On Oxohalogeno Niobates(V) M₂[Nb₃O₅X₇] (M = NH₄, K, Rb, Cs; X = Cl, Br) – New Members of a Compound Family with a Layered Structure

Abstract

The reaction of alkali chlorides MCl with NbOCl 3 yields melts which on cooling solidify under crystallization. In the case of KCl / NbOCl 3 , the pink coloured regulus was investigated by powder-XRD and shown to be biphasic, consisting of K[NbOCl 4 ] (primitive orthorhombic lattice, a ϭ 13.467(2); b ϭ 7.9362(8); c ϭ 14.041(2) Å ) and K 2 [NbOCl 5 ] (F centred cubic lattice, a ϭ 9.8291(2) Å ). To a small amount vapour phase transport occurs and colourless crystals of M 2 [Nb 3 O 5 Cl 7 ] (M ϭ K, Rb, Cs) are deposited in the colder parts of evacuated glass tubes containing molten mixtures of MCl and NbOCl 3 or MCl, Nb 2 O 5 and NbCl 5 in a temperature gradient of 500°C to 450°C for some days. Green crystals of (NH 4 ) 2 [Nb 3 O 5 Br 7 ] are obtained as a by-product in the reaction of NH 4 Br with NbOBr 3 in sealed ampoules at temperatures of 300°C. All compounds are isotypic and belong to the M 2 [Nb 3 O 5 X 7 ] structure type of which (NH 4 ) 2 [Nb 3 O 5 Cl 7 ] was already known (Schweda, 1997) (monoclinic, C2/c, Z ϭ 4,

Coexistence of spin ordering on ladders and spin dimer formation in a new-structure-type compound Sr2Co3S2O3

“…mer -[Co(dien)(NO 2 ) 3 ] (dien = diethylenetriamine)19, [Co(dien) 2 ] X 3  · 2H 2 O ( X  = Cl, Br)20 and mer -[Ni(dien) 2 ][SCN] 2 21 or heteroleptic coordination by N and O in [Cr(HP 2 O 7 )(NH 3 ) 3 (H 2 O)] · 2H 2 O22. For non-complex inorganic materials, the mer -heteroleptic coordination exists in M 2 [Nb 3 O 5 X 7 ] ( M  = NH 4 , K, Rb, Cs; X  = Cl, Br) and in La 6 Ti 2 S 8 O 5 , where the octahedra are composed by a Nb 5+ (Ti 4+ ) ion surrounding by three O 2− and three X − (S 2− ) ions232425. According to powder x-ray diffraction data and theoretical calculations, mer -TaN 3 O 3 octahedera are also reported in diamagnetic γ - and δ -TaON2627.…”