Use of bis-aminoalcohol benzoquinones and dihydroxybenzoquinones in the formation of mono and polymeric structures of diorganotin(IV) derivatives

Article abstract of DOI:10.1016/j.jorganchem.2010.10.040

Reaction of three hexadentate ligands (L1-L3) derived from 1,4-benzoquinone bis(aminoalcohols) with diorganotin oxides (R₂Sn-O)_n (with R = Me, nBu, Ph) in 1:2 stoichiometric proportions lead to the formation of dinuclear tin compounds of the composition [(R₂Sn) ₂(L)], wherein the five-coordinate metal centers are embedded in distorted trigonal-bipyramidal polyhedra. X-ray diffraction analysis revealed that diorganotin complexes carrying n-butyl groups tend to associate further through intermolecular O?Sn interactions to give 1D polymeric chains, while diphenyltin analogues tend to be monomeric. On the other hand, using 2,5-dihydroxy-3,6-dichloro-1,4-benzoquinone as ligand (L4) in 1:1 reactions with the diorganotin oxide derivatives, 1D polymeric complexes of the composition [R₂Sn(L4)(DMSO)]_n with seven-coordinate metal centers in distorted pentagonal-bipyramidal coordination polyhedra were obtained. In this case, the presence of different substituents attached to the tin atoms (Me, nBu, Ph) had no influence on the molecular composition of the products, but on the conformation of the polymeric chain, which was either planar (R = Me), slightly distorted from planarity (R = nBu) or ondulated (R = Ph).

Full text of DOI:10.1016/j.jorganchem.2010.10.040

Journal of Organometallic Chemistry 696 (2011) 1949e1956
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Use of bis-aminoalcohol benzoquinones and dihydroxybenzoquinones in the
formation of mono and polymeric structures of diorganotin(IV) derivatives
,
a
a
b
Victor Barba a , Jonathan Zaragoza , Herbert Höpfl , Norberto Farfán ,
*
Hiram I. Beltrán c, Luis S. Zamudio-Rivera d
a Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209 Cuernavaca, Morelos, Mexico
b Facultad de Química, Departamento de Química Orgánica, Universidad Nacional Autónoma de México, México D.F. 04510, Mexico
c Departamento de Ciencias Naturales, DCNI, Universidad Autónoma Metropolitana, Unidad Cuajimalpa, Pedro Antonio de los Santos 84, 11850 Mexico D.F., Mexico
d Laboratorio de Síntesis Química y Electroquímica, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, Col. San Bartolo Atepehuacan, México D.F., Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of three hexadentate ligands (L1eL3) derived from 1,4-benzoquinone bis(aminoalcohols) with
diorganotin oxides (R2Sn-O)n (with R ¼ Me, nBu, Ph) in 1:2 stoichiometric proportions lead to the
formation of dinuclear tin compounds of the composition [(R2Sn)2(L)], wherein the five-coordinate metal
centers are embedded in distorted trigonal-bipyramidal polyhedra. X-ray diffraction analysis revealed
that diorganotin complexes carrying n-butyl groups tend to associate further through intermolecular
O/Sn interactions to give 1D polymeric chains, while diphenyltin analogues tend to be monomeric. On
the other hand, using 2,5-dihydroxy-3,6-dichloro-1,4-benzoquinone as ligand (L4) in 1:1 reactions with
the diorganotin oxide derivatives, 1D polymeric complexes of the composition [R2Sn(L4)(DMSO)]n with
seven-coordinate metal centers in distorted pentagonal-bipyramidal coordination polyhedra were
obtained. In this case, the presence of different substituents attached to the tin atoms (Me, nBu, Ph) had
no influence on the molecular composition of the products, but on the conformation of the polymeric
chain, which was either planar (R ¼ Me), slightly distorted from planarity (R ¼ nBu) or ondulated
(R ¼ Ph).
Received 21 September 2010
Received in revised form
13 October 2010
Accepted 18 October 2010
Keywords:
Organotin compounds
Tin
Quinone ligands
Aminoalcohol ligands
Hexadentate ligands
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
from corrosion. In particular poly(aminoquinones) (PAQs) provide
excellent anticorrosive coatings for metal surfaces [8]. It is also
The biological and chemical properties of quinones have been
widely studied. For example, it is well known that 1,4-benzoqui-
none derivatives participate as electron and proton carriers in
biochemical redox processes [1]. The presence of donor or acceptor
substituents in the 1,4-benzoquinone skeleton allows to modify
their redox potential and, therefore, their biological activity [2]. To
evaluate and rationalize these effects in a quantitative fashion,
electrochemical [3] and structural [4] studies have been performed.
Aminobenzoquinones are among the most explored quinone
derivatives, both in form of monomeric [5] as well as polymeric [6]
systems. The electron-donor properties of these quinones are
worthwhile to mention that the 1,4-benzoquinone moiety forms
part of the structural skeleton of mitomycin C, an antibiotic that
also presents anticancer activity [9].
Recently, we reported on a bis(di-n-butyltin) 1,4-benzoquinone
derivative having simultaneously chemo- and bioactive corrosion
inhibitor properties. This compound has shown a corrosion inhibi-
tion efficiency of 75% when used for the protection of the metallic
surface of mild steel samples, which previously had been exposed to
a sour brine environment. In vitro tests demonstrated that at the
same time this compound displays bactericidal activity against
a wide range of aerobic and anaerobic bacteria, but has relatively
low acute toxicity [10]. This shows that the analysis of tin quinone
derivatives is an interesting subject, especially because organotin
compounds have emerging biological applications. The biochemical
activity of organotin compounds is influenced by the molecular
structure of the ligand and the coordination number of the metal
atom [11]. Of these, organotin complexes based on chelating ONO
donor ligands have received much attention [12], mainly because
they frequently exhibit bactericidal and antitumor activities [13].
increased by the presence of substituents carrying p-electrons and
unshared electron pairs of adjacent oxygen or nitrogen atoms [7].
The elevated electron density allows for a strong interaction with
metal surfaces such as steel, capable of protecting the metal surface
* Corresponding author. Tel./fax: þ52 777 3297997.
E-mail address: vbarba@ciq.uaem.mx (V. Barba).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.10.040

1950
V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
As a part of our interest in organotin aminoquinone derivatives,
we have first prepared three ONO chelating agents derived from
1,4-benzoquinone and different aminoalcohols, which were then
reacted with diorganotin oxides carrying different organic
substituents. In the second part, a dihydroxybenzoquinone deriv-
ative was condensed with diorganotin oxides in order to form
polymeric diorganotin compounds.
2. Results and discussion
Scheme 2. Synthesis of dinuclear tin compounds using an aromatic aminoalcohol (L3)
as ligand.
2.1. Preparation and structural characterization of compounds
1ae1f and 2ae2c
In accordance to the procedure previously described for
compound 1b [10], compounds 1a, 1ce1f (Scheme 1) and 2ae2c
(Scheme 2) were synthesized from 1,4-benzoquinone bis(amino-
alcohols) L1eL3 and diorganotin oxides (R2Sn-O)n with R ¼ Me,
nBu and Ph. The starting aminoalcohols used for the preparation
of ligands L1eL3 were 2-aminoethanol (L1), ephedrine (L2) and
2-aminophenol (L3). All reactions were carried out in ethanol
under reflux. After 10 h a red precipitate was observed, which was
filtered to separate the products in moderate to good yields,
ranging from 49 to 95%. The stability of the isolated compounds is
not affected by moisture exposition, which can be attributed to the
presence of strong SneO covalent bonds and the formation of
chelate rings.
lower wavenumbers after complexation, owing to the formation of
the coordinative covalent O/Sn bonds. For ligands L1eL3 the C]O
vibration band is observed at 1546, 1561 and 1586 cmꢀ1, respec-
tively. The same band was found at 1523, 1534 and 1539 cmꢀ1 for
compounds 1ae1c, at 1525, 1534 and 1538 cmꢀ1 for 1de1f, and at
1509, 1512 and 1516 cmꢀ1 for 2ae2c. These values indicate that the
largest changes occurred for compounds 2ae2c, for which an
enhanced electron delocalization is expected due to the presence of
aromatic rings in the tridentate ligand skeleton. The formation of
covalent SneO and SneN bonds can be deduced also from the
disappearance of vibration bands corresponding to the OeH and
NeH bonds.
In almost all cases the mass spectra gave a peak corresponding
to the molecular ion, evidencing the formation of a dinuclear tin
compound. Exceptions were compounds 1a and 1d, for which the
observed peaks correspond to fragments resulting from the loss of
one of the organic groups attached to the tin atom. In mass spec-
trometric analysis the rupture of SneC bonds and the corre-
sponding loss of an organic group attached to the metal is indeed
characteristic for this type of compounds [12].
The formation of dinuclear tin compounds was evidenced also
by NMR (1H, 13C and 119Sn) spectroscopy. Only compound 2b could
not be analyzed because of its insolubility. For compounds 1ae1f
the 1H NMR analysis reveals a single signal in the range from 5.89 to
6.61 ppm, corresponding to the hydrogen atoms of the quinone
moiety. For compounds 2a and 2c this signal is shifted significantly
to lower fields (6.85 and 7.03 ppm, respectively), which confirms
the results obtained from the IR analysis. This observation can be
However, the aminoalcohol moieties are responsible for inter-
esting changes in the physical properties of the products. For
instance, the 2-aminoethanol derivatives 1ae1c are less soluble
than the ephedrine derivatives 1de1f, while the 2-aminophenol
derivatives 2ae2c are practically insoluble in all common solvents.
Ligands L1eL3 contain two OH and two NH groups in the
aminoalcohol residue and two oxygen atoms in the quinone
moiety, which provide the system with a total of six coordination
sites for the combination with two tin centers. Considering the
organic groups (alkyl or aryl) attached to the metal, for each tin
atom a five-coordinate geometry can be expected. The condensa-
tion reaction between diorganotin oxides and 1,4-benzoquinone
bis(aminoalcohols) generates covalent SneN and SneO bonds, as
a result of the deprotonation of both the NH and OH groups. The
quinone oxygen atoms participate in coordinative covalent O/Sn
bonds. Thus, compounds 1ae1f and 2ae2c contain two tin atoms,
each being surrounded by two oxygen atoms, one nitrogen and two
carbon atoms.
attributed to electronic deshielding resulting from p-delocalization
throughout the aromatic rings. The chemical shifts for the
hydrogen atoms of the ethylene moieties appeared in the range of
3.30e5.09 ppm. An interesting point is the observation that the
organic groups attached to the tin atoms in compounds 1de1f are
diastereotopic, thus giving two signals for each diorganotin group.
For instance, for the Me2Sn groups in 1d two single signals were
observed at 0.66 and 0.76 ppm, while only one single signal was
observed for the hydrogens of the same group in 1a (0.68 ppm) and
2a (0.78 ppm). In all three cases, the 2JSneH coupling constants are
similar (75, 69 and 63 Hz, for 1a, 1d and 2a, respectively), which in
accordance to Lockhart’s equation [17] corresponds to CeSneC
bond angles of 125, 119 and 122ꢁ, indicating the equatorial position
of the methyl groups attached to the tin center.
Comparison of the IR spectra between ligands L1eL3 and the
corresponding products shows that the stretching band corre-
sponding to the carbonyl group of the quinone moiety is shifted to
Unfortunately, the low solubility of compounds 1a, 1c, 2aec in
most of the common solvents disabled their complete character-
ization by 13C and 119Sn NMR spectroscopy. Nonetheless, the data for
compounds 1de1f indicate that the chemical shifts of the coordi-
nated ligand moieties are very similar for the three compounds. For
example, the chemical shift for the CeN carbon atoms in the
quinone rings (C3) are 159.1 ppm in all three cases. The chemical
shifts for the C]O carbon atoms of the quinone moiety (C1) are
slightly different and low-field shifted when compared to the free
Scheme 1. Synthesis of dinuclear tin compounds using aliphatic aminoalcohols
(L1 and L2) as ligands.

V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
1951
Fig. 3. Perspective view of the molecular structure of compound 1f.
In the crystal structure of compound 1e, the complex molecules
are associated through intermolecular O/Sn interactions
(Sn1eO2 ¼ 2.509 Å) that give rise to four-membered Sn2O2 rings.
The resulting linear 1D polymeric chains have been observed
previously also for 1b [10] and related compounds [12] (Figs. 1
and 2). The six-coordinate tin atoms have a distorted octahedral
geometry, in which the organic groups have approximate trans-
Fig. 1. Fragment of the polymeric structure of compound 1e. Selected bond lengths [Å]
and angles [ꢁ]: Sn1-O1 2.093(3), Sn1-N1 2.198(4), Sn1-O3 2.321(4), Sn1-C25A 2.1303
(11), Sn1-C29B 2.1299(11), O1-Sn1-O3 146.22(12), O1-Sn1-N1 75.84(14), O3-Sn1-N1
70.46(14), C25A-Sn1-C29B 140.2(5).
ꢁ
0
disposition (C
aeSneC
a
¼ 140.2(5) ). The donor atoms of the ligand
ligands (168.7, 169.1 and 168.4 ppm for 1de1f, respectively). For the
remaining carbon atoms of the 1,4-benzoquinone ring (C2), the
chemical shifts were 93.4, 93.3 and 94.1 ppm for 1de1f, respec-
tively. As in the 1H NMR spectra, the diastereotopic character of the
organic groups attached to the tin atoms is also observed in the 13C
NMR spectra, giving two signals for each R2Sn moiety. The 119Sn
NMR spectra provided evidence for the five-coordinate geometry
for the tin atoms. The chemical shifts were ꢀ91, ꢀ113 and ꢀ251 ppm
for 1de1f, respectively, which are typical for diorganotin complexes
carrying ONO ligands [14]. The previously reported derivative 1b
gave a 119Sn NMR signal at ꢀ129 ppm [10].
are distributed among the equatorial sites. The bond distances and
angles in complex 1e are comparable to those observed for
compound 1b. For example, the covalent Sn1eO1 bond distance of
2.093(3) Å is significantly shorter than the coordinate covalent
Sn1eO3 bond with the quinone oxygen (bond distance of 2.321(4)
Å). The largest bond angle with a value of 146.22(12)ꢁ corresponds
to atoms O1eSneO3.
Compound 1f is monomeric and the coordination geometry
of the tin atoms is distorted trigonal-bipyramidal. In this case,
intermolecular O/Sn interactions were not found, which can
be attributed to the steric and electronic effects of the phenyl rings
attached to tin atom. This observation has been noticed also for
similar compounds derived from hexadentate ligands [12].
Crystals suitable for X-ray diffraction analysis were grown for
complexes 1e and 1f by slow diffusion of dichloromethane into
a diluted solution in methanol. For both compounds data were
collected at low temperature (T ¼ 100 K). Perspective views of the
molecular and crystal structures are shown in Figs. 1e3. The most
relevant crystallographic data are described in Table 1.
Table 1
Crystallographic data for compounds 1e and 1f.
Identification code
1e
1f
Empirical formula
Formula weight
Crystal size [mm3]
Crystal system
Space group
C40H58N2O4Sn2
868.26
C48H42N2O4Sn2
948.22
0.32ꢂ0.24ꢂ0.18
Monoclinic
P21/c
0.40ꢂ0.36ꢂ0.32
Triclinic
P-1
Unit cell dimensions
a [Å]
b [Å]
c [Å]
10.1663(11)
11.3111(13)
19.701(2)
86.953(2)
85.145(2)
66.706(2)
2072.8(4)
2
13.802(2)
8.0855(14)
18.365(3)
90.00
92.445(3)
90.00
2047.7(6)
2
1.538
a
b
g
[Å]
[ꢁ]
[ Å]
Volume [Å3]
Z
rcalcd [g/cm3]
1.391
1.243
m
[mmꢀ1
]
1.267
Collected refl.
12596
12971
Independent refl. (Rint
Parameters
)
5743 (0.024)
561
3598 (0.109)
325
R1 [I > 2
wR2 (all data)
GOOF
s
(I)]
0.0366
0.1086
1.113
0.0995
0.1983
1.224
Fig. 2. Fragment of the polymeric structure due to Sn2O2 ring formation in compound
1e, showing the planarity of the quinone ring system (lateral and top view).

1952
V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
O
O
Cl
Cl
DMSO
R
Sn
R
R
HO
Cl
Cl
O
O
O
O
O
O
O
2 R2SnO
*
*
1
Sn
2
*
EtOH/DMSO
3
*
DMSO
OH
O
R
Cl
Cl
n
3a: R = Me, 3b: R = nBu, 3c: R = Ph
Scheme 3. Synthesis of polymeric tin compounds using 2,5-dihydroxy-3,6-dichloro-
1,4-benzoquinone (L4) as ligand.
Fig. 4. Fragment of the polymeric structure of compound 3a.
2.2. Preparation and structural characterization
of compounds 3ae3c
The 1H NMR spectrum of compound 3a was recorded in DMSO-
d6 and showed a single signal placed at 0.71 ppm with a JSn-H
The synthesis of polymers 3ae3c was achieved by combination of
one equivalent of the tetradentate 2,5-dihydroxy-3,6-dichloro-1,4-
benzoquinone with one equivalent of the diorganotin oxide
(R2SneO)n with R ¼ Me, nBu and Ph, using a solvent mixture of
ethanol/dimethylsulfoxide (5:1 ratio). The reaction mixtures were
stirred for 6 h at room temperature, where after the precipitated
products were recovered by filtration (Scheme 3). The 2,5-dihy-
droxy-3,6-dichloro-1,4-benzoquinone has been used previously for
the complexation of transition metals to give related polymeric 1D
structures [15]. However, with rare earth metals 2D polymeric
structures were found [16].
Compounds 3ae3c were obtained as dark solids in moderate to
good yields (62e84%). All three tin complexes are stable under
atmospheric conditions and have high melting points (>350 ꢁC).
The IR spectra gave C]O stretching bands at 1630, 1629 and
1675 cmꢀ1 for 3ae3c, respectively, providing evidence for the
formation of the O/Sn coordination bond. The mass spectra (FABþ)
gave peaks at 434, 519 and 560 m/z for 3a, 3b and 3c, respectively,
which can be assigned to monomeric species with coordinated
dimethylsulfoxide molecules. It is important to remark that peaks
with larger m/z values were also observed, which could not be
assigned to molecular fragments and might result from fragmention
of the polymeric species. Elemental analyses were acquired for
crystalline samples, showing the presence of two DMSO solvent
molecules for 3a and 3c, but only one DMSO molecule for 3b. This
indicates that compounds 3a and 3c crystallized in form of solvates,
which has been confirmed by X-ray diffraction analysis (vide infra).
2
coupling constant of 104 Hz, which in accordance to Lockhart’s
equation [17] corresponds to a CeSneC bond angle of 170ꢁ, indi-
cating trans-disposition of the methyl groups attached to the tin
center. Unfortunately, the poor solubility of this compound did not
allow for the acquisition of 13C and 119Sn NMR spectra. Compound
3b was insoluble in all organic common solvents, but compound 3c
was fairly soluble in DMSO, which enabled the complete 1H, 13C and
119Sn NMR analysis. The 1H NMR spectrum of 3c showed signals for
the phenyl groups in the range from 7.38 to 7.68 ppm. The 13C NMR
spectrum provided the chemical shifts for the quinone carbon
atoms at 172.9 (C1), 162.4 (C2) and 104.2 (C3) ppm. The 119Sn NMR
spectrum gave a signal at ꢀ439 ppm, which is indicative of a six-
coordinate coordination geometry.
The structural analysis was completed by X-ray diffraction
analysis. All three compounds were crystallized by slowevaporation
of solutions of the starting materials dissolved in DMSO/ethanol
(1:5 ratio). Data were acquired at 100 K. The most relevant crys-
tallographic data are described in Table 2. The molecular structures
for 3ae3c are given in Figs. 4e6. Selected bond lengths and bond
angles are given in Table 3.
From Figs. 4e6 it can be seen that the three compounds have
similar structures, in which the quinone ring systems adopt
a planar conformation. All structures are 1D polymeric chains, in
which the metal centers are bonded to four oxygen atoms from two
different quinone ligands and two carbon atoms from the organic
groups attached to the tin atoms. Additionally, in all three cases one
DMSO molecule is coordinated to each tin center to give seven-
coordinate complexes with distorted pentagonal-bipyramidal
geometries. As already indicated by the results of the elemental
analyses, the crystal structures of compounds 3a and 3c contain an
Table 2
Crystallographic data for compounds 3a, 3b and 3c.
Identification code
3a
C12H18Cl2O6S2Sn1 C16H24Cl2O5S1Sn1 C22H22Cl2O6S2Sn1
511.97 518.00 636.11
3b
3c
Empirical formula
Formula weight
Crystal size [mm3]
Crystal system
Space group
0.35ꢂ0.26ꢂ0.20 0.29ꢂ0.10ꢂ0.08 0.34ꢂ0.28ꢂ0.20
Orthorhombic
Triclinic
Orthorhombic
Pnma
P-1
P212121
Unit cell dimensions
a [Å]
b [Å]
c [Å]
16.045(3)
7.8567(15)
15.064(3)
90
90
90
1899.0(6)
4
1.791
1.869
10467
9.0115(10)
9.7389(11)
12.4987(14)
87.499(2)
87.862(2)
74.337(2)
1054.8(2)
2
1.631
1.585
10202
3708 (0.048)
230
8.8942(17)
15.982(3)
17.698(3)
90
90
90
2515.7(8)
4
1.679
a
b
g
[Å]
[ꢁ]
[ Å]
Volume [Å3]
Z
rcalcd [g/cm3]
m
[mmꢀ1
]
1.430
Collected refl.
Independent refl. (Rint) 1803 (0.038)
Parameters
R1 [I > 2 (I)]
wR2 (all data)
13940
2644 (0.029)
302
0.0196
0.0512
1.075
140
s
0.0427
0.1055
1.079
0.0508
0.1105
1.089
GOOF
Fig. 5. Fragment of the polymeric structure in compound 3b.

V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
1953
Fig. 6. Fragment of the polymeric structure of compound 3c.
Fig. 7. Lateral view of the polymeric structures of compounds 3ae3c, showing the
almost planar (3a) and ondulated (3b, 3c) conformations. The syndiotactic distribution
of the coordinated DMSO solvent molecules can be seen also.
additional DMSO molecule present in the asymmetric unit without
further significant geometric or structural contributions.
The five oxygen atoms coordinated to each tin atom occupy
equatorial sites, while the organic fragments are located at the axial
positions. The CeSneC bond angles are 176.0(3), 173.7(2) and
171.68(17)ꢁ for 3a, 3b and 3c, respectively. In the case of compound
3a the experimental bond angle is in good agreement with the
solvent-free form in solution. In complexes 3ae3c, the SneO
distances in the five-membered chelate rings range from 2.250(3)
to 2.412(3) Å, and are similar to those reported for related systems.
The SneO distances for the coordinated DMSO molecules are 2.297
(5), 2.253(4) and 2.195(3) Å for 3aec, respectively. These values are
smaller than the sum of the covalent radii of Sn and O (2.56 Å) and
should, therefore, be considered strong bonding interactions. The
CeO distances in the range from 1.247(6) to 1.269(5) Å are similar
for all three compounds. These findings indicate that the quinone
system should be involved in a complete delocalization.
Lateral views of the polymeric structures are shown in Fig. 7.
Compound 3a is completely planar; nonetheless, this planarity
vanishes in the presence of larger substituents at the tin atom as
can be seen for 3b and 3c. The polymeric chain starts to be dis-
torted, which is shown by the fact that the diphenyltin derivative is
ondulated. A further interesting point is that the DMSO solvent
molecules are oriented in alternate directions, giving syndiotactic
arrangements as depicted in Fig. 7.
1
value calculated from the H NMR data in solution (170ꢁ). Never-
theless, the coordination number suggested in solution (six) is
increased to seven in the solid state. The close proximity between
the CeSneC bond angles in solution and the solid state might
indicate equilibrium between the solvent-coordinated and the
Table 3
Selected bond distances (Å) and bond angles (ꢁ) for compounds 3a, 3b and 3c.
3a
2.294(5)
3b
2.266(3)
3c
2.368(3)
Sn1eO1
Sn1eO2
Sn1eO3
Sn1eO4
Sn1eO5
Sn1eCa
2.329(4)
2.336(4)
2.388(5)
2.297(5)
2.093(6)
2.093(6)
1.264(7)
1.260(8)
1.522(9)
1.387(9)
2.332(4)
2.384(4)
2.364(4)
2.253(4)
2.123(6)
2.114(6)
1.256(6)
1.247(6)
1.519(7)
1.390(7)
2.250(3)
2.412(3)
2.301(3)
2.195(3)
2.153(4)
2.134(4)
1.256(5)
1.269(5)
1.521(6)
1.385(3)
Sn1eCa
’
C1eO1
C2eO2
C1eC2
C2eC3
3. Conclusions
This contribution has shown that molecular reactions between
diorganotin oxides and symmetric hexadentate 1,4-benzoquinone
bis(aminoalcohols) in 2:1 stoichiometric proportions give discrete
dinuclear tin compounds, in which the tin atoms are either five- or
six-coordinate and embedded in distorted trigonal-bipyramidal or
octahedral coordination geometries. In accordance to the X-ray
diffraction analysis, enhanced coordination numbers are the result
of intermolecular O/Sn interactions, giving a polymeric 1D chain
in the case of the di-n-butyltin derivatives characterized in the solid
state.
On the other hand, using a tetradentate 1,4-dihydroxybenzo
quinone derivative as ligand in 1:1 molecular reactions with dio-
rganotin oxides, 1D polymeric structures were obtained. In all three
cases examined herein, additionally one DMSO molecule is coor-
dinated to each metal center, leading to a seven-coordinate
pentagonal-bipyramidal coordination geometry. The coordinated
solvent molecules are distributed along the chain in a syndiotactic
arrangement. The organic substituents present in the organome-
tallic reagent have no influence on the product composition, but
O1eSn1eO2
O1eSn1eO3
O1eSn1eO4
O1eSn1eO5
O1eSn1eCa
68.85(16)
71.61(16)
139.27(16)
146.47(16)
91.99(17)
91.99(17)
140.46(16)
151.88(17)
77.62(16)
90.46(15)
90.46(15)
67.66(16)
141.92(16)
90.89(17)
90.89(17)
74.26(17)
88.67(16)
88.67(16)
88.19(17)
88.19(17)
176.0(3)
69.59(12)
144.10(13)
148.81(13)
73.71(13)
93.55(19)
92.52(19)
74.51(12)
141.58(12)
143.19(13)
90.2(2)
68.99(10)
76.09(3)
143.68(10)
142.44(10)
86.31(14)
89.24(14)
144.97(10)
147.18(10)
74.00(11)
93.40(15)
91.56(15)
67.67(10)
140.95(10)
86.10(13)
86.00(14)
73.74(10)
92.31(14)
87.12(14)
89.76(13)
98.04(14)
171.68(17)
O1eSn1eCa
’
O2eSn1eO3
O2eSn1eO4
O2eSn1eO5
O2eSn1eCa
O2eSn1eCa
90.4(2)
’
O3eSn1eO4
O3eSn1eO5
O3eSn1eCa
67.08(12)
142.13(13)
87.8(2)
86.3(2)
75.19(13)
88.8(2)
86.9(2)
88.4(2)
94.9(2)
173.7(2)
O3eSn1eCa
’
O4eSn1eO5
O4eSn1eCa
O4eSn1eCa
’
O5eSn1eCa
O5eSn1eCa
’
CaeSn1eCa
’

1954
V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
generate variations in the molecular conformation, giving more
pronounced ondulated shape for the diphenyltin derivative.
These polymeric structures could be used as anticorrosive
coatings for the protection of metal surfaces from harsh media, as it
has been determined previously for related compounds.
Elemental Anal. Calc. for C14H22N2O4Sn2: C 32.35, H 4.26, N 5.38%.
Found: C 32.94, H 4.40, N 5.31%.
4.4.2. Preparation of [(Ph2Sn)2(L1)] (1c)
Compound 1c was prepared from 0.30 g (1.33 mmol) of ligand
L1 and 0.77 g (2.66 mmol) of diphenyltin oxide. The product was
obtained as a red powder. Yield 0.70 g (69%); mp > 370 ꢁC 1H NMR
4. Experimental part
(400 MHz, CDCl3)
d: 7.77 (dd, 8H, J ¼ 6.4, 2.8 Hz, Ho), 7.43e7.38 (m,
12H, Hm,p), 5.89 (s, 2H, H-3), 4.22 (t, 4H, J ¼ 5.7 Hz, H-5), 3.50 (t, 4H,
J ¼ 5.7 Hz, H-4) ppm. IR (KBr) v (cmꢀ1) ¼ 3434 (w), 3053 (w), 2896
(w), 2849 (w), 1539 (s), 1429 (m), 1393 (w), 1285 (m), 1058 (m), 918
(w), 804 (w), 733 (w), 696 (w), 591 (w), 452 (m). FAB-MS m/z (%):
769 ([M þ H ]þ, 66), 738 (16), 691 (15), 661 (14), 613 (100), 596 (30),
583 (15) 566 (15) 534 (14) 499 (24). Elemental Anal. Calc. for
C34H30N2O4Sn2: C 53.17, H 3.93, N 3.64%. Found: C 53.15, H 4.19,
N 3.89%.
4.1. Materials
All reagents and solvents were acquired from commercial
suppliers and used without further purification.
4.2. Instrumentation
The 1H, 13C and 119Sn NMR spectra were recorded at room
temperature using a Varian Unit 400 spectrophotometer. As stan-
4.4.3. Preparation of [(Me2Sn)2(L2)] (1d)
dard references were used TMS (internal, 1H,
d
¼ 0.00 ppm, 13C,
Compound 1d was prepared from 0.10 g (0.24 mmol) of ligand
L2 and 0.08 g (0.48 mmol) of dimethyltin oxide. The product was
obtained as a red powder. Yield 0.175 g (95%); mp > 370 ꢁC. 1H NMR
d
¼ 0.0 ppm) and SnMe4 (external, 119Sn,
¼ 0.0 ppm). 2D COSY and
d
HETCOR experiments have been carried out for the unambiguous
assignment of the 1H and 13C signals present at the NMR spectra.
Infrared spectra have been recorded on a Bruker Vector 22 FT-IR
spectrophotometer. Mass spectra were obtained with Jeol JMS 700
equipment. Melting points were determined with a Büchi B-540
digital apparatus.
(400 MHz, CDCl3) d: 7.30e7.50 (m, 10H, Harom), 5.68 (s, 2H, H-3),
4.89 (d, 2H, J ¼ 4.2 Hz, H-5), 3.90 (dq, 2H, J ¼ 6.0, 4.2 Hz, H-4), 0.79
(d, 6H, J ¼ 6.0 Hz, MeeC4), 0.76 (s, 6Ha, 2JSn-H ¼ 69 Hz, MeeSn), 0.66
(s, 2JSn-H ¼ 69 Hz, 6Hb, MeeSn), ppm. 13C NMR (100 MHz, CDCl3)
d:
168.71 (C-1), 159.14 (C-2), 143.07 (Ci), 128.40 (Cm), 127.22 (Cp),
126.17 (Co), 93.41 (C-3), 73.59 (C-5), 57.10 (C-4), 13.07 (MeeC4),
0.32 (MeeSna), 0.30 (Me-Snb). 119Sn NMR (75 MHz, CDCl3)
4.3. X-ray crystal-structure determination
d
: ꢀ91 ppm. IR (KBr) v (cmꢀ1) ¼ 3445 (w), 2979 (w), 1525 (s), 1391
X-ray diffraction studies were performed on a Bruker-APEX
(w), 1295 (m), 991 (w), 912 (w), 782 (m), 702 (w), 645 (w) 475 (w).
EI-MS m/z (%): 687 ([MꢀCH3]þ, 19), 473 (100), 443 (34), 309 (15),
244 (35), 214 (16), 105 (15). Elemental Anal. Calc. for
C28H34N2O4Sn2: C 48.04, H 4.89, N 4.00%. Found: C 48.76, H 5.19,
N 4.18%.
diffractometer with a CCD area detector, using Mo K
a-radiation,
(l
¼ 0.71073 Å) and a graphite monochromator. Frames were
collected at T ¼ 100 K for compounds 1e and 1f and at 293 K for
3ae3c. The measured intensities were reduced to F2 [17]. Structure
solution, refinement and data output were carried out with the
SHELXTL-NT program package [18,19]. All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were placed in
geometrically calculated positions using a riding model. Compound
1f gave somewhat elevated R and wR2 values owing to molecular
disorder in the ephedrine moiety. This disorder was treated using
DFIX, AFIX66, SIMU, DELU and ISOR instructions during the refine-
ment. Nonetheless, the atomic positions of the non-hydrogen atoms
and the overall molecule conformation were clearly evidenced.
4.4.4. Preparation of [(nBu2Sn)2(L2)] (1e)
Compound 1e was prepared from 0.30 g (0.74 mmol) of ligand
L2 and 0.37 g (1.48 mmol) of dibutyltin oxide. The product was
obtained as a red powder. Yield 0.32 g (50%); mp > 370 ꢁC. 1H NMR
(400 MHz, CDCl3)
d
: 7.43 (d, 4H, J ¼ 7.3 Hz, Ho), 7.36 (t, 4H,
J ¼ 7.3 Hz, Hm), 7.26 (t, 2H, J ¼ 7.3 Hz, Hp), 5.69 (s, 2H, H-3), 4.89 (d,
2H, J ¼ 3.6 Hz, H-5), 3.91 (dq, 2H, J ¼ 6.8, 3.6 Hz, H-4), 1.50e1.34 (m,
24H, H
a
, H
b
, H
g
), 0.93 (t, 6H, J ¼ 7.4 Hz,H-da), 0.90 (t, 6H, J ¼ 7.4 Hz,
H-db), 0.77 (d, 6H, J ¼ 6.8 Hz, Me-C4) ppm. 13C NMR (100 MHz,
4.4. General method for the preparation of tin complexes
CDCl3) d: 169.17 (C-1), 159.15 (C-2), 143.50 (Ci), 128.28 (Cm), 127.0
1ae1f and 2ae2c
(Cp), 126.17 (Co), 93.39 (C-3), 76.50 (C-5), 56.90 (C-4), 19.75 (C-
19.71 (C- b), 27.91 (C- a), 27.62 (C- b), 27.13 (C- a), 27.04 (C-
13.86 (C- a),13.82 (C-
CDCl3)
1391 (w), 1283 (m), 997 (w), 910 (w), 811 (w), 698 (w), 642 (w), 542
(w), 474 (w). EI-MS m/z (%): 869 ([M]þ, 16), 763 [M-2Bu]þ (77), 649
(100), 543 (53), 533 (54), 427 (96), 400 (40). Elemental Anal. Calc.
for C40H58N2O4Sn2: C 55.32, H 6.73, N 3.22%. Found: C 54.21, H 6.71,
N 3.38%.
a
a),
a
d
b
d
b
g
g
b),
Compounds 1ae1f were synthesized by reacting one equivalent
of ligand L1 (for 1ae1c), ligand L2 (for 1de1f) or ligand L3 (for
2ae2c) with two equivalents of the corresponding diorganotin
oxide (R2SnO)n (with R ¼ Me, nBu and Ph) using 30 mL of ethanol as
solvent. The reaction mixtures were heated under reflux for 10 h
under stirring. Then, the products were isolated by filtration and
purified by recrystallization from ethanol. Compound 1b has been
reported in a previous communication [10].
b),13.33 (MeeC4), ppm. 119Sn NMR (75 MHz,
d
: ꢀ113 ppm. IR (KBr) v (cmꢀ1) ¼ 3433 (w), 2956 (w), 1534 s,
4.4.5. Preparation of [(Ph2Sn)2(L2)] (1f)
4.4.1. Preparation of [(Me2Sn)2(L1)] (1a)
Compound 1f was prepared from 0.30 g (0.74 mmol) of ligand L2
and 0.43 g (1.49 mmol) of diphenyltin oxide. The product was
obtained as a red powder. Yield 0.59 g (84%); mp > 370 ꢁC. 1H NMR
Compound 1a was prepared from 0.30 g (1.33 mmol) of ligand
L1 and 0.44 g (2.67 mmol) of dimethyltin oxide. The product was
obtained as a red powder. Yield 0.52 g (75%); mp > 370 ꢁC. 1H NMR
(400 MHz, CDCl3)
d
: 7.79 (d, 8H, J ¼ 6.4 Hz, HoeSn), 7.59 (d, 4H,
(400 MHz, CDCl3)
d
: 5.65 (s, 2H, H-3), 4.06 (t, 4H, J ¼ 5.7 Hz, H-5),
J ¼ 6.4 Hz, Ho), 7.47e7.30 (m, 22H, Harom), 5.89 (s, 2H, H-3), 5.09 (d,
2H, J ¼ 3.6 Hz, H-5), 4.08 (dq, 2H, J ¼ 6.0, 3.6 Hz, H-4), 0.84 (d, 6H,
3.40 (t, 4H, J ¼ 5.7 Hz, H-4), 0.64 (s, 2JSn-H ¼ 75 Hz, 12H, Me) ppm. IR
(KBr) v (cmꢀ1) ¼ 3436 (w), 3256 (w), 1534 (s), 1434 (w), 1398 (m),
1290 (m), 1068 (m), 788 (w). EI-MS m/z (%): 490 [M-2CH3]þ, (77),
445 (74), 400 (76), 311 (44), 281 (57), 215 (100), 152 (68), 135 (45).
J ¼ 6.0 Hz, MeeC4), 13C NMR (100 MHz, CDCl3)
d: 168.41 (C-1),
159.14 (C-2), 143.44 (Ci), 138.92, 138.57 (CieSn), 136.67, 136.62
(CoeSn), 130.66, 130.58 (CpeSn), 129.11, 129.08 (CmeSn), 128.45

V. Barba et al. / Journal of Organometallic Chemistry 696 (2011) 1949e1956
1955
(Cm), 127.27 (Cp), 126.33 (Co), 94.1 (C-3), 75.90 (C-5), 57.05 (C-4),
4.5.2. Preparation of [nBu2Sn(L4)]n (3b)
13.74 (C-6) ppm. 119Sn NMR (75 MHz, CDCl3)
d: ꢀ251 ppm. IR (KBr) v
Compound 3b was prepared from 0.30 g (1.69 mmol) of quinone
L4 and 0.42 g (1.69 mmol) of dibutyltin oxide. The product was
obtained as a dark red powder. Yield 80% (0.70 g); m.p. > 370 ꢁC. IR
(KBr) v (cmꢀ1) ¼ 3235 (m), 1665 (w), 1629 (s), 2863 (m), 1367 (m),
1269 (s), 981 (m), 848 (w), 754 (w), 692 (w), 568 (w). FAB-MS m/z
(%): 595 (5), 519 (10), 460 (5), 424 (5), 379 (5), 345 (15), 307 (30),
289 (20), 273 (15), 192 (100), 165 (8). Elemental Anal. Calc.
for C14H18 Cl2O4Sn$DMSO: C 37.09, H 4.66%. Found: C 36.78,
H 4.56%.
(cmꢀ1) ¼ 3432 (w), 3057 (w), 2365 (w),1538 (s), 1437 (w),1388 (w),
1265 (m), 1111 (w), 1071 (w), 1002 (w), 733 (w), 698 (w). EI-MS m/z
(%): 949 ([M]þ, 3), 763 (4), 460 (9), 407 (36), 307 (100), 289 (78),
242 (34), 163 (49). Elemental Anal. Calc. for: C48H42N2O4Sn2: 60.79,
H 4.46, N 2.95%. Found: C 60.57, H 4.57, N 2.82%.
4.4.6. Preparation of [(Me2Sn)2(L3)] (2a)
Compound 2a was prepared from 0.30 g (0.93 mmol) of ligand
L3 and 0.31 g (1.88 mmol) of dimethyltin oxide. The product was
obtained as a red powder. Yield 0.37 g (65%); mp > 370 ꢁC 1H NMR
4.5.3. Preparation of [Ph2Sn(L4)]n (3c)
(400 MHz, CDCl3)
d
: 7.72 (dd, 2H, J ¼ 8.4, 1.4 Hz, H-9), 7.17 (ddd, 2H,
Compound 3c was prepared from 0.50 g (2.82 mmol) of
quinone L4 and 0.81 g (2.82 mmol) of diphenyltin oxide. The
product was obtained as a dark red powder. Yield: 62% (1.11 g);
m.p. > 370 ꢁC, IR (KBr) v (cmꢀ1) ¼ 3441 (m), 1675 (s), 1504 (s),
1371 (m), 1072 (w), 855 (w), 730 (w), 694 (w), 577 (w), 446 (w). 1H
J ¼ 8.4, 7.2,1.6 Hz, H-8), 6.90 (dd, 2H, J ¼ 8.0,1.6 Hz, H-6), 6.85 (s, 2H,
H-3), 6.73 (ddd, 2H, J ¼ 8.0, 7.2, 1.4 Hz, H-7), 0.78 (s, 2JSn-H ¼ 73 Hz,
12H, Me) ppm. IR (KBr) v (cmꢀ1) ¼ 3436 (w), 2990 (w), 29.18 (w),
1569 (w), 1509 (m), 1461 (w), 1268 (m), 1189 (w), 755 (w), 578 (w),
435 (s). EI-MS m/z (%): 616 ([M]þ, 100), 586 (89), 556 (43), 422 (15),
293 (16), 278 (16). Elemental Anal. Calc. for C22H22N2O4Sn2: C
42.90, H 3.60, N 4.54%. Found: C 42.67, H 3.48, N 4.18%.
NMR (400 MHz, DMSO-d6)
(m, 6H, Hm, Hp) ppm. 13C NMR (100 MHz, DMSO-d6)
1), 162.42 (C-2), 147.17 (Ci), 134.93 (Co), 128.83 (Cp), 128.20 (Cm),
104.25 (C-3). 119Sn NMR (75 MHz, DMSO-d6)
d
: 7.68 (d, 4H, J ¼ 6.8 Hz, Ho), 7.38e7.46
d
: 172.91 (C-
d
: ꢀ439.4 ppm. FAB-
4.4.7. Preparation of [(nBu2Sn)2(L3)] (2b)
MS m/z (%): 871 (5), 754 (8), 672 (15), 560 (12), 488 (40), 460 (15),
307 (100), 289 (65), 219 (36), 165 (15). Elemental Anal. Calc.
for C18H10Cl2O4Sn,2DMSO: C 41.53, H 3.48%. Found: C 41.32,
H 3.27%.
Compound 2b was prepared from 0.30 g (0.93 mmol) of ligand
L3 and 0.47 g (1.88 mmol) of dibutyltin oxide. The product was
obtained as a red powder. Yield 0.54 g (74%); mp > 370 ꢁC. IR (KBr) v
(cmꢀ1) ¼ 3436 (w), 2656 (m), 2922 (m), 2861 (w), 1631 (s), 1489 (s),
1220 (s), 1081 (w), 1021 (w), 806 (w), 677 (w), 598 (m). EI-MS m/z
(%): 784 ([M]þ, 100), 633 (14), 575 (16), 519 (13), 405 (12), 269 (5).
Elemental Anal. Calc. for C34H46N2O4Sn2: C 52.07, H 5.91, N 3.57%.
Found: C 51.59, H 5.82, N 3.34%.
Acknowledgements
The authors thank Consejo Nacional de Ciencia y Tecnología
(CONACyT) and Instituto Mexicano del Petróleo (IMP) for financial
support.
4.4.8. Preparation of [(Ph2Sn)2(L3)] (2c)
Compound 2c was prepared from 0.30 g (0.93 mmol) of ligand
L3 and 0.54 g (1.87 mmol) of diphenyltin oxide. The product was
obtained as a red powder. Yield 0.59 g (74%); mp > 370 ꢁC 1H NMR
Supplementary information
CCDC Nos. 794133 - 794137 contain the supplementary crys-
tallographic data for 1e, 1f and 3ae3c, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Center via www.ccdc.cam.ac.uk/data_request/cif.
(400 MHz, CDCl3)
d
: 7.82e7.79 (m, 8H, Ho), 7.75 (dd, 2H, J ¼ 8.4,
1.6 Hz, H-9), 7.43e7.40 (m, 12H, Hm,p), 7.23 (ddd, 2H, J ¼ 8.4, 7.2,
1.4 Hz, H-8), 7.13 (dd, 2H, J ¼ 8.4, 1.4 Hz, H-6), 7.03 (s, 2H, H-3), 6.79
(ddd, 2H, J ¼ 8.4, 7.2,1.6 Hz, H-7) ppm. IR (KBr) v (cmꢀ1) ¼ 3432 (m),
3054 (w), 1656 (m), 1516 (s), 1461 (m), 1271 (s), 1147 (w), 822 (w),
736 (m), 550 (w), 446 (w). EI-MS m/z (%): 864 ([M]þ, 4), 785 (4), 710
(4), 621 (4), 559 (3), 429 (25), 345 (35), 307 (65), 389 (45) 192 (100).
Elemental Anal. Calc. for C42H30N2O4Sn2: C 58.37, H 3.49, N 3.24%.
Found: C 58.01, H 3.52, N 3.16%.
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4.5.1. Preparation of [Me2Sn(L4)]n (3a)
Compound 3a was prepared from 0.50 g (2.82 mmol) of quinone
L4 and 0.46 g (2.82 mmol) of dimethyltin oxide. The product was
obtained as a dark red powder. Yield: 84% (1.21 g); m.p. > 370 ꢁC, 1H
NMR (400 MHz, DMSO-d6)
d
: 0.71 (s, 2JSn-H ¼ 104 Hz, SneMe) ppm.
IR (KBr) v (cmꢀ1) ¼ 3437 (w), 1630 (m), 1518 (s), 1369 (m), 1275 (m),
1000 (w), 854 (w), 783 (m), 575 (m). FAB-MS m/z (%): 460(7), 434
(5), 367 (5), 345 (10), 307(28), 289 (18), 273 (5), 235 (5), 214 (100),
192 (25), 165 (7). Elemental Anal. Calc. for C8H6Cl2O4Sn$2DMSO: C
28.14, H 3.54%. Found: C 27.87, H 3.46%.
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