Cerium Tetrafluoride. I. Preparation and reactions

Abstract

Pure anhydrous cerium tetrafluoride is best prepared by fluorinating cerium dioxide at 350-500�. A monohydrate can be obtained from aqueous solution in a variety of ways, but it cannot be dehydrated without decomposition. It loses water "zeolitically" in vacuum, showing relatively small changes in lattice parameters for loss of 70% of its water content. Thereafter the lattice collapses, forming well-crystallized cerium trifluoride and poorly crystallized "anhydrous" cerium tetrafluoride. The refractive indices of anhydrous monoclinic cerium tetrafluoride have been measured and its fluorine dissociation pressure at 500� shown to be less than 0.5 mm. At higher temperatures the tetrafluoride sublimes incongruently, and at 835-841� it melts with extensive decomposition into a fluorine-poor liquid and a fluorine-rich vapour. Cerium tetrafluoride is easily reduced to the trifluoride by ammonia and by water vapour at low temperatures. At higher temperatures it is quantitatively converted by water vapour to cerium dioxide and hydrogen fluoride. When heated with cerium dioxide it is reduced to the trifluoride with liberation of oxygen.

Cerium Tetrafluoride: Sublimation, Thermolysis, and Atomic Fluorine Migration

“…On the contrary, thermal decomposition of CeF 4 (s) with formation of CeF 3 (s) is accompanied by CeF 4 (s) transition to the gaseous phase that has been experimentally proved by means of chemical analysis and Xray powder diffraction. 4 This fact has been additionally proved by mass spectrometric investigations of CeF 4 saturated vapor. 5−7 Considerably higher thermal stability of CeF 4 (s) in comparison with TbF 4 (s) is also confirmed by experimentally determined enthalpies of formation of cerium and terbium fluorides.…”

“…The different morphology of the layer on the Ni ring is caused by a different mechanism of its formation. In contrast to uniform drain of F s atoms on the Pt surface, the CeF 3 (s) layer on the Ni surface is being formed due to a reaction of solid-state fluorination + = + 2CeF (s) Ni(s) 2CeF (s) NiF (s) 4 3 2…”

“…The mass-balance equation for cerium tetrafluoride evaporation in the effusion cell is 4 4 dec (10) where Q↓(CeF 4 ) and Q↑(CeF 4 ) are sorption and desorption flows of CeF 4 molecules to and from the inner surface of the cell, Q dec is a rate of CeF 4 (s) decomposition to nonvolatile CeF 3 (s), which is equal to flow of F s fluorine atoms directed to drain zones Q(F s ). In ideal case, when Q dec = 0 and Q↓(CeF 4 ) = Q↑(CeF 4 ), an achieved flow of sorption/desorption of CeF 4 molecules is maximal and corresponds to saturated vapor pressure of CeF 4 .…”

Synthesis and structure of [CeF4(Me2SO)2]—A rare neutral ligand complex of a lanthanide tetrafluoride

“…Anhydrous CeF 4 is an inert and extensively F-bridged polymer, but by analogy with the Zr/Hf chemistry [4], we proposed that using the hydrate CeF 4 ÁxH 2 O (x 1 and varies with the drying method) [5,6] [5], although the former had much sharper diffraction lines, indicative of increased crystallinity. It is likely that the lower crystallinity/particle size of the freshly prepared sample results in its higher reactivity.…”

“…Although their study was neglected for many years, recent work has revealed an extensive coordination chemistry of early transition metal fluorides, including TiF 4 , ZrF 4 , HfF 4 , NbF 5 , TaF 5 and WF 6 [1]. In marked contrast, the coordination chemistry of lanthanide fluorides is limited to a range of fluorometallate anions, and a few, usually poorly characterised hydrates [1,2].…”