MOLECULAR-STRUCTURES AND RELATIVE STABILITY OF SIH2N2 AND CH2N2 ISOMERS

Ab initio molecular orbital calculations have been carried out on SiH2 N2 and CH2N2 isomers. The structures have been optimized at the HF/6-3 1G* and MP2(full)/6-31G** levels and the vibrational frequencies have been characterized. The relative stability has been obtained.with MP4 SDTQ/6-31G*. As a result, ten singlet and five triplet equilibrium st ructures are predicted to be SiH2N2 isomers, while eight singlet and f ive triplet equilibrium structures are predicted for the CH2N2 isomers . The order of stability of the SiH2N2 isomers is quite different from that of the CH2N2 isomers. The stability order for the singlet CH2N2 isomers at MP4SDTQ/6-31G* agrees with the MP3/6-31G*//HF/3-21G result reported previously by Thomson and Glidewell (J. Comput. Chem., 4 (19 83) 1), but that for the singlet SiH2N2 isomers is inconsistent.