Three new acid M⁺ arsenates and phosphates with multiply protonated As/PO₄ groups.

ABSTRACT: The crystal structures of caesium dihydrogen arsenate(V) bis[trihydrogen arsenate(V)], Cs(H₂AsO₄)(H₃AsO₄)₂, ammonium dihydrogen arsenate(V) trihydrogen arsenate(V), NH₄(H₂AsO₄)(H₃AsO₄), and dilithium bis(dihydrogen phosphate), Li₂(H₂PO₄)₂, were solved from single-crystal X-ray diffraction data. NH₄(H₂AsO₄)(H₃AsO₄), which was hydrothermally synthesized (T = 493?K), is homeotypic with Rb(H₂AsO₄)(H₃AsO₄), while Cs(H₂AsO₄)(H₃AsO₄)₂ crystallizes in a novel structure type and Li₂(H₂PO₄)₂ represents a new polymorph of this composition. The Cs and Li compounds grew at room temperature from highly acidic aqueous solutions. Li₂(H₂PO₄)₂ forms a three-dimensional (3D) framework of PO₄ tetrahedra sharing corners with Li₂O₆ dimers built of edge-sharing LiO₄ groups, which is reinforced by hydrogen bonds. The two arsenate compounds are characterized by a 3D network of AsO₄ groups that are connected solely via multiple strong hydrogen bonds. A statistical evaluation of the As-O bond lengths in singly, doubly and triply protonated AsO₄ groups gave average values of 1.70?(2)?Å for 199 As-OH bonds, 1.728?(19)?Å for As-OH bonds in HAsO₄ groups, 1.714?(12)?Å for As-OH bonds in H₂AsO₄ groups and 1.694?(16)?Å for As-OH bonds in H₃AsO₄ groups, and a grand mean value of 1.667?(18)?Å for As-O bonds to nonprotonated O atoms.

SUBMITTER: Schwendtner K 

PROVIDER: S-EPMC6681722 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature