Strontium nickel and barium nickel selenites: Synthesis and X-ray diffraction parameters

Abstract

A new strontium nickel selenite, Sr2Ni(SeO3)3, was prepared and structurally characterized. The compound crystallizes in triclinic system (space group P\( \bar 1 \), a = 7.2860(10) A, b = 7.581(2) A, c = 8.722(2) A, α = 103.02(2)°, β = 105.580(10)°, γ = 95.260(10)°, Z = 2) and is isostructural to cobalt and copper analogues. The structure of Sr2Ni(SeO3)3 is a three-dimensional framework built of eight-vertex polyhedra [SrO8] and distorted octahedra [NiO6] sharing edges and vertices. The framework channels accommodate selenium atoms bonded to the framework oxygen atoms. The selenite groups SeO3 are pyramidal, which is indicative of high stereochemical activity of the Se(IV) lone pair. The possibility of replacement of some Ni atoms by Cu in Sr2Ni(SeO3)3 was studied. The search for analogous barium phases did not reveal such compounds, but BaM(SeO3)2 phases were found, where M = Co, Ni, or Cu. The unit cell parameters of the new selenite BaM(SeO3)2 were determined: space group Pnma, a = 14.989(5) A, b = 5.439(2) A, c = 7.161(3) A, Z = 4.