Question

If the bond length of $CO$ bond in carbon monoxide is $1.128\mathring{A},$ then what is the value of $CO$ bond length in $Fe(CO{)}_5?$

• A. $1.15\mathring{A}$
• B. $1.128\mathring{A}$
• C. $1.72\mathring{A}$
• D. $1.118\mathring{A}$

Answer 1

Answer: (A)

In $CO$, bond order $=3$. In metal carbonyls like $Fe(CO{)}_5,$ due to $d\pi -p\pi$ back-bonding, bond order of $CO$ decreases slightly therefore, bond length increases slightly