Hydrothermal syntheses and structural chemistry of Mn(II), Co(II) and Ni(II) coordination polymers with xylyl-diphosphonate ligands

The hydrothermal reactions of the appropriate metal salt, a xylyldiphosphonic acid and a secondary organonitrogen chelating ligand yielded a series of coordination polymers of the M(II)/xylyldiphosphonate/(organoimine chelate family) with M(II) represented by Mn(II), Co(II) and Ni(II); the 1,2-, 1,3- and 1,4-isomers of xylyldiphosphonate; and the organoimine chelate present as 2,2'-bipyridine (bpy), o-phenanthroline (o-phen) or tetra-2-pyridinylpyrazine (tpyprz). Several representative structural types were observed related to the constraints imposed by the xylyldiphosphonate ligand: the two-dimensional materials [Mn(bpy)(1,2-HO₃PC₈H₈PO ₃H)] (1), [Mn(o-phen)(1,2-HO₃PC₈H ₈PO₃H)] (4) and [Co(o-phen)(1,2-HO₃PC ₈H₈PO₃H)] (7) constructed from {M ₂(N^N)₂(HO₃PR)₂} clusters linked through the xylyl backbone of the ligands; the network structures of the series [M(bpy)(1,3-HO₃PC₈H₈PO₃H)] (MMn (2), Co (6), Ni (12) and [M(o-phen)(1,3-HO₃PC₈H ₈PO₃H)] (MMn (5) and Co (8)) which consists of {M ₂(N^N)₂(HO₃PR)₂}_n chains linked through the xylyl tethers; and the virtual two-dimensional series [M(N^N)₂(1,4-H₂O₃PC₈H ₈PO₃H₂)(1,4-HO₃PC₈H ₈PO₃H)] (MMn, N^Nbpy (3); MCo, N^No-phen (10); and MNi, N^No-phen (14)) which contain one-dimensional {M(N^N)₂(1,4-H ₂O₃PC₈H₈PO₃H ₂)}_n ²ⁿ⁺ chains hydrogen-bonded to (HO₃PC₈H₈PO ₃H)^2- anions to provide expansion in two dimensions. The unique example of a three-dimensional material is [Co(o-phen)(1,4-HO ₃PC₈H₈PO₃H)] (9). The tpyprz containing compounds [M(tpyprz)(1,2-HO₃PC₈H ₈PO₃H)] (MCo (11), Ni (15)) and [Ni₂(tpyprz)(1, 4-HO₃PC₈H₈PO₃H)]·4H ₂O (16) are one-dimensional.