Hafnium's triumph over titanium and zirconium! Unusual tandem Si-C and C-H bond activations by hafnium to form the alkenyl complex 2 and the silahafnacyclopentene 3 were observed in the reaction of decamethylhafnocene and bis(trimethylsilyl)acetylene. The higher reactivity of hafnocene compounds relative to their titanocene and zirconocene congeners is of general importance for synthesis and catalytic applications. (Chemical Equation Presented).