The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysis. Lutetium, ytterbium, cerium(III), scandium, gadolinium, terbium, dysprosium, holmium, erbium, and thulium florides can be hydrolyzed in 30 min or less. Yttrium, lanthanum, praseodymium, neodymium, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U₃O₈), chromium(III) oxide, and a mixture of these oxides have been used successfully to reduce the tune required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium and neodymium.     

The Gas Chromatographic Separation of Volatile Fluorides Using a Hydrogen Diffusion Flame as Detector

Abstract

An account is given of the preparation, separation and detection of volatile fluorides. These fluorides are formed by the reaction of chlorine trifluoride with the elements in a specially designed PTFE reaction vessel enclosed in an HF coil. A comparison is also made of a spectroscopic detector with a katharometer for the detection of the fluorides.

The separation of volatile fluorides has been reported to be partially successful on perfluorinated materials such as Kel-F oils or waxes on PTFE supports.^1–3 The present communication describes a more detailed investigation of these separations and also compares the performance of a newly developed spectroscopic detector⁴ with a conventional katharometer detector.     

FeO(OH)@C-Catalyzed Selective Hydrazine Substitution of p-Nitro-Aryl Fluorides and their Application for the Synthesis of Phthalazinones

An efficient hydrazine substitution of p-nitro-aryl fluorides with hydrazine hydrates catalyzed by FeO(OH)@C nanoparticles is described. This hydrazine substitutions of p-nitro-aryl fluorides bearing electron-withdrawing groups proceeded efficiently with high yield and selectivity. Similarly, hydrogenations of p-nitro-aryl fluorides containing electron-donating groups also smoothly proceeded under mild conditions. Furthermore, with these prepared aryl hydrazines, some phthalazinones, interesting as potential structures for pharmaceuticals, have successfully been synthesized in high yields.     

Thiophosphonigsäurefluoride (Organofluorphosphansulfide)

Phosphinothioic Acid Fluorides Representatives of the phosphinothioic acid fluorides, RPFHS, are produced by reaction of hydrogen sulfide with phosphonous fluorides. — ¹⁹F- and ³¹P-NMR data of some phosphonamidous fluorides are reported.     

XAFS analyses of molten metal fluorides

X-ray absorption fine structure studies of molten metal fluorides containing the materials related to nuclear engineering are intensively summarized. By using XAFS spectra data of divalent and trivalent cation metal fluorides in molten state which have been collected by authors’ group for a few years, local structure have been extracted and discussed systematically in conjunction with other spectroscopic studies and numerical calculations. In molten divalent fluorides, tetrahedral coordination of fluorides around a cation is predominant. In the case of pure molten trivalent fluorides, structure with more than 6-coordination has been suggested in some cases, but octahedral coordination structure is much stabilized at heavier rare earth metal fluorides. By mixing with alkali metal fluorides, it is a general trend that inter-ionic distances keep constant, but coordination number of fluorides decreases. In experimental chapter, all the details of sample preparation, furnace installation, X-ray optics setups and data analyses procedures are explained. Finally, future expectations of XAFS technique are also suggested.     

An easy access to nanocrystalline alkaline earth metal fluorides – just by shaking

High energy ball milling as fast, direct and solvent free method allows an easy access to nanocrystalline alkaline earth metal fluorides MF₂ (M: Mg, Ca, Sr, Ba). Comparable metal sources (acetates, carbonates, hydroxides, alkoxides) were used for the reaction with NH₄F as fluorinating agent. Even very simple manual shaking experiments between NH₄F and the corresponding hydroxides in the stoichiometric ratio (M:F = 1:2, M: Ca, Sr, Ba) give phase pure fluorides. Moreover, comparable classical thermal reactions in closed crucibles at higher temperatures provide phase pure crystalline fluorides in nearly all cases as well.     

Synthesis of Highly Enantioenriched Sulfonimidoyl Fluorides and Sulfonimidamides by Stereospecific Sulfur–Fluorine Exchange (SuFEx) Reaction

Sulfonimidamides present exciting opportunities as chiral isosteres of sulfonamides, with potential for additional directional interactions. Here, we present the first modular enantioselective synthesis of sulfonimidamides, including the first stereoselective synthesis of enantioenriched sulfonimidoyl fluorides, and studies on their reactivity. A new route to sulfonimidoyl fluorides is presented from solid bench-stable, N-Boc-sulfinamide (Boc=tert-butyloxycarbonyl) salt building blocks. Enantioenriched arylsulfonimidoyl fluorides are shown to be readily racemised by fluoride ions. Conditions are developed, which trap fluoride and enable the stereospecific reaction of sulfonimidoyl fluorides with primary and secondary amines (100 % es, es=enantiospecificity) generating sulfonimidamides with up to 99 % ee. Aryl and alkyl sulfonimidoyl fluoride reagents are suitable for mild late stage functionalisation reactions, exemplified by coupling with a selection of complex amines in marketed drugs.     

Arenesulfonyl Fluoride Synthesis via Copper‐free Sandmeyer‐type Fluorosulfonylation of Arenediazonium Salts

The limited availability of highly valuable arenesulfonyl fluorides seriously hinders their further application in many research fields including medicinal chemistry and chemical biological, organic synthesis, polymer preparation, etc. We report herein a mild and efficient copper‐free Sandmeyer‐type fluorosulfonylation reaction of various arenediazonium salts to prepare valuable arenesulfonyl fluorides using K₂S₂O₅ as both a reductant and a practical sulfonyl source in combination with N‐fluorobenzenesulfonimide as an effective fluorine source. This methodology provides an attractive route to diverse important arenesulfonyl fluorides given the overall practicality and scope.     

Recent Advances in the Synthesis and Transformation of Carbamoyl Fluorides,Fluoroformates, and Their Analogues

Carbamoyl fluorides, fluoroformates, and their analogues are a class of important compounds and have been evidenced as versatile building blocks for the preparation of useful molecules in organic chemistry. While major achievements were made in the synthesis of carbamoyl fluorides, fluoroformates, and their analogues in the last half of 20^th century, an increasing number of reports have focused on using O/S/Se=CF₂ species or their equivalents as the fluorocarbonylation reagents for the direct construction of these compounds from the parent heteroatom-nucleophiles in recent years. This review mainly summarizes the advances in the synthesis and typical application of carbamoyl fluorides, fluoroformates, and their analogues by the halide exchanges and fluorocarbonylation reactions since 1980.     

Fast Ion Conducting Nanocrystalline Alkaline Earth Fluorides Simply Prepared by Mixing or Manual Shaking

Simple mixing or shaking of alkaline earth hydroxides with ammonium fluoride results in nanocrystalline phase pure metal fluorides MF₂ (M: Ca, Sr, Ba). The formation of the alkaline earth fluorides was investigated by varying the reaction conditions. Evidence was found that just the contact between the starting materials is sufficient for the reaction to take place. X‐ray diffraction, elemental analysis, ¹⁹F MAS NMR spectroscopy, and measurements of DC conductivities were used to characterize the fluorides regarding properties like crystal structure, crystallite sizes, local fluorine coordination, and fluorine ion conductivity. The ¹⁹F MAS NMR spectra of the phase pure fluorides prepared showed several signals, which were assigned to defects, impurities, or geometric distortions. The fluorides prepared by mixing or shaking revealed fluorine ion conductivities several orders of magnitude higher than observed for the respective microcrystalline alkaline earth fluorides. Therefore, the synthesis routine presented in this study may open a path to a very quick and simple synthesis of nanocrystalline fast fluorine ion conductors.     

Zur reaktionvon cyclotri- und cyclotri- und cyclotetrasilazanen mit silylfluoriden

Fluorosilyl substituted cyclosilazanes are formed by treating lithium salts of hexamethylcyclotri- and octa-methylcyclotetrasilazanes with silicon tetrafluoride and organo-substituted silicon fluorides. Disubstituted compounds are obtained by the reaction of dilithium hexamethylcyclotrisilazane with silicon fluorides or by the reaction of lithium hexamethylcyclotrisilazane with silicon fluorides at higher temperature. Cyclosilazanes with bulky ligands react with butyllithium with elimination of butane as a first step and then react further with a silicon fluoride compound, with LiF-elimination, to give a mixed substituted cyclosilazane. Ring coupling through a silicon bridge is achieved by the reaction of a fluorosilyl-substituted cyclotrisilazane with lithium hexamethylcyclotrisilazane. The mass,¹H and¹⁹F NMR spectra of the compounds are reported.     

Non-aqueous sol-gel synthesis of nano-structured metal fluorides

This review summarises the progress, achieved in the last 5 years, in the field of synthesis of nano-structured metal fluorides. The main focus is laid on the non-aqueous sol-gel-synthesis, which is opening a wide window toward nanoscopic metal fluorides with properties remarkably different from that of crystalline metal fluorides. Based on examples of binary as well as complex metal fluorides prepared via this new sol-gel-route it will be shown how the physical properties of nanoscopic compounds deviate from their macroscopic counterparts.     

Synthesis of acylphosphine sulfides by rhodium-catalyzed reaction of acid fluorides and diphosphine disulfides

A rhodium complex catalyzed the reaction of acid fluorides and tetraethyldiphosphine disulfide giving acylphosphine sulfides. Aromatic acid fluorides with electron donating p-groups reacted smoothly giving the products in high yields. Aliphatic acid fluorides with secondary and tertiary α-carbons were also converted to alkanoylphosphine sulfides, whereas the reaction of a substrate with an α-methylene carbon was accompanied by enol ester formation.     

Novel synthetic route to fluorofullerenes: reaction with binary and complex lead fluorides

We have recently developed methods of preparation of fluorofullerenes with specific fluorine content. Our previous successful synthesis of C₆₀F₃₆ and C₆₀F₁₈ with the use of transition metal fluorides inspired us to probe other high oxidation metal fluorides. In this work we report on the use of the binary lead fluorides (PbF₂, PbF₄, Pb₂F₆) and their complexes with alkali metal and alkaline earth metal fluorides (M₂PbF₆, M₃PbF₇ and M′PbF₆) as fluorinating reagents for fullerenes.     

Alumina-accelerated methanolysis and hydrolysis of acyl and phosphoryl fluorides

We have discovered that Woelm chromatographic γ-alumina substantially accelerates hydrolysis (and methanolysis) of acyl and phosphoryl fluorides. Compared to the corresponding $\text{homogeneous}$ reactions, these $\text{heterogeneous}$ alumina-promoted reactions occur about 250–350 times faster for acyl fluorides and about 1800–3000 times faster for phosphoryl fluorides.     

Über die eigenionisation der halogenfluoride

A model is given for the self-ionization of halogen fluorides, in particular for bromine trifluoride, and the arguments for and against the self-ionization are critically discussed. From our work and based on ¹⁸F tracer exchange studies and electrochemical, spectroscopic and chemical investigations, it appears as if the ionization of BrF₅ is very small and relatively unimportant. The halogen fluorides react with Lewis acids and bases as molecular compounds involving donor-acceptor mechanisms.     

On the dichotomy of the SN2/ET reaction pathways: an apparent SN2 reactivity in the reaction of naphthalene dianion with alkyl fluorides

Dilithium naphthalene (Li₂C₁₀H₈) displays a S_N2 reactivity profile in its reaction with alkyl fluorides (n-, s- and t-octyl fluoride). S_N2 seems to be the dominant mechanism operating with primary alkyl fluorides, which presumably turns into competition with ET as we move to secondary and tertiary alkyl fluorides. Significantly, lithium naphthalene (LiC₁₀H₈) seems to have also an important nucleophilic component when reacting with alkyl fluorides, in contrast to the previously proposed general ET process valid for all alkyl halides. These results explain the observed distribution of products and are reinforced by a complete analysis of the products originated by the reaction with 6-halohexenyl radical probes, whose main alkylation products are described here for the first time.     

An efficient preparation of new sulfonyl fluorides and lithium sulfonates

An efficient preparation of several polyfluoroalkanesulfonyl fluorides is reported. This method, based on the synthesis of polyfluoroalkyl trimethyl silanes (precursors of polyfluoroalkylsulfinates) as intermediates, allows the successive transformations to be carried out in one pot. Moreover, these sulfonyl fluorides can be obtained from the corresponding sulfinates by electrophilic fluorination. This original approach avoids isolation and purification of some thermally or hydrolytically unstable intermediates. A series of new sulfonyl fluorides have been thus prepared from halogenodifluoromethylated precursors RCF2X (X = F, Br; R = ArC(O), ArS(O)n(CF2)m; n = 0, 1, 2; m = 1, 2) and have been transformed into the corresponding lithium sulfonates, which have potential applications as electrolytes for lithium batteries.     

Interaction of sulphur hexafluoride with metals and oxides

The interaction of SF₆ with metals and oxides has been studied by thermal analysis techniques. It has been shown that sulphur hexafluoride is an active fluorinating agent. It reacts both with oxides at temperatures about 600–700° and with metals at about 500–600°, to produce fluorides with the former and fluorides as well as sulphides with the latter. Higher temperatures bring about transformation of metals and their sulphides into pure fluorides.Thermodynamic evaluation of possible processes taking place in the fluorination of metals and oxides has been carried out.X-Ray diffraction and chemical analyses were used to identify final products for such metals and oxides as Zn, Cd, La₂O₃, Nd₂O₃ and Pr₆O₁₁.     

Nickel-catalyzed Suzuki-Miyaura reaction of aryl fluorides

Two protocols for the nickel-catalyzed cross-coupling of aryl fluorides with aryl boronic esters have been developed. The first employs metal fluoride cocatalysts, such as ZrF(4) and TiF(4), which enable Suzuki-Miyaura reactions of aryl fluorides bearing electron-withdrawing (ketones, esters, and CF(3)), aryl and alkenyl groups as well as those comprising fused aromatic rings, such as fluoronaphthalenes and fluoroquinolines. The second protocol employs aryl fluorides bearing ortho-directing groups, which facilitate the difficult C-F bond activation process via cyclometalation. N-heterocycles, such as pyridines, quinolines, pyrazoles, and oxazolines, can successfully promote cross-coupling with an array of organoboronic esters. A study into the substituent effects with respect to both coupling components has provided fundamental insights into the mechanism of the nickel-catalyzed cross-coupling of aryl fluorides.