Edge-shared octahedral structure

Zr, Hf, Th, and Sn) are coordinatively unsaturated and are potential Lewis acids for ligating alcohol molecules during their syntheses (see Section III.A). The dimeric nature of the molecular adduct with an empirical formula Zr(0-i-Pr)4(HO-/ -Pr) in benzene solution led Bradley et al. (213) to suggest an edge-shared octahedral structural (III) as early as 1953,... 

Octahedral Six Coordinate In addition to the tris-bidentate complexes and the unidentate complexes discussed above, there are many other examples of chiral metal complexes that are based on octahedral geometry. For example, there are a number of reports of edge-sharing binuclear structures containing four bidentate chelates. The individual metal centers in these binuclear species can exist as either A or A enantiomers, and, therefore, the overall structure can be chiral AA and AA, or the achiral (meso) AA pair as illustrated in Figure 5.12a and b. Studies of complexes of this type were important in the proof of Werner s coordination theory. In these pioneering studies, Werner was able to prove by experiment the existence of the three isomers (AA, AA, and AA) of [Co2(p-NH2)( l-NC>2)(en)2]4 +. 23 For Cr(III) complexes, Werner showed that the / >.vo-AA- Cr2(p-OH)2(en)414 1 may be prepared by... 

In the crystal structure of neptunite, KNajLiFe ijSigO, Fe and Ti occur in two interconnecting chains of edge-shared octahedral chains in which nearest cations are 314 pm and 328 pm apart and the interaction vectors have substantial components in all three optical directions. An ordered arrangement exists within the chains so that Fe2 ions alternate with Ti4 ions. The optical spectra of neptunite show a very broad and intense band centred at 24,100 cm-1 (415 nm) which lies well outside the range of Fe2 CF transitions and can be unequivocally assigned to Fe2 —> Ti4 IVCT (Mattson and Rossman, 1988). Other examples are listed in table 4.2. 

Nature of sites in crystal structure Vastly different, e.g., cube-octahedron octahedron-tetrahedron Similar, e.g., octahedra with slightly different bond lengths or ligands Identical, finite clusters, e.g., edge-shared octahedral dimers Identical, continuous chains, e.g., chains of edge-shared octahedra... 

Layered Silicates The structure of Layered silicates (LS)/clays consists of a 2-D layer of two fused silicate tetrahedral sheet with an edge-shared octahedral sheet of metal atoms, such as A1 or Mg. This model was proposed by Hofifinann et al. [19]. 

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