Structures of N,N’-bis(tert-Butyl)-N-Formylethylenediamine Halides obtained by Salt Metathesis from Metal Precursors

Abstract

N,N’-bis(tert-butyl)-N-formylethylenediamine iodide 1 and N,N’-bis(tert-butyl)-N-formylethylenediamine chloride 2 were obtained in an attempt to synthesize N-heterocyclic carbene iron(II) complexes via the free carbene route. In the process of generating the free carbenes for subsequent coordination to the iron(II) centres, 1 and 2 were isolated as products of imidazolinium salt hydrolysis. The iron(II) precursor salts were non-innocent in these reactions as the amine salts bear counter-anions of metathesis from the respective precursors used in each case, CpFe(CO)2I for 1 and FeCl2 for 2. Compounds 1 and 2 were characterized by single crystal diffraction analysis, 1H and 13C NMR, IR spectroscopy and HRMS. The single crystal X-ray diffraction results reveal that compound 1 crystallizes in the orthorhombic P2(1)2(1)2(1) space group while compound 2 crystallizes in the triclinic P-1 space group. In compound 1, the molecules are packed with the cations related through a centre of inversion about a pair of iodide anions while in 2 the smaller chloride counter anions are sandwiched between the cations. The interionic distance is shorter in compound 2 at 2.26 A as compared to 2.59 A in compound 1. An attempted synthesis of N-heterocyclic carbene iron(II) complexes via the free carbene route resulted in the isolation of N,N’-bis(tert-butyl)-N-formylethylenediamine iodide and N,N’-bis(tert-butyl)-N-formylethylenediamine chloride as hydrolysis products incorporating anions from the corresponding iron(II) metal precursors.