Latent and Air-Stable Pre-Catalysts for the Polymerization of Dicyclopentadiene: From Penta- to Hexacoordination in Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes

Autor:	Iris Elser, Roman Schowner, Michael R. Buchmeiser, Kordes Benjamin Richard, Katharina Herz, Laura Stöhr, Wolfgang Frey, Hagen J. Altmann
Rok vydání:	2018
Předmět:	010405 organic chemistry Ligand Organic Chemistry chemistry.chemical_element General Chemistry ROMP 010402 general chemistry Metathesis 01 natural sciences Catalysis 0104 chemical sciences chemistry.chemical_compound Polymerization chemistry Molybdenum Dicyclopentadiene Polymer chemistry Carboxylate Carbene
Zdroj:	Chemistry - A European Journal. 24:12652-12659
ISSN:	0947-6539
DOI:	10.1002/chem.201801862
Popis:	The pentacoordinated, 16-valence electron (VE) Mo imido alkylidene N-heterocyclic carbene (NHC) complexes I1-I5 and the hexacoordinated 18-VE Mo imido alkylidene NHC complexes 1-4, 8, 10 and 12 containing a chelating ligand have been prepared and used as thermally latent catalysts in the ring-opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD). Both 10 and 12 are the first Mo imido alkylidene complexes with a chelating alkylidene featuring a carboxylate group. Complexes I1-I3 and I5 as well as 1-4 proved to be fully thermally latent in the presence of DCPD. With the changes in both the electronic and steric situation at the imido ligand provided by these pre-catalysts, different temperatures of the onset of polymerization (Tonset =65-140 °C) and for the exothermic maximum of the curing curve (Texo,max =98-183 °C) of DCPD were achieved. Also, the degree of crosslinking was successfully varied as indicated by swelling experiments in toluene, which revealed degrees of swelling between 0 and 50 %. While the introduction of a chelating alkylidene increases Tonset , the introduction of more electron-donating anionic ligands (tert-butoxide, phenoxide) resulted in a drastic reduction in Tonset , underlining the high flexibility of these systems. The hexacoordinated high-oxidation state molybdenum imido alkylidene NHC complexes 2, 3 and 4 were stable under air for at least twelve hours in the solid state.
Databáze:	OpenAIRE
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