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Possible Strategies toward the Elusive Tetraaminodisilene Thomas Mu ller*, and Yitzhak Apeloig*,
 

Summary: Possible Strategies toward the Elusive Tetraaminodisilene
Thomas Muš ller*, and Yitzhak Apeloig*,
Contribution from the Institut fušr Anorganische Chemie der Goethe UniVersitašt Frankfurt,
Marie Curie-Strasse 11, D-60439 Frankfurt/Main, Federal Republic of Germany, and
Department of Chemistry and the Lise Meitner-MinerVa Center for Computational Quantum
Chemistry, Technion-Israel Institute of Technology, 32000 Haifa, Israel
Received August 13, 2001
Abstract: In this paper we predict, using quantum mechanical calculations, which diaminosilylenes would
dimerize to produce strongly bound tetraaminodisilenes, which so far have proven to be elusive. The central
idea is that diaminosilylenes with a small singlet-triplet energy difference would dimerize to strongly bonded
disilenes. Calculations at the B3LYP/6-311++G(3df,2p)//MP2/6-31G(d) level of theory showed that the
energy difference between the singlet and the triplet states (EST) of diaminosilylenes (R2N)2Si: (1) strongly
depends on (i) the twist angle between the SiN2 and the R2N planes and (ii) the NSiN bond angle R at
the divalent silicon. EST decreases with increased twisting (larger ) and with widening of R. EST is
reduced from 70.7 kcal mol-1 for planar (H2N)2Si: (1a) to EST ) 21.7 kcal mol-1 when is held at 90°.
Likewise, the bicyclic diaminosilylenes 1,4-diaza-7-silabicyclo[2.2.1]hepta-7-ylidene and 1,5-diaza-9-
silabicyclo[3.3.1]nona-9-ylidene (4a,b), with the nitrogens in the bridgehead positions ( ) 90°), have EST
values of 45.1 and 38.3 kcal mol-1, respectively. When dimerized, these silylenes form strongly bonded
disilenes 5 (Edim ) -32.2 kcal mol-1
(4a) and -41.3 kcal mol-1

  

Source: Apeloig, Yitzhak - Department of Chemistry, Technion, Israel Institute of Technology

 

Collections: Chemistry