Iridium tetrafluoride, structure

Although a number of complex fluorides of quinquevalent iridium, (e.g. KIrF,) are known, previous attempts to establish the simple fluoride have failed. The absence of a pentafluoride of iridium has become increasingly anomalous as the pentafluorides of the neighbouring elements, rhenium, osmium, and platinum have been prepared. Previous work - indicated that reactions which might have yielded the pentafluoride gave the tetrafluoride instead. The physical properties of this tetrafluoride. (m.p. 106—107 b.p. > 300 ), however, resembled those of a pentafluoride or oxide tetrafluoride. This indicated that iridium tetrafluoride differed structurally from its neighbouring tetrafluorides. 

The tetrafluorides of iridium, rhodium and palladium [13] have been established by the work reported in this paper and together with Ptp4 constitute a structurally related set. 

The dark-brown product disproportionates above 400° into Irp3 and the volatile IrPs. The structure features (IrPe) octahedra which share 4 P atoms, each with one other IrPg group, leaving a pair of cis vertices unshared this is essentially a rutile type structure (p. 961) from which alternate metal atoms have been removed from each edge-sharing chain. It was the first 3D structure to have been found for a tetrafluoride. Claims have been made for the isolation of all the other iridium tetrahalides, but there is some doubt as to whether these can be substantiated. This is an unexpected situation since -1-4 is one of iridium s common oxidation states and, indeed, the derived anions [IrXe] - (X = P, Cl, Br) are well known. 

---