Coordination geometries inorganic compounds

As a consequence of its electronic configuration, a variety of coordination numbers and geometries have been observed for copper(I) compounds, especially for inorganic representatives (see Fig. 1.3) [32]. In the organometallic chemistry of copper, the linear and trigonal coordination geometries in particular, though distorted towards T-shaped, are frequently encountered. 

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 stereochemistry of uranium alkoxides is very diverse, and it is possible to conclude that the geometry of the metal atom is independent on its oxidation state and the coordination numbers are in general lower than those observed for the inorganic compounds. In the series of monomeric U(IV) molecules — e.g., [U(OC6H3Bu 2-2,6)4] [1669], [UI2(OC6H3Bu 2-2,6)2THF] [79],... 

Furthermore, inorganic compounds present coordination geometries different from those found for carbon. For example, although 4-coordinate carbon is nearly always tetrahedral, both tetrahedral and square planar shapes occur for 4-coordinate compounds of both metals and nonmetals. When metals are the central atoms, with anions or neutral molecules bonded to them (frequently through N, O, or S), these are called coordination complexes when carbon is the element directly bonded to metal atoms or ions, they are called organometaUic compounds. 

The tetrahedral geometry usually found in 4-coordinate compounds of carbon also occurs in a different form in some inorganic molecules. Methane contains four hydrogens in a regular tetrahedron around carbon. Elemental phosphorus is tetratomic (P4) and also is tetrahedral, but with no central atom. Examples of some of the geometries foimd for inorganic compounds are shown in Figure 1-4. 

Much of our current knowledge of bonding geometry of atoms has been derived from crystal structure determinations. Atomic coordinate data that have been published are included in databases, as will be described in more detail in Chapter 16. For organic compounds the Cambridge Structural Database " can be accessed by computer. Similar data for inorganic compounds are found in the Inorganic Crystal Structure Database. Comparisons with other experimental methods, such as... 

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