Публикации

A novel approach was developed to prepare Pd nanoparticles with organic ligands in high yields. The structural unit of the Pd species was constructed involving Pd−S bonds. The synthesized Pd particles were highly selective catalysts of S−H bond addition to alkynes under microwave heating. An X-ray diffraction study of one of the products of the addition reaction revealed unusual supramolecular organization of cation/anion layers.

A theoretical ONIOM study has been carried out to understand the influence of phosphane ligands on the structure of Pd complexes and their reactivity in C–C bond formation. The calculations were performed for Me–Me reductive elimination with the ligands L = PPh₃, PCy₃, PMe₃, PH₃, and vinyl–vinyl, Ph–Ph, ethynyl–ethynyl, vinyl–Me, vinyl–Ph and vinyl–ethynyl couplings with L = PPh₃ for [PdR₂L_n] complexes (n = 1, 2). The calculations revealed critical changes in the reactivity of palladium complexes depending on the mechanism and ligand type. In the case of the standard four-coordinate pathway (n = 2) the relative reactivity in carbon–carbon bond formation follows the order: L = PPh₃ > PH₃ > PCy₃ > PMe₃. However, for reductive elimination involving T-shaped complexes by the ligand predissociation pathway (n = 1), the relative reactivity changes in the order: L = PCy₃ > PPh₃ > PH₃ > PMe₃. The theoretical study suggested that the steric effect of phosphane ligands has the largest impact on the structure of the initial palladium complexes, while the electronic effect is most influential on the transition states of C–C coupling in these complexes.

In the presence of transition metal catalysts, hydrothiolation and hydroselenation reactions, as well as bisthiolation and bisselenation reactions, have been successfully carried out with high selectivities and yields. New transition metal-catalyzed synthetic methods have been developed for the preparation of vinyl sulfides and vinyl selenides of various types. Mechanistic study has revealed that a homogeneous catalytic system based on phosphine complexes of palladium is the best choice for carrying out stereoselective additions of disulfides and diselenides to alkynes. A heterogeneous Ni-catalyzed reaction with a unique self-organized nanostructured catalyst was superior for carrying out regioselective additions of thiols and selenols to alkynes

The synthetic application and mechanistic aspects of transition-metal (Ni, Pd, Pt) catalyzed addition of E-E and E-H (E=S, Se) bonds to alkynes were investigated in detail. This study revealed major factors controlling the selectivity of such addition reactions. A new Ni-based catalytic system with a self-organized nanostructured catalyst has been designed to perform chemical transformations in high yield, under mild conditions.

A simple heterogeneous Ni-based catalytic methodology was developed for regioselective hydroselenation of terminal alkynes and stereoselective hydroselenation of internal alkynes. The developed heterogeneous catalytic system is superior to the known homogeneous and heterogeneous catalysts for the Se−H bond addition to the triple bond of alkynes. The catalytic transformation was performed under mild conditions, thus avoiding byproducts formation. The mechanistic study revealed that the yield of the addition products depends on the catalyst particle size and rapidly increases upon decreasing particle size into the nanosized region. The present study describes a simple and efficient procedure for the formation of a self-organized nanosized catalytic system starting from an easily available precursor, Ni(acac)₂, without any special treatment.