A DENSITY-FUNCTIONAL STUDY OF THE INTERNAL-ROTATION IN THE QUADRUPLY BONDED MO2CL4(PH3)(4) COMPLEX

Internal rotation around the Mo-Mo bond in Mo2Cl4(PH3)(4) is studied b y DFT calculations with the B3LYP functional. The lowest singlet ((1) delta(2)) and triplet ((3) delta delta) states are studied, full geom etry optimization bring performed for each value of the rotational ang le (chi). Compared to experimental data and to previous CASSCF calcula tions, the singlet-triplet energy separation is satisfactorily reprodu ced provided approximate spin-projected broken-symmetry calculations a re used for the singlet state. The geometrical changes due to the inte rnal rotation or the nature of the electronic state are discussed with respect to experimental data. Structural correlations are derived fro m the geometry optimizations for both singlet and triplet states. (C) 1998 Elsevier Science B.V. All rights reserved.