Molecular structures, metallotropic and prototropic shifts of cyclopentadienyl(trimethyl)silane (1), cyclopentadienyl(trimethyl)germane (2), and cyclopentadienyl(trimethyl)stannane (3) were investigated using ab initio molecular orbital and the Becke, Lee, Yang, and Parr density functional (B3LYP) methods. The results show that the most stable structure of compounds 1-3 has the (CH 3 ) 3 M fragment in the allylic position. The energy barrier of metallotropic shifts in compound 1 is higher than in 2, and in compound 2 higher than in 3, in good agreement with experimental data. The cyclopentadienyl rings in compounds 1-3 are found to be planar but this result contradicts the reported experimental data.