LAUSR

[MoOF4(MeCN)], prepared from reaction of MoF6 with (Me3Si)2O in anhydrous MeCN solution, reacts with the neutral O-donor ligands, thf, Ph3PO, Me3PO, dmf and dmso, (L) in a 1:1 molar ratio under rigorously anhydrous conditions to form six-coordinate [MoOF4(L)], which have been characterised by microanalysis, IR, 1H, 19F{1H} and 95Mo NMR spectroscopy. In the presence of moisture the major products are [MoO2F2(L)2], which can be made directly by reaction of [MoOF4(L)] with a further equivalent of L and (Me3Si)2O. [MoOF4(MeCN)] and 2,2′-bipyridyl produce the insoluble [MoOF4(bipy)], which is probably 7-coordinate. Ph3AsO is quantitatively converted to Ph3AsF2 by [MoOF4(MeCN)], and soft ligands, including Me2S, Me3P and Me3As, reduce the oxide fluoride on contact. Unstable [MoO2F2(MeCN)2] has also been prepared and the X-ray structure of [MoO2F2(MeCN)2]·MeCN is reported. X-ray crystal structures are reported for [MoOF4(Ph3PO)], [MoO2F2(Ph3PO)2], [MoO2F2(Me3PO)(H2O)] and [Mo2O4F2(μ-F)2(Me3PO)2]. Comparisons with the corresponding chemistries of WOF4 and WO2F2 are described.