Darstellung, Kristall‐ und Molekülstruktur eines zwölfgliedrigen N,N′‐Di‐Lithium‐cyclosiloxazans [Me2SiOSiMe2N(Li)SiMe2O]2

Abstract

AbstractThe twelve membered and eighteen membered cyclosiloxazanes [Me2SiOSiMe2N(H)SiMe2O]2 (3) and [Me2SiOSiMe2N(H)SiMe2O]3 (4) have been obtained as colourless liquids from the reaction of 1,5‐Dichlorohexamethyltrisiloxane with ammonia at–50 °C without any solvent. For compound 3 and 4, the yield is 30 % and 43 %, respectively. The treatment of 3 with two equivalents of n‐butyllithium in n‐hexane leads in almost quantitative yield (93 %) to the dilithiumsilylamide [Me2SiOSiMe2N(Li)SiMe2O]2 (5). Compound 5 can be isolated at room temperature and recrystallized from benzene without any decomposition or contraction of the ring size. An X‐ray structure determination on [Me2SiOSiMe2N(Li)SiMe2O]2 (5) reveals a waved crown‐like twelve membered Si6N2O4‐cycle. Each of the two lithium ions is coordinated by two nitrogen and two oxygen atoms leading to a square pyramid, in which the metal occupies the apex. The two square‐pyramidal coordination figures are located above and below the waved crown‐like Si6N2O4‐ring sharing a common edge by the atoms N(1) and N(2). All synthesised compounds have been characterised by spectroscopic methods. Because of the lower solubility of the dilithiumsilylamide 5, only a 1H‐NMR could be applied for further characterisation in solution.