Synthesis and characterization of diorganotin(IV) complexes of tetradentate Schiff bases: Crystal structure of n-Bu2Sn(Vanophen)

Article abstract of DOI:10.1016/S0277-5387(99)00171-0

Diorganotin(IV) complexes of the general formula R₂SnL (R=Ph, n-Bu and Me) have been prepared from diorganotin(IV) dichlorides (R₂SnCl₂) and tetradentate Schiff bases (H₂L) containing N₂O₂ donor atoms in the presence of triethylamine in benzene. The Schiff bases, H₂L, were derived from salicylaldehyde, 3-methoxysalicylaldehyde (o-vanillin), 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and diamines such as o-phenylenediamine and 1,3-propylenediamine. The complexes were characterized by IR, NMR (¹H, ¹³C, ¹¹⁹Sn) and elemental analysis. The structure of the complex, n-Bu₂Sn(Vanophen), was determined using single crystal X-ray diffraction. The tin atom has a distorted octahedral coordination, with the Vanophen ligand occupying the four equatorial positions and the n-butyl groups in the trans axial positions. Six-coordinated distorted octahedral structures have been proposed for all diorganotin(IV) complexes studied here, as they possess similar spectroscopic data. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00171-0

Polyhedron 18 (1999) 2687–2696
Synthesis and characterization of diorganotin(IV) complexes of tetradentate
Schiff bases: crystal structure of n-Bu2Sn(Vanophen)
Dilip Kumar Deya , , Manas Kumar Saha , Mrinal Kanti Das , Neetu Bhartiya , R.K. Bansal ,
a
a,1
b
b
*
Georgina Rosairc, Samiran Mitraa,2
aDepartment of Chemistry, Jadavpur University, Calcutta-700 032, India
bDepartment of Chemistry, University of Rajasthan, Jaipur-302004, India
cDepartment of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS, UK
Received 8 March 1999; accepted 16 June 1999
Abstract
Diorganotin(IV) complexes of the general formula R2SnL (R5Ph, n-Bu and Me) have been prepared from diorganotin(IV) dichlorides
(R2SnCl2) and tetradentate Schiff bases (H2L) containing N2O2 donor atoms in the presence of triethylamine in benzene. The Schiff
bases, H2L, were derived from salicylaldehyde, 3-methoxysalicylaldehyde (o-vanillin), 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and
diamines such as o-phenylenediamine and 1,3-propylenediamine. The complexes were characterized by IR, NMR (1H, 13C, 119Sn) and
elemental analysis. The structure of the complex, n-Bu2Sn(Vanophen), was determined using single crystal X-ray diffraction. The tin atom
has a distorted octahedral coordination, with the Vanophen ligand occupying the four equatorial positions and the n-butyl groups in the
trans axial positions. Six-coordinated distorted octahedral structures have been proposed for all diorganotin(IV) complexes studied here,
as they possess similar spectroscopic data.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Diorganotin(IV) complexes; 13C/ 119Sn NMR spectra; Crystal structure; Tetradentate Schiff bases
1. Introduction
Hence, little information is available regarding the mode of
interaction between diorganotin(IV) moieties and Schiff
bases, and the behaviour of these complexes in the solid
state and solution. Continuing our previous study [26],
here we report the synthesis and characterization of some
chelated diorganotin(IV) complexes of deprotonated tetra-
dentate Schiff bases.
The coordination chemistry of mostly bidentate Schiff
bases with inorganic tin(IV) and organotin(IV) compounds
has recently received increased attention [1–12]. Or-
ganotin(IV) complexes of deprotonated Schiff bases are
also known [13–16]. Our interest in the chemistry of
organotin(IV) complexes of Schiff bases has stemmed
from the reported biocidal [17–21] and antitumour [22–
24] activities of organotin(IV) complexes, and the be-
haviour of Schiff bases as models for biological systems
[25].
2. Experimental
However, few studies have been conducted with the
diorganotin(IV) chelated complexes containing dianionic
tetradentate Schiff bases in comparison to their adducts.
2.1. General
All chemicals and reagents were of reagent-grade qual-
ity. Diphenyltin dichloride (Aldrich), di-n-butyltin dichlor-
ide (Alfa), dimethyltin dichloride (Fluka), o-phenylene-
diamine (Fluka), 1,3-propylenediamine (Fluka), salicylal-
dehyde (Merck) and 3-methoxysalicylaldehyde (o-vanillin)
(Lancaster) were used as received. 1-Phenyl-3-methyl-4-
benzoyl-5-pyrazolone (PMBP) was prepared as reported
[27] from 1-phenyl-3-methyl-5-pyrazolone (Lancaster).
*Corresponding author. Fax: 191-33-473-4266.
E-mail address: pkbose@cal.vsnl.net.in (D.K. Dey)
1Deceased.
2Corresponding author. This author is also a Senior author.
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00171-0
1999 Elsevier Science Ltd. All rights reserved.

2688
D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
Triethylamine (S.D. Fine Chemicals, India) was dried over
KOH.
Benzene (AR, thiophene-free) and petroleum ether (40–
608C) were dried by refluxing over freshly cut sodium. All
solvents were distilled prior to use. Other solvents were
dried and purified by standard procedures.
2.3. Crystallography: X-ray crystal structure
determination of di-n-butyl[N,N9-bis(3-
methoxysalicylaldehyde)-1,2-phenylenediiminato]tin(IV),
(n-Bu)2Sn(Vanophen) (2a)
Crystals of 2a were grown by slow evaporation of a
cyclohexane solution and were subsequently coated in
nujol and vacuum grease and mounted on a glass fibre and
cooled to 160 K using an Oxford Cryosystems Cryostream
on a Siemens P4 diffractometer. Data collection as v scans
was performed with the program XSCANS [28]. No
significant crystal decay was found. Data were corrected
for absorption by psi scans and the structure was solved by
direct and difference Fourier methods and refined by full-
matrix least squares against F2. All non-hydrogen atoms
were refined anisotropically. All methylene, phenyl and
methyl H atom positions were calculated and treated as
riding models. Methylene, phenyl and methyl H-atom
displacement parameters were treated as riding models,
with Uiso being 1.2, 1.2 and 1.5 times the bound carbon
atom Ueq, respectively. Crystallographic computing was
performed using the SHELXTL [29,30] suite of programs
on a Pentium 90 MHz PC. Further details are given in
Table 1.
2.2. Physical measurements
Infrared spectra were recorded on a Perkin-Elmer 883
infrared spectrophotometer from 4000–200 cm21 as KBr
discs and were calibrated with respect to the 1601 cm21
band of polystyrene film. 1H NMR spectra were recorded
on a Bruker DPX-300 (300 MHz), a Jeol JNM FX-100
(100 MHz) or a Varian EM-360 (60 MHz) NMR spec-
trometer in CDCl3 relative to internal tetramethylsilane
(TMS). 13C NMR spectra were recorded on a Bruker
DPX-300 (at 75.47 MHz) NMR spectrometer in CDCl3
with respect to TMS as the internal standard. 119Sn NMR
spectra were recorded on a Jeol JNM FX-90Q (at 33.35
MHz) in CHCl3 as solvent (locking with D2O) with
reference to external tetramethyltin. Tin was estimated
gravimetrically as SnO2 after decomposition with conc.
HNO3. Analysis of carbon, hydrogen and nitrogen was
carried out on a Perkin-Elmer 240C or 2400 II elemental
analyser. Melting points (uncorrected) were recorded on an
electrical heating-coil apparatus. All synthetic manipula-
tions were carried out under a dry nitrogen atmosphere.
2.4. Preparation of Schiff bases
The Schiff bases, H2Salophen (1) and H2Vanophen (2)
have been prepared by refluxing o-phenylenediamine with
Table 1
Crystal data and data collection parameters of (n-Bu)2Sn(Vanophen) (2a)
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C30H36N2O4Sn
607.30
160(2)
Triclinic
P-1
13.428(2)
14.013(2)
16.498(3)
˚
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
71.590(10)
69.610(10)
88.130(10)
2750.5(8)
3
˚
V (A )
Z
4
r (calcd.), (mg/m3)
1.467
0.967
1248
u (mm21
F(000)
)
Crystal habit, size (mm)
u range (data collection) (8)
Reflections collected
Rectangular block, 0.5030.8830.58
2.09 to 25.00
10 814
Independent reflections
Observed reflections (I.2sI)
Completeness u525.008
Parameters
9499 [R(int)50.0260]
8827
97.8%
667
Goodness-of-fit on F2
Final R indices [I.2s(I)]
R indices (all data)
0.958
R1 50.0267, wR2 50.0694
R1 50.0291, wR2 50.0713
0.419 and 20.811
23
˚
Largest diff. peak and hole (e/A
)

D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
2689
The crude product was obtained after evaporation of
solvent washed with petroleum ether (40–608C) and was
finally crystallized from an appropriate solvent. The prepa-
ration of di-n-butyl[N,N9-bis(3-methoxysalicylaldehyde)-
1,2-phenylenediiminato]tin(IV), (n-Bu)2Sn(Vanophen) (2a)
is described as an example.
Compound 2a was prepared from 0.496 g (1.32 mmol)
of ligand 2 (H2Vanophen) and 0.40 g (1.32 mmol) of
(n-Bu)2SnCl2. The crude product was crystallized from hot
cyclohexane. Single crystals suitable for X-ray crystal-
lography of 2a were obtained by slow evaporation of
Fig. 1. Structure of ligands (1–4)
R0
R9
Abbreviations
H2Salophen
H2Vanophen
H2Salpn
Melting point (8C)
159–160
168–169
1
2
3
4
C6H4
C6H4
(CH2)3
(CH2)3
H
OCH3
H
50–51
OCH3
H2Vanpn
94–95
cyclohexane at room temperature. Yield: 0.685
g
(85.44%); m.p. 142–1438C. Found: C, 59.04; H, 6.00; N,
4.82; Sn, 19.88. Calcd. for C30H36N2O4Sn (607.33): C,
59.33; H, 5.98; N, 4.61; Sn, 19.54.
Yields, melting points, solvent used for crystallisation
and analytical data for other compounds are given below.
salicylaldehyde and 3-methoxysalicylaldehyde (o-vanillin),
respectively, in ethanol, while H2Salpn (3) and H2Vanpn
(4) have been prepared by the same procedures using
1,3-propylenediamine with salicylaldehyde and 3-methox-
ysalicylaldehyde, respectively. H2PMBP–o-phd (5) and
H2PMBP-pn (6) were obtained by reacting 1-phenyl-3-
methyl-4-benzoyl-5-pyrazolone (PMBP) with o-phenyl-
enediamine and 1,3-propylenediamine, respectively, in
refluxing ethanol. The diamines are mixed with aldehydes
or ketone in a 1:2 mole ratio. The crude Schiff bases were
recrystallized from ethanol before use. The molecular
structures of Schiff bases 1–6 used in the synthesis of
diorganotin(IV) complexes are shown, with abbreviations
and melting points, as follows (Figs. 1 and 2).
2.5.1. Ph2Sn(Salophen) (1a)
Compound 1a was recrystallized from toluene. Yield:
90.88%; m.p. 226–2288C. Found: C, 65.70; H, 4.30; N,
4.46; Sn, 20.45. Calcd. for C32H24N2O2Sn (587.26): C,
65.45; H, 4.12; N, 4.77; Sn, 20.21.
2.5.2. (n-Bu)2Sn(Salophen) (1b)
Compound 1b was recrystallized from chloroform–pe-
troleum ether. Yield: 91.25%; m.p. 101–1038C. Found: C,
61.75; H, 5.58; N, 4.84; Sn, 21.78. Calcd. for
C28H32N2O2Sn (547.28): C, 61.45; H, 5.89; N, 5.12; Sn,
21.69.
2.5. Synthesis of diorganotin(IV) complexes
All the complexes were similarly prepared from dior-
ganotin(IV) dichlorides and the appropriate Schiff base
ligands as follows. In a three-necked round-bottomed flask
fitted with a reflux condenser and a dry nitrogen gas inlet,
a solution of the appropriate Schiff base in dry benzene
(50 ml) and triethylamine, in a 1:2 mole ratio (10% excess
of the latter) was taken and stirred continuously. To this
solution, a solution of the appropriate diorganotin(IV)
dichlorides in benzene (20 ml) (in the same mole pro-
portions to that of the Schiff base) was added slowly.
When all of the diorganotin(IV) dichloride solution had
been added, the mixture was refluxed for ca. 6 h. Then the
reaction mixture was cooled to room temperature and the
precipitated triethylamine hydrochloride was filtered off.
2.5.3. Me2Sn(Salophen) (1c)
Compound 1c was recrystallized from toluene. Yield:
85.86%; m.p..2448C. Found: C, 57.45; H, 4.34; N, 5.84;
Sn, 25.35. Calcd. for C22H20N2O2Sn (463.12): C, 57.06,
H, 4.35; N, 6.05; Sn, 25.63.
2.5.4. Ph2Sn(Salpn) (3a)
Compound 3a was recrystallized from chloroform–pe-
troleum ether. Yield: 83%; m.p. 92–958C. Found: C, 62.78;
H, 4.62; N, 4.97; Sn, 21.06. Calcd. for C29H26N2O2Sn
(553.24): C, 62.96; H, 4.74; N, 5.06; Sn, 21.45.
2.5.5. Ph2Sn(Vanpn) (4a)
Compound 4a was recrystallized from chloroform–pe-
troleum ether. Yield: 84.10%; m.p. 118–1208C. Found: C,
60.46; H, 4.81; N, 4.93; Sn, 19.46. Calcd. for
C31H30N2O4Sn (613.30): C, 60.71; H, 4.93; N, 4.57; Sn,
19.35.
2.5.6. Ph2Sn(PMBP–o-phd) (5a)
Fig. 2. Structure of ligands (5 and 6).
Compound 5a was recrystallized from toluene. Yield:
79.65%; m.p..2448C. Found: C, 69.98; H, 4.80; N, 9.65;
Sn, 13.28. Calcd. for C52H40N6O2Sn (899.63): C, 69.42;
H, 4.48; N, 9.34; Sn, 13.20.
R0
C6H4
(CH2)3
Abbreviations
H2PMBP–o-phd
H2PMBP-pn
Melting point (8C)
216–218
103–104
5
6

2690
D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
2.5.7. Ph2Sn(PMBP-pn) (6a)
by the X-ray crystal structure determination of one repre-
sentative compound (n-Bu)2Sn(Vanophen) (2a). The
elemental analysis data for compounds 1a–6a are con-
sistent with those calculated from the formula shown in
Eq. (1).
Although the reactions seem to be instantaneous when
the reactants are mixed, refluxing for ca. 6 h was carried
out to ensure complete reaction. The resulting compounds
are stable under atmospheric conditions for a considerable
length of time, and are thermally stable up to their melting
points. They all have intense colour (red to yellow–green)
and are soluble in most common organic solvents.
The crude product was extracted with benzene, evapo-
rated, then dissolved in benzene and reprecipitated using
n-pentane. Yield: 71.26%; m.p. 138–1408C. Found: C,
68.12; H, 5.03; N, 10.08; Sn, 13.89. Calcd. for
C49H42N6O2Sn (865.62): C, 67.99; H, 4.89; N, 9.71; Sn,
13.71.
3. Results and discussion
Many Schiff bases form complexes with organotin(IV),
and inorganic tin(II) and tin(IV) in both neutral and
deprotonated forms [1–16,26]. With the neutral forms of
Schiff bases, adducts are formed by reactions in alcoholic
media, while organotin(IV) complexes of deprotonated
Schiff bases are formed in the presence of a base such as
alkoxide ion or by the exchange reaction between a Tl
Schiff base complex [e.g., Tl2(Salen)] and an or-
ganotin(IV) halide [15]. However, the chelating complex,
Ph2Sn(NAPPDI), has been reported in which the reaction
was carried out in ethanol without the presence of an
auxiliary base [16].
Preliminary reports have dealt with the formation of
H2Acen adducts [H2Acen5bis(acetylacetone)ethylene-
diamine] of organotin(IV) chlorides, R2SnCl2(H2Acen)
[31], the adduct SnCl4(H2Salen) and complexes of dian-
ion, R2Sn(Salen) (R5Me, Ph) [14]. Chelating complexes
of the type R2SnL (R5Me, Ph; H2L5dibasic tetradentate
Schiff bases) have been synthesized by the reaction of
R2SnCl2 with Schiff bases, H2L, in a 1:1 molar ratio in
ethanol in the presence of an appropriate amount of
triethylamine [13].
The reactions in this study were performed by stirring
diorganotin(IV) dichloride, R2SnCl2 [R5Ph, n-Bu, Me]
and appropriate Schiff bases (1–6) in the presence of
triethylamine as a Lewis base in refluxing benzene. The
HCl formed during the reaction was removed as triethyl-
amine hydrochloride, which precipitated in benzene and
served as the driving force for completion of the reaction.
The diorganotin(IV) dichloride, (R2SnCl2), Schiff base
(H2L) and triethylamine were mixed in a 1:1:2 mole ratio
(with a 10% excess of the latter) as shown below (Eq. (1)).
3.1. IR spectra
The infrared spectra of the Schiff bases and their
diorganotin(IV) complexes have been recorded along with
those of the starting diorganotin(IV) dichlorides. Some
important assignments are shown in Table 2. A weak broad
band in the region 3250–2350 cm21, which has been
assigned to the intramolecularly hydrogen-bonded OH in
the Schiff bases, is not observed in the infrared spectra of
these complexes (1a–6a). This indicates that the reactions
have taken place through the replacement of the phenolic
hydrogen in the complexes, contrary to what was observed
with adduct formation when the reactions were carried out
solely in alcoholic medium [6–11]. This also confirms that
organotin(IV) complexes are indeed those of the deproto-
nated forms of Schiff bases. The strong n(CH5N) band
occurring in the range 1630–1595 cm21 is shifted con-
siderably towards lower frequencies compared to that of
the free Schiff bases (occurring at 1634–1612 cm21),
indicating the coordination of an azomethine nitrogen to
the diorganotin(IV) moiety. In contrast, when adduct
formation takes place [32], the HC5N stretch shifts to
higher frequencies.
3.2. 1H NMR spectra
The 1H NMR data for the diorganotin(IV) complexes
(1a–6a) are shown in Table 3. The absence of the OH
proton signal in the complexes suggests the binding of a
tin atom to the ligand oxygen atoms through the replace-
ment of phenolic protons (for 1–4) or enolic protons (for 5
and 6). This observation supports the infrared data. The
chemical shift values of the aromatic and aliphatic protons
are as expected. A high field shift in the d values of
azomethine (HC5N) proton resonances, seen on com-
plexation, supports the ligation of azomethine nitrogens to
tin. The HC5N protons are observed as one sharp singlet
in the Schiff base ligands (occurring at 8.61–8.99 ppm), as
well as in the metal chelates (1a–c and 2a–4a), which
suggests that the two HC5N protons in Schiff bases (1–4)
and in the metal chelates (1a–c and 2a–4a) are equivalent.
In the metal chelates of the planar tetradentate H2Salen
ligand, both the HC5N proton and (CH2)2 proton reso-
(1)
Analytical data and melting points of the synthesized
compounds are given in the Experimental section. The
compounds have been characterized by elemental analysis
1
and IR, H, 13C, 119Sn NMR spectra. Spectroscopically
derived structures of the compounds have been confirmed

D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
2691
Table 2
a
Characteristic infrared bands (cm21
)
for diorganotin(IV) chelates
n(C–H)
Compound
no.
n(C–H)
(aryl)
n(CH5N)b
n(Sn–N)
459 m
n(Sn–O)
592 m
n(Sn–C)
364 m
(alkyl)
1a
3065 m
3055 m
1605 s
(1612)
1b
3057 mw
3013 w
2954 m
2927 m
2867 m
2861 m
1607 s
(1612)
482 m
604 m
588 m
1c
2a
3050 m
3014 m
2914 m
2900 w
1608 s
(1612)
471 m
498 s
599 m
547 m
588 s
3061 mw
3034 w
2993 w
2955 m
2923 m
2869 m
2832 w
1603 vs
(1612)
534 m
3a
4a
3062 m
3042 m
2922 m
2850 w
1630 s
(1634)
455 s
600 m
602 w
400 w
353 w
3064 w
3052 m
3000 m
2936 m
2854 w
2836 m
1624 vs
(1634)
455 m
5a
6a
3064 m
3050 m
2987 m
2968 w
2926 w
1625 s
(1634)
456 s
590 m
557 m
327 m
382 w
3060 m
3020 m,sh
2952 m
2922 m
2872 w
2862 m
1595 s
(1616)
450 m
a s5strong, m5medium, w5weak, v5very, br5broad, sh5shoulder.
b Figures in parentheses indicate the corresponding n(CH5N) stretching frequencies of the tetradentate Schiff bases.
nances each occur as singlets [33–35], suggesting the
equivalence of two HC5N protons and (CH2)2 protons,
respectively, and, hence, the planarity of the ligand moiety.
In the dimethyltin(IV) chelate, Me2Sn(acac)2, the methyl
resonances of the Me2Sn moiety are observed as a sharp
singlet [36–38], which is consistent with a trans configura-
tion of the two methyl groups, as is also suggested on the
basis of IR and Raman spectra [36]. In the dimethyltin(IV)
chelate 1c, there is only one sharp singlet at d 0.79 ppm
for the Me2Sn moiety: this also indicates that the complex
has a trans structure. Moreover, since the HC5N proton
resonances appear as a singlet (only one for two HC5N
protons) in all of the diorganotin(IV) chelates studied here
(with the exception of 5a and 6a), it may be deduced that
the ligand moieties lie in a plane and the two hydrocarbon
groups on tin are trans to each other. For complexes 5a
and 6a, there are no azomethine protons, but two methyl
groups occupying 3-positions on the two pyrazolyl rings,
which appear as one singlet (at d 1.67 for 5a and d 1.36
ppm for 6a), indicating that they equivalent, as one would
expect from the planar arrangement of the ligand moiety
(structure IV). For the complexes 2a and 4a, signals due to
OCH3 proton resonances appear at d 3.83 and 3.86 ppm,
respectively, as singlets, which further support the equival-
ence of the two OCH3 groups.
There are single peaks for each of the following groups:
two OCH3 in 2a and 4a, two 3-CH3 in 5a and 6a, two
Sn–CH3 groups in 1c, and HC5N protons in all of the
complexes (except 5a and 6a), which indicates that both of
the respective groups are equivalent, which is only pos-
sible for a symmetrical arrangement of the chelate ligand
moiety and trans arrangement of the two hydrocarbon
groups on tin. Thus, the 1H NMR data suggest an
octahedral ligand environment around a central tin atom
1
(Figs. 3 and 4). This interpretation, which is based on H
NMR results, is further supported by a 13C NMR and
X-ray structural study of one representative complex, 2a.
3.3. 13C NMR spectra
The 13C NMR spectral data were recorded at room
temperature in CDCl3 and key signal assignments are
shown in Table 4. For each compound, the number of
signals observed is in good agreement with the numbering
shown in Figs. 3 and 4. However, some general trends may
be noted. The C5N carbon signal occurring as a sharp

2692
D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
Table 3
1H and 119Sn NMR spectral chemical shifts (d in ppm) data of diorganotin(IV) chelates, R2SnLa
Compound
no.
Aromatic
protons
Alkyl
protons
CH5N
protons
d(119Sn)
2533.40
1ab
6.49 t [2]
8.52 s [2]
6.76 d [2]
6.96–7.68 m [18]
1bc
6.67–7.53 m [12]
0.61 t (Sn–(CH2)3 –CH3) [6]
8.43 s [2]
2414.50
0.80–1.56 m [Sn–(CH2)3 –] [12]
1cc
2ad
6.73–7.61 m [12]
0.79 s (Sn–CH3) [6]
8.48 s [2]
8.46 s [2]
2390.70
2414.20
6.48 t [2]
6.80–6.83 m [4]
7.38 s [4]
0.55 t [Sn–(CH2)3 –CH3] [6]
0.98–1.07 m [Sn–(CH2)2 –CH2 –] [4]
1.28–1.38 m
[Sn–(CH2)2 –CH2 –] [8]
1.42–1.47 m
3.83 s (OCH3) [6]
3ac
4ac
6.67–7.66 m [18]
6.49–7.33 m [16]
2.03 q (N–CH2 –CH2 –CH2 –N) [2]
3.68 t (N–CH2 –CH2 –CH2 –N) [4]
8.37 s [2]
8.33 s [2]
2219.56
2227.45
2.03 q (N–CH2 –CH2 –CH2 –N) [2]
3.66 t (N–CH2 –CH2 –CH2 –N) [4]
3.86 s (OCH3) [6]
5ac
6ac
7.10–8.33 m [34]
1.67 s (3-CH3 of pyrazolyl group) [6]
2626.20
7.06–7.80 m [26]
7.97 t
8.09 d [4]
1.72 q (N–CH2 –CH2 –CH2 –N) [2]
3.13 t (N–CH2 –CH2 –CH2 –N) [4]
1.36 s (3-CH3 of pyrazolyl group) [6]
a Measured as saturated solutions in CDCl3 (99.8%) using TMS as the internal reference; s5singlet, d5doublet, t5triplet, q5quintet, m5multiplet.
The italicised proton indicates the resonances due to that proton.
b Measured on a 100-MHz instrument.
c Measured on a 60-MHz instrument.
d Measured on a 300-MHz instrument.
singlet at d 165.50–161.68 ppm in the ligands moves
downfield, to d 171.98–163.39 ppm, upon complexation,
indicating the coordination of azomethine nitrogens to tin.
Also, the occurrence of C5N carbon as one sharp singlet
indicates the equivalence of the two C5N carbon atoms
both in the Schiff bases and their organotin(IV) complex-
es. The signal for carbon atoms of OCH3 groups occurs at
the usual position. In the complexes 2a and 4a, the
resonances appear as singlets at d 55.76 and 56.00 ppm,
respectively. The two 3-CH3 groups of the pyrazolyl rings
in complex 6a appear as a singlet at d 15.25 ppm,
indicating that they are equivalent. For the pro-
pylenediamine fragment (N–CH2 –CH2 –CH2 –N) in com-
plexes 3a, 4a and 6a, two signals are observed for three
carbon atoms, indicating the equivalence of the two
carbons attached to nitrogen atoms. For the butyl groups of
Sn–butyl, and phenyl groups of Sn–phenyl, four signals
appear for each of two organic groups and they are
assigned tentatively [39,40] (Table 4). Thus, the 13C NMR
data also support the arrangement of donor atoms around
tin in which the ligand system lies symmetrically in the
equatorial plane, with the two organic groups on tin being
trans to each other. For a cis configuration, more signals
would be expected in the 13C NMR spectra.
Fig. 3. Structure of compounds 1a–c and 2a–4a
R05C6H4
R05C6H4
R05C6H4
R05C6H4
R05(CH2)3
R05(CH2)3
R95H
R95H
R95H
R95OCH3
R95H
R5Ph
R5n-Bu
R5Me
R5Ph
R5Ph
R5Ph
(1a)
(1b)
(1c)
(2a)
(3a)
(4a)
R95OCH3
Fig. 4. Structure of compounds 5a and 6a
R05C6H4
R5Ph
R5Ph
(5a)
(6a)
R05(CH2)3

D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
2693
Table 4
13C chemical shift data (d in ppm) of diorganotin(IV) chelates, R2SnLa
Compound
no.
C5N
carbon
Ph2Snb /Bu2Snc /
Me2Sn carbons
Aromatic
carbons
Other carbons (OCH3,
CH3, N–(CH2)3 –Nd)
1a
1b
2a
3a
4a
6a
170.41
171.98
163.39
165.46
165.53
165.61
ipso-C:139.20
ortho-C:127.44
meta-C:137.05
para-C:127.78
163.22, 146.53, 136.07
135.09, 128.29, 124.53
119.66, 117.65, 115.52
a-C: 28.64
b-C: 26.88
g-C: 26.79
d-C: 14.09
164.23, 141.38, 137.85
136.73, 128.93, 124.78
120.29, 118.50, 115.62
a-C: 27.97
b-C: 26.98
g-C: 25.95
d-C: 13.21
162.49, 152.77, 140.79,
127.92, 126.91, 119.08
117.69, 115.32, 113.50
55.76 (OCH3)
ipso-C:136.46
ortho-C:129.01
meta-C:135.82
para-C: 130.24
161.35, 132.38, 131.31
118.59, 118.55, 117.06
56.55 (1C)
31.57 (2C)
ipso-C:134.46
ortho-C:127.42
meta-C:128.36
para-C:128.26
151.83, 148.36, 122.84
118.37, 117.88, 113.82
56.88 (1C)
31.54 (2C)
56.00 (OCH3)
ipso-C:139.01
ortho-C:128.65
meta-C:136.12
para-C:130.48
130.77, 130.28, 129.13,
129.01, 127.13, 124.23,
119.22, 119.05
41.02 (1C)
30.74 (2C)
15.25,147.67, 99.98
(3-CH3, C-3 and C-4
of pyrazolyl ring)
a Measured in CDCl3 (99.8%) using TMS as the internal reference.
b
c Sn–Bu2 5Sn–aCH2 –bCH2 –gCH2 –dCH3.
d N–(CH2)3 –N5N–1CH2 –2CH2 –1CH2 –N.
3.4. 119Sn NMR spectra
values are comparable with the differences found in
starting diorganotin(IV) dichlorides [47]. These d(119Sn)
values compare well with the six-coordinated tin com-
pounds of the type R2Sn(Vanophen) [R5Ph (2542.95);
R5Me (2398.15 ppm)] [26]. Thus, OCH3 groups have no
significant effect on the shielding or deshielding of tin
nucleus. From 119Sn NMR spectra, it is also evident that
the solid state structure (confirmed for 2a) is retained in
solution. The relatively low d values of 3a and 4a may be
due to weaker ligand bonding with tin, as 3 and 4, derived
from 1,3-propylenediamine, will not be stabilised by
resonance effects, compared with ligands 1, 2 and 5,
derived from o-phenylenediamine. Alternatively, there
could be some dissociation of complexes 3a and 4a in
solution, at least on the NMR time scale.
The 119Sn NMR spectra have been recorded in CHCl3
(locking with D2O) and data are shown in Table 3. A d
value in the range 2219.56 to 2626.20 ppm is obtained
for the complexes, in agreement with the range of ca.
2125 to 2525 ppm reported for six-coordinated tin
compounds [41,42]. It is well known that an increase in the
coordination number of tin should give rise to a high field
shift of d(119Sn) [43]. The d(119Sn) values also depend on
the ligand [44,45] and show an upfield shift with increas-
ing distance between the two coordinating atoms [46]. The
d(119Sn) values also depend on the groupings attached to
tin. For complexes 1a and 5a, which have phenyl sub-
stituents on tin, d(119Sn) values appear at 2533.40 and
2626.20 ppm, respectively, but for the complexes 1b, 1c
and 2a, which have n-butyl and methyl substituents on tin,
d(119Sn) values appear at 2414.50, 2390.70 and
2414.20 ppm, respectively. These differences in the d
3.5. Description of X-ray crystal structure
The X-ray structural investigation of (n-Bu)2S-

2694
D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
n(Vanophen) (2a) shows that the ligand behaves as a
tetradentate agent via two phenolic oxygen and two imino
nitrogen atoms. As predicted, the two organic groups
(n-butyl) on tin take the axial positions and four donor
atoms from ligand are in the equatorial positions. The
vanophen ligand is not completely planar, but is slightly
bow shaped. The molecular structure of one molecule (A)
is shown in Fig. 5 and selected bond lengths and angles are
given in Table 5. However, there are two crystallographi-
cally independent molecules [denoted A and B (primed
labels)], which differ most significantly in the Cbutyl –Sn–
C
bond angles [C(30)–Sn(1)–C(34), 156.76(9);
butyl
C(309)–Sn(19)–C(34)9, 166.87(10)8]. In both molecules,
the n-butyl groups are of a gauche conformation within the
fold of the bow-shaped Vanophen ligand, and trans on the
opposing side, yet the n-butyl groups are not superimpos-
able, as shown by their respective torsion angles in Table
5.
The greatest distortion from regular octahedral geometry
results from the constraints of the tetradentate Vanophen
Fig. 5. Molecular structure and atom numbering scheme of the dior-
ganotin(IV) complex (2a), molecule A.
Table 5
˚
Selected bond lengths (A) and angles (8) for compound 2a
A
B
Sn(1)–C(30)
Sn(1)–C(34)
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–N(1)
Sn(1)–N(2)
O(1)–C(7)
O(2)–C(21)
N(1)–C(1)
N(1)–C(9)
N(2)–C(15)
N(2)–C(10)
2.139(2)
2.140(2)
2.2347(16)
2.2374(16)
2.266(2)
2.2797(19)
1.308(3)
1.296(3)
1.305(3)
1.422(3)
1.304(3)
1.422(3)
Sn(19)–C(309)
Sn(19)–C(349)
Sn(19)–O(19)
Sn(19)–O(29)
Sn(19)–N(19)
Sn(19)–N(29)
O(19)–C(79)
O(29)–C(219)
N(19)–C(19)
N(19)–C(99)
N(29)–C(159)
N(29)–C(109)
2.138(2)
2.131(3)
2.2190(17)
2.2370(17)
2.277(2)
2.280(2)
1.303(3)
1.301(3)
1.297(3)
1.423(3)
1.304(3)
1.423(3)
C(30)–Sn(1)–C(34)
C(30)–Sn(1)–O(1)
C(34)–Sn(1)–O(1)
C(30)–Sn(1)–O(2)
C(34)–Sn(1)–O(2)
O(1)–Sn(1)–O(2)
C(30)–Sn(1)–N(1)
C(34)–Sn(1)–N(1)
O(1)–Sn(1)–N(1)
O(2)–Sn(1)–N(1)
C(30)–Sn(1)–N(2)
C(34)–Sn(1)–N(2)
O(1)–Sn(1)–N(2)
O(2)–Sn(1)–N(2)
N(1)–Sn(1)–N(2)
C(7)–O(1)–Sn(1)
C(21)–O(2)–Sn(1)
C(1)–N(1)–Sn(1)
C(9)–N(1)–Sn(1)
C(15)–N(2)–Sn(1)
C(10)–N(2)–Sn(1)
C(31)–C(30)–Sn(1)
C(35)–C(34)–Sn(1)
C(30)–C(31)–C(32)–C(33)
C(34)–C(35)–C(36)–C(37)
156.76(9)
83.30(8)
87.57(8)
82.62(8)
86.61(8)
128.81(6)
103.26(8)
95.86(8)
C(349)–Sn(19)–C(309)
C(309)–Sn(19)–O(19)
C(349)–Sn(19)–O(19)
C(309)–Sn(19)–O(29)
C(349)–Sn(19)–O(29)
O(19)–Sn(19)–O(29)
C(309)–Sn(19)–N(19)
C(349)–Sn(19)–N(19)
O(19)–Sn(19)–N(19)
O(29)–Sn(19)–N(19)
C(309)–Sn(19)–N(29)
C(349)–Sn(19)–N(29)
O(19)–Sn(19)–N(29)
O(29)–Sn(19)–N(29)
N(19)–Sn(19)–N(29)
C(79)–O(19)–Sn(19)
C(219)–O(29)–Sn(19)
C(19)–N(19)–Sn(19)
C(99)–N(19)–Sn(19)
C(159)–N(29)–Sn(19)
C(109)–N(29)–Sn(19)
C(319)–C(309)–Sn(19)
C(359)–C(349)–Sn(19)
C(309)–C(319)–C(329)–C(339)
C(349)–C(359)–C(369)–C(379)
166.87(10)
90.09(8)
87.87(9)
84.46(8)
86.73(8)
128.80(6)
97.32(9)
95.06(9)
79.54(7)
151.66(7)
94.87(8)
78.98(7)
152.21(7)
101.24(8)
97.10(8)
150.95(6)
80.19(6)
93.18(9)
151.04(7)
80.13(7)
72.04(7)
71.53(7)
122.40(15)
126.32(14)
123.78(16)
116.21(14)
124.43(16)
115.53(14)
116.83(16)
115.24(16)
179.83(23)
280.6(3)
124.90(15)
124.56(15)
125.03(17)
115.77(15)
124.14(16)
115.58(15)
119.64(17)
117.63(17)
172.62(23)
71.4(3)

D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
2695
ligand where the N–Sn–N angles are compressed, [N(1)–
Sn(1)–N(2), 72.04(7) and N(19)–Sn(19)–N(29), 71.53(7)8
in A and B, respectively]. Correspondingly, the O–Sn–O
angles are opened to 128.81(6) and 128.80(6)8. In similar
uranium [48] and tin [16,26,49] complexes, the O–M–O
(M5U or Sn) angle was open enough to allow coordina-
tion of another ligand into the equatorial plane.
are available on request, quoting the deposition number
CCDC 115795).
Acknowledgements
We acknowledge the financial assistance from UGC
(New Delhi) and DST (Grant No. SP/S1/F-71/90), Gov-
ernment of India.
The Sn–O bond lengths differ more within molecule B,
which has a greater Cbutyl –Sn–C
bond angle than
butyl
between A and B [Sn(1)–O(1), 2.2347(16), Sn(1)–O(2)
2.2374(16) cf. Sn(19)–O(19), 2.2190(17), Sn(19)–O(29),
˚
2.2370(17) A]. This range is similar to that seen in the
˚
References
dimethyl [2.236(2), 2.197(1) A] tin Vanophen complex
[26]. In the diphenyl tin Vanophen species [26], the Sn–O
˚
[1] K. Kawakami, M. Miya-Uchi, T. Tanaka, J. Inorg. Nucl. Chem. 33
(1971) 3773.
bond lengths are slightly shorter [2.188(7), 2.202(8) A].
The Sn–N bond lengths are also very similar between
these tin Vanophen species. The Sn–N bond distances
[2] K. Kawakami, T. Tanaka, J. Organomet. Chem. 49 (1973) 409.
[3] J.N.R. Ruddick, J.R. Sams, J. Organomet. Chem. 60 (1973) 233.
[4] T.N. Srivastava, A.K.S. Chauhan, J. Inorg. Nucl. Chem. 39 (1977)
371.
[5] B.S. Saraswat, G. Srivastava, R.C. Mehrotra, Inorg. Chim. Acta 36
(1979) 289.
[6] L.E. Khoo, J.P. Charland, E.J. Gabe, F.E. Smith, Inorg. Chim. Acta
128 (1987) 139.
[7] L.E. Khoo, F.E. Smith, Polyhedron 1 (1982) 213.
[8] B.S. Saraswat, G. Srivastava, R.C. Mehrotra, J. Organomet. Chem.
164 (1979) 153.
[9] J.P. Charland, F.L. Lee, E.J. Gabe, L.E. Khoo, F.E. Smith, Inorg.
Chim. Acta 130 (1987) 55.
[10] H.K. Fun, S.B. Teo, S.G. Teoh, G.Y. Yeap, T.S. Yeoh, Acta
Crystallogr., Sect. C 47 (1991) 1602.
[11] M.E. Kamwaya, L.E. Khoo, Acta Crystallogr., Sect. C 41 (1985)
1027.
[12] L.E. Khoo, Y. Xu, N.K. Goh, L.S. Chia, L.L. Koh, Polyhedron 16
(1997) 573, and references cited therein.
˚
˚
[2.266(2) and 2.2797(19) A in A; 2.277(2) and 2.280(2) A
in B] are similar to those in Me2Sn(Salen) derived from
Me2SnCl2 and N,N9-bis(salicylaldehyde)ethylenediimine
[49] and R2Sn(Vanophen) (R5Ph, Me) [26]. The Sn–N
distances are longer than the average Sn–N bond distance,
˚
2.235 A, found in Ph2(NAPPDI) [NAPPDI5N,N9-bis(2-
hydroxy-1-naphthaldehyde)-1,2-phenylenediimine] [16].
The Sn–N bond distances are all very similar between the
R2Sn(vanophen) species, (R5Ph, Me [26]) with no obvi-
ous trends.
˚
The average Sn–C bond length (2.137 A) in 2a is
midway between those of the diphenyl and dimethyl
Sn(Vanophen) analogues [26] [2.168(2), 2.172(12) and
˚
2.100(3), 2.115(3) A, respectively]. In this case, the Sn–C
bond lengths appear to be influenced by steric bulk on the
hydrocarbon ligands rather than by donor ability. More-
[13] B.N. Ghose, Synth. React. Inorg. Met.-Org. Chem. 12 (1982) 835.
[14] A. van-den Bergen, R.J. Cozens, K.S. Murray, J. Chem. Soc. (A)
(1970) 3060, and references cited therein.
˚
over, the Sn–C bonds [both 2.138(3) A] in a six-coordi-
nated tin Schiff base adduct species [50], are closer to
those in 2a than the diphenyl and dimethyl Vanophen
analogues. Similar seven-coordinated dibutyl tin com-
pounds [51,52] tend to have shorter Sn–C bonds, in the
[15] F. Maggio, R. Bosco, N. Cefalu, R. Barbieri, Inorg. Nucl. Chem.
Lett. 4 (1968) 389.
[16] S.G. Teoh, G.Y. Yeap, C.C. Loh, L.W. Foong, S.B. Teo, H.K. Fun,
Polyhedron 16 (1997) 2213.
[17] A.K. Saxena, F. Huber, Coord. Chem. Rev. 95 (1989) 109, and
references cited therein.
˚
range 2.086(5)–2.114(8) A.
[18] M. Gielen, Tin-Based Antitumour Drugs, Coord. Chem. Rev. 151
(1996) 41.
[19] A.J. Crowe, P.J. Smith, C.J. Cardin, H.E. Parge, F.E. Smith, Cancer
Lett. 24 (1984) 45.
4. Conclusion
[20] A.J. Crowe, P.J. Smith, J. Organomet. Chem. 244 (1982) 223.
[21] F. Huber, G. Roge, L. Carl, G. Atassi, F. Spreafico, S. Filippeschi,
R. Barbieri, A. Silvestri, E. Rivarola, G. Ruisi, F. Di Bianca, G.
Alonzo, J. Chem. Soc., Dalton Trans. (1985) 523.
[22] M. Gielen, Metal-Based Drugs 1 (1994) 213.
[23] A.J. Crowe, Drugs Future 12 (1987) 40.
[24] A.J. Crowe, P.J. Smith, G. Attasi, Chem.–Biol. Interact. 32 (1980)
171.
The similarities in the spectra of all of the compounds
studied here and the X-ray crystal structure of one repre-
sentative compound (2a) indicate that a six-coordinated
distorted octahedral structure should be proposed for all of
these diorganotin(IV) compounds.
[25] S.R. Collinson, D.E. Fenton, Coord. Chem. Rev. 148 (1996) 19.
¨
[26] D.K. Dey, M.K. Das, H. Noth, Z. Naturforsch. 54b (1999) 145.
[27] H.C. Arora, G.N. Rao, Ind. J. Chem. 20A (1981) 539.
[28] XSCANS, Data Collection and Reduction Program, Version 2.2,
Siemens Analytical X-ray Instruments Inc, Madison, WI, 1994.
[29] G.M. Sheldrick, Structure Determination and Refinement Programs.
Version 5.03, Siemens Analytical X-ray Instruments Inc, Madison,
WI, 1994.
Supplementary data
Crystallographic data have been deposited with the
CCDC (12 Union Road, Cambridge, CB2 1EZ, UK, and

2696
D.K. Dey et al. / Polyhedron 18 (1999) 2687–2696
[30] G.M. Sheldrick, SHELXL-97, Structure Determination and Refine-
[43] J. Holecek, M. Nadvornik, K. Handlir, A. Lycka, J. Organomet.
Chem. 241 (1983) 177.
¨
ment Program, University of Gottingen, Germany, 1997.
[31] G. Faraglia, F. Maggio, R. Cefalu, R. Bosco, R. Barbieri, Inorg.
Nucl. Chem. Lett. 5 (1969) 177.
[32] A.D. Garnovskii, A.L. Nivorozhkin,V.I. Minkin, Coord. Chem. Rev.
126 (1993) 1.
[33] H.A.O. Hill, K.G. Morallee, G. Pellizer, G. Mestroni, G. Costa, J.
Organomet. Chem. 11 (1968) 167.
[34] C. Floriani, M. Puppis, F. Calderazzo, J. Organomet. Chem. 12
(1968) 209.
[44] J.S. Casas, A. Castineiras, E. Garcia Martinez, A. Sanchez Gon-
zalez, J. Sordo, E.M. Vazquez Lopez, U. Russo, Polyhedron 15
(1996) 891, and references cited therein.
[45] V.K. Jain, Coord. Chem. Rev. 135–136 (1994) 809, and references
cited therein.
[46] W.F. Howard Jr., R.W. Crecely, W.H. Nelson, Inorg. Chem. 24
(1985) 2204.
[47] P.J. Smith, A.P. Tupciauskas, Ann. Rep. NMR Spectrosc. 8 (1978)
291.
[48] G. Bandoli, D.A. Clemente, U. Croatto, M. Vidali, P.A. Vigato, J.
Chem. Soc., Chem. Commun. (1971) 1330.
[49] M. Calligaris, G. Nardin, L. Randaccio, J. Chem. Soc., Dalton
Trans. (1972) 2003.
[50] G.Y. Yeap, N. Ishizawa, Acta Crystallogr., Sect. C 54 (1998) 720.
[51] F. Huber, H. Preut, E. Hoffmann, M. Gielen, Acta Crystallogr., Sect.
C 45 (1989) 51.
[35] R.J. Cozens, G.B. Deacon, P.W. Felder, K.S. Murray, B.O. West,
Aust. J. Chem. 23 (1970) 481.
[36] M.M. McGrady, R.S. Tobias, J. Am. Chem. Soc. 1965 (1909) 87.
[37] K. Kawakami, R. Okawara, J. Organomet. Chem. 6 (1966) 249.
[38] W. Kitching, J. Organomet. Chem. 6 (1966) 586.
[39] W. Plass, J. Pinkas, J.G. Verkade, Inorg. Chem. 1997 (1973) 36.
[40] V.K. Jain, J. Mason, B.S. Saraswat, R.C. Mehrotra, Polyhedron 4
(1985) 2089.
[41] J. Otera, J. Organomet. Chem. 221 (1981) 57.
[42] D.K. Dey, M.K. Das, R.K. Bansal, J. Organomet. Chem. 535 (1997)
7.
[52] S.W. Ng, Acta Crystallogr., Sect. C 54 (1998) 914.