Nature of active centers and stereospecificity of tetravalent titanium benzyl derivatives in polymerization of butadiene

Stereospecificity of tetrabenzyltitanium and its halogeno-derivatives in the polymerization of butadiene has been investigated. The content of 1,2-units decreases while the content of 1,4-cis-units increases in the resulting polybutadiene for the series (C₆H₅CH₂)₄Ti, (C₆H₅CH₂)₃TiCl, (C₆H₅CH₂)₃TiBr, (C₆H₅CH₂)₃Til. Tribenzyltitanium iodide exhibits high stereospecificity for the formation of 1,4-cis-units and their content reaches 94–97%. By determining the number of benzyl groups linked with titanium at different degrees of conversion, it has been shown that the active centre formed from tetrabenzyltitanium contains three benzyl groups and one polymer chain. Two benzyl groups, one iodine atom and one polymer chain are attached to a titanium atom in the active centre for the case of tribenzyltitanium iodide. Electron donors sharply change the stereospecificity of tribenzyltitanium iodide: the content of 1,2-units in the polymer rises to 68%.     

Cyclization of 3-methoxy-Δ1,3,5,(10)-8,14-secoestratriene-14,17-dione

Conclusions Depending on the conditions, 3-methoxy-^1,3,5(10)-8,14-secoestratriene-14,17-dione (III) under the influence of acid agents is cyclized to estradiol, equilenol, 18-norequilenane, and cyclopentanophenanthrene derivatives. As a result, the spatial factor determines the course of the reaction even if the ⁹⁽¹¹⁾-double bond, which activates the H atoms at C₇, is absent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1628–1632, July, 1973.     

Formation of organometallic compounds of carbene and carbine types by the interaction of RLi with neodymium and yttrium chlorides in various media

It has been established that in the interaction of NdCl₃ and YCl₃ with RLi, where R  CH₂C₆H₅, CH₂C(CH₃)₂C₆H₅, CH₂Si(CH₃)₃, unusual organometallic compounds are formed. They are stable in hydrocarbon solutions. The benzyl and neophyl derivatives are carbene type complexes containing one R group at a trivalent metal atom. In all cases the reaction is accompanied by the evolution of RH as the main product and some stilbene and tolan when R  CH₂C₆H₅. The mechanism of this reaction is discussed.