We have applied a newly developed energy and density decomposition scheme to the study of unsupported multiple metal–metal bonds between two Group 6D transition elements. The new scheme combines the extended transition state (ETS) energy decomposition method (Ziegler and Rauk, Theor. Chim. Acta 1977, 46, 1) with the natural orbitals for chemical valence (NOCV) density decomposition theory (Michalak et al., J. Phys. Chem. A 2008, 112, 1933) within a single framework. The ETS–NOCV scheme is here applied to the quadruply metal–metal bonded complexes L2L′2MML2L′2 (1σ2π4δ2) and L3MML3 with a metal triple bond(1σ2π4). © 2012 Wiley Periodicals, Inc.