Disilynes. III [1] - A relatively stable disilyne RSi SiR (R = SiMe(SitBu(3))(2))

The disilyne R**SidropSiR** (R** = SiMe(SitBu(3))(2)), prepared as the first isolable and realtively stable silicon compound with a SiSi triple bond two years ago by dehalogenation of trans-R**ClSi=SiClR** with LiC10H8 in thf at -78degreesC (calc.: SidropSi distance 2.072 Angstrom, Si-SidropSi bond angle 148degrees), forms with CH2=CH2 a [2+2] and with CH2=CH-CH=CH2 a [2+4] cycloadduct. The ethene adduct takes up oxygen very easily with change of the Si=Si group into a SiOSiO ring with formation of R**Si(mu-O)(mu-O)(mu-C2H4)SiR**. By heating the disilyne in heptane to ca. 50degreesC in the presence of traces of thf it transforms into a monoxide of the ethene adduct with formation of R**Si(mu-O)(mu-C2H4)SiR**. In thf, the disilyne rearranges at r.t. and below by migration of a SitBu(3) group with formation of a silyl substituted cyclotrisilene. X-ray structure determinations of the ethene adduct and its mono- and dioxide are presented.