Self-assembled diorganotin(IV) moieties with 2,3,4,5-tetrafluorobenzoic acid: Syntheses, characterizations and crystal structures

Article abstract of DOI:10.1016/j.ica.2006.07.001

A series of new organotin(IV) derivatives with 2,3,4,5-tetrafluorobenzoic acid: {[(2,3,4,5-F₄C₆HCO₂)R₂Sn]₂O}₂ (R = Et 1, n-Bu 2, Ph 3), [R₂Sn(O₂CC₆F₄H)₂]_n (R = n-Bu 4, Et 5, Ph 6), and Sn₂R₄(O₂CC₆F₄H)₃(OH) (R = Et 7, n-Bu 8, Ph 9), were synthesized by the reaction of diorganotin oxide and 2,3,4,5-tetrafluorobenzoic acid. All the complexes 1-9 have been characterized by elemental analysis, IR, ¹H, ¹³C, ¹¹⁹Sn NMR spectra. Among them complexes 2, 4, 8 were also characterized by X-ray crystallography diffraction analyses. The crystal structure of complex 2 exhibited a tetra-nuclear geometry with the Sn₂O₂ symmetry core. Complex 4 formed a 1D helical double-chain structure through intermolecular O→Sn coordinating and completed a DNA-like assembly. Complex 8 revealed that the both Sn atoms were held together by hydroxide and acetate bridges, forming a chair-like six-membered ring. Moreover, the supramolecular structures of dimer, 1D chain or 2D network have been found in complexes 4 and 8 by intermolecular C-H?F weak hydrogen bond and non-bonded F?F or F?Sn interaction, which were highly effective in the assembly of supramolecular structures and could lead to the formation of complexes with fascinating topologies properties.

Full text of DOI:10.1016/j.ica.2006.07.001

Inorganica Chimica Acta 359 (2006) 4179–4190
www.elsevier.com/locate/ica
Self-assembled diorganotin(IV) moieties with 2,3,4,5-tetrafluorobenzoic
acid: Syntheses, characterizations and crystal structures
a,b,
a
a
a
Chunlin Ma
*, Junshan Sun , Rufen Zhang , Daqi Wang
a
Department of Chemistry, Liaocheng University, Wenhua Road 34, Liaocheng, Shandong 252059, PR China
b
Taishan University, Taian 271021, PR China
Received 20 May 2006; received in revised form 2 July 2006; accepted 3 July 2006
Available online 11 July 2006
Abstract
A series of new organotin(IV) derivatives with 2,3,4,5-tetrafluorobenzoic acid: {[(2,3,4,5-F4C6HCO2)R2Sn]2O}2 (R = Et 1, n-Bu 2, Ph
3), [R2Sn(O2CC6F4H)2]n (R = n-Bu 4, Et 5, Ph 6), and Sn2R4(O2CC6F4H)3(OH) (R = Et 7, n-Bu 8, Ph 9), were synthesized by the reac-
tion of diorganotin oxide and 2,3,4,5-tetrafluorobenzoic acid. All the complexes 1–9 have been characterized by elemental analysis, IR,
1H, 13C, 119Sn NMR spectra. Among them complexes 2, 4, 8 were also characterized by X-ray crystallography diffraction analyses. The
crystal structure of complex 2 exhibited a tetra-nuclear geometry with the Sn2O2 symmetry core. Complex 4 formed a 1D helical double-
chain structure through intermolecular O!Sn coordinating and completed a DNA-like assembly. Complex 8 revealed that the both Sn
atoms were held together by hydroxide and acetate bridges, forming a chair-like six-membered ring. Moreover, the supramolecular
structures of dimer, 1D chain or 2D network have been found in complexes 4 and 8 by intermolecular C–Hꢀ ꢀ ꢀF weak hydrogen bond
and non-bonded Fꢀ ꢀ ꢀF or Fꢀ ꢀ ꢀSn interaction, which were highly effective in the assembly of supramolecular structures and could lead to
the formation of complexes with fascinating topologies properties.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: 2,3,4,5-Tetrafluorobenzoic acid; Double-chain structure; Diorganotin; Self-assembly; Supramolecular structure
1. Introduction
which have been synthesized by Marcel [4], and these com-
plexes exhibited different anti-tumor activities when the
number of fluorine atoms on the benzoate moiety was
increased [5]. Moreover, owing to the presence of fluorine
atom, these ligands presented a number of opportunities
for creating supramolecular arrangement via weak inter-
molecular contacts. In recent literatures, evidences have
been provided for the property of the formation of interac-
tions such as C–Hꢀ ꢀ ꢀF–C and C–Fꢀ ꢀ ꢀp [6]. So one of our
research interests has now focused on the study of the fluo-
rinated complexes.
In this work, we selected 2,3,4,5-tetrafluorobenzoic acid
as ligand and successfully obtained several new complexes
{[(2,3,4,5-F4C6HCO2)R2Sn]2O}2 (R = Et 1, n-Bu 2, Ph 3),
[R2Sn(O2CC6F4H)2]n (R = n-Bu 4, Et 5, Ph 6), and
Sn2R4(O2CC6F4H)3(OH) (R = Et 7, n-Bu 8, Ph 9) through
controlling the ratios of reactants. It is worthwhile to note
that these complexes were synthesized by different molar
Organotin carboxylates have been the subjects of inter-
est for some time owing to their biochemical properties
and commercial applications [1]. These complexes may
adopt a variety of structural modes depending on the nat-
ure of organic ligand and the ratio of the reactant [2]. Espe-
cially the presence of much higher electro-negativity of
fluorine atom in the ligand strongly affected the elec-
tronic-density in the molecular. Moreover, the substitution
of hydrogen on the aromatic carboxylic acid by fluorine
influenced markedly the biological activity of organic mol-
ecule [3]. In recent years, there have been a series of reports
about organotin complexes of fluorinated aromatic carbox-
ylic acids containing mono- or polyfluorophenyl groups,
*
Corresponding author. Tel.: +86 635 8230660; fax: +86 538 6715521.
E-mail address: macl@lctu.edu.cn (C. Ma).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.07.001

4180
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
2.2.2. {[(2,3,4,5-F4C6HCO2)Bu2Sn]2O}2 (2)
Sn
Sn
O
Sn
Sn
O
O
II
O
O
The synthesis procedure was the same as 1, recrystal-
lized from ether–petroleum. Yield: 68%, m.p. 134–
136 ꢁC. Anal. Calc. for C60H76F16O10Sn4: C, 41.51; H,
4.41. Found: C, 41.55; H, 4.43%. IR (KBr, cmꢁ1):
m(C@O) 1695; m(COOasym) 1617; m(COOsym) 1472, 1352;
O
C
C
R
R
C
R
O
Sn
III
m(C–F) 1995; m(Sn–O–Sn) 631; m(Sn–O) 473 cmꢁ1 1H
.
Scheme 1. Different coordination modes of the carboxylate group.
NMR (CDCl3, ppm): d 0.910 (t, 12H, 4CH3); 1.464 (m,
8H, 4CH2); 1.892 (m, 16H, 4CH2CH2), 7.70–7.77 (m,
3H, 3Ph-H). 13C NMR (CDCl3): d 168 (COO), 42.8 and
41.2 (a-CH2, 1J(119Sn–13C), 986.8 Hz), 30.6 (b-CH2),
27.8 and 27.2 (c-CH2), 13.7 (CH3). 119Sn NMR (CDCl3,
298 K): ꢁ192.8, ꢁ168.6 ppm,
ratios of 1:1, 1:2, and 2:3 in the same solvent of benzene.
Moreover, the COO group shows different coordination
to the center tin(IV) atom. All complexes were characterized
1
by elemental, IR, H, 13C, and 119Sn NMR spectroscopy
analysis and the structures of 2, 4, 8 were also determined
by X-ray crystallography. Different coordination modes
of the carboxylate group were shown in Scheme 1.
2.2.3. {[(2,3,4,5-F4C6HCO2)Ph2Sn]2O}2 (3)
The synthesis procedure was the same as 1, recrystal-
lized from ether–petroleum. Yield: 75%, m.p. 128–
130 ꢁC. Anal. Calc. for C36H28O10F16Sn4: C, 30.90; H,
2.02. Found: C, 30.88; H, 2.18%. IR (KBr, cmꢁ1):
m(C@O) 1698s; m(COOasym) 1619s; m(COOsym) 1475s,
1446s; m(C–F) 1997s; m(Sn–O–Sn) 635 m; m(Sn–O) 472 m.
1H NMR (CDCl3, ppm): d 7.70–7.77 (m, 1H, 1Ph-H);
6.80–7.67 (m,10H, Ph-H); 1.78 (m, a-CH2); 1.46 (m, b-
CH2); 1.34 (tq, c-CH2); 0.88 (t, CH3). 13C NMR (CDCl3):
d 164.6 (COO), 152, 148, 146, 143, 141, 114 (Ph-C). 119Sn
NMR (CDCl3, 298 K): ꢁ196.6, ꢁ172.1 ppm.
2. Experimental
2.1. Materials and measurements
Di-n-butyltin oxide, diphenyltin oxide, diethyltin oxide
and 2,3,4,5-tetrafluorobenzoic acid were commercially
available, and they are used without further purification.
The melting points were obtained on a Kofler micro-melt-
ing point apparatus and were uncorrected. Infrared-spectra
were recorded on a Nicolet–460 spectrophotometer using
1
KBr discs and sodium chloride optics. H, 13C, 19F and
2.2.4. [Bu2Sn(O2CC6F4H)2]n (4)
119Sn NMR spectra were recorded on a Varian Mercury
Plus 400 spectrometer operating at 400, 100.6 and
149.2 MHz, respectively. The spectra were acquired at
room temperature (298 K) unless otherwise specified; 13C
spectra are broadband proton decoupled. The chemical
shifts are reported in ppm relative to Me4Si in CDCl3 as
solvent. Elemental analyses (C, H) were performed with a
PE-2400II apparatus.
The synthesis procedure was the same as 1. Recrystal-
lized from hexane. Yield: 72%, m.p. 102–104 ꢁC. Anal.
Calc. for C22H20O4F8Sn: C, 42.68; H, 3.26. Found: C,
42.92; H, 2.96%. IR (KBr, cmꢁ1): m(COOasym), 1611;
m(COOsym), 1379; m(Sn–O–Sn), 694; m(Sn–C), 588; m(Sn–
1
O), 532, 461. H NMR (CDCl3): d 0.910 (t, 12H, 4CH3);
1.464 (m, 8H, 4CH2); 1.892 (m, 16H, 4CH2CH2); 7.70–
7.76 (m, 1H, 3Ph-H). 13C NMR (CDCl3): d 170 (COO),
150, 147, 145, 142, 140, 114(Ph-C). 29.9 (a-CH2,
1J(119Sn–13C), 992.6 Hz); 26.9 (b-CH2); 26.5 and 26.0 (c-
CH2); 13.7 (CH3). 119Sn NMR (CDCl3, 298 K):
ꢁ216.6 ppm.
2.2. Syntheses
2.2.1. {[(2,3,4,5-F4C6HCO2)Et2Sn]2O}2 (1)
The reaction was carried out under nitrogen atmo-
sphere. The diethyltin oxide (0.250 g, 1 mmol) and
2,3,4,5-tetrafluorobenzoic acid (0.19 4 g, 1 mmol) were
added to a solution of dry benzene (30 ml) in a Schlenk
flash and stirred refluxing 16 h at 80 ꢁC. The solvent was
removed by evaporation under vacuum until solid product
was obtained. Recrystallized from ether–petroleum. Yield:
75%, m.p. 128–130 ꢁC. Anal. Calc. for C44H44O10F16Sn4:
C, 34.96; H, 2.93. Found: C, 35.03; H, 2.98%. IR (KBr,
cmꢁ1): m(C@O) 1740; m(COOasym) 1693; m(COO), 1448,
1420; m(C–F) 1874; m(Sn–O–Sn) 632; m(Sn–O) 476. 1H
NMR (CDCl3, ppm): d 7.70–7.77 (d, 1H, Ph-H), 1.46 (m,
2H, CH2); 0.89 (t, CH3). 13C NMR (CDCl3): d 168
(COO), 154, 150, 148, 146, 142, 118. 29.9 (a-CH2,
1J(119Sn–13C), 980.4 Hz), 26.9 (b-CH2), 26.5 and 26.0 (c-
CH2), 13.7 (CH3). 119Sn NMR (CDCl3, 298 K): ꢁ192.7,
ꢁ170.2 ppm.
2.2.5. [Et2Sn(O2CC6F4H)2]n (5)
The synthesis procedure was the same as 1. Recrystal-
lized from hexane. Yield: 72%, m.p. 102–104 ꢁC. Anal.
Calc. for C18H12O4F8Sn: C, 38.40; H, 2.15. Found: C,
38.52; H, 2.04%. IR (KBr, cmꢁ1): m(COOasym), 1613;
m(COOsym), 1380; m(Sn–O–Sn), 689; m(Sn–C), 586; m(Sn–
1
O), 532, 461. H NMR (CDCl3): d 0.912 (t, 6H, 2CH3);
1.886 (m, 4H, 2CH2); 7.71–7.79 (m, 1H, 3Ph-H). 13C
NMR (CDCl3): d 172 (COO), 148, 145, 143, 140, 138,
118 (Ph-C). 29.6 (a-CH2, 1J(119Sn–13C), 982.2 Hz); 13.8
(CH3). 119Sn NMR (CDCl3, 298 K): ꢁ215.8 ppm.
2.2.6. [Ph2Sn(O2CC6F4H)2]n (6)
The synthesis procedure was the same as 1. Recrystal-
lized from hexane. Yield: 72%, m.p. 102–104 ꢁC. Anal.
Calc. for C26H12O4F8Sn: C, 47.38; H, 1.84. Found: C,

C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
4181
47.52; H, 1. 72%. IR (KBr, cmꢁ1): m(COOasym), 1611; m
(COOsym), 1379; m(Sn–O–Sn), 694; m(Sn–C), 582; m(Sn–O),
531, 464 cmꢁ1 1H NMR (CDCl3): d 0.912 (t, 12H,
4CH3); 1.460 (m, 8H, 4CH2); 1.891 (m, 16H, 4CH2CH2);
7.70–7.77 (m, 1H, 3Ph-H). 13C NMR (CDCl3): d 172
(COO), 152, 149, 147, 144, 142, 135, 126, 124, 116 (Ph-
C). 119Sn NMR (CDCl3, 298 K): ꢁ217.8 ppm.
hydrogen atoms were calculated, and their contributions
in structure factor calculations were included. Crystal data
and experimental details of the structure determinations
are listed in Table 4.
3. Results and discussion
3.1. Synthesis
2.2.7. [Et4Sn2(O2CC6F4H)3(OH)] (7)
The synthesis procedure was the same as 1. Recrystal-
lized from dichloromethane. Yield: 68%, m.p. 156–
158 ꢁC. Anal. Calc. for C29H24O7F12Sn2: C, 36.67; H,
2.55. Found: C, 36.63; H, 2.50%. IR (KBr, cmꢁ1):
m(COOasym), 1698, 1656; m(COOsym), 1368, 1334; m(Sn–
The new diorganotin carboxylates containing the
2,3,4,5-tetrafluorophenyl moiety are {[(2,3,4,5-F4C6HCO2)-
R2Sn]2O}2 (R = Et 1, n-Bu 2, Ph 3), as obtained from a
1:1 condensation, [R2Sn(O2CC6F4H)2]n (R = n-Bu 4, Et
5, Ph 6), as obtained from 2:1 condensation, and
R4Sn2(O2CC6F4H)3(OH) (R = Et 7, n-Bu 8, Ph 9), as
obtained from a 3:2 condensation of the appropriate car-
boxylic acid with diorganotin(IV) oxide, which exhibit
strongly structural orderliness. The synthetic procedures
are shown in Scheme 2.
1
O–Sn), 689; m(Sn–C), 572; m(Sn–O), 512, 487. H NMR
(CDCl3): d 6.80–7.67 (m, 10H, Ph-H); 7.70–7.77 (m,
1H, Ph-H). 13C NMR (CDCl3): d 165 (COO), 150,
147, 145, 142, 140, 115 (Ph-C). 24.9 (a-CH2,
1J(119Sn–13C), 986.6 Hz); 22.9 (b-CH2); 119Sn NMR
(CDCl3, 298 K): ꢁ164.8 ppm.
3.2. Spectroscopic studies
2.2.8. [Bu4Sn2(O2CC6F4H)3(OH)] (8)
The synthesis procedure was the same as 1. Recrystallized
from dichloromethane. Yield: 76%, m.p. 168–170. ꢁC. Anal.
Calc. for C37H40F12O7Sn2: C, 41.86; H, 3.80. Found: C,
41.83; H, 3.76%. IR (KBr, cmꢁ1): m(COOasym), 1696, 1653;
m(COOsym), 1369, 1336; m(Sn–O–Sn), 686; m(Sn–C), 578;
m(Sn–O), 512, 487. 1H NMR (CDCl3): d 0.90 (t, 12H,
4CH3); 1.45 (m, 8H, 4CH2); 1.86 (m, 16H, 4CH2CH2);
1.20 (m, 3H, 3Ph-H). 13C NMR (CDCl3): d 13C NMR
(CDCl3): d 170 (COO), 150, 147, 145, 142, 140, 116(Ph-C);
3.2.1. IR spectra
The stretching frequencies of interest are those associ-
ated with the C(O)O, Sn–C and Sn–O and Sn–O–Sn
groups. The strong absorption appears in the region of
568–596 cmꢁ1 in the respective spectra of 1–9, which is
absent in the spectra of the free ligand, is assigned to the
Sn–O stretching mode of vibration. All these values are
consistent with that detected in number of organotin(IV)-
oxygen derivatives [7,8].
1
29.9 (a-CH2, J(119Sn–13C), 988.7 Hz); 26.9 (b-CH2); 26.5
In organotin(IV) carboxylate complexes, the IR spec-
troscopy can provide useful information concerning the
coordinate formation of the carboxylate. Based on the pre-
vious reports, it is possible to distinguish the coordination
mode of the COOꢁ group [9]. The IR spectrums of 1–3
shows characteristic bands of carboxylate groups occur at
near 1697 and 1619 cmꢁ1 for asymmetric stretching and
at near 1513 and 1279 cmꢁ1, which are higher than that
for non-fluorinated carboxylates [10]. For complexes 7–9,
the characteristicꢁb1ands of carboxylate groups at near
1684 and 1640 cm for asymmetric stretching and at near
1355 and 1320 cmꢁ1 for symmetric stretching. Owing to the
presence higher electro-negativity of fluorine atoms, these
data are higher than that observed for non-fluorinated
carboxylates [10]. The magnitude of Dm (m(COOasym) ꢁ
m(COOsym)) about 185 and 350 cmꢁ1, respectively, which
suggest that the coordinate formation for complexes 1–3
e acid (480 cmꢁ1) and comparable with that of the sodium
salt of the acid (275 cmꢁ1). A strong band in the 662–
685 cmꢁ1 region for complexes 1–3, 7–9 and is assigned
to m(Sn–O–Sn), indicating and 7–9 are both bidentate mode
and monodentate mode under the conditions employed
[11]. In complexes 4–6, the Dm (m(COOasym) ꢁ m(COOsym))
is near 272 cmꢁ1, which is lower than that observed in
the spectrum of the fre a Sn–O–Sn bridged structure [12].
The absorption bands at 581 cmꢁ1 are attributed to
and 26.0 (c-CH2); 13.7 (CH3); 119Sn NMR (CDCl3,
298 K): ꢁ160.8 ppm.
2.2.9. [Ph4Sn2(O2CC6F4H)3(OH)] (9)
The synthesis procedure was the same as 1. Recrystal-
lized from dichloromethane. Yield: 68%, m.p. 156–
158 ꢁC. Anal. Calc. for C45H24O7F12Sn2: C, 47.32; H,
2.12. Found: C, 47.38; H, 2.14%. IR (KBr, cmꢁ1):
m(COOasym), 1698, 1656; m(COOsym), 1368, 1334; m(Sn–
1
O–Sn), 689; m(Sn–C), 572; m(Sn–O), 512, 487. H NMR
(CDCl3): d 6.80–7.67 (m, 10H, Ph-H); 7.70–7.77 (m, 1H,
Ph-H). 13C NMR (CDCl3): d 165 (COO), 152, 148, 146,
143, 138,136, 126, 112 (Ph-C). 119Sn NMR (CDCl3,
298 K): ꢁ170.2 ppm.
2.3. X-ray structures determination
Crystals were mounted in Lindemann capillaries under
nitrogen. All X-ray crystallographic data were collected
on a Bruker SMART CCD 1000 diffractometer with
graphite monochromated Mo Ka radiation (k =
˚
0.71073 A). A semi-empirical absorption correction was
applied to the data. The structure was solved by direct-
methods using SHELXLS-97 and refined against F2 by full-
matrix least squares using SHELXL-97. The positions of

4182
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
F
R
O
F
R
F
F
O
Sn
F
F
R
F
O
O
O
F
R=Et
R=nBu 2
R=Ph
1
R
R
Sn
Sn
1 : 1
2 : 1
3 : 2
F
O
R
O
3
F
F
O
F
O
O
Sn
F
F
F
R
R
F
F
F
F
F
F
F
R
R=nBu 4
OH
O
O
O
O
refluxing
5
6
R=Et
R=Ph
+ R2SnO
Sn
R
F
O
F
n
F
F
F
F
F
F
F
F
R
R
O
O
R=Et
7
O
R
R=nBu 8
Sn
R
Sn
o
O
O
O
R=Ph
9
F
F
F
F
F
F
F
F
Scheme 2.
m(Sn–C) and m(Sn–O), respectively [13]. This is also consis-
tent with the X-ray diffraction study.
cˇek and Lycˇka equation [14] is 165.4ꢁ, which is close to
the angles observed in the solid state for complex 4.
The 119Sn NMR chemical shifts of tin complexes appear
to depend not only on coordination number, but also on
the type of donor atoms bonds to the metal ion [15]. The
119Sn NMR data show only signal at ꢁ216.8 ppm for com-
plexes 4–6, typical of a six-coordination species, and has
been found in accordance with the solid state structure
[16]. However, the chemical shift of complexes 1–3 present
at ꢁ193.0 ppm. Though d(119Sn) is influenced by several
factors, including the aromatic or aliphatic of the R group
bound to the tin atom (and possibly the type of donor
atoms of the ligand), it may be used with a cation to infer
the coordination number of the tin atom [17]. As for com-
plexes 7–9, the 119Sn NMR spectra shows a single reso-
nance at d ꢁ 165.3 ppm, indicating the presence of only
signal of five-coordination tin atom in solution.
3.2.2. NMR spectra
The 1H NMR spectra show the expected integration and
peak multiplicities. In the spectrum of the free ligand, the
resonance observed at about d = 10.114 ppm, which is
absent in the spectra of the complexes, indicates the
replacement of the carboxylic acid proton on complex for-
mation. The chemical shifts of the signals for the butyl
group exhibit resonance in the 0.87–1.89 ppm region. Sig-
nals for the other groups, such as phenyl H appear at the
same as in the ligand. In the spectrum of the complexes,
the absence of the signal (d = 9.6 ppm) in the spectrum of
the complex indicates the replacement of the carboxyl pro-
ton by organotin (IV) on complexation.
The 13C NMR spectra of all complexes show a signifi-
cant downfield shift of all carbon resonance, compared
with the free ligand. The shift is a consequence of an elec-
tron density transfer from the ligand to the acceptor.
Although at least two different types of carboxyl groups
are present, only single resonance are observed for the
COO group in the 13C spectra. The possible reason is that
either accidental magnetic equivalence of the carbonyl car-
bon atoms or the separation between the two sets of reso-
nance is small to be resolved. Complementary information
4. Crystal structures
4.1. Crystal structure of {Bu2Sn(O2CC6HF4)2O}2 (2)
The molecular structure and cell packing of complex 2
are shown in Figs. 1 and 2, selected bond lengths and
angles are given in Table 1. The structure is centrosymmet-
ric about a Bu4Sn2O2 core. Attached to each bridging
oxygen atom is an exocyclic Bu2Sn unit leading to a
three-coordinate O(5) atom. Further connections between
the tin atoms arise as a result of bridging carboxylate
1
is given by the values of the coupling constant. The JSn–C
value for 4 is 902.6 Hz, similar to that of the hexa-coordi-
nate complex, and the calculated h(C–Sn–C) by the Hole-

C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
4183
Table 1
Selected bond lengths (A) and angles (ꢁ) of complex 2
˚
˚
Bond lengths (A)
Sn(1)–O(5)a
Sn(1)–C(19)
Sn(1)–O(1)
Sn(2)–O(5)
O(2)–Sn(2)CC
2.049(5)
2.126(9)
2.271(6)
2.023(5)
2.280(6)
Sn(1)–C(15)
Sn(1)–O(5)
Sn(2)–O(2)a
Sn(2)–O(4)
2.125(10)
2.182(5)
2.280(6)
2.845(7)
Bond angles (ꢁ)
C(15)–Sn(1)–C(19)
O(5)a–Sn(1)–C(15)
O(5)a–Sn(1)–O(1)
C(19)–Sn(1)–O(5)
C(19)–Sn(1)–O(1)
142.0(4)
C(23)–Sn(2)–C(27)
O(5)a–Sn(1)–O(5)
O(5)a–Sn(1)–O(1)
C(15)–Sn(1)–O(1)
C(19)–Sn(1)–O(3)
140.2(5)
107.9(4)
142.8(2)
97.4(4)
85.9(4)
77.6(2)
90.6(3)
87.2(5)
76.8(4)
a
Symmetry transformations used to generate equivalent atoms: ꢁx + 1/2,
ꢁy + 1/2, ꢁz + 1.
which has the effect of opening up the C(15)–Sn(1)–C(19)
˚
angle to 141.8(5)ꢁ. Similarly, a contact of 2.838(8) A
between the Sn(2) and O(4) atoms results in the expansion
of the C(23)–Sn(2)–C(27) angle to 140.6(6)ꢁ. Whereas the
intramolecular Snꢀ ꢀ ꢀO contacts are well within the van
der Waals distance for these atoms, the relatively large sep-
arations and the minor perturbations from the ideal trigo-
nal bipyramidal geometries indicate that these interactions
must be considered much weaker. The dihedral angles of
118.8ꢁ and 62.0ꢁ between the O(1)–C(1)–O(2)/C(2)–C(7)
and the O(4)–C(8)–O(3)/C(9)–C(14) planes, respectively,
indicate little conjugation between the carboxylate and
C6F4H groups. Other parameters associated with the car-
boxylate residues are as expected. In the lattice, there is a
close intermolecular contact between each Sn(2) atom
and a centrosymmetrically related O(4) atom, i.e. a non-
Fig. 1. ORTEP view of tetraorganodistannoxane of the molecular
structure 2 (the fluorine atoms of phenyl ring is somewhat disordered).
˚
coordinating atom, of 3.204(5) A. This loose association
between Sn(2) and O(4) atoms leads to chains of weakly
connected dimers of distannoxanes running parallel to
the c-axis, as shown in Fig. 1. Similar chains, involving
the equivalent Sn and O atoms, are observed in the crystal
lattice of {[(MeCOO)Me2Sn]2O}2 [18], however, in this
structure the intermolecular contacts were significantly clo-
˚
ser at 2.56(1) A. A further difference arises between the two
as a result of the presence of three bidentate, bridging car-
boxylate ligands rather than two as in the present of deter-
mination. In this structure, the non-coordinating atom of
the carboxylate ligand, O(4), is orientated so that it is direc-
ted away from the rest of the molecule but nevertheless
does form weak intramolecular interactions with the
Sn(2) atom. In the case of three of the R = n-Bu deriva-
tives, the O(4) also forms weak intermolecular interactions
with the Sn0(2) atoms of neighboring molecules such that
Fig. 2. Unit cell packing of complex 2.
ligands which form almost equal Sn–O bond distances to
the endo- and exo-cyclic tin atoms, i.e. [Sn(1)–O(1)]
˚
2.272(7) and [Sn(2A)–O(2)] 2.277(7) A. The remaining
˚
independent carboxylate ligand coordinates in the monod-
entate mode to the exocyclic tin atom exclusively with
Sn(2)ꢀ ꢀ ꢀO(4 ) contacts of >3.0 A are found [19]. The pres-
ence of bulkier R groups residing on the Sn atoms (and/
or on the carboxylate ligands) in the remaining structures
apparently precludes close intermolecular contacts of this
type. The molecular structure for {[(F4HCOO)Bu2Sn]2O}2
conforms with the common structural motif found for
complexes with the general formula {[(R0COO)R2Sn]2O}2
[20].
˚
Sn–O 2.195(5) A. This configuration leads to two five-coor-
dinate tin centers, each existing in a distorted trigonal bipy-
ramidal geometry. Distortion from ideal geometries may be
traced, in part, to the presence of close intramolecular
Snꢀ ꢀ ꢀO interactions. Thus, the centrosymmetrically related
˚
O(3) atom forms a contact of 2.844(6) A with the Sn(1),

4184
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
Fig. 3. Molecular structure of complex 4.
Table 2
Selected bond lengths (A) and angles (ꢁ) of complex 4
˚
˚
Bond lengths (A)
Sn(1)–C(19)
Sn(1)–C(15)
Sn(1)–O(3)
Sn(1)–O(2)b
O(4)–Sn(1)b
2.096(18)
2.115 (17)
2.246(17)
2.250(15)
2.246(17)
Sn(1)–O(1)
Sn(1)–O(4)a
Sn(1)–O(2)
O(2)–Sn(1)a
2.236(14)
2.246(17)
4.060(12)
2.250(15)
Bond angles (ꢁ)
C(19)–Sn(1)–C(15)
C(15)–Sn(1)–O(1)
C(15)–Sn(1)–O(4)a
C(19)–Sn(1)–O(3)
O(3)–Sn(1)–O(1)
C(15)–Sn(1)–O(2)b
O(1)–Sn(1)–O(2)b
C(19)–Sn(1)–O(2)
O(1)–Sn(1)–O(2)
O(4)a–Sn(1)–O(2)
Sn(1)a–O(2)–Sn(1)
C(1)–O(2)–Sn(1)a
C(8)–O(3)–Sn(1)
172.1(8)
C(19)–Sn(1)–O(1)
C(19)–Sn(1)–O(4)a
O(1)–Sn(1)–O(4)a
C(15)–Sn(1)–O(3)
C(19)–Sn(1)–O(2)b
O(4)a–Sn(1)–O(2)b
O(3)–Sn(1)–O(2)b
C(15)–Sn(1)–O(2)
O(3)–Sn(1)–O(2)
O(2)b–Sn(1)–O(2)
C(1)–O(1)–Sn(1)
C(1)–O(2)–Sn(1)
C(8)–O(4)–Sn(1)b
90.2(6)
96.4(6)
96.9(5)
86.6(6)
81.0(6)
173.3(7)
86.6(5)
112.9(5)
159.3(4)
99.5(4)
134.0(15)
43.5(11)
128.2(13)
89.3(6)
91.6(7)
93.3(5)
174.1(6)
91.1(6)
89.3(5)
68.4(5)
26.1(4)
85.1(4)
99.5(4)
134.4(14)
139.7(15)
Fig. 4. Unit cell packing of complex 4.
Symmetry transformations used to generate equivalent atoms: ax + 1, y, z;
bx ꢁ 1, y, z.
4.2. Crystal structure of {Bu2Sn(O2C6F4H)2}n (4)
The representative X-ray structure and cell packing for
complex 4 are shown in Figs. 3 and 4, selected band dis-
tances and angles are summarized in Table 2. The Sn atom
exists in a square planar geometry defined by two ipso-C
atoms [C(15) and C(19)] of the butyl groups and oxygen
atoms [O(1) and O(3)] of two carboxyl groups. The major
departure from the ideal plane geometry is found in the
Bu–Sn–Bu angle of 172.1(8)ꢁ and the angle of O(1)–
Sn(1)–O(3) is 174.1ꢁ(6), which is slightly departure of the
bond angles of C(15)–Sn(1)–O(1) and C(19)–Sn(1)–O(1)
are 89.3(6)ꢁ and 90.2(6)ꢁ, respectively, which illustrates
the Sn atom with two O atoms of carboxyl groups and
two trans-n-butyl groups exhibit a similarly square geome-
try. Moreover, the bond distance of O(2)–Sn(1) is
˚
4.060(12) A, larger than the van der Waals’ sum of Sn
b
˚
and O (3.68 A) [21], but the bond distance of O-Sn (sym-
˚
metry operations x + 1, y, z) is (2.250(15)) A, close to the
covalent sum of Sn and O (2.13 A) [21], which illustrates
˚
˚
ideal plane, out of which the Sn atom lies 0.0293 A. The
˚
distances of the Sn–O are 2.236(14) A [O(1)–Sn(1)],
the bidentate coordination mode of carboxyl group. The
molecular structure of 4 corresponds to a centrosymmetric
dimer based on an eight-membered ring containing two
˚
2.247(14) [O(3)–Sn(1)] and the Sn–C are 2.115(17) A
˚
[C(15)–Sn(1)], 2.096(18) A [C(15)–Sn(1)], respectively. The

C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
4185
five-coordinate tin atoms which exhibits distorted tetrago-
nal pyramid environment with the O(4)A atom in apical
position, and the equatorial planar position is occupied
by two O atoms from two carboxyl groups and two
trans-n-butyl groups (Fig. 5). The distortion lies the angle
of O(1)–Sn(1)–O(4)a [96.9(5)ꢁ] (symmetry operation
x + 1, y, z). Two carboxyl groups form a non-symmetrical
bridging (C(1)–O(1) = 1.29(2) and C(1)–O(2) = 1.25(2),
O(1)–Sn(1) = 2.236(14) and O(2)–Sn(1)a = 2.250(14)). Fur-
ther, the link of the dimer unit through intermolecular
C@O!Sn coordination interaction leads to infinite 1D
helical double-chain structure along a axis (Fig. 6), which
is similar to another organotin complex that has been
reported [22]. In this structure, the tin atom displays a
six-coordinated distorted octahedron geometry with four
O atoms from four carboxyl groups and two C atoms from
trans-n-butyl groups (it may alternately be described as a
bicapped tetrahedron with oxygens), The deviation from
Fig. 5. The dimer grid unit of structure of complex 4 via O!Sn
Fig. 6. Perspective view shows the 1D helical double-chain polymeric
structure of complex 4 (the butyl groups have been omitted for clarity).
coordination (the butyl groups have been omitted for clarity).
Fig. 7. Perspective view showing 1D chain structure of complex 4 connected by intermolecular C–Hꢀ ꢀ ꢀF weak hydrogen bond (a) and non-bonded Fꢀ ꢀ ꢀF
interaction (b) (the butyl groups have been omitted for clarity).

4186
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
the standard octahedron environment is also confirmed by
the value of the C(15)–Sn(1)–C(19) angle, 172.1(8)ꢁ and
two C atoms of the butyl groups occupied the axial apical
position. This monoorganotin oxo clusters based on dou-
bly bridging carboxyl oxo derivatives and hexa-coordi-
nated tin atoms have been reported by Holmes and
co-workers [23,24].
nevertheless smaller than the sum of van der Waals radii
(2.67 and 2.94 A) [22]. These contacts assemble the com-
˚
plex 4 into 2D planar structure through C–Hꢀ ꢀ ꢀF and
Fꢀ ꢀ ꢀF along the ab axis. The network structure extended
along c axis and formed a infinite 3D metal-organic frame-
work, showing a channel-like supramolecular structure,
whose structure unit is shown in Fig. 8(c).
Worth mentioning here is that supramolecular structure
of complex 4 is shown in Figs. 7 and 8, owing to intermo-
lecular C–Hꢀ ꢀ ꢀF and Fꢀ ꢀ ꢀF weak interaction, which are
4.3. Crystal structure of {Bu2Sn2(O2CC6HF4)3(OH)} (8)
˚
2.350 and 2.725 A, respectively, smaller than the sum of
The molecular structure and unit cell of the complex 8
depicted in Figs. 9 and 10, selected bond lengths and angles
are given in Table 3. Both of Sn atoms exist in distorted tri-
gonal bipyramidal geometries with two carboxylate O
atoms at an axial position and the bridging OH atom
and two butyl groups from decreases in O(2)–Sn(2)–O(5)
and O(1)–Sn(1)–O(3) axial angles to 175.0(5)ꢁ and
˚
van der Waals radii (2.67 and 2.94 A) [21]. These contacts
form a infinite 1D chain structure, respectively.
The supramolecular structure of 4, as shown in
Fig. 8(b), exhibits a 2D network structure unit, in which
the corner of this structure is composed of weak C–
˚
Hꢀ ꢀ ꢀF and Fꢀ ꢀ ꢀF contact (2.350 and 2.725 A, respectively),
Fig. 8. (a) Perspective view shows grid unit of supramolecular structure 4. (b) Perspective view shows the 2D grid diagram of intermolecular structure of
complex 4 weak C–Hꢀ ꢀ ꢀF hydrogen bond and non-bonded Fꢀ ꢀ ꢀF interaction. (c) A 3D metal-organic framework, showing the infinite channel-like
structure unit of complex 4.

C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
4187
Table 3
Selected bond lengths (A) and angles (ꢁ) of complex 8
˚
˚
Bond lengths (A)
Sn(1)–C(22)
Sn(1)–C(26)
Sn(1)–O(7)
Sn(1)–O(3)
Sn(1)–O(1)
Sn(2)–O(2)
2.006(17)
1.986(17)
2.123(11)
2.183(11)
2.275(12)
2.235(14)
Sn(2)–C(30)
Sn(2)–O(7)
Sn(2)–C(34)
Sn(2)–O(5)
O(2)–C(1)
O(1)–C(1)
2.12(2)
2.028(11)
2.07(2)
2.153(12)
1.21(2)
1.22(2)
Bond angles (ꢁ)
C(22)–Sn(1)–C(26)
C(26)-Sn(1)–O(7)
C(26)–Sn(1)–O(3)
C(34)–Sn(2)–O(5)
C(34)–Sn(2)–O(2)
C(34)–Sn(2)–C(30)
C(30)–Sn(2)–O(2)
O(7)–Sn(2)–O(5)
O(7)–Sn(2)–O(2)
O(7)–Sn(2)–C(34)
C(1)–O(1)–Sn(1)
C(8)–O(3)–Sn(1)
Sn(2)–O(7)–Sn(1)
151.6(8)
100.0(6)
97.2(6)
99.1(7)
83.2(7)
135.4(9)
88.5(7)
87.6(5)
C(22)–Sn(1)–O(3)
C(22)–Sn(1)–O(1)
C(22)–Sn(1)–O(7)
C(26)–Sn(1)–O(1)
O(3)–Sn(1)–O(1)
O(7)–Sn(1)–O(1)
O(7)–Sn(1)–O(3)
O(5)–Sn(2)–O(2)
O(5)–Sn(2)–C(30)
O(7)–Sn(2)–C(30)
C(1)–O(2)–Sn(2)
C(15)–O(5)–Sn(2)
97.4(7)
85.7(7)
106.8(7)
87.7(7)
160.0(5)
84.4(4)
77.8(4)
175.0(5)
92.9(7)
111.9(7)
138.0(13)
132.7(13)
87.4(5)
111.5(8)
142.8(12)
122.2(12)
140.2(6)
151.6(8)ꢁ in C(22)–Sn(1)–C(26), whereas for the C–Sn–
O(7), the mean value is only 100.0ꢁ.
Fig. 9. Molecular structure of complex 6.
Although the Sn atom environments are similar, there
are two distinct carboxylate groups in the structure. There
is a total of three 2,3,4,5-tetrafluorobenzoic acid ions in
the title complex. One of these is bidentate bridging and
bridges both the Sn atoms via O(1) and O(2) atoms.
These Sn–O bond distances, [Sn(1)–O(1) 2.275(12) and
˚
Sn(2)–O(2) 2.235(14) A] and the C–O bond distances
˚
[C(1)–O(1) 1.22(2), C(1)–O(2) 1.21(2) A] are dissimilar,
so that the bonds bridges the Sn atoms in an asymmetric
fashion. The other two carboxyl ligands coordinate to
each Sn atom in the monodentate mode via the O(3)
and O(5) atoms, respectively. The non-coordinating atoms
of these second carboxylate ligands, O(4) and O(6), are
orientated so that they are directed away from the rest
of the molecule. The hydroxy bridge is almost symmetri-
cal, the difference between Sn(1)–O(7) and Sn(2)–O(7)
˚
bond distances being only 0.095 A. The Sn–O and C–O
bond distances are non-equivalent between the bidentate
and the monodentate ligands. The Sn–O bond lengths
for the bidentate coordinating (2.235(14) and
˚
2.275(12) A) are both longer than those for Sn–O in the
˚
monodentate coordinating (2.153(12) and 2.183(11) A).
The difference in the C–O bond length in the bidentate
2,3,4,5-tetrafluorobenzoate is small, only 0.01 A, indicat-
Fig. 10. Unit cell of complex 8.
˚
ing delocalization of the double bond, whereas for the
monodentate 2,3,4,5-tetrafluorobenzoate the significant
difference of C–O bond character of one C–O at the
expense of the other C–O bond of the carboxylate. The
tin–carbon distances (mean value 2.12(2) A) appear to
be normal [25].
As shown in Fig. 11, the intermolecular C@O!Sn coor-
dination bonds are recognized, which associate the discrete
molecule into a eight-membered ring dimer structure, in
162.0(5)ꢁ, respectively, which is coupled with severe angu-
lar distortion in the equatorial planes. Angular distortion
in the equatorial planes seem to be only an effect on the
adjustment of bond angles according to the electronegativ-
ity of the attached groups [25]. The mutual repulsions
between the two butyl groups which are less electronegative
than the O-hydroxy result in expanding of the C–Sn–C
angle from 120ꢁ to 135.4(9)ꢁ in C(30)–Sn(2)–C(34) and to
˚

4188
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
Table 4
Crystal data and structure refinement parameters for complexes 2, 4, 8
Complex
2
4
8
Empirical formula
Formula weight
Crystal system
Space group
C60H76F16O10Sn4
1735.97
monoclinic
C2/c
18.174(6)
18.913(6)
20.921(7)
90
97.242(5)
90
C22H20F8O4Sn
619.07
triclinic
P1
4.955(2)
C37H40F12O7Sn2
1062.07
triclinic
ꢀ
P1
˚
a (A)
11.763(3)
12.196(3)
15.782(4)
107.520(4)
91.652(4)
91.264(4)
2
1.253
0.62 · 0.55 · 0.36
1.635
˚
b (A)
9.904(4)
˚
c (A)
12.252(5)
99.657(6)
97.299(6)
97.077(5)
1
1.190
0.42 · 0.36 · 0.28
1.768
a (ꢁ)
b (ꢁ)
c (ꢁ)
Z
4
Absorption coefficient (mmꢁ1
Crystal size (mm)
)
1.476
0.50 · 0.48 · 0.47
1.616
Dc (g cmꢁ3
)
h Range for data collection (ꢁ)
Reflections collected
2.37–25.01
18316
2.95–24.99
2973
2.42–25.01
11289
Unique reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
6267 (0.0435)
6267/21/416
1.007
2568 (0.0213)
2433/25/316
1.005
7457 (0.0449)
7457/38/527
0.994
Final R indices [I > 2r(I)]
R1 = 0.0495,
Wr2 = 0.1262
R1 = 0.0981,
Wr2 = 0.1720
R1 = 0.0435,
Wr2 = 0.1184
R1 = 0.0436,
Wr2 = 0.1185
R1 = 0.0672,
Wr2 = 0.1512
R1 = 0.1774,
Wr2 = 0.2147
R indices (all data)
˚
which O–Sn distances are 2.183 and 2.636 A, respectively.
In contrast, the geometry about the Sn(1) atom is based
on a trigonal bipyramid with the two butyl groups and
the hydroxyl group defining the trigonal plane and two O
(carboxyl) atoms occupying apical axial positions.
In Fig. 12(a), the 1D chain of ring structure is connected
via intermolecular non-bonded Fꢀ ꢀ ꢀSn and Fꢀ ꢀ ꢀF weak
interaction, forming a centrosymmetric macrocycle with a
The Oꢀ ꢀ ꢀO, O–Hꢀ ꢀ ꢀO distances and the O–Hꢀ ꢀ ꢀO angle
˚
˚
are 2.634 A, 1.798 A and 149.19ꢁ, respectively. In the
dimerization, there are two tin environments: the Sn(2)
atom geometry is distorted octahedral with the two trans-
n-butyl groups and four O atoms from two carboxyl
groups, and two n-butyl C occupy apical axis positions.
˚
Fig. 11. The dimer structure via O!Sn coordination. The intramolecular O–Hꢀ ꢀ ꢀO hydrogen bonds distance and the O–Hꢀ ꢀ ꢀO angle are 2.648 A and
˚
1.819 A and 147.17ꢁ, respectively. (For clarity, the butyl groups are omitted.)

C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
4189
Fig. 12. The supramolecular structure of complex 8. (a) 1D chain structure connected by intermolecular C–Hꢀ ꢀ ꢀF interaction and non-bonded Fꢀ ꢀ ꢀSn and
Fꢀ ꢀ ꢀF interaction. (For clarity, the butyl groups are omitted.) (b) 1D chain structure connected by the intermolecular C–Hꢀ ꢀ ꢀF hydrogen bonds. (The
excessive hydrogen atoms are omitted for clarity.)
head-to-tail arrangement [26]. The distances are 3.600 and
2.949 A, respectively, which are significantly considerably
Acknowledgement
˚
smaller than the corresponding sum of van der Waals radii
(3.70 and 2.98 A) [21]. The dimer of the complex 8 are fur-
We thank the National Natural Science Foundation of
China (20271025) for financial support.
˚
ther linked by intermolecular C–Hꢀ ꢀ ꢀF weak hydrogen
bonds and formed a infinite 1D infinite chain structure
[Fig. 12(b)]. The C–Hꢀ ꢀ ꢀF distances are 2.539, 2.665, and
References
˚
[1] C.J. Evans, S. Karpel, Organotin compounds in modern technology,
J. Organomet. Chem. Library, 16, Elsevier, Amsterdam, 1985.
[2] (a) E.R.T. Tiekink, Appl. Organomet. Chem. 1 (1991) 5;
(b) S.G. Teoh, E.S. Looi, S.B. Teo, S.W. Ng, J. Organomet. Chem.
50 (1996) 957.
[3] J.T. Welch, Tetrahedron 43 (1987) 3123.
[4] (a) M. Gielen, A. El Khloufi, M. Biesemans, R. Willem, Appl.
Organomet. Chem. 7 (1993) 119;
2.613 A, respectively, which are smaller than the sum of
˚
van der Waals radii (2.67 A) [21]. The corresponding angles
are 159.51ꢁ, 164.50ꢁ and 155.82ꢁ, respectively, which are
consistent with those reported by Dautel [27]. Despite these
weak C–Hꢀ ꢀ ꢀF, Fꢀ ꢀ ꢀSn and Fꢀ ꢀ ꢀF interaction often being
neglected, they clearly govern these self-assembly of the
molecules into 1D chain structure.
(b) M. Gielen, M. Biesemans, A. El. Khloufi, J. Meunier-Piret, F.
Kayser, R. Willem, J. Fluorine Chem. 64 (1993) 279;
(c) M. Gielen, A. El Khloufi, D. de Vos, H.J. Kolker, J.H.M.
Schellens, R. Willem, Bull. Soc. Chim. Belg. 102 (1993) 761;
(d) M. Gielen, A. El Khloufi, M. Biesemans, F. Kayser, R. Willem,
Appl. Organomet. Chem. 7 (1993) 201;
5. Supplementary material
Crystallographic data (excluding structure factors) for
the structure reported in this paper (2, 4, and 8) have been
deposited with the Cambridge Crystallographic Data Cen-
ter as Supplementary Publication Nos. CCDC – 600208
(for 2), 600207 (for 4), 600206 (for 8). Copies of the data
can be obtained free of charge on application to the Direc-
tor, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk
or http://www.ccdc.cam.ac.uk).
(e) M. Gielen, M. Boualam, A. Meriem, B. Mahieu, M. Biesemans,
R. Willem, Heteroatom. Chem. 3 (1992) 449.
[5] Siang-Guan Teoh, Show-Hing Ang, Eng-Seng Looi, Chye-Aun
Keok, J. Organomet. Chem. 523 (1996) 75.
[6] Vadapalli Chandrasekhar, Selvarajan Nagendran, Chem. Commun.
(2003) 862.
[7] R.R. Holmes, C.G. Schmid, V. Chandrasekhar, R.O. Day, J.M.
Homels, J. Am. Chem. Soc. 109 (1987) 1048.
[8] G.K. Sandhu, R. Hundal, J. Organomet. Chem. 412 (1991) 31.

4190
C. Ma et al. / Inorganica Chimica Acta 359 (2006) 4179–4190
[9] M. Gielen, M. Melotte, G. Atassi, R. Willem, Tetrahedron 45 (1989)
1219.
[19] (a) R. Faggiani, J.P. Johnson, I.D. Brown, T. Birchall, Acta
Crystallogr. B 34 (1978) 3743;
[10] C.L. Ma, Y.F. Han, R.F. Zhang, D.Q. Wang, Eur. J. Inorg. Chem.
(2005) 3024.
(b) G. Valle, V. Peruzzo, G. Tagliavini, P. Ganis, J. Organomet.
Chem. 276 (1984) 325;
[11] G.K. Sandhu, R. Gupta, S.S. Sandhu, R.V. Parish, Polyhedron 4
(1985) 81.
(c) T. Birchall, C.S. Frampton, J.P. Johnson, Acta Crystallogr. C 43
(1987) 1492.
[12] G.K. Sandhu, N. Sharma, E.R.T. Tiekink, J. Organomet. Chem. 403
(1991) 119.
[20] E.R.T. Tiekink, Appl. Organomet. Chem. 5 (1991) 1.
[21] A. Bondi, J. Phys. Chem. 68 (1964) 441.
[13] V. Peruzzo, G. Plazzogna, G. Tagliavini, J. Organomet. Chem. 40
(1972) 121.
[22] Vadapalli Chandrasekhar, Selvarajan Nagendran, Viswanathan Bas-
kar, Coord. Chem. Rev. 235 (2002) 1.
[14] (a) J. Holecˇek, A. Lycˇka, Inorg. Chim. Acta 118 (1986) L15;
(b) T.P. Lockhart, F. Davidson, Organometallics 6 (1987) 2471;
(c) T.P. Lockhart, W. Manders, J. Am. Chem. Soc. 109 (1987) 7015.
[15] C.H. Yoder, L.A. Margolis, J.M. Horne, J. Organomet. Chem. 633
(2001) 33.
[23] K.C.K. Swamy, C.G. Schmid, R.O. Day, R.R.J. Holmes, Am. Chem.
Soc. 112 (1990) 223.
[24] (a) R.R. Holmes, Acc. Chem. Res 22 (1989) 190;
(b) R.O. Day, J.M. Holmes, V. Chandrasekhar, R.R. Holmes, J.
Am. Chem. Soc 109 (1987) 940.
[16] J. Otera, J. Organomet. Chem. 221 (1981) 57.
[25] R. Graziani, G. Bombieri, E. Forsellini, P. Furlan, V. Peruzzo, G.
Tagliavini, J. Organomet. Chem. 125 (1977) 43.
[26] D.L. Reger, J.R. Gardinier, R.R. Semeniuc, M.D. Smith, Dalton
Trans. (2003) 1712.
´
´
´
[17] J. Holecˇek, A. Lycˇka, K. Handlır, M. Nadvomık, Collect. Czech.
Chem. Commun. 55 (1990) 1193.
[18] T.P. Lockhart, W.F. Manders, E.M. Holt, J. Am. Chem. Soc. 108
(1986) 6611.
[27] O.J. Dautel, M.F. Ourmigue, J. Org. Chem. 65 (2000) 6479.