Mixed halo

In contrast to the trichloro compound, these mixed halo compounds, as well as trihromodiphenylantimony [62170-61 -0], (CgH3)2SbBr2, are monomeric ia the sohd state. 

Os(V) complexes are relatively rare and generally unstable toward disproportionation or other reactions. Authentic complexes that have been isolated include [OsFs]4, [OS2CI10], salts of [OsX6] (X = F- or Cl-), and mixed halo/aqua or halo/oxo complexes, all of which are octahedral (2, 5, 6). Recently, the tetrahedral [Os(2-MeC6H4)4JT and five-coordinate [0s(0)(ehba)2]- complexes have been isolated and characterized (23). 

Infrared spectroscopy is not as inherently informative with regard to metal interactions in highly symmetrical metal-metal bound dimers as is Raman spectroscopy, since the totally symmetric metal-metal stretch is a forbidden absorption in the infrared experiment. Oldham and Ketteringham have prepared mixed-halide dimers of the type Re2ClxBr 2xto lower the symmetry and hence introduce some infrared allowedness into the Re-Re stretching mode (206). Indeed, the appearance of a medium-intensity band at 274 cm 1 in the infrared spectrum of the mixed-halo species was considered to be the result of absorption by the metal—metal stretching vibration, which was also observed in the Raman spectrum at 274 cm ". ... 

Although there is a small chemistry of [OsX ]3- and an even smaller chemistry of [OsCl6], it is the IV oxidation state that predominates in the chloro, bromo and iodo chemistry of osmium, whereas for ruthenium it is probably true to say that the chemistry of [RuX6]3 is more extensive, or at least has been more extensively investigated, that that of [RuXj]2-. Much work has been done on the mixed halo species [OsXxY5 ]2 . 

For the mixed halo species see under the appropriate substituting ligand (e.g. oxo halo complexes, p. 594 nitrido halo species, p. 563). 

In strong acid media mixed halo cations [PX Y4 ]+ can be generated by reactions of PX3 with Y2. 

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