The microwave-driven synthesis of a heteropoly blue cluster yields a redox active cluster, [(HPO3)6Mo21O60(H2O)4](8-), templated by six phosphite anions whereby two phosphites template a tri-lucunary {Mo15} Dawson structure, and one templates a {Mo6} ring with two of the three remaining phosphites acting as bridging ligands connecting the ring to the {Mo15}.