The effect of water content in [Pt(NH3)(4)](2+) NaX on the direct synthesis of Pt Chini complexes [Pt-3(CO)(6)](2)(2-) embedded in zeolitic cavities as well as the carbonylation process of PtNaX to the same anionic complex were studied using in situ FTIR and UV-Vis spectroscopies. It was found that the presence of water affects carbonylation route of the Pt tetrammine complexes; low water content makes this carbonylation similar to that of PtNaX. The interplay of water content and active sites needed for its decomposition via WGS reaction is assumed to play the decisive role in the reaction route. The rate of carbonylation is affected by the amount of zeolitic water, which supports migration of Pt species and supplies protons to the charge-compensating species, accelerating thus the carbonylation process. IR wavenumbers of both bridge and on-top bonded CO in platinum Chini complexes depend on the amount of water Ligands.