Computational study of heterocyclic thione ligands. Part I. Five-membered heteroatomic thiones possessing an α-nitrogen heteroatom

1988 ◽  
Vol 66 (11) ◽  
pp. 2835-2838 ◽  
Author(s):  
George S. Kapsomenos ◽  
Pericles D. Akrivos
Keyword(s):  
Metal Complexes ◽  
Computational Study ◽  
Heterocyclic Ring ◽  
Specific Site ◽  
Atomic Charges ◽  
Nitrogen Heteroatom

A SCF-MNDO study is made of the equilibrium between the "thiol" and "thione" tautomers of four species possessing a five-membered heterocyclic ring, where nitrogen and oxygen or sulfur are the α-heteroatoms. Based on the computationally derived Δ(ΔHf) values for each pair of forms, evidence is presented for the possibility of co-occurrence of the two forms in solution. The tautomerism is particularly interesting in this class of compounds, since it offers the possibility for a sulfur, nitrogen, or sulfur and nitrogen coordination. The nucleophilicity of each specific site in both forms is discussed in terms of net atomic charges and the HOMO constitution of the molecules. Results concerning the study of metal complexes are generally in accordance with these considerations, since the preference for a specific donation scheme is governed by an HSAB criterion.

Theoretical Investigation of Main-Group Element Hydride Insertion into Phosphorus-Heterocyclic Carbenes (PHCs)

2020 ◽  
Vol 73 (8) ◽  
pp. 787
Author(s):  
Khalidah H. M. Al Furaiji ◽  
Andrew Molino ◽  
Jason L. Dutton ◽  
David J. D. Wilson
Keyword(s):  
Computational Study ◽  
Ring Expansion ◽  
Heterocyclic Ring ◽  
Main Group ◽  
Heterocyclic Carbenes ◽  
Group Element ◽  
Steric Effects ◽  
Main Group Element ◽  
Theoretical Investigations ◽  
Electronic And Steric Effects

Initial reports of ring expansion reactions (RER) of N-heterocyclic carbenes (NHCs) with main-group element hydrides have led to several synthetic and theoretical investigations, which include reports of insertion by Be, B, Al, Si, and Zn hydrides. The RERs generally lead to insertion of the heteroatom into the endocyclic C–N bond with formation of an expanded heterocyclic ring. Following the recent isolation of a P-heterocyclic carbene (PHC), here we report results from a computational study (RI-SCS-MP2/def2-TZVP//M06–2X/def2-TZVP) of RERs with a series of PHCs for the ring-insertion of silicon (SiH4, SiH2Ph2) and boron (BH3, BH2NMe2) hydrides. In order to explore the roles of both electronic and steric effects on PHCs and their reactivity, a series of P-substituent PHCR (R=H, Me, Ph, and bulky Ar groups) were investigated. Bulky R groups serve to maximise ring planarity and the σ-donating capability of the PHC. For RER, the PHC analogues exhibit facile initial hydride transfer from the main-group hydrides to the carbene carbon, with barriers that are substantially lower than with NHCs. However, the full ring insertion mechanisms for PHCs are, in general, kinetically unfavourable due to a large barrier associated with the ring-expansion step. While bulky P-substituents maximise heterocycle planarity towards that of NHCs, the RER reactivity with bulky PHCs does not reflect that of an NHC.

scholarly journals Metal Complexes of Oxadiazole Ligands: An Overview

2019 ◽  
Vol 20 (14) ◽  
pp. 3483 ◽  
Author(s):  
Giovanni Salassa ◽  
Alessio Terenzi
Keyword(s):  
Metal Complexes ◽  
Medicinal Chemistry ◽  
Heterocyclic Ring ◽  
Organic Ligands ◽  
Ring Systems ◽  
General Overview ◽  
Research Fields ◽  
Scientific Disciplines ◽  
Synthetic Approaches

Oxadizoles are heterocyclic ring systems that find application in different scientific disciplines, from medicinal chemistry to optoelectronics. Coordination with metals (especially the transition ones) proved to enhance the intrinsic characteristics of these organic ligands and many metal complexes of oxadiazoles showed attractive characteristics for different research fields. In this review, we provide a general overview on different metal complexes and polymers containing oxadiazole moieties, reporting the principal synthetic approaches adopted for their preparation and showing the variety of applications they found in the last 40 years.

Synthetic, Structural, NMR, and Computational Study of a Geminally Bis(peri-substituted) Tridentate Phosphine and Its Chalcogenides and Transition-Metal Complexes

2013 ◽  
Vol 52 (8) ◽  
pp. 4346-4359 ◽  
Author(s):  
Matthew J. Ray ◽  
Rebecca A. M. Randall ◽  
Kasun S. Athukorala Arachchige ◽  
Alexandra M. Z. Slawin ◽  
Michael Bühl ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Computational Study

scholarly journals Should External Heavy-Atom Effects be Expected in Transition Metal Complexes?

2018 ◽  
Author(s):  
Justin Lomont ◽  
Son Nguyen ◽  
Charles Harris
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Spin State ◽  
Computational Study ◽  
Heavy Atom ◽  
Minimum Energy ◽  
Free Energy Barrier ◽  
Heavy Atom Effect ◽  
Atom Effect

Spin state changes frequently play a key role in the reactivity of transition metal complexes. The rates of spin-forbidden reactions are mediated both by the free energy barrier connecting reactants and products, as well as the strength of spin-orbit coupling (SOC) between the relevant electronic states. Since the 1950’s, there have been numerous demonstrations of external heavy-atom effects on organic molecules, in which a heavy atom, not chemically bonded to the molecule undergoing a change in spin state, perturbs the strength of SOC via an intermolecular effect. However, the potential role of external heavy atom effects on the rates of reactions involving transition metal complexes remains almost entirely unexplored. We report a computational investigation into the changes in SOC that occur along a bimolecular reaction coordinate when an incoming atom coordinates to the prototypical triplet reaction intermediate Fe(CO)4. The calculated changes in SOC are compared for molecules containing atoms ranging in atomic number from Z = 8 to Z = 53 approaching the Fe center (ZFe =26). No evidence for an external heavy atom effect was found, and the changes in SOC with the approach of each incoming group were similar in magnitude. In fact, when taking into account the different minimum energy crossing point geometries for the different incoming groups, the opposite of an external heavy atom effect trend is predicted for this reaction. The results of this computational study suggest that external heavy atom effects are unlikely to have a significant effect on the rates of spin-forbidden reactions for transition metal complexes. <br>

Computational study of metal complexes formed with EDTA, melatonin, and its main metabolites: implications in lead intoxication and clues to a plausible alternative treatment

2019 ◽  
Vol 25 (1) ◽  
Author(s):  
Erik Díaz-Cervantes ◽  
Marco A. García-Revilla ◽  
Karla Soto-Arredondo ◽  
Tayde Villaseñor-Granados ◽  
Minerva Martínez-Alfaro ◽  
...  
Keyword(s):  
Metal Complexes ◽  
Alternative Treatment ◽  
Computational Study ◽  
Lead Intoxication

o-Quinone phenalenyl derivatives as expedient ligands for the design of magnetically active metal complexes: A computational study

2020 ◽  
Vol 740 ◽  
pp. 137073 ◽  
Author(s):  
Andrey G. Starikov ◽  
Alyona A. Starikova ◽  
Ruslan M. Minyaev ◽  
Vladimir I. Minkin ◽  
Alexander I. Boldyrev
Keyword(s):  
Metal Complexes ◽  
Computational Study ◽  
Active Metal

Reactions of Pendant Boryl Groups in Cp–Metal Complexes: Heterocyclic Ring Annelation in a CpIr System (Eur. J. Inorg. Chem. 14/2008)

2008 ◽  
Vol 2008 (14) ◽  
pp. 2250-2251
Author(s):  
Christoph Herrmann ◽  
Gerald Kehr ◽  
Roland Fröhlich ◽  
Gerhard Erker
Keyword(s):  
Metal Complexes ◽  
Heterocyclic Ring

N-Heterocyclic Phosphenium, Arsenium, and Stibenium Ions as Ligands in Transition Metal Complexes: A Comparative Experimental and Computational Study

2005 ◽  
Vol 631 (8) ◽  
pp. 1403-1412 ◽  
Author(s):  
Sebastian Burck ◽  
Jörg Daniels ◽  
Timo Gans-Eichler ◽  
Dietrich Gudat ◽  
Kalle Nättinen ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Computational Study
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