Reactivity of the isolable disilene R*PhSi=SiPhR* (R* = SitBu3). 
The disilene R*PhSi=SiPhR* (R* = supersilyl = SitBu3), which can be quantitatively prepared by dehalogenation of the disilane R*PhClSi-SiBrPhR* with NaR* (yellow, water- and air-sensitive crystals; decomp at ca.  70 degrees C; Si=Si distance 2.182 A), is comparatively reactive.  It transforms 1) with Cl2, Br2, HCl, HBr, and HOH under 1,2-addition into disilanes R*PhXSi-SiX'PhR* (X/X' = Hal/Hal, H/Hal, H/OH), 2) with O2, S8, and Sen under insertion into 1,3-disiletanes R*PhSi(-Y-)2SiPhR* (Y = O, S, Se), 3) with Me2C=CH2 under ene reaction into the disilane R*PhRSi-SiHPhR* (R = CH2-CMe=CH2), 4) with N2O, Ten, tBuN identical to C, and Me3SiN=N=N under [2 + 1] cycloaddition into disiliranes -R*PhSi-Y-SiPhR*- (Y = O, Te, C=NtBu, NSiMe3; P4 adds 2 molecules of disilene), 5) with CO2, COS, PhCHO, and Ph2CS under [2 + 2] cycloaddition into disiletanes -R*PhSi-SiPhR*-Y-CO- (Y = O, S) as well as -R*PhSi-SiPhR*-Y-CRPh- (Y/R = O/H, S/Ph), 6) with CS2 and CSe2 under [2 + 3] cycloaddition into ethenes R*2Ph2Si2Y2C = CY2Si2Ph2R*2 (Y = S, Se), and 7) with CH2 = CMe-CMe=CH2 and Ph2CO under [2 + 4] cycloaddition into "Diels-Alder adducts".  X-ray structure analyses of seven of these compounds are presented.