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 gÁmol À1 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) À1 h À1 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) À1 h À1 at 60 C after 4 h was obtained using [Al]/[Pd] = 1750, 7 μmol

Ru/Pd Complex and Its Monometallic Fragments as Catalysts for Norbornene Polymerization via ROMP and Addition

“…geometry. Mono-Pd showed a typical distorted square planar molecular geometry, where the NPdO bond angle and PdP bond distance have values close to those predicted for similar complexes [11,19,[31][32]. The bond angle and distance values of the monometallic complexes and their fragments in the heterobimetallic species were very similar.…”

“…Complexes based on late-transition metals have been widely used as catalysts in a large number of catalytic reactions, such as the reactions of olefins and acetylenes with hydrogen, carbon monoxide, water, or other nucleophiles, as well as the isomerization, oligomerization, and polymerization of olefins [1,2]. Especially, ruthenium (Ru) and palladium (Pd) metallic centers have emerged as multifunctional catalysts [3][4][5][6][7][8][9][10][11]. These transition-metals have demonstrated high catalytic activity in polymerization reactions [11].…”

“…Especially, ruthenium (Ru) and palladium (Pd) metallic centers have emerged as multifunctional catalysts [3][4][5][6][7][8][9][10][11]. These transition-metals have demonstrated high catalytic activity in polymerization reactions [11]. Based on the functionality of these metals, and aiming to increase the range of catalytic reactions, a large number of studies using heterobimetallic complexes composed of Ru(II) and Pd(II) fragments have been conducted [11][12][13].…”

“…These transition-metals have demonstrated high catalytic activity in polymerization reactions [11]. Based on the functionality of these metals, and aiming to increase the range of catalytic reactions, a large number of studies using heterobimetallic complexes composed of Ru(II) and Pd(II) fragments have been conducted [11][12][13]. Furthermore, the use of bimetallic complexes as homogeneous catalysts can increase reactivity via synergistic cooperation [14,15].…”

“…In studies conducted by our research group, ROMP has been initiated using noncarbene amine-based Ru complexes, where the active species is obtained in situ through reaction between the Ru complex and ethyl diazoacetate (EDA) [11,[23][24][25][26][27]. Recently, heterobimetallic systems for multifunctional catalysts, mainly in the polymerization mechanism, have been addressed [11,28]. This study reports on the synthesis and characterization of a new heterobimetallic complex based on Ru(II) and Pd(II) for ROMP and vinyl polymerization of norbornene.…”