Crystal structures of MnNbOF5 · 4H2O at 153 and 297 K

Crystals of MnNbOF₅ · 4H₂O were studied by X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetry. DSC showed a phase transition in the temperature range of 282 to 296.3 K. The compound is dehydrated in two stages in the temperature ranges of 65–131.1 and 131.1–190°C, two H₂O molecules being removed in each stage. The structure of MnNbOF₅ · 4H₂O was determined at 153 K (α phase; space group P2₁/c) and at 297 K (β phase, space group C2/m). The structure of both phases is formed of the octahedral complexes [NbF₄(O/F)_2/2]^0.5? and [Mn(H₂O)₄(O/F)_2/2]^0.5+ linked by bridging O and F atoms to infinite chains. The isolated niobium-manganese chains are connected by O-H…F hydrogen bonds. In the α phase, the Nb, O, and F atoms in the trans position relative to O are disordered with respect to the inversion center of the structure. Transition to the β phase is accompanied by splitting of all ligand positions at the Nb and Mn atoms into two equally probable positions.     

Synthesis and physicochemical investigation of hexafluoro complexes of germanium with mixed alkali metal cations

Hexafluoro complexes of germanium with mixed alkali-metal cations having the composition formula MM'GeF₆, which crystallize in a rhombic syngony were synthesized. The unit cell parameters of the compounds have been determined. It was found that MM'GeF₆ are biaxial optical crystals, and their optical and refractometric constants are given. It was shown that the substitution of the Na⁺ cation in Na₂GeF₆ by K⁺, Rb⁺, Cs⁺ leads to a varied degree of distortion of the hexafluoro ion. It was found (NMR data) that a change in the dynamic state of the octahedral ions is due to a transition from a restrained rotation to an isotropic one.Institute of Chemistry of the Far-Eastern Scientific Center, Russian Academy of Sciences, 690022 Vladivostok. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2473–2482, November, 1992.     

Complex Ions in Ammonium Hexafluorohafnate: Crystal Structure and Internal Dynamics

The crystal structure of (NH₄)₂HfF₆ was determined using a SMART 1000 CCD diffractometer (MoK radiation, graphite monochromator). The unit cell parameters are a = 13.3902(7) Å, b = 7.6850(4) Å, c = 11.6731(6) Å, space group Pca2₁, and Z = 8; least-square refinement in the anisotropic approximation gave R ₁ = 0.0299 and wR ₂ = 0.0682. The compound is isostructural to (NH₄)₂ZrF₆. The dynamics of the complex ions was examined in the temperature range 200–425 K; the energy of their activation was estimated. It was found that compounds of the (NH₄)₂AF₆ type (A = Zr or Hf) can be classified as superionic conductors at 380 to 425 K.     

Reaction of methyl 3-phenyl-3-chloro-2-oxopropionate with 2-mercapto- and 2-hydroxy-ethanolamines: The products and some of their transformations

It was found that the nature of the SH and OH groups in 2-mercapto- and 2-hydroxyethanolamines plays a decisive role in the reactions between these compounds and methyl 3-phenyl-3-chloro-2-oxopropionate, the products comprising 1,4-thiazine and 1,4-oxazane derivatives, respectively. Some of the reactions of these products were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 250–252, February, 1993.     

Thiophene-2-aldehyde in the Darzens reaction

The reaction of the title compound with dichloroacetic acid esters in the presence of butyllithium gave esters of 3-thienyl-3-hydroxy-2,2-dichloropropionic acid.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center of the Russian Academy of Sciences, 420083 Kazan', Russia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1870–1873, August, 1992.     

The synthesis of esters of phosphinic acids containing heterocyclic radicals

Summary By the interaction of the mono-N- and di-N-oxides of 2,3-di-(w-bromomethyl)-quinoxallne with trialkyl phosphites there was synthesized a series of esters of phosphinic acid containing mono-N- and di-N-oxidoquinoxalinic radicals; some of their properties were studied.