Terbium tetrafluoride

Cerium and terbium tetrafluoride can be prepared by the action of fluorine, xenon difluoride, and chlorine trifluoride on Ce02 or CeFs, and Tb407 or TbFs, respectively. These reactions are carried out at temperatures of 300-400 C in nickel or monel containers with exclusion of moisture and oxygen, For further details see the Gmelin Handbook (1976) and the literature cited therein. The preparation of... 

The most common valence state in solid compounds is -i-3. A +4 valence state is known for the metal in its dioxide, Tb02, and tetrafluoride, TbF4. Terbium also forms several nonstoichiometric oxides of approximate composition Tb407. 

The lanthanides, unlike the transition metals and the actinides, tend not to form compounds over a range of oxidation states. The +3 oxidation state is characteristic of all of the lanthanides, and the oxide fluorides of formula LnOF (Ln = lanthanide metal) are well known. The less stable oxidation states of + 2 and + 4 are known, but the latter is represented only by the dioxides and tetrafluorides of cerium, praseodymium, and terbium, and no tetravalent oxide fluorides have been reported. 

For these elements, the correspondence of the actinide and the lanthanide series becomes most clearly revealed. The position of curium corresponds to that of gadolinium where the / shell is half-filled. For curium, the +3 oxidation state is the normal state in solution, although, unlike gadolinium, a solid tetrafluoride, CmF4, has been obtained. Berkelium has +3 and +4 oxidation states, as would be expected from its position relative to terbium, but the +4 state of terbium does not exist in solution whereas for Bk it does. 

Tellurium dioxide complexes with thiourea, 305 Tellurium dithiocyanate complexes, 303 Tellurium hexafluoride complexes, 303 with amines, 304 Tellurium sulfate complexes, 303 Tellurium tetrabromide complexes, 302 Tellurium tetrachloride complexes with acetamide, 304 with amines, 304 with pyridine N-oxide, 304 Tellurium tetrafluoride complexes with amines, 304 with dioxane, 304 Tellurotungstates, 1042 Tempera ture-jump studies molybdenum(VI) complexes, 1259 Terbium complexes p diketones, 1081... 

The tetrafluorides are white solids which are only slightly soluble in water, but decompose slowly to form trifluorides. The cerium compound which is appreciably more stable than those of praseodymium and terbium, reacts with moist air above 500°C to form Ce02 and HP. Additional properties of the tetrafluorides are described by B atsanova (1971). 

---