Theoretical studies are carried out on the doublet and quartet states of three isomeric forms of the species Si2N. Correlation effects on the structural parameters, harmonic frequencies, and relative energies are investigated at increasingly higher levels of theory (MP2, MP4, and CCSD(T)) and basis sets (DZP, cc-pVTZ-f, and cc-pVTZ). At the highest level of theory (CCSD(T)/cc-pVTZ) all three isomers are found to be thermodynamically stable species with the symmetric linear structure (SiNSi) as the global minimum; a symmetric cyclic structure (93.1 degrees) lies only 4.90 kcal/mol higher in energy, while the asymmetric linear isomer (SiSiN) is much higher located (85.23 kcal/mol). Dissociation of the most stable isomer into the channels SiN + Si and Si-2 + N would require 123 and 148 kcal/mol, respectively, including the zero-point energies. Chemical bonding as reflected in bond distances indicates a SiN bond character intermediate between that of a single and a double bonds in the linear SiNSi isomer (1.644 Angstrom), changing then to a single bond in the cyclic structure (1.695 Angstrom) and a double bond in SiSiN (1.608 Angstrom). The energetics involved in various dissociation channels is also analyzed, as well as the strength of the vibronic interaction in the linear isomer estimated by the computation of the Renner parameter. A comparison with the molecules C2N, Si2C, Si2C-, and Si2O clearly shows structural and stability trends among these triatomics.