A cyclopentadienyl functionalized silylene - a flexible ligand for Si- and C-coordination

The synthesis of a 1,2,3,4-tetramethylcyclopentadienyl (Cp 4 ) substituted four-membered N-heterocyclic silylene [{PhC(N t Bu) 2 }Si(C 5 Me 4 H)] is reported first. Then, selected reactions with transition metal and a calcium precursor are shown. The proton of the Cp 4 -unit is labile. This results in two different reaction pathways: (1) deprotonation and (2) rearrangement reactions. Deprotonation was achieved by the reaction of [{PhC(N t Bu) 2 }Si(C 5 Me 4 H)] with suitable zinc precursors. Rearrangement to [{PhC(N t Bu) 2 }(C 5 Me 4 )SiH], featuring a formally tetravalent silicon R 2 C&z.dbd;Si(R′)-H unit, was observed when the proton of the Cp 4 ring was shifted from the Cp 4 -ring to the silylene in the presence of a Lewis acid. This allows for the coordination of the Cp 4 -ring to a calcium compound. Furthermore, upon reaction with transition metal dimers [MCl(cod)] 2 (M = Rh, Ir; cod = 1,5-cyclooctadiene) the proton stays at the Cp 4 -ring and the silylene reacts as a sigma donor, which breaks the dimeric structure of the precursors. A cyclopentadienyl functionalized silylene or its derivatives can be coordinated in all three forms: silylene ( A ), anion ( B ), and sila fulvene ( C ).