Formation, Expansion, and Interconversion of Metallarings in a Sulfur-Bridged AuICoIII Coordination System


  • This work was supported in part by Grants-in-Aid for Science Research (23350026) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (T.K.).


A novel AuICoIII coordination system that is derived from the newly prepared [Co(D-nmp)2] (1; D-nmp=N-methyl-D-penicillaminate) and a gold(I) precursor AuI is reported. Complex 1 acts as a sulfur-donating metallaligand and reacts with the gold(I) precursor to give [Au2Co2(D-nmp)4] (2), which has an eight-membered AuI2CoIII2 metallaring. Treatment of 2 with [Au2(dppe)2]2+ (dppe=1,2-bis(diphenylphosphino)ethane) leads to the formation of [Au4Co2(dppe)2(D-nmp)4]2+ (32+), which consists of an 18-membered AuI4CoIII2 metallaring that accommodates a tetrahedral anion (BF4, ClO4, ReO4). In solution, the metallaring structure of 32+ is readily interconvertible with the nine-membered AuI2CoIII metallaring structure of [Au2Co(dppe)(D-nmp)2]+ (4+); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au[BOND]S and Au[BOND]P bonds, which is essential for metallaring expansion and contraction.