The electronic spectrum of Ni(H2O)62+ shows a band at 8500 cm-1 due to d-d transition. [Ph4As][Ni2Cl4] will have such a transition in cm-1 at ?
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The absorption spectra of octahedral complexes of nickel(II) are often used to illustrate basic aspects of metal-ligand bonding in coordination compounds. A number of practical guides for the analysis of such spectra in order to determine crystal field parameters or the equivalent quantities in the angular overlap molecular orbital model have been published. (1, 2) The band maxima of the spin allowed transitions are used to determine 10Dq and B and the spectrochemical series can be established from a comparison of absorption maxima for a series of compounds. (3) The goal of this work is to extend the traditional crystal field analysis and to give the undergraduate student an opportunity to explore quantitative models linking point group symmetry, electronic states and potential energy surfaces. Octahedral nickel complexes are well suited for this purpose, and group theory provides a full description of their electronic states in the energy range of the absorption spectra. (4) The concept of molecules moving on one or several potential energy surfaces is important for many areas of chemistry; examples include detailed reaction dynamics (5) electron transfer processes, (6) where multiple potential energy surfaces similar to those presented in the following, are essential.
An aspect of the absorption spectra of some octahedral nickel(II) complexes that is discussed only in a very cursory manner in the standard texts concerns the shape of the absorption bands, leading to the following questions from our undergradua