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Transition metal fluoride derivatives with nitrogen-containing ligands.

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posted on 19.11.2015, 08:45 by G. A. Griffith
The reaction between WF6 and C6F5NH2 is found to proceed via iminolysis. 19F NMR analysis of acetonitrile (MeCN) solutions show the product to be a mixture containing [C6F5NH3]+[WF5(NC6F5)]-, [C6F5NH3]+[W2F9(NC6F5)2]-, [C6F5NH3]+F- and the unique mixed imido-, oxo-species [O=WF4-F-WF4(NC6F5)] - formed from traces of oxyfluoride impurities. The 19F nmr spectrum of a trifluoroacetic acid (TFA) solution showed the presence of the dimeric anion salt and fluorination products. An X-ray crystallographic study of a single crystal of [C6F5NH3]+[W2F9(NC6F5)2]-, grown from TFA, revealed the compound to adopt a triclinic (space group P1)structure, with two formula units in the unit cell, each with a slightly differing geometry about the bridging fluorine atom. The reaction of Me3SiNCO with MF6 (M= Mo,W) was examined. The products are assigned as MF5NCO3 from IR spectra recorded. The reaction between MoF6 and (Me3Si)2NH results in the formation of MoF4NH. Addition of MeCN to MoF4NH produces a 1:1 adduct, MoF4NH.MeCN. Analysis of the IR spectra of the two compounds indicates that MoF4NH adopts a cis-fluorine bridged chain structure, and MoF4NH.MeCN adopts a pseudo-octahedral (C4), monomeric stucture in the solid state. WOF4 reacts with Me3SiNCO to form WOF3NCO, identified from its mass spectrum. The hexafluorides MF6 (M= Mo,Re), when allowed to react with tetrakis-tri-methylsilylhydrazine (TTSH) undergo reduction to the pentafluoride in approximately 80% yield. Tungsten hexafluoride is believed to react with TTSH to form the diazene compound, WF4N-MWF4.


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University of Leicester

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