Syntheses and crystal structures of novel functionalized lithium silylamides R(4-n)Si(N(Li)CH2CH2NR' 2)n (R = Me, Ph, R' = Me, iPr; N = 2, 3)

Abstract

The difunctional aminosilanes Ph2Si(NHCH2CH 2NMe2)2 (1), Me2Si(NHCH 2CH2NiPr2)2 (2) and Ph 2Si(NHCH2CH2NiPr2)2 (3) were prepared by aminolysis of the chlorosilanes R2SiCl2 (R = Ph, Me) and the corresponding ethylenediamine derivatives H 2NCH2CH2NR'2 (R' = Me, iPr). The trifunctional aminosilane MeSi(NHCH2CH2NiPr 2)3 (4) was synthesized from MeSiCl3 and H 2NCH2CH2NiPr2 in the presence of triethylamine as auxiliary base. Compounds 1-4 were obtained as pale yellow viscous oils that have been characterized by 1H, 13C and 29Si NMR spectroscopy. Treatment of the aminosilanes 1-3 with two equivalents and 4 with three equivalents of nBuLi in hexane led to the corresponding lithium salts, which were recrystallized from n-hexane at -25°C. The crystal structure analysis of Ph2Si(N(Li)CH 2CH2NMe2)2 (5) and Me 2Si(N(Li)CH2CH2NiPr2)2 (6) revealed dimeric molecules which contain a central Li4N 4 heterocubane core. Additionally, the lithium atoms are coordinated intramolecularly by NR2 donor groups. For Ph2Si(N(Li) CH2CH2NiPr2)2 (7) dimers with Si2N4Li4 adamantane core were observed. MeSi(N(Li)CH2CH2NiPr2)3 (8) displays dimers with a rhombododecahedral Si2N6Li6 core. Like in compounds 5-7 the cluster structure is supported by intramolecular coordination of the NiPr2 donor group. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.