Ligand-dictated geometry

There are rather trivial solutions to the former problem1291. Fortunately, the electronic influence exerted by the metal ion is most often a relatively small effect which may be added as a minor perturbation to the ligand-dictated geometry. As discussed in the Introduction (Fig. 1.1), this emerges from experimental structural and spectroscopic data1161.5... 

These and many similar examples resulted in a highly successful general picture of transition-metal ions M coordinated by closed-shell ligands L (anionic or neutral) to form complex cluster ions [ML ]9 in solution. The characteristic coordination shell of each M corresponds to a specific number of sites, with idealized geometry that dictates the possible number of distinct [M(Li) (L2)m. .. ]q structural isomers. Each cluster ion is subject to equilibria with other cluster ions or dissociated ligands in solution,... 

An octahedral geometry (Oh symmetry) is, of course, an ideal case, which virtually none of our systems match. All have lower symmetry (typically >3 or Ci), which further splits the dlevels. However, the octahedral model is a starting point. Lowering the symmetries does not affect the basic nature of the types of excited states. Further, such important features as the d state energies are still dictated by the average A of the ligands. 

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