Synthesis and spectral characterization of stannocanes of the type [O(CH2CH2S)2SnR2](R=Me1,Bu n2,Ph3)

Article abstract of DOI:10.2478/s11532-013-0250-3

The stannocanes of the type [O(CH₂CH₂S) ₂SnR₂](R=Me1,Buⁿ 2,Ph3) have been synthesized in an improved method by the reaction of R₂SnCl₂ with 2, 2′-oxydiethanethiol O(CH₂CH₂SH)₂ in molar ratio of 1:1 at the presence of sodium ethoxide in anhydrous ethanol. The reactions are carried out under inert atmosphere. These compounds have been extensively characterized by FT-IR, UV-Vis spectrophotometry, multi-nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, elemental analysis and mass spectrometry. The obtained data clearly indicates that, there is a strong interaction between oxygen atom of the ligand as a donor and Sn atom of the organotin species as a Lewis acid acceptor. Therefore, the resulted dithiostannocanes possess a transannular secondary bonding and hypervalency at the central Sn atom which leads to an increase in the coordination number of tin from four to five-coordinated tin. [Figure not available: see fulltext.]

Full text of DOI:10.2478/s11532-013-0250-3

Cent. Eur. J. Chem. • 11(7) • 2013 • 1248-1254
DOI: 10.2478/s11532-013-0250-3
Central European Journal of Chemistry
Synthesis and spectral characterization of
stannocanes of the type [O(CH2CH2S)2SnR2]
(R=Me1,Bun2,Ph3)
Research Article
Abbas Tarassoli*, Adibeh Kord
Department of Chemistry,
College of Science,
Shahid Chamran University,
61357-13655 Ahvaz, Iran
Received 26 September 2012; Accepted 30 March 2013
n
Abstract:
The stannocanes of the type [O(CH2CH2S)2SnR2](R=Me1,Bu 2,Ph3) have been synthesized in an improved method by the reaction
of R2SnCl2 with 2, 2’-oxydiethanethiol O(CH2CH2SH)2 in molar ratio of 1:1 at the presence of sodium ethoxide in anhydrous ethanol.
The reactions are carried out under inert atmosphere. These compounds have been extensively characterized by FT-IR, UV-Vis
spectrophotometry, multi-nuclear (1H, 13C, 119Sn) NMR, elemental analysis and mass spectrometry. The obtained data clearly indicates
that, there is a strong interaction between oxygen atom of the ligand as a donor and Sn atom of the organotin species as a Lewis acid
acceptor. Therefore, the resulted dithiostannocanes possess a transannular secondary bonding and hypervalency at the central Sn atom
which leads to an increase in the coordination number of tin from four to five-coordinated tin.
Keywords: Stannocanes • Transannular bondings • 2-2-oxydiethanethiol ligand • Organotin compounds • Spectral characterization
© Versita Sp. z o.o.
are best described by means of a three-center four-
electron interaction [7,8]. These rings possess a strong
1. Introduction
Metallocanesofthetype[X(CH2CH2S)2]MRR’(X=O,S,NR”; intramolecular interaction through the
as a Lewis
Sn
M=Ge, Sn) have been studied for a long time in order to acid acceptor and oxygen as a donor, leading to a
understand the nature of the intramolecular secondary transannular secondary bonding in stannocanes and
bonding and its relation with the so-called hypervalency subsequently an increase in the coordination number
group 14 elements [1,2]. Among the large number of of tin [2,9,10]. The factors that influence the strength of
structural reports of this group, stannocanes are the most transannular bonding and hypervalency at the central
widely and systematically investigated [3]. Dräger et al.
-atom in stannocanes have been studied [2,10].
Sn
[4-8] and Cea-Olivares et al. [1,3,9,10] have dealt with this The importance of this type of bonding have also been
research field for a long time. The stannocanes Cl2/Br2/ revised in metallocanes of type [X(CH2CH2Y)2MRR’]
I2-Sn(SCH2CH2)2O and Cl/Br/I/Me-(Me)Sn(SCH2CH2)2O and [X(CH2CH2Y)2M’R] (M=Ge(IV), Sn(IV) and Pb(IV);
have been prepared from (HSCH2CH2)2O with SnHal4 or M’=As(III), Sb(III) and Bi(III); X=NR’’,O, S; Y=O, S [3].
MeSnHal3, respectively [2,4,6,7]. In these compounds Once again, the transannular interaction is observed
the conformation preference is the formation of an between the X (donor group) and M, a situation that leads
eight-membered ring and comprise of molecules in to an increase in the coordination number of M. The spiro-
which the Sn-atom approaches a trigonal-bipyramidal bis(oxadithiastannocane)
[Sn(SCH2CH2OCH2CH2S)2]
penta-coordination with two sulfur-atoms and Hal(eq) is also prepared from O(CH2CH2SNa)2 and SnCl4 and
as equatorial ligands and with oxygen-atom and Hal(ax) its molecular structure have been studied [9]. In this
as axial ligands [7]. Therefore O….Sn….Hal(ax) bond compound the
secondary bond distance in the
Sn...O
* E-mail: tarassoli@scu.ac.ir
1248

A. Tarassoli, A. Kord
observed eight – membered ring is larger than distances beam GBC model Cintra 101 spectrophotometer in
found in the related monocyclic diorgano stannocances CHCl3 as a solvent. The mass spectra determinations
[2,4]. Since the tin compounds which most often used of these compounds were performed on a Shimadzu
for the synthesis of the above stannocanes were either spectrometer model GCMS-QP 1000 EX.
tin tetrachloride or monoorganotin halides, we decided
to employ diorganotin dichloride instead to see the 2.2. Synthesis of [O(CH2CH2S)2SnMe2] (1)
possible effect of the replacement of chlorine atoms in To a stirring solution of 2.2-oxydiethanethiol (0.138 g,
4 by two alkyl groups. Moreover, to the best of our 1 mmol) in 40 mL of dry benzene under N2(g) atmosphere.
SnCl
knowledge it seems that the dibutyl derivative of the 0.136 g (2 mmol) of sodium ethoxide solution in ethanol
thiastannocanes (2) which is reported here is a new was slowly added. Then dimethyltin dichloride (0.219 g,
compound. In addition, in the case of the stannocanes (1) 1 mmol) dissolved in 10 mL of dry benzene was added
and (3), the employed base in our experiments is sodium dropwise to the above mixture at room temperature and
ethoxide in anhydrous ethanol which is also different was stirred for another 10 h at refluxing temperature
from the most reported procedures [2,3]. Therefore, to (70-75°C) under nitrogen atmosphere. After cooling
continue our study of ligands containing S-reactive sites and filtering the colorless solid (NaCl), the solvent
and their reactions towards organotin halides [11-17] was removed on a rotary evaporator in vacuo and the
and considering additional importance due to already resulting white solid was washed with n-hexane and
established biological effects of organotin complexes dried under vacuum. Yield 85%, m.p. 192ºC, Anal. Calc.
[18-21], the interaction between 2,2-oxydiethanethiol for C6H14OS2Sn(%): C, 25.26; H, 4.95. Found:C, 25.18;
(HSCH2CH2)2O, and R2SnCl2(R=Me, Bun, Ph) (in H, 4.91. IR(KBr, Cm-1): ν (C-H)2917, 2875, δ CH2-S
the presence of sodium ethoxide) is investigated 662, νas,sC-O-C1050-985, ν Sn-C(eq) 536, ν Sn-C(ax) 516,
1
here. Dialkyl-1-oxa-4,6-dithiastannocanes such as ν Sn-S(eq) <400. H NMR (δ, ppm, CDCl3): 3.54 (t, 4H,
[O(CH2CH2S)2SnMe2] (1), [O(CH2CH2S)2SnBun2] (2) and CH2-O), 2.84 (t, 4H, CH2-S), 0.54 (s, 3H, CH3(ax)), 0.71(s,
[O(CH2CH2S)2SnPh2] (3) are synthesized and reported. 3H, CH3(eq)). 13C{1H} NMR (δ, ppm, CDCl3): 27.9 (CH2-S),
These compounds have been fully characterized by 72.1(CH2-O) [2J(117/119Sn-13C) 20.2 and 3J(117/119Sn-13C)
using elemental analysis, IR, UV-Vis, multinuclear 14.1 Hz], 0.9 (CH3(ax)), 1.1 CH3(eq). 119Sn NMR (δ, ppm,
(1H, 13C, 119Sn) NMR spectroscopy, as well as mass CDCl3): -91.2. Ms: m/z, 275, 273, 271, 269, 267, 266, 265,
spectrometry. The formation of eight-membered rings 263, 213, 211, 209, 197, 195, 193, 167, 165, 163, 150,
and transannular secondary bonding at the central tin 149, 148, 137, 135, 133, 120, 118, 116, 61, 60, 59, 58, 57,
atom will also be discussed on the basis of the obtained 47, 46, 45, 43, 28, 27, 26,15. UV-Vis (λmax nm): 231.
spectroscopic data.
2.3. Synthesis of [O(CH2CH2S)2SnBu2n] (2)
The synthesis procedure was almost the same as (1)
2. Experimental procedure
in section 2.2 and the resulting product was obtained
in a similar way. A solution of di-n-butyltin dichloride
2.1. Materials and instrumentation
(0.303g,
1 mmol) in benzene (45 mL) was slowly
(0.138 g,
All experiments requiring inert atmosphere were carried added to a solution of 2.2-oxydiethanethiol
out in N2-flushed glove bags or standard Schlenk 1 mmol) in 20 mL dry benzene which contained sodium
apparatus. All solvents, sodium ethoxide, dimethyltin ethoxide in ethanol (0.136 g, 2 mmol) to afford a white
o
dichloride, dibutyltin dichloride and O(CH2CH2SH)2 were solid product. Yield 82%, m.p.215 C Anal. Calc. for
purchased from Merck, and diphenyltin dichloride was C12H26OS2Sn(%):C, 39.02: H, 7.10. Found: C, 39.11; H,
purchased from Acros company. The FT-IR spectra 7.04. IR(KBr, Cm-1): ν (C-H) 2955, 2921, 2854, ν CH2-S
were recorded using KBr- pellets in the range of 4000- 400, νas,sC-O-C1060-980, ν Sn-C(eq) 593, ν Sn-C(ax) 665,
1
400cm-1 on Bomen FT-IR spectrophotometer. NMR ν Sn-S(eq) <400. H NMR (δ, ppm, CDCl3): 3.56 (t, 4H,
spectra were obtained on a Bruker Avance 400MHz CH2-O), 2.87 (t, 4H, CH2-S), [1.2(Hα), 1.5(Hβ), 1.3(Hγ),
at ambient temperature. H NMR (400.13 MHz) and 0.8(Hδ)] Bunax, or Buneq
,
13C{1H} NMR (δ, ppm, CDCl3):
1
13C NMR (100.61MHz) were recorded using CDCl3 as 27.8 (CH2-S), 71.1(CH2-O) [2J(117/119Sn-13C) 21.5 and
solvent with TMS as an external reference. 119Sn NMR 3J(117/119Sn-13C) 16.8 Hz], [12(Cα), 17(Cβ), 24(Cγ), 27(Cδ)]
spectra were recorded at 149.21 MHz in CDCl3 with Bunax [14(Cα), 19(Cβ), 26(Cγ), 28(Cδ)] Buneq
.
119Sn NMR
SnMe4 as an external reference. Elemental analysis (δ, ppm, CDCl3): -95.5. Ms: m/z, 317, 315, 313, 311,
(C and H) were performed by the microanalytical 309, 257, 256, 255, 253, 251, 201, 199, 197, 195, 193,
service of the N.I.O.C. Research Institute of Petroleum 152, 151, 149, 60, 47, 46, 45, 44, 41, 29. UV-Vis (λmax
Industry. The UV-Vis spectra were recorded on double nm): 209.
1249

Synthesis and spectral characterization of stannocanes
of the type [O(CH2CH2S)2SnR2](R=Me1,Bun2,Ph3)
Scheme 1. The reaction procedure for the production of the stannocanes (1), (2) and (3).
This method is a convenient approach to the
synthesis of diorgano-derivaties of thiastannocanes;
O(CH2CH2S)2SnMe2 (1), O(CH2CH2S)2SnBun2 (2) and
O(CH2CH2S)2SnPh2 (3). It should be mentioned that
this method is a modified procedure with a higher
yield than previously reported [3-10]. The proposed
structures of (1) to (3) are illustrated in Fig. 1, and are
in a good agreement with those reported earlier. As it
is mentioned in the introduction section, this kind of
eight-membered rings containing transannular
Sn.....O
secondary interaction structures are well known for the
thiastannocanes and are suggested by a considerable
number of authors working in this field [3-10]. The
compounds (1-3) were fully characterized by UV-Vis,
FT-IR, mass spectrometry and multinuclear (1H, 13C,
119Sn) NMR spectroscopy, as well as elemental analysis.
Spectroscopic data are discussed and interpreted below
and the most significant FT-IR bands; (1H, 13C, and 119Sn)
NMR signals are summarized in Table 1.
Figure 1. The structure of stannocanes of the type O(CH2CH2S)2SnR2
(R=Me1, Bun2, Ph3).
2.4. Synthesis of [O(CH2CH2S)2SnPh2] (3)
The same method as (1) and (2) was also used to
obtain (3). A solution of diphenyltin dichloride (0.343 g,
1 mmol) in dry benzene (45 mL) was gradually added
to a solution of 2.2-oxydiethanethiol (0.138 g, 1 mmol) 3.1. IR spectra
in 10 mL of dry benzene containing sodium ethoxide in The IR spectra of (1) and (2) show the (C-H)aliphatic
anhydrous ethanol (0.136 g, 2 mmol) to obtain a white stretching absorptions at 2917, 2875 and 2955, 2921,
solid product. Yield 87%, m.p. 126°C , Anal. Calc. for 2854, respectively. The absorption bands which are
C16H18OS2Sn(%): C,46.95; H, 4.43. Found: C, 46.87; H, seen in the region 1060-985 cm-1 are characteristic of
4.35. IR(KBr, Cm-1): ν (C-H) 3060, 2865, ν CH2-S 658, symmetrical and asymmetrical stretching vibrations
ν
as,sC-O-C1055-990, ν Sn-C(eq), ν Sn-C(ax), ν Sn-S(eq) for, C-O-C group in stannocanes. In these compounds
<400. 1H NMR (δ, ppm, CDCl3): 3.61 (t, 4H, CH2-O), 2.92 the absorption band of the S-H group is eliminated
(t, 4H, CH2-S), [3.6(H1), 7.5(H2,6), 7.3(H3,5), 7.2(H4)] Phax, indicating that the O(CH2CH2SH)2 is coordinated to
[3.8(H1), 7.9(H2,6), 7.5(H3,5), 7.3(H4)] Pheq, 13C{1H} NMR Sn as an anionic ligand. The bands at 662, 665, and
(δ, ppm, CDCl3): 28.1 (CH2-S), 71.5(CH2-O) [2J(117/119Sn- 658 cm-1 are corresponding to
groups in (1),
CH2 − S
13C) 18.4.2 and 3J(117/119Sn-13C) 14.7 Hz], 129-135 {[(C1), (2) and (3) respectively. The IR spectra of compound (1)
(C2,6), (C3,5), (C4)] Phax and [(C1), (C2,6), (C3,5), (C4)] Pheq}. clearly exhibits absorption bands for Sn-C(ax) and Sn-C(eq)
119Sn NMR (δ, ppm, CDCl3): -108.7. Ms: m/z, 337, 335, at 516 and 536, respectively and Sn-C(ax) and Sn-C(eq) for
333, 332, 331, 330, 274, 272, 271, 270, 232, 230, 229, (2) are seen at 593 and 665 cm-1 respectively. In these
227, 225, 224, 222, 197, 195, 193, 154, 153, 152, 151, compounds due to the nucleophilic attack of oxygen
137, 136, 135, 78, 77, 76, 62, 61, 60, 59, 58, 57. UV-Vis donor atom at the tin central atom, the bond length of
(λmax nm): 252.
the axial groups increase while the bond length of the
equatorial groups slightly decrease. This leads to an
elongation of the axial bonds and consequently result in a
shift of the corresponding stretching vibrations ν(Sn-Rax)
to lower energy compared to ν(Sn-Raq). The absorption
bands at 3060 and 2865 cm-1 in (3) are belong to (C-H)
aromatic and (C-H)aliphatic, respectively (Table 1).
3. Results and discussion
The reactions of diorganotin dichloride R2SnCl2 (R; Me1,
Bun2, Ph3) with 2,2-oxydiethanethiol were conducted in
dry benzene in a 1:1 stochiometric ratio in the presence
of sodium ethoxide in anhydrous ethanol and an inert
atmosphere for all the compounds (1) to (3). The
synthesis procedure was shown in Scheme 1.
3.2. 1H NMR spectra
1
The H NMR spectra of (1), (2) and (3) clearly exhibit
signals for the protons of
groups at δ 3.54, 3.56
CH2 − O
1250

A. Tarassoli, A. Kord
Table 1. Selected spectroscopic results for the stannocanes (1) to (3).
O(CH2CH2S)2SnR2
R= Bun(2)
Assignment
R= Me(1)
R= Ph(3)
(a) IR Data (ν, cm-1)
(CH2-O)
(CH2-S)
(C-H)
1050-985
662
1060-980
665
1055-990
658
2917, 2875
516
2955, 2921, 2854
3060(Ar), 2865
(Sn-Cax
)
593
665
-
-
(Sn-Ceq
)
536
(b) 1H NMR Data (δ, ppm)
CH2-O
CH2-S
Sn-CH3
3.45
2.84
3.56
3.61
2.87
2.92
0.54, 0.71
-
-
-
-
Sn-αCH2-βCH2-γCH2-δCH3
1.2(α),1.5(β),1.3(γ),0.8(δ)
2
3
3.6(H1),7.5(H2,6)7.3(H3,5),7
.2(H2)
Sn
4
-
1
6
5
(c) 13C NMR Data (δ, ppm)
CH2-O
CH2-S
Sn-CH3
72.1
27.9
71.1
27.8
-
71.5
28.1
-
0.9, 1.1
14, 19, 26, 28
12, 17, 24, 27
Sn-αCH2-βCH2-γCH2-δCH3
-
-
2
3
Sn
4
-
-
129-135
1
6
5
(d) 119Sn NMR Data (δ, ppm)
-95.5
119Sn
-91.2
-108.7
Note: NMR data for the starting ligand O(CH2CH2SH)2: δ(1H); (CH2-O)=3.51(t), (CH2-S)=2.62(doublet of triplet); (SH)=2.10(t). δ(13C); (CH2-S)=24.1,
(CH2-O)=72.2 ppm.
and 3.61 ppm respectively (Table 1). These chemical equatorial position of methyl groups and are assigned
shifts are almost identical to those measured for CH2-O to the Me(ax) and Me(eq), respectively. A similar situation is
1
moieties in O(CH2CH2SH)2 at 3.51 ppm. The H NMR also seen for butyl- and phenyl-groups in compounds (2)
signals at δ 2.84, 2.87 and 2.92 are related to the CH2-S and (3); however, in these compounds exact values of
groups in (1), (2) and (3) respectively. These signals are chemical shifts for different protons in two groups cannot
shifted down field in comparison to the protons of CH2-S be easily extracted due to the complexity of multiplets.
groups in the free ligand, which appears at δ 2.62 ppm It seems that the alkyl or the aryl groups in the axial
due to coordination and subsequently formation of an position are much more shielded than the equatorial
1
eight–membered ring. In H NMR spectrum of (1), two ones in the approach of the oxygen donor atom to the
singlets are seen for the methyl groups at δ 0.54 and central tin atom (see Table 1).
0.71 ppm. This should be related to the axial and
1251

Synthesis and spectral characterization of stannocanes
of the type [O(CH2CH2S)2SnR2](R=Me1,Bun2,Ph3)
3.3. 13C NMR spectra
interaction in (1), (2) and (3) is responsible
Sn ← O
As expected, the 13C NMR spectra exhibit two signals for increasing the coordination number in these
for the eight –membered ring which belong to CH2-O stannocanes and thus, confirming the presence of the
and CH2-S groups in each compound. These signals secondary intramolecular bonding.
are at δ 72.1 and 27.9 for (1); 71.1 and 27.8 for (2);
71.5 and 28.1 ppm for (3); in CH2-O and CH2-S groups, 3.5 UV-Vis spectra
respectively. The 13C chemical shift value for CH2-O The n → σ* absorption band of O(CH2CH2SH)2
groups are almost the same as the chemical shift for appeared at λmax 198nm. This absorption is shifted and
CH2-O group in the ligand (72.2ppm), while the carbon broadened and is seen at λmax/nm (log e ): 231 (3.62),
signals belongs to CH2-S in these compounds are 209 (3.48), 252 ( 3.21) for the compounds (1), (2) and
shifted towards down field in comparison to the free (3) respectively.
ligand which appears at 24.1 ppm. These observations
indicate that the coordination is taken place between 3.6 Mass spectra
sulfur and tin atom. In 13C NMR spectrum of (1), two 13
C
The mass spectrum of (1) shows expected peaks at
signals appeared for methyl groups at 0.9 and 1.1 ppm, m/z 275, 273, 271, 269, 267, 266, 265, 263 which are
indicating that the two methyl groups are non-equivalent. attributable to (M.+-Me 100%) or [O(CH2CH2S)2SnMe].+
This should be related to the axial (Me(ax) 0.9ppm) and with 124Sn, 122Sn, 120Sn, 119Sn, 118Sn, 117Sn, 116Sn and 112Sn
the equatorial (Me(eq) 1.1ppm) position of methyl groups. isotopes, respectively. It should be noted that the tin
There is a link between the chemical shifts and electron atom has ten naturally occurring isotopes which eight
densities on the carbon atoms. It seems that the carbon of them have the relative abundance more than 0.95%.
115 Sn
114 Sn
are
atoms in the axial positions are much more shielded that The natural relative abundance of
and
the equatorial carbon atoms.
0.34% and 0.65%, respectively [22,23]. This quasi ion is
In 13C NMR spectrum of (2) two sets of 13C signals consistent with the structure proposed for (1) on the basis
are also seen for butyl groups and each set compose of other spectroscopic data [24]. The mass spectrum of
of four signals, indicating that the two butyl groups (1) also exhibits peaks at m/z 213 (Me2120SnS2)+ 45%,
are not equivalent. It seems that the signals at 12(Cα), 211(Me2118SnS2)+ 85%, and 209 (Me2116SnS2)+ 70%
17(Cβ), 24(Cγ) and 27(Cδ) are corresponding to the butyl which indicates the formation of S-Sn-S bonds. The
group at the axial position and the signals at 14(Cα), spectrum of (1) clearly shows a number of important
19(Cβ), 26(Cγ) and 28(Cδ) belong to the butyl at the fragments at m/z 197,195,193 for (MeSnS2)+ 30%, 167,
equatorial position. In 13C NMR spectrum of (3), 13C 165, 163 for (MeSnS)+ 42%, 150, 149, 143 for (SnS)+
signals for phenyl groups are appear in the range of δ 38%, , 137, 135, 133 for (MeSn)+ 70% and 120, 118, 116
129-135 ppm. These signals can be assigned for either for Sn+. The mass spectrum of (1) exhibits peaks at m/z
axial or equatorial position and the exact chemical 61, 60, 59, 58, 57 which belong to (S-CH2- CH2)+ 65%
shift can not be extracted due to complexity of signals and peaks at m/z 47, 46, 45, 43 which is attributable to
(Table 1).
fragments such as (CH2- O-CH2)+.
The mass spectrum of (2) exhibits expected quasi-
ion peaks at m/z 317, 315, 313, 311 and 309 which is
3.4. 119Sn NMR spectra
The 119Sn NMR spectra of the stannocanes (1), (2) attributable to (M.+-Bun 100%) or [O(CH2CH2S)2SnBu].+
and (3) in CDCl3 exhibit signals as singlets at -91.2, with 124Sn, 122Sn, 120Sn, 118Sn, and 116Sn isotopes,
-95.5 and -108.7 ppm respectively. These resonances respectively. The peaks at m/z 257, 256, 255, 253 and
appear significantly at higher magnetic field than those 251 are related to the [OSn(CH2CH2S)2]+ 42% with
of the organotin halides precursors [MeSnCl2, δ+137, the isotopes of 124Sn, 122Sn, 120Sn, 118Sn, and 116Sn.
Bun2SnCl2 δ+123 and Ph2SnCl2, δ-27] [22,23], partly The peaks at m/z 201, 199, 197, 195 and 193 belong
due to the elimination of the halogen withdrawing to [SnS2-CH2]+ 22% with 124Sn, 122Sn, 120Sn, 119Sn, and
groups and mainly because of increasing coordination 116Sn, respectively. These fragments clearly indicate the
number. It should also be noted that the 119Sn chemical coordination of tin and the formation of S-Sn-S bonds.
shift is strongly dependent on the coordination number The peaks at m/z 152, 151, 149 and 148 are attributable
of tin and an increase in the coordination number to S120Sn, S119Sn, S117Sn and S116Sn, respectively. In the
produces large upfield shifts. These chemical shifts spectrum of (2), [S-CH2CH2]+ fragment is seen at m/z
which are observed in the 119Sn NMR spectra of (1), (2) 60, and a (CH2-O-CH2)+ fragment at m/z 46, 45 and 44.
and (3) in comparison with those values reported for Finally, the butyl group and its fragmentations are also
similar organotin compounds are consisted with a five seen at m/z 57 (C4H9+), 41(C3H5+), 29 (C2H5+) and 15
coordinated tin atom. It seems that the transannular (CH3+).
1252

A. Tarassoli, A. Kord
The mass spectrum of (3) shows Sn-containing agreement with the assumed transannular secondary
fragments (124Sn-115Sn) at m/z 337, 335, 333, 332, 331, bonding at Sn atom and the formation of an eight-
330, attributable to [O(CH2CH2S)SnPh]+ 98% which is membered ring such as proposed structure shown
the molecular ion after eliminating one phenyl group. in the Fig. 1. It should be noted that the nature of the
This spectrum also exhibits peaks at m/z 274, 272, 271 substituents at
atom and their positions play an
Sn
and 270 which belong to [Ph2Sn]+ 35% with 120Sn, 118Sn, important role in the formation of O….Sn…R(axial) bond,
117Sn, 116Sn isotopes. The peaks at m/z 232, 230, 229, because, their influence depends on, whether if they are
227, 225, 224 and 224 are due to [SnS(CH2CH2)2O]+ equatorial or axial substituents. It is worth to note that
32% with 122Sn-116Sn 54%. The peaks at m/z 197, 195, the O-Sn-R bond is preserved in solution because the
193 are corresponding to Ph120Sn 42%, Ph118Sn 55% 119Sn NMR clearly shows the increase in the coordination
1
and Ph116Sn 35%,
respectively. The spectrum of (3) number of tin and H and 13C NMR spectra exhibit two
also shows Sn-containing fragments at m/z 154, 153, groups instead of one in the form of two singlets. Finally
152, 151 for (SnS)+ 26%. The peaks at m/z 137, 136, the mass and IR spectra data supports the presence
135 belong to O(CH2CH2S)+ 45%.
of the transannular secondary bonding also in the solid
state.
4. Conclusion
Acknowledgements
The stannocanes (1), (2) and (3) have been prepared
in an improved method and fully characterized by the The authors wish to thank the Shahid Chamran
various spectroscopic techniques. All the experimental University, Research Council for financial support of this
results and the spectroscopic data are in an excellent project (Grant 1391).
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