Crystal Structure of N,N′-Di-tert-Butylurea as a N,O-Donating Ligand

Russian Journal of Coordination Chemistry -     

Interaction of Fluosilicic Acid with <Emphasis Type="Italic">N-tert</Emphasis>-Butyl-Substituted Urea. Crystal Structure of <Emphasis Type="Italic">N,N</Emphasis>-Di-<Emphasis Type="Italic">tert</Emphasis>-butylurea

Fluosilicic acid reacts with solutions of N,N-di-tert-butylurea (DTBU) in methanol or acetone to form crystalline compounds 2DTBU ? H₂SiF₆ and 2DTBU ? H₂SiF₆ ? Me₂CO, which were characterized by the IR and ¹⁹F NMR spectra and mass spectroscopy supplemented by theoretical calculations. According to the data of IR and ¹⁹F NMR spectra, the complexes are hexafluorosilicates of O-protonated DTBU. They undergo hydrolysis in organic media with water traces; their solubility in water is very low (0.10 and 0.14 wt %, respectively). In the DTBU structure, two independent ligand molecules are joined by hydrogen bonds NH?O(N?O) 2.888(5)–2.944(5) Å).     

Crystal Structure of Hexafluosilicates of Protonated Thiosemicarbazide and 2,5-Diamino-1,3,4-thiadiazole Produced in the Reaction of Thiosemicarbazide with Fluosilicic Acid

The structure of the crystal complex (L¹H)₂(L²H)(SiF₆)_1.5(L¹is thiosemicarbazide, L²is 2,5-diamino-1,3,4-thiadiazole) was studied by X-ray diffraction analysis. The complex was prepared by reacting an aqueous solution of L¹with 45% fluosilicic acid. The crystals are monoclinic: a= 16.080(3) Å, b= 5.4860(8) Å, c= 20.079(4) Å, = 91.46(1)°, Z= 4, space group P2/n, R= 0.0427. The components of the ionic structure of the complex are L¹H⁺and L²H⁺cations and SiF^2– ₆anions combined by a system of H bonds of the NH···S and NH···F types, the -nitrogen atom of the hydrazine fragment and the endocyclic nitrogen atom of the heterocycle being the protonation centers in L¹H⁺and L²H⁺, respectively. The bond lengths in the SiF^2– ₆anions range within 1.621(6)–1.691(2) Å.     

NMR Spectra of Guest–Host Complexes of Boron and Silicon Fluorides with Crown Ethers in Nonaqueous Solutions

¹⁹F, ¹¹B, and ²⁹Si NMR spectroscopy was used to examine the behavior of the guest–host complexes (BF₃· H₂O)₂· 18-crown-6 · 2H₂O, (BF₃· H₂O)₂· DCH-6B, and (DCH-6A · H₃O)SiF₅in acetone (DCH-6B and DCH-6A are the cis-anti-cis- and cis-syn-cis-isomers of dicyclohexano-18-crown-6, respectively). It was shown that molecular boron fluoride complexes undergo partial solvolysis in acetone to yield BF₃· acetone as the main product; the ionic pentafluorosilicate complex does not experience significant solvolysis transformations.     

Crystal structure of hydrazine 5-amino-1-benzyl-1,2,3-triazole-4-carboxylate hexafluorosilicate trihydrate

Hydrazine 5-amino-1-benzyl-1,2,3-triazole-4-carboxylate hexafluorosilicate trihydrate (I) is synthesized. The crystal structure of the compound synthesized is determined. Crystals I are monoclinic, a = 13.353(1) Å, b = 21.094(2) Å, c = 20.233(2) Å, β = 94.05(3)°, space group P2₁/c, and R = 0.0584 for 16 601 reflections with I > 2σ(I). In the asymmetric part of the unit cell, four organic cations protonated at the terminal hydrazine nitrogen atoms, two hexafluorosilicate anions, and six water molecules are linked into a three-dimensional framework through hydrogen bonds of the N-H?F, N-H?O, and O-H?F types.     

Hydroxonium Hexafluorosilicate as the Simplest “Hydrate” of Fluosilicic Acid: Unusual Course of Synthesis and Crystal Structure

Russian Journal of Coordination Chemistry -     

Synthesis and Crystal Structure of Isonicotinic Acid Diprotonated Hydrazide Hexafluorosilicate

Russian Journal of Coordination Chemistry -     

Structural Aspects of Fluorosilicic Acid Reaction with Organic Bases

The results of systematic studies into the structures of products formed in reactions between fluorosilicic acid (FSA) and organic bases are presented. Different hydrolytically labile silicon fluoride complexes contained in these products are stabilized. A debatable problem of FSA state in aqueous solutions is discussed in the light of the data obtained.     

Interaction of Fluorosilicic Acid with N,O- and N,S-Ambidentate Organic Bases

Syntheses, structural studies, and thermochemical transformations of fluorosilicic acid complexes with N,O-ambidentate ureas, hydrazides of carboxylic acids, and their thioderivatives are presented in a general form.