Geometric and electronic Structure of carbocene, (C5R5)(2)C, versus silicocene, (C5R5)(2)Si (R = H, Me)

The electronic structures of carbocene and silicocene have been investigate d by density functional calculations. Accordingly, carbocene behaves entire ly different compared to silicocene. The former prefers a classical dicyclo pentadienylcarbene structure, while the latter adopts a slightly distorted sandwich structure. Methyl substitution at the cyclopentadienyl unit does n ot exert a considerable effect on the resulting equilibrium structure. A de tailed analysis of the electron distribution based on an analysis of the La placian of the charge density is given.