Metallophilic interactions in dimeric and trimeric [X-M-PH3](n) (n = 2-3) complexes are studied using density functional and second order Moller Plesset perturbation theory together with energy-consistent, small-core scalar-relativistic pseudopotentials and corresponding large sized valence basis sets. A many-body decomposition of the interaction energy shows that the three-body contribution to the metallophilic interaction is repulsive at all levels of theory and non-negligible. However, the two-body contribution of the two end units dominates over the three-body effect, giving a net stabilizing effect in the metal metal interaction from the dimer to the trimer, and resulting in a further contraction of the trimer metal-metal bond. (c) 2008 Elsevier B. V. All rights reserved.