Formation, Expansion, and Interconversiori of Metallarings in a Sulfur-Bridged Au~ICo~(III) Coordination System

摘要

A novel Au~ICo~(III)coordination system that is derived from the newly prepared [Co(p-nmp)]~-(I~-; D-nmp = N-methyl-D-penicillaminate) and a gold(I) precursor Au~I is reported. Complex 1~-acts as a sulfur-donating metallaligand and reacts with the gold(I) precursor to give [Au2Co2(p-nmp)4] (2), which has an eight-membered Au~I2Co~(III)2 metallaring. Treatment of 2 with [Au2(dppe)2]~(2+) (dppe = l,2-bis(diphenyl-phosphino)ethane) leads to the formation of [Au4Co2(dppe)2-(D-nmp)4]~(2+) (3~(2+)), which consists of an 18-membered Au~(I)4Co~(III)2 metallaring that accommodates a tetrahedral anion (BF4~-, ClO4~-, ReO4~-). In solution, the metallaring structure of 3~(2+) is readily interconvertible with the nine-membered Au~I2Co~(III) metallaring structure of [Au2Co(dppe)(u-nmp)]~+ (4~+); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the AuS and Au~P bonds, which is essential for metallaring expansion and contraction.