Rhodium pentafluoride

Table I. Magnetic susceptibility—temperature data for rhodium pentafluoride...

Rhodium pentafluoride is isomorphous with its ruthenium, osmium, and iridium analogues, the crystal data being a, 12-28 b, 9-86 c, 6-48 A ]3, 99-2° Uobs-, 654-2 A Z = 8. Presumably the structural unit of this compound is a fluorine-bridged tetramer, as in ruthenium pentafluoride. It is noteworthy that the unit-cell volume is smaller than in the ruthenium analogue, possibly as a... 

Rhodium Pentafluoride Table 1. RhF Positional and Thermal Parameters and Standard DevUitions... 

Crystal Data. Rhodium pentafluoride was prepared as described in a forthcoming paper,Crystals were grown by vacuum sublimation in a quartz tube, the parent sample being at "-100 . A ruby-red crystal grown in this way, approximately 0.130 X 0.11 X... 

B. K. Morrell, A. Zalkin, A. Tressaud and N. Bartlett, Crystal Structure of Rhodium Pentafluoride, Inorg. Chem. 12 (1973) 2640-2644. 

Because coordination compounds are usually considered to be covalently bonded, to a first approximation (see Chapter II), extended complex structures in the solid can readily be related to them. Consider, for example, rhodium pentafluoride. Obviously, it could be considered as an ionic structure. Rh F , and indeed Ihe crystal structure7 consists, in part, of /top-arranged fluoride ions with rhodium in octahedral holes. However, closer inspection of the structure reveals that it consists of tetrameric units, Rh4F2l that are distinct from one another (Fig. 7.7). The environment about each rhodium atom, an octahedron of six fluorine atoms, is what we... 

The V—F—V angle of 150° in the vanadium pentafluoride structure lies between those for the niobium and rhodium compounds. Thus, the structure cannot be described in terms of either of the close-packed arrangements. Although in the structure some approach toward close-packed planes of fluorine atoms can be seen, a comparison of volume per formula unit for the pentafluorides shows that for the second and... 

SAFETY PROFILE Handle carefully. It may be a sensitizer but not to the same extent as platinum. Most rhodium compounds have only moderate toxicity by ingestion. Flammable when exposed to heat or flame. Violent reaction with chlorine, bromine pentafluoride, bromine trifluoride, and OF2. A catalytic metal. 

Three binary fluorides of rhodium have been reported a trifluoride, a tetrafluoride, and a hexafluoride. Rufi and Ascher obtained the trifluoride, plus a small amount of red-brown sublimate, by the fluorination of rhodium at SOO-600°, and suggested that the sublimate was either a tetrafluoride or a pentafluoride. Sharpe, in his report of the tetrafluoride, concluded that this was identical with Rufi and Ascher s sublimate. The... 

The establishment of pentafluorides of rhodium and iridium [5] as well as the trifluorides raised the possibility of each element also making a tetrafluoride[17]. On the other hand the mixed oxidation state character [13] of PdFj (Pd(II)Pd(IV)F6) raised the possibility of the tetrafluorides RhF4 and IrF4 being M(III)M(V)F8 compounds. At the same time the existence of Pd(IV) in the compound Pd(II)Pd(IV)F6 indicated the probable existence of PdF4. 

Rhodium(VI) and iridium(VI) occur only in black RhFg and yellow IrFg, formed by heating the metals with F2 under pressure and quenching the volatile products. Both RhFg and IrFg are octahedral monomers. The pentafluorides are made by direct combination of the elements (equation 22.100) or by reduction of MFg, and are moisture-sensitive (reaction 22.101) and very reactive. They are tetramers, structurally analogous to NbFs (22.5). 

RhFj has a tetrameric structure analogous to RuFj and IrFs (128). Each rhodium is coordinated by six fluorine atoms in an approximately octahedral arrangement. The terminal Rh—F distance averages 1.808 A, while the Rh—F distance is significantly longer (2.01 A) for the bridging fluorines. This compound is isostructural with the pentafluorides of Ru, Os and... 

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