Reaction of “Non‐Symmetrical” 1,2,4‐Trithiolanes with [(phosphane)Pt 0 (η 2 ‐nbe)] Complexes

Two unsymmetrical 1,2,4‐trithiolanes ( 1d and 1e ) were reacted with [Pt 0 (PPh 3 ) 2 (η 2 ‐nbe)] ( 6 ; nbe=norborn‐2‐ene) and [Pt 0 (dppn)(η 2 ‐nbe)] ( 11 ; dppn=1,8‐bis(diphenylphosphanyl)naphthalene)), respectively. Their treatment with compound 6 resulted in the formation of six‐membered platinacycles of type 7 , which selectively underwent fragmentation into dithiolato complexes and thiobenzophenone ( 4b ). The isolation of the first stable C‐substituted member of this class of compounds (i.e., compound 7e ) permitted kinetic studies of this process by using UV/Vis spectroscopy. These results, together with DFT calculations, allowed us to propose a mechanism for the reactions of compound 6 with 1,2,4‐trithiolanes. In contrast, similar treatment of compound 11 with compounds 1d and 1e at room temperature did not result in any reaction. Heating the appropriate samples to 110 °C led to the formation of dithiolato complexes and η 2 ‐thioketone compounds, thus pointing to a thermally induced [3+2]‐cycloreversion of the heterocycles as an initial step of the reaction.