Recent efforts in this laboratory have concentrated on synthesizing metallaspiropentane compounds (I) with M = C, Si, Ge, Sn, Ni, and Zn. To date, the molecule with M = Si and R = methyl has been successfully prepared, 1 while attempts to synthesize the corresponding carbon compound have not reached fruition. This paper presents initial ab initio calculations on the species with M = C and Si and with R = H. Geometries for all species were calculated with the