If the bond length of \(CO\) bond in carbon monoxide is 1.128 Å, then what is the value of \(CO\) bond length in \(Fe(CO)_5\)?

1.15 Å

The correct answer is option 1. 1.15 Å.

The bond length of \(CO\) in \(Fe(CO)_5\) is slightly longer than the bond length of \(CO\) in carbon monoxide. This is because the metal-ligand bonding in \(Fe(CO)_5\) weakens the \(C-O\) bond. The weakening of the \(C-O\) bond is due to the donation of electrons from the filled metal orbitals to the antibonding molecular orbitals of \(CO\). This back bonding, as it is called, increases the electron density on the oxygen atom, which weakens the \(C-O\) bond.

The bond length of \(CO\) in \(Fe(CO)_5\) is typically around 1.15 Å, which is about 2% longer than the bond length of \(CO\) in carbon monoxide.