Metathesis Activity and Stability of New Generation Ruthenium Polymerization Catalysts

Abstract

A kinetic study of three ruthenium carbene catalysts, (H 2IPr)(PCy3)(Cl)2RudCHPh, 3 (investigated extensively by Mol), (H2IMes)(Cl)2RudCH(o-iPrOC6H4), 4 (Hoveyda's catalyst), and (H2-IPr)(Cl)2RudCH(o-iPrOC6H4), 5 (a new catalyst structure), was conducted under ADMET polymerization conditions. The kinetic behavior of these catalysts was compared to the classical first-and secondgeneration Grubbs' complexes at 30, 45, and 60 °C. Complex 3 exhibits the highest initial ADMET rate (80 DP s -1 ) of any phosphine complex to date and efficiently promotes metathesis even at temperatures as low as 0 °C. Complex 4 alone does not polymerize 1,9-decadiene in the bulk; however, addition of a polar solvent induces polymerization. Combining elements of catalysts 3 and 4 yielded the new complex 5. This complex results in higher polycondensation rates than previous Hoveyda-type structures and exhibits an increased stability over its parent phosphine complex. The new catalyst polymerizes 1,9decadiene in the bulk to high polymer (M n ) 40 000 g/mol) using low catalyst loadings (0.1 mol %). The isomerization chemistry induced by complexes 3 and 5 was investigated using a model compound, 1-octene.

Synthesis, structure of functionalized N-heterocyclic carbene complexes of Fe(II) and their catalytic activity for ring-opening polymerization of ε-caprolactone

“…For example, the NHC complexes of ruthenium show excellent catalytic activity in the atom transfer radical polymerization (ATRP) of styrene [2], the ring-opening metathesis polymerizations (ROMP) of norbornene [3] and 1,5-cyclooctadiene [4], the acyclic diene metathesis (ADMET) polymerization of 1,9-decadiene [5]. NHC-Pd(II) complexes can also efficiently catalyze the ring-opening metathesis polymerizations (ROMP) of norbornene [6] and the copolymerizations of carbon monoxide with ethylene [7a] or bisphenol A [7b], and the NHC-Ni(II) complexes show catalytic activity in dimerizations of ethylene [8], propene and 1-butene [9], the addition polymerization of norbornene and the polymerization of ethylene [10].…”

NHC Backbone Configuration in Ruthenium-Catalyzed Olefin Metathesis

“…An important role on the catalytic activity is also played by the bulkiness of N-aryl substituents, as generally reported for Ru complex, even with backbone unsubstituted NHCs [41][42][43][44][45]. Phosphine-containing Ru catalysts bearing N-o-isopropylphenyl groups in place of N-o-tolyl (8-synGII and 8-antiGII, Figure 6) can be prepared in good yields (60%-65%) with the same procedures adopted for 7-synGII and 7-antiGII [27].…”

“…Figure 6) can be prepared in good yields (60%-65%) with the same procedures adopted for 7-synGII and 7-antiGII [27]. As expected by the increased catalyst bulkiness, 8-synGII and 8-antiGII exhibited higher activity in the RCM of substrates 1 and 9 [41][42][43][44][45] with respect to the corresponding o-tolyl N-substituted catalysts (Tables 1 and 2), whereas the RCM of the more encumbered 11 appeared slowed down (Table 3). The increase of catalyst bulkiness was counterproductive also in the ROMP of 13 (Scheme 2), where 8-antiGII gave lower conversion to polymer (8%) with respect to its analogous with N-o-tolyl groups, 7-antiGII (44%) [40].…”

Acyclic diene metathesis (ADMET) polymerization of allyl undec-10-enoate and some related esters

“…Initially, to establish our polymerization procedure, we polymerized deca-1,9-diene (8) [28,29]. The neat diene 8 was first stirred with 1 mol% of catalyst 1 at 20°C under an atmosphere of dry argon.…”