Compounds of silicon and homologues, 134 - Supersilyl compounds of boron and homologues, 10 - Tri(supersilyl)dialanyl (tBu(3)Si)(3)Al-2(center dot) and tetra(supersilyl)cyclotrialanyl (tBu(3)Si)(4)Al-3(center dot) - New stable radicals of a group 13 element from thermolysis of (tBu(3)Si)(4)Al-2

The thermolysis of tetra(supersilyl)dialane R*Al-2-AlR*(2) (R* = SitBu(3) = Supersilyl) in heptane or cyclohexane at 50 degrees C leads under Al-Al di ssociation reversibly to monoalanyl radicals [R*Al-2]*, which could be trap ped by hydrogen or iodine (formation of R*2AlH, R*2AlI). Simultaneously, Si Al dissociation and elimination of supersilyl radicals tBu(3)Si* leads irre versibly and slowly to radicals [R*Al-2-AlR*]*, the existence of which coul d be established by ESR spectroscopy. The structure was clarified by ab ini tio calculations (nearly planar Si2Al-AlSi and linear Al-Al-Si skeleton; sh ort Al-Al distance). By thermolyzing R*Al-2-AlR*(2) at 100 degrees C, the r adical [R*Al-4(3)]* (ESR spectroscopically detected) and the tetrahedro-tet raalane R*Al-4(4) (NMR spectroscopically seen) are formed via radicals [R*A l-3(2)]*; the supersilyl radicals tBu(3)Si*, formed at the same time, are s tabilized by dimerization to superdisilane R*-R* and by taking up hydrogen, giving supersilane R*-H. According to X-ray structure analysis, the Al ato ms in [R*Al-4(3)]* 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 sub stituent R* in different ways.