NaMn(6)(P(2)O(7))(2)(P(3)O(10)) and KCd(6)(P(2)O(7))(2)(P(3)O(10))

The crystal structures of two new diphosphates, sodium hexamanganese bis(diphosphate) triphosphate, NaMn(6)(P(2)O(7))(2)(P(3)O(10)), and potassium hexacadmium bis(diphosphate) triphosphate, KCd(6)(P(2)O(7))(2)(P(3)O(10)), confirm the rigidity of the M(6)(P(2)O(7))(2)(P(3)O(10)) matrix (M is Mn or Cd) and the relatively fixed dimensions of the tunnels extending in the a direction of the unit cell. The compounds are isomorphous; the P(2)O(7)(4-) anion and the alkali metal cations lie on mirror planes. Bond-valence analysis of the bonding details of the atoms found within the tunnels permits a prediction of the conductivity.