Alexander F. Janzen

Fluorination of methionine and methionylglycine derivatives with xenon difluoride

Abstract A mild procedure for the fluorination of methionine and methionylglycine derivatives is described. Fluorination with xenon difluoride occurs at −20 to 20°C within 20–30 minutes in 70–90% yield, exclusively at the methylthio position. The products were characterized by elemental analysis, fluorine, proton and carbon NMR spectroscopy.

Oxidative fluorination of S, Se and Te compounds ☆

Abstract The synthesis and mechanism of formation of cis- and trans-Ph2SF4 is described. Starting compounds are Ph2S or Ph2SF2 and the oxidizing agent is XeF2 in the presence of Et4NCl. Also described is the synthesis of related chalcogen(IV and VI) fluorides such as t-butylSF3, difluorodibenzothiophene, PhSeF3, Ph2SeF2, PhSF5, p-MeC6H4SF5, PhSeF5, and PhTeF5. The reactions of Ph2S(O)F2 with alcohols and with the H2O–HF-glass system are briefly described.

Organotellurium(VI) fluorides

Abstract A series of phenyltellurium(VI) fluorides have been prepared by the oxidative-fluorination of tellurium compounds with xenon difluoride. The compounds were characterized by elemental analysis, fluorine and tellurium nmr, and mass spectrometry.

Ligand exchange and reaction mechanisms offluorinated compounds

Abstract The topic of ligand exchange and reaction mechanisms of fluorinated compounds is reviewed, with emphasis on the main group fluorides. Mechanisms are divided into a series of elementary steps of bond formation and bond dissociation, using the coordination model of reaction mechanisms as an organizing principle. Included in this review is an analysis of the stercochemical behavior of pentacoordinated molecules, as well as a discussion of the role of impurities, anionie, cationie, free radical and fluorine-bridged intermediates, and fluoride-induced reactions.

Reactions of xenon difluoride. Part 6. Some reactions of phosphorus, arsenic and iodine compounds

Abstract The reaction of XeF 2 with some organo-phosphorus, -arsenic and-iodine compounds is described. The products were identified by fluorine nmr spectroscopy and the conditions under which fluorine exchange occurs were briefly investigated. Organoiodine (III) difluorides are suitable for the conversion of Ph 2 Te to Ph 2 TeF 2 ; the decomposition of RIF 2 liberates IF and fluoroalkane.

A 31p and 15N NMR study of the extraction of uranyl nitrate by Di-2-ethylhexyl phosphoric acid

Low temperature 31P and 15N NMR spectroscopy was used to investigate the species forming in the organic layer following the extraction of uranium from nitric acid solutions with di-2-ethylhexyl phosphoric acid. It was found that uranium is extracted from neutral solutions as the 1:2 complex UO2A2 regardless of what anion is present. For dilute nitric acid solutions, the uranium is extracted both as associated and mixed nitrato species. As the nitric acid concentration of the aqueous layer increases, the mixed nitrato complex, UO2(NO3)A·HA, becomes predominant.

4-Fluoro-2,2′-bipyridine (fbpy) complexes of cobalt(II/III) and iron(II/III) and electron transfer in the Co(bpy)32+–Co(fbpy)33+ system

Abstract A variety of cobalt(II/III) and iron(II/III) complexes were prepared containing the ligands 4-fluoro-2,2′-bipyridine (fbpy), 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen) and water, and anions hexafluorophosphate, chloride, perchlorate and sulfate. These complexes were characterized by a combination of 19 F , 1 H , 13 C , 15 N NMR and elemental analysis, and used for a mechanistic study of electron transfer in the Co II (bpy) 3 2+ –Co III (fbpy) 3 3+ system.

OXIDATIVE ADDITION AND ISOMERIZATION REACTIONS : THE STEREOSELECTIVE SYNTHESIS OF CIS- AND TRANS-PH2TEX4

Abstract A study of the stereoselective synthesis of cis- and trans-Ph2TeX4 (X=F,Cl) supports a two pathway mechanism in which oxidative addition leads to the cis isomer while subsequent isomerization leads to the trans isomer.

Reaction mechanisms of phosphorus fluorides: An ab initio study

Abstract Reaction mechanisms of phosphorus fluorides may be analyzed on the basis of the coordination model of reaction mechanisms. Some of the intermediates and mechanistic details arising out of such an analysis have been investigated by ab initio molecular orbital calculations. The rapid equilibrium between five- and six-coordinate phosphorus fluorides, and exchange of axial and equatorial fluorines in PF 5 , is investigated by calculating the structures of adducts of phosphorus pentafluoride, i.e. D-PF 5 where D = NH 3 , H 2 O, CH 3 F, HF, PF 5 and PF 6 . Bond cleavage in phosphorus fluorides is investigated by calculating the structure of a fluorine-bridged anion P 2 F 11 − . A reaction pathway is proposed for the fluoride-catalyzed oxidation of phosphorus (III) to phosphorus(V) fluorides which involves the known species PF 3 , PF 4 − , PF 4 and PF 5 .

Ligand exchange in adducts of triphenyltin fluoride

Abstract A 19 F and 119 Sn NMR study of Ph 3 SnX 2 − (XF, Cl) and Ph 3 SnF:B (BHMPA, DMSO) has shown that fluorine exchange occurs between four- and five-coordinate tin complexes, presumably via fluorine- and chlorine-bridged intermediates. The results point to a modified view of the isomerization and racemization of triorganoelement halides. Some reactions of Ph 3 SnF 2 − with tellurium and phosphorus compounds are described and the synthesis of PhSnF 5 2− reported, but attempts to prepare six-coordinate adducts Ph 3 SnX 3 2− or Ph 3 SnX 2 :B − were unsuccessful, although their presence in solution was indicated by NMR spectroscopy.