Sulfur chloride pentafluoride

Sulfur chloride pentafluoride is an inorganic compound with the formula SF5Cl. It exists as a colorless gas at room temperature and is highly toxic, like most inorganic compounds containing the pentafluorosulfide (–SF5) functional group. The compound adopts an octahedral geometry with symmetry. Sulfur chloride pentafluoride is the only commercially available reagent for adding the –SF5 group to organic compounds.

Reactivity
SF5Cl is highly reactive and toxic. In contrast, sulfur hexafluoride (SF6) is inert and nontoxic despite having a closely related chemical formula. This difference highlights the lability of the S–Cl bond in SF5Cl.

Under free-radical conditions, SF5Cl adds across double bonds. The following reaction occurs with propene:
 * + → CH3CHClCH2SF5

The addition reaction is catalyzed by (CH3CH2)3B at around −30 °C. SF5Br is used similarly.

SF5Cl is also a precursor to O(SF5)2 and F2NSF5 (from tetrafluorohydrazine).

Synthesis
Sulfur chloropentafluoride can be synthesized by several routes, starting from two lower sulfur fluorides, sulfur tetrafluoride and disulfur decafluoride:
 * SF4 + Cl2 + CsF  → SF5Cl + CsCl
 * ClF + SF4 → SF5Cl
 * S2F10 + Cl2 → 2 SF5Cl

The corresponding is prepared similarly from in-situ generated bromine monofluoride.