Revisiting the π-Back-Donation in the NHC–B≡B–NHC Molecule

2021 ◽  
Author(s):  
Chang Xu ◽  
Yingying Ma ◽  
Longjiu Cheng
Keyword(s):  
Back Donation

scholarly journals Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2669
Author(s):  
Łukasz Kuterasiński ◽  
Jerzy Podobiński ◽  
Jerzy Datka
Keyword(s):  
Ethanol Oxidation ◽  
Produced Water ◽  
Acid Sites ◽  
No Adsorption ◽  
Ir Studies ◽  
Oxygen Donor ◽  
Before And After ◽  
Acetate Formation ◽  
Back Donation

In this study, IR studies of the coadsorption of ethanol and CO on Cu+ cations evidenced the transfer of electrons from ethanol to Cu+, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu+ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu+exch also produced ethene, but in this case, the ethene was bonded to Cu+ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm−1 was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu+exch and bigger amounts of Cu+ox, Cu2+exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH3COO-). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu+ox and Cu2+ (Cu2+exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu2O as well as zeolites, in which the contribution of Cu+ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu2+ox (the role of Cu+ox could not be elucidated), but Cu+ox was the oxygen donor in the acetate formation.

π Back-Donation from a Beryllium Dibromide Fragment at the Expense of Its σ Strength

2021 ◽  
Author(s):  
Lewis R. Thomas-Hargreaves ◽  
Sudip Pan ◽  
Sergei I. Ivlev ◽  
Gernot Frenking ◽  
Magnus R. Buchner
Keyword(s):  
Back Donation

Hapticity of asymmetric rhodium-allyl compounds in the light of real-space bonding indicators

2018 ◽  
Vol 233 (9-10) ◽  
pp. 615-626
Author(s):  
Stefan Mebs ◽  
Sabrina Imke Kalläne ◽  
Thomas Braun
Keyword(s):  
Real Space ◽  
Molecular Structures ◽  
Dft Study ◽  
Interaction Patterns ◽  
Ligand Interaction ◽  
Complex Metal ◽  
Allyl Compounds ◽  
Back Donation ◽  
Metal Ligand

Abstract Rhodium boryl complexes are valuable catalysts for hydro- or diboration reactions of alkenes, but can also react with ketones (R2C=O) and imines (R2C=NR′) giving rise to insertion products having formally Rh–R2C–O/NR′–B linkages. The resulting molecular structures, however, may show complex metal–ligand and ligand–ligand interaction patterns with often unclear metal–ligand connectivities (hapticities, ηn). In order to assign the correct hapticity in a set of asymmetric rhodium-allyl compounds with molecular structures indicating η1−5 bonding, a comprehensive DFT study was conducted. The study comprises determination of a variety of real-space bonding indicators derived from computed electron and pair densities according to the AIM, ELI-D, NCI, and DORI topological and surface approaches, which uncover the metal–ligand connectivties and suggest an asymmetric ligand–metal donation/metal–ligand back-donation framework according to the Dewar–Chatt–Duncanson model.

Helium Accepts Back-Donation In Highly Polar Complexes: New Insights into the Weak Chemical Bond

2017 ◽  
Vol 8 (14) ◽  
pp. 3334-3340 ◽  
Author(s):  
Francesca Nunzi ◽  
Diego Cesario ◽  
Fernando Pirani ◽  
Leonardo Belpassi ◽  
Gernot Frenking ◽  
...  
Keyword(s):  
Chemical Bond ◽  
Back Donation ◽  
Weak Chemical

Asymmetrical π back-donation of hetero-dicationic Mo4+-Mo6+ pairs for enhanced electrochemical nitrogen reduction

Nano Research ◽  
2021 ◽  
Author(s):  
Hao Tan ◽  
Qianqian Ji ◽  
Chao Wang ◽  
Hengli Duan ◽  
Yuan Kong ◽  
...  
Keyword(s):  
Nitrogen Reduction ◽  
Back Donation

Darstellung und Redoxverhalten aller bindungsisomeren Hexakis(thiocyanato(N)-thiocyanato(S))-osmate(III) und (IV), [Os(NCS)n(SCN)6-n]3-/2-, n = 0—6, einschließlich der Stereoisomeren / Preparation and Electrochemical Behaviour of All Bond-Isomeric Hexakis(thiocyanato(N)-thiocyanato(S))osmates(III) and (IV), [Os(NCS)n(SCN)6-n]3-/2-, n = 0—6, Including Stereoisomers

1988 ◽  
Vol 43 (4) ◽  
pp. 382-388 ◽  
Author(s):  
K. Bütje ◽  
W. Preetz
Keyword(s):  
Electron Transfer ◽  
Electrochemical Behaviour ◽  
Deae Cellulose ◽  
Transfer Reactions ◽  
Cyclic Voltammograms ◽  
Geometric Isomers ◽  
Cellulose Oxidation ◽  
Half Wave ◽  
Complete Series ◽  
Back Donation

AbstractThe first two complete series of all 10 possible linkage and geometric isomers of the general formula [Os(NCS)n(SCN)6-n]3-/2- have been obtained. The Os(III) complexes, some of which have been previously known, are prepared from the reactions of K2[OsX6], X = Cl. Br. I, and K2[OsO2(OH)4] with excess aqueous or methanolic KSCN solution and subsequent chromato­graphic separation on DEAE cellulose. Oxidation with Ce(IV) in acetone or methanol yields the corresponding Os(IV) compounds without changes in the ligand sphere except for n = 0, but pure salts of [Os(SCN)6]2“ are isolated by repeated recrystallization. S-bonding is less favoured in Os(IV) than in Os(III), proving that Os(IV) is the harder Lewis acid. Cyclic voltammograms of all isomers show two waves, a mainly irreversible Os(II)/Os(III) couple and a reversible Os(III)/Os(IV) couple. Characteristic shifts of the half-wave potentials of both electron transfer reactions within the series give strong evidence of π-back donation to -NCS.

THEORETICAL STUDY OF NITROGEN MONOXIDE ADSORPTION ON RHODIUM CLUSTERS AT DIFFERENT SITES

2008 ◽  
Vol 07 (04) ◽  
pp. 669-679 ◽  
Author(s):  
JIAN CHEN ◽  
KAI TAN ◽  
MENG-HAI LIN
Keyword(s):  
Density Functional ◽  
Nitrogen Monoxide ◽  
Density Functional Theory Calculations ◽  
Frontier Orbitals ◽  
Functional Theory ◽  
Orbital Interactions ◽  
Adsorption Sites ◽  
Rhodium Clusters ◽  
Adsorption Of Nitrogen ◽  
Back Donation

The adsorption of nitrogen monoxide NO with charged and neutral [Formula: see text] clusters at atop, bridge, and threefold hollow sites had been investigated by density functional theory calculations. The results showed that rhodium clusters had strong orbital interactions with NO and formed the complex [ Rh n NO ]-/0/+. The stretching vibrational frequencies of the N–O bonds changed with the different adsorption sites and clusters sizes. The interactions between rhodium clusters and NO molecular could be described through the donation and back-donation of their frontier orbitals. The more back donation from Rh to NO , the weaker the N–O bonds, exhibiting that the lengthening of the N–O bond length and the lowering of its vibrational frequency. In general, the donation and back-donation interactions followed the tendencies: anionic > neutral > cationic, big size > small size, threefold hollow site > bridge site > atop site.

Inter-ligand azo (NN) unit formation and stabilization of a Co(ii)-diradical complex via metal-to-ligand dπ–pπ* back donation: synthesis, characterization, and theoretical study

2015 ◽  
Vol 44 (8) ◽  
pp. 3724-3727 ◽  
Author(s):  
Richa Rakshit ◽  
Samir Ghorai ◽  
Amrit Sarmah ◽  
Archana Tiwari ◽  
Ram Kinkar Roy ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Bond Formation ◽  
Unit Formation ◽  
Back Donation

Ligand H2Rich(AP)N3 provided a diradical-containing Co(ii) complex via an inter-ligand azo (NN) bond formation.

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