S–S Bond Activation in Multi‐Copper ­Aggregates Containing Perthiocarboxylato Ligands

Abstract

AbstractThe direct reaction between [Cu(OAc)2·(H2O)]2 and n‐butyldithiocarboxylic acid affords two copper(I) aggregates with dithiocarboxylato, [Cu(S2C‐n‐butyl)]4 (1), and perthiocarboxylato ligands, [Cu(S3C‐n‐butyl)]4 (2), in which the oxidation of dithiocarboxylato ligand is triggered by the CuII centers. The activation of the S–S bond in 2 by two reducing agents, PPh3 and NaBH4, has been investigated both experimentally and by DFT calculations. The successive S–S activation in 2 by reaction with 4 equiv. of PPh3 is a cooperative process, which implies that the intermediate species remain elusive. Such intermediates have been analyzed by DFT calculations, which established that the reactivity of the multi‐copper structures depends on the balance between the interactions in the different coordination spheres imposed on the copper centers and the Cu···Cu distances. Furthermore, weak cuprophilic interactions are conditioned by the orbital orientation imposed by the structure. This implies that these metal–metal interactions are not always found between the pairs of Cu atoms with the shortest distances. Although different products have been isolated depending on the reducing agent, the overall theoretical data indicate that the reagent always attacks the terminal sulfur atom of the perthio group.