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Enhancing Performance of a Bis(arylimino)pyridine‐Iron Precatalyst for Ethylene Polymerization by Substitution with a 2,4‐Bis(4,4′‐dimethoxybenzhydry…

2021

A series of unsymmetrical 2-(2,4-bis(bis(4-methoxyphenyl)methyl)-6-MeC6H2N)-6-(1-(arylimino)ethyl)pyridine-iron halides has been synthesized and characterized. The molecular structure of two representative species was determined by the single-crystal X-ray diffraction. Activated with either MAO or MMAO, the precatalysts displayed high activity, reaching 2.19×107 g PE (mol Fe)−1 h−1 at 60 °C in ethylene polymerization. The microstructural analysis of the polymers obtained indicates highly linear polyethylene containing a vinyl chain end.

Solution Chemistry of Element 106:  Theoretical Predictions of Hydrolysis of Group 6 Cations Mo, W, and Sg

2001

Fully relativistic molecular density-functional calculations of the electronic structure of hydrated and hydrolyzed complexes have been performed for the group 6 elements Mo, W, and element 106, Sg. By use of the electronic density distribution data, relative values of the free energy changes and constants of hydrolysis reactions were defined. The results show hydrolysis of the cationic species with the formation of neutral molecules to decrease in the order Mo > W > Sg, which is in agreement with experiments for Mo, W, and Sg. For the further hydrolysis process with the formation of anionic species, the trend is reversed:  Mo > Sg > W. A decisive energetic factor in the hydrolysis process …

Construction of a General Library for the Rational Design of Nanomagnets and Spin Qubits Based on Mononuclear f-Block Complexes. The Polyoxometalate …

2014

This paper belongs to a series of contributions aiming at establishing a general library that helps in the description of the crystal field (CF) effect of any ligand on the splitting of the J ground states of mononuclear f-element complexes. Here, the effective parameters associated with the oxo ligands (effective charges and metal-ligand distances) are extracted from the study of the magnetic properties of the first two families of single-ion magnets based on lanthanoid polyoxometalates (POMs), formulated as [Ln(W5O18)2](9-) and [Ln(β2-SiW11O39)2](13-) (Ln = Tb, Dy, Ho, Er, Tm, Yb). This effective CF approach provides a good description of the lowest-lying magnetic levels and the associate…

Cover Feature: A Route toward (Aminomethyl)cyclopentadienide Ligands and Their Group 4 Metal Complexes (Eur. J. Inorg. Chem. 34/2018)

2018

Increasing the Nuclearity of Magnetic Polyoxometalates. Syntheses, Structures, and Magnetic Properties of Salts of the Heteropoly Complexes [Ni3(H2O)…

1998

The rational synthesis and the structural and magnetic characterization of three different nickel clusters encapsulated in Keggin trivacant fragments are presented. The three complexes show how it is possible to increase the nuclearity of the clusters (from 3 and 4 to 9) by slightly changing the synthetic conditions. These three anionic clusters crystallize as mixed salts of K+ and Na+. The trimeric complex [Ni3(H2O)3PW10O39H2O]7- (Ni3) crystallizes in the triclinic space group P1 (a = 10.896(6) A, b = 12.869(5) A, c = 20.373(6) A, α = 94.67(6)°, β = 101.12(8)°, γ = 110.72(8)°, Z = 2) and presents a ferromagnetic triangular cluster. The tetranuclear complex [Ni4(H2O)2(PW9O34)2]10- (Ni4) cry…

Microphase separation in ternary ABC block copolymers: Ordering control in molten diblock AB copolymers by attaching a short strongly interacting C b…

1997

Some specific features of the microphase separation in molten ternary ABC triblock copolymers (in particular, modifications of the molten AB diblock copolymers by attaching a short third block C strongly incompatible with both A and B blocks) are studied rigorously within the framework of the weak segragation approach. It is shown that via such a modification one can control both the stability as to the microphase separation transition (i.e., the corresponding spinodal temparatures) and the smoothness of such a transition. Two modes of such modifications for every composition are studied in detail:  (i) those resulting in the minimal spinodal temperatures and (ii) those that result in the s…

Synthesis and stereochemistry of some new derivatives of cis-dihydropinol

1999

Abstract The synthesis of four new derivatives of cis-hydroxy-cis-dihydropinol with allyl-, epoxyalkyl-, hydroxyalkyl- and ketoalkyl-groups substituted on the cyclohexane ring is presented. The cis-orientation of hydroxyl group at C-2 and the configuration of all stereogenic centers is confirmed by X-ray crystallography.

Über Tetraaryl-methan-analoga in der gruppe 14

1993

The title compounds have been synthesized by Li and Grignard reactions. The crystal structure of Ph3Si-p-Tol has been determined. The substitution of only one phenyl by one p-tolyl group causes only a slight deviation from the ideal S4 symmetry of Ph4Si. Gradual replacement of phenyl by p-tolyl groups leads to increasing low field shifts for all 13C(ipso) atoms. The substitution of the first phenyl group by p-tolyl in Ph4Si and Ph4Sn results in a high field shift both for δ(29Si) (−0.3 ppm) and for δ(119Sn) (−1 ppm). Further replacement shows nearly linear dependencies (Δδ(29Si) = −0.1 ppm, Δδ(119Sn) = + 1.5 ppm per p-tolyl group).

Enhancing performance of α‐diiminonickel precatalyst for ethylene polymerization by substitution with the 2,4‐bis(4,4'‐dimethoxybenzhydryl)‐6‐methylp…

2020

High activities in ethylene polymerization predetermine α‐diiminonickel precatalysts for potential industrial applications. In our study, we have synthesized and characterized a series of unsymmetrical 1‐(2,4‐bis(4,4′‐dimethoxybenzhydryl)‐6‐MeC6H2N)‐2‐arylimino‐acenaphthylene nickel(II) halides. The single‐crystal X‐ray diffraction study of representative compounds reveals distorted tetrahedral geometry. On activation with either Me2AlCl or modified methylaluminoxane, these nickel complexes exhibit high activities of the order of 106 g of PE (mol of Ni)−1 h−1 and produce polyethylene of generic application characterized by high molecular weight, narrow molecular weight distribution, and mod…

Slow and fast methyl group rotations in fragile glass-formers studied by NMR

2000

Abstract The spin-lattice relaxation times of the selectively ring deuterated, fragile glass-formers propylene carbonate and toluene were compared with those measured for species which were specifically labeled at the methyl groups. It was found that the dynamics of the CD 3 group is strongly decoupled from that associated with the primary response of toluene, while for propylene carbonate the degree of decoupling is relatively weak. The experimental results could be described successfully using a model which takes into account the ring dynamics as well as those of the methyl group.