Photochemical Unmasking of 1,3‐Dithiol‐2‐ones: An Alternative Route to Heteroleptic Dithiolene Complexes from Low‐Valent Molybdenum and Tungsten Precursors

Abstract

Mono‐dithiolene complexes [Mo(CO)2(dt)(dppe)] and [W(CO)2(dt)(dppe)] {dt = cyclohex‐1‐ene‐1,2‐dithiol; 5,6‐dihydro‐2H‐pyran‐3,4‐dithiol and dppe= 1,2‐bis(diphenylphosphino)ethane} were synthesized by a photochemical procedure. The typical basic de‐protection of the dithiolene ligand precursor was replaced by a light‐induced opening of the 1,2‐dithiole‐2‐one moiety. Advantages of this targeted approach comprise higher yields, cleaner transformations, and the possibility to continuously and precisely monitor the reaction progress. The light induced pericyclic reaction of the protection group releases carbon monoxide with formation of a 1,2‐dithione, which is capable of oxidizing the electron rich metal precursor due to its non‐innocence character. This procedure works well with molybdenum(0) and tungsten(0) precursors and particularly well with dithiolene ligands bearing aliphatic backbones, which are typically and notoriously difficult to handle when applying strictly chemical procedures.