Features of Polymerization of Methyl Methacrylate in the Presence of New Ruthenium(II) and Ruthenium(III) Carborane Complexes with Chelate P‒O‒P Ligands

The radical polymerization of methyl methacrylate by the atom transfer radical polymerization (ATRP) mechanism under the action of systems based on ruthenium(II) and ruthenium(III) carborane complexes containing chelate P‒O‒P ligands of various structures has been studied. It has been shown that systems based on these metal complexes, carbon tetrachloride, and isopropylamine as a reducing agent are capable of initiating the radical polymerization of methyl methacrylate. The most effective among those studied are systems based on ruthenacarboranes containing 9,9-dimethyl-4,5-bis-(diphenylphosphino)xanthene as a ligand. These compounds are capable of carrying out the process in a controlled manner, as evidenced by a linear increase in the molecular weight of the polymer and a decrease in dispersity values with increasing conversion. The controlled process according to the ATRP mechanism is confirmed by the presence of chlorine atoms at the ends of the polymer chains, as it has been detected by MALDI mass spectrometry. It has been shown that the possibility of coordination of the ruthenium atom with the oxygen atom of the ligand reduces the rate of the polymerization process and the degree of control over it.