Reaction of the Al/P-based frustrated Lewis pair (FLP) Mes 2 P-C(CH-C 6 H 5 )-Al(CMe 3 ) 2 1 with heavier chalcogens (E = S, Se and Te) yielded by oxidation of the P atoms the respective phosphorus(V) compounds Mes 2 P(E)-C(CH-C 6 H 5 )-Al(CMe 3 ) 2 (2a, E =S, 2b, E = Se, 2c, E = Te) in good yield. The chalcogen atoms were coordinated to the Lewis-acidic Al atoms, which, in the case of the dark red Te compound 2c, resulted in a stabilization of the P−Te bond. Unique fourmembered, slightly puckered P-C-Al-E heterocycles were formed with P−E bond lengths in the normal range of terminal chalcogen atoms and comparatively long Al−E bonds, which are consistent with relatively weak Al−E interactions. Both the Se and more pronounced the Te compound formed dimers in the solid state as a result of closed-shell chalcogen−chalcogen interactions. While the Se···Se distance was only slightly shorter than the sum of the van der Waals radii (3.8 Å), the Te···Te separation (3.33 Å) was relatively short and in the characteristic range of significant intermolecular Te···Te interactions, which may result from a double donor−acceptor interaction. Quantum chemical calculations suggested a Te−Te bond energy of about −16.5 kcal/mol. The corresponding oxygen derivative could not be isolated in a pure form, but it may be formed by thermal decomposition of the new FLP adduct 1·ONMe 3 .