Pseudo-bases, pyridine ligands

Figure 8-17. Gillard s proposal for the formation of pseudo-bases of co-ordinated pyridine ligands. It was suggested that the formation of these species allowed a simple explanation for the observed pH dependence of a variety of reactions of complexes of pyridine derivatives.

The crystals with the axial base ligands of 9-16 have two crystaUographically independent molecules, A and B, in the asymmetric unit (Z = 2). Among of them, the crystals with 9-11 showed a similar type of racemization. For the crystal with pyridine as an axial base ligand, 9, the initial structure is shown in Fig. 3.4a. The space group is F2, and there are two molecules in an asymmetric unit. Two molecules are related by a pseudo inversion center between the two molecules. When the crystal was exposed to X-rays, the volume of the unit cell gradually contracted. 

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