Syntheses, crystal structure, spectroscopic characterization and antifungal activity of novel dibutylbis(N-R-sulfonyldithiocarbimato)stannate(IV) complexes

Article abstract of DOI:10.1016/j.poly.2012.08.037

Five new complexes of the general formula: (Ph₄P) ₂[Sn(Bu)₂(RSO₂NCS₂)₂], where Ph₄P = tetraphenylphosphonium cation, Bu = n-butyl and R = C₆H₅ (1), 4-FC

Full text of DOI:10.1016/j.poly.2012.08.037

Polyhedron 47 (2012) 30–36
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses, crystal structure, spectroscopic characterization and antifungal
activity of novel dibutylbis(N-R-sulfonyldithiocarbimato)stannate(IV) complexes
Letícia C. Dias a, Mayura M.M. Rubinger a, João P. Barolli a, José D. Ardisson b, Isolda C. Mendes c,
Geraldo M. de Lima c, Laércio Zambolim d, Marcelo R.L. Oliveira a,
⇑
a Departamento de Química, Universidade Federal de Viçosa, Viçosa MG, CEP 36570-000, Brazil
b Laboratório de Física Aplicada, Centro de Desenvolvimento de Tecnologia Nuclear, CDTN-CNEN, Belo Horizonte MG, CEP 31270-901, Brazil
c Departamento de Química, Universidade Federal de Minas Gerais, Belo Horizonte MG, CEP 31270-901, Brazil
d Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa MG, CEP 36570-000, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Five new complexes of the general formula: (Ph4P)2[Sn(Bu)2(RSO2N@CS2)2], where Ph4P = tetraphenyl-
phosphonium cation, Bu = n-butyl and R = C6H5 (1), 4-FC6H4 (2), 4-ClC6H4 (3), 4-BrC6H4 (4), 4-IC6H4 (5)
were obtained by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimates K2(RSO2
N@CS2) and tetraphenylphosphonium chloride with di-n-butyltin dichloride. The compounds 1–5 were
characterized by multinuclear NMR (1H, 13C{1H} and 119Sn{1H}), 119Sn Mössbauer and vibrational spec-
troscopies. The crystal structures of 1 and 2 were determined by X-ray diffraction techniques. The
in vitro antifungal activity of the tin(IV) complexes was evaluated against Colletotrichum gloeosporioides
by the Poisoned food test. All compounds were active and complex 2 displayed the best result, presenting
Received 28 June 2012
Accepted 15 August 2012
Available online 30 August 2012
Keywords:
Dithiocarbimates
Tin(IV) organometallic complexes
Structure determination
Antifungal activity
an IC50 of 6.2 lM.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
The compounds here studied are the first examples of com-
plexes of organotin with dithiocarbimato ligands. The use of such
anionic compounds shall provide an interesting possibility of mod-
ulation of the above mentioned applications. For example, the
improvement of the antifungal activity should be possible either
by the use of active counter ions, or by the variation on the solubil-
ity of the salts of the complexes due to the use of different cations.
The antifungal activity of the new compounds was evaluated
against C. gloeosporioides, the causal agent of anthracnose, the main
post-harvest disease of papaya [12]. It also affects humans, causing
ocular keratomycosis [13].
Dithiocarbamate (R2NCS2À) complexes are worldwide used as
agrochemicals due to their low acute toxicity, strong activity and
low cost of production [1]. Organotin compounds also present
important biological activities being antiviral, anticancer, antibac-
terial and antifungal agents [2–7]. Further, the literature reports
that dithiocarbamato-tin(IV)-complexes showed good activity
against the fungus Candida albicans [8,9].
Dithiocarbimate (RN@CS22À) complexes are less common in the
literature than the dithiocarbamates. Our interest in the syntheses
of tin(IV) complexes with dithiocarbimates is due to their similar-
ities with the dithiocarbamato analogues, and to the recently
discovered antifungal activity of sulfonyldithiocarbimato-zinc
complexes against Colletotrichum gloeosporioides [10,11].
Here we describe the syntheses of five tetraphenylphospho-
nium salts of anionic dithiocarbimate-tin(IV) complexes with the
general formula [Sn(Bu)2(RSO2N@CS2)2]2À where Bu = n-butyl and
R = C6H5 (1), 4-FC6H4 (2), 4-ClC6H4 (3), 4-BrC6H4 (4), 4-IC6H4 (5).
The new compounds 1–5 were characterized by elemental analy-
ses, 1H, 13C and 119Sn NMR, 119Sn Mössbauer and vibrational spec-
troscopy. Structural studies by X-ray diffraction on compounds 1
and 2 are also reported.
2. Experimental
2.1. Materials and methods
Concentrated ammonia aqueous solution, carbon disulfide,
potassium hydroxide and dimethylformamide were purchased
from Vetec and were used as supplied. The 4-fluorobenzenesulfona-
mide, 4-chlorobenzenesulfonamide, 4-bromobenzenesulfonamide,
tetraphenylphosphonium chloride and di-n-butyltin dichloride
were purchased from Alfa Aesar. Benzenesulfonamide was acquired
from Aldrich. The 4-iodobenzenesulfonamide was prepared from
the 4-iodobenzenesulfonyl chloride with concentrated ammonia
aqueous solution, according to the methodology applied for the syn-
theses of similar compounds [14]. The N-R-sulfonyldithiocarbimate
⇑
Corresponding author. Tel.: +55 31 3899 3059; fax: +55 31 3899 3065.
E-mail address: marcelor@ufv.br (M.R.L. Oliveira).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.08.037

L.C. Dias et al. / Polyhedron 47 (2012) 30–36
31
potassium salts dihydrate were prepared in dimethylformamide
from the sulfonamides using procedures described in the literature
for analogous compounds [15]. These salts are soluble in water and
insoluble in most of the organic solvents. Melting points (mp) were
determined with a Mettler FPS equipment and are reported without
correction. The IR spectra were recorded with a Perkin-Elmer 283B
infrared spectrophotometer using CsI pellets. Microanalyses of C, H
and N were obtained from a Perkin-Elmer 2400 CHN Elemental Ana-
lyzer. The 1H (300 MHz) and 13C (75 MHz) NMR spectra were re-
corded with a Varian Mercury 300 spectrophotometer in CDCl3
with TMS as internal standard and the 119Sn (75 MHz) NMR spectra
were recorded with a Bruker Avance DPX 200 spectrophotometer in
CDCl3. The values were referenced to internal SnMe4. 119Sn
Mössbauer measurements were performed on a conventional appa-
ratus with the samples at 78 K and a CaSnO3 source kept at room
temperature.
968
m
as(CS2) and 343
m
(SnS). 1H NMR (d, CDCl3): 7.98–7.93 (m,
4H, H2, H6), 6.91 (t, 4H, J = 8.7 Hz, H3, H5), 1.77–1.35 (m, 8H, H8,
H9), 1.21–1.07 (m, 4H, H10), 0.66 (t, 6H, H11). 13C{1H} NMR (d,
CDCl3): 209.21 (C7), 139.46 (C1), 130.63 (C2, C6), 114.08 (C3, C5,
d, J = 22.4 Hz), 163.77 (C4, d, J = 247.9 Hz), 28.20 (C8), 27.21 (C9),
26.67 (C10), 13.83 (C11). 119Sn{1H} NMR (d, CDCl3): 128.3,
À170.7, À220.0. 119Sn Mössbauer: d = 1.48,
D = 2.64, C = 0.86
mm sÀ1
.
(Ph4P)2[Sn(Bu)2(4-ClC6H4SO2N@CS2)2] (3): Elemental analysis:
Anal. Calc. for C70H66Cl2N2O4P2S6Sn: C, 58.25; H, 4.61; N, 1.94.
Found: C, 57.01; H, 4.77; N, 1.85%. Mp (°C): 106.1–107.9 IR (se-
lected bands) (cmÀ1): 1316
955 as(CS2) and 342
m
(C@N); 1273
mas(SO2); 1142 ms(SO2);
m
m
(SnS). 1H NMR (d, CDCl3): 7.91 (d, 4H,
J = 1.2 Hz, H2, H6), 7.25 (d, 4H, J = 9.3 Hz, H3, H5), 1.71–1.35 (m,
8H, H8, H9), 1.28–1.14 (m, 4H, H10), 0.72 (t, 6H, J = 7.2 Hz, H11).
13C{1H} NMR (d, CDCl3): 209.44 (C7), 142.05 (C1), 129.77 (C2,
C6), 127.33 (C3, C5), 135.97 (C4), 28.18 (C8), 27.20 (C9), 26.66
(C10), 13.81 (C11). 119Sn{1H} NMR (d, CDCl3): 128.7, À219.1.
For the biological tests, C. gloeosporioides were isolated from in-
fected banana fruits and incubated for 12 days at 25 °C. Streptomy-
cin sulfate was purchased from Sigma. The culture medium PDA
(Potato Dextrose Agar) was purchased from Oxoid and was previ-
ously sterilized in autoclave for 25 min at 121 °C. Glassware and
spatulas were sterilized at 150 °C for 3 h.
119Sn Mössbauer: d = 1.48,
D = 2.54, C .
= 0.89 mm sÀ1
(Ph4P)2[Sn(Bu)2(4-BrC6H4SO2N@CS2)2] (4): Elemental analysis:
Anal. Calc. for C70H66Br2N2O4P2S6Sn: C, 54.87; H, 4.34; N, 1.83.
Found: C, 53.38; H, 4.16; N, 1.82%. Mp (°C): 123.7–124.9. IR (se-
lected bands) (cmÀ1): 1313
953 as(CS2) and 339
m
(C@N); 1273
mas(SO2); 1141 ms(SO2);
m
m
(SnS). 1H NMR (d, CDCl3): 7.89–7.83 (m,
2.2. Syntheses
4H, H2, H6), 7.35 (d, 4H, J = 8.4 Hz, H3, H5), 1.85–1.35 (m, 8H,
H8, H9), 1.16–1.11 (m, 4H, H10), 0.66 (t, 6H, J = 7.2 Hz, H11).
13C{1H} NMR (d, CDCl3): 209.76 (C7), 142.85 (C1), 130.27 (C2,
C6), 130.57 (C3, C5), 124.83 (C4), 28.46 (C8), 27.50 (C9), 26.94
(C10), 14.10 (C11). 119Sn{1H} NMR (d, CDCl3): 128.9, À218.7.
The syntheses of the tin(IV) N-R-sulfonyldithiocarbimate com-
plexes were performed according to the Scheme 1. Di-n-butyltin
dichloride (1.0 mmol) was added to a solution of the appropriated
potassium N-R-sulfonyldithiocarbimato dihydrate (2.0 mmol) in
water/dimethylformamide 1:1 (10 mL). Tetraphenylphosphonium
chloride (2.0 mmol) was added and the mixture was stirred for
1.5 h at room temperature. The white solid thus obtained was fil-
tered, washed with distilled water and dried under reduced pres-
sure, yielding (Ph4P)2[Sn(Bu)2(RSO2N@CS2)2] (80–99%). Single
white crystals of 1 and 2 suitable for X-ray structure analyses were
obtained after slow evaporation of the solutions of the compounds
in hot acetone/water 3:1. The compound 2 was monohydrated.
(Ph4P)2[Sn(Bu)2(C6H5SO2N@CS2)2] (1): Elemental analysis: Anal.
Calc. for C70H68N2O4P2S6Sn: C, 61.17; H, 4.99; N, 2.04. Found: C,
61.06; H, 4.95; N, 1.96%. Mp (°C): 129.8–130.7. IR (selected bands)
119Sn Mössbauer: d = 1.48,
D = 2.63, C .
= 0.85 mm sÀ1
(Ph4P)2[Sn(Bu)2(4-IC6H4SO2N@CS2)2] (5): Elemental analysis:
Anal. Calc. for C70H66I2N2O4P2S6Sn: C, 51.70; H, 4.09; N, 1.72.
Found: C, 49.30; H, 3.89; N, 1.76%. Mp (°C): 121.2–122.9. IR (se-
lected bands) (cmÀ1): 1306
964 as(CS2) and 336
m
(C@N); 1268
mas(SO2); 1144 ms(SO2);
m
m
(SnS). 1H NMR (d, CDCl3): 7.90–7.85 (m,
4H, H2, H6), 7.49–7.35 (m, 4H, H3, H5), 1.84–1.37 (m, 8H, H8,
H9), 1.28–1.15 (m, 4H, H10), 0.69 (t, 6H, H11). 13C{1H} NMR (d,
CDCl3): 209.85 (C7), 142.50 (C1), 130.27 (C2, C6), 136.61 (C3, C5),
96.00 (C4), 28.45 (C8), 27.51 (C9), 26.85 (C10), 14.13 (C11).
119Sn{1H} NMR (d, CDCl3): 128.8, À230.7. 119Sn Mössbauer:
d = 1.49,
D = 2.58, C .
= 0.89 mm sÀ1
(cmÀ1): 1306
and 348
(SnS). 1H NMR (d, CDCl3): 7.95–7.93 (m, 4H, H2, H6),
m(C@N); 1284 mas(SO2); 1143 ms(SO2); 965 mas(CS2)
All IR and NMR spectra showed the expected bands or signals
for the tetraphenylphosphonium cation.
m
7.27–7.23 (m, 6H, H3, H4, H5), 1.84–1.38 (m, 8H, H8, H9), 1.14–
1.08 (m, 4H, H10), 0.64 (t, 6H, J = 7.2 Hz, H11). 13C{1H} NMR (d,
CDCl3): 209.12 (C7), 143.81 (C1), 130.34 (C2, C6), 128.34 (C3, C5),
127.54 (C4), 28.47 (C8), 27.45 (C9), 26.94 (C10), 14.13 (C11).
119Sn{1H} NMR (d, CDCl3): 128.4, À221.1. 119Sn Mössbauer:
2.3. X-ray crystallography
X-ray diffraction data were collected on an Oxford-Diffraction
GEMINI diffractometer (LabCri) using Enhance Ultra Cu Ka
d = 1.49,
D
= 2.73,
C
= 0.85 mm sÀ1
.
(Ph4P)2[Sn(Bu)2(4-FC6H4SO2N@CS2)2]ÁH2O (2): Elemental analy-
sis: Anal. Calc. for C70H68F2N2O5P2S6Sn: C, 58.86; H, 4.80; N, 1.96.
Found: C, 58.40; H, 4.55; N, 1.94%. Mp (°C): 122.6–123.2. IR (se-
(k = 1.5418 Å) radiation source at 150 K. Data integration and scal-
ing of the reflections were performed with the Crysalis suite [16].
Final unit cell parameters were based on the fitting of all reflec-
tions positions. The structures were solved by direct methods
lected bands) (cmÀ1): 1317
m(C@N); 1280 mas(SO2); 1142 ms(SO2);
Bu2SnCl2, 2 Ph4PCl, DMF/H2O
4 H O,
2 RSO2N=CS2K2.2H2O
(Ph4P)2[Sn(Bu)2(RSO2N=CS2)2]
-
- 4 KCl
2
1, 2, 3, 4, 5
(3)
(1)
(2)
R =
H
Cl
F
(4)
(5)
Br
I
Scheme 1. Syntheses of the organotin(IV) complexes 1–5.

32
L.C. Dias et al. / Polyhedron 47 (2012) 30–36
Table 1
3. Results and discussion
Crystal data and refinement results for compounds 1 and 2.
Compound
1
2
The compounds 1–5 are stable at the ambient conditions. They
are insoluble in water, ethyl acetate, hexane, diethyl ether and eth-
anol, being soluble in methanol, chloroform, dichloromethane,
dimethylsulfoxide and acetone. The purity of the complexes was
confirmed by elemental analysis and melting points.
In order to determine the fine structural details, single crystal
X-ray diffraction studies were performed. Selected geometrical
parameters for 1 and 2 are listed in Table 2. The molecular struc-
ture of the complexes 1 and 2 are illustrated in Figs. 2 and 3,
respectively.
The coordinated geometry of the Sn(IV) atom of compounds 1
and 2, can be described as distorted octahedral, with two butyl
groups occupying the axial positions and the dithiocarbimate act-
ing as a bidentate ligand through sulfur and nitrogen atoms occu-
pying the equatorial positions (see Figs. 1 and 2). The Sn1–N1
distances of 2.578 in 1, and 2.620 and 2.760 Å in 2, are much short-
er than the sum of the van der Waals radii of tin and nitrogen
(3.74 Å) [22] and longer than the sum of the covalent radii
(2.10 Å) [22,23]. The Sn1–N1 interaction lengths values 2.578 Å
in 1 and 2.620 Å in 2 are shorter than other Sn–N bond lengths re-
ported for bidentade (S,N) dibutyltin(IV) complexes with thioami-
date (ca. 2.74 Å) and 2-mercapto-4-pyrimidine (2.70–2.93 Å)
ligands [24,25], indicating stronger intramolecular interactions in
compounds 1 and 2.
The lengths of the Sn1–C8 bonds in compounds 1 (2.141 Å) and
2 (2.141, 2.135 Å) are close to values presented in the literature for
dibutyltin(IV)-dithiocarbamato complexes [9,26,27], and dibutyl-
tin(IV) complexes with thioamidate and 2-mercapto-4-pyrimidine
ligands [24,25]. The Sn1–S2 bond lengths observed for 1 and 2
(ranging from 2.487 to 2.522 Å) are also consistent with the values
observed for the above mentioned classes of compounds. The C7–
S3 bond lengths (ca. 1.68 Å) in the compounds 1 and 2 are shorter
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
C
70H68N2O4P2S6Sn
C70H68F2N2O5P2S6Sn
1428.25
triclinic
1374.25
monoclinic
C12/c1
ꢀ
P1
13.3438(7)
23.9627(18)
26.6226(17)
90
119.876(8)
90
6516.8(6)
4, 1.401
5.775
10.1231(5)
12.9163(9)
26.248(2)
93.387(6)
94.623(5)
96.253(5)
3392.5(4)
2, 1.398
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z, Dcalc (Mg/m3)
Absorption coefficient (mmÀ1
F(000)
)
5.623
1472
2840
Crystal size (mm)
h range for data collection (°)
Index range (h)
0.32 Â 0.30 Â 0.08
3.30–62.53
À31 6 h 6 34
À13 6 k 6 7
À22 6 l 6 23
97.1%
multi-scan
0.988
9258/5051
(0.0485)
0.46 Â 0.36 Â 0.06
3.39–62.84
À11 6 h 6 11
À14 6 k 6 13
À27 6 l 6 30
96.8%
multi-scan
1.003
18863/10574
(0.0710)
Completeness h = 62.53°
Absorption correction
Goodness-of-fit (GOF) on F2
Reflections collected/unique
(Rint
Data/restraints/parameters
Observed reflections, I > 2
)
5051/0/384
4028
10574/2/799
6212
r(I)
Final R indices [I > 2
r(I)]
R1 = 0.0569,
wR2 = 0.1500
R1 = 0.0745,
wR2 = 0.1644
2.285/À1.393
R1 = 0.0751,
wR2 = 0.1772
R1 = 0.1392,
wR2 = 0.2139
1.141/À0.998
R indices (all data)
Largest difference in peak and
hole (e ÅÀ3
)
and refined on F2 by full-matrix least-squares using the SHELX-97
[17,18]. Details of the data collection parameters, crystallographic
data and final agreement parameters are collected in Table 1.
Although some of the hydrogen atoms could be identified in a
Fourier difference map, in the final model they were geometrically
positioned and refined using a riding model. All non-H atoms were
refined anisotropically. Molecular graphics and packing figures
were obtained from Ortep [19,20].
Table 2
Selected bond lengths and angles for compounds 1 and 2.
Atoms
1
2
Bond length (Å)
Sn1–S2
Sn1–S2(x)
Sn1–N1
Sn1–N1(x)
Sn1–C8
Sn1–C8(x)
C7–N1
C7(x)–N1(x)
C7–S2
C7(x)–S2(x)
C7–S3
2.5219(12)
–
2.578(4)
–
2.141(5)
–
1.344(7)
–
1.757(5)
–
1.684(5)
–
2.487(3)
2.510(2)
2.620(8)
2.760(8)
2.141(9)
2.135(8)
1.311(12)
1.332(10)
1.779(9)
1.763(9)
1.683(11)
1.678(8)
2.4. Biological assay
The antifungal activity of the new compounds was evaluated by
the Poisoned food technique [21] against C. gloeosporioides. Discs of
mycelia of the fungus (diameter of 6 mm) were placed on the cen-
ter of Petri dishes containing 10 mL of the culture medium (PDA)
homogeneously mixed with dimethylsulfoxide (0.1 mL), the antibi-
otic streptomycin sulfate (25.0 mg), and the tested compounds 1–5
at the concentrations of 97.90; 48.95; 24.48; 12.24; 6.12; 3.06;
C7(x)–S3(x)
1.53; 0.76 and 0.38 lM. Each treatment consisted of four repeti-
Bond angle (°)
S2–Sn1–N1
60.53(10)
60.53(10)
151.53(10)
151.53(10)
91.01(6)
147.34(19)
106.89(16)
106.89(16)
107.55(15)
107.55(15)
83.43(19)
83.43(19)
83.17(18)
83.17(18)
130.0(3)
59.89(9)
57.92(10)
144.31(10)
145.86(10)
86.50(8)
155.8 (2)
109.1(4)
113.6(3)
107.1(3)
107.3(3)
90.7(2)
tions and the dishes were incubated at 25 °C for 12 days. The con-
trol (negative check treatment) was prepared with PDA,
dimethylsulfoxide and streptomycin sulfate only. Two positive
check treatments were prepared with the same procedure using
the fungicides bis(dimethylcarbamate)zinc and triphenyltin
hydroxide. Both compounds showed 100% inhibition at the con-
centrations tested. Tetraphenylphosphonium chloride was inactive
S2(x)–Sn1–N1(x)
S2–Sn1–N1(x)
S2(x)–Sn1–N1
S2–Sn1–S2(x)
N1–Sn1–N1(x)
C8–Sn1–S2
C8(x)–Sn1–S2
C8–Sn1–S2(x)
C8(x)–Sn1–S2(x)
C8–Sn1–N1
at the concentration of 97.90 lM. The diameter of the fungus col-
ony was measured with a caliper vernier every 24 h from the sec-
ond day of incubation. The results were statistically analyzed by
nonlinear regression using the concentration versus percent inhi-
bition results. The colony diameters (mm) were submitted to anal-
ysis of variance and means, and were compared by the Tukey test
(p 6 0.05).
C8(x)–Sn1–N1
C8–Sn1–N1(x)
C8(x)–Sn1–N1(x)
C8–Sn1–C8(x)
83.3(3)
81.7(2)
82.6(3)
125.7(4)
(x) is (i) for (1) and (e) for (2).

L.C. Dias et al. / Polyhedron 47 (2012) 30–36
33
Fig. 1. The molecular structure of the anion of the compound 1 with a crystallographic twofold rotation axis and the atom numbering scheme.
than the C7–S2 (1.76–1.78 Å range) indicating the greater double
bond character for the C7–S3 bond. In (Ph4P)2[Sn(CH3SO2N@CS2)3],
the first reported tris(R-sulfonyldithiocarbimato)tin(IV) complex
[28], the Sn–S bond lengths lie within the range of 2.441–
2.646 Å. In this case each dithiocarbimato ligand is coordinated
to the tin(IV) by two sulfur atoms and the C–S bond distances
(1.748–1.751 Å) are similar to the values found for the C7–S2 bond
lengths in compounds 1 and 2.
bonds between the water molecule and the oxygen atoms of the
ligand [d(O1wÁ Á ÁO2) = 2.869 Å, \(O1wHO2) = 146° and d(O1wÁ Á Á
O2e) = 3.256 Å, \(O1wHO2e) = 163°].
Mössbauer spectroscopic data of complexes 1–5 are given in
Table 3 and the spectra at 78 K are illustrated in Fig. 4. The spectra
show a characteristic doublet absorption with narrow line width,
C
, indicating the occurrence of unique tin coordinated sites in all
compounds. The isomer shifts observed are characteristic of tin(IV)
[29]. The data show lower isomer shift (d) values for all complexes
when compared to the parent organotin(IV) dichloride, confirming
Fig. 3 shows the molecular packing of compound 2, with the an-
ionic complex, tetraphenylphosphonium cation and hydrogen
Fig. 2. The molecular structure of the anion of the compound 2 and the atom numbering scheme.

34
L.C. Dias et al. / Polyhedron 47 (2012) 30–36
Fig. 3. The molecular structure packing of the compound 2.
Table 3
119Sn Mössbauer spectral data for compounds 1–5 compared to dibutyltin(IV)
dichloride.
Compounds Doublets db (mm sÀ1
)
Db (mm sÀ1
)
Cb (mm sÀ1
)
Areab
a
Sn(Bu)2Cl2
1.75
1.49
1.48
1.48
1.48
1.49
3.50
2.73
2.64
2.54
2.63
2.58
1
2
3
4
5
(1)
(1)
(1)
(1)
(1)
0.85
0.86
0.89
0.85
0.89
100
100
100
100
100
a
Ref. [30].
The errors associated to d,
b
D, and C .
are 0.05 mm sÀ1
the complexation. The quadrupole splitting (D) values in the range
of 2.54–2.73 mm sÀ1 show that the electric field gradient around
the tin nucleus is produced by the inequalities in the tin-sulfur/
nitrogen/carbon bonds and is also due to geometric distortions.
Complexes of dialkyltin(IV) with thioamide ligands presenting dis-
torted octahedral or tetrahedral geometry exhibit quadrupole
splitting parameters in the region of 2.40–3.03 mm sÀ1 [24]. The
Mössbauer spectroscopic data of complexes 1 and 2 are also con-
sistent with the great distortions in the octahedral geometry ob-
served in the X-ray experiments. Compounds 1–5 showed similar
spectra indicating that the compounds 3–5 present tin coordina-
tion environment analogous to those of 1 and 2 in the solid state.
A strong band observed between 1300 and 1350 cmÀ1 in the IR
spectra of the complexes was assigned to the m(C@N). This band is
shifted to higher wavenumbers with respect to the spectra of the
parent potassium dithiocarbimate salts [10,31]. Conversely, the
m
as(CS2) band was observed at lower wavenumber (953–
968 cmÀ1) in the spectra of the complexes in relation to the spectra
of the free ligands. Strong bands were observed at the 1268–1284
and 1140–1145 cmÀ1 regions and were assigned to the
and
m
as(SO2)
m
s(SO2), respectively. The bands at 528–530 cmÀ1 were assigned
to the asymmetric and symmetric vibrations of Sn–C bonds,
whereas the bands of low intensity between 400 and 470 cmÀ1 were
assigned to m(Sn–N) vibrations [32]. The spectra of the complexes
also showed the expected medium band in the 300–390 cmÀ1 range
assigned to the Sn–S stretching vibration [24,33]. However the anal-
ysis of the 500–300 cmÀ1 region was complicated by the presence of
Fig. 4. 119Sn Mössbauer spectra obtained at 78 K for complexes 1–5.

L.C. Dias et al. / Polyhedron 47 (2012) 30–36
35
Bu
Sn
Bu
cation and the pertinent signals for the carbon atoms of the com-
plexes anions.
The in vitro antifungal activity of the complexes 1–5 was evalu-
ated against C. gloeosporioides by the Poisoned food test at various
concentrations. As the tetraphenylphosphonium chloride was
Bu
Sn
Bu
Bu
Sn
Bu
S
S
S
S
S
S
C
S
S
C
C
S
S
C
C
S
S
C
N
N
N
N
N
N
SO2R
SO2R
RO2S
RO2S
SO2R
RO2S
inactive at the concentration of 97.90 lM, the activities presented
Scheme 2. Equilibrium between hexa-, penta- and tetracoordinated species in
solution.
by the compounds 1–5 can be attributed to the anionic complexes.
Table 4 shows the inhibition of the fungus colony on the 12th
day of incubation at the different concentrations tested for com-
pounds 1–5. It clearly shows that 2 was the most active compound.
The concentrations of the compounds 1–5 needed to inhibit 50% of
the colony growth (IC50) could be calculated through the equations
obtained from nonlinear regression analysis of the dose–response
curves (Table 4). Compound 2 showed a remarkable activity, with
several bands of the ligands and the tetraphenylphosphonium
cation.
The 1H NMR spectra of all the compounds showed the signals
for the hydrogen atoms of the tetraphenylphosphonium cation.
The integration curves in the 1H NMR spectra were consistent with
2:1 stoichiometric ratios of the cations to the complex anions. The
literature suggests typical signals in the 119Sn spectra of n-butyl-
tin(IV) complexes according to their coordination numbers in the
following ranges: d À210 to À400 (six-coordinated), d À90 to
À190 (five-coordinated) and d +200 to À60 (four-coordinated)
[25,34]. Thus, the intense signals observed at d 128.3–128.9 in
the spectra of complexes 1–5 indicated the presence of tetracoor-
dinated species in solution. Other less intense signals in the range
of d À170.7 to À230.7 were also observed, suggesting that penta-
or hexacoordinated isomers were also present. Probably the weak
interaction between tin and the nitrogen atoms are mainly dissoci-
ated in solution and there is a dynamic equilibrium between the
species (Scheme 2).
an IC50 of 6.2 lM.
The Fig. 5 shows the fungus colony growth over the 12 days of
incubation at 25 °C (control) in comparison with the growth in
the presence of compound 2 at 6.12 lM. In the first measurements,
after 48 h of incubation, it was already possible to see the inhibitory
effects of compound 2 in the colony growth. It is interesting to note
that, while C. gloeosporioides continued to develop linearly in the
control dishes over the 12 days of incubation, under the compound
2 treatment a variable slope logarithmic growth was observed.
The compound 2, bearing the fluorine substituent, was the most
active complex in all concentrations tested, and the bromine sub-
stituent (compound 4) provided the second best results in most
of the experiments (Table 4). However, there is no straightforward
correlation between the activity of the new compounds and the
substituents on the phenyl rings of their complex anions. For
example, in the lower dose range the compound 3 with the chlo-
rine substituent was the less active, rapidly improving its results
at higher doses. The opposite behavior is observed for the com-
pound 5, bearing the iodine substituent (Table 4).
In the 13C NMR spectra of the complexes the signal due to the
carbon of the dithiocarbimate moiety (N@CS2, ca. 210 ppm) is
shifted to higher field when compared to the correspondent signal
in the potassium dithiocarbimates spectra (ca. 225 ppm) as ob-
served with analogous compounds [10,11,31]. The 13C NMR spectra
also showed the expected signals for the tetraphenylphosphonium
Table 4
Inibition of C. gloeosporioides growth by the complexes 1–5 at different concentrations on the 12th day of incubation at 25 °C and the 50% inhibitory concentration obtained from
nonlinear regression analysis of the dose–response curves.
Substance
Inhibition (%)a (SD), concentration (
lM)
IC50 (lM)
97.90
48.95
24.48
12.24
6.12
3.06
1.53
0.76
0.38
1
2
3
4
5
57.4 ( 2.9)
74.1 ( 3.8)
73.6 ( 2.7)
65.9 ( 1.6)
50.5 ( 1.5)
54.5 ( 2.2)
68.3 ( 3.0)
61.0 ( 3.6)
63.0 ( 2.7)
47.6 ( 2.2)
48.9 ( 1.9)
64.7 ( 3.8)
49.8 ( 1.1)
52.3 ( 1.8)
44.1 ( 1.8)
37.6 ( 0.9)
51.1 ( 1.6)
36.0 ( 1.3)
49.6 ( 1.6)
37.7 ( 1.4)
28.0 ( 1.3)
46.9 ( 1.0)
26.1 ( 0.8)
45.1 ( 1.3)
30.5 ( 0.9)
23.2 ( 0.7)
40.6 ( 1.4)
18.2 ( 0.4)
39.1 ( 0.8)
20.8 ( 0.5)
11.1 ( 0.9)
38.4 ( 0.8)
14.9 ( 0.4)
35.2 ( 1.0)
20.4 ( 0.5)
8.5 ( 0.2)
34.1 ( 0.7)
8.0 ( 0.2)
24.3 ( 0.7)
19.3 ( 0.4)
5.7 ( 0.1)
30.2 ( 1.1)
6.9 ( 0.1)
17.7 ( 0.5)
18.5 ( 0.4)
39
6.2
25
13
89
a
Calculated according to the equation: Inhibition % = 100(Cc À Cs)/Cc, where Cc is the average growth of the control and Cs is the average growth of the fungus in contact
with the substance in test.
Fig. 5. Colony diameter of C. gloeosporioides over the 12 days of incubation at 25 °C when treated with compound 2 (at 6.12 lM) in comparison with the control (100%
growth).

36
L.C. Dias et al. / Polyhedron 47 (2012) 30–36
Comparing the biological activity observed for the tin com-
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
plexes 1–5 with the reported activity of zinc complexes bearing
the same dithiocarbimato ligands and general formula (Bu4N)2[-
Zn(RSO2N@CS2)2], it was observed that the IC50 for the zinc com-
plexes were in the range of mM against C. gloeoesporioides [11],
while the complex here studied were more active, inhibiting the
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Appendix A. Supplementary data
CCDC 885170 and 885169 contain the supplementary crystallo-
graphic data for 1 and 2. These data can be obtained free of charge