NBO analysis and density functional theory (DFT) based methods (B3LYP/3-21G, B3LYP/3-21G* and B3LYP/LANL2DZ*) were used to investigate the aptitude of the alkyl 1,2-shift in 5- tert-butylcyclopentadiene ( 1) and metallotropic 1,2-shifts in cyclopentadienyl(trimethyl)silane ( 2), cyclopentadienyl(trimethyl)germane ( 3) and cyclopentadienyl(trimethyl)stannane ( 4). The obtained B3LYP/3-21G, B3LYP/3-21G* and B3LYP/LANL2DZ* results showed that the M(CH 3) 3 group (M=C ( 1), Si ( 2), Ge ( 3) and Sn ( 4)) migration barrier heights around cyclopentadienyl rings decrease from compounds 1 to 4. For compounds 1– 3, the calculations were also performed at MP2/6-311+G**//B3LYP/3-21G*, MP2/6-31G*//B3LYP/3-21G*, B3LYP/6-311+G**//B3LYP/3-21G* and B3LYP/6-31G*//B3LYP/3-21G* levels of theory. However, the comparison showed that the results at B3LYP/3-21G* level, although with larger difference compared to the experimental values, correlated well with those obtained at MP2/6-311+G**//B3LYP/3-21G* and MP2/6-31G*//B3LYP/3-21G* levels of theory. Based on the optimized ground state geometries using B3LYP/3-21G, B3LYP/3-21G* and B3LYP/LANL2DZ* methods, the NBO analysis of donor–acceptor (bond–antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from σ C5–M bonding orbitals to π* C1 C2 and π* C3 C4 antibonding orbitals of cyclopentadienyl ring, increase from compounds 1 to 4. Also, the donor–acceptor interactions, as obtained from NBO analysis, could fairly explain the decrease of occupancies of σ C5–M bonding orbital and the increase of occupancies of both π C 1 = C 2 * and π C 3 = C 4 * anti–bonding orbitals in cyclopentadienyl rings, from compounds 1 to 4. Therefore, the results suggest that in compounds 1– 4, the metallotropic shifts are controlled by σ→π* energetic stabilizations, and also the increase of the σ→π* delocalization energy facilitates the M(CH 3) 3 group migration around cyclopentadienyl ring in these compounds.