Charge-Separation-Type Ionic Crystals with Mixed Au^I₄Co^III₂ and Au^I₄Ni^IICo^III Hexanuclear Complexes

Treatment of a digold­(I) metalloligand, [Au^I₂(dppe)­(d-Hpen)₂] (H₂L^Au; d-H₂pen = d-penicillamine, dppe = 1,2-bis­(diphenylphosphino)­ethane), with a 1:1 mixture of Co­(OAc)₂ and Ni­(OAc)₂ under aerobic conditions resulted in the formation of three types of hexanuclear complexes: [Co^III₂(L^Au)₂]²⁺, [Ni^IICo^III(L^Au)₂]⁺, and [Ni^II₂(L^Au)₂]. The addition of NaNO₃, M¹NO₃ (M¹ = K, Rb, Cs), and M²(NO₃)₂ (M² = Ca, Sr, Ba) to the reaction mixture led to co-crystallization of [Co^III₂(L^Au)₂]²⁺ and [Ni^IICo^III(L^Au)₂]⁺ as a solid solution to form the charge-separation (CS)-type ionic crystals 1_Na, 1_M1, and 1_M2, respectively, while [Ni^II₂(L^Au)₂] independently crystallized as a single species (2). In 1_Na, [Co^III₂(L^Au)₂]²⁺ and [Ni^IICo^III(L^Au)₂]⁺ cations assemble in a 1:2 ratio to form a cationic supramolecular octahedron accommodating 4 H₃O⁺ ions, while 10 nitrate ions are packed in each hydrophilic tetrahedral interstice of the crystal to form an anionic adamantane cluster. The overall structures of 1_M1 and 1_M2 are very similar to that of 1_Na, having a CS-type structure composed of cationic supramolecular octahedra with a +12 charge and anionic inorganic clusters with a −10 charge. However, 1_M1 contains M¹ ions in place of the H₃O⁺ ions in 1_Na, and furthermore, a novel rhombic dodecahedron cluster composed of 14 nitrate ions, which encapsulates two M² ions, is formed in each hydrophilic tetrahedral interstice in 1_M2.