Coordination chemistry tetrahedral geometries

At an early stage in the development of coordination chemistry, tetrahedral and square coplanar geometries were identified. More recently, geometries intermediate between these extremes have been observed. 

In terms of its coordination chemistry, the silver(I) ion is typically characterized as soft . Although originally believed to only bind ligands in a linear arrangement, it was soon shown that it can adopt a variety of coordination environments, the most common one being a four-coordinate tetrahedral geometry. Square-planar complexes are not rare, and various silver(I) cluster complexes also contain three-and five-coordinate sUver(I) ions. 

The same coordination geometry was also inferred from the analysis of the lowest energy LMCT bands (see Ligand-to-Metal Charge Transfer) in the far-UV absorption spectra of Zu7- and Cd7-MT, and those of corresponding tetrahedral halide complexes (see Cadmium Inorganic Coordination Chemistry see Zinc Inorganic Coordination Chemistry) Further support came from... 

The coordination chemistry of iron in such melts is a little better understood. Fe " and Fe" can act as network formers and modifiers in both tetrahedral and octahedral coordination geometries. It is also of interest to note in the light of the above results on Ni" that multiple site occupancy is also indicated for Fe" . In a number of Ca0-Al203-Si02-Fe0 glasses two different tetrahedral complexes of this ion can be observed using Mossbauer spectroscopy. 

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