A discrete dichloride tetrahydrate cluster, [Cl2(H2O)4]2−, was obtained as a salt of the bis(diphenylamino)diethylamino cyclopropenium cation [C3(NPh2)2(NEt2)]+ and characterized by single-crystal X-ray diffraction and infrared spectroscopy. This chloride–chloride ion-pair cluster consists of a [Cl2(H2O)2]2− square with opposite edges bridged by water molecules to give a chair-like structure of the non-hydrogen atoms. The solid-state structure is essentially the same as the calculated gas-phase structure. Infrared spectra were also collected on the deuterium analogue [Cl2(D2O)4]2−. Computational studies were carried out on gas-phase [Cl2(H2O)4]2− to confirm the infrared band assignments in the solid state. The structure and infrared spectrum are consistent with the discrete nature of the cluster.