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Bis(trimethylislyl)zinc and -cadmium.

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Fig. 1. Crystal structure of ~5-pentamethylcyclopentad~enyltin(~l)
tetrafluorohorate ( 2 )
Bis(trimethylsily1)zincand -cadmium[**I
of well-known pentagonal-pyramidal ni~lo-clusters[~!As in
the case of comparable cyclopentadienyl systems the accuracy
of the X-ray structure analysis[51 of (2) is reduced because
of rotational disorders which manifest themselves in high
thermal vibration parameters of the lighter atoms.
The Sn-C bond length in (2) (2.462i0.016 x IO-''m)
is considerably shorter than in Cp2SnL6I(2.71) or CpSnC1[zbl
(2.61 mean value); in the ring the average bond length is
1.39k0.03, the C-methyl bond length 1.51 k0.03. Surprisingly['], the methyl groups are oriented away from the central
atom in the same fashion, and are bent at an average angle
of O = -4" (corresponding to 0.11) to the plane through the
C p ring (planar kO.01). The shortest SnB distance in the
lattice is 3.590 (Sn-F 2.97-2.99).
By Lutz Riisck and Gerald Alttiuu[*]
Organozinc derivatives number among the first organomet a l k compounds to be synthesized and are well established
reagents in preparative chemistry. In contrast, the homologous
silylzinc derivatives were hitherto virtually unknown; the first
representative of this series of compounds, bis(triphenylsily1)zinc was only briefly described in 1963"l.
We have now been able to synthesize the first alkylsilylzinc
compound bis(trimethylsily1)zinc ( I ) by reaction of zinc chloride or zinc acetate with lithium tetrakis(trimethylsilyI)aluminate"] in diethyl ether.
7MX2 LiAI(SiMe3)4,2DME --+
D M E = 1,2-Dirnethoxyethane
A 54 % ether solution of HBF4 (14.3 nimol) is added dropwise with stirring to a solution of ( 1 ) (5.59g, 14.4mmol)
in 300ml diethyl ether cooled to -78°C. After concentration
of the mixture to ca. 50ml the resulting pale yellow precipitate
is filtered off, recrystallized from toluene and dried in a high
vacuum. Yield: 1.5Og (31 %) of (2), m.p. 210-218°C
Received: October 6. 1978 [Z I17 IE]
German version: Angew. Chem. 91. 81 (1979)
J. Lewis, A. R. Murininy. J. R. Miller, J . M . Wilson, J . Chem. Soc.
A 1966, 1663.
a) P. G. Hurrison, J. J . Zuckermun, J . Am. Chem. Soc. YZ, 2577 (1970):
b) K . D. Bos, E. J . Bulreri, J. G . Noltes. J. Organomet. Chem. 3Y, C 5 2
(1972); c ) H . J. Albert, U . Schriier, ibid. 6O. C 6 (1973): d ) P. J u f z i ,
F. Kohl. rhid., in press.
K . Wude, Chem. Br. 11, 177 (1975); R. M! Rudulph, Acc. Chem. Res.
9, 446 (1976).
P. J u t z i . Nachr. Chem. Tech. Lab. 26, 422 (1978).
Crystallographicdata:a=ZI.555(2),b= I1.6905(X),c = 10 7813(7)(alldata
in lO-"rn), p=l01.925(6)", space group C2/c. Z = 8 , d,,1,=1.703gcm':
p=19.46cm-' (MoKX).3832correctedreflections, 1139unobserved(20),
R=0.057 (R,=0.075).
A. Alr?ieiiiiiriyen, A . Hoaluiid, 7: Motzfildi. J. Organomet. Chem. 7, 97
( 1 967).
Cf. D. M . P. Miriqos, Adv. Organomet. Chem. / 5 , 3 3 (1977). and references
cited therein.
2M(SiMe3)*+ ...
( I ) , M=Zn
(2). M =Cd
The pale yellow crystalline product ( I ) , which is isolable
by vacuum sublimation, ignites spontaneously and is readily
soluble in ethers, benzene and pentane. On treatment with
dilute hydrochloric acid, a strongly exothermic reaction ensues
with formation of trimethylsilane. The composition of ( I )
was confirmed by elemental analysis and by the mass spectrum
(molecular peak with calculated isotope distribution). The
'H-NMR spectrum (benzene) shows a sharp signal at 6=0.20.
Only one absorption band is observed in the expected range
for the ZnSi stretching vibration, both in the IR spectrum
(305cm-') and in the Raman spectrum (330cm-'). These
findings indicate that the molecule is linear, i. e. the structure
corresponds to that of the homologous bis(trimethylsily1)merc ~ r y [ ~Compound
( 1 ) is not very stable thermally; slow
decomposition with separation of metal takes place even at
room temperature. However, it can be stored for C L I . three
weeks at -20°C.
[*] Prw-Doz. Dr. L Rosch, Dipl.-Chem. G. Altnau
lnstitut f u r Anorganische und Analytiache Chemie der Technischen Universitit
Strasse des 17. Juni 135, D-I000 Berlin 12 (Germany)
[**I This
work was supportcd hy the Deutsche Forschungsgemeinschaft.
Anye\>. Chiw.
Ed. Enyl. 18 ( I 975') N o . 1
Bis(trimethylsilyl)cadmium ( 2 ) , which was likewise previously unknown, can be synthesized in the same way. Its
properties are similar to those of the zinc compound. However.
it is even less stable thermally; at -20"C, (2) decomposes
within cti. 2days with precipitation of the metal. The 'H-NMR
spectrum contains only one signal near that of the TMS
standard, which still shows no splitting at - 10°C. This signal
would be expected to be flanked by two satellite bands [coupling with '"Cd (13%, Z=1/2) and '13Cd (12%, I='/2)]. The
absence of satellites points to rapid exchange of the trimethylsilyl groups, as observed in the case of dimethylcadmi~m[~~
and divinylcadmi~m'~~.
According to the IR spectrum (CdSi
stretching vibration at 320cm- '), ( 2 ) should also be a linear
molecule: a Raman spectrum could not be recorded because
the compound is kery sensitive to light.
The preparatively important bis(trimethylsily1)mercury can
also be conveniently synthesized by reaction of lithium tetrakis(trimethylsi1yl)aluminate with mercury acetate. We are presently investigating the general utility of this synthetic route
as a method for the preparation of trimethylsilylmetal compounds.
exposure to air. The reaction product was therefore handled
under absolutely dry argon, and single crystals were selected
and picked out under the microscope.
According to Weissenberg photographs Nal o[Co409] crystallizes triclinically with u= 12.181, b=8.52,, c=8.32,A;
Y. = 1 19.96,, p= 87.89,,y = 1 16.75,"; Z = 2 (four circle diffractometer data). Thestructure was determined with 4928 symmetry
independent reflections (Mo-Kcr, graphite monochromator,
3" < 0 < 34")[31 by direct methods[41and interpretation of the
three-dimensional Patterson synthesis. Refinement with anisotropic temperature parameters for all particles gave for 3364
reflections the R value 6.10 "/, (space group Pi).
All operations must be carried out in the absence of air
and moisture (argon as inert atmosphere).
( 1 ) : Zn(OOCCH3)2(0.9g) is added portionwise at room
temperature to a vigorously stirred solution of LiAI(SiMe3)4.2DME in EtzO (50ml) with continuous passage of
argon. After one hours' stirring, the solvent is removed at
0°C in an oil-pump vacuum. Sublimation of the residue (room
temperature/- 20°C) from the reaction flask affords pale yellow star-shaped crystals, which immediately ignite and decompose on exposure to air. Yield 0.23 g (25 %).
( 2 ) : CdClz (1.8g) is allowed to react in the same way
as above. Cd(SiMe3)2is obtained in the form of yellow crystals,
yield 0.35 g (27%). This compound is also light-sensitive, and
can be stored for only short periods in an ice-box.
Received: October 10. 1978 [Z I20 IE]
German version: Angew. Chem. 9f. 62 (1979)
E. M.7hrr.q. 0 . S r t d i r r . H.-J. ,41irlrmc/i~!,,L. Kreirzbichlrr. E. Sruude.
Angew. Chcm. 75. 516(1963): Angew. Chem. Int. Ed. Engl. 2. 507 (1963).
L. R;idi. J . Organomet. Cheni. I Z I . C 15 (1976): L. Riisdi, G . A/muu.
131 H . Biirqo., Organomel. Chem. Rev. A 3, 425 ( 1 968), P. B k kmu111. M .
Sdiiiz~ii!. K Rrirrrr. W P. N r u n i u r ~ i i .J. Organomet. Chem. 108. C 18
1 19761.
~ 4 1W. Brciriwr. .If. Li'iriokur.. J . D. Roberts, J. Am. Chem. Soc. 9-7, 1080
( I 970).
151 H . D Vis,wr. L. P. S~o[lul.skl,J . P. O/IL.CI..J . Organomet. Chem. 24.
563 ( 1969).
Fig. I . Crystal structure of Nalo[Co4O9]; projection along [OOl]. Heights
I in fractions of c.
Primary structure: Each Co atom is surrounded trigonal
planar by three 0 atoms [bridging 0 atoms (Co-0 bond
Table I . Assignment of atoms In Na,o[Co,09]
CN 4
I 4 d
Coordination Number 3 in Co":
Na , l,[Co409], an Oligooxocobaltate(II)"]
CN 6
By Wilfrierl Burow and RudoIf'Hoppe[*]
In the newly prepared oxide Nalo[Co409] we find the
first example of cobalt coordinated in an almost trigonal
planar environment. Lustrous red, robust single crystals of
Nalo[Co409] are obtained on heating an intimate mixture
of NazO and "active" COO in a cobalt tube['] [Na:Co
=2.2: I , 500"C, 30dl. The crystals are extremely sensitive
towards moisture (hydrolysis) and immediately deliquesce on
[*] Pro1 DI- R. Hoppe, Dip].-Chem, W. Burow
lnstitut fur Anorganische und Analytische Chemie der Universitiit
Heinrich-Buff-Ring 58. D-6300 Giessen (Germany)
8:Symbol for bridging oxygen atoms of the [Co409] group: particles in [ )
belong tn a [Co,Oq] group.
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cadmium, bis, zinc, trimethylislyl
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