Calcium hexa-kis(dihydrogen-phosphito)-stannate(IV), Ca[Sn(H2PO2)6], with some remarks on the so-called Ge2(H2PO2)6 structure type.

The title compound, Ca[Sn(H2PO2)6], was formed after a few days when tin(II) fluoride was allowed to react with phosphinic acid at ambient conditions. The structure consists of chains of Ca(2+) and Sn(4+) cations in octa-hedral sites with -3 symmetry bridged by bidentate hypophosphite anions. The chains are hexa-gonally close packed along [001]. The discovery of the compound and the successful structure refinement provides strong evidence that an isostructural compound, originally described as the mixed-valence compound, Ge2[H2PO2]6 [Weakley (1983 ▶). J. Chem. Soc. Pak. 5, 279-281], must be reformulated as Ca[Ge(H2PO2)6].