A quantum chemistry-like approach has been recently developed in our group to deal with HeN–BC doped helium clusters, where the BC dopant is a conventional diatomic molecule. The central idea is to consider the He atoms as “electrons” while the B and C atoms play the role of the nuclei in standard electronic structure calculations. The procedure provides energies and wavefunctions allowing to perform spectral simulations and, hence, making feasible to do proper comparisons with current experiments. However, because of the large difference of masses of He and electrons, and also to the replacement of Coulomb potentials by molecular interactions, it is worthy to assess to what extent the approximations involved in this model (decoupling of orbital angular momenta of the He atoms from the BC rotation and adiabatic separation of the BC stretch versus the He motions) lead to accurate results. In this work we address these issues on the 4He2–Br2(X) system, containing a couple of bosonic He atoms for which variational calculations can be performed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007