The reaction of decamethylsilicocene, (Me 5 C 5 ) 2 Si, with the proton-transfer reagent Me 5 C 5 H 2 + B(C 6 F 5 ) 4 – produces the salt (Me 5 C 5 )Si + B(C 6 F 5 ) 4 (2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic π complex with an η 5 -pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29 Si nuclear magnetic resonance at very high field (δ = – 400.2 parts per million) is typical of a π complex of divalent silicon. The (η 5 -Me 5 C 5 )Si + cation in 2 can be regarded as the “resting state” of a silyliumylidene-type (η 1 -Me 5 C 5 )Si + cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsilyl)amide to give the disilene E -{(η 1 -Me 5 C 5 )[N(SiMe 3 ) 2 ]Si} 2 (3).