A First Approach to Borophosphate Structural Chemistry

Abstract

Borophosphates (intermediate compounds of the system MxOy-B2O3-P2O5-(H2O)) contain complex anionic structures built of BO4, BO3, and PO4 groups and their partially protonated species, respectively. A first approach to the development of a structural chemistry of borophosphates is based on linking principles of the primary building units following the general Line of silicate crystal chemistry. The crystal structures of borophosphates are first divided into anhydrous and hydrated phases. Further gradings are based on the (molar) B:P ratios. The structural chemistry of borophosphate anions already extends from isolated species, oligomers, rings, and chains to layers and frameworks. Additional characteristics are integration of planar BO3 groups, preferred formation of 3-membered rings, and unusual branching of tetrahedral chains. P-O-P linking in borophosphates is not observed up to now

Novel Fundamental Building Blocks and Site Dependent Isomorphism in the First Actinide Borophosphates

“…1 The term "borophosphate" is used to denote phases in which borate groups are directly connected with phosphate groups. Compounds containing isolated borate and phosphate groups are referred to as "borate-phosphate".…”

Crystal structure of dimagnesium (monohydrogenmonophosphate-dihydrogenmonoborate-monophosphate), Mg2[BP2O7(OH)3]

“…According to geometrical aspects (short interatomic O-O contacts) hydrogen bridges are supposed to be located between 01-Ό14 (257 pm) and 02--02 (276 pm) or 016-019 (275 pm), respectively. Based on general principles of borophosphate structural chemistry [2] the terminal corners of the BO4 groups are assumed to be protonated. The metrical transformation by applying matrix (-1 -1 0,1 -1 0,0 0 1 ) results in a pseudo monoclinic space group C2lm, in which the structure can not be refined.…”

NH4[BAsO4F] – a New Layer Fluoro‐boroarsenate with a Silicate Related Topology

“…The quest for structural diversity in framework materials has lead to the use of more uncommon units, e.g. borate BO 4 , together with other oxospecies, for example phosphate PO 4 , to produce a range of new structures [1].…”

“…Borate groups in a 1:1 combination with group 15 oxotetrahedra, such as PO 4 , produce building-blocks isoelectronic with silicates and lead to analogous structures, such as the quartz heterotype BPO 4 [2], chain structures and three-dimensional frameworks [3,4]. This compositional equivalence also holds for the combination of borate groups with arsenate groups, where detailed investigations have only recently started [5].…”

“…As BPO 4 and BAsO 4 are III/V-heterotype variants of quartz SiO 2 [2] the potential for structural similarities among the borophosphates, boroarsenates and classical tectosilicates exists. Where F substitutes, or partially substitutes, for oxygen or hydroxide in the silicates equivalent formulae to families such as the sorosilicates and inosilicates may be derived.…”