Discrete Oligomers and Polymers of Chloride Monohydrate Can Form in Encapsulated Environments: Structures and Infrared Spectra of [Cl4(H2O)4] 4– and {[Cl(H2O)]–}∞

Abstract

A discrete tetrachloride tetrahydrate cluster, [Cl4(H2O)4]4−, was obtained with a partially-fluorinated triaminocyclopropenium cation, [C3(N(CH2CF3)2)(NEt2)(NPr2)]+. The cluster consists of a [Cl2(H2O)2]2− square with each Cl− coordinated by another H2O bridged to another Cl−. A 1D polymer of chloride monohydrate, {[Cl(H2O)]−}∞, was obtained with [C3(N(CH2CF3)2)2(NBuMe)]+. The tetrameric and polymeric structures were found to be computationally-unstable in the gas phase which indicates that an encapsulated environment is essential for their isolation. DFT and DFTB calculations were carried out on gas-phase [Cl4(H2O)4]4− to assist the infrared assignments. Anharmonically-corrected B3LYP transition frequencies were in close agreement with experiment, but DFTB models were only appropriate for qualitative interpretation. Solid-state DFTB calculations allowed the vibrational modes to be assigned. The results found are consistent with “discrete” chloride hydrates.