Monometallic and heterobimetallic ruthenium (II) and palladium (II) complexes based on a pyridine‐hydrazone ligand as bifunctional catalysts for ROMP of norbornene and ethylene polymerization

Abstract The monometallic complex [Pd(L)(PPh 3 )] ( mono‐Pd ) was synthesized using a potentially tridentate hydrazone (H 2 L) and used as precursor to prepare a heterobimetallic ruthenium (II)‐palladium (II) complex [Cl 2 ( p ‐cymene)Ru(μ‐L)Pd (PPh 3 )] ( Ru‐Pd ). Mono‐Pd and Ru‐Pd were characterized by fourier transform infrared spectroscopy (FTIR), ultraviolet‐visible spectroscopy (UV–Vis), 1 H, 13 C{ 1 H} and 31 P{ 1 H} nuclear magnetic ressonance(NMR) spectroscopy, elemental analysis, cyclic voltammetry, matrix‐assisted laser desorption/ionization ‐ time of flight (MALDI‐TOF) mass spectrometry, and computational methods. The mono‐Pd was additionally studied by single‐crystal X‐ray diffraction. The complex [RuCl 2 ( p ‐cymene)(Isoniazid)] ( mono‐Ru ) was also obtained following literature methods aiming a comparison in the catalytic activity. The ring opening metathesis polymerization (ROMP) of norbornene (NBE) using mono‐Ru or Ru‐Pd as precatalysts in the presence of ethyl diazoacetate (EDA) was evaluated as a function of time (10–60 min) using [NBE]/[EDA]/[Ru] = 5000/28/1 at 50°C. The time increases produced good yields of polyNBE, reaching 38% and 46% for mono‐Ru and Ru‐Pd , respectively. The polyNBE produced was measured by size‐exclusion chromatography (SEC) and reached an order of magnitude of 10 5 g·mol −1 of M n , with Ð values ranging from 2.51 to 1.86 for mono‐Ru and from 3.50 to 1.66 for Ru‐Pd . The catalytic activity of mono‐Pd and Ru‐Pd on ethylene polymerization was assessed with a range of [Al]/[Pd] molar ratio between 350 and 1750, 30–70°C temperature, 2 to 4 h reaction time, and total reaction volume of 25 and 50 ml. Mono‐Pd achieved an activity of 22.80 kg PE (mol Pd) −1 h −1 at 60°C after 4 h using [Al]/[Pd] = 1050, 7 μmol of catalyst in 25 ml of toluene, and 116 psi ethylene. For Ru‐Pd , an activity of 20.35 kg PE (mol Pd) −1 h −1 at 60°C after 4 h was obtained using [Al]/[Pd] = 1750, 7 μmol of catalyst in 25 ml of toluene, and 116 psi ethylene. Overall, Ru‐Pd showed to be active in both ROMP and ethylene polymerization reactions, being categorized as a bifunctional catalyst.