The thermodynamic parameters of formation of ions in the interaction of alkylaluminum with electron donors

The thermodynamic parameters of formation of ions in the system AlMe₃ + electron donor (D) in the presence and absence of water microimpurities were determined. The structure of these ions was studied and their concentration in nonpolar media was estimated for the example of D = pyridine. The conclusion was drawn from the results of calculations that the participation of water resulted in a substantial increase in the concentration of ions.     

Redox properties of rhodium diene-cyclopentadienyl complexes

The electrochemical behavior of rhodium sandwich complexes containing η⁴-pentamethylcyclopentadiene or tetramethylfulvene fragments has been studied by cyclic voltammetry. The complexes undergo one-electron oxidation to give unstable 17-electron radical cations which are converted into rhodocenium salts as a result of elimination or uptake of hydrogen or C-C bond cleavage. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1802–1805, October, 1993.     

NMR spectroscopy of metal cyclopentadienyls VIII. Prototropism and dimerisations of silicon cyclopentadienyls

Studies have been made of the slow dynamic processes which occur with the silicon cyclopentadienyls C₅H₅Si(CH₃)Cl₂, such as prototropic rearrangement and dimerisation. The product formed through spontaneous dimerisation has been found to consist almost entirely of the dimer of the main vinylic isomer of C₅H₅Si(CH₃)Cl₂. The dimeric structure has been proved by means of PMR spectra (100 MHz). From kinetic studies values of the rate constants at temperatures of 20,44,55, and 65° have been obtained and an approximate plot of log kvs. (1/T)x10³, has enabled the thermodynamic characteristics of the prototropic rearrangement and of the dimerisation to be calculated. The ability of cyclopentadienyl systems to undergo hydrogen migration is discussed and the reactivity of fluxional systems is shown to be governed by the rate of metallotropic rearrangement.     

Electrochemical reduction of phenylethynyl halides and related compounds

Reduction of phenylethynyl halides PhCCHal (Hal = I (1), Br (2), Cl (3)), diiodoacetylene (4), (phenylethynyl)triphenylphosphonium bromide (5), and related compounds in THF was studied by means of cyclic voltammetry using a glassy-carbon electrode. Compounds1–5 are reduced with cleavage of the C-Hal bond, and the reduction potentials increase in the order3 <2 <1 <4 <5.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2055–2057, October, 1995.     

Transformed steroids

Russian Chemical Bulletin -     

Synthesis of the first kinetically stable dibenzosilafulvene

The first stable dibenzosilafulvene, 9-{[8-(dimethylaminomethyl)-1-naphthyl]phenylsil-1-ylium}fluoren-9-ide (7a), was obtained in one step from 9-fluorenyllithium and chloro[8-(dimethylaminomethyl)-1-naphthyl]phenylsilane as a stable solvate with THF. The structure of the zwitterionic compound7a was established by¹H,¹³C, and²⁹Si NMR in solution and in the solid state. The reactions of compound7a with crotonaldehyde, ethanol, and triethylethylidenephosphorane are described. The data on the synthesis of alkoxy- and alkylthiochloro-9-fluorenylsilanes and their phosphonium salts are given. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 486–491, March, 1998.     

Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(⁴-C₅Me₅H)Pt(⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.