First heterobimetallic Ag^I–Co^III coordination compound with both bridging and terminal –NO₂ coordination modes: Synthesis, characterization, structural and computational studies of (PPh₃)₂Ag^I– (μ-κ²O,O′:κN-NO₂)–CO^III(DMGH)₂(κN-NO₂)

An unusual heterobimetallic bis(triphenylphosphane)(NO₂)Ag^I–Co^III(dimethyl-glyoximate)(NO₂) coordination compound with both bridging and terminal –NO₂ (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)₂(PPh₃)] (DMGH₂ is dimethylglyoxime or N,N′-di-hydroxybutane-2,3-diimine) with excess AgNO₂. In the title compound, namely bis(dimethylglyoximato-1κ²O,O′)(μ-nitro-1κN:2κ²O,O′)(nitro-1κN)bis(triphenyl-phosphane-2κP)cobalt(III)silver(I), [AgCo(C₄H₇N₂O₂)₂(NO₂)₂(C₁₈H₁₅P)₂], one of the ambidentate –NO₂ ligands, in a bridging mode, chelates the Ag^I atom in an isobidentate κ²O,O′-manner and its N atom is coordinated to the Co^III atom. The other –NO₂ ligand is terminally κN-coordinated to the Co^III atom. The structure has been fully characterized by X-ray crystallography and spectroscopic methods. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been used to study the ground-state electronic structure and elucidate the origin of the electronic transitions, respectively.