A Series of Discrete Dichloride Dihydrates: Characterisation and Symmetry Effects

A series of three discrete dichloride dihydrates [Cl 2 (H 2 O) 2 ] 2− have been isolated with different triaminocyclopropenium (TAC) cations and with different crystallographic symmetries. The cluster exhibits D 2h symmetry with the tris(dimethylamino)cyclopropenium cation [C 3 (NMe 2 ) 3 ] + , C 2h symmetry with the fluorinated cation [C 3 (N(CH 2 CF 3 ) 2 )(NBu 2 ) 2 ] + (containing two 2,2,2‐trifluoroethyl substituents) and C 2v symmetry with the more fluorinated [C 3 (N(CH 2 CF 3 ) 2 ) 2 (NBu 2 )] + cation. The effect of symmetry on the infrared spectra of the dichloride ion‐pair clusters, as well as deuterated analogues, has been investigated. The D 2h ‐ and C 2h ‐symmetric clusters each exhibit two stretching bands in the infrared at 3427 and 3368 cm −1 for D 2h symmetry and 3444 and 3392 cm −1 for C 2h symmetry, whereas the C 2v ‐symmetric cluster exhibits three bands at 3475, 3426 and 3373 cm −1 . Computational studies were carried out on a [Cl 2 (H 2 O) 2 ] 2− cluster with C 2v symmetry to aid the infrared band assignments.