Nanoclustered Pt-0 catalysts based on cross-linked macromolecular matrices are evaluated in the hydrogenation of an alpha, beta-unsaturated aldehyde (citral). Matrices and catalysts are characterized by inverse steric exclusion chromatography, scanning electron microscopy, X-ray microprobe analysis, and transmission electron microscopy. The monometallic catalysts exhibit remarkable selectivity for geraniol/nerol when 2-3-nm, regularly shaped, spherical metal nanoclusters are deposited on the Supports from solutions of solvated platinum atoms prepared by metal vapor synthesis (MVS). The immobilization in the polymer framework of ions of a second metal such as Fe(II), Co(II), or Zn(II) enhances the selectivity of the Pt catalysts by up to more than 90%. (C) 2004 Elsevier Inc. All rights reserved.