Eight-coordinate compounds

Spot tests, 1, 552 Square antiprisms dodecahedra, cubes and, 1, 84 eight-coordinate compounds, 1,83 repulsion energy coefficients, 1, 33, 34 Square planar complexes, 1,191, 204 structure, 1, 37 Square pyramids five-coordinate compounds, 1,39 repulsion energy coefficients. 1,34 Squares... 

Cationic complexes of Tl3+ with oxygen donors are known, and can be regarded as substitution products of [T1(C)H2)6]3+ (c/. Section 25.2.8.3.1). The DMSO product has been characterized with various anions,403 and there seems no reason to suppose that similar compounds cannot be prepared with donor ligands which are resistant to oxidation. The cation [Tl(pyNO)8]3+ (prepared as the perchlorate) may be an indication that eight-coordinate compounds are also accessible in thallium(III) chemistry.404... 

Eight-coordinate compounds containing three bidentate ligands can be classified into the following three types, depending on the normalized bite of the bidentate ligands ... 

The structures are known for a number of these compounds thus, of the eight-coordinate compounds, Eu(acac)3(phen) is square antiprismatic, Eu(dpm)3(py)2 and Nd(tta)3(Ph3PO)2 are dodecahedral seven-coordinate Lu(dpm)3(3-picoline) is a face-capped trigonal prism and Eu(dpm)3(quinuclidine) a capped octahedron. Nine-coordination is found in Eu(dpm)3(terpy) and also in Pr(facam)3(DME)3(facam = 3-trifluoroacetyl-D-camphorate). 

The most common coordination number of titanium is six, although four-, five-, seven-, and eight-coordinate compounds are known (Table 2). Table 3 summarizes the common oxidation states of titanium with the associated coordination numbers and stereochemistries. Zirconium shows a similar range of oxidation states (see Zirconium Hafnium Inorganic Coordination Chemistry), however, Zr and Flfr are much less stable, relative to Zr and Hf, than is the case for titanium. 

Such a structure would require four positive ions (protons) for electrostatic neutrality. However, while zirconium is one of the few elements which have been found to form eight-coordinated compounds (Penney... 

Edge-coalesced icosahedra eleven-coordinate compounds, 99 repulsion energy coefficients, 33, 34 Effective atomic number concept, 16 Effective bond length ratios non-bonding electron pairs, 37 Effective Eight-coordinate compounds stereochemistry, 86-94 Electrochemistry, 475-477 aqueous solution, 479-490 multimetallic systems, 485 non-aqueous solutions, 493 Electrodes... 

The two most common geometries for eight-coordinate compounds (a) the trigonal dodecahedron and (b)the square antiprism. 

The example of this net is found in the eight coordinated compound [La(2,2 -bipyridine-A/ iV -dioxide)4](BPh4)(C104)2-2.75MeOH, [18] see Figure 9.15. 

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