Synthesis, spectroscopic characterization and X-ray structures of five-coordinate diorganotin(IV) complexes containing 5-hydroxypyrazoline derivatives as ligands

Article abstract of DOI:10.1016/j.molstruc.2010.07.023

Four new diorganotin(IV) complexes have been prepared from R ₂SnCl₂ (R = Me, Ph) with the ligands 5-hydroxy-3-metyl-5- phenyl-1-(S-benzildithiocarbazate)-pyrazoline (H₂L₁) and 5-hydroxy-3-methyl-5-phenyl-1-(2-th

Full text of DOI:10.1016/j.molstruc.2010.07.023

Journal of Molecular Structure 981 (2010) 46–53
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, spectroscopic characterization and X-ray structures
of five-coordinate diorganotin(IV) complexes containing
5-hydroxypyrazoline derivatives as ligands
a
a
a
b
Gerimário F. de Sousa a, , Edgardo Garcia , Claudia C. Gatto , Inês S. Resck , Victor M. Deflon ,
*
José D. Ardisson c
a Instituto de Química, Universidade de Brasília, 70919-970 Brasília – DF, Brazil
b Instituto de Química de São Carlos, Universidade de são Paulo, 1350-250 São Carlos, SP, Brazil
c Laboratório de Física Aplicada, Centro de Desenvolvimento de Tecnologia Nuclear, 30123-970 Belo Horizonte, MG, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 May 2010
Received in revised form 15 July 2010
Accepted 15 July 2010
Available online 22 July 2010
Four new diorganotin(IV) complexes have been prepared from R2SnCl2 (R = Me, Ph) with the ligands 5-
hydroxy-3-metyl-5-phenyl-1-(S-benzildithiocarbazate)-pyrazoline (H2L1) and 5-hydroxy-3-methyl-5-
phenyl-1-(2-thiophenecarboxylic)-pyrazoline (H2L2). The complexes were characterized by elemental
analysis, IR, 1H, 13C, 119Sn NMR and Mössbauer spectroscopies. The complexes [Me2SnL1], [Ph2SnL1]
and [Me2SnL2] were also studied by single crystal X-ray diffraction and the results showed that the Sn(IV)
central atom of the complexes adopts a distorted trigonal bipyramidal (TBP) geometry with the N atom of
the ONX-tridentate (X = O and S) ligand and two organic groups occupying equatorial sites. The C–Sn–C
angles for [Me2Sn(L1)] and [Ph2Sn(L1)] were calculated using a correlation between 119Sn Mössbauer and
X-ray crystallographic data based on the point-charge model. Theoretical calculations were performed
with the B3LYP density functional employing 3–21G(ꢀ) and DZVP all electron basis sets showing good
agreement with experimental findings. General and Sn(IV) specific IR harmonic frequency scale factors
for both basis sets were obtained from comparison with selected experimental frequencies.
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Diorganotin(IV) complexes
Pyrazoline derivatives
Crystal structure
1. Introduction
ate)-pyrazoline] and H2L2 is [5-hydroxy-3-methyl-5-phenyl-1-(2-
thiophenecarboxylic)-pyrazoline]. As far as we know, the 5-
NNO-, ONO- and specially ONS-tridentate Schiff bases, synthe-
sized from 2-acetylpyridine, 2-hydroxyacetophenone, salicylalde-
hyde with hydrazides are among the most extensively chelating
agents investigated over the past several years [1–5]. These chelat-
ing semicarbazones and thiosemicarbazones compounds are of
considerable interest, most because of their pharmacological appli-
cations and ability to form interesting chelates with heavy metals,
which in some cases possess enhanced biological activity com-
pared with the uncomplexed ligand [6–8]. Recently the ONO-coor-
dination behavior of 4-phenyl-2-4-butanedionebenzoylhydrazone
(5-hydroxypyrazoline derivative) towards diorganotin(IV) deriva-
tives have been reported [4]. However, diorganotin(IV) complexes
prepared from ONS-tridentate thiohydrazones have been much
less studied [6,9]. In view of this, we are reporting the synthesis
and characterization of four new five-coordinated diorganotin(IV)
complexes, [R2Sn(L1)] and [R2Sn(L2)] (R = Me and Ph), in which
the H2L1 is [5-hydroxy-3-metyl-5-phenyl-1-(S-benzildithiocarbaz-
hydroxypyrazolinol (H2L1) ligand have been prepared for the first
time and similar complexes of the kind [Me2Sn(L1)] and [Ph2Sn(L1)]
have not yet been reported. The structures of H2L1 and H2L2 are
illustrated in Scheme 1.
The C–Sn–C angle (h) in five-coordinated diorganotin(IV) com-
plexes was first estimated by Bancroft et al. [10] using established
point-charge procedures. Sham’s group found partial quadrupole
splitting (PQS) values of [R] of ꢁ1.03 mm/s and ꢁ0.98 mm/s for
dialkyl- and diaryltin(IV) five-coordinate complexes, respectively.
This work allowed us to calculate new refined values for [alkyl]
of ꢁ0.84 mm/s and [Ph] of ꢁ0.77 mm/s in five-coordinated diorga-
notin(IV) complexes embodying ONS-tridentate ligands using crys-
tallographic data (h) and quadrupole splitting (D) values.
2. Experimental
2.1. Materials and methods
Solvents were purified and dried according to standard procedures.
The compounds 2,4-pentanedione, 4-phenyl-2,4-butanedione,
* Corresponding author. Tel.: +55 61 3307 3873; fax: +55 61 273 4149.
E-mail address: gfreitas@unb.br (G.F. de Sousa)
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.07.023

G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
47
7
7
1CH3
1CH3
8
8
6
6
5
2
3
2
3
5
4
4
N
N
S
N
HO
N
HO
10
12
9
9
S
11
10
13
14
O
S
13
11
12
H2L2
H2L1
Scheme 1.
2-thiophenecarboxylic hydrazide, dimethyltin(IV) dichloride and
diphenyltin(IV) dichloride were of the highest commercially
available grade. The starting material S-benzyldithiocarbazate was
prepared by a previously reported method [11].
groups, in 10 mL of MeOH was added to a solution of the appropri-
ated hydrazide derivative (4.0 mmol) in 10 mL of MeOH. The mix-
ture was refluxed for 1 h, after that yellow solutions for both
compounds were obtained. Perfectly clear solutions were obtained
after filtration of the original ones and slow evaporation of the sol-
vent led to the appearance of a colorless crystalline product. The
crystals were filtered, washed with n-hexane and dried in air.
The 5-hydroxypyrazoline derivatives H2L1 and H2L2 can easily be
obtained as single crystals using CH2Cl2 as solvent of reaction.
The complexes were prepared using the methodology reported
by Rosair and collaborators [4]. The methyl derivatives were
recrystallized using a mixture of MeOH/H2O (3:1, v/v), whereas
the phenyl ones from a mixture of MeOH/CH2Cl2 (3:1, v/v). Anal.
Calcd for C20H23N2OS2Sn ([Me2Sn(L1)]): C 49.00, H 4.73, N 5.71, S
13.08. Found: C 48.89, H 4.69, N 5.68, S 12.81%, color: yellow, yield:
IR spectra were recorded on a BOMEN spectrophotometer in the
4000–400 cmꢁ1 range using KBr pellets. NMR spectra were re-
corded at room temperature on a Varian Mercury plus spectrome-
ter (7.05 T) operating at 300 MHz for 1H, at 75.46 MHz for 13C and
at 134.3 MHz for 119Sn. Compound was dissolved in CDCl3 contain-
ing TMS as internal reference (see Scheme 1 for atom numbering).
Chemical shifts were expressed in d (ppm) and coupling constants
as J (Hz). 119Sn Mössbauer spectra were collected at 80 K in the
transmission geometry on a constant-acceleration conventional
spectrometer by using a CaSnO3 source kept at room temperature.
All isomer shift values reported in this work are given with respect
to this source. All Mössbauer spectra were computer-fitted assum-
ing Lorentzian line shapes and the resulting isomer shifts and
quadrupole splittings are accurate to ca. 0.05 mm/s. CHNS ele-
mental analyses were performed on a FISSONS EA 108 analyzer.
Geometries for both ligands and all four complexes were fully
optimized and verified for the absence of imaginary harmonic fre-
quencies. The B3LYP hybrid density functional method was used in
all calculations with a fine integration grid and tight energy crite-
rion. Two all electron basis sets, 3–21G(ꢀ) and DZVP, were com-
pared against experimental geometries and IR frequencies.
Calculations were performed on an personal computer with an In-
tel Q6600 quad-core processor and the software Gaussian G03W
version D01.
74%, m.p.: 106–108 °C. Anal. Calcd for
C30H26N2OS2Sn
([Ph2Sn(L1)]): C 58.75, H 4.27, N 4.57, S 10.45. Found: C 58.56, H
4.51, N 4.49, S 10.31%, color: yellow, yield: 78%; m.p.: 152–
154 °C. Anal. Calcd for C17H18N2O2SSn ([Me2Sn(L2)]): C 47.15, H
4.19, N 6.47, S 7.40. Found: C 46.81, H 3.98, N 6.35, S 7.29%, color:
orange, yield: 74%; m.p.: 160–163 °C. Anal. Calcd for
C30H26N2OS2Sn ([Ph2Sn(L2)]): C 58.75, H 4.27, N 4.57, S 10.45.
Found: C 58.89, H 4.53, N 4.72, S 11.89%, color: orange, yield:
78%, m.p.: 130 °C (dec.)
3. Results and discussion
3.1. Crystal structures of [Me2Sn(L1)] and [Ph2Sn(L1)]
2.2. Crystal structure determination
The ORTEP plots of both complexes are shown in Figs. 1 and 2,
and their bond lengths and angles are summarized in Table 2. The
X-ray structure determination revealed that the substitution of Me
group in [Me2Sn(L1)] by the Ph group in [Ph2Sn(L1)] leads to mod-
ifications in the crystal packing of the complex molecules in each
case (Table 1). The complex [Me2Sn(L1)] crystallizes in the mono-
The data collections were performed with Mo K
a radiation
(k = 71.073 pm) on a Bruker Kappa APEX II-CCD diffractometer
for [Me2Sn(L1)], [Ph2Sn(L1)] and [Me2Sn(L2)]. The structures were
solved by the heavy atom method with SHELXS-97 [12] and refined
with SHELXL-97 [13]. Hydrogen atom positions were calculated at
idealized positions using the riding model option of SHELXL-97
[13]. Additional crystal data and more information about the X-
ray structural analyses are shown in Table 1. The ORTEP diagrams
of the complexes indicating atom numbering scheme with thermal
ellipsoids at 30% probability are illustrated in Figs. 1–3. All of rele-
vant crystallographic informations are presented in Table 1,
whereas selected bond lengths and angles in Table 2.
ꢀ
clinic (P21/c) system while [Ph2Sn(L1)] in the triclinic (P1) one. In
both complexes the ligand binds tridentately forming ONS-donor
systems containing five- and six-membered chelate rings. The
geometry around the Sn(IV) nucleus is well described as a distorted
trigonal bipyramid (TBP), with the two organic groups and azome-
thine N1 atom of the ligand occupying the equatorial positions, the
phenolate O1 and thiolate S1 atoms occupy axial sites. As in other
complexes [2,5] containing ONS-tridentate thiosemicarbazones,
the main distortion from regular TBP geometry comes from the
stereochemical constraints imposed by the ligand, which reduce
the O1–Sn–S2 angle from the ideal value of 180° to the values of
157.0(2) for [Me2Sn(L1)] and 162.85(6)° for [Ph2Sn(L1)]. The C19–
Sn–C20 and C21–Sn–C31 angles values of 127.1(5) and
2.3. Synthesis
The compounds H2L1 and H2L2 were prepared as follow: a solu-
tion of 1,3-diketone RCOCH2COMe (4.0 mmol), where R is Me or Ph

48
G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
Table 1
Crystallographic data for Sn(IV) complexes.
[Me2Sn(L1)]
20H23N2OS2Sn
490.21
Monoclinic
P21/c
[Ph2Sn(L1)]
[Me2Sn(L2)]
Empirical formula
Formula weight
Crystal system
Space group
Crystal color
Crystal size (mm)
Z
C
C30H26N2OS2Sn
613.34
C17H18N2O2SSn
433.08
Monoclinic
P21/c
Triclinic
ꢀ
P1
Yellow
Yellow
Orange
0.57 ꢂ 0.23 ꢂ 0.04
0.12 ꢂ 0.12 ꢂ 0.10
0.25 ꢂ 0.08 ꢂ 0.05
4
2
4
T (K)
293(2)
293(2)
293(2)
a (Å)
b (Å)
c (Å)
7.1391(2)
25.7575(8)
11.7189(4)
102.822(2)
2101.20(11)
1.550
9.8660(4)
10.3975(5)
13.6100(7)
80.879(2)
1343.60(11)
1.516
11.9839(2)
7.75690(10)
19.5813(4)
100.2800(10)
1791.02(5)
1.606
b (°)
V (Å3)
qcalcd (g cm–3
)
Index ranges
ꢁ7 6 h 6 7
–26 6 k 6 26
ꢁ12 6 l 6 12
988
ꢁ14 6 h 6 15
–16 6 k 6 16
ꢁ21 6 l 6 20
620
ꢁ17 6 h 6 17
–11 6 k 6 11
ꢁ28 6 l 6 28
864
F(0 0 0)
l
(mm–1
)
1.426
1.132
1.553
a
a
a
Refinement method
Reflections collected
Data/parameters
40,546
2421/235
1.438
0.0460
0.1471
29,110
10,513/325
1.116
0.0337
0.0982
22,810
60/49
1.108
0.0469
0.1597
1.667 and ꢁ1.331
Goodness-of-fit on F2
R1 [I > 2
wR2 [I > 2
Largest diff. peak and hole (eÅ–3
r
(I)]b
r
(I)]c
)
0.636 and ꢁ0.784
0.782 and ꢁ1.233
a
b
c
Full-matrix least-squares on F 2.
P
P
R1 = ||Fo| ꢁ |Fc||/ |Fo|.
P
P
wR2 = [ w(|Fo|2 ꢁ |Fc|2)2/ w|Fo2|2]1/2
.
Fig. 2. ORTEP plot with atom-labeling scheme of [Ph2SnL1] with displacement
ellipsoids at the 30% probability level.
The bond lengths values of, respectively, 1.748(11), 1.276(13),
0
1.412(12), 1.321(12), 1.418(15), 1.373(15), and 1.305(12) AÅ, found
in the skeleton S2–C8–N2–N1–C9–C11–C12–O1 of [Me2Sn(L1)],
indicate that it has a conjugated double bond character. The short-
ening of the N2–C8 and C11–C12 bonds and lengthens of the S1–C8
bond upon complex formation, show that the double deprotona-
tion of the ligand results in a conversion from thione to thiolate
sulfur. These results were also observed in complex [Ph2Sn(L1)]
Fig. 1. ORTEP plot with atom-labeling scheme of [Me2SnL1] with displacement
ellipsoids at the 30% probability level.
115.14(9)° found, respectively, in [Me2Sn(L1)] and [Ph2Sn(L1)] also
contribute to the distortion.

G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
49
3.2. Crystal structures of [Me2Sn(L2)]
The ORTEP plot of the complex [Me2Sn(L2)] is shown in Fig. 3,
and their bond lengths and angles are summarized in Table 2. In
[Me2Sn(L2)] the ligand is ONO-donor tridentate via its O1, O2 and
N2 atoms, giving a coordination polyhedron around the Sn(IV)
atom described as a distorted trigonal bipyramid with the enolate
ligand occupying the two axial positions via O1 and O2 atoms and
one equatorial position via N2 nucleus (Fig. 3). The main distortion
from regular bipyramidal geometry comes from the stereochemi-
cal limitations imposed by the planar tridentate ligand, which re-
duces the O1–Sn–O2 from the ideal value of 180° to the value of
158.61(13)°. This compression of O1–Sn–O2 is comparable with
that found in [Me2Sn(L1)] and other reported similar compound,
namely Me2Sn[Ph(O)C@CH–C(Me)@N–N@C(O)Ph] [4]. The angles
O1–Sn–N2 = 74.06(12) and O2–Sn–N2 = 85.22(13)° are also com-
pressed from 90° and also contribute to the expected distortion.
The Sn–O1 = 2.122(3), Sn–O2 = 2.100(3), Sn–N2 = 2.136(3), Sn–
C21 = 2.088(5) and Sn–C31 = 2.138(5) Å bond lengths, are very
similar with those reported values for Me2Sn[Ph(O)C@CH–
C(Me)@N–N@C(O)Ph] [4], a similar diorganotin(IV) complex con-
taining dinegative ONO-donor tridentate chelating agent.
3.3. IR spectroscopy
Fig. 3. ORTEP plot with atom-labeling scheme of [Me2SnL2] with displacement
ellipsoids at the 30% probability level.
Tables 5 and 6 show the assignments of the main IR absorption
bands for 5-hydroxypyrazoline derivatives H2L1 and H2L2, respec-
tively, and Tables 7 and 8 for their Sn(IV) complexes. The IR spectra
of the four complexes, when compared with that of the free
Table 2
Selected bond distances (Å) and angles (°) for Sn(IV) complexes.
ligands, show that the
1440 cmꢁ1 absorptions observed in H2L1, and
(C@N) = 1630 and d(CH2) = 1445 cmꢁ1 bands observed in H2L2
m
(O–H) = 3356,
m
(C@N) = 1629 and d(CH2) =
m
(O–H) = 3411,
[Me2Sn(L1)]
[Ph2Sn(L1)]
[Me2Sn(L2)]
m
S1–C7
S1–C8
S2–C8
O1– C12
N1–C9
N1–N2
N2–C8
C9–C10
C9–C11
C11–C12
C12–C13
Sn–C19
Sn–C20
Sn–O1
1.810(11)
1.746(11)
1.748(11)
1.305(12)
1.276(13)
1.412(12)
1.321(12)
1.510(14)
1.418(15)
1.373(15)
1.478(15)
2.120(11)
2.127(10)
2.135(7)
2.182(8)
2.538(3)
101.9(5)
112.9(6)
128.2(9)
118.9(8)
116.6(8)
114.2(8)
122.8(9)
127.4(9)
121.5(10)
115.4(9)
103.1(4)
129.5(4)
81.4(3)
1.805(3)
1.754(2)
1.734(3)
1.290(3)
1.276(3)
1.396(3)
1.335(3)
1.509(3)
S1–C1
S1–C4
O2–C9
O1– C5
N1–C5
N1–N2
N2–C6
C6–C7
C6–C8
C8–C9
C9–C11
Sn–C21
Sn–C31
Sn–O2
Sn–N2
Sn–O1
S1–C1–C5
C1–C5–O1
O1–C5–N1
C1–C5–N1
C5–N1–N2
N1–N2–C6
N2–C6–C8
C6–C8–C9
C8–C9–C11
O2–C9–C11
C21–Sn–N2
C31–Sn–N2
N2–Sn–O2
O2–Sn–O1
N2–Sn–O1
C21–Sn–C31
1.680(4)
1.658(5)
1.297(6)
1.303(5)
1.275(5)
1.406(4)
1.328(5)
1.512(6)
1.418(5)
1.365(5)
1.500(5)
2.088(5)
2.138(5)
2.100(3)
2.136(3)
2.122(3)
120.5(3)
116.5(4)
125.7(4)
117.8(4)
111.5(4)
115.9(3)
122.8(4)
127.9(4)
120.1(4)
114.5(4)
117.9(2)
119.5(2)
85.22(13)
158.61(13)
74.06(12)
122.3(3)
disappear, suggesting double deprotonation of the ligands upon
complex formation. However, new bands observed at 1585 for
[Me2Sn(L1)], at 1586 for [Ph2Sn(L1)], at 1590 for [Me2Sn(L2)] and
at 1593 cmꢁ1 for [Ph2Sn(L2)] are attributed to
m
(C@N–N@C)
stretching vibration [4]. The IR spectra of complexes also exhibit
(C@N) bands shifted to both higher and lower wave numbers
m
{[Me2Sn(L1)]: 1553/1517; [Ph2Sn(L1)]: 1554/1528; [Me2Sn(L2)]:
1572/1537; [Ph2Sn(L2)]: 1573/1542 cmꢁ1}, evidencing double
deprotonation and tridentate bibasic behavior of the ligands
1.410(3)
1.374(3)
1.484(3)
2.130(3)a
2.149(3)b
2.1030(19)
2.1777(19)
2.5173(7)
102.59(13)
111.71(14)
128.79(19)
119.51(19)
117.5(2)
[2,5,14]. The m
(S–C–S) absorption at 981 cmꢁ1 observed in H2L1
spectrum, is observed at lower frequencies on complexation
{[Me2Sn(L1)]: 970; [Ph2Sn(L1)]: 967 cmꢁ1}, indicating that this
group takes part in the chelating process [15].
Sn–N1
Sn–S2
C7–S1–C8
S1–C8–S2
S2–C8–N2
S1–C8–N2
C8–N2–N1
N2–N1–C9
N1–C9–C11
C9–C11–C12
C11–C12–C13
O1–C12–C13
C19–Sn–N1
C20–Sn–N1
N1–Sn–O1
O1–Sn–S2
N1–Sn–S2
C19–Sn–C20
3.4. NMR spectroscopy
The 1H NMR spectra of the derivatives H2L1 and H2L2 measured
in CDCl3 (Table 3 and Scheme 1 for atom numbering) show that
they exist exclusively in the cyclic (5-hydroxypyrazoline) form.
The signal of the terminal 1CH3 appears at 2.09 ppm for H2L1 and
at 2.15 ppm for H2L2; whereas the magnetically and chemically
nonequivalent 3CH2 methylene hydrogens appear as double dou-
blet at 3.23 ppm (JHH = 18.8 Hz) for H2L1 and at 3.16 ppm
(JHH = 18.0 Hz) for H2L2, similar results have been reported by Zele-
nin and collaborators [15,16]. The spectrum of H2L1 also showed
10CH2 methylene signal at 4.35 ppm as a double doublet due to
geminal 2J coupling (JHH = 13.2 Hz). The OH proton appears as a
broad peak at 6.47 ppm in H2L1 and at 5.29 ppm in H2L2. For these
compounds, the phenyl hydrogen signals are observed as a multi-
plet in the region at 7.26–7.40 ppm and the thiophene hydrogens
11CH, 12CH, and 13CH appear as doublet of doublet at 8.10, 7.10,
and 7.60 ppm, respectively. The 1H NMR spectra (CDCl3) of the four
diorganotin(IV) complexes showed the disappearance of the sig-
nals assigned to methylene (3CH2) and hydroxy (OH) hydrogens
112.72(19)
124.3(2)
128.4(2)
122.0(2)
115.5(2)
117.75(8)c
126.87(8)d
83.58(7)
157.0(2)
78.2(2)
127.1(5)
162.85(6)
79.35(5)
115.14(9)e
a
b
c
Sn–C21 instead of Sn–C19.
Sn–C31 instead of Sn–C20.
C21–Sn–N1 instead of C19–Sn–N1.
C31–Sn–N1 instead of C20–Sn–N1.
C21–Sn–C31 instead of C19–Sn–C20.
d
e
and the comparison among the bond parameters found in both
complexes is unremarkable.

50
G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
Table 3
1H, (13C) and 119Sn NMR chemical shifts and 2J (119/117Sn–1H) and 1J (119/117Sn–13C) for hydrazine derivatives and their Sn(IV) complexes.
nC
H2L1
[Me2Sn(L1)]a
[Ph2Sn(L1)]
H2L2
[Me2Sn(L2)]b
[Ph2Sn(L2)]
1C
2.09 d (16.0)
(158.4)
3.23 dd (54.6)
(97.3)
(142.3)
(128.3)
(128.0)
(123.8)
(191.2)
2.51 s (23.5)
(161.0)
5.62 s (94.3)
(169.5)
(138.5)
(128.4)
(128.0)
(126.5)
(173.6)
2.35 s (26.3)
(161.4)
5.79 s (94.6)
(173.0)
(136.7)
(128.5)
(128.1)
(126.9)
(177.1)
2.15 d (16.1)
(155.0)
3.16 dd (53.5)
(94.5)
(143.5)
(126.8)
(128.0)
(128.6)
(160.2)
2.51s (23.5)
(161.0)
5.62 s (94.2)
(169.4)
(138.6)
(128.1)
(128.0)
(126.4)
(173.6)
2.50 s (24.0)
(161.2)
5.78 s (95.0)
(169.5)
(138.4)
(128.2)
(128.0)
(126.6)
(173.6)
2C
3C
4C
5C
6C
7C
8C
9C
10C
11C
12C
13C
14C
4.35 dd (39.2)
(135.5)
(129.3)
(128.6)
(127.2)
4.35 s (36.1)
(138.6)
(130.2)
(128.8)
(127.1)
4.37 s (36.1)
(137.7)
(130.0)
(129.2)
(127.1)
(135.0)
(138.5)
(138.4)
8.10 dd (134.8)
7.10 dd (123.8)
7.60 dd (133.4)
7.76 dd (130.1)
7.04 dd (127.2)
7.61 dd (128.0)
7.77 dd (130.3)
7.11 dd (127.3)
7.60 dd (128.0)
Abbreviations and attributions: s = singlet, d = doublet, dd = double doublet, qd = quartet deformated.
a
d(1H) = 0.79, d(13C) = 1.3, d(119Sn) = ꢁ149.4 ppm, 2J (119/117Sn–1H) = 78.7/75.3, 1J (119/117Sn–13C) = 644/617 Hz.
b
d(1H) = 0.79, d(13C) = 1.3, d(119Sn) = ꢁ147.2 ppm, 2J (119/117Sn–1H) = 78.6/75.3, 1J (119/117Sn–13C) = 647/618 Hz.
Table 4
128.6° and 128.5°, closer to the values found by X-ray diffraction,
127.1(5)° and 122.3(3)°, respectively. The 2J (119Sn–1H) = 78.6 Hz
and 1J (119Sn–13C) = 647 Hz coupling constants observed for our
complex [Me2Sn(L2)] are comparable with the values of 78.5 and
649.9 Hz found to Me2Sn[Ph(O)C@CH–C(Me)@N–N@C(O)Ph] [4].
119Sn chemical shifts, d(119Sn), relative to Me4Sn in five-coordi-
nate dimethyltin(IV) derivatives have been empirically reported by
Otera [19] located between ꢁ90 and ꢁ330 ppm, while Holecek
et al. [20] have been reported that five-coordinated diorganotin(IV)
adducts have d(119Sn) values of ꢁ90 to ꢁ190 ppm. However, values
of d(119Sn) for [Me2Sn(L1)] and [Me2Sn(L2)] of ꢁ149.4 and
ꢁ147.2 ppm are inside these range, suggesting that both our
methyl complexes do not dissociate in solution. The five-coordi-
nated complexes Me2Sn [Ph(O)C@CH–C(Me)@N–N@C(O)Ph] and
Ph2Sn[Ph(O)C@CH–C(Me)@N–N@C(O)Ph] showed d(119Sn) signal
at ꢁ146.8 and ꢁ151.5 ppm [4].
Selected observed and calculated IR absorptions bands for H2L1.
Vibration mode
(C9–N1) + (C2–C3) +
d(C10–H)S umbrela
d(C–H) in plane ; C14 to C18
d(C–H); C11 + d(C–H); C7 + (C12–C13)
d(C–H); C11 + (C9–C10)
DZVP
3–21G(ꢀ)
H2L1
m
m
m
(C5–C6)
1655
1422
1361
1276
1246
1000
793
784
701
621
1635
1464
1385
1290
1246
1116
772
705
716
626
1628
1440
1378
1256
1220
981
789
776
707
593
m
m
m(S1–C8–S2)a
m(C7–S1–C8)a
m(C7–S1–C8)s
(N1–N2) ring breath
d(O–H)
Table 5
Selected observed and calculated IR absorptions bands for H2L2.
Vibration mode
DZVP
3–21G(ꢀ)
H2L2
m
m
m
(C6–N2) + d(C7–H) + d(C8–H)
(C5–O1) + d(O2–H)
(C1–C2) + m(C3–C4)
1704
1662
1563
1464
1420
1379
1359
1347
882
1648
1609
1554
1450
1435
1393
1321
1314
859
1630
1610
1514
1445
1414
1377
1338
1313
861
3.5. Mössbauer spectroscopy
119Sn Mössbauer spectral parameters for the diorgantin(IV)
complexes are reported in Table 4, which includes parameters
from the literature for comparison, and the spectra of the com-
plexes are shown in Fig. 4. The line-width (U) values of the com-
plexes 1, 2, 6 and 7 were found in the range 0.80–0.83 ( 0.05)
mm/s, removing any possibility of the existence of a second Sn(IV)
atom with different coordination. The isomer shift (d) is very sen-
sitive to the first coordination sphere and it is correlated to the
change of s-electron density on the metal by means of +I inductive
effect imposed by the ligands. A result of this is the inverse depen-
dence of d with electronegativity [4]. Thus, d decrease on replacing
the phenyl by alkyl groups (Table 4). This behavior can clearly be
seen in complexes 1–5 (1.12–1.31 mm/s) as compared to com-
plexes 6–11 (0.93–1.30 mm/s).
k(C7–H)a umbrela +
m
m
(C5–N1) +
(C5–N1) +
(N1–C5) + m(C1–C2) + m(C3–C4)
(C–C); phenyl ring
(C6–C8)
m
(C2–C3)
k(C7–H)s umbrela +
m(C2–C3)
m
m
m
m
(C6–C8) + m(C9–N1)
Molecule breath
834
821
829
in the free ligands and appearing of absorptions in the range 5.79–
5.62 ppm attributed to the sp2 hydrogens (3CH). These observa-
tions suggest that double deprotonation give rise the tridentate
bibasic behavior of the ligands H2L1 and H2L2.
According to the 13C NMR spectroscopy, the spectra of com-
pounds H2L1 and H2L2 showed signal arising from 3C atom at
54.6 and 53.5 ppm, respectively, whereas the asymmetrical 4C
atom signal was observed at 97.3 and 94.5 ppm (Zelenin’s group
has been observed at 93–95 ppm) [16]. The 13C NMR spectra of
the complexes showed that both signals relative to the 3C and 4C
in the uncomplexed ligand H2L1 and H2L2, are shifted downfield
from its original positions upon coordination (see Table 3). This
is due to the rehybridization process of these atoms from Csp3 to
Csp2 with ring-opening reaction upon complex formation. Accord-
ing to the Lochart’s [17] equation 1J (119Sn–13C) = 10.7h–778, the C–
Sn–C angles of [Me2Sn(L1)] and [Me2Sn(L2)] were calculated as
being 133.2° and 133.5°, respectively. However, using the alterna-
tive Locart’s [18] equation h = 0.0161(|2J (119Sn–1H)|)2–1.32(|2J
From the quadrupole splitting (
approach, the Eq. (1).
D
) value and the point-charge
2
1=2
jD
j ¼ ꢁ4½Rꢃð1 ꢁ 0:75 sin hÞ
ð1Þ
gives an estimate of h, where h is the C–Sn–C bond angle and [R]
denotes the partial quadrupole splitting (PQS) value of group R
[4,10,21–23]. Considering the complexes
(2.43 mm/s), 4 (2.41 mm/s), and 5 (2.62 mm/s) and using h and
values (Table 4), the PQS values can be estimated. Eq. (1) yields
[alkyl] = ꢁ0.81, ꢁ0.83, ꢁ0.88, and ꢁ0.83 mm/s, respectively, and
allows us to evaluate an average value for [alkyl] = –0.84 mm/s
in five-coordinated dialkylorganotin(IV) complexes embodying
1
(2.33 mm/s),
3
D
(
119Sn–1H)|) + 133.4, the C–Sn–C angles were calculated as being

G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
51
Table 6
Selected observed and calculated IR absorptions bands for [Me2SnL1] and [Ph2SnL1].
Vibration mode
DZVP
3–21G(ꢀ)
[Me2SnL1]
DZVP
3–21G(ꢀ)
[Ph2SnL1]
m
m
m
m
(C2–C3) +
(C8–N2) +
(C8–N2) +
(C9–N1)
m
m
m
(C5–C6)
(C9–C11–C12)a
(C11–C9–N1)a
1655
1572
1539
1476
1418
1435
1364
1316
1269
1205
1091
979
1634
1564
1628
1553
1517
1494
1453
1440
1380
1316
1256
1220
1063
970
1655
1574
1539
1475
1416
1435
1364
1316
1271
1205
1094
979
1635
1563
1545
1498
1459
1441
1388
1308
1274
1246
1085
955
1555
1528
1488
1450
1428
1377
1300
1299
1238
1065
967
1497
1462
1442
1389
1309
1272
1246
1085
955
k(C10–H)S umbrela
(C11–C9–N1)a (C11–C12–O1)a
d(C–H) in plane; C14 to C18
(C12–C13) + (C9–C10)
m
+ m
m
m
d(C–H); C11 + d(C–H); C7
d(C–H) in plane; C14, C15, C17, C18
m
m
m
m
m
m
m
m
m
(N1–N2) + d(C–H); C10, C11
(S1–C8–S2)a
(S1–C8–S2)s
(C8–S1) +
(C7–S1)
(C8–S2)
(C7–S1)
(C7–S1) +
(Sn–O1)
909
872
786
948
894
898
852
775
910
948
900
m
(C9–C10) +
(C8–S2)
m
(C12–C13)
788
750
698
683
542
768
733
707
695
548
752
704
693
572
698
544
705
575
707
543
m
Table 7
Selected observed and calculated IR absorptions bands for [Me2SnL2] and [Ph2SnL2].
Vibration mode
DZVP
3–21G(ꢀ)
[Me2SnL2]
DZVP
3–21G(ꢀ)
[Ph2SnL2]
m
m
m
m
m
m
m
m
m
m
(C1–C2) +
(C1–C2) +
(C1–C2) +
(C3–C4) +
(C8–C9–O2)a
(C4–S)
(Sn–N2)
(Sn–N2)
(O1–Sn–O2)a
(O1–Sn–O2)s
m
m
m
m
(C6–N2) +
(C6–N2) +
(C3–C9) +
m
m
(C5–N1) +
(C5–N1) +
m
m
(C8–C9–O2)a
(C8–C9–O2)a
1607
1584
1564
1489
1443
865
709
664
555
529
1604
1575
1562
1466
1444
874
722
683
586
559
1591
1572
1537
1455
1433
859
710
656
563
521
1610
1585
1562
1488
1440
866
710
665
555
528
1607
1574
1559
1465
1439
874
722
684
587
559
1594
1573
1542
1444
1432
846
m(C6–C8) + m(C5–N1) + m(C9–O2)
(C1–C5) + k(C7–H)S umbrela
656
527
451
d(Sn–O2) + d(Sn–N2) + d(Sn–O1)
451
461
445
452
460
Table 8
Mössbauer data and C–Sn–C angles (°) for five-coordinated Sn(IV) complexes.
Compound
d(mm/s)
D
(mm/s)
PQS (mm/s)
–0.81
C–Sn–C (exptl)
C–Sn–C (calcd)
1. [Me2Sn(L1)]a
1.14
1.12
1.27
1.18
1.31
1.08
0.93
1.30
1.10
1.10
1.09
2.33
2.78
2.43
2.41
2.62
2.03
2.16
2.30
1.88
1.93
2.03
127.1
122.3
127.5
122.5
134.4
115.1
123.7
180.0
127.1
126.4
133.7
119.7
124.6
129.8
113.8
115.9
119.8
2. [Me2Sn(L2)]a
3. [Me2Sn(HBT)]b
4. [Me2Sn(DAP4P)]c
5. [Bu2Sn(DAP4P)]
6. [Ph2Sn(L1)]a
–0.83
–0.88
–0.83
–0.82
7. [Ph2Sn(L2)]a
8. [Ph2Sn(HBT)]b
9. [Ph2Sn(hacm)]c
10. [Ph2Sn(hacmm)]c
11. [Ph2Sn(DAP4P)]c
–0.79
–0.72
–0.74
127.0
119.4
118.9
Abbreviations: PQS = partial quadrupole splitting, H2L1 = 4-phenyl-2,4-butanedione-1-(S-benzyldithiocarbazate), H2L = salicylaldehydethiosemicar-
bazone, H2DAP4P = 2-hydroxyacetophenone-N4-phenylthiosemicarbazone, H2hacm = 2-hydroxyaceto-phenone-N4-morpholylthiosemicarbazone,
H2hacmm = 2-hydroxyacetophenone-N4-2,6-dimethylmorpholylthiosemicarbazone.
a
This work.
Ref. [18].
Ref. [22].
b
c
ONS-tridentate ligands. Similarly, from complexes 6, 8, 9 and 10
we obtain a value for [Ph] = ꢁ0.77 mm/s (average of ꢁ0.82,
ꢁ0.79, ꢁ0.72, and ꢁ0.74 mm/s, respectively) in similar five-coordi-
nated diorganotin(IV) derivatives containing ONS-tridentate diba-
sic ligands. Now, using our alternative values for [Me] =
ꢁ0.84 mm/s and for [Ph] = ꢁ0.77 mm/s, we predict Me–Sn–Me
and Ph–Sn–Ph angles of 123.7° and 119.7° for complexes 1 and 6,
respectively. The average value of ꢁ0.77 mm/s is very far from
the value for [Ph] = ꢁ0.98 mm/s previously reported [10] by Ban-
croft’s team, but it is in good agreement with calculated value of
[Ph] = ꢁ0.75 mm/s reported recently by us [24].
3.6. Theoretical calculations
The B3LYP hybrid density functional method [25] with all elec-
tron basis sets DZVP [26,27] and the smaller 3–21G(ꢀ) [28], were

52
G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
(a)
(b)
1.00
1.000
0.995
0.990
0.985
0.99
0.98
-6
-4
-2
0
2
4
6
-6
-4
-2
0
2
4
6
Velocity (mm/s)
Velocity (mm/s)
(c)
(d)
1.00
0.98
0.96
1.000
0.995
0.990
-4
0
4
-6
-4
-2
0
2
4
6
Velocity (mm/s)
Velocity (mm/s)
Fig. 4. 119Sn Mössbauer effect spectra obtained at 80 K to complexes [Ph2Sn(L1)] (a), [Me2Sn(L1)] (b), [Ph2Sn(L2)] (c) and [Me2Sn(L2)] (d).
applied to obtain the global minimum energy geometry and IR har-
monic frequencies for all molecules presented here. All calcula-
tions were done with the software Gaussian G03W D01, using a
fine integration grid, tight energy minimization and verified for
the absence of imaginary frequencies. The B3LYP method was cho-
sen because it gives good accuracy for single molecule geometries
and reasonably accurate IR frequencies for a wide variety of molec-
ular systems [29] as well as for Sn(IV) compounds [30–32]. Geom-
etries were compared only for the three complexes for which X-ray
data was available. Since calculations were done in vacuum and
zero Kelvin it would be expected that theoretical bond lengths
should be shorter than experimental ones. However, larger bond
lengths were observed with mean signed differences (MSD) of
+0.026 Å for both basis sets. This particular behavior can be due
to deficiencies such as an inadequate treatment of electron corre-
lation effects, leading to stronger electron repulsion, and lack of
relativistic effects [30]. Even with this bias the B3LYP method per-
forms quite well as a practical option for predicting molecular
geometries in our systems, with mean absolute differences
(MAD) of 0.029 Å (3–21G(ꢀ)) and 0.031 Å (DZVP). Maximum differ-
ences were smaller than 0.099 Å for both basis sets, i.e., less than
8% differences to the crystal X-ray bond lengths. Surprisingly
although 3–21G(ꢀ) has about 73% of DZVP’s basis functions, it per-
formed a little better for all complexes. This difference was more
striking when only the 15 Sn(IV) bonds were included on statistics,
MADs of 0.034 Å (3–21G(ꢀ)) and 0.049Å (DZVP), the latter showing
a more pronounced bias in overestimating Sn(IV) bond lengths.
Smaller bias were observed for bond angles, MSD of ꢁ0.08° (3–
21G(ꢀ)) and +0.34° (DZVP). In absolute values both basis sets had
similar results, MADs of 1.95° and 1.74° respectively. It is well
known from the literature that IR absorption frequencies are usu-
ally overestimated by ab initio methods, requiring correction with
general purpose scaling factors or functional groups specific ones.
General and specific average scaling factors were calculated for
both basis sets from all 75 (four complexes and two ligands) and
10 (involving Sn(IV) atom) harmonic frequency values respec-
tively. While general MADs were 19 cmꢁ1 (3–21G(ꢀ)) and
17 cmꢁ1 (DZVP), suggesting that both basis sets might have similar
quality, specific Sn(IV) MADs of 24 cmꢁ1 and 5 cmꢁ1 were found
respectively, proving the superior quality of DZVP predicted Sn(IV)

G. F. de Sousa et al. / Journal of Molecular Structure 981 (2010) 46–53
53
harmonic frequencies. The calculated general average scaling fac-
Acknowledgements
tors were 0.9866 (3–21G(ꢀ)) and 0.9929 (DZVP), when using all
75 frequencies, and 0.9587 (3–21G(ꢀ)) and 0.9967 (DZVP) for
Sn(IV) specific frequencies. The larger difference between 3 and
21G(ꢀ) general and specific factors is due to it’s poorer perfor-
mance on Sn(IV) specific frequencies.
The authors are grateful to CNPq, FAPESP and FINEP (CT INFRA
0970/01) for financial support. GFS also gratefully acknowledges
the financial support of the CNPq (Edital Universal-2007, Processo
307412/2008-3).
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Crystallographic data for the structural analysis of the com-
plexes have been deposited at the Cambridge Crystallographic Data
Center with the deposition numbers CCDC 697620 for [Me2Sn(L1)],
CCDC 697621 for [Ph2Sn(L2)] and CCDC 742944 for [Me2Sn(L2)].
Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB21EZ, UK (Fax: +44 1223
336033 or e-mail: deposit@ccdc.cam.ac.uk).