Di-n-octyltin(IV) complexes with 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid: Syntheses and assessment of solid state structures by 119Sn M?ssbauer and X-ray diffraction and further insight into the solution structures using electrospray ionization MS, 119Sn NMR and variable temperature NMR spectroscopy

Article abstract of DOI:10.1016/j.jorganchem.2007.04.044

Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L¹HH′: X = H; L²HH′: X=2′-OCH₃; L³HH′: X = 3′-CH₃; L⁴HH′: X = 4′-CH₃; L⁵HH′:X = 4′-Cl) with ⁿOct₂SnO in 2:1 and 1:1 molar ratios have been investigated. Two types of complexes, ⁿOct₂Sn(LH)₂ and {[ⁿOct₂Sn(LH)]₂O}₂, were isolated and they have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn M?ssbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of ⁿOct₂Sn(L¹H)₂ (1), {[ⁿOct₂Sn(L²H)]₂O} ₂ (3) and {[ⁿOct₂Sn(L³H)]₂O} ₂(4) were determined. The mononuclear complex 1 was found to adopt a skew-trapezoidal bipyramidal arrangement around the tin atom while 3 and 4 are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn₄O₂ core in which two μ₃-oxo O-atoms connect an Sn₂O₂ ring to two exocyclic Sn-atoms. The solution structures were confirmed by ¹¹⁹Sn NMR spectroscopy by observing one tin resonance in compound 1 and two tin resonances in {[ⁿOct₂Sn(L⁵H)]₂O} ₂ (5). {[ⁿOct₂Sn(L²H)]₂O} ₂ (3) and {[ⁿOct₂Sn(L³H)]₂O} ₂ (4) undergo very complex exchange processes in deuteriochloroform solution, which has been confirmed by variable temperature ¹H NMR spectroscopy. The cleavage of the most labile bond in the molecule was studied by ESI mass spectrometry.

Full text of DOI:10.1016/j.jorganchem.2007.04.044

Journal of Organometallic Chemistry 692 (2007) 3625–3635
www.elsevier.com/locate/jorganchem
Di-n-octyltin(IV) complexes with 5-[(E)-2-(aryl)-1-diazenyl]-
2-hydroxybenzoic acid: Syntheses and assessment of solid
119
state structures by Sn Mossbauer and X-ray diffraction and further
¨
insight into the solution structures using electrospray ionization MS,
119Sn NMR and variable temperature NMR spectroscopy
a,
a
b
c
Tushar S. Basu Baul *, Wandondor Rynjah , Eleonora Rivarola , Claudio Pettinari ,
d
d
e
f, ,1
*
ˇ
´
Michal Holcapek , Robert Jirasko , Ulli Englert , Anthony Linden
a
Department of Chemistry, North-Eastern Hill University, NEHU Permanent Campus, Umshing, Shillong 793 022, India
`
Dipartimento di Chimica, Inorganica e Analitica,‘‘Stanislao Cannizzaro’’ Universita di Palermo, Viale delle Scienze, Parco D’Orleans II,
b
Edificio 17, 90128 Palermo, Italy
Universita di Camerino, Dipartimento di Scienze Chimiche, Via S. Agostino 1, 62032 Camerino, Italy
c
`
d
ˇ
University of Pardubice, Faculty of Chemical Technology, Department of Analytical Chemistry, na´m. Cs. legiı 565, 53210 Pardubice, Czech Republic
´
e
Institut fu¨r Anorganische Chemie, RWTH Aachen University, 52056 Aachen, Germany
Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
f
Received 13 April 2007; received in revised form 27 April 2007; accepted 28 April 2007
Available online 8 May 2007
Abstract
Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH0, where the aryl group is an R-substituted phenyl ring such that
for L1HH0:X = H; L2HH0:X=20-OCH3; L3HH0:X = 30-CH3; L4HH0:X = 40-CH3; L5HH0:X = 40-Cl) with nOct2SnO in 2:1 and 1:1 molar
n
ratios have been investigated.Two types of complexes, Oct2Sn(LH)2 and {[nOct2Sn(LH)]2O}2, were isolated and they have been char-
acterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mo¨ssbauer spectroscopic techniques in combination with elemental analyses.
n
The crystal structures of Oct2Sn(L1H)2 (1), {[nOct2Sn(L2H)]2O}2 (3) and{[nOct2Sn(L3H)]2O}2 (4) were determined. The mononuclear
complex 1 was found to adopt a skew-trapezoidal bipyramidal arrangement around the tin atom while 3 and 4 are centrosymmetric tet-
ranuclear 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 solution structures were confirmed by 119Sn NMR spectroscopy by observing one tin reso-
nance in compound 1 and two tin resonances in {[nOct2Sn(L5H)]2O}2 (5). {[nOct2Sn(L2H)]2O}2 (3) and {[nOct2Sn(L3H)]2O}2 (4) undergo
very complex exchange processes in deuteriochloroform solution, which has been confirmed by variable temperature 1H NMR spectros-
copy. The cleavage of the most labile bond in the molecule was studied by ESI mass spectrometry.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Di-n-octyltin; Carboxylates; 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid; NMR; ESI-MS; Mo¨ssbauer; Crystal structure
1. Introduction
Recently, we have been investigating the coordination
behaviour of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic
*
Corresponding authors. Tel.: +91 364 272 2626; fax: +91 364 2550076/
2721000.
acids towards organotin(IV), owing to possible biological
E-mail addresses: basubaul@nehu.ac.in, basubaul@hotmail.com (T.S.
applications and their structural diversity in the crystalline
Basu Baul), alinden@oci.uzh.ch (A. Linden).
1
state (Scheme 1). The triorganotin(IV) complexes of the
Tel.: +41 44 635 4228; fax: +41 44 635 6812.
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.04.044

3626
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
general formula R3Sn(O2CC6H4(OH-2)(N@NC6H4(X)-5))
in great detail [1–3]. The triphenyltin(IV) compounds
provided diffraction quality crystals and their solid state
structures revealed a monomeric distorted tetrahedral
n
(R = Me, Bu or Ph; X = H, 20-CH3, 30-CH3, 40-CH3,
40-Br, 40-Cl, 40-NO2, 40-OCH3) have been investigated
OH
N
O
N
Ph
Sn
X
Ph
O
H
Ph
O
H
Ph
Ph
O
Sn
Ph
X
N
N
N
O
N
OH
(X = H, 2’-CH3, 3’-CH3, 4’-CH3, 4’-OCH3, 4’-Cl)
(X = 2’-CH3)
I
II
X
N
X
N
N
N
Bu
O
OH
O
O
Sn
O
Bu
OH
Bu
Bu
OH
O
Sn
Sn
Bu
O
O
OH
OH
O
O
OH
O
O
O
Bu
N
N
N
N
N
N
N
N
X
X
X
X
(X = H, 2’-CH3, 3’-CH3, 4’-CH3, 4’-Cl, 4’-Br)
(X = H, 2’-CH3, 3’-CH3)
IIIa
IIIb
X
N
N
OH
Bu
Sn
O
O
Bu
X
OH
R
O
O
O
O
Bu
N
N
Sn
R
O
O
OH
OH
Bu
Sn
Sn
Bu
N
O
O
N
Bu
O
O
OH
O
O
Sn
X
Bu
N
N
N
N
Bu
OH
N
N
X
Y
X
(X = 4’-CH3, 4’-Cl; Y = 4’-Cl, 4’-Br )
(X = H, 4’-CH3, 4’-Cl, 4’-Br)
IIIc
IV
Scheme 1. An overview showing the coordination behaviour of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids towards organotin(IV).

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
3627
geometry where the carboxylate ligand coordinates to
Sn in an usual monodentate fashion (Scheme 1, I). The
reactivity of the tetrahedral triphenyltin(IV) complex
Ph3Sn(O2CC6H4(OH-2)(N@NC6H4 (20-CH3)-5)) towards
2,20-bipyridine (bipy) has been investigated to ascertain
the ability of bipy to coordinate to the Sn-complex and
the resultant changes in the molecular architecture. The
crystal structure of the product revealed that the bipy moi-
ety does not coordinate to the Sn atom, but forms a cyclic
tetrameric adduct of formula [Ph3Sn(O2CC6H4(OH-2)
(N@NC6H4(20-CH3)-5))(H2O)]2 Æ bipy2 through hydrogen
bonding between the water ligand of Ph3SnL1H(H2O)
and the bipy N atoms (Scheme 1, II) [3]. Furthermore, a
series of di-n-butyltin(IV) complexes of the aforementioned
ligands of the formulations of nBu2Sn(O2CC6H4(OH-2)
(N@NC6H4(X)-5))2 (and mixed ligand complexes) and
{[nBu2Sn(O2CC6H4(OH-2)(N@NC6H4(X)-5))]2O}2 were pre-
pared and their structures were determined. In general,
the X-ray diffraction studies divulge that nBu2Sn(O2
CC6H4(OH-2) (N@NC6H4(X)-5))2 (X = H, 20-CH3, 30-
CH3, 40-CH3, 40-Br, 40-Cl) complexes [4–6] adopt a skew-
trapezoidal bipyramidal arrangement around the tin atom
(Scheme 1, IIIa). In addition, there are weak bridging inter-
molecular Snꢀ ꢀ ꢀO contacts in the di-n-butyltin(IV) com-
plexes (X = H, 30-CH3), but not in the 40-substituted
analogues. In the case of the di-n-butyltin(IV) complex
with the substituent X = H, the Snꢀ ꢀ ꢀO interaction links
the molecules into polymeric chains, while in the other
complex (X = 30-CH3), these interactions link pairs of mol-
ecules into head-to-head dimeric units. In these two
structures, the open side of the Sn atom actually allows
one of the hydroxy oxygen atoms from the 2-hydroxy-
benzoate moiety of one ligand of a neighboring molecule
to form a bridge and coordinate very weakly with the Sn
atom, thereby completing a seventh coordination site in
the extended Sn coordination sphere (Scheme 1, IIIb)
[6]. In all of the above-described instances, the Sn atom
is always coordinated by two chemically equivalent
carboxylates. Attempts were also made with two different
carboxylic acids in order to obtain mixed ligand com-
plexes with the R2Sn(O2CC6H4(OH-2)(N@NC6H4(X)-5))
(O2CC6H4(OH-2)(N@NC6H4(Y)-5)) formulation. The solid
Sn(O2CC6H4(OH-2) (N@NC6H4(X)-5))2 were screened for
larvicidal activity against the second larval instar of the
Aedes aegypti mosquito and have shown promise as
larvicides [5]. On the other hand, the di-n-butyltin
(IV) compounds of the type {[nBu2Sn(O2CC6H4(OH-2)
(N@NC6H4(X)-5))]2O}2 were found to be more active
n
in vitro than Bu2Sn(O2CC6H4(OH-2) (N@NC6H4(X)-5))2
when investigated for cytotoxic potential against human
tumour cell lines [8]. In addition, diorganotin(IV) com-
pounds are used extensively as heat stabilizers for processing
polyvinyl chloride. The three major types of tin stabilizers
are distinguished by their respective alkyl groups, such as
octyl, butyl, and methyl, and the ligands normally used are
thioglycolic acid esters, reverse esters and carboxylic acids
[9,10].
Given the synthetic and structural importance and the
potential biological activity of the organotin(IV) complexes
of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acid, it is of
interest to explore the chemistry of the analogous complexes
n
of these ligands with OctSn(IV). The present contribution
details the preparation and spectroscopic characterization of
some di-n-octyltin(IV) complexes of 5-[(E)-2-(aryl)-1-diaze-
nyl]-2-hydroxybenzoic acid (Fig. 1), along with the crystal
structures of three compounds, viz., nOct2Sn(L1H)2, {[nOct2-
Sn(L2H)]2O}2 and {[nOct2Sn(L3H)]2O}2.
2. Experimental
2.1. Materials
Di-n-octyltin oxide (Fluka) was used as received. The
solvents used in the reactions were of AR grade and were
dried using the standard literature procedures. Toluene
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 cmꢁ1 were obtained
on a BOMEM DA-8 FT-IR spectrophotometer as KBr
n
1
discs. The H, 13C and 119Sn NMR spectra were recorded
state structures of three such complexes (R = Me or Bu,
and X = 40-Cl (held constant) and Y = 40-CH3 or 40-Br)
were accomplished by single crystal X-ray crystallogra-
phy [7]. These complexes were found to adopt the usual
dicarboxylato structural type with a skew-trapezoidal
bipyramidal arrangement around the tin atom (Scheme
1, IIIc). On the other hand, the di-n-butyltin (IV) com-
plexes of the type {[nBu2Sn(O2CC6H4(OH-2) (N@NC6H4-
(X)-5))]2O}2 (X = H, 20-CH3, 30-CH3, 40-CH3, 40-Cl, 40-
Br) are centrosymmetric tetranuclear species containing
a planar Sn4O2 core in which two l3-oxo O-atoms con-
nect an Sn2O2 ring to two exocyclic Sn-atoms (Scheme
1, IV) [8].
3'
4'
5'
2'
1'
O
X
6
N
1
5
N
OH
6'
2
4
OH
3
Fig. 1. Ligands used in the present work. Abbreviations: L1HH0: X = H;
L2HH0: X = 20-OCH3; L3HH0: X = 30-CH3; L4HH0: X = 40-CH3; L5HH0:
X = 40-Cl, where H and H0 represent hydroxy and carboxylic acid H-
atoms, respectively.
The organotin(IV) complexes of the types R3Sn(O2C-
n
C6H4(OH-2))(N@NC6H4(X)-5) (R = nBu or Ph) and Bu2

3628
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
on a Bruker ACF 300 spectrometer and measured at
300.13, 75.47 and 111.92 MHz, respectively, or on a Mer-
cury Plus Varian 400 NMR spectrometer measured at
400.44, 100.69 and 149.32 MHz, respectively. The 1H,
13C and 119Sn chemical shifts were referenced 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
electrospray ionization (ESI) mass spectra were measured
on an ion trap analyzer Esquire 3000 (Bruker Daltonics,
Bremen, Germany) in the range m/z 50–2600. The sam-
ples were dissolved in methanol (100%) and analyzed by
direct infusion using a flow rate of 5 ll/min. The selected
precursor ions were further analyzed by MS/MS analyses
under the following conditions: an isolation width of m/
z = 8 for ions containing one tin atom and m/z = 12 for
ions containing multiple tin atoms, a collision amplitude
in the range 0.7–1.0 V depending on the precursor ion sta-
bility, an ion source temperature of 300 ꢁC, and a flow
rate and pressure of nitrogen of 4 l/min and 10 psi,
respectively. The tuning parameter ‘‘compound stability’’
was set to 100% in the positive-ion mode and 20% in
the negative-ion mode. The software IsoPro 2.1 (freeware,
http://members.aol.com/msmssoft/) was used for the the-
oretical calculation of relative isotopic abundances. Mo¨ss-
bauer spectra were recorded on solid samples at liquid
nitrogen temperature by using a conventional constant
acceleration spectrometer, coupled with a multichannel
analyser (a.e.n., Ponteranica (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 temperature with constant accel-
eration in a triangular waveform was used. The velocity
calibration was made using a 57Co Mo¨ssbauer source,
10 mCi and an iron foil as absorber (from Ritverc, St.
Petersburg, Russia).
[C-1], 116.6 [C-3], 118.9 [C-6], 120.6 [C-50], 127.4 [C-4],
128.2 [C-40], 132.2 [C-30], 141.8 [C-20], 145.4 [C-5], 156.5
[C-10], 164.0 [C-2], 172.3 [CO2] ppm.
2.4. Synthesis of di-n-octyltin(IV) complexes
The di-n-octyltin(IV) complexes of composition nOct2Sn
(LH)2 (1–2) and {[nOct2Sn(LH)]2O}2 (3–5) were prepared
n
by reacting the appropriate LHH0 with Oct2SnO in 2:1
and 1:1 molar ratios in anhydrous toluene under reflux
conditions. A typical procedure is described below.
n
2.4.1. Oct2Sn(L1H)2 (1)
A suspension of nOct2SnO (0.56 g, 1.54 mmol) and
L1HH0 (0.75 g, 3.09 mmol) in 50 ml anhydrous toluene
were refluxed for 6 h in a flask equipped with a Dean-Stark
water separator and a water cooled condenser. After the
reaction, an orange colored solution was obtained and fil-
tered while hot. The solvent was concentrated on a hot
plate and precipitated with petroleum ether. The orange
colored precipitate was filtered and washed thoroughly
with petroleum ether (60–80 ꢁC) and dried in vacuo. The
dried product was dissolved in anhydrous benzene–hexane
(v/v 2:1), filtered off to remove any undissolved particles
and the filtrate left to crystallize at room temperature.
The orange crystals were isolated from the mother liquor
and dried in vacuo. Yield: 1.15 g (89.8%), m.p.: 84–86 ꢁC.
Anal. Calc. for C42H52N4O6Sn: C, 60.9; H, 6.3; N, 6.8.
Found: C, 61.2; H, 6.1; N, 6.5%. IR (KBr, cmꢁ1): 1630
1
m(OCO)asym. H NMR (CDCl3, 300.13 MHz); dH: ligand
skeleton: 7.13 [d, 1H, H-3], 7.49 [m, 3H, H-30, H-40 and
H-50], 7.93 [m, 2H, H-20 and H-60], 8.14 [dd, 1H, H-4],
8.66 [d, 1H, H-6], 11.03 [s, 1H, OH]; Sn-nOct skeleton:
0.83 [m, 3H, CH3], 1.10–2.0 [m, 14H, CH2], ppm. 13C
NMR (CDCl3, 75.47 MHz); dC: ligand skeleton: 113.0
[C-1], 118.5 [C-3], 122.9 [C-20 and C-60], 128.7 [C-6],
129.1 [C-4], 129.3 [C-30 and C-50], 130.9 [C-40], 145.7 [C-
5], 152.7 [C-10], 164.1 [C-2], 177.3 [CO2]; Sn-nOct skeleton:
14.2 [CH3], 22.7 [gCH2], 24.7 [fCH2], 27.4 [eCH2], 28.1
[dCH2], 28.3 [cCH2], 31.9 [bCH2], 33.1 [aCH2], ppm.
119Sn NMR (CDCl3, 111.92 MHz); dSn: ꢁ114.3 ppm. ESI-
MS: MW = 828, Mmono = 586 = L1SnOct2-H. Positive-ion
MS: m/z 1173 [2*Mmono+H]+, 100%; m/z 587 [Mmono+H]+.
MS/MS of m/z 587: m/z 569 [Mmono+HꢁH2O]+; m/z 543
[Mmono+HꢁCO2]+; m/z 361 [Mmono+Hꢁoctene–octane]+;
m/z 317 [Mmono+Hꢁoctene–octane–CO2]+; m/z 233
[SnOct]+. Negative-ion MS: m/z 827 [MꢁH]ꢁ, 100%; m/z
621 [Mmono+Cl]ꢁ; m/z 241 [L1]ꢁ; m/z 197 [L1–CO2]ꢁ. MS/
¨
2.3. Synthesis of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxy-
benzoic acids
The 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids
(L1HH0, L3ꢁ5HH0) were prepared as described in earlier
reports [1,2,4,5] except for L2HH0 which is described here.
The ligand, L2HH0 (5-[(E)-2-(2-methoxyphenyl)-1-diaze-
nyl]-2-hydroxybenzoic acid) was prepared by a diazo-
coupling reaction using o-anisidine and salicylic acid in
alkaline medium [2]. The brown coloured precipitate was
recrystallized from methanol to give pure L2HH0. Yield:
31.5%, m.p.: 185–187 ꢁC. Anal. Calc. for C14H12N2O4Sn:
C, 43.01; H, 3.09; N, 7.17. Found: C, 43.09; H, 3.03; N,
MS of m/z 827: m/z 241 [L1]ꢁ. 119Sn Mossbauer: d = 1.46,
7.12%. IR (KBr, cmꢁ1): 1661 m(OCO)asym 1H NMR
;
D = 3.41, C1 = 0.83, C2 = 0.82 mm sꢁ1, q = 2.34, C–Sn–C =
142ꢁ.
(DMSO-d6, 300.13 MHz); dH: Ligand skeleton: 4.04
[s, 3H, OCH3], 7.04 [ddd, 1H, H-3], 7.11 [dd, 2H, H-30
and H-40], 7.45 [ddd, 1H, H-50], 7.68 [dd, 1H, H-60], 8.14
[dd, 1H, H-4], 8.54 [d, 1H, H-6] ppm. Signals for the phenol
and carboxylic acid were exchanged due to presence of
water in the solvent. 13C NMR (DMSO-d6, 75.47 MHz);
dC: Ligand skeleton: 56.0 [OCH3], 112.7 [C-60], 112.9
n
2.4.2. Oct2Sn(L4H)2 (2)
Compound 2 was prepared analogously by following the
method and conditions described for 1 and using L4HH0
(0.75 g, 2.93 mmol) and nOct2SnO (0.53 g, 1.47 mmol).

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
3629
The orange product was recrystallized from a benzene–
2.4.4. {[nOct2Sn(L3H)]2O}2 (4)
hexane mixture. Yield: 1.16 g, 92.8%. m.p.: 124–126 ꢁC. Anal.
Orange prismatic crystals of compound 4, m.p.
74–76 ꢁC, were obtained from benzene–acetonitrile (v/v
2:1) in 65.6% yield. Anal. Calc. for C120H180N8O14Sn: C,
59.24; H, 7.47; N, 4.61. Found: C, 59.30; H, 7.51; N,
4.65%. IR (KBr, cmꢁ1): 1628 m(OCO)asym, 623m(Sn–O–Sn).
For NMR: refer to Section 3.2 for specific comments.
ESI-MS: MW = 2436. Mmono = 600 = L3SnOct2-H. Posi-
tive-ion MS: m/z 601 [Mmono+H]+. MS/MS of m/z 601: m/z
583 [Mmono+HꢁH2O]+; m/z 557 [Mmono+HꢁCO2]+; m/z
+Hꢁoctane–octene]+; m/z 331 [Mmono+Hꢁoctane–octene–
CO2]+. Negative-ion MS: m/z 2453 [MꢁH+H2O]ꢁ; m/z
2435 [MꢁH]ꢁ; m/z 2311 [3*Mmono+L3+L3H]ꢁ; m/z 2055
[3*Mmono+L3]ꢁ; m/z 1711 [2*Mmono+L3+L3H]ꢁ; m/z 1491
[2*Mmono+Cl+L3H]ꢁ; m/z 1455 [2*Mmono+L3]ꢁ; m/z 1235
[2*Mmono+Cl]ꢁ; m/z 855 [Mmono+L3]ꢁ; m/z 635
[Mmono+Cl]ꢁ; m/z 255 [L3]ꢁ, 100%; m/z 211 [L3–CO2]ꢁ.
MS/MS of m/z 2435: m/z 2417 [MꢁH–H2O]ꢁ; m/z 2179
[MꢁH–L3H]ꢁ; m/z 1817 [MꢁH–MmonoꢁH2O]ꢁ; m/z 1579
[MꢁH–L3H–Mmono]ꢁ; m/z 1217 [MꢁHꢁ2*MmonoꢁH2O]ꢁ;
m/z 855 [Mmono+L3]ꢁ. MS/MS of m/z 2055: m/z 1455
[2*Mmono+L3]ꢁ; m/z 855 [Mmono+L3]ꢁ. MS/MS of m/z 855:
m/z 255 [L3]ꢁ. 119Sn Mo¨ssbauer: d = 1.37, D = 3.46,
C1 = 0.81, C2 = 0.81 mm sꢁ1, q = 2.53, C–Sn–C = 141ꢁ.
Calc. for C44H56N4O6Sn: C, 61.77; H, 6.60; N, 6.0. Found: C,
61.9; H, 6.7; N, 6.2%. IR (KBr, cmꢁ1): 1628m (OCO)asym
.
1H NMR (CDCl3, 300.13 MHz); dH: Ligand skeleton: 2.45
[s, 3H, CH3], 7.13 [d, 1H, H-3], 7.32 [d, 2H, H-20 and H-60],
7.85 [d, 2H, H-30 and H-50], 8.12 [dd, 1H, H-4], 8.64 [d, 1H,
H-6], 10.98 [s, 1H, OH]; Sn-nOct skeleton: 0.83 [m, 3H,
CH3], 1.10–2.0 [m, 14H, CH2], ppm. 13C NMR (CDCl3,
75.47 MHz); dC: Ligand skeleton: 21.5 [CH3], 112.9 [C-1],
118.3 [C-3], 122.8 [C-20 and C-60], 128.4 [C-6], 129.0 [C-4],
129.7 [C-30 and C-50], 141.2 [C-40], 145.7 [C-5], 150.8
[C-10], 163.7 [C-2], 177.5 [CO2]; Sn-nOct skeleton: 14.0
[CH3], 22.6 [gCH2], 24.5 [fCH2], 26.9 [eCH2], 28.9 [dCH2],
29.1 [cCH2], 31.7 [bCH2], 33.3 [aCH2], ppm. 119Sn NMR
(CDCl3, 111.92 MHz); dSn: ꢁ115.0 ppm. ESI-MS:
MW = 856. Mmono = 600 = L4SnOct2-H. Positive-ion MS:
m/z 601 [Mmono+H]+. MS/MS of m/z 601: m/z 583 [Mmono
+HꢁH2O]+; m/z 557 [Mmono+HꢁCO2]+; m/z 443 [Mmono
+Hꢁoctane–CO2]+; m/z 375 [Mmono+Hꢁoctane–octene]+;
m/z 331 [Mmono+Hꢁoctane–octene–CO2]+. Negative-ion
MS: m/z 855 [MꢁH]ꢁ; m/z 635 [Mmono+Cl]ꢁ; m/z 255
[L4]ꢁ, 100%; m/z 211 [L4-CO2]ꢁ. MS/MS of m/z 855: m/z
255 [L4]ꢁ. 119Sn Mo¨ssbauer: d = 1.49, D = 3.51, C1 = 0.80,
C2 = 0.83 mm sꢁ1, q = 2.36, C–Sn–C = 143ꢁ.
443
[Mmono+Hꢁoctane–CO2]+;
m/z
375
[Mmono
2.4.5. {[nOct2Sn(L5H)]2O}2 (5)
2.4.3. {[nOct2Sn(L2H)]2O}2 (3)
Compound 5 was prepared by following the method
and conditions described for 1 and using L5HH0 (0.50 g,
1.81 mmol) and nOct2SnO (0.65 g, 1.81 mmol). The
dried orange product was recrystallized from hot hexane.
Yield: 0.61 g, 55%. m.p.: 74–76 ꢁC. Anal. Calc. for
Orange prismatic crystals of compound 3, m.p.
74–76 ꢁC, were obtained from petroleum ether in 50%
yield. Anal. Calc. for C120H180N8O18Sn4: C, 57.71; H,
7.26; N, 4.49. Found: C, 57.65; H, 7.30; N, 4.52%. IR
(KBr, cmꢁ1): 1622 m(OCO)asym, 620 m(Sn–O–Sn). For
NMR: refer to Section 3.2 for specific comments. ESI-
MS: MW = 2500. Mmono = 616 = L2SnOct2-H. Positive-
ion MS: m/z 1233 [2*Mmono+H]+; m/z 927 [Mmono
+K+L2H]+; m/z 911 [Mmono+Na+L2H]+; m/z 655 [Mmono
+K]+; m/z 639 [Mmono+Na]+; m/z 617 [Mmono+H]+. MS/
MS of m/z 617: m/z 599 [Mmono+HꢁH2O]+; m/z 573 [Mmo-
no+HꢁCO2]+; m/z 391 [Mmono+Hꢁoctene–octane]+; m/z
347 [Mmono+Hꢁoctene–octane–CO2]+. Negative-ion MS:
m/z 2517 [MꢁH+H2O]ꢁ; m/z 2499 [MꢁH]ꢁ; m/z
2391 [3*Mmono+L2+L2H]ꢁ; m/z 2119 [3*Mmono+L2]ꢁ;
m/z 1775 [2*Mmono+L2+L2H]ꢁ; m/z 1539 [2*Mmono
+Cl+L2H]ꢁ; m/z 1503 [2*Mmono+L2]ꢁ; m/z 1267
[2*Mmono+Cl]ꢁ; m/z 1159 [Mmono+L2+L2H]ꢁ; m/z 887
[Mmono+L2]ꢁ; m/z 651 [Mmono+Cl]ꢁ; m/z 271 [L2]ꢁ,
100%; m/z 227 [L2-CO2]ꢁ; m/z 212 [L2–CH3OH–N2]ꢁ.
MS/MS of m/z 2499: m/z 2481 [MꢁH–H2O]ꢁ; m/z 2227
[MꢁH–L2H]ꢁ; m/z 1883 [MꢁH–Mmono]ꢁ; m/z 1865
[MꢁH–Mmono–H2O]ꢁ; m/z 1611 [MꢁH–L2H–Mmono]ꢁ;
m/z 1249 [MꢁH-2*Mmono-H2O]ꢁ; m/z 887 [Mmono+L2]ꢁ.
MS/MS of m/z 2391: m/z 2119 [3*Mmono+L2]ꢁ; m/z 1775
[2*Mmono+L2+L2H]ꢁ; m/z 1503 [2*Mmono+L2]ꢁ; m/z
887 [Mmono+L2]ꢁ. MS/MS of m/z 887: m/z 271 [L2]ꢁ.
119Sn Mo¨ssbauer: d = 1.33, D = 3.41, C1 = 0.78,
C2 = 0.78 mm sꢁ1, q = 2.56, C–Sn–C = 140ꢁ.
C
116H168N8O12Cl4Sn4: C, 56.11; H, 6.82; N, 4.51. Found:
C, 56.15; H, 6.86; N, 4.54%. IR (KBr, cmꢁ1): 1628
m(OCO)asym 615m(Sn–O–Sn). 1H NMR (CDCl3, 300.
13 MHz); dH: Ligand skeleton: 7.08 [d, 1H, H-3], 7.30 [d,
2H, H-20 and H-60], 7.73 [d, 2H, H-30 and H-50], 8.10
[dd, 1H, H-4], 8.37 [d, 1H, H-6], 11.75 [brs, 1H, OH];
Sn-nOct skeleton: 0.77 [brm, 6H, CH3], 0.80–2.0 [brm,
28H, CH2], ppm. 13C NMR (CDCl3, 75.47 MHz); dC:
Ligand skeleton: 114.4 [C-1], 118.6 [C-3], 124.0 [C-20 and
C-60], 126.7 [C-6], 129.3 [C-30 and C-50], 136.5 [C-4],
145.1 [C-40], 150.6 [C-5], 155.3 [C-10], 164.7 [C-2], 175.5
[CO2]; Sn-nOct skeleton: 14.3 [CH3], 22.7, 25.2, 25.4, 25.7,
27.4, 29.3, 29.8, 30.2, 31.9, 33.9, 34.0 [CH2 carbons],
ppm. 119Sn NMR (CDCl3, 111.92 MHz); dSn: ꢁ187.2 and
ꢁ189.7 ppm. ESI-MS: MW = 2516. Mmono = 620 = LS-
nOct2-H. Positive-ion MS: m/z 621 [Mmono+H]+; m/z 459
[SnOct3]+. Negative-ion MS: m/z 2533 [MꢁH+H2O]ꢁ;
m/z 2515 [MꢁH]ꢁ; m/z 2411 [3*Mmono+L5+LH]ꢁ; m/z
2249 [2*Mmono+L5+L5SnOct3]ꢁ; m/z 2135 [3*Mmono+L5]ꢁ;
m/z 1791 [2*Mmono+L5+L5H]ꢁ; m/z 1629 [Mmono+L5
+L5SnOct3]ꢁ; m/z 1551 [2*Mmono+Cl+L5H]ꢁ; m/z 1515
[2*Mmono+L5]ꢁ; m/z 1275 [2*Mmono+Cl]ꢁ; m/z 1009
[L5SnOct3+L5]ꢁ; m/z 895 [Mmono+L5]ꢁ; m/z 655
[Mmono+Cl]ꢁ; m/z 275 [L5]ꢁ, 100%; m/z 231 [L5ꢁCO2]ꢁ.
MS/MS of m/z 2515: m/z 2497 [MꢁH–H2O]ꢁ; m/z 2239

3630
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
[MꢁH–L5H]ꢁ; m/z 1877 [MꢁH–Mmono–H2O]ꢁ; m/z 1619
[MꢁH–L5H–Mmono]ꢁ; m/z 1257 [MꢁH–2*Mmono–H2O]ꢁ;
m/z 895 [Mmono+L5]ꢁ. MS/MS of m/z 895: m/z 275
[L5]ꢁ. 119Sn Mo¨ssbauer: d = 1.34, D = 3.45, C1 = 0.82,
C2 = 0.82 mm sꢁ1, q = 2.57, C–Sn–C = 141ꢁ.
to correspond with the direction that would bring the
H-atom closest to the nearest hydrogen bond acceptor.
The refinement of each structure was carried out on F2
using full-matrix least-squares procedures, which mini-
mised the function Rw(Fo ꢁ Fc ) . One reflection in 4,
whose intensity was considered to be an extreme outlier,
was omitted from the final refinement. All calculations
were performed using the SHELXL97 program [18]. The data
collection and refinement parameters are given in Table 1
and views of the molecules of 1, 3 and 4 are shown in Figs.
2–4.
2
2 2
2.5. X-ray crystallography
Crystals of compounds 1, 3 and 4 suitable for an X-ray
crystal-structure determination were obtained from ben-
zene-n-hexane (v/v 2:1), petroleum ether and benzene–ace-
tonitrile (v/v 2:1), respectively. The measurements were
made at 293 K (1), 110 K (3) and 160 K (4) and with graph-
3. Results and discussion
˚
ite-monochromated Mo Ka radiation (k = 0.71073 A). For
1, a Nonius CAD4 diffractometer was used and an empir-
ical absorption correction based on azimuthal scans [11]
was applied. For 3, a Bruker SMART APEX CCD diffrac-
tometer and an Oxford Cryosystems Cryostream 800 cooler
were employed. Data reduction was performed with SAINT
[12] and a multi-scan absorption correction was applied
using SADABS [13]. For 4, a Nonius KappaCCD diffractom-
eter [14] and an Oxford Cryosystems Cryostream 700
cooler were employed and data reduction was performed
with HKL DENZO and SCALEPACK [15]. An absorption correc-
tion based on the multi-scan method was applied using
SORTAV [16]. For each structure, the intensities were cor-
rected for Lorentz and polarization effects, equivalent
reflections were merged and the structures were solved by
direct methods using SHELXS97 [17]. In 3 and 4, the
molecule of the tetranuclear Sn-complex sits about a crys-
tallographic centre of inversion. The octyl residues are dis-
ordered in all three compounds. In complex 1, all atoms of
the octyl groups were treated as disordered over two closely
neighbouring equally occupied positions. In 3, equally
occupied split positions were defined for the terminal
methyl group of one octyl residue and for all atoms of
two other alkyl chains. In 4, for the two octyl groups on
the exocyclic Sn-atoms, two sets of positions were defined
for all atoms of one octyl group and for the terminal ethyl
segment in the other octyl group. The site occupation fac-
tors of the major conformations of these groups refined to
0.539(6) and 0.71(5), respectively. In addition, the m-tolyl
substituent in the carboxylate ligand that bridges one endo-
cyclic and one exocyclic Sn-centre is disordered over two
equally occupied conformations. In each structure, similar-
ity restraints were applied to the bond lengths and angles
involving the disordered C atoms, while neighbouring C
atoms along the disordered alkyl chains in 1 and 4 were
restrained to have similar atomic displacement parameters.
All disordered atoms in 3 were assigned isotropic displace-
ment parameters.
3.1. Synthesis
The 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids
(LHH0) react with di-n-octyltin(IV) oxide in anhydrous
toluene in a 2:1 and 1:1 molar ratio to give compounds
with the formulations Oct2Sn(LH)2 (1–2) and {[nOct2Sn
n
(LH)]2O}2 (3–5). The complexes were isolated as orange
crystalline solids in moderate yield and are stable in
air. They are soluble in common organic solvents. Com-
pounds
3 and 4 slowly decompose in chloroform
solution.
3.2. Spectroscopy
Diagnostically important infrared absorption frequen-
cies for the carboxylate antisymmetric [masym(OCO)] stretch-
ing vibration of the di-n-octyltin(IV) complexes appears
at around 1628 cmꢁ1. 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 at around 620 cmꢁ1 was detected for
the complexes 3–5, which was assigned to the m(Sn–O–Sn)
mode [8,19,20].
The 1H and 13C NMR data of the ligands are reported in
Refs. [1,2]. The signals were assigned by the use of correlated
spectroscopy (COSY), heteronuclear single-quantum corre-
lation (HSQC) and Constant time Inverse-detection Gradi-
ent Accordion Rescaled (CIGAR) heteronuclear multiple-
bond connectivities (HMBC) [21] experiments using
gradient coherence selection. Rotating-frame Overhauser
enhancement spectroscopy (ROESY) spectra were required
in order to assign the aromatic protons adjacent to the
methyl groups of the ligands. The conclusions drawn from
the ligand assignments were subsequently extrapolated to
the spectra of the complexes owing to the similarity of
the spectra. The H and 13C chemical shift assignments of
1
the octyltin moiety are readily deducible from the multiplic-
ity patterns and resonance intensities. The assignments of
the signals for compounds 1, 2 and 5 are reported in Section
2.4.
In all structures, the H-atoms were placed in geometri-
cally calculated positions and refined using a riding model
where each H-atom was assigned a fixed isotropic displace-
ment parameter with a value equal to 1.2 Ueq of its parent
atom (1.5 Ueq for the methyl and hydroxy groups). The
orientation of each hydroxy O–H vector was optimised
The solution 119Sn NMR resonances for the compounds
of the type nOct2Sn(LH)2 (1–2) in CDCl3 solution are
around ꢁ114 ppm and the values are consistent with those

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
3631
Table 1
Crystallographic data and structure refinement parameters for the di-n-octyltin(IV) complexes 1, 3 and 4
1
3
4
Empirical formula
Formula weight
Crystal size (mm)
Crystal color, habit
Temperature (K)
Crystal system
C42H52N4O6Sn
827.57
0.10 · 0.30 · 0.30
Orange, plate
293(2)
C120H180N8O18Sn4
2497.48
0.06 · 0.19 · 0.49
Orange, plate
110(2)
Monoclinic
P21/c
16.2650(8)
20.1517(9)
18.7260(9)
90
93.6520(10)
90
6125.3(5)
2
1.354
0.871
C120H180N8O14Sn4
2433.18
0.07 · 0.27 · 0.27
Orange, plate
160(1)
Monoclinic
P21/c
18.9370(4)
17.9197(3)
18.8501(3)
90
107.664(1)
90
6095.1(2)
2
1.326
0.870
Triclinic
ꢀ
Space group
P1
˚
a (A)
9.7452(14)
11.658(4)
19.413(5)
95.12(2)
102.673(15)
102.50(2)
2079.0(9)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dx (g cmꢁ3
)
1.322
0.664
l (mmꢁ1
)
Transmission factors (min, max)
2hmax (ꢁ)
0.826, 0.937
52
0.68, 0.95
54.5
0.809, 0.956
50
Reflections measured
16066
60247
79934
Independent reflections (Rint
Reflections with I > 2r(I)
Number of parameters
Number of restraints
R(F) (I > 2r(I) reflections)
wR(F2) (all data)
)
8131 (0.046)
4839
528
365
0.049
0.105
1.02
0.57, ꢁ0.31
13628 (0.076)
10324
661
286
0.054
0.115
1.09
1.13, ꢁ0.80
10715 (0.054)
8360
825
424
0.042
0.124
1.11
0.97, ꢁ0.70
Goodness-of-fit (F2)
3
˚
Max, min Dq (e/A )
reported for R2Sn(O2CR0)2 systems [6,22–24]. On the other
hand, the 119Sn NMR spectrum for compound 5, which is
of the {[nOct2Sn(LH)]2O}2 type, displays a pair of reso-
nances of equal intensities at ꢁ187.2 and ꢁ189.7 ppm,
which confirms the presence of endo- and exo-cyclic tin
atoms [25,26]. Although it is difficult to assign coordination
with certainty to the tin atoms 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 associ-
ated with six-, five- and four-coordinate tin centres bearing
n-alkyl groups, respectively [27]. On this basis, two chemi-
cally different five-coordinate tin centres (endocyclic and
exocyclic) are present in solution for the di-n-octyltin com-
plex 5. 119Sn Mo¨ssbauer data for complexes 3, 4 and 5 are
of the same order of magnitude (see Section 2), indicating
that they are isostructural in the solid state which is also
reflected in the crystal structures of compounds 3 and 4
(vide infra). On the other hand, compounds 3 and 4 deserve
or hundredths of ppm or the signal was rather broadened.
Proton exchange between the hydroxy and the benzoic
groups is likely with concomitant rearrangement of ligand
coordination around the tin atom, which generates differ-
ent isomers. The exchange is quenched at low temperature
where more than six different signals for the acidic protons
are detected. However, the presence of two or more broad
1
signals also at 323 K in the H NMR spectrum of 3 and 4
and the presence of several resonances of different relative
intensities and different line half-widths in the range of
ꢁ120.3 to ꢁ195.6 ppm and in the range of ꢁ155.0 to
ꢁ189.8 ppm, in the 119Sn NMR spectra of 3 and 4, respec-
tively, in accordance with the presence of different tin cen-
ters, indicates also the occurrence of decomposition or
hydrolytic cleavage reactions generating different species
[28–32].
First-order positive-ion ESI mass spectra provide charac-
teristic molecular adducts for the determination of molecu-
lar weights. The interpretation is complicated by the fact
that unusual adducts with tin-containing fragment ions are
observed as well. The characteristic neutral losses observed
in tandem mass spectra, such as octane, octene, CO2, etc.,
confirm the presence of these functional features in the struc-
ture. The complementary information is provided by nega-
tive-ion mode, where the ion of the deprotonated molecule
[MꢁH]ꢁ is the most important for the interpretation of all
studied compounds. Moreover, the dimeric and trimeric ions
probably formed during the ionization process are identified
1
specific mention. In the H NMR spectra of these com-
pounds, signals both for acidic, aromatic and aliphatic pro-
tons were considerably broadened. The acidic proton part
of the 1H NMR spectrum of compounds 3 and 4 measured
in the temperature range 223–323 K are shown in Fig. 5.
The aromatic and aliphatic proton signals behaved simi-
larly. It is, thus, clear that both samples undergo very com-
plex exchange processes in deuteriochloroform solution.
Each particular resonance in the 13C NMR spectra of com-
pounds 3 and 4 consisted of several lines differing in tenths

3632
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
Fig. 3. The molecular structure of {[nOct2Sn(L2H)]2O}2 (3) with 50%
probability ellipsoids, carbon-bonded H-atoms omitted for clarity, and
only one of the disordered arrangements of the nOct lilgands shown.
Fig. 2. The molecular structure of nOct2Sn(L1H)2 (1) with 50% probability
ellipsoids, carbon-bonded H-atoms omitted for clarity, and only one of the
disordered arrangements of the nOct lilgands shown.
the ideal trans-R2Sn octahedral structure and the angle
for 1 corresponds closely with the value found in the crys-
tal structure determination (Table 2). The 119mSn Mo¨ss-
bauer data for the complexes 3, 4 and 5 are of the same
order of magnitude (see Section 2), which indicates that
they are isostructural in the solid state. This conclusion
is also reflected in the crystal structures of compounds 3
by their m/z values and the comparison with theoretically
calculated isotopic patterns. Among other ions listed in Sec-
tion 2.4, the negative-ion spectra also show the presence
of adducts with the ligand and the neutral losses of ligand
during the fragmentation in tandem mass spectrometric
experiments.
and
4 (vide infra). These complexes with formula
{[nOct2Sn(LH)]2O}2 all show one well resolved single dou-
blet with C values of 0.78–0.82 mm sꢁ1, which indicates
that the four tin centres present in the molecule have a
similar environment. The D values lie in the narrow range
of 3.41–3.46 mm sꢁ1, which is consistent with a five-coor-
dinate or a six-coordinate tin atom [33]. The isomer shifts
of the complexes were found in the restricted range 1.33–
1.37 mm sꢁ1, which is typical of quadrivalent tin centres
[33]. Furthermore, the ratio of the D value to d value
(q = D/d) indicates a coordination number greater than
four [35]. A similar D range was observed recently for
the di-n-butyltin(IV) complexes of analogous ligands hav-
ing a R2SnO4 arrangement, which were also characterized
by X-ray crystallography [7,8]. Thus, the Mo¨ssbauer
results are consistent with hexa-coordinated tin atoms
with a distorted trans-R2Sn octahedral geometry. Further-
more, the Mo¨ssbauer results for the present investigation
neither distinguish the exo- and endo-cyclic tin centres nor
their calculated C–Sn–C angles (the median value was
about 141ꢁ) obtained from the Parish approach [34].
119mSn Mo¨ssbauer spectra of complexes 1–5, in the
solid state, all show a well resolved single doublet with
C values 0.78–0.83 mm sꢁ1. The Mo¨ssbauer parameter
isomer shift (d) is 1.46 and 1.49 mm sꢁ1, respectively for
n
complexes 1 and 2, with formula Oct2Sn(LH)2, which is
typical of quadrivalent organotin derivatives, and the full
width of half maximum (C ) of these resonance absorp-
tions are approximately 0.80 mm sꢁ1, further suggesting
the presence of a single tin centre in the complexes [33].
The quadrupole splitting (D) value for complexes 1 and
2 is 3.41 and 3.51 mm sꢁ1, respectively, consistent with
hexa-coordinated tin atoms with a distorted trans-R2Sn
octahedral geometry [5,33]. This conclusion is in agree-
ment with the structures determined by X-ray crystallog-
raphy (see below). Both complexes display similar
Mo¨ssbauer parameters, which further indicate that they
are isostructural in the solid state. Using the Parish rela-
tionship between the D parameter value and the C–Sn–C
bond angle [34], the calculated angles are 142ꢁ and 143ꢁ
for 1 and 2, respectively, which indicate a distortion from

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
3633
Fig. 4. The molecular structure of {[nOct2Sn(L3H)]2O}2 (4) with 50% probability ellipsoids, most H-atoms omitted for clarity, and only one disordered
conformation shown.
3.3. X-ray crystallography
The results of the X-ray crystallographic study on com-
pound 1 are fully consistent with the other spectroscopic
evidence described in Section 3.2. The molecular structure
of compound 1 is depicted in Fig. 2, while selected geomet-
ric parameters are given in Table 2. The compound has a
monomeric six-coordinate structure very similar to the
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for 1
Sn–O(1)
Sn–O(2)
Sn–O(4)
Sn–O(5)
Mean Sn–C
2.089(3)
2.586(3)
2.089(3)
2.623(4)
2.109(9)
O(1)–C(1)
O(2)–C(1)
O(4)–C(14)
O(5)–C(14)
1.281(5)
1.253(5)
1.277(5)
1.251(5)
O(1)–Sn–O(2)
O(1)–Sn–O(4)
O(1)–Sn–O(5)
Mean O(1)–Sn–C
O(2)–Sn–O(4)
O(2)–Sn–O(5)
Mean O(2)–Sn–C
O(4)–Sn–O(5)
54.57(11)
82.80(11)
136.72(11)
104.9(10)
137.32(11)
168.65(11)
87.8(9)
Mean O(4)–Sn–C
Mean O(5)–Sn–C
Mean C–Sn–C
C(1)–O(1)–Sn
C(1)–O(2)–Sn
C(14)–O(4)–Sn
C(14)–O(5)–Sn
105.1(8)
88.2(9)
139.3(10)
104.3(3)
81.8(3)
105.2(3)
80.8(3)
Fig. 5. Acidic proton part of the 1H NMR spectra of compounds 3 and 4
measured from 223 to 323 K.
53.92(11)

3634
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for 3 and 4
3a
4a
3
4
Sn(1)–O(1)
Sn(1)–O(4)
Sn(1)–O(5)
Sn(1)–O(7)
Mean Sn(1)–C
Sn(2)ꢀ ꢀ ꢀSn(2)i
2.232(3)
2.197(3)
2.799(3)
2.042(3)
2.133(4)
3.2961(6)
2.262(3)
2.199(3)
2.825(3)
2.045(2)
2.132(8)
3.2924(6)
Sn(2)–O(2)
Sn(2)–O(4)i
Sn(2)–O(7)
Sn(2)–O(7)i
Mean Sn(2)–C
2.374(3)
2.760(3)
2.051(3)
2.134(3)
2.119(6)
2.350(3)
2.800(3)
2.053(3)
2.133(3)
2.131(5)
O(1)–Sn(1)–O(4)
O(1)–Sn(1)–O(5)
O(1)–Sn(1)–O(7)
O(4)–Sn(1)–O(5)
O(4)–Sn(1)–O(7)
O(5)–Sn(1)–O(7)
Mean C–Sn(1)–C
a
164.92(11)
143.15(10)
88.14(11)
50.65(9)
77.82(11)
128.48(10)
140.16(18)
168.63(10)
140.68(10)
90.47(11)
50.20(9)
78.63(10)
128.81(10)
138.9(12)
O(2)–Sn(2)–O(7)
O(2)–Sn(2)–O(7)i
O(7)–Sn(2)–O(7)i
Mean C–Sn(2)–C
Sn(1)–O(7)–Sn(2)
Sn(1)–O(7)–Sn(2)i
Sn(2)–O(7)–Sn(2)i
88.46(11)
88.14(11)
163.05(11)
76.29(11)
137.70(19)
133.77(14)
120.99(13)
103.71(11)
162.96(10)
76.11(11)
139.6(4)
134.04(14)
120.91(13)
103.89(11)
Symmetry operation ‘‘i’’ moves the specified atom through the molecular crystallographic centre of inversion to the position 1 ꢁ x, ꢁy, ꢁz in 3 and to
1 ꢁ x, 1 ꢁ y, ꢁz in 4.
n
˚
structures of Bu2Sn(O2CC6H4(OH-2) (N@NC6H4(X)-5))2
compounds [4–7]. The carboxylate groups on the ligands
act as bidentate chelating agents, giving an equatorial plane
around the tin of four asymmetrically coordinated oxygen
atoms, whereas the octyl groups are in the axial positions,
but pinned back somewhat to produce a skew-trapezoidal
bipyramidal structure. The shorter Sn–O bonds are
long Snꢀ ꢀ ꢀO bond [2.800(3) A] to an endocyclic Sn-atom.
Each Sn-atom is also coordinated by two octyl groups.
The Sn-atoms and carboxylate ligands form an essentially
planar system with the octyl groups extending roughly
perpendicular to this plane. Some of the octyl groups in
complexes 3 and 4 are disordered, while, in complex 4,
the m-toluyl substituent in the carboxylate ligand that
bridges one endocyclic to one exocyclic Sn-centre is disor-
dered over two approximately equally occupied conforma-
tions which result from a small rotation of the ring plane
(see Section 2.5 for further details). Each hydroxy group
forms a hydrogen bond with the carbonyl O-atom of the
adjacent carboxylate group within the same ligand, thereby
creating six-membered loops.
˚
˚
<2.1 A and the longer Sn–O bonds are >2.5 A, while the
two octyl substituents are disposed over the longer Sn–O
vectors with a C–Sn–C angle of 140.1(2)ꢁ. Each hydroxy
group forms a hydrogen bond with the carbonyl O-atom
of the adjacent carboxylate group within the same ligand.
The compounds 3 and 4 are centrosymmetric tetranu-
clear bis(dicarboxylatotetrabutyldistannoxane) complexes
containing a planar Sn4O2 core in which two l3-oxo
O-atoms connect an Sn2O2 ring to two exocyclic Sn-atoms
to give a R8Sn4O2 central unit. Views of the molecular
structures of 3 and 4 are shown in Figs. 3 and 4, while
selected geometric parameters are collected in Table 3. In
both the structures, the molecule sits across a crystallo-
graphic centre of inversion. The molecule is a tetranuclear
Sn-complex of the same type and molecular structure as
that recently described for {[nBu2Sn(2-OHC6H4C(CH3) =
N(CH2)2COO)]2O}2 and its analogue [26]. The following
specific details are given for the structure of 4, but the
comments apply equally well to the structure 3. Each Sn-
atom has six coordination, excluding the central Snꢀ ꢀ ꢀSn
4. Supplementary material
CCDC643300, 643301and 643302contain the supplemen-
tary crystallographic data for 1, 3 and 4. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
Acknowledgements
˚
contact of 3.2924(6) A. The exo-Snꢀ ꢀ ꢀendo-Sn distances
The financial support of the Department of Science &
Technology, New Delhi, India (Grant No. SR/S1/IC-03/
2005, TSBB), and the Ministry of Education, Youth and
Sports of the Czech Republic (Project No. MSM002-
1627502, MH) are gratefully acknowledged. ER and CP
˚
are 3.6371(4) and 3.7689(4) A. The molecule contains two
O-atoms which each bridge three Sn-centres, these being
the two endocyclic and one of the exocyclic Sn-atoms.
Two carboxylate ligands each bridge one endocyclic to
one exocyclic Sn-centre via the two carboxylate O-atoms,
with the Sn–O distances being quite similar. Two addi-
tional carboxylate ligands each have asymmetric bidentate
coordination via the two carboxylate O-atoms to an exocy-
clic Sn-atom, with the longer Snꢀ ꢀ ꢀO interactions being
`
are indebted to the Universita di Palermo, Italy and Uni-
versity of Camerino, Italy, respectively, for support.
References
˚
very long [2.825(3) A]. Additionally, the other carboxylate
[1] T.S. Basu Baul, S. Dhar, N. Kharbani, S.M. Pyke, R. Butcher, F.E.
Smith, Main Group Met. Chem. 22 (1999) 413.
O-atom in each of these ligands coordinates via a second

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 3625–3635
3635
[2] T.S. Basu Baul, S. Dhar, S.M. Pyke, E.R.T. Tiekink, E. Rivarola, R.
Butcher, F.E. Smith, J. Organomet. Chem. 633 (2001) 7.
[3] T.S. Basu Baul, W. Rynjah, E. Rivarola, A. Linden, J. Organomet.
Chem. 690 (2005) 613.
[4] T.S. Basu Baul, S. Dhar, E.R.T. Tiekink, Main Group Met. Chem.
24 (2001) 293.
[18] G.M. Sheldrick, SHELXL97, Program for the Refinement of Crystal
Structures, University of Go¨ttingen, Germany, 1997.
[19] T.P. Lockhart, F. Davidson, Organometallics 6 (1987) 2471.
[20] J.A. Zubieta, J.J. Zuckerman, Prog. Inorg. Chem. 24 (1987) 251.
[21] C.E. Hadden, G.E. Martin, V.V. Krishnamurthy, Magn. Reson.
Chem. 38 (2000) 143.
[5] T.S. Basu Baul, S. Dhar, E. Rivarola, F.E. Smith, R. Butcher, X.
Song, M. McCain, G. Eng, Appl. Organomet. Chem. 17 (2003) 261.
[6] T.S. Basu Baul, W. Rynjah, R. Willem, M. Biesemans, I. Verbruggen,
M. Holcˇapek, D. de Vos, A. Linden, J. Organomet. Chem. 689 (2004)
4691.
[22] J. Otera, T. Hinoishi, Y. Kawabe, R. Okawara, Chem. Lett. (1981) 273.
[23] T.P. Lockhart, W.F. Manders, Inorg. Chem. 25 (1986) 892.
[24] T.P. Lockhart, Organometallics 7 (1988) 1438.
[25] T. Yano, K. Nakashima, J. Otera, R. Okawara, Organometallics 4
(1985) 1501.
[7] T.S. Basu Baul, W. Rynjah, E. Rivarola, C. Pettinari, A. Linden, J.
Organomet. Chem. 690 (2005) 1413.
[26] T.S. Basu Baul, C. Masharing, S. Basu, E. Rivarola, M. Holcˇapek,
´
ˇ
R. Jirasko, A. Lycka, D. de Vos, A. Linden, J. Organomet. Chem.
[8] T.S. Basu Baul, W. Rynjah, E. Rivarola, A. Lycˇka, M. Holcˇapek, R.
691 (2006) 952.
´
´
ˇ
´
´
ˇ
ˇ
Jirasko, D. de Vos, R.J. Butcher, A. Linden, J. Organomet. Chem.
[27] J. Holecek, M. Nadvornık, K. Handlır, A. Lycka, J. Organomet.
691 (2006) 4850.
Chem. 315 (1986) 299.
[9] C.J. Evans, S.J. Karpel, J. Organomet. Chem. Libr. 16 (1985) 1.
[10] T.P. Lockhart, J.C. Calabrese, F. Davidson, Organometallics 6
(1987) 2479.
[11] A.C.T. North, D.C. Phillips, F.S. Mathews, Acta Crystallogr, Sect. A
24 (1968) 351.
[12] SAINT+. Version 6.02. Program for Reduction of Data Collected on
Bruker CCD Area Detector Diffractometer, Bruker AXS Inc.,
Madison, WI, USA.
[28] D.L. Tierney, P.J. Moeha, D.L. Hasha, J. Organomet. Chem. 620
(2001) 211.
[29] C. Pettinari, F. Marchetti, R. Pettinari, A. Gindulyte, L. Massa, M.
Rossi, F. Caruso, Eur. J. Inorg. Chem. (2002) 1447.
[30] E.R.T. Tiekink, M. Gielen, A. Bouhdid, M. Biesemans, R. Willem, J.
Organomet. Chem. 494 (1995) 247.
[31] V. Chandrasekhar, S. Nagendran, V. Baskar, Coord. Chem. Rev. 235
(2002) 1.
[13] G.M. Sheldrick, SADABS, Program for Empirical Absorption Correc-
tion of Area Detector Data, University of Go¨ttingen, Germany, 1996.
[14] R. Hooft, KAPPACCD Collect Software, Nonius BV, Delft, The
Netherlands, 1999.
[15] Z. Otwinowski, W. Minor, in: C.W. CarterJr., R.M. Sweet (Eds.),
Methods in Enzymology, vol. 276, Macromolecular Crystallography,
Part A, Academic Press, New York, 1997, pp. 307–326.
[16] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33.
[17] G.M. Sheldrick, SHELXS97, Program for the Solution of Crystal
Structures, University of Go¨ttingen, Germany, 1997.
[32] W. Henderson, M.J. Taylor, Polyhedron 15 (1996) 1957.
[33] R. Barbieri, F. Huber, L. Pellerito, G. Ruisi, A. Silvestri, in: P.J.
Smith (Ed.), 119Sn Mo¨ssbauer Studies on Tin Compounds, Chemistry
of Tin, Blackie Academic Press & Professional, London, 1998, pp.
496–540.
[34] R.V. Parish, in: G.J. Long (Ed.), Mo¨ssbauer Spectroscopy Applied to
Inorganic Chemistry, Plenum Press, New York, 1984, pp. 527–575
(Chapter 16).
[35] R.H. Herber, H.A. Stockler, W.T. Reichle, J. Chem. Phys. 42 (1965)
2447.