Catalytic oxidation of diorganotin(IV) carboxylates to mixed-ligand monoalkyltin(IV) carboxylates by Ag+ and structure characterization of the mixed-ligand monoalkyltin(IV) 2-pyridinecarboxylate (2-ClPhCH2)Sn(2-ClPhCO2)(O<

Article abstract of DOI:10.1016/j.jorganchem.2006.02.037

The complexes of the type (ArCH₂)₂SnO were catalytic-oxygenated by Ag⁺ and yielded mixed-ligand organotin(IV) complexes (ArCH₂)(2-C₅H₄NCO₂)₂(ArCOO)tin(IV) (Ar = C

Full text of DOI:10.1016/j.jorganchem.2006.02.037

Journal of Organometallic Chemistry 691 (2006) 3331–3335
www.elsevier.com/locate/jorganchem
Catalytic oxidation of diorganotin(IV) carboxylates to mixed-ligand
monoalkyltin(IV) carboxylates by Ag+ and structure characterization
of the mixed-ligand monoalkyltin(IV) 2-pyridinecarboxylate
(2-ClPhCH2)Sn(2-ClPhCO2)(O2CC5H4N-2)2
*
Hao Long Xu, Han Dong Yin , Zhong Jun Gao, Gang Li
Department of Chemistry, Liaocheng University, Liaocheng 252059, China
Received 30 January 2006; received in revised form 16 February 2006; accepted 24 February 2006
Available online 6 March 2006
Abstract
The complexes of the type (ArCH2)2SnO were catalytic-oxygenated by Ag+ and yielded mixed-ligand organotin(IV) complexes
(ArCH2)(2-C5H4NCO2)2(ArCOO)tin(IV) (Ar = C6H5 (1), 2-ClC6H4 (2), 2-CNC6H4 (3), 4-ClC6H4 (4), 4-CNC6H4 (5), 2-FC6H4 (6)).
The complexes 1–6 are characterized by elemental analyses, IR and NMR (1H, 13C, 119Sn) spectroscopies. Single X-ray crystal structure
analysis has been determined, which reveals that the center tin atom of complex 2 is seven-coordinated geometry.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Diorganotin oxide; Mixed-ligand; 2-Pyrazinecarboxylic acid; Synthesis; Catalytic oxidation; Crystal structure
1. Introduction
which may lead to complexes with different activity
[9,11,13,14].
The chemistry of organotin(IV) complexes has devel-
oped considerably during last 30 years, highlighting the
syntheses of a number of complexes with interesting prop-
erties [1–3]. Organotin carboxylates are widely used owing
to their potential biocidal activity [4] and cytotoxicity [5] as
well as their industrial and agricultural applications [6–10].
In general, the biocidal activity of organotin complexes
is greatly influenced by the molecular structures and coor-
dination number of the tin atoms [11]. Crystallographic
studies have reveal that organotin carboxylates adopt
structures which are dependent on both the nature of the
substitute bond to the tin atom and on the type of carbox-
ylate ligand [12,13]. Studies on organotin(IV) derivatives
containing carboxylate ligands with additional donor
atom, such as nitrogen, have revealed new structural types
Less attention has been devoted to the mixed-ligand
complexes [15]. To the best of our knowledge, no organo-
tin(IV) complexes presenting as the seven-coordinate
mixed-ligand complex has ever been obtained by means of
catalytic oxidation: oxidating R2Sn group. Differing from
the methods of adding two different types of ligands into
SnR2 group to obtain a mixed-ligand complex, in this paper,
we introduce a novel means and obtained new mixed-ligand
complexes (Scheme 1). All the complexes had been charac-
terized by FT-IR, 1H, 13C, and 119Sn NMR spectroscopies,
elemental analyses. They are stable in air. Single X-ray crys-
tal structure analyses have been determined for complex 2,
and the result of this study is reported herein.
2. Experimental
2.1. Materials and measurements
*
The (ArCH2)2SnO was prepared by the reported method
[16]. The melting points were obtained with Kofler
Corresponding author. Tel.:/fax: +86 6358239121.
E-mail address: handongyin@lctu.edu.cn (H.D. Yin).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.02.037

3332
H.L. Xu et al. / Journal of Organometallic Chemistry 691 (2006) 3331–3335
O2/Ag+
Ac-
140.23, 143.8, 146.1, 147.7, 150.7 (C5H4N1–), 177.04,
-H2O
[(ArCH2)2SnL2]
[(ArCH2)(ArCOO)SnL2]
(ArCH2)2SnO + 2HL
180.27 (COO). 119Sn NMR (CDCl3, ppm): ꢀ412.5.
COO-
L =
N
2.2.3. (2-CN-PhCH2)Sn(2-CN-PhCO2)(O2CC5H4N-2)2
(3)
Scheme 1.
Yield: 56.4%. M.p. 192–194 °C. Anal. Calc. for
C28H18N4O6Sn: C, 53.79; H, 2.90; N, 8.96. Found: C,
53.78; H, 2.93; N, 8.96%. IR (KBr, cmꢀ1): mas(COO),
1654, 1576; ma(COO), 1403, 1329; m(C@N), 1550; m(Sn–C),
560; m(Sn–O), 485; m(Sn–N), 456. 1H NMR (CDCl3,
ppm): d 3.25 (s, 2H, JSn–H = 77 Hz, SnCH2), 7.04–7.69
(m, 8H, Ph–H), 8.63–9.22 (m, 8H, pyrazine-H). 13C
NMR (CDCl3, ppm): d 29.61 (CH2Ar, 1J(119Sn–13C),
588 Hz), 129.02, 129.62, 131.15, 131.46, 133.43, 133.71
136.00, 136.37, 137.92, 138.45 140.11, 140.32 (Ar–C),
146.47, 146.94 (CN–), 141.15, 144.03, 146.17, 147.72,
150.52 (C5H4N1–), 172.55, 177.09 (COO). 119Sn NMR
(CDCl3, ppm): ꢀ403.7.
micro-melting points apparatus and were uncorrected.
Infrared spectra were recorded on a Nicole-460 spectro-
photometer using KBr discs and sodium chloride optics.
1H, 13C and 119Sn NMR spectra were recorded on a Mer-
cury Plus-400 NMR spectrometer. Chemical shifts are
given in ppm relative to Me4Si and Me4Sn in CDCl3 sol-
vent. Elemental analyses were performed on PE-2400-II
elemental analyzer.
2.2. Synthesis of (ArCH2)(2-C5H4NCO2)2(ArCOO)tin-
(IV) (Ar = C6H5 (1), 2-ClC6H4 (2), 2-CNC6H4 (3), 4-Cl
C6H4 (4), 4-CNC6H4 (5), 2-FC6H4 (6))
2.2.4. (4-Cl-PhCH2)Sn(4-Cl-PhCO2)(O2CC5H4N-2)2 (4)
Yield: 56.5%. M.p. 197–199 °C. Anal. Calc. for
C26H18Cl2N2O6Sn: C, 48.49; H, 2.82; N, 4.35. Found: C,
48.43; H, 2.86; N, 4.39%. IR (KBr, cmꢀ1): mas(COO),
1663, 1567; ms(COO), 1404, 1335; m(Sn–C), 563; m(Sn–O),
488; m(Sn–N), 454. 1H NMR (CDCl3, ppm): d 3.22 (s,
2H, JSn–H = 74 Hz, SnCH2), 7.36–7.68 (m, 8H, Ph–H),
8.612–9.20 (m, 8H, pyrazine-H). 13C NMR (CDCl3,
ppm): d 27.61 (CH2Ar, 1J(119Sn–13C), 583 Hz), 127.02,
127.41, 128.25, 128.77, 129.80, 130.14, 134.01, 134.44,
136.12, 136.30, 138.05, 138.54 (Ar–C), 139.97, 143.82,
146.15, 147.78, 150.71 (C5H4N1–), 177.01, 180.24 (COO).
119Sn NMR (CDCl3, ppm): ꢀ426.1.
The diorganotin oxide (2.0 mmol) and the 2-pyrazine-
carboxylic acid (4.0 mmol) were dissolved in dry benzene
(37 ml) and stirred at reflux for 7 h under nitrogen atmo-
sphere. After cooling to room temperature, then, the Sil-
ver(I) sulfite (0.312 g, 1.00 mmol) and CH3COONa
(0.06 g, 0.1 mol) were added to the solution and stirring
for 5 h under oxygen atmosphere. After cooling to room
temperature, the solvent was filtrated and evaporated
under vacuum. The crude adduct was recrystallized from
dichloromethane–hexane to give colorless crystals.
2.2.1. PhCH2Sn(PhCO2)(O2CC5H4N-2)2 (1)
Yield: 55%. M.p. 201–203 °C. Anal. Calc. for
C26H20N2O6Sn: C, 54.29; H, 3.50; N, 4.87. Found: C,
54.32; H, 3.53; N, 4.86%. IR (KBr, cmꢀ1): mas(COO),
1643, 1573; ms(COO), 1405, 1326; m(C@N), 1547; m(Sn–C),
568; m(Sn–O), 480; m(Sn–N), 448. 1H NMR (CDCl3,
ppm): d 3.07 (s, 2H, JSn–H = 75 Hz, SnCH2), 7.17–7.65
(m, 10H, Ph–H), 8.60–8.73 (m, 8H, pyrazine-H). 13C
NMR (CDCl3, ppm): d 29.55 (CH2Ar, 1J(119Sn–13C),
589 Hz), 126.41, 126.71 127.54, 127.92, 129.15,129.97,
132.05, 132.32, 133.45, 133.89, 135.63, 136.08 (Ar–C),
139.10, 142.43, 145.91, 146.58, 150.74 (C5H4N1–), 175.31,
178.27 (COO). 119Sn NMR (CDCl3, ppm): ꢀ432.1.
2.2.5. (4-CN-PhCH2)Sn(4-CN-PhCO2)(O2CC5H4N-2)2
(5)
Yield: 66.1%. M.p. 200–202 °C. Anal. Calc. for
C28H18N4O6Sn: C, 53.79; H, 2.90; N, 8.96. Found: C,
53.74; H, 2.95; N, 8.95%. IR (KBr, cmꢀ1): mas(COO),
1650, 1579; ma(COO), 1409, 1327; m(Sn–C), 561; m(Sn–O),
484; m(Sn–N), 454. 1H NMR (CDCl3, ppm): d 3.26 (s,
2H, JSn–H = 76 Hz, SnCH2), 7.03–7.69 (m, 8H, Ph–H),
8.65–9.27 (m, 8H, pyrazine-H). 13C NMR (CDCl3,
ppm): d 29.57 (CH2Ar, 1J(119Sn–13C), 589 Hz), 129.10,
129.60, 131.14, 131.45, 133.44, 133.71 136.03, 136.37,
137.92, 138.48 140.10, 140.33 (Ar–C), 146.49, 146.98
(CN–), 142.88, 144.09, 146.17, 147.78, 150.53
(C5H4N1–), 172.55, 177.04 (COO). 119Sn NMR (CDCl3,
ppm): ꢀ419.5.
2.2.2. (2-Cl-PhCH2)Sn(2-Cl-PhCO2)(O2CC5H4N-2)2 (2)
Yield: 37%. M.p. 189–191 °C. Anal. Calc. for
C26H18Cl2N2O6Sn: C, 48.49; H, 2.82; N, 4.35. Found: C,
48.46; H, 2.85; N, 4.36%. IR (KBr, cmꢀ1): mas(COO),
1669, 1569; ms(COO), 1401, 1337; m(C@N), 1557; m(Sn–C),
564; m(Sn–O), 487; m(Sn–N), 454. 1H NMR (CDCl3,
ppm): d 3.30 (s, 2H, JSn–H = 74 Hz, SnCH2), 7.39–7.71
(m, 8H, Ph–H), 8.62–9.23 (m, 8H, pyrazine-H). 13C
NMR (CDCl3, ppm): d 27.6 (CH2Ar, 1J(119Sn–13C),
586 Hz), 127.01, 127.40, 128.28, 128.73, 129.83, 130.14,
134.02, 134.45, 136.10, 136.31, 138.0, 138.51 (Ar–C),
2.2.6. (2-FPhCH2)Sn(2-FPhCO2)(O2CC5H4N-2)2 (6)
Yield: 35%. M.p. 172–174 °C. Anal. Calc. for
C26H18F2N2O6Sn: C, 51.10; H, 2.97; N, 4.58. Found: C,
50.05; H, 3.00; N, 4.58%. IR (KBr, cmꢀ1): mas(COO),
1667, 1572; ma(COO), 1404, 1337; m(Sn–C), 558; m(Sn–O),
488; m(Sn–N), 452. 1H NMR (CDCl3, ppm): d 3.28 (s,
2H, JSn–H = 79 Hz, SnCH2), 7.49–7.89 (m, 6H, Ph–H),
8.63–9.23 (m, 8H, pyrazine-H). 13C NMR (CDCl3, ppm):

H.L. Xu et al. / Journal of Organometallic Chemistry 691 (2006) 3331–3335
3333
C6H5CHꢀ is replaced by CH3COOꢀ, and the active
Table 1
2
C6H5CHꢀ ion were catalytic oxidated to C6H5COOꢀ by
Crystal data collection and structure refinement parameters for complex 2
2
Ag+ under oxygen atmosphere, then, the C6H5COOꢀ
replaces CH3COOꢀ as bidentate ligand and yielded
mixed-ligand organotin(IV) complexes (ArCH2)(2-C5H4-
NCO2)2(ArCOO)tin. The possible mechanism is given in
Scheme 2.
Empirical formula
M
C26H18Cl2N2O6Sn
644.01
298(2)
Monoclinic, P2(1)/c
7.555(2)
16.317(6)
T/K
Crystal system, space group
˚
a (A)
˚
b (A)
˚
c (A)
20.152(7)
b (°)
92.682(4)
2481.4(14)
4
3.2. Spectroscopic studies
3
˚
V (A )
Z
Calculated density (Mg mꢀ3
)
1.724
3.2.1. IR spectra
The stretching frequencies of interesting are those asso-
ciated with the acid COO, Sn–C, Sn–O and Sn–N groups.
The spectra of the complexes 1–6 show some common
characters. The assignments of the IR bands of the com-
plexes 1–6 have been made by comparison with the IR
spectra of the free ligands. The free acid shows a broad
O–H absorption at 3000–2500 cmꢀ1, which is absent in
the spectra of the eight title compounds, showing the
deprotonation of the COOH groups, during the reactions.
The explicit feature in the infrared spectra of the com-
plexes, strong absorption appearing at 480–488 cmꢀ1 in
the respective spectra of the complexes, which is absent
in the free ligand, is assigned to the Sn–O stretching mode
of vibration. Compared with the free ligand the new occur-
rence of the bands in the region of 448–456 cmꢀ1 for all the
eight compounds were assigned to the Sn–N vibrations,
which provides prove for the existence of Sn–N bonds for
all of the six complexes [17].
F(000)
1280
1.291
2.02–5.01
l (mmꢀ1
)
Scan range h (°)
Reflections collected/unique [Rint
Data/restraints/parameters
Maximum/minimum transmission
GOF
R1, wR2 [I > 2r(I)]
R1, wR2 (all data)
Largest difference peak, hole (e A
]
12367/4299 [0.0566]
4299/126/334
0.7384, 0.6131
0.999
0.0610, 0.1530
0.0948, 0.1750
2.208, ꢀ0.726
ꢀ3
˚
)
d 35.0 (CH2Ar, 1J(119Sn–13C), 594 Hz), 129.34, 129.95,
138.51, 139.018, 140.66, 141.14, 141.75, 142.51, 135.31,
135.87, 131.64, 132.29 (Ar–C), 142.95, 143.53, 146.71,
148.26, 150.82 (C5H4N1–), 173.54, 175.08 (COO). 119Sn
NMR (CDCl3, ppm): ꢀ438.9.
2.3. X-ray crystallographic studies
X-ray crystallographic data for complexes 2 were col-
The Dm (mas(CO2) ꢀ ms(CO2)) value is used to determine
the type of bonding between metal and carboxyl group
[18]. It is generally believed that the difference in Dm between
asymmetric mas(CO2) and symmetric ms(CO2) absorption
frequencies below 200 cmꢀ1 for the bidentate carboxylate
moiety, but greater than 200 cmꢀ1 for the unidentate car-
boxylate moiety [19,20]. Some obvious differences among
the spectra of the complexes are also observed. In com-
plexes 1–6, the presence of two values for each of mas(CO2)
and ms(CO2) indicates that there are two different types of
carboxylate groups. The two bands which occur at 1643–
1667 and 1567–1579 cmꢀ1 were assigned to mas(CO2), while
the bands at 1326–1337 and 1401–1409 cmꢀ1 were assigned
to ms(CO2). The magnitudes of Dm1 [mas(CO2)1 ꢀ ms(CO2)1]
and Dm2 [mas(CO2)2 ꢀ ms(CO2)2] for complexes 1–6 are
317–332 and 163–173 cmꢀ1 which indicate the presence of
bidentate and monodentate carboxylate groups in these
complexes [21,22].
lected on a Bruker Smart-1000 CCD diffractometer using
Mo Ka radiations (0.71073 A). The structures were solved
˚
by direct method and difference Fourier map using SHELXL-
97 program, and refined by full-matrix least-squares on F2.
All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were located at calculated positions and
refined isotropically. Further details are given in Table 1.
3. Results and discussion
3.1. Preparations
The diorganotin(IV) carboxylates, (ArCH2)2(2-C5H4-
NCO2)2tin(IV) were produced by the reaction of 2-pyrazin-
ecarboxylic acid with dibenzyltin oxide or bis(substituted-
benzyl)tin in 2:1 molar ratio, and the complexes
(ArCH2)(2-C5H4NCO2)2(ArCOO)tin(IV) were produced
by dibenzyltin carboxylates through oxidative cleavage of
one of benzyl-tin bonds. It is clear that the CH3COOꢀ
ion accelerates cleavage of one of benzyl-tin bonds, and
3.2.2. NMR spectroscopic
In 1H NMR spectra of the free ligand, single resonances
are observed at 8.43 ppm, which are absent in the spectra
of the complexes 1–6, indicating the replacement of the car-
boxylic acid proton by a organotin moiety. The spectra
show that the chemical shifts of the phenyl or the substi-
tuted phenyl, 7.03–7.89 and 8.60–9.27 ppm for the Py
group. All upfield shifts as compared with those of their
corresponding precursors. The six complexes generally
-
-
[(ArCH )(Ac)SnL ] + ArCH
2
(ArCH ) SnL + Ac
2
2
2 2
2
O2/Ag+
-
-
ArCOO
ArCH
2
-Ac-
+Ac-
-
[(ArCH )(ArCOO)SnL ]
[(ArCH )(Ac)SnL ] + ArCOO
2
2
2
2
Scheme 2.

3334
H.L. Xu et al. / Journal of Organometallic Chemistry 691 (2006) 3331–3335
Table 2
show broad signals for the protons of Py ligands, shifted to
high field with respect to the value for Py, which could be
interpreted in terms of the Sn N interaction.
˚
Selected bond lengths (A) and bond angles (°) of the complex 2
Sn(1)–O(5)
Sn(1)–O(3)
Sn(1)–O(1)
Sn(1)–C(20)
Sn(1)–N(2)
Sn(1)–N(1)
Sn(1)–O(2)
2.087(5)
2.143(5)
2.147(6)
2.164(8)
2.253(6)
2.255(6)
2.522(6)
The 13C NMR spectra of the complexes show a signifi-
cant upfield shift of all carbon resonance, compared with
the free ligand. The shift is a consequence of an electron
density transfer from the ligand to the acceptor.
119Sn NMR spectra of 1–6 display only one resonance
and the 119Sn chemical shift values in complexes 1–6 are
found to be in the range of ꢀ403.7 to ꢀ438.9 ppm. The
appearance of chemical shift values in this region is agree-
ment with the seven-coordinated tin atom [23].
O(5)–Sn(1)–C(20)
O(1)–Sn(1)–O(2)
O(3)–Sn(1)–N(1)
O(1)–Sn(1)–N(1)
N(2)–Sn(1)–O(2)
O(3)–Sn(1)–N(2)
176.4(3)
54.5(2)
74.0(2)
80.6(2)
71.7(2)
77.2(2)
3.3. Crystal structure of (2-Cl-PhCH2)Sn(2-Cl-PhCO2)-
(O2CC5H4N-2)2 (2)
The molecular structure of 2 is shown in Fig. 1 and
selected bond lengths and bond angles are presented in
Table 2. It can be seen that the tin atom has a coordination
number of seven. There are two types of ligands, two 2-
pyridinecarboxylate and 2-chlorobenzoxylate, which are
found to be chelating to the Sn atom, respectively. The
Sn atom exits in a distorted-pentagonal-bipyramidal geom-
etry, with the axial positioning occupied by the 2-chlorob-
enzyl and one O-atom of one 2-pyridinecarboxylate
moiety. And the O(5)–Sn(1)–C(20) linkage is not linear,
having an angle of 176.4(3), which is smaller than the value
expected for a regular pentagonal-bipyramid. This coordi-
nation geometry is best described as distorted-pentagonal-
bipyramid. Another important distortion is caused by the
asymmetric Sn–O bond lengths, since there are two types
of O atoms. The pentagonal plane is defined by the O(1)
and O(2) atoms of the 2-chlorobenzoxylate group, the
N(2) atom of the 2-pyridinecarboxylate moiety, the O(3)
and N(1) atoms of the other 2-pyridinecarboxylate moiety.
Fig. 2. The unit cell of complex 2.
˚
The O(2)–Sn(1) distance of 2.522(6) A is longer than O(1)–
The unit cell of complex 2 is shown in Fig. 2.
Sn(1) and O(3)–Sn(1) and O(5)–Sn(1) distances; of
˚
2.147(6), 2.143(5) and 2.087(5) A, respectively.
4. Supplementary material
Crystallographic data for complex 2 has been deposited
at the Cambridge Crystallographic Data Center as supple-
mentary publication numbers CCDC 291882. Copies of
available material may be obtained on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
+44 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk).
Acknowledgments
Authors acknowledge the financial support of the Shan-
dong Province Science Foundation, and the State Key Lab-
oratory of Crystal Materials, Shandong University, PR
China.
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