Halides tetrahalides

The phenyl derivatives of these acids were known as early as 1876, owing to the fact that they are obtainable from halogenated arsines when the latter are treated with water. The older methods for isolating arylarsinic acids consist in decomposing aryl or diarylarsine halides, tetrahalides, or oxyhalides by water ... 

All Group IV elements form tetrachlorides, MX4, which are predominantly tetrahedral and covalent. Germanium, tin and lead also form dichlorides, these becoming increasingly ionic in character as the atomic weight of the Group IV element increases and the element becomes more metallic. Carbon and silicon form catenated halides which have properties similar to their tetrahalides. 

Like all the lead tetrahalides, lead tetrafluoride [7783-59-7] is very reactive. It is relatively the most stable halide, however. PbF is a white crystalline... 

Diphosphorus tetrahalides and other tower halides of phosphorus... 

All the tetrahalides, but especially the chlorides and bromides, behave as Lewis acids dissolving in polar solvents to give rise to series of addition compounds they also form complex anions with halides. They are all hygroscopic and hydrolysis follows the same pattern as complex formation, with the chlorides and bromides being more vulnerable than the fluorides and iodides. TiCU fumes in and is completely hydrolysed by... 

The known halides of this triad are listed in Table 26.3. It can be seen that, apart from C0F3, C0F4 and the doubtful iridium tetrahalides, they fall into three categories ... 

I. Halides from Alcohols by Triphenylphosphine-Carbon Tetrahalide... 

Reductive methods form B—B bonds from B—X bonds. For B2X4 (X = Cl, Br, I) from BXj, an electric discharge is supplemented by the presence of a metal, or metal atoms, as halide scavenger. The passage of BX3 at low pressure through a rf discharge in the presence of Hg produces the diboron tetrahalides B2X4 at 300 mg h ... 

The advantages of the carbon tetrahalide-organophosphine-alcohol reaction to prepare halides are simplicity of experimental procedure good yields relatively mild, essentially neutral reaction conditions absence of allylic rearrangements. The reaction proceeds with inversion of configuration and is a useful simple device for converting optically active alcohols to chiral halides in high optical purity.12-22... 

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