Butter of tin is
SnCl2⋅5H2O
SnCl2⋅2H2O
SnCl4⋅4H2O
SnCl4⋅5H2O
Tin(IV) chloride pentahydrate is butter of tin.
It is represented as [SnCl4(H2O)2]⋅3H2O or SnCl4.5H2O.