New Low-Dimensional Zinc Compounds Containing Zinc-Oxygen-Phosphorus Frameworks: Two-Layered Inorganic Phosphites and a Polymeric Organic Phosphinate

Two new zinc phosphites have been prepared by reaction of zinc chloride with either calcium or strontium phosphite in aqueous phosphorous acid. The compounds have been characterized by single-crystal X-ray diffraction techniques. ZnCa(HPO₃)₂(H₂O)₂: P2₁/n, a = 7.131 (2) Å, b = 7.766 (2) Å, c = 14.479 (2) Å, β = 97.30 (2)°, V= 795.3 (3) ų, Z = 4, R(F₀) = 0.045 for 1063 observations (I > 3σ(I)) and 109 variables. ZnSr(HPO₃)₂(H₂O)₂: {formula-omited}, a = 7.728 (2) Å, b = 7.967 (2) Å, c = 7.448 (2) Å, α = 99.56 (2)°, β = 107.93 (2)°, γ = 100.51 (2)°, V= 416.6 (2) Å₃, Z = 2, R(F₀) = 0.034 for 1187 observations (I> 3σ(I)) and 109 variables. Both compounds have layered structures in which the zinc atoms are tetrahedrally coordinated and the Ca or Sr atoms are 8-coordinate. In each case, the interlayer region is lined with water molecules coordinated to the alkaline-earth-metal Ion. The modes in which Ca and Sr bridge the phosphite groups are different, however, resulting in layers with different topographies. These results, together with earlier work on Na⁺, K⁺, and Ba²⁺, are discussed in terms of the effect of the alkali or alkaline-earth metals on the observed structural trends. A new polymeric zinc phenylphosphinate has also been synthesized and its structure determined. Crystal data for ZnO₂PHC₆H₅)₂: C2/c, a = 15.763 (2) Å, b = 11.162 (2) Å, c = 8.272 (2) Å, β = 109.34 (2)°, V = 1373.2 (6) ų, Z = 4, R(F₀) = 0.047 for 480 observations (I > 3σ(I)) and 105 variables. The structure is compared with known phosphinates and phosphonates.