Structural differences in eight- and ten-membered heterocyclic tin compounds displaying transannular interactions O?Sn: An experimental and theoretical study

Article abstract of DOI:10.1016/j.poly.2012.04.004

Two series of heterocyclic tin compounds of general formula [(S{C ₆H₃(CH₂)_nS}₂O)SnR ¹R²] with different central ring sizes were prepared. The ten-membered series includes the compounds with n = 1 and R¹ = R ² = Ph (5); R¹ = Cl, R² = Ph (6); R¹ = Cl, R² = n-Bu (7); R¹ = R² = Cl (8); the eight-membered series includes the compounds with n = 0 and R¹ = R² = Ph (10); R¹ = Cl, R² = n-Bu (11) and R¹ = R² = Cl (12). The compounds 5, 7, 8, 10, and 11 were investigated by single-crystal X-ray diffraction. The chloro compounds 7, 8, and 11 displayed a bipyramidal geometry at the tin atom with different degrees of distortion ranging from 57% to 62%. The diphenyl compounds 5 and 10 displayed a tetrahedral geometry at Sn. The conformation of the central ring in the ten-membered series is similar and is described as boat; the other series displayed two different conformations described as boat-chair and boat-boat. The possible conformers in the gas state of compounds 5, 7, 8, 10, 11, and 12 were investigated by MMFF, LSDA, BLYP, B3LYP, and M06 functionals using the DGDZVP and TZVP basis sets. The structural data of the total optimization agreed with the experimental results. The topological analysis indicated that bond critical points are present along the O?Sn direction in the compounds 7, 8, 11, and 12.

Full text of DOI:10.1016/j.poly.2012.04.004

Polyhedron 40 (2012) 1–10
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural differences in eight- and ten-membered heterocyclic tin compounds
displaying transannular interactions Oꢀ ꢀ ꢀSn: An experimental and theoretical study
a
Diego Martínez-Otero a, Benito Flores-Chávez b, José G. Alvarado-Rodríguez a, , Noemí Andrade-López ,
⇑
Julián Cruz-Borbolla a, Thangarasu Pandiyan b, Vojtech Jancik c, Enrique González-Jiménez a,
Christiaan Jardinez a
a Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, km. 4.5 Carretera Pachuca-Tulancingo, Col. Carboneras, C.P. 42184 Mineral de la Reforma,
Hidalgo, Mexico
b Facultad de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, C.P. 04510 D. F., México, Mexico
c Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, km 14.5 Carr. Toluca-Atlacomulco, Unidad San Cayetano, C.P. 50200 Toluca, Edo. de México, Mexico
a r t i c l e i n f o
a b s t r a c t
Two series of heterocyclic tin compounds of general formula [(S{C6H3(CH2)nS}2O)SnR1R2] with different
Article history:
Received 18 January 2012
Accepted 11 April 2012
Available online 24 April 2012
central ring sizes were prepared. The ten-membered series includes the compounds with n = 1 and
R
1 = R2 = Ph (5); R1 = Cl, R2 = Ph (6); R1 = Cl, R2 = n-Bu (7); R1 = R2 = Cl (8); the eight-membered series
includes the compounds with n = 0 and R1 = R2 = Ph (10); R1 = Cl, R2 = n-Bu (11) and R1 = R2 = Cl (12).
The compounds 5, 7, 8, 10, and 11 were investigated by single-crystal X-ray diffraction. The chloro com-
pounds 7, 8, and 11 displayed a bipyramidal geometry at the tin atom with different degrees of distortion
ranging from 57% to 62%. The diphenyl compounds 5 and 10 displayed a tetrahedral geometry at Sn. The
conformation of the central ring in the ten-membered series is similar and is described as boat; the other
series displayed two different conformations described as boat–chair and boat–boat. The possible con-
formers in the gas state of compounds 5, 7, 8, 10, 11, and 12 were investigated by MMFF, LSDA, BLYP,
B3LYP, and M06 functionals using the DGDZVP and TZVP basis sets. The structural data of the total opti-
mization agreed with the experimental results. The topological analysis indicated that bond critical
points are present along the Oꢀ ꢀ ꢀSn direction in the compounds 7, 8, 11, and 12.
Keywords:
Organotin compounds
Dithioligands
Hypercoordinated compounds
Non-bonded interactions
DFT studies
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
attached to A. For the compounds of types I and III, the Dꢀ ꢀ ꢀA
interaction has recurrently been observed with several degrees
The hypercoordination through intramolecular as well as inter-
molecular non-covalent donor–acceptor interactions is well docu-
mented in compounds containing group 14 elements [1,2], where
the donor atom is usually a Lewis base as nitrogen [3], oxygen
[4] or sulfur [5]. In particular, for organotin compounds, this do-
nor-Sn non-covalent bonding has been suggested to be important
for their biological activity [6].
With respect to the hypercoordination, we are interested in
the synthesis and design of ligands capable of increasing the
coordination number of heavy elements of the groups 14 and
15. We have studied the coordination chemistry of dithioligands
such as D(C6H4SH)2 [D = O, S] and the more rigid S(C6H3SH)2O in
order to synthesize compounds of the types I and II, respectively
(Scheme 1). For a given ligand, its coordination pattern can be
influenced by the adequate choice of the exocyclic ligands R
of magnitude, distorting the local geometry at the central accep-
tor A atom; some examples are with A = Ge [7], Sn [8,9], Pb [10],
As [11], and Sb [12]. In addition, it has been observed that the
more electronegative are the pendant ligands R, the stronger is
the interaction, leading to tridentate coordination patterns of
the trichalcogenate ligand. On the other hand, in the case of
the compounds of type II with a more rigid dithioligand, two dif-
ferent coordination modes have been observed in the solid state
for compounds with A = Ge [13] and Pb [10]; when the acceptor
atom has two organic exocyclic ligands, a bidentate coordination
mode is observed and A displays a distorted tetrahedral local
geometry. In the case of the germanium compounds with halo-
gen pendant ligands where its Lewis acidity has been enhanced,
the same dithioligand displays a tridentate coordination, and the
acceptor Ge atom exhibits a trigonal bipyramidal coordination
geometry with significantly strong Oꢀ ꢀ ꢀGe intramolecular
interactions.
⇑
Corresponding author. Tel.: +52 771 7172000.
E-mail addresses: jgar@uaeh.edu.mx, josegalvarado@yahoo.com (J.G. Alvarado-
Following with the study of hypercoordination in the elements
of the group 14, we report herein the synthesis, characterization,
Rodríguez).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.04.004

2
D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
S
S
D
A
D
O
O
S
S
S
S
S
S
S
S
A
A
A
R
R
R
R
R
R
R
R
I
II
III
IV
Scheme 1. Eight- and ten-membered heterocyclic compounds displaying transannular donor-acceptor interactions (R = alkyl, aryl, halogen, lone pair, etc.).
and theoretical studies of heterocyclic tin compounds of the types
II (8-R series) and IV (10-R series) containing a transannular Oꢀ ꢀ ꢀSn
interaction, where the flexibility of the ligands is crucial for the
achievement of hypercoordination at the tin atom. The molecular
and crystal structures of five compounds containing ten-mem-
bered (10-R) or eight-membered (8-R) central rings were obtained
by X-ray diffraction studies. The detailed description of the synthe-
sis, spectroscopic characterization, crystallographic data, and theo-
retical results is presented and discussed.
2.2.1. Synthesis of S(C6H3CHO)2O (1)
A solution of n-BuLi 2.5 M (26 mL, 65 mmol) was slowly added
to a cold solution (0 °C) of phenoxatiin (5.0 g, 25 mmol) and anhy-
drous TMEDA (19.4 mL, 250 mmol) in anhydrous THF (30 mL). The
cold mixture was stirred for 24 h. Then, DMF (19.4 mL, 250 mmol)
was then slowly added for 3 h and then refluxed for 3 h more. The
cold mixture was acidified with HCl to pH 2 and extracted with
dichloromethane (3 ꢂ 50 mL). The organic layers were dried with
Na2SO4 and evaporated under reduced pressure; the yellow solid
obtained was recrystallized with chloroform to yield yellow crys-
tals. Yield: 36% (2.3 g, 9 mmol). M.p.: 237 °C. Anal. Calc. for
2. Experimental
C14H8O3S: C, 65.61; H, 3.15. Found: C, 65.50; H, 3.14%. IR (CsI):
m
= 3346, 3049, 3001, 2856, 2811, 2737, 1683, 1600, 1576, 1453,
1427, 1382, 1376, 1240, 1220, 1179, 779, 741, 716 cmꢁ1. NMR: 1
H
2.1. Materials and physical methods
3
(CDCl3) d = 10.56 s [1H, H-1], 7.68 dd [1H, H-3, JH3–H4 = 7.7,
4JH3–H5 = 1.7 Hz], 7.33 dd [1H, H-5, JH4–H5 = 7.7, JH3–H5 = 1.7 Hz],
3
4
All the starting reagents such as the tin chlorides, phenoxathiin,
n-BuLi (1.6 M, in hexanes), TMEDA, thiourea 1,4-diazabicyclo
[2.2.2] octane (DABCO), Na[BH4], and Li[AlH4] were purchased
from Aldrich and used as supplied. The dithioligand 9 was pre-
pared according to the reported method [13]. All manipulations
of the tin compounds, n-BuLi, Li[AlH4], and Na[BH4] were per-
formed under a dry, oxygen-free dinitrogen atmosphere using
standard Schlenk techniques unless noted otherwise. Solvents
were dried by standard methods and distilled prior to use. Melting
points were determined with a Mel-Temp II instrument and are
uncorrected. The elemental analyses were recorded with a Per-
kin–Elmer Series II CHNS/O Analyzer. The IR spectra were recorded
in the 4000–400 cmꢁ1 range with a Perkin–Elmer System 2000 FT-
IR spectrometer, as KBr pellets or CsI films. The 1H, 13C{1H} and
119Sn{1H} NMR spectra were recorded on a Jeol Eclipse 400 and
Varian VNMRS 400 spectrometers operating at 399.78, 100.53,
and 149.03 MHz, respectively. The chemical shifts are reported in
ppm with respect to the references and stated relative to external
tetramethylsilane (TMS) for 1H and 13C NMR, and SnMe4 for 119Sn
NMR spectroscopy. All the spectra were acquired at room temper-
ature (25 °C) unless otherwise specified.
7.17 td [1H, H-4, JH3–H4 = 7.7, JH4–H5 = 7.7 Hz]; 13C{1H} (CDCl3):
d = 188.0 (C1), 152.8 (C7), 132.4 (C5), 127.9 (C3), 125.6 (C2), 125.3
(C4), 121.1 (C6).
3
3
2.2.2. Synthesis of S(C6H3CH2OH)2O (2)
1 (1.0 g, 3.9 mmol) was suspended in ethanol (15 mL) and
cooled to 0 °C in an ice-bath; then, Na[BH4] (0.74 g, 19.6 mmol)
was added in small portions. The suspension was warmed to room
temperature and stirred until the yellow color vanished. The sus-
pension was acidified with HCl to pH 2 and extracted with dichlo-
romethane (2 ꢂ 50 mL). The organic layers were dried with Na2SO4
and evaporated under reduced pressure; a white solid was ob-
tained. Yield: 97% (1.0 g, 3.8 mmol). M.p.: 135 °C. Anal. Calc. for
C
m
14H12O3S: C, 64.60; H, 4.65. Found: C, 64.72; H, 4.70%. IR (CsI):
= 3265(OH), 3154, 3066, 2952, 2923, 2852, 1722, 1586, 1426,
1356, 1291, 1255, 1211, 1056, 1020, 984, 877, 770 cmꢁ1. NMR:
1H (CDCl3) d = 7.01 m [2H, H-3, H-5,], 6.91 t [1H, H-4, JH3–
3
3
H4 = 7.5, JH4–H5 = 7.5 Hz], 4.63 s [2H, H-1], 3.60 s [1H, OH];
13C{1H} (CDCl3): d = 150.3 (C7), 129.0 (C2), 128.7 (C5), 126.7 (C3),
124.4 (C4), 120.1 (C6), 60.8 (C1).
2.2. Synthesis of the dithioligand S(C6H3CH2SH)2O (4)
2.2.3. Synthesis of S(C6H3CH2Br)2O (3)
Aqueous HBr (1.7 mL, 15.0 mmol) was added to a solution of 2
(1.0 g, 3.8 mmol) dissolved in toluene (15 mL); the solution was re-
fluxed for 24 h. After the reaction, the organic layers were ex-
tracted with chloroform (2 ꢂ 50 mL) and dried with Na2SO4. After
evaporation to dryness, a white solid was obtained. Yield: 92%
(1.38 g, 3.6 mmol). M.p.: 174 °C. Anal. Calc. for C14H10Br2OS: C,
The dithioligand 4 was prepared by a linear synthesis from phe-
noxathiin. The dialdehyde (1), diol (2), and dibromo (3) intermedi-
ate compounds were isolated and characterized (Scheme 2). For
the chemical shifts assignments in the NMR spectroscopy of all
compounds, we have used the general numbering scheme showed
in the compound 4.
43.55; H, 2.61. Found: C, 43.98; H, 2.62%. IR (CsI):
m = 2965, 2857,
5
6
S
S
S
S
S
4
3
7
O
O
O
O
O
2
CH2OH
CH2OH
CH2Br
CH2Br
CH2SH
CH2SH
CHO
CHO
1
1
2
3
4
Scheme 2. Linear synthesis of dithiol 4.

D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
3
1919, 1772, 1713, 1583, 1445, 1430, 1289, 1268, 1229, 1202, 1076,
912, 776, 726, 665, 606, 553, 483 cmꢁ1. NMR: 1H (CDCl3) d = 7.10
2.3.3. Synthesis of [{S(C6H3CH2S)2O}SnCl(n-Bu)] (7)
Compound
(0.30 g, 1.02 mmol), nBuSnCl3 (0.17 mL,
1.02 mmol) and DABCO (0.092 g, 0.82 mmol). Yield: 0.45 g (87%).
4
3
4
dd [1H, H-3, JH3–H4 = 7.5, JH3–H5 = 1.8 Hz], 6.97 dd [1H, H-5,
4
3
3JH4–H5 = 7.7, JH3–H5 = 1.8 Hz], 6.92 dd [1H, H-4, JH3–H4 = 7.5,
3JH4–H5 = 7.7 Hz], 4.67 s [2H, H-1]; 13C{1H} (CDCl3): d = 149.3 (C7),
129.3 (C3), 127.3 (C5), 127.0 (C2), 124.7 (C4), 120.1 (C6), 27.8 (C1).
M.p.: 120 °C. Anal. Calc. for C18H19ClOS3Sn: C, 43.09; H, 3.82.
Found: C, 43.46; H, 3.66%. IR (KBr):
m = 3054, 2926, 2854, 1712,
1459, 1435, 1232, 1209, 1176, 1076, 705 cmꢁ1. NMR: 119Sn
(CDCl3): d = 28.0; 1H (CDCl3) d = 7.13 m [2H, H-3], 7.09 m [4H,
2
3
H-4, H-5], 4.45 d [2H, H-1a, JH1a–H1b = 13.5, JH1aꢁ
= 35.6 Hz],
119Sn
2.2.4. Synthesis of S(C6H3CH2SH)2O (4)
2
3
3
3.70 d [2H, H-1b, JH1b–H1a = 13.5, JH1bꢁ
= 119.1, JH1bꢁ
=
119Sn
117Sn
Thiourea (0.94 g, 12.3 mmol) was added to a solution of 3
(1.60 g, 4.1 mmol) in ethanol (30 mL); the mixture was refluxed
for 24 h. An aqueous solution of potassium hydroxide (1.40 g,
25 mmol) was then added to the warm mixture and refluxed for
four hours and allowed to reach room temperature. The mixture
was acidified with HCl to pH 2 and extracted with chloroform
(2 ꢂ 50 mL); the organic layers were dried with Na2SO4. After
evaporation of the organic solvent, a yellow solid was obtained.
Yield: 75% (0.90 g, 3.1 mmol). M.p.: 103 °C. Anal. Calc. for
3
3
114.2 Hz], 1.88 td [2H, H–8, JH8–H9 = 7.7, JH8ꢁ
= 64.4 Hz], 1.45
119Sn
3
3
q [2H, H-9, JH8–H9 = 7.7, JH9–H10 = 7.3 Hz], 1.23 sx [2H, H-10,
3JH9–H10 = 7.3, 3JH10–H11 = 7.3 Hz], 0.73
t
[3H, H-11, 3JH10–
H11 = 7.3 Hz]; 13C{1H} (CDCl3): d = 147.3 (C7), 131.8 (C2), 128.3
(C3), 126.3 (C4), 126.3 (C5), 120.3 (C6), 31.6 (C8), 28.4 (C1), 27.6
(C9), 25.7 (C11), 13.5 (C10).
2.3.4. Synthesis of [{S(C6H3CH2S)2O}SnCl2] (8)
Compound 4 (0.20 g, 0.68 mmol), SnCl4 (0.08 mL, 0.68 mmol)
and DABCO (0.061 g, 0.54 mmol). Yield: 0.24 g (74%). M.p.:
146 °C. Anal. Calc. for C14H10Cl2OS3Sn: C, 35.03; H, 2.10. Found: C,
C14H12S3O: C, 57.50; H, 4.14. Found: C, 58.24; H, 4.18%. IR (CsI):
m
= 3162, 3053, 2934, 2553 (SH), 1584, 1461, 1430, 1293, 1265,
1211, 1182, 1078, 970, 889, 780, 735 cmꢁ1. NMR: 1H (CDCl3)
35.05; H, 2.03%. IR (KBr):
m = 2920, 2850, 1585, 1459, 1451, 1435,
3
4
d = 7.04 dd [1H, H-3, JH3–H4 = 6.6, JH3–H5 = 2.6 Hz], 6.90 m [2H,
1226, 1206, 1172, 1155, 1076, 1058, 967, 675, cmꢁ1. NMR: 119Sn
3
H-4, H-5,], 3.81 d [2H, H-1, JH1–SH = 7.6 Hz], 1.92 t [1H, SH,
(CDCl3): d = ꢁ97.3; 1H (CDCl3) d = 7.10 m [3H, H-3, H-4, H-5],
3JH1–SH = 7.6 Hz]; 13C{1H} (CDCl3): d = 146.1 (C7), 130.2 (C2),
4.19 s [1H, H-1, JH1bꢁ
= 137.6, JH1bꢁ
= 131.8 Hz ]; 13C{1H}
3
3
119Sn
117Sn
128.1 (C3), 125.8 (C5), 124.7 (C4), 120.2 (C6), 23.7 (C1).
(CDCl3): d = 145.8 (C7), 129.3 (C2), 127.6 (C3), 126.9 (C4), 126.2
2
(C5), 120.8 (C6), 29.4 (C1, JC1ꢁ
= 31.9 Hz).
119Sn
2.3. General synthesis of the 10-R compounds of formula
[{S(C6H3CH2S)2O}SnR1R2]
2.4. Synthesis of the 8-R compounds of formula [{S(C6H3S)2O}SnR1R2]
A tin compound was added to a solution of 4 and DABCO in
dichloromethane; the reaction mixture was stirred for 12 h. After
the reaction, the DABCO chlorohydrate was filtered off and the
remaining solution was slowly evaporated to dryness to get a solid
product.
2.4.1. Synthesis of [{S(C6H3S)2O}SnPh2] (10)
Compound 9 (0.23 g 0.87 mmol) was dissolved in 25 mL of dry
chloroform at room temperature. DABCO (0.13 g, 1.16 mmol) was
added and the mixture was stirred for 15 min. Ph2SnCl2, (0.40 g,
1.16 mmol) was added to the above mixture and refluxed over-
night; during this time the mixture acquired clear yellow colora-
tion. The hot mixture was filtered producing an oily compound
that was dissolved in chloroform. The chloroform solution was
slowly evaporated giving a yellow solid. Yield: 0.32 g (68%). M.p.:
120 °C. Anal. Calc. for C16H15ClOS3Sn: C, 53.85; H, 3.01. Found: C,
2.3.1. Synthesis of [{S(C6H3CH2S)2O}SnPh2] (5)
Compound 4 (0.20 g, 0.68 mmol), Ph2SnCl2 (0.23 g, 0.67 mmol)
and DABCO (0.061 g, 0.54 mmol). Yield: 0.22 g (57%). M.p.:
145 °C. Anal. Calc. for C26H20OS3Sn: C, 55.43; H, 3.58. Found: C,
55.52; H, 3.49%. IR (KBr):
m = 3051, 3018, 2984, 2918, 1586,
53.75; H, 2.99%. IR (KBr):
m = 3048, 2917, 2849, 1629, 1582, 1407,
1455, 1436, 1234, 1217, 1180, 1073, 997, 697 cmꢁ1
. NMR:
1229, 1067, 835, 769, 724, 693, 442 cmꢁ1. NMR: 119Sn (CDCl3):
119Sn (CDCl3): d = 6.5; 1H (CDCl3) d = 7.27 tt [1H, H-11,
d = ꢁ11.7; 1H (CDCl3): d = 7.50 m [4H, H-9], 7.40 dd [2H, H-3,
4
3JH10–H11 = 8.0, JH9–H11 = 1.2 Hz], 7.15 m [2H, H-3, H10], 7.08 dd
4
3JH3–H4 = 7.8, JH3–H5 = 1.3 Hz], 7.34 m [6H, H-10, H-11], 6.95 t
3
4
[1H, H-9, JH9–H10 = 8.8, JH9–H11 = 1.2 Hz], 6.93
t [1H, H-4,
3
3
[2H, H-4, JH3–H4 = 7.8, JH4–H5 = 7.8 Hz], 7.86 dd [2H, H-5,
3JH4–H5 = 7.7, JH4–H3 = 7.7 Hz], 6.67 dd [1H, H-5, JH4–H5 = 7.7,
JH3–H5 = 1.6 Hz], 4.14 s [1H, H-1, JH1ꢁ
3
3
4
3JH4–H5 = 7.8, JH3–H5 = 1.3 Hz]; 13C{1H} (CDCl3): d = 148.0 (C7),
4
= 56.6 Hz]; 13C{1H}
3
119Sn
1
2
139.5 (C8, JC8-Sn = 632, 604 Hz), 135.4 (C9, JC9-Sn = 50 Hz), 130.6
(CDCl3): d = 147.3 (C7), 138.3 (C8), 135.2 (C9), 130.3 (C2), 129.7
(C11), 128.8 (C10), 128.7 (C3), 125.4 (C4), 124.7 (C5), 119.2
(C6), 25.9 (C1).
3
4
(C3, JC8-Sn = 28 Hz), 130.4 (C11, JC11-Sn = 14 Hz), 129.2 (C10,
3JC8-Sn = 68 Hz), 125.4 (C4), 124.8 (C2, JC8-Sn = 24 Hz), 123.9 (C5),
2
121.4 (C6).
2.3.2. Synthesis of [{S(C6H3CH2S)2O}SnClPh] (6)
2.4.2. Synthesis of [{S(C6H3S)2O}SnCl(n-Bu)] (11)
Compound 11 was prepared in a similar approach to 10 except
for the addition of DABCO.
Compound 4 (0.30 g, 1.02 mmol), PhSnCl3 (0.17 mL, 1.02 mmol)
and DABCO (0.092 g 0.82 mmol). Yield: 0.19 g (35%). M.p.: 156 °C.
Anal. Calc. for C20H15ClOS3Sn: C, 46.05; H, 2.9. Found: C, 45.47; H,
Compound
9 (0.75 g, 2.84 mmol) and BuSnCl3 (0.5 mL,
2.79%. IR (KBr):
m
= 3047, 2955, 2923, 2851, 1585, 1462, 1435,
2.85 mmol). Brown solid. Yield: 0.66 g (50%). M.p.: 85 °C. Anal. Calc.
for C16H15ClOS3Sn: C, 40.57; H, 3.19. Found: C, 40.35; H, 3.15%. IR
1234, 1210, 1180, 1068, 914, 692 cmꢁ1. NMR: 119Sn (CDCl3):
d = ꢁ16.6; 1H (CDCl3) d = 7.39 tt [1H, H-11, JH10–H11 = 7.6,
(KBr): m = 3062, 2956, 2920, 2846, 1653, 1561, 1440, 1408, 1239,
3
4JH9–H11 = 1.4 Hz
],
7.20
t
[2H,
H-10,
3JH9–H10 = 7.6,
913, 871, 839, 764, 704 cmꢁ1. NMR: 119Sn (CDCl3): d = ꢁ15.2; 1H
3JH10–H11 = 7.6 Hz], 7.11 m [4H, H-9, H-3], 6.98
t
[2H, H-4,
(CDCl3): d = 7.29 dd [2H, H-3, JH3–H4 = 7.8, JH3–H5 = 1.6 Hz], 7.02 t
3
4
3
3
3
3
3JH3–H4 = 7.7, JH4–H5 = 7.7 Hz], 6.77 dd [2H, H-5, JH4–H5 = 7.7,
[2H, H-4, JH3–H4 = 7.8, JH4–H5 = 7.8 Hz], 6.96 dd [2H, H-5,
3
2
4
3
JH3–H5 = 1.6 Hz], 4.45 dd [2H, H-1a, JH1a–H1b = 13.5, JH1aꢁ
=
3JH4–H5 = 7.8, JH3–H5 = 1.6 Hz], 2.04 dd [2H, H-8, JH8–H9 = 8.2,
3
119Sn
2
3
39.5 Hz], 3.7 ddd [2H, H-1b, JH1b–H1a = 13.5, JH1bꢁ
= 136.2,
3JH8–H9 = 7.6 Hz], 1.74 q [2H, H-9, JH8–H9 = 7.7 Hz], 1.39 sx [2H,
3
119Sn
3
3
3JH1bꢁ
= 130.3 Hz]; 13C{1H} (CDCl3): d = 146.1 (C7), 141.1 (C8),
H-10, JH9–H10 = 7.4 Hz], 0.85
t
[3H, H-11, JH10–H11 = 7.4 Hz];
117Sn
3
133.3 (C9), 130.9 (C2), 130.5 (C11), 129.3 (C10), 127.9 (C3), 125.8
(C4), 125.7 (C5), 119.8 (C6), 28.1 (C1).
13C{1H} (CDCl3): d = 147.5 (C7, JC7-Sn = 14 Hz), 129.5 (C3,
3JC3-Sn = 44 Hz), 126.7 (C4), 125.5 (C2), 124.0 (C5), 123.4 (C6),

4
D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
31.5 (C8), 27.2 (C9, 2JC9-Sn = 48 Hz), 25.6 (C10, 3JC10-Sn = 34 Hz), 13.6
(C11).
calculations were performed with the GAUSSIAN 09 program [22].
The ground-state wave-function was used for ‘‘atoms in mole-
cules’’ (AIM) calculation [23] to determine bond critical points
(BCPs) and ring critical points (RCPs); the results were analyzed
2.4.3. Synthesis of [{S(C6H3S)2O}SnCl2] (12)
SnCl4 (0.5 mL, 4.27 mmol) was dissolved in dry toluene (20 mL)
at ꢁ78 °C. The solution was stirred for 30 min, then 9 (1.13 g,
4.27 mmol) in dry toluene (20 mL) was added with a syringe. The
solution was kept at 5 °C overnight. The mixture was then filtered
and the toluene fraction was slowly evaporated. A yellow solid was
obtained. Yield: 0.78 g (41%). M.p.: 54 °C. Anal. Calc. for
in terms of electron densities (
q
) ellipticity (
r
e), energy density
[Ed(r)] and their Laplacians (L = ꢁ1/4
2q). The Bader theory is ap-
plied in the AIM 2000 program [24].
3. Results and discussion
C
12H6Cl2OS3Sn: C, 31.89; H, 1.34. Found: C, 31.53; H, 1.99%. IR
3.1. Synthesis of the dithioligands S(C6H3CH2SH)2O (4) and
S(C6H3SH)2O (9)
(KBr):
m = 3058, 2913, 2849, 1610, 1589, 1458, 1440, 1416, 1224,
877, 839, 764, 704 cmꢁ1. NMR: 119Sn (CDCl3): d = ꢁ134.9; 1H
3
4
(CDCl3): d = 7.32 dd [2H, H-3, JH3–H4 = 7.9, JH3–H5 = 1.4 Hz], 7.11
Ditihioligand 4 was prepared by linear synthesis from pheno-
xathiin by taking advantage of the regioselectivity of the dilithia-
tion reaction in the ortho-position with respect to the oxygen
atom; the dialdehyde (1), diol (2), and dibromo (3) intermediate
compounds were isolated and structurally characterized (See Sec-
tion 2 and Scheme 2 for details). Compound 9 was prepared via a
one-pot four-step reaction from phenoxathiin [13].
3
3
t [2H, H-4, JH3–H4 = 7.9 Hz, JH4–H5 = 7.9 Hz], 7.03 dd [2H, H-5,
3JH4–H5 = 7.9, JH3–H5 = 1.4 Hz]; 13C{1H} (CDCl3): d = 144.8 (C7),
4
129.0 (C3), 126.7 (C4), 124.9 (C5), 122.5 (C2), 121.4 (C6).
2.5. X-ray Crystallography and structure solution
Suitable single crystals of the compounds 5, 7, 8, 10, and 11
were grown by slow evaporation from a chloroform solution.
X-ray diffraction data for 7 and 8 were collected at 141 K on an
Oxford Diffraction Gemini CCD diffractometer with graphite-
3.2. Synthesis of the tin compounds 5–8 and 10–12
The reaction of 4 or 9 with the corresponding chlorotin com-
pound dissolved in dry dichloromethane or chloroform in the pres-
ence of the deprotonating reagent DABCO yielded the
corresponding compounds 5–8 and 10 with moderate yields. 11
was similarly prepared but without DABCO. The treatment of 9
with SnCl4 in dry toluene at ꢁ78 °C afforded the dichlorotin com-
pound 12. The general reactions are shown in the Scheme 3. All
compounds are air-stable. 6, 8, and 12 are slightly soluble in chlo-
roform, methylene chloride and benzene; the remaining com-
pounds are quite soluble in these solvents. All tin compounds are
insoluble in n-hexane, pentane, methanol, and 2-propanol.
monochromated Mo K
a radiation (k = 0.71073 Å) was used. Data
were integrated, scaled, sorted, and averaged using the CRYSALIS soft-
ware package [14]. An analytical numeric absorption correction
using a multifaceted crystal model was applied by using the CRY-
SALIS Software. Data of compound 5 were collected on a Bruker
SMART X2S benchtop crystallographic system with monochromat-
ed (doubly curved silicon crystal) Mo Ka radiation (0.71073 Å) from
a sealed microfocus tube at 300 K. Data for 10 and 11 were col-
lected at room temperature on a CCD SMART 6000 diffractometer
through the use of Mo Ka radiation (k = 0.71073 Å, graphite mono-
chromator). Data of 5, 10, and 11 were integrated, scaled, sorted,
and averaged using the SMART software package. An empirical
absorption correction based on the multiple measurement of
equivalent reflections was applied with the program SADABS [15].
All the structures were solved by direct methods, using SHELXTL
NT Version 5.10 and refined by full-matrix least squares against
F2 [16]. The displacement parameters of non-hydrogen atoms were
anisotropically refined. The positions of the hydrogen atoms were
kept fixed with a common isotropic displacement parameter. Se-
lected crystallographic data are given in Table 1.
3.3. NMR spectra
NMR spectra of all the compounds were recorded in CDCl3 solu-
tions at room temperature and the chemical shifts are relative to
TMS. Assignment of all compounds was performed by 1H, 13C and
119Sn experiments; the signals were corroborated for some se-
lected compounds by two dimensional 1H–1H gCOSY, 1H–13
C
gHMBCAD, and 1H–13C HSQC experiments. In solution the two
(S{C6H3(CH2)nS}O)Sn (n = 1, 0) halves are equivalent.
2.6. Theoretical study
1H NMR spectra of compounds 1–6 and 10–12 showed three
signals in an ABC pattern for the protons of the phenoxathiin rings;
7 and 8 displayed a higher order spectra for the aromatic protons of
these rings.
To study the conformational preference,
a conformational
search was performed by molecular mechanics force field (MMFF)
in the selected compounds 5, 7, 8, 10, 11, and 12; the SPARTAN 08
program [17] employing the Monte–Carlo algorithm was used.
The conformations were generated by systematic change of torsion
angles of the freely rotating bonds. The low-energy conformers
were preselected in range the 10 kcal/mol. The most stable con-
formers of these selected compounds were subjected to quantum
chemical geometrical optimization using several functionals
(LSDA, BLYP, B3LYP, and M06) using the DGDZVP or TZVP basis
set in gaseous phase for all the atoms except Sn, for which a rela-
tivistic effect core potential RECP was used [18,19]. These calcula-
tions were denoted as functional/TZVP+RECP(Sn). For the total
optimization in chloroform as solvent, we employed the integral
equation formalism polarizable continuum model (IEFPCM)
[20,21]. For all the systems, the lowest state energy from the sec-
ond derivative calculation was used to analyze the stability of
the systems. The nature of the chemical bonding was analyzed in
For 4, the signal for the –SH proton at 3.81 ppm is displayed as a
triplet because of the coupling with the CH2-S protons resonating
at 1.92 ppm; for 9, the –SH is displayed as a single signal at
4.05 ppm. These signals and the couplings vanished when the li-
gands 4 or 9 were coordinated with the appropriate starting mate-
rial of tin.
The 1H NMR spectra of the compounds in the 10-R series deserve
a more thorough discussion. In the case of compounds 5 and 8, the
CH2-S-Sn protons are observed as single signals, while for the com-
pounds 6 and 7 these protons are displayed as an AB system, with
geminal coupling constants of 13.5 and 13.6 Hz, respectively; all
10-R compounds displayed these signals assigned to the methylen-
ic protons with satellites that are caused by spin–spin interactions
with the tin isotopes 117/119Sn (Fig. 1). In 6 and 7, the most shifted
signals towards higher frequencies with respect to the free ligand
4 were assigned to the endo protons, with a variation of the chem-
terms of the topology of the electronic density
[
q(r)]. All
ical shift, Dd, of 0.64 ppm; these endo and exo protons were also

D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
5
Table 1
Selected crystallographic data for compounds 5, 7, 8, 10, and 11.
Compound
5
7
8
10
11
Empirical formula
Molecular weight (g/mol)
Crystal size (mm)
Color
C
26H20OS3Sn
C18H19ClOS3Sn
501.65
0.38 ꢂ 0.26 ꢂ 0.10
colorless
monoclinic
P21/c
C14H10Cl2OS3Sn
479.99
C24H16OS3Sn
535.24
C16H15ClOS3Sn
473.60
563.29
0.60 ꢂ 0.60 ꢂ 0.50
colorless
monoclinic
P21/n
0.59 ꢂ 0.52 ꢂ 0.23
0.27 ꢂ 0.21 ꢂ 0.09
0.40 ꢂ 0.40 ꢂ 0.30
yellow
colorless
colorless
Crystal System
Space group
monoclinic
P21/n
1.974
triclinic
triclinic
ꢀ
ꢀ
P1
P1
qcalc (mgmꢁ3
)
1.596
1.790
1.606
1.741
Z
4
4
4
2
2
a (Å)
b (Å)
c (Å)
7.6372(8)
20.694(3)
14.8330(19)
90
90.056(4)
90
9.2062(2)
15.4747(4)
13.0972(3)
90
94.090(2)
90
8.4276(3)
14.2829(3)
13.8622(4)
90
104.585(3)
90
9.1578(13
10.5411(15)
12.3659(17)
77.378(3)
71.886(3)
85.748(3)
1107.1(3)
1.450
7.4311(8)
8.3387(9)
14.8568(16)
85.267(2)
85.119(2)
80.822(2)
903.30(17)
1.906
a
(°)
b (°)
(°)
V (Å3)
c
2344.3(5)
1.374
1861.12(9)
1.856
1614.84(8)
2.294
l
(mmꢁ1
)
F(000)
1128
1000
936
532
468
h range (°)
Completeness to h
0.98–25.07
99.1
3.39–26.06
99.8
3.53–26.05
99.7
1.77–26.09
99.8
1.38–26.08
99.1
Goodness of fit
1.070
1.032
1.080
0.984
1.080
Reflections collected
Unique reflections, (Rint
22729
4129
13675
3670
10939
3190
13764
4383
6042
3563
)
R1, wR2 [I > 2
r
(I)]
0.0429, 0.1167
0.0499, 0.1232
1.061 and ꢁ0.859
0.0187, 0.0449
0.0242, 0.0461
0.373 and ꢁ0.293
0.0301, 0.0769
0.0358, 0.0794
0.644 and ꢁ0.912
0.0475, 0.0870
0.0947, 0.1042
0.620 and ꢁ0.314
0.0261, 0.0639
0.0296, 0.0658
0.297 and ꢁ0.355
R1, wR2 (all data)
Large residuals (eÅꢁ3
)
S
S
S
v-viii
i-iv
O
O
O
SH
SH
SH HS
9
4
RmSnCl4-m
RmSnCl4-m
S
S
O
O
S
S
R2
S
R1
S
Sn
R1
Sn
R2
10 - 12
5 - 8
10-R series
8-R series
series
10-R
8-R
m
R1
R2
119Sn{1H} NMR
(ppm)
5
6
2
1
1
0
2
1
0
Ph
Cl
Cl
Cl
Ph
Cl
Cl
Ph
Ph
6.5
−16.6
28.0
7
n-Bu
Cl
8
−97.3
−11.7
−15.2
−134.9
10
11
12
Ph
n-Bu
Cl
Scheme 3. Synthesis of compounds 4–12. (i) n-BuLi/TMEDA/DMF/hexane; (ii) Na[BH4]/ethanol; (iii) HBr/toluene; (iv) Thiourea/KOH/H+/ethanol; (v) n-BuLi/TMEDA/THF; (vi)
Elemental sulfur; (vii) Li[AlH4]; (viii) HCl/H2O.
observed in the correspondent molecular structures studied by X-
ray single crystal diffraction experiments (vide infra). The exo pro-
couplings of 39.5 Hz and 35.6 Hz for 6 and 7, respectively, while
for the exo protons there were observed two couplings of 130.3/
136.2 Hz for 6 and 114.2/119.1 Hz for 7. The large values of the cou-
plings found for the exo protons in 6, 7 and for the H1 proton in 8 are
in good agreement with couplings reported in some organotin com-
pounds with different substituents at the tin atom containing weak
intramolecular Dꢀ ꢀ ꢀSn interactions in solution [25].
tons were observed at low frequencies with
Dd 0.11 ppm; their
assignment was confirmed with a 1H–1H noesy experiment. For
example, for 7, a 1H–1H correlation was observed for the signals
at 3.70 and 7.13 ppm, where this last frequency is assigned to the
proton ortho to the CH2-S-Sn fragment. For compounds 5 and 8
the CH2-S-Sn protons showed 3J(1H–117/119Sn) coupling constants
of 56.6 and 131.8/137.6 Hz, respectively. On the other hand, these
protons in the compounds 6 and 7 displayed two different
3J(1H–117/119Sn) couplings: for the endo protons were observed
The 119Sn NMR spectra for compounds 5–12 in the poor-coordi-
nating CDCl3 solvent displayed a single signal indicating the
presence in solution of a unique tin compound (data tabulated in
Scheme 3). The 119Sn resonances for the 8-R series are generally

6
D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
Fig. 1. 1H NMR spectra at 400 MHz at 25 °C in CDCl3 of compounds 5–8 in the region of the methylenic protons for the CH2-S-Sn fragment showing the satellites with the tin
isotopes 117/119Sn. 2J(1H–1H)/Hz = 13.5 (6); 13.6 (7). 3J(1H–117/119Sn)/Hz = 56.6 (5); 39.5 and 130.3/136.2 (6); 35.6 and 114.2/119.1 (7); 131.8/137.6 (8).
shifted to lower frequencies with respect to the 10-R series, with
the dichloro compounds 8 and 12 displaying the highest shifting.
In several studies, it has been stated that the 119Sn chemical shifts
move to lower frequencies as the coordination number increases
[26–28]; thus, according to the reported ranges, just 8 and 12
display a coordination number of five in solution. The penta-
coordination is explained by the covalent bonding of the tin atom
with the electronegative chloro groups and the tridentate ligand
(S{C6H3(CH2)nS}2O)2ꢁ (n = 1, 0), where a Oꢀ ꢀ ꢀSn coordination is
present because the enhancement of the Lewis acidity on the tin
atom. For the remaining compounds, the 119Sn chemical shifts at
higher frequencies indicate the presence in solution of tetra-coor-
dinate tin compounds, i.e., the Oꢀ ꢀ ꢀSn interaction is weak.
3.4. Description of the structures of 5, 7, 8 (10-R series), 10, and 11
(8-R series) compounds
Fig. 2. Molecular structure of [{S(C6H3CH2S)2O}SnPh2] (5).
The crystal structures of the compounds were determined by
single-crystal X-ray diffraction analyses. The molecular drawings
of 5, 7, 8 (10-R series), 10 and 11 (8-R series) are depicted in Figs.
2–6 and selected bond lengths, angles and some relevant structural
features are given in Table 2.
In spite of the structural differences, some general features are
common for the 10-R and 8-R series with the general formula
[(S{C6H3(CH2)nS}2O)SnR1R2] (n = 1, 0). For example, all tin-carbon
bond distances agree very well with the corresponding sum of
covalent radii [29]. Likewise, the Sn–S(thiolate-like) distances also
agree with those reported for eight-membered heterocycles and
several other compounds with tin–sulfur bonds [9]. In addition,
the tricyclic phenoxathiin moiety present in the compounds
compels a mirror-related conformation of the ten- and eight-mem-
bered central ring, with angles between the aromatic rings ranging

D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
7
Fig. 5. Molecular structure of [{S(C6H3S)2O}SnPh2] (10).
Fig. 3. Molecular structure of [{S(C6H3CH2S)2O}SnCl(n-Bu)] (7).
Fig. 6. Molecular structure of [{S(C6H3S)2O}SnCl(n-Bu)] (11).
Fig. 4. Molecular structure of [{S(C6H3CH2S)2O}SnCl2] (8).
compounds in the 8-R series because of the smaller ring size; with-
in each series, the BO is larger as the number of the chloro groups
increases, i.e., the compound 8 displays the larger BO because of
the higher Lewis acidity of the Sn atom.
from 170 to 142°. It is noteworthy that in all compounds there is
observed an Oꢀ ꢀ ꢀSn transannular distance shorter than the sum
of the van der Waals radii [3.281(4), (5); 2.7560(13), (7);
The conformation of the compounds deserves a detailed discus-
sion; firstly, in compounds 5, 7 and 8 (10-R series) the conforma-
tion of the [{S(C6H3CH2S)2O}Sn] tetracyclic moiety is very similar,
with the methylenic hydrogen atoms of the CH2-S-Sn fragment
located on endo and exo positions, a situation similar to that ob-
served in the NMR studies in solution (vide supra). The conforma-
tion of the eight-membered central rings in this series can be
described as boat, despite the different pendant ligands. On the
other hand, the conformation of the [{S(C6H3S)2O}Sn] moiety in
compounds 10 and 11 (8-R series) is totally different; the confor-
mation of the central ring in 10 can be described as boat-chair
meanwhile in 11 is described as boat-boat, very similar to what
is observed in the germanium and lead analog compounds
[10,13]. Secondly, with respect to the ligands attached to the tin
atom, the organic group is stacked directly above the aromatic sys-
tem of the phenoxathiin moiety in the organotin compounds 5 and
2.7426(19), (8); 3.002(3), (10); 2.4720(16) Å (11);
RrvdW (Sn,
O) = 3.69 Å] [30]; this short distance is usually related to the pres-
ence of secondary bonding [29].
From the analysis of the bond angles around the tin atom, it is
possible to see that the Oꢀ ꢀ ꢀSn interaction influences the tin local
geometry along the path from tetrahedral to trigonal bipyramidal
(tbp). In order to evaluate this displacement of geometry (tbp%),
the difference between the sum of the equatorial and axial angles
[
D
=
R
(h)equatorial
ꢁ
R(h)axial] was used [31]; the evaluation of the
magnitude of the Oꢀ ꢀ ꢀSn interaction was carried out from the Paul-
ing-type Bond Order (BO) based on interatomic distances [32,33].
The data are listed in Table 2. The local tin geometry in the chloro
compounds 7, 8 and 11 can be described as distorted tbp, whereas
in the diphenyl compounds 5 and 10 the geometry is best de-
scribed as tetrahedral. In general, the BO becomes smaller for the

8
D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
Table 2
Selected bond lengths (Å), angles (°), and structural parameters for heterocyclic compounds 5, 7,
8
(10-R series), 10 and 11 (8-R series) with general formula
8-R
[(S{C6H3(CH2)nS}2O)SnR1R2] (n = 1, 0).
10-R
5
1
7
1
8
1
10
0
11
0
n
R1
R2
Ph
Ph
Cl
n-Bu
Cl
Cl
Ph
Ph
Cl
n-Bu
Oꢀ ꢀ ꢀSn
3.281(4)
2.4107(18)
2.4144(17)
2.145(5)
2.146(5)
178.94(15)
70.89(16)
115.09(6)
108.9(2)
102.73(15)
114.14(15)
100.97(15)
113.33(16)
122.7(4)
101.4(2)
170.1
2.7560(13)
2.4108(5)
2.4032(5)
2.3645(5)
2.1331(19)
175.77(3)
77.76(6)
115.87(2)
102.49(6)
100.673(18)
119.45(6)
94.668(19)
116.91(5)
120.47(15)
99.95(9)
2.7426(19)
2.3617(8)
2.3621(9)
2.3399(8)
2.3360(8)
175.94(5)
76.72(5)
123.61(3)
99.26(3)
99.03(3)
113.96(3)
98.95(3)
115.07(3)
120.0(2)
99.62(16)
159.3
3.002(3)
2.4267(16)
2.4276(16)
2.120(5)
2.128(5)
150.42(16)
92.55(15)
119.10(6)
117.0(2)
103.98(16)
108.14(16)
101.69(16)
107.38(15)
117.6(4)
98.4(3)
2.4720(16)
2.4131(7)
2.4139(8)
2.3685(8)
2.127(3)
166.51(5)
87.03(9)
116.31(3)
106.29(8)
95.22(3)
115.89(10)
97.94(3)
119.13(9)
116.99(17)
98.64(11)
142.3
Sn–S1
Sn–S2
Sn–R1a
Sn–R2a
Oꢀ ꢀ ꢀSn–R1a
Oꢀ ꢀ ꢀSn–R2a
S1–Sn–S2
R1–Sn–R2a
S1–Sn–R1a
S1–Sn–R2a
S2–Sn–R1a
S2–Sn–R2a
C–O–C
C–S3–C
FAb
161.9
60.4
0.1353
145.0
13.3
0.0609
tbp%c
33.3
0.0246
61.6
0.1414
57.6
0.3403
BOd
a
b
c
R1 and R2 mean an atom directly attached to the central tin atom (v.gr. carbon in the phenyl group).
Folding angle between the two C6 aromatic planar rings of the phenoxathiin moiety.
tbp%: displacement from tetrahedral to trigonal bipyramidal local geometry at Sn; calculation according to the method of differences in angles
D
=
R
(h)equatorial
ꢁ
R(h)axial,
see text.
d
D
Pauling-type bond order: BO = 10ꢁ(1.41 d), where
D
d = (Oꢀ ꢀ ꢀSn)exp
ꢁ
Rrcov, according to the covalent radii sum Rrcov(Sn, O) = 2.14 Å.
7 (10-R series), with distances calculated from the centroid of the
O1–C7–C6–S3–C13–C14 six-membered ring to the C15 atom smal-
ler than 3.393 Å. By contrast, in the more rigid compounds 10 and
11 (8-R series) the organic ligands are far from the phenoxathiin
moiety.
A subtle difference in the conformations is the dihedral angle
between the rings of the phenoxathiin moiety. In the case of 5
the S(C6H3S)2O moiety is concave, with the phenyl group inside
the concavity and an Oꢀ ꢀ ꢀSn distance of 3.281(4) Å. For 7 the
moiety is convex, with a short Oꢀ ꢀ ꢀSn distance of 2.7560(13) Å.
The same convexity is observed in the dichloro compound with
the shortest Oꢀ ꢀ ꢀSn distance in the 10-R series. With respect to
the 8-R series, a similar situation is observed; for 10 the phenyl
group is inside the concavity whereas the n-butyl group is outside
in the compound 11.
observed in solid state. The results show that the functionals LSDA
and M06 reproduce better the molecular structure, matching with
the X-ray structures than others functionals (see the Supplemen-
tary material, Table 1S). For example, for the conformers of com-
pound 10, the energy difference is 0.36 kcal/mol for LSDA and
1.55 kcal/mol for M06 with the DGDZVP basis set; the same ten-
dency was observed when the optimization for all the systems
was performed with IEFPCM in chloroform as solvent. Moreover,
the total optimization of the conformers by LSDA and M06 but
using TZVP+RECP(Sn) basis set in the gaseous state as well as in
chloroform as solvent also reproduced the X-ray structure (see
Table 2S). The results indicated that LSDA and M06 functionals
with the DGDZVP or TZVP+RECP(Sn) basis set are more suitable
to describe the X-ray structure than any other functional, because
the largest energy difference between the conformers was ob-
served when greater basis sets were used. It was also observed that
the combination M06/TZVP+RECP(Sn) produced a smaller error
than other combinations in the chloroform solvent [(Error calcula-
tion = (Experimental data ꢁ calculated data)/Experimental data]
(See Supplementary material, Table 3S). Thus, the geometrical
parameters such as bond lengths and bond angles obtained
through M06/TZVP+RECP(Sn) employing IEFPCM in chloroform as
solvent were used to explain the molecular structures. The crystal
structure of compound 12 was not obtained; however, its theoret-
ical study was carried out for the sake of comparison. The confor-
mations for the compound 7 are showed in the Fig. 7 (see the
Supplementary material for the conformations of the other com-
pounds). For all compounds the most stable conformer agreed with
that observed in solid state; the relative differences between the
two most stable isomers are small. These small differences can ex-
plain the NMR data in solution for the compounds 7 and 11 where
a coordination number of four was proposed, a different situation
with respect to that observed in solid state where these com-
pounds displayed a coordination number of five because of the
electronegativity of the chloro group. Selected bond lengths and
angles for the optimized structures obtained from M06/
3.5. Theoretical studies of 5, 7, 8 (10-R), 10, 11, and 12 (8-R)
compounds
The conformational diversity of the compounds in the 8-R and
10-R series has been posed by the results of the NMR and single
crystal X-ray studies. For example, the most dramatic difference
in the conformation of the eight-membered central ring in the 8-
R series is displayed by the 10 and 11 compounds, where the for-
mer adopted a boat-chair conformation with a long transannular
Oꢀ ꢀ ꢀSn distance while 11 adopted a boat-boat conformation with
a significant Oꢀ ꢀ ꢀSn interaction. Thus, in order to study the confor-
mational preferences and the bonding situation, we performed a
molecular mechanics force field (MMFF) conformational search in
the selected compounds 5, 7, 8, 10, 11, and 12. For 5, 8, 10, and
12 there were found two conformers while for 7 and 11 were found
four (See the Supplementary material, Figs. 1S–6S). A structural
optimization was then performed for these conformers by using
several functionals (LSDA, BLYP, B3LYP, and M06) and DGDZVP
and TZVP basis set in gaseous phase to find out a suitable func-
tional to reproduce the overall structure of the compounds

D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
9
X-ray structure
Fig. 7. Conformations of compound 7 in gas phase (g) and in solvent (s); relative energies
DE for each phase are in kcal/mol (LSDA in blue and M06 in red, both with
TZVP+RECP(Sn) basis set).
TZVP+RECP(Sn) employing IEFPCM in chloroform are given in the
Table 4S of the supplementary material. The theoretical calcula-
tions at the level show that the distances and angles around the
Sn atom are in good agreement with the experimental structural
data; the Oꢀ ꢀ ꢀSn calculated distances are slightly longer than the
experimental ones. In the case of both 8-R and
10-R series, the folding of the phenoxathiin system as well as the
convexity calculated are also in good agreement with the dihedral
angles and relative positions of the pendant R ligands observed
experimentally.
4. Conclusion
In order to study the hypercoordination in heterocyclic tin com-
pounds we have synthesized, characterized and studied by theo-
retical calculations two series of compounds with general
formula [(S{C6H3(CH2)nS}2O)SnR1R2] (n = 1, 0). In the solid state,
the 10-R and 8-R chloro compounds 7, 8, and 11 displayed a dis-
torted tetrahedral local geometry at the Sn center, whereas the di-
phenyl compounds 5 and 10 displayed a distorted tetrahedral
geometry. In the 10-R series, the flexible ligand {S(C6H3CH2S)2O}2ꢁ
showed coordination modes similar to the (SnR1R2)2+ fragment
with different Oꢀ ꢀ ꢀSn distances depending on the Lewis acidity of
the Sn acceptor. On the other hand, the more rigid ligand
{S(C6H3S)2O}2ꢁ present in the 8-R series displayed bi- and a triden-
tate coordination modes toward Sn with different conformations.
In general, the distances and Pauling-type bond orders are smaller
for the eight-membered compounds when they are compared with
the ten-membered analog compounds; however, these larger rings
in the 10-R series can also form a transannular interaction by
adopting an adequate boat conformation. These findings were sup-
ported by the conformational study by MMFF and the optimization
of the structures with M06/TZVP+RECP(Sn) with calculations in
chloroform, and by the topological analysis, where the bonds
around the tin atom have an important ionic contribution.
For the optimized systems of the most stable conformers, the
bond critical points of the electron density (BCPs) and the gradient
paths were determined. The topological analysis of the electron
density is presented in Table 5S and 6S; the molecular graphs for
the compounds 5 and 7 are depicted in the Fig. 7S of the Supple-
mentary material. The molecular graphs show that the BCP’s are
present along with the Oꢀ ꢀ ꢀSn direction. The values of qc for the
interaction Oꢀ ꢀ ꢀSn range from 0.007 to 0.044 a.u. and the values
of
r
2qc are positive; in particular, the qc are the smaller when
the two pendant ligands are phenyl groups and they are larger as
the number of the chloro groups increases, supporting the experi-
mental data for the oxygen-tin distances observed in solid state by
means of the X-ray single crystal diffraction studies.
It is important to note that the L values of all bond critical points
connecting Sn with its neighbors are negative, ranging from
ꢁ0.005 to ꢁ0.036 a.u. where the Sn–S and Sn–R bonds have a very
important closed shell contribution. In addition, the parameters
Acknowledgments
such as ellipticity (e) and energy density Ed(r) for Sn and O atoms
were also calculated through a Bader’s theory point of view (see
Supplementary material, Tables 5S and 6S). The results showed
DMO and EJG fully acknowledge CONACYT for his fellowship.
This research was supported by CONACyT (Project 83157).
that for all cases
e
> 0,
q
(r) is small,
r
2q(r) > 0, and Ed(r) > 0; these
data suggest that the Oꢀ ꢀ ꢀSn interaction in the complexes corre-
sponds, in fact, to a typical closed-shell (electrostatic) interaction.
This situation is consistent with the Hirschfeld charge with a posi-
tive value for Sn (0.03–0.13) and a negative value for O (ꢁ0.09 to
ꢁ0.05), indicating that the presence of an ionic type of interaction
between Sn and O atoms. The analyses presented above allow us to
classify as intramolecular donor-acceptor compounds, in which Sn
acts as an acceptor and the oxygen atom as a donor.
Appendix A. Supplementary data
CCDC 862761, 862762, 862763, 862759, and 862760 contain the
supplementary crystallographic data for 5, 7, 8, 10, and 11. These
data can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.

10
D. Martínez-Otero et al. / Polyhedron 40 (2012) 1–10
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