Calcium-bis[N,N'-bis(trimethylsilyl)benzamidinat]-THF (1/2) - Synthese, spektroskopische Charakterisierung und Struktur/Calcium-bis[N,N'-bis(trimethylsilyl)benzamidinate]-THF (1/2) - Syntheses, Spectroscopic Characterization and Structure

Abstract

The reaction of calcium-bis[bis(trimethylsilyl)amide]-THF (1/2) with benzonitrile in THF nearly quantitatively yields the title compound calcium-bis[N,N'-bis(trimethylsilyl)- benzamidinate]-THF (1/2). Under similar conditions pivalonitrile substitutes an ether ligand of calcium-bis[bis(trimethylsilyl)amide]-DME (1/2) without the formation of the corresponding amidinate derivative. The calcium-di(benzamidinate) [H5C6-C(NSiMe3)2]2Ca · 2THF crystallizes in the space group Pbcn with {a = 188.8(6); b = 1286.0(3); c = 1802.5(5) pm; Z = 4}. The calcium atom is hexa-coordinate with a distorted octahedral trans-configuration and with Ca - O and Ca - N bond distances of 238 and 243 pm, respectively. The bond lengths within the NCN moiety with values of 132 pm are characteristic of a diazaallylic system. The short N - Si bond lengths of about 170.5 pm as well as the high field shift of the 29Si{1H} NMR signal are evidence for an effective backdonation of the anionic charge from the nitrogen to the silicon atoms.