Publications

⁷⁷Se NMR offers superior sensing of chirality within the structure of the diastereomers (Δδ up to 6.1 ppm), compared to ¹³C (Δδ < 1 ppm) and ¹H (Δδ < 0.2 ppm). The developed procedure is equally well suitable for determination of the enantiomeric purity of chiral alcohols and amines as pure samples as well as reaction mixtures and crude products.

The coordination of phosphine ligands to nickel acetylacetonate was studied in toluene solution, and the first X-ray structure of the unstable complex trans-[Ni(acac)₂(PMe₂Ph)₂] has been reported. A convenient procedure was developed to generate Ni(0) species in situ in solution from a Ni(acac)₂ precursor, and their application in catalysis was demonstrated. A study of the reaction mechanism has suggested that water may play an important role in the formation of zerovalent nickel species. The nature of the Ni(0) species was confirmed by trapping with Ph₂S₂, and the structure of the resulting complexes trans-[Ni(SPh)₂L₂] was established by X-ray analysis for L = PMe₂Ph, PMePh₂, PBu₃.

The present study reports the evidence for the multiple carbon–carbon bond insertion into the metal–heteroatom bond via a five-coordinate metal complex. Detailed analysis of the model catalytic reaction of the carbon–sulfur (CS) bond formation unveiled the mechanism of metal-mediated alkyne insertion: a new pathway of CS bond formation without preliminary ligand dissociation was revealed based on experimental and theoretical investigations. According to this pathway alkyne insertion into the metal–sulfur bond led to the formation of intermediate metal complex capable of direct CS reductive elimination. In contrast, an intermediate metal complex formed through alkyne insertion through the traditional pathway involving preliminary ligand dissociation suffered from "improper" geometry configuration, which may block the whole catalytic cycle. A new catalytic system was developed to solve the problem of stereoselective SS bond addition to internal alkynes and a cost-efficient Ni-catalyzed synthetic procedure is reported to furnish formation of target vinyl sulfides with high yields (up to 99 %) and excellent Z/E selectivity (>99:1).

Utilization of NMR spectroscopy and mass spectrometry for joint mechanistic and structural studies is a well-known practice. Several opportunities have appeared in recent years because of new hardware development and design of novel experimental procedures. Recent progress in this area and leading examples of new development, as well as already distinguished techniques, are discussed.

Main factors have been analyzed necessary for creation of an efficient catalytic system for alkynes hydrophosphorylation based on nickel complexes, and a valid model system was suggested for the comparison with palladium complexes. It has been discovered for the first time that the insertion of an alkyne into the metal-hydrogen bond occurs with a considerably lower activation barrier than into the metal-phosphorus bond, whereas the variation in the reaction energy corresponds in both cases to an exothermic reaction. Under the optimized conditions the transformation catalyzed by nickel complexes does not require acid addition and may proceed even in the absence of a phosphine ligand.

The nickel catalyst prepared in situ from nickel bis(acetylacetonate) [Ni(acac)₂] precursor and bis(diphenylphosphino)ethane (DPPE) ligand has shown excellent performance in the hydrophosphorylation of alkynes. Markovnikov-type regioselective addition to terminal alkynes and stereoselective addition to internal alkynes were carried out with high selectivity without an acidic co-catalyst (in contrast to the palladium/acid catalytic system). Various H-phosphonates and alkynes reacted smoothly in the developed catalytic system with up to 99% yield. The mechanisms of catalyst activation and CP bond formation were revealed by experimental (NMR, ESI-MS, X-ray) and theoretical (density functional calculations) studies. Two different pathways of the alkyne insertion in the coordination sphere of the metal are reported for the first time.