The isolation, characterisation, gas phase electron diffraction and crystal structure of the thermally stable radical [CF3
CSNSC
CF3]˙
†
Abstract
The first structural characterisation of a heterocyclic free radical in all phases has been achieved. 4,5-Bis(trifluoromethyl)-1,3,2-dithiazol-2-yl, [CF3CSNSC
CF3]˙
4d, a 7π radical, was prepared quantitatively on
CSSC
CF3 (and its oligomers) and CF3
CNSNC
CF3. The reaction chemistry is described. The crystal structure shows radical 4d to be a planar heterocyclic ring which associates in the solid as a diamagnetic tetramer. The structure of the gaseous monomer determined by
CSNSC
R˙ (R = H, CH3 or CF3) given by the
CSNSC
R+ on increase of concentrations of radical is reported, including the isolation of H
CSNSC
CF3˙ at low temperature. The experimental and calculated [UMPW1PW91/6-31+G*] structures of 4d are in good agreement. These and related calculations also support the interpretation of the vibrational and photoelectron spectra, and the thermodynamic properties of 4d, as well as provide possible explanations for the relative stabilities of R
CSNSC
R˙, and imply that the weak intramolecular interactions in 4d in the solid state are largely ionic Sδ+
⋯
Nδ− interactions.