On the ethenolysis of end-of-life tire granulates

A hexahydro-s-indacene based NHC ligand for olefin metathesis catalysts

“…The Ir(I/II) redox potential of complex 5 is E ¼ þ0.729 V (separation of anodic and cathodic redox potential DE 1/2 ¼ 78 mV) and thus nearly the same as that of the respective (SIMes)IrCl(cod) complex (E ¼ þ0.735 V). Due to the higher signal dispersion of the redox potential, the determination of electron donation is more precise than with IR [31]. The redox potentials of complexes 10 and 11 are E ¼ þ0.515 V (DE 1/2 ¼ 75 mV) and E ¼ þ0.527 V (DE 1/2 ¼ 72 mV), which is slightly more cathodic (ca.…”

“…The IR spectrum of 6 displays symmetric and asymmetric carbonyl stretches at 1979, 2066 cm À1 and a TEP ¼ 2053.5 cm À1 was calculated [29]. This is slightly more donating than the respective SIMes ligand, but weaker than an NHC derived from SIMes, in which the two 4-methyl groups are replaced by 4-NEt 2 [15,30,31]. The Ir(I/II) redox potential of complex 5 is E ¼ þ0.729 V (separation of anodic and cathodic redox potential DE 1/2 ¼ 78 mV) and thus nearly the same as that of the respective (SIMes)IrCl(cod) complex (E ¼ þ0.735 V).…”

Olefin metathesis meets rubber chemistry and technology

“…These multicomponent materials contain-as most technical rubber products-large amounts of vulcanized elastomers (mainly natural rubber), inorganic fillers (carbon black, silica), and a number of other additives. Plenio et al were able to degrade these ETL granulates to organic solubles-primarily oligomeric cis-1,4-isoprene (as evidenced by NMR and HPLC)-using Grubbs or Hoveyda second-generation catalyst (3 or 5) in a reactor with an ethene pressure of 7 bar at 80°C for 12 h. The so-performed ethenolysis had a conversion rate of around 50 %, meaning that 1.0 g of granulate led to the isolation of approximately 0.5 g of oligomeric isoprenes, which are useful starting products for the synthesis of various chemical compounds [155].…”

“…Recently, Wolf and Plenio investigated the reversed ADMET reaction (ethenolysis) of rubber waste in detail [155]. Old car and truck tires are very often shredded to so-called end-of-life tires (ELT) granulates.…”

Converting natural rubber waste into ring-opening metathesis polymers with oligo-1,4-cis-isoprene sidechains

“…4 In particular, the commercial availability and the high functional group tolerance of ruthenium based olefin metathesis catalysts enabled the preparation of various chain-end functionalized oligomeric 1,4-cis-isoprenes from NR 5 and in further course also from (vulcanized) NR based products. The ethenolysis of end-of-life tire granulates (containing primarily NR) yielding oligomeric 1,4-cis-isoprene 6 and the conversion of waste tires into telechelic polyisoprene can be considered as benchmarks in the field. 7 Herein we wish to report our results on using electron deficient olefins, namely acrylates, instead of ethene or allylic olefins as the cross metathesis partner in the degradation of NR.…”