Question

Which can act as a reducing agent?
A) ${\left[ {Co\left( {C{O_4}} \right)} \right]^ - }$
B) $\left[ {Mn{{\left( {CO} \right)}_6}} \right]$
C) $\left[ {Mn{{\left( {CO} \right)}_5}} \right]$
D) $\left[ {Co{{\left( {CO} \right)}_4}} \right]$

Answer 1

A reducing agent is a compound that loses or "donates" an electron to an electron recipient in a redox chemical reaction. The reducer's oxidation kingdom will increase whilst the oxidizer's decreases; that is expressed through pronouncing that reducers "go through oxidation" and "are oxidized" whilst oxidizers "go through reduction" and "are reduced”. Thus, lowering agents "reduce" oxidizers through reducing their oxidation kingdom whilst oxidizing agents "oxidize" reducers through growing their oxidation kingdom.

Complete answer:
The given options are coordination complexes, so to find out the reducing agent among them we need to find the EAN i.e. effective atomic number which can be calculated by using the formula:
EAN= Atomic number of Central atom- oxidation state of central atom + No. of electron shared or donated.
The total number of electrons present with a central metal atom or ion in a coordination complex plus the electrons donated by the ligands is known as Effective Atomic Number (EAN).
Option A)
This is an incorrect option, EAN$= 27 + 4(2) - 1 = 34$ it cannot act as a reducing agent.
Option B)
This option is correct as $\left[ {Mn{{\left( {CO} \right)}_6}} \right]$ can act as a reducing agent.
EAN$= 25 + 6(2) = 37$
It has one more electron, so it can donate it and act as a reducing agent.
Option C)
This is an incorrect option, as $\left[ {Mn{{\left( {CO} \right)}_5}} \right]$cannot act as a reducing agent.
EAN$= 25 + 5(2) = 35$
Option D)
This is an incorrect option, as $\left[ {Co{{\left( {CO} \right)}_4}} \right]$cannot act as a reducing agent.
EAN$= 25 + 4(2) = 33$

Option B is the correct answer.

Note:
Coordination compounds are chemical substances that include an array of anions or impartial molecules which are sure to a relevant atom through coordinate covalent bonds. Coordination compounds also are called coordination complexes. These molecules or ions which are sure to the relevant atom are called ligands (additionally called complexing agent.