Synthesis and Structure of Aminopyridinato-Stabilized Yttrium and Lanthanum Amides and Their Reactivity towards Alkylaluminium Compounds

Graphical Abstract

Aminopyridinato-stabilized (silylamido)lanthanoid complexes were synthesized and investigated with regard to coordinative chain transfer polymerization. Such complexes are not stable in the presence ofalkylaluminium compounds and decompose by aminopyridinato ligand transfer from the rare earth metal to the aluminium atom.

Abstract

A series of aminopyridinato-stabilized (amido)lanthanide complexes has been synthesized and characterized. The bulky aminopyridines (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine (1a) and [6-(2,4,6-triisopropylphenyl)pyridin-2-yl](2,4,6-trimethylphenyl)amine (1b) were introduced by amine elimination reaction with [Ln{N(SiHMe₂)₂}₃(thf)₂] (Ln = Y, La, thf = tetrahydrofuran, Me = methyl) to obtain the corresponding mono(aminopyridinato) complexes. Single-crystal X-ray analyses were carried out for the yttrium derivatives. The complexes are not able to undergo coordinative chain transfer polymerization with ethylene in the presence of alkylaluminium compounds as the corresponding dialkyl complexes do. Investigations of the reactions of the lanthanide aminopyridinato complexes with triethylaluminium or diisobutylaluminium hydride reveal a fast transfer of the aminopyridinato ligand to the aluminium atom. The products of this transfer reaction are aminopyridinato-stabilized dialkylaluminium compounds. One example of these aluminium complexes was characterized by X-ray crystal structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)