Activation of C--H bonds in C1-C3 alkanes by titanium(iv) and zirconium(iv) cationic complexes: a DFT study

A DFT study of a model reaction [(⁵-C₅H₅)₂MCH₃]⁺ + RH [(⁵-C₅H₅)₂MR]⁺ + CH₄ (M = Ti^IV, Zr^IV; R = Me, Et, Pr, Prⁱ) was carried out with the PBE density functional. Exchange of -bonded ligand proceeds through the formation of agostic complexes [Cp₂M(RH)CH₃]⁺ followed by their isomerization into complexes [Cp₂M(CH₄)R]⁺ via an inner-sphere migration of a hydrogen atom. The calculated rate constants for such migrations involving the primary and secondary C--H bonds of propane molecule differ by 930 times for Ti^IV complexes and by 47 times for Zr^IV complexes, which is due to the effect of steric factors.     

Magnetic isotope effect in the photolysis of organotin compounds

Photolysis of organotin molecules RSnMe3 is shown to be a spin selective radical reaction accompanied by fractionation of magnetic, (117,119)Sn, and nonmagnetic, (118,120)Sn, isotopes between starting reagents and products. A primary photolysis process is a homolytic cleavage of the C-Sn bond and generation of a triplet radical pair as a spin-selective nanoreactor. Nuclear spin dependent triplet-singlet conversion of the pair results in the tin isotope fractionation. Experimentally detected isotope distribution unambiguously demonstrates that the classical, mass-dependent isotope effect is negligible in comparison with magnetic, spin-dependent isotope effect.     

Synthesis,structure, and rearrangements of new tricarbonylchromium complexes of substituted heptalenes

Reactions of 1,2,5,6,8,10-hexamethylheptalene (1) and its bond isomer, 1,4,5,6,8,10-hexamethylheptalene (2), with tricarbonylchromium complexes L{in3}Cr(CO){in3} (L=NH{in3} and Py) have been investigated. Thermodynamically less stable complex 1 exhibits higher reactivity with respect to Py{in3}Cr(CO){in3}/BF{in3} · Et{in2}O under the conditions of Öfele's reaction than complex2. At 10–30 °C, the Cr(CO){in3} group is coordinated to the asymmetrically substituted ring, which is accomplished by the shift of double bonds in the ligand, to afford tricarbonyl-[1,4,5,6,8,10-hexamethyl-{su6}-(10a, 1–5)heptalene]-chromium (6) as the only mononuclear complex. Under more drastic conditions (Raush's reaction, 80 °C),1 2 interconversion proceeds faster than the reaction of individual bond isomers with coordinatively unsaturated hot particles (solv){inn}Cr(CO){in3}. In this case, all of the four possible isomeric mononuclear complexes (6–9) and two binuclear complexes (10 and 11) are formed. The structures of complexes 6–11 have been studied by NMR and mass spectrometry, the structure of6 has been established by X-ray diffraction analysis. Heating a solution of6 in octane at 115 °C results in the isomerization of6 into complex7 through the intracycle 1,2-shift of the Cr(CO){in3} group and also in its conversion into complex8, which is the first example of interring {su6}{su6}-haptotropic rearrangement in nonplanar seven-membered -systems.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2220–2226, December, 1994.We would like to thank N. S. Kulikov for measuring mass spectra and L. A. Aslanov for helpful discussion of the results of X-ray diffraction analysis.The Research Group from the Moscow State University gratefully acknowledges the support of this work by the International Science Foundation (Grant No. MQ 5000) and the Russian Foundation for Basic Research (Project No. 94-03-08325).     

Synthesis of dibenzocymantrene derivatives (η5-9-RC13H8)Mn(CO)3 (R = Ph and But). Crystal structure of (η5-9-PhC13H8)Mn(CO)3

⁵-Fluorenyl complexes of manganese (⁵-9-RC₁₃H₈)Mn(CO)₃, where R = Ph (1) and But (2), have been prepared and characterized for the first time. The structure of complex1 has been established by X-ray structural analysis.Yu T. Yanovsky deceased in 1995.Translated fromIZvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 199–203, January, 1996.     

Metallocenes in oxidative-reductive transmetallzation with bis[tris(pentafluorophenyl)germyl]mercury

Conclusions The oxidative-reduction transmetallation reaction between bis[tris(pentafluorophenyl)-germyl]mercury and the dicyclopentadienyl derivatives of various metals can yield ionic multinuclear ate-type complexes, covalent compounds with a metal-metal bond, or ionic complexes that form by transfer of a cyclopentadienyl anion from the central metallocene atom to mercury.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2548–2555, November, 1986.The authors thank N. Walker and D. Stuart for providing the DIFABS program.     

Electrochemical study of allylbenzene and allylcyclohexadienyl complexes of ruthenium

Cyclic voltammetry has been used to study the electrochemical behavior of RuCl(³-C₃H₅)(⁶-C₆H₆) (1), [Ru(PPh₃) · (³-C₃H₅)(⁶-C₆H₆)]BF₄ (2), and Ru(PPh₃)· (³-C₃H₅)(⁵-C₆H₇) (3); the latter was prepared by reacting2 with LiAlH₄. The reduction of1 and2 gives the 19-electron complexes1 ^–. and 2^·, whereas oxidation of3 gives the 17-electron complex3 ^+·. The reactivities of1 ^–·,2 ^·, and3 ^+· are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1126–1128, June, 1993.     

New Stable Germylenes,Stannylenes, and Related Compounds II. Bis(butylthio)tin(II) and ate-Complexes [(Me3Si)3CE(μ-SBu)2Li(THF)2] (E = Ge,Sn). Synthesis and Structure

By reaction of Me₃SiSBu with anhydrous tin(II) chloride bis(butylthio)tin was obtained that exemplified a coordination polymer [Sn(SBu)₂] _n , whose elementary unit contained according to X-ray diffraction study three independent four-membered rings Sn₂S₂ of unusual geometry. It was demonstrated that polymeric thiolates [E(SBu)₂] _n (E = Ge, Sn) readily reacted with TsiLi (Tsi = C(SiMe₃)₃) in a mixed solvent ether THF affording in a good yield ate-complexes [(Me₃Si)₃CE(-SBu)₂Li(THF)₂]. Both complexes contain a four-membered ring in a butterfly conformation where the lithium atom is symmetrically bonded to both sulfur atoms, and the coordination polyhedra of Ge and Sn atoms may be regarded as distorted tetrahedra AB₃X, where one of coordination places is occupied by unshared electron pair. The structure of the ate-complexes observed in a crystal is conserved also in solution of nonpolar solvents.