Coordination characteristics of four isomeric a-diimine ligands. p Molecular orbital perturbation calculations for the bidiazines and their correlation with the properties of group 6 metal carbonyl complexes. Journal of the American Chemical Society, (108)13:3578--3586, 1986. [PUMA: Group bidiazine;molybdenum bidiazine bidiazine;Group bidiazine;bipyrazine configuration carbonyl;bipyrimidine bidiazine;redox carbonyl VIB bidiazine;electron bidiazine;tungsten carbonyl;bipyridazine carbonyl;chromium basicity potential]