In the present study, the structural and bonding properties of F--(H-2)(n) and Cl--(H-2)(n) (n = 1-8) anion complexes have been investigated by quantum chemical calculations at the MP2/aug-cc-pVTZ level. The computations gave different global minimum structures for most of the F--(H2), and Cl--(H2), complexes. The strength of the F--H-2 interaction depends strongly, while that of the Cl--H-2 one only marginally on the number of H-2 ligands. Our NBO analysis revealed a considerable charge transfer from the halide ion to the sigma*(H-2) orbital. (c) 2006 Elsevier B.V. All rights reserved.