Synthesis and Characterization of the Face-Sharing Bioctahedral [Mo₂O₆F₃]^3- Anion

The face-sharing bioctahedral molybdenum(VI) oxide fluoride anion [Mo2O6F3]3- has been isolated in the new compound [Cu(3-apy)4]3(Mo2O6F3)2 (3-apy = 3-aminopyridine) and has been characterized by experimental and computational techniques. Single-crystal X-ray diffraction studies show that the structure of the [Mo2O6F3]3- anion resembles two distorted face-sharing octahedra, each with three short terminal metal−ligand bonds and three long metal−ligand−metal bridging interactions. Aspects of the electronic structure, as well as geometric comparisons of the bond lengths and angles in [Mo2O6F3]3- with those in the similarly distorted [MoO3F3]3- anion, suggest that the six terminal ligand positions of the confacial bioctahedra are occupied exclusively by oxide ligands and that the three bridging sites are occupied by fluorides. Crystal data for [Cu(3-apy)4]3(Mo2O6F3)2: trigonal space group R3̄ (No. 148) with hexagonal axes of a = 13.881(1) Å and c = 31.783(3) Å (Z = 3).