Synthesis, characterization, cytotoxic activity and crystal structures of tri- and di-organotin(IV) complexes constructed from the β-{[(E)-1-(2- hydroxyaryl)alkylidene]amino}propionate and β-{[(2Z)-(3-hydroxy-1-methyl-2- butenylidene)]amino}propionate ske

Article abstract of DOI:10.1016/j.jorganchem.2005.10.057

Reactions of potassium β-{[(E)-1-(2-hydroxyaryl)alkylidene]amino} propionates (L¹HK-L³HK) and potassium β-{[(2Z)-(3- hydroxy-1-methyl-2- butenylidene)]amino}propionate (L⁴HK) with R ₃SnCl (R = Ph and ⁿ

Full text of DOI:10.1016/j.jorganchem.2005.10.057

Journal of Organometallic Chemistry 691 (2006) 952–965
www.elsevier.com/locate/jorganchem
Synthesis, characterization, cytotoxic activity and crystal structures of
tri- and di-organotin(IV) complexes constructed from the b-{[(E)-1-(2-
hydroxyaryl)alkylidene]amino}propionate and b-{[(2Z)-(3-hydroxy-1-
methyl-2-butenylidene)]amino}propionate skeletons
a,
a
a
b
Tushar S. Basu Baul *, Cheerfulman Masharing , Smita Basu , Eleonora Rivarola ,
c
c
d
e
f,
*
´
ˇ
Michal Holcˇapek , Robert Jirasko , Antonin Lycka , Dick de Vos , Anthony Linden
a
Department of Chemistry, North-Eastern Hill University, NEHU Permanent Campus, Umshing, Shillong 793 022, India
b
`
Dipartimento di Chimica Inorganica e Analitica ‘‘Stanislao Cannizzaro’’ Universita di Palermo, Viale delle Scienze,
Parco DÕOrleans II, Edificio 17, 90128 Palermo, Italy
University of Pardubice, Department of Analytical Chemistry, Studentska 95, CZ-532 18 Pardubice, Czech Republic
c
d
Research Institute for Organic Syntheses, Rybitvi 296, CZ-532 18 Pardubice 20, Czech Republic
e
Pharmachemie BV, P.O. Box 552, 2003 RN Haarlem, The Netherlands
Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
f
Received 7 October 2005; received in revised form 25 October 2005; accepted 25 October 2005
Available online 20 December 2005
Abstract
Reactions of potassium b-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionates (L1HK-L3HK) and potassium b-{[(2Z)-(3-hydroxy-
n
n
1-methyl-2- butenylidene)]amino}propionate (L4HK) with R3SnCl (R = Ph and Bu) and Bu2SnCl2 yielded complexes of composition
n
Ph3SnL1H (1), Ph3SnL2H (2), Ph3SnL4H (3), Bu3SnL1H (4), and {[nBu2Sn(L2H)]2O}2 (5) and {[nBu2Sn(L3H)]2O}2 (6), respectively.
These complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mo¨ssbauer spectroscopic techniques in com-
bination with elemental analyses. The crystal structures of 1, 4, 5 and 6 were determined. In the solid state, compound 1 is a one-dimen-
sional polymer built from SnPh3 moieties bridged by single carboxylate ligands, but two alternating modes of bridging are present along
the polymeric chain. Compound 4 is also a one-dimensional polymer built from SnBu3 moieties bridged by the two carboxylate O-atoms
of a single ligand, but only one mode of bridging is present. Di-n-butyltin compounds 5 and 6 are centrosymmetric tetranuclear
bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn4O2 core in which two l3-oxo O-atoms connect an Sn2O2 ring
to two exocyclic Sn-atoms. The four carboxylate ligands display two different modes of coordination where both modes involve bridging
of two Sn-atoms. The solution structures were predicted by 119Sn NMR spectroscopy. The in vitro cytotoxic activity of compound 5
against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumor cell lines is reported.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Di-n-butyltin; Carboxylates; b-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionic acid and b-{[(2Z)-(3-hydroxy-1-methyl-2-butenylid-
ene)]amino}propionic acid; NMR; ESI-MS; Mo¨ssbauer; Crystal structure; Cytotoxic activity
1. Introduction
Information on the structures of organotin(IV) carboxy-
*
Corresponding authors. Tel.: +91 364 2722626; fax: +91 364 2550486/
lates continues to accumulate, and at the same time, new
2721000 (T.S. Basu Baul); Tel.: +41 44 635 4228; fax: +41 44 635 6812 (A.
applications of such compounds are being discovered,
Linden).
which are relevant for industrial, ecological and medicinal
E-mail addresses: basubaul@nehu.ac.in, basubaul@hotmail.com (T.S.
applications. The increasing interest in the chemistry of
Basu Baul), alinden@oci.unizh.ch (A. Linden).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.10.057

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
953
organotin(IV) compounds has led to extended studies on
their reactions with different biomolecules, e.g., carbohy-
drates [1–3], nucleic acid derivatives [4–6], amino acids
[7–11] and peptides [12–16]. In general, triorganotin(IV)
compounds display a larger array of biological activity than
their di- and mono-organotin(IV) analogues. This has been
attributed to their ability to bind proteins [17–19]. Further-
more, many organotin(IV) derivatives have been found to
possess anticancer activity in a variety of tumour cells and
the structures of these organotin(IV) complexes are well
characterized in the solid state [20,21]. Organotin(IV)
complexes with Schiff bases, such as organotin(IV) esters
of N-arylidene-amino acids, have also been shown to exhi-
bit notable antitumour activity against human tumour cell
lines [22], as well as fungicidal activity [23]. On the other
hand, dialkyltin(IV) compounds have selective effects on
lymphocytes [24–26], which can be used in cancer chemo-
therapy or to control other pathological effects. Among
diorganotin(IV) compounds, tetraorganodistannoxanes
are an important class of compounds owing to their appli-
cations as catalysts [27] and their interesting biological
activity [21,28]. In view of this, and the recent reports on
the synthesis, characterization and structure elucidation
of organotin(IV) complexes of N-arylidene-amino acids
[29–36], we now report on some organotin(IV) complexes
of composition [R3SnLH]n (R = nBu and Ph) and
{[nBu2Sn(LH)]2O}2 (refer to Fig. 1 for ligand description).
The latter compounds possess a bis(dicarboxylatotetraorg-
anodistannoxane) framework and a representative exam-
ple, 5, was tested across a panel of human cell lines viz.,
WIDR (colon cancer), M19 MEL (melanoma), A498 (renal
cancer), IGROV (ovarian cancer) and H226 (non-small cell
3
2b
O
9
4
5
8
7
N
2a
K+
1
OH
O-
6
Potassiu
-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}propionate (L1HK)
8
9
4
7
2a
N
O-
6
3
K+
1
5
2b
OH
O
3'
Potassiu
-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}propionate (L2HK)
8
7
9
4
2a
N
O-
6
3
K+
1
5
6'
2b
OH
O
3'
Potassiu
-{[(E)-1-(2-hydroxy-3-methylphenyl)ethylidene]amino}propionate (L3HK)
3'
3
5'
O
2b
K+
1
5
-O
N
OH
2a
4
Potassiu
-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}propionate (L4HK)
Fig. 1. Generic structure of the ligands, their abbreviations and numbering scheme.

954
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
lung cancer), MCF7 (breast cancer), EVSA-T (breast can-
cer) to establish the activity.
2.3. Synthesis of ligands
A typical procedure is described below.
2. Experimental
2.3.1. Synthesis of potassium b-{[(E)-1-(2-
hydroxyphenyl)methylidene]amino}propionate (L1HK)
A cold aqueous solution (3 ml) of KOH (0.36 g,
6.41 mmol) was mixed with a cold aqueous solution (1 ml)
containing b-alanine (0.57 g, 6.40 mmol) and was held at
15–20 ꢁC in an ice bath with continuous stirring. A methan-
olic solution (15 ml) of 2-hydroxybenzaldehyde (0.78 g,
6.40 mmol) was added drop-wise. A deep-yellow colour
developed almost immediately and stirring was continued
for 1 h, followed by 5 h stirring at room temperature. The
volatiles were removed carefully; the yellow mass was stirred
in diethylether and filtered. The residue was dissolved in a
minimum amount of anhydrous methanol and filtered.
The filtrate was precipitated with diethylether, which affor-
ded the crude product. Repeated precipitations from a
methanol–diethylether mixture yielded L1HK in 94%
(1.40 g) yield. M.p.: 105–106 ꢁC. Anal. Calc. for
C10H10NKO3: C, 51.92; H, 4.35; N, 6.05. Found: C, 52.01;
H, 4.43; N, 6.15%. IR (cmꢀ1): 1646 m(OCO)asym, 1592
m(C@N), 1307 m(Ph(C–O)).
The other potassium salts (Fig. 1), viz. potassium
b-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}propionate
(L2HK), potassium b-{[(E)-1-(2-hydroxy-3-methylphe-
nyl)ethylidene)]amino}propionate (L3HK) and potassium
b-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}propi-
onate (L4HK) were prepared analogously by reacting
2-hydroxyacetophenone, 2-hydroxy-3-methylacetophenone
and acetylacetone, respectively, with b-alanine.
2.1. Materials
n
n
Ph3SnCl (Fluka AG), Bu3SnCl, Bu2SnCl2 (Merck), b-
alanine, 2-hydroxybenzaldehyde, acetylacetone (Sisco),
and 2-hydroxyacetophenone (Aldrich) were used without
further purification, while 2-hydroxy-3-methylacetophe-
none was a gift sample. The solvents used in the reactions
were of AR grade and dried using standard procedures.
Benzene was distilled from sodium benzophenone ketyl.
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 cmꢀ1 were obtained on a
BOMEM DA-8 FT-IR spectrophotometer with samples
investigated as KBr discs. The H and 13C NMR spectra
1
of the ligands were acquired on a Bruker Avance 500 spec-
trometer operating at 500.13 and 125.76 MHz, respectively.
For the organotin compounds, the 1H, 13C and 119Sn NMR
spectra were recorded on a Bruker AMX 400 spectrometer
and measured at 400.13, 100.62 and 149.18 MHz and on a
Bruker AVANCE 500 spectrometer and measured at
500.13, 125.67 and 186.18 MHz, respectively. The H, 13C
1
and 119Sn chemical shifts were referred to Me4Si set at
0.00 ppm, CDCl3 set at 77.0 ppm and Me4Sn set at
0.00 ppm, respectively. Positive-ion and negative-ion elec-
trospray ionization (ESI) mass spectra were measured on
an ion trap analyzer Esquire 3000 (Bruker Daltonics, Bre-
men, Germany) in the range m/z 50–2000. The complexes
2, 4, 5, 6 and 1, 3 were dissolved in acetonitrile and meth-
anol, respectively, and analyzed by direct infusion at a flow
rate of 5 ll/min. The selected precursor ions were further
analyzed by MS/MS analyses under the following condi-
tions: an isolation width of m/z = 8 for ions containing
one tin atom and m/z = 12 for ions containing more tin
atoms, the collision amplitude in the range 0.8–1.0 V
depending on the precursor ion stability, an ion source
temperature of 300 ꢁC, a tuning parameter of compound
stability 100%, a flow rate and pressure of nitrogen of
4 l/min and 10 psi, respectively. Mo¨ssbauer spectra were
recorded on solid samples at liquid nitrogen temperature
by using a conventional constant acceleration spectrome-
ter, coupled with a multichannel analyser (a.e.n., Pontera-
nica (BG), Italy) equipped with a cryostat Cryo (RIAL,
Parma, Italy). A Ca119SnO3 Mo¨ssbauer source, 10 mCi
(from Ritverc, St Petersburg, Russia) moving at room tem-
perature with constant acceleration in a triangular wave-
form was used. The velocity calibration was made using a
57Co Mo¨ssbauer source, 10 mCi, and an iron foil as absor-
ber (from Ritverc, St Petersburg, Russia).
2.3.2. Potassium b-{[(E)-1-(2-hydroxyphenyl)ethylidene]-
amino}propionate (L2HK)
Recrystallized from methanol to give a yellow precipi-
tate in 84% yield. M.p.: 105 ꢁC (decomp.). Anal. Calc.
for C11H12NKO3: C, 53.90; H, 4.93; N, 5.71. Found: C,
54.06; H, 5.01; N, 5.82%. IR (cmꢀ1): 1675 m(OCO)asym
1614 m(C@N), 1304 m(Ph(C–O)).
,
2.3.3. Potassium b-{[(E)-1-(2-hydroxy-3-
methylphenyl)ethylidene]amino}propionate (L3HK)
Recrystallized from methanol to give a yellow precipi-
tate in 70% yield. M.p.: 105 ꢁC (decomp.). Anal. Calc.
for C12H14NKO3: C, 55.57; H, 5.44; N; 5.40. Found: C,
55.70; H, 5.58; N, 5.55%. IR (cmꢀ1): 1667 m(OCO)asym
1601 m(C@N), 1269 m(Ph(C–O)).
,
2.3.4. Potassium b-{[(2Z)-(3-hydroxy-1-methyl-2-
butenylidene)]amino}propionate (L4HK)
Recrystallized from methanol to give a yellow precipi-
tate in 71% yield. M.p.: 95–96 ꢁC (decomp.). Anal. Calc.
for C8H12NKO3: C, 45.01; H, 5.77; N; 6.69. Found: C,
45.21; H, 6.01; N, 7.10%. IR (cmꢀ1): 1706 m(OCO)asym
1605 m(C@N), 1295 m(Ph(C–O)).
,

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
955
2.4. Synthesis of the organotin complexes
2a and H-2b), 2.27 (s, 3H, H-30); Sn–Ph Skeleton: 7.70
(m, 6H, H-2*), 7.40–7.45 (m, 9H, H-3* and H-4*),ppm.
13C NMR (CDCl3): Ligand skeleton: 178.1 (C-1), 172.0
(C-3), 163.6 (C-5), 132.4 (C-7), 128.9 (C-9), 119.3 (C-4),
118.6 (C-6), 117.0 (C-8), 45.8 and 35.3 (C-2b and C-2a),
14.5 (C-30); Sn–Ph skeleton: 138.0 (C-1*), 136.7 (C-2*)
130.1 (C-4*), 128.1 (C-3*), ppm. 119Sn NMR (CDCl3 solu-
tion): ꢀ108.6 ppm. 119Sn Mo¨ssbauer: d = 1.24, D = 3.06,
[M+SnPh3]+, 100%; m/z 830 [M+SnPh3-benzene]+; m/z
719 [HOSnPh3+SnPh3]+; m/z 580 [M+Na]+; m/z 369
[SnPh3+H2O]+; m/z 351 [SnPh3]+. MS/MS of m/z 908:
m/z 830 [M+SnPh3-benzene]+; m/z 480 [M+H-benzene]+;
m/z 420 [M+H-benzeneꢀCH3COOH]+; m/z 351 [SnPh3]+;
m/z 330 [M+H-2*benzeneꢀCO2-ethene]+. MS/MS of m/z
830: m/z 420 [M+H-benzeneꢀCH3COOH]+; m/z 351
[SnPh3]+; m/z 330 [M+H-2*benzeneꢀCO2-ethene]+. MS/
MS of m/z 719: m/z 659 [(SnPh3)2O+H-benzene+H2O]+;
m/z 581 [(SnPh3)2O+H-2*benzene+H2O]+; m/z 351
[SnPh3]+. MS/MS of m/z 580: m/z 562 [M+NaꢀH2O]+;
m/z 502 [M+Na-benzene]+; m/z 443 [M+Na-ben-
zeneꢀCH3COOH]+.; m/z 351 [SnPh3]+. MS/MS of m/z
351: m/z 369 [SnPh3+H2O]+; m/z 197 [SnPh]+. Negative-
ion MS: m/z 439 [SnPh3+Cl2+H2O]ꢀ; m/z 351 [SnPh3]ꢀ;
m/z 206 [ligand]ꢀ; m/z 162 [ligand-CO2]ꢀ; m/z 134
[ligand-CO2-ethene]ꢀ. MS/MS of m/z 439: m/z 351
[SnPh3]ꢀ. MS/MS of m/z 206: m/z 162 [ligand-CO2]ꢀ;
m/z 134 [ligand-CO2-ethene]ꢀ.
2.4.1. Synthesis of Ph3SnL1H (1)
Ph3SnCl (0.5 g, 1.30 mmol) in 10 ml anhydrous chloro-
form was added drop-wise to a stirred suspension of
L1HK (0.30 g, 1.30 mmol) in 20 ml chloroform. The stir-
ring was continued for 6 h at ambient temperature and
the reaction mixture was filtered. The filtrate was allowed
to evaporate at ambient temperature to leave a dry yellow
mass which was then triturated with hexane and filtered.
The precipitate was washed several times with hexane,
dried in vacuo and recrystallized from ethanol to yield yel-
low crystals of 1 in 70% (0.49 g) yield. M.p.: 131–132 ꢁC.
Anal. Calc. for C28H25NO3Sn: C, 62.03; H, 4.64; N, 2.58.
Found: C, 62.23; H, 4.60; N, 2.70%. IR (cmꢀ1): 1639
m(OCO)asym, 1615 m(C@N), 1281 m(Ph(CO)). 1H NMR
(CDCl3): 13.18 (brs, 1H, OH), 8.33 (s, 1H, H-3), 7.29 (t,
1H, H-7), 7.10 (d, 1H, H-9), 6.93 (d, 1H, H-6), 6.84 (t,
1H, H-8), 3.87 and 2.81 (t, 4H, H-2a and H-2b); Sn–Ph
Skeleton: 7.65 (m, 6H, H-2*), 7.37–7.41 (m, 9H, H-3*
and H-4*), ppm. 13C NMR (CDCl3): Ligand skeleton:
177.9 (C-1), 166.0 (C-3), 161.2 (C-5), 132.1 (C-7), 131.4
(C-9), 118.7 (C-4), 118.4 (C-6), 117.0 (C-8), 55.5 and 35.4
(C-2b and C-2a); Sn–Ph skeleton: 138.0 (C-1*), 136.7 (C-
2*), 130.1 (C-4*), 128.8 (C-3*) ppm. 119Sn NMR (CDCl3):
C
= 0.92 mm sꢀ1, q = 2.47. Positive-ion MS: m/z 908
ꢀ108.6 ppm. 119Sn Mo¨ssbauer: d = 1.24, D = 3.13, C
=
0.87 mm sꢀ1
,
q = 2.46. Positive-ion MS: m/z 894
[M+SnPh3]+, 100%; m/z 733 [CH3OSnPh3+SnPh3]+; m/z
719 [(SnPh3)2O+H]+; m/z 582 [M+K]+; m/z 566
[M+Na]+; m/z 544 [M+H]+; m/z 351 [SnPh3]+. MS/MS
of m/z 894: m/z 816 [M+SnPh3-benzene]+; m/z 466
[M+H-benzene]+; m/z 406 [M+H-benzeneꢀCH3COOH]+;
m/z 316 [M+H-2*benzeneꢀCO2-ethene]+. MS/MS of m/z
733: m/z 351 [SnPh3]+. MS/MS of m/z 719: m/z 659
[(SnPh3)2O+H-benzene+H2O]+; m/z 581 [(SnPh3)2O+H-
2*benzene+H2O]+; m/z 351 [SnPh3]+. MS/MS of m/z
566: m/z 488 [M+Na-benzene]+; m/z 351 [SnPh3]+. MS/
MS of m/z 544: m/z 466 [M+H-benzene]+; m/z 406
[M+H-benzeneꢀCH3COOH]+. Negative-ion MS: m/z
735 [M+ligand]ꢀ; m/z 542 [MꢀH]ꢀ; m/z 439
[SnPh3+Cl2+H2O]ꢀ; m/z 192 [ligand]ꢀ; m/z 148 [ligand-
CO2]ꢀ , 100%. MS/MS of m/z 735: m/z 542 [MꢀH]ꢀ.
MS/MS of m/z 542: m/z 498 [MꢀHꢀCO2]ꢀ; m/z 351
[SnPh3]ꢀ. MS/MS of m/z 439: m/z 351 [SnPh3]ꢀ. MS/MS
of m/z 192: m/z 148 [ligand-CO2]ꢀ.
2.4.3. Synthesis of Ph3SnL4H (3)
An identical method to that of 1 was followed using
Ph3SnCl and L4HK except that the reaction was conducted
in anhydrous methanol and refluxed for 10 h. The solvent
was then distilled off to dryness and the residue was dried
in vacuo. The solid mass was washed several times with hex-
ane, extracted into warm chloroform and filtered. The yel-
low-coloured filtrate was concentrated, precipitated with
hexane and dried in vacuo. The crude product was recrystal-
lized from a chloroform-ethanol mixture (3:1 v/v) to afford a
lemon yellow microcrystalline product in 60% yield. M.p.:
115–116 ꢁC. Anal. Calc. for C26H27NO3Sn: C, 62.03; H,
5.23; N, 2.69. Found: C, 62.10; H, 5.36; N, 2.90%. IR
(cmꢀ1): 1639 m(OCO)asym, 1606 m(C@N), 1275 m(Ph(CO)).
1H NMR (CDCl3): Ligand skeleton: 10.80 (brs, 1H, OH),
4.88 (s, 1H, 4-H), 3.49 and 2.62 (t, 4H, H-2a and H-2b),
1.93 and 1.85 (s, 6H, H-30 and H-50); Sn–Ph skeleton: 7.74
(m, 6H, H-2*), 7.43 (m, 6H, H-4*), 7.34 (m, 6H, H-3*),
ppm. 13C NMR (CDCl3): Ligand skeleton: 194.8 (C-1),
177.0 (C-3), 162.6 (C-5), 95.6 (C-4), 39.3 and 35.3
(C-2b and C-2a); 28.6 and 18.7 (C-30 and C-50); Sn–Ph
skeleton: 138.3 (C-1*), 136.7 (C-2*), 130.0 (C-4*), 128.8
(C-3*), ppm. 119Sn NMR (CDCl3): ꢀ108.3 ppm. 119Sn
Mo¨ssbauer: d = 1.27, D = 3.04, C = 1.20 mm sꢀ1, q = 2.47.
Positive-ion MS: m/z 1393 [2*M+SnPh3]+; m/z 1081
[2*M+K]+; m/z 1065 [2*M+Na]+; m/z 872 [M+SnPh3]+,
100%; m/z 733 [CH3OSnPh3+SnPh3]+; m/z 719 [HOSnPh3+
SnPh3]+; m/z 560 [M+K]+; m/z 544 [M+Na]+; m/z 522
2.4.2. Synthesis of Ph3SnL2H (2)
An identical method to that of 1 was followed using
Ph3SnCl and L2HK, except that the reaction was con-
ducted in anhydrous benzene for 4 h. Yellow crystals of
compound 2 were obtained from ethanol in 75% yield.
M.p.: 161–162 ꢁC. Anal. Calc. for C29H27NO3Sn: C,
62.64; H, 4.89; N, 2.52. Found: C, 62.84; H, 5.05; N, 2.67
%. IR (cmꢀ1): 1637 m(OCO)asym, 1611 m(C@N), 1281
m(Ph(CO)). 1H NMR (CDCl3): Ligand skeleton: 16.14
(brs, 1H, OH), 7.40 (m, 1H, H-9), 7.25 (t, 1H, H-7), 6.87
(d, 1H, H-6), 6.75 (t, 1H, H-8), 3.83 and 2.86 (t, 4H, H-

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T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
[M+H]+; m/z 351 [SnPh3]+. MS/MS of m/z 1393: m/z
872 [M+SnPh3]+. MS/MS of m/z 1081: m/z 560 [M+K]+.
MS/MS of m/z 1065: m/z 544 [M+Na]+. MS/MS of m/z
872: m/z 444 [M-benzene+H]+; m/z 384 [M-benzeneꢀ
CH3COOH+H]+; m/z 294 [M+H-2*benzeneꢀCO2-eth-
ene]+. MS/MS of m/z 733: m/z 351 [SnPh3]+. MS/MS of
m/z 719: m/z 659 [(SnPh3)2O+H-benzene+H2O]+; m/z 581
[(SnPh3)2O+H-2*benzene+H2O]+; m/z 351 [SnPh3]+. MS/
MS of m/z 544: m/z 502 [M+NaꢀCH2@C@O]+; m/z 351
[SnPh3]+; m/z 197 [SnPh]+. MS/MS of m/z 522: m/z 444
[M-benzene+H]+. Negative-ion MS: m/z 691 [M+ligand]ꢀ;
m/z 439 [SnPh3+Cl2+H2O]ꢀ; m/z 170 [ligand]ꢀ, 100%; m/z
128 [ligand-CH2@C@O]ꢀ; m/z 98 [ligand-CO2-ethene]ꢀ.
MS/MS of m/z 691: m/z 520 [MꢀH]ꢀ . MS/MS of m/z 439:
m/z 351 [SnPh3]ꢀ. MS/MS of m/z 170: m/z 128 [ligand-
CH2@C@O]ꢀ ; m/z 98 [ligand-CO2-ethene]ꢀ.
N4O14Sn4: C, 51.04; H, 6.76; N, 3.13. Found: C, 51.21;
H, 6.83; N, 3.21%. IR (cmꢀ1): 1619 m(OCO)asym, 1573
m(C@N), 1275 m(Ph(CO)), 645 m(Sn–O–Sn). 1H NMR
(CDCl3): Ligand skeleton: 15.84 (brs, 1H, OH), 7.50 (d,
1H, H-9), 7.25 (t, 1H, H-7), 6.87 (d, 1H, H-6), 6.75 (t,
1H, H-8), 3.79 and 2.67 (t, 4H, H-2a and H-2b), 2.35 (s,
3H, H-30); Sn–nBu skeleton: 1.60 (m, 4H, H-1*), 1.30–
1.41(m, 8H, H-2* and H-3*), 0.85 (t, 6H, H-4*), ppm.
13C NMR (CDCl3): Ligand skeleton: 177.4 (C-1), 171.7
(C-3), 163.5 (C-5), 132.3 (C-7), 128.0 (C-9), 119.5 (C-4),
118.6 (C-6), 117.0 (C-8), 46.0 and 37.2 (C-2b and C-2a),
14.4 (C-30); Sn–nBu skeleton: 27.6, 27.4, 26.8, 26.7, 21.4
(C-2*, C-3* and C-4*), 13.6 br (C-4*), ppm. 119Sn NMR
(CDCl3): ꢀ200.2, ꢀ212.7 ppm , [2J(Sn–O–Sn) = 140 Hz].
119Sn Mo¨ssbauer: d = 1.30, D = 3.28, C = 0.95 mm sꢀ1
,
q = 2.52. Positive-ion MS: m/z 958 [Mmono+H+OSn-
Bu2+(OH)2SnBu2]+; m/z 940 [Mmono+ H+2*OSnBu2]+;
m/z 751 [(OSnBu2)3+H]+; m/z 690 [Mmono+H+OSnBu2]+,
100%; m/z 672 [Mmono+HꢀH2O+ OSnBu2]+; m/z 501
n
2.4.4. Synthesis of Bu3SnL1H (4)
Preparation of compound 4 was accomplished accord-
ing to the procedure used for 1 by using equimolar
amounts of nBu3SnCl and L1HK. Yellow prismatic crystals
of 4 were obtained from a hexane–chloroform mixture (4:1
v/v) in 62% yield. M.p.: 79–80 ꢁC. Anal. Calc. for
C22H37NO3Sn: C, 54.79; H, 7.73; N, 2.90. Found: C,
[(OSnBu2)2+H]+; m/z 462 [Mmono+Na]+; m/z 440 [Mmono
+
H]+; m/z 326 [Mmono-butane-butene+H]+. MS/MS of m/z
958: m/z 940 [Mmono+ H+2*OSnBu2]+; m/z 690 [Mmono
H+OSnBu2]+. MS/MS of m/z 940: m/z 922 [Mmono
+
+
H+2*OSnBu2ꢀH2O]+; m/z 501 [(OSnBu2)2+H]+. MS/
MS of m/z 751: m/z 733 [(OSnBu2)3+H–H2O]+; m/z 655
[(OSnBu2)3+H-butene-butane+H2O]+; m/z 619 [(OSn-
Bu2)3+H-butene-butane-H2O]+; m/z 541 [(OSnBu2)3+H-
2*butene-2*butane+H2O]+; m/z 523 [(OSnBu2)3+H-
2*butene-2*butane]+; m/z 501 [(OSnBu2)2+H]+; m/z
465; m/z 427 [(OSnBu2)3+H-3*butene-3*butane+H2O]+;
m/z 409 [(OSnBu2)3+H-3*butene-3*butane]+; m/z 387
[(OSnBu2)2+H-butene-butane]+; m/z 273 [(OSnBu2)2+
H-2*butane-2*butene]+. MS/MS of m/z 690: m/z 672
55.04; H, 7.67; N, 3.02%.IR (cmꢀ1): 1631 m(OCO)asym
,
1578 m(C@N), 1281 m(Ph(CO)). 1H NMR (CDCl3): Ligand
skeleton: 13.30 (brs, 1H, OH), 8.39 (s, 1H, H-3), 7.26 (t,
1H, H-7), 7.1 (d, 1H, H-9), 6.92 (d, 1H, H-6), 6.85 (t,
1H, H-8), 3.85 and 2.71 (t, 6H, H-2a and H-2b); Sn–nBu
skeleton: 1.56 (m, 6H, 1*), 1.32 (m, 12H, 2* and 3*), 0.87
(t, 9H, 4*), ppm. 13C NMR (CDCl3): Ligand skeleton:
176.7 (C-1), 165.7 (C-3), 161.1 (C-5), 132.1 (C-7), 131.1
(C-9), 118.7 (C-4), 118.3 (C-6), 116.9 (C-8), 55.7 and 35.9
(C-2b and C-2a); Sn–nBu skeleton: 27.7 (C-2*), 27.0 (C-3*),
16.4 (C-1*), 13.6 (C-4*), ppm. 119Sn NMR (CDCl3):
[Mmono+H–H2O+OSnBu2]+;
m/z
654
[Mmono+H–
2*H2O+OSnBu2]+; m/z 556 [Mmono+H–H2O+ OSnBu2-
2*butane]+; m/z 422 [Mmono+H–H2O]+. MS/MS of m/z
672: m/z 654 [Mmono+H-2*H2O+OSnBu2]+; m/z 556
110.8 ppm. 119Sn Mo¨ssbauer: d = 1.46, D = 3.56, C
=
0.87 mm sꢀ1, q = 2.44. Positive-ion MS: m/z 796 [M+
SnPh3-H+Na]+; m/z 774 [M+SnPh3]+; m/z 522 [M+K]+;
m/z 506 [M+Na]+, 100%. MS/MS of m/z 796: m/z 581
[M+SnPh3-H+NaꢀLNa]+; m/z 506 [M+Na]+; m/z 334
[M+Na-2*butane-butene]+. MS/MS of m/z 774: m/z 426
[MꢀBu]+; m/z 312 [MꢀBu-butane-butene]+; m/z 291
[SnBu3]+; m/z 235 [HSnBu2]+. MS/MS of m/z 506: m/z
448 [M+Na-butane]+; m/z 334 [M+Na-2*butane-butene]+;
m/z 235 [HSnBu2]+; m/z 179 [BuSnH2]+. Negative-ion MS:
m/z 482 [MꢀH]ꢀ; m/z 192 [ligand]ꢀ; m/z 148 [ligand-
CO2]ꢀ, 100%. MS/MS of m/z 482: m/z 438 [MꢀHꢀCO2]ꢀ;
m/z 289 [MꢀHꢀLH]ꢀ. MS/MS of m/z 192: m/z 148
[ligand-CO2]ꢀ.
[Mmono+H–H2O+OSnBu2-2*butan]+; m/z 538 [Mmono
+
H-2*H2O+OSnBu2-2*butane]+; m/z 422 [Mmono+H–
H2O]+; m/z 308 [Mmono+H–H2O-butane-butene]+. MS/
MS of m/z 501: m/z 483 [(OSnBu2)2+H–H2O]+; m/z
445 [(OSnBu2)2+H-butene]+; m/z 389 [(OSnBu2)2+H-2*
butene]+; m/z 331 [(OSnBu2)2+H-2*butene-butane]+; m/z
289 [(OSnBu2)2+H-3*butane-butene+H2O]+; m/z 273
[(OSnBu2)2+H-2*butane-2*butene]+. MS/MS of m/z 462:
m/z 348 [Mmono+Na-butane-butene]+. MS/MS of m/z
440: m/z 422 [Mmono+H-H2O]+; m/z 380 [Mmono+H-
HAC]+; m/z 369; m/z 326 [Mmono+H-butane-butene]+;
m/z 233 [BuSn@Bu]+; m/z 177 [SnBu]+. Negative-ion
MS: m/z 438 [Mmono-H]ꢀ, 100%. MS/MS of m/z 438: m/z
394 [Mmono-HꢀCO2]ꢀ; m/z 160 [MmonoꢀH-SnBu2ꢀCO2]ꢀ
(Note: Mmono = LSnBu2 = 439).
2.4.5. Synthesis of {[nBu2Sn(L2H)]2O}2 (5)
This compound was prepared in the same manner as
described for 1 by using nBu2SnCl2 (0.4 g, 1.31 mmol)
and L2HK (0.70 g, 2.85 mmol). Yellow crystals of 5 were
obtained from a hexane–chloroform mixture (4:1 v/v) in
2.4.6. Synthesis of {[nBu2Sn(L3H)]2O}2 (6)
An identical method to that used for the preparation of
5 was followed by using nBu2SnCl2 and L3HK. Yellow
crystals of 6 were obtained from a hexane–chloroform
60% yield. M.p.: 125–126 ꢁC. Anal. Calc. for C76H120
-

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
957
mixture (4:1 v/v) in 65% yield. M.p.: 159–160 ꢁC. Anal.
Calc. for C80H128N4O14Sn4: C, 52.09; H, 6.99; N, 3.03.
Found: C, 52.31; H, 7.18; N, 3.25%. IR (cmꢀ1): 1618
m(OCO)asym, 1573 m(C@N), 1268 m(Ph(CO)), 645 m(Sn–O–
CO2-ethene]ꢀ; m/z 133 [ligand-CO2-CH3CHNH]ꢀ; m/z
107 [o-cresol-H]ꢀ. MS/MS of m/z 452: m/z 408
[MmonoꢀHꢀCO2]ꢀ; m/z 380 [Mmonoꢀ HꢀCO2-ethene]ꢀ;
m/z 174 [ligand-HCOOH]ꢀ. MS/MS of m/z 220: m/z 176
[ligand-CO2]ꢀ; m/z 148 [ligand-CO2-ethene]ꢀ. MS/MS of
m/z 176: m/z 133 [ligand-CO2ꢀCH3CHNH]ꢀ; m/z 107
[o-cresol-H]ꢀ. MS/MS of m/z 148: m/z 107 [o-cresol-H]ꢀ
(Note: Mmono = LSnBu2-H = 453).
1
Sn). H NMR (CDCl3): Ligands skeleton: 16.21 (brs, 1H,
OH), 7.35 (d, 1H, H-9), 7.14 (t, 1H, H-7), 6.66 (t, 1H,
H-8), 3.85 and 2.71 (t, 4H, H-2a and H-2b), 2.35 and
2.22 (s, 6H, H-30 and H-60); Sn–nBu skeleton: 1.59 (m,
4H, H-1*), 1.30–1.42 (m, 8H, H-2* and H-3*), 0.85 (t,
6H, H-4*), ppm. 13C NMR (CDCl3): Ligands skeleton:
177.5 (C-1), 172.0 (C-3), 162.0 (C-5), 133.0 (C-7), 127.2
(C-9), 125.6 (C-4), 118.3 (C-6), 116.3 (C-8), 45.7 and 37.1
(C-2b and C-2a), 15.7 and 14.6 (C-60 and C-30); Sn–nBu
skeleton: 27.6, 27.3, 26.8, 26.6, 21.0 (C-2*, C-3* and C-
4*), 13.6, 13.5 (C-4*), ppm. 119Sn NMR (CDCl3):
ꢀ200.7, ꢀ213.2 ppm, [2J(Sn–O–Sn) = 140 Hz]. 119Sn
2.5. X-ray crystallography
Crystals of compounds 1, 4, 5 and 6 suitable for an
X-ray crystal-structure determination were obtained from
ethanol (1), hexane (4), benzene/hexane (5) or hexane/
chloroform (6). All measurements were made on a Non-
ius KappaCCD diffractometer [37] with graphite-mono-
= 0.87 mm sꢀ1
,
chromated Mo Ka radiation (k = 0.71073 A) and an
˚
Mo¨ssbauer: d = 1.17, D = 3.28,
C
q = 2.80. Positive-ion MS: m/z 1871 [M+Na]+ a m/z
Oxford Cryosystems Cryostream 700 cooler. Data reduc-
tion was performed with HKL Denzo and Scalepack
[38]. The intensities were corrected for Lorentz and
polarization effects, and empirical absorption corrections
based on the multi-scan method [39] were applied.
Equivalent reflections were merged, other than the Fri-
edel pairs for 1. The data collection and refinement
parameters are given in Table 1, and views of the mole-
cules are shown in Figs. 2–5. The structures were solved
by direct methods using SIR92 [40] for 1, 4 and 5, and
SHELXS97 [41] for 6, and the non-hydrogen atoms were
refined anisotropically.
For 6, the molecule sits about a crystallographic centre
of inversion. One butyl group on each of the two symme-
try-independent Sn-atoms is disordered over two confor-
mations. Two sets of overlapping positions were defined
for the atoms of each disordered butyl group and the site
occupation factor of the major conformation of these
groups refined to 0.647(7) and 0.789(6) for the disordered
group at the exo- and endo-cyclic Sn-atoms, respectively.
Similarity restraints were applied to the chemically equiv-
alent bond lengths and angles involving all disordered C-
atoms, while neighbouring atoms within and between
each conformation of the disordered butyl groups were
restrained to have similar atomic displacement parame-
ters. In the structure of 5, the molecule also sits about a
crystallographic centre of inversion, but there is no
disorder.
The hydroxy and ammonium H-atoms of 1 and the
hydroxy H-atoms of 4 and 6 were placed in the positions
indicated by a difference electron density map and their
positions were allowed to refine together with individual
isotropic displacement parameters. All other H atoms in
all structures were placed in geometrically calculated posi-
tions and refined using a riding model where each H atom
was assigned a fixed isotropic displacement parameter with
a value equal to 1.2Ueq of its parent C atom (1.5Ueq for the
methyl groups). The orientation of each hydroxy O–H vec-
tor in 5 was optimised to correspond with the direction that
would bring the H-atom closest to the nearest hydrogen
1887 [M+K]+; m/z 1628 [MꢀL]+; m/z 1425 [2*Mmono
+
H+OSnBu2+(OH)2SnBu2]+; m/z 972 [Mmono+H+OSn-
Bu2+(OH)2SnBu2]+; m/z 954 [Mmono+H+2*OSnBu2]+;
m/z 929 [2*Mmono+Na]+; m/z 751 [(OSnBu2)3+H]+; m/z
704 [Mmono+H+OSnBu2]+; m/z 492 [Mmono+K]+; m/z
476 [Mmono+Na]+; m/z 454 [Mmono+H]+, 100%. MS/MS
of m/z 1628: m/z 1157 [MꢀLꢀMmonoꢀH2O]+; m/z 704
[Mmono+H+OSnBu2]+. MS/MS of m/z 1425: m/z 972
[Mmono+H+OSnBu2+(OH)2SnBu2]+; m/z 954 [Mmono
+
H+OSnBu2+(OH)2SnBu2ꢀH2O]+; m/z 751 [(OSn-
Bu2)3+H]+; m/z 704 [Mmono+H+OSnBu2]+; m/z 501
[(OSnBu2)2+H]+. MS/MS of m/z 972: m/z 954 [Mmono
+
H+2*OSnBu2]+; m/z 936 [Mmono+H+2*OSnBu2ꢀH2O]+;
m/z 751 [(OSnBu2)3+H]+; m/z 704 [Mmono+H+OSnBu2]+;
m/z 501 [(OSnBu2)2+H]+. MS/MS of m/z 954: m/z 936
[Mmono+H+2*OSnBu2ꢀH2O]+; m/z 501 [(OSnBu2)2+H]+.
MS/MS of m/z 929: m/z 476 [Mmono+Na]+. MS/MS of m/z
751: m/z 733 [(OSnBu2)3+HꢀH2O]+; m/z 655 [(OSn-
Bu2)3+H-butene-butane+H2O]+; m/z 619 [(OSnBu2)3+
H-butene-butaneꢀH2O]+; m/z 541 [(OSnBu2)3+H-2*butene-
2*butane+H2O]+;
m/z
523
[(OSnBu2)3+H-2*-but-
ene-2*butane]+; m/z 501 [(OSnBu2)2+H]+; m/z 465;
m/z 427 [(OSnBu2)3+H-3*butene-3*butane+H2O]+; m/z
409 [(OSnBu2)3+H-3*butene-3*butane]+; m/z 387 [(OSn-
Bu2)2+H-butene-butane]+; m/z 273 [(OSnBu2)2+ H-2*
butane-2*butene]+. MS/MS of m/z 704: m/z 686 [Mmono+H+
OSnBu2-H2O]+; m/z 668 [Mmono+H+ OSnBu2-2*H2O]+;
m/z 554 [Mmono+H+OSnBu2ꢀ2*H2O-butene-butane]+;
m/z 436 [Mmono+H-H2O]+. MS/MS of m/z 492: m/z 474
[Mmono+KꢀH2O]+; m/z 379 [Mmono+K-butene-butane]+..
MS/MS of m/z 476: m/z 458 [Mmono+NaꢀH2O]+; m/z
362 [Mmono+Na-butene-butane]+. MS/MS of m/z 454:
m/z 436 [Mmono+HꢀH2O]+; m/z 382 [Mmono+HꢀCO2-
ethene]+; m/z 340 [Mmono+H-butene-butane]+; m/z 305
[Mmono+H-butene-butane-2*H2O]+Å; m/z 268; m/z 233
[Bu–Sn@Bu]+; m/z 177 [SnBu]+. Negative-ion MS: m/z
452 [Mmono-H]ꢀ; m/z 357 [MmonoꢀH-butene-butane+
H2O]ꢀ.; m/z 339 [MmonoꢀH-butene-butane]ꢀ.; m/z 220
[ligand]ꢀ; m/z 176 [ligand-CO2]ꢀ, 100%; m/z 148 [ligand-

958
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
Table 1
Crystallographic data and structure refinement parameters for compounds 1 and 4–6
1
4
5
6
Empirical formula
Formula weight
Crystal size (mm)
Crystal shape
C56H50N2O6Sn2
1084.22
0.08 · 0.23 · 0.25
Tablet
C22H37NO3Sn
482.14
0.08 · 0.12 · 0.20
Prism
C76H120N4O14Sn4
1788.20
0.07 · 0.20 · 0.25
Tablet
C80H128N4O14Sn4
1844.30
0.10 · 0.20 · 0.25
Prism
Temperature (K)
Crystal system
Space group
160(1)
Monoclinic
Pc
160(1)
Monoclinic
P21/n
13.7830(3)
9.9060(2)
17.7972(4)
90
109.616(1)
90
160(1)
Triclinic
160(1)
Triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
9.8671(1)
10.0853(1)
24.7096(3)
90
102.4277(6)
90
2401.30(5)
2
1.499
12.475(1)
13.574(1)
14.212(1)
94.149(5)
113.754(5)
109.696(5)
2012.5(3)
1
13.0368(3)
13.6627(3)
14.7318(3)
113.936(1)
102.200(1)
108.279(1)
2096.86(9)
1
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
2288.91(9)
4
1.399
Z
Dc (g cmꢀ3
)
1.475
1.287
1.460
1.238
l (mmꢀ1
)
1.093
1.135
Transmission factors (min, max)
2hmax (ꢁ)
0.656, 0.936
60
0.770, 0.929
60
0.671, 0.937
50
0.722, 0.887
55
Reflections measured
Independent reflections; Rint
Reflections with I > 2 r(I )
Number of parameters
Number of restraints
R(F) [I > 2 r(I ) reflns]
wR(F2) (all data)
59217
13972; 0.077
11998
604
2
0.037
0.080
1.04
1.07, ꢀ0.97
56647
6675; 0.076
5108
251
0
0.035
0.079
1.08
1.59, ꢀ0.92
22961
7078; 0.071
5438
450
0
0.053
0.137
1.09
1.47, ꢀ1.12
43463
9586; 0.058
7459
550
220
0.040
0.105
1.03
1.07, ꢀ1.53
GOF (F2)
ꢀ3
˚
Dqmax,min (e A
)
Fig. 2. The unique repeat unit in the polymeric [Ph3SnL1H]n chain structure of 1 (50% probability ellipsoids).
bond acceptor. The refinement of each structure was car-
2.6. Biological tests
ried out on F2 by using full-matrix least-squares proce-
2
dures, which minimized the function RwðF 2o ꢀ F c2Þ .
The in vitro cytotoxicity test of compound 5 was per-
formed using the SRB test for the estimation of cell viabil-
ity. The cell lines WIDR (colon cancer), M19 MEL
(melanoma), A498 (renal cancer), IGROV (ovarian cancer)
and H226 (non-small cell lung cancer) belong to the
currently used anticancer screening panel of the National
Corrections for secondary extinction were not applied.
For 1, refinement of the absolute structure parameter [42]
yielded a value of 0.53(1), which indicates that the crystals
1 are inversion twins. All calculations were performed
using the SHELXL 97 program [43].

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
959
Fig. 3. A three-unit segment of the polymeric [nBu3SnL1H]n chain in 4
(50% probability ellipsoids).
Fig. 5. The molecular structure of {[nBu2Sn(L3H)]2O}2 (6) (50% proba-
bility ellipsoids).
tive. All cell lines were maintained in a continuous logarith-
mic culture in RPMI 1640 medium with Hepes and phenol
red. The medium was supplemented with 10% FCS, penicil-
lin 100 lg/ml and streptomycin 100 lg/ml. The cells were
mildly trypsinized for passage and for use in the experi-
ments. RPMI and FCS were obtained from Life Technolo-
gies (Paisley, Scotland). SRB, DMSO, Penicillin and
streptomycin were obtained from Sigma (St. Louis MO,
USA), TCA and acetic acid from Baker BV (Deventer,
NL) and PBS from NPBI BV (Emmer-Compascuum, NL).
The test compound 5 and reference compounds were
dissolved to a concentration of 250000 ng/ml in full med-
ium, by 20 fold dilution of a stock solution which con-
tained 1 mg of compound 5/200 ll. Compound 5 was
dissolved in DMSO. Cytotoxicity was estimated by the
microculture sulforhodamine B (SRB) test [45].
2.6.1. Experimental protocol and cytotoxicity tests
The experiment was started on day 0. On day 0, 150 ll
of trypsinized tumor cells (1500–2000 cells/well) were pla-
ted in 96-well flat-bottomed micro-titer plates (falcon
3072, BD). The plates were pre-incubated for 48 h at
37 ꢁC, 5.5% CO2 to allow the cells to adhere. On day 2, a
threefold dilution sequence of ten steps was made in full
medium, starting with the 250000 ng/ml stock solution.
Every dilution was used in quadruplicate by adding 50 ll
to a column of four wells. This results in a highest concen-
tration of 62500 ng/ml being present in column 12. Col-
umn 2 was used for the blank. To column 1, PBS was
added to diminish interfering evaporation. On day 7, wash-
ing the plate twice with PBS terminated the incubation.
Fig. 4. The molecular structure of {[nBu2Sn(L2H)]2O}2 (5) (50% proba-
bility ellipsoids).
Cancer Institute, USA [44]. The MCF7 (breast cancer) cell
line is estrogen receptor (ER)+/progesterone receptor
(PgR)+ and the cell line EVSA-T (breast cancer) is
(ER)ꢀ/(Pgr)ꢀ. Prior to the experiments, a mycoplasma
test was carried out on all cell lines and found to be nega-

960
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
Subsequently, the cells were fixed with 10% trichloroacetic
acid in PBS and placed at 4 ꢁC for an hour. After three
washings with tap water, the cells were stained for at least
15 min with 0.4% SRB dissolved in 1% acetic acid. After
staining, the cells were washed with 1% acetic acid to
remove the unbound stain. The plates were air-dried and
the bound stain was dissolved in 150 ll (10 mM) Tris–base.
The absorbance was read at 540 nm using an automated
microplate reader (Labsystems Multiskan MS). Data were
used for construction of concentration-response curves and
the determination of ID50 values by use of Deltasoft 3
software.
The assignment of the symmetric [msym(OCO)] stretching
vibration band could not be made owing to the complex
pattern of the spectra. In addition, a strong broad band
in the region 645 cmꢀ1 has been detected for the com-
plexes 5 and 6 and is assigned to the m(Sn–O–Sn) mode
[47,48].
1
The H and 13C NMR signals were assigned by the use
of homonuclear correlated spectroscopy (COSY), hetero-
nuclear single-quantum correlation (HSQC) and heteronu-
clear multiple-bond correlation (HMBC) experiments. The
1H and 13C chemical shift assignment (Section 2.4) of the
organotin moiety is straightforward from the multiplicity
1
patterns and resonance intensities. The H NMR integra-
tion values were completely consistent with the formulation
of the products. The 13C NMR spectra of the ligand and
Sn–R skeletons displayed the expected carbon signals in
all cases, except for the di-n-butyltin(IV) complexes 5 and
6, which displayed two sets of Sn–nBu resonances, consis-
tent with a dicarboxylatotetraorganodistannoxane struc-
ture. Owing to the low intensities of the Sn–nBu
resonances, a poor signal to noise ratio prevented identifi-
3. Results and discussion
3.1. Synthetic aspects
Organotin(IV) complexes of composition R3SnLH
(R = nBu and Ph) and {[nBu2Sn(LH)]2O}2 were prepared
by reacting potassium salts of the ligands (Fig. 1) with
the appropriate organotin(IV) halide(s) in 1:1 and 2:1
molar ratios, respectively. The reactions could be con-
ducted in anhydrous chloroform, benzene or methanol,
which resulted in the smooth formation of the complexes
1–6 (see Section 2.4). The synthesis of complexes of the
type R3SnLH is straightforward, however, the formation
of diorganotin(IV) complexes deserve specific comments.
Recently, we have demonstrated that 2-{[(E)-1-(2-hydroxy-
aryl)alkylidene]amino}acetic acid forms a great variety of
diorganotin(IV) complexes, viz., [R2SnL(OH2)]2 (R = Me
n
cation of J(Sn–C). The 119Sn NMR chemical shifts of the
organotin complexes in CDCl3 solution are listed in Sec-
tion 2.4. The triorganotin complexes exhibit a single sharp
resonance at around ꢀ108 ppm for R = Ph (1–3) and
111 ppm for R = nBu (4). The d (119Sn) chemical shifts
are consistent with the range specified for tetrahedral
triorganotin compounds [49,50,32]. These results demon-
strate that the polymeric structure with five-coordinate
tin atoms found in the solid state is lost upon dissolution
(see Section 3.3). On the other hand, the bis(dicarboxyla-
totetraorganodistannoxanes) (5 and 6) exhibit two distinct
119Sn NMR resonances of equal intensities at around ꢀ200
and ꢀ213 ppm characteristic for the endocyclic and exocy-
clic tin atoms [51]. Although it is difficult to assign coordi-
nation to the tin atoms with certainty on the basis of their
119Sn chemical shifts, values of d (119Sn) in the ranges ꢀ200
to ꢀ400, ꢀ90 to ꢀ190 and 200 to ꢀ60 ppm have been asso-
ciated with six-, five- and four-coordinate tin centres,
respectively, bearing n-butyl groups [52]. On this basis,
two chemically different six-coordinate tin centres (endocy-
clic and exocyclic) are present in solution for the di-n-butyl-
tin complexes 5 and 6, which is consistent with the X-ray
structures (vide infra). Thus, the 13C and 119Sn NMR data
for the complexes 5 and 6 provide reasonable support for
the formation of a dimeric tetraorganodistannoxane struc-
ture [51,53]. Although two different types of carboxylate
groups are present (as revealed by the X-ray analysis; see
below), only single broad resonances are observed for the
COO group in the 13C NMR spectra of 5 and 6, which
might also correspond to the situation when two 13C reso-
nances of two carboxyl groups exist, however, the differ-
ence between them is rather small. 119Sn chemical shifts
are much more sensitive to subtle structural changes and
the observed difference between two tin resonances was
only 13 ppm. The difference in 13C resonances should,
therefore, be considerably smaller. This may be due to
n
[35], Vin [29], Bu [35]), [R2SnL]3 (R = nBu [35]), [R2SnL]
(R = Ph [29], Bz [36]) and [R2SnL]n (R = Ph [35]). In each
case, the labile functional group (phenolic hydrogen atom)
is removed, thereby forming a bicycloazadiorganostannox-
ides. In the present case, the unsymmetrical bi-functional
potassium b-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}pro-
pionate and potassium b-{[(2Z)-(3-hydroxy-1-methyl-
2-butenylidene)]amino}propionate ligands react with
nBu2SnCl2 to give a bis(dicarboxylatotetraorganodistan-
noxane), {[nBu2Sn(LH)]2O}2 (5 and 6), where the labile
phenolic group remains intact. The reaction possibly pro-
ceeds via the formation of di-n-butyltin dicarboxylates,
which can undergo hydrolysis, presumably mediated by
adventitious moisture present in the solvent or a slight
excess of base present in the starting potassium salt, to
yield the product of composition {[nBu2Sn(LH)]2O}2 [46].
The complexes were isolated as yellow crystalline solids
in good yield (>60 %) and purity. They are stable in air
and are soluble in common organic solvents.
3.2. Spectroscopy
Diagnostically important infrared absorption frequen-
cies for the carboxylate antisymmetric [masym(OCO)]
stretching vibration of the complexes appears in the range
1630–1640 cmꢀ1 (for 1–4) and 1618 cmꢀ1 (for 5 and 6).

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
961
the accidental magnetic equivalence of the carbonyl carbon
atoms on the NMR time scale.
value to isomer shift value (q = D/d) indicates coordination
greater than four [54].
The triorganotin complexes 1–4 are characterized by a
single doublet spectrum in the Mo¨ssbauer spectra, reveal-
ing the occurrence of only one type of tin atom in the solid
state, while the di-n-butyltin complexes 5 and 6 displayed
two doublets of equal intensities, as expected. These results
are in agreement with the 119Sn NMR data. The triorgano-
tin complexes exhibited quadrupole splitting (D) values of
approximately 3.00 mm sꢀ1 (1–3) and 3.56 mm sꢀ1 (4).
These values are within the range 3.0–4.1 mm sꢀ1, which
are consistent with a trans-trigonal bipyramidal geometry
with a planar R3Sn unit and two axial carboxylate oxygen
atoms [54]. Similar ranges of values were also found in the
triorganotin derivatives of cognate ligands with a trans-
trigonal bipyramidal geometry [32]. In contrast, the Mo¨ss-
bauer data could not be fitted into two doublets, as
expected for di-n-butyltin complexes of the type
{[nBu2Sn(LH)]2O}2 (5 and 6) having exo-cyclic and endo-
cyclic- tin centers [46]. The complexes 5 and 6 both exhib-
ited good single doublet spectra indicating that the two
types of tin centers are similar. The isomer shifts of the
complexes were found in the usual range of 1.17–
1.30 mm sꢀ1, which indicates the presence of quadrivalent
tin centers. Further, the ratio of the quadrupole splitting
The typical ions in the first-order positive-ion ESI mass
spectra of compounds 1–4 are adducts with the SnPh3 group
and with alkali metal ions, such as [M+SnPh3]+, [M+K]+
and [M+Na]+ (typical ions for this type of compounds)
[55]. The presence of these ions was used for the determina-
tion of the molecular weights of the analyzed compounds.
The second mechanism of the ion formation is the cleavage
of the most labile bond Sn–O in the molecules, which yields
two complementary ions, where the cationic part (SnPh3) of
the molecule is measured in the positive-ion mode and the
anionic part (L) in the negative-ion mode [56]. The ion
m/z 351 [SnPh3]+ forms the other adduct ion at m/z 719
[(SnPh3)2+H]+. The ions observed in the first-order nega-
tive-mass spectra are [LꢀCO2]ꢀ and [M+L]ꢀ. On the other
hand, compounds 5 and 6 are complex di-n-butyltin com-
pounds with four tin atoms. In the case of 6, low abundant
ions corresponding to molecular adducts were identified
after longer averaging of mass spectra, which enabled posi-
tive confirmation of the tetranuclear structure of this com-
pound. The molecular adducts were not found in the
background noise in the case of 5, so only ions correspond-
ing to the monomeric unit Mmono are observed (see Section
2.4 for more details). The typical feature of the spectra is the
HO
HO
N
N
O–
NH+
O
Ph
Sn
Ph
Ph
Ph
O
O
Bu Bu
Sn
Ph
O
Sn
O
O
Ph
Bu
n
n
1
4
L
Bu
Bu
Bu
O
O
Sn
O
R
OH
L
O
Bu
O
N
Sn
O
Sn
O
L =
Bu
O
Bu
L
Sn
O
O
Bu
Bu
L
5 R = H; 6 R = Me
Scheme 1. Structures of the complexes 1, 4–6.

962
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
Table 3
formation of adduct ions with tetranuclear character, where
the OSnBu2 group is a monomeric unit.
a
˚
Selected bond lengths (A) and angles (ꢁ) for compound 4
Sn–O(1)
Sn–O(2)i
Snꢁ ꢁ ꢁO(1)i
2.460(2)
2.181(2)
3.043(2)
Sn–C(11)
Sn–C(15)
Sn–C(19)
2.147(2)
2.151(2)
2.140(2)
3.3. X-ray crystallography
O(1)–Sn–O(2)i
O(1)–Snꢁ ꢁ ꢁO(1)i
O(1)–Sn–C(11)
O(1)–Sn–C(15)
O(1)–Sn–C(19)
O(2)i–Snꢁ ꢁ ꢁO(1)i
O(2)i–Sn–C(11)
O(2)i–Sn–C(15)
a
172.11(6)
139.44(5)
83.56(8)
79.50(8)
85.47(8)
46.58(5)
96.51(8)
94.27(8)
O(2)i–Sn–C(19)
O(1)i ꢁ ꢁ ꢁ Sn–C(11)
O(1)iꢁ ꢁ ꢁSn–C(15)
O(1)iꢁ ꢁ ꢁSn–C(19)
C(11)–Sn–C(15)
C(11)–Sn–C(19)
C(15)–Sn–C(19)
100.21(8)
75.13(9)
140.80(7)
77.80(9)
114.5(1)
122.3(1)
118.7(1)
Views of the structures of compounds 1 and 4–6 are
shown in Figs. 2–5 (see Scheme 1 for line diagrams), while
selected geometric parameters are collected in Tables 2–5.
The solid-state structure of complex 1 is a one-dimensional
polymer in which the repeat unit contains two Sn-atoms
with distinct coordination environments (Fig. 2). The
structure is built from SnPh3 moieties bridged by single car-
boxylate ligands, but two modes of bridging are present
with these modes alternating along the polymeric chain.
The first bridge links two Sn-atoms via the two carboxylate
O-atoms of the carboxylate ligand, while the second bridge
links two Sn-atoms via one of the carboxylate O-atoms and
the phenoxide O-atom. The pattern then repeats. The
repeat Snꢁ ꢁ ꢁSn distances in this pattern are 5.3882(3) and
Atom labels with superscript ‘‘i’’ refer to atoms from the next sym-
metrically-related ligand in the polymeric chain (symmetry code: 1 12 ꢀ x,
1
1
2 þ y, 2 ꢀ z).
Table 4
a
˚
Selected bond lengths (A) and angles (ꢁ) for diorganotin(IV) compound 5
Sn(1)–O(1)
Sn(1)–O(4)
Sn(1)–O(5)
Sn(1)–O(7)
Sn(1)–C(23)
Sn(1)–C(27)
2.278(4)
2.174(4)
2.810(5)
2.030(4)
2.132(7)
2.135(7)
Sn(2)–O(2)
Sn(2)–O(4)i
Sn(2)–O(7)
Sn(2)–O(7)i
Sn(2)–C(31)
Sn(2)–C(35)
2.272(4)
2.790(5)
2.043(4)
2.171(4)
2.121(7)
2.140(7)
˚
8.5119(4) A, respectively, for the two coordination motifs.
The primary coordination sphere of each Sn-atom is trigo-
nal bipyramidal with the phenyl ligands in the equatorial
plane. Atom Sn(1) is coordinated by the three phenyl
ligands, a carboxylate O-atom from one carboxylate ligand
and the phenoxide O-atom from a second carboxylate
ligand. In addition, the second carboxylate O-atom of the
first carboxylate ligand, which coordinates strongly to
Sn(2), also has a weak interaction with Sn(1) with an
O(1)–Sn(1)–O(4)
O(1)–Sn(1)–O(5)
O(1)–Sn(1)–O(7)
O(1)–Sn(1)–C(23)
O(1)–Sn(1)–C(27)
O(4)–Sn(1)–O(5)
O(4)–Sn(1)–O(7)
O(4)–Sn(1)–C(23)
O(4)–Sn(1)–C(27)
O(5)–Sn(1)–O(7)
O(5)–Sn(1)–C(23)
O(5)–Sn(1)–C(27)
O(7)–Sn(1)–C(23)
O(7)–Sn(1)–C(27)
C(23)–Sn(1)–C(27)
O(2)–Sn(2)–O(4)i
O(2)–Sn(2)–O(7)
a
170.4(2)
O(2)–Sn(2)–O(7)i
O(2)–Sn(2)–C(31)
O(2)–Sn(2)–C(35)
O(4)i–Sn(2)–O(7)
O(4)i–Sn(2)–O(7)i
O(4)i–Sn(2)–C(31)
O(4)i–Sn(2)–C(35)
O(7)–Sn(2)–O(7)i
O(7)–Sn(2)–C(31)
O(7)–Sn(2)–C(35)
O(7)i–Sn(2)–C(31)
O(7)i–Sn(2)–C(35)
C(31)–Sn(2)–C(35)
Sn(1)–O(7)–Sn(2)
Sn(1)–O(7)–Sn(2)i
Sn(2)–O(7)–Sn(2)i
164.3(2)
138.6(2)
90.2(2)
84.9(2)
87.5(2)
50.4(2)
80.7(2)
95.8(2)
98.2(2)
131.0(2)
76.0(2)
83.7(2)
113.0(2)
107.5(2)
138.8(3)
129.2(2)
89.9(2)
82.9(2)
91.4(2)
140.8(2)
65.2(1)
77.9(2)
78.5(2)
75.7(2)
109.6(2)
106.0(2)
95.8(2)
98.6(2)
143.9(3)
135.6(2)
119.7(2)
104.3(2)
˚
Snꢁ ꢁ ꢁO distance of 3.202(3) A (Table 2), thus completing
six-coordination of Sn(1) in the extended coordination
sphere. Atom Sn(2) is coordinated in the primary coordina-
tion sphere by the three phenyl ligands, a carboxylate
Table 2
a
˚
Selected bond lengths (A) and angles (ꢁ) for compound 1
Sn(1)–O(1)
Sn(1)ꢁ ꢁ ꢁO(2)
Sn(1)–O(33)i
Sn(1)–C(11)
Sn(1)–C(17)
Sn(1)–C(23)
2.204(2)
3.202(3)
2.244(2)
2.123(3)
2.136(3)
2.135(3)
Sn(2)–O(2)
2.396(3)
2.148(3)
2.986(3)
2.141(3)
2.134(4)
2.119(4)
Sn(2)–O(31)
Sn(2)ꢁ ꢁ ꢁO(32)
Sn(2)–C(41)
Sn(2)–C(47)
Sn(2)–C(53)
Atom labels with superscript ‘‘i’’ refer to symmetrically-related atoms
generated by the centre of inversion (symmetry code: ꢀx, ꢀy, ꢀz).
O(1)–Sn(1)ꢁ ꢁ ꢁO(2)
O(1)–Sn(1)–O(33)i
O(1)–Sn(1)–C(11)
O(1)–Sn(1)–C(17)
O(1)–Sn(1)–C(23)
O(2)ꢁ ꢁ ꢁSn(1)–O(33)i
O(2)ꢁ ꢁ ꢁSn(1)–C(11)
O(2)ꢁ ꢁ ꢁSn(1)–C(17)
O(2)ꢁ ꢁ ꢁSn(1)–C(23)
O(33)i–Sn(1)–C(11)
O(33)i–Sn(1)–C(17)
O(33)i–Sn(1)–C(23)
C(11)–Sn(1)–C(17)
C(11)–Sn(1)–C(23)
C(17)–Sn(1)–C(23)
a
43.93(7)
174.64(9)
93.2(1)
87.1(1)
92.6(1)
135.95(7)
69.0(1)
130.0(1)
78.6(1)
82.5(1)
91.7(1)
O(31)–Sn(2)ꢁ ꢁ ꢁO(32)
O(31)–Sn(2)–O(2)
O(31)–Sn(2)–C(41)
O(31)–Sn(2)–C(47)
O(31)–Sn(2)–C(53)
O(32)ꢁ ꢁ ꢁSn(2)–O(2)
O(32)ꢁ ꢁ ꢁSn(2)–C(41)
O(32)ꢁ ꢁ ꢁSn(2)–C(47)
O(32)ꢁ ꢁ ꢁSn(1)–C(53)
O(2)–Sn(2)–C(41)
O(2)–Sn(2)–C(47)
O(2)–Sn(2)–C(53)
C(41)–Sn(2)–C(47)
C(41)–Sn(2)–C(53)
C(47)–Sn(2)–C(53)
47.98(9)
177.71(9)
88.7(1)
99.7(1)
94.0(1)
131.90(8)
136.7(1)
80.8(1)
73.1(1)
91.3(1)
82.4(1)
83.9(1)
112.9(1)
115.9(1)
129.4(1)
O-atom from one carboxylate ligand and the carboxyl O-
atom from a second carboxylate ligand. In addition, the
carbonyl O-atom of the second carboxylate ligand coor-
dinates weakly to Sn(2) with an Snꢁ ꢁ ꢁO distance of
˚
2.986(3) A, thus completing six-coordination in the
extended coordination sphere of Sn(2) as well. In the car-
boxylate ligand that coordinates via its two carboxylate
O-atoms, the phenolic hydroxy group forms an intraligand
hydrogen bond with the adjacent N-atom. In the carboxyl-
ate ligand that coordinates via one carboxylate O-atom
and the phenoxide O-atom, the phenolic hydroxy H-atom
has migrated to the N-atom, thus forming a zwitterionic
ligand. In this ligand, the protonated N-atom then forms
an intraligand hydrogen bond back to the phenoxide O-
atom.
92.5(1)
113.7(1)
125.2(1)
121.0(1)
Atom labels with superscript ‘‘i’’ refer to atoms from the next sym-
metrically-related ligand in the polymeric chain (symmetry code: x, 1ꢀy,
1
z ꢀ 2).

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
963
Table 5
Selected bond lengths (A) and angles (ꢁ) for diorganotin(IV) compound 6
a
˚
Sn(1)–O(1)
Sn(1)–O(4)
Sn(1)–O(5)
Sn(1)–O(7)
Sn(2)–O(2)
Sn(2)–O(4)i
2.232(3)
2.174(3)
2.967(3)
2.025(2)
2.290(3)
2.676(3)
Sn(2)–O(7)
2.052(2)
2.171(2)
2.138(4)
2.119(6)/2.120(5)
2.135(3)
Sn(2)–O(7)i
Sn(1)–C(25)
Sn(1)–C(29a/b)
Sn(2)–C(33)
Sn(2)–C(37a/b)
2.150(5)/2.05(2)
O(1)–Sn(1)–O(4)
O(1)–Sn(1)–O(5)
O(1)–Sn(1)–O(7)
O(1)–Sn(1)–C(25)
O(1)–Sn(1)–C(29a/b)
O(4)–Sn(1)–O(5)
O(4)–Sn(1)–O(7)
O(4)–Sn(1)–C(25)
O(4)–Sn(1)–C(29a/b)
O(5)–Sn(1)–O(7)
O(5)–Sn(1)–C(25)
O(5)–Sn(1)–C(29a/b)
O(7)–Sn(1)–C(25)
O(7)–Sn(1)–C(29a/b)
C(25)–Sn(1)–C(29a/b)
O(2)–Sn(2)–O(4)i
O(2)–Sn(2)–O(7)
a
167.3(1)
144.61(9)
89.38(9)
89.8(2)
85.9(8)/89.5(4)
47.87(9)
78.28(9)
93.3(2)
100.8(8)/97.1(4)
126.00(8)
75.7(1)
81.3(7)/78.6(4)
117.0(1)
109.2(2)/109.6(3)
133.1(4)/133.8(2)
129.51(9)
O(2)–Sn(2)–O(7)i
O(2)–Sn(2)–C(33)
O(2)–Sn(2)–C(37a/b)
O(4)i–Sn(2)–O(7)
O(4)i–Sn(2)–O(7)i
O(4)i–Sn(2)–C(33)
O(4)i–Sn(2)–C(37a/b)
O(7)–Sn(2)–O(7)i
O(7)–Sn(2)–C(33)
O(7)–Sn(2)–C(37a/b)
O(7)i–Sn(2)–C(33)
O(7)i–Sn(2)–C(37a/b)
C(33)–Sn(2)–C(37a/b)
Sn(1)–O(7)–Sn(2)
Sn(1)–O(7)–Sn(2)i
Sn(2)–O(7)–Sn(2)i
164.4(1)
84.6(1)
90.7(2)/77.1(4)
140.77(9)
65.39(8)
81.7(1)
72.7(1)/86.1(6)
75.9(1)
108.0(1)
109.3(2)/103.0(7)
94.4(1)
99.3(2)/111.3(4)
142.4(2)/143.7(6)
136.6(1)
119.3(1)
104.1(1)
89.64(9)
Atom labels with superscript ‘‘i’’ refer to symmetrically-related atoms generated by the centre of inversion (symmetry code: ꢀx, 1ꢀy, ꢀz). Double
entries refer to the alternate positions of atoms in the disordered butyl groups.
˚
Complex 4 also forms a one-dimensional polymer in the
solid state, but with only one Sn-atom and coordination
motif in the repeat unit. The two carboxylate O atoms of
a single alaninate ligand bridge two SnBu3 moieties and
the pattern then repeats itself to give a continuous single-
stranded polymeric structure, as illustrated in Fig. 3. The
primary coordination sphere of the Sn-atom has a slightly
distorted trans-Bu3SnO2 trigonal bipyramidal geometry
(Table 3) with equatorial butyl groups and carboxylate O
atoms occupying axial positions, one being from each of
two alaninate ligands. The carboxylate C–O bond lengths
are not equivalent, which shows some distinction between
the carbonyl and carboxylic acid O atoms. Correspond-
ingly, the Sn–O bond lengths involving these O atoms are
also not equivalent, with the Sn–O bond to the carbonyl
O atom being the longer. The length of the intramolecular
5.19 0.21 A [58] and shows that the repeat distance is
independent of the nature of the tin-bound substituents
and carboxylate residues. As in the earlier reports [50,57],
the polymeric chain in the structure of 4 propagates in a
21 screw fashion coincident with a crystallographic 21 screw
axis. As complexes 1 and 4 involve the same carboxylate
ligand, the different structural motifs observed are most
likely a result of the spatial influence of the different R
ligands in the SnR3 moiety; i.e., butyl versus phenyl.
The crystal structure determination of 5 and 6 confirmed
the bis(dicarboxylatotetraorganodistannoxane) formula-
tion (Figs. 4 and 5). The molecules are centrosymmetric tet-
ranuclear complexes containing a planar Sn4O2 core in
which two l3-oxo O-atoms connect an Sn2O2 ring to two
exocyclic Sn-atoms. Two carboxylate ligands each bridge
one endocyclic to one exocyclic Sn-centre via the two car-
boxylate O-atoms, with the Sn–O distances being quite
similar (Tables 4 and 5). Two additional carboxylate
ligands each have asymmetric bidentate coordination via
the two carboxylate O-atoms to an exocyclic Sn-atom, with
˚
Snꢁ ꢁ ꢁO(1) separation in 4 is 3.043(2) A. Although this dis-
tance is well inside the sum of the van der Waals radii of
˚
the Sn and O atoms (ca. 3.6 A), the trigonal bipyramidal
coordination geometry of the primary coordination sphere
distorted to only a small extent. The phenolic hydroxy
group in each ligand forms an intraligand hydrogen bond
with the adjacent N-atom.
˚
the longer Snꢁ ꢁ ꢁO interactions being quite long: 2.810(5) A
˚
in 5 and 2.967(3) A in 6. Additionally, the other carboxyl-
ate O-atom in each of these ligands coordinates via a sec-
˚
˚
The structure of 4 corresponds with the type II poly-
meric motif described by Willem et al. for similar
R3SnO2CR0 compounds [50] and observed in the crystal
structures of the closely related compounds (nBu3Sn-
[O2CC6H4{N@N(C6H3-4-OH-5-CHO)}-o])n and (nBu3Sn-
[O2CC6H4{N@N(C6H3-4-OH(C(H)@NC6H4Cl-4))}-o])n
ond long Snꢁ ꢁ ꢁO bond [2.790(5) A in 5 and 2.676(3) A in
6] to an endocyclic Sn-atom. Each Sn-atom is also coordi-
nated by two butyl groups. Each Sn-atom, therefore, has
six coordination, excluding the central Snꢁ ꢁ ꢁSn contact of
˚
˚
3.3277(7) A in 5 and 3.3320(4) A in 6. However, the pri-
mary coordination sphere at each Sn-atom looks more like
a slightly distorted trigonal bipyramid than an octahedron.
In this description, the butyl groups always occupy equato-
rial positions. The sixth coordination site is then occupied
˚
[57]. In 4, the repeat Snꢁ ꢁ ꢁSn distance is 5.2166(2) A, which
agrees very well with the mean repeat distance found in
other type II carboxylate-bridged triorganotin species of

964
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
Table 6
In vitro ID50 values (ng/ml) of test compound 5 along with some reported {[nBu2Sn(L)]2O}2 compounds used a cell viability test in seven human tumour
cell linesa
Test compoundb
Cell lines
A498
EVSA-T
H226
IGROV
M19 MEL
MCF-7
WIDR
{[nBu2Sn(2-OHC6H4C(CH3)@N(CH2)2COO)]2O}2 (5)
DOX
CDDP
5-FU
376
51
539
146
44
119
25
–
–
–
–
–
34
26
251
382
10
395
4
–
–
–
–
237
20
650
531
168
159
5
–
–
–
–
174
120
72
799
285
1387
78
–
–
–
–
–
225
80
980
495
45
1513
14
–
–
–
–
–
147
21
480
373
15
296
3
60
895
36
491
556
15
MTX
ETO
TAX
457
5
{[(CH3CH(OH)COO)nBu2Sn]2O}2 [61]
248
210
1661
624
31
{[(C6H5CH(OH)COO)nBu2Sn]2O}2 [61]
54
{[(C6H4(2-OCH3)COO)nBu2Sn]2O}2 [62]
156
850
63
CDDP
DOX
–
–
ETO
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
187
44
51
190
29
42
624
330
316
1794
122
330
280
624
390
967
11
{[(C6H3(3-CH3)(2- OH)COO)nBu2Sn]2O}2 [63]
{[(C6H3(4-CH3)(2-OH)COO)nBu2Sn]2O}2 [63]
{[(C6H3(4-OCH3)(2-OH)COO)nBu2Sn]2O}2 [64]
{[(C6H3(5-OCH3)(2-OH)COO)nBu2Sn]2O}2 [63]
{[(C6H3(4-NH2)(2-OH)COO)nBu2Sn]2O}2 [63]
{[(C6H3(5-Cl)(2-OH)COO)nBu2Sn]2O}2 [64]
CDDP
31
850
160
699
10
{[(C23H38(OH)COO)nBu2Sn]2O}2 [21]
CDDP
220
2253
90
60
422
8
420
3269
199
160
169
60
120
558
16
DOX
a
Abbreviation: DOX, doxorubicin; CDDP, cisplatin; 5-FU, 5-fluorouracil; MTX, methotrexate; ETO, etoposide and TAX, paclitaxel.
Standard drug reference values are cited immediately after the test compounds under identical conditions.
b
by one of the longer Snꢁ ꢁ ꢁO interactions, which approaches
from other related di-n-butyltin(IV) compounds of the
bis(dicarboxylatotetraorganodistannoxane) type, {[nBu2-
Sn(LH)]2O}2, with respect to the standard drugs that are
in current clinical use as antitumour agents. In general,
the {[nBu2Sn(LH)]2O}2 compounds have shown quite
promising antitumour activity (see Table 6) [61–64], espe-
cially when compared with CDDP (cisplatin). This encour-
aging in vitro cytotoxic effect may be predictive of in vivo
antitumour activity. Compound 5 may be a suitable candi-
date for modification in order to improve cytotoxic and
dissolution properties.
in rather a skew manner, presumably as a result of bite
angle constraints. In 5 and 6, the exo-Snꢁ ꢁ ꢁendo-Sn dis-
˚
tances are 3.6322(7) and 3.7711(7) A and 3.6209(4) and
˚
3.7870(4) A, respectively. The Sn4O10 core of the molecule
forms an essentially planar system, but the remaining
atoms of the carboxylate ligands, as well as the butyl
ligands extend roughly perpendicular to this plane. In 6,
one butyl group on each Sn-atom is disordered over two
conformations. The phenolic hydroxy group in each car-
boxylate ligand forms an intraligand hydrogen bond with
the adjacent N-atom.
The bis(dicarboxylatotetraorganodistannoxane) motif
occurs frequently amongst dialkyltin(IV) carboxylate com-
plexes. The Cambridge Structural Database [59] contains 80
entries for such structures and, in all of these structures, the
Sn-coordination geometry, as well as the distribution of Sn–
O distances, is usually much the same. The structure of the
methylidine analogue of the ethylidine complex, 5, namely
bis[(l3-oxo)-(l2-2-hydroxyphenylmethylimino-b-alaninato-
O,O0)-(2-hydroxyphenylmethylimino-b-alaninato-O)-tetra-
n-butylditin], is, apart from the missing methyl group, in all
other respects the same as that of 5 [60].
4. Supplementary material
CCDC nos. 263959–263962 contain the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
Acknowledgments
The financial support of the Department of Science &
Technology, New Delhi, India (Grant No. SP/S1/IC-03/
2005, TSBB) and the Czech Science Foundation (Grant
No. 203/03/1071, MH and Grant No. 203/03/1118, AL)
are gratefully acknowledged. E.R. is indebted to the Uni-
3.4. In vitro cytotoxicity
The results of the in vitro cytotoxic tests performed with
a representative compound, 5, are summarized in Table 6
and the screening results are compared with the results
`
versita di Palermo, Italy for support.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 691 (2006) 952–965
965
[34] A. Linden, T.S. Basu Baul, C. Masharing, Acta Crystallogr. Sect. E
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