Chain transfer during the aqueous ring-opening metathesis polymerization of 7-oxanorbornene derivatives

Abstract

Ring-opening metathesis polymerization (ROMP) of exo,exo-5,6-bis(methoxymethyl)-7oxabicyclo[2.2.1]hept-2-ene (3) catalyzed by Run(H20)e(tos)2 (tos = p-toluenesulfonate) (1) in the presence of terminal acyclic olefins such as 3-buten-l-ol and methyl acrylate affords low molecular weight polymeric materials. Analysis of these oligomer samples by one-and two-dimensional NMR spectroscopy identifies them as resulting from a true metathesis chain transfer mechanism. These data and the identification of the ring-opened monomer units with alkylidene end groups corresponding to the acyclic chain transfer agent by high resolution mass spectrometry confirm this study as the first example of metathesis of an acyclic olefin by 1. A comparison of the chain transfer activities of a series of acyclic esters yields a reactivity order of terminal olefins > deactivated terminal olefins > internal olefins > deactivated internal olefins, consistent with the behavior of well-characterized homogeneous alkylidene complexes.

Aqueous Catalytic Polymerization of Olefins

“…Acyclic olefins can function as chain‐transfer agents to regulate molecular weights 147, 149, 153. The analysis of the resulting oligomeric products supported the presence of ruthenium alkylidene species 153. Also in accordance with intermediacy of a ruthenium alkylidene species in the aqueous polymerization, the addition of ethyl diazoacetate as a carbene source to [Ru ii (OH 2 ) 6 ](OTs) 2 enabled ROMP of less reactive low‐strain cyclic olefins such as cyclooctene 154…”

“…Although this issue was only mentioned as an aside, probably in all these cases the catalyst precursor and the monomer ( 12 – 16 ) initially formed a homogeneous solution, and the water‐insoluble polymer precipitated during the polymerization reaction when a largely aqueous reaction medium was employed. Acyclic olefins can function as chain‐transfer agents to regulate molecular weights 147, 149, 153. The analysis of the resulting oligomeric products supported the presence of ruthenium alkylidene species 153.…”

Olefin metathesis in air

“…In 1992, Grubbs and co-workers synthesized the first well-defined ruthenium(II) complex ( 5 , Scheme 2 ) bearing a carbene moiety, able to perform ring-opening metathesis polymerization (ROMP) reactions of low-strained olefins [ 34 – 35 ] and ring-closing metathesis (RCM) reactions of functionalized dienes [ 36 ]. In the solid state, this complex was reported to be indefinitely stable under inert atmosphere whereas it could survive for only several minutes in air.…”

Katalytische Olefinpolymerisation in wässerigen Systemen

“…Obgleich in den Veröffentlichungen nichts Detailliertes zu finden ist, bildeten vermutlich in allen diesen Fällen der Katalysatorvorläufer und das Monomer ( 12 – 16 ) zunächst eine homogene Lösung, und das wasserunlösliche Polymer fiel während der Polymerisationsreaktion aus, sofern ein weitgehend wässeriges Reaktionsmedium verwendet wurde. Acyclische Olefine können als Kettenüberträger fungieren und das Molekulargewicht regulieren 147, 149, 153. Die Analyse von oligomeren Produkten stützt die Annahme einer intermediären Alkylidenruthenium‐Spezies 153.…”

“…Acyclische Olefine können als Kettenüberträger fungieren und das Molekulargewicht regulieren 147, 149, 153. Die Analyse von oligomeren Produkten stützt die Annahme einer intermediären Alkylidenruthenium‐Spezies 153. Ebenfalls in Einklang mit dem Auftreten einer solchen Spezies in der wässerigen Polymerisation ist die Beobachtung, dass mit Ethyldiazoacetat als Carbenquelle und [Ru II (OH 2 ) 6 ](OTs) 2 die ROMP eines wenig reaktiven, ungespannten cyclischen Olefins wie Cycloocten möglich ist 154…”