The bonding order of multiply bonded main-group elements is conventionally thought to be limited to triple bonds. Now, using high-level theoretical methods, it is shown that C2 and its isoelectronic molecules CN+, BN and CB− are quadruply bonded, featuring not only one σ - and two π-bonds, but also one weak ‘inverted’ bond.
- Sason Shaik
- David Danovich
- Philippe C. Hiberty