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Title: Fluorinations of tungsten and molybdenum carbonyl complexes
Authors: Walker, Daniel James.
Award date: 1997
Presented at: University of Leicester
Abstract: The dimeric complexes (n5-C5H5)M(CO)3 2 (where M = W or Mo) and (H3C{lcub}ti5-C5H4{rcub})Mo(CO)3 2 have been treated with XeF2 in organic solvents. All three materials react to form air sensitive products which solid-phase IR studies show to contain highly oxidised metal carbonyl components. The product from the fluoridation of (H3C{lcub}T 5-C5H5{rcub})Mo(CO)3 2 is insufficiently stable in solution for it to be characterised further. 19F NMR studies show that (n5-C5H5)W(CO)3 2 reacts to form the new complex (T 5-C5H5)WF5, but that the molybdenum analogue reacts to form an unidentified product which, although it produces an AB4 pattern in the 19F NMR, does not appear structurally related to (n5-C5H5)WFs. (n5-C5H5)W(CO)3 2 was found to react with AgF in anhydrous HF solution to give (t 5-C5H5)WF5. Solid-phase IR studies showed that a highly oxidised metal carbonyl, identical to that obtained in the XeF2 reaction, was also formed. Reaction of (T 5-C5H5)M(CO)3(CH3) (where M = W or Mo) with anhydrous HF was found to yield the complexes (n5-C5H5)M(CO)3 2 (where M = W or Mo). The molybdenum product was characterised by X-ray crystallography, whilst the tungsten dimer was characterised using mass spectroscopy. The mechanism for this redox process is unknown, but is believed to involve formation of the complexes (T 5-C5H5)M(CO)3F, as intermediates. Although solid-phase IR shows that both Mo(CO)6 and W(CO)6 react with XeF2 to give oxidised metal carbonyls, the products appear very different. W(CO)6 yields a variety of salts of the W202F9 " anion, none of which dissociate fully in solution, and which thus give separate 19F NMR spectra, for the anion. One of these salts may contain the W2(CO)8 2+ cation, which has been characterised in the product mixture by +EI MS. Mo(CO)6 reacts to form a molybdenum fluoride whose 19F NMR spectrum has been observed, but which has not been identified.
Type: Thesis
Level: Doctoral
Qualification: PhD
Rights: Copyright © the author. All rights reserved.
Appears in Collections:Theses, Dept. of Chemistry
Leicester Theses

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