Manganese-Catalyzed Asymmetric Hydrogenation of Pyridyl Cyclic -Alkyl Imines: A Direct Route to -Nicotine and Derivatives.

The asymmetric hydrogenation (AH) of cyclic -alkyl imines offers an elegant and efficient method to afford chiral amines, especially for -nicotine and its derivatives. However, this approach remains an ongoing challenge due to undesirable coordination of pyridyl-containing substrates to the active metal catalyst. Herein, we disclose a manganese-catalyzed AH that allows access to -nicotine and other chiral α-(hetero)aryl pyrrolidines and provides an example of a base-metal catalyst that displays superior performance to its noble metal counterparts.

Finely-Tuned Bis(imino)pyridylcobalt Complexes Enhance Ethylene Polymerization: The Role of Bulky and Halogen Substituents.

The bis(imino)pyridylcobalt complexes have been finely tuned through using the aniline derivative bearing a -chloro substituent, besides its - and -di(4-fluorophenyl)methyl and -methyl substituents for the series of 2-[1-(3-chloro-4,6-bis((di(4-fluorophenyl)methyl)-2-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(II) chlorides (2,6-MePh, ; 2,6-EtPh, ; 2,6-PrPh, ; 2,4,6-MePh, ; and 2,6-Et-4-MePh, ). The compounds were characterized using elemental analysis, H/C NMR, FT-IR spectroscopy, and the single-crystal X-ray diffraction used in confirming the molecular structures of and . The newly synthesized precatalysts, maintaining steric influences with the addition of an electron-withdrawing -chloro group, achieved higher activities along with better thermal stability, and controlled molecular weights of polyethylenes obtained.

Multifluoro-Modification Enhancing Catalytic Activity and Thermal Stability of Bis(imino)pyridylcobalt Chlorides for Linear Polyethylene.

The multifluoro aniline, 2,6-bis[bis(4-fluorophenyl)methyl]-4-trifluoromethoxy-phenylamine, is meticulously synthesized and utilized to form a series of bis(imino)pyridine derivatives. These derivatives react with cobalt chloride to give six bis(imino)pyridylcobalt (II) complexes (alkyl: 2,6-dimethyl Co1; 2,6-diethyl Co2; 2,6-diisopropyl Co3; 2,4,6-trimethyl Co4; 2,6-diethyl-4-methyl Co5; 2,6-bis[bis(4-fluorophenyl)methyl]-4-trifluoromethoxy Co6). High activity and good thermal stability in ethylene polymerization are achieved by these cobalt complexes in the presence of MAO or MMAO.

Achieving Linear α-Macro-olefins in Ethylene Polymerization through Precisely Tuned Bis(imino)pyridylcobalt Precatalysts with Steric and Electronic Parameters.

Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization. In the present study, a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions. By incorporation of strong electron-withdrawing groups (F and NO) and a steric component (benzhydryl) into the parent bis(imino)pyridine ligand, the catalytic performance of these precatalysts was optimized.

Achieving isopropenyl-enriched polyisoprene: unraveling the role of bidentate tridentate iron precatalysts through ligand framework design.

The coordination sphere and steric variations in iron catalysts present a fascinating strategy for adjusting monomer regio- and stereoselective enchainment, leading to the development of novel polymer structures in isoprene polymerization. This study investigates a range of iron complexes with variations in the coordination spheres (bidentate and tridentate) and steric/electronic properties of side arms to evaluate their impact on isoprene polymerization. X-ray analysis revealed that the tridentate Fe-NMe2 complex has a dinuclear structure with a -O bridge, where each iron center is monoligated in an octahedral geometry.

Thermally stable -symmetric α-diimine nickel precatalysts for ethylene polymerization: semicrystalline to amorphous PE with high tensile and elastic properties.

In α-diimine nickel catalyst-mediated ethylene polymerization, adjusting catalytic parameters such as steric and electronic factors, as well as spectator ligands, offers an intriguing approach for tailoring the thermal and physical properties of the resulting products. This study explores two sets of -symmetric α-diimine nickel complexes-nickel bromide and nickel chloride-where -steric and electronic substituents, as well as nickel halide, were varied to regulate simultaneously chain walking, chain transfer, and the properties of the polymers produced. These complexes were activated with EtAlCl, resulting in exceptionally high catalytic activities (in the level of 10-10 g (PE) mol (Ni) h) under all reaction conditions.

Synthesis of low-molecular weight and branched polyethylenes ethylene polymerization using 9-(arylimino)-5,6,7,8-tetrahydrocyclohepta-pyridylnickel precatalysts.

Targeting pour point depressants of low-molecular weight and branched polyethylenes, a series of 9-[2,4-bis(benzhydryl)-6--phenylimino]-5,6,7,8-tetrahydro-cycloheptapyridine-nickel complexes (Ni1-Ni10) were developed as efficient precatalysts. Upon activation with either EASC or MAO, all nickel complex precatalysts exhibited high activity [up to 8.12 × 10 g PE (mol of Ni) h] with single-site behavior toward ethylene polymerization, producing low-molecular weight and unimodal polyethylenes.

Intensive Cycloalkyl-Fused Pyridines for Aminopyridyl-Zinc-Heteroimidazoles Achieving High Efficiency toward the Ring-Opening Polymerization of Lactides.

The model precatalyst - and -N dinitrogen-coordinated zinc-heteroimidazole has been used as an efficient catalyst for the ring-opening polymerization of cyclic esters. Subsequent to our exceptional active 5,6,7-trihydroquinolin-8-amine-zinc catalysts for the ring-opening polymerization (ROP) of -caprolactone, various pyridine-fused cycloalkanones (ring size from five to eight) are developed for the correspondent fused amine-pyridine derivatives and their zinc-heteroimidazole chloride complexes - (ZnCl) bearing -diphenylphosphinoethyl pendants. Activated with two equivalents of LiN(SiMe), the title zinc complexes efficiently promote the ROP of -lactide (-LA) in situ; among them, /2Li(NSiMe) catalyzed 500 equivalent -LA at 80 °C with 92% conversion in 5 min (TOF: 5520 h).

Catalytic Activity of 2-Imino-1,10-phenthrolyl Fe/Co Complexes via Linear Machine Learning.

In anticipation of the correlations between catalyst structures and their properties, the catalytic activities of 2-imino-1,10-phenanthrolyl iron and cobalt metal complexes are quantitatively investigated via linear machine learning (ML) algorithms. Comparatively, the Ridge Regression model has captured more robust predictive performance compared with other linear algorithms, with a correlation coefficient value of 0.952 and a cross-validation value of 0.

Predicting the catalytic activities of transition metal (Cr, Fe, Co, Ni) complexes towards ethylene polymerization by machine learning.

The study aims to execute machine learning (ML) method for building an intelligent prediction system for catalytic activities of a relatively big dataset of 1056 transition metal complex precatalysts in ethylene polymerization. Among 14 different algorithms, the CatBoost ensemble model provides the best prediction with the correlation coefficient (R ) values of 0.999 for training set and 0.

Enhancing isoprene polymerization with high activity and adjustable monomer enchainment using cyclooctyl-fused iminopyridine iron precatalysts.

In this study, a series of structurally rigid cyclooctyl-fused iminopyridine iron complexes, [LFeCl][FeCl] and [2LFe][Cl][3FeCl], was synthesized a one-pot method and investigated as precatalysts in conjunction with methylaluminoxane for isoprene (Ip) polymerization. Combined characterization through FTIR analysis, elemental analysis and single crystal XRD analysis fully verified the structure of these complexes. The most active iron complex, FeH, exhibited a trisligated nature, with its cation adopting an octahedral geometry around the metal center.

-(2-(Diphenylphosphino)ethyl)-2-alkyl-5,6,7,8-tetrahydro-quinolin-8-amines iron(ii) complexes: structural diversity and the ring opening polymerization of ε-caprolactone.

A series of -(2-(diphenylphosphino)ethyl)-2-alkyl-5,6,7,8-tetrahydroquinolin-8-amines was prepared and used in individually reacting with iron chloride under nitrogen atmosphere to form their iron(ii) complexes Fe1-Fe6. All compounds were characterized using FT-IR spectroscopy and elemental analyses, the organic compounds were confirmed with NMR measurements, and the iron complexes were submitted to single-crystal X-ray diffraction, revealing Fe1, Fe2, Fe4, Fe5, and Fe6 as either mono- or di-nuclear forms. Forming a binary system with two equivalents of LiCHSiMe, all iron complexes Fe1-Fe6 efficiently initiated the ring opening polymerization of ε-caprolactone, achieving the TOF up to 8.

Robust and efficient transfer hydrogenation of carbonyl compounds catalyzed by -Mn(I) complexes.

A series of manganese(I) carbonyl complexes bearing structurally related - and -chelating ligands have been synthesized and assessed as catalysts for transfer hydrogenation (TH). Notably, the -systems based on -R functionalized 5,6,7,8-tetrahydroquinoline-8-amines, proved the most effective in the manganese-promoted conversion of acetophenone to 1-phenylethanol. In particular, the -isopropyl derivative, Mn1, when conducted in combination with -BuONa, was the standout performer mediating not only the reduction of acetophenone but also a range of carbonyl substrates including (hetero)aromatic-, aliphatic- and cycloalkyl-containing ketones and aldehydes with especially high values of TON (up to 17 200; TOF of 3550 h).

,-Bis(2,4-Dibenzhydryl-6-cycloalkylphenyl)butane-2,3-diimine-Nickel Complexes as Tunable and Effective Catalysts for High-Molecular-Weight PE Elastomers.

Four examples of ,-bis(aryl)butane-2,3-diimine-nickel(II) bromide complexes, [ArN=C(Me)-C(Me)=NAr]NiBr (where Ar = 2-(CH)-4,6-(CHPh)CH (), Ar = 2-(CH)-4,6-(CHPh)CH (), 2-(CH)-4,6-(CHPh)CH () and 2-(CH)-4,6-(CHPh)CH ()), disparate in the ring size of the -cycloalkyl substituents, were prepared using a straightforward one-pot synthetic method. The molecular structures of and highlight the variation in the steric hindrance of the -cyclohexyl and -cyclododecyl rings exerted on the nickel center, respectively. By employing EtAlCl, EtAlCl or MAO as activators, - displayed moderate to high activity as catalysts for ethylene polymerization, with levels falling in the order (cyclohexyl) > (cyclopentyl) > (cyclododecyl) > (cyclooctyl).

Exploring fluoride effects in sterically enhanced cobalt ethylene polymerisation catalysts; a combined experimental and DFT study.

The fluoro-substituted 2,6-bis(arylimino)pyridine dichlorocobalt complexes, [2-{CMeN(2,6-(PhCH)-3,4-FCH)}-6-(CMeNAr)CHN]CoCl (Ar = 2,6-MeCH Co1, 2,6-EtCHCo2, 2,6-iPrCHCo3, 2,4,6-MeCHCo4, 2,6-Et-4-MeCHCo5), were synthesized in good yield from the corresponding unsymmetrical ,,'-ligands, L1-L5. Besides characterization of Co1-Co5 by FT-IR spectroscopy, F NMR spectroscopy and elemental analysis, the molecular structures of Co2 and Co5 were also determined highlighting the unsymmetrical nature of the terdentate ligand and the -square pyramidal geometry about the metal center. When either MAO or MMAO were employed as activators, Co1-Co5 were able to achieve a wide range of catalytic activities for ethylene polymerisation.

Unusual Effect of α-olefins as Chain Transfer Agents in Ethylene Polymerization over the Catalyst with Nonsymmetrical Bis(imino)pyridine Complex of Fe(II) and Modified Methylalumoxane (MMAO) Cocatalyst.

Ethylene polymerization with bis(imino)pyridlyiron precatalysts generally produces linear polyethylene (PE) even with the presence of α-olefins because α-olefins are not incorporated into polymeric products. Interestingly, α-olefins, such as hexene-1 or butene-1, have been found to act as effective chain transfer agents in the ethylene polymerization promoted by nonsymmetrical bis(imino)pyridyliron complexes with modified methylalumoxane (MMAO), resulting in higher catalytic activities with higher amounts of polymers with lower molecular weights, and, more importantly, narrower molecular weight distributions of the resultant polyethylenes (PE). This phenomenon confirms the assistance of α-olefins in the chain-termination reaction of iron-initiated polymerization and regeneration of the active species for further polymerization.

High molecular weight PE elastomers through 4,4-difluorobenzhydryl substitution in symmetrical α-diimino-nickel ethylene polymerization catalysts.

The following family of ,-diaryl-2,3-dimethyl-1,4-diazabutadienes, ArN[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]NAr (Ar = 2,6-Me-4-{CH(4-FCH)}CHL1, 2-Me-6-Et-4-{CH(4-FCH)}CHL2, 2,4-{CH(4-FCH)}-6-MeCHL3, 2,4-{CH(4-FCH)}-6-EtCHL4, 2,4-{CH(4-FCH)}-6-iPrCHL5), each incorporating -substituted 4,4-difluorobenzhydryl groups but differing in the -pairing, have been synthesized and used as precursors to their respective nickel(ii) bromide complexes, Ni1-Ni5. Compound characterization has been achieved through a combination of FT-IR, multinuclear NMR spectroscopy (H, C, F) and elemental analysis. In addition, L1, Ni1 and Ni5 have been structurally characterized with Ni1 and Ni5 revealing similarly distorted tetrahedral geometries about nickel but with distinct differences in the steric protection offered by the -substituents.

Catalytic Performance of Cobalt(II) Polyethylene Catalysts with Sterically Hindered Dibenzopyranyl Substituents Studied by Experimental and Methods.

Given the great importance of cobalt catalysts supported by benchmark bis(imino)pyridine in the (oligo)polymerization, a series of dibenzopyran-incorporated symmetrical 2,6-bis(imino) pyridyl cobalt complexes (-) are designed and prepared using a one-pot template approach. The structures of the resulting complexes are well characterized by a number of techniques. After activation with either methylaluminoxane (MAO) or modified MAO (MMAO), the complexes - are highly active for ethylene polymerization with a maximum activity of up to 7.

Structural evolution of iminopyridine support for nickel/palladium catalysts in ethylene (oligo)polymerization.

The interest in the late transition metal catalyst based design of new architectures of polyethylene (PE) has continuously been increasing over the last few years. The structure of these catalysts is predominantly important in controlling the morphological and architectural properties of the resulting polyethylene. Particularly, iminopyridine is a versatile bidentate support for Ni and Pd catalysts in ethylene (oligo)polymerization providing a wide variety of products ranging from volatile oligomers to ultra-high molecular weight polyethylene.

Differences in neuroanatomy and functional connectivity between motor subtypes of Parkinson's disease.

Background: The "postural instability/gait difficulty" (PIGD) and "tremor-dominant" (TD) motor subtypes of Parkinson's disease (PD) differ in their clinical manifestations. The neurological basis of these differences is unclear.

Methods: We performed voxel-based morphometric analysis and measured amplitudes of low-frequency fluctuation (ALFF) on 87 PIGD patients and 51 TD patients.

Efficient transfer hydrogenation of ketones using molybdenum complexes by comprehensively verifying the auxiliary ligands.

Molybdenum complexes ligated with ,-dialkyl--(5,6,7,8-tetrahydroquinolin-8-yl)ethane-1,2-diamines and auxiliary ligands, providing various structural features, were developed: [NN/NNN]Mo(CO) (Mo1-Mo3), [NNN]Mo(CO)Br (Mo4-Mo5), [NN]Mo(CO)(η-CH)Br (Mo6) and [NNN/S]Mo(CO)(PPh) (Mo7-Mo8). All the complexes were highly active in the transfer hydrogenation (TH) of a model substrate (acetophenone), providing excellent yields of 1-phenylethanol. The structural variation in the ligand framework had a modest effect on the catalyst performance as compared to the changes in the auxiliary ligands Br, PPh and CO.

Excessive Daytime Sleepiness in Parkinson's Disease is Related to Functional Abnormalities in the Left Angular Gyrus.

Purpose: Excessive daytime sleepiness (EDS) is a common non-motor symptom in Parkinson's disease (PD), but its neuropathology remains elusive. Our goal is to explore the potential neural substrates of EDS in a large sample of individuals with PD.

Methods: We recruited 48 PD patients with and 87 PD patients without EDS.

Differences in Brain Activity Between Dopa-Responsive and -Unresponsive Pain in Parkinson's Disease.

Introduction: Pain in Parkinson's disease is poorly understood, and most patients with pain do not respond to dopaminergic drugs. We aimed to explore the mechanisms of dopa-responsive and -unresponsive pain by comparing such patients against patients without pain in terms of neural activity and functional connectivity in the brain.

Methods: We prospectively examined 31 Parkinson's patients with dopa-responsive pain, 51 with dopa-unresponsive pain and 93 without pain using resting-state functional magnetic resonance imaging.

4,4'-Dimethoxybenzhydryl substituent augments performance of bis(imino)pyridine cobalt-based catalysts in ethylene polymerization.

A series of cobalt complexes with bis(imino)pyridine derivatives featuring unsymmetrical substitution with bulky groups has been synthesized and characterized. The molecular structures of two representatives have been determined by the single-crystal X-ray diffraction study, revealing distorted tetrahedral geometry with different degrees of steric hindrance imparted by the two inequivalent aryl groups attached to the imine nitrogen atoms. On activation with either MAO or MMAO, these complexes display high activity toward ethylene polymerization, reaching 8.