STRUCTURES AND CONFORMATIONAL PROPERTIES OF TRIFLUOROMETHYLSULFONYL ISOCYANATE, CF3SO2NCO, AND TRIFLUOROMETHYLSULFONYL AZIDE, CF3SO2N3

The geometric structures of trifluoromethylsulfonyl isocyanate, CF3SO2 NCO, and trifluoromethylsulfonyl azide, CF3SO2N3, have been determined by gas electron diffraction and by theoretical methods (HF/3-21G, HF /6-31G, MP2/6-31G*, B3P91/6-31G*), Both compounds possess a single co nformation with eclipsed or nearly eclipsed orientation of the NCO or N-3 group relative to one S=O double bond and dihedral angles phi(O=S- N=C)=4(8)degrees and phi(O=S-N=N)= -24(6)degrees. The negative sign in dicates that the azide group is rotated towards the CF3 group. The S-N bonds in both compounds are very similar(1.653(5) and 1.668(4) Angstr om, respectively). The nitrogen bond angle in the isocyanate (S-N=C=12 6.5(15)degrees) is larger by 15 degrees than that in the azide (S-N=N= 111.6(15)degrees), All theoretical methods reproduce the experimental structures satisfactorily except for the S-C and S-N bond lengths, (C) 1998 Elsevier Science B.V.