Antimony pentachloride activator

The effectiveness of antimony fluoride is increased if it is used in conjunction with chlorine or with antimony pentachloride. The formation of either SbCl2F2 or a complex of SbF and SbCl probably accounts for the increased activity (4). 

THF can be polymerized only with cationic initiators, for example, boron trifluoride or antimony pentachloride. The initial step consists of the formation of a cyclic oxonium ion one of two activated methylene groups in the a-position to the oxonium ion is then attacked by a monomer molecule in an S 2-reaction, resulting in the opening of the ring. Further chain growth proceeds again via tertiary oxonium ions and not, as formerly assumed, via free carbonium ions ... 

The initiation of tetrahydrofuran polymerization by direct addition of oxonium salts is of interest because it reveals a good deal about the mechanism, but for practical purposes the salts may be formed in the reaction mixture. The obvious method is, of course, to add a little epichlorohydrin to the mixture of monomer and Friedel Crafts reagent for only antimony pentachloride is sufficiently active to start the reaction with monomer alone, but other reactions which accomplish the same purpose are ... 

The antimony pentachloride-benzyltriethyl ammonium chloride complex (SbCls-TEBA, Figure 3.1), shows quite interesting catalytic efficiency in the acylation of activated aromatic compounds (i.e., toluene, xylenes, aryl ethers) with aromatic and chloroacetyl chlorides. Reactions are carried out with SbCls-TEBA (5% mol) in boiling nitromethane, giving ketones in 73%-96% yield. The catalyst has many advantages, such as ready access, minimal toxicity, reusability, insensitivity to atmosphere and moisture. 

Moissan and Lebeau (1901) produced sulfuryl fluoride by the combination of sulfur dioxide with fluorine (217). Other processes which have been used to produce the gas are (a) the thermal decomposition of barium fluorosulfonate or certain other fluorosulfonates (188, 221, 808), (b) the reaction of sulfur dioxide with chlorine and hydrogen fluoride in the presence of activated charcoal at 400° (11), (c) the reaction of sulfur dioxide and chlorine with potassium or sodium fluoride at 400° (328), (d) the disproportionation of sulfuryl chlorofluoride at 300-400° (328), (e) the reaction of sulfuryl chloride with a mixture of antimony trifluoride and antimony pentachloride at about 250° (86), (f) the reaction of sulfur dioxide with silver difluoride (86), (g) the reaction of thionyl fluoride with oxygen in an electrical discharge (314), (h) electrolysis of a solution of fluorosulfonic acid in hydrogen fluoride (264), ( ) the reaction of fluorine with sodium sulfate, sodium sulfite or sodium thiosulfate (229, 239), (j) the reaction of hydrogen fluoride with sulfuryl chloride (820). 

The polymerization of propiolactone in methylene chloride with an antimony pentachloride-dieth te catalyst was investigated. The results show that the concentration of the active centers is dependent upon catalyst concentration and upon the initial concentration of the monomer. They also support the concept that opening of the lactone rings includes initial formation of oxonium ions ... 

Hofmann found that antimony pentachloride facilitates the action of chlorine on carbon disulphide or ethylene, and so discovered a halogen carrier . H. Muller found that iodine markedly accelerates the action of chlorine on benzene and other compounds, e.g. acetic acid at the boiling-point forms monochloracetic acid antimony pentachloride gives mostly more highly chlorinated compounds. B. Aronheim, at the suggestion of Lothar Meyer, found that molybdenum pentachloride acted in the same way as iodine, and A. G. Page that ferric chloride is also an active chlorine... 

Ethylene is treated with an excess of chlorine at 300—350°C in the presence of activated charcoal to give hexachloroethane. This product is then treated with hydrogen fluoride in the presence of antimony pentachloride to yield trichloro-trifluo roe thane. Dechlorination in the liquid phase with zinc dust and ethanol... 

Gutmann s DN values are based on reaction enthalpies, so a correlation with SH rather than with AG is not unreasonable. This tentatively emerging correlation with DN values is, however, easily upset by steric factors, either in the form of ligand bulk 2 or of solvent bulk. Activation enthalpies for solvent exchange at metal(ii) centres, for instance Fe +, do not correlate satisfactorily with values, nor do activation enthalpies for Na+ release from the 2,2,2-cryptate (1). The noncorrelation of activation enthalpies with DN values in many systems need not cause too much surprise, as these DN values are based on enthalpies of reaction of the respective solvents with antimony pentachloride, a process significantly different from that involved in metal ion solvation. 

---