{Sn9[Si(SiMe3)3]2} 2-: A metalloid tin cluster compound with a Sn9 core of oxidation state zero

Article abstract of DOI:10.1021/ic3011647

The disproportionation reaction of the subvalent metastable halide SnCl proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Now we present the synthesis and structural characterization of the anionic metalloid cluster compound [Sn₉[Si(SiMe ₃)₃]₂]^2-3 where the oxidation state of the tin atoms is zero. Quantum chemical calculations as well as Moessbauer spectroscopic investigations show that three different kinds of tin atoms are present within the cluster core. Compound 3 is highly reactive as shown by NMR investigations, thus being a good starting material for further ongoing research on the reactivity of such partly shielded metalloid cluster compounds.

Full text of DOI:10.1021/ic3011647

Article
pubs.acs.org/IC
2
‑
{
Sn [Si(SiMe ) ] } : A Metalloid Tin Cluster Compound With a Sn
9 3 3 2 9
†
Core of Oxidation State Zero
Claudio Schrenk, Florian Winter, Rainer Po
‡
§
§
,‡
̈
ttgen, and Andreas Schnepf*
‡
Chemistry Department, University Duisburg-Essen, Universitat
̈
sstrasse 5-7, D-45117 Essen, Germany
̈
Munster, Corrensstrasse 30, D-48149 Munster, Germany
§
Institut fu
̈
r Anorganische und Analytische Chemie, Universitat
̈
̈
*
S Supporting Information
ABSTRACT: The disproportionation reaction of the subvalent metastable
halide SnCl proved to be a powerful synthetic method for the synthesis of
metalloid cluster compounds of tin. Now we present the synthesis and structural
2‑
characterization of the anionic metalloid cluster compound [Sn [Si(SiMe ) ] ]
9
3 3 2
3
where the oxidation state of the tin atoms is zero. Quantum chemical
calculations as well as Mossbauer spectroscopic investigations show that three
̈
different kinds of tin atoms are present within the cluster core. Compound 3 is
highly reactive as shown by NMR investigations, thus being a good starting
material for further ongoing research on the reactivity of such partly shielded
metalloid cluster compounds.
INTRODUCTION
RESULT AND DISCUSSION
■
1
■
Polyhedral cluster compounds of the heavier elements of group
4 have attracted much interest in recent years as these
compounds might give insight into the area between molecules
and the solid state on a molecular level, being thus also of
Recently, we could show that metalloid tin clusters can be
obtained by the reaction of a Sn(I) halide solution using
1
3
LiSi(SiMe ) as a metathesis reagent. Thereby it becomes
3 3
1
obvious that the product (the metalloid cluster) obtained
strongly depends on the subvalent halide source applied
Scheme 1). The subvalent halide source is thereby obtained by
central interest for nanotechnology. For the synthesis of ligand
(
stabilized clusters of group 14, different synthetic routes have
14
2
a preparative cocondensation technique which leads to a
been identified. One synthetic route applies the disproportio-
Sn(I) halide emulsion when NBu is used as a donor molecule
nation reaction of a metastable subhalide while another one
applies reductive coupling reactions, where ligand stripping can
lead to naked, ligand free tetrel atoms pushing the average
oxidation state of the tetrel atoms to the value zero of the solid
3
while an isolable solution is obtained when the donor PBu is
3
15
used. In both cases the solvent is toluene. Applying now the
emulsion as the subhalide source in the reaction with
3
LiSi(SiMe
1 is obtained. Besides this, using the isolable solution the
15
) , the neutral metalloid cluster Sn10[Si(SiMe ) ]
3 3 3 3 6
16
state. Another synthetic route starts from polyhedral Zintl
1
anions, and recently, it was shown that also clusters with a
−
anionic metalloid cluster {Sn [Si(SiMe ) ] } 2 is obtained.
10
3 3 5
positive oxidation state of the tetrel atoms are available from
Zintl anions, where the average oxidation state of the tetrel
Hence, the product of the reaction strongly depends on the
reactivity of the subhalide and thereby on the donor applied.
Another important factor which can be manipulated and
which might influence the reactivity of the subhalide source is
the Sn/halide ratio within the subhalide solution, being
normally in the range between 1.1 and 1.2, i.e., the ratio of
17
4
‑
atoms is negative. Hence the reaction of Ge with Cl−
9
−
4
Si(SiMe ) gives {Ge [Si(SiMe ) ] } 1, which is also available
3
3
9
3 3 3
5
from the reaction of GeBr with LiSi(SiMe ) , showing a direct
correlation between metalloid clusters and substituted Zintl
anions.
3
3
Sn(I)X with respect to Sn(II)X (X = halide like Cl, Br) varies
2
Interestingly, in the area of polyhedral group 14 clusters,
besides a variety of ligand stabilized germanium clusters of
between 90:10 and 80:20. The Sn/halide ratio is thereby
adjusted by the temperature of the reactor during the synthesis
of the high temperature molecule SnX, i.e., the lower the
2
‑
6
7
8
composition Ge9R2 [R = Ph Bi; Ph/SbPh ; Ph Sn/Ph Ge;
2
2
3
3
9
10
14
CHCHFc (Fc = ferrocenyl); C H /CH −CH(CH ) ],
temperature the higher the Sn(II) halide ratio. In the case of
2
3
2
2 2
4
‑
2‑
which are available from the Zintl anion Ge , no Sn R
9 2
the synthesis of the metalloid cluster 2, a SnCl solution with a
Sn/Cl ratio of ca. 1.1 was used. When the reaction is now
performed applying a SnCl solution with a Sn:Cl ratio of 1.2,
where the amount of Sn(II)Cl2 is significantly higher, a
different behavior is observed; i.e., during workup we were not
9
3
‑
compound could be isolated so far. However, Sn R clusters
9
with one substituent have already been structurally charac-
1
1,12
terized,
and mass spectroscopic investigations hint to the
2‑
12
presence of Sn9R2 species in solution. We now present the
2
‑
first structurally characterized Sn9R2 cluster, which could be
synthesized applying the disproportionation reaction of a Sn(I)
halide solution.
Received: June 1, 2012
Published: July 17, 2012
©
2012 American Chemical Society
8583
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Inorganic Chemistry
Article
Scheme 1. Schematic Presentation of the Synthesis of Metalloid Sn-Clusters Applying Various Sn(I) Halide Precursors
(Emulsion or Solution) Depending on the Donor Applied During the Cocondensation Reaction
18
able to isolate 2 or 1. However, mass spectra of the crude
synthetic routes starting from Zintl anions or monohalide
reaction mixture clearly show that anionic clusters are formed
solutions. The Sn polyhedron within 3 is comparable to the
Ge9 polyhedron found within Ge9R2 clusters, however,
9
19
2‑
during the reaction. As the reaction is performed within
toluene as solvent it is unlikely that separated ions are present
within the solution, which should be insoluble and precipitate.
Consequently, contact ion pairs should be present within the
solution; i.e., to precipitate an ionic product we added
tetramethylethylendiamine (TMEDA) as a complexing reagent
for the lithium cations to the reaction solution and obtained
first of all black, blocklike crystals, whose crystal structure could
exhibiting longer E−E distances due to the larger covalent
21
radius of tin with respect to germanium. The capped Sn
4
square (Sn4, Sn5, Sn4a, Sn5a) is thereby distorted to a
rectangle in which the longest Sn−Sn distances of 325.07 pm
(Sn5−Sn5a) and 310.91 pm (Sn4−Sn5) are found. Besides
this, within the noncapped Sn square (Sn1, Sn3, Sn2, Sn3a)
4
the Sn−Sn distances are in a narrow range (289.1−289.5 pm),
exhibiting a dihedral angle of 1.5°. However, a diamond
arrangement is realized as diagonal distances of 349 pm (Sn1−
Sn2) and 462 pm (Sn3−Sn3a) are found. All other tin−tin
distances within the cluster core vary in a small range between
289.09 pm (Sn1−Sn3) and 306.15 pm (Sn3−Sn6). The
arrangement of the nine tin atoms within the cluster core might
also be described as a tricapped trigonal prismatic arrangement,
where two ligand bound tin atoms (Sn1, Sn2) bear a ligand and
the third one (Sn6) is naked.
20
not be solved so far, due to severe crystallographic problems.
However, on concentrating the filtrated solution another
compound is obtained in the form of dark- red needlelike
crystals. Crystal structure solution of these crystals shows that
2
‑
the metalloid cluster compound {Sn [Si(SiMe ) ] } 3 ha+s
9
3 3 2
formed, which crystallizes together with two [Li(TMEDA)2]
cations in the orthorhombic space group Pnma. The molecular
structure of 3 is shown in Figure 1 and is best described as a
However, the trigonal prism is strongly distorted as the
heights of the prism differ by more than 100 pm (Sn3−Sn3a
4
62 pm, Sn4−Sn4a 322 pm, Sn5−Sn5a 325 pm). Nevertheless,
the tin−tin distances to the capping tin atoms are very similar
as the ligand bound tin atoms show average tin−tin distances of
2
93.4 pm (289.1−298.6) while the naked capping tin atom
(
Sn6) is bound to the cluster core with average tin tin distances
of 295.5 pm (295.3−295.7), being thereby the naked tin atom
with the shortest tin−tin contacts within the cluster core.
Hence, the capping tin atom (Sn6) exhibits an emersed
position, and is also easily available for further reactions as to be
seen from the space filling model in Figure 2.
2‑
Figure 1. Molecular structure of {Sn [Si(SiMe ) ] } 3. Displacement
9
3 3 2
ellipsoids are shown at the 50% probability level. Selected bond
distances (pm) and angles (deg): Sn1−Sn3 289.09(7), Sn3−Sn2
2
3
2
2
89.50(7), Sn1−Sn5 298.58(9), Sn2−Sn4 296.29(9), Sn4−Sn4a
21.97, Sn5−Sn5a 325.07, Sn4−Sn5 310.91(8), Sn4−Sn6
95.73(10), Sn5−Sn6 295.33(10), Sn1−Si2 258.0(3), Sn2−Si1
57.9(3), Si1−Si11 234.3(4), Si2−Si20 234.7(5), Si2−Si21 233.4(3),
2
‑
Si11−C11A 187.0(12), Si11−C11B 187.3(10), Sn1−Sn3−Sn2
4.17(2), Sn3−Sn1−Sn3a 105.92(3), Sn4−Sn3−Sn5 61.41(2), Sn5−
Sn4−Sn4a 90.29(2), Sn5−Sn1−Si2 106.71(7), Si1−Si11−C11A
12.5, Si1−Si11−C11B 109.0(3).
Figure 2. Space filling model of {Sn [Si(SiMe ) ] } 3; view along
9 3 3 2
two perpendicular directions.
7
1
As discussed before the arrangement of the nine tin atoms
within the cluster core of 3 can be described as being between a
closo (tricapped trigonal prism) and a nido (monocapped square
monocapped square antiprismatic arrangement of nine tin
atoms, where two tin atoms in the noncapped rectangle (Sn1
and Sn2) are bound to one ligand each. Compound 3 is thus
antiprism) structure as it is frequently observed in group 14 E
9
2
‑
22
the first example of an E9R2 cluster in tin chemistry which is
obtained via the disproportionation reaction of a tin subhalide.
The oxidation state of the tin atoms within the cluster core is
zero as is the case for the isostructural germanium clusters
cluster compounds. Additionally, quantum chemical calcu-
23
2‑
2
lations on the model compound Sn H , for which a similar
9
structure as found in 3 is calculated, show significant leaps in
the orbital energy between HOMO − 9 and HOMO − 11,
indicating the presence of 20−22 skeletal electrons, being thus
Ge9R22
−
6−10
obtained from a reaction of Ge . Consequently,
4‑
9
24
3
is another example of a direct connection of the two different
in line with Wade's rules, where 2n + 4 (2n + 2) bonding
8
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Inorganic Chemistry
Article
electrons are expected for a nido (closo) cluster compound like
most reactive place for subsequent reactions applying electro-
philes. However, only the capping tin atom (Sn6) is easily
available (Figure 2). Additionally, HOMO − 4 (Figure 4) is
localized at the open side of 3 exhibiting a high lone-pair
character at Sn6, being perfectly oriented for further reactions.
3
(n = 9). Further calculations on 3 show that the nine tin
atoms within the cluster core of 3 can be divided into three
different groups of tin atoms with respect to their calculated
charge based on occupation numbers; i.e., tin atoms with
average charges of −0.35, −0.12 and +0.16 are present (Figure
2
5
3
). The presence of three different kinds of tin atoms as
2
‑
Figure 4. Representation of HOMO − 4 of {Sn [Si(SiMe ) ] } 3.
9
3 3 2
Figure 3. Experimental and simulated 119Sn Mo
Sn [Si(SiMe ) ] }{Li(TMEDA) } at 78 K. The subspectra of the tin
species 1, 2, and 3 are drawn in blue, green, and violet, similar to the
tin cluster. The calculated charges of the three sets of tin atoms are
indicated.
ssbauer spectrum of
̈
Consequently, 3 is a perfect starting material for further
{
9
3
3
2
2 2
investigations on the reactivity of such a polyhedral tin cluster
2
7
compound (vide infra). However, to perform further
reactions 3 has to be dissolved first. Thereby, 3 is easily
dissolved in tetrahydrofuran (THF), leading to a dark red,
nearly black solution. However, proton NMR measurements of
the THF solution of 3·[Li(TMEDA) ] unambiguously show
indicated by the calculations is corroborated experimentally by
1
19
119
2
2
Sn Mo
̈ ̈
ssbauer spectroscopy. The Sn Mossbauer spectrum
not only that 3·[Li(TMEDA) ] is dissolved in THF but also
2
2
of {Sn [Si(SiMe ) ] }{Li(TMEDA) } recorded at 78 K is
9
3 3 2
2 2
that subsequent reactions take place as we find a time
presented in Figure 3 together with a transmission integral fit.
The corresponding fitting parameters are listed in Table 1.
28
dependency of the spectra. These subsequent reactions lead
29
at the end to a black precipitate of unknown composition,
while a colorless solution is obtained. Mass spectroscopic
Table 1. Fitting Parameters of a 119Sn Mo
Spectroscopic Measurement for
ssbauer
̈
investigations of a THF solution of 3·[Li(TMEDA) ] also hint
2
2
a
to a dynamic system in solution, as we see besides cluster
compounds exhibiting nine tin atoms also compounds
{
Sn [Si(SiMe ) ] }{Li(TMEDA) } at 78 K
9
3 3 2
2
2
−
1
−1
Γ/mm s−1
site
δ/mm s−
ΔE /mm s
exhibiting 10 tin atoms, e.g., {Sn [Si(SiMe ) ] } (m/z =
10
3 3 3
Q
1
5
1
940), which can be identified by its isotopic pattern (Figure
). Additionally, the signal with the highest intensity at m/z =
Sn1 (blue)
Sn2 (green)
Sn3 (violet)
2.35(2)
1.97(3)
2.82(5)
0.63(4)
0.84(7)
0.5(1)
0.79(2)
0.64(2)
0.81(3)
820 au is not the monoanionic compound {Sn [Si-
9
−
a
(SiMe ) ] } but the monoanionic compound {Sn [Si-
3
3
2
9
Numbers in parentheses represent the statistical errors in the last
digit. δ, isomer shift; ΔE , electric quadrupole splitting; Γ,
experimental line width. The intensities of Sn1:Sn2:Sn3 were fixed
−
30
(
SiMe ) ] } 4, which is also clearly identified by its isotopic
3 3 3
Q
pattern. Hence, a complex reaction cascade is taking place on
dissolving crystals of 3·[Li(TMEDA) ] in THF as indicated by
NMR and mass spectroscopy.
at 4:2:3.
2 2
Sadly, 3·[Li(TMEDA) ] is insoluble in, e.g., toluene, and the
2
2
A reasonable fit of the spectrum was possible with three
superimposed subspectra which are all subjected to quadrupole
splitting. The correct assignment of these sites was possible via
the calculated partial charges. The population analyses (vide
supra) revealed three groups of tin atoms with charges of
reaction pathway of the decomposition reaction is unclear up to
now. Nevertheless, we assumed that the countercation might
play an important role during the decomposition, and thus, we
added a stronger complexing reagent to the solution.
The addition of 12-crown-4 thereby leads to a THF solution
of 3 with enhanced stability as can be seen in the proton NMR
spectra, where we now observe the signal of 3 for a longer
period of time (Figure 6); i.e., the degradation of 3 is now
taking place within a couple of days and not minutes, maybe
being enough for subsequent reactions.
−
0.35, −0.12, and +0.16 in 3:4:2 ratio. A higher negative charge
is in line with a higher electron density at the tin nucleus and
26
thus with a higher isomer shift. When constraining the signal
areas in the above ratio we got a good reproduction of the
experimental spectrum. The highest quadrupole splitting
parameter is observed for the Sn2 atoms which are connected
to the ligands.
As a proof of principle reaction we added Cl−Si(SiMe ) to
3
3
the THF solution of 3, exhibiting 12-crown-4, leading to a
stable reaction solution with a white precipitate of LiCl.
Workup of the reaction mixture leads to the anticipated
Due to the quantum chemical calculations as well as 119Sn
̈
Mossbauer experiments, three different kinds of tin atoms are
presents within 3, where three (Sn3, Sn3a, Sn6) of the nine tin
−
compound {Sn [Si(SiMe ) ] } 4 in 60% isolated yield,
9
3 3 3
atoms exhibit a comparably high negative charge, being thus the
showing that 3 can be used as a starting material for a variety
8
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Inorganic Chemistry
Article
In summary, we presented the synthesis and structural
characterization as well as Mo
̈
ssbauer and NMR spectroscopic
2
‑
investigations of {Sn [Si(SiMe ) ] } 3, being the first
9
3 3 2
structurally characterized tin cluster, where the tin atoms
exhibit the oxidation state zero. Compound 3 can be dissolved
in THF leading to a highly dynamic system in solution which
can be altered by complexing the countercation with 12-crown-
4
. Thereby the reaction of 3 with Cl−Si(SiMe ) leads to
9 3 3 3
3
3
−
{Sn [Si(SiMe ) ] } 4 in good yield showing that 3 can be
used as a starting material for further ongoing build-up
reactions.
EXPERIMENTAL SECTION
■
Synthesis of {Sn [Si(SiMe ) ] } (3)·[Li(TMEDA) ] . A metastable
9
3 3 2
2 2
Sn(I)Cl solution was prepared by using a cocondensation technique,
where 3.95 g (33.2 mmol) of tin reacted with 40 mmol of HCl at 1240
°
C and the resulting gaseous Sn(I)Cl was condensed at −196 °C with
a mixture of toluene and P(n-Bu) (volume ratio 10:1). After warming
3
up to −78 °C, a dark red solution is obtained. A 20 mL portion of this
solution (4 mmol SnCl) is added to 2.1 mg (4.4 mmol) of
LiSi(SiMe ) ·3THF at −78 °C. The reaction mixture was slowly
3
3
warmed up to room temperature, and a black reaction solution is
obtained. To this solution is added 2 mL (12 mmol) of tetramethyl-
ethylene-diamine (TMEDA) leading to black crystals of so far
unknown composition (200 mg). The crystals are separated, and the
mother solution is concentrated in vacuo. After the addition of 1 mL
(
6 mmol) of TMEDA the solution is stored at room temperature for
2
4 h, leading to dark red crystals of {Sn [Si(SiMe ) ] }·[Li-
9
3 3 2
Figure 5. Top: Mass spectra of a THF solution of dissolved crystals of
(
TMEDA) ] (100 mg, 0.05 mmol, 11%).
2 2
3
·[Li(TMEDA) ] applying electrospray ionization. Bottom: Calcu-
2 2
−
−
NMR Spectroscopy.
(a) A couple of crystals of {Sn [Si(SiMe ) ] }·[Li(TMEDA) ] are
lated and measured isotopic pattern of Sn9R3 4 (left) and Sn10R3
(right); R = Si(SiMe ) .
3
3
9
3
3
2
2 2
placed within an NMR tube. After the addition of 0.6 mL of
THF-d , the solution is freezed with liquid nitrogen and the
8
of further reactions. Thereby a second reaction applying Cl-
NMR tube is flame-sealed under vacuum. After melting of the
solution the NMR tube is directly put in the NMR
spectrometer, and proton NMR spectra are measured every
SiMe did not lead to a stable compound, which can be seen
3
from a tin mirror that formed on the walls of the flask during
1
5 min.
the reaction. Hence, the possible product {Sn [Si-
9
−
(
SiMe ) ] SiMe } 5 seems to be unstable and decomposes
(b) A couple of crystals of {Sn [Si(SiMe ) ] }·[Li(TMEDA) ] are
3
3 2
3
9
3
3
2
2 2
among others to elemental tin. The highly dynamic behavior of
might be due to weak tin−tin bonds within the cluster core.
This property of 3 is first of all negative due to the challenging
handling but might be also a chance for further build up
reactions on the way to larger clusters with more than nine tin
atoms.
placed within an NMR tube. After the addition of 0.6 mL of
3
THF-d and 0.1 mL of 12-crown-4, the resulting solution is
8
frozen with liquid nitrogen, and the NMR tube is flame-sealed
under vacuum. After melting of the solution the NMR tube is
directly put in the NMR spectrometer, and proton NMR
spectra are measured every day.
Figure 6. Time dependency of the proton NMR spectra of a THF solution of 3·[Li(TMEDA) ] stabilized by 12-crown-4.
2
2
8
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Inorganic Chemistry
Article
1
H NMR (THF-d ): 0.08 (s, 54 H, SiMe ), 3.63 (s, 64 H, O−CH ).
graphical data of this paper. These data can be obtained free of charge
at www.ccdc.cam.ac.uk/data_request/cif.
8
3
2
13
29
The measurement of C and Si NMR spectra was not possible due
to the poor stability of compound 3.
Mass Spectrometry. The anionic cluster compounds were
brought into the gas phase by electrospraying a THF solution of
ASSOCIATED CONTENT
31
■
*
S
Supporting Information
dissolved crystals of {Sn [Si(SiMe ) ] }·[Li(TMEDA) ] . The end-
9
3
3
2
2 2
plate of the electrospray source was typically held at a potential of +3.2
kV relative to the electrospray needle which was grounded. A potential
of +3.3 kV was applied to the entrance of the metal coated quartz
capillary.
Additional figures. Crystallographic data in CIF format. This
material is available free of charge via the Internet at http://
pubs.acs.org.
119
Sn Mo
̈
ssbauer Spectroscopy. A Ca119mSnO source was used
3
AUTHOR INFORMATION
Corresponding Author
*E-mail: andreas.schnepf@uni-due.de.
for the 1 Sn Mo
19
■
̈
ssbauer spectroscopic investigation. The sample was
placed within a thin-walled glass container at a thickness of about 10
2
mg Sn/cm . A palladium foil of 0.05 mm thickness was used to reduce
the tin K X-rays concurrently emitted by this source. The
measurement was conducted in the usual transmission geometry at
Notes
The authors declare no competing financial interest.
7
8 K with a total counting time of one day.
X-ray Crystallography. Table 2 contains the crystal data and
ACKNOWLEDGMENTS
details of the X-ray structural determination for {Sn [Si-
9
■
This work was financially supported by the Deutsche
Forschungsgemeinschaft.
Table 2. Crystal Data and Details of Structural
Determination
DEDICATION
3
·[Li(TMEDA)2]2 3·[Li(THF) ] ·3THF
■
4
2
†
Dedicated to Professor Jurkschat on the occasion of his 60th
birthday.
fw
2042.25
100
1560.80
100
T [K]
cryst syst
space group
a [Å]
orthorhombic
Pnma
monoclinic
P21
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13.3508(6)
24.2803(11)
90
14.949(3)
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4912(2)
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(
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0.710 73
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(
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(
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(
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R(int)
0.0585
0.0560
GOF
1.188
1.078
params/restraints
min/max e density [e Å−3]
Flack param
415/12
−1.57/1.97
805/1
8) Ugrinov, A.; Sevov, S. C. Chem.Eur. J. 2004, 10, 3727−3733.
−0.87/0.78
0.007(19)
R1 = 0.0394
wR2 = 0.0999
R1 = 0.0425
wR2 = 0.1023
884227
9) Hull, M. W.; Sevov, S. C. Angew. Chem. 2007, 119, 6815−6818;
Angew. Chem., Int. Ed. 2007, 46, 6695−6698.
(10) Hull, M. W.; Sevov, S. C. J. Am. Chem. Soc. 2009, 131, 9026−
9037.
final R indices I > 2σ
R1 = 0.0587
wR2 = 0.1083
R1 = 0.1094
wR2 = 0.1307
884226
final R indices (all data)
(11) Kocak, F. S.; Zavalij, P. Y.; Lam, Y.-F.; Eichhorn, B. W. Chem.
Commun. 2009, 4197−4199.
12) Chapman, D. J.; Sevov, S. C. Inorg. Chem. 2008, 47, 6009−6013.
13) Pacher, A.; Schrenk, C.; Schnepf, A. J. Organomet. Chem. 2010,
(
(
CCDC number
6
(
95, 941−944.
14) Schrenk, C.; Koppe, R.; Schellenberg, I.; Pottgen, R.; Schnepf,
̈
̈
(
(
SiMe ) ] }·[Li(TMEDA) ] and {Sn [Si(SiMe ) ] }·[Li-
A. Z. Anorg. Allg. Chem. 2009, 635, 1541−1548.
3
3
2
2
2
9
3 3 2
THF) ] ·3THF. The data were collected at 150 K on a Bruker
(15) Schrenk, C.; Helmlinger, J.; Schnepf, A. Z. Anorg. Allg. Chem.
2012, 638, 589−593.
4
2
APEX II (3·[Li(TMEDA) ] ) or a STOE IPDS II (3·[Li-
2
2
(
THF) ] ·3THF) diffractometer employing monochromated Mo Kα
(16) Schrenk, C.; Schellenberg, I.; Po
Trans. 2010, 39, 1872−1876.
̈
ttgen, R.; Schnepf, A. Dalton
4
2
(λ = 0.710 73 Å) radiation from a sealed tube and equipped with an
Oxford Cryosystems cryostat. The structure was solved by direct
(17) Besides the influence of the donor applied on the constitution as
well as the reactivity of the subhalide, a direct influence of the halide
used (SnBr or SnCl) is not obvious.
methods and refined by full-matrix least-squares techniques (programs
32
used: SHELXS and SHELXL). The non-hydrogen atoms were
refined anisotropically, and the hydrogen atoms were calculated using
a riding model. CCDC-884226 (3·[Li(TMEDA) ] ) and CCDC-
(18) Additionally, NMR spectroscopic investigations on the crude
reaction solution show that the neutral compound Sn [Si(SiMe ) ] 1
is not present in the solution.
2
2
10
3 3 6
8
84227 (3·[Li(THF) ] ·3THF) contain the supplementary crystallo-
4
2
8
587
dx.doi.org/10.1021/ic3011647 | Inorg. Chem. 2012, 51, 8583−8588

Inorganic Chemistry
Article
(
19) A 5 mL portion of the reaction solution is dried under reduced
pressure, and the resulting black residue is redissolved in THF leading
to a dark brown solution. Mass spectra of this THF solution are
obtained applying electrospray ionization leading to various signal
groups in the mass range between 1500 and 3000 au exhibiting
complex isotopic patterns that hint to Sn cluster compounds with a
couple of tin atoms.
(
20) Due to a possible pseudo-symmetry, space group determination
is difficult, and only the cluster core could be localized indicating that a
cluster compound with 10 tin atoms within the cluster core is present.
(
21) Holleman−Wiberg Lehrbuch der Anorganischen Chemie, 102nd
ed.; Wiberg, N., Wiberg, E., Holleman, A., Eds.; de Gruyter & Co.:
Berlin, 2007.
(
22) Fas
̈
sler, T. F. Coord. Chem. Rev. 2001, 215, 347.
(
23) Quantum-chemical calculations were carried out with the RI-
DFT version of the Turbomole program package, by employing the
Becke−Perdew 86-functional. The basis sets were of SVP quality. The
electronic structure was analyzed with the Ahlrichs−Heinzmann
population analysis based on occupation numbers. Turbomole:
Treutler, O.; Ahlrichs, R. J. Chem. Phys. 1995, 102, 346−354. BP-86-
functional: Perdew, J. P. Phys. Rev. B 1986, 33, 8822−8824. Becke, A.
D. Phys. Rev. A 1988, 38, 3098−3100. RI-DFT: Eichkorn, K.;
̈
Treutler, O.; Ohm, H.; Has
̈
er, M.; Ahlrichs, R. Chem. Phys. Lett. 1995,
2
1
40, 283−290. SVP: Schafer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys.
̈
992, 97, 2571−2577. Ahlrichs−Heinzmann population analysis:
Davidson, E. R. J. Chem. Phys. 1967, 46, 3320−3324. Roby, K. R.
Mol. Phys. 1974, 27, 81−104. Heinzmann, R.; Ahlrichs, R. Theor. Chim.
Acta 1976, 42, 33−45. Erhardt, C.; Ahlrichs, R. Theor. Chim. Acta
1
(
985, 68, 231−245.
24) Wade, K. Adv. Inorg. Chem. Radiochem. 1976, 18, 1.
(
25) A figure of the calculated structure together with all calculated
partial charges is given in the Supporting Information Figure S2.
(
(
26) Lippens, P. E. Phys. Rev. B 1999, 60, 4576−4586.
27) As HOMO − 3, which is also partly localized at Sn6 (for a
picture see Supporting Information Figure S3), exhibits a different
symmetry a “transition metal like” chemistry might be possible as
lately discussed by Power: Power, P. P. Nature 2010, 463, 177.
(
28) A picture of the evolution of the proton NMR in time is given in
Supporting Information Figure S4.
29) During one attempt to crystallize one of the products of the
subsequent reaction we were able to obtain another arrangement of
(
2
‑
{
Sn [Si(SiMe ) ] } 3 in the solid state where the countercation is
9 3 3 2
+
now [Li(THF) ] and which crystallizes together with 3 molecules of
4
THF. Nevertheless within 3·[Li(THF) ] ·3THF the arrangement of
4
2
the tin atoms within the cluster core as well as Sn−Sn distances are
similar to the one found in 3·[Li(TMEDA) ] . A picture of
2
2
3
·[Li(THF) ] ·3THF is given in the Supporting Information Figure
4 2
S1.
(
30) Schrenk, C.; Neumaier, M.; Schnepf, A. Inorg. Chem. 2012, 51,
989−3995.
31) Fenn, J. B. Angew. Chem. 2003, 115, 3999−4024; Angew. Chem.,
Int. Ed. 2003, 42, 3871−3894.
32) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.
3
(
(
8
588
dx.doi.org/10.1021/ic3011647 | Inorg. Chem. 2012, 51, 8583−8588