Polymerization of coordinated monomers. XI. Structure and reactivity of the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene

The time‐averaged orientation of styrene in the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene was determined by use of the chemical shift changes of the protons in the methyl methacrylate on the ternary molecular complex formation. The observed chemical shift change for each of the protons in the methyl methacrylate is expressed by the weighted average of the shifts due to the anisotropic shielding of the benzene ring of styrene for conformations I and II, using the common statistical weight. Conformations I and II correspond to the cis and trans rotational isomers, respectively, of methyl methacrylate with respect to the rotation of the methoxymethyl group around the carbonyl carbon‐ether oxygen bond. Extended Hückel calculations were made on the methyl methacrylate monomer coordinated to stannic chloride and styrene monomer as well as the growing radicals corresponding to the monomers. The energy levels of the frontier orbitals of the species were determined by use of the ionization potentials, the absorption maxima, and the results of the extended Hückel calculations. The high reactivity of the ternary molecular complex is discussed in terms of the interactions between the frontier orbitals of the styrene and those of the coordinated methyl methacrylate.