The structures of 1-fluorosilatrane and the silatranyl cation were calculated by Hartree-Fock (HF), Mofller-Plesset second order (MP2), and various density functional theory (DFT) methods using many different basis sets, demonstrating that the Si-N bonds in two species are quite different. The N${ ightarrow}$Si bond distance of 1-fluorosilatrane from the hybrid DFT calculations $({sim}2.32{AA})$ using the Perdew-Wang correlation functional agrees with the gas phase experimental value $(2.324{AA})$, while other functionals yield larger distances. The MP2 bond distance (2.287${AA}$ with 6-311$G^{ast}$) is shorter, and the HF one (2.544 ${AA}$ with 6-311$G^{ast}$) larger than those of DFT calculations. The MP2 bond distance is in good agreement with experiment indicating that the electron correlations are crucial for the correct description of the N${ ightarrow}$Si interaction. The silatranyl cation is a stable local minimum on the potential energy surface in all methods employed suggesting that the cation could be a reaction intermediate. The Si-N bond length for the cation is about 1.87 ${AA}$ for all calculations tested implying that the Si-N bond is mainly conventional. Bonding characteristics of the Si-N bond in two species derived from the natural bond orbital analysis support the above argument based on calculated bond lengths.