We have used density functional theory and ab initio methods to study different mechanistic possibilities for the formation of decamethyldizincocene from the reaction between decamethylzincocene and diethylzinc. Our results suggest that decamethyldizincocene could form from the combination of two pentamethylcyclopentadienylzinc radicals. More importantly, our data show that homolytic dissociation of decamethylzincocene into pentamethylcyclopentadienylzinc and pentamethylcyclopentadienyl radicals is 6.7 kcal/mol less costly than the analogous dissociation of zincocene. If such an energy difference is coupled with the fact that the activation barrier to form the half-sandwich product pentamethylcyclopentadienylethylzinc is 11.8 kcal/mol more costly than to form cyclopentadienylethylzinc, we can rationalize why dizincocene does not form experimentally.