Yttrium complexes containing heteroscorpionate ligands [(3,5-But 2C3HN2)2CHC(Ph)2O]– and [o-Me2NC6H4CH2C(NCy)2

Abstract

A reaction of benzophenone with bis(3,5-di-tert-butylpyrazolyl)methyllithium (3,5-But2C3HN2)2CHLi (obtained in situ by metallation of (3,5-But2C3HN2)2CH2 with n-butyllithium in THF at–70 °C) led to the synthesis of alkoxide lithium complex [(3,5-But2-C3HN2)2CHCPh2O]Li(THF) (1) containing a new monoanionic heteroscorpionate ligand [(3,5-But2C3HN2)2CHCPh2O]–. Hydrolysis of complex 1 gave 2,2-bis(3,5-di-tert-butylpyrazolyl)-1,1-diphenylethanol (2) in 90% yield. The structure of alcohol 2 was established by X-ray crystallography. A reaction of anhydrous YCl3 with two molar equivalents of lithium alkoxide 1 in THF furnished yttrium monochloride complex [(3,5-But2C3HN2)2CHCPh2(μ-O)]2-YCl(THF)[(μ-Cl)Li]2 (3). According to X-ray diffraction data, chloride 3 is a monomeric ate-complex with one terminal and two bridging chloride ligands. The nitrogen atoms of the pyrazole rings are not involved in the coordination of the ligand with the yttrium ion. The bisalkyl complex [(3,5-But2C3HN2)2CHCPh2O]Y(CH2SiMe3)2(THF)2 (4) obtained by the reaction of alcohol 2 with an equimolar amount of Y(CH2SiMe3)3(THF)2 turned out to be unstable and completely decomposed in solution in C6D6 at 25 °C within two hours. An exchange reaction of equimolar amounts of YCl3 and {[o-Me2NC6H4CH2C(NCy)2]Li(THF)2}2 (5) (Cy is the cyclohexyl) in THF led to the formation of a neutral monochloride complex [o-Me2NC6H4CH2C(NCy)2]2YCl(THF)2 (6). A reaction of complex 6 with an equimolar amount of o-Me2NC6H4CH2Li in toluene led to the synthesis of a new yttrium aminobenzyl complex [o-Me2NC6H4CH2C(NCy)2]2Y[CH2C6H4-o-NMe2] (7). X-ray diffraction studies showed that in complexes 6 and 7 the donor NMe2 groups of amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 4 and 7 exhibited catalytic activity in polymerization of isoprene.