Molybdenum is a major industrial metal and occurs naturally in various oxidation states as molybdenite. It is also recovered as a byproduct of copper and tungsten mining. As a metal it is relatively insoluble in organic solvents but readily forms complexes with alkali and rare earth fluorides. These compounds are of interest in many current technologies and applications, especially in oxygen-sensitive areas such as etching, metal production and synthetic organic chemistry.
The oxide fluorides of molybdenum are a useful starting point in synthesising molybdenum(VI) compounds, which have a wide range of uses in industry. In particular, the ionic hydrate MoF2(CO)3 is widely used as an oxygen carrier in molecular oxygen generators. In addition, the ionic hydrate of difluorotricarbonyl molybdenum (MoF2(CO)3) is a key component in high-power mid-infrared optical frequency combs.
In the solid phase, MoOF4 is polymeric with two cis fluoride bridges and a distorted octahedral molybdenum centre. In solution, it forms a range of complexes with N- and O-donor ligands. The X-ray structure of the six-coordinate complex [MoOF4(Ph3PO)] has been determined and is comparable to that of the molybdenum(VI) analogue tungsten(V) oxide fluoride, [WOF4(Ph3PO)].
The reaction of MoF4 with thf, Ph3PO, Me3PO, dmf or dmso in rigorously anhydrous conditions yields the corresponding complexes [MoOF4(L)], which are characterised by microanalysis, IR and 19F