Molecular structures of acetylene derivatives of tin: Part III. Gas phase electron diffraction study of tetrakis(trifluoropropynyl)-tin, Sn(CC-CF 3) 4

Abstract

A gas phase electron diffraction study of tetrakis(trifluoropropynyl)tin is reported. The model, based on T d symmetry for the carbon—tin skeleton and C 3v symmetry for the CF 3 groups, refines to the following parameters (bond lengths, r a, in nm; valence angles in degrees): Sn—C0.2070(7), CC 0.1215(6), C—C 0.1460(7), C—F 0.1343(2), CCF 111.3(0.2). The uncertainties (given in parentheses) represent three times the standard deviation values. The results obtained point to practically free rotation of the CF 3 groups. The presence of electronegative CF 3 causes shortening of the Sn-C bonds in Sn(CC—CF 3) 4 from Me 3SnCCH and Me 3 SnCCSnMe 3. The triple CC bond length is larger than in hexafluoro-2-butyne and nearly the same as in dimethylacetylene.