Angular overlap model ligand field theory

Warren KD (1984) Calculations of the Jahn-Teller Coupling Constants for d Systems in Octahedral Symmetry via the Angular Overlap Model. 57 119-145 Warren KD (1977) Ligand Field Theory off-Orbital Sandwich Complexes. 33 97-137 Warren KD (1976) Ligand Field Theory of Metal Sandwich Complexes. 27 45-159 Watson RE, Perlman ML (1975) X-Ray Photoelectron Spectroscopy. Application to Metals and Alloys. 24 83-132... 

Although essentially within the spirit of ligand field theory as enunciated in introductory remarks, there is an approach to dealing with the metal-ligand bonding which has developed into a field of its own, and deserves separate treatment. It is the so-called Angular Overlap Model (AOM). The choice of name arose from the early ways iif which its procedures were applied, and is no longer particularly apt. Nevertheless the name persists and is likely to do so, and will be employed here. Some of the reasons for the initial choice of the name will become obvious as the subject is outlined. 

Our approach throughout this review has not been to provide a means for some ab initio computation of ligand field properties rather it has been to demonstrate that the formalism of ligand field theory in general, grows naturally and definitively from the concepts of quantum chemistry, and that in the particular form of the angular overlap approach leads to obvious chemical significance for the model parameters. With this analysis as a backdrop, future empirical studies may proceed with renewed confidence and utility. 

VanQuickenbome and Ceulemans have advanced a model, based on the angular overlap model variant of ligand field theory, to rationalize the observations of the preferentially labilized ligand [68], This model was focussed mainly on T2 as the reactive state. Although not a necessary feature of their treatment, they concluded that a dissociative mechanism was operative. Kirk suggested an edge displacement mechanism, which is associative [5], but he also considered a dissociative mechanism [12], An associative mechanism for the prompt T2 reaction has been inferred on the basis of symmetry arguments [6]. 

Under the second topic of Ligand-field Theory and its Extensions we describe the basic concepts behind the various versions of LFT - the angular-overlap model (AOM) and its extensions. In the section named The physical background conditions for the applicability of the ligand-field approach we sketch briefly the theoretical foundation and limits of applicability of the effective-hamiltonian approach with special attention to electronic multiplets. In the theory section, we describe various approaches in current calculations of electronic structure, such as LFDFT, SORCI and TDDFT, with the various applications detailed in the following section, before an outlook for further developments. 

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