For hydrogen bonding, the size of the atom should be small and electronegativity must be high for e.g. F, O, N. Although chlorine has high electronegativity but due to its larger size hydrogen bonding is not possible with it. KHCl2(HCl2−) don't exists but KHF2(HF2−) exists due to lack of H-bonding in HCl but possible in HF.