An exact coordination mode of 6-thiopurine with an organotin(IV): Preparation and crystal structure of triphenyl(6-thiopurinyl)tin(IV)

Article abstract of DOI:10.1016/j.ica.2004.03.002

Triphenyl(6-thiopurinyl)tin has been prepared and its structure reinvestigated by X-ray diffraction. In the structure, a new coordination mode was observed that was different from those reported previously from investigations by infrared and M?ssbauer spectroscopy. In the molecule, 6-thiopurine coordinated to tin by the S and N(1) atoms. The discrete molecules were connected to form a zigzag 1D network through intermolecular H?N hydrogen bonds. The tin environment is pentacoordinated with cis-trigonal bipyramidal geometry.

Full text of DOI:10.1016/j.ica.2004.03.002

Inorganica Chimica Acta 357 (2004) 2759–2762
www.elsevier.com/locate/ica
Note
An exact coordination mode of 6-thiopurine with an
organotin(IV): preparation and crystal structure of
triphenyl(6-thiopurinyl)tin(IV)
a
Rufen Zhang , Feng Li , Chunlin Ma
a
a,b,
*
a
Department of Chemistry, Liaocheng University, 34 Wenhua Road, Liaocheng 252059, PR China
b
Taishan University, Taian 271021, PR China
Received 17 June 2003; accepted 6 March 2004
Available online 6 May 2004
Abstract
Triphenyl(6-thiopurinyl)tin has been prepared and its structure reinvestigated by X-ray diffraction. In the structure, a new co-
€
ordination mode was observed that was different from those reported previously from investigations by infrared and Mossbauer
spectroscopy. In the molecule, 6-thiopurine coordinated to tin by the S and N(1) atoms. The discrete molecules were connected to
form a zigzag 1D network through intermolecular Hꢀ ꢀ ꢀN hydrogen bonds. The tin environment is pentacoordinated with cis-tri-
gonal bipyramidal geometry.
Ó 2004 Published by Elsevier B.V.
Keywords: Crystal structure; Coordination mode; Donor atom; 6-Thiopurine
1. Introduction
the selection of coordination modes and donor atoms.
€
According to the data of infrared and Mossbauer spec-
6-Thiopurine (6-TPH) is an anticancer antimetabolite
(inter alia), clinically effective against human leukemias
[1], so its complexes with organotin(IV) derivatives also
exhibiting anticancer activity have been studied [2–4]. It
has been observed that 6-TPH showed tautomerism
between the thiol and thione isomers. Depending on the
different alkyl groups in organotin compounds, 6-TPꢁ
coordinated to tin by different donor atoms and pre-
sented different coordination modes. For instance, in
Me3Sn(6-TP), 6-TPH adopted the thione form and co-
ordinated to tin by the N(1) and N(2) atoms, attaining a
polymeric trigonal bipyramidal structure, as shown in
Fig. 1(a). As far as nBu2Sn(6-TP)2 is concerned, it
adopted the thiol form and the primary Sn–S bond was
stabilized through chelation of tin by the N(3) atom of
the purine ring, as shown in Fig. 1(b).
troscopy, Barbieri et al. [3,4] concluded that the product
of the reaction of Ph3Sn(IV) derivatives with 6-TPH was
a unique complex. Its possible structure was assumed to
be a linear polymer, in which 6-TPꢁ is coordinated to the
tin atom by S, N(2) and N(4) atoms, as shown in Fig. 1(c).
Based on the interest in the metabolic coordination be-
havior of 6-TPH, we prepared Ph3Sn(6-TP) and rein-
vestigated its crystal structure by X-diffraction. This
work is performed to ascertain the coordination mode
that would be adopted and which nitrogen atoms of the
purine ring would be attacked by Ph3Snþ. The result did
not agree with Barbieri’s previous conclusion [2,3].
2. Results and discussion
With three bulky phenyl groups, Ph3Sn(IV) is much
represented in studies about the effect of alkyl groups on
2.1. Synthesis aspects of C23H18N4SSn
It has been reported that the reactions of Ph3SnOH
with 6-TPH (1:1) in hot acetone [2] and hexaphenyl-
distannoxane with 6-TPH in boiling acetone afforded a
* Corresponding author. Tel.: +866358238121; fax: +866358238274.
E-mail address: macl@lctu.edu.cn (C. Ma).
0020-1693/$ - see front matter Ó 2004 Published by Elsevier B.V.
doi:10.1016/j.ica.2004.03.002

2760
R. Zhang et al. / Inorganica Chimica Acta 357 (2004) 2759–2762
N
Me
N
Ph
Ph
Sn
Sn
Me
S
S
Ph
Me
H
N
N1
N
3
N
1
3
4
2
N
4
N
N
2
N
Ph
Sn
Me
Ph
Ph
Bu
Sn
Sn
Me
Me
HN4
H
N
N
N
S
N
3 N
S
1
1
N2
Me
Sn
2N
N
2
N
N
Me
N
1
N
NH
3
3
S
Ph
S
N
4
4
Ph
N
N
NH
Sn
Ph
(a)
Me
(b)
(c)
Bu
Fig. 1. The possible coordination modes for Me3Sn(6-TP), nBu2Sn(6-TP)2 and Ph3Sn(6-TP).
Table 1
Crystal data and measurement conditions for C23H18N4SSn
product with the unexpected stoichiometry Ph3Sn(IV):
6-TPH ¼ 3:2 [5]. Instead, another synthetic route was
taken: reaction of Ph3SnCl with 6-TPH(1:1) in hot
methanol, the product being obtained by deprotonation
of 6-TPH with methoxide. In this reaction, 6-TPꢁ was
electrophilically attacked by Ph3Snþ. Mono-deproto-
nation of 6-TPH would take place at N(1) [6,7], with the
negative charge residing on the sulfur atom of the re-
sulting ‘aromatic’ tautomer [6]. As a consequence, it
could be expected that S-stannylation of 6-TPH pri-
marily occurs, where one 6-TPꢁ is bound to Ph3Sn(IV).
Empirical formula
Formula weight
T (K)
C23H18N4SSn
501.16
298(2)
Crystal system
Space group
Unit cell dimensions
orthorhombic
Pbca
ꢀ
a (A)
15.437(3)
19.135(4)
36.213(6)
10697(3)
16
ꢀ
b (A)
ꢀ
c (A)
3
ꢀ
V (A Þ
Z
Absorption coefficient, l (mmꢁ1
h Range for data collection (°)
Number of reflections collected
)
1.046
1.12–24.84
50985
8913
2.2. Description of the crystal structure of C23H18N4SSn
Number of independent reflections (Rint
Goodness-of-fit (on F 2)
)
0.817
Further structural information was obtained by X-
ray diffraction characterization of the solid (Table 1). In
the unit cell of this compound, there are two crystallo-
graphically independent molecules that show only minor
differences. A molecular view is shown in Fig. 2 and the
unit cell is shown in Fig. 3.
Final R indices [I > 2:0rðIÞ]
R1 ¼ 0:0622,
wR2 ¼ 0:1426
R1 ¼ 0:2233,
wR2 ¼ 0:2203
0.086 and )0.517
R indices (all data)
ꢁ3
ꢀ
Largest difference peak and hole (e A
)
From the X-ray diffraction data (Table 2), there exist
two monomers in the asymmetric unit which are differ-
ent from a crystallographic point of view. Conforma-
tions of the two independent molecules are almost the
same, with only little differences in bond lengths and
bond angles. For molecular A, it may be seen that the
donor atoms [10–16]. The bond distance of Sn(1)–N(1)
ꢀ
(2.95(5) A) is midway between the sums of the van der
Waals and covalent radii of tin and nitrogen (2.15–3.74
ꢀ
A) [17], and the interaction can be regarded as a weak
ꢀ
coordinate bond. The bond C(4)–S(1) (1.726 A) is con-
ꢀ
sistent with the C–S single bonds (1.724 and 1.730 A) in
products of the reaction of triphenyltin with 1-methyl-
tetrazole-5-thiolate and benzoxazole-2-thiolate ligands,
respectively [18], and this shows that C–S exists as single
bond and is indirect evidence that the ligand is coordi-
nated to tin as the thiol but not as the thione isomer.
The coordination mode is in accordance with the nature
of the Sn–S chemical bond.
ꢀ
bond length of Sn(1)–S(1) (2.442(4) A) lies toward the
middle of the range reported for triphenyltin heteroa-
ꢀ
renethiolates (2.405–2.481 A) and approaches the sum
ꢀ
of the covalent radii of tin and sulfur (2.42 A) [8,9],
which proves that the sulfur atom is coordinated to the
tin atom by a strong chemical bond. Besides the Sn–S
primary bond, there is also an intramolecular Sn–N
interaction, common in thiolate ligands having nitrogen

R. Zhang et al. / Inorganica Chimica Acta 357 (2004) 2759–2762
2761
Fig. 2. An ORTEP representation of the molecular structure of the title compound.
Described as above, besides the primary S atom, the
N atom attacked by Ph3Snþ was N(1) but not N(2)
atom, which is not in agreement with Barbieri’s previous
conclusion [2,3]. According to the infrared and
€
Mossbauer spectroscopic data reported previously, it
has been predicted that the sites of primary attack of 6-
TP by RnSn(IV) moieties are the S and N(2) atoms, and
Fig. 1(c) shows the possible structure of Ph3Sn(6-TP) [3].
But now, the X-ray diffraction data testify that 6-TPꢁ is
attacked by Ph3Snþ at S and N(1) sites and the structure
of Ph3Sn(6-TP) is as shown in Fig. 3. The results exhibit
a new coordination mode for 6-TPH, which proves that,
besides N(2), N(3) and N(4) atoms [2,3], the N(1) atom
also has coordination ability.
As shown in Fig. 3, there are also intermolecular
hydrogen bonds (Nꢀ ꢀ ꢀH) between N and H atoms, such
Fig. 3. Unit cell of the title compound.
Table 2
ꢀ
Selected bond lengths (A) and angles (°) for C23H18N4SSn
Molecule A
Molecule B
Sn(1)–C(6)
Sn(1)–C(12)
Sn(1)–C(18)
Sn(1)–S(1)
Sn(1)–N(1)
C(4)–S(1)
2.063(15)
2.108(15)
2.138(15)
2.442(4)
2.958(11)
1.726(14)
0.860
Sn(2)–C(35)
Sn(2)–C(29)
Sn(2)–C(41)
Sn(2)–S(2)
Sn(2)–N(5)
C(4)–S(1)
2.125(13)
2.126(14)
2.132(14)
2.444(4)
2.978(11)
1.748(14)
0.860
N(4)–H(4)
N(3)–H(7)
N(7)–H(7)
N(8)–H(4)
1.913
1.910
C(6)–Sn(1)–C(12)
C(12)–Sn(1)–S(1)
C(6)–Sn(1)–S(1)
C(6)–Sn(1)–C(18)
C(12)–Sn(1)–C(18)
C(18)–Sn(1)–S(1)
N(1)–Sn(1)–C(6)
N(1)–Sn(1)–C(12)
N(1)–Sn(1)–C(18)
N(1)–Sn(1)–S(1)
N(4)–H(4)–N(8)
116.5(5)
C(35)–Sn(2)–C(29)
C(35)–Sn(2)–C(41)
C(29)–Sn(2)–C(41)
C(35)–Sn(2)–S(2)
C(29)–Sn(2)–S(2)
C(41)–Sn(2)–S(2)
N(5)–Sn(2)–C(29)
N(5)–Sn(2)–C(35)
N(5)–Sn(2)–C(41)
N(5)–Sn(2)–S(2)
N(7)–H(7)–N(3)
118.0(5)
113.2(4)
110.9(4)
108.4(5)
107.0(5)
99.2(3)
81.0(4)
85.5(5)
157.4(4)
58.3(2)
158.63
108.4(5)
106.4(5)
112.3(3)
111.2(4)
98.6(3)
80.4(4)
86.8(4)
156.6(4)
58.5(2)
158.28

2762
R. Zhang et al. / Inorganica Chimica Acta 357 (2004) 2759–2762
ꢀ
as H(4) and N(8) (1.910 A), and H(7) and N(3) (1.913
ꢀ
A), which associate discrete molecules into a zigzag 1D
network.
192934. Copies of the data can be obtained free of
charge on application to the Director, CCDC, 12 Union
Road, Cambrige, CB2 1EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www http://
www.ccdc.cam.ac.ck).
Around the tin atom, the angles C(6)–Sn–C(12)
(116.5(5)°), C(12)–Sn–S(1) (113.2(4)°) and C(6)–Sn–S(1)
(110.9)(4)°) are wider while C(6)–Sn–C(18) (108.4(5)°)
and C(12)–Sn–C(18) (107.0(5)°) are narrower than the
ideal tetrahedral angle. Considering the Snꢀ ꢀ ꢀN weak
coordination, the structural distortion for the tin atom is
best described as a displacement from tetragonal to-
wards trigonal bipyramidal geometry.
Acknowledgements
We are grateful to the National Natural Science
Foundation of China (20271025) and the Natural Sci-
ence Foundation of Shandong Province for financial
support.
3. Experimental
3.1. Preparation of C23H18N4SSn
References
The reaction was carried out under nitrogen atmo-
sphere with use of standard Schlenk technique. 6-TPH
(0.17 g, 1 mmol) was added to the solution of methanol
(20 ml) with sodium methoxide (0.054 g, 1 mmol), and
the mixture was stirred for 30 min, after which Ph3SnCl
(0.385 g, 1 mmol) was added, the reaction continuing for
12 h at 60 °C. After cooling to room temperature, the
mixture was filtered and the solvent was gradually re-
moved from filtrate by evaporation under a vacuum
until a solid product was obtained. This was then re-
crystallized from methanol to form colorless crystals of
the complex. Yield, 72%. M.p. 218–220 °C The C, H, N
and S analyses were performed using a Perkin–Elmer
PE-2400II CHNS Micro-analyser. Found: C, 55.10; H,
3.63; N, 11.21; S, 6.41%. Anal. Calc. for C23H18N4SSn:
C, 55.12; H, 3.62; N, 11.18; S, 6.40. IR(KBr, cmꢁ1): 3330
(s, N–H), 535 (m, Sn–C), 307 (m, Sn–S).
[1] P. Calabresi, R.E. Parks Jr., Alkylating agents, antimetabolites,
hormones and other antiproliferative agents, in: L.S. Goodman,
A. Gilman (Eds.), The Pharmacological Basis of Therapeutics,
MacMillan, New York, 1975 (Chapter 62).
[2] R. Barbieri, E. Rivarola, F. Dibianca, Inorg. Chim. Acta 57
(1982) 37.
[3] R. Barbieri, F. Dibianca, E. Rivarola, Inorg. Chim. Acta 108
(1985) 141.
[4] F. Huber, G. Roge, L. Carl, J. Chem. Soc., Dalton Trans. (1985)
523.
[5] E.J. Kupchik, E.F. McInerney, J. Organomet. Chem. 11 (1968)
291.
[6] F. Bergmann, M. Kleiner, Z. Neiman, M. Rashi, Israel J. Chem. 2
(1964) 185.
[7] D. Lichtenberg, F. Bermann, Z. Neiman, Israel J. Chem. 10 (1972)
805.
[8] B.D. James, R.J. Magee, W.C. Patalinghug, B.W. Skelton, A.H.
White, J. Organomet. Chem. 467 (1994) 51.
[9] J.S. Casas, A. Castineiras, E.G. Martinez, A.S. Gonzalez, A.
Sanchez, J. Sordo, Polyhedron 16 (1997) 795.
[10] N.G. Furmanova, Yu.T. Struchkov, E.M. Rokhlina, D.N.
Kravtsov, J. Struct. Chem. Engl. Trans. 21 (1980) 766.
[11] C.-W. Ng, S.W. Wei, V.G. Kumar Das, T.G.W. Mak, J.
Organomet. Chem. 334 (1987) 283.
3.2. X-ray structure analysis for C23H18N4SSn
A crystal was mounted in a Lindemann capillary
under nitrogen. Diffraction data were collected using a
Siemens CCD area-detector and graphite monochro-
[12] N.G. Furmanova, Y.u.T. Struchkov, E.M. Rokhlina, D.N.
Kravtsov, J. Struct. Chem. Engl. Trans. 22 (1981) 569.
[13] L. Petrilli, F. Caruso, E. Rivarola, Main Group Met. Chem. 17
(1994) 293.
ꢀ
mated Mo Ka radiation (k ¼ 0:71073 A). A semiem-
[14] J. Bravo, M.B. Cordero, J.S. Casas, A. Sanchez, J. Sordo, E.Z.
Castellano, J. Zuckerman-Schpector, J. Organomet. Chem. 482
(1994) 147.
pirical absorption correction was applied to the data.
The structure was solved by direct methods using
SHELXS-97 [19] and refined against F 2 by full-matrix
least-squares using SHELXL-97 [20]. Hydrogen atoms
were placed in calculated positions.
[15] N.G. Bokii, Y.u.T. Struchkov, D.N. Kravtsov, E.M. Rokhlina, J.
Struct. Chem. Engl. Trans. 14 (1973) 258.
[16] R. Cea-Olivares, O. Jimenez-Sandoval, G. Espinosa-Perez, C.
Silvestru, J. Organomet. Chem. 484 (1994) 33.
[17] J.E. Huheey, E.A. Keiter, R.L. Keiter, Principles and Applica-
tions of Inorganic Chemistry, fourth ed., Harper Collins, New
York, 1993.
4. Supplementary material
€
[18] C.V.R. Moura, A.P.G. Sousa, R.M. Silva, A. Abras, M. Horner,
A.J. Bortoluzzi, C.A.L. Filgueiras, J.L. Wardell, Polyhedron 18
(1999) 2961.
Crystallographic data (excluding structure factors)
for the structure reported in this paper have been de-
posited with the Cambridge Crystallographic Data
Center as supplementary publication no. CCDC-
[19] G.M. Sheldrick, Acta Crystallogr. Sec. A 46 (1990) 467.
[20] G.M. Sheldrick, SHELXL97, Programs for Structure Refinement,
€
Universitat Gottingen, Gottingen, Germany, 1997.
€
€