Role of d and f orbitals in the geometries of low-valent actinide compounds. Ab initio studies of U(CH3)3, Np(CH3)3, and Pu(CH3)3

Ab initio electronic structure techniques are utilized in the investigation of the low-valent actinide complexes U(CH3)3, Np(CH3)3 and Pu(CH3)3. Complete active space calculations are performed in a valence double zeta basis set involving relativistic effective core potentials. The optimum geometry for both the pyramidal and planar AnMe3 forms are determined for the ground electronic state of each molecule. Results show a preference for the pyramidal structure, arising from the involvement of the 6d character in the An-C bonding orbitals as a function of bending angle.