A Discrete Dichloride Tetrahydrate Trapped by a Cyclopropenium Cation: Structure and Spectroscopic Properties

Abstract

A discrete dichloride tetrahydrate cluster, [Cl 2 (H 2 O) 4 ] 2À , was obtained as a salt of the bis(diphenylamino)diethylamino cyclopropenium cation [C 3 (NPh 2 ) 2 (NEt 2 )] + and characterized by single-crystal X-ray diffraction and infrared spectroscopy. This chloride-chloride ion-pair cluster consists of a [Cl 2 (H 2 O) 2 ] 2À 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 gasphase structure. Infrared spectra were also collected on the deuterium analogue [Cl 2 (D 2 O) 4 ] 2À . Computational studies were carried out on gas-phase [Cl 2 (H 2 O) 4 ] 2À to confirm the infrared band assignments in the solid state. The structure and infrared spectrum are consistent with the discrete nature of the cluster.[a] M.

Structures and Spectra of Halide Hydrate Clusters in the Solid State: A Link between the Gas Phase and Solution State

“… Mid‐IR spectra in the O−H stretching region for encapsulated chloride hydrates in the solid state: (a) [Cl(H 2 O)] − ; (b) [Cl 2 (H 2 O)] 2− ; (c) D 2h [Cl 2 (H 2 O) 2 ] 2− ; (d) C 2h [Cl 2 (H 2 O) 2 ] 2− ; (e) C 2v [Cl 2 (H 2 O) 2 ] 2− ; (f) [Cl 2 (H 2 O) 4 ] 2− ; (g) [Cl 2 (H 2 O) 6 ] 2− ; (h) [Cl 4 (H 2 O) 4 ] 4− ; (i) {[Cl(H 2 O)] − } ∞ [6,9,11–14] …”

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

“…We have also reported three other discrete dichloride hydrates: the monohydrate [Cl 2 (H 2 O)] 2− , the tetrahydrate [Cl 2 (H 2 O) 4 ] 2− , and the hexahydrate [Cl 2 (H 2 O) 6 ] 2− (Figures 1c–e, respectively) [17–19] . The monohydrate is not predicted to be stable in the gas phase (the hydrogen bonds are unable to make up for the electrostatic repulsion between the chloride ions), [4,8] whereas dichloride hydrates with at least three waters are predicted to be stable in the gas phase according to ab initio quantum chemical calculations [4,7,8,20] …”

“… The structures of known discrete chloride hydrates (a) [Cl(H 2 O)] − ; (b) [Cl 2 (H 2 O) 2 ] 2− ; (c) [Cl 2 (H 2 O)] 2− ; (d) [Cl 2 (H 2 O) 4 ] 2− ; (e) [Cl 2 (H 2 O) 6 ] 2− [1,9,17–19] …”

“…However, vibrational modes associated only with chloride hydrates can be hard to pinpoint due to the presence of overlapping bands from other species present (e. g. OH and/or NH stretching modes). We have recently reported infrared and far‐infrared band centres for several discrete chloride hydrate species encapsulated within cyclopropenium salts, using a selective deuteration strategy to clearly and uniquely identify the relevant vibrational transitions [1,9,17–19] …”

A Series of Discrete Dichloride Dihydrates: Characterisation and Symmetry Effects

“…Although there is good evidence for the formation of chloride‐chloride ion pairs in aqueous solution,− the number of isolated discrete dichloride hydrate species [Cl 2 (H 2 O) n ] 2− is very limited. We have recently reported examples of the monohydrate and tetrahydrate, as well as having reported a hexahydrate several years ago . There are a few examples of dihydrate clusters, and two of these might be described as discrete: Kleinman reported the first example of a discrete [Cl 2 (H 2 O) 2 ] 2− cluster in 1992 with a fluorinated oxo‐benzoquinolizine and Wang et al .…”