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Molecular Structure of [Pd6Cl12] in Single Crystals Chemically Grown at Room Temperature.

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Molecular Structure of [Pd6CI,,] in Single
Crystals Chemically Grown at Room
Temperature**
Daniela Belli Dell'Amico,* Fausto Calderazzo,*
Fabio Marchetti, and S t e f a n 0 Ramello
[Pd,CI,(CO),]. which according to spectroscopic data is a
centrosyminetric chloro-bridged dimer (Cco = 2163 c m - ' in
thionyl chloride(solv.)). can be prepared by carbonylation of
palladiuin(ii) chloride."' The thermodynamic data of the equilibrium ( a ) w r e established as A H o = - (56.9k1) kJmol-'
and A.Y0 = - (128.7k3) J m o l - ' K - ' ) .
We reckoned that slow decrease of the partial pressure of CO
over a solution of the dimer could give single crystals of palladium(ir) chloride. This experiment could be of interest for many
reasons. It should provide a) information about the crystal
phase in equilibrium with the carbonyl compound; b) the possibility o f ad.justing our earlier estimate of the bond dissociation
energy (BDE) for the Pdii-CO bond;"] and c) the possibility of
growing single crystals of PdCl, at room temperature, an experiment which had no precedent in the literature. Furthermore. as
both ?-Iz1 and /bPdC12[31are reported to sublime as [Pd,CI,,],
HS confirmed bb mass spectrometric experiments.13. 41 growing
crystals from the experimental setup based on Equation (a)
would exploit ;I well-established dinuclear precursor, different
from that operating in the Pd,,, +CI, experiments at high temp e r a t ~ i r e ~('i~n 'the
~ range 400-600 C). Further points of interest are that the bonding parameters of [Pd,CI,,] are still unknown. since the original structural assignment[31was based on
a Guinier data collection on a microcrystalline sample. Moreover. the data of the z-modification, reported by A. F. Wells[zI
to be composed of infinite. linear chains of chloro-bridged
square-planai- palladium atoms. were collected with a less sophisticated X-ray diffractometer than those available nowadays.lhJ
A solution o f [Pd2CI,(CO),] (about 3 x 1 0 - 2 ~ in
) thionyl
chloride i n 21 Schlenk tube open to the atmosphere over several
days at rooin temperature. deposited well-formed single crystals
of PdClz (elemental analysis). which were only sparingly soluble
in thionyl chloride.[8' The single-crystal X-ray structure analysis
showed the compound to be the hexanuclear [Pd,Cl,,] compound, described by H. Schifer and c o - w o r k e r ~and
' ~ ~ classified
as the /hodification. to distinguish it from the r-one.['] The
molecular structure (Fig. 1 ) is similar, but not identical, to that
o f [Pt,CI I J. prepared by G. Thiele and c o - ~ o r k e r s [ by
' ~ vaporphase recrystollization of microcrystalline PrC1, a r 550 C in the
presence of dichIorine."Ol
The hexanucleur [Pd,CI, ,] molecule can be described as a
cube whose edges are approximately 4.62 8, long; the central
points of faces and edges are occupied by the palladium atoms
and by the chlorine atoms. respectively. The coordination
around the palladium atoms is almost exactly square-planar;
the most notable deviations are the short Pd-CI(1) distance of
[*] Prof D Hclli DcI1' Amico, Prof E Calderarro. Dr. F. mar chert^. S. Ramello
Dip;ii-timento di Chimica e Chimica lndustriale. Unwersiti di Pisa
Vie Risorgiineiito 35. 1-56176 Pisa (Ital))
F i i ~I n i . code r(50)20-737
[*"I
T h i \ w o r k n i i \ \upported by the Consiglio Nazionale delle Ricerche ( C N R ) .
Pi-ogctio Sli-atcspo Tccnologie Chimiche Innovative. We thank Chimet
S.p. A.. Badia <ilPino. (Italy) for a loan of palladium
l(2")
Fig. 1. The molecular structure of [Pd,CI,,I The ellipsoids dre represented at 50%
,/,,
prohabilit~.' = j . :..\: = - z. -.I. -I: "' = :. I . I..
= - I.. -:.
- Y. Bond
lengths [A] and mgles [ 1: Pd-CI(Ij 2.304(1). Pd-CI(1'j 2..310(1), Pd-Cl(2)
2.314(1), Pd- Cl(7") ?.3t7(1); Cl(t)-Pd-Cl(t')90.16(9). Cl(l')-Pd-Ci(7)178.40(3).
CI(l)-Pd-C1(2)
90.37(5). CI(I'j-Pd-Cl(2'')90.13(5), CI(1 )-Pd-C1(2")178.65(3).Cl(2)Pd-CI(Z") 89.18(3). Pd"-CI(l)-Pd
90 70(5). Pd-CI(Z)-Pd"", 9?.fJ4(5).
"
2.304(1) A and the distance of the palladium atom from the
plane Cl(l)-Cf(l')-C1(2)-C1((O.OZS(l)
2")
A). The bond angles at
the chloro ligands range between 90.70(5) and 92.04(5)'. The
average Pd-CI distance of 2.310(4) A, which is the same as that
observed in r-PdC1,[21 (2.31
corresponds to a rather strong
palladium-chlorine bond, taking into consideration that for a
considerable number of known crystal structures the average
Pd"-CI distance is 2.43(6) (for bridging chloro ligands with
A value of
bond angles at palladium of approximately 9 0 ' )
2.36 A was reported for [Pt,CI,,]. alias fl-PtC12.rq1as expected
for metal cations with very similar ionic radii.[t31The six palladium atoms define an octahedron, whose tetragonal planes contain four bridging chloro ligands each; the shortest intramolecular Pd . . Pd distances of 3.283(1) and 3.329(2) A are considerably longer than the distance in palladium metal (2.750
Polycrystalline samples of the palladium(ii) chloride that had
been prepared from the carbonyl derivative were subjected to
X-ray diffraction experiments with a Gandolfi camera : the diffraction pattern corresponded satisfactorily to that calculate d [ t 5 1from the single-crystal structure (Table 1 ) . thus showing
that the bulk of the palladium chloride in equilibrium with the
carbonyl-chloropalladium complex is [Pd,CI I J ,
On the basis of these new findings on the nature of the palladium(i1) chloride involved in equilibrium (a)* a A@ value of
-(478+ 10) kJmol- was calculated['71 for [Pd,CI,(CO),]~,,;
the Pd'l-CO BDE in the dinuclear carbonyl derivative was estimated as 104$4 kJ mol- I , thus confirming the earlier results."'
In conclusion. we have confirmed that palladiuin(ii) chloride,
which plays a role as a precursor in several catalytic processes," 'I if prepared at room temperature is the hexanuclear compound [Pd,CI 12]. regardless of the method of
Furthermore we have established its metrical parameters. The
best method for preparing [Pd6C1,,] appears to be equilibration
of palladium(ir) chloride suspended in thionyl chloride with CO
at atmospheric pressure and rooin temperature. The result is. of
course, independent of the nature of the chloride initially used.
The Pd-CO bond is confirmed as atypical["] and is characterized by a moderate bond strength and by a high qc0 stretching
frequency, comparable to that of [BH,(CO)][211(Cco =
2165 cm-' in the gas phase) and [CaCpT(CO)]'"'] (fco =
21 58 cm-', toluene), suggestive of a predominant o-contribution.
A).
A
'
E.vperinmtd Procedure
In a Schlenk tube. PdC1, (1.06 g, 6.0 mmol) [as obtained hy e\,,iporatton under
reduced pressure of a n aqueous acidic solution of [ P d C I J - follobed hy treatment
ofthe resulting solid with SOCI, at room temperature (satisfdctor! Pd. CI analyses)]
was suspended in SOCI, (100 mL) and stirred under CO at atmospheric pressure at
I 8 C for 70 h. This resulted in a red solution of[Pd,CI,(CO),j. The container was
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Table I . Calculated and observed X-ray poudei- diffraction patterns o f [Pd,,CI,,]
"a].
d (c'llcd.)
/I/\/
~
[A]
I,,,
d ( c x p ) [A]
100
50
6.85
6.46
4.72
I
~
0
1
1
1
1
1
1
1
0
0
1
0
1 2 0
1 1 1
0
2
1
1
1
3
1
1
2
3
2
0
2
2 0
2 0
2 1
2 1
1 1
1 1
2 0
3 0
3 0
2 1
2 2
3 0
3 1
3 2 1
3
3
1
3
220. 4
1
2
4
1
3
3
4
3
2
0
341. 2
1
1
4
521. 2
3
1
2
3
1
0
1
1
1
1
3 0
4
2
4
2
4
3
2
4
4
0
2
0
3
0
1
1
1
0
6.844
6.524
4.722
4.020
3 825
3.766
3.422
3 262
3.030
2.944
2.867
2.684
2 625
2.533
2.482
2.466
3.361
2.281
2 220
2.186
2 175
2.154
2.113
2.072
2.000
1921
1-913
1.883
I.870
11
1.835
1.816
1809
1.773
1.733
1.711
1.705
4
3
4
3
1.655
1.646
1.631
1.599
1
1
0
0
9
27
Received. January 15, 1996 [Z87221E]
1996. 108. 1430- 1432
German version: A n R m C/i~~i?i.
4.01
2
16
1
3.76
IilU
27
17
20
2
I6
11
80
3 25
3.04
1 94
m
1.68
2.62
2.54
U
W
w
VS
YU
9
2 46
2.36
2.28
6
4
2
1
5
2 12
vw
2.00
m
1.915
vw
1.869
x
1.811
1.771
vu
\U
W
7
23
3
2
4
I1
4
5
I1
32
3
\h.
1
4
2
1
22
3
i 633
[a] Similar result^ were obtained on a microcrystalline simple sealed in ii glass
capillary. or on a small polycrystalline aggregate of almost spherical shape glued iit
the end of a glass fiber. The sample for the X-ray powder diffraction experiment
should not be milled. Although crystalline palladiiini(li) chloride is :apparently
stable in air over extended periods of time. milling i n air resulted in the appearance
of spurious lines. similar to those attributed in the literature to commercial palladium chloride [16]. ahas the low-temperature form [ 5 ] . alias ;.-PdCI, [llc.4]
left open to the atiiiosphere for 22 days: the led-broun cr)stiilline deposit of
[Pd,CI,,] h a s collected b? filtration and dried iii ~ i c u o(0.52 g. 499b hield). The
crystals of [Pd,CI,2] were smalli-eddish-black rhombohedra bounded by a n faceso f
the form :l00;. A crystal of approximate dimensions 0.14 x 0.14 x 0.072 min uils
glued ai the end o f a glass fiber and its X--a) diffraction pattern u ~ i studied
s
uith
a Weissenberg camera. It showed trigonal symmetry ujithout systematic absences.
Cell parameters were measured and inteiisity data were collected on ii Siemens P4
single-crystal automatic diffractonieter equipped with graphite-monochromatized
Mo,, radiation ( i = 0.71069 A). Cell parameters uere mlciikited based on the
accui-,itel> centered setting angles 01' 11 strong refections uiih 12.610s 19 2
Crcstal data. Pd,CI,,. .Lf, =1063.9. T = 296(2) K . spice group R3 (no. 148).
( I = 8.0600(9)A. ~ = 1 0 8 . 0 7 ( ? ) .L'=422.63(X)A3.
% = I . { J ~ . > , ~ ,=4.180gcni-?
,
p(Mo&,) = 8.1 15 mm". F(000) = 480 The collected inten5ities o f 1477 retlections
with 3 ~ 1 1 1 3 5. on merging the equnnlent ones ;itid aftci- correction for Lorentz
;itid polarization effects. resulted in iiii intern;il R viilue of 0.16. the application o f
a Gaussian absorption cori-ectioii [13]based on crystul shape and bize reduced it to
0 025 The diffraction syminetr? iiidic'ited the spice groups R3 or R3. We placed the
Pd and C1 iitoms in the positions the appropriate doins hake in [Pt,,CI,2][9]. and
first tined to refine t h e structure in the R3iii space group. that i s the s m i e u s that for
[Pt,CI,,]. The R factor decreased to 0.192: then the niirroi plane\ were removed.
refinement u:is continued i n the R3 space gi-oiip. m d misoti-opy in the theriii,il
i n m i o n was introduced- the K vdlue dropped t o 0 . 0 2 2 . 29 p r a m r t e r s were retined
baaed on 806 independent reIlections [ H ,= 0.022 = ZII&,I - I F , ~zl&,~;
I
,,K,=
0 055 = [Z!l-(F?- Ff)' Z:I'(F;)']' ': I I ' = ~ [c' (F:) +(0.0164P)' + 0 3 3 P ] where
P = JMAX(<?.O) +2c'I. S = 1.133 = (.Z,I(F~
- F;)? (,v - P)]'2; [33]
ca]cu.
1332
-
Keywords: chlorine compounds palladium compounds . structure elucidation
U
3
8
4
latioiis and drawings w'ere performed by using the SHELXTL [24a] and ORTEPII
[24b] programs. respectively. For the X-ray diffraction experiments on polycrystalline snmples (Tzble 1 ) B small polycrystalline aggregate of [Pd,Cl,,] of almost
spherical shape wiis glued at the end of ii glass fiber and the diffraction pattern was
measured uith a Gandolfi camerli ( I 14.6 mm) and Ni-filtered Cu,, ( i = 1.54178 A)
radiation. The positions of the lines were measured with a precision caliper equipped
with an optical iilignment device 1251.
[ I ] D. Belli Dell' Ainico, F. Calderazzo. N. Zandonh. Inorg. C/ieiii. 1984. 23.
137.
[2] A. F.Wells. Z. K r i s r d o g r . 1938. 100. 189. L. Pauling. The Nrirrrre of tiic Chriiii
d Boiid. 3rd ed.. Cornell University Press. Ithaca. NY, 1960. p. 157.
[3] H . Schafer. U. Wiese, K. Rinke. K. Brendel, AII~('II..Cheiri. 1967. 7Y. 244:
rliiscw. C ' l i c ~ i i i . I i i r . E d € j i g / . 1967. 6 , 253.
[4] A. Yatsiniirski. R. Ugo. Initi'g. Ch~tii.1983. 22. 1395.
[5] J. R. Soulen, W. H. Chappell. Jr.. .
I
PIrjx C h i . 1965, 69. 3669.
[6] Some of the reported experiments uith PdCI2 have been carried out o n samples
that had been prepared in an external laboratory [2.5.7] or by an unspecified
procedure 131.
[7] W. van Bronswyk. R. Nyholm. J. Chriii. Soc. 1968, 2084.
[C;] Although it may appear so. this is not a fortuitous experiment: slow diffusion
of moisture in the air into the reactor has the beneficial effect of decreasing the
partial pressure of CO o n the solution due to the formation of SO, and HCI
from the solvent. The preparation has been repeated several times successfully.
Depending on the rate of admission of air into the reactor single crystals or
inicrocrystalliiie samples can be obtained.
[S] a ) K. Brodcrsen. G Thiele. H. G. Schnering. Z. A i ? o r ~,447.
.
Clicwi. 1965,337.
120: b) G Thiele. K. Brodersen. Forr.\c/i. C/ioii. Forccii. 1968. 10. 631.
[IO] Another modification of PtCl,. H polynuclear compound, classified as x-PtCI2.
was identified on the basis of both Guinier data on a microcrystalline sample
[IIc] and X-ray diffraction data on B single crystal [Ilc]; this substance was
obtained [ l l ] by heating [Pt,CI,,] for 1 - 7 days at 500 C or by treating
plntinum metal with dichlorine ( 3 atm) in several temperature gradients ranging between 520 and 440 C and 800 and 780 C. The x-modilications of palladitim(ti) and platinum(i1) chlorides were reported [Ilc] not to be isotypic.
111) a ) U Wiese. H. Schifer. H. G von Schnering. C. Brendel. K. Rinke, A~igeii..
C'hrwi. 1970. A?.'. 135: Aiig[w. C/rcrii I i i r . Ed EiigI. 1970. 9. 158. b) H. Schafer,
U. Wosiewtz. 2 .Aii(~i-g.
A& C/i~wi.1975. 415. 202: c) B. Krebs, C. Brendel,
H. Schiifer. ihid 1988. 5151. 119.
[I?] A. G . Orpen. L. Briimmer. F. H. Allen. 0 . Kennard. D. G . Watson. R. Fdylor.
J, C ' h e i r i Sor. D d r r ~ i iPms. 1989. S1 S83.
[I31 R. D. Shannon. Acro C i - j . ~ r r i / / o g rS P ( . [ .A 1976. 32. 751
[I41 a) K . L. Shelton. P. A. Merewether. B. J. Skinner. CNII..Mhirrri/. 1981. I Y . 599.
~ . . ed.. Clarendon Press. Oxb) A. F. Wells. Srr~icriirdhorgmiic C h m i i ~ f r5th
ford. 1986. p. 1288.
[IS] W. Kraus. G . Nolze. POWDER CELL. Program for X-ray powder patterns
ciilculation. Federiil Institute for Materials Research and Test, Berlin. Germany. 1995: we thank D r G. Nolre for providing a copy of the program prior
to publication.
[I61 a ) JCPDS. Joint Committee on Powder Diffraction Standards, I601 Park
Lane. Suarthmore. PA. USA.card No. 1-278: b) J. D. Hanawalt. H. W. Rinn.
L. K . Frc\cI. Iird &q. Chtwi. A w l . ti/ 1938. i0. 457. Table XII: JC%miA h v r .
1938. 32. 78411. This is a collection of powder diffraction data for 1000 chemical substances: the data referring to PdCI, were collected on a sample of
unspecified origin.
[I71 The c;ilculation requires the following data from the literature:
AH:' = - 167 kJinol-' for PdCl, a s 1 6 of [Pd,CI,,] 1181. BDE values for
tcrminnl and bridging Pd -C! bonds 1.11. 359 and 194 kJmo1-l. respectively.
Other datci tire fi-om ref. [I]
[I81 a ) W. E. Bell. U . Merten. M Tagami. J P h i x Clirwii 1961. 65. 510: b) H.
Schifer. Z.AiiorX. Allg. Clieiri. 1975, 415. 217.
[I91 P. M. Maitlis. T/ic Oi-soiric Cht~irii.srri~
o/ Pu//cidiion. &I/.I , 2. Academic Press.
London. 1971.
[lo] D. Belli Dell' Ainico. F. Calderazzo. Piire Appl. Chriii 1986. SH. 561. This
;article pointed out the atypical nature of meral-CO bonds Cor palladium(ii).
platinum(ii).and gold(i).due toil largelq predominant ocontribution. Systems
with siniiLir properties have been more recently described for silver([). paliadiuin(ii).and mercury. all characteri~edby extremely high
values. Relevant
references on this subject are- P. K. Hurlburt. 0. P. Anderson, S. H. Strauss.
J. hi.Clrtwi Sotc 1991. 1 / 3 . 6277: C. Wang. H. Willner. M. Bodenbinder. R. J.
Batchelor. F. W. B Einstein. F.Aubke. /mir~?.C/i@in.1994.33. 3521. M . Bodenbinder. ti. Baker-.lollenbeck. H. Willner. R. J. Batchelor. F. W. B. Einstein. C.
Wang. F.Aubke. f n o r g . Chriri. 1996. 35. 82.
[-'I] G !A! Bethke. M.K Wilson. J C%rni Phi..\ 1957. 26. 1 118.
~
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P. Selg. H H . Brintringer. R. A. Andersen, I Horvith. Arigeir. C/IPI?I.
1995.
107. 877. An,qeii. Cheni. Int. Ed. Engl. 1995. 34. 791.
Further derails of the crystal structure investigation are available on request
from the F3chinformationszentrum Karlsruhe. D-76344 Eggenstein-Leopoldshafen (Germany). on quoting the depository number CSD-404624.
a ) <i M Sheldrick. SHELXTL-Plus. Rel. 5.03. Siemens Analytical X-ray Instruments Inc.. Madison. Wisconsin. 1995. b) C. K . Johnson. ORTEP 11: a
Fortran Thermal-Ellipsoid Plot Program for Crystal Structure Illustrations.
ORNL-513X. Oak Ridge National Laboratory. Oak Ridge. TN. U S A . March
1976.
After submission of this paper. we learned that Prof. G. Thiele. Universitit
Freiburg. Germany. and his group had obtained complementary crystallographic data on single crystals of solvated (benzene or chloroform) [Pd,CI,,].
grohn ,it room temperature from the corresponding solutions Satisfactory
agreement has heen found between the sets of data obtained independently in
the two laboratories. We thank Prof. G. Thiele for communicating his results
prior t o publication.
Tetrakis(tri-tevt-butylsily1)-tetrahedvotetragermane (tBu,Si),Ge,-The
First Molecular
Germanium Compound with a Ge, Tetrahedron**
Nils Wiberg,* Walter Hochmuth, Heinrich Noth,
Andrea Appel, and Martin Schmidt-Amelunxen
According to a b initio calculations,". 21 the strain energy of
(EH), polyhedra (E = Si, Ge) increases with the number of the
three-membered rings in the framework of the polyhedron, thus
in the order /zc~rahedro-octasilane(-germane) A, triprismo-hexasilane (-germane) B, and tetrn/zedro-tetrasilane (-germane)
In an effort to obtain a molecular germanium compound with
a Ge, tetrahedron by an analogous route, we treated tetrachloro-l,2-bis(supersilyl)digermane fBu,Si-GeC1,-GeC12SitBu, (4). which formed from GeCI, and tBu,SiNa in T H F at
room temperature along with other products (tBu,SiGeCI, ,
(tBu,Si),GeCI,, (tBu,Si), , tBu,SiCI), and was characterized by
X-ray crystallography, with tBu,SiNa in T H F at - 78 'C. This
reaction led to the tetrnhedro-tetragermane 2 in low yield
[Eq. (b)] together with other products containing supersilyl
groups that are also formed in the reaction of GeCI,.C,H,O,
and tBu,SiNa (see below). Compound 4 reacts with sodium in
C,D, at room temperature initially to give the tetrahedrane 2,
which is, however, attacked by sodium; one of the resulting
products, namely rBu,SiNa, reacts as described with unconverted 4.@]rBu,SiNa reacts with GeCl,.C,H,O, in T H F via a series
of-in part isolable-intermediates['l likewise to give 2 and additional products [Eq. (c)].
-4
c&o2
The tetragermane 2 forms intense red crystals, which are hydrolyzed slowly by water, and are rapidly oxidized by air. Compound 2 can be reduced with sodium; among the products of the
reaction is tBu,SiNa, which can be identified by conversion with
Me,SnCI into tBu,Si-SnMe,.
So far we have only been able to obtain crystals suitable for
X-ray diffraction[' 21 from solutions prepared according to
Equation (c) after exchanging T H F by pentane. However, in
addition to 2 these contain superdisilane tBu,Si -SitBu,," 'I
which fills the large holes between the almost spherical molecules of 2 in the crystal, and thereby stabilizes the structure of
the crystal. The monoclinic unit cell of the crystals with the
composition 2(tBu,Si),Ge, '(tBu,Si), (2a) contains four molecules of 2 and-in the cavities-two molecules of rBu,Si-SitBu, (Fig. 1 ) . The building unit 2 in the crystal of 2a contains
almost regular G e tetrahedra (Fig. 2). The Ge- G e (av. 2.44 A)
and Ge-Si (2.38
distances are slightly longer than those in
H,Ge-GeH, (2.41 A[',]) and H,Ge-SiH, (2.36 A['31), respectively; for comparison Si-Si distances in 1 are 2.35 (endo) and
2.37 8, ( e ~ o ) in
, ~H,Si-SiH,
~~
and Me,Si-SiMe, 2.331 and
The fact that tBu,Si-SitBu, in crystals
2.338 A. respecti~ely['~].
1)
Consequently. initially the hexahedranes (ER), (E/R =
Si/SiMe,tB~.[~"l Si/CMe2iPr,[4b1 Si/2,6-C,H,Et,.[4c1 Ge/
CMeEt, ,I4'] Ge/2,6-C,H,Et214c]) and triprismanes (ER),
(E/R = Si/2,6-C,H3iPr, ,[4e1
Ge/CH(SiMe,), ,[4d1
Ge/2,6C,H,iPr,[4e1) were obtained. We synthesized the first molecular
silicon compound I with a Si, t e t r a h e d r ~ n ~by~ .the
~ ] reaction
of tetrabromo-l.2-bis(supersilyl)disilane tBu,Si -SiBr2 - SiBr, SitBu, (3) with supersilylsodium tBu,SiNa in tetrahydrofuran
(THF) [Eq. (a); supersilyl = SitBu,[']].
R
R-EX-
EX2- R
+2RNa
-2RX-2NaX
I
R
3.4
(a) E = Si; X = Br
(b) E = a;
x = C]
R = SitBu3
1, E = S i
2. E = G e
[*] Prof. Dr. N . Wiherg, DipLChem. W. Hochmuth. Prof. Dr. H. Noth.
DiplLChem A. Appel. Dr. M. Schmidt-Amelunxen
lnstitut fur Anorgdnische Chemie der Universitil
Meiserstrass~.I . D-80333 Munchen (Germany)
Fax. Int. code +(89)5902-578
[**I Compounds of Silicon and Its Group Analogues Part 108; Stencally Overlodded Supersilyl Compounds. Part 10. This work was supported by the Deutsche
Forschunpsgemeinschdft. Part 107 and 9: Ref 131.
Fig. 1. Perspective view of the monoclinic unit cell of 2 a along the c axis.
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