The development of modular platforms that can undergo postfunctionalization reactions permits coupling of inorganic clusters with different organic functionalities, thereby expanding the range of key physicochemical properties that are relevant for applications in different areas of science. In this work, a novel hybrid Wells-Dawson polyoxometalate (POM) platform was developed and successfully used for postfunctionalization via a nucleophilic substitution reaction. Two new halogen-functionalized bis-organosilyl Wells-Dawson POMs TBA6[α2-P2W17O61{O(SiC3H6-X)2}] (X = Cl or I) were synthesized, and their coupling with amine substrates was explored in a one-step postfunctionalization reaction. The iodide form of the POM has proven to be much more reactive, and its reaction with a range of primary and secondary amines resulted in a series of new bis-substituted Wells-Dawson POMs with the general formula TBA6[α2-P2W17O61{O(SiC3H6-NR1R2)2}]. Coupling of 18 amines with R1 and R2 groups, which exhibited a wide variety in terms of both chemical nature and bulkiness, was achieved under mild conditions via a catalyst-free approach. Using Na2CO3 as a base in acetonitrile solutions at 55 °C resulted in hybrid products that were obtained in high purity and good yields, after a simple isolation and purification procedure.