 Quadruple bond

A formal fourfold bond. In the familiar d-metal example, one sigma bond, two pi bonds and one delta bond are occupied, giving the configuration ${\sigma }^2{\pi }^4{\delta }^2$ and formal bond order four.

A quadruple bond is a type of chemical bond that involves the sharing of four pairs of electrons between two atoms. This bond type is relatively rare and is typically found in certain transition metal complexes. In a quadruple bond, the bond can be conceived as comprising: 1. **One sigma (σ) bond**: A sigma bond is formed by the head-on overlap of atomic orbitals.