Synthesis and chemical properties of metalladithiolene and metalladithiazole rings. Unique reactions due to coexistence of aromaticity and unsaturation

Article abstract of DOI:10.1246/bcsj.72.879

The syntheses and unique chemical properties of metalladithiolene rings (especially in [CpM(S₂C₂R¹R²)]-type complexes) found by our research group are reviewed. The constructions of metalladithiolene rings by one-pot reaction among [CpM(CO)(n)], alkyne, and elemental sulfur and by the reaction between [CpM(CO)n] and sulfur-containing heterocyclic compounds are described. Several ionic and radical substitution reactions are presented. The substitutions by carbon-centered and sulfur-centered radicals occur in the metalladithiolene rings. Benzoyloxy-substitution by dibenzoyl peroxide (BPO) and succinimido-substitution by N-halosuccinimides (NXS) proceed via ionic mechanisms induced by the heterolysis of BPO and NXS in the interaction with the lone pair electrons at the sulfur atoms. These substitutions are due to the aromatic character of the metalladithiolene rings. The unique addition reactions due to the unsaturated character of the metalladithiolene rings are also described. Diazo compounds and azides react with [CpM(S₂C₂R¹R²)]type metalladithiolenes to form alkylidene- and imido-bridges between metal and sulfur. Quadricyclane and dimethyl acetylenedicarboxylate add between metal and sulfur. These addition products undergo a variety of types of dissociation: by heating, illumination, or electrochemical redox.