SRN-002

The compounds SrN and SrN₂ were prepared by heating the nitride Sr₂N in a Mo boat under a N₂ atmosphere at 920 K for 72 h.The reaction took place in an autoclave at different pressures (400 bar for SrN and 5500 bar for SrN₂).Inelastic-neutron scattering (INS) spectra were recorded using the time-of-flight spectrometers TOSCA and MARI at the ISIS facility of the Rutherford Appleton LaboratoryThe INS spectra are depicted and discussed and the mol. structure of the compounds is deduced.The observed TOSCA INS spectrum of SrN₂ was in good agreement with the calculated spectrum obtained with the program CLIMAX.The compound SrN is more correctly formulated as Sr₄[N₂][N₂] or (Sr²⁺)₄[N^3-]₂[N₂^2-] in the ionic form.For SrN₂, the formulation Sr₄[N₂]₄ or (Sr²⁺)₄[N₂^2-]₄ is reasonable.The bond lengths and stretching frequencies for the N₂ species in the gas phase and for the diazenides in the solid state were calculated using the unrestricted-d.-functional theory with the 6-31G++ basis set implemented in the Gaussian 98.The obtained theor. values were compared with calculated ones.In the compounds, the bond length in the (N:N)^2- ions is shorter than in the gas phase and the frequency is higher, indicating that the charge of the diazenide ion is not as large as 2-.Either some degree of covalency is present in the compounds, or the charge state of Sr²⁺ is < 2+.