Stimulated by the recent experiment that has added one silicon atom to C-60, endohedral and exohedral complexes of silicon with C-60 are investigated via semiempirical and first principles calculations. The ground state of the endohedral complex is the triplet state with the encased Si positioned off center, while the ground state of the exohedral complex is the singlet state with higher stability than the endohedral one. The Hartree-Fock HOMO and LUMO of the endohedral complex and the LUMO of the exohedral complex are localized at the dopant Si site. Both adducts have C-2v symmetry and enhanced chemical reactivity.