02091nas a2200193 4500008004100000022001400041245010700055210006900162260000800231300001600239490000700255520138000262100002401642700002401666700003101690700002001721700002401741856013201765 2024 eng d a1463-926200aDepolymerization of waste polyethylene to linear alkenes via sequential dehydrogenation and metathesis0 aDepolymerization of waste polyethylene to linear alkenes via seq cOCT a10558-105660 v263 a

Polyethylene (PE) is the most abundantly sourced plastic and significant efforts are needed for its end-of-life management. The deconstruction of PE is an uphill task and requires the breaking of highly stable C-C bonds. Here we demonstrate that PE can be deconstructed to value-added dodecene, along with other long-chain alkenes. The PCP-iridium complex catalyzes the dehydrogenation of commercial and post-consumer polyethylene waste to produce dehydrogenated polyethylene (DHP) with 0.5-1.0% unsaturation. The DHP was subjected to an ethylene cross-metathesis reaction in the presence of suitable catalysts. Through meticulous optimization of reaction parameters, 63% selectivity toward dodecene, with 26% overall yield, was achieved. The practical significance of our method has been demonstrated by subjecting post-consumer plastic waste to dehydrogenation followed by ethylene metathesis to produce dodecene as a major product, together with long-chain alkenes. The PE deconstruction has been confirmed by recording molar mass before and after depolymerization using high-temperature gel permeation chromatography. The existence of dodecene has been unambiguously ascertained using GC, GC-MS, NMR, and IR spectroscopy. Thus, these results demonstrate the conversion of waste PE to value-added dodecene and long-chain alkenes under mild reaction conditions.

1 aKhopade, Kishor, V.1 aRajput, Nikhita, S.1 aRangappa, Raghavendrakumar1 aBarsu, Nagaraju1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/depolymerization-waste-polyethylene-linear-alkenes-sequential-dehydrogenation-and-metathesis02488nas a2200277 4500008004100000022001400041245010000055210006900155260000800224520154900232653001701781653000801798653003001806653002701836653001701863100002401880700001901904700002101923700002101944700002801965700002201993700002502015700001702040700002402057856012902081 2024 eng d a1060-132500aDesigning of imine thiophene-ligated metal-complexes and implication in ethylene polymerization0 aDesigning of imine thiopheneligated metalcomplexes and implicati cSEP3 a

Polyethylene is the single largest volume polymer produced globally using Ziegler-type catalysts. Numerous modifications have been reported in search of a better catalyst that can control molecular weight, polydispersity, and branching. In our attempts to identify a suitable imine thiophene-ligated chromium complex, we examined 9 different titanium complexes computationally. The DFT investigations considered barriers for insertion, propagation, and termination by beta-H elimination or chain transfer, and identified N-(4-methoxyphenyl)-2-phenyl-1-(thiophen-2-yl)ethan-1-imine(L9) as the most suitable ligand. Subsequently, L9 was prepared in good yield (70%) by condensing 2-phenyl-1-(thiophen-2-yl)ethan-1-one with 4-methoxyaniline. Ligand L9 was treated with early transition metal precursors (Ti, Cr, Zr) to generate a homogenous catalyst. The identity of these catalysts was unambiguously ascertained using a combination of NMR, ICP, FT-IR, UV-Vis spectroscopy, and ESI-MS. The performance of L9-ligated titanium complex [Cat.1] was examined in ethylene polymerization using MMAO as a co-catalyst. Insertion of ethylene was tracked using high-pressure NMR experiments and Cat.1 was found to be active in the polymerization. Ethylene polymerization conditions were optimized to obtain high activity and molecular weight polyethylene. The chromium complex [Cat.2] outperformed the Ti and Zr-derived catalysts with the highest TOF of 6294 mol of PE/mol of Cr/h. Cat.2 produced high molecular weight, high-density polyethylene.

10aCr-complexes10aDFT10ahigh-density polyethylene10aImine thiophene ligand10aPolyethylene1 aShaikh, Maulali, H.1 aRamekar, Rohan1 aJawoor, Shailaja1 aDash, Soumya, R.1 aBirajadar, Rajkumar, S.1 aPawal, Sandip, B.1 aThenmani, Nandakumar1 aVanka, Kumar1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/designing-imine-thiophene-ligated-metal-complexes-and-implication-ethylene-polymerization01640nas a2200229 4500008004100000022001400041245012500055210006900180260000900249300001100258490000700269520081400276653002901090653002601119653001801145653002001163653002401183100002701207700002401234700002401258856012801282 2026 eng d a2365-654900aDirect synthesis of phosphine-phosphite ligand and its implication in asymmetric hydrogenation of functionalized olefins0 aDirect synthesis of phosphinephosphite ligand and its implicatio cFEB  ae075480 v113 a

Phosphine-phosphite (P-OP) ligands constitute a privileged class of chiral ligands in asymmetric catalysis owing to their modular structures and tunable steric and electronic properties. Herein, we report a direct, one-pot, synthesis of a new flexible P-OP ligand (L) derived from BINOL-PCl and its in situ complexation with rhodium (Rh) for catalytic evaluation. The resulting Rh/L system efficiently hydrogenates a diverse library of 19 functionalized olefins under mild conditions, delivering moderate to excellent enantioselectivities, with ee values reaching up to 99%. Several of the hydrogenated products correspond to valuable chiral building blocks relevant to pharmaceutical synthesis, underscoring the practical utility of flexible P-OP ligand architectures in asymmetric hydrogenation.

10aasymmetric hydrogenation10afunctionalized alkene10aligand design10ametal catalyzed10aphosphine-phosphite1 aChandanshive, Amol, C.1 aKhopade, Kishor, V.1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/direct-synthesis-phosphine-phosphite-ligand-and-its-implication-asymmetric-hydrogenation