Geometries of inorganic compounds

Let us consider the structure of inorganic compounds which may have trigonal bipyramid geometry, such as phosphorous penta-fluoride. The structure of PFs is such that two fluorine atoms are at the apical positions, while three are at the equatorial positions. Since the fluorine atoms are not in equivalent positions, there should be two lines in the fluorine magnetic resonance spectrum of this compound. Infrared spectroscopy could not be used to detect the difference in position of the fluorine atoms in this compound. 

Phosphorus compounds, 19 19-73 bond properties of, 19 26 chemical properties of, 19 20-31 chiral-centered, 19 25-26 economic aspects of, 19 67-69 as flame retardants, 19 51 inorganic, 11 487-488 oxidation states, coordination numbers, and geometries of, 19 20-26 as oxyacid derivatives, 19 20 reactive organic, 11 496 497 titanium in, 25 56-57 triply connected, 19 25 U.S. prices of, 19 68t U.S. production of, 19 67t... 

The search for inorganic compounds that can act as model systems of the tetranuclear manganese centre of photosystem II, responsible for the oxidation of water, has led to the characterization of a number of complexes of diverse nature and geometry. 

The lanthanides in several complexes exhibit mixed (promiscuous) coordination numbers and geometries, similar to the presence of mixed oxidation states in a inorganic compound. We shall only discuss a few cases here to make the readers aware of this interesting situation. 

The PM3 model qualitatively accounts for equilibrium geometries in these compounds, but does not afford the quantitative descriptions available from density functional models. None of the systems is particularly poorly described, but individual bond length errors are often significant (as reflected in the large mean absolute error). The PM3 model certainly has a role in surveying the geometries of transition-metal inorganic compounds, but it is not a replacement for better models. 

An important part of the inorganic chemist s contribution has been the preparation and characterization of transition metal complexes with unsaturated boron rings as ligands. They have also settled the geometry of a number of compounds using X-ray methods. 

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