Photoelectron spectra at variable temperatures demonstrate that the rate of thermal isomerization of pyrazoline-5-thione (1 a) into methylthiopyrazole (s) in the gaseous phase is metal catalysed. Similar isomerizations of triazolethione (2 a and 3 a) are at best only slightly so. Furthermore, photoelectron spectra and MNDO calculations show that gaseous methylthiopyrazoles (1 b and 1 c) and methylthiotriazoles (2 b and 2 c) exist ...
