Oxo compounds are organic compounds that contain the karbonyl group, C=O. The term thus embraces aldehydes, carboxylic acids, ketones, amides, and esters.
Polydentant ligands contain more co-ordination points (can give more electron pairs) and they form complex ringlike structures (celate complexes) by replacing two or more monodentant ligands. That kind of ligand is EDTA which has 6 co-ordinational points and with metals it creates complexes, always in 1:1 ratio.
This group of metals is distinguished from other metals not by their physical properties, but by their electronic structure. Transition metals are elements characterized by a partially filled d subshell. The First Transition Series comprises scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu). The Second and Third Transition Series include the lanthanides and actinides, respectively.
The transition metals are noted for their variability in oxidation state. Thus, manganese has two electrons in its outside shell and five electrons in the next shell down, and exhibits oxidation states of +1, +2, +3, +4, +5, +6, and +7.
They are also characterised by the fact that well into the series, going from left to right, the properties of the succeeding metals do not differ greatly from the preceding ones.
Generalic, Eni. "Kompleks." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table