Reactivity of (C5Me5)2Sm and related species with alkenes: synthesis and structural characterization of a series of organosamarium allyl complexes

Synthesis and X-ray structure of a borohydrido metallocene of neodymium and its use as pre-catalyst in Nd/Mg dual-component ethylene and isoprene polymerisations

“…While it was reported that the presence of two THF per Sm sensibly lowers the activity of Cp* 2 Sm vs. ethylene [41] no great difference of activity and productivity is observed with 50 equivalent of THF in our case (run 5). One can only notice the shift of A max to earlier times, corresponding to the shortening of the steady ethylene consumption period.…”

“…In a previous study, we found that the borohydrido Nd(BH 4 ) 3 (THF) 3 [41]. Surprisingly, preliminary isoprene polymerisation studies show that the 1/1BEM combination displays some activity, giving 56 % conversion in 90 h at 50 °C, and a polymer that is 87 % trans-regular.…”

Recent Advances in Rare Earth Complexes Bearing Allyl Ligands and Their Reactivity towards Conjugated Dienes and Styrene Polymerization

“…The monocationic allyl complexes 1 RE showed no activity towards the polymerization of 1,3-butadiene at room temperature [21]. In contrast, these complexes were active when combined with Al( i Bu) 3 as co-catalyst. The catalyst made from the yttrium complex 1 Y was found to be the most active (TOF 10,000 h −1 ) leading to the formation of PB with the highest 1,4-cis stereoregularity of 90% in comparison to those made from 1 La and 1 Nd complexes (low yields and 33% and 75% of 1,4-cis units, respectively).…”

“…However, the polymerizations carried out with 1 Y as precatalyst gave much broader dispersity, i.e., a less controlled process. Interestingly, the lanthanum-based precatalyst 1 La showed reverse stereo-selectivity when used with Al( i Bu) 3 [21]. Little rigidity was noticed for the allyl group of 2 La by 1 H NMR, whereas 2 Y displayed higher fluxionality with fast syn/anti exchange.…”

“…However, since the 1970s, with the advent of modern techniques of analysis and synthesis, it became possible to better apprehend the structure and reactivity of organometallic RE complexes, which promoted the growth of research in this field of chemistry and its application to catalysis. Thenceforth, chemists realized that the thorough study of the reactivity of allyl derivatives of the rare earths, besides alkyl and hydride derivatives, could greatly benefit the comprehension of mechanisms involved in rare earth-catalyzed polymerization of olefins and conjugated dienes [2][3][4][5][6].…”