C,N-chelated organotin(IV) trifluoroacetates. Instability of the mono- and diorganotin(IV) derivatives.

Article abstract of DOI:10.1016/j.jorganchem.2010.09.050

The C,N-chelated tri-, di- and monoorganotin(IV) halides react with equimolar amounts of CF₃COOAg to give corresponding C,N-chelated organotin(IV) trifluoroacetates. The set of prepared tri-, di- and monoorganotin(IV) trifluoroacetates bearing the L^CN ligand (where L^CN is 2-(N,N-dimethylaminomethyl)phenyl-) was structurally characterized by X-ray diffraction analyses, multinuclear NMR and IR spectroscopy. In the case of triorganotin(IV) trifluoroacetates and (L ^CN)₂Sn(OC(O)CF₃)₂, no tendency to form hydrolytic products, or instability towards the moisture was observed. L^CNRSn(OC(O)CF₃)₂ (where R is n-Bu or Ph) and L^CNSn(OC(O)CF₃)₃ forms upon crystallization from THF in the air mainly dinuclear complexes in which the two tin atoms are interconnected either by hydroxo-bridges or by an oxo-bridge and/or by a bridging trifluoroacetate(s). In the case of hydrolysis of L^CN(n-Bu) Sn(OC(O)CF₃)₂, a zwitterionic stannate of formula L ^CN(n-Bu)Sn(OC(O)CF₃)₂·CF ₃COOH was isolated from the mother liquor, too. Products of hydrolysis of L^CN(n-Bu)Sn(OC(O)CF₃)₂ and L ^CNSn(OC(O)CF₃)₃, and some other oxygen bridged organotin(IV) compounds containing the same ligand, were tested as possible catalysts of some transesterification reactions as well as in direct dimethyl carbonate (DMC) synthesis from CO₂ and methanol.

Full text of DOI:10.1016/j.jorganchem.2010.09.050

Journal of Organometallic Chemistry 696 (2011) 676e686
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
C,N-chelated organotin(IV) trifluoroacetates. Instability of the mono- and
diorganotin(IV) derivatives.
a
a
a
,
b
b
c
ꢀ
*
ꢀ
ꢀ
ꢀ ꢁꢀ ꢀ
ꢀ
ꢀ
Petr Svec , Zdenka Padelková , Ales Ruzicka , Tomás Weidlich , Libor Dusek , Laurent Plasseraud
a Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-532 10, Pardubice, Czech Republic
b Institute of Environmental and Chemical Engineering, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-532 10, Pardubice, Czech Republic
c Institut de Chimie Moléculaire de l’Université de Bourgogne (ICMUB), UMR CNRS 5260, UFR Sciences et Techniques, 9 allée A. Savary, BP 47870, F-21078 DIJON Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The C,N-chelated tri-, di- and monoorganotin(IV) halides react with equimolar amounts of CF3COOAg to give
corresponding C,N-chelated organotin(IV) trifluoroacetates. The set of prepared tri-, di- and monoorganotin
(IV) trifluoroacetates bearing the LCN ligand (where LCN is 2-(N,N-dimethylaminomethyl)phenyl-) was
structurally characterized by X-ray diffraction analyses, multinuclear NMR and IR spectroscopy. In the case of
triorganotin(IV) trifluoroacetates and (LCN)2Sn(OC(O)CF3)2, no tendency to form hydrolytic products, or
instability towards the moisture was observed. LCNRSn(OC(O)CF3)2 (where R is n-Bu or Ph) and LCNSn(OC(O)
CF3)3 forms upon crystallization from THF in the air mainly dinuclear complexes in which the two tin atoms
are interconnected either by hydroxo-bridges or by an oxo-bridge and/or by a bridging trifluoroacetate(s). In
the case of hydrolysis of LCN(n-Bu)Sn(OC(O)CF3)2, a zwitterionic stannate of formula LCN(n-Bu)Sn(OC(O)
CF3)2$CF3COOH was isolated from the mother liquor, too. Products of hydrolysis of LCN(n-Bu)Sn(OC(O)CF3)2
and LCNSn(OC(O)CF3)3, and some other oxygen bridged organotin(IV) compounds containing the same
ligand, were tested as possible catalysts of some transesterification reactions as well as in direct dimethyl
carbonate (DMC) synthesis from CO2 and methanol.
Received 17 August 2010
Received in revised form
22 September 2010
Accepted 22 September 2010
Available online 1 October 2010
Keywords:
Organotin(IV) compounds
C,N-Ligand
Trifluoroacetate
Hydrolysis
Catalysis
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Depending on the nature of the carboxylic acid used and the
stoichiometry of the reactants, several products such as monomers,
There is a long-standing interest in chemistry and generally the
structure of triorganotin(IV) esters of carboxylic acids both in
academia and industry, because of known catalytic and medicinal
activity [1,2]. The structural motifs of these compounds are well
established and studied by X-ray diffraction techniques [3], Möss-
bauer spectroscopy [4] and CP/MAS NMR techniques in the solid
state, and mainly by multinuclear NMR spectroscopy in solution
[5]. The tin atom in these compounds is mainly four-coordinated
(Scheme 1A) or five coordinated with major occurrence in the solid
state. In this case, the tin atom is surrounded by three carbon atoms
originated from organo substituents and two oxygen atoms from
carboxylate group, whereas the carboxylate can act as a bidentate
or bidentate-bridging (or anisobidentate) ligand (Scheme 1B and
1C). Scheme 1D shows another general ability of the COO group to
bridge two tin atoms. Compounds where the bidentate-bridging
bond fashion occurs, tend to form infinite polymeric networks in
the solid state [3], which can be often fragmented into oligomeric
or monomeric particles in solutions of coordinating solvents [6].
dimers, tetramers, oligomeric ladders, and hexameric drums can be
isolated [3,7]. Diorganotin carboxylates have been an extensively
investigated class of compounds over the last several decades. The
most common reaction product of a reaction between R2SnO (or
R2SnX2) and R’COOH (in a 1:2 ratio) is the hexacoordinate mono-
nuclear tin dicarboxylate of formula [R2Sn(OOCR’)2], where the tin
centre exists in a skewed trapezoidal geometry [8]. The same reaction,
when carried out with a strict 1:1 stoichiometry of the reactants,
yields tetrameric compounds [R2(OOCR’)SnOSn(OOCR’)]2 [3,9]. On the
other hand, monoorganotin carboxylates are predominately known
to exist as drum-shaped hexameric clusters [10], although a few
examples of other structural types are also known [11].
There is a plenty of examples of tri- and diorganotin(IV)
compounds containing the 2-(N,N-dimethylaminomethyl)phenyl
group as a C,N-chelating ligand in the literature [12]. All referred
compounds of this type reveal significant intramolecular contact
between tin and nitrogen which is changing their properties,
mainly preventing their oligo- or polymerization. This coordination
bond has been proven by means of X-ray diffraction analyses and
119Sn CP-MAS NMR techniques in the solid state [13], and recently
by multinuclear NMR spectroscopy in solution [14].
* Corresponding author. Tel.: þ420 466037151; fax: þ420 466037068.
ꢁꢀ ꢀ
E-mail address: ales.ruzicka@upce.cz (A. Ruzicka).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.09.050

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P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
677
Table 1
Sn
Sn
O
R3Sn
O
R3Sn
O
O
R3Sn
O
O
Numbering of prepared compounds.
'
'
C
R
'
R
C
R
C
'
R
C
O
Compound
O
L
L
CN(n-Bu)2SnOC(O)CF3
1
2
3
4
4a
4b
5
5a
6
A
B
C
D
CNPh2SnOC(O)CF3
(LCN)2Sn(OC(O)CF3)2
Scheme 1. Possible structural motifs for triorganotin(IV) esters of carboxylic acids.
L
L
CN(n-Bu)Sn(OC(O)CF3)2
CN(n-Bu)Sn(OC(O)CF3)2$CF3COOH
[LCN(n-Bu)SnOC(O)CF3]2(
m
-OH)2
We have published recently about zwitterionic tri- and
diorganostannates containing protonated 2-(N,N-dimethylamino-
methyl)phenyl- moiety which were prepared by reactions of C,N-
chelated organotin(IV) chlorides with various protic acids. These
zwitterionic stannates were structurally characterized both by multi-
nuclear NMR spectroscopy and X-ray diffraction techniques [15].
L
CNPhSn(OC(O)CF3)2
[LCNPhSnOC(O)CF3]2(
[LCNSnOC(O)CF3]2(
-O)(
m
-OH)(
m-OC(O)CF3)
m
m-OC(O)CF3)2
necessary multiple filtration of the reaction mixtures in order to
eliminate finely suspended silver(I) halide.
Promising results concerning reaction of
L
CN(n-Bu)2SnCl with
CF3COOH were also described there. Latter results led us to a concept
to prepare and structurally characterize some C,N-chelated organotin
(IV) trifluoroacetates since no information is related with the prepa-
ration and structural characterization of these compounds. Although
a plethora of tin(IV) compounds is known, there are only two exam-
ples of organotin(IV) trifluoroacetates bearing the N,C,N-bischelating
ligand (LNCN ¼ [2,6-(Me2NCH2)2C6H3]ˉ) which can be directly related
to the suggested compounds containing C,N-chelating ligand. These
two compounds (LNCNSn(H2O)(OC(O)CF3)3 and presumably the ionic
[LNCNPh2Sn]þ[CF3COO]ˉ were prepared and structurally characterized
recently [16]. Other known organotin(IV) trifluoroacetates are used in
glycosidation of sugar peracetates [17], as initiators of the ring-
opening polymerization of 3-caprolactone [18], as precursors for AP
CVD of fluorine-doped SnO2 thin films [19] and are investigated as
potential metal-based antitumor drugs [20], too.
In this paper, we report on the reactivity of various C,N-chelated
tri-, di- and monoorganotin(IV) halides [21] towards CF3COOAg (for
1H NMR numbering see Scheme 2). The structure of products of
hydrolysis of di- and monoorganotin(IV) trifluoroacetates bearing
the C,N-chelating ligand is also discussed.
2.2. Triorganotin(IV) trifluoroacetates containing the C,N-chelating
ligand
Prepared C,N-chelated triorganotin(IV) trifluoroacetates of the
general formula LCNR2SnOC(O)CF3 (where R ¼ n-Bu (1) or Ph (2))
were characterized by multinuclear NMR spectroscopy and, in
addition, by X-ray diffraction analysis in the case of 2 (Fig. 1).
According to recorded multinuclear NMR spectra and X-ray
diffraction analysis one can assume that the central tin atom is five-
coordinated and reveals distorted trigonal bipyramidal geometry.
Owing to the Bent’s rule [22], both electronegative atoms X (X ¼ N
and O) occupy axial positions and all three carbon atoms are situ-
ated in equatorial positions, independently whether R is n-Bu or Ph.
ꢁ
In the case of 2, the interatomic distances Sn1-N1 (2.451(3) A) and
Sn1-O1 (2.187(3) A) are similar to previously published results
[23b]. The interatomic distance Sn1-O2 (3.384(3) A) proves that the
ꢁ
ꢁ
2. Results and discussion
2.1. General remarks
L
CN(n-Bu)2SnCl, LCNPh2SnCl, LCN(n-Bu)SnCl2, LCNPhSnCl2,
(LCN)2SnBr2 and LCNSnBr3 reacted with equimolar amount of
CF3COOAg to give corresponding organotin(IV) trifluoroacetates
(for numbering of compounds see Table 1) while attempts to
prepare mixed organotin(IV) halogenides-trifluoroacetates were
not carried out. All reactions were protected from exposure to light.
Reactions of triorganotin(IV) chlorides and (LCN)2SnBr2 with
CF3COOAg were carried out in the air due to the stability of corre-
sponding triorganotin(IV) trifluoroacetates. On the other hand,
preparation of C,N-chelated di- and monoorganotin(IV) tri-
fluoroacetates requires anhydrous THF and strictly anaerobic
conditions. In the case of preparation of LCN(n-Bu)2SnOC(O)CF3 and
L
CNPh2SnOC(O)CF3 high yields (89% and 85%, respectively) are
obtained, which is in contrast with the preparation of the rest of the
desired products (for example only 62% yield for (LCN)2Sn(OC(O)
CF3)2). This is caused by low solubility of these products as well as
N(CH3)2
3'
2'
2''
3''
1
3
1''
Fig. 1. Molecular structure of 2 (ORTEP view, 40% probability level). Hydrogen atoms
4'
4''
Sn
4
Sn
ꢀ
ꢁ
1'
2
are omitted for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-N1 2.451
(3), Sn1-O1 2.187(3), Sn1-O2 3.384(3), O1-C22 1.276(4), O2-C22 1.204(4), Sn1-C1 2.115
(3), Sn1-C10 2.123(3), Sn1-C16 2.123(3), N1-Sn1-O1 162.99(10), N1-Sn1-C1 76.24(11),
O1-Sn1-C1 88.79(11), C1-Sn1-C10 116.30(13), C1-Sn1-C16 125.52(12), O1-Sn1-C10
100.94(11), O1-Sn1-C16 90.44(11), C10-Sn1-C16 117.27(13), N1-Sn1-C10 93.02(11),
N1-Sn1-C16 91.77(11).
Sn
6'
5'
LCN
n-Bu
Ph
Scheme 2. General 1H NMR numbering.

ꢀ
678
P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
trifluoroacetate acts as a monodentate substituent. The N1-Sn1-O1
interatomic angle (162.99(10)ꢀ) differs relatively roughly from the
ideal flat angle due to the sterical hindrance of the two phenyl
substituents. For 2, the sum of all equatorial CeSneC angles is
359.1ꢀ. The monodentate bonding fashion of the CF3COO substit-
uent in neat 1 and 2 is confirmed by IR (ATR) spectroscopy, too (see
Experimental).
The 1H NMR spectra of these two compounds display signals of
n-Bu or Ph and LCN moieties that are bonded to the central tin atom.
The 1H chemical shift values of the N(CH3)2 groups differs signifi-
cantly for 1 (
d
(1H) ¼ 2.36 ppm in CDCl3) in comparison with 2 (
d
(1H) ¼ 1.88 ppm in CDCl3). On the other hand, the chemical shift
values of the CH2N moiety are nearly equivalent (3.62 ppm for 1
and 3.56 ppm for 2). The position and the value of the 3J(119Sn, 1H)
satellites of the doublet of the H(60) signal in the 1H NMR spectra is
another useful tool for characterizing all C,N-chelated organotin
compounds. Prepared triorganotin(IV) trifluoroacetates exhibit the
coupling constant 3J(119Sn, 1H) being 58.8 Hz in the case of 1 and
60.5 Hz in the case of 2. In contrast, diorganotin(IV) bis(tri-
fluoroacetates) containing the LCN ligand exhibit higher coupling
constant 3J(119Sn, 1H) within the range of 90e110 Hz, which is in
good agreement with previously published results [13,14,21]. The
values of these coupling constants, as well as the 1J(119Sn, 13C), are
naturally influenced by the s-electron density (e.g. sp2 vs. sp
hybridization) on the tin atom. According to measured coupling
constant 1J(119Sn, 13C) ¼ 501.1 Hz in 1 the interatomic angle CeSneC
value was calculated using the empirical equation [24b] to be
124.5ꢀ. Similarly, the CeSneC angle in 2 was calculated to 123.3ꢀ (1J
Fig. 2. Molecular structure of 3 (ORTEP view, 30% probability level). Hydrogen atoms
ꢀ
ꢁ
are omitted for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-N1 2.506
(3), Sn1-N2 2.516(4), Sn1-O1 2.114(3), Sn1-O2 3.416(5), Sn1-O3 2.108(3), Sn1-O4 3.404
(5), O1-C19 1.275(6), O2-C19 1.219(7), O3-C21 1.270(6), O4-C21 1.188(6), Sn1-C1 2.115
(3), Sn1-C10 2.115(3), N1-Sn1-O1 161.50(11), N2-Sn1-O3 161.58(12), N1-Sn1-C1 75.04
(12), N2-Sn1-C10 75.09(12), N1-Sn1-N2 106.70(12), O1-Sn1-O3 85.35(12), C1-Sn1-C10
154.68(17), O1-Sn1-C1 92.36(13), O1-Sn1-C10 106.76(12), O3-Sn1-C1 106.71(15), O3-
Sn1-C10 91.56(13).
(
119Sn, 13C) ¼ 795.3 Hz).
The 13C and 19F NMR spectra of 1 and 2, respectively, were
recorded in order to elucidate the presence of the CF3COO
substituent. There are two characteristic quartets in each 13C NMR
spectra, first one at 160.8 ppm (160.4 ppm, respectively) (COO) with
coupling constant 2J(19F, 13C) ¼ 37.2 Hz (37.5 Hz, respectively) and
the second one at 116.3 ppm (116.0 ppm, respectively) with much
higher coupling constant 1J(19F, 13C) ¼ 291.1 Hz (290.0 Hz, respec-
tively) (CF3). The signal of the CF3 group in the 19F NMR spectra was
found at ꢁ74.7 ppm and ꢁ74.5 ppm, respectively. The 119Sn NMR
chemical shift values of these C,N-chelated triorganotin(IV) tri-
fluoroacetates are shifted by 17 and 27 ppm, respectively, to lower
frequencies relative to the starting LCNR2SnCl (R ¼ n-Bu or Ph).
ꢁ
Sn2-O4 2.120(3) A) [23c]. From the X-ray diffraction analysis, it is
evident that both CF3COO substituents are bonded by the mono-
ꢁ
dentate bond fashion to the tin atom (Sn1-O1 2.114(3) A and Sn1-
ꢁ
ꢁ
ꢁ
O2 3.416(5) A; Sn1-O3 2.108(3) A and Sn1-O4 3.404(5) A). The SneC
ꢁ
distances, both being 2.115(3) A, are similar to previously published
results [21].
Compound 3 was characterized by multinuclear NMR spec-
troscopy in THF-d8, too. The 1H NMR spectra of this compound
display only one signal for both CH2N moieties at 3.74 ppm. On the
other hand, the N(CH3)2 groups are unequivalent in solution since
two signals at 2.31 ppm and 2.01 ppm, each with appropriate
integral intensity, are present in the same 1H NMR spectrum, which
is in the strong contrast to the spectra of starting halides, where AX
pattern is found for CH2 moieties and one very broad signal for
methyl groups [21]. The doublet assigned to the H(60) is positioned
at 8.15 ppm with coupling constant 3J(119Sn, 1H) ¼ 97.9 Hz. The 119Sn
NMR chemical shift value of this C,N-chelated diorganotin(IV) bis
(trifluoroacetate) is found at ꢁ381.3 ppm which matches with six-
coordinated tin species. The 13C and 19F NMR spectra were also
recorded to elucidate the presence of the CF3COO substituents.
Similarly to triorganotin(IV) trifluoroacetates discussed (vide
supra), there are two characteristic quartets in the 13C NMR spectra,
first one at 161.0 ppm (COO) with coupling constant 2J(19F,
13C) ¼ 38.5 Hz and the second one at 115.9 ppm (CF3) with naturally
higher coupling constant 1J(19F, 13C) ¼ 282.2 Hz. Only one signal in
19F NMR spectrum at ꢁ75.0 ppm attributed to the CF3 moiety is
found. According to the 13C and 19F NMR spectra we suggest on the
2.3. Diorganotin(IV) trifluoroacetates containing the C,N-chelating
ligand(s)
Another air-stable product was prepared by the reaction of
(LCN)2SnBr2 with two equivalents of CF3COOAg. Resulting (LCN)2Sn
(OC(O)CF3)2 (3) was isolated as a yellowish crystalline solid. The
stability of this compound towards hydrolysis is probably caused by
sterical hindrance of the two C,N-chelating ligands which protect
the central tin atom from nucleophilic attack of water. The tin atom
is six-coordinated with heavily distorted octahedral geometry
having both carbon atoms in trans positions (Fig. 2). The inter-
ꢁ
ꢁ
atomic distances Sn1-N1 (2.506(3) A) and Sn1-N2 (2.516(4) A) are
nearly equivalent and are similar with analogous halides (LCN)2SnF2
(Sn1-N1 2.496(2) A, Sn1-N2 2.597(1) A) [25], (LCN)2SnCl2 (Sn1-N1
ꢁ
ꢁ
2.6179(13) A, Sn1-N2 2.6179(13) A) [21] or (LCN)2SnI2 (Sn1-N1 2.537
ꢁ
ꢁ
ꢁ
ꢁ
(2) A, Sn1-N2 2.648(2) A) [21]. The interatomic angle N1-Sn1-N2
(106.70(12)ꢀ) is similar when compared to (LCN)2SnF2 (N1-Sn1-N2
104.05(4)ꢀ), (LCN)2SnCl2 (N1-Sn1-N2 108.47(4)ꢀ) and (LCN)2SnI2
(N1-Sn1-N2 103.65(7) ), too. The Sn1-O1 (2.114(3) A) and Sn1-O3
(2.108(3) A) interatomic distances are nearly identical and are
equality of both CF3COO substituents in solution. These 13C and 19
F
NMR chemical shift values and the values of 2J(19F, 13C) and 1J(19F,
13C) are similar to discussed triorganotin(IV) trifluoroacetates.
In contrast to 3, other two prepared diorganotin(IV) bis(tri-
fluoroacetates), bearing only one C,N-chelating ligand, reveal
strong tendency to hydrolyze in the presence of moisture. Despite
ꢀ
ꢁ
ꢁ
a little bit shorter when compared to corresponding SneO distance
ꢁ
in 2 (Sn1-O1 2.187(3) A) or in bis{[2-(dimethylaminomethyl)
ꢁ
phenyl]diphenyltin}-4-oxoheptanedioate (Sn1-O1 2.133(3) A and

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P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
679
this instability, both LCN(n-Bu)Sn(OC(O)CF3)2 (4) and LCNPhSn(OC
(O)CF3)2 (5) were prepared under anhydrous conditions in argon
atmosphere and characterized by multinuclear NMR spectroscopy.
The 1H NMR spectra of these two compounds reveal signals of both
n-Bu or Ph and LCN moieties that are bonded to the central tin atom.
The 1H chemical shift values of the N(CH3)2 groups differs only by
0.1 ppm for 4 (
d
(1H) ¼ 1.82 ppm in C6D6) in comparison with 5
(d
(1H) = 1.72 ppm in C6D6). On the other hand, the chemical shift
values of the CH2N moieties are significantly different (3.13 ppm for
4 and 3.48 ppm for 5). As mentioned above, the coupling constants
of the H(60) protons 3J(119Sn, 1H) are significantly higher for dio-
rganotin(IV) species (89.9 Hz for 4 and 106.3 Hz in the case of 5) in
comparison to triorganotin(IV) species due to the higher s-electron
density on the tin atom. The probable structural assignment for 4
comes from the 119Sn NMR spectra of the compound, which gives
a single resonance at ꢁ282.8 ppm, indicating the presence of only
one type of tin atom. Compound 5 has a single resonance (
(
d
119Sn) ¼ ꢁ366.5 ppm) in the 119Sn NMR spectra, too. The 119Sn
NMR chemical shift values of these two C,N-chelated diorganotin
(IV) bis(trifluoroacetates) are shifted to higher field relative to
starting LCN(n-Bu)SnCl2 (
(
d(
119Sn) ¼ ꢁ104.8 ppm) and LCNPhSnCl2 (
d
119Sn) ¼ ꢁ164.8 ppm). From these experimental data one could
deduce that the tin atom is six-coordinated in solution in both cases
with dynamic bonding fashion of both CF3COO substituents (fast
equilibrium between monodentately and bidentately bonded
CF3COO substituents). The 13C and 19F NMR spectra in C6D6 of both
4 and 5 reveal only one set of corresponding signal(s) of the CF3COO
moieties, indicating thus their bonding equality in solution.
Multiplicity and coupling constants of the signals of CF3COO
moieties in these 13C and 19F NMR spectra are nearly the same as for
Fig. 3. Molecular structure of 5$DMSO (ORTEP view, 40% probability level). Hydrogen
atoms and one of two positions of disordered CF3 group as well as a positional disorder
of Ph and LCN moieties are omitted for clarity. Selected interatomic distances [A] and
ꢁ
angles [ꢀ]: Sn1-N1 2.389(6), Sn1-O1 2.152(3), Sn1-O2 2.201(3), Sn1-O3 3.745(4), Sn1-
O4 2.213(3), Sn1-O5 3.461(4), Sn1-C1 2.099(6), Sn1-C10 2.145(5), N1-Sn1-O1 167.34
(15), O2-Sn1-O4 170.35(11), N1-Sn1-C1 77.8(2), N1-Sn1-O2 78.70(16), C1-Sn1-C10
169.6(2), O1-Sn1-C1 91.19(18), O1-Sn1-C10 98.90(17), O4-Sn1-C1 84.4(2), O2-Sn1-C10
93.52(17).
1 and 2. The only difference is a slight shift of the d(
13C) value to
lower field (by ca. 2 ppm relative to 1 and 2 in the case of dio-
rganotin(IV) bis(trifluoroacetates)) which further supports our
hypothesis of the fast equilibrium between monodentately and
bidentately bonded CF3COO substituents in the NMR time scale.
Multinuclear NMR spectra of 5 in DMSO-d6 as a coordinating
solvent were also recorded. The presence of the coordinated DMSO
molecule in 5 in DMSO-d6 has no effect on 1H, 13C and 19F NMR
spectra pattern but shifts the 119Sn NMR chemical shift value by ca.
previously published results [21]. The monodentate bonding
fashion of the CF3COO substituents in neat 3, 4 and 5 is confirmed
by IR (ATR) spectroscopy, too.
55 ppm relative to compound
(
5 to lower frequencies (d
119Sn) ¼ ꢁ422.9 ppm).
2.4. Hydrolysis of instable diorganotin(IV) bis(trifluoroacetates)
Unfortunately, compound 4 was isolated as yellowish oil which
cannot be crystallized but the structure of 5$DMSO was determined
by X-ray diffraction analysis (Fig. 3). This compound was isolated
from a sealed tube containing concentrated solution of 5 in dime-
thylsulfoxide. The strong coordination of the DMSO molecule to the
Unsuccessful attempts to crystallize compound 4 under an
argon atmosphere in a freezing box led to an idea to crystallize this
compound from THF (0.1% H2O) in the air in order to verify the
expectation of its instability. In the case of 4, the crystallization
from wet THF provided two different hydrolytic products (see
Scheme 3).
The first one isolated can be considered to be a zwitterionic
stannate of formula LCN(n-Bu)Sn(OC(O)CF3)2$CF3COOH (4a, Fig. 4).
This compound reveals structure similar to previously published
zwitterionic stannates [15]. The compound bears two CF3COO
substituents which are monodentately bonded to the tin atom in
ꢁ
tin atom (Sn1-O1 2.152(3) A) probably prevents oligomerization or
hydrolysis of the compound. The tin atom in 5$DMSO is six-coor-
dinated with nearly octahedral geometry having both carbon atoms
mutually in trans positions. Oxygen atoms of CF3COO substituents
are mutually in trans position, too, as well as the nitrogen atom is in
trans position to the oxygen atom of DMSO. The Sn1-N1 (2.389
ꢁ
(6) A) interatomic distance is very close to corresponding SneN
ꢁ
ꢁ
ꢁ
ꢁ
distance in compound 2 (2.451(3) A). The Sn1-O2 (2.201(3) A) and
the solid state (Sn1-O3 2.163(5) A and Sn1-O4 2.906(7) A; Sn1-O5
ꢁ
ꢁ
ꢁ
Sn1-O4 (2.213(3) A) interatomic distances for the monodentately
2.092(4) A and Sn1-O6 3.108(7) A). The third CF3COO substituent is
bonded to the tin atom and is also connected by a hydrogen bond
bonded carboxylates are longer than the interatomic distance Sn1-
O1 of coordinated DMSO molecule via the O1 atom. These inter-
atomic distances between the tin atom and carboxylic oxygen
atoms are even longer in comparison to corresponding distances
ꢁ
(N1-H1.O2 2.833(7) A) with the nitrogen atom of the ligand
which decreases the differences in the O1-C14 (1.251(8) A) and O2-
C14 (1.216(7) A) interatomic distances when compared with strictly
ꢁ
ꢁ
ꢁ
ꢁ
Sn1-O1 (2.114(3) A) and Sn1-O3 (2.108(3) A) in 3 or Sn1-O1 (2.187
monodentately acting CF3COO substituent (for example O3-C21
ꢁ
ꢁ
ꢁ
(3) A) in 2. As well as in previous cases, both CF3COO substituents
1.270(6) A and O4-C21 1.188(6) A in the case of 3). The negative
charge on the tin atom is compensated by the protonated nitrogen
atom possessing thus a positive charge. The central tin atom
remains five-coordinated having distorted trigonal bipyramidal
are bonded monodentately to the tin atom in the solid state
ꢁ
ꢁ
ꢁ
(Sn1-O2 2.203(4) A and Sn1-O3 3.745(4) A; Sn1-O4 2.213(3) A and
ꢁ
ꢁ
Sn1-O5 3.461(4) A). The SneC distances, being 2.099(6) A (Sn1-C1)
ꢁ
ꢁ
ꢁ
and 2.145(5) A (Sn1-C10), respectively, are comparable with
geometry. The Sn1-O1 (2.237(5) A), Sn1-O3 (2.163(5) A) and

ꢀ
680
P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
THF
4 LCN(n-Bu)Sn(OC(O)CF3)2 + 2 H2O
2 LCN(n-Bu)Sn(OC(O)CF3)2·CF3COOH
+ [LCN(n-Bu)SnOC(O)CF3]2(µ-OH)2 (4b)
(4a)
air
Scheme 3. The hydrolysis of compound 4.
ꢁ
Sn1-O5 (2.092(4) A) interatomic distances are within the range of
signals assigned to the CF3COO moieties in the 13C NMR spectrum
(quartet for COO at 162.5 ppm, 2J(19F, 13C) ¼ 37.5 Hz and quartet for
CF3 at 117.5 ppm, 1J(19F, 13C) ¼ 286.5 Hz) presumes the equality of
all three CF3COO substituents in solution. The 119Sn NMR chemical
shift value shifts upfield to ꢁ315.3 ppm in the case of 4a relative to
ꢁ
SneO distances of previously discussed 2 (Sn1-O1 2.187(3) A), 3
ꢁ
ꢁ
(Sn1-O1 2.114(3) A and Sn1-O3 2.108(3) A) or in already published
zwitterionic stannate
L
CN(n-Bu)2SnOC(O)CF3$CF3COOH [15]
ꢁ
ꢁ
(Sn1-O1 2.232(2) A and Sn1-O3 2.334(2) A). The interatomic
angle O1-Sn1-O3 (161.50(19)ꢀ) differs relatively roughly from the
ideal flat angle. The sum of all interatomic angles in the equatorial
plane is 358.8ꢀ. There is a relatively narrow band (1728 cmꢁ1) and
a very broad band with shoulders (1662 cmꢁ1) in the IR (ATR)
spectrum. These bands were assigned to the nas(COO) vibration.
Exactly the same situation occurs for the ns(COO) vibration (rela-
tively narrow band at 1510 cmꢁ1 and broadened band with
shoulders at 1404 cmꢁ1). This may indicate two non-equivalent
types of trifluoroacetate groups, the first one reveals the H-bond
with the protonated amino group and the second one is attributed
to the two monodentately bonded trifluoroacetate moieties. The
characteristic vibration for NeH group was not observed probably
due to the broadening of band.
starting 4 (
d
(
119Sn) ¼ ꢁ282.8 ppm).
The second hydrolytic product isolated from the mother liquor
is a centrosymmetric dimeric species of formula [LCN(n-Bu)SnOC(O)
CF3]2(m-OH)2 (4b, Fig. 5). Tin atoms are interconnected by two
hydroxo bridges forming thus four-membered rhombic planar ring
(torsion angle Sn1-O1-Sn1a-O1a 0.02(12)ꢀ). The interatomic angle
Sn1-O1-Sn1a (109.57(12)ꢀ) is much more wide than the O1-
Sn1-O1a interatomic angle (70.43(10)ꢀ). Each tin atom is six-coor-
dinated with roughly distorted octahedral geometry. Both CF3COO
substituents are bonded monodentately to the tin atom via O2 and
ꢁ
O2a (both Sn1-O2 and Sn1-O2a 2.412(3) A) atoms and the
remaining O3 and O3a atoms (both Sn1-O3 and Sn1-O3a 3.692
ꢁ
(3) A) are bonded to the hydroxo bridging groups (connecting the
ꢁ
The multinuclear NMR spectra in C6D6 of this compound reveal
patterns characteristic for the n-butyl and protonated LCN moieties
[15]. Very broad signal of the NH moiety was observed at
10.25 ppm in the 1H NMR spectra, too. The presence of only one
resonance at ꢁ74.7 ppm in the 19F NMR spectrum and one set of
tin atoms) (O1-H1.O3 2.652(4) A). This bond fashion again
ꢁ
decreases the differences in the O2-C14 (1.241(4) A) and O3-C14
ꢁ
(1.228(5) A) interatomic distances when compared with strictly
monodentately bonded CF3COO substituent (for example O3-C21
ꢁ
ꢁ
1.270(6) A and O4-C21 1.188(6) A in the case of 3). The Sn1-O2
ꢁ
(2.412(3) A) and Sn1a-O2a, respectively, interatomic distances are
identical and are apparently longer when compared with prepared
ꢁ
ꢁ
compounds 2 (Sn1-O1 2.187(3) A), 3 (2.114(3) A) and Sn1-O3 (2.108
ꢁ
ꢁ
ꢁ
(3) A) or 5$DMSO (Sn1-O2 (2.203(4) A) and Sn1-O4 (2.215(4) A))
described vide supra. Both SneN interatomic distances are 2.520
Fig. 4. Molecular structure of 4a (ORTEP view, 30% probability level). Hydrogen atoms
Fig. 5. Molecular structure of 4b (ORTEP view, 30% probability level). Hydrogen atoms
bonded to carbon atoms and one of the positions of disordꢀered CF3 groups are omitted
bonded to carbon atoms and one of the positions of disordered CF3 groups are omitted
ꢀ
ꢁ
ꢁ
for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-O1 2.237(5), Sn1-O2
for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-O1 2.094(3), Sn1-O1a
2.106(3), Sn1-O2 2.412(3), Sn1-O3 3.692(3), Sn1-C1 2.116(3), Sn1-N1 2.520(3), Sn1-C10
2.126(4), O2-C14 1.241(4), O3-C14 1.228(5), Sn1-O1-Sn1a 109.57(12), O1-Sn1-O1a
70.43(10), O1-Sn1-O2 80.20(9), O1a-Sn1-O2 150.63(10), N1-Sn1-C10 89.84(13),
N1-Sn1-O2 125.92(9), N1-Sn1-O1 152.23(10), N1-Sn1-O1a 83.06(10), N1-Sn1-C1 74.68
(12), O1-Sn1-C1 101.55(12), O1a-Sn1-C1 100.45(11). H-bonding (visualized by dashed
line): O1-O3 2.652(4), O1-H1.O3 143.8.
3.474(5), Sn1-O3 2.163(5), Sn1-O4 2.906(7), Sn1-O5 2.092(4), Sn1-O6 3.108(7), Sn1-C1
2.129(7), Sn1-C10 2.072(11), O1-C14 1.251(8), O2-C14 1.216(7), O3-C16 1.262(10), O4-C16
1.205(11), O5-C18 1.261(9), O6-C18 1.204(10), O1-Sn1-O3 161.50(19), O1-Sn1-C1 88.3(2),
O3-Sn1-C1 96.7(2), O1-Sn1-O5 82.21(18), O1-Sn1-C10 88.1(3), C1-Sn1-O5 109.9(2),
C1-Sn1-C10 129.2(4), O5-Sn1-C10 119.7(4). H-bonding (visualized by dashed line):
N1-O2 2.833(7), N1-H1.O2 155.8.

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P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
681
(3) A. The bands attributed to nas(COO) (1666 cmꢁ1, very broad with
O3 (from the CF3COO moiety) atoms are connected by hydrogen
ꢁ
shoulders) and ns(COO) (1457 and 1423 cmꢁ1, broadened bands) in
the IR (ATR) spectrum predicate only about uncertain bonding
fashion of the CF3COO substituents.
bond (O1-O3 2.727(7) A). This bonding fashion decreases the
ꢁ
ꢁ
ꢁ
differences in the O2-C16 (1.255(7) A) and O3-C16 (1.199(10) A)
interatomic distances when compared with strictly monodentately
bonded CF3COO substituent as discussed above. The interatomic
angle Sn1-O1-Sn2 (142.27(18)ꢀ) is forced out by the geometry of
the whole molecule. The presence of both bridging and mono-
dentately bonded CF3COO substituents, in the solid state, is further
supported by IR (ATR) spectroscopy. Two sets of broadened bands
assigned to nas(COO) (1714 and 1684 cmꢁ1) and ns(COO) (1478 and
1402 cmꢁ1) were observed in the IR spectrum.
The 1H NMR spectrum of 4b in THF-d8 reveals all signals of the
n-butyl and LCN moieties, the signal of bridging OH moieties was
not found. The possible explanation for this is that the OH bridges
may be NMR silent. According to the 13C and 19F NMR spectra, both
CF3COO substituents are equivalent in solution similarly as well as
in the case of 4a. There is only one resonance in the 119Sn NMR
spectra at ꢁ344.6 ppm proving the existence of only one tin-con-
taining species.
Due to the very low solubility of 5a, only 1H and 19F NMR spectra
in THF-d8 were recorded. The 1H NMR spectra pattern prove the
presence of both phenyl and LCN moieties. The signal of the bridging
OH moiety was not found in the spectra since the signal is probably
very broad. A broad multiplet is observed at ꢁ74.0 ppm in the 19F
NMR spectrum which is attributed to the two different CF3COO
substituents (two monodentately bonded ones and the bridging
one). Compound 5a is probably formed by the reaction of two
molecules of 5 with one molecule of water giving trifluoroacetic
acid as the by-product
On the other hand, the dinuclear product obtained by crystal-
lization of 5 from the THF (0.1% H2O) in the air, exhibits a new type
of the bonding fashion. The two tin atoms in [LCNPhSnOC(O)
CF3]2(
m-OH)(m-OC(O)CF3) (5a) are interconnected by one hydroxo
bridge and by one bridging trifluoroacetate substituent (inter-
atomic distances Sn1-O1 2.119(4) A, Sn2-O1 2.134(4) A, Sn1-O4
2.256(4) A and Sn2-O5 2.327(4) A) (Fig. 6). Both tin atoms are six-
coordinated with nearly octahedral geometry. Each tin atom also
bears another monodentately bonded trifluoroacetate substituent
(Sn1-O2 2.165(4) A and Sn1-O3 3.467(6) A; Sn2-O6 2.170(5) A and
Sn2-O7 3.545(5) A), phenyl substituent and bidentately bonded L
moieties (very strong intramolecular interaction Sn1-N1 2.425(6) A
and Sn2-N2 2.465(5) A). The nitrogen atoms are in trans position to
oxygen atom originating from the hydroxo bridge as well as oxygen
atoms of CF3COO substituents (bridging and two monodentately
bonded) are mutually in trans position. Both carbon atoms (from Ph
and LCN) are mutually in trans position, too. The O1 (bridging) and
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
CN
ꢁ
2.5. Instability of C,N-chelated tin(IV) tris(trifluoroacetate)
ꢁ
ꢁ
The most complicated situation involves the preparation and
structure determination of the LCNSn(OC(O)CF3)3. The preparation
of this compound, even carried out under an argon atmosphere and
anhydrous conditions, resulted in a mixture of two inseparable
products (with approximate ratio of 2:3), which was confirmed by
multinuclear NMR spectroscopy (in THF-d8). The 1H NMR spectrum
displays two sets of signals owing to the presence of two different
species in the reaction mixture. The value of the coupling constants
of satellites (3J(119Sn, 1H) ¼ 124.1 Hz and 118.8 Hz, respectively) of
the doublet of the H(60) signals at 7.97 ppm and 7.74 ppm respec-
tively, matches perfectly with previously published monoorganotin
(IV) species [21d]. Two broad signals assigned to CH2N
(d
(1H) ¼ 3.92 ppm) and N(CH3)2 (
d
(1H) ¼ 2.67 ppm) are present, too.
Surprisingly, only one set of signals assigned to the CF3COO moie-
ties was observed in the 13C NMR spectrum (quartet at 158.7 ppm 2J
(
19F, 13C) ¼ 38.0 Hz and quartet at 116.9 ppm 1J(19F, 13C) ¼ 285.5 Hz)
but two sets of signal belonging to LCN moieties are distinct. The
existence of two products in the reaction mixture is further proven
by 19F NMR and 119Sn NMR spectroscopy since there are two signals
in each NMR spectrum (ꢁ78.0 and ꢁ78.6 ppm in 19F NMR spectrum
and ꢁ525.8 and ꢁ544.3 ppm in 119Sn NMR spectrum. The signals in
119Sn NMR spectrum are shifted by ca. 110 ppm and 130 ppm,
respectively, to lower frequencies relative to starting LCNSnBr3
(d
(
119Sn) ¼ ꢁ413.5 ppm). Unfortunately no single crystals were iso-
lated from the reaction mixture up to now and therefore the real
identity of these compounds still remains doubtable. Despite these
complications, it is highly probable that one of the compounds is
the desired LCNSn(OC(O)CF3)3 and the second one could be dimeric
or oligomeric species.
Hence the reaction mixture was afterwards left in the air, single
crystals of [LCNSn(OC(O)CF3)]2(
m-O)(m-OC(O)CF3)2 (6) were
obtained as a major hydrolytic product in ca. 65% yield. Compound
6 is virtually formed by the reaction of two molecules of LCNSn(OC
(O)CF3)3 with one molecule of water giving two molecules of tri-
fluoroacetic acid as the by-product. Both tin atoms are six-coordi-
nated again in this dinuclear complex and are interconnected by
Fig. 6. Molecular structure of 5a (ORTEP view, 30% probability level). Hydrogen atoms
bonded to carbon atoms and one of the positions of disordered CF3 groups are omitted
ꢀ
ꢁ
for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-O1 2.119(4), Sn1-O2
2.165(4), Sn1-O3 3.467(6), Sn1-O4 2.256(4), Sn2-O1 2.134(4), Sn2-O5 2.327(4), Sn2-O6
2.170(5), Sn2-O7 3.545(5), Sn1-N1 2.425(6), Sn2-N2 2.465(5), Sn1-C1 2.120(6), Sn2-C20
2.126(6), Sn1-C10 2.123(6), Sn2-C29 2.115(6), O2-C16 1.255(7), O3-C16 1.199(10),
O4-C18 1.247(8), O5-C18 1.224(7), O6-C35 1.120(10), O7-C35 1.233(9), Sn1-O1-Sn2
142.27(18), O1-Sn1-N1 167.76(17), O1-Sn2-N2 174.02(17), O2-Sn1-O4 177.15(13),
O5-Sn2-O6 166.38(18), C1-Sn1-C10 164.0(2), C20-Sn2-C29 159.8(2), N1-Sn1-C1 76.0(2),
N2-Sn2-C20 76.1(2). H-bonding (visualized by dashed line): O1-O3 2.727(7),
O1-H1.O3 147.4.
ꢁ
one nearly symmetric oxo-bridge (Sn1-O1 1.939(2) A and Sn2-O1
ꢁ
1.931(2) A) and two bridging trifluoroacetates (Fig. 7). There is
a difference between the OeC interatomic distances in bridging
ꢁ
ꢁ
(nearly symmetric O2-C19 1.253(4) A and O3-C19 1.240(4) A;
symmetric O4-C21 1.251(4)
ꢁ
ꢁ
A and O5-C21 1.251(4) A) and

ꢀ
682
P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
seems that the structure of 6 is somewhat instable in solution and
repeated dissolution of this complex results in formation of further
unidentified hydrolytic products.
2.6. Catalytic experiments
Due to high Lewis acidity of the tin centres in both 4b and 6 the
possible catalytic activity of these compounds was also investi-
gated. Other oxygen bridged organotin(IV) compounds bearing the
same ligand were investigated for the same purpose, too.
2.6.1. Synthesis of Dimethyl carbonate (DMC) in supercritical carbon
dioxide using (LCN(n-Bu)2Sn)2O, LCN(t-Bu)2SnOH, (LCN)2Sn]O and
organotin(IV) trifluoroacetates as pre-catalysts
One of possible uses of the organotin(IV) compounds is their use
as catalysts in the synthesis of linear carbonates from alcohols and
carbon dioxide [26e28] in the presence of dehydrating reagents as
well as in the production of polycarbonates via ring-opening
polymerization of cyclic carbonates [29]. The use of above
mentioned compounds, described recently, as well as those
appeared in this paper as pre-catalysts of the synthesis of DMC in
supercritical CO2 was tested in order to evaluate the tin-containing
species activity in the use of CO2 as a cheap source of organic carbon
as published elsewhere.
Fig. 7. Molecular structure of 6$C6H6 (ORTEP view, 40% probability level). Benzene
molecule, hydrogen atoms and one of the positions of disordered CF3 moiety are
ꢀ
ꢁ
omitted for clarity. Selected interatomic distances [A] and angles [ ]: Sn1-O1 1.939(2),
Sn2-O1 1.931(2), Sn1-O2 2.151(3), Sn1-04 2.259(2), Sn1-O6 2.107(2), Sn1-O7 3.449(4),
Sn2-O3 2.281(2), Sn2-O5 2.150(2), Sn2-O8 2.118(2), Sn2-O9 3.432(3), Sn1-N1 2.275(4),
Sn2-N2 2.288(4), Sn1-C1 2.104(3), Sn2-C10 2.104(4), O2-C19 1.253(4), O3-C19 1.240(4),
O4-C21 1.251(4), O5-C21 1.251(4), O6-C23 1.268(4), O7-C23 1.212(5), O8-C25 1.270(5),
O9-C25 1.213(5), Sn1-O1-Sn2 129.02(13), N1-Sn1-O2 173.77(11), N1-Sn1-C1 79.76(13),
N2-Sn2-C10 80.54(12), N2-Sn2-O5 171.76(10), O1-Sn1-C1 170.18(12), O1-Sn2-C10
168.01(12), O4-Sn1-O6 179.06(9), O3-Sn2-O8 178.27(9), O1-Sn1-N1 91.82(11), N2-Sn2-
O1 90.61(10).
The reaction of (LCN(n-Bu)2Sn)2O [30] (1.190 g, 1.586 mmol)
with 20 mL of methanol at 220 bar of CO2 and 150 ꢀC for 20 h led
to the formation of 1.2 mmol of DMC. After this experiment, the
volatiles were removed and the NMR spectra were recorded. The
very major signal in 119Sn NMR spectrum was observed at
ꢁ71.4 ppm belonging to LCN(n-Bu)2SnOH [30] as a product of
hydrolysis of (LCN(n-Bu)2Sn)2O by water formed by reaction of
methanol and CO2. Two additional very minor signals for starting
oxide and the appropriate carbonate were also detected in the
ꢁ
ꢁ
monodentate (O6-C23 1.268(4) A and O7-C23 1.212(5) A; O8-C25
ꢁ
ꢁ
1.270(5) A and O9-C251.213(5) A) trifluoroacetate substituents. The
same spectrum [30]. Using of the solid residue - 0.986 g
monodentate bonding fashion of the two CF3COO moieties is also
clearly seen from the SneO distances (Sn1-O6 2.107(2) A and Sn1-
(2.57 mmol, calculated for LCN(n-Bu)2SnOH) led to the formation of
2.31 mmol of DMC at the same conditions. The next recycling of
0.534 g (1.39 mmol, calculated to LCN(n-Bu)2SnOH) of solid residue
gave 2.30 mmol of DMC. Then the nature of alcohols (methanol to
isopropanol) was changed in order to observe the possible
versatility of the catalyst but no trace of diisopropyl carbonate was
observed.
ꢁ
ꢁ
ꢁ
ꢁ
O7 3.449(4) A; Sn2-O8 2.118(2) A and Sn2-O9 3.432(3) A). The
vicinity of both tin atoms reveals slightly distorted octahedral
geometry. This hydrolytic product exhibits extremely strong
ꢁ
intramolecular interactions N/Sn (Sn1-N1 2.275(4) A and Sn2-N2
2.288(4) A) when compared with 4b (both SneN 2.520(3) A), 3
(Sn1-N1 2.506(3) A and Sn1-N2 2.516(4) A) or 5a (Sn1-N1 2.425(6)
and Sn2-N2 2.465(5) A) discussed above. The Sn1-O1-Sn2 inter-
ꢁ
ꢁ
ꢁ
ꢁ
Enormous increase of catalytic activity going from oxide to
hydroxide led us to the idea to use the sterically hindered and
stable LCN(t-Bu)2SnOH for the same reaction. After one night under
CO2 at atmospheric pressure, the analysis of the tin-based residue
ꢁ
atomic angle (129.02(13)ꢀ) is forced out by the presence of two
bridging trifluoroacetates connecting the tin atoms, which also
influences the geometry of the whole molecule. The IR (ATR)
spectroscopy confirms the presence of both monodentately bonded
CF3COO and bridging CF3COO substituents in the solid state since
two sets of broadened bands attributed to nas(COO) (1719 and
1685 cmꢁ1) and ns(COO) (1475 and 1416 cmꢁ1) are found in the IR
spectrum.
The interpretation of multinuclear NMR spectra of this dinuclear
complex in THF-d8 provided rather disputable results. There are
very broad signals in the aromatic region in the 1H NMR spectrum.
Two broad resonances assigned to CH2N and N(CH3)2 moieties are
the only signals in the aliphatic region of the same proton NMR
spectrum. Parallel to NMR investigation of the reaction mixture
containing presumably LCNSn(OC(O)CF3)3 only one set of signals of
the CF3COO groups (quartet at 161.8 ppm 2J(19F, 13C) ¼ 40.4 Hz and
quartet at 116.1 ppm 1J(19F, 13C) ¼ 289.8 Hz) was found in the 13C
NMR spectrum. This indicates presumably fast equilibrium
between mono- and bidentately bonded trifluoroacetates in the
NMR time scale. One major broad signal at ꢁ575.5 ppm and several
minor signals within the range of ꢁ500 to ꢁ750 ppm are found in
the 119Sn NMR spectrum. According to these interpretations it
L
CN(t-Bu)2SnOH by IR (ATR) showed two new strong absorptions
located at 1582 and 1318 cmꢁ1, respectively. The 119Sn NMR spec-
trum (in C6D6) displays a major signal (broad) at ꢁ65.9 ppm
attributable to the carbonate species. In the 13C NMR (in C6D6), the
presence of a signal at 163.4 ppm confirms the formation of
a CO2-adduct complex. In the reactor (200 bar, 150 ꢀC,15 h, 20 mL of
CH3OH), the complex LCN(t-Bu)2SnOH seems to be active for the
synthesis of DMC. However, at the end of the reaction, the IR
fingerprint of the tin-based residue collected does not correspond
to the initial species. In fact, the 2-(N,N-dimethylaminomethyl)
phenyl- ligand is lost during the reaction involving the formation of
the known trimeric complex, {[OC(OSnt-Bu2)2O$t-Bu2Sn(OH)2] in
the reactor [26c]. This observation is confirmed by comparison
between the IR and 119Sn NMR spectra. Single crystals in the NMR
tube using CD3OD as deuterated solvent were also isolated. The cell
parameters are strictly identical to the structure of {[OC(OSnt-
Bu2)2O$t-Bu2Sn(OH)2]3$(CH3OH)3}n.
The next experiment using [(LCN)2SnO]n (n ¼ 1e4) [31] (0.163 g,
0.141 mmol, yellow crystalline powder) as the catalyst precursor
under pressure of CO2 (200 bar,150 ꢀC) and in presence of methanol

ꢀ
P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
683
(20 mL) was carried out. Initially, the tin-compound is completely
soluble in methanol giving a solution slightly colour in yellow. After
20 h, no formation of DMC was observed. The tin-based residue was
also analysed (yellowish oil) by 119Sn NMR spectroscopy. Two weak
signals located at ꢁ284.3 ppm (attributable to [(LCN)2Sn(OH)]2
was also synthesized from DEC and phenol in 1.4% yield using
mixed niobium and titanium oxide catalyst with 37.6% of MPC as
a by-product [37]. Other possible pathways to produce DPC are the
reaction of dibutyl carbonate with phenol catalyzed by lead(II)
oxide (yield 1% wt. of DPC and 21% wt. of butyl phenyl carbonate
[38]) or lead(II) phenoxide (yield 62.5% wt. of DPC [39]).
Resorcylic acid can be decarboxyled at elevated temperatures
(ca. 270 ꢀC) to give pure resorcinol by treating the substrate with
NaOH or KOH in satisfactory yields [40] but there is still a demand
for lower temperature process.
And finally diphenyl carbonate reacts with aniline using NaOH as
a catalyst to give diphenyl urea in 38% yield [41]. On the other hand,
when compound 6 was used as a catalyst in related reactions
described vide infra, no formation of by-products was observed with
relatively high yields of desired products (see below). All the reactions
proceeded at lower temperatures (ca. 127 ꢀC) in comparison to
reported reactions.
(m
-OH) and ꢁ313.3 ppm for oxo-carbonate species were observed
[31b].
The reaction of 6 (0.884 g, 0.91 mmol) with 20 mL of methanol at
200 bar of CO2 and 150 ꢀC for 20 h led to the formation of only
0.3 mmol of DMC. The catalyst was not recycled due to its poor
catalytic activity and no additional runs were carried out. When the
same reaction was catalyzed by 4b (0.922 g, 1.05 mmol) under the
same conditions, somewhat higher yield of DMC was obtained
(0.7 mmol).
2.6.2. Preparation of carbonates, urea derivatives and
decarboxylation of resorcylic acid
Alkylation reactions are among the key industrial/organic
transformations for the production of a variety of fine and bulk
chemicals [32]. In this field, particularly in the past two decades, the
need for more environmentally acceptable processes has fuelled
a great interest towards dialkylcarbonates ((RO)2C]O) as innova-
tive alkylating agents [33b]. These compounds, in fact, possess
physico-chemical and reactivity features which make them
appealing for general synthetic applications, including, for
example, the selective alkylation of amines and phenols carried out
by both linear and cyclic organic carbonates [34]. The diethyl
carbonate (DEC) is a well-known non-toxic reagent and solvent
that have been used for many green applications, namely the
substitution of toxic reagents such as alkyl halides and phosgene for
the selective alkylation and carboxyalkylation, respectively, of
numerous nucleophiles [32]. The alkylation reactions of DEC with
phenols normally occurred in presence of overstoichiometric
amounts of base [35]. For preparation of diphenyl carbonate (DPC)
from DMC and phenol various organotin(IV) compounds (such as
Bu2SnO and Bu2Sn(OAc)2) were tested [36]. The best results were
obtained using minimally 1 M percent of [Bu2Sn(OH)(OTf)]2 (20.0%
yield of DPC), Bu2SnO/CH3C6H4SO3H system (20.8% yield of DPC)
and [Bu2Sn(OPh)]4(m3-O)2/CF3SO3H system (20.4% yield of DPC) as
catalysts. In all described reactions a methyl phenyl carbonate
(MPC) was also obtained as a by-product in high yields (up to 40.9%
in the case of Bu2Sn(OH)(OTf)]2). The plausible reaction mechanism
of formation of DPC was also described in the same paper [36]. DPC
In general, carbamates and urea derivatives are widely
encountered in the structure of biologically active compounds.
These compounds are usually prepared from phosgene [42],
phosgene derivatives [43] or isocyanates [44] in reaction with
alcohols in the case of carbamates and amines in the case of
ureas. Nevertheless, none of these methods are environmentally
benign (use of toxic reagents and generation of by-products).
Heterogeneous catalysis has also been reported for carbamate
and urea synthesis. For example, platinum group metals have
been developed to catalyze the alkoxycarbonylation of amines
leading to carbamates [45] but this reaction requires the use of
carbon monoxide. Only reactions of resorcinol with chlor-
oformates were previously investigated to the best of our
knowledge [46].
In the course of our studies on the use of catalysis in organic
chemistry, we developed a method which allows the direct
synthesis of ureas from amines and DEC. These reactions are
theoretically possible to run without catalysts but in that case they
are too slow to be useful in preparative scale. We have tested
various organotin(IV) catalysts. Best results were obtained with
compound 6 which was used as a catalyst for this reaction.
Compound 6 was selected to potentially catalyze also other reac-
tions of DEC with resorcinol (Scheme 4A), resorcylic acid (Scheme
4B), above mentioned aniline (Scheme 4C) and 4-bromoaniline
(Scheme 4D). The yields of desired products are essentially quan-
titative in the case of reactions C and D.
OH
HO
O
O
HO
HO
O
5 mol. % of 6
Et
+
A
Et
Et
- EtOH
O
O
O
OH
HO
OH
5 mol. % of 6
(EtO)2CO
- CO2
B
COOH
H
H
N
N
NH2
O
5 mol. % of 6
C
+
Et
Et
- EtOH
O
O
O
H
H
N
NH2
N
O
5 mol. % of 6
D
+
Et
Et
- EtOH
O
O
O
Br
Br
Br
Scheme 4. Selected reactions catalyzed by 5 mol % of 6 (conversion 9.2% (A), 73.5% (B), 100% (C) and 100% (D) relative to starting aromatic substrate).

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P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
3. Experimental
3.5. Preparation of 1
3.1. NMR spectroscopy
L
CN(n-Bu)2SnCl (687 mg, 1.71 mmol) was dissolved in THF
(15 mL) and solution of CF3COOAg (377 mg, 1.71 mmol) in THF
(10 mL) was added. AgCl precipitated immediately. The reaction
mixture was filtered and the filtration cake was washed with 10 mL
of THF. Oily colourless product was isolated after removing the
solvent in vacuo. Yield 730 mg (89%). 1H NMR (CDCl3, 295 K, ppm):
7.87 (d, 1H, H(60), 3J(1H(50), 1H(60)) ¼ 5.9 Hz, 3J(119Sn, 1H) ¼ 58.8 Hz);
7.30 (m, 2H, H(40, 50)); 7.13 (d, 1H, H(30)); 3.62 (s, 2H, NCH2); 2.36 (s,
6H, N(CH3)2); 1.62 (m, 4H, H(1)); 1.51 (m, 4H, H(2)); 1.41 (m, 4H, H
(3)); 0.85 (t, 6H, H(4)). 13C NMR (CDCl3, 295 K, ppm): 160.8 (q, OCO,
2J(19F, 13C) ¼ 37.2 Hz); 142.3 (C(20), 2J(119Sn, 13C) ¼ 36.4 Hz); 140.3 (C
(10), 1J(119Sn, 13C) ¼ 500.0 Hz); 137.6 (C(60), 2J(119Sn, 13C) ¼ 34.7 Hz);
129.6 (C(40)); 128.3 (C(50), 3J(119Sn, 13C) ¼ 59.9 Hz); 126.9 (C(30), 3J
The NMR spectra were recorded from solutions in CDCl3,
benzene-d6, THF-d8 and DMSO-d6 on a Bruker Avance 500 spec-
trometer (equipped with Z-gradient 5 mm probe) at frequencies 1H
(500.13 MHz), 13C{1H} (125.76 MHz), 19F{1H} (470.57 MHz) and
119Sn{1H} (186.50 MHz) at 295 K. The solutions were obtained by
dissolving of approximately 40 mg of each compound in 0.6 ml of
deuterated solvent. The values of 1H chemical shifts were calibrated
to residual signals of CDCl3 (7.27 ppm), benzene-d6
(
d
(1H) ¼ 7.16 ppm) or THF-d8 (
d
(1H) ¼ 3.57 ppm). The values of 13C
chemical shifts were calibrated to signals of CDCl3
(d
(
(
13C) ¼ 77.2 ppm), benzene-d6 (
d
(
13C) ¼ 128.4 ppm) or THF-d8 (
d
13C) ¼ 67.4 ppm). The values of 19F chemical shifts were calibrated
(
119Sn, 13C) ¼ 54.8 Hz); 116.3 (q, CF3, 1J(19F, 13C) ¼ 291.1 Hz); 65.8
to external standard CCl3F (
d
(
19F) ¼ 0.0 ppm). The 119Sn chemical
(CH2N); 45.8 (N(CH3)2); 28.1 (C(2), 2J(119Sn, 13C) ¼ 30.8 Hz); 27.3 (C
(3), 3J(119Sn, 13C) ¼ 87.5 Hz); 16.6 (C(1), 1J(119Sn, 13C) ¼ 501.1 Hz);
13.7 (C(4)). 19F NMR (CDCl3, 295 K, ppm): ꢁ74.7. 119Sn NMR (CDCl3,
295 K, ppm): ꢁ64.5. IR analysis (cmꢁ1, selected bands): 1698
shift values are referred to external neat tetramethylstannane (
d
(
119Sn) ¼ 0.0 ppm). Positive chemical shift values denote shifts to
the higher frequencies relative to the standards. 119Sn NMR spectra
were measured using the inverse gated-decoupling mode.
(nas(COO), s), 1405 (ns(COO), m), 1185 (n(CF3), vs), 1138 (n(CF3), vs).
Elemental analysis (%): found: C, 47.7; H, 6.6; N, 2.6. Calcd. for
C19H30F3NO2Sn (480.14): C, 47.53; H, 6.30; N, 2.92.
3.2. Crystallography
3.6. Preparation of 2
The X-ray data (Tables S1eS3, see Supporting Material) for
colourless crystals of all compounds were obtained at 150 K using
L
CNPh2SnCl (300 mg, 0.68 mmol) was dissolved in THF (15 mL).
Oxford Cryostream low-temperature device on a Nonius KappaCCD
AgCl precipitated upon addition of a solution of CF3COOAg (150 mg,
0.68 mmol) in THF (10 mL). The reaction mixture was filtered and
the filtration cake was washed with 10 mL of THF. White crystalline
product was isolated after removing the solvent in vacuo. Yield
300 mg (85%). M.p. 157e160 ꢀC. 1H NMR (CDCl3, 295 K, ppm): 8.15
(d, 1H, H(60), 3J(1H(50), 1H(60)) ¼ 7.0 Hz, 3J(119Sn, 1H) ¼ 60.5 Hz); 7.70
(d, 4H, H(2000), 3J(1H(3000), 1H(2000)) ¼ 6.6 Hz, 3J(119Sn, 1H) ¼ 61.2 Hz);
7.44 (m, 4H, LCN and Ph group); 7.38 (m, 4H, LCN and Ph group); 7.19
(d, 1H, H(30), 3J(1H(40), 1H(30)) ¼ 7.5 Hz); 3.56 (s, 2H, NCH2); 1.88 (s,
6H, N(CH3)2). 13C NMR (CDCl3, 295 K, ppm): 160.4 (q, OCO, 2J(19F,
13C) ¼ 37.5 Hz); 143.0 (C(20), 2J(119Sn, 13C) ¼ 38.9 Hz); 139.1 (C(1000),
ꢁ
diffractometer with MoKa radiation (
l
¼ 0.71073 A), a graphite
monochromator, and the and
4
c
scan mode. Data reductions were
performed with DENZO-SMN [47]. The absorption was corrected by
integration methods [48]. Structures were solved by direct
methods (Sir92) [49] and refined by full matrix least-square based
on F2 (SHELXL97) [50]. Hydrogen atoms were mostly localized on
a difference Fourier map, however to ensure uniformity of the
treatment of the crystal, all hydrogen atoms were recalculated into
idealized positions (riding model) and assigned temperature
factors Hiso(H) ¼ 1.2 Ueq(pivot atom) or of 1.5Ueq for the methyl
ꢁ
1J(119Sn, C) ¼ 795.3 Hz); 138.3 (C(60), 2J(119Sn, 13C) ¼ 38.8 Hz);
moiety with CeH ¼ 0.96, 0.97, and 0.93 A for methyl, methylene
13
ꢁ
136.6 (C(10), 1J(119Sn, C) ¼ 814.8 Hz); 136.1 (C(2000), 2J(119Sn,
and hydrogen atoms in aromatic rings, respectively, and 0.82 A for
13
13C) ¼ 45.3 Hz); 130.5 (C(40)); 130.0 (C(4000)); 129.1 (C(3000), 3J(119Sn,
13C) ¼ 69.9 Hz); 128.7 (C(50), 3J(119Sn, 13C) ¼ 68.4 Hz); 127.5 (C(30), 3J
NeH and OeH groups. The molecules of 4b, 5a and 6$C6H6 reveal
the disordered CF3 groups, molecule of 4a the n-butyl group and
a positional disorder of phenyl and LCN moieties is found in
5$DMSO. All these disorders were solved by constraint and
restraint options available in SHELXL97 software giving the best
results in crystallographic parameters.
(
119Sn, 13C) ¼ 64.0 Hz); 116.0 (q, CF3, 1J(19F, 13C) ¼ 290.0 Hz); 64.9
(CH2N); 46.0 (N(CH3)2). 19F NMR (CDCl3, 300 K, ppm): ꢁ74.5. 119Sn
NMR (CDCl3, 300 K, ppm): ꢁ204.2. IR analysis (cmꢁ1, selected
bands): 1684 (nas(COO), s), 1402 (ns(COO), m), 1179 (n(CF3), s), 1136
(n(CF3), vs). Elemental analysis (%): found: C, 53.2; H, 4.4; N, 2.6.
Calcd. for C23H22F3NO2Sn (520.12): C, 53.11; H, 4.26; N, 2.69.
3.3. IR spectroscopy
3.7. Preparation of 3
IR spectra were recorded on Bruker Vector 22 spectrometer
using ATR technique at ambient temperature.
L
CN)2SnBr2 (608 mg, 1.11 mmol) was dissolved in THF (20 mL)
and solution of CF3COOAg (491 mg, 2.22 mmol) in THF (15 mL) was
added. AgCl precipitated immediately. The reaction mixture was
filtered and the filtration cake was washed with THF (10 mL).
Yellowish crystalline product was isolated after removing the
solvent in vacuo. Yield 422 mg (62%). M.p. 246e248 ꢀC. 1H NMR
(THF-d8, 295 K, ppm): 8.15 (d, 2H, H(60), 3J(1H(50), 1H(60)) ¼ 6.0 Hz,
3J(119Sn, 1H) ¼ 97.9 Hz); 7.43 (m, 4H, H(40, 50); 7.23 (dd, 2H, H(30), 3J
(1H(40), 1H(30)) ¼ 5.2 Hz, 4J(119Sn, 1H) ¼ 47.0 Hz); 3.74 (s, 4H, NCH2);
2.31 (s, 6H, N(CH3)2); 2.01 (s, 6H, N(CH3)2). 13C NMR (THF-d8, 295 K,
ppm): 161.0 (q, OCO, 2J(19F, 13C) ¼ 38.5 Hz); 141.8 (br, C(20)); 139.0
(br, C(10)); 137.2 (br, C(60)); 131.3 (br, C(40)); 129.1 (br, C(50)); 128.5
(br, C(30)); 115.9 (q, CF3, 1J(19F, 13C) ¼ 282.2 Hz); 64.7 (CH2N); 46.6
(br, N(CH3)2). 19F NMR (THF-d8, 295 K, ppm): ꢁ75.0. 119Sn NMR
3.4. Synthesis
L
CN(n-Bu)2SnCl [14], LCNPh2SnCl [13], LCN(n-Bu)SnCl2 [21c],
CNPhSnCl2 [21b], (LCN)2SnBr2 [21b] and LCNSnBr3 [21d] were
L
prepared according to published procedures. All solvents and
CF3COOAg (98%) were obtained from commercial sources (Sigma-
eAldrich). THF was dried by distillation from sodium-potassium alloy,
degassed and stored over a potassium mirror. All reactions were
carried out under an argon atmosphere using standard Schlenk
techniques. Single crystals suitable for X-ray diffraction analyses were
obtained from corresponding solutions of products by slow evapo-
ration of the solvent in the air. Melting points are uncorrected.

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P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
685
(THF-d8, 295 K, ppm): ꢁ381.3. IR analysis (cmꢁ1, selected bands):
1H, LCN); 3.92 (br, 4H, NCH2); 2.67 (br, 6H, N(CH3)2). 13C NMR
(THF-d8, 295 K, ppm): 158.7 (q, OCO, 2J(19F, 13C) ¼ 38.0 Hz); 138.9
(br, C(20)); 135.6 (very broad signal, C(10)); 134.5 (br, C(60)); 132.0
(br, C(40)); 130.0 (br, C(50)); 128.7 (br, C(30)); 116.9 (q, CF3, 1J(19F,
13C) ¼ 285.5 Hz); 63.8 (CH2N); 63.3 (CH2N); 46.7 (N(CH3)2); 45.9 (N
(CH3)2). 19F NMR (THF-d8, 295 K, ppm): ꢁ78.0; ꢁ78.6. 119Sn NMR
(THF-d8, 295 K, ppm): ꢁ525.8; ꢁ544.3. IR analysis (cmꢁ1, selected
bands): 1719 and 1685 (nas(COO, vs), 1416 and 1370 (ns(COO), s),
1696 (nas(COO), s), 1396 (ns(COO), m), 1181 (n(CF3), vs), 1142 (n(CF3),
vs). Elemental analysis (%): found: C, 43.0; H, 4.0; N, 4.6. Calcd. for
C22H24F6N2O4Sn (613.13): C, 43.10; H, 3.95; N, 4.57.
3.8. Preparation of 4
L
CN(n-Bu)SnCl2 (826 mg, 2.17 mmol) was dissolved in THF
(20 mL) and solution of CF3COOAg (958 mg, 4.34 mmol) in THF
(20 mL) was added. AgCl precipitated immediately. The reaction
mixture was filtered and the filtration cake was washed with THF
(10 mL). The solvent was evaporated in vacuo giving yellow oil as
the sole product. Yield 498 mg (78%). 1H NMR (C6D6, 295 K, ppm):
8.00 (d,1H, H(60), 3J(1H(50), 1H(60)) ¼ 6.3 Hz, 3J(119Sn, 1H) ¼ 89.9 Hz);
7.08 (m, 1H, H(40)); 7.00 (t, 1H, H(50)); 6.74 (d, 1H, H(30)); 3.13 (s, 2H,
NCH2); 1.82 (s, 6H, N(CH3)2); 1.75 (br, 4H, H(1, 2)); 1.27 (m, 2H, H
1178 (
n(CF3), vs), 1140 (n(CF3), vs).
3.11. Isolation of 6
Compound 6 was crystallized in the air from the THF (0.1% H2O)
solution of reaction mixture of LCNSnBr3 and CF3COOAg described
above. Yield 1.86 g (65%erelative to starting LCNSnBr3). M. p.
98e100 ꢀC. Multinuclear NMR spectra are described in results and
discussion section.
(3)); 0.84 (t, 3H, H(4)). 13C NMR (C6D6, 295 K, ppm): 163.1 (q, OCO, 2J
13
(
19F, C) ¼ 34.5 Hz); 140.3 (br, C(20)); 139.0 (very broad signal, C
(10)); 135.1 (C(60), 2J(119Sn, 13C) ¼ 61.4 Hz); 128.4 (C(40)); 127.2 (C(30),
3J(119Sn, 13C) ¼ 86.2 Hz); 116.5 (q, CF3, 1J(19F, 13C) ¼ 288.8 Hz); 63.1
(CH2N); 44.7 (N(CH3)2); 26.9 (C(2), 2J(119Sn, 13C) ¼ 48.4 Hz); 26.1 (C
(3), 119Sn satellites were not found); 25.5 (C(1), 119Sn satellites were
not found); 13.3 (C(4)); the resonance for the C(50) atom is over-
lapped by the signal of C6D6. 19F NMR (C6D6, 295 K, ppm): ꢁ74.5.
119Sn NMR (C6D6, 295 K, ppm): ꢁ282.8. IR analysis (cmꢁ1, selected
3.12. Catalytic experiments
General procedure for reactions of methanol with CO2: The
reaction was carried out in a 125 mL stainless steel reactor equip-
ped with a magnetic stirrer. The reactor was purged with argon and
a 20 mL solution of the appropriate tin(IV) complex in methanol
was introduced by syringe. Then, CO2 was admitted to the desired
amount. The reaction temperature was controlled by an internal
thermocouple. After a reaction time of 20 h the reactor was cooled
down to 0 ꢀC, pressure was gently released and the liquid phase was
transferred to a Schlenk tube. Trap-to-trap distillation under
vacuum at ambient temperature allowed separation of volatiles
compounds that were quantitatively analysed by GC (DEC external
standard, Fisons 8000, J&W Scientific DB-WAX 30 m capillary
column, FID detector). Tin-based residue was characterized by IR
and multinuclear NMR spectroscopy. Recycling experiments con-
sisted of taking the tin-based residue for successive runs under the
same experimental conditions.
General procedure for other reactions catalyzed by 6: 1M solu-
tions of appropriate substrate (resorcinol, resorcylic acid, aniline
and 4-bromoaniline) in diethyl carbonate were prepared by dis-
solving 0.1 mol of the substrate in 100 mL volume of DEC.
The reaction was carried out in a 50 mL round-bottomed flask
equipped with a magnetic stirrer and a reflux condenser. The outlet
of the condenser was fitted to a glass tube filled with granulated
charcoal. The reaction flask was immersed in an oil bath. The
catalyst (compound 6; 5 mol %) and 5 mL of 1M DEC solution of
appropriate substrate (5 mmol) was added. The reaction mixture
was heated to reflux for 16 h under vigorous stirring and evapo-
rated to dryness in the next step. The 20 mg portion of the residue
of reaction mixture was dissolved in DMSO-d6. The 1H NMR spectra
then indicate the conversion of substrate to products (products
were identified using commercially available or synthesized
internal standards).
bands): 1666 (nas(COO), s), 1400 (ns(COO), m), 1180 (
n(CF3), vs),1132
(n
(CF3), vs). Elemental analysis (%): found: C, 38.3; H, 4.1 N, 2.4.
Calcd. for C17H21F6NO4Sn (536.04): C, 38.09; H, 3.95; N, 2.61.
3.9. Preparation of 5
L
CNPhSnCl2 (844 mg, 2.10 mmol) was dissolved in THF (20 mL) and
solution of CF3COOAg (930 mg, 4.20 mmol) in THF (15 mL) was added.
AgCl precipitated upon addition. The reaction mixture was filtered
and the filtration cake was washed with THF (10 mL). After removing
the solvent in vacuo yellowish crystalline product was isolated. Yield
655 mg (56%). M.p. 145e147 ꢀC. 1H NMR (C6D6, 295 K, ppm): 8.25 (d,
1H, H(60), 3J(1H(50), 1H(60)) ¼ 6.8 Hz, 3J(119Sn, 1H) ¼ 106.3 Hz); 8.04 (d,
2H, H(2000), 3J(1H(3000), 1H(2000)) ¼ 7.0 Hz, 3J(119Sn, 1H) ¼ 107.5 Hz); 7.31
(t, 2H, H(3000)); 7.20 (m, 2H, LCN and Ph group); 7.14 (m, 1H, H(4000));
6.85 (d, 1H, H(30), 3J(1H(40), 1H(30)) ¼ 7.0 Hz, 4J(119Sn, 1H) ¼ 106.3 Hz);
3.48 (s, 2H, NCH2); 1.72 (s, 6H, N(CH3)2). 13C NMR (C6D6, 295 K, ppm):
161.7 (q, OCO, 2J(19F, 13C) ¼ 39.3 Hz); 142.0 (br, C(20)); 141.0 (br, C(1000));
138.9 (br, C(60)); 137.1 (br, C(10)); 136.0 (very broad signal, C(2000));
131.5 (very broad signal, C(4000)); 130.5 (br, C(40)); 129.9 (very broad
signal, C(3000)); 128.4 (br, C(30)); 116.0 (q, CF3, 1J(19F, 13C) ¼ 289.2 Hz);
64.0 (CH2N); 45.9 (N(CH3)2), the resonance for the C(50) atom is
overlapped by the very broad signal of the C(30’) atom. 19F NMR (C6D6,
295 K, ppm): ꢁ74.7. 119Sn NMR (C6D6, 295 K, ppm): ꢁ366.5 (very
broad signal). IR analysis (cmꢁ1, selected bands): 1685 (nas(COO), s),
1402 (ns(COO), m), 1182 (n(CF3), vs), 1144 (CF3, s). Elemental analysis
(%): found: C, 40.9; H, 3.2; N, 2.6. Calcd. for C19H17F6NO4Sn (556.03): C,
41.04; H, 3.08; N, 2.52.
Acknowledgments
3.10. Attempt to prepare LCNSn(OC(O)CF3)3
The Pardubice group would like to thank the Grant Agency of
the Czech Republic (grant no. 104/09/0829) and the Ministry of
Education of the Czech Republic (VZ 0021627501) for financial
support. The Barrande bilateral programme (MEB021040) is also
greatly acknowledged by both French and Czech side. The French
side also gratefully acknowledges the Centre National de la
Recherche Scientifique (France) as well as the French Ministry of
Foreign Affairs and French Ministry of Education and Research
(Czech-French project Barrande 2010 no. 21880RL) for the financial
support of this work.
LCNSnBr3 (2.150 g, 4.36 mmol) was dissolved in THF (20 mL) and
solution of CF3COOAg (2.892 g, 13.09 mmol) in THF (15 mL) was
added. AgBr precipitated immediately. The reaction mixture was
filtered and the filtration cake was washed with THF (2 ꢂ 10 mL). A
mixture of two yellowish crystalline inseparable products resulted
from the reaction residue after removing the solvent in vacuo. 1H
NMR (THF-d8, 295 K, ppm): 7.97 (d, H(60), 3J(1H(50), 1H(60)) ¼ 6.8 Hz,
3J(119Sn, 1H) ¼ 124.1 Hz); 7.74 (d, H(60), 3J(1H(50), 1H(60)) ¼ 7.0 Hz, 3J
(
119Sn, 1H) ¼ 118.8 Hz); 7.40 (m, 2H, LCN); 7.35 (m, 1H, LCN); 7.23 (m,

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686
P. Svec et al. / Journal of Organometallic Chemistry 696 (2011) 676e686
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ꢀ
ꢁꢀ ꢀ
ꢀ
[21] (a) Z. Padelková, I. Císarová, A. Ruzicka, Acta Crystallogr. E 61 (2005) M2691;
Appendix. Supplementary material
ꢀ
ꢀ
ꢁꢀ ꢀ
ꢀ
(b) P. Novák, Z. Padelková, L. Kolárová, I. Císarová, A. Ruzicka, J. Holecek, Appl.
Organomet. Chem. 19 (2005) 1101;
(c) P. Svec, Z. Padelková, I. Císarová, A. Ruzicka, J. Holecek, Main Group Met.
Chem. 31 (2008) 305;
ꢀ
Supplementary material associated with this article can be found
in the online version, at doi:10.1016/j.jorganchem.2010.09.050.
ꢀ
ꢀ
ꢁꢀ ꢀ
ꢀ
ꢀ
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Crystallographic data for structural analysis have been deposited
with the Cambridge Crystallographic Data Centre. Copies of this
information may be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge CB2 1EY, UK (fax: þ44-1223-336033; e-
mail: deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
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