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Abstract
Four new sodium complexes of phenolate and bisphenolate ligands have been synthesized and characterized by NMR spectroscopy and X-ray crystallography to study their coordination chemistry. The monoanionic tridentate [ONN] phenolate ligand gave a dimeric compound [Na2L2] (2), which crystallized in the orthorhombic crystal system, where the sodium ions have four coordination environments. The dianionic tridentate [ONO] phenolate ligand gave a dimeric [Na2(LIH)2] (4) compound in the tetragonal crystal system. The sodium ions Na(1) and Na(1ʹ) are four-coordinate both having a tetrahedral geometry with the O–Na–O angle being ca. 93°, the O^N^O ligand string comprising a tridentate ligand. Interestingly, despite the steric bulk of N(SiMe3)2, a mixture of compounds [NaL] (2) and NaN(SiMe3)2 was isolated as a dimeric structure [Na2L(N(SiMe3)2)]2 (5) crystallized in the monoclinic crystal system. Na(1) is four-coordinate bonding to the phenolic oxygen atom and two N atoms of the ligand L and the N of the N(SiMe3)2 ligand. The coordination around Na(1) is tetrahedrally distorted square planar with the ‘cis’ angles ranging from 75.11(4) to 117.40(5)° and the ‘trans’ angles being 140.87(4) and 154.82(5)°. Na(2) is three-coordinate, bonding to the two phenolate oxygen atoms and the N atom of the N(SiMe3)2 ligand. Na(2), however, is not coplanar with these atoms being displaced 0.42 Å from it. The coordination chemistry for 5 is very intriguing as the sodium ions have mixed four- and three-coordination numbers, probably due to the steric hindrance of the silylamide groups.
