The unusual properties of small (1-2 nm) Pt particles within a zeolite support are documented by diffuse reflectance infrared spectroscopy of the metal-carbon bond of linearly adsorbed CO. The wave number of the metal-carbon stretching frequency is found to be about 60 cm-1 higher compared to larger particles (2-3 nm) or to the bulk metal. The stronger bond is attributed to a negative charge on the small metal particles.