Structure and spectroscopy of diorganotin(IV) complexes derived from N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide

Article abstract of DOI:10.1016/j.poly.2011.06.036

Three new diorganotin(IV) complexes of the general formula R ₂Sn[3-(OMe)-2-OC₆H₃CHN-NC(O)Ph] (R = Ph, Ia; R = Me, Ib; R = n-Bu, Ic) have been synthesised from the corresponding diorganotin(IV) dichlorides and the ligand, N

Full text of DOI:10.1016/j.poly.2011.06.036

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Polyhedron 30 (2011) 2544–2549
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structure and spectroscopy of diorganotin(IV) complexes derived from
N0-(2-hydroxy-3-methoxybenzylidene)benzohydrazide
b
Dilip Kumar Dey a, , Sankar Prasad Dey , Antonin Lycka c,1, Georgina M. Rosair d,
⇑
⇑
a Department of Chemistry, Raja Peary Mohan College, Uttarpara 712 258, Hooghly, West Bengal, India
b Department of Chemistry, Sri Krishna College, Bagula, District – Nadia, West Bengal, India
c Research Institute for Organic Syntheses, 532 18 Pardubice-Rybitvi, Czech Republic
d Department of Chemistry, William Perkin Building, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, Scotland, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new diorganotin(IV) complexes of the general formula R2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph]
(R = Ph, Ia; R = Me, Ib; R = n-Bu, Ic) have been synthesised from the corresponding diorganotin(IV) dichlo-
rides and the ligand, N0-(2-hydroxy-3-methoxybenzylidene)benzohydrazide in methanol at room tem-
perature in the presence of trimethylamine. All the complexes have been characterized by elemental
analysis, IR and 1H, 13C, 15N, 119Sn NMR spectra, and their structures have been confirmed by single crys-
tal X-ray diffraction analysis of one representative compound Ia. Complex Ia crystallises in the ortho-
rhombic system, space group Pna21 with a = 12.424(5), b = 9.911(5), c = 18.872(5) Å; Z = 4. The ligand
N0-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H2L) coordinates to the metal centre in the eno-
late form via the phenolic O, imino N and enolic O atoms. In Ia, the central tin atom adopts a distorted
trigonal bipyramidal coordination geometry with the oxygen atoms in axial positions, while the imino
nitrogen atom of the Schiff base and the two phenyl groups occupy the equatorial sites. The d(119Sn) val-
ues for the complexes Ia, Ib and Ic are ꢀ327.3, ꢀ151.7 and ꢀ187.2 ppm, respectively, thus indicating
penta-coordinated Sn centres in solution.
Received 5 January 2011
Accepted 29 June 2011
Available online 22 July 2011
Keywords:
Crystal structures of diorganotin(IV)
complexes
13C/119Sn NMR
H,H-COSY
gs-HMQC and gs-HMBC
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
performance as PVC (polyvinyl chloride) stabilizers [18], biocides,
metal-based drugs [19], anion-recognition agents [20] and cata-
The coordination chemistry of d-block metals has been exten-
sively studied, but the complexes of p-block metals are less com-
monly studied due to their hydrolytic instability and significant
lability in solution. Tin(IV) complexes containing (O,O) [1], (N,O)
and (O,S) [2–5] donor atoms are most noteworthy for their
excellent fungicidal, bactericidal and anti-inflammatory activities
[6–9]. A series of organotin(IV) derivatives and a number of diorga-
notin halides and pseudohalides [SnR2X2L2] [L = amino ligand, e.g.
pyridine (py), bipyridyl (bpy), 1,10-phenanthroline (phen) and eth-
ylenediamine (en)] have displayed modest antitumour activity
both in vitro and in vivo [10–14]. These di- and tri-organotin(IV)
complexes show important anti-tumour activities. In addition to
the aforesaid applications, organotin compounds are also of inter-
est in view of their considerable structural diversity. A series of
diorganotin carboxylates have been synthesised, either for investi-
gating their structural chemistry [15–17], or for assessing their
lysts for polyurethane foams [21], room temperature vulcanization
of silicone rubbers [22], trans-esterifications [23], acetylations of
alcohols [24], dehydration of alcohols to ethers [25] and as homo-
geneous catalysts [26]. At present, the synthesis of tin(II) and dior-
ganotin(IV) derivatives with polydentate Schiff bases has become a
popular topic of research. A systematic study of the coordination
chemistry of diorganotin(IV) complexes with biologically or phar-
macologically active ONO, NNS and ONS tridentate ligands may
provide further information concerning the structural characteris-
tics required for their antitumour and cytotoxic activities. Hydra-
zones, RR0C@N–NR00R000, are used as intermediates in syntheses
[27], as functional groups in metal carbonyls [28], in organic com-
pounds [29,30] and are employed in dinuclear catalysts [31,32].
Furthermore, hydrazones exhibit physiological activities in the
treatment of several diseases such as tuberculosis, which is attrib-
uted to the formation of stable chelate complexes with transition
metals that then catalyze physiological processes [33].
Recently, the coordination chemistry and mode of interaction of
the tridentate ONO donor ligands N-(2-carboxyphenyl)salicylide-
neimine dianion and N-(2-carboxyphenyl)-5-bromosalicylidenei-
mine dianion towards diorganotin have been reported [34,35].
However, few investigations have been devoted to diorganotin(IV)
⇑
Corresponding authors.
E-mail addresses: deydk@yahoo.com (D.K. Dey), g.m.rosair@hw.ac.uk
(G.M. Rosair).
1
Also University of Hradec Kralove, Faculty of Education, Rokitanskeho 62, CZ-
50003 Hradec Kralove, Czech Republic.
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.06.036

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2545
OMe
on a PerkinElmer 2400 II elemental analyser. Melting points
(uncorrected) were recorded on an electrical heating-coil
apparatus.
OMe
O
O
O
O
M
N
M
N
1H (360.13 MHz), 13C (90.566 MHz), 119Sn (134.3 MHz) and 15N
(36.50 MHz) NMR spectra were recorded at 300 K on a Bruker AMX
360 spectrometer equipped with a 5 mm broadband inverse probe
and a Silicon Graphics Indy computer. The compounds studied
were measured in CDCl3 and 1H and 13C chemical shifts were re-
ferred to the central signal of the solvent [d = 7.25 (1H) and
d = 77.00 (13C)]. The 15N and 119Sn chemical shifts were referred
to external nitromethane and tetramethylstannane, respectively,
(d = 0.0) placed in a coaxial capillary. Positive values of the chemi-
cal shifts denote downfield shifts with respect to the standards.
Two dimensional H,H-COSY, gs(gradient selected)-HMQC and gs-
HMBC techniques were measured using the standard software pro-
vided by Bruker [38].
Ph
Ph
N
H
N
H
(I-A)
(I-B)
OMe
O
O
M
N
Ph
N
(I-C)
Fig. 1. Different possible binding modes of the ligand, N0-(2-hydroxy-3-methoxy-
benzylidene)benzohydrazide (I).
2.3. X-ray structure analysis of Ia
complexes derived from benzoic acid hydrazone [6]. In order to
facilitate the preparation of these types of diorganotin(IV) com-
plexes, our group has initiated the present study with substituted
salicylaldehyde hydrazone ligands [36,37]. The Cu(II) complex
[Cu(Hsb)Cl]ꢁH2O containing the tridentate ligand salicylaldehyde
benzoylhydrazone (Hsb) was shown to be a potent inhibitor of
DNA synthesis and cell growth and to be more potent than the free
ligand [1,2]. It was therefore suggested that the metal complex is
the biologically active form. This ligand also has mild bacteriostatic
activity [3] and a range of analogues have been investigated as
potential oral iron-chelating drugs for genetic disorders such as
thalassemia [4]. Related to this system is the ligand N0-(2-hydro-
Single crystals of Ph2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph]
(Ia) suitable for X-ray crystallography were obtained from CHCl3/
petroleum ether (40–60 °C) mixture. Diffraction measurements of
Ia [100(2) K on a BrukerAXS X8 CCD diffractometer] using graph-
ite-monochromated Mo K
a radiation (k = 0.71073 Å) were cor-
rected for absorption. The structure was solved by direct
methods SIR-97 [39] (Ia) and subsequently refined by full-matrix
least-squares procedures on F2
(SHELXL-97 [40]) with an allowance
for anisotropic motion of all the non-hydrogen atoms. Hydrogen
atom positions were calculated assuming an ideal geometry and
using the appropriate riding models. Further details are given in
Table 1.
xy-3-methoxybenzylidene)benzohydrazide (I). It is already
a
known fact that aryl hydrazones of ortho-hydroxyaldehydes and
ketones possess a third potential coordination site, which makes
them tridentate ligands. The ligand, N0-(2-hydroxy-3-methoxy-
benzylidene)benzohydrazide (I) can either act as a monobasic
bidentate (I–A), monobasic tridentate (I–B) or dibasic tridentate
(I–C) chelator, as illustrated in Fig. 1. We wanted to observe the
mode of coordination of this ligand with diorganotin(IV) dichlo-
rides in both the solid and solution state.
2.4. Synthesis and characterization of the ligand (H2L)
The ligand N0-(2-hydroxy-3-methoxybenzylidene)benzohydr-
azide (H2L) has been prepared by refluxing
a mixture of
1-benzoylhydrazide (0.918 g, 6.74 mmol) and 3-methoxysalicylal-
dehyde (o-vanillin) (1.026 g, 6.74 mmol) in dry methanol (25 ml)
for 2.5 h. A light yellow crystalline solid was separated out on cool-
ing the reaction mixture to room temperature. This was filtered,
washed with methanol and dried. Yield: 1.40 g (77%). Anal. Calc.
for C15H14N2O3 (formula weight: 270.28): C, 66.66; H, 5.22; N,
This study describes the syntheses of the ligand, N0-(2-hydroxy-
3-methoxybenzylidene)benzohydrazide (I) and three diorgano-
tin(IV) complexes, R2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph]
(R = Ph, Ia; R = Me, Ib; R = n-Bu, Ic) derived from this ligand. This
study also describes detailed NMR studies of the complexes and the
solid state structure by single crystal X-ray diffraction of one repre-
sentative complex, Ph2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph] (Ia).
Table 1
Crystal data and structure refinement for Ph2Sn[3-(OMe)-2-OC6H3CH@N-N@C(O)Ph]
(Ia).
Ia
2. Experimental
Empirical formula
Formula weight
T (K)
C27H22N2O3Sn
541.16
293(2)
2.1. Materials
Space group
Crystal system
a (Å)
Pna2(1)
orthorhombic
12.424(5)
9.911(5)
18.872(5)
2323.8(16)
4
1.547
All chemicals and reagents were of reagent grade quality.
Diphenyltin dichloride (Aldrich), dimethyltin dichloride (Fluka),
di-n-butyltin dichloride (Fluka), 3-methoxysalicylaldehyde (o-van-
illin) (Aldrich), benzoylhydrazide (Aldrich) and trimethylamine
(S.D. Fine Chemicals, India) were used as received. Methanol
(Ranbaxy, India) was dried over CaO and distilled prior to use.
b (Å)
c (Å)
V (Å3)
Z
Dcalc (g cmꢀ3
)
h range for data collection (°)
Reflections collected
Independent reflections
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
2.63–37.68
44 297
11 144 [Rint = 0.0498]
0.893 and 0.699
11 144/1/299
1.038
R1 = 0.0358, wR2 = 0.0757
R1 = 0.0593, wR2 = 0.0831
1.992 and ꢀ1.511
2.2. Physical measurements
Infrared spectra were recorded on a PerkinElmer 883 infrared
spectrophotometer from 4000 to 200 cmꢀ1 as KBr discs and were
calibrated with respect to the 1601 cmꢀ1 band of polystyrene film.
Tin was estimated gravimetrically as SnO2 after decomposition
with concentrated HNO3. C, H and N analyses were carried out
Final R indices [I > 2
r
(I)]
R indices (all data)
Largest difference peak and hole (e A3)

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D.K. Dey et al. / Polyhedron 30 (2011) 2544–2549
OMe
(20 ml) in a 100 ml beaker, triethylamine (0.52 g, 5.14 mmol)
was added and the resulting yellow triethylammonium salt solu-
tion of the ligand was filtered to remove any insoluble impurities.
To this solution, a solution of n-Bu2SnCl2 (0.775 g, 2.27 mmol) in
15 ml of dry methanol was added slowly at room temperature.
After 50 min shiny yellow crystals of compound Ic separated out
on standing the reaction mixture at room temperature. These were
filtered, washed with petroleum ether (40–60 °C) and dried in vacuo.
Yield: 0.945 g (74%); m.p. 98 – 99 °C. Anal. Calc. for C23H30N2O3Sn
(formula weight 501.21): C, 55.12; H, 6.03; N, 5.59; Sn, 23.68. Found:
C, 54.91; H, 6.12; N, 5.67; Sn, 23.35%.
OH
O
OMe
N
OH
C
H
N
H
Ph
O
Ligand/Keto form
C
H
Methanol
reflux
+
OMe
O
3. Results and discussion
OH
NH2
OH
Ph
N
3.1. Synthesis
H
N
C
H
N
Ph
The diorganotin(IV) complexes reported here have been
synthesized from diorganotin(IV) dichlorides (Ph2SnCl2, Me2SnCl2,
n-Bu2SnCl2) and N0-(2-hydroxy-3-methoxybenzylidene)benzohyd-
razide (H2L) in methanol at room temperature in the presence of
triethylamine (Eq. (1) below) in a 1:1:2 ratio with a slight excess
of Et3N. The complexes separated out from the reaction mixture.
These were filtered, washed with petroleum ether (40–60 °C) and
dried in vacuo. Compounds Ia, Ib and Ic are stable under atmo-
spheric conditions.
Ligand/Enol form
Fig. 2. Synthesis and tautomerism of the ligand, N0-(2-hydroxy-3-methoxybenzyl-
idene)benzohydrazide (I).
10.36. Found: C, 66.23; H, 5.13; N, 10.51%. The probable molecular
structure of the ligand is given in Fig. 2.
R2SnCl2 þ H2L þ 2Et3N Methanol
!
R2SnL þ 2Et3N ꢁ HCl
ð1Þ
2.5. Syntheses and characterization of the diorganotin(IV) complexes
Ia, Ib and Ic
r:t:
(R = Ph: 1; R = Me: 2; R = n-Bu: 3).
2.5.1. Ph2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph] (Ia)
To a solution of the ligand, N0-(2-hydroxy-3-methoxybenzyli-
dene)benzohydrazide, (H2L) (0.643 g, 2.38 mmol) in dry methanol
(20 ml) in a 100 ml beaker, triethylamine (0.53 g, 5.24 mmol)
was added and the resulting yellow triethylammonium salt solu-
tion of the ligand was filtered to remove any insoluble impurities.
To this solution, a solution of Ph2SnCl2 (0.818 g, 2.38 mmol) in
20 ml of dry methanol was added slowly at room temperature.
Shiny yellow crystals of the compound Ia separated out on stand-
ing the reaction mixture for 12 h at room temperature. These were
filtered, washed with petroleum ether (40–60 °C) and dried in
vacuo. Single crystals suitable for X-ray crystallography were
obtained from CHCl3/petroleum ether (40–60 °C) mixture. Yield:
1.06 g (82%); m.p. 149–150 °C. Anal Calc. for C27H22N2O3Sn (for-
mula weight 541.19): C, 59.92; H, 4.10; N, 5.18; Sn, 21.94. Found:
C, 59.46; H, 4.16; N, 5.25; Sn, 22.08%.
3.2. Spectroscopic studies
The infrared spectra of the ligand N0-(2-hydroxy-3-methoxy-
benzylidene)benzohydrazide (H2L) is consistent with the forma-
tion of an imine bond and it exists exclusively in the keto form
in the solid state as there is a band at 1669 cmꢀ1 corresponding
to an amido carbonyl m(C@O) vibration (Fig. 2). From the X-ray
structures of some related ligands, 4-hydroxy-N0-(2-hydroxy-3-
methoxybenzylidene)benzohydrazide [41], N0-(2-hydroxybenzy-
lidene)-2-methoxybenzohydrazide [42] and 4-chloro-N0-(2-
hydroxybenzylidene)benzohydrazide [43], it is revealed that they
also exist in the keto form in the solid state. The –OH and –NH
stretching vibrations for the phenolic–OH and –NH groups appear
as a strong envelope in the range 3296–2680 cmꢀ1. One strong
band at 1601 cmꢀ1 is assigned to an azomethine
m(C@N) stretching
mode [44]. The O–H bending and C–O stretching vibrations are
found around 1166 and 1349 cmꢀ1, respectively [45]. In all three
complexes we have not found any –O–H and C@O stretching
bands, which clearly indicates that the ligand is coordinated to
the metal in its deprotonated enol form. Strong bands at
1607 cmꢀ1 for complex Ia, 1614 cmꢀ1 for complex Ib and
2.5.2. Me2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph] (Ib)
To a solution of the ligand, N0-(2-hydroxy-3-methoxybenzyli-
dene)benzohydrazide, (H2L) (0.754 g, 2.79 mmol) in dry methanol
(25 ml) in a 100 ml beaker, triethylamine (0.626 g, 6.18 mmol)
was added and the resulting yellow triethylammonium salt solu-
tion of the ligand was filtered to remove any insoluble impurities.
To this solution, a solution of Me2SnCl2 (0.613 g, 2.79 mmol) in
15 ml of dry methanol was added slowly at room temperature.
After 10 min shiny green-yellow crystals of compound Ib sepa-
rated out on standing the reaction mixture at room temperature.
These were filtered, washed with petroleum ether (40–60 °C) and
dried in vacuo. The crude compound was recrystallized from
CHCl3/petroleum ether (40–60 °C) mixture. Yield: 0.92 g (79%);
m.p. 207–208 °C. Anal. Calc. for C17H18N2O3Sn (formula weight
417.05): C, 48.96; H, 4.35; N, 6.72; Sn, 28.46. Found: C, 48.73; H,
4.27; N, 6.65; Sn, 28.27%.
1609 cmꢀ1 for complex Ic, are assigned to
m(C@N) stretching. For
complex Ic, stretching vibrations for n-butyl groups appear at
2961, 2927, 2873 and 2856 cmꢀ1. The above assignments suggest
the coordination of the imino nitrogen and deprotonated enolic
oxygens to the central tin(IV), and therefore a tridentate dibasic
nature of the coordinated ligand.
The NMR spectra (1H, 13C, 15N and 119Sn) for the compounds
Ph2SnL (Ia), Me2SnL (Ib) and n-Bu2SnL (Ic) were measured and ana-
lysed. Two-dimensional NMR spectra were used to assign proton
and carbon chemical shifts unambiguously. H,H-COSY, gs(gradient
selected)-HMQC and gs-HMBC techniques were also applied
[46,47]. The 15N NMR spectra were measured using the gs-HMBC
technique (the experiment being optimised for nJ(15N, 1H) = 6 Hz).
Both 15N signals in the two-dimensional spectra correlate with
C(8)–H only, giving two signals of approximately the same
2.5.3. n-Bu2Sn[3-(OMe)-2-OC6H3CH@N–N@C(O)Ph] (Ic)
To a solution of the ligand, N0-(2-hydroxy-3-methoxybenzyli-
dene)benzohydrazide, (H2L) (0.69 g, 2.55 mmol) in dry methanol

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D.K. Dey et al. / Polyhedron 30 (2011) 2544–2549
2547
Table 2
1H, 13C, 119Sn and 15N chemical shifts and nJ(119Sn,1H) and nJ(119Sn,13C) coupling constants for Ia, Ib and Ic in CDCl3. Coupling constants values (Hz) are given in parentheses.
H/C No.
Compound Ia
d(1H)
Compound Ib
d(1H)
Compound Ic
d(1H)
d(13C)
d(13C)
d(13C)
1
2
3
4
5
6
–
–
7.04
6.73
6.85
–
157.74 (33.0)
151.77 (9.0)
116.52
116.73
125.87
–
–
6.91
6.67
6.80
–
156.74 (32.6)
151.15 (8.5)
116.48
115.42
125.71
–
–
6.90
6.65
6.80
–
157.51 (31.9)
151.21
115.64
115.99
125.75
116.82
116.62
116.55
7
8
9
4.01
8.79 (52.0)
–
56.55
3.85
8.75 (45.8)
–
–
8.07
7.41
7.44
0.89 (79.7)
–
–
–
–
–
–
56.08
3.85
8.76 (42.2)
–
56.07
161.55 (23.25)
169.03 (3.5)
133.14
127.72
128.26
161.51 (21.9)
169.17 (9.7)
133.36
127.56
128.13
131.01
2.35 (654.2)
–
161.28 (20.9)
169.42 (13.2)
133.36
127.52
128.09
10
11
12
13
10
20
30
40
Sn
N
N
–
–
8.31
7.55
7.53
–
7.99
7.45
7.42
8.10
7.42
7.46
1.58
1.64
1.33
0.84
–
131.23
130.86
138.92 (993.9)
136.22 (55.5)
128.83 (88.1)
130.47 (18.0)
ꢀ327.3a
22.67 (602.4)
26.74 (27.0)
26.33 (87.8)
13.47
–
–
ꢀ151.7a
ꢀ130.6b
ꢀ160.7b
ꢀ187.2a
ꢀ115.8b
ꢀ121.0b
ꢀ125.8b
–
–
ꢀ132.2b
C–Sn–C angle calculated from 1J(119Sn,13C) (993.9 Hz) = 135.6 for compound Ia.
C–Sn–C angle calculated from 1J(119Sn,13C) (602.4 Hz) = 135.0 for compound Ic.
a
d(119Sn).
b
d(15N).
intensities and, hence, differentiation between them was not
possible. The 1H, 13C, 15N and 119Sn chemical shifts are collected
in Table 2. We have been able to detect all proton and carbon
signals separately for compounds Ia–Ic. For each compound the
number of 1H, 13C and 15N signals observed is in good agreement
with the numbering shown in Fig. 3.
For the diphenyltin(IV) compound (Ia), detection of the
2J(119Sn,13C) coupling (23.5 and 3.5 Hz) with the C(8) and C(9) car-
bons, respectively, indicates the coordination of the nitrogen atom
(Na) and enolic oxygen of the ligand with tin. Detection of a
3J(119Sn,1H) coupling of 52.0 Hz with the hydrogen attached to
C(8) indicates further support for the coordination of the nitrogen
atom (Na) to tin. Also detection of 2J(119Sn,13C) coupling (33.0 Hz)
with the C(1) carbon and 3J(119Sn,13C) coupling (9.0 Hz) with C(2)
indicates the coordination of the phenolic oxygen atom of the
ligand with tin.
C(8) indicates coordination of the nitrogen atom (Na) to tin. Also
detection of 2J(119Sn,13C) coupling (32.6 Hz) with the C(1) carbon
and 3J(119Sn,13C) coupling (8.5 Hz) with C(2) indicates the coordi-
nation of the phenolic oxygen atom of the ligand with tin.
For the di-n-butyltin(IV) compound (Ic), detection of
2J(119Sn,13C) coupling (20.9 and 13.2 Hz) with the C(8) and C(9)
carbons, respectively, indicates the coordination of the nitrogen
atom (Na) and enolic oxygen of the ligand with tin. Detection of
a
3J(119Sn,1H) coupling of 42.2 Hz with the hydrogen attached to
C(8) indicates coordination of the nitrogen atom (Na) to tin. Also
detection of 2J(119Sn,13C) coupling (31.9 Hz) with the C(1) carbon
indicates the coordination of the phenolic oxygen atom of the li-
gand with tin.
The 1J(119Sn,13C) coupling constant of 993.9 Hz with the phenyl
carbon for Ia is comparable with the value (993.2 Hz) seen in the
hydrazone complex Ph2Sn[2-OC6H4CH@N–N@C(O)C6H5] [36], but
it is higher than the reported values for other phenyltin com-
pounds [48–50]. The corresponding 1J(119Sn,13C) coupling constant
of 654.2 Hz with the methyl carbon of Ib is slightly higher than
that seen for Me2Sn[2-OC6H4CH@N–N@C(O)C6H5] (647.9 Hz) [36]
and Me2Sn[Ph(O)C@CH–C(Me)@N–C6H4(O)] (648.5 Hz) [51]. The
corresponding 1J(119Sn,13C) coupling constant of 602.4 Hz with
the n-butyl carbon (C1) of Ic is lower than that found in
Me2Sn[2-OC6H4CH@N–N@C(O)C6H5] [36] and Me2Sn[Ph(O)-
C@CH–C(Me)@N–C6H4(O)] [51].
For the dimethyltin(IV) compound (Ib), detection of
2J(119Sn,13C) coupling (21.9 and 9.7 Hz) with the C(8) and C(9) car-
bons, respectively, indicates the coordination of the nitrogen atom
(Na) and enolic oxygen of the ligand with tin. Detection of a
3J(119Sn,1H) coupling of 45.8 Hz with the hydrogen attached to
7
OCH3
R
R
The C–Sn–C angle in solution can be estimated from the
1J(119Sn,13C) coupling constant value [49]. Using the equation
|1J(119Sn,13C)| = (15.91 0.72)h ꢀ (1164 84), with a 1J(119Sn,13C)
value of 993.9 Hz, the Cphenyl–Sn–Cphenyl angle was found to be
135.6° [cf. 127.09(8)° in the X-ray study] for compound Ia. For
compound Ib, the Cmethyl–Sn–Cmethyl angle was calculated using
the equation |1J(119Sn,13C)| = 10.7h ꢀ 778 [52], with a 1J(119Sn,13C)
value of 654.2 Hz, and the angle was determined as 133.85°. The
2J(Sn–CH3) value of 79.7 Hz is in agreement with values reported
(77–81 Hz) for dimethyltin(IV) complexes with ONO donor
tridentate ligands [35,36,53,54]. Using Lockhart’s equation
2
O
Sn
1
3
4
O
9
11
Na
10
6
C
H
Nb
12
13
8
5
1'
CH3
2' 3'
for Ib:
for Ic:
R =
1'
for Ia:
4'
R =
3' 4'
2'
1'
R = CH2CH2CH2CH3
[|MeSnMe| = 0.0161(|2J(119Sn,1H)|)2
1.32(|2J(119Sn,1H)|) + 133.4]
[54], the C–Sn–C angle for Ib is estimated to be ca. 130.46°. For
the di-n-butyltin(IV) compound Ic, the Cbutyl–Sn–Cbutyl angle was
Fig. 3. Constitution of the compounds Ia, Ib and Ic and the numbering scheme for
NMR assignments.