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Metallocenes are well-established compounds in organometallic chemistry, and can exhibit either a coplanar structure or a bent structure according to the nature of the metal center (E) and the cyclopentadienyl ligands (Cp). Herein, we re-examine the chemical bonding to underline the origins of the geometry and stability observed experimentally. To this end, we have analysed a series of group 2 metallocenes [Ae(C5R5)2] (Ae = Be–Ba and R = H, Me, F, Cl, Br, and I) with a combination of computational methods, namely energy decomposition analysis (EDA), polarizability model (PM), and dispersion interaction densities (DIDs). Although the metal–ligand bonding nature is mainly an electrostatic interaction (65–78%), the covalent character is not negligible (33–22%). Notably, the heavier the metal center, the stronger the d-orbital interaction with a 50% contribution to the total covalent interaction. The dispersion interaction between the Cp ligands counts only for 1% of the interaction. Despite that orbital contributions become stronger for heavier metals, they never represent the energy main term. Instead, given the electrostatic nature of the metallocene bonds, we propose a model based on polarizability, which faithfully predicts the bending angle. Although dispersion interactions have a fair contribution to strengthen the bending angle, the polarizability plays a major role. [ABSTRACT FROM AUTHOR]

Electrophilic AlIII species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low‐valent AlI aluminyl anions have showcased oxidative additions towards arenes C−C and/or C−H bonds. Herein, we communicate compelling evidence of an AlII radical addition reaction to the benzene ring. The electron reduction of a ligand stabilized precursor with KC8 in benzene furnishes a double addition to the benzene ring instead of a C−H bond activation, producing the corresponding cyclohexa‐1,3(orl,4)‐dienes as Birch‐type reduction product. X‐ray crystallographic analysis, EPR spectroscopy, and DFT results suggest this reactivity proceeds through a stable AlII radical intermediate, whose stability is a consequence of a rigid scaffold in combination with strong steric protection. [ABSTRACT FROM AUTHOR]

Herein, we report the first 1,4‐diphosphinine‐1,4‐diide compound [(ADCPh)P]2 (5‐Ph) (ADCPh=PhC{(NDipp)C}2; Dipp=2,6‐iPr2C6H3) derived from an anionic dicarbene (ADCPh) as a red crystalline solid. Compound 5‐Ph containing a 16π‐electron planar fused‐tricyclic ring system was obtained by the 4e reduction of [(ADCPh)PCl2]2 (4‐Ph) with Mg (or KC8) in a quantitative yield. Experimental and computational results imply that the central 8π‐electrons C4P2 ring of 5‐Ph, which is fused between two 6π‐electrons C3N2 aromatic rings, is antiaromatic. Thus, each of the phosphorus atoms of 5‐Ph has two electron‐lone‐pairs, one in a p‐type orbital is in conjugation with the C=C bonds of the C4P2 ring, while the second resides in a σ‐symmetric orbital. This can be shown with the gold complex [(ADCPh)P(AuCl)2]2 (6‐Ph) obtained by reacting 5‐Ph with (Me2S)AuCl. A mixture of 5‐Ph and 4‐Ph undergoes comproportionation in the presence of MgCl2 to form the intermediate oxidation state compound [(ADCAr)P]2(MgCl4) (7‐Ph), which is an aromatic species. [ABSTRACT FROM AUTHOR]

The series of 6-substituted 3-R1-2 H-[1,2,4]triazino[2,3- c]quinazolin-2-one was prepared via condensation of 3-(2-aminophenyl)-6-R1-1,2,4-triazin-5-ones with acylating reagents. Particularities of 1H NMR spectra have been also discussed based on the comparison of experimental and theoretical results for 3-methyl-6-phenyl-2 H-[1,2,4]triazino[2,3- c]quinazolin-2-one and its 4,3-isomer. [ABSTRACT FROM AUTHOR]

The article presents information on catalytic enantioselective synthesis of Indanes by a cation-directed 5-endo-trig cyclization. Topics discussed include research at the University of Oxford on the application of asymmetric phase-transfer catalysis to new reaction manifolds; stereocontrolled cyclization reactions for constructing complex structural scaffolds of natural and biologically active molecules; and the development of new cyclization methodologies in organic chemistry.

It has been shown that heating of3-R-[1,2,4]triazino[2,3-c]quinazolin-2-oneswith 5-fold excess of hydrazine hydrate in propanol-2 gave the corresponding3-(2-aminophenyl)-6-R-1,2,4-triazin-5-ones with high yields. The mechanismof the reaction has been proposed based on the results of theoreticalinvestigation at B3LYP and MP2 levels of theory. According to calculations,an attack of the hydrazine molecule on the C6N7double bond leads to ring-opening with N5–C6bond cleavage. The process continues by addition of the secondnucleophile molecule and elimination of the formazan fragment througha series of transformations that yield the target product. [ABSTRACT FROM AUTHOR]

Metallocenes are well-established compounds in organometallic chemistry, and can exhibit either a coplanar structure or a bent structure according to the nature of the metal center (E) and the cyclopentadienyl ligands (Cp). Herein, we re-examine the chemical bonding to underline the origins of the geometry and stability observed experimentally. To this end, we have analysed a series of group 2 metallocenes [Ae(C 5 R 5 ) 2 ] (Ae = Be-Ba and R = H, Me, F, Cl, Br, and I) with a combination of computational methods, namely energy decomposition analysis (EDA), polarizability model (PM), and dispersion interaction densities (DIDs). Although the metal-ligand bonding nature is mainly an electrostatic interaction (65-78%), the covalent character is not negligible (33-22%). Notably, the heavier the metal center, the stronger the d-orbital interaction with a 50% contribution to the total covalent interaction. The dispersion interaction between the Cp ligands counts only for 1% of the interaction. Despite that orbital contributions become stronger for heavier metals, they never represent the energy main term. Instead, given the electrostatic nature of the metallocene bonds, we propose a model based on polarizability, which faithfully predicts the bending angle. Although dispersion interactions have a fair contribution to strengthen the bending angle, the polarizability plays a major role.

Several new diphenylamino- and diphenylphosphanyldialkylalanes are reported, which were characterized in solution and in the solid state, assisted by in-depth bonding analysis within the DFT framework. In the case of bulky alkyl substituents on the aluminum atom, the species are stable in their monomeric form and were structurally characterized by single crystal X-ray diffraction, expanding the relatively small field of monomeric pnictogenylalanes. In the case of oligomeric diphenylpnictogenyldimethylalanes, their reactivity toward different σ-donor ligands was studied, and several examples of monomeric adducts could be structurally characterized, including the first cyclic(alkyl)(amino)carbene complexes. The reactivity of these CAAC complexes, their oligomeric precursors, and an unstabilized monomeric aminoalane toward CO 2 was probed, leading to different insertion products that could be characterized. Additionally, the mechanism was elucidated by DFT calculations.