Novel ruthenium(ii) and (iii) carborane complexes with diphosphine ligands and their application in radical polymerization

Abstract

Ruthenium(ii) and (iii) carborane complexes containing XantPhos as a ligand were synthesized for the first time. It was shown that the reaction of the known complex exo-5,6,10-[Cl(Ph3P)2Ru]-5,6,10-(µ-H)3-10-H-nido-7,8-C2B9H8 with a 10% molar excess of XantPhos in benzene at 80 °C leads to a new closo-ruthenacarborane 3-Cl-3,3-[x2-XantPhos]-closo-3,1,2-RuC2B9H11, which can be easily converted to the corresponding acetonitrile complex 3-CH3CN-3,3-[x2-XantPhos]-closo-3,1,2-RuC2B9H11 by the reaction with isopropylamine in a dichloromethane—acetonitrile solvent mixture at 40 °C. These compounds, as well as previously synthesized ruthenium(ii) carborane complexes, were used as a basis for new catalyst systems allowing to conduct controlled radical polymerization at high rates even at low catalyst loading. The specific features of methyl methacrylate polymerization under the action of the indicated catalyst systems were considered and the mechanism of the process was investigated.