Quantum chemistry of unusual oxidation degrees of lanthanides and actinides

The electronic structure and properties of actinides in unusual valence forms were considered in the framework of quantum-mechanical concepts. Hartree-Fock atomic calculations of the actinide series as well as molecular orbital calculations of octahedral oxydions of uranium, neptuniun, plutonium and americium in hight and higher valence forms, octahedral tri-and tetravalent chloride complexes from protactinium through einsteinium were conducted. A possible existence of some new valence forms of actinides was considered, based on such calculations. The cation-cation interaction mechanism was suggested. Peculiarities of the trans-effect manifestation in actinide chemistry were considered. New possibilities were shown of using the Moessbauer isomer shifts on actinide nuclei to interpret the chemical properties. The influence of relativi;tic effects on the actinide chemical properties was analyzed. A high value of the spin-orbital splitting Was snown to determine a gradual stabilization and stability of bivalent state at the and of the actinide series, substantial difference in stability of the tetravalent state of lanthanides and actinides, conceptual possibility of preparing lanthanyl groups at the end of the lanthanide series