Halides of the Group IVA Elements

With three pairs of electrons surrounding the central atom, the monomeric molecules are expected to have the nonlinear structure shown here (for example, the bond angle is 101 ° in SiF2), and as a result they are polar  

However, the EX4 molecules have tetrahedral structures and they are nonpolar. As a consequence, the compounds having the formula EX4 are more soluble in organic solvents than are those of the EX2 type. 

In general, the ability of the halides to function as Lewis acids results in their being able to react with halide ions (Lewis bases) to form complex ions. Examples of this type of behavior are illustrated by the following equations  

This tendency is greater for the halides of the elements in the +4 oxidation state than it is for those of the +2 state owing to the greater Lewis acid strength of the EX4 compounds. 

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