Synthesis of SnI4

Direct reaction of tin metal with iodine in methylene chloride yields SnI4 as the principal product, with formation of SnI2 as a side reaction.

Sn + 2I2 + SnI4
Sn + I2 + SnI2

SnI4 is a red-orange solid; SnI2 is a yellow-red solid.

Color due to polarizability of I–, probably involving charge transfer (I+Sn).

SnI2 is polar, and SnI4 is non-polar, As a result SnI2 is slightly more soluble in CH2Cl2.

SnI2 is somewhat more ionic and has a higher m.p.

SnI2 m.p. 330C SnI4 m.p. = 143-144C