Counter‐Anion‐Regulated Mixed‐Valency of Cobalt(II/III) Centers in a Metallosupramolecular Framework

Abstract

A diamagnetic AuI 4 CoIII 2 hexanuclear complex, [Au4 Co2 (dppe)2 (l-nmc)4 ]2+ ([1L -nmc ]2+ ; dppe=1,2-bis(diphenylphosphino)ethane, l-H2 nmc=N-methyl-l-cysteine), was newly synthesized by the reaction of [Co(l-nmc)2 ]- with [Au2 Cl2 (dppe)] and crystallized with different inorganic anions (X=ClO4 - , NO3 - , Cl- , SO4 2- ) to produce ionic solids ([1L -nmc ]Xn ). Single-crystal X-ray analysis revealed that all the solids crystallize in the chiral space group F432 with a face-centered-cubic lattice structure consisting of supramolecular octahedra of complex cations. The paramagnetic nature of all the solids was evidenced by magnetic susceptibility measurements, showing the variation of the oxidation states of two cobalt centers in [1L -nmc ]n+ from CoII 1.00 CoIII 1.00 for X=ClO4 - or NO3 - to CoII 0.67 CoIII 1.33 for X=Cl- , via CoII 0.83 CoIII 1.17 for X=SO4 2- . The difference in the CoII/III mixed-valences was explained by the difference in sizes and charges of counter anions accommodated in lattice interstices with a fixed volume.