274430
The number of bridging $\mathrm{CO}$ ligand(s) and $\mathrm{Co}-$ Co bond(s) in $\mathrm{Co}_{2}(\mathrm{CO})_{8}$ respectively are
1 2 and 0
2 0 and 2
3 4 and 0
4 2 and 1
Explanation:
(D) : The compound is $\mathrm{Co}_{2}(\mathrm{CO})_{8}$. It is a low nudearity carbonyl cluster. Formula for $\mathrm{M}-\mathrm{M}$ Bond: - $A=$ no. of valence $\mathrm{e}^{-}$of metal + no. of $\mathrm{e}^{-}$from each ligand \pm charge $\mathrm{B}=(18 \times \mathrm{n}-\mathrm{A})(\mathrm{n}=$ no. of metal atom $)$ total number of $\mathrm{M}-\mathrm{M}$ bond $(\mathrm{c})=\frac{\mathrm{B}}{2}$ $\therefore$ For $\mathrm{Co}_{2}(\mathrm{CO})_{8}-$ $\mathrm{A}=2(9)+3(2)=18+16=34$ $\mathrm{~B}=2 \times 18-34=2$ $\mathrm{C}=\frac{\mathrm{B}}{2}=\frac{2}{2}=1$ Number of bridging $\mathrm{CO}=2$ Number of $\mathrm{M}-\mathrm{M}$ bond $=1$
