New bis-o-benzosemiquinonato tin(IV) complexes

Article abstract of DOI:10.1016/j.ica.2012.08.018

New bis-o-benzosemiquinonato tin(IV) complexes (3,6-SQ) ₂SnCl₂, (3,6-SQ)₂SnBr₂ and (3,6-SQ)₂SnPh₂ (3,6-SQ is radical-anion 3,6-di-tert-butyl-o-benzosemiquinone) were synthesized by differen

Full text of DOI:10.1016/j.ica.2012.08.018

Inorganica Chimica Acta 394 (2013) 282–288
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
New bis-o-benzosemiquinonato tin(IV) complexes
a,
⇑
a
a
b
Ekaterina V. Ilyakina , Andrey I. Poddel’sky , Alexandr V. Piskunov , Nikolay V. Somov ,
a
a
Gleb A. Abakumov , Vladimir K. Cherkasov
a
G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhniy Novgorod, GSP 445, Russia
Nizhniy Novgorod State University, Physical Faculty, Building 3, Gagarina Av. 23, 603950 Nizhniy Novgorod, Russia
b
a r t i c l e i n f o
a b s t r a c t
Article history:
New bis-o-benzosemiquinonato tin(IV) complexes (3,6-SQ) SnCl , (3,6-SQ) SnBr and (3,6-SQ) SnPh2
2
2
2
2
2
Received 25 January 2012
Received in revised form 21 August 2012
Accepted 22 August 2012
Available online 31 August 2012
(
3,6-SQ is radical-anion 3,6-di-tert-butyl-o-benzosemiquinone) were synthesized by different methods.
The reaction of tin(IV) catecholates (3,6-Cat)SnX
Á2THF (X = Cl, Br) with nitrogen(IV) oxide leads to
EPR-active six-coordinated mono-o-benzosemiquinonato complexes of (3,6-SQ)SnX (NO
)ÁTHF type
which undergo symmetrization to the corresponding diradical bis-o-benzosemiquinonato species (3,
-SQ) SnX . Diphenyltin(IV) catecholate (3,6-Cat)SnPh , I and NO to give five-coor-
ÁTHF reacts with Br
dinated species (3,6-SQ)SnPh X (X = Br, I, NO ) which transform to bis-(o-benzosemiquinonato)diphenyl-
tin(IV) (3,6-SQ) SnPh . The molecular structures of (3,6-SQ) SnBr and (3,6-SQ) SnPh were determined
by X-ray analysis.
2
2
2
6
2
2
2
2
2
2
Keywords:
Tin(IV)
o-Benzosemiquinone
Radical-anion
EPR spectroscopy
X-ray analysis
2
2
2
2
2
2
2
2
Ó 2012 Elsevier B.V. All rights reserved.
1
. Introduction
The coordination chemistry of tin(IV) complexes containing re-
EMX (working frequency ꢀ9.7 GHz) spectrometer. The g
i
values
were determined using DPPH as the reference (g = 2.0037). HFC
i
constants were obtained by simulation with the WINEPR SIMFONIA Soft-
ware (Bruker).
X-ray diffraction data for 8 and 13 were collected using Oxford
Diffraction (Gemini S) diffractometer with graphite monochromat-
dox-active o-quinonato ligands is rapidly developing [1]. Despite
this, there are only two examples of bis-o-semiquinonato tin(IV)
complexes which have been isolated and characterized by physico-
chemical methods [2]. Some techniques to synthesize tin(IV) com-
plexes, based on o-quinonato ligands, such as interaction of tin
salts with o-quinones and o-semiquinonato alkali metal or thal-
lium derivatives, as well as fixation of small molecules, for example
halogens, by catecholate tin(IV) complexes are well known at pres-
ent [3]. However, neither of these methods, nor a new method –
disproportionation – has been exploited to synthesize tin(IV) bis-
o-semiquinolates. In this paper, we report the synthesis of new
bis-o-benzosemiquinonato tin(IV) complexes, along with physico-
chemical and EPR investigations of these compounds.
ed Mo-K
a
radiation (l = 0.71073 Å) and with CCD detector Sap-
phire III in the
x
-scan mode. X-ray data on samples 8 and 13
were collected at temperature 100 K. The crystal structure was
solved by direct methods (SHELX97) [4] and refined by full matrix
method (WINGX and SHELX97) [5]. The reflection data were processed
using the analytical absorption correction algorithm [6]. All non-
hydrogen atoms were refined with anisotropic correction. All H
atoms were placed in calculated positions and refined in the ‘‘rid-
2
ing-model’’ (Uiso(H) = 1.2ÁUeq(carbon) A for aromatic hydrogen
2
and 1.5ÁUeq(carbon) A for alkyl hydrogen). The follow minimal
1 1
R -factors obtained for 8 and 13 correspond to R = 0.0346 and
0
.0399, respectively. The selected bond distances and angles for 8
and 13 are given in Table 1. Table 2 summarizes the crystal data
and some details of the data collection and refinement.
2
. Experimental
The 3,6-di-tert-butyl-o-benzoquinone was obtained using
method described in [7a]. Other starting reagents were purchased
in Aldrich. Solvents were purified following standard procedures
Infrared spectra of complexes were recorded in the 400–
À1
3
500 cm range on a FSM-1201 spectrophotometer in Nujol mulls
À1
and reported in cm . X-band EPR spectra were recorded on Bruker
[
7b]. All manipulations on complexes were performed under
conditions excluding air oxygen and moisture. (3,6-Di-tert-butyl-
o-benzosemiquinonato)tallium(I) ((3,6-SQ)Tl, 1) [8], bis-(3,
6
Cat)
-di-tert-butylcatecholato) tin(IV) ditetrahydrofuranate ((3,6-
⇑
Corresponding author. Tel.: +7 831 462 76 89; fax: +7 831 462 74 97.
E-mail address: ekaterin_from_nn@bk.ru (E.V. Ilyakina).
2
SnÁ2THF, 2) [1c], (3,6-di-tert-butylcatecholato)dichlorotin(IV)
0
020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.08.018

E.V. Ilyakina et al. / Inorganica Chimica Acta 394 (2013) 282–288
283
Table 1
of 3,6-di-tert-butyl-o-benzoquinone (2 mmol, 0.440 g) in 20 ml of
the same solvent. The color of reaction mixture turned from
green–red to dark-green. The dark-green residue of complex 7
Selected bonds and angles in complexes 8 and 13.
Bond, Å
(3,6-SQ)
2
SnBr
2
2 2
(3,6-SQ) SnPh
(
0.480 g, yield is 76%) precipitated from reaction mixture after
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–O(3)
Sn(1)–O(4)
O(1)–C(1)
O(2)–C(2)
O(3)–C(7)
O(4)–C(8)
C(1)–C(2)
C(1)–C(6)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(7)–C(8)
C(7)–C(12)
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(11)–C(12)
Sn(1)–Br(1)
Sn(1)–Br(2)
Sn(1)–C(13)
Sn(1)–C(14)
2.0804(13)
2.1080(14)
2.0805(13)
2.1080(14)
1.298(2)
1.293(2)
1.298(2)
1.293(2)
1.470(3)
1.427(3)
1.415(3)
1.363(3)
1.424(3)
1.365(3)
1.470(3)
1.427(3)
1.415(3)
1.363(3)
1.424(3)
1.365(3)
2.4902(3)
2.4902(3)
2.124(2)
2.217(2)
2.111(2)
2.188(2)
1.295(3)
1.260(4)
1.301(4)
1.283(4)
1.485(4)
1.412(4)
1.453(4)
1.337(5)
1.433(5)
1.372(4)
1.469(4)
1.418(4)
1.441(4)
1.359(5)
1.416(5)
1.371(5)
some minutes.
Method IV, Scheme 1: The one equivalent of gaseous NO
2
(
0
1 mmol, 0.046 g) was added to the solution of complex 3 (1 mmol,
.554 g) in the mixture of 10 ml of acetonitrile and 10 ml of tolu-
ene. The dark-green crystals of complex 7 (0.205 g, yield is 65%)
was obtained after 12 h storage at À12 °C.
2 4
Anal. Calc. for C28H40Cl O Sn,%: C, 53.36; H, 6.40; Cl, 11.25; Sn,
1
8.84. Found: C, 53.41; H, 6.37; Cl, 11.28; Sn, 18.93.
À1
IR(nujol, cm ):1482s., 1437s., 1416s., 1392 m., 1366s., 1351w.,
1332 w., 1281 m., 1208 m., 1183 w., 1027 w., 970 m., 954 s., 931 w.,
850 w., 842 w., 806 w., 685 s., 652 m., 581 m., 494 m.
2
(
.2. Bis-(3,6-di-tert-butyl-o-benzosemiquinonato)tin(IV) dibromide,
3,6-SQ) SnBr (8)
2
2
Method II, Scheme 1: The solution of Br
in 10 ml of THF was drop added to the solution of 2 (1 mmol,
.559 g) in 20 ml of THF. The color of reaction mixture changed
2
Ádiox (1 mmol, 0.248 g)
0
2.155(3)
2.146(3)
from yellow to dark-green). The solvent was evaporated and the
residue was dissolved in 15 ml of toluene. The dark-green crystals
of 8 (0.575 g, yield is 80%) were isolated from this solution after
12 h storage at À12 °C.
Angle
O(1)–Sn(1)–O(2)
O(1)–Sn(1)–O(3)
O(1)–Sn(1)–O(4)
O(2)–Sn(1)–O(4)
O(2)–Sn(1)–O(3)
O(3)–Sn(1)–O(4)
O(1)–Sn(1)–Br(1)
O(1)–Sn(1)–Br(2)
O(2)–Sn(1)–Br(1)
O(2)–Sn(1)–Br(2)
O(3)–Sn(1)–Br(1)
O(3)–Sn(1)–Br(2)
O(4)–Sn(1)–Br(1)
O(4)–Sn(1)–Br(2)
Br(1)–Sn(1)–Br(2)
O(1)–Sn(1)–C(13)
O(1)–Sn(1)–C(14)
O(2)–Sn(1)–C(13)
O(2)–Sn(1)–C(14)
O(3)–Sn(1)–C(13)
O(3)–Sn(1)–C(14)
O(4)–Sn(1)–C(13)
O(4)–Sn(1)–C(14)
C(13)–Sn(1)–C(14)
77.21(5)
153.93(8)
83.39(5)
83.50(8)
83.39(5)
77.21(5)
93.22(4)
103.50(4)
168.31(4)
88.79(4)
103.50(4)
93.22(4)
88.79(4)
168.31(4)
100.100(13)
75.07(8)
151.34(8)
83.53(8)
76.66(8)
82.19(8)
74.31(8)
Method III, Scheme 1: The solution of SnBr
.367 g) in 10 ml of acetonitrile was drop added to the solution of
2
Ádiox (1 mmol,
0
3
,6-di-tert-butyl-o-benzoquinone (2 mmol, 0.440 g) in 20 ml of the
same solvent. The color of reaction mixture turned from green–red
to dark-green. The dark-green residue of complex 8 (0.582 g, yield
is 81%) precipitated from reaction mixture after some minutes.
Method IV, Scheme 1: The one equivalent of gaseous NO
2
(1 mmol, 0.046 g) was added to the solution of complex 4 (1 mmol,
0.643 g) in the mixture of 10 ml of acetonitrile and 10 ml of tolu-
ene. The dark-green crystals of complex 8 (0.244 g, yield is 68%)
suitable for X-ray analysis were obtained after 12 h storage at
À12 °C.
92.77(10)
103.52(10)
162.48(10)
88.47(10)
104.33(10)
93.66(10)
90.10(10)
162.13(10)
106.33(12)
2 4
Anal. Calc. for C28H40Br O Sn,%: C, 46.76; H, 5.61; Br, 22.22; Sn,
16.51. Found: C, 46.71; H, 5.65; Br, 22.15; Sn, 16.48.
À1
IR (nujol, cm ): 1484 s., 1415 s., 1391 s., 1370 m., 1360 s., 1351 w.,
1
334 m., 1289 w., 1276 m., 1208 m., 1183 w., 1029 w., 968 s., 956 s.,
932 w., 836 s., 807 m., 686 s., 651 s., 578 m., 494 s.
2.3. Bis-(3,6-di-tert-butyl-o-benzosemiquinonato)diphenyl tin(IV),
(
3,6-SQ) SnPh (13)
2
2
Method I, Scheme 2: The one equivalent of gaseous NO
1 mmol, 0.046 g) was added to the solution of complex 9 (1 mmol,
2
ditetrahydrofuranate ((3,6-Cat)SnCl
2
Á2THF, 3) [3c], (3,6-di-tert-
(
butylcatecholato)dibromotin(IV)
ditetrahydrofuranate ((3,6-
0
.565 g) in 20 ml of acetonitrile. The dark-violet residue of complex
Cat)SnBr
tin(IV) tetrahydrofuranate ((3,6-Cat)SnPh
thesized according to literature procedures.
2
Á2THF, 4) [3d], (3,6-di-tert-butylcatecholato)diphenyl-
1
3 (0.271 g, yield is 76%) precipitated from reaction mixture imme-
2
ÁTHF, 9) [3b] were syn-
diately. The suitable crystals for X-ray analysis were obtained after
prolonged crystallization from the mixture of toluene and
acetonitrile.
2
.1. Bis-(3,6-di-tert-butyl-o-benzosemiquinonato)tin(IV) dichloride,
Method II, Scheme 2: The solution of Br
2
Ádiox (0.5 mmol,
(
3,6-SQ) SnCl (7)
2
2
0.124 g) in 10 ml of acetonitrile was drop added to the solution
of complex 9 (1 mmol, 0.565 g) in 20 ml of the same solution.
The dark-violet residue of complex 13 (0.253 g, yield is 71%) pre-
cipitated from reaction mixture immediately.
4
Method I, Scheme 1: SnCl (2.5 mmol, 0.29 ml) was added to the
solution of complex 1 (5 mmol, 2.13 g) in 50 ml of toluene.
The white residue of TlCl precipitated from reaction mixture. The
dark-green solution of complex 7 was filtered using glass Shott fil-
ter No. 4. The dark-green fine-crystalline powder of complex 7
2
Method III, Scheme 2: The solution of I (1 mmol, 0.254 g) in
10 ml acetonitrile was drop added to the solution of complex 9
(1 mmol, 0.565 g) in 20 ml of the same solvent. The dark-violet res-
idue of complex 13 (0.267 g, yield is 75%) precipitated from reac-
tion mixture immediately.
(
1.23 g, yield is 78.4%) was obtained by recrystallization from tol-
uene–hexane mixture.
Method III, Scheme 1: The solution of SnCl
.277 g) in 10 ml of acetonitrile was drop added to the solution
2
Ádiox (1 mmol,
Anal. Calc. for C40
C, 67.21; H, 7.12; Sn 16.71.
50 4
H O Sn,%: C, 67.33; H, 7.06; Sn, 16.64. Found:
0

2
84
E.V. Ilyakina et al. / Inorganica Chimica Acta 394 (2013) 282–288
Table 2
Summary of crystal and refinement data for complexes 8 and 13.
Formula
C
28
H
40Br
2
O
4
Sn
40 50 4
C H O Sn
M
T (K)
719.11
100 (2)
713.49
100 (2)
Crystal system
Space group
Monoclinic
C 1 2/c 1
Monoclinic
C 1 2/c 1
Unit cell dimensions
a (Å)
b (Å)
c (Å)
16.7018 (5)
12.8969 (3)
15.7698 (4)
90
111.628 (3)
90
35.1558 (8)
10.2093 (2)
20.6444 (5)
90
96.520 (2)
90
a
(°)
b (°)
(°)
c
3
V (Å )
3157.69 (15)
4
7361.7 (3)
8
Z
F (000)
1440
1.513
3.368
3.44 ꢁ h ꢁ 32.91
À23 ꢁ h ꢁ 23
À10 ꢁ k ꢁ 18
À21 ꢁ l ꢁ 22
1 and 0. 88993
4767
2976
1.288
0.731
3.43 ꢁ h ꢁ 23.26
À28 ꢁ h ꢁ 38
À11 ꢁ k ꢁ 11
À21 ꢁ l ꢁ 22
0.948 and 0.872
5264
3
Calculated density, (mg/m )
Absorption coefficient, (mm
h (°)
À1
)
Limiting indices
Maximum and minimum transmission
Reflections collected
Independent reflections (Rint
Absorption correction
Refinement method
Data/restraints/parameters
)
3148 (0.0324)
Multi-scan
Full-matrix least-squares on F2
3148/0/159
3817 (0.0411)
Analytical
Full-matrix least-squares on F2
3817/0/406
Final R indices [I > 2
R indices (all data)
r
(I)]
R
R
1
= 0.0346, wR
= 0.0585, wR
2
= 0.0668
= 0.069
R
R
1
= 0.0399, wR
= 0.0604, wR
2
= 0.0768
= 0.0798
1
2
1
2
2
Goodness-of-fit (GOF) on (F )
0.849
1.748/À0.711
0.997
2.549/À0.611
À3
D
q
max
/
D
q
min, (e Å
)
À1
IR (nujol, cm ): 1578 w., 1548 w., 1493 m., 1428 s., 1356 m.,
338 m., 1277 w., 1201 w., 1182 w., 1154 w., 1074 w., 1059 w.,
The interaction of o-semiquinonato alkali metal or thallium
1
1
6
derivatives with nontransition metal salts is one of the widely
used synthetic methods to o-semiquinonato metal complexes
[3a,12]. As shown in present work, the exchange interaction of
024 w., 997 w., 967 m., 955 s., 930 w., 834 m., 807 w., 697 s.,
79 m., 652 m., 552 m., 496 m.
3
4
,6-di-tert-butyl-o-benzosemiquinonato tallium(I) and SnCl in
toluene solution in the molar ratio 2:1 (Scheme 1, method I) leads
to the formation of bis(3,6-di-tert-butyl-o-benzosemiquinona-
to)tin(IV) dichloride (7).
3
. Results and discussion
The main methods of synthesis of nontransition metal o-semi-
As shown earlier, the fixation of O-, N-, S-centered free radicals
and other species, for example halogens, by catecholate non-tran-
sition metal complexes is attended by one-electron oxidation of
the catecholate dianion to the o-semiquinonato radical-anion [3].
As reported in [3d] the addition of halogens to the catecholate ti-
n(IV) complexes 3 and 4 yields the monoradical (3,6-di-tert-bu-
tyl-o-benzosemiquinonato)trihalogenotin(IV) complexes. The
quinonato complexes consist in the interaction of low valence me-
tal salts or metal amalgams with o-quinones, the addition of the
different species to catecholate nontransition metal complexes
and the exchange interaction of o-semiquinonato alkali metal or
thallium complexes with nontransition metal salts [3a].
For the preparation of o-quinonato nontransition metal com-
plexes, the solution medium plays an important role [2b,3c,9]. As
shown in work [3c] the addition of 3,6-di-tert-butyl-o-benzoqui-
2
interaction of nitrogen dioxide NO with 3 and 4 gives firstly 3,6-
di-tert-butyl-o-benzosemiquinonato tin(IV) species 5 and 6 with
the appearance of EPR activity (see Section 3.2), however at the
next stage the symmetrization of these complexes to the diradical
derivatives 7 and 8 takes place (Scheme 1, method IV). The oxida-
none to SnCl
Sn(IV), the reduction of o-quinone to catecholate dianion and the
formation of catecholate complex (3,6-Cat)SnCl
complex 3 is generated independently of the molar ratio of 3,6-
di-tert-butyl-o-quinone to tin (1:1 or 2:1). This fact can be ex-
plained by the high coordination ability of THF towards tin as
shown in work [10]. The formation of catecholate tin(IV) complex
stabilized by two THF molecules is more thermodynamically
advantageous than the replacement of coordinated THF in complex
2
in THF solution leads to the oxidation of Sn(II) to
2
Á2THF (3). The
tive addition of Br
leads to diradical complex 8 (Scheme 1, method II).
The oxidative addition of halogens and NO to (3,6-di-tert-bu-
2
to bis-catecholate 2 in equimolecular ratio also
2
tyl-catecholato)diphenyltin(IV) tetrahydrofuranate (9) resulting
at the first stage in formation of monoradical species 10–12 which
are characterized by EPR (see Section 3.2, Table 3), leads to the
symmetrization of these monoradical species to the stable diradi-
cal complex 13 (Scheme 2, methods I–III).
3
by 3,6-di-tert-butyl-o-benzoquinone followed by the intramolec-
ular redox process between redox-active ligands. However the
change of THF with acetonitrile as weaker base [11] allows to ob-
tain diradical tin(IV) complex 7 (Scheme 1, method III). Worthy of
It should be noted that authors [13] supposed that the product
of exchange interaction between Ph
ratio 1:2) in n-hexane-dichloromethane mixture – bis-(3,5-di-
tert-butyl-o-benzosemiquinonato)diphenyltin(IV) is unstable
2 2
SnCl and (3,5-SQ)Na (molar
note that the dissolution of diradical complex (3,6-SQ)
2 2
SnCl (7) or
its dibromine analogue (3,6-SQ) SnBr (8) and their storage in THF
2
2
–
leads to the elimination of 3,6-di-tert-butyl-o-benzoquinone and
the formation of corresponding monocatecholates (3,6-Cat)SnCl2-
and undergoes intermolecular electron-transfer process with for-
mation of catecholate tin(IV) complex and free neutral 3,5-di-
Á2THF (3) or (3,6-Cat)SnBr Á2THF (4).
2

E.V. Ilyakina et al. / Inorganica Chimica Acta 394 (2013) 282–288
285
Scheme 1.
Scheme 2.
tert-butyl-o-benzoquinone. The present results demonstrate that
bis-o-benzosemiquinonato tin(IV) complexes (SQ) SnX are stable
compounds and can be isolated without decomposition under cer-
tain conditions.
Complexes were characterized by IR, EPR spectroscopy and ele-
À1
2
2
mental analysis. The typical vibration bands in 1460–1350 cm
.
. .
range in IR-spectra corresponding to C O one-and-half bonds con-
firm the radical-anion nature of complexes 7, 8 and 13.

2
86
E.V. Ilyakina et al. / Inorganica Chimica Acta 394 (2013) 282–288
Table 3
EPR spectral parameters on complexes 5, 6 and 10–12.
Complex
g
i
a
i
(1H), G
a
i
(117Sn)/a
i
(119Sn), G
a
i
(Hal), G
5
6
2.0033
2.0036
2.0012
2 1H 3.86
7.31/7.65
4.95/5.18
16.25/17.0
35Cl/37Cl 0.6/0.5
Br/ Br 2.26/2.44
1
79
81
2
H 3.9
1
1
1
1
0
1
2
H 2.96
H 4.7
1
1
1
1
1
2.0038
2.004
H 2.81
H 4.71
H 2.88
H 4.72
15.97/16.7
15.53/16.24
Toluene, RT.
3.1. Structural studies
The X-ray suitable crystals of 8 and 13 were obtained by the
prolonged crystallization from the mixture of toluene and acetoni-
trile. Fig. 1 shows the molecular structures of 8 and 13. The se-
lected bond lengths and angles are listed in Table 1. The tin(IV)
atom in both complexes has the distorted octahedral environment
formed by two o-benzosemiquinonato ligands and two bromine
atoms (complex 8) or two carbon atoms of phenyl groups (complex
1
3). The geometrical features of chelating ligands confirm their
radical-anion forms. The O–C distances in both o-benzosemiquino-
nato ligands of complexes 8 and 13 lie in the range of 1.293–
Fig. 2. Experimental X-band EPR spectrum of complex 5 (RT, toluene) and its
computer simulation (WINEPR SIMFONIA Software).
1
.301 Å and correspond the one-and-half O–C distances in such
type ligands [3d,9,14] but shorter than in catecholate dianion li-
gands (1.33–1.39 Å) [3b,3c,14a,15]. The six-membered carbon
rings of chelating ligands demonstrate the quinoid-type distortion
expressing by nonequivalence of C–C distances. Both complexes
adopt cis-configuration and the angle between chelating ligands
planes is 76.45° in 8 and 73.27° in 13. The trans effect of bromine
and phenyl ligands in complexes 8 and 13 is reflected in the elon-
gation of the corresponding Sn–O bonds (Sn(1)–O(2) and Sn(1)–
O(4)) and the shortening of the corresponding O–C bonds of SQ li-
gands (O(2)–C(2) and O(4)–C(8)) (Table 1).
The hyperfine structure (HFS) of EPR spectra of these complexes
is caused by hyperfine coupling (HFC) of unpaired electron with
1
two equivalent protons ( H, 99.98%, I = 1/2,
N
l = 2.7928 [16]) (4th
and 5th positions of aromatic ring of 3,6-SQ ligand) and halogen
35
37
atom in apical position ( Cl, 75.77%, I = 3/2,
= 0.68412; 79Br, 50.69%, I = 3/2,
l
N
l
N
= 0.82187, Cl,
2
4.23%, I = 3/2,
Br, 49.31%, I = 3/2, = 2.2706 [16]) in case of six-coordinated
complexes 5–6 and with two nonequivalent protons in case of
l
N
= 2.1064,
81
l
N
117
five-coordinated complexes 10–12. The satellite splitting on
Sn
1
19
117
3.2. EPR studies
and
Sn magnetic isotopes ( Sn, 7.68%, I = 1/2,
l
N
= À1.000,
1
19
Sn, 8.58%, I = 1/2,
l
N
= À1.046 [16]) also takes place in all EPR
The addition of NO
2
to 3, 4 and 9 and Br
2
and I
2
to 9 leads firstly
spectra of obtained o-benzosemiquinonato derivatives (Figs. 2
to the formation of paramagnetic mono-o-benzosemiquinonato
complexes 5, 6 and 10–12, respectively. The EPR spectral parame-
ters on complexes are collected in Table 3. Figs. 2 and 3 show the
X-band EPR spectra of complexes 5 and 11, respectively.
and 3).
According to EPR data, complexes 5 and 6 are six-coordinated
and have the octahedral environment with the first halogen atom
and oxygen atom of THF molecule in the apical positions and
Fig. 1. The molecular structures of complexes 8 (left) and 13 (right) with ellipsoids of 30% probability. The hydrogen atoms are omitted for clarity.

E.V. Ilyakina et al. / Inorganica Chimica Acta 394 (2013) 282–288
287
4
.3 Å for 8 and 4.4 Å for 13. These values are very close to the dis-
tances between the centroids of the bands C–C of SQ chelating
rings (4.25 Å in 8 and 4.28 Å in 13).
4
. Conclusions
2 2
New bis-o-benzosemiquinonato tin(IV) complexes (3,6-SQ) SnX
(
X = Cl, Br, Ph) were synthesized by different methods such as the
substitution reaction between tin(IV) halide and alkali metal o-semi-
quinolate (1:2); the oxidative addition of o-quinone to SnX in aceto-
2
nitrile; oxidation of bis-catecholato tin(IV) with bromine. It is
important to note that, in some methods, the solvent nature plays
a crucial role: the target synthesis of tin(IV) bis-o-benzosemiquino-
2 2
lates SQ SnX proposes the use of acetonitrile instead of THF which
is common solvent in syntheses of tin(IV) catecholates.
The reaction of tin(IV) monocatecholates (3,6-Cat)SnX
2
ÁnTHF
(
2
X = Cl, Br, n = 2; X = Ph, n = 1) with NO proceeds through the for-
mation of monoradical five- or six-coordinated o-semiquinonato
species which undergo symmetrization to the corresponding
diradical complexes (3,6-SQ)
place in the case of mono-o-semiquinonato-diphenyltin(IV) com-
plexes with halides (3,6-SQ)SnPh X (X = Br, I) and lead to (3,6-
SQ) SnPh
2 2
SnX . The same transformations take
2
2
2
.
Fig. 3. Experimental X-band EPR spectrum of complex 11 (RT, toluene) and its
computer simulation (WINEPR SIMFONIA Software).
Acknowledgements
This work was made according to FSP ‘‘Scientific and Scientific-
Pedagogical Cadres of Innovation Russia’’ for 2009–2013 years (GK
P982 from 27.05.2010).We are grateful to RFBR (No. 12-03-33058
mol_a_ved), President of Russian Federation (Grants NSh-
oxygen atoms of o-benzosemiquinonato ligand, the second halogen
atom and NO -group in the basal plane. Complexes 10–12 are five-
2
coordinated and have a square-pyramidal geometry with phenyl
group in the apical position and oxygen atoms of o-semiquinonato
1
113.2012.3 and MK-614.2011.3), Russian Science Support Foun-
dation (E.V.I.) for supporting of this work.
2
ligand, other phenyl group and substituent Y (NO , Br, I) in the
basal plane. The unsymmetrical position of substituents at tin
atom relative to the plane of SQ ligand reflects in the unequiva-
lence of protons in 4th and 5th positions of SQ ligand (Table 3).
Appendix A. Supplementary material
CCDC 863613 and 863612 contain the supplementary crystallo-
graphic data for compounds 8 and 13, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
1
17
119
The values of
Sn and
Sn HFC constants for complexes 5–6
are typical for six-coordinated o-semiquinonato tin(IV) complexes
while for 10–12 are typical for five-coordinated o-semiquinonato
tin(IV) complexes (4–7 G for six-coordinated and 9–20 G for five-
coordinated complexes [3,1a,1b,17]).
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