Unusual reactivity of a C,N-chelated stannylene with siloxanes and silanols

Article abstract of DOI:10.1021/om400123y

The reactivity of stannylene (L^CN)₂Sn (1), where L^CN is the 2-(N,N-dimethylaminomethyl)phenyl substituent, toward (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), silicon grease, and triphenylsilanol was explored. The reaction of 1 with one equivalent of TEMPO and silicon grease yielded cyclo-[(L^CN)₂SnOSn(L ^CN)₂OSiMe₂O] (6a), whereas the addition of two equivalents of TEMPO afforded cyclo-[(L^CN)(L^CN - O)SnOSiMe₂OSiMe₂O] (6b), in which the amine nitrogen atom of one of the L^CN ligands is oxidized to N-oxide. The reaction of 1 with one equivalent of TEMPO and subsequent addition of triphenylsilanol gave (L^CN)₂Sn(OSiPh₃)₂ (5), which further reacted with air in a chloroform solution to provide [(L^CN)(L ^CN=O)Sn(OSiPh₃)Cl] (7), containing one of the chelating L^CN ligands in the corresponding N-oxide form. In contrast, the direct reactions of 1 with one or two equivalents of triphenylsilanol gave rise to the adduct [Sn(OSiPh₃)₂]·C₆H ₅CH₂NMe₂ (8a) and the salt [C₆H ₅CH₂N(H)Me₂]⁺[Sn(OSiPh ₃)₃]^- (8b), respectively. All compounds were characterized by NMR spectroscopy and by X-ray diffraction. Analogous reactions of 1 with activated silica were shown to yield tin-doped silica, which was characterized by powder X-ray diffraction and various spectroscopic and microscopic techniques.

Full text of DOI:10.1021/om400123y

Article
pubs.acs.org/Organometallics
Unusual Reactivity of a C,N-Chelated Stannylene with Siloxanes and
Silanols
,†
†
†
‡
§
§
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Zdenka Padelkova,* Petr Svec, Hana Kampova, Jan Sykora, Miloslav Semler, Petr Stepnicka,
̌
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Snejana Bakardjieva,⊥ Rudolph Willem,∥ and Ales Ruzicka†
†Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentska
10, Pardubice, Czech Republic
‡Institute of Chemical Process Fundamentals of the Academy of Sciences of the Czech Republic, Rozvojova 2/135, CZ-165 02 Prague
̌
̌
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95, CZ-532
6−Suchdol, Czech Republic
§Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague, Czech Republic
⊥
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Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 Rez, Czech Republic
̌
∥Department of Materials and Chemistry, High Resolution NMR Centre, Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050
Brussels, Belgium
S
* Supporting Information
ABSTRACT: The reactivity of stannylene (LCN)2Sn (1), where LCN is the 2-(N,N-
dimethylaminomethyl)phenyl substituent, toward (2,2,6,6-tetramethylpiperidin-1-yl)oxyl
(TEMPO), silicon grease, and triphenylsilanol was explored. The reaction of 1 with one
equivalent of TEMPO and silicon grease yielded cyclo-[(LCN)2SnOSn(LCN)2OSiMe2O]
(6a), whereas the addition of two equivalents of TEMPO afforded cyclo-[(LCN)(LCN

O)SnOSiMe2OSiMe2O] (6b), in which the amine nitrogen atom of one of the LCN ligands
is oxidized to N-oxide. The reaction of 1 with one equivalent of TEMPO and subsequent
addition of triphenylsilanol gave (LCN)2Sn(OSiPh3)2 (5), which further reacted with air in a
chloroform solution to provide [(LCN)(LCNO)Sn(OSiPh3)Cl] (7), containing one of the
chelating LCN ligands in the corresponding N-oxide form. In contrast, the direct reactions of
1 with one or two equivalents of triphenylsilanol gave rise to the adduct [Sn-
(OSiPh3)2]·C6H5CH2NMe2 (8a) and the salt [C6H5CH2N(H)Me2]+[Sn(OSiPh3)3]−
(8b), respectively. All compounds were characterized by NMR spectroscopy and by X-ray
diffraction. Analogous reactions of 1 with activated silica were shown to yield tin-doped silica, which was characterized by powder
X-ray diffraction and various spectroscopic and microscopic techniques.
O)2 (2,6 LCN = 2-[(CH3)2NCH2]C6H4; Scheme 1), viz., cyclo-
1. INTRODUCTION
[(LCN)2SnO(Me)2SiO)]2 (4).7 An alternative approach to the
The cyclic heterometallic oxides attract considerable attention
synthesis of this eight-membered cyclic disilastannoxane from
mostly because of growing interest in special, mainly ceramic,
materials and their applications.1 In the case of the siloxane
cycles, some unexpected and fortuitous results2 have been
Scheme 1. The Previously Reported Reactivity of 1 and the
Numbering of the LCN Ligand
obtained by the reactions of strongly polar reagents with silicon
grease, which is generally granted to be a nonreactive material.
In the field of organotin(IV) siloxanes, the tricyclic species t-
Bu4Sn(Me2Si)O3·t-Bu2Sn(OH)2 was reported by Pannell and
co-workers.3 Structurally related but branched systems
containing electronegative (halogen or oxygen atoms) sub-
stituents were prepared by substitution4 or condensation5
reactions of tin and silicon oxides and/or hydroxides and, in
some cases, were isolated as byproducts of polymerization
reactions. They revealed high structural differences, featuring
for example six-membered rings with one or two tin atoms,
different eight-membered rings in either chair- or boat-like
conformation with one to three tin atoms, and, last but not
least, oligocyclic structures.
Recently, we have isolated an unusual product from the
Received: February 14, 2013
Published: April 8, 2013
metathesis of silicon grease and organotin oxide [(LCN)2Sn]2(μ-
© 2013 American Chemical Society
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(LCN)2SnBr2, Me2SiCl2, and four equivalents of NaOH or from
[(LCN)2SnO]n (2) and cyclic siloxanes D3 or D4 (i.e.,
(Me2SiO)3 or (Me2SiO)4) in refluxing xylene has been reported
also.7 Oxide 2 reacts with carbon dioxide to give carbonate 3
and also condensates with triphenylsilanol to produce acyclic
compound 5 (Scheme 1).7 All compounds mentioned in our
previous work as well as in the present study contain a C,N-
chelating ligand, which is, according to the work done by
Jurkschat et al.,8 probably responsible for a higher reactivity of
organotin species and formation of cyclic structures. These
compounds are also relevant to the nowadays popular area of
mimicking heterogeneous catalysts immobilized over silica
supports or zeolites by molecular models represented by
silanols and polyhedral oligomeric silsesquioxanes.9
numbering see Scheme 1). Signals of the benzylic CH2 protons
coalesce into an unresolved hump, and a single signal for the
Me2SiO group is found at δH −0.4 ppm. The 119Sn NMR
spectra of 6a were recorded in two different solvents (toluene-
d8 and THF-d8) in order to explore a possible dependence of
chemical shift on the solvent. The 119Sn chemical shifts are very
close to each other (δSn −292 ppm in THF-d8, and −288 ppm
in toluene-d8), comparable to values found for other pseudo-
octahedrally coordinated tin atoms in 2 and 3.6,7 The 119Sn
signal observed in toluene-d8 displays coupling satellites of 458
Hz, typical for two-bond 119Sn−117Sn couplings in stannox-
anes.14 When the solution of 6a is allowed to stand for a longer
period (ca. 2 months), the formation of stannoxane 2 is
detected by 119Sn NMR.
The complex reactivity suggested by our previous studies led
us to further explore the reactivity of C,N-chelated tin(II/IV)
species with simple siloxanes (silicone grease), triphenylsilanol,
and silica. The results of this study are presented in this paper.
The solid-state structure of 6a consists of a six-membered
ring constituted by two tin atoms and one SiMe2 moiety
alternating with three oxygen atoms, displaying an approximate
twisted boat conformation (Figure 1). The tin atoms in 6a are
2. RESULTS AND DISCUSSION
The present study started with an oxidation reaction of
stannylene 110 using (2,2,6,6-tetramethylpiperidin-1-yl)oxyl
(TEMPO) according to an approach of Kira,11 who oxidized
his low-valent group 14 species with this reagent essentially
quantitatively. After the oxidation, we isolated 6a as a very
minor species and characterized it by X-ray diffraction analysis
(Scheme 2). The yield of 6a improved when the same amount
Scheme 2. Reactivity of 1 toward TEMPO and Silicon
Grease (2: n = 1−4)
Figure 1. Molecular structure of 6a (ORTEP view, 30% probability
level). Hydrogen atoms are omitted for clarity. Selected interatomic
distances [Å] and angles [deg]: Sn1−O1 1.991(4), Sn1−O2 2.004(4),
Sn1−N1 2.736(5), Sn1−N2 2.693(4), Sn1−C1 2.134(4), Sn1−C10
2.132(6), Sn2−O1 1.981(4), Sn2−O3 2.019(3), Sn2−N21 2.674(4),
Sn2−N22 2.796(5), Sn2−C201 2.125(5), Sn2−C210 2.160(12);
Sn1−O1−Sn2 127.44(17), Sn1−O1−Sn2 127.44(17), O1−Sn1−N1
171.77(16), O2−Sn1−N2 167.90(16), C1−Sn1−C10 147.7(2), O1−
Sn2−N22 171.48(15), O3−Sn2−N21 167.84(14), C201−Sn2−C210
142.5(4).
of Wacker silicon grease or one molar equivalent of freshly
prepared Me2Si(OH)2 was added to the system directly after
oxidation. Surprisingly, the same product was obtained in a
nearly quantitative yield when two equivalents of lithium metal,
12-crown-4, and silicon grease were mixed in diethyl ether for
three weeks.
It should be noted that the course of the reaction between 1,
TEMPO, and silicon grease depends on the order of addition
and the amount of reagents (Scheme 2). For instance,
increasing the amount of TEMPO to two or more equivalents
results in the formation of disilastannoxane 6b, in which one of
the chelating LCN ligands is oxidized to the corresponding N-
oxide. Similar results of nitrogen oxidation were observed for
other tin and also bismuth species in which, however, harsh
reaction conditions had to be applied to complete the
oxidation.12
[4+2] coordinated, adopting a heavily distorted octahedral
geometry. The interatomic Sn−N distances varying in the range
2.674(4) Å (Sn2−N21) to 2.796(5) Å (Sn2−N22) indicate
very weak intramolecular N→Sn interactions, affecting never-
theless the coordination of the tin atoms.
The 1H NMR spectrum of 6b recorded at room temperature
in THF-d8 suggests some dynamic behavior. Similar dynamic
behavior has been reported by Jurkschat et al. for the closely
related hypercoordinated organotin(IV) species according to
NMR spectroscopy measurements performed at variable
temperature.13 The methyl groups at the N-oxide moiety give
rise to two singlets, while those in the amino group give rise to
a broad singlet, indicating some exchange process. Upon
lowering the temperature, the latter signals split into two
1
The H NMR spectrum of 6a, which is quite insoluble in all
common deuterated solvents, is rather complex due to mutual
nonequivalence of the organic ligands connected to the tin
atom, similarly to that described in the literature.13 One broad
and one doublet resonance is observed for the H6 protons (for
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singlets (δH 2.36 and 1.96 ppm at −25 °C), whereas raising the
temperature led to a broadening of the N-oxide methyl
resonances as well, suggesting that the N-oxide arm likewise
undergoes a similar dynamic process at higher temperature (the
temperature was limited to 40 °C because of using a sealed
NMR tube). The assumed dynamic process averages only the
methyl resonances but not the benzyl CH2 resonances, which
remain unaffected. The 29Si NMR spectrum of 6b recorded at
room temperature revealed two broad signals. Even in this case,
the temperature lowering caused the signals to sharpen, while
increasing the temperature led to their coalescence into an
extremely broad resonance. The dynamic behavior averaging
the 29Si resonances can be due to either ring dynamics or
decoordination of the nitrogen atoms and their exchange
around the tin center. Methyl group exchange under
configuration inversion of the nitrogen atom of the LCN ligand
is another possibility that needs to be taken into consideration.
The 119Sn NMR resonance of 6b (−456 ppm) appears about
200 ppm upfield when compared to 2, 3, and 6a, which
suggests a very strong coordination of the N-oxide group to the
tin atom.
An unexpected result was obtained from the already reported
condensation reaction7 leading to compound 5. When 5 was
exposed to air in benzene solution, it was converted mainly into
carbonate 3 (Scheme 1).7 Our further reactivity studies of
diorganotin(IV) species 5 led to the isolation of novel
compound 7, resulting from air oxidation of 5 in chloroform
(Scheme 3). During this oxidation, one of the two Sn−
Scheme 3. Preparation of 7
O(SiPh3) bonds was cleaved under the action of chloroform
(or HCl formed from this solvent), giving rise to a new Sn−Cl
bond. Simultaneously, one of the amine nitrogen atoms is
oxidized to the corresponding N-oxide with air oxygen.
Compound 7 displays two sets of broad signals for the
1
Unequivocal confirmation of the structure of 6b is provided
by the X-ray crystallographic analysis (Figure 2). The tin atom
nonequivalent ligands in the H NMR spectrum, similarly to
6b, but the δ(119Sn) chemical shift for 7 (−304 ppm) is very
close to the value found for carbonate 3 (−319 ppm).
The central tin atom in 7 exhibits distorted octahedral
coordination geometry (Figure 3). Similarly to 6b, one of the
Figure 2. Molecular structure of 6b (ORTEP view, 50% probability
level). Hydrogen atoms are omitted for clarity. Selected interatomic
distances [Å] and angles [deg]: Sn1−O1 2.226(3), Sn1−O2 2.036(3),
Sn1−O4 2.055(2), Sn1−N2 2.584(3), Sn1−C1 2.146(5), Sn1−C10
2.141(4), N1−O1 1.403(4), Si1−O2 1.611(3), Si1−O3 1.642(3),
Si2−O3 1.640(3), Si2−O4 1.598(3); O1−Sn1−O4 173.81(11), Sn1−
O1−N1 125.2(2), O2−Sn1−N2 170.72(10), C1−Sn1−C10
160.13(14), Sn1−O2−Si1 129.87(15), Sn1−O4−Si2 129.29(14),
Si1−O3−Si2 134.46(18).
Figure 3. Molecular structure of 7 (ORTEP view, 30% probability
level). Hydrogen atoms and the modeled disordered part are omitted
for clarity. Selected interatomic distances [Å] and angles [deg]: Sn1−
Cl 2.521(3), Sn1−O1X 2.031(13), Sn1−C19X 2.108(17), Sn1−C27X
2.185(14), Sn1−O2X 2.28(2), Sn1−N2X 2.597(19), Si1−O1X
1.619(14); Sn1−O1X-Si1 154.0(8), O1X−Sn1−N2X 173.5(6), Cl−
Sn1−O2X 171.4(5), C19X−Sn1−C27X 160.4(7).
in 6b is six-coordinated with a distorted octahedral geometry.
The unaffected LCN ligand expectedly binds in C,N-chelating
fashion, while the second one forms a C,O-chelate ring,
resulting in the formation of a new nonplanar six-membered
heteroazaoxastanna cycle with a chairlike conformation. Both
intramolecular distances N→Sn (2.584(3) Å) and O→Sn
(Sn1−O1 2.226(3) Å) are indicative of medium6,7 to very
strong interactions. Despite the fact that the observed Sn1−O1
interatomic distance is somewhat longer when compared to
that reported in the literature for Me2(O)N(CH2)3Sn-
(OCOCH2)3N (Sn−(O) = 2.101(6) Å), it still represents
very strong intramolecular O→Sn interaction.12b
organic ligands coordinates as a C,O-chelate donor, thereby
forming a six-membered ring with very strong O→Sn
interaction (Sn1−O2X = 2.28(2) Å) similarly to those found
in 6b and Me2(O)N(CH2)3Sn(OCOCH2)3N.12b The second,
unaffected ligand behaves as a regular C,N-chelating ligand
(Sn1−N2X = 2.597(19) Å).
Surprisingly, the reaction of 1 with Ph3SiOH in 1:1 molar
ratio did not provide the expected product of simple oxidative
addition or silanol reduction and further hydrolysis. Instead,
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inorganic Sn(II) disiloxane 8a, crystallizing as an adduct with
HLCN formed as a side product by protonolysis, was isolated
from the reaction mixture (Scheme 4). The observed reaction
Scheme 4. Reactivity of 1 toward Ph3SiOH
requires two equivalents of silanol, as evidenced by the
presence of nonreacted 1 detected by NMR spectroscopy in
the reaction mixture. To the best of our knowledge, there is
only one report15 describing the preparation and character-
ization of a compound resulting from protonolysis of a
stannylene with a silanol. The archetypal Lappert’s stannylene
Sn[N(SiMe3)2]2 was shown to react with two equivalents of
triphenylsilanol and further with potassium triphenylsilanolate
to give stannate K(dme)[Sn(OSiPh3)3] (dme = 1,2-dimethoxy-
ethane).15
When 1 was reacted with two equivalents of Ph3SiOH, the
Sn(II) salt 8b was obtained (Scheme 4). Similar reactions
between 1 and Ph3GeOH or Ph3SnOH led to oxide 2 and, in
the case of triphenylstannol, also to hexaphenyldistannane and
hexaphenyldistannoxane, according to the 119Sn NMR spec-
tra.16
Figure 4. Molecular structure of 8a (ORTEP view, 50% probability
level). Hydrogen atoms are omitted for clarity. Selected interatomic
distances [Å] and angles [deg] (corresponding values for the second
polymorph are given in parentheses): Sn1−O1 2.012(3) (1.996(2)),
Sn1−O2 2.031(3) (2.011(2)), Sn1−N1 2.341(4) (2.345(2)), Si1−O1
1.604(3) (1.606(2)), Si2−O2 1.603(3) (1.617(3)); O1−Sn1−O2
94.84(12) (94.52(10)), O1−Sn1−N1 87.89(14) (87.22(9)), O2−
Sn1−N1 84.07(14) (85.18(9)), Sn1−O1−Si1 152.23(19)
(146.15(14)), Sn1−O2−Si2 135.04(19) (133.21(14)).
The NMR spectra of 8a were recorded in a noncoordinating
solvent, benzene-d6, in order to avoid alternations of the
1
coordination environment by solvent coordination. The H
NMR spectrum reveals a set of narrow signals at predictable
chemical shifts. On the other hand, the 119Sn NMR spectrum
reveals a broad signal at −157 ppm consistent with values
reported for three-coordinate tin atoms.16 The 1H NMR
spectrum of 8b in benzene-d6 is similar to the spectrum of 8a
except that the benzylic proton signal is broadened, and the
119Sn NMR spectrum shows a signal at −341 ppm comparable
to the value observed for K(dme)[Sn(OSiPh3)3] (−360.5
ppm).15
Two polymorphs, 8a and 8a′, were isolated and characterized
by X-ray crystallography (Table S1). Only hardly significant
differences in the interatomic bonds and angles are observed
(Figure 4). The central tin atom in 8a is three-coordinate with
trigonal pyramidal geometry. One HLCN ligand is coordinated
to the tin atom at a distance suggesting a strong intermolecular
N→Sn interaction (Sn1−N1 = 2.341(4) and 2.345(2) Å). Two
oxygen atoms from the two silanolate moieties complete the
primary coordination sphere of the tin atom in 8a.
The solid-state structure of 8b (Figure 5) reveals, similarly to
8a, the central tin atom to be three-coordinate, with trigonal
pyramidal geometry. All three Sn−O interatomic distances lie
within the range typical for the Sn−O bonds.17 The negative
charge of the [(Ph3SiO)3Sn]− unit is compensated by the
presence of free-protonated ligand ([H2LCN]+) interacting with
the O1 atom in 8b via a N−H···O hydrogen bond (N1···O1 =
2.818(2) Å).
Figure 5. Molecular structure of 8b (ORTEP view, 40% probability
level). Hydrogen atoms bound to carbon atoms are omitted for clarity.
Selected interatomic distances [Å] and angles [deg]: Sn(1)−O(1)
2.1033(14), Sn(1)−O(2) 2.0601(14), Sn(1)−O(3) 2.0347(14),
O(1)−Si(1) 1.6281(15), O(2)−Si(2) 1.6071(15), O(3)−Si(3)
1.5947(15); O(1)−Sn(1)−O(2) 89.42(6), O(1)−Sn(1)−O(3)
91.54(6), O(2)−Sn(1)−O(3) 91.25(6), Sn(1)−O(1)−Si(1)
125.52(8), Sn(1)−O(2)−Si(2) 136.83(9), Sn(1)−O(3)−Si(3)
154.05(9). Hydrogen bonding: N(1)−H(1)···O(1) 2.818(2), 162.6.
In order to prepare an analogous, silica-based material from 1
using a similar protolytic reaction, which could be used, for
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example, as a solid-supported tin material for catalytic
purposes,18 the stannylene 1 was reacted with activated silica.
The tin-doped silica gel materials 9a and 9b were prepared by
treatment of freshly calcinated, conventional chromatography
grade, silica gel with two different concentrations of toluene
solutions of stannylene 1 followed by the removal of nongrafted
modifier using air-exposed Soxhlet extraction. The resulting
materials were characterized by elemental analysis (conven-
tional combustion and ICP-OES analysis), powder X-ray
diffraction, and IR spectra.
The amounts of grafted tin in materials 9a and 9b (1.18%
and 0.57%, respectively) are practically identical to the values
calculated from the mass balance (1.18% and 0.59%), thereby
indicating complete grafting of the tin species from the
solution. The X-ray diffraction patterns of 9a and 9b (see
Supporting Information, Figure S1) displayed only a single
broad peak at 2θ ca. 21−22°. The IR spectra of materials 9a
and 9b did not differ much from that of the parent silica gel,
showing mainly intense broad bands due to Si−O stretching
vibrations (composite band centered at ca. 1080 cm−1), a broad
band of associated OH groups (ca. 2800−3900 cm−1), and a
sharp band due to free OH groups (3746 cm−1). Bands
assignable to organic moieties of the organometallic modifier
were only very weak, which mainly reflects the essentially very
low degree of functionalization of the solid support.
silica. Unfortunately the prepared composite material proved to
be inactive as a catalyst in all carbonations and esterifications
screened.
4. EXPERIMENTAL SECTION
4.1. Methods. NMR spectra were recorded in CDCl3, C6D6,
toluene-d8, and THF-d8 solutions with a Bruker Avance 500
spectrometer (equipped with a z-gradient 5 mm probe) at frequencies
1
of 500.13 MHz for H, 125.73 MHz for 13C, and 186.50 MHz for
119Sn at 295 K. The solutions were obtained by dissolving ca. 40 mg of
the analyzed compound in 0.6 mL of the appropriate deuterated
solvent. Chemical shifts were calibrated to residual signals of
chloroform (δ(1H) = 7.27 ppm), benzene (δ(1H) = 7.16 ppm, δ(13C)
= 128.4 ppm), or THF (δ(1H) = 3.57 ppm, δ(13C) = 67.4 ppm)). The
119Sn{1H} chemical shift values are given relative to external neat
tetramethylstannane (δ(119Sn) = 0.0 ppm). 119Sn{1H} NMR spectra
were measured using the inverse gated-decoupling mode. 1H, 13C, and
29Si NMR spectra of 6b were measured in THF-d8 on a Varian
1
UNITY-500 spectrometer operating at 499.9 MHz for H, at 125.7
1
MHz for 13C, and at 99.3 MHz for 29Si NMR. The H and 13C NMR
spectra were referenced to the line of the solvent (THF, δ(1H) = 1.73
ppm, δ(13C) = 24.58 ppm). The 29Si NMR spectra were measured
with the insensitive nuclei enhanced by polarization transfer (INEPT)
pulse sequence modified for the Si(CH3)2 groups and were referenced
to hexamethyldisiloxane (δ = −19.79 ppm).
Elemental analyses were determined with an EA 1108 automatic
analyzer (FISONS Instruments). Tin loading in 9a and 9b was
determined with an ICP-OES spectrometer (IRIS Intrepid Duo;
Thermo Fisher Scientific) equipped with a Burgener nebulizer
(conditions: plasma power 1150 W, sample uptake 1.0 mL min−1,
axial plasma observation). The samples (20 mg) were mineralized in a
poly(propene) vial by a consecutive addition of 36% HCl, 30%
hydrogen peroxide, and 48% HF (0.50 mL each; in this order) and
standing at room temperature for 1 h. The mineralized samples were
diluted with redistilled water and directly used for the measurement.
The calibration was performed over a range of 0−20 ppm using a
commercial 1000 ppm Sn standard solution (Analytika, Prague), and
the results are the average of three independent measurements. The
content of C and N was determined by conventional combustion
analysis.
According to the elemental analysis of both samples (based
on the ratio of tin to carbon and tin to nitrogen, respectively)
and EDS measurements for 9a, it appears likely that one or
even two ligand(s) remained in the material, presumably
1
binding the tin atom. This finding is supported by the H and
13C solid-state CP-MAS NMR spectra of the sample with
higher tin content (9a), where the signals assignable to the LCN
ligands were found (Supporting Information, Figures S2−S4).
The solid-state 117Sn NMR spectra revealed a broad signal
(Figure S5) ranging from −600 to −700 ppm, which is typical
for six- or seven-coordinate tin atoms. A nonsymmetric, low-
field shouldered signal was found in the solid-state 29Si MAS
NMR spectrum of 9a at −110.7 ppm, the shoulder being at ca.
−104 ppm (Figure S6). This is consistent with a low degree of
grafting but still characteristic for a highly condensed silica
network with mainly Q3 and Q4 sites.19 Finally, the HRTEM
images showed (Figure S8) that material 9a is rather
amorphous, with only partially crystallized spots containing
tin atoms.
FTIR spectra were recorded for neat samples using a Nicolet 7600
(Thermo Fisher Scientific) spectrometer (range 500−4000 cm−1,
resolution 4 cm−1). Powder X-ray diffraction patterns were recoded
with a PANalytical X’Pert Pro diffractometer (Cu Kα radiation, PIXcel
detector, 2θ range: 10−80°, 2θ step: 0.1°, integration time: 10 s per
step).
A sample of 9a was studied by HRTEM (high-resolution
transmission electron microscopy) measurements on a JEOL JEM
3010 microscope operated at 300 kV (LaB6 cathode, 1.7 Å point
resolution) with an EDX (energy dispersive X-ray INCA Oxford)
detector. Samples were ground in an agate mortar, the powder was
dispersed in ethanol, and the suspension was treated in an ultrasound
bath for 10 min. A drop of a very dilute suspension was placed on a
carbon-coated Cu grid and allowed to dry by evaporation at ambient
temperature.
Based on literature data, several catalytic screenings,
including the reaction of carbon dioxide with methanol to
form dimethylcarbonate18b,20 and some esterification and
transesterification reactions21 were conducted with 9a.
Unfortunately, no catalytic activities higher than with pure
silica taken as a “blank” catalyst could be obtained.
3. CONCLUSION
1
The solid-state H and 13C NMR spectra were measured at 11.7 T
Our investigations into reactions of low-valent organotin
compounds, TEMPO, and silicon grease, silanols, and silica
presented in this paper have revealed some unexpected
reactivity, for instance the spontaneous oxidation of the
amino group in the LCN supporting ligand by TEMPO or
even air. The starting stannylene 1 was shown to undergo
unprecedented protolysis with triphenylsilanol, which also
served as a proton source for the released N,N-dimethylbenzyl-
amine. No formation of free ligand was observed in the
analogous reaction with activated silica, and the prepared
material consisted probably of an (LCN)2Sn fragment grafted to
using a Bruker Avance 500 WB/US NMR spectrometer in a double-
resonance 4 mm probe head. Direct-polarization MAS NMR
experiments with a high-power dipolar decoupling and sufficiently
long recycle delays were preformed to obtain quantitative NMR
spectra.
The solid-state 117Sn NMR spectra were acquired at 89.12 MHz,
using a Bruker Avance 250 NMR spectrometer in a double-resonance
4 mm probe head. Typically, a contact time of 2 ms, a relaxation delay
of 2, and 30 000 scans were used for 117Sn CP-MAS measurements.
The 119Sn chemical shifts were referenced indirectly to tetracyclohex-
yltin (δ = −97.4 ppm with respect to tetramethyltin). The 119Sn NMR
chemical shift was read as the center of gravity of the signal. Standard
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ZrO2 rotors (7 mm) were used at spinning rates between 7000 and
9000 Hz.
overnight prior to another portion of TEMPO (0.032 g, 0.21 mmol)
together with silicon grease (50 mg) being added, and the solution was
stirred for another three weeks. The reaction mixture was filtered and
evaporated to dryness. The solid residue was washed with hexane (20
mL) and extracted into THF (30 mL). Subsequent crystallization of
the THF extract at −30 °C gave 6b as a colorless crystalline solid
29Si MAS NMR spectra were recorded with a relaxation delay of 5
and 2000 scans, while CP-MAS spectra were recorded with contact
times varying from 2 to 8 ms and 2000 scans. The Hartmann−Hahn
22
1
condition for H−29Si cross-polarization was set on kaolinite.
1
X-ray diffraction data (Tables S1 and S2; see Supporting
Information file) were obtained at 150 K on a Nonius KappaCCD
diffractometer equipped with an Oxford Cryostream low-temperature
device using Mo Kα radiation (λ = 0.71073 Å), a graphite
monochromator, and the ϕ and χ scan mode. Data reductions were
performed with DENZO-SMN.23 The absorption was corrected by
integration methods.24 The structures were solved by direct methods
(SIR92)25 and refined by full matrix least-squares based on F2
(SHELXL97).26 Hydrogen atoms could mostly be localized on the
difference Fourier maps. However, to ensure uniformity of the
treatment of the crystal data, they were recalculated into idealized
positions (riding model) and assigned temperature factors set to a
multiple of that of their pivotal atom. Some atoms in the structures of
6b and 7 were disordered, but these disorders were treated with the
standard restraint and constraint procedures as incorporated in the
SHELXL9726 program.
(0.113 g, 69%). Mp: 118−123 °C. H NMR (THF-d8, 295 K, ppm):
the N-oxide group containing ligand: 7.93 (d, 1H, H(6)); 7.15 (dd,
1H, H(5)), 7.10 (dd, 1H, H(4)); 6.91 (d, 1H, H(3)); 3.74 and 3.33
(d, 2 × 1H, CH2N); 2.16 (broad, 6H, NMe); the amine group
containing ligand: 8.21 (d, 1H, H(6)); 7.40 (dd, 1H, H(5)), 7.27 (dd,
1H, H(4)); 7.18 (d, 1H, H(3)); 5.40 and 4.24 (d, 2 × 1H, CH2N);
3.28 and 2.89 (broad, 2 × 3H, NMe); −0.01 and −0.43 ppm (s, 2 × 3
H, Si(1)Me2); −0.12 and −0.38 (s, 2 × 3 H, Si(2)Me2). 13C{1H}
NMR (THF-d8, 295 K, ppm): the amine group containing ligand:
140.7 (C1), 149.6 (C2), 125.8 (C3), 127.1 (C4), 126.4 (C5), 135.5
(C6), 64.5 (NCH2), 45.8 (N(CH3)2); the N-oxide group containing
ligand: 137.3 (C1), 154.6 (C2), 130.0 (C3), 127.8 (C4), 127.9 (C5),
136.5 (C6), 70.2 (NCH2), 59.4 and 56.0 (N(CH3)2); 2.0−1.8 (m, 4 C
n.r., Si(1)Me2 and Si(2)Me2). 29Si{1H} NMR (THF-d8, 295 K, ppm):
−14.3 and −14.5 (Si(1) and Si(2)). 119Sn{1H} NMR (THF-d8, 295 K,
ppm): −456. Anal, Found: C, 46.7; H, 6.6; N, 5.0. Calcd for
C22H36N2O4Si2Sn (567.41): C, 46.57; H, 6.40; N, 4.94.
Crystallographic data 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: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk). CCDC deposi-
tion numbers 921175−921180.
4.2.4. Preparation of [(LCN)(LCNO)Sn(OSiPh3)Cl] (7). (LCN)2Sn-
(OSiPh3)2 (5) (1.0 g, 0.11 mmol) was dissolved in chloroform (50
mL), and the solution was exposed to air for one week. The resulting
slurry was filtrated, and the solid was crystallized from chloroform to
1
give white crystals of 7 (0.274 g, 36%). Mp: 269−270 °C. H NMR
4.2. Synthesis. 4.2.1. Materials. All solvents and starting materials
such as SnCl2, n-BuLi, Ph3SiOH, and dimethylbenzylamine were
purchased from Sigma-Aldrich and were used without further
purification. (LCN)2Sn (1) and (LCN)2Sn(OSiPh3)2 (5) were
synthesized according to the literature.7,10 Dow Corning high-vacuum
silicon grease was used in the syntheses. Solvents were distilled from
K/Na alloy and stored over a potassium mirror under an argon
atmosphere or dried and degassed using a commercial drying column
apparatus (Innovative Technology Inc., USA).
(CDCl3, 295 K, ppm): the N-oxide group containing ligand: 8.13
(broad, 1H, H(6)); 6.85 (broad, 1H, H(3)); 3.71 and 3.23 (d, 2 × 1H,
CH2N); 1.75 (broad, 6H, NMe); the amine group containing ligand:
8.01 (broad, 1H, H(6)); 6.83 (broad, 1H, H(3)); 5.32 and 3.99 (d, 2
× 1H, CH2N); 2.04 and 1.24 (broad, 2 × 3H, NMe); 7.10 (m, 4H,
H(4, 5)); 7.62 (d, 2H, SiPh3) and 7.50 (d, 2H, SiPh3) and 7.41 (d, 2H,
SiPh3) and 7.36 (m, 9H, SiPh3). 119Sn{1H} NMR (CDCl3, 295 K,
ppm): −304. Anal. Found: C, 60.7; H, 5.6; N, 4.0. Calcd for
C36H39N2O2SiSnCl (713.95): C, 60.57; H, 5.51; N, 3.92.
4.2.2. Preparation of cyclo-[(LCN)2SnOSn(LCN)2OSiMe2O] (6a).
(LCN)2Sn (1) (1.01 g, 2.61 mmol) was dissolved in toluene (50
mL), and TEMPO (0.421 g, 2.69 mmol) was added in five portions.
The resulting solution was stirred overnight. Subsequently, in a first
experiment, 0.234 g (ca. 3 mmol calculated to a monomeric unit) of
silicon grease was added and the solution was stirred for one day.
Afterward, the reaction mixture was evaporated to dryness and the
solid residue was washed with 20 mL of hexane and extracted with 30
mL of diethyl ether to give, after crystallization at −30 °C, 6a as
colorless crystals (0.643 g, 56%).
4.2.5. Preparation of [Sn(OSiPh3)2].C6H5CH2NMe2 (8a). Triphe-
nylsilanol (0.714 g, 2.58 mmol) in diethyl ether (20 mL) was added
dropwise to 1 (1.0 g, 2.58 mmol) dissolved in the same solvent (20
mL). The resulting solution was stirred overnight and crystallized at
−30 °C to afford 8a as a colorless, crystalline solid (1.393 g, 67%).
1
Mp: 218−220 °C. H NMR (C6D6, 295 K, ppm): 7.84 (m, 4H, H(2,
3)); 7.07 (dd, 1H, H(4)), 7.33 (d, 12H, SiPh3); 7.18 (m, 18H, SiPh3);
3.25 (s, 2H, CH2N); 2.06 (s, 6H, NMe2). 119Sn{1H} NMR (C6D6, 295
K, ppm): −157. Anal. Found: C, 67.3; H, 5.4; N, 1.8. Calcd for
C45H43NO2Si2Sn (804.71): C, 67.17; H, 5.39; N, 1.74.
27
4.2.6. Preparation of [C6H5CH2N(H)Me2]+[Sn(OSiPh3)3]− (8b). A
solution of triphenylsilanol (1.428 g, 5.17 mmol) in diethyl ether (50
mL) was added dropwise to a solution of 1 (1.0 g, 2.583 mmol) in the
same solvent (50 mL). The resulting mixture was stirred and then
evaporated to dryness. The solid residue was washed with hexane (30
mL) and extracted with diethyl ether (30 mL). Subsequent
crystallization at −30 °C gave 8b as a colorless solid (2.008 g,
In another experiment, freshly prepared Me2Si(OH)2 (0.120 g,
1.31 mmol) was added in toluene (15 mL), and the mixture stirred
overnight and then heated under a Dean−Stark apparatus for 3 h. The
resultant solution was concentrated to ca. 5 mL and crystallized at −30
°C to give 6a (0.530 g, 46%).
Alternatively, compound 6a was obtained from the reaction of 1
(2.197 g, 5.68 mmol) with metallic lithium (40 mg, 5.68 mmol), 12-
crown-4 (1.0 g, 5.68 mmol), and silicon grease (0.21 g, 2.84 mmol) in
diethyl ether (30 mL). These starting materials were stirred for 3
weeks. The obtained suspension was filtered through Celite and
extracted with THF (50 mL). The combined organic solution was
concentrated to ca. 6 mL and crystallized at −30 °C to afford 6a
(1.374 g, 55%).
1
73%). Mp: 150−152 °C. H NMR (C6D6, 295 K, ppm): 7.87 (broad,
20H); 7.18 (broad, 29H), 6.97 (broad, 1H, H(4)); 3.28 (broad, 2H,
CH2N); 1.89 (broad, 6H, NMe2).119Sn{1H} NMR (C6D6, 295 K,
ppm): −341. Anal. Found: C, 71.2; H, 5.6; N, 1.3. Calcd for
C63H59NO2Si3Sn (1065.13): C, 71.04; H, 5.58; N, 1.32.
4.2.7. Preparation of Materials 9a and 9b. Twenty grams of
conventional chromatography-grade silica gel (70−230 mesh), which
was calcinated at 500 °C for 12 h and cooled in a desiccator prior to
use, was suspended in dry toluene (100 mL). A solution of 1 in dry
toluene (22 mL of 0.09 M solution) was introduced, and the resulting
suspension was stirred at room temperature for 4 days. Subsequently,
the solid was filtered off and extracted with dichloromethane in a
Soxhlet extractor for 24 h. The solid residue was dried in air, first at
room temperature and then at 100 °C, to give material 9a. Material 9b
was prepared in exactly the same way, using only a half-volume of the
stannylene solution (11 mL).
Analytical data for 6a. Mp: 204−207 °C. 1H NMR (THF-d8, 295 K,
ppm): 7.86 (broad, 2H, H(6′)), 7.80 (d, 2H, H(6)); 7.30 (m, 12H,
H(3, 4, 5)), 3.47 (broad, 8H, CH2N); 2.03 (s, 24H, N(CH3)2).
119Sn{1H} NMR (THF-d8, 295 K, ppm): −292, (toluene-d8): −288.2,
3J(119Sn−117Sn) = 458 Hz. Anal. Found: C, 51.9; H, 6.3; N, 6.4. Calcd
for C38H54N4O3SiSn2 (880.35): C, 51.85; H, 6.18; N, 6.36.
4.2.3. Preparation of cyclo-[(LCN)(LCNO)SnOSiMe2OSiMe2O]
(6b). A solution of TEMPO (0.032 g, 0.21 mmol) in toluene (20
mL) was added dropwise to a solution of stannylene 1 (0.08 g, 0.21
mmol) in the same solvent (50 mL). The resulting solution was stirred
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Analytical data for material 9a. Analysis: C 2.36, N 0.21, Sn 1.18%.
Powder X-ray diffraction: 2θ = 21−22° (very broad). IR (neat): 3476
(w), ca. 2800−3700 (br m), 1867 (w), 1626 (w), ca. 1465 (vw), 1080
+ shoulder at ca. 1190 (vs), 811 (m) cm−1. For 1H, 13C, 29Si, and 117Sn
NMR in the solid state see Supporting Information Figures S2−S6.
Analytical data for material 9b. Analysis: C 1.64, N 0.11, Sn 0.57%.
Powder X-ray diffraction: 2θ = 21−22° (very broad). IR (neat): 3476
(w), ca. 2800−3700 (br m), ca. 1975 (w, shoulder), 1868 (w), 1628
(w), 1475 (w), 1460 (w), 1080 + shoulder at ca. 1190 (vs), 980 (m),
807 (m) cm−1.
1994, 465, 145−151. (f) Beckmann, J.; Jurkschat, K.; Rabe, S.;
Schurmann, M. Phosphorus Sulfur Silicon Relat. Elem. 1999, 150−151,
̈
357−365. (g) Pavel, I.; Cervantes-Lee, F.; Pannell, K. H. Phosphorus
Sulfur Silicon Relat. Elem. 1999, 150−151, 223−236. (h) Beckmann, J.;
Jurkschat, K.; Mahieu, B.; Schurmann, M. Main Group Met. Chem.
̈
1998, 21, 113−122. (i) Beckmann, J.; Jurkschat, K.; Schurmann, M.;
̈
Suter, D.; Willem, R. Organometallics 2002, 21, 3819−3822.
(j) Graalmann, O.; Meyer, M.; Klingebiel, U. Z. Anorg. Allg. Chem.
1986, 534, 109−114.
̌
(6) Padel
̌
kova,
́
Z.; Nechaev, M. S.; Cernose
̌
k, Z.; Brus, J.; Ruzick
a, A.
̊
̌
̌
Organometallics 2008, 27, 5303−5308.
(7) Padelkova, Z.; Vankatova, H.; Císaro
Zevaco, T. A.; Walter, O.; Ruzicka, A. Organometallics 2009, 28, 2629−
ASSOCIATED CONTENT
* Supporting Information
̌
́
̌
́
́
̌ ́
va, I.; Nechaev, M. S.;
■
̊
̌
̌
S
2632.
Solid-state NMR spectra and further details of the structure
determination of all compounds, including atomic coordinates,
anisotropic displacement parameters, and geometric data, are
available free of charge via the Internet at http://pubs.acs.org.
(8) Beckmann, J.; Jurkschat, K.; Pieper, N.; Schurmann, M. Chem.
̈
Commun. 1999, 1095−1096.
(9) For example: (a) Harrison, P. G. J. Organomet. Chem. 1997, 542,
141−183. (b) Hanssen, R. W. J. M.; van Santen, R. A.; Abbenhuis, H.
C. L. Eur. J. Inorg. Chem. 2004, 675−683. (c) Duchateau, R. Chem. Rev.
2002, 102, 3525−3542. (d) Lorenz, V.; Edelmann, F. T. Adv.
Organomet. Chem. 2005, 53, 101−153.
AUTHOR INFORMATION
Corresponding Author
*Fax: +420 466037151. E-mail: zdenka.padelkova@upce.cz.
■
(10) Angermund, K.; Jonas, K.; Kruger, C.; Latten, J. L.; Tsay, Y.-H. J.
Organomet. Chem. 1988, 353, 17−25.
(11) (a) Iwamoto, T.; Masuda, H.; Ishida, S.; Kabuto, C.; Kira, M. J.
Am. Chem. Soc. 2003, 125, 9300−9301. (b) Iwamoto, T.; Masuda, H.;
Ishida, S.; Kabuto, C.; Kira, M. J. Organomet. Chem. 2004, 689, 1337−
1341.
(12) (a) Balazs, L.; Breunig, H. J.; Lork, E.; Soran, A.; Silvestru, C.
Inorg. Chem. 2006, 45, 2341−2346. (b) Dakternieks, D.; Dyson, G.;
Jurkschat, K.; Tozer, R. J. Organomet. Chem. 1993, 458, 29−38.
(13) (a) Jurkschat, K.; Van Dreumel, S.; Dyson, G.; Dakternieks, D.;
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors would like to thank Czech Science Foundation for
financial support of this work (grant nos. P207/10/P092 and
104/09/0561). R.W. is indebted to the VUB research council
(grant GOA 31) and to the Fund for Scientific Research
Flanders (Belgium; grant G.0029.10) for financial support.
Bastow, T. J.; Smith, M. E.; Drager, M. Polyhedron 1992, 11, 2747−
̈
2755. (b) Pieper, N.; Klaus-Mrestani, C.; Schurmann, M.; Jurkschat,
̈
K.; Biesemans, M.; Verbruggen, I.; Martins, J. C.; Willem, R.
DEDICATION
This paper is dedicated to Professor Dr. Jaroslav Holece
the occasion of his 80th birthday for his gigantic and
outstanding contribution to the chemistry of coordination
and organometallic compounds, NMR spectroscopy, and the
development of his parent faculty.
Organometallics 1997, 16, 1043−1052. (c) Jurkschat, K.; Pieper, N.;
■
Seemeyer, S.; Schurmann, M.; Biesemans, M.; Verbruggen, I.; Willem,
̈
̌
k on
R. Organometallics 2001, 20, 868−880.
(14) Lockhart, T. P.; Puff, H.; Schuh, W.; Reuter, H.; Mitchell, T. N.
J. Organomet. Chem. 1989, 366, 61−72.
(15) McGeary, M. J.; Cayton, R. H.; Folting, K.; Huffman, J. C.;
Caulton, K. G. Polyhedron 1992, 11, 1369−1382.
(16) (a) Wrackmeyer, B. Annu. Rep. NMR Spectrosc. 1985, 16, 73−
186. (b) Wrackmeyer, B. Annu. Rep. NMR Spectrosc. 1999, 38, 203−
264.
REFERENCES
■
(1) Murugavel, R.; Voigt, A.; Walawalkar, M. G.; Roesky, H. W.
Chem. Rev. 1996, 96, 2205−2236.
(17) Cordero, B.; Gom
Echeverría, J.; Cremades, E.; Barragan
2008, 2832−2838.
́
ez, V.; Platero-Prats, A. E.; Reves
́
, M.;
́
, F.; Alvarez, S. Dalton Trans.
(2) Haiduc, I. Organometallics 2004, 23, 3−8.
(3) Cervantes-Lee, F.; Sharma, H. K.; Haiduc, I.; Pannell, K. H. J.
Chem. Soc., Dalton Trans. 1998, 1−2.
(18) (a) Boutet, S.; Jousseaume, B.; Toupance, T.; Biesemans, M.;
Willem, R.; Labrugere, C.; Delattre, L. Chem. Mater. 2005, 17, 1803−
1811. (b) Ballivet-Tkatchenko, D.; Bernard, F.; Demoisson, F.;
Plasseraud, L.; Sanapureddy, S. R. Chem. Sus. Chem 2011, 4, 1316−
1322.
(19) (a) Engelhardt, G.; Michel, D. High-Resolution Solid-State NMR
of Silicates and Zeolites; John Wiley & Sons: Chichester, 1987.
(b) Leonardelli, S.; Facchini, L.; Fretigny, C.; Tougne, P.; Legrand, A.
P. J. Am. Chem. Soc. 1992, 114, 6412−6418.
(4) (a) Reyes-Garcia, E. A.; Cervantes-Lee, F.; Pannell, K. H.
Organometallics 2001, 20, 4734−4740. (b) Beckmann, J.; Mahieu, B.;
Nigge, W.; Schollmeyer, D.; Schurmann, M.; Jurkschat, K. Organo-
̈
metallics 1998, 17, 5697−5712. (c) Beckmann, J.; Jurkschat, K.;
Schurmann, M.; Dakternieks, D.; Lim, A. E. K.; Lim, K. F.
̈
Organometallics 2001, 20, 5125−5133. (d) Beckmann, J.; Jurkschat,
K.; Kaltenbrunner, U.; Pieper, N.; Schurmann, M. Organometallics
̈
1999, 18, 1586−1595. (e) Englich, U.; Prass, I.; Ruhlandt-Senge, K.;
̌
(20) (a) Svec, P.; Padel
Plasseraud, L. J. Organomet. Chem. 2011, 696, 676−686. (b) Svec, P.;
Olejník, R.; Padelkova, Z.; Ruzicka, A.; Plasseraud, L. J. Organomet.
Chem. 2012, 708, 82−87.
(21) (a) Padelkova, Z.; Weidlich, T.; Kolar
Císarova, I.; Zevaco, T. A.; Ruzicka, A. J. Organomet. Chem. 2007, 692,
5633−5645. (b) Padel Z.; Weidlich, T.; Císarova, I.; Ruzicka, A.
̊
̌
̌ ́ ̌ ̌
kova, Z.; Ruzicka, A.; Weidlich, T.; Dusek, L.;
Schollmeier, T.; Uhlig, F. Monatsh. Chem. 2002, 133, 931−943.
̌
(f) Pieper, N.; Schurmann, M.; Jurkschat, K. Acta Crystallogr. Sect. C:
̈
̌
́
̌
̌
̊
Cryst. Struct. Commun. 1998, C54 (8), 1097−1099. (g) Jurkschat, K.;
Rosche, F.; Schurmann, M. Phosphorus Sulfur Silicon Relat. Elem. 1996,
̈
̌
́
́ ̌ ́
ova, L.; Eisner, A.;
115, 161−167.
̌
́
̌
̌
̊
(5) (a) Beckmann, J.; Jurkschat, K.; Rabe, S.; Schurmann, M.;
̈
̌
kova,
́
̌
́
̌
̌
̊
Dakternieks, D.; Duthie, A. Organometallics 2000, 19, 3272−3279.
(b) Beckmann, J.; Jurkschat, K.; Muller, D.; Rabe, S.; Schurmann, M.
Organometallics 1999, 18, 2326−2330. (c) Beckmann, J.; Jurkschat, K.;
Kaltenbrunner, U.; Pieper, N.; Schurmann, M. Organometallics 1999,
Appl. Organomet. Chem. 2009, 23, 253−257. (c) Weidlich, T.; Duse
̌
k,
̈
̈
̌
L.; Vystrci
̌
lova,
́
B.; Eisner, A.; Svec, P.; Ruzick
a, A. Appl. Organomet.
̊
̌
̌
Chem. 2012, 26, 293−300.
(22) Rocha, J.; Klinowski, J. J. Magn. Reson. 1990, 90, 567−568.
(23) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307−
̈
18, 1586−1595. (d) Beckmann, J.; Jurkschat, K.; Schollmeyer, D.;
Schurmann, M. J. Organomet. Chem. 1997, 543, 229−232. (e) Brisdon,
̈
B. J.; Mahon, M. F.; Molloy, K. C.; Schofield, P. J. Organomet. Chem.
326.
2404
dx.doi.org/10.1021/om400123y | Organometallics 2013, 32, 2398−2405

Organometallics
Article
(24) Coppens, P. In Crystallographic Computing; Ahmed, F. R.; Hall,
S. R.; Huber, C. P., Eds.; Munksgaard: Copenhagen, 1970; pp 255−
270.
(25) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J.
Appl. Crystallogr. 1993, 26, 343−350.
(26) Sheldrick, G. M. SHELXL-97; University of Gottingen:
̈
Gottingen, 1997.
̈
(27) Kantor, S. W. J. Am. Chem. Soc. 1953, 75, 2712−2714.
2405
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