Synthetic Methods of Organometallic and Inorganic Chemistry, Volume 4, 1997

1.7 Sulfur-Halogen-Oxygen Compounds

Sulfur forms two series of halogen oxides, the thionyl halides SOX2 (CS symmetry) and the sulfuryl halides SO2X2 (C2v symmetry). Some physical properties are summarized in ▶ Table 1.13.

▶ Table 1.13 Some properties of sulfur halogen oxides.

Thionyl Fluoride — SOF2

Procedure

As reaction vessel a steel bottle is used with an inlet and outlet tube (steel, iron) for gases. A second steel bottle is connected to the first one in the reversed sense to withhold any traces of HF (▶ Figure 1.35). The gases are passed through a cold trap (Dewar) and a drying tube filled with KF. The reaction vessel is charged with 500 g of SOCl2 and 50 g of SbCl5 (as catalyst). Anhydrous HF is passed into the reactor. HF is absorbed and converted into SOF2 and HCl which are collected in the cold trap. The reaction is endothermic, and the reaction vessel slowly becomes covered with ice on its outer walls. SOCl2 can be recharged during the reaction.

▶ Figure 1.35 Apparatus for the preparation of SOF2.

The separation of SOF2 and HCl can be accomplished by distillation or by bubbling the gas rapidly through ice-cold water to absorb HCl completely. SOF2 is not affected to any extent. The gaseous product is dried with concentrated H2SO4 or P4O10.

Alternative Procedure

This very convenient reaction requires distilled CH3CN as solvent. The apparatus consists of reaction vessel containing a Pyrex glass flask, addition funnel, thermometer, stirrer, and reflux condenser with cold traps (−78 °C) connected to the condenser. SOCl2 (60 g) is added dropwise to a vigorously stirred suspension of 168 g of dry and finely divided NaF in 100 g of CH3CN. The addition is done at room temperature. SOF2 leaves the reaction vessel and is condensed into the cold trap. Purification requires low temperature rectification. Yield: 77% referred to SOCl2.

Storage of the product compressed in steel cylinders is recommended.

Properties

The colorless gas is thermally very stable, mp −110.5 °C, bp −43.7 °C, critical temperature 88 °C, D (liquid, −100 °C): 1.780 g · cm−3, D (solid, −183 °C): 2.095 g · cm−3. The metals Fe, Ni, Co, Fig, Si, Mn, B, Mg, Al, and Zn do not react with SOF2 up to 125 °C and glass is not etched. SOF2 has an unpleasant odor, and is only slowly hydrolysed by water.

References

1 J. Söll, W. Kwasnik, Naturforschung und Medizin in Deutschland, 1939 - 1946 (FIAT Review) 23, 192.

2 H. S. Booth, F. C. Mercila, J. Am. Chem. Soc. 62, 640 (1940).

3 U. Wannagat, G. Mennicken, Z. Anorg. Allgem. Chem. 278, 310 (1955).

4 C. W. Tullock, D. D. Coffman, J. Org. Chem. 25, 2016 (1960).

Sulfuryl Fluoride — SO2F2

Procedure

Freshly distilled tetramethylene sulfone is used as solvent. A 1-L autoclave equipped for addition, temperature measurement, and stirring is charged with 168 g of dry and finely divided NaF in 300 g of tetramethylene sulfone. To this vigorously stirred suspension, 135 g of SO2Cl2 are slowly added. The temperature should not rise above 100 °C. As soon as the addition of SO2Cl2 has been completed, the mixture is heated for 1 h each to 60 °C, 80 °C, 100 °C, 125 °C, and for 2 h to 150 °C, with stirring. After completion of the reaction, any excess of SO2F2 is released and the contents of the autoclave are condensed into a cold trap at −78 °C. Yield: 85%.

Properties

The colorless and odorless gas is thermally stable up to 400 °C and chemically unreactive, bp 121.4 °C, mp −49.7 °C, D (liquid): 1.7 g · cm−3. The compound does not hydrolyse with water, however, it is well soluble in alkaline solutions with hydrolysis. Solubilities at 16.5 °C: in water, 4–5 mL SO2F2 gas/100 mL; in alcohol, 24 – 27 mL SO2F2 gas/100 mL; in toluene, 210 – 220 mL of SO2F2 gas/100 mL; in CCl4, 136 – 137 mL of SO2F2 gas/100 mL.

Related Compounds

In a similar way, also selenyl fluoride, SeOF2, is accessible:

SeOCl2 + 2 NaF → SeOF2 + 2 NaCl.

An autoclave is not necessary for this reaction since it can be performed at normal pressure and temperatures of 60 – 115 °C; yield: 28%.

References

1 C. W. Tullock, D. D. Coffmann, J. Org. Chem. 25, 2016 (1960).

Sulfur(IV) Oxoletrafluoride — SOF4

Although SF6 is exceptionally inert towards oxygen, reaction can be initiated by the electrical explosion of extremely small masses of platinum in SF6/O2 mixtures. The major reaction product is SOF4. Reaction of SF4 or SF5Cl with oxygen or oxidizing agents affords SO2F2, small amounts of SOF4, and other products (SO2, SF6).

An alternative synthesis involves the reaction:

SOF2 + O2F2 → SOF4 + O2.

References

1 B. Siegel, P. Breisacher, J. Inrg. Nucl. Chem. 31, 675 (1969).

2 I. J. Solomon, A. J. Kacmarek, J. M. McDonlugh, J. Chem. Eng. Data 13, 529 (1968).

Thionyl Chloride Fluoride — SOClF

Procedure

IF5 (45 g) is placed in a flask fitted with a reflux condenser and an addition funnel. Then, 60 g of SOCl2 are added dropwise. The mixture turns dark with evolution of heat. The volatile gases, which pass through the reflux condenser, are condensed in a cold trap (liquid N2). The trap is connected to a drying tube (KF) and a bubbler. The condensate is distilled from antimony powder or mercury until it is colorless. The crude product is subjected to fractionated distillation, first cut: SiF4, HCl, SOF2, last cut: SOClF. The fraction collected between 10 and 18 °C/760 torr is SOClF. Yield: 42% referred to SOCl2.

Properties

The colorless gas is not thermally stable at room temperature for indefinite periods (it decomposes into SOCl2 and SOF2) and is malodorous, mp −110 to −139 °C (isomers), bp 12.3 °C, D (liquid, 0 °C): 1.576 g · cm−3. SOClF disproportionates in contact with Cu, Hg, and with Fe at above 70 °C. It is hydolysed in water and NaOH but is stable towards glass.

References

1 O. Ruff, H. Jonas, Naturforschung und Medizin in Deutschland, 1939 – 1946 (FIAT-Review), 23, 192.

2 H. Jonas, Z. Anorg. Allgem. Chem. 265, 273 (1951).

Sulfuryl Chloride Fluoride — SO2ClF

Procedure

The apparatus consists of an autoclave or steel bottle of 1-L capacity fitted with a steel reflux condenser bearing a manometer and a valve on top. The system has to withstand a pressure of 11 bar. The release valve is connected to two quartz traps immersed in liquid nitrogen. At the end of the system is placed a drying tube filled with dry KF. The reaction vessel is filled with 220 mL (365 g) of SO2Cl2, 187 g of finely divided SbF3, and (as catalyst) 40 mL of SbCl3. The autoclave is slowly heated to 300 °C with the pressure rising to 8 bar. The release valve is now opened and the volatile gases are condensed into the cold traps, until the pressure inside the autoclave has dropped to 7.3 bar. A reaction time of about 2 hours yields ca. 80 mL of condensate. The crude product is distilled whereupon SO2 and HCl are released. A higher boiling fraction contains SO2Cl2.

SO2ClF can also be prepared at normal pressure in a solvent such as CH3CN in a satisfactory yield.

Procedure

The apparatus consists of a Pyrex glass vessel equipped with an addition funnel, thermometer, mechanical stirrer, and a reflux condenser with two cold traps (−78 °C) placed behind the condenser. Dry, finely divided NaF (144 g, 2.48 mol) is suspended in 133 g (3.24 mol) of freshly distilled CH3CN. SO2Cl2 (68 g, 0.5 mol) is added with vigorous stirring. After completion of the addition, the mixture is heated to 80 °C for 3.5 h. Gaseous SO2ClF is formed and condenses into the cold traps. Yield: 64% referred to SO2Cl2.

Properties

The colorless gas with a pungent smell similar to SO2Cl2 fumes in air and reacts rapidly with water and basic solutions, mp −124.7...