Question

Why is (SiF6)2- possible and not (ClF6)2-?

Answer 1

SiF6 exists but not SiCl6 cannot be formed because -

-Cl is comparatively larger in size thus lone pair interactions are weak.

-F is more electronegative than Cl.

Thus F finds it easier to bond with SI whereas, Chlorine being less electronegative and larger in size is not able to bond with silicon.

Answer 2

$\huge\boxed{\underline{\mathcal{\red{A}\green{N}\pink{S}\orange{W}\blue{E}\purple{R}}}}$

❤⭐MAIN REASONS:- ⭐❤

1. six large chloride ions cannot be accomodated around ${Si}^4+$ due to $\purple{\tt{Limitation}}$of its size.
2. Interaction between lone pair of chloride ion and${Si^4+}$ is not very strong.