Through-space and through-bridge components of chemical bonds

The direct (through-space) and indirect (through-bridge) components of chemical interactions between atomic orbitals are identified in both the Wiberg bond-order formalism and the Orbital Communication Theory of the chemical bond. The illustrative examples using the Hückel description of the conjugated π-bonds in benzene and butadiene are given and the existence of the through-bridge bond between bridgehead carbons in small propellanes is conjectured.