Synthesis and characterization of diorganotin(IV) complexes bearing binary schiff-bases and crystal structure of nBu2SnL1

Article abstract of DOI:10.1002/zaac.200900362

Four novel diorganotin(IV) complexes with general formula R₂SnL (R = nBu, PhCH₂) were synthesized from diorganotin dichlorides and binary Schiff-bases (H₂L) containing N₂O₂ donor atoms in the presence

Full text of DOI:10.1002/zaac.200900362

ARTICLE
DOI: 10.1002/zaac.200900362
Synthesis and Characterization of Diorganotin(IV) Complexes Bearing
Binary Schiff-Bases and Crystal Structure of nBu2SnL1
Qibao Wang,*[a] Ruifang Ding,[a] Ning Wang,[a] Daodong Zhang,[a] and Jikun Li[b]
Keywords: Diorganotin(IV) complexes; X-ray diffraction; Tin; Schiff bases; Antitumor agents
Abstract. Four novel diorganotin(IV) complexes with general formula ylbenzaldehyde (H2L1) and salicylaldehyde (H2L2) respectively. The
R2SnL (R = nBu, PhCH2) were synthesized from diorganotin dichlo- compounds were characterized by elemental analyses, IR, and NMR
rides and binary Schiff-bases (H2L) containing N2O2 donor atoms in spectroscopy. The solid-state crystal structure of the compound
the presence of sodium ethoxide. The Schiff bases were prepared by nBu2SnL1 was determined by single-crystal structural analysis.
reactions of o-phenylenediamine with 3-tert-butyl-2-hydroxy-5-meth-
Introduction
Organotin(IV) complexes with Schiff base ligands have been
extensively studied because of their antitumor activities [1–
15]. Particularly diorganotin(IV) complexes of deprotonated
Schiff bases have been the focus owing to the versatile coordi-
nation modes and biocide activities in recent years. Previous
studies were mostly related to diorganotin complexes of mono
Schiff bases [10–15]. However, to the best of our knowledge,
only a few studies on diorganotin complexes of binary Schiff
bases were carried out [16–22]. The structural investigation of
these complexes showed that the dianionic Schiff bases usually
act as multidentate ligands chelating to the central tin atom.
Herein we report the synthesis and characterization of four
Scheme 1.
novel diorganotin(IV) complexes with dianionic Schiff base
ligands. The crystal structure of the compound nBu2SnL1 was
confirmed by X-ray diffraction; it reveals that the dianionic
Schiff base coordinates in tetradentate manner to the central
tin atom.
The infrared spectra of the two Schiff bases and their diorga-
notin compounds were recorded along with the two diorgano-
tin dichloride complexes. In the IR spectra of compounds 1–
4, the weak O–H signals of the starting material in the region
3250–2350 cm–1 disappeared, which indicates that the reac-
tions have taken place through the replacement of the phenolic
hydrogen in the four compounds [18]. The CH=N signals of
compound 1 exhibit two bands at 1611 and 1607 cm–1 respec-
tively, whereas in compounds 2–4 the CH=N signals were
found in the region 1608–1613 cm–1 as one band, which indi-
cates that in compound 1 the two CH=N groups are probably
inequivalent; this conjecture was verified by X-ray diffraction.
In compounds 1–4, the CH=N signals were considerably
shifted to lower frequencies with respect to those of the free
Schiff bases (1627 and 1618 cm–1 for H2L1 and H2L2, respec-
tively), which confirms the coordination of the azomethine ni-
trogen atom to the diorganotin(IV) moiety [10].
Results and Discussion
Preparation and Characterization
Compounds 1–4 were prepared by salt metathesis reactions
of the corresponding sodium salts with dibutyltin dichlorides
and dibenzyltin dichlorides in 1:1 ratio. Crystals of 1–4 are
stable at ambient conditions and nonsensitive to moisture (see
Scheme 1)
* Dr. Q. Wang
E-Mail: wqb_wangqibao@163.com
[a] Department of Pharmacy
Jining Medical College
Xueyuan Road 669
In the 1H NMR spectra, the absence of the O–H proton signal
suggested the replacement of the phenolic protons for com-
pounds 1–4, which is in accordance with the information of
276826 Rizhao, P. R. China
[b] Department of Materials and Chemical Engineering
Taishan University
Taian, P. R. China
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
861

Q. Wang, R. Ding, N. Wang, D. Zhang, J. Li
ARTICLE
the infrared data. The chemical shift of the azomethine (HC= bow shaped towards the C31 atom. The four donor atoms O1/
N) proton resonances exhibit singlet signals at δ = 8.33–8.47 O2/N1/N2 and the Sn1 atom are almost coplanar with the
for compounds 1–4, which indicate that the two CH=N groups mean deviation 0.0493 Å. The two n-butyl groups are bending
are equivalent in solution. The singlet signal of the methyl and to one side of the N/O chelating part. Three carbon atoms of
tert-butyl groups for compound 1 and 2 gave another evidence one n-butyl group are disordered, and was refined with sof
for the symmetric arrangement of the two CH=N groups in 0.49 and 0.51, respectively. Therefore, the two n-butyl groups
solution, from which it can be inferred that compounds 1–4 are asymmetrical and as a result the whole molecule is asym-
adopt symmetric arrangement in solution [17].
metrical in the solid state (Figure 1).
The axial angle C(31)–Sn(1)–C(35) [156.30(14)°] is similar
The 13C NMR spectra were recorded at room temperature
in CDCl3. The CH=N carbon signal is shifted downfield for with the compound (nBu)2Sn(Vanophen) reported by Dey et
compounds 1–4 with respect to the Schiff base ligands, which al. [17]. The bond lengths Sn(1)–O(1) [2.2440(19) Å] and
indicates the coordination of the azomethine nitrogen atoms to Sn(1)–N(1) [2.283(2) Å] from the one side are slightly shorter
tin. For compounds 1–4, the CH=N carbon atoms show singlet than Sn(1)–O(2) [2.221(2) Å] and Sn(1)–N(2) [2.265(2) Å]
signals at δ = 167.1–170.2, which indicate that the two CH=N from the other side because of the bulky effect of the tert-butyl
groups in compounds 1–4 are equivalent. This is in accordance group. As a result the two Sn–C bonds are also inequivalent
1
with the results of the H NMR spectroscopic data.
[2.131(3) and 2.143(3) Å]. The Sn–O bond lengths are similar
The 119Sn NMR spectroscopic signals in compounds 1–4 are to those in (nBu)2Sn(Vanophen) [2.2347(16) and
found to be in the range of –419 to –477 ppm. The appearance 2.2374(16) Å] and Me2Sn(Vanophen) [2.236(2) and
of chemical shift values in this region indicates a hexacoordi- 2.197(1) Å] [18]. The Sn–N bond lengths are also similar to
nate environment [10, 17] around the central tin atoms in these those in the (nBu)2Sn(Vanophen) [2.266(2), 2.2797(19) Å]
compounds.
[17] and R2Sn(Vanophen) (R = Me, Ph) species [18].
Crystal and Molecular Structures
Conclusions
In the solid-state structure of compound 1, the ligand acts as
tetradentate ligand through two phenolic oxygen and two im-
ino nitrogen atoms. The central tin atom is octacoordinate in a
skew-trapezoidal bipyramidal arrangement. The two tin-
bounded n-butyl groups occupy the axial positions and four
donor atoms O1/O2/N1/N2 from the ligand are in the equato-
rial plane. The ligand is not completely planar, but slightly
Four novel diorganotin(IV) complexes bearing binary Schiff
base ligands were prepared by salt metathesis reactions of the
corresponding sodium salts with dibutyltin dichlorides and di-
benzyltin dichlorides in 1:1 ratio, respectively. The solid-state
crystal structure of the compound nBu2SnL1 was determined
by single-crystal structural analysis. Studies showed that in the
solid state the molecule is asymmetrical, whereas it adopts a
symmetric arrangement in solution.
Experimental Section
All experimental manipulations were carried out under nitrogen atmos-
phere using standard Schlenk techniques. Dibenzyltin dichloride was
prepared according to the published method [23]. All other chemicals
were obtained from commercial supplies and used without further puri-
fication. The solvents were purified according to conventional proce-
dures and were freshly distilled prior to use. NMR spectra were re-
corded with a Bruker Avance 300 spectrometer.
Preparation of Schiff Base H2L1 and H2L2
The Schiff bases were prepared by heating 5-tert-butyl-2-hydroxy-3-
methylbenzaldehyde and salicylaldehyde, respectively with o-phenyl-
enediamine in ethanol in 2:1 ratio under reflux. The orange-red precipi-
tates were washed with ethanol and used without further purification.
Figure 1. Solid-state structure of compound 1, all the hydrogen atoms
are omitted for clarity. Selected bond lengths /Å and angles /° for
compound 1: Sn(1)–C(31) 2.131(3); Sn(1)–C(35) 2.143(3); Sn(1)–
O(2) 2.221(2); Sn(1)–O(1) 2.2440(19); Sn(1)–N(2) 2.265(2); Sn(1)–
N(1) 2.283(2); N(1)–C(7) 1.297(4); N(2)–C(19) 1.299(4); C(31)–
Sn(1)–C(35) 156.30(14); C(31)–Sn(1)–O(2) 86.32(12); C(35)–Sn(1)–
O(2) 87.06(11); C(31)–Sn(1)–O(1) 81.17(11); C(35)–Sn(1)–O(1)
86.49(10); O(2)–Sn(1)–O(1) 132.03(7); C(31)–Sn(1)–N(2) 100.29(12);
C(35)–Sn(1)–N(2) 100.70(11); O(2)–Sn(1)–N(2) 78.89(8); O(1)–
Sn(1)–N(2) 148.88(8); C(31)–Sn(1)–N(1) 101.62(13); C(35)–Sn(1)–
N(1) 95.15(11); O(2)–Sn(1)–N(1) 150.98(8); O(1)–Sn(1)–N(1)
76.98(8); N(2)–Sn(1)–N(1) 72.26(9).
Preparation of nBu2SnL1 (1)
A solution of H2L1 (1 mmol, 0.455 g) in dichloromethane (20 mL)
was added to C2H5ONa (2 mmol, 0.136 g). After the mixture was
stirred at room temperature for 0.5 h, it took a yellow color. After-
wards, a solution of dibutyltin(IV) dichloride (1 mmol, 0.304 g) in
dichloromethane (15 mL) was added. The suspension was stirred over-
862
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Diorganotin(IV) Complexes with Binary Schiff-Bases
night, afterwards it was filtered through Celite. The filtrate was evapo- package. Three carbon atoms (C32, C33, and C34) of one of the tin-
rated to dryness under reduced pressure. The residue was recrystallized bound butyl groups were found to be disordered, and were refined with
from acetonitrile to give compound 1 as fine block orange-red crystals the site occupy factors 0.49 and 0.51. A summary of crystal data and
suitable for X-ray diffraction. Yield: 0.483 g, 70 %. Elemental analy- refinement parameters is given in Table 1.
sis: C38H52N2O2Sn (687.54): calcd. C 66.38; H 7.62; N 4.07 %; found
C 66.20; H 7.51; N 4.25 %. IR (KBr): ν = 3055 m, 1611 s, 1607 s,
˜
Table 1. Details of the X-ray data collections and refinements of com-
pound 1.
1
607 m, 579, 481 m cm–1. H NMR (300 MHz, CDCl3, 297 K): δ =
0.66 [t, 6 H, Sn–(CH2)3CH3], 0.83–1.51 [m, 12 H, Sn–(CH3)3–], 1.41
Formula
C38H52N2O2Sn
(s 18 H, Ar–tBu), 2.06 (s, 6 H, Ar–CH3), 6.73–7.41 (m, 8 H, Ar–H),
8.41 (s, 2 H, CH=N). 13C NMR (75 MHz, CDCl3, 297 K): δ = 168.7 Crystal system
Monoclinic
0.35 x 0.30 x 0.25
P21/c
Crystal size / mm
Space group
a /Å
(CH=N), 163.2, 147.9, 141.6, 138.0, 132.4, 130.0, 127.1, 123.5, 117.4
(Ar–C), 34.5, 30.1, 28.0, 26.8, 25.9, 19.6, 13.1 (aliphatic–C). 119Sn
NMR (33.35 MHz, CDCl3, 297 K): δ = –427.
23.167(3)
7.8214(11)
20.415(3)
105.717(2)
3560.8(9)
4
b /Å
c /Å
β /°
Preparation of (PhCH2)2SnL1 (2)
V /Å3
Z
The preparation follows the procedure described for compound 1.
Yield 76 %. Elemental analysis: C44H48N2O2Sn (755.57): calcd. C
Diffractometer
Temperature /K
μ (radiation used) /cm–1
Trans. factors
Dcalcd /g·cm–3
F(000)
CCD area detector
273(2)
0.751
69.94; H 6.40; N 3.71 %; found C 69.81; H 6.55; N 3.77 %. IR (KBr):
1
ν = 3057 m, 1613 vs, 596 m, 568, 447 m cm–1. H NMR (300 MHz,
˜
CDCl3, 297 K): δ = 1.39 (s, 18 H, Ar–tBu), 2.07 (s, 6 H, Ar–CH3),
1.282
1440
25.03
2.73 (s, 4 H, PhCH2–), 6.72–7.49 (m, 18 H, Ar–H), 8.33 (s, 2 H, CH=
N). 13C NMR (75 MHz, CDCl3, 297 K): δ = 167.1 (CH=N), 163.8, θmax /°
Reflns meas.
149.6, 144.8, 143.7, 137.6, 133.4, 132.5, 128.3, 127.5, 126.4, 124.1,
123.9, 116.8 (Ar–C), 34.1, 30.5, 19.3 (aliphatic–C), 30.1 (PhCH2Sn).
119Sn NMR (33.35 MHz, CDCl3, 297 K): δ = –477.
Reflns unique, Rint
Reflns with I ≥ nσ(I)
Weighting Scheme
R(F or F2), Rw(F or F2)
ρ /e·Å–3
6280,0.0924
5307
calcd.
0.0358, 0.0953
0.592, –0.715
SHELXS-97
Preparation of nBu2SnL2 (3)
Programs used
The preparation follows the procedure described for compound 1.
Yield 81 %. Elemental analysis: C28H32N2O2Sn (547.27): calcd. C
66.45; H 5.89; N 5.12 %; found C 66.37; H 5.91; N 5.20 %. IR (KBr):
˜
Crystallographic data for the structures have been deposited with
the Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB21EZ. Copies of the data can be obtained on quoting
the depository numbers CCDC-749851. (Fax: +44-1223-336-033;
E-Mail: deposit@ccdc.cam.ac.uk).
1
ν = 3047 m, 1608 vs, 605 m, 574, 487 m cm–1. H NMR (300 MHz,
CDCl3, 297 K): δ = 0.63 [t, 6 H, Sn–(CH2)3CH3], 0.84–1.53 [m, 12
H, Sn–(CH3)3], 6.67–7.54 (m, 12 H, Ar–H), 8.47 (s, 2 H, CH=N). 13C
NMR (75 MHz, CDCl3, 297 K): δ = 170.2 (CH=N), 161.8, 144.6,
138.1, 136.6, 129.7, 124.5, 120.6, 119.4, 115.3 (Ar–C), 29.7, 26.5,
25.4, 14.8 (aliphatic–C). 119Sn NMR (33.35 MHz, CDCl3, 297 K):
δ = –419.
Acknowledgement
This work was supported by the S&R Project-Starting Off Found of
JMC.
Preparation of (PhCH2)2SnL2 (4)
The preparation follows the procedure described for compound 1.
Yield 70 %. Elemental analysis: C34H28N2O2Sn (615.31): calcd. C
References
66.37; H 4.59; N 4.55 %; found C 66.34; H 4.46; N 4.61 %. IR (KBr):
1
ν = 3061 m, 1612 vs. 595 m, 557, 451 m cm–1. H NMR (300 MHz,
˜
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ARTICLE
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