The coordination numbers of Co and Al in $\left[\mathrm{Co}(\mathrm{Cl})(\mathrm{en})_{2}\right] \mathrm{Cl}$ and $\mathrm{K}_{3}\left[\mathrm{Al}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]$, respectively, are (en = ethane-1,2-diamine)

JEE Main · 2019 · 12 Apr 2019 · Shift 2 · Coordination Compounds

The coordination numbers of Co and Al in

[Co (Cl) (en)_{2}] Cl

and

K_{3} [Al (C_{2} O_{4})_{3}]

, respectively, are
(en = ethane-1,2-diamine)

(A)6 and 6
(B)5 and 3
(C)3 and 3
(D)5 and 6✓ Correct

Answer: (D)

Solution

Coordination number counts the donor atoms actually bonded to the metal. In

[Co (Cl) (en) X_{2}] Cl

the chloride inside the sphere donates once and each ethylenediamine is bidentate, so cobalt has

1 + 2 \times 2 = 5

. In

K X_{3} [Al (C X_{2} O X_{4}) X_{3}]

each oxalate is bidentate, so aluminium has

3 \times 2 = 6

. The coordination numbers are

5

and

6

JEE Main · 2019 · 12 Apr 2019 · Shift 2 · Single correct option

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