Question

The most stable complex among the following is

• A. $[Pd(CN{)}_4{]}^{4-}$
• B. $[Fe(CO{)}_5]$
• C. $[Ni(CN{)}_4{]}^{4-}$
• D. $[Ni(CN{)}_4{]}^{3-}$

Answer 1

Answer: (B)

Stability of a complex depends upon the strength of ligand and charge of the central metal ion.
Stability of complex $\propto$ strength of ligand $\propto$ charge of central metal ion.
Among the given complexes, in $[Ni(CN{)}_4{]}^{3-},$ the charge of central metal ion is highest, i.e., + 1 while CO is the strongest field ligand. Hence, $[Fe(CO{)}_5]$ is the most stable complex among the given complexes.