We present here the first results that show the different thermal stabilities of the complex (eta(6)-benzene) tricarbonylchromium(0), [Cr(eta(6)-C6H6)(CO)(3)], when anchored at different sites inside the alpha-cages of zeolite Na56Y, sites 1 and 2. When the system is heated under dynamic vacuum, the complex anchored at site 1, in which the interactions C-6 H-6-Na+ and Na+-OC are stronger, decomposes slower than the complex anchored at site 2, in which such interactions are weaker. When the system is heated under static vacuum, the rates of decomposition of the complex anchored in both sites are comparable. The complex inside Na56Y is less stable than the same complex in the solid state.15179