Hydrothermal Synthesis of Two Mixed‐Valence Copper Complexes with Mixed Ligands

Hydrothermal reactions of copper salts with fumaric acid, 1, 10‐phenanthroline or 2, 2‐bipyridine in basic aqueous solution gave rise to two mixed‐valence copper complexes [Cu₄(ophen)₄(fum)] ( 1 ) and [Cu₄(obipy)₄(fum)]·6H₂O ( 2 ) (fum = fumarate dianion, Hophen = 2‐hydroxy‐1, 10‐phenanthroline and Hobpy = 6‐hydroxy‐2, 2′‐bipyridine), which were characterized by single crystal X‐ray analysis. [Cu₄(ophen)₄(fum)] (1) crystallizes in the monoclinic space group P2₁/n, with a = 10.4749(8), b = 13.4210(9), c = 15.1090(10)Å, β = 103.811(3)° Z = 2; [Cu₄(obipy)₄(fum)]·6H₂O ( 2 ) has the triclinic space group P1¯, with a = 10.1302(11), b = 10.4406(12), c = 11.4450(13)Å, α = 84.384(2)°, β = 79.064(2)°, g = 67.734(2)° and Z = 1. The fumaric acid ligand acts as a multi‐dentate bridging ligand in both compounds, 1 and 2 , to link copper atoms into dumbbell structure. During the reactions, 1, 10‐phenanthroline and 2, 2′‐bipyridine ligands are all hydroxylated into ophen and obipy, which provide useful structural evidence for the study on the Gillard mechanism.     

Mixed‐Valence Nickel Bis(azamacrocycle) Compounds with Ghost‐Leg‐type Sheets

The fabrication of so‐called ghost‐leg sheets and their electronic properties is reported. This unique sheet structure is composed of one‐dimensional mixed‐valence nickel chains, which are linked with one another by bis(azamacrocycle) ligands. They are also topologically unique Ni^II/Ni^III mixed‐valence complexes, as confirmed by X‐ray and optical measurements. Moreover, their magnetic susceptibilities indicated two‐dimensional antiferromagnetic behavior following the Fisher 1D chain model with interchain interactions, where spins on Ni^III sites mutually interact antiferromagnetically in the sheets.     

Binuclear,High‐Valent Nickel Complexes: Ni−Ni Bonds in Aryl–Halogen Bond Formation

Metal–metal bonds play a vital role in stabilizing key intermediates in bond‐formation reactions. We report that binuclear benzo[h ]quinoline‐ligated Ni^II complexes, upon oxidation, undergo reductive elimination to form carbon–halogen bonds. A mixed‐valent Ni(2.5+)–Ni(2.5+) intermediate is isolated. Further oxidation to Ni^III, however, is required to trigger reductive elimination. The binuclear Ni^III–Ni^III intermediate lacks a Ni−Ni bond. Each Ni^III undergoes separate, but fast reductive elimination, giving rise to Ni^I species. The reactivity of these binuclear Ni complexes highlights the fundamental difference between Ni and Pd in mediating bond‐formation processes.