Among $\mathrm{V}(\mathrm{CO})_6, \mathrm{Cr}(\mathrm{CO})_5, \mathrm{Cu}(\mathrm{CO})_3,…
Among $\mathrm{V}(\mathrm{CO})_6, \mathrm{Cr}(\mathrm{CO})_5, \mathrm{Cu}(\mathrm{CO})_3, \operatorname{Mn}(\mathrm{CO})_5, \mathrm{Fe}(\mathrm{CO})_5,\left[\mathrm{Co}(\mathrm{CO})_3\right]^{3-},\left[\mathrm{Cr}(\mathrm{CO})_4\right]^{4-}$, and $\operatorname{Ir}(\mathrm{CO})_3$, the total number of species isoelectronic with $\mathrm{Ni}(\mathrm{CO})_4$ is ________.
[Given, atomic number: $\mathrm{V}=23, \mathrm{Cr}=24, \mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27, \mathrm{Ni}=28, \mathrm{Cu}=29, \mathrm{Ir}=77$]
Solution
In case of complexes, isoelectronic species should be those having same effective atomic number (EAN)
$\mathrm{Ni}(\mathrm{CO})_4 \Rightarrow 28+4 \times 2=36$
(i) $\mathrm{V}(\mathrm{CO})_6 \Rightarrow 23+2 \times 6=35$
(ii) $\operatorname{Cr}(\mathrm{CO})_5 \Rightarrow 24+2 \times 5=34$
(iii) $\mathrm{Cu}(\mathrm{CO})_3 \Rightarrow 29+2 \times 3=35$
(iv) $\mathrm{Mn}(\mathrm{CO})_5 \Rightarrow 25+2 \times 5=35$
(v) $\mathrm{Fe}(\mathrm{CO})_5 \Rightarrow 26+2 \times 5=36$
(vi) $\left[\mathrm{Co}(\mathrm{CO})_3\right]^{3-} \Rightarrow 27+3+2 \times 3=36$
(vii) $\left[\mathrm{Cr}(\mathrm{CO})_4\right]^{4-} \Rightarrow 24+4+2 \times 4=36$
(viii) $\left[\operatorname{Ir}(\mathrm{CO})_3\right] \Rightarrow 77+2 \times 3=83$