Recommendations for the Evaluation of Aromatic Stabilization Energies

Schleyer, Paul von Ragué; Pühlhofer, Frank G.

doi:10.1021/ol0261332

Cited by 384 publications

(402 citation statements)

References 10 publications

Supporting

Mentioning

358

Contrasting

Unclassified

Order By: Relevance

“…Structure 2a(T 1 ) is highly destabilized, evident from the computed ISE values. On the other hand, the ISE values reported for benzene in S 0 state is −33.2 kcal/mol [57]. Thus, the ISE values support our hypothesis that 2a(T 1 ) is destabilized to the same extent as 1a(T 1 ) is stabilized.…”

Section: Isomerization Stabilization Energy (Ise) Valuessupporting

confidence: 83%

See 1 more Smart Citation

The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity

2017

View full text Add to dashboard Cite

Baird's rule tells that the electron counts for aromaticity and antiaromaticity in the first ππ* triplet and singlet excited states (T 1 and S 1 ) are opposite to those in the ground state (S 0 ). Our hypothesis is that a silacyclobutene (SCB) ring fused with a [4n]annulene will remain closed in the T 1 state so as to retain T 1 aromaticity of the annulene while it will ring-open when fused to a [4n + 2]annulene in order to alleviate T 1 antiaromaticity. This feature should allow the SCB ring to function as an indicator for triplet state aromaticity. Quantum chemical calculations of energy and (anti)aromaticity changes along the reaction paths in the T 1 state support our hypothesis. The SCB ring should indicate T 1 aromaticity of [4n]annulenes by being photoinert except when fused to cyclobutadiene, where it ring-opens due to ring-strain relief.

show abstract

Section: Isomerization Stabilization Energy (Ise) Valuessupporting

confidence: 83%

“…Clock-wise ring-currents indicates aromaticity and counter clock-wise ring-currents indicates antiaromaticity. Isomerization stabilization energies (ISE) [32,33,57] were calculated at the (U)B3LYP/6-311G(d,p) level.…”

Section: Methodsmentioning

confidence: 99%

The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity

2017

View full text Add to dashboard Cite

show abstract

“…5 have the same total number of anti-diene units in the reactants and in their products. The large negative energy of the first reaction (-25.7 kcal mol À 1 ) is approximately four-fifths of benzene's ISE (-33.2 kcal mol À 1 ) value 29 , in sharp contrast to the positive (8.8 kcal mol À 1 ) pentalene value 19 . The second (Fig.…”

Section: Resultsmentioning

confidence: 94%

“…We first evaluated the 'isomerization stabilization energy' (ISE) using effective variations of the Schleyer-Pühlhofer method 29,30 . The ISE values of osmapentalene in Fig.…”

Section: Resultsmentioning

confidence: 99%

Planar Möbius aromatic pentalenes incorporating 16 and 18 valence electron osmiums

et al. 2014

View full text Add to dashboard Cite

Aromaticity, a highly stabilizing feature of molecules with delocalized electrons in closed circuits, is generally restricted to 'Hückel' systems with 4n þ 2 mobile electrons. Although the Möbius concept extends the principle of aromaticity to 4n mobile electron species, the rare known examples have complex, twisted topologies whose extension is unlikely. Here we report the realization of osmapentalenes, the first planar Möbius aromatic complexes with 16 and 18 valence electron transition metals. The Möbius aromaticity of these osmapentalenes, documented by X-ray structural, magnetic and theoretical analyses, demonstrates the basis of the aromaticity of the parent osmapentalynes. All these osmapentalenes are formed by both electrophilic and nucleophilic reactions of the in-plane p component of the same carbyne carbon, illustrating ambiphilic carbyne reactivity, which is seldom observed in transition metal chemistry. Our results widen the scope of Möbius aromaticity dramatically and open prospects for the generalization of planar Möbius aromatic chemistry.

show abstract

“…To further confirm that 16 is not antiaromatic,w eh ave also calculated its stability relative to the isomer 17 with an exo-methylene group, [21] as well as the free energy change for hydrogenation of 16 to 18. [22] Calculations at the B3LYP/6-31G(d) level indicate that the complex 16 is 13.9 kcal mol À1 more stable than the isomer 17 ( Figure 2).…”

mentioning

confidence: 99%

Synthesis and Characterization of Dirhenadehydro[12]annulenes

et al. 2016

View full text Add to dashboard Cite

The 12-membered-ring metallacycles [mer-Re{ CCH = C(R)C C À }Cl(PMe 2 Ph) 3 )] 2 (R = CMe 3 ,1 -adamantyl), which are organometallic analogues of antiaromatic octadehydro [12]annulene,a re prepared by heating the methyl carbyne complexes mer-Re{ CCH=C(R)C CH}-(CH 3 )Cl(PMe 2 Ph) 3 .A ni ntermolecular s-bond metathesis between the Re À CH 3 bond and the acetylenic C À Hb ond is proposed for their formation.An [n]annulene is am onocyclic hydrocarbon comprising alternating single and double bonds (for example,c yclobutadiene (1), benzene (2)). Dehydroannulenes are annulene derivatives with one or more triple bonds (for example, benzyne). Annulenes and dehydroannulenes have inspired numerous theoretical and experimental studies as ar esult of their interesting properties.[1] Fore xample,t hey can be used as aromaticity probes,a si ntermediates in the action of enediyne antitumor agents and as precursors in the preparation of novel carbon containing compounds.Formal replacement of carbon atoms or CH groups in annulenes and dehydroannulenes by an isolobal transitionmetal fragment would give metallaannulenes and metalladehydroannulenes.W hile annulenes with the number of ring carbon atoms up to 30 and dehydroannulenes with the number of ring carbon atoms up to 38 are known, reported examples of metallaannulenes and metalladehydroannulenes are mainly those with six or less ring atoms,f or example, metallacyclobutadienes (3), [2,3] metallabenzenes (4), [4,5] dimetallabenzenes (5), [6] and metallabenzynes (6). [7,8] Larger metallaannulenes and metalladehydroannulenes are very rare.V ery recently,X ia nd his co-workers reported the synthesis and characterization of the first dimetalla-[10]annulenes (7).[9]Herein, we report the synthesis and characterization of dimetalladehydro [12]annulenesw hich are closely related to octadehydro[12]annulenes 8,s pecies that have been previously studied for their aromaticity/antiaromaticity and interesting materials properties. [10] We have shown that the rhenium hydridocarbyne complexes 9 can thermally isomerize to the rhenabenzynes 11 via bicyclicmetallacycle complexes 10 (Scheme 1).[11] Continuing our efforts at making new metallabenzynes,wehave prepared rhenium carbyne complexes 14 (see Scheme 2), analogous to 9 with the hydride ligand of 9 being replaced by am ethyl group.These carbyne complexes may be expected to undergo similar methyl migration reactions to give bicyclic metallacycles,a nalogous to 10,t hat can be converted to methylsubstituted rhenabenzynes. Thep recursor methyl carbyne rhenium complexes merRe{ CCH = C(R)C CH}(CH 3 )Cl(PMe 2 Ph) 3 (R = CMe 3 , 14 a;1 -adamantyl, 14 b)w ere prepared by the route shown in Scheme 2. Tr eatment of the SiMe 3 -protected dichloro carbyne complexes mer,cis-Re{ CCH=C(R)C CSiMe 3 }Cl 2 (PMe 2 Ph) 3 (12)w ith CH 3 MgCl in THF gave the methyl carbyne complexes 13,w hich were isolated as green solids (Scheme 2). Thed esired carbyne complexes 14 were then obtained by desilylation of the complexes 13 with nBu 4 NF.When atoluene solutio...

show abstract

Recommendations for the Evaluation of Aromatic Stabilization Energies

Cited by 384 publications

References 10 publications

The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity

The Silacyclobutene Ring: An Indicator of Triplet State Baird-Aromaticity

Planar Möbius aromatic pentalenes incorporating 16 and 18 valence electron osmiums

Synthesis and Characterization of Dirhenadehydro[12]annulenes

Contact Info

Product

Resources

About