Reactivity of the p‐Cymene‐Ruthenium Complex with Two Phenylamines for Metathesis Polymerization of Norbornene Compared to the Reactivity of Complexes with a Single Benzylamine or Dibenzylamine

Abstract The complexes [RuCl(Cy)(NH 2 Ph) 2 ]Cl ( 1 ), [RuCl 2 (Cy)(NH 2 Bz)] ( 2 ), and [RuCl 2 (Cy)(NHBz 2 )] ( 3 ) were synthesized under identical conditions from [RuCl 2 (Cy)] 2 , where Cy= η 6 ‐ p ‐cymene, Ph=phenyl, and Bz=benzyl. X‐ray crystallography revealed an additional NH 2 Ph ligand in 1 , distinguishing it from the neutral mono‐amine complexes 2 and 3 . The number of amines in these complexes did not correlate clearly with the σ‐donor character or steric hindrance of the amines. Different reactivities were observed for the ROMP of norbornene (NBE), as measured by batch reactions and kinetic studies using Raman and 1 H NMR spectroscopy. Semiquantitative conversions reached up to 90 % with complex 1 and around 40 % with complexes 2 and 3 . DFT calculations supported the hypothesis that the reaction for complex 1 involves the release of an amine through a dissociative mechanism, whereas complexes 2 and 3 react through an associative mechanism involving amine loss. The presence of an amine in the propagation species of complex 1 suggests the participation of the amine as an ancillary ligand. All carbene species are of the η 2 ‐ p ‐cymene type, and the catalytic cycle follows a 14–16‐14 electron counting mechanism.