The correct statement(s) regarding the binary transition metal carbonyl compounds is (are)\ (Atomic

Question

The correct statement(s) regarding the binary transition metal carbonyl compounds is (are)\ (Atomic numbers : $\mathrm{Fe}=26, \mathrm{Ni}=28$ )\

Professor PC Thomas Classes · Answer

(b, c) : (a) Total number of valence shell electrons in central metal atom are $\mathrm{Fe}(\mathrm{CO})_{5} ; 8+2 \times 5=18$\ $\mathrm{Ni}(\mathrm{CO}){ }_{4} ; 10+2 \times 4=18$\ (b)Due to the presence of strong field ligand (CO) both complexes are low spin in nature.\ (c)In lower oxidation state, number of electrons in $d$-subshell are higher, so due to $\pi$ - backbonding, electrons from filled $t_{2 g}$ of metal are transferred to vacant $\pi^{\phi}$ of CO which strengthens the $M-\mathrm{C}$ bond in complexes.\(d)In higher oxidation number, metal may have less number of electrons in $d$-orbitals, which decreases the extent of synergic bonding. So, in this case $M-\mathrm{C}$ bond is weaker while $\mathrm{C}-\mathrm{O}$ bond is stronger.\