Grigory G. Aleksandrov

Mechanistic study of palladium catalyzed S–S and Se–Se bonds addition to alkynes

The mechanistic study of palladium catalyzed S � /S and Se � /Se bonds addition to alkynes revealed the involvement of dinuclear transition metal complexes in the catalytic cycle. Coordination of alkyne to dinuclear transition metal complex was found to be the rate determining step of the reaction. An unusual phosphine ligand effect increasing the yield of addition reaction was found in the studied system. A new synthetic procedure was developed to perform the catalytic reaction using easily available Pd(II) complex. The scope of the reaction and the reactivity of S � /S and Se � /Se bonds toward alkynes were investigated. The X-ray structure of the product of S � /S bond addition reaction showed favorable geometry for the possible application as a chelate ligand. # 2003 Elsevier B.V. All rights reserved.

Palladium and platinum catalyzed hydroselenation of alkynes: SeH vs SeSe addition to CC bond

Abstract A mechanistic study of the hydroselenation of alkynes catalyzed by Pd(PPh3)4 and Pt(PPh3)4 has shown that the palladium complex gives products of both SeH and SeSe bond addition to the triple bond of alkynes, while the platinum complex selectively catalyzes SeH bond addition. The key intermediate of PhSeH addition to the metal center, namely Pt(H)(SePh)(PPh3)2, was detected by 1H-NMR spectroscopy. The analogous palladium complex rapidly decomposes with evolution of molecular hydrogen. A convenient method was developed for the preparation of Markovnikov hydroselenation products H2CC(SePh)R, and the scope of this reaction was investigated. The first X-ray structure of the Markovnikov product H2CC(SePh)CH2N+HMe2·HOOCCOO− is reported.

Solvent-Induced Change of Electronic Spectra and Magnetic Susceptibility of CoII Coordination Polymer with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

One-dimensional coordination polymer [Co(Piv)2(4-ptz)(C2H5OH)2]n (compound 1, Piv(-) = pivalate, 4-ptz = 2,4,6-tris(4-pyridyl)-1,3,5-triazine) was synthesized by interaction of Co(II) pivalate with 4-ptz. Desolvation of 1 led to formation of [Co(Piv)2(4-ptz)]n (compound 2), which adsorbed N2 and H2 at 78 K as a typical microporous sorbent. In contrast, absorption of methanol and ethanol by 2 at 295 K led to structural transformation probably connected with coordination of these alcohols to Co(II). Formation of 2 from 1 was accompanied by change of color of sample from orange to brown and more than 2-fold decrease of molar magnetic susceptibility (χM) in the temperature range from 2 to 300 K. Resolvation of 2 by ethanol or water resulted in restoration of spectral characteristics and χM values almost to the level of that of 1. χMT versus T curves for 1 and samples, obtained by resolvation of 2 by H2O or C2H5OH, were fitted using a model for Co(II) complex with zero-field splitting of this ion.

A new route to 6,6′′-dicyano-2,2′:6′,2′′-terpyridines and their complexes with Ni(II)

Abstract A new methodology for the synthesis of functionalised 2,2′:6′,2′′-terpyridine systems is suggested: sequential synthesis of the heterocyclic assemblies based on the 1,2,4-triazine ring, direct introduction of the cyano group in the 1,2,4-triazine ring and the transformation of the latter to a pyridine ring via an aza-Diels–Alder reaction.

Self-assembly and decay of Mn(II) pivalate–phosphonate complexes

A series of new manganese(II) pivalate–phosphonate complexes with various nuclearities (Mn4, Mn10, and Mn20) under aerobic conditions was synthesized by self-assembly of simple reagents. The constitution of polynuclear architectures is affected by the reaction temperature. The structures of the complexes were determined by single crystal X-ray analysis. Magnetic behavior of the compounds points to dominant antiferromagnetic exchange interactions. Antiferromagnetic coupling with JMn–Mn = −0.097(1) cm−1, gMn = 1.993(1) for an equilateral tetrahedron model simulates the magnetic behavior of the tetranuclear complex Mn4 with a cube-like core.

Reactions of heterocumulenes with organometallic reagents: XVI. Quantum-chemical study on the mechanisms of formation of homo- and heteroannular azacycloheptadienes in reactions of 2-aza-1,3,5-trienes with potassium tert-butoxide

Mechanisms of intramolecular transformations of carbanions generated from 2-aza-1,3,5-trienes by the action of potassium tert-butoxide, which could lead to homo- or heteroannular azacycloheptadienes, were studied by quantum-chemical methods in terms of the density functional theory. The corresponding gradient channels were localized for model 1-methylsulfanyl-1-(cyclopentylideneamino)- and 1-methylsulfanyl-1-(cyclohexylideneamino)buta-1,3-dien-2-ols. Analysis of the kinetic and thermodynamic parameters showed that carbanion generated from N-cyclopentylidenebuta-1,3-dien-1-amine undergoes rearrangement mainly into homoannular azacycloheptadiene and that analogous N-cyclohexylidene derivative gives rise to heteroannular isomer. The results of calculations were consistent with the experimental data.