Coordination geometry tris complexes

Figure 15.16 Coordination geometries of bis- and tris-l,2-dithiolene complexes (see text).

Properties of nickel poly(pyrazol-l-yl)borate complexes such as solubility, coordination geometry, etc., can be controlled by appropriate substituent groups on the pyrazol rings, in particular in the 3- and 5-positions. Typical complexes are those of octahedral C symmetry (192)°02-604 and tetrahedral species (193). In the former case, two different tris(pyrazolyl)borate ligands may be involved to give heteroleptic compounds.602,603 Substituents in the 5-position mainly provide protection of the BH group. Only few representative examples are discussed here. 

The coordination geometry of these Cu(III) complexes is presumed to be square planar, indicative of high field d complexes. This has been demonstrated in the crystal structure of deprotonated tri-a-aminobutyric acid, Cu "(H 2Aib3), in which the copper-donor atom bonds were found to be 0.12-0.17 A shorter than for the corresponding Cu(II) complex... 

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