What part does the oxalate ion play in these reactions other than that of a bidentate ligand?

In addition to functioning as a bidentate ligand, the oxalate ion can act as a reducing agent in certain reactions, participating in electron transfer processes. It can also help stabilize metal ions in solution by forming chelates, which can enhance the solubility and bioavailability of metal complexes. Furthermore, the oxalate ion may influence the coordination environment of metal centers, affecting their reactivity and interaction with other substrates.