Three new acidM⁺arsenates and phosphates with multiply protonated As/PO₄groups

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.

Synthesis and crystal structure of (NH4)[Ni3(HAsO4)(AsO4)(OH)2]

“…The As V atom in (I) is tetrahedrally coordinated by oxygen atoms, spanning a range from 1.679 (10) to 1.701 (6) A ˚. Contrary to expectations (Schwendtner & Kolitsch, 2019), the longest As-O bond is not associated with the OH functionality (O2), which instead shows the shortest of all As-O bonds and is located at the apex of the tetrahedron pointing away from the hexagonal layer. Apart from the bonded H atom, O2 solely belongs to the arsenate group and is not shared with other building blocks.…”

The Pnictogen Bond: The Covalently Bound Arsenic Atom in Molecular Entities in Crystals as a Pnictogen Bond Donor

“…In the case of ammonium dihydrogen arsorate arsoric acid (CSD ref. HORWET [ 189 ]), there are a variety of As···O contacts; one of them has an r (As···O) = 3.476 Å and ∠O–As···O = 178.2° and occurs between two negative sites (Type-III). Similarly, one of the significantly distorted crystals identified was that of bis(tetra- n -butylammonium) octakis( m -hydroxo)-octadecakis( m -pyrazolato)-pentadeca-copper diarsenate (bromobenzene nitrobenzene solvate), [C 54 H 62 Cu 15 N 36 O 8 4+ , 2(C 16 H 36 N + ), 2(AsO 4 3− )]·2(C 6 H 5 Br)·2(C 6 H 5 NO 2 ), CSD ref LUDZOB [ 190 ], with r (O–As···O) = 3.320 Å and ∠O–As···O = 179.3°.…”