{"id":15552,"date":"2016-01-16T16:50:37","date_gmt":"2016-01-16T16:50:37","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=15552"},"modified":"2016-01-17T19:24:09","modified_gmt":"2016-01-17T19:24:09","slug":"vsepr-theory-a-closer-look-at-trifluorothionitrile-nsf3","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=15552","title":{"rendered":"VSEPR Theory: A closer look at trifluorothionitrile, NSF3."},"content":{"rendered":"
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The post on applying<\/a> VSEPR ("valence shell electron pair repulsion") theory to the geometry of ClF3<\/sub> has proved perennially popular. So here is a follow-up on another little molecue, F3<\/sub>SN<\/a>. As the name implies, it is often represented with an S≡N bond. Here I take a look at the conventional analysis.<\/p>\n

\"trifluoorothionitrile\"<\/a><\/p>\n

This<\/a> is as follows:<\/p>\n

    \n
  1. \n Six valence electrons on the central S atom.\n <\/li>\n
  2. \n Three F atoms contribute one electron each.\n <\/li>\n
  3. \n One electron from the N σ-bond.\n <\/li>\n
  4. \n Donate two electrons from S to the two π-bonds.\n <\/li>\n
  5. \n Eight electrons left around central S, ≡ four valence shell electron pairs.\n <\/li>\n
  6. \n Hence a tetrahedral<\/strong> geometry.\n <\/li>\n
  7. \n The bond-bond repulsions however are not all equal. The SN bond repels the three SF bonds more than the S-F bonds repel each-other.\n <\/li>\n
  8. \n Hence the N-S-F angle is greater than the F-S-F angle, a distorted tetrahedron.\n <\/li>\n<\/ol>\n

    Now for a calculation[1]<\/a><\/span>;  ωB97XD\/Def2-TZVP, where the wavefunction is analysed using ELF (electron localisation function), which is a useful way of locating the centroids of bonds and lone pairs (click on diagram below to see 3D model).<\/p>\n

    \"Trifluorosulfonitrile\"<\/p>\n