The first silver catechol complexes: Crystal structures of triphenylphosphine stabilized silver tetra-bromo and tetra-chloro-catechols

We report the solid-state structures of the first verifiable silver complexes containing bound catechol ligands, Ag(Br4C6(OH)O)(Ph3P)2 and Ag(Cl4C6(OH)O)(Ph3P)2. Only highly electron-withdrawing groups, such as tetra-substituted catechols coupled with triphenylphosphine stabilizing ligands, can be used to obtain stable silver catechol complexes. Without these features, the silver is too readily reduced to the metal. In both cases where the halide is either chloride or bromide, only one of the catechol oxygens is coordinated to the silver along with the ortho-halogen, which forms the chelate ring with the metal. The second phenolic group is not involved with the coordination of the metal. Additional hydrogen bonding between the catechol groups provides for the formation of dimeric species in the solid state.

Graphical abstractThe solid-state structures of the first verifiable silver complexes containing bound catechol ligands, Ag(Br4C6(OH)O)(Ph3P)2 and Ag(Cl4C6(OH)O)(Ph3P)2, are reported. In both complexes, only one of the catechol oxygens is coordinated to the silver along with the ortho-halogen, which forms the chelate ring with the metal. Additional hydrogen bonding is observed between the catechol groups to form a dimeric species in the solid state.Figure optionsDownload full-size imageDownload as PowerPoint slide