Synthesis and characterization of triorganotin(IV) complexes of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids. Crystal and molecular structures of a series of triphenyltin 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates (aryl = phenyl, 2-methylphenyl, 3-methylphenyl and 4-methoxy...)

Article abstract of DOI:10.1016/S0022-328X(01)01024-5

The triphenyltin and tri-n-butyltin complexes of some 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids have been synthesized and characterized by 1H-, 13C-, 119Sn-NMR, IR and 119mSn Moessbauer spectroscopic techniques in combination with elemental analysis. The crystal structures of triphenyltin 5-[(E)-2-(aryl-1-diazenyl]-2-hydroxybenzoates (aryl = phenyl, 2-methoxyphenyl, 3-metylphenyl and 4-methoxyphenyl) are reported. Both X-ray and 119Sn Moessbauer data indicate that the triphenyltin complexes adopt a monomeric distorted tetrahedral configuration with the carboxylate ligand coordinating in a monodentate mode. By contrast, 119Sn Moessbauer spectroscopy shows that each tributyltin complex is polymeric and features a trans-trigonal bipyramidal geometry with a planar SnBu3 unit and two apical carboxylate oxygen atoms derived from bidentate bridging carboxylate ligands. This is a solid-state effect, as both 119Sn-NMR and ¹(13C-119/117Sn) coupling constant data indicate tetrahedral geometries in solution for the triphenyl and tri-n-butyl complexes.

Full text of DOI:10.1016/S0022-328X(01)01024-5

Journal of Organometallic Chemistry 633 (2001) 7–17
www.elsevier.com/locate/jorganchem
Synthesis and characterization of triorganotin(IV) complexes of
5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids.
Crystal and molecular structures of a series of triphenyltin
5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates (aryl=phenyl,
2-methylphenyl, 3-methylphenyl and 4-methoxyphenyl)
Tushar S. Basu Baul a,*, Sushmita Dhar a, Simon M. Pyke b, Edward R.T. Tiekink b,*,
Eleonora Rivarola c, Ray Butcher d, Frank E. Smith e,*
a Chemical Laboratory, Regional Sophisticated Instrumentation Centre, North-Eastern Hill Uni6ersity, Bijni Complex, Bhagyakul,
Shillong 793 003, India
b Department of Chemistry, The Uni6ersity of Adelaide, Adelaide, South Australia 5005, Australia
c Dipartimento di Chimica Inorganica, Uni6ersita di Palermo, Palermo 90123, Italy
d Department of Chemistry, Howard Uni6ersity, Washington, DC 20059, USA
e School of Graduate Studies and Research, Laurentian Uni6ersity, Sudbury, Ont., Canada P3E 2C6
Received 18 October 2000; received in revised form 6 March 2001; accepted 13 March 2001
Abstract
The triphenyltin and tri-n-butyltin complexes of some 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids have been synthesized
1
and characterized by H-, 13C-, 119Sn-NMR, IR and 119mSn Mo¨ssbauer spectroscopic techniques in combination with elemental
analysis. The crystal structures of triphenyltin 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoates (aryl=phenyl, 2-methylphenyl,
3-methylphenyl and 4-methoxyphenyl) are reported. Both X-ray and 119Sn Mo¨ssbauer data indicate that the triphenyltin
complexes adopt a monomeric distorted tetrahedral configuration with the carboxylate ligand coordinating in a monodentate
mode. By contrast, 119Sn Mo¨ssbauer spectroscopy shows that each tributyltin complex is polymeric and features a trans-trigonal
bipyramidal geometry with a planar SnBu3 unit and two apical carboxylate oxygen atoms derived from bidentate bridging
carboxylate ligands. This is a solid-state effect, as both 119Sn-NMR and 1J(13C–119/117Sn) coupling constant data indicate
tetrahedral geometries in solution for the triphenyl and tri-n-butyl complexes. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Organotin; Carboxylates; 5-[(E)-2-(Aryl)-1-diazenyl]-2-hydroxybenzoic acids; NMR; Mo¨ssbauer; X-ray
1. Introduction
compounds have not been shown to be neurotoxins,
mutagens, teratogens, or carcinogens in humans [3].
Triphenyltin compounds, including triphenyltin acetate,
have achieved commercialization as agricultural fungi-
cides [4–8]. In addition to their commercial applica-
tions, triorganotin carboxylates present an interesting
variety of structural possibilities [9,10]. Much current
organotin research is concentrated on their biomedical
applications, particularly their anticancer properties.
Against human tumour cell lines, triphenyltin deriva-
tives are highly active, being characterized by very low
ID50 values [11]. In general, triorganotin compounds
display a higher biological activity than their di- and
Triorganotin compounds have been the subject of
interest for some time because of their biomedical and
commercial applications. Tributyltin, in the form of
halides, oxides and acetates, displays a large array of
biocidal properties and is used extensively in wood
preservatives and in marine anti-fouling paints [1], al-
though there has been considerable environmental con-
cern about their latter use [2]. However, the tributyltin
* Corresponding authors. Fax: +91-364-228213.
E-mail address: basubaul@hotmail.com (T.S. Basu Baul).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01024-5

8
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
cal shifts were referred to Me4Si set at 0.00 ppm, CDCl3
set at 77.0 ppm and tetramethyltin set at 0.00 ppm
respectively. 119Sn Mo¨ssbauer spectra of the complexes
in the solid state were recorded on an Elscient–Laben
spectrometer equipped with an AERE cryostat at liq-
uid-nitrogen temperature. The Ca119mSnO3 Mo¨ssbauer
source (10 mCi; Radiochemical Centre, Amersham,
UK) moved with constant acceleration and triangular
waveform. The velocity calibration was made using a
57Co Mo¨ssbauer source (10 mCi). An iron foil enriched
to 95% in 57Fe (DuPont Pharma Italia, Firenze, Italy)
was used as the absorber.
mono-organotin analogues. This has been attributed to
their ability to bind proteins [12–14]. For this reason, a
number of triphenyltin salicylates have been synthesized
[15–17] and screened against human tumour cell lines
(MCF-7 and WiDr). The results were found to be
comparable with those of mitomycin C [17]. In line
with these developments, we have recently reported
some triorganotin complexes of azo-salicylic acid [18].
As a continuation of this line of investigation, we now
describe some triphenyltin and tri-n-butyltin complexes
derived from a number of 5-[(E)-2-(aryl)-1-diazenyl]-2-
hydroxybenzoic acids, since the structural motif and
activity are likely to be influenced by a steric effect
associated with the carboxylate residue. The generic
structure of the acid is shown in Fig. 1.
2.3. Synthesis of 5-[(E)-2-(aryl)-1-diazenyl]-2-
hydroxybenzoic acids
A typical procedure is described below.
2. Experimental
2.3.1. Preparation of 5-[(E)-2-phenyl-1-diazenyl]-2-
hydroxybenzoic acid (L1HH%)
2.1. Materials
Aniline (5.0 g, 53.8 mmol) was mixed with HCl
(16 ml) and water (16 ml) and digested in a water bath
for 30 min. The hydrochloride was cooled to 5 °C and
diazotized with ice-cold aqueous NaNO2 solution
(3.7 g, 20 ml). A cold solution of salicylic acid (7.42 g,
53.8 mmol), previously dissolved in 10% NaOH soution
(50 ml), was then added to the cold diazonium salt
solution with vigorous stirring. A yellow colour devel-
oped almost immediately and the stirring was continued
for 1 h. The reaction mixture was kept overnight in a
refrigerator, followed by 3 h. at room temperature, and
then acidified with dilute acetic acid, whereupon a
yellow precipitate separated out. The precipitate was
filtered, washed several times with water to remove
excess acetic acid and water-soluble materials, and then
dried in air. The crude product was washed with hexane
to remove any tarry materials and recrystallized from
methanol to yield pure L1HH% (4.72 g, 33%). M.p.:
212–214 °C. Anal. Found: C, 64.30; H, 4.10; N, 11.46.
Calc. for C13H10N2O3: C, 64.46; H, 4.16; N, 11.57%.
1H-NMR (DMSO-d6/600 MHz); lH: 6.98 [d, 8.4 Hz,
1H, H3], 7.46 [m, 1H, H4%], 7.50 [m, 2H, H3% & H5%],
7.81 [m, 2H, H2% & H6%], 7.94 [dd, 8.4 & 2.4 Hz, 1H,
H4], 8.29 [d, 2.4 Hz, 1H, H6] ppm. Signals for the
phenol and carboxylic acid were exchanged due to
presence of water in the solvent. 13C-NMR (DMSO-d6/
150 MHz); lC: 116.3 [C1], 118.1 [C3], 122.3 [C2% & C6%],
125.9 [C6], 128.4 [C4], 129.5 [C3% & C5%], 130.7 [C4%],
143.8 [C5], 152.1 [C1%], 165.7 [C2], 171.3 [CO2H] ppm.
The other 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxyben-
zoic acids, viz. L2HH%–L7HH% were prepared
analogously with appropriate anilines and their analyti-
cal data are presented below. Note: the quantities of
HCl and NaOH used for the preparations were found
to be important. Quantities less than those specified
produced either oils or unidentified products. The
(Bu3Sn)2O (Merck), Ph3SnCl (Fluka AG), salicylic
acid (Merck) and the substituted anilines (reagent
grade) were used without further purification. All the
solvents used in the reactions were of AR grade and
dried using standard literature procedures.
2.2. Physical measurements
Carbon, hydrogen and nitrogen analyses were per-
formed with a Perkin–Elmer 2400 series II instrument.
IR spectra in the range 4000–400 cm−1 were obtained
on a Perkin–Elmer 983 spectrophotometer with sam-
1
ples investigated as KBr discs. The H- and 13C-NMR
spectra of the ligands were acquired on either a Varian
Gemini 2000 spectrometer (operating at 300.13 and
75.47 MHz respectively) or a Varian Inova spectrome-
ter (operating at 599.91 and 150.85 MHz respectively).
1
For the organotin compounds, the H-, 13C- and 119Sn-
NMR spectra were recorded on a Bruker ACF 300
spectrometer and measured at 300.13, 75.47 and
1
111.92 MHz respectively. The H, 13C and 119Sn chemi-
Fig. 1. Generic structure of the acid. Abbreviations: L1HH%: R=H;
L2HH%: R=2%-CH3; L3HH%: R=3%-CH3; L4HH%: R=4%-CH3;
L5HH%: R=4%-Br; L6HH%: R=4%-NO2; L7HH%: R=4%-OCH3, where
H and H% represent hydroxyl and carboxyl protons, respectively.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
9
quantities of HCl and NaOH (10%) used were as
2.3.5. 5-[(E)-2-(4-Bromophenyl)-1-diazenyl]-
2-hydroxybenzoic acid (L5HH%)
follows. For L2HH%–L4HH%: 12 ml and 31 ml; for
L5HH%: 9 ml and 36.7 ml; for L6HH%: 9 ml and 28 ml;
and for L7HH%: 9 ml and 35.5 ml, HCl and NaOH
respectively.)
Recrystallized from methanol to give brown precipi-
tate in 50% yield. M.p.: 242–244 °C. Anal. Found: C,
48.59; H, 2.80; N, 8.68. Calc. for C13H9BrN2O3: C,
48.63; H, 2.83; N, 8.72%. 1H-NMR (DMSO-d6/
300 MHz); lH: 7.04 [d, 9.0 Hz, 1H, H3], 7.63 [AA%
portion of AA%XX%, 2H, H2% & H6%], 7.78 [XX% portion
of AA%XX%, 2H, H3% & H5%], 8.04 [dd, 9.0 & 2.1 Hz, 1H,
H4], 8.45 [d, 2.1 Hz, 1H, H6] ppm. Signals for the
phenol and carboxylic acid were exchanged due to
presence of water in the solvent. 13C-NMR (DMSO-d6/
75 MHz); lC: 113.2 [C1], 118.1 [C3], 124.1 [C2% & C6%],
124.6 [C6], 127.4 [C4], 128.3 [C4%], 132.2 [C3% & C5%],
144.8 [C5], 151.0 [C1%], 164.5 [C2], 172.2 [CO2H]
ppm.
2.3.2. 5-[(E)-2-(2-Methylphenyl)-1-diazenyl]-
2-hydroxybenzoic acid (L2HH%)
Recrystallized from methanol to give brown precipi-
tate in 50% yield. M.p.: 190–191 °C. Anal. Found: C,
65.50; H, 4.57; N, 11.01. Calc. for C14H12N2O3: C,
65.63; H, 4.72; N, 10.93%. 1H-NMR (DMSO-d6/
600 MHz); lH: 2.64 [s, 3H, CH3], 7.14 [d, 9.0 Hz, 1H,
H3], 7.30 [m, 1H, H5%], 7.41 [m, 2H, H3% & H4%], 7.55
[d, 7.8 Hz, 1H, H6%], 8.06 [dd, 9.0 & 2.4 Hz, 1H, H4],
8.32 [d, 2.4 Hz, 1H, H6] ppm. Signals for the phenol
and carboxylic acid were exchanged due to presence of
water in the solvent. 13C-NMR (DMSO-d6/150 MHz);
lC: 17.0 [CH3], 113.6 [C1], 115.1 [C6%], 118.3 [C3], 126.3
[C6], 126.6 [C5%], 128.3 [C4], 130.9 [C4%], 131.3 [C3%],
137.2 [C2%], 144.9 [C5], 149.8 [C1%], 163.4 [C2], 171.3
[CO2H] ppm.
2.3.6. 5-[(E)-2-(4-Nitrophenyl)-1-diazenyl]-
2-hydroxybenzoic acid (L6HH%)
Recrystallized from methanol to give orange–red
precipitate in 49% yield. M.p.: 234–236 °C. Anal.
Found: C, 54.28; H, 3.25; N, 14.78. Calc. for
2.3.3. 5-[(E)-2-(3-Methylphenyl)-1-diazenyl]-
1
C13H9N3O5: C, 54.37; H, 3.16; N, 14.63%. H-NMR
2-hydroxybenzoic acid (L3HH%)
(DMSO-d6/300 MHz); lH: 6.64 [d, 9.0 Hz, 1H, H3],
7.60 [AA% portion of AA%XX%, 2H, H2% & H6%], 7.66
[XX% portion of AA%XX%, 2H, H3% & H5%], 7.96 [dd, 9.0
& 2.1 Hz, 1H, H4], 8.08 [d, 2.1 Hz, 1H, H6] ppm.
Signals for the phenol and carboxylic acid were ex-
changed due to the presence of water in the solvent.
13C-NMR (DMSO-d6/75 MHz); lC: 113.6 [C1], 118.2
[C3], 123.2 [C2% & C6%], 124.6 [C3% & C5%], 125.6 [C6],
128.4 [C4], 144.7 [C4%], 148.3 [C5], 155.4 [C1%], 165.5
[C2], 172.0 [CO2H] ppm.
Recrystallized from methanol to give yellow precipi-
tate in 50% yield. M.p.: 196–198 °C. Anal. Found: C,
65.55; H, 4.70; N, 10.85. Calc. for C14H12N2O3: C,
65.63; H, 4.72; N, 10.93%. 1H-NMR (DMSO-d6/
600 MHz); lH: 2.40 [s, 3H, CH3], 7.14 [d, 9.0 Hz, 1H,
H3], 7.34 [dquin, 7.2 & 1.0 Hz, 1H, H4%], 7.45 [t, 7.2 Hz,
1H, H5%], 7.66 [m, 2H, H2% & H6%], 8.06 [dd, 9.0 &
2.4 Hz, 1H, H4], 8.31 [d, 2.4 Hz, 1H, H6] ppm. Signals
for the phenol and carboxylic acid were exchanged due
to presence of water in the solvent. 13C-NMR (DMSO-
d6/150 MHz); lC: 20.8 [CH3], 113.6 [C1], 118.3 [C3],
119.9 [C6%], 122.4 [C2%], 125.6 [C6], 128.8 [C4], 129.1
[C5%], 131.7 [C4%], 138.8 [C3%], 144.5 [C5], 151.8 [C1%],
163.4 [C2], 171.3 [CO2H] ppm.
2.3.7. 5-[(E)-2-(4-Methoxyphenyl)-1-diazenyl]-
2-hydroxybenzoic acid (L7HH%)
Recrystallized from methanol to give brown precipi-
tate in 52% yield. M.p.: 209–210 °C. Anal. Found: C,
61.60; H, 4.41; N, 10.35. Calc. for C14H12N2O4: C,
61.77; H, 4.44; N, 10.29%. 1H-NMR (DMSO-d6/
300 MHz); lH: 3.86 [s, 3H, OCH3], 7.02 [d, 9.0 Hz, 1H,
H3], 7.06 [AA% portion of AA%XX%, 2H, H2% & H6%],
7.84 [XX% portion of AA%XX%, 2H, H3% & H5%], 8.00 [dd,
9.0 & 2.1 Hz, 1H, H4], 8.35 [d, 2.1 Hz, 1H, H6] ppm.
Signals for the phenol and carboxylic acid were ex-
changed due to presence of water in the solvent. 13C-
NMR (DMSO-d6/75 MHz); lC: 54.0 [OCH3], 111.7
[C1], 112.8 [C2% & C6%], 116.5 [C3], 122.9 [C3% & C5%],
124.5 [C6], 126.8 [C4], 143.3 [C4%], 144.8 [C5], 160.2
[C1%], 162.0 [C2], 170.6 [CO2H] ppm. Recrystallization
of L7HH% from benzene solution gave orange–red crys-
tals suitable for X-ray crystallography; results have
been reported elsewhere [19].
2.3.4. 5-[(E)-2-(4-Methylphenyl)-1-diazenyl]-
2-hydroxybenzoic acid (L4HH%)
Recrystallized from methanol to give yellow precipi-
tate in 50% yield. M.p.: 217–218 °C. Anal. Found: C,
65.51; H, 4.63; N, 10.80. Calc. for C14H12N2O3: C,
65.63; H, 4.72; N, 10.93%. 1H-NMR (DMSO-d6/
300 MHz); lH: 2.41 [s, 3H, CH3], 7.06 [d, 9.0 Hz, 1H,
H3], 7.31 [AA% portion of AA%XX%, 2H, H2% & H6%],
7.78 [XX% portion of AA%XX%, 2H, H3% & H5%], 8.05 [dd,
9.0 & 2.1 Hz, 1H, H4], 8.48 [d, 2.1 Hz, 1H, H6] ppm.
Signals for the phenol and carboxylic acid were ex-
changed due to presence of water in the solvent. 13C-
NMR (DMSO-d6/75 MHz); lC: 20.7 [CH3], 112.4 [C1],
117.3 [C3], 121.8 [C2% & C6%], 126.3 [C6], 127.6 [C4],
129.0 [C3% & C5%], 140.4 [C4%], 144.4 [C5], 149.7 [C1%],
163.3 [C2], 171.7 [CO2H] ppm.

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T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
2.6.2. Synthesis of Bu3SnL2H
2.4. Preparation of sodium salts of 5-[(E)-2-
The compound was synthesized by mixing L2HH%
(0.50 g, 1.95 mmol) and (Bu3Sn)2O (0.58 g, 0.97mmol)
in 50 ml of anhydrous toluene, in a 100 ml flask
equipped with a Dean–Stark moisture trap and a wa-
ter-cooled condenser. The mixture was refluxed for 3 h.
The solvent was distilled off to half of the initial solvent
volume. The remaining solvent was removed using a
rotary evaporator. The dark-red oil that remained was
dissolved in 20 ml of petroleum ether (40–60 °C) and
triturated under cold conditions. A dark-red solid was
obtained upon refrigeration. The crude product was
recrystallized from petroleum ether, which yielded
dark-red solid upon refrigeration for several days.
(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHNa)
The sodium salts of 5-[(E)-2-(aryl)-1-diazenyl]-2-hy-
droxybenzoic acids, viz. L1HNa–L7HNa, were pre-
pared by reacting stoichiometric amounts of the acids
with a slight excess of NaHCO3 in water. The reaction
mixture was heated on a hot plate until the dissolution
was complete and filtered while hot. The filtrate was
evaporated on the water bath to dryness. The dry
residue was extracted with anhydrous methanol and the
solvent was distilled off. The residue was then washed
with diethyl ether and dried in vacuo prior to its use for
the preparation of the triphenyltin complexes.
2.7. X-ray crystallography
2.5. Preparation of 5-[(E)-2-(4-chlorophenyl)-
1-diazenyl]-2-hydroxymethylbenzoate, LHMe
Crystallographic data, collection and refinement de-
tails are given in Table 1. Corrections for absorption
were made using a semi-empirical method 20a for 1 and
3 and an empirical procedure [20b] for 5 and 12. The
structures were solved by heavy-atom methods [20c]
and refined by a full-matrix least-squares procedure
based on F2 (1 and 3) or F (5 and 12) [20d]. Non-hy-
drogen atoms were refined employing anisotropic dis-
placement parameters and hydrogen atoms were
included in the models at their calculated positions. The
hydroxyl hydrogen atom was located from a difference
map in each case. The weighting scheme employed for
5-[(E)-2-(4-Chlorophenyl)-1-diazenyl]-2-hydroxyben-
zoic acid [18] (0.56 g) was dissolved in anhydrous
methanol (20 ml) and refluxed for 5 h with concentrated
H2SO4 (0.6 ml). The solvent was distilled off and the
residue was dissolved in diethyl ether and washed with
water to remove any acid. The ether extract was passed
through anhydrous Na2SO4 and the filtrate was evapo-
rated to dryness. The yellow-coloured methylated
product was dried in vacuo. Yield: 90%; m.p.: 152–
153 °C. Anal. Found: C, 57.79; H, 3.89; N, 10.02. Calc.
1
for C14H11ClN2O3: C, 57.85; H, 3.81; N, 9.64%. H-
1
was of the form w=1/[|2(F)+(0.0308P)2+
NMR (CDCl3/300 MHz); lH: 4.02 [s, 3H, OCH3], 7.08
[d, 9.0 Hz, 1H, H3], 7.46 [AA% portion of AA%XX%, 2H,
H2% & H6%], 7.82 [XX% portion of AA%XX%, 2H, H3% &
H5%], 8.06 [dd, 9.0 & 2.1 Hz, 1H, H4], 8.42 [d, 2.1 Hz,
1H, H6], 11.08 [brs, 1H, OH] ppm. 13C-NMR (CDCl3/
75 MHz); lC: 52.3 [OCH3], 112.1 [C1], 118.4 [C3], 123.8
[C2% & C6%], 126.9 [C6], 128.6 [C4], 129.1 [C3% & C5%],
136.5 [C4%], 144.7 [C5], 157.5 [C1%], 164.1 [C2], 170.0
[CO2] ppm.
0.6912P], where P=(F2o+2Fc2)/3, w=1/[|2(F)+
2
(0.0319P)2+1.3971P] for 3, and w=1/[|2(F)+gꢀFoꢀ ]
(g=0.000 04 for 5 and g=0.000 05 for 12). The abso-
lute structure of 12 was not determined, as there were
no significant differences in measured Friedel pairs
included in the data set. The structures of 1, 3 and 12
each feature multiple independent molecules, i.e. two,
two and four, in their respective asymmetric units. No
evidence was found for additional symmetry in these
structures that would reduce the number of indepen-
dent molecules [20d,e]. The molecular structures, show-
ing the crystallographic numbering schemes employed,
are shown in Figs. 2–5 and were drawn with ORTEP at
the 35% (1 and 3) and 50% (5 and 12) probability
levels, respectively [20f]. PLATON [20e] was employed in
the analysis of the crystal structures.
2.6. Synthesis of the triorganotin complexes
Two typical methods are described below.
2.6.1. Synthesis of Ph3SnL1H
Ph3SnCl (0.50 g, 1.30 mmol) in methanol (30 ml) was
added dropwise with continuous stirring to a hot
methanol solution (50 ml) containing L1HNa (0.34 g,
1.30 mmol). The reaction mixture was then refluxed for
5 h and the solvent was removed using a rotary evapo-
rator. The residue was washed with hexane, extracted
into chloroform and filtered. The crude product was
obtained after evaporation of the chloroform. This was
then recrystallized from a large volume of hot hexane
to yield orange blocks of the desired product at room
temperature.
3. Results and discussion
3.1. Syntheses
The 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid
ligands were prepared by the diazonium coupling reac-
tion between the appropriate anilines and salicylic acid
in alkaline medium under cold conditions. The basic

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
11
Table 1
Crystallographic data and structure refinement parameters for the triorganotin complexes 1, 3, 5 and 12
1
3
5
12
Empirical formula
Formula weight
Diffractometer
Temperature (K)
Crystal system
Space group
C31H24N2O3Sn
591.2
Rigaku AFC6S
293
C
605.3
Rigaku AFC6S
293
Triclinic
32H26N2O3Sn
C32H26N2O3Sn
605.3
Rigaku AFC7R
173
Monoclinic
P21/c
12.534(2)
16.467(2)
13.334(4)
90
101.33(2)
90
2698.7(9)
4
1.490
9.83
C32H26N2O4Sn
621.3
Rigaku AFC7R
173
Monoclinic
P21
10.595(2)
19.692(4)
27.305(2)
90
100.19(1)
90
5607(1)
8
1.472
9.51
Triclinic
(
(
P1
P1
,
a (A)
11.4219(11)
13.8246(13)
18.711(2)
105.627(6)
91.646(7)
100.900(7)
2784.0(5)
4
11.1765(15)
14.538(2)
18.485(3)
105.688(12)
93.007(11)
98.215(8)
2848.9(7)
4
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dx (g cm−3
)
1.411
9.51
1.411
9.31
v (cm−1
)
Reflections measured
qmax (°)
12 773
27.5
12 631
27.5
6699
27.5
13 941
27.5
Unique reflections
Refined parameters
Reflections with
I]n|(I)
12 629
722
12 006
745
6418
343
13 243
1404
9311, n=2
0.054
0.087
9563, n=2
0.046
0.092
4190, n=3
0.027
0.030
7843, n=3
0.039
0.034
a
R
Rwa
−3
zmax (e−
)
0.28
0.55
0.28
0.48
,
A
a All reflections.
Fig. 2. Molecular structure and crystallographic numbering scheme for 1.
ligand framework is shown in Fig. 1, along with the
abbreviations of the ligands and numbering scheme for
spectroscopic analysis. The details of their synthesis and
characterization are presented in Section 2.
The new organotin complexes are abbreviated as
R3SnLH, where R=phenyl or n-butyl. They were ob-
tained either from the reaction of sodium salts of the
ligands with Ph3SnCl in methanol solution or by the
condensation of the appropriate ligands with (Bu3Sn)2O
in toluene solution. The influence of different sub-
stituents on phenyl ring B did not cause obvious varia-
tion in the yield of the reaction. The characterization
data of the complexes are listed in Table 2. These
confirm the formulation of the products. They are
stable in air and are soluble in all common organic
solvents.
3.2. IR data
Diagnostically important IR absorption frequencies
for the carboxylic antisymmetric [wasym(OCO)] stretch-
ing vibration are shown in Table 3. The assignment of

12
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
comparison with the methylated product (LHMe). The
antisymmetric [wasym(OCO)] stretching vibrations for
the uncomplexed ligands have been detected in the
1652–1670 cm−1 region. The lower value of this ab-
sorption band, compared with the methyl ester, is due
the symmetric [wsym(OCO)] stretching vibration band
could not be made owing to the complex pattern of the
spectra. The assignment of the band is based on com-
parison with the spectra of the free ligands (LHH%),
their sodium salts (LHNa) and also, in one case, by
Fig. 3. Molecular structure and crystallographic numbering scheme for 3.
Fig. 4. Molecular structure and crystallographic numbering scheme for 5.
Fig. 5. Molecular structure and crystallographic numbering scheme for 12.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
13
Table 2
Characterization data for the triorganotin complexes
Complex
Crystallization solvent
Colour
Yield (%)
M.p. (oC)
Elemental analysis, found (calc.) (%)
C
H
N
Ph3SnL1H (1)
Bu3SnL1H (2)
Ph3SnL2H (3)
Bu3SnL2H (4)
Ph3SnL3H (5)
Bu3SnL3H (6)
Ph3SnL4H (7)
Bu3SnL4H (8)
Bu3SnL5H (9)
Ph3SnL6H (10)
Bu3SnL6H (11)
Ph3SnL7H (12)
Bu3SnL7H (13)
Hexane
Petroleum ether
Hexane
Petroleum ether
Hexane
Petroleum ether
Hexane
Petroleum ether
Petroleum ether
Hexane
Petroleum ether
Hexane
Orange
Yellow
Orange
Brick-red
Orange
Brick-red
Orange
Light-orange
Yellow
Orange
Orange–red
Orange
63
60
50
89
40
61
52
82
83
40
93
47
50
136–138
32–34
158–160
42–44
140–141
46–48
140–141
35–36
38–40
138–140
36–38
150–152
34–36
62.9 (62.98)
56.50 (56.52)
63.50 (63.50)
57.40 (57.27)
63.48 (63.50)
57.30 (57.27)
63.50 (63.50)
57.30 (57.27)
49.00 (49.21)
58.50 (58.53)
52.24 (52.11)
61.50 (61.87)
55.67 (55.64)
4.00 (4.09)
6.70 (6.83)
4.50 (4.33)
7.00 (7.02)
4.33 (4.33)
7.06 (7.02)
4.50 (4.33)
7.00 (7.02)
5.70 (5.78)
3.60 (3.64)
6.00 (6.12)
4.22 (4.22)
6.80 (6.82)
4.80 (4.74)
5.30 (5.27)
4.60 (4.63)
5.14 (5.14)
4.70 (4.63)
5.20 (5.14)
4.60 (4.63)
5.26 (5.14)
4.60 (4.59)
6.75 (6.60)
7.32 (7.29)
4.50 (4.51)
5.08 (4.99)
Petroleum ether
Yellow
Table 3
IR data [wasym(OCO)] (cm−1) for the ligands (LHH%), sodium salts (LHNa) and triorganotin complexes (R3SnLH) a
LHH%
IR
LHNa
IR
Ph3SnLH
IR
Bu3SnLH
IR
L1HH%
L2HH%
L3HH%
L4HH%
L5HH%
L6HH%
L7HH%
1659
1668
1652
1653
1657
1675
1673
L1HNa
L2HNa
L3HNa
L4HNa
L5HNa
L6HNa
L7HNa
1583
1583
1583
1583
1587
1588
1587
1
3
5
7
–
1586
1589
1588
1587
–
2
4
6
8
9
1637
1618
1620
1590
1637
1636
1630
10
12
1622
1600
11
13
a Complex numbers as shown in Table 2.
(ROESY) spectra were required in order to assign the
aromatic protons adjacent to the methyl groups of
ligands (in L2HH% and L3HH%) due to overlapped B ring
to the strong intramolecular hydrogen bonding estab-
lished between the OH and COOH groups of ring A
[18]. For example, for 5-[(E)-2-(4-chlorophenyl)-1-di-
azenyl]-2-hydroxybenzoic acid wasym(OCO) is at
1658 cm−1 and at 1670 cm−1 for 5-[(E)-2-(4-
chlorophenyl)-1-diazenyl]-2-hydroxy methyl benzoate.
In the complexes, the carbonyl stretching frequencies
are found to be shifted to lower wavenumber, which is
ascribed to carboxylate coordination in accord with
earlier reports [18]. It should be noted that intramolecu-
lar O–H···O hydrogen bonding involving ring A is also
present in the solid state, as revealed by the results of
the X-ray crystallographic study (see Section 3.5).
1
signals in the H-NMR spectra (in the case of L2HH%,
the B ring 1H signals were severely distorted due to very
similar chemical shifts for H3 and H4). The conclusions
drawn from the ligand assignments were then extrapo-
lated to the complexes owing to the data similarity. The
1H and 13C chemical shift assignment (Tables 4 and 5
respectively) of the triorganotin moiety is straightfor-
ward from the multiplicity patterns, resonance intensi-
ties and also by examining the nJ(13C–119/117Sn)
coupling constants [18,22]. The 1H-NMR integration
values were completely consistent with the formulation
of the products.
1
3.3. H-, 13C- and 119Sn-NMR data
Holecˇek and coworkers [23–26] have shown that the
1J(13C–119/117Sn) coupling constants can be used as an
indicator of the coordination number of the tin atom in
triorganotin compounds. Four-coordinated triphenyltin
compounds exhibit couplings in the range 550–650 Hz
and five-coordinated analogues in the range 750–
850 Hz. Four-coordinated tributyltin compounds, how-
ever, exhibit couplings in the range 325–390 Hz, and
five-coordinated ones in the range 440–540 Hz. The
The 1H-NMR data of the ligands are given in Section
2. The signals were assigned by the use of correlated
spectroscopy (COSY), heteronuclear single-quantum
correlation (HSQC) and Constant time Inverse-detec-
tion Gradient Accordion Rescaled (CIGAR) heteronu-
clear multiple-bond connectivities (HMBC) [21]
experiments using gradient coherence selection. Rotat-
ing-frame Overhauser enhancement spectroscopy

14
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
Table 4
1H-NMR data (l, ppm) for the triorganotin complexes in CDCl3
Compound
Ligand skeleton a
SnꢀR skeleton b
113
114
116
H2%
H3%
H4%
H5%
H6%
R
OH
1*
2*
3*
4*
1
2
3
4
5
6
7
8
7.05
7.03
6.95
7.02
6.94
6.99
6.88
7.02
7.01
7.02
7.02
6.92
6.96
7.86
8.04
7.96
8.00
7.98
8.00
7.94
8.02
8.00
8.33
8.34
7.99
8.02
8.62
8.51
8.58
8.47
8.57
8.43
8.53
8.46
8.45
8.64
8.51
8.54
8.47
7.82
7.87
–
7.49
7.45
7.21
7.26
–
7.49
7.38
7.21
7.26
7.12
7.18
–
–
–
–
–
7.49
7.45
7.18
7.20
7.26
7.31
7.37
7.77
7.74
8.04
8.04
7.84
7.86
7.82
7.87
7.60
7.62
7.63
7.65
7.11
7.23
7.58
7.47
7.97
6.98
7.03
–
–
11.57
11.95
11.33
11.94
11.34
11.77
11.30
11.89
11.93
11.59
12.01
11.38
11.95
–
1.68
–
1.68
–
1.67
–
1.69
1.70
–
1.71
–
7.82
1.38
7.76
1.38
7.70
1.38
7.70
1.39
1.39
7.76
1.40
7.77
1.40
7.49
1.38
7.43
1.38
7.38
1.38
7.37
1.39
1.39
7.47
1.40
7.46
1.40
7.49
0.95
7.43
0.94
7.38
0.96
7.37
0.93
0.95
7.47
0.97
7.46
0.95
2.69
2.70
2.44
2.44
2.34
2.40
–
–
–
3.64
3.88
–
7.63
7.65
7.11
7.23
7.58
7.47
7.97
6.98
7.03
–
7.37
7.77
7.74
8.04
8.04
7.84
7.86
9
10
11
12
13
–
–
1.70
a Refer to Fig. 1. for numbering scheme. No change is observed in the multiplicity and coupling constants when compared with the respective
ligands. OH signal is broad singlet in all cases.
b Numbering scheme for SnꢀR skeleton as shown below:
The signals due to SnꢀR protons were multiplets except for 4* of SnꢀBu3 complexes, which is triplet, and the coupling constant was 7 Hz.
triorganotin complexes of the present investigation ex-
order to obtain further insight into the structure in the
solid state in the absence of crystallographic data [22].
The quadrupole splitting (QS) values for triphenyltin
complexes are found to be in the range 2.55–
2.63 mm s−1 and match quite well in the range of
2.3–3.0 mm s−1 characteristic for a tetrahedral geome-
try [22,28]. This conclusion is in excellent agreement
with the structures determined by X-ray crystallogra-
phy (see Section 3.5). In contrast to the triphenyltin
complexes, the tributyltin complexes exhibit a QS value
at approximately 3.61 mm s−1 and the values fall in the
range 3.0–4.1 mm s−1 specified for a trans-trigonal
bipyramidal geometry with a planar Bu3Sn unit and
two apical carboxylates giving rise to polymeric struc-
tures [22,28]. Thus, the QS values strongly suggest that,
in the smaller tin-bound organic substitutents (e.g.
Bu3Sn), aggregation occurs via SnꢀO contacts, leading
to polymeric arrays; this is in contrast to the larger
tin-bound substitutents (e.g. Ph3Sn), where such aggre-
gation is not possible owing to steric hindrance, and
hence monomeric species are found in the solid state
[22]. The isomer shifts (ISs), which lie in the range
1.19–1.50 mm s−1, are typical of quadrivalent organ-
otin derivatives and the full width of half maximum
(Y9) of these resonance absorptions is approximately
0.85 mm s−1, further suggesting the presence of a single
tin centre in the complexes [28].
1
hibit J(13C–119/117Sn) coupling satellites of the order of
645 Hz in the case of triphenyltin and 335 Hz in the
tri-n-butyltin complexes in CDCl3 solution, suggesting
that the tin atom is four-coordinate in solution. In the
case of the tributyltin complexes, a polymeric structure
is possible in the solid state (see Section 3.4) [22]; this is
possibly lost in solution to generate a monomeric four-
coordinated tetrahedral structure. Further, the 13C
chemical shift of the ipso-carbon (C1*) of the SnꢀPh3
moiety is around 138 ppm (see Table 5), which is also
characteristic for a tetrahedral tin atom [27], since for
five-coordinated triphenyltin carboxylates a value at
approximately 4 ppm higher frequency is found.
The 119Sn-NMR chemical shifts of triorganotin com-
plexes in CDCl3 solution are listed in Table 6. The
complexes exhibit a single sharp resonance in the
ranges −86.9 to −91.6 ppm (triphenyltin) and 130.8
to 138.7 ppm (tri-n-butyltin) consistent with the range
specified for tetrahedral triorganotin compounds [24].
This is further supported by recent work on analogous
triorganotin azocarboxylates [18,22]. The 119Sn-NMR
chemical shifts show obvious dependence on the nature
of the substituents in the ligand B rings, whereas l(13C)
chemical shifts of the carbon atoms of the triorganotin
n
group and the values of J(13C–119/117Sn) coupling con-
stants are not affected.
3.4. 119Sn Mo¨ssbauer data
3.5. X-ray crystallography
The Mo¨ssbauer spectra of some representative tri-
organotin complexes have been recorded (Table 6) in
The crystal structures of four of the triphenyl species
have been determined. The structures conform to the

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
15
same motif and are illustrated in Figs. 2–5. Selected
geometric parameters are given in Table 7. Compounds
1 and 3 are isomorphous and crystallize in the triclinic
(
space group P1 with two independent molecules com-
prising the asymmetric unit (labelled a and b); 5 crystal-
lizes in the monoclinic space group P21/c with one
molecule in the asymmetric unit; and finally, 12 crystal-
lizes in the space group P21 with four independent
molecules in the asymmetric unit (labelled a–d). A
careful examination of the crystallographic data did not
reveal the presence of any additional symmetry in the
structures [20d,e].
As indicated by the spectroscopic evidence, the
molecules are monomeric in the solid state. To a first
approximation the tin atom is four-coordinate, existing
in a distorted tetrahedral geometry defined by a C3O
donor set. The range of tetrahedral angles for the nine
molecules is 93.5(1) to 121.0(1)°, with the narrow and
wide angles being ascribed to the influence of the
non-coordinating O(2) atom. The O(2) atom ap-
proaches the tin atom at distances ranging from
,
,
2.752(2) A in 1a to 2.863(8) A in 12a. Although not
considered to represent a significant bonding interac-
tion, the influence of the O(2) atom is such that it
causes the expansion of the C(21)ꢀSnꢀC(27) angle and
the concomitant contraction in the O(1)ꢀSnꢀC(15) an-
gle. Support for the conclusion that the O(2) atom does
not form a significant interaction with tin is found in
the disparity in the C(1)ꢀO(1) and C(1)ꢀO(2) distances
(Table 7). This disparity would be even greater in the
absence of the intramolecular O(3)ꢀH···O(2) interac-
tion. Other parameters within the molecules are as
expected [18,22]. The relatively small ranges observed
for the geometric parameters across the series provide
evidence that the variable substitution in phenyl ring B
has little influence on the tin atom geometry.
Table 6
119Sn Mo¨ssbauer parameters (mm s−1) for the triorganotin complexes
Compound
119Sn Mo¨ssbauer data a
IS
QS
Y1
Y2
1
3
5
7
1.19
1.26
1.28
1.27
1.50
1.50
1.28
1.32
2.55
2.55
2.63
2.59
3.61
3.62
2.63
2.98
0.90
0.86
0.88
0.84
0.87
0.87
0.86
0.83
0.87
0.87
0.89
0.86
0.88
0.87
0.86
0.85
9
11
12
14 b
a Parameters: QS, quadrupole splitting; IS, isomer shifts with re-
spect to a room temperature spectrum of CaSnO3; Y1 and Y2: line
widths.
b Compound 14 is included for comparison: Ph3SnLH (LH=5-
[(E)-2-(4-chlorophenyl)-1-diazenyl]-2-hydroxybenzoic acid), see Ref.
[18].

16
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
Table 7
,
Selected geometric parameters (A, °) for the triorganotin complexes 1, 3, 5 and 12
Parameter
1a
1b
3a
3b
5
12a
12b
12c
12d
SnꢀO(1)
SnꢀO(2)
2.075(2)
2.752(2)
2.137(3)
2.125(3)
2.127(3)
1.291(3)
1.249(3)
1.243(4)
2.068(2)
2.786(2)
2.136(3)
2.123(3)
2.129(3)
1.301(3)
1.249(3)
1.239(3)
2.070(2)
2.773(2)
2.136(3)
2.124(3)
2.123(3)
1.297(3)
1.243(4)
1.244(3)
2.068(2)
2.787(2)
2.137(3)
2.119(3)
2.131(3)
1.300(4)
1.243(4)
1.240(4)
2.079(2)
2.779(2)
2.130(3)
2.122(3)
2.127(3)
1.297(4)
1.246(4)
1.266(4)
2.091(6)
2.863(8)
2.13(1)
2.099(8)
2.093(9)
1.29(1)
1.23(1)
1.23(1)
2.063(7)
2.835(7)
2.11(1)
2.14(1)
2.122(9)
1.31(1)
1.22(1)
1.21(1)
2.088(6)
2.782(6)
2.151(9)
2.10(1)
2.108(9)
1.31(1)
1.23(1)
1.26(1)
2.055(6)
2.822(6)
2.11(1)
2.123(9)
2.13(1)
1.29(1)
1.25(1)
1.26(1)
SnꢀC(15)
SnꢀC(21)
SnꢀC(27)
C(1)ꢀO(1)
C(1)ꢀO(2)
N(1)ꢀN(2)
O(1)ꢀSnꢀO(2)
O(1)ꢀSnꢀC(15)
O(1)ꢀSnꢀC(21)
O(1)ꢀSnꢀC(27)
O(2)ꢀSnꢀC(15)
O(2)ꢀSnꢀC(21)
O(2)ꢀSnꢀC(27)
C(15)ꢀSnꢀC(21)
C(15)ꢀSnꢀC(27)
C(21)ꢀSnꢀC(27)
SnꢀO(1)ꢀC(1)
SnꢀO(2)ꢀC(1)
C(6)ꢀN(1)ꢀN(2)
N(1)ꢀN(2)ꢀC(8)
52.04(4)
94.27(9)
109.7(1)
109.26(9)
146.26(9)
86.43(9)
83.31(9)
109.9(1)
110.8(1)
119.9(1)
109.3(2)
78.3(2)
51.68(8)
94.3(1)
108.3(1)
110.5(1)
145.78(9)
85.3(1)
51.76(8)
94.5(1)
51.63(8)
95.6(1)
51.68(7)
93.5(1)
50.0(2)
94.8(3)
106.2(2)
109.6(3)
144.9(3)
83.4(3)
50.9(2)
95.1(3)
110.4(3)
104.7(3)
145.9(3)
81.3(3)
51.3(2)
94.0(3)
111.8(3)
107.9(3)
145.2(3)
82.6(3)
51.2(2)
95.8(3)
107.7(3)
112.0(3)
147.0(3)
82.6(3)
109.3(1)
109.2(1)
146.23(9)
85.68(9)
84.14(9)
108.2(1)
112.3(1)
120.3(1)
109.8(2)
77.8(2)
107.7(1)
110.3(1)
147.01(9)
84.60(9)
85.3(1)
113.0(1)
106.4(1)
121.0(1)
110.1(2)
77.6(2)
108.2(1)
110.3(1)
144.96(9)
85.41(8)
84.19(9)
113.0(1)
108.7(1)
119.9(1)
109.8(2)
78.0(2)
84.0(1)
84.5(3)
82.1(3)
85.1(3)
83.7(3)
113.1(1)
108.5(1)
119.3(1)
110.3(2)
77.6(2)
110.1(4)
113.0(4)
120.0(4)
111.7(6)
76.3(6)
115.1(4)
112.5(4)
116.3(4)
110.9(6)
76.6(6)
113.7(4)
111.6(4)
115.7(4)
109.5(6)
78.6(5)
112.9(4)
113.0(4)
114.0(4)
110.9(7)
75.8(5)
114.3(2)
114.6(3)
114.3(3)
113.7(3)
114.6(2)
114.7(3)
115.1(3)
114.6(3)
113.0(3)
114.1(3)
112.7(9)
113.6(9)
109.5(9)
110(1)
115.1(8)
115.9(8)
111.6(8)
113.6(8)
In 1, centrosymmetrically related pairs of 1a aggre-
gate such that the two carboxylate ligands are ‘face-to-
face’, being associated via p–p interactions between
rings A and B (Fig. 1) such that the distance between
The structural motif found here resembles one of the
two predominant motifs for structures of the general
formula R3Sn(O2CR%) although others are known
[9,10]. The second motif features a polymeric array
generated by the presence of bidentate, bridging car-
boxylate ligands. It has been argued recently, for re-
lated systems [22], that the appearance of one or other
motif can be rationalised in terms of steric demands of
the triorganotin residue in that bulky substituents pre-
clude intermolecular association via Sn“O interac-
tions. The results reported herein are consistent with
this explanation.
Thus, for the series of R3Sn(O2CR%) structures where,
referring to Fig. 1, the carboxylate is the ligand and the
hydroxy group is in the 2% position and a methyl group
is in 5%, both the monomeric and polymeric motifs are
found. For the structures with the smaller tin-bound
substitutents, viz. methyl, ethyl and n-butyl, the poly-
meric motif with five-coordinate tin is found. When
these were substituted for the larger groups, viz. phenyl
and cyclohexyl, a monomeric structure was found with
four-coordinate tin [22] as for 1, 3, 5 and 12. The
appearance of the two motifs was explained in terms of
the competition between the formation of intramolecu-
lar Sn“O interactions, leading to a polymeric array,
and other, notably, p···p interactions [22]. The respec-
tive crystal lattices are stabilized by a variety of inter-
,
the ring centroids is 3.88 A, the dihedral angle is 7.7°
and the symmetry operation is 1−x, 1−y, z; the
,
analogous parameters for 1b are 4.07 A, 9.8°, and
2−x, 1−y, 1−z. A similar situation pertains in the
lattice of 3: for 3a the distance between the ring cen-
,
troids of A and B is 3.72 A, the dihedral angle between
them is 3.5° and the symmetry operation is 2−x,
,
−2−y, −z; for 3b these are 3.92 A, 8.2° and 1
−x, −y, 1−z respectively. In the structure of 5, cen-
trosymmetrically related pairs of carboxylate residues
also face each other, but in this case the ring centroid
,
separations are greater than 4.2 A. The closest p–p
contacts involve the tin-bound phenyl group,
C(21)ꢀC(26), with
a
centrosymmetrically related
C(21)ꢀC(26) ring such that the separation between the
,
ring centroids is 3.89 A (symmetry operation: −x,
−y, 1−z). Thus, the shift of a methyl group from the
2- (as in 3) to 3-position (as in 5) on ring B induces a
subtle change in the molecular packing. In 12, no
evidence for short p–p contacts is found, with the
,
shortest separation of 4.17 A between ring centroids
being found for two tin-bound phenyl groups of differ-
ent molecules. It would appear that the presence of the
methoxy group in 12 is sufficient to preclude associa-
tion between molecules via p–p interactions involving
the carboxylate ligand, as, in the recently determined
structure of the acid, no evidence for base stacking was
molecular
interactions
including
CꢀH···O,
CꢀH···(centroid of aromatic ring) and p–p base
stacking.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 633 (2001) 7–17
17
[7] S.J. Blunden, P.A. Cusack, R. Hill, The Industrial Uses of Tin
Chemicals, Royal Society of Chemistry, London, 1985.
[8] A.G. Davies, P.J. Smith, in: G. Wilkinson, F.G.A. Stone, E.W.
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[9] E.R.T. Tiekink, Appl. Organomet. Chem. 5 (1991) 1.
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[12] A.G. Davies, P.J. Smith, Adv. Inorg. Chem. Radiochem. 1
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[13] W.N. Aldridge, in: J.J. Zuckerman (Ed.), Organotin Com-
pounds. New Chemistry and Applications. In: Advances in
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ington, DC, 1976, p. 157.
found [19]. Of all four structures, it is noteworthy that,
in the absence of significant p–p interactions, 12 con-
tains the closest contact of the type CꢀH···ring-centroid
,
of 2.60 A (the angle at H is 161.0°). The O(3) atom in
all structures participates in an intermolecular contact
of the type O···HꢀC; however, no such interactions are
found for the methoxy oxygen atom in 12. From the
foregoing it is clear that, although the substitution
pattern in ring B has no profound influence on the
molecular geometry at tin, changes in the mode of
crystal packing are apparent.
[14] B.M. Elliot, W.N. Aldridge, J.M. Bridges, Biochem. J. 177
(1979) 461.
[15] R.G. Swisher, J.F. Vallano, V. Chandrasekhar, R.O. Day, R.R.
Holmes, Inorg. Chem. 23 (1984) 3147.
4. Supplementary material
Crystallographic data have been deposited at the
Cambridge Crystallographic Data Centre with deposi-
tion numbers: 149081–149084 for complex nos. 1, 3, 5
and 12. Copies of the information may be obtained free
of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://www.
ccdc.cam.ac.uk).
[16] J.F. Vallano, R.O. Day, D.N. Rau, V. Chandrasekhar, R.R.
Holmes, Inorg. Chem. 23 (1984) 3153.
[17] M. Gielen, R. Willem, M. Biesemans, M. Boualam, A. El
Khloufi, D. de Vos, Appl. Organomet. Chem. 6 (1992) 287.
[18] T.S. Basu Baul, S. Dhar, N. Kharbani, S.M. Pyke, R. Butcher,
F.E. Smith, Main Group Met. Chem. 22 (1999) 413.
[19] T.S. Basu Baul, S. Dhar, E.R.T. Tiekink, Acta Crystallogr. Sect.
C 56 (2000) 1280.
[20] (a) D.C. Phillips, A.C.T. North, F.S. Mathews, Acta Crystallogr.
24 (1968) 351;
(b) N. Walker, D. Stuart, Acta Crystallogr. Sect. A 39 (1983)
158;
(c) P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, S.
Garcia-Granda, J.M.M. Smits, C. Smykalla, The DIRDIF pro-
gram system, Technical Report of the Crystallography Labora-
tory, University of Nijmegen, 1994;
(d) TEXSAN: Structure Analysis Software, Molecular Structure
Corp., The Woodlands, TX;
(e) A.L. Spek, PLATON, a Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, The Netherlands 2000; http://
www.cryst.chem.uu.nl/platon/;
(f) C.K. Johnson, ORTEP. Report ORNL-5138, Oak Ridge Na-
tional Laboratory, TN, 1976.
Acknowledgements
The financial support of the Department of Science
& Technology, New Delhi, India (Grant No. SP/S1/
F26/99, TSBB), of the MURST, Italy (60%, ER), and
the support of the X-ray crystallographic facility by the
Australian
Research
Council
are
gratefully
acknowledged.
[21] C.E. Hadden, G.E. Martin, V.V. Krishnamurthy, Magn. Reson.
Chem. 38 (2000) 143.
[22] R. Willem, I. Verbruggen, M. Gielen, M. Biesemans, B. Mahieu,
T.S. Basu Baul, E.R.T. Tiekink, Organometallics 17 (1998) 5758.
[23] J. Holecˇek, M. Nadvornik, K. Handlir, A. Lycka, J. Organomet.
Chem. 241 (1983) 177.
[24] M. Nadvornik, J. Holecˇek, K. Handlir, A. Lycka, J. Organomet.
Chem. 275 (1984) 43.
[25] A. Lycka, J. Holecˇek, M. Nadvornik, K. Handlir, J. Organomet.
Chem. 280 (1985) 323.
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