A “Solvent-Free” Crystal Structure of [Fe{N(SiMe3)2}3] – Synthesis, Structure and Properties

Abstract

For the synthesis of the ferric bis(trimethylsilyl)amido complex [Fe{N(SiMe3)2}3] literature gives differing synthetic protocols based on crystallization from solution. In this report we present a ‘solvent-free’ structural phase of [Fe{N(SiMe3)2}3] which was isolated by sublimation of the product obtained from the reaction of 2 eq FeCl3 with 3 eq LiN(SiMe3)2 in benzene. It could be characterized by single crystal as well as powder XRD and elemental analysis. However, 57Fe Mößbauer spectroscopy suggests a contamination of the main product with an Fe(II) species. Also, a part of the solid reaction byproducts from the reactions in solution were identified by powder XRD and 7Li MAS NMR which indicate distinct redox side reactions between oxidizing FeCl3 and reducing LiN(SiMe3)2, a fact which rationalizes the lower than expected yields and the observation of an Fe(II) impurity compound. AC magnetic measurements of [Fe{N(SiMe3)2}3] have been performed in an extended frequency range up to 104 s−1, allowing for a more precise evaluation of the magnetic relaxation parameters when compared to previously published measurements.