Poly[3-methylpyridinium [(μ2-dihydrogen phosphito)bis(μ3-hydrogen phosphito)dizinc]]

The title compound features bifurcated template-to-framework N—H⋯(O,O) hydrogen bonds.

In the extended structure of (I), the constituent ZnO 4 , HPO 3 and H 2 PO 3 polyhedra are linked by Zn-O-P bonds into infinite (010) sheets (Fig. 2).Polyhedral 4-and 8-rings are present and the zinc and phosphorus nodes strictly alternate.The most distinctive building unit is a centrosymmetric 8-ring incorporating two bifurcated 4-rings reinforced by a pair of O9-H1O� � �O4 intra-layer hydrogen bonds (Fig. 3).These are linked by 4-rings involving the Zn2-O6-P2 bonds into [100] chains and crosslinked in the [001] direction by Zn1-O2-P1 bonds into the (010) sheets.The template interacts with the inorganic layers via an unusual bifurcated N1-H1B� � �(O1,O2) link (Fig. 1): the vast majority of template-to-framework hydrogen bonds are associated with a single acceptor O atom.Some weak nonclassical C-H� � �O interactions occur, as listed in Table 1.As is normal, the P-H unit does not participate in hydrogen bonding (Katinaite ˙& Harrison, 2017).There are no aromatic �-� stacking interactions in (I), the shortest centroid-centroid separation being greater than 5.68 A ˚, and inter-layer cohesion must be largely due to van der Waals forces.

Figure 1
The asymmetric unit of (I), expanded to show the complete zinc-atom coordination spheres, showing 50% displacement ellipsoids.[Symmetry codes:

Synthesis and crystallization
Compound (I) was prepared by mixing 0.41 g of ZnO, 0.82 g of H 3 PO 3 and 0.47 g of 3-picoline (Zn:P:template molar ratio ' 1:2:1), which were placed in a 50 ml polypropylene bottle with 20 ml of water and shaken well to result in a white slurry.The bottle was placed in a 353 K oven for 48 h and then removed and allowed to cool to room temperature over about 2 h.The solids were recovered by vacuum filtration to result in a mass of rod-like colourless crystals accompanied by some white solids.IR (diamond window): 3400-2800 cm À 1 (O-H, N-H stretch), 2450 cm À 1 (P-H stretch; Ma et al., 2007).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.The O-bound H atom was located in a difference map and refined as riding in its as-found relative location.The P-, N-and C-bound H atoms were located geometrically (P-H = 1.32,N-H = 0.88 and C-H = 0.95-0.98A ˚) and refined as riding atoms.The methyl group was allowed to rotate, but not to tip, to best fit the electron density.The constraint U iso (H) = 1.2U eq (N, O or P) or 1.5U eq (methyl C) was applied in all cases.Two peaks greater than 1 e A ˚À 3 were found in the final difference map for (I) in the vicinity of the Zn atoms, but they did not correspond to plausible chemical features.

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.
) � for Zn1 and 102.86 (14)-112.73(14) � for Zn2] indicate modest degrees of distortion, with � 4 0 values (Okuniewski et al., 2015) of 0.95 (Zn1) and 0.96 (Zn2), where a value of 1.00 corresponds to a regular tetrahedron.The [HPO 3 ] 2À groups adopt their usual tetrahedral (including the H atom) or pseudo-pyramidal (excluding H) shape and the mean P-O separations are 1.506A ˚for P1 and 1.516A ˚for P2.The O-P-O bond angles around P1 show a larger than typical range of 107.52 (19)-114.3(2) � , with the smallest O1-P1-O2 angle associated with the bifurcated hydrogen bond from the protonated template (Fig. 1), whereas the P2 bond angles are tightly clustered [112.38 (19)-112.74(18) � ].The [H 2 PO 3 ] À dihydrogen phosphite group containing atom P3 includes a notably longer vertex [P3-O9 = 1.543 (3) A ˚] to the protonated O atom.Apart from O9, each O atom in (I) is bonded to one Zn and one P atom: the Zn-O-P bond angles vary from 128.89 ( to April 2024) revealed 217 crystal structures containing zinc cations and hydrogen phosphite anions based on a search for a Zn-O-P-H fragment.Structures containing zinc and a dihydrogen phosphite unit are uncommon with just three examples found, viz.bis(� 2 -data reports 2 of 3 Love-Jennings et al. � (

Figure 2
Figure 2 The unit-cell packing in (I), viewed down [100].Hydrogen bonds are shown as dashed lines.

Table 2
Experimental details.