Two mixed valent molybdenophosphates with a tunnel structure closely related to K0.17MoP2O7: Pb2(PbO)2Mo8(P2O7)8 and PbK2Mo8(P2O7)8

Two new mixed valent Mo(III)/Mo(IV) diphosphates containing lead Pb2(PbO)2Mo8(P2O7)8 and PbK2Mo8(P2O7)8 have been synthesized. The [Mo8P16O56]∞ frameworks of these phosphates are closely related to that of K0.17MoP2O7: the MoO6 octahedra and P2O7 groups form two sorts of large eight-sided tunnels. They are occupied in an ordered way by PbO chains and Pb2+ cations in Pb2(PbO)2Mo8(P2O7)8 and by K+ and Pb2+ cations in PbK2Mo8(P2O7)8. It results in different symmetries of these two structures, which are tetragonal and monoclinic, respectively, showing the great flexibility of these mixed frameworks, susceptible to accommodate various species with different sizes. - Graphical abstract: The [Mo8P16O56]∞ framework showing the two kinds of eight-sided tunnels able to accept univalent or divalent ions