Theoretical investigations on NSR3 molecules and their isomers

Results of ab initio calculations, mostly at the SCF level, are reported for the molecules NSCl3, NSOF, RNSF2 and NSF2R for R  F, CH3, CF3. It is concluded that NSCl3 is thermodynamically unstable with respect to NSCl + Cl2 but kinetically stable at low temperatures, e.g. in matrices. NSOF is stable with respect to NSF + O and has about the same energy as NSF + 0.5 O2. The stability of RNSF2 with respect to NSF2R decreases in the series R  CF3, CH3, F, and NSF2R is more stable only for R  F. The stability of molecules considered is discussed by means of computed equilibrium geometries and especially the results of population analyses which allow us to rationalize the trends observed. The computed structure parameters are in close agreement with available experimental data, with deviations of a few pm, with the exception of CF3NSF2 where the present results strongly indicate problems with the experimental structure determination.