Question

The pair(s) of complexes wherein both exhibit tetrahedral geometry is(are)
(Note: $py=$ pyridine
Given: Atomic numbers of $Fe,Co,Ni$ and $Cu$ are $26,27,28$ and $29$ , respectively)

• A. ${\left[FeC{l}_4\right]}^{-}$and ${\left[Fe(CO{)}_4\right]}^{2-}$
• B. ${\left[Co(CO{)}_4\right]}^{-}$and ${\left[CoC{l}_4\right]}^{2-}$
• C. $\left[Ni(CO{)}_4\right]$ and ${\left[Ni(CN{)}_4\right]}^{2-}$
• D. ${\left[Cu(py{)}_4\right]}^{+}$and ${\left[Cu(CN{)}_4\right]}^{3-}$

Answer 1

Answer: (A), (B), (D)

(A) ${\left[FeC{l}_4\right]}^{-}$
$F{e}^{+3}=3d^5,C{l}^{-}$ weak field liganol $s{p}^3$
${\left[Fe(CO{)}_4\right]}^{-2}$
$F{e}^{-2}=3d^{8}4s^2$
$CO$ strong field liganol pairing occurs
$F{e}^{-2}=3d^{10}$
hence $s{p}^3$
(B) ${\left[Co(CO{)}_4\right]}^{-}$
$Co=3d^{8}4s^2$
due to $CO$ pairing occurs
Hence $=3d^{10}$
${\left[CoC{l}_4\right]}^{-2}$
$C{o}^{+2}=3d^7$,
$C{l}^{-}$ weak field liganol $s{p}^3$
(D) ${\left[Cu(Py{)}_4\right]}^{+1}$
$C{u}^{+1}=3d^{10},s{p}^3$
${\left[Cu(CN{)}_4\right]}^{-3}$
$C{u}^{+1}=3d^{10},s{p}^3$