Fluoro complexes structural chemistry

The Mo04+ core structure is found in MoVI chemistry in a relatively small number of authenticated structures and in a few suggested examples shown in Table 3. The simplest set of complexes which potentially contains the Mo04+ core is MoOX4(X = F, Cl, Br). While a square pyramidal structure seems probable for the chloro and bromo complexes,232 the fluoro complex is polymeric in the solid state and in solution as well.233-235... 

Halide complexes of Group 14 metals continue to offer surprises in their structural chemistry. A new fluoro complex of germanium GeyFig has been isolated from the decomposition of germanium(IV) fluoride and shown by crystallography to comprise sheets of [GegFio] clusters... 

As for the previous oxidation state, the chemistries of Mo" and W are much more extensive than that of Cr which is largely confined to peroxo- and fluoro- complexes. [Cr(02)2(NH3)3], which has a dark red-brown metallic lustre, may be obtained either by treating [Cr(02)4] with warm aqueous ammonia or by the action of H2O2 on ammoniacal solutions of (NH4)2Cr04. It has a pentagonal bipyramidal structure in which the peroxo- groups occupy... 

The structural chemistry of six-coordinated fluoro complexes of the d-transition elements is the subject of an entire review paper by Babel (7). In contrast, six coordination is rare in actinide fluoro-complexes. The relatively large sizes of the actinide ions (Fig. 3) suggest that low coordination numbers should be found only in the fluoride complexes of the higher oxidation states. The radius ratio, r+/r, predicted for the lower hmit of stabihty of octahedral coordination is ]/2 — 1, which corresponds to a positive ion radius of 0.55 A in coordination with fluoride (1.33 A). 

Given the structure of InF3-3H20 (see above) and the tendency of indium(III) to be six-coordinate with hard ligands, it is reasonable that the mixed fluoro/aqua anionic complexes should also be [InF4(H20)2] and [InF5(H20)]2. This is compatible with the evidence from aqueous solution chemistry, where stability constants and thermochemical results indicate a series of [In(H20)6-nFn]l3 n)+ species.9 These complexes still await detailed systematic structural investigation. 

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