POLYMERIZATION OF COORDINATED MONOMERS .20. ABINITIO MOLECULAR-ORBITAL STUDY ON THE BINARY MOLECULAR-COMPLEX COMPOSED OF METHYL-METHACRYLATE AND BORON-TRICHLORIDE

The stereo and the electronic structures of methyl methacrylate and the binary molecular complex composed of methyl methacrylate and boron trichloride are determined by quantum chemical calculations based on ab initio molecular orbital methods with the STO-3G basis set. The stable structures of methyl methacrylate in the free state are a transoid form and a cisoid form. The transoid form is slightly (0.5 kcal/mol) more stable than the cisoid form. The total energy change accompanying binary molecular complex formation is calculated to be -43 kcal/mol. The most stable structure of the binary molecular complex composed of methyl methacrylate and boron trichloride is a twisted form in which the dihedral angle between the vinyl group and the ester group is 19.7-degrees. A large amount of electron transfer from methyl methacrylate to boron trichloride is calculated to occur on binary molecular complex formation. Mulliken's population analysis shows the electron transfer to be the origin of the twist of the binary molecular complex. The energy level of the lowest unoccupied molecular orbital is substantially lowered by the coordination of boron trichloride.