Organometallics

Probing the Strongest Aromatic Cyclopentadiene Ring by Hyperconjugation

Hyperconjugation, an interaction of electrons in a σ orbital or lone pair with an adjacent π or even σ antibonding orbital, can have a strong effect on aromaticity. However, most work on hyperconjugative aromaticity has been limited to main-group substituents. Here, we report a thorough density functional theory study to evaluate the aromaticity in various cyclopentadienes that contain both main-group and transition-metal substituents.

To Be Bridgehead or Not to Be? This is a Question of Metallabicycles on the Interplay between Aromaticity and Ring Strain

Transition-metal-containing metallaaromatics have attracted considerable interest from both experimental and computational chemists because they can display properties of both organometallic compounds and aromatic organic compounds. In general, the transition metal in a metallabicycle prefers a nonbridged position to the bridgehead one because of the larger ring strain caused by the rigidity in the bridgehead position, as exemplified by metallanaphthalene and metallanaphthalyne.

Craig-Type Möbius Aromaticity and Antiaromaticity in Dimetalla[10]annulenes: A Metal-Induced Yin-and-Yang Pair

Aromaticity, one of the most fundamental concepts in chemistry, can be classified as Hückel- and Möbius-type according to the electron count and topology. In comparison with numerous Hückel aromatics containing 4n+2 π-electrons, Möbius aromatics with 4n π-electrons, especially the Craig-type species are particularly limited.

Isolation of a Heavier Cyclobutadiene Analogue: 2,4-Digerma-1,3-diphosphacyclobutadiene

The heavier cyclobutadiene analogue 2,4-digerma-1,3-diphosphacyclobutadiene ([L12Ge2P2], 4; L1 = CH{(CMe)(2,6-iPr2C6H3N)}2), featuring a planar Ge2P2 four-membered ring, has been synthesized via the elimination of carbon monoxide from the corresponding phosphaketenyl germylene [L1GePCO] (2) under UV irradiation.

http://pubs.acs.org/doi/abs/10.1021/acs.organomet.6b00187

Why Does Activation of the Weaker C═S Bond in CS2 by P/N-Based Frustrated Lewis Pairs Require More Energy Than That of the C═O Bond in CO2? A DFT Study

The sequestration of carbon disulfide (CS2), a common pollutant in environmental systems, is of great importance due to its physical harm to human beings. Compared with CO2 capture, that of CS2 is much less developed. The use of P/N-based frustrated Lewis pairs (FLPs) has been proven, both experimentally and theoretically, to be an alternative strategy to efficiently sequestrate CO2. Therefore, we pose the question of whether the analogue CS2 could also be sequestrated by the same FLPs, given that the C═S bond in CS2 is weaker than the C═O bond in CO2.

Interconversion between Ruthenacyclohexadiene and Ruthenabenzene: A Combined Experimental and Theoretical Study

Treatment of ruthenabenzene [(C9H6NO)Ru{CC(PPh3)CHC(PPh3)CH}(C9H6NO)(PPh3)]Cl2 (1) with NaBH4 produces the first ruthenacyclohexa-1,4-diene [(C9H6NO)Ru{CC(PPh3)CH2C(PPh3)CH}(C9H6NO)(PPh3)]Cl (2), which was fully characterized. Under an oxygen atmosphere, complex 2 can easily convert to complex 1. DFT calculations were carried out to rationalize the high regioselectivity in the reaction of the ruthenabenene 1 with NaBH4 and the interconversion between 1 and 2.

Unconventional Facile Way to Metallanaphthalenes from Metal Indenyl Complexes Predicted by DFT Calculations: Origin of Their Different Thermodynamics and Tuning Their Kinetics by Substituents

Metallaaromatics have attracted considerable interest from both experimentalists and theoreticians over the past three decades. However, most studies in this field have focused on metallabenzene, in which a CH group is replaced by a transition metal fragment. In comparison with monocyclic metallabenzenes, bicyclic metallanaphthalenes are rather limited. Thus, it is urgent to explore more synthetic approaches to this less developed system. One of the difficulties in the synthesis of metallanaphthalenes could be due to its low thermodynamic stability relative to the metal indenyl complexes.

Theoretical Study on the Stability and Aromaticity of Metallasilapentalynes

Antiaromatic compounds and small cyclic alkynes or carbynes are both challenging for synthetic chemists because of the destabilization caused by their antiaromaticity and highly distorted triple bonds, respectively. These dual destabilizations could be the reason why pentalyne (I), a highly antiaromatic and extremely strained cyclic alkyne, has never been synthesized.

Computations Offer an Unconventional Route to Metallaphosphabenzene from a Half-Phosphametallocene

Metallaaromatics have attracted continuing interest of both theoretical and experimental chemists since the first metallabenzene was predicted by Hoffmann and isolated by Roper. In sharp contrast to metallabenzenes, metallaphosphabenzene (MPB) is much less developed and has not been synthesized so far. Thus, developing synthetic approaches is urgent. Here we present thorough density functional theory (DFT) calculations on the thermodynamics and kinetics of the rearrangement between MPBs and the corresponding η5-phosphacyclopentadiene (η5-PCp) complexes.

Interconversion of Metallanaphthalynes and Indenylidene Complexes: A DFT Prediction

Metallaaromatics have attracted considerable interest of both theoretical and experimental chemists. However, there have been only two metallanaphthalynes isolated so far. Thus, developing new synthetic approaches is urgent. Here we present thorough density functional theory (DFT) calculations on the thermodynamics and kinetics of the isomerization between metallanaphthalynes and metal indenylidene complexes. The effects of metal centers, ligands, and substituents on the metallabicycles were examined systematically.

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