Discrete Oligomers and Polymers of Chloride Monohydrate Can Form in Encapsulated Environments: Structures and Infrared Spectra of [Cl4 (H2 O)4 ]4- and {[Cl(H2 O)]- }∞.

Abstract

A discrete tetrachloride tetrahydrate cluster, [Cl4 (H2 O)4 ]4- , was obtained with a partially-fluorinated triaminocyclopropenium cation, [C3 (N(CH2 CF3 )2 )(NEt2 )(NPr2 )]+ . The cluster consists of a [Cl2 (H2 O)2 ]2- square with each Cl- coordinated by another H2 O bridged to another Cl- . A 1D polymer of chloride monohydrate, {[Cl(H2 O)]- }∞ , was obtained with [C3 (N(CH2 CF3 )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 (H2 O)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.