This paper focuses on the intra-zeolite anchoring of platinum carbonyl dianion clusters and their catalytic performances. The synthesis involves the dispersion of PtCl2 vapor followed by reductive carbonylation under a mixed CO and H2O or a CO atmosphere. The characterization of Pt carbonyl dianions was based on a multianalytical approach including powder X-ray diffraction (PXRD), infrared spectroscopy, CO/H-2 gas chemisorption,(CO)-C-13 isotopic exchange, NO interaction, and reversible decarbonylation. The results provide an informative picture for the formation of the intra-zeolite anchoring of [Pt-3(CO)(3)(mu(2)-CO)(3)](n)(2-) (n = 3 or 4) dianions. [Pt-3(CO)(3)(mu(2)-CO)(3)](4)(2-) can be converted into [Pt-3(CO)(3)(mu(2)-CO)(3)](3)(2-) under a H2O or H-2 atmosphere. The decarbonylated [Pt-3(CO)(3)(mu(2)-CO)(3)](4)(2-)/Na56Y shows catalytic activity for methane homologation.