Effects of the electronic structure of five-membered N-heterocyclic carbenes on insertion of silanes and boranes into the NHC C–N bond

2015 ◽  
Vol 44 (7) ◽  
pp. 3318-3325 ◽  
Author(s):  
Kalon J. Iversen ◽  
David J. D. Wilson ◽  
Jason L. Dutton
Keyword(s):  
Electronic Structure ◽  
Ring Expansion ◽  
Heterocyclic Carbenes ◽  
Theoretical Methods

The effect of varying the N-heterocyclic carbene (NHC) ligand on the ring expansion and endocyclic C–N activation of NHCs by silanes and boranes has been investigated with theoretical methods.

Aryl-substituted Triarsiranes: Synthesis and Reactivity

2020 ◽  
Author(s):  
André Schumann ◽  
Jonas Bresien ◽  
Malte Fischer ◽  
Christian Hering-Junghans
Keyword(s):  
Organic Chemistry ◽  
Electronic Structure ◽  
Heterocyclic Carbenes ◽  
Synthetic Approaches ◽  
Inorganic And Organic

Cyclotriarsanes are rare and limited synthetic approaches have hampered reactivity studies on these systems. Described in here is a scalable synthetic protocol towards (AsAr)<sub>3</sub> (Ar = Dip, 2,6-<sup>i</sup>Pr<sub>2</sub>-C<sub>6</sub>H<sub>3</sub>; Tip, 2,4,6-<sup>i</sup>Pr<sub>3</sub>-C<sub>6</sub>H<sub>2</sub>), which allowed to study their reactivity towards [Cp<sub>2</sub>Ti(C<sub>2</sub>(SiMe<sub>3</sub>)<sub>2</sub>], affording titanocene diarsene complexes and towards N-heterocyclic carbenes (NHCs) to give straightforward access to a variety of NHC-arsinidene adducts. The electronic structure of the titanium diarsene complxes has been studied and they are best described as Ti(IV) species with a doubly reduced As<sub>2</sub>Ar<sub>2</sub> ligand. These findings will make (AsAr)<sub>3</sub> valuable precursors in the synthetic inorganic and organic chemistry.

Crystal excitation: survey of many-electron Hartree-Fock calculations of self-trapped excitons in insulating crystals

1992 ◽  
Vol 341 (1661) ◽  
pp. 221-231 ◽  
Keyword(s):  
Electronic Structure ◽  
Alkali Halides ◽  
Oxide Materials ◽  
Theoretical Methods ◽  
Hartree Fock ◽  
Cluster Calculations ◽  
Quantum Cluster ◽  
Similarities And Differences

To model successfully the diversity of electronic structure exhibited by excitons in alkali halides and in oxide materials, it is necessary to use a variety or combination of theoretical methods. In this review we restrict our discussion to the results of embedded quantum cluster calculations. By considering the results of such studies, it is possible to recognize the general similarities and differences in detail between the various exciton models in these materials.

Coumaraz-2-on-4-ylidene: Ambiphilic N-Heterocyclic Carbenes with a Tunable Electronic Structure

2018 ◽  
Vol 130 (28) ◽  
pp. 8739-8743 ◽  
Author(s):  
Hayoung Song ◽  
Hyunho Kim ◽  
Eunsung Lee
Keyword(s):  
Electronic Structure ◽  
Heterocyclic Carbenes

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.

25 years of N-heterocyclic carbenes: activation of both main-group element–element bonds and NHCs themselves

2016 ◽  
Vol 45 (14) ◽  
pp. 5880-5895 ◽  
Author(s):  
Sabrina Würtemberger-Pietsch ◽  
Udo Radius ◽  
Todd B. Marder
Keyword(s):  
Ring Expansion ◽  
Main Group ◽  
Heterocyclic Carbenes ◽  
Group Element ◽  
Main Group Element ◽  
The 1960S

Expanding the belt! NHC ring expansion reactions and E–E activation from the 1960s till the present are summarized.

Room Temperature Ring Expansion of N-Heterocyclic Carbenes and BB Bond Cleavage of Diboron(4) Compounds

2015 ◽  
Vol 21 (25) ◽  
pp. 9018-9021 ◽  
Author(s):  
Sabrina Pietsch ◽  
Ursula Paul ◽  
Ian A. Cade ◽  
Michael J. Ingleson ◽  
Udo Radius ◽  
...  
Keyword(s):  
Room Temperature ◽  
Bond Cleavage ◽  
Ring Expansion ◽  
Heterocyclic Carbenes

scholarly journals NHC Ligated Oximes: Exploring the Electronic Structure and Properties

2021 ◽  
Author(s):  
Mohammad Ovais Dar ◽  
Gurudutt Dubey ◽  
Tejender Singh ◽  
Prasad Bharatam
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Functional Group ◽  
Functional Unit ◽  
Chemical Species ◽  
Heterocyclic Carbenes ◽  
Coordination Interaction ◽  
Structure And Properties ◽  
Main Group Elements ◽  
The Past

Compounds with (NHC)→E coordination bond are being generated and their chemistry is being explored over the past 15 years (NHC= N-heterocyclic carbenes, E = main group elements). Many examples of species with N-heterocyclic olefins (NHOs) are known, which exhibit umpolung chemistry. Increasing number of chemical species, which carry NHC as a functional unit, are being reported. There is a need to understand their electronic structure. Alkylated imidazole oximes (cationic, found useful in medicinal chemistry) ((NHC)-C(H)=N-OH(+)) carry NHC unit as a functional group. Similarly, the corresponding nitroso-N-heterocyclic olefins ((NHC)=C(R)-N=O) also carry NHC as a functional unit. It is important to establish the interaction between the NHC unit and the rest part of the molecule in these species. Density functional (DFT) study has been carried out to explore the electronic structure details of a few oximes and nitroso NHOs. The results indicate that a structure with NHC→C coordination interaction can be considered as one of the resonance structures of these species.

scholarly journals From cyclic nanorings to single-walled carbon nanotubes: disclosing the evolution of their electronic structure with the help of theoretical methods

2019 ◽  
Vol 21 (5) ◽  
pp. 2547-2557 ◽  
Author(s):  
A. Pérez-Guardiola ◽  
R. Ortiz-Cano ◽  
M. E. Sandoval-Salinas ◽  
J. Fernández-Rossier ◽  
D. Casanova ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electronic Structure ◽  
Finite Size ◽  
Single Walled Carbon Nanotubes ◽  
Electronic Effects ◽  
Theoretical Methods ◽  
Single Walled Carbon ◽  
Walled Carbon Nanotubes

We systematically investigate the relationships between structural and electronic effects of finite size zigzag or armchair carbon nanotubes of various diameters and lengths, starting from a molecular template of varying shape and diameter.

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