Reactivity Modes of Cp*M-Type Half-Sandwich Dichalcogenolate Complexes with 2,6-Disubstituted Aryl Azides: The Effects of the Metal Center, Chalcogen, and Ligand Moiety on Product Formation

Abstract

Cp*M-type half-sandwich dichalcogenolate complexes bearing either carborane or benzene moieties show diverse reactivity patterns toward two selected 2,6-disubstituted aryl azides under thermal or photolytic conditions. The chalcogen (S and Se) has little effect on the formation of final products. However, the effects of both the metal center and the ligand moiety of the metal precursor on the reactions were significant. Compared to iridium precursor Cp*IrS2C2B10H10 (1a), rhodium and cobalt analogues (1b: Cp*RhS2C2B10H10, 1c: Cp*CoS2C2B10H10) demonstrated no reactivity toward aryl azides. The reaction of Cp*IrSe2C2B10H10 (1d) with 2,6-Me2C6H3N3 led to the clean formation of complex 2 with C(sp3)–H activation of one methyl group of the Cp* ligand and loss of N2 along with the rearrangement of the benzene ring of the original azide ligand, whereas the treatment of Cp*IrS2C6H4 (1e) with 2,6-Me2C6H3N3 under the same reaction conditions gave a 16-electron half-sandwich complex 5 featuring C–N coupling on one methyl group from the Cp* ligand. When 2-Me-6-NO2C6H3N3 was employed, the same reaction patterns for forming products (3 and 6) with the nitro group migrating to the para-position versus the original aryl azide were observed. In addition, the reaction with metal precursor 1d generated another product 4 featuring the exchange of nitro and azido groups, while the reaction with 1e afforded another complex 7 with the formation of the N–NO2 moiety. All new complexes were characterized by spectroscopy methods, and single-crystal X-ray analyses were performed for complexes 2 and 5–7. Furthermore, radical mechanisms for the formation of complexes 2–7 were proposed.