Chemistry - Coordination Chemistry Question with Solution | TestHub

In synergic bonding, the metal donates electrons into the ${\pi }^{\ast }$ antibonding orbital of carbon monoxide (CO). This back-donation increases the $M-C$ bond order (making it stronger) and decreases the $C-O$ bond order (making it weaker). Consequently, the $C-O$ bond length increases and its vibrational frequency ($\nu$) decreases.