Several poly(siloxane)s and a poly(silazane) were bound to gold surfaces by activation of Si-H bonds with cis-[PtCl2(PhCH=CH2)(2)]. Under the reaction conditions used here, adsorption of the poly(siloxane) is observed exclusively in presence of the platinum compound. The resulting ultrathin layers were studied with IR spectroscopy at grazing incidence reflection, X-ray photoelectron spectroscopy, contact angle measurements, and ellipsometry. The layer thicknesses (2.9-5.2 nm) are in the typical range of polymer monolayers adsorbed on gold. The wetting properties of the modified gold substrates correspond to those of the pure polymers, indicating that the gold is covered to a high extent or completely with polymer. The highest contact angles of water (115 degrees) were observed with Si-H-terminated poly(dimethylsiloxane) and are among the highest reported for an ultrathin layer on gold. We assume that the activator cleaves Si-H bonds. The polymers might be bound to the surface by Au-Si bonds or via Pt-Si species.