Triphenylphosphonium Hexachlorocerate

With the heavy lanthanides, the oxides do not dissolve readily in HCl-ethanol. The oxides (2.5 g.) are dissolved in boiling, concentrated aqueous HC1 in a small beaker. With some oxides, even dissolution in aqueous HC1 is fairly slow and evaporation to a concentrated lanthanide chloride solution of higher boiling point speeds the dissolution of the last traces of oxide. The aqueous solutions are taken to dryness, and the residues are heated strongly ( 300°) to effect complete dehydration and conversion to LnOCl and LnCl3. The residue is transferred as completely as possible to a suitable container, 15 ml. of absolute ethanol is added, and the solids are dissolved by addition of HC1 gas with further heating if necessary. The solutions are cooled and HC1 gas is added until complete saturation at 25° is achieved. Ten milliliters of absolute ethanol is added to produce a 

Although a small amount of water can be tolerated, and indeed is produced by dissolution of the oxides and oxychlorides, the solutions should be kept as dry as possible, and exposure to atmospheric moisture should be minimized. One hundred-milliliter screw-capped bottles with polyethylene-lined caps are convenient containers for the preparation because they are easily closed when HC1 or reagent addition is not being made. They can be heated in a water bath if necessary to promote dissolution of the Ln203 or LnOCl while the caps are quite loose or while fitted with a rubber stopper with a small-diameter vent tube to prevent pressurization. 

The salts are filtered with suction on a coarse-fritted funnel and washed, in the case of the light lanthanide salts, with HCl-saturated or nearly saturated ethanol and, in the case of the heavy lanthanide salts, with absolute ethanol containing 60 % of the 25° equilibrium saturation concentration of HC1. The complexes dissociate in contact with solvents such as ethanol or acetone not containing HC1. They are also moisture-sensitive, and excess air should not be pulled 

The pyridinium salts of [LnCl6]3 can be made by essentially the same method as the triphenylphosphonium salts but are more rapidly hydrolyzed by atmospheric moisture. 

This salt of the well-known [FeCl4] ion is easily precipitated by adding a small excess of [(C2H5)4N]C1 in 12M HC1 to a 12M HC1 solution of iron(III) chloride. It is washed with 12M HC1 and dried by mild heating. Anal. Calcd. for C8H20Cl4FeN Fe, 17.0. Found 17.3. The [AuC14] salt is prepared similarly from a solution of gold(III) chloride (chloroauric acid) in 12M hydrochloric acid. 

---