| Popis: |
Application of the simple VSEPR model to hydride and alkyl derivatives of Main Group and transition elements is considered, and successes and failures of the model are outlined. A survey is presented of the difficulties inherent in the precise location of hydrogen atoms in molecules, and of techniques developed to surmount these problems. Consideration is given to a selection of Main Group and d 0 transition metal molecules which do not comply with the expectations of the model. These include halides such as MF 2 (M=Ca, Sr or Ba), permethyl complexes like WMe 6 , and mixed-ligand species such as Me 2 TiCl 2 and Me 3 ReO 2 . Theoretical attempts to account for this behavior, including extensions to the simple VSEPR model, are described. The phenomenon of ‘agostic’ M⋯H interaction is considered in the context of d 0 transition metal complexes. Whilst rationalization of the phenomenon is beyond the remit of the VSEPR approach, a molecular orbital model is shown to give more insight than does an earlier valence-bond approach in explaining the salient features of the interaction. |
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