Gas phase structure of ((fluoroformyl)imido)sulfuryl difluoride, FC(O)NS(O)F2

The geometric structure and conformational properties of gaseous ((fluoroformyl)imido) sulfuryl difluoride, FC(O)NS(O)F2, was investigated by gas electron diffraction (GED) and quantum chemical methods (MP2 and B3LYP with 6-31G(d) and 6-311+G(2df) basis sets). In combination with earlier reported infrared spectra, the GED study results in a mixture of at least three conformers, 71(10)% syn(NS)-syn(N-C), 14(8)% anti(NS)-syn(N-C) and 15(5)% syn(NS)-anti(N-C). Syn(NS) or anti(NS) implies synperiplanar or anticlinal orientation of the FC(O) group with respect to the SF2 bisector and syn(N-C) or anti(N-C) implies synperiplanar or antiperiplanar orientation of the CO bond with respect to the NS bond. The anti(NS)-anti(N-C) conformer has not been observed, but a small amount (<5%) cannot be excluded. These conformational properties are well reproduced by quantum chemical calculations with small basis sets and the geometric parameters are reproduced satisfactorily with large basis sets.