Crystal field stabilization energies lanthanides

Variable coordination numbers. The coordinating stabilization energy (about 4.18 kJ-mol ) of lanthanide ions is much smaller than the crystal field stabilization energy of transition metals (typically >418 kJ moP ). Therefore, the coordinating bonds of lanthanide complexes are not directional and the coordination number varies from 3 to 12. 

The order can be explained by the decrease in metal-ion radius fix m Mn to Zn, and by the increase of crystal-field stabilization energy fi om Fe to Cu. The d orbitals of Zn (II) are full, so no stabilization energy is gained through the complex. That is the main reason that Zn (II) AcAc behaved similarly to that of the alkaline earth metal ions and the lanthanide and actinide ions, initiating curing at low temperature but giving poor mechanical properties after cure. 

Fig. 13.6 (a) Octahedral crystal field stabilization energies of the tripositive lanthanide ions, (b) Enthalpy data related to the formation of (octahedral) complexes of the ligand shown in Fig. 13.7 (see also the caption to Fig. 13.2). 

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