Tetra-tert-butyldisilene and di-tert-butylsilylene, generated by photolysis of hexa-tert-butylcyclotrisilane (1), react with the triple bonds of hexa-2,4-diyne to provide the addition products octa-tert-butyl-2-methylene- 5-methyl-3,4,7,8-tetrasilabicyclo[4.2.0]oct-1(6)-ene ( 5) and di-tert-butyl-2-methyl-3-propynylsilirene ( 6). Further treatment of 6 with 1 is thought to proceed via a bis(silirene) derivative to furnish the rearranged tetratert-butyl-3,6-dimethyl-2,5-disilabicyclo[2.2.0]hexa-1(6), 3diene (12). The structures of 5 and 12 were determined by X-ray crystallography.
Photolytisch aus Hexa‐tert‐butylcyclotrisilan erzeugtes Di‐tert‐butylsilylen reagiert mit Selenophen oder 2,5‐Dimethyltellurophen unter Chalkogenabstraktion zum 1,3‐Diselena‐2,4‐disiletan 6 und 1,3‐Ditellura‐2,4‐disiletan 7. Die Röntgenstrukturanalysen von 6 und 7 zeigen das Vorliegen planarer Vierringe mit den kleineren endocyclischen Winkeln an den Chalkogen‐ und den größeren an den Siliciumatomen.
DiscussionThe crystal structure analysis reveals a distorted tetrahedral environment of the middle silicon atom. The most conspicuous features are the short Si-C bond lengths to the acetylenic carbon atoms of 184.4(2) pm and 185.2(3) pm and the considerable widened C-Si-C bond angle of 119.7(1
, generated by photolysis of hexa-tert-butylcyclotrisilane, reacts with Nmethylpyrrole possibly via an intermediate 7). On heating, 7 rearranges by an electrocyclic reaction to provide the correspondingly substituted 1-aza-2-silacyclohexa-3,5diene 8. Further treatment of 7 with 2 gives, presumably through a tricyclic compound, the final product 2,2,5,5tetra-tert-butyl-1-methyl-1-aza-2,5-disilacyclohepta-3,6diene (10), which was characterized by an X-ray structure analysis.
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