Synthesis and reactivity of novel alkali metal stannides

Article abstract of DOI:10.1515/znb-2004-11-1215

Reactivity and side products of reactions of diorganodihydridostannanes (R₂SnH₂, R = Me, ⁿBu, ^tBu)) with various alkali metal compounds have been discussed. Alternatively, the synthesis and characterization of a family of novel potassium stannides are described as well. The compounds of type (RR′₂Si)R″₂SnK (R, R′= Me, Ph; R″= , Me, ^tBu, Ph) 4-9 were synthesized by reaction of potassium hydride with bis(silyl)stannides ((RR′ ₂Si)₂SnR″₂). All compounds were characterized by multinuclear NMR spectroscopy. In addition, the tri-tert-butyltin compound 3 (LiSn^tBu₃) and the unsymmetrical silyl substituted stannane 10 were characterized by X-ray crystallography.

Full text of DOI:10.1515/znb-2004-11-1215

Synthesis and Reactivity of Novel Alkali Metal Stannides
Thorsten Schollmeierb, Ulrich Englichc, Roland Fischera, Ingo Prassb, Karin Ruhlandtc,
Markus Schu¨rmannb, and Frank Uhliga
a Institut fu¨r Anorganische Chemie, Technische Universita¨t Graz,
Stremayrgasse 16, A-8010 Graz, Austria
b Fachbereich Chemie der Universita¨t Dortmund, Anorganische Chemie II,
Otto-Hahn-Straße 6, D-44221 Dortmund, Germany
c Syracuse University, Department of Chemistry, 1-014 Center of Science and Technology,
Syracuse, N.Y., USA
Reprint requests to Prof. Dr. F. Uhlig. Fax: +43-316-873-8701. E-mail: frank.uhlig@tugraz.at
Z. Naturforsch. 59b, 1462 – 1470 (2004); received August 24, 2004
Dedicated to Professor Hubert Schmidbaur on the occasion of his 70th birthday
Reactivity and side products of reactions of diorganodihydridostannanes (R2SnH2, R = Me, nBu,
tBu)) with various alkali metal compounds have been discussed. Alternatively, the synthesis and
characterization of a family of novel potassium stannides are described as well. The compounds of
t
type (RR’2Si)R”2SnK (R, R’= Me, Ph; R”= , Me, Bu, Ph) 4 – 9 were synthesized by reaction of
potassium hydride with bis(silyl)stannides ((RR’2Si)2SnR”2). All compounds were characterized by
t
multinuclear NMR spectroscopy. In addition, the tri-tert-butyltin compound 3 (LiSn Bu3) and the
unsymmetrical silyl substituted stannane 10 were characterized by X-ray crystallography.
Key words: Alkali Metal Stannides, Preparation, Reactivity, 119Sn and 29Si NMR Spectroscopy,
Structure Elucidation
Introduction
Nevertheless such reactive groups Z are necessary
for the build up of more complex structures. For ex-
ample we described recently the exploration of syn-
thetic avenues, structural features, and the reactiv-
ity of linear (tBu2Sn(Z)-(SiMe2)n-Sn(Z)tBu2; Z = H,
Cl, Br, Me3Si, Li; n = 1 − 6) [7 – 11] and branched
(MeSi[SiMe2-Sn(Z)R2]3; Z = H, Me, Ph, Cl, Br,
R = Me, tBu, Ph) [12] stannaoligosilanes (eq. (1 – 4)).
A number of triorgano substituted alkali metal stan-
nides (A) is known from literature and has found
widespread use in different types of organic and
organometallic reactions [1]. However, compounds of
type M-SnR2Z (B), where is Z at least one “reactive”
group such as for example hydrogen, halogen or a tri-
organosilyl moiety are still rather exotic species and
only very few examples have been reported [2 – 6].
LiR+tBu2SnH2 −→ Bu2Sn(H)Li+RH
(1)
t
2t Bu2Sn(H)Li+Cl-(SiMe2)n-Cl −→
(2)
HtBu2Sn-(SiMe2)n-SntBu2H+2LiCl, n = 1 – 6
R
R
3tBu2Sn(H)Li+MeSi[(SiMe2)-Cl]3 −→
(3)
(4)
R’
Sn
M
Z
Sn
M
MeSi(SiMe2SntBu2H)3 +3LiCl
CCl4,CHBr3
RSiMe2SntBu2H −−−−−−−→
R”
R’
RSiMe2SntBu2X, X = Cl, Br
A
B
Such chain type stannasilanes containing func-
tional groups are potential precursors for the synthe-
sis of polymeric materials as well as the formation
of cyclic or dendrimeric derivatives. Our special in-
terest is focused on cyclic silicon and tin containing
R, R’, R” = alkyl, aryl
Z = H, halogene, R3Si
M = Li, Na, K, Rb, Cs
Scheme 1. Functionalized and non-functionalized organo-
stannides.
c
0932–0776 / 04 / 1100–1462 $ 06.00 ꢀ 2004 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
1463
−LiR
t
t
tBu2SnH2 −−−→ Bu2SnA(H)Li −−−→ LiSnB Bu2SnHC(H)tBu2
−LiH
Fig. 1. Time dependent
119Sn NMR spectroscopy
proofing the formation
of 2. a) After a period
of 4 h; b) after a period
of 72 h; c) after 5 – 7 d
(identical with
a com-
parable spectra resulting
from the reaction of
tBu2Sn(H)-Sn(H)tBu2
with lithium diisopropyl-
amide (LDA) [13]).
Table 1. Metallation of hydridostannanes reported in litera-
ture.
compounds due to their possible applications in ring
opening polymerizations as well as their differences in
structural and spectroscopic features in comparison to
well known cyclic oligosilanes.
Starting material
Metallating Product
reagent
Solvent
Ref.
Ph3SnH
MeLi
LDA
Ph3SnLi
Et2O, THF [4, 14]
Key step of these syntheses is the formation of
lithium di-tert-butylstannide (LiSn(H)tBu2 (1) see
eq. (1)). Unfortunately, this reaction pathway brings
along a large number of disadvantages. Unexpected
side reactions are usual and the outcome of the reac-
tion depends on the conditions in a complicated and
hardly predictable way (i.e. solvent system, concentra-
tion, metallating agent, reaction time a. s. o.).
nBu3SnH
nBu3SnLi THF
[15]
Et2O, THF, [16]
DME
[17]
PMDETA, [18]
toluene
R3SnH (R = Ph, Bu) KH, NaH R3SnM
nBu3SnH
Ph3SnH
nBuLi
nBuLi
nBu3SnLi THF
Ph3SnLi
RR’SnH2
t BuLi
RR’SnHLi THF
[3]
(R = Tb, Tip, Mes)
R2SnH2 (R=nBu, cy) LDA
R2SnHLi THF
[4, 14]
This paper is one attempt to explain some of these
side reactions, and how to avoid them by carefully
choosing the reaction conditions or by using silyl sub-
stituted stannanes (Me3Si)2SnR2 as starting materials
instead of the dihydrido derivatives R2SnH2.
umdiorganostannides by reacting lithiumdiisopropy-
lamide with diorganodihydridostannanes (see eq. (1)).
Our investigations using di-tert-butylstannane as
starting material revealed that the corresponding re-
t
actions with BuLi or MN(SiMe3)2 (M = Na, K) are
t
surprisingly time dependent. The reaction with BuLi
according to eq. (1) is quantitative after 30 min., how-
ever, after a period of 12 – 48 h a significant amount
of the LiSn(H)tBu2 (1) is converted into the monolithi-
ated distannane 2 (LiSntBu2-Sn(H)tBu2). The forma-
tion of compound 2 is quantitative at least after a period
of 5 – 7 days. A series of 119Sn NMR spectra proofing
this fact is shown in Fig. 1.
A higher concentration of LiSn(H)tBu2 (1) leads
to a faster conversion into the monolithiated distan-
nane 2 (Scheme 2) as one would expect for dimeriza-
tion processes. The byproduct lithiumhydride was iso-
Results and Discussion
Although stannyl mono- and dihydrides can conve-
niently be prepared reports on metallation reactions
of these compounds are scarce. Due to the difficul-
ties when trying to metallate hydrostannanes it is not
surprising that only a small number of reactions have
been reported in literature and no generally applica-
ble method has been suggested so far. A brief sum-
mary about methods proposed in literature is given in
Table 1.
In 1996 Jousseaume and coworkers [4] published lated and proven by titration with HCl. Similar results
a remarkable and elegant synthesis towards lithi- are observed for the use of tert-butyl lithium instead
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
tBu2SnH2
+tBuLi
✲
R2SnH2
R2Sn(H)Li
for R = tBu
✁
✁
❆
+tBuLi or
iPr2NLi
❆ +KH, NaN(SiMe3)2 or
+tBuLi
− LiH
✁
❆
KN(SiMe3)2
✁
❆
❄
✁
❆
R2SntBu2 +...
✁
❆
✁☛
❆
48 – 240 h
– LiH
tBu2Sn(H)Li
MtBu2Sn-Sn(H)tBu2
✲
for R = Me, nBu
Scheme 3. Reactivity of different diorganostannanes with
tBuLi.
1
2
M = Li, Na, K,
Scheme 2. Chemical reactivity of tBu2SnH2 with alkali
metal derivatives.
+MeLi
+PhLi
Ph3SnLi ←−−−− Ph3SnH −−−−→ Ph4Sn
Scheme 4. Substitution versus metallation of Ph3SnH with
different RLi.
of LDA as metallating reagent. A comparable cou-
pling reaction yielding Me3SnSnMe3 and LiH starting
from Me3SnH and LDA was previously described by
Kuivila and coworkers [19].
We tried to avoid this unexpected coupling reac-
tion by using other alkali metal derivatives, how-
ever it could clearly be shown that the conver-
+tBuLi
✲
tBu2SnH2
+tBuLi
− LiH
❄
tBu3SnH
tBu2Sn(H)Li
1
+tBuLi
− LiH
❄
tBu3SnLi
t
sion of the Bu2SnH2 into the monometallated dis-
+tBuLi
✲
tannane 2 is much faster when using alkali metal
bis(trimethylsilyl)amides (MN(SiMe3)2, M = Na, K)
or potassium hydride. In both cases only the formation
of the monometallated distannane 2 is observed. No
evidence for the formation of a MSn(H)tBu2 species
was found suggesting that formation of compound 2
is the rate determining step. This fact may be due
to the higher nucleophilicity of sodium or potassium
stannides in comparison to the lithium derivatives.
We reported the formation of derivative 2, its reac-
tivity and the NMR spectroscopic details in the reac-
tion of tBu2Sn(H)-Sn(H)tBu2 with various alkali metal
derivatives recently [13].
3
Scheme 5. Formation of tBu3SnLi (3) from tBu2SnH2.
tion from lithium to a Sn-H function was reported for
the first time by Wittig, Meyer and Lange in 1951 [14].
The difference in reactivity may be understood in terms
of the different nucleophilicity and basicity of methyl
and phenyl lithium (Scheme 4).
We observed such migration reactions also for the
ditbutylstannane (tBu2SnH2) but in this case they are
only side reactions with minor importance (Scheme 4)
t
with a yield of less than 5% whereas Bu2Sn(H)Li
t
(1) is the major product. Bu3SnLi (3) is most prob-
ably formed via a Bu3SnH intermediate as substitu-
t
The situation becomes a lot more complex when
other diorganodihydridostannanes(R2SnH2, R = alkyl) tion reactions on tBu2Sn(H)Li with excess tBuLi never
are investigated. We like to underline this fact by proved to happen (Scheme 5).
one example only. In contrast to ditbutylstannane the
We were able to isolate derivative 3 by fractionated
reactions of sterically less hindered dialkylstannanes
with tert-butyl lithium do not yield the expected lithi-
umstannides. Instead a complex mixture of different
tetraorgano tin compounds is obtained as reactions of
the alkyl groups including migration, metallation and
insertion come into play (Scheme 3).
crystallisation and to confirm the structure by X-ray
analysis. Fig. 2 displays the solid state structure of
compound 3, consisting of a cation and an anion with
a direct lithium-tin contact.
The lithium atom is surrounded by one tBu3Sn
unit, in addition to three thf molecules, resulting in an
Formation of the finally obtained reaction prod- overall coordination number of four. The coordination
ucts obviously proceeds via a series of intermediates. sphere exhibits a slight distortion from ideal tetrahe-
Again, similar reactions were investigated by Kuivila dral geometry. The Li-O distances range from 1.91(2)
˚
in 1985 for methyltin derivatives [21] and a detailed to 1.956(9) A, while the Li-Sn distance is observed at
˚
discussion would go beyond the topic of this paper. 2.876(14) A. This is in the range of a direct tin-lithium
˚
Nevertheless the possibility of an organyl group migra- contact (sum of covalent radii = 2.75 A). The value is
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
Table 2. Crystal data and structure refinement for 3 and 10.
Table 4. Selected bond angles (◦) for compounds 3.
1465
3
10
C(5)-Sn(1)-C(9)
C(5)-Sn(1)-C(1)
C(9)-Sn(1)-C(1)
C(5)-Sn(1)-Li(1)
C(9)-Sn(1)-Li(1)
C(1)-Sn(1)-Li(1)
C(25)-O(1)-C(28)
C(25)-O(1)-Li(1)
C(28)-O(1)-Li(1)
C(21)-O(2)-C(24)
C(21)-O(2)-Li(1)
C(24)-O(2)-Li(1)
O(2)-Li(1)-O(1a)1
O(2)-Li(1)-O(1)
O(1a)1-Li(1)-O(1)
O(2)-Li(1)-Sn(1)
104.1(5)
102.0(5)
102.8(4)
114.0(4)
115.9(3)
116.1(4)
110.5(9)
131.9(9)
115.3(7)
102.9(9)
145.5(8)
111.5(5)
102.9(5)
102.9(5)
102.9(7)
112.7(6)
C(3)-C(1)-Sn(1)
C(4)-C(1)-Sn(1)
C(7)-C(5)-C(8)
C(7)-C(5)-C(6)
C(8)-C(5)-C(6)
C(7)-C(5)-Sn(1)
C(8)-C(5)-Sn(1)
C(6)-C(5)-Sn(1)
C(12)-C(9)-C(10)
C(12)-C(9)-C(11)
C(10)-C(9)-C(11)
C(12)-C(9)-Sn(1)
C(10)-C(9)-Sn(1)
C(11)-C(9)-Sn(1)
O(2)-C(21)-C(22)
105.4(7)
107.4(8)
106.1(11)
108.0(14)
107.2(11)
110.6(10)
116.8(9)
107.8(8)
109.0(11)
107.2(11)
109.0(12)
117.0(8)
107.8(10)
106.6(7)
119.2(11)
Formula
fw [g/mol]
C24H51LiO3Sn
513.28
orthorhombic
C29H42Si2Sn
565.60
monoclinic
Crystal system
Crystal size [mm3]
Space group
0.10×0.80×0.80 0.40×0.40×0.30
Pbcm
9.4020(1)
15.4299(2)
19.5664(3)
90
P21/c
11.405(1)
29.882(2)
17.079(1)
90.741(1)
5826.5(5)
8
1.289
0.973
2352
1.37 to 28.31
−13 ≤ h ≤ 14
−36 ≤ k ≤ 39
−22 ≤ l ≤ 12
39450
˚
a [A]
˚
b [A]
˚
c [A]
β [◦]
3
˚
V [A ]
2838.54(6)
4
1.201
0.918
1088
3.00 to 27.48
−12 ≤ h ≤ 12
−24 ≤ k ≤ 24
−20 ≤ l ≤ 20
17773
Z
ρcalcd [g/cm3]
µ [mm−1
F(000)
]
θ Range [◦]
C(21)-C(22)-C(23) 102.7(9)
C(24)-C(23)-C(22) 102.0(10)
C(23)-C(24)-O(2)
O(1a)1-Li(1)-Sn(1) 116.8(4)
Index ranges
O(1)-Li(1)-Sn(1)
C(2)-C(1)-C(3)
C(2)-C(1)-C(4)
C(3)-C(1)-C(4)
C(2)-C(1)-Sn(1)
116.8(4)
108.4(11) O(1)-C(25)-C(26)
108.0(10) C(25)-C(26)-C(27) 101(2)
108.8(9)
118.5(8)
104.2(10)
108.9(16)
No. of reflections collected
No. of indep reflns/Rint
GooF (F2)
C(28)-C(27)-C(26) 106.2(15)
O(1)-C(28)-C(27) 105.3(11)
3275 / 0.032
1.201
14130 / 0.1283
0.870
R1(F)(I > σ2(I))
0.0492
0.1349
0.0556
0.0967
0.765 / −1.206
wR2(F2) (all data)
3
˚
Largest diff. peak/hole [e/A ] 0.711 / −0.730
√
R1 = ΣꢀFo|−|Fcꢀ/Σ|Fo|, wR2 = Σw{(Fo)2 −(Fc)2}/Σw{(Fo)2} .
2
˚
Table 3. Selected bond lengths (A) for compounds 3.
Sn(1)-C(5)
Sn(1)-C(9)
Sn(1)-C(1)
Sn(1)-Li(1)
O(1)-C(25)
O(1)-C(28)
O(1)-Li(1)
O(2)-C(21)
O(2)-C(24)
O(2)-Li(1)
C(1)-C(2)
C(1)-C(3)
C(1)-C(4)
2.259(14)
2.261(12)
2.265(12)
2.876(14)
1.327(14)
1.458(15)
1.956(9)
1.261(13)
1.673(13)
1.910(15)
1.521(17)
1.532(15)
1.557(16)
C(5)-C(7)
C(5)-C(8)
C(5)-C(6)
1.49(2)
1.546(17)
1.547(19)
1.522(16)
1.535(18)
1.555(18)
1.494(16)
1.629(14)
1.516(17)
1.52(3)
C(9)-C(12)
C(9)-C(10)
C(9)-C(11)
C(21)-C(22)
C(22)-C(23)
C(23)-C(24)
C(25)-C(26)
C(26)-C(27)
C(27)-C(28)
1.54(3)
1.50(2)
˚
also comparable with the Sn-Li distance of 2.87 A in
Li(PMDTA)SnPh3 [21] one of only three examples for
alkali metal triorganostannides with a direct tin-alkali
metal contact ([K(η6-C6H5Me)3Sn(CH2-tBu)3] [22]).
The [SntBu3]− anion exhibits also a distor-
tion from tetrahedral geometry. The average of
Fig. 2. General view (SHELXTL) of the molecule 3 showing
30% probability displacement ellipsoids and the atom num-
bering scheme. (Symmetry transformations used to generate
equivalent atoms: a = x, y, 0.5−z).
the C-Sn-C angles is around 103◦. This angle is pyramidal geometry in such triorganotin units has been
slightly larger than the angles observed for [K(η 6- explained by a high p-character in the tin-carbon bond,
C6H5Me)3Sn(CH2-tBu)3] (average C-Sn-C angles affected by the differences in energy between the s
of 91.7◦ [22]), and Li(PMDTA)SnPh3 (PMDTA = and p orbitals [21 – 23]. Consequently, the lone pair,
(Me2NCH2CH2)2NMe) (average C-Sn-C angles of and the tin-alkali metal bond possess high s-character
96.1◦ [21]) but can be simply explained by the ster- explaining the similar geometries between the sepa-
t
ically more demanding butyl groups. This significant rated and contact species of triorganostannides [23].
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R
Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
Table 5. 119Sn and 29Si NMR
(RR’2Si)2R”2SnK
(RR’2Si)2SnR”2
δ119
1J29
[ppm]
R’
R”
δ29
δ29
δ119
1J29
119/117
119/117
data of (RR’2Si)2SnR”2 and
the resulting stannides 4 – 9
(solvent C6D6).
Si
Sn
Si
Sn
Si−
Sn
Si−
Sn
[Hz]
[ppm]
[Hz]
Me Me Me
Me Me Ph
Ph
Me Ph
Ph
Ph
−10.4 −274.4
−7.0 −255.2
−12.8 −269.9
525/501
520/497
525/500
385/368
536/512
348/333
4
5
6
7
8
9
−8.4 −346.8
−9.7 −227.0
−14.7 −349.4
456/436
402/384
a
Me Me
401/383
No coupling observed, broad
a,b
tBu −10.3 −188.2
−9.3
−9.0
−6.9
5.2
−330
−4.8
lines, half width > 250 Hz; b sol-
vent: D2O-cap./n-hexane.
a
Ph
Ph
Me
−8.72 −264.9
tBu −7.46 −170.6
663/634
Selected bond lengths, angles and further crystallo- side reactions as well as longer reaction times. Tri-
graphic details are given in Tables 2 – 4.
organosilanes of type RR’2SiH are formed as second
reaction products and were identified via 29Si NMR
spectroscopy (Me3SiH, δ29 : −16.5 ppm; PhMe2SiH,
δ29 : −17.3 ppm; MePhS2iSiH, δ29Si : −17.6 ppm;
Ph3SSi iH, δ29Si: −18.2 ppm). With the exception of the
triphenylsilane these hydridosilanes can be separated
from the reaction mixture by condensation in vacuum
very easily.
The resulting stannides 4 – 9 are now useful start-
ing materials for a huge number of reactions not only
in Si-Sn chemistry, especially due to the remaining
highly reactive triorganosilyl group in the molecule.
For example, the stannides 7 and 9 can be converted
easily into unsymmetrical disilylstannanes 10 and 11
(eq. (6)). The yields are nearly quantitative and we
were able to isolate both compounds as colourless
crystals.
As conclusion it should be marked that all metal-
lation reactions with dihydridotin derivatives must be
carried out under strictly controlled reaction conditions
and on a defined time scale to omit the formation of un-
wanted side products.
Problems with migration of hydrido-groups or self
condensation reactions of metallated stannanes under
formation of a complex product mixture can easily be
overcome when triorganosilyl groups as masked hy-
drido functionalities are used. Cleavage of Si-Sn bonds
by various metallating agents has intensely been stud-
ied in the past and was recently reviewed [1]. However,
to the best of our knowledge no successful attempts
to cleave silicon-tin bonds with potassium hydride
to give potassium stannides have been reported so
far. Reaction of bis(triorganosilyl)diorganostannanes
((RR’2Si)2SnR”2, R, R’, R”= alkyl, aryl) with
potassium hydride in the presence of crown ether
(18crown6) in dimethoxyethane (DME) was found to
be a fast and convenient method for the preparation
of the corresponding stannide derivatives of potas-
sium (eq. (5)).
+PhMe SiCl
(RRꢁ2Si)tBu2Sn-K −−−−−−−→
RRꢁ2Si-tBu2Sn-SiPhMe2
2
−KCl
(6)
7
9
R = Me; R’=Ph
10
R = R’ = Ph
11
The first synthesis of derivative 10 on another reac-
tion pathway was described recently, this time we were
able to isolate good quality crystals useful for X-ray
analysis. These crystals were obtained by crystalliza-
tion from n-hexane. Derivative 10, depicted in Fig. 3,
exhibits an almost perfect tetrahedral geometry around
the silicon and tin atoms. Small deviations from tetra-
hedral geometry are due to the sterically more demand-
ing tert-butyl groups at the tin atom.
The Sn-Si bond lengths are 2.599(1) for the Sn(1)-
Si(1) and 2.602(2) for the Sn(1)-Si(2). Sn-C con-
tacts are observed between 2.191(5) (Sn(1)-C(34)) and
2.209(5) (Sn(1)-C(30)). The Si-phenyl distances are
+KH
−RRꢁ2SiH
(RRꢁ Si)2SnRꢁꢁ
−−−−−−→ (RRꢁ2Si)Rꢁꢁ2Sn−K
2
2
(5)
(4−9)
Comp.
R
R’
R”
RR’2SiH
4
5
6
7
8
9
Me
Me
Ph
Me
Ph
Ph
Me
Me
Me
Ph
Ph
Ph
Me
Ph
Me
tBu
Me
tBu
Me3SiH
Me3SiH
PhMe2SiH
Ph2MeSiH
Ph3SiH
Ph3SiH
The 119Sn and 29Si NMR data of the starting ma- around 1.875 and the Si-methyl distances differ be-
terials as well as of the resulting stannides 4 – 9 are tween 1.689(5) and 1.691(5). All of these values are in
summerized in Table 5. Tetrahydrofuran (thf) can be a good accordance with those of compounds reported
used instead of the DME, however, one has to expect recently [7, 8]. Additional crystallographic details are
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
1467
˚
Table 6. Selected bond lengths (A) for compounds 10.
were dried by standard methods and freshly distilled prior
to use. The bis(silyl)stannanes used as starting materials
were prepared according to published procedures [7, 8, 25].
All other chemicals used as starting materials were obtained
Sn(1)-Si(1)
Sn(1)-Si(2)
Sn(1)-C(1)
Sn(1)-C(5)
2.602(2)
2.599(1)
2.191(5)
2.209(5)
Si(1)-C(9)
Si(1)-C(15)
Si(2)-C(17)
Si(2)-C(29)
1.875(6)
1.875(5)
1.875(5)
1.869(5)
1
commercially. H and 13C NMR spectra were recorded us-
ing a Bruker DPX 400 spectrometer. 29Si and 119Sn NMR
spectra were measured using a Bruker DPX 400, a Bruker
DRX 300, or a Varian Inova 300 MHz spectrometer. Inter-
nal standards were Me4Si and Me4Sn. If not stated other-
wise, the NMR experiments were carried out 1H decoupled.
GC-MS analyses were recorded using a Finnigan ETD 800.
Elemental analyses were performed on a LECO-CHNS-932
analyzer.
Table 7. Selected bond angles (◦) for compounds 10.
Si(1)-Sn(1)-Si(2)
C(1)-Sn(1)-C(5)
C(1)-Sn(1)-Si(1)
C(1)-Sn(1)-Si(2)
C(5)-Sn(1)-Si(1)
C(5)-Sn(1)-Si(2)
C(9)-Si(1)-Sn(1)
C(15)-Si(1)-Sn(1)
C(16)-Si(1)-Sn(1)
108.02(5)
111.2(2)
111.5(1)
112.0(1)
107.3(1)
106.7(1)
111.1(2)
112.5(2)
108.0(2)
C(9)-Si(1)-C(15)
C(9)-Si(1)-C(16)
C(15)-Si(1)-C(16) 110.5(2)
C(17)-Si(2)-Sn(1)
C(23)-Si(2)-Sn(1)
C(29)-Si(2)-Sn(1)
C(17)-Si(2)-C(23) 109.9(2)
C(17)-Si(2)-C(29) 106.6(2)
C(23)-Si(2)-C(29) 108.9(2)
106.9(3)
107.8(2)
113.3(2)
110.2(2)
107.8(2)
Selected reactions of R2SnH2 with alkali metal reagents,
MR
G e n e r a l p r o c e d u r e
6.4 mmol of an alkali metal reagent (tBuLi, (Me3Si)2NM,
LDA, KH) and 15 ml thf were placed in a 50 ml Schlenk
vessel. The solution was cooled down and 6.4 mmol of
the diorganodihydridostannane were added via a syringe.
The solution was stirred x h at the given temperatures and
additional 12 h at room temperature. The resulting mixtures
were examined by 119Sn NMR spectroscopy.
R e a c t i o n s w i t h tB u2S n H2,
s t a r t i n g m a t e r i a l : 1.5 g (6.4 mmol) tB u2S n H2
a) With tBuLi at 0 ◦C
1
x = 2 h; – 119Sn{ H} NMR (111.92 MHz, D2O-
capillary): 1 [10%]: δ = −9.8 (s, 1J(119Sn-1H)=287 Hz);
tBu2Sn(H)-Sn(H)tBu2 [40%]: δ = −83.4 (s); tBu2SnH2
[10%]: δ = −117.0 (s); not classified signals: [10%]
δ = −18.5; [5%] δ = −22.9; [20%] δ = −34.4; [5%]
δ = −49.4.
Fig. 3. General view (SHELXTL) of the molecule 10 show-
ing 50% probability displacement ellipsoids and the atom
numbering scheme.
given in Tables 2, 6 and 7, the experimental section, as
well as in the supplementary material.
b) With tBuLi at −45 ◦C
1
x = 4 h; – 119Sn{ H} NMR (111.92 MHz, D2O-
One of the main goals of our chemistry is still the
synthesis of precursors for Si-Sn materials; neverthe-
less, this contribution is a side product of this chem-
istry potentially useful also for chemists beyond the
circle of Si-Sn specialists. A more detailed study on
cleavage reactions of silicon tin bonds with various
other metallating reagents will be reported shortly [24].
capillary): 1 [100%]: δ = −9.7 (s, 1J(119Sn-1H)=287 Hz).
Evaporation of the solvent and crystallisation attempts with
n-hexane gave ∼ 50 mg of colourless crystals of com-
pound 3.
1
x = 72 h; – 119Sn{ H} NMR (111.92 MHz, D2O-
capillary): 1 [50%]: δ = −5.8 (s, 1J(119Sn-1H)=287 Hz);
tBu2SnA(H)SnBtBu2Li,
2
[50%]: δ = 137.7; −42.6
(1J(119Sn-119/117Sn)=6930/6610 Hz).
Experimental Section
◦
1
x = 120 h at −45 C, 48 h at r. t.; – 119Sn{ H} NMR
General methods
(111.92 MHz, D2O-capillary): tBu2SnA(H)SnBtBu2Li,
All reactions were carried out under an atmosphere of in-
ert gas (N2 or Ar) using Schlenk techniques. All solvents 119/117Sn)=6930/6610 Hz).
2
[> 90%]:
δ
=
134,4;
−43.2
(1J(119Sn-
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
General procedure for the formation of compounds (4−9)
c) With LDA at −50 ◦C
x = 4 h; – 119Sn{ H} NMR (111.92 MHz, D2O-
capillary): 1 [100%]: δ = −9.7 (s, 1J(119Sn-1H)= 287 Hz).
1
To a solution of 0.5 mmol of a bis(triorganylsilyl)di-
organostannane and 140 mg (0.530 mmol) 18crown6 in
2 ml DME or thf, 21 mg (0.523 mmol) KH are added
with stirring. Upon addition the reaction immediately turns
yellow to red under slight gas evolution. An aliquot of the
reaction mixture was used for NMR spectroscopy. For 29Si
and 119Sn NMR shifts see Table 5.
x = 72 h; – 119Sn{ H} NMR (111.92 MHz, D2O-
1
capillary): 1 [45%]: δ = −6.0 (s, 1J(119Sn-1H)=286 Hz);
tBu2SnA(H)SnBtBu2Li,
2
[50%]: δ = 132.5; −42.8
(1J(119Sn-119/117Sn)=6930/6610 Hz); not classified sig-
nals: [5%] δ = −22.9.
d) With KN(SiMe3)21at -50 ◦C
D i m e t h y l ( t r i m e t h y l s i l y l ) s t a n n y l p o t a s s i u m
(4)
x = 2 h; – 119Sn{ H} NMR (111.92 MHz, D2O-capil-
lary): tBu2SnA(H)SnBtBu2K [> 90%]: δ = 126.8 (1J(119Sn-
119/117Sn)=7700/7360 Hz),
δ
= −43.5 (1J(119Sn-
Starting materials: 150 mg (0.508 mmol) dimethyl-
bis(trimethylsilyl)stannane; 2 ml DME, 21 mg (0.512 mmol)
KH, 140 mg (0.530 mmol) 18crown6.
1H)=808 Hz, 1J(119Sn-119/117Sn)=7700/7360 Hz); not
classified signals: [5%] δ = −22,2; [< 5%] δ = −35.0.
Similar results are observed for using the sodium instead
of the potassium amide.
D i p h e n y l ( t r i m e t h y l s i l y l ) s t a n n y l p o t a s s i u m
(5)
e) With KH at −50 ◦C (10 fold excess KH)
Starting materials: 150 mg (0.358 mmol) diphenyl-
bis(trimethylsilyl)stannane; 2 ml DME, 15 mg (0.36 mmol)
KH; 95 mg (0.36 mmol) 18crown6.
1
x = 4 h; - 119Sn{ H} NMR (111.92 MHz, D2O-capil-
lary): Bu2SnA(H)SnBtBu2K [80%]: δ = 127.1 (1J(119Sn-
t
119/117Sn)=7700/7360 Hz),
δ
= −43.3 (1J(119Sn-
1H)=808 Hz, 1J(119Sn-119/117Sn)=7700/7355 Hz);
tBu2Sn(K)SntBu2K [15%]: δ = 16.8; not classified signals:
[5%] δ = −23.2.
D i m e t h y l ( d i m e t h y l p h e n y l s i l y l ) s t a n n y l
p o t a s s i u m (6)
Starting materials: 201 mg (0.48 mmol) dimethylbis(dimeth-
ylphenylsilyl)stannane; 2 ml DME, 20 mg (0.49 mmol) KH,
132 mg (0.5 mmol) 18crown6.
E x a m p l e f o r r e a c t i o n s w i t h nA l k y l2S n H2
1 g (4.25 mmol) nBu2SnH2; 5 ml (8.5 mmol) of a 1.7 M
tBuLi/nhexane solution; reaction temperature: −50 ◦C, reac-
tion time 2 h. The solution was separated from the resulting
solid by filtration (G3).
D itb u t y l ( m e t h y l d i p h e n y l s i l y l ) s t a n n y l
p o t a s s i u m (7)
Starting materials: 2.57 g (4.1 mmol) ditbutylbis(methyl-
diphenylsilyl)stannane; 15 ml thf, 168 mg (4.2 mmol) KH,
1.12 g (4.2 mmol) 18crown6, reaction time 48 h.
Colourless solid: The solid reacted slowly with water
(bubbling) and the resulting solution was investigated by
titration with HCl. The result strongly indicates that the
colourless precipitate was pure LiH.
D i m e t h y l ( t r i p h e n y l s i l y l ) s t a n n y l p o t a s s i u m
(8)
1
Solution: 119Sn{ H} NMR (111.92 MHz, D2O-
capillary): [45%] δ = 12.8, [5%] δ = 3.4, [25%] δ = −1.3,
[25%] δ = −5.7.
Starting materials: 427 mg (0.64 mmol) dimethylbis(tri-
phenylsilyl)stannane; 15 ml DME, 26 mg (0.63 mmol) KH,
169 mg (0.64 mmol) 18crown6, reaction time 48 h.
GC-MS: Column CP-SIL-5CB (25 m), solvent: diethyl
ether, 40 ml/min), 4 signals with retention times of 5.85;
7.12; 7.75 and 8.35 min. with a ratio of 2:15:70:13.
D itb u t y l ( t r i p h e n y l s i l y l ) s t a n n y l p o t a s s i u m (9)
5.85 min. [2%]: no successful mass spectra could be ob-
tained.
Starting materials: 1.57 g (2.1 mmol) ditbutylbis(tri-
phenylsilyl)stannane; 15 ml DME, 90 mg (2.2 mmol) KH,
0.528 mg (2.0 mmol) 18crown6, reaction time 48 h.
7.12 min. [15%]: m/z: 291 [80%], 235 [80%], 172 [BuSn,
100%].
7.75 min. [70%]: m/z: 374 [tBu2BuSnCH2CH2(tBu),
100%],
General procedure for the formation of the triphenylsilyl
(diphenylmethylsilyl)dit butylstannanes 10 and 11
t
317 [M+-CH2CH2 Bu, 40%], 175 [tBuSn, 100%].
◦
8.35 min. [13%]: m/z: 346 [Bu2Sn(tBu)2, 100%], 235
[80%], 316 [M+ -2 CH3, 40%].
To a cooled solution (−30 C) of 4.0 mmol potassium
ditbutyl(triorganosilyl)stannide in 50 ml DME or thf was
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
1469
added drop wise a solution of dimethylphenylchlorosilane disordered, the other atoms are disordered over two sites with
(0.69 g, 4.1 mmol) in n-hexane. The reaction mixture was an occupancy of 0.5.
slowly warmed to room temperature, the solvents were
Crystallography of 10
evaporated and the resulting residues were examined by
119Sn and 29Si NMR spectroscopy.
The crystal was mounted on the diffractometer as de-
scribed previously [28]. Intensity data were collected at
−182 ◦C with graphite monochromated Mo-Kα radiation
D i m e t h y l p h e n y l s i l y l ( d i p h e n y l m e t h y l s i l y l )
d itb u t y l s t a n n a n e (10)
˚
(α = 0.71073 A), using a Siemens SMART system, com-
1
plete with 3-circle goniometer and CCD detector operating
at −54 ◦C. Details regarding instrumentation and data treat-
ment have been reported previously [29]. An absorption cor-
rection was applied utilizing the program SADABS [30].
The crystal structure was solved by Direct Methods, as in-
cluded in the SHELXTL-Plus program package [31]. Miss-
ing atoms, including the hydrogen atoms on Si and Sn, were
located in subsequent difference Fourier maps and included
in the refinement. Remaining hydrogen atoms were placed
geometrically and refined using a riding model with Uiso
constrained at 1.2 for non-methyl groups and 1.5 for methyl
groups times Ueq of the carrier C atom. The structure was re-
fined by full-matrix least-squares refinement on F2 (SHELX-
93) [32]. Scattering factors were those provided with the
SHELX program system. All non-hydrogen atoms, with the
Solvent: thf; 29Si{ H} NMR (59.63 MHz, D2O/n-hexane):
δ = −11.4 (SiPhMe2, 1J
: 387/370 Hz),
29Si−119/117Sn
29Si−119/117Sn
δ = −10.0 (SiPh2Me, 1J
= 379/362 Hz);
1
119Sn{ H} NMR (111.92 MHz, D2O/nhexane) δ = −185.1.
T r i p h e n y l s i l y l ( d i p h e n y l m e t h y l s i l y l )
d itb u t y l s t a n n a n e (11)
1
Solvent: DME; 29Si{ H} NMR (59.587 MHz, C6D6):
δ = −12.0 (SiPhMe2, 1J
(111.817 MHz, C6D6) Sδn= −183.6.
119/117Sn: 385/368 Hz), δ = −8.1
29Si−
1
1
(SiPh2Me, J
= 393/376 Hz); 119Sn{ H} NMR
119/117
29Si−
I s o l a t i o n o f 10
The isolation of 10 was following the procedure described exception of some disordered or restrained positions were re-
in literature [12]. The residue was dissolved in 50 ml of fined anisotropically. Disorder was handled by including split
nhexane, and hydrolyzed by addition of 10 ml of water. The positions for the affected groups, and included in the refine-
organic layer was separated and dried over calcium chloride. ment of the respective occupancies. A set of restraints was
After filtration (G3) and evaporation of the solvents the re- applied to aid in modeling the disorder.
sulting crude product was purified by column chromatog-
Atomic scattering factors for neutral atoms and real
raphy (silica gel 60, hexane) to give 1.36 g (35%) of 10 and imaginary dispersion terms were taken from Interna-
as a colorless solid, m.p. 67 – 68 ◦C. Elemental analysis for tional Tables for X–ray Crystallography [33]. The figures
C29H42Si2Sn (565.52 g/mol): calcd. C 61.59, H 7.43; found were created by SHELXTL (Sheldrick 1997) [34]. Full de-
C 61.8, H 7.5.
tails for the structural analysis have been deposited with
the Cambridge Crystallographic Data Centre, CCDC No.
257226 for compound 3, CCDC No. 257167 for compound
10. Copies of data can be obtained free of charge on ap-
plication to The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: int.code +(1223)336-033; e-mail:
teched@chemcrys.cam.ac.uk), and are also available in CIF
format from the authors.
Crystallography of 3
The crystal was mounted on the diffractometer in a
sealed ◦Lindemann capillary. The data were collected at
−182 C to a maximum θ of 27.48◦ with 360 frames via
ω-rotation (∆/ω = 1◦) twice 10s per frame on a Nonius
Kappa CCD diffractometer using graphite monochromated
˚
Acknowledgements
Mo-Kα radiation (α = 0.71073 A). The structure was
solved by Direct Methods (SHELXS97) [26] missing atoms,
including the hydrogen atom bound to Sn(1), were located
in subsequent Difference Fourier cycles and refined by
full-matrix least-squares of F2 (SHELXL97) [27]. All other
hydrogen atoms were placed geometrically and refined using
The authors thank funds from the Graz University
of Technology (Austria), the Deutsche Forschungsgemein-
schaft (DFG, Germany) and the Fonds der chemischen In-
dustrie (Germany). KRS is grateful for support by Syra-
cuse University, the National Science Foundation (CHE-
9702246) and the W. M. Keck Foundation. We also ac-
knowledge Prof. Dr. K. Hassler (Graz University of Tech-
nology) for his interest in this work and donating the
bis(triphenylsilyl)diorganostannanes to our disposal.
a riding model with a common isotropic temperature factor
2
˚
˚
(C-Hprim. 0.96 A, Uiso 0.147(10) A ). All non-hydrogen
atoms were refined using anisotropic displacement pa-
rameters. Only Sn(1), O(1), O(2), Li(1), and C(22) are not
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Th. Schollmeier et al. · Synthesis and Reactivity of Novel Alkali Metal Stannides
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