The M∙∙∙HCCX∙∙∙NH₃ (M = Li⁺, Na⁺, Cu⁺, Ag⁺, Au⁺; X = Cl, Br) complexes were designed to study the influence of cation-π interaction on the X∙∙∙N halogen bonds under M05-2X/aug-cc-pVDZ(PP) level. In comparison with the HCCX∙∙∙NH₃ complexes, the bond distances of the halogen bonds have decreased, and the interaction energies become more negative. The results show that the X∙∙∙N halogen bonds have been strengthened by the cation-π interactions. For different cations, the enhancing effect is more intensive in the order of Au⁺ > Cu⁺ > Ag⁺ > Li⁺ > Na⁺, which indicates that transition metal cations can enhance the halogen bond in a stronger manner. Molecular electrostatic potential and second-order perturbation stabilization energy were calculated to deepen the discussion. In addition, atoms in molecules analysis was performed and the electron density shift was studied.

With the especial reactivity, selectivity, availability and stability, the allenamides have got more and more attention, and the reports on allenamides cyclization grow rapidly. This review gives an up-to-date overview of transition-metal-catalyzed allenamides cyclization, which are sorted by metal catalysts in eight categories of Pd, Ru, Rh, Au, Co, Ag, Pt and Ni. For most of these transformations, the plausible mechanisms are demonstrated in details. Clarification of these issues is the key point for understanding the transition-metal-catalyzed allenamides cyclization and developing new high performance methodologies for chemists.

This report describes the systematic incorporation of gold nanoparticles (AuNPs) onto mesoporous TiO2 (MPT) particles without strong attractive forces to efficiently serve as reactive and recyclable catalysts in the homocoupling of arylboronic acid in green reaction conditions. Unlike using nonporous TiO2 particles and conventional SiO2 particles as supporting materials, the employment of MPT particles significantly improves the loading efficiency of AuNPs. The incorporated AuNPs are less than 10 nm in diameter, regardless of the amount of applied gold ions, and their surfaces, free from any modifiers, act as highly reactive catalytic sites to notably improve the yields in the homocoupling reaction. The overall physical properties of the AuNPs integrated onto the MPT particles are thoroughly examined as functions of the gold content, and their catalytic functions, including the rate of reaction, activation energy, and recyclability, are also evaluated. While the rate of reaction slightly increases with the improved loading efficiency of AuNPs, the apparent activation energies do not clearly show any correlation with the size or distribution of the AuNPs under our reaction conditions. Understanding the formation of these types of composite particles and their catalytic functions could lead to the development of highly practical, quasi-homogeneous catalysts in environmentally friendly reaction conditions.