Novel carborane complexes of ruthenium with tridentate phosphine ligands: Synthesis and application in Atom Transfer Radical Polymerization

Novel complexes of ruthenium with tridentate phosphine ligands: tris(diphenylphosphinomethyl)ethane and bis(2-diphenylphosphinoethyl)phenylphosphine were synthethised starting from the well-known exo-nido-ruthenacarborane [exo-5,6,10-{Ru(Ph3P)2Cl}-5,6,10-(μ-H)3-10-H-nido-7,8-C2B9H8] via ligand substitution followed by exo-nido- to closo-rearrangement in toluene. The novel compounds were characterized by NMR or EPR spectrometry, MALDI TOF mass-spectrometry and cyclic voltammetry. A single-crystal X-ray diffraction study confirmed closo-structure of the obtained complexes and the presence of η3-coordinated triphosphine ligands in it structures. The correlations between ligand structure and complex stability and reactivity were established. The possibility of application of ruthenacarboranes with tridentate phosphine ligands in Atom Transfer Radical Polymerization (ATRP) was explored. It was found out that complexes based on tris(diphenylphosphino)methane are the most suitable catalysts.