Scandium aminopyridinates: Synthesis, structure and isoprene polymerization

Abstract

Alkane elimination reactions of [Sc(CH2SiMe3) 3(thf)2] or [Sc(CH2Ph)3(thf) 3] with aminopyridines (1a = (2,6-diisopropylphenyl.)-[6-(2,4,6- triisopropylphenyl)pyridin-2-yl]amine, 1b = [6-(2,4,6-triisopropylphenyl) pyridin-2-yl]-(2,4,6-trimethylphenyl)amine, 1c = (2,6-diisopropylphenyl)-[6-(2, 6-dimethylphenyl)pyridin-2-yl]amine) led to selective formation of dialkyl complexes of scandium, stabilized by one amlnopyridinato (Ap) ligand, The reaction of these compounds with anilinium borate leads to the elimination of one of the two alkyl functions and affords organoscandium cations, The amine elimination reaction of [Sc[N(SiHMe2)2]3(thf)] with the aminopyridine 1a yields the corresponding mono(aminopyridinato) complex, Single-crystal X-ray analyses were carried out for [Ap*Sc(CH 2Ph)2(IhI)] (3a), [Ap*Sc(CH2Ph)(thf) 3][B(C6H5)4] (4a) and [Ap*Sc{N(SiHMe 2)2}2] (6a) (Ap*-H = 1a), The aminopyridinato-stabilized dialkylscandium complexes [ApScR2(thf)] (R = CH2SiMe3, CH2Ph) are initiators for controlled 3,4-selective isoprene polymerization after activation with perfluorinated tetraphenyl borates. Variation of the polymerization temperature as well as the addition of different alkylaluminium compounds influence the microstructure of the obtained polymer, Bis(dimethylsilyl)amides of scandium polymerize isoprene in the presence of aniliniuni borate and alkylaluminium compounds with high cis-1,4-selectivity. © Wiley-VCH Verlag GmbH & Co. KGaA,.