Hydrated tetrahalides

Hydrated IV-pentylisonicotinate adducts, ThX4 yL-zH20 (X = Cl, y= 2, z - 8 X = Br, y = 4, z = 9 X = I, y = 2, z = 9) have been obtained by grinding the solid, hydrated tetrahalide with an excess of the ester, but their IR spectra indicate that the ester molecules are not bonded to the metal atom. 

Silicon tetrafluoride is a colourless gas, b.p. 203 K, the molecule having, like the tetrahalides of carbon, a tetrahedral covalent structure. It reacts with water to form hydrated silica (silica gel, see p. 186) and hexafluorosilicic acid, the latter product being obtained by a reaction between the hydrogen fluoride produced and excess silicon tetrafluoride ... 

One of the most important methods of pyrazole synthesis involves the reaction of 1,3-diketones with hydrazine derivatives. The method has wide scope, especially considering that the diketones may be replaced by acetals, hemiacetals, chlorovinyl ketones, tetrahalides, etc. Most accessible by this path is 3,5-dimethylpyrazole (10), obtained in 85% yield from acetylacetone and hydrazine hydrate.134-138... 

All of the SiX4 tetrahalides except the fluoride hydrolyze rapidly to give hydrated sihca the fluoride also undergoes partial hydrolysis but also forms the hexafluorosilicate ion (equation 19). 

The lanthanide and actinide halides remain an exceedingly active area of research since 1980 they have been cited in well over 2500 Chemical Abstracts references, with the majority relating to the lanthanides. Lanthanide and actinide halide chemistry has also been reviewed numerous times. The binary lanthanide chlorides, bromides, and iodides were reviewed in this series (Haschke 1979). In that review, which included trihalides (RX3), tetrahalides (RX4), and reduced halides (RX , n < 3), preparative procedures, structural interrelationships, and thermodynamic properties were discussed. Hydrated halides and mixed metal halides were discussed to a lesser extent. The synthesis of scandium, yttrium and the lanthanide trihalides, RX3, where X = F, Cl, Br, and I, with emphasis on the halide hydrates, solution chemistry, and aspects related to enthalpies of solution, were reviewed by Burgess and Kijowski (1981). The binary lanthanide fluorides and mixed fluoride systems, AF — RF3 and AFj — RF3, where A represents the group 1 and group 2 cations, were reviewed in a subsequent Handbook (Greis and Haschke 1982). That review emphasized the close relationship of the structures of these compounds to that of fluorite. 

Hydrated phases are known for both the tetrahalides and the dihalides, but neither has been extensively characterized. Cerium tetrafluoride monohydrate, CeF4 H20, has been prepared by several procedures (Asker and Wylie, 1964). The product of digesting Ce02 in concentrated aqueous HF solution at 100-130° is CeF4.o-l.OH2O, while that obtained by reaction of the dioxide with anhydrous HF is CeF4.o-O.8H2O. Powder X-ray diffraction data are reported the structure is unknown and different from that of the anhydrous tetrafluoride. 

Tin(IV) chloride forms a number of hydrates, but that stable at ordinary temperature and pressure is SnCU.SHaO. TinflV) tetrahalides are all hydrolysed by aqueous alkali. 

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