Geometries and vibrational frequencies of complexes of cationic coinage metal clusters M-n(+) (M = Cu, Ag, Au; n = 1-4) and H2S are computed using density functional theory. Thermochemical values for Mn+H2S decomposition channels involving loss of an H atom, H-2 molecule, M atom, or M-2 molecule are also computed. Significantly different results are obtained for closed-shell (n odd) and open-shell (n even) complexes. (C) 2004 Elsevier B.V. All rights reserved.