Coordination chemistry octahedral geometries

Chirality is an important part of today s chemistry and, in this respect, the pseudo-octahedral geometry of hexacoordinated phosphorus derivatives is interesting as it suffices to coordinate to the central atom three identical sym-... 

This is by for the most common coordination number. With certain ions si -coordinate complexes are predominant. For example. chromhim(lll) and cobah(MI) are almost exclusively octahedral in their complexes. It was this large series of octahedral Cr(III) and Co(III) complexes which led Werner to formulate his theories of coordination chemistry and which, with square planar plalinum(II) complexes, formed the basis for almost all of the classic work on complex compounds. Before discussing the various isomeric possibilities for octahedral complexes, it is convenient to dispose of the few nonoctahedral geometries. 

Hexavalent. The majority of An(VI) coordination chemistry with N-donors has been explored with the uranyl cation, 50i. Stable adducts with the hgands discussed in the tri- and tetravalent complexes have been described, for example, U02X2L (X = halide, OR, NO3, RCO2). The coordination numbers observed for these complexes are typically 6, 7, or 8 with octahedral, pentagonal bipyramidal, or hexagonal bipyramidal geometries, respectively. Neutral and anionic thiocyanates have also been isolated, for example [U02(NCS)j2- yH20(x = 2 5). 

The coordination chemistry of Cr can be subdivided into the realm of mononuclear coordination compounds, which can be derived (at least formally) from the blue [Cr(OH2)e] ion, and the chemistry of metal-metal bonded species (analogs of Cr2(OAc)4). Most of the former are octahedral high-spin complexes with distinct tetragonal distortions caused by the Jahn - Teller Effect. With strong-field ligands, low-spin octahedral complexes are formed, and there are also some four-coordinate complexes of various coordination geometries. The metal-metal bonded species are described in Section 5. 

The coordination geometry around copper(II) peptide complexes is generally tetragonally distorted octahedral, although there are some cases where square planar and square pyramidal geometries can also be found. X-ray crystal stmcture determinations have shown that copper(III) peptide complexes have square-planar geometry (see Copper Inorganic Coordination Chemistry). In this section, we discuss copper(II) peptide complexes copper(III) peptide complexes are reviewed elsewhere. ... 

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