Could uranium(XII)hexoxide, UO6 (O-h) exist?

The formally dodecavalent, octahedral (UO6)-O-XII is found to be a local en ergy minimum at Several theoretical levels, including quasirelativistic sin gle-reference (HF, B3LYP, MP2 and CCSD(T)) and multireference CI approaches . The fully relativistic, single-configuration Dirac-Fock (DF) approach giv es similar U-O bond lengths but has one imaginary frequency. In this hypoth etical compound the largest formal oxidation state of uranium would be incr eased from +VI to +XII. (C) 2000 Elsevier Science B.V.