2014
DOI: 10.1021/jo500117t
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Theoretical Study on the Effect of Annelation and Carbonylation on the Electronic and Ligand Properties of N-Heterocyclic Silylenes and Germylenes: Carbene Comparisons begin To Break Down

Abstract: Quantum chemical calculations have been carried out to investigate the effect of annelation and carbonylation on the electronic and ligand properties of N-heterocyclic silylenes and germylenes. The thermodynamic stability of these ligands has been found to increase with annelation, while the reverse is true for carbonylation. This is in sharp contrast to N-heterocyclic carbenes (NHCs) where annelation leads to a decrease in their thermodynamic stabilities. Compared to nonannelated derivatives, annelated and ca… Show more

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Cited by 16 publications
(6 citation statements)
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“…Phukan and collaborators, [155][156][157][178][179][180][181][182][183][184] have again used a range of descriptors to assess carbenes; while the exact selection varied with application and no single coherent database has been presented, capturing carbene properties across a wide range of structural modifications, most of these studies have included calculated singlet-triplet gaps as a measure of the thermodynamic stability of carbenes, along with HOMO-LUMO gaps as a measure of the kinetic stability (PBE1PBE/6-31G*, SDD on metals). Studies have included comparison of carbenes with silylenes, germylenes and abnormal carbenes, 178,182 analysis of ring size and heterocycles on carbene properties, 179 the introduction of boron substituents to carbene (NHC and PHC) backbones, 156 the effect of additional rings and carbonyl substituents on normal and abnormal NHCs, 157 analysis of remote carbenes, 181,183 consideration of adduct formation for normal and abnormal NHCs, 180 and small molecule activation by cyclic (alkyl)(amino) carbenes (CAACs). 184 Overlap with our core set of carbenes (Table 1c) is quite poor as these studies have been focussed on novel/unusual structures, so data have not been compiled in this case.…”
Section: Electronic Structure Trendsmentioning
confidence: 99%
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“…Phukan and collaborators, [155][156][157][178][179][180][181][182][183][184] have again used a range of descriptors to assess carbenes; while the exact selection varied with application and no single coherent database has been presented, capturing carbene properties across a wide range of structural modifications, most of these studies have included calculated singlet-triplet gaps as a measure of the thermodynamic stability of carbenes, along with HOMO-LUMO gaps as a measure of the kinetic stability (PBE1PBE/6-31G*, SDD on metals). Studies have included comparison of carbenes with silylenes, germylenes and abnormal carbenes, 178,182 analysis of ring size and heterocycles on carbene properties, 179 the introduction of boron substituents to carbene (NHC and PHC) backbones, 156 the effect of additional rings and carbonyl substituents on normal and abnormal NHCs, 157 analysis of remote carbenes, 181,183 consideration of adduct formation for normal and abnormal NHCs, 180 and small molecule activation by cyclic (alkyl)(amino) carbenes (CAACs). 184 Overlap with our core set of carbenes (Table 1c) is quite poor as these studies have been focussed on novel/unusual structures, so data have not been compiled in this case.…”
Section: Electronic Structure Trendsmentioning
confidence: 99%
“…Phukan and collaborators , have again used a range of descriptors to assess carbenes. While the exact selection varied with application and no single coherent database has been presented, capturing carbene properties across a wide range of structural modifications.…”
Section: Ligand Descriptorsmentioning
confidence: 99%
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“…A similar method for the assessment of the π-acceptor strength of NHCs has been developed by exploiting 77 Se chemical shifts in the corresponding selanourea compounds by the groups of Ganter , and Nolan . The ligating properties and bonding features of normal NHCs and the corresponding silylenes and germylenes have been explored earlier by employing the 31 P NMR chemical shifts of the carbene–phenylphosphinidene ( C-PPh ) adducts. Similar theoretical studies on the coordinating properties of boron-substituted heterocyclic carbenes of different ring sizes , and that of remote NHCs have been previously reported.…”
Section: Introductionmentioning
confidence: 99%
“…[2] The variation of Group 14 element and incorporation of heteroatoms into the aromatic system of various NHCs and corresponding analogues provide a useful means for tuning their reactivity and catalytical properties. [3] Benzannulated carbenes [2a, 4] and their analogues with divalent Group elements ranging from Si to Pb (I, Scheme 1) have been successfully prepared and characterized. [1d, 5] Incorporation of the nitrogen atom into the benzene ring of benzannulated system (pyridoannulation, II) does not greatly alter the electronic structure of the resulting species, and their representatives with E=CÀSn have been isolated.…”
mentioning
confidence: 99%