Ruthenium(II) complexes of Schiff base derived from cycloalkylamines as pre-catalysts for ROMP of norbornene and ATRP of methyl methacrylate

摘要

AbstractRuthenium(II) complexes of Schiff base derived from cycloalkylamines (cycloalkyl?=?cyclopentyl (1a), cyclohexyl (1b), cycloheptyl (1c), and cyclooctyl) (1d) were synthesized: [RuCl(CyPen-Salen)(PPh3)2] (2a), [RuCl(CyHex-Salen)(PPh3)2] (2b), [RuCl(CyHep-Salen)(PPh3)2] (2c), and [RuCl(CyOct-Salen)(PPh3)2] (2d). The Schiff base-RuIIcomplexes2a-dwere characterized by elemental analysis, FTIR, UV-Vis,1H-,13C and31P NMR, and cyclic voltammetry. The complexes2a-dwere evaluated as catalytic precursors for ROMP of norbornene (NBE) and for ATRP of methyl methacrylate (MMA). The syntheses of polynorbornene (polyNBE) via ROMP with complexes2a-das pre-catalysts were evaluated under different reaction conditions ([HCl]/[Ru], [EDA]/[Ru], [NBE]/[Ru], and temperature). The highest yields of polyNBE were obtained with [NBE]/[HCl]/[Ru]?=?5000/25/1?M ratio in the presence of 5?μL of EDA for 60?min at 50?°C. MMA polymerization via ATRP was conducted using the complexes2a-din the presence of ethyl-α-bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru]?=?1000/2/1?at 85?°C. The linear correlation of ln([MMA]0/[MMA]) and time indicates that the concentration of radicals remains constant during the polymerization and that the ATRP of MMA mediated by2a-dproceeds in a controlled manner. Molecular weights increased linearly with conversion, however, the experimental molecular weights were higher than the theoretical ones.Graphical abstractDisplay OmittedHighlights?A series of phosphine ruthenium(II) complexes of Schiff base derived from cycloalkylamines (2a-2d) have been synthesized and characterized.?All Schiff-base ligands and their ruthenium complexes (2a-2d) were fully characterized by1H and13C NMR spectra, UV-vis, and infrared spectrometry.?<