Oxidations of Some Non Metals in Acetonitrile

[摘要] The oxidation of some non-metals in acetonitrile is described in this thesis. The iodine cation I(NCMe)2+ is linear and centrosymmetric and iodine EXAFS data show the I-N bond distances to be similar in the solid 2.17 A and in MeCN solution 2.14 A. Bond distances were determined for [I(py)2][NO3] and [I(py)2][MoF6] for comparison purposes. Molybdenum EXAFS data were used to determine the Mo-F distance in the MoF6- anion. The three compounds studied were [I(py)2][MoF6] in MeCN 1.77 A, [I(NCMe2)][MoF6] in MeCN 1.77 A, and [Ag(py)4][MoF6] solid 1.79 A. The MoF6-anion bond length had previously been determined by powder diffraction and was found to be 1.74 A. The oxidation of bromine in MeCN by UF6 gives the salt [Br(C6H9N3)][UF6] but no reaction occurs between Br2 and MoF6 in MeCN; this provides the first chemical reaction which differentiates between the oxidising abilities of these two hexafluorides. The cation Br(C6H9N3)+ oxidises NO gas to NO+, I2 to I+ and the solvated Cu(I) cation to the solvated Cu(II) cation. No simple [Cl(NCMe)x]+ cations are obtained using the conditions adopted in this study; UF6 is reduced to UF5NCMe in the presence of Cl2 in MeCN and substitution takes place to give UF5-x ClxNCMe species in solution. Similar reactions occur between HCl and UF6 in MeCN. Tellurium is oxidised in MeCN by MF6 where M = Mo or U, to give [TeF3(NCMe)2][MF6].3MF5NCMe. Although SbF5 and AsF5 are strong oxidising agents in acidic media, the complexes SbF5. NCMe and AsF5. NCMe are weak oxidising agents in MeCN. Oxidation of tellurium by these species is limited to the formation of Te42+ , whereas oxidising agents MoF6 and UF6 oxidise the tellurium through to Te iv. The NO cation shows intermediate oxidising behaviour and WF6 does not oxidise tellurium in MeCN. The order of oxidising ability established experimentally is UF6>MoF6 >NO+>SbF5NCMe, AsF5. NCMe>WF6. The brominating ability of Br(C6H9N3)+ was studied using several aromatic compounds. Two other sources of electrophilic bromine were prepared, Nafion-Br and [Br3][SbF6]; these were used to compare the brominating capabilities of the Br(C6H9N3)+ cation. [Br(C6H9N3)][UF6] brominates, toluene, anisole, 9-methylanthracene, 4-s-butylphenol, benzaldehyde and nicotinic acid. It does not brominate phthalic anhydride or pentafluorobenzene. The salt [Br3][SbF6] brominates 4-s-butylphenol, nicotinic acid and benzaldehyde. This salt reacts exothermically with the organic compounds studied in this work and causes fragmentation of the organic molecules. The halogenating powers of Nafion derivatives were studied. Nafion-Br proved to be a poor brominating agent, due to the slow release of the active "Br+" species. Nafion-Cl was found to behave similarly.

[发布机构] University:University of Glasgow

[关键词] Organic chemistry