Ligand-stabilized heteronuclear diatomics of group 13 and 15

A theoretical investigation of ligand-stabilized MX diatomics (M = group 13, X = group 15 element) with N-heterocyclic carbene (NHC) ligands has been carried out to assess bonding and electronic structure. Binding of two ligands in the form L-MX-L is generally preferred over binding of a single ligand as L-MX or MX-L. Binding of carbene donor ligands is predicted to be thermodynamically favorable for all the systems, and is very favorable for the lighter group 15 systems (nitrogen and phosphorus). Detailed analysis of the bonding in these complexes has been carried out with energy decomposition analysis (EDA). In all cases, the carbene to boron and carbene to nitrogen bonding is described as an electron-sharing double bond with both σ and π bonding interactions. For the heavier elements, bonding to C (except for P-C interactions) is best described as a donor-acceptor σ single bond

Prediction of Covalent Metal-Metal Bonding in Cp-M-M'-Nacnac Complexes of Group 2 and 12 Metals (Be, Mg, Ca, Zn, Cd, Hg)

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M=Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal-metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal-metal bonding. In all cases the metal-metal bonds are characterized as electron-sharing covalent single bonds from natural bond orbital (NBO) and energy-decomposition analysis with natural orbitals of chemical valence (EDA-NOCV) analysis. The sum of [MM′] charges is relatively constant, with all complexes exhibiting a [MM′]2+ core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non-nuclear attractors (NNA) in the metal-metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75–1.33 e) associated with the NNAs, which indicates that these metal-metal bonds, while classified as covalent electron-sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal-metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal-metal bonds

NMR parameters of FNNF as a test for coupled-cluster methods: CCSDT shielding and CC3 spin–spin coupling

NMR shielding and spin-spin coupling constants of cis and trans isomers of FNNF have been determined to near-quantitative accuracy from ab initio calculations. The FNNF system, containing multiple N-F bonds and fluorine atoms, provides a severe test of computational methods. Coupled-cluster methods were used with large basis sets and complete basis set (CBS) extrapolations of the equilibrium geometry results, with vibrational and relativistic corrections. Shielding constants were calculated with basis sets as large as aug-cc-pCV7Z, together with coupled-cluster expansions up to CCSDT, at the all-electron CCSD(T)/aug-cc-pCVQZ optimized geometries. Spin-spin coupling constants have been determined with specialized versions of the correlation consistent basis sets ccJ-pVXZ, further augmented with diffuse functions. All-electron coupled-cluster methods up to CC3 were applied in these calculations. The results of this work highlight the application of state-of-the-art theoretical techniques, and provide the most accurate NMR properties of FNNF to date, which can serve to guide and supplement NMR experimentation.</p

On the potential intermediacy of PhIBr2 as a brominating agent

No description supplied </p

Direct C4 and C2 C-H Amination of Heteroarenes Using I(III) Reagents via a Cross Azine Coupling

Aminated nitrogen heterocycles are valuable motifs across numerous chemical industries, perhaps most notably in small molecule drug discovery. While numerous strategies for installing nitrogen atoms onto azaarenes exist, most require prefunctionalization and methods for direct C-H amination are almost entirely limited to position C2. Herein, we report a method for the direct C2 and C4 C-H amination of fused azaarenes via in situ activation with a bispyridine-ligated I(III) reagent, [(Py)2IPh]2OTf, or Py-HVI. Unlike commonly used N-oxide chemistry, the method requires no preoxidation of the azaarene and provides unprecedented direct access to C4 amination products. The resulting N-heterocyclic pyridinium salts can be isolated via simple trituration. The free amine can be liberated under mild Zincke aminolysis, or the amination and cleavage can be telescoped to a one-pot process. The scope of the method is broad; the conditions are mild and operationally simple, and the aminated products are produced in good to excellent yields. Computational studies provide insights into the mechanism of activation, which involves an unusual direct nucleophilic functionalization of an I(III) ligand, as well as a kinetic basis for the observed C2 and C4 amination products.</p

Revisiting the Perfluorinated Trityl Cation

Although ultimately not isolable for X-ray structural characterization, the free perfluorinated trityl cation was shown to be observable in neat triflic acid, which represents milder conditions than previous reports of this cation in “magic acid” or oleum. A triflate-bound species could be generated in organic solvents using stoichiometric amounts of triflic acid and was shown to be synthetically viable for hydride abstraction from Et SiH. It was demonstrated that the para-position on the -C F rings is the primary point of attack for decomposition of the cation. 3 6 5</p

Revisiting the Perfluorinated Trityl Cation

Although ultimately not isolable for X-ray structural characterization, the free perfluorinated trityl cation was shown to be observable in neat triflic acid, which represents milder conditions than previous reports of this cation in “magic acid” or oleum. A triflate-bound species could be generated in organic solvents using stoichiometric amounts of triflic acid and was shown to be synthetically viable for hydride abstraction from Et SiH. It was demonstrated that the para-position on the -C F rings is the primary point of attack for decomposition of the cation. 3 6 5</p

Lewis acid activation of Weiss' reagents ([PhI(Pyr)2]²⁺) with boranes and isolation of [PhI(4-DMAP)]²⁺

Abstraction of a pyridine ligand from Weiss' reagent ([PhI(Pyr)2]2+) using BF3-Et2O was found to activate Weiss' reagent towards electrophilic aromatic substitution reactions. The activated species can be isolated when 4-DMAP is used as the pyridine ligand and was determined to be [PhI(4-DMAP)]2+ in solution. The isolated cation was reactive in electrophilic aromatic substitution reactions towards mesitylene, xylene and toluene that Weiss' reagent itself does not react with.</p

Borataalkene Hydrofunctionalization Reactions

The hydrofunctionalization of alkenes is a foundational class of reactions; however, the analogous reactions for B═C bond-containing species have been virtually unexplored. This work unearths a range of B═C hydrofunctionalization reactions with the 9-borataphenanthrene anion, including hydroalkylation, hydroarylation, hydroalkynylation, hydroamination, hydroalkoxylation, and hydration. The unique reactivity represents an addition to the synthetic chemist's toolbox to access functionalized tetracoordinate borates.</p

Photochemically and Thermally Generated BN-Doped Borafluorenate Heterocycles via Intramolecular Staudinger-Type Reactions

No description supplied.</p