Hartmut Vogt

Synthesis and Crystal Structure of Halomethyltriphenylphosphonium Halides and Bromotriphenylphosphonium Tribromide

Abstract The phosphonium salts have been prepared by the reaction of triphenylphosphine with the corresponding halomethanes (eq. (1)) and bromine (eq.(2)), respectively.

Fluoridolysis of N-phosphoryl phosphazenes and diphosphoryl compounds

Abstract The present work deals with the use of the adduct Et 3 N· n HF as fluorination agent for heteroatom bridged phosphorus compounds of the structure X 2 P(O)NPX 3 ( I ) ( X Cl, Ph, PhO, EtO, NEt 2 ) and X 2 P(O) Y P(O) X 2 ( II ) ( X Cl, PhO, EtO, NEt 2 ; Y NH, NMe, O). Facilities and limits of the substitution of fluoride for phosphorus-bonded groups X are shown. The mechanism of the reaction and therewith the type of resulting products depends on the concentration of protons in the reaction medium as well as the concentration and nucleophilic force of the free fluoride ions. Furthermore, the temperature, the base used and the presence of other nucleophiles competing with fluoride play an important role. Both N-phosphoryl phosphazenes ( I ; X Cl, Ph, PhO, NEt 2 ) and imidodiphosphoric acid derivatives ( II ; X =Cl, PhO; Y NH) give defined X /F replacement products. Under certain conditions pentafluorophosphates of the structure [F 5 P- Y -P(O) X 2 ] − ( X Cl, PhO, F; Y NH, O) may be obtained from N-phosphoryl phosphazenes ( I ; X Cl, PhO) and pyrophosphoryl chloride ( II ; X Cl; Y O). All reactions were studied by means of NMR spectroscopy ( 1 H, 19 F, 31 P). The mechanism of the fluoridolysis is discussed.

Syntheses and Crystal Structures of Phosphonium Bromides

Abstract As part of our studies on the crystal structures of phosphonium halides [1] we haveprepared various phosphonium bromides. These can been obtained by the reaction of a phosphine with aryl or alkyl bromides in acetonitrile or methylene chloride:

Formation and Stability of Difluoromethylene Phospho-Raiies, R3P=CF2

Abstract Carbonyl compounds react with CBr2F2 in the presence of phosphanes, RP (R = Ph, NR;), and metals (M = Zn, Cd, Pb) forming geminal difluoroolefins (eq. 1)1. R′CHO + CBr2F2 + R3P + M → R′CH=CF2 + MBr2 + R3PO (1) Without any doubt this reaction has to occur via the intermediate formation of difluoromethylene phosphoranes, which then undergo the Wittig reaction with carbonyl compounds (eq. 2). R3P=CF2 + R′CHO → R3PO + R′CH=CF2 (2).

Reaction of difluorocarbene with covalent halides

Abstract In order to investigate the reaction of the halides MX3 (M = P, As; X = F, Cl, Br, I), PCl5, POCl3, POBr3, RSCl (R = Ph3C, Ph, Et, Cl, SCl), SOCl2, and WF6 with CF2 we used the complex Cd(CF3)2·2 CH3CN as precursor of CF2. In accordance with Krause and Morrison [1] we found that this complex can also react as trifluoromethylation agent depending on the nature of the covalent halide and the reaction conditions. Already at room temperature Cd(CF3)2·2 CH3CN reacts with MX3 (M = As; X = Cl, Br, I; M = P; X = Br, I), PCl5, and S2Cl2 forming difluorohalomethyl compounds, e. g. X2MCF2X, by insertion of CF2. The reaction products are thermically stable substances being rather resistant to hydrolysis in some cases. Only the iodo- derivatives decompose slowly to CI2F2 and to diphosphanes or diarsanes, resp.. In the reaction of CF2 with oxohalides, however, COF2 and the corresponding reduced halides are formed. On the other hand the cadmium complex reacts with RSCl (R = Cl, SCl, Et) as trifluoromethylation agent under substitution of chlorine by a CF3-group forming trifluoromethylsulfanes and CClF3.