Mechanism and Activity of Ruthenium Olefin Metathesis Catalysts

Abstract

This report details the effects of ligand variation on the mechanism and activity of ruthenium-based olefin metathesis catalysts. A series of ruthenium complexes of the general formula L(PR(3))(X)(2)Ru=CHR(1) have been prepared, and the influence of the substituents L, X, R, and R(1) on the rates of phosphine dissociation and initiation as well as overall activity for olefin metathesis reactions was examined. In all cases, initiation proceeds by dissociative substitution of a phosphine ligand (PR(3)) with an olefinic substrate. All of the ligands L, X, R, and R(1) have a significant impact on initiation rates and on catalyst activity. The origins of the observed substituent effects as well as the implications of these studies for the design and implementation of new olefin metathesis catalysts and substrates are discussed in detail.

Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions

“…64 In order to deconvolute these potential contributions to khomo, we examined the mechanism of ROMP. Based on previously reported results for related phosphine-based catalysts, [65][66][67] we proposed a dissociative pathway ( Figure 5A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 intermediate. Subsequent cycloreversion yields a Pn+1 alkylidene and regenerates the 14-electron species.…”

Enantioseparation of doubly functionalized polar norbornenes by HPLC and their ruthenium‐catalyzed ring‐opening metathesis polymerization

“…In addition, the polymerization for the chiral monomer (þ)-1 proceeds in a living fashion 44 : the molecular weights of poly-2 were varied by controlling the molar ratio of monomer to initiator ( The control of the molecular weight is attributed to the fact that for the catalyst 3, k i /k p is high enough that all the chains initiate and grow at a similar rate. 45,46 For this reason, catalyst 3 promotes living ROMP for a novel chiral norbornene (þ)-1 bearing both cyano and ester groups with both higher activity and better molecular weight control.…”

Self-healing polymers and composites

“…Preliminary systems used styrene/polystyrene blends 18 and phenolic based resins 19 in their microcapsules with varying results, but the healing chemistry found to most completely fulfil this daunting set of healing agent requirements is the ring opening metathesis polymerisation (ROMP) [20][21][22] of dicyclopentadiene (DCPD) with the popular ruthenium based olefin metathesis catalyst bis(tricyclohexylphosphine) benzylidine ruthenium dichloride, colloquially referred to as 'Grubbs' catalyst'. [23][24][25][26][27] In this reaction, the highly strained olefin of DCPD coordinates to the ruthenium catalyst, followed by a cycloaddition with the ruthenium-carbene to form a metallocyclobutane intermediate, and finally a cycloreversion to open dicyclopentadiene's strained ring and add an ultimate unit to the growing polymer chain (Fig. 2).…”