2) becz. if EAN is more than 36 than complex is act as Reducing agent..

Reducing Agents in Metal Carbonyls

Metal carbonyls are coordination compounds that contain metal atoms and carbonyl ligands. The carbonyl ligands, CO, are known for their ability to donate electrons to the metal center, forming strong metal-carbon bonds. However, in some cases, the carbonyl ligands can also act as reducing agents, donating electrons to other species.

1. [CO(CO)4]-

The anion [CO(CO)4]- is known as tetracarbonylnickelate(II). It contains a nickel atom coordinated by four carbonyl ligands. The negative charge is balanced by a counterion, such as Na+ or K+. The carbonyl ligands in [CO(CO)4]- are not good reducing agents because they are already coordinated to a metal center and are stabilized by the electron-withdrawing effect of the metal atom.

2. [Mn(CO)6]

Hexacarbonylmanganese is a neutral complex that contains a manganese atom coordinated by six carbonyl ligands. The carbonyl ligands in [Mn(CO)6] are not strong reducing agents because they are stabilized by the electron-withdrawing effect of the manganese atom. However, [Mn(CO)6] can be reduced by strong reducing agents, such as sodium amalgam or lithium aluminum hydride, to form lower carbonyl complexes, such as [Mn(CO)5]-

3. [Mn(CO)5]-

Pentacarbonylmanganese is a neutral complex that contains a manganese atom coordinated by five carbonyl ligands. The carbonyl ligands in [Mn(CO)5]- are stronger reducing agents than those in [Mn(CO)6] because the loss of one carbonyl ligand destabilizes the complex and makes the remaining ligands more prone to donation of electrons. [Mn(CO)5]- can be further reduced to form [Mn(CO)4]2- or [Mn(CO)3]-

4. [Cr(CO)6]

Hexacarbonylchromium is a neutral complex that contains a chromium atom coordinated by six carbonyl ligands. The carbonyl ligands in [Cr(CO)6] are not strong reducing agents because they are stabilized by the electron-withdrawing effect of the chromium atom. However, [Cr(CO)6] can be reduced by strong reducing agents, such as sodium amalgam or lithium aluminum hydride, to form lower carbonyl complexes, such as [Cr(CO)5]- or [Cr(CO)4]2-

Overall, the ability of carbonyl ligands to act as reducing agents depends on the nature of the metal center, the number of carbonyl ligands, and the presence of other electron-donating or electron-withdrawing groups.