Coordination Number and Geometry

Limitations of space preclude a comprehensive survey of the coordination chemistry of minerals. The reader is referred to the general references in this section for more information. Naturally, many other examples might have been chosen to exemplify various coordination numbers, geometries and complexes found in minerals. Nevertheless, the various species mentioned above do indicate the wide range of coordination chemistry in the solid state found in the mineral kingdom and the complexity of coordination compounds in the natural environment. 

The first row d8 transition metal ion, nickel(II) provides an excellent system in which to investigate how the nature of the metal ion and its ligands affect coordination number, geometry, and stability. Nickel(II) offers a plethora of stereochemistries with various ligands and, further, complexes of the same chemical constituency can adopt different geometries with a range of stabilities. This behavior of nickel(II) complexes was first noted in 1939 by coordination chemist Lifschitz and his co-workers. Lifschitz reported that several... 

In the EXAFS technique the incident X-rays are absorbed by the atom which is being studied. In doing so they interact directly with the electrons of the atom and the excited electrons then probe the immediate environment of the atom. As a result X-rays are emitted and this appears as fine strucmre in an absorption. From this it is possible to deduce coordination numbers, geometry and mean distances of the atom under study to its nearest neighbours, i.e. to give information about the primary solvation of an ion. Recently it has proved useful in probing the secondary solvation shell. 

Complex Ions Coordination Numbers, Geometries, and Ligands... 

A complex ion is described by the metal ion and the number and types of ligands attached to it. Its structure has three key characteristics—coordination number, geometry, and number of donor atoms per ligand ... 

Be familiar with the coordination numbers, geometries, and ligands of complex ions name and write formulas for coordination... 

Table 2.3 Proposed correlation amongst empirical formula of a metal alkoxide, coordination number, geometry, and molecular association ...

Be familiar with the coordination numbers, geometries, and ligands of complex ions name and write formulas for coordination compounds describe the types of constitutional and stereoisomerism they exhibit ( 22.2) (SPs 22.2, 22.3) (EPs 22.18-22.39)... 

The ability of metal complexes to form more than one bond to the polynucleotide, especially in Form HI, results in various forms of cross link between the complementary strands of the helix. The coordination number, geometry, and types of ligand all dictate a remarkable range of conformational changes and interactions with DNA, including base pair specificity. 

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