Interactions between SF4 and Fluoride: A Crystallographic Study of Solvolysis Products of SF4·Nitrogen-Base Adducts by HF.

Adducts between SF4 and a nitrogen base are easily solvolyzed by HF, yielding the protonated nitrogen base and fluoride. Salts resulting from the solvolysis of SF4·NC5H5, SF4·NC5H4(CH3), SF4·NC5H3(CH3)2, and SF4·NC5H4N(CH3)2 have been studied by Raman spectroscopy and X-ray crystallography. Crystal structures were obtained for pyridinium salts [HNC5H5(+)]F(-)·SF4 and [HNC5H5(+)]F(-)[HF]·2SF4, the 4-methylpyridinium salt [HNC5H4(CH3)(+)]F(-)·SF4, the 2,6-methylpyridinium salt [HNC5H3(CH3)2(+)]2[SF5(-)]F(-)·SF4, and 4-(dimethylamino)pyridinium salts [HNC5H4N(CH3)2(+)]2[SF5(-)]F(-)·CH2Cl2 and [NC5H4N(CH3)2(+)][HF2(-)]·2SF4. In addition, the structure of [HNC5H4(CH3)(+)][HF2(-)] was obtained. 4,4'-Bipyridyl reacts with SF4 and 1 and 2 equiv of HF to give the 4,4'-bipyridinium salts [NH4C5-C5H4NH(+)]F(-)·2SF4 and [HNH4C5-C5H4NH(2+)]2F(-)·4SF4, respectively. These structures exhibit a surprising range of bonding modalities and provide an extensive view of SF4 and its contacts with Lewis basic groups in the solid state. The interactions range from the strong F4S-F(-) bond in the previously observed SF5(-) anion to weak F4S---F(-), F4S(---F(-))2, and F4S(---FHF(-))2 dative bonds.