Search results for "Periodic table"
showing 10 items of 262 documents
Synthesis and characterisation of p-block complexes of biquinoline at different ligand charge states
2017
The first examples of p-block coordination complexes of biquinoline, namely [(biq)BCl2]Cl and [(biq)BCl2]˙, were synthesized and structurally characterized. The acquired data allowed the estimation of the ligand charge state based on its metrical parameters. The subsequent use of this protocol, augmented with theoretical calculations, revealed ambiguities in the published data for transition metal complexes of biquinoline. peerReviewed
NbxRu6-xTe8, New Chevrel-Type Clusters Containing Niobium and Ruthenium,
1996
Phases of composition Nb(x)()Ru(6)(-)(x)()Te(8) were prepared by reacting stoichiometric mixtures of the elements at high temperature in evacuated silica ampules. The structure of Nb(3.33)Ru(2.67)Te(8) was refined from X-ray powder data using the Rietveld method. Nb(3.33)Ru(2.67)Te(8) crystallizes isotypic with Mo(6)Q(8) (Q = S, Se, Te) in the rhombohedral space group Rthremacr; with the hexagonal lattice parameters a = 10.34106(5) Å, c = 11.47953(7) Å, and Z = 3. Its structure consists of M(6)Te(8) mixed-metal clusters (M = Nb, Ru) which are connected by intercluster M-Te bonds to form a three-dimensional network. Metal-metal bonding in these phases is analyzed in terms of Pauling bond ord…
K2AuPS4, TI2AuPS4, K2AuAsS4, and KAu5P2S8: Syntheses, structures, and properties of quaternary gold thiophosphate and thioarsenate compounds
1998
The novel compounds K2AuPS4 (1), Tl2AuPS4 (2), K2AuAsS4 (3), and KAu5P2S8 (4) have been synthesized by direct reaction of the elements with a molten alkaline polythiophosphate(arsenate) flux at 550°C. The crystal structures of these compounds have been determined by single-crystal X-ray diffraction techniques. 1, 2, and 3 crystallize in the monoclinic space group P21/m. The structures of 1, 2, and 3 consist of infinite, one-dimensional anionic chains running along the crystallographic b axis. The chains are separated by potassium or thallium ions. Neighbouring Au atoms are bridged by MS43− tetrahedra (M = P, As) in a trans orientation. Compound 4 crystallizes in the space group P21/c. The a…
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.