Showing papers on "Ring-opening metathesis polymerisation published in 1979"
TL;DR: In this paper, a novel metathesis reaction of olefins proceeds without hydrogen scrambling of isomerization through alkyl or carbonium ion intermediates: the catalyst was prepared by treating reduced MoOx-β-TiO2 with a mixture of N2O and H2 at 200 °C.
Abstract: A novel catalyst is reported on which the metathesis reaction of olefins proceeds without hydrogen scrambling of isomerization through alkyl or carbonium ion intermediates: the catalyst was prepared by treating reduced MoOx–β-TiO2 with a mixture of N2O and H2 at 200 °C.
11 citations
01 Jan 1979
TL;DR: In this article, the stereoselectivity of metathesis of cis and trans R−CH = CH−CH3 has been determined by the trans/cis ratio of but-2-enes (C4) at 0% conversion.
Abstract: With the catalyst Mo (NO) 2X2 (PPh3)2 + EtAlCl2, X=Cl, Br, I, the stereoselectivity of metathesis of cis and trans R−CH = CH−CH3 has been determined by the trans/cis ratio of but-2-enes (C4) at 0% conversion. For R=H, trans/cis C4 is equal to 1. For R=Et, trans/cis ratios of C4 are equal to 0.20 and 12.5 respectively for cis and trans olefin; increasing bulkiness of R results is a significant decrease of stereoselectivity (and activity): with a cis olefin the trans/cis ratio of C4 increases when the bulkinesse of R increases (trans/cis ratio = 0.44 for R=t-C4H9). With a trans olefin the trans/cis ratio of but-2-ene decreases when the R size increases (trans/cis ratio of but-2-ene = 8.3 for R=t−C4H9). This effect does not seem to be the result of an electronic effect of the R group since similar stereoselectivities are obtained with trans R−CH=CH−CH3 where R = t−Bu, phenyl or totyl. Changing the coordination sphere of the precursor catalyst (X = Cl, Br, I) does not result in a meaningful variation of stereoselectivity whereas going from Cr to Mo to W does decrease the stereoselectivity. With cis or trans pent-2-ene, the trans/cis ration of hex-3-enes is always higher than the trans/cis ratio of but-2-enes, with M = Mo or W. This result which is related to a 1–2 repulsive a-e ⇄ e-a interaction in the metallocyclobutane is corroborated by the stereoselectivities of the metathesis of α olefins : propylene, but-1-ene and pent-1-ene. The trans/cis ratio of the products increases in the order : but-2-ene (1.1.) < hex-3-ene (1.42) < oct-4-ene (2.0). If one assumes that stereoselectivity reflects steric interaction during olefin coordination or in the metallo-cyclobutane intermediates, simultaneous steric repulsions seem to account for the observed selectivities : I-2, I-3 and olefin-metal (and or its ligands).
4 citations
TL;DR: Some π-allylpalladium complexes containing a free double bond were treated with the WCl 6 /EtOH/EtAlCl 2 olefin metathesis catalyst as mentioned in this paper.
2 citations
2 citations
1 citations
TL;DR: W2[CH2Si(CH3)3]6 initiates the polymerization of cyclic olefins and in combination with WCl6 is active in the metathesis of both linear and cyclic OleFins.
Abstract: W2[CH2Si(CH3)3]6 initiates the polymerization of cyclic olefins, and in combination with WCl6 is active in the metathesis of both linear and cyclic olefins.
01 Jan 1979
TL;DR: The disproportionation of olefins and the ring-opening polymerization of cycloalkenes are trans-alkylidenation reactions as discussed by the authors, where double bonds are opened and closed.
Abstract: The disproportionation of olefins first reported by Banks and Bailey1) and — as a special case — the ring-opening polymerization of cycloalkenes2, 3) comprise a re-arrangement of the carbon skeleton of the olefins by opening and closure of double bonds. Thus the reaction — generally referred to as metathesis reaction — is a trans-alkylidenation reaction.