A C2-Linked Bis-silene Formed without Using Metals and the Transformation into the Bis-silyl and Bis-silylium C4-Cumulenes

Reaction of silylene L(Cl)Si: (1; L = PhC(NtBu)2) with 1,3-diyne Me3SiC≡CC≡CSiMe3 produced bis-silene L(Cl)Si═C(SiMe3)C≡C(SiMe3)C═Si(Cl)L (2). This shows a route by oxidative coupling reaction to silenes. Reaction of 2 with AgOSO2CF3 resulted in [L(Cl)(F3CO2SO)Si](Me3Si)C═C═C═C(SiMe3)[Si(OSO2CF3)(Cl)L] (3) and a silver mirror. From the reaction of 2 and B(C6F5)3 were isolated compounds {[L(Cl)Si](Me3Si)C═C═C═C(SiMe3)[Si(Cl)L]}2+·2[ClB(C6F5)3]− (4) and {LSi[μ2-C2(SiMe3)(C≡CSiMe3)]}2 (5). When 2 was treated with [Ph3C]+[B(C6F5)4]−, compounds [L2(Cl)Si]+[B(C6F5)4]− (6) and Ph2C═-cyclo-C(CH═CH)2CHCPh3 (7) were formed. These reactions exhibit reduction of the polar Si═C bond to create unusual species of neutral and dicationic C4-cumulenes. The formation, bonding, and reactivity of compound 2 is explored by the computational quantum mechanical calculations.