Zur thermolyse von silyltriazenen

Whilst mono(silyl)triazenes R′N=N---NR′(SiR₃) and organyl triazenes R′N=N---NR′₂ are of comparable thermal stability and decay by a radical reaction, bis(silyl)triazenes R′N=N---N(SiR₃)₂ (R′=aryl, R=Me, Et, OMe) decompose at room temperature in a non-radical reaction to yield amines R′N(SiR₃)₂ and nitrogen. Kinetic investigations of the mechanism of the non-radical thermolysis of triazenes show that the rate of the thermolysis of R′N=N---N(SiR₃)₂ is determined both from an isomerisation equilibrium forming (R₃Si)R′N---N=N(SiR₃) and from the rate of decomposition of this compound to the thermolysis products. Tris(silyl)triazenes, (R₃Si)₂N---N=N(SiR₃), hitherto not synthesized, are expected to be even more unstable than the bis(silyl)triazenes which have been examined by us.     

Darstellung und thermolyse von hexakis(perfluororganylthio/seleno)ethanen

Thiocarbonylcompounds such as 1a, 1b, 1c, 1d, 1e and 1f were prepared and irradiated with UV- light in hexane solution. The products obtained in this photolyses are 3a, 3b and 3c. Only 3c dissociates in the temperature range 140-190° reversible to 2c. The others, 3a and 3b, decompose yielding bis(trifluoromethyl)diselenide, 6b and 6d, without forming the corresponding methyl radical 2a and 2b. This was proved by spin-trapping experiments utilizing phenyl-t-butylnitrone. Attempts to prepare 3e were unsuccessful but led to the new compounds 7a, 7b, 7c, 1,1,1-tris(trifluoromethylseleno)ethan (7d) and, surprisingly, 9. Physical and spectroscopic data of the newly prepared substances are provided.     

Thermolyse und photolyse einiger sila- und disilacyclobutane

The thermolysis of some 1,1-di- or 1,1,2-tri-substituted 1-silacyclobutanes leads to 1,3-disilacyclobutanes or to polymeric products. A possible intermediate silaalkene could not be stabilized, even in the presence of bulky substituents at the silicon atom. Photolysis of some di- or tri-substituted silacyclobutanes in methanol results in ring opening or in elimination of an alkene with further reaction of the intermediates with the solvent. Photolysis of the 1,1-diphenyl-2-methyl-l-silacyclobutane in cyclohexane leads to the 1,1,3,3-tetraphenyl-l,3-disilacyclobutane. The influence of the substituents at the silicon or the carbon atom on the reaction pathways is discussed. Photolysis of the 1,1,3,3-tetramethyl-2,4-diphenyl-l,3-disilacyclobutane occurs with ring opening and addition of methanol, whereas the 1,1,3,3-tetraphenyl-l,3-disilacyclobutane does not show any reaction.