Compounds of Silicon and Homolgues, 134~[dot =] Supersilyl Compounds of Boron and Homologues, 10~[dot=dot=] Tri (supersilyl)dialanyl (tBu_3Si)_3Al_2~(cendre dot) and Tetra(supersilyl)cyclotrialanyl (tBu_3Si)_4Al_3~(cendre dot) -New Stable Radicals of

摘要

The thermolysis of tetra (supersilyl)dialane R~*_2Al-AlR~_2 (R~*=SitBu_3=Supersilyl) in heptane or cyclohexane at 50deg C leads under Al-Al dissociation reversibly to monoalanyl radicals [R~*_2Al]~*, which could be trapped by h7ydrogen or iodine (formation of R~*_2AlH,R~*_2AlI). Simultaneously, SiAl dissociation and elimination of supersilyl radicals tBu_3Si~(centre dot) leads irreversibly and slowly to radicals [R~*_2Al-AlR~*]~(centre dot),the existence of which could be established by ESR spectroscopy. The structure was clarified by ab initio calculations (nearly planar Si_2Al-AlSi and linear Al-Al-Si skeleton;short Al-Al distance). By thermolyzing R~*_2Al-AlR~*_2 at 100deg C,the radical [R~*_4Al_3]~(centre dot) (ESR spectroscopically detected)and the tetrahedro-tetraalane R~*_4Al_4 (NMR spectroscopically seen)are formed via radicals [R~*_3Al_2]~(centre dot);the supersilyl radicals tBu_3Si~(centre dot),formed at the same time, are stabilized by dimerization to superdisilane R~*-R~* and by taking up hydrogen, givig supersilane R~*-H. Accoriding to X-ray structure analysis, the Al atoms in [R~*_4Al_3]~(centre dot) are located at the corners of a triangle;one Al atom is connected with two groups R~*, the remaining two Al atoms each bind one substituent R~* in different ways.