Diffusion-based room temperature syntheses using K8{Ta6O19}·16H2O, d-block metal (M) salts (M = Cu, Zn, or Cd), and the macrocyclic ligand 1,4,8,11-tetraazacyclotetradecane (cyclam) led to crystallization of the three new polyoxotantalates with the composition K4{[Cu(cyclam)]2Ta6O19}·18H2O (I), K4{[Zn(cyclam)]2Ta6O19}·18H2O (II), and {[Cd(cyclam)]4Ta6O19}·19H2O (III). The latter two compounds represent the first polyoxotantalates (POTas) with Zn2+ and Cd2+ centered amine complexes and also the first POTas synthesized using a macrocyclic amine. Compounds I and II are isostructural with two complexes attached to the anionic cluster via Cu–O–Ta respectively Zn–O–Ta bonds. Despite that these two compounds are isostructural, the geometry of the M2+ complexes differs significantly with Cu2+ in a square-pyramidal and Zn2+ in a trigonal-bipyramidal environment. In the structure of III, the Cd2+ cations are in the rare hepta-coordinated monocapped trigonal prismatic geometry covalently linked to the anionic core via Cd–O–Ta bonds. While compounds I and II are quite stable under ambient conditions, III shows a fast loss of crystal water molecules. Temperature-dependent in situ XRD measurements were performed with I demonstrating stepwise structural rearrangements caused by water release.