**COMPOUNDS CONTAINING COORDINATE BONDS SHOW MELTING AND BOILING POINTS HIGHER THAN THOSE OF PURE COVALENT COMPOUNDS AND LOWER THAN THOSE OF IONIC COMPOUNDS - WHY ?

Coordinate bond is somewhat similar to the covalent bond, It i also known as dative covalent bond. The difference between these two is that coordinate bond is one side sharing of electrons while covalent bond involves sharing of electrons between both the atoms.

Covalent and coordinate bonds both are weaker than ionic bonds and thus their melting and boiling points are lower than those of ionic bonds.
However, the melting point and boiling point of covalent and coordinate bonds are almost similar.