David E. Laycock

Fluoride ion donor properties of UF2O2; preparation and characterization of the adducts UF2O2·nSbF5(n= 2 or 3) and crystal structure of UF2O23SbF5

The adducts UF2O2·nSbF5(n= 2 or 3) have been obtained as pale green and pale yellow-green solids respectively from the reaction of UF2O2 with SbF5 in HF solvent. The solid adducts have been characterized by observation of reaction stoicheiometries, chemical analyses, and vibrational spectra. An X-ray diffraction study has shown that crystals of UF2O2·3SbF5 are monoclinic, space group P21/n, with unit-cell dimensions a= 11.040(7), b= 12.438(12), c= 12.147(8)A, β= 111.16(20)°, and Z= 4. The structure has been refined by three-dimensional least-squares methods to R= 0.0773 for 1 613 reflections. The structure is best regarded as a fluorine-bridged network of UF2O2 and SbF5 molecules in which the antimony is surrounded by a distorted octahedron of fluorine atoms and the uranium by a pentagonal-bipyramidal array of five fluorines and two oxygens. Two of the uranium–fluorine distances are long and this means that the structure can also be described in terms of zigzag chains of UO2 groups fluorine-bridged to SbF6 units with Sb2F11 side-chains attached to the uraniums.

Preparation and characterization of the uranyl fluoride–antimony pentafluoride adduct, UF2O2·4SbF5

When UF4O·2SbF5 is treated with anhydrous hydrogen fluoride a slow reaction in solution takes place. Investigation of this reaction and those of UF4O–SbF5–HF solutions on standing have shown that, in both cases, UF6 and a new uranyl fluoride derivative, UF2O2·4SbF5 are produced.

13C NMR studies of the complexes [η5-C5H5Fe(CO)2(olefin)]BF4

Abstract The 13 C nmr spectra of a series of eighteen complexes of the type [η 5 C 5 H 5 Fe(CO) 2 (olefin)]BF 4 are presented. It is suggested that there is a correlation between bond strengths and coordination shifts, both of which are affected by both steric and electronic factors.

Mass spectrometry of compounds of the type [Fe(CO)2(η-C5H5)R](R = alkyl)

The electron-impact mass spectra of a series of compounds of the type [Fe(CO)2(η-C5H5)R](R = alkyl) have been obtained. Three major fragmentation routes commence with loss of alkyl (R), alkene (R–H), or carbonyl groups. Particularly intense peaks are also formed by loss of one, two, or three molecules of H2 from the [M– 2CO]+ ions, leading to species which presumably contain η3-allylic and η5-pentadienyl moieties.

Hydride addition reactions of the olefin complexes [Fe(η5-C5H5)-(CO)2(olefin)][BF4]; formyl formation as the kinetically preferred process; regio- and stereo-selectivity during addition to the Co-ordinated olefins

Reactions of the complexes [Fe(cp)(CO)2(olefin)]+(cp =η5-C5H5; olefin = CH2CH2, CH2CHMe, 1-hexene, or methylenecyclohexane) with hydride donors under a variety of conditions normally yield the alkyl products of hydride addition to the olefin, and the hydride [Fe(cp)(CO)2H], a product which has not been previously noted. Detailed examination of the addition reactions of the complexes of CH2CHMe, 1-hexene, and methylenecyclohexane show that the reactions exhibit no recognizable patterns of regioselectivity, in contrast to many other metal–olefin systems. Addition of deuteride to [Fe(cp)(CO)2(C6H10)]+(C6H10= cyclohexene) gives only the trans isomer of the 2-deuteriocyclohexyl complex, consistent with exo attack by the nucleophile on the co-ordinated olefin. Reaction of [Fe(cp)(CO)2(CH2CH2)]+ with NaBH4 in acetone at low temperature gives an unstable formyl compound, presumably [Fe(cp)(CO)(C2H4)(CHO)], as the kinetic product. On warming, the formyl compound converts smoothly to the above-mentioned hydride complex rather than to the corresponding ethyl complex. The mechanistic implications of these results are discussed.

Interaction between uranium tetrafluoride oxide and the pentafluorides of arsenic, niobium, tantalum, and bismuth

No reaction occurs between UF4O and AsF5 but UF4O·3MF5(M = Nb and Ta) and UF4O·2BiF5 have been obtained as yellow or orange solids by warming mixtures of UF4O with excess of the appropriate pentafluoride in anhydrous HF or by combination of the oxide tetrafluoride with excess of the pentafluoride as a melt. The solid adducts have been characterized by their reaction stoicheiometries, chemical analyses, and vibrational spectra. Like UF4O·2SbF5, the adducts are fluorine bridged with some ionic character. The thermal decomposition of the adducts results in the production of uranyl species.