Non-carbene Complex [RuCl₂(PPh₃)₂(azocane)] as Active Catalyst Precursor for ROMP and ATRP

Abstract: The novel, non-carbene complex [RuCl₂(PPh₃)₂(azocane)] (1) of trigonal bipyramid geometry was synthesized, characterized (CHN elementary analysis, FTIR, EPR, and ³¹P NMR), and applied as catalyst precursor for ring opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). ROMP of norbornene (NBE) resulted in 70% yield at 50 °C in 60 min, with [NBE]/[1] = 5000, and 15% yield from ROMP of norbornadiene was obtained under the same conditions. ATRP of methyl methacrylate (MMA) resulted in ca. 20% conversion at 85 °C in 9 h, with [MMA]/[1] = 1000, and increased to ca. 50% in the presence of Al(OiPr)₃, with narrower PDI values. With [MMA]/[1] = 200, ca. 50% yield was obtained at 85 °C in 6 h either in the absence or presence of Al(OiPr)₃. ATRP of styrene resulted in 9 and 16% conversion at 110 °C in 7 h in the absence or presence of Al(OiPr)₃, respectively, with [St]/[1] = 1000. Results are discussed considering the five-coordinated molecular geometry of the starting complex and the arrangements required in ROMP and ATRP to initiate the reactions. Graphical Abstract: [Figure not available: see fulltext.].