Theoretical Prediction and Explanation of Reaction Site Selectivity in the Addition of a Phenoxy Group to Perfluoropyrimidine, Perfluoropyridazine, and Perfluoropyrazine

Perfluoroaromatics, such as perfluoropyridine and perfluorobenzene, are privileged synthetic scaffolds in organofluorine methodology, undergoing a series of regioselective substitution reactions with a variety of nucleophiles. This unique chemical behavior allows for the synthesis of many perfluoroaromatic derived molecules with unique and diverse architectures. Recently, it has been demonstrated that perfluoropyridine and perfluorobenzene can be utilized as precursors for a variety of materials, ranging from high performance polyaryl ethers to promising drug scaffolds. In this work, using density functional theory, we investigate the possibility of perfluoropyrimidine, perfluoropyridazine, and perfluoropyrazine participating in similar substitution reactions. We have found that the first nucleophilic addition of a phenoxide group substitution on perfluoropyrimidine and on perfluoropyridazine would happen at a site para to one of the nitrogen atoms. While previous literature points to mesomeric effects as the primary cause of this phenomenon, our work demonstrates that this effect is enhanced by the fact that the transition states for these reactions result in bond angles that allow the phenoxide to π-complex with the electron-deficient diazine ring. The second substitution on perfluoropyrimidine and on perfluoropyridazine is most likely to happen at the site para to the other nitrogen. The second substitution on perfluoropyrazine is most likely to happen at the site para to the first substitution. The activation energies for these reactions are in line with those reported for perfluoropyridine and suggest that these platforms may also be worth investigation in the lab as possible monomers for high performance polymers.

SYNTHESIS, CRYSTAL STRUCTURE, HIRSHFELD SURFACE ANALYSIS AND QUANTUM CHEMICAL CALCULATIONS OF [Cu2(C6H9N3S)2(ClO4)2] π-COMPLEX WITH 2-ALLYLAMINO-5-METHYL-1,3,4-THIADIAZOLE

This work is focused on the synthesis and structure characterization of the novel Cu(I) π-complex [Cu2(Thiaz1)2(ClO4)2] (1) with 2-allylamino-5-methyl-1,3,4-thiadiazole (Thiaz1) ligand. The crystals of the compound were obtained by means of the alternating-current electrochemical technique and studied using single crystal X-ray diffraction. The crystal structure of the complex 1 is constructed from the centrosymmetric dimers, in which two copper(I) ions are coordinated by two Thiaz1 molecules through thiadiazole N atoms and allylic C=C bond. Energy framework computational analysis for structure 1 has been performed.

Synthesis, structure and computational study of 5-[(prop-2-en-1-yl)sulfanyl]-1,3,4-thiadiazol-2-amine (Pesta) and its heterometallic π,σ-complex [Cu2FeCl2(Pesta)4][FeCl4]

Copper(I) π-coordination compounds with allyl derivatives of azoles are an interesting subject of current research, but CuI π-complexes with other transition-metal ions incorporated in the structure have been virtually uninvestigated. The present work is directed toward the synthesis and structural characterization of the novel heterometallic CuI/FeII π-complex di-μ2-chlorido-1:2κ2 Cl;2:3κ2 Cl-tetrakis[μ2-5-(prop-2-en-1-ylsulfanyl)-1,3,4-thiadiazol-2-amine]-1:2κ2 N 4:N 3;1(η2),κN 4:2κN 3;2:3κ2 N 3:N 4;2κN 3:3(η2),κN 4-dicopper(I)iron(II) tetrachloridoferrate(II), [Cu2FeCl2(C5H7N3S2)4][FeCl4] (1). The structure of the 5-[(prop-2-en-1-yl)sulfanyl]-1,3,4-thiadiazol-2-amine (Pesta, C5H7N3S2) ligand is also presented. The cationic substructure in 1 consists of one FeII and two CuI ions bridged by two chloride ions along with two σ,σ- and two π,σ-coordinated ligands, whereas the anionic part is built of isolated tetrahedral [FeCl4]2− ions. π-Coordination of the Pesta allyl group to the CuI ions prevents agglomeration of the inorganic Cu–Cl–Fe–Cl–Cu part into infinate chains. An energy framework computational analysis was performed for Pesta.

Co-Catalyzed E-(β)-Selective Hydrogermylation of Terminal Alkynes

<a></a><a>We demonstrated unprecedentedly that Co complexes can catalyze hydrogermylation of alkynes. Subsequently, a selective, accessible method was developed to synthesize E-(β)-vinyl(trialkyl)germanes from various terminal alkynes with high yields. As shown on multiple examples, the developed method demonstrates broad functional group tolerance and practical utility for late-stage hydrogermylation of drugs and natural products. The method is compatible with alkynes bearing both aryl and alkyl substituents, providing unrivaled selectivity for previously challenging 1° alkyl-substituted alkynes. Moreover, the catalyst used in this method, Co₂(CO)₈, is a cheap and commercially available reagent. Conducted mechanistic studies supported syn-addition of Bu₃GeH to an alkyne</a> π-complex.

Co-Catalyzed E-(β)-Selective Hydrogermylation of Terminal Alkynes

<a></a><a>We demonstrated unprecedentedly that Co complexes can catalyze hydrogermylation of alkynes. Subsequently, a selective, accessible method was developed to synthesize E-(β)-vinyl(trialkyl)germanes from various terminal alkynes with high yields. As shown on multiple examples, the developed method demonstrates broad functional group tolerance and practical utility for late-stage hydrogermylation of drugs and natural products. The method is compatible with alkynes bearing both aryl and alkyl substituents, providing unrivaled selectivity for previously challenging 1° alkyl-substituted alkynes. Moreover, the catalyst used in this method, Co₂(CO)₈, is a cheap and commercially available reagent. Conducted mechanistic studies supported syn-addition of Bu₃GeH to an alkyne</a> π-complex.

Key Role of π–π Complex in Diary Cross-Coupling between Aryldiazonium Salts and Arylboronic Acids using Photosensitizer-Free Gold/Photoredox Catalysis

DFT and TD-DFT calculations were performed to better understand the photosensitizer-free visible-light-mediated Au-catalyzed cross-couplings between aryldiazonium salts and arylboronic acids. The π–π type complex between the aryldiazonium salt and the...

Halogen bonding in crystals of free 1,2-diiodo-ethene (C2H2I2) and its π-complex [CpMn(CO)2](π-C2H2I2)

Abstract1,2-trans-diiodo-ethene (C2H2I2) – is an overlooked halogen bond donor, which demonstrate the distinct similarity of the geometry and directionality of I···I halogen bonds around the iodine atoms in its native and CpMn(CO)2(C2H2I2) π-complex crystals. Distortion of the planar geometry of C2H2I2 upon the π-coordination result the distortion of the native planar layered geometry of C2H2I2, so that [CpMn(CO)2](π-C2H2I2) features more complex I···I XB assisted 3D network. Unusual structural parallels between the native C2H2I2 crystals and solid iodine are discussed.

New insights into prediction of weak π–π complex association through proton-nuclear magnetic resonance analysis

For analysis of weak π–π complexes proton-nuclear magnetic resonance (proton-NMR) simultaneously provides information of stacking configurations and association constants $$\left( K \right)$$ K However, an apparent issue for this approach is inconsistent/impossible constant estimation which often leads to unreasonable interpretation for π–π complexation. Whether or not this proton-dependent constant variation could be attributed to simple experimental uncertainties or to more sophisticated additional unspecific shielding effects (AUS effects) was addressed by means of hypothesis tests using a robust bootstrap technique in this report. Our analysis shows the significance of AUS effects on such variation in constant estimation. A following study using numeric simulation further reveals the variation patterns induced by AUS effects and concludes that the largest $$K$$ K among the obtained $$K$$ K estimates of a complex is considered as the best estimate of $$K$$ K due to minimum deviation from the true value of K and the multiple $$K$$ K estimates of a π–π complex could provide preferable inferences for complex geometries.