Question

why SiF6 2- is known but where as SiCl6 2- is not known?​

Answer 1

due to small size of F, siF6 2-, is existing but cl atom have larger size so it can't exist.

Answer 2

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

❤⭐MAIN REASONS:- ⭐❤

1. six lagre 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.