Coordination chemistry of a multidentate pyrrolylaldiminate ligand. X-ray crystal structure of double-helical bis-μ-[N,N′-ethylenedi(5-tert-butyl-pyrrol-2-ylaldiminate)]-dimagnesium

The coordination chemistry of N,N′-ethylenedi(5-tert-butyl-pyrrol-2-ylaldiminate) dianion (L2−) is described. The ligand precursor H2L was prepared in high yield from the condensation reaction of ethylenediamine with 5-tert-butylpyrrole-2-carbaldehyde. Treatment of H2L with Zr(CH2Ph)4 generated mononuclear ZrL(CH2Ph)2 (1), whereas the reaction of H2L with MgnBu2 or ZnEt2 produced dinuclear M2L2 (M=Mg, 2; Zn, 3). In addition to spectroscopic characterizations of all new compounds, X-ray crystal structure of 2 was obtained. The X-ray study revealed a double-stranded helical structure in which the magnesium atoms are bound to two interwined L2− ligands with a Mg⋯Mg separation of 4.116 Å.