Anionic interactions antimony

Antimony(V) chloride also forms a 1 1 complex with PhjSbClj, but here the increased Lewis acidity of antimony pentachloride leads to strong interaction with one of the axial chlorines and the product, [Ph3SbCl] [SbClg], is basically ionic. There is a residual Sb---Cl cation-anion interaction at 3.231 A and the cation geometry is intermediate between the trigonal bipyramidal and tetrahedral extremes. 

The SbjFfi anion itself is symmetric, namely the distances between both antimony atoms and the bridging fluorine are the same 2.00 A. This is in contrast to many other salts with this dimeric anion in which these distances are non-equal. The cation-anion interaction causes a movement of the closest fluorine to the cation towards the central atom in it, as well as some charge donation to the cation. This in turn involves some loss of electron density at the Sb atom of that half closer to the... 

As with the previous element, the dangerous reactions of antimony derivatives are linked to the behaviour of the anion. The element is reducing and apart from its interaction with two metals it gives rise to dangerous reactions with strong oxidants. 

One of the more notable features of antimony(V) halide chemistry is the tendency to achieve a CN of six, thus resulting in the facile formation of complex anions, particularly with halide donors (Table 21) the d(Sb—F) depends on the nature of the cation. Their structures are related to the F—Sb- -F interactions between crystal structure units, which is dependent upon the potential field of the cation. 

A slightly different pattern of reactivity is seen when 3.8 interacts with antimony(m) fluoride in methanol. In this case, the product contains a ligand derived from the hemia-cetal, but the hydroxy group is deprotonated and co-ordinated to the metal centre, to give an N,iV,0-bonded anionic ligand (Fig. 3-17). It is not known whether the co-ordination of the oxygen to the metal centre occurs after the hydration reaction (in which case we are... 

Antimony pentachloride, SbCh, is a liquid (mp 4°C, bp 140 °C dec ), which can be obtained by reaction of SbCls with elemental chlorine. Sohd SbCls exists in two modifications above 54.1 °C, it is trigonal bipyramidal, below this temperature, it changes reversibly into a double chlorine-bridged dimer. SbCls decomposes at 140 °C with formation of SbCls and CI2. It is a Lewis acid with a strong tendency to interact with a ligand (L) to give octahedral complexes LSbCls. Reactions with chloride ion donors lead to ionic compounds with SbCle" anions and unusual cations. Examples are shown in equations (10) and (11). 

Separation of chiral isomers requires chiral counterions. Cations are frequently resolved by using the anions z -tartrate, antimony d-tartrate, and a-bromocamphor-iT -sulfonate anionic complexes are resolved by the bases brucine or strychnine or by using resolved cationic complexes such as [Rh(en)3] " . In the case of compounds that racemize at appreciable rates, adding a chiral counterion may shift the equilibrium even if it does not precipitate one form. Apparently, interactions between the ions in solution are sufficient to stabilize one form over the other. 

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