Coordination Compounds 1 Question 1

1. The coordination numbers of $Co$ and $Al$ in $\left[CoCl(en) _2\right] Cl$ and $K _3\left[Al\left(C _2 O _4\right) _3\right]$, respectively, are (en = ethane-$1, 2$-diamine)

(a) $5$ and $3$

(b) $3$ and $3$

(c) $6$ and $6$

(d) $5$ and $6$

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Answer:

Correct Answer: 1. (d)

Solution:

  1. Key Idea: The total number of ligands to which the metal is directly attached is called coordination number.

The coordination numbers of $Co$ and $Al$ in $\left[Co(Cl)(en) _2\right] Cl$ and $K _3\left[Al\left(C _2 O _4\right) _3\right]$ are $5$ and $6$ respectively.

In first complex, ’en’ is a didentate ligand and ’ $Cl$ ’ is a unidentate ligand.

$\left[Co(Cl)(en) _2\right] Cl$, coordination number $=1+2 \times 2=1+4 \Rightarrow 5$

So, the coordination number is $5$ .

For $K _3\left[Al\left(C _2 O _4\right) _3\right.$ ], ’ $ C _2 O _4^{2-} $ ’ , is a didentate ligand.

Coordination number $=3 \times 2=6$.

Hence, coordination number is $6$ .