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Bis(trimethylsilyl)diimine and Tetrakis(trimethylsilyl)hydrazine.

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Bis(trimethylsily1)diimine and
Tetrakis(trimethylsily1)hydrazine [I1
By N . Wiberg, W.-Ch. Joo, and W. Uhlenbrock [*I
Whereas bisalkyldiimines (azoalkanes) which contain the
characteristic atomic grouping ( I ) have long been known,
attempts to synthesize bissilyldiimines (azosilanes) [2,31,
which contain the atomic grouping (2) have hitherto remained unsuccessful [41.
In reaction of p-toluenesulfonyl azide [51 with tris(trimethy1sily1)hydrazide we have obtained access to the class of bissilyldiimines:
The product is light blue [Amax = 786 nm (ether)], volatile in
a high vacuum at -4OoC, and sensitive to hydrolysis.
That it is bis(trimethylsily1)diimine (hexamethylazosilane)
follows from elemental analysis, the mass spectrum (base
peak for the molecular ion at mje = 174), the 1H-NMR
spectrum (one signal at 6 = -12.5 Hz referred to TMS as
internal standard; determined in ether at -40 "C), and thermolysis. The azo compound (3) decomposes quantitatively
above about -35 "C according to the scheme:
This affords molecular nitrogen and the sterically hindered
tetrakis(trimethylsily1)hydrazine (4) which was previously
unknown. The structure of (4). m.p. 271 "C, was proved by
analyses, mass spectrum, IH-NMR spectrum (only one
proton signal, namely, at 6 = -13.0 Hz referred to TMS as
internal standard, recorded in benzene), and by independent
synthesis as follows:
(RsSi)zN-NLi(SiR3)
+ R3SiCI
-100°C
-+ LiCl+
Benzene
(4);
R = CH3
Experimental:
Preparation of (3): Suspensions of p-toluenesulfonyl azide
(12.0 mmoles) and lithium tris(trimethylsi1yl)hydrazide
(12.0 mmoles) each in ether (25 ml) were mixed at -78 "C
with exclusion of moisture and oxygen. After reaction for 2 h
at -78 O C , during which 12.2 mmoles of nitrogen was evolved,
first the ether was condensed off from the reaction mixture in
a high vacuum at -55 "C, and then pure ( 3 ) at -5 "C (yield 50
to 60 %). N-Lithio-N-(trimethylsilyl)-p-toluenesulfonamide,
containing (4) as an impurity, remained as a solid residue.
Preparation of (4): Equimolar amounts of N-lithium tris(trimethylsily1)hydrazide and trimethylchlorosilane in benzene are heated in a Carius tube at 120'C for 48 h. After
separating off the lithium chloride which has been formed,
the benzene is distilled from the reaction solution and the
residue (4) remaining is purified by several sublimations in
high vacuum at 65 "C.
Received: April 5th, 1968
IZ 824 IE]
German version: Angew. Chem. 80, 661 (1968)
Publication delayed at the authors' request.
[*I Priv.-Doz. Dr. N. Wiberg, Dr. W.-Ch. Joo, and
W. Uhlenbrock
Institut fur Anorganische Chemie der Universitat
8 Munchen 2, Meiserstr. 1 (Germany)
[I] Part 7 of "Silicon Compounds". - Part 6: N. Wiberg,
F. Raschig, and K . H . Schmid, J. organometallic Chem. 10, 29
(1967).
[ZJ H. Bock, Z. Naturforsch. 176, 423 (1962).
[31 U . Wannugut and C. Kriiger, Z . anorg. allg. Chem. 326, 288
(1964).
\
/
[4] Azo compounds containing the grouping -C-N=N-Siare known [3].
/
[5] Or p-toluenesulfonyl chloride.
CONFERENCE REPORTS
International Symposium on the Chemistry of Small Rings
The Sociitd Chimique de Belgique held a symposium on the
chemistry of small rings at Louvain (Belgium) from September 12 to 15. 1967.
afford the cyclopropane derivatives ( 5 ) and ( 6 ) . 93 % of ( 5 )
and 1% of ( 6 ) are obtained independently of whether one
starts from the cis- or the trans-ester.
F r o m the lectures:
cis- or trans-(I) and the alkylidenephosphorane ( 3 ) give the
sterically homogeneous cyclopropane derivative (7). The
benzylidenephosphorane ( 4 ) and the ester ( I ) afford the
derivatives (8) (11%). (9) (33%). and (10) (56%).
Syntheses of Cyclopropanes and Azirines by Means of
Alkylidenephosphoranes
By H . J. Bestmann[*l
In the reaction of alkylidenephosphoranes with compounds
containing "electron-deficient" double bonds, cyclopropane
derivatives and triphenylphosphine are formed
by way of
an intermediate betaine that is formed in a reversible reaction.
The stereochemistry of this cyclopropane formation has been
studied in detail. The ylide (2) and methyl 2-butenoate ( I )
640
Reaction of the diylide (11) with 1,2-diketones (12) gives
sterically homogeneous dibenzonorcaradiene derivatives
(13) [21, whose structure was determined by nuclear resonance and in particular the solvent-dependence of the chemical shift [31 of the cyclopropane protons.
When heated above the melting point, the phosphonium salt
(14) loses COz and gives cyclopropyltriphenylphosphonium
bromide (IS) 141, which can be converted into cyclopropylidenetriphenylphosphorane (16) by phenyllithium. This
product (16) reacts as nucleophile with many compounds,
Angew. Chem. infernat. Edit. / Vol. 7 (1968) / No. 8
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