QUANTUM-CHEMICAL INVESTIGATION OF THE STRUCTURE AND REACTIVITY OF INDOLE-DERIVATIVES OF TRICARBONYLCHROMIUM(0)

In a theoretical investigation of the structure and reactivity of indo le derivatives of tricarbonylchromium(0), we have used two different s emi-empirical quantum chemical models derived from the extended Huckel molecular-orbital (EHMO) formalism. The first one, based on the atom- superposition and electron-delocalization (ASED) method, is used to op timize the geometry of the systems; it is shown to lead to results in satisfactory agreement with experiment in the case of the complex for which X-ray structural data are available, the average errors being 0. 03-0.05 Angstrom for bond distances and 5 degrees for bond angles. The second one consists of a local reactivity index, made of the intermol ecular interaction energy between the organometallic substrate and a m odel reactant. It is seen that this procedure is able to reproduce the experimental trends as to the most reactive regions of the systems in vestigated towards nucleophilic and electrophilic addition reactions.