Question: why snf4 and pbf4 are ionic?
Answer: Sn+4 has a strong polarising power. ... So Sn+4 can easily polarise Cl- ion which make Sn-Cl bond covalent. On the other hand Sn+4 can't polarise F-, so it's ionic. Besides it the electronegativity difference between Sn and F is higher than Sn and Cl , which make Sn-F bond more polar in nature than Sn-Cl bond.