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

AbstractThe difunctional aminosilanes Ph2Si(NHCH2CH2NMe2)2 (1), Me2Si(NHCH2CH2NiPr2)2 (2) and Ph2Si(NHCH2CH2NiPr2)2 (3) were prepared by aminolysis of the chlorosilanes R2SiCl2 (R = Ph, Me) and the corresponding ethylenediamine derivatives H2NCH2CH2NR'2 (R' = Me, iPr). The trifunctional aminosilane MeSi(NHCH2CH2NiPr2)3 (4) was synthesized from MeSiCl3 and H2NCH2CH2NiPr2 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)CH2CH2NMe2)2 (5) and Me2Si(N(Li)CH2CH2NiPr2)2 (6) revealed dimeric molecules which contain a central Li4N4 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.