Crystal and molecular structure of tris(dimethylamino)sulfonium trifluoromethoxide. Evidence for negative fluorine hyperconjugation

Fluorine Compounds, Organic

“…The perfluoroalkoxides are moderately nucleophilic and are used in situ to prepare compounds containing perfluoroalkoxy groups (see Section 6.3). Tris(dialkylamino)sulfonium perfluoroalkoxides are unusually stable and, in some cases, have been isolated as crystalline solids [173]. Tertiary perfluoro alcohols, e.g., perfluoro-tert-butanol (1,1,1,3 trifluoroacetic acid with metal hydrides [179].…”

A General Approach to (Trifluoromethoxy)pyridines: First X‐ray Structure Determinations and Quantum Chemistry Studies

“…[22] These values are comparable to those reported in the Cambridge Crystallographic Database. In tris-(dimethylamino)sulfonium (TAS) trifluoromethoxide, for example, the C-O bond is contracted by 0.09 Å relative to trifluoromethanol [23] and by 0.21 Å relative to methanol. [24] We have also performed single-crystal X-ray analyses for 3-trifluoromethoxy-substituted pyridines.…”

Conversion of Carbon–Fluorine Bonds α to Transition Metal Centers to Carbon–Hydrogen, Carbon–Carbon, and Carbon–Heteroatom Bonds

“…[154][155][156][157][158] A spectacular example of such a groundstate effect occurs in the structure of the CF 3 O -anion, in which backbonding, or negative hyperconjugation, from O lone pairs to C-F σ* orbitals results in a structure with a virtual C=O double bond and extremely long C-F bonds ( Figure 1A). [159] There is no reason why a transition metal heteroatom should not have the same capabilities based on orbital symmetry requirements ( Figure 1C), but clearly the energy match between M(nd) and C-F(σ*) will not be as good as that with an oxygen atom lone pair. Nevertheless, the proposition that C-F bonds α to metals could be weakened by backbonding from filled M(d) orbitals to low-lying C-F(σ*) orbitals has been put forth, [154][155] and subsequently rejected, [156] at least as an explanation for lower C-F stretching frequencies in transition metal CF 3 compounds.…”