01, Bruker/Siemens Area Detector Absorption Correction
Program, Bruker AXS, Madison, Wisconsin, USA, 1998.
[37] H. D. Flack, Acta Crystallogr., Sect. A 1983, 39, 876.
Received May 16, 2005