Pilot applications of Pade-resummed fourth-order many-body perturbation theory to the description of chemical bonds with strong contributions from the interactions of filled d-shells (Au-Au, Au-Hg, and Hg-Hg) are reported. The employed Pade approximants, especially the constrained [0/1, 1] quadratic one, ensure radical improvements of accuracy with respect to the partial summation. The non-separability problem is discussed and bypassed through the direct resummation of perturbative expansions for differential correlation energies. (C) 2010 Elsevier B.V. All rights reserved.