Does #SF_4# have geometrical isomers?

1 Answer
May 29, 2016

No, and nor would #SF_2X_2# at room temperature.

Explanation:

The structure of #SF_4# is based on a trigonal bipyramid to a first approximation, i.e. there are 5 electron pairs, bonding and non-bonding around the central sulfur atom. Because we do not describe the structure of the molecule based on lone pairs, a see-saw or Canada goose type structure is indicated,

The #/_S-F-S# bond angles would be #180""^@# and #120""^@# in a perfect trigonal bipyramid. Because of the stereochemically active lone pair on sulfur, these angles are compressed to approx. #170""^@# and #110""^@# in the actual molecule (you'll have to search the interwebz for confirmation/contradiction).

At room temperature, all of the fluorine atoms would be equivalent in a suitable experiment (#""^19F# NMR spectroscopy would be definitive). You would have to chill the molecule substantially to freeze out the axial/equatorial exchange.