Tuning the Latent Behavior of Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes in Dicyclopentadiene Polymerization

Abstract

We report the synthesis of O- and N-chelated hexacoordinated molybdenum imido alkylidene N-heterocyclic carbene (NHC) bistriflate and pentacoordinated molybdenum imido alkylidene NHC monotriflate monoalkoxide complexes and their use as thermally latent and in some cases air-stable precatalysts in the ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD). Introduction of electron-withdrawing and electron-donating groups at the O-chelated alkylidene ligand allowed for the tuning of both the onset temperature of polymerization (T onset) and the temperature of the exotherm maximum (T exo,max). In addition, N-chelated complexes were synthesized using easily available 2-vinylpyridine or 2-vinyl-N,N-dimethylaniline to yield five-membered and, for the first time, four-membered molybdenum imido alkylidene NHC chelates. With these precatalysts, T onset and T exo,max could be varied between 52 and 142 °C and between 99 and 174 °C, respectively.

Tungsten Oxo and Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes for the Visible-Light-Induced Ring-Opening Metathesis Polymerization of Dicyclopentadiene

“…The comparably low swelling of pDCPD prepared by the action of W-1 to W-4 suggests a high degree of cross-linking. This is in line with the T g values, at least found with DCPD concentrations between 3.3 and 5 M . Thus, the T g values of pDCPD synthesized by the action of W-2 , W-3 , and W-4 showed a similar, though a less pronounced trend as for the conversion (lower T g at higher concentrations), which might also originate from poor TPPT solubility and inefficient olefin metathesis precatalyst activation.…”

“…The comparably low swelling of pDCPD prepared by the action of W-1 to W-4 suggests a high degree of cross-linking. This is in line with the T g values, at least found with DCPD concentrations between 3.3 and 5 M. 95 Thus, the T g values of pDCPD synthesized by the action of W- We sought to interrogate our ability to exert spatial control with this system to enable potential applications in material science such as photolithography or 3D printing. Therefore, we irradiated a sample of W-2 (0.01 mol %) and TPPT (0.02 mol %) in a 5 M DCPD solution through a photomask.…”

“…Most of the tested Mobased precatalysts were previously successfully employed as latent initiators in the thermally induced ROMP of DCPD. 94,95 However, to our great surprise, those precatalysts were not latent anymore in the mixture with the photoredox catalyst, i.e., with TPPT. This can be explained by the high Lewis acidity of TPPT, 51 which alters the latency of the system, presumably by interference with the chelating heteroatom of the alkylidene ligand or by other interactions with ligands, e.g., the lone pair of the imido ligand.…”

“…Lastly, we probed a selection of five molybdenum-based precatalysts; one example is depicted in Figure C. Most of the tested Mo-based precatalysts were previously successfully employed as latent initiators in the thermally induced ROMP of DCPD. , However, to our great surprise, those precatalysts were not latent anymore in the mixture with the photoredox catalyst, i.e. , with TPPT .…”

Hybridization of a Polymer inside the Pores of Activated Carbon and Pore Structural Characterization

“…The structure of polydicyclopentadiene (PDCPD) prepared by thermal polymerization is different from that prepared via ROMP and radical polymerization (Scheme ). − It is well known that DCPD readily undergoes thermal decomposition into cyclopentadiene (CPD) (eq 1 in Scheme ). The polymerization of DCPD is driven by a Diels–Alder reaction through the successive addition of CPD according to eq 2 in Scheme .…”