Coordination spheres geometries

Fluorine ions form the first coordination sphere around the tantalum ion, which is the central atom of the complex. Potassium ions form the second coordination sphere, which significantly affects the geometry and force field of the first coordination sphere. The melting of K2TaF7 leads to the dissociation of the compound into ions, as follows ... 

Most tin(II) compounds display structures with a trigonal pyramidal coordination. This is of course to be expected as the tin atom is in the first place electrophilic in order to complete its outer electron configuration (cf. Chapter 5 and 6). To illustrate the resemblance of this geometry between ionic and molecular compounds, the structure of NH4SnF3 (5) 31) is compared with that of the cage compound (Me3CN)3(Me3A10)Sn4 (6) 32). The coordination sphere of the tin atom is the same in 5 and 6 (for the complete structure of 6 see Sect. 6.5) ... 

The [Pt(Se4)2]2 complex (133) has been prepared by the reduction of the platinum(IV) species [Pt(Se4)3]2 with excess borohydride.328 The X-ray structure of the complex shows that each of the five-membered rings adopts a half-chair conformation, with the platinum coordination sphere exhibiting slight distortion from a square-planar geometry.329... 

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