Density functional theory (DFT) calculations were performed to examine the substituent effects on the interconversion of silabenzenes and their monocyclic non-aromatic isomers. A previous study suggested that aromaticity is the driving force for this process. Interestingly, our systematic calculations reveal that the contribution from aromaticity can be evaluated quantitatively (ca. 30 kcal mol-1). Thus it is the interplay of aromaticity and Bent's rule that determine their relative stabilities.
Density functional theory (DFT) calculations were carried out to investigate the [2+2], [3+2] and [4+2] cycloadditions of the phosphaethynolate anion (PCO−). The results reveal that the electronic properties of different unsaturated compounds play a crucial role in reactivity and regioselectivity.
The reaction mechanism of copper-catalyzed phosphorylation of terminal alkynes under different conditions has been investigated experimentally and theoretically. The important role of dioxygen has been elucidated, including the formation of η1-superoxocopper(II), η2-superoxocopper(III), μ-η2:η2-peroxodicopper(II), and bis(μ-oxo)dicopper(III) complexes.
Highly efficient Pd-catalyzed asymmetric allylic alkylation reaction of ethyl-2-fluoro-2-(diethoxyphosphoryl)acetate with monosubstituted allylic substrates has been developed, affording corresponding α-fluorophosphonates with two chiral centers in high regio-, diastereo- and enantio-selectivities. The usefulness of the products in organic synthesis has been demonstrated.
Density functional theory calculations (DFT) have been performed on Rh(III)-catalyzed phosphoryl-directed oxidative C–H activation/cyclization to investigate the detailed mechanism, including four basic steps: C–H activation, alkyne insertion, reductive elimination, and catalyst recycling, each of which consists of different steps. Interestingly, the Rh(III)–AgOAc catalyst system was found to be more favorable in the C–H activation step in comparison with the Rh(III)–Ag2CO3 system, whereas the Rh(I)–Ag2CO3 catalyst system was more efficient for catalyst recycling.
The water-mediated neutral hydrolysis mechanism of carbonyl sulfide (OCS) has been re-examined using the hybrid supramolecule/continuum models with n = 2–8 explicit water cluster at the level of MP2(fc)(CPCM)/6-311++G(d,p)//MP2(fc)(CPCM) /6-31+G(d). Present calculations indicate that the potential energy surface in water solution is different from the one in the gas-phase, and only stepwise mechanism is observed in aqueous solution, i.e., monothiocarbonic acid (H2CO2S) is formed via monothiocarbonate (OCSOH–, MTC) and its counterion, protonated water cluster, (H2O)nH3O+.
We have made an extensive theoretical exploration of gas-phase N-alkylamino cation affinities (NAAMCA), including amino cation affinities (AMCA) and N-dimethylamino cation affinities (NDMAMCA), of neutral main-group element hydrides of groups 15–17 and periods 2–4 in the periodic table by using the G2(+)M method. Some similarities and differences are found between NAAMCA and the corresponding alkyl cation affinities (ACA) of HnX.
Aromaticity is one of the most important concepts in organic chemistry. A variety of metalla-aromatic compounds have been recently prepared and in most of those examples, the metal participates only in a monocyclic ring. In contrast, metal-bridged bicyclic aromatic molecules, in which a metal is shared between two aromatic rings, have been less developed. Herein, we report the first metal-bridged tricyclic aromatic system, in which the metal center is shared by three aromatic five-membered rings. These metalla-aromatics are formed by reaction between osmapentalyne and arene nucleophiles.
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.
Metallabenzyne has attracted considerable interest from theoreticians and experimentalists since its first isolation in 2001. However, metallasilabenzyne, formed by the replacement of the carbyne carbon with a silicon atom in metallabenzyne, has never been reported either theoretically or experimentally. Here we carry out density functional theory (DFT) calculations on this system for the first time. Our results reveal a polarized and weak Os–Si triple bond in osmasilabenzyne due to the reluctance of the silicon to participate in π bonding.