| Abstract
| - The geometries and energetics of different conformations of sulfur and selenium diimides E(NR)2 (E = S, Se; R= H, Me, tBu, C6H3Me2-2,6, SiMe3) have been studied by using various ab initio and DFT molecular orbital techniques.The syn,syn conformation is found to be most stable for parent E(NH)2, but in general, the preferred molecularconformation for substituted chalcogen diimides is syn,anti. In the case of E(NH)2 the present calculations furtherconfirm that syn,syn and syn,anti conformations lie energetically close to each other. From the three differenttheoretical methods used, B3PW91/6-31G* proved to be the most suitable method for predicting the geometries ofchalcogen diimides. The optimized geometrical parameters are in a good agreement with all available experimentaldata. While qualitative energy ordering of the different conformations is independent of the level of theory, thequantitative energy differences are dependent on the method used. The performance and reliability of higher levelab initio calculations and DFT methods using large basis sets were tested and compared with experimental informationwhere available. All of the higher level ab inito methods give very similar results, but the use of large basis setswith the B3PW91 method does not increase the reliability of the results. The combination of CCSD(T)/cc-pVDZwith the B3PW91/6-31G*-optimized geometries is found to be the method of choice to study energetic propertiesof chalcogen diimides.
- The geometries and energetics of syn,syn, syn,anti, and anti,anti conformations of sulfur and selenium diimides E(NR)2 (E = S, Se; R = H, Me, tBu, C6H3Me2-2,6, SiMe3) have been investigated by ab initio and DFT techniques. The syn,anti conformation is found to be most stable for most chalcogen diimides. The qualitative energy ordering of the different conformations is independent of the level of theory, but the quantitative energy differences are highly method-dependent.
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