shows that redox reactivity of anions may be controlled by heteroleptic coordination in mixed-anion systems. The new disulfide and diselenide-containing products have the ideal composition Sr2MnO2Ch2, but regions with such a composition are found to co-exist in complex intergrowth phases with approximated overall composition Sr2MnO2(Cu,Li)0.5Ch2, modelled using stacking faults in which monoclinic Sr2MnO2Ch2 regions intergrow with parent-type Sr2MnO2Cu1.5S2 slabs. Substantial regions are shown from HAADF-STEM imaging and Li NMR to consist of periodic intergrowths of Sr2MnO2Ch2 and Sr2MnO2(Cu,Li)2S2-type layers which may provide clues to the mechanism of the deintercalation reactions and which suggest that targeted synthesis of perfectly periodic intergrowth phases should be pursued.