Problem #6

Get low

Oxidation state is an profound concept in modern chemistry which enables us to predict properties of chemical compounds as well as their structural units. We know a lot about the extremely high oxidation states and how those are stabilised. For instance, in IrO4+ ion reported to exist in the gas phase formal oxidation state of iridium is +9. Theoretically, there may be relatively stable compounds containing Au+11 or Hg+12.
Extremely low oxidation states are also readily accessed. There are examples of compounds which contain an atom in -4 oxidation state such as methane CH4 and certain metal carbonyl complexes, e.g. [Cr(CO)4]4-. Selected intermetallides featuring Group 13 elements with formal -5 oxidation state were reported as well.
Can compounds with even lower oxidation states exist at normal pressure and (273/298) K? Propose a list of such hypothetical substances.
What are the stabilising factors for the ‘super-low’ oxidation states and how do they contribute to stability of the compounds you have suggested?