SYNTHESIS AND STRUCTURES OF 2 ISOSTRUCTURAL PHOSPHITES, FE11(HPO3)8(OH)6 AND MN11(HPO3)8(OH)6

Iron hydroxyphosphite [undecairon octakis(hydrogen-phosphite) hexahydroxide, Fe11(HPO3)8(OH)6] and manganese hydroxyphosphite [undecamanganese octakis(hydrogenphosphite) hexahydroxide, Mn11(HPO3)8(OH)6] were prepared hydrothermally in Teflon-lined steel autoclaves at 458 K. The compounds are isostructural with Zn11(HPO3)8(OH)6. The structure contains highly distorted MO6 octahedra, which share a common face to form M2O9 dimers. These dimeric units link together through two common edges to give infinite chains of dimers running along the [001] direction. Each chain is connected to four other such chains, by corner sharing, to form an open structure containing two types of channel, both of which run parallel to the c axis. One channel is triangular and occupied by one quarter of the phosphite groups, the other is hexagonal and lined by the remaining three quarters.