SnCl2 is solid at room temperature. Its melting point is 247 °C.
SnCl4 is liquid at room temperature. Is melting point is - 33°C.
The reason of this is every molecule of SnCl2 has a pair of non shared electrons which form a chloride bridge with neighbors molecules (the highly electronegative Cl attracts the pair of non shared electrons of the SnCl2 molecule), so they form a crystalline network.