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Synthesis, characterization and determination of absolute structures of palladium complexes of novel chiral acyclic tellurated Schiff base ligands†
H. R. Rajegowda,P. Raghavendra Kumar,Amar Hosamani,R. J. Butcher
New Journal of Chemistry Pub Date : 03/08/2018 00:00:00 , DOI:10.1039/C8NJ00727F
Abstract

Enantiomerically pure chiral hybrid organotellurium ligands (R)-L1H, (S)-L2H and (R)-L3H have been synthesized via condensation of the chiral β-organotellurated amines 2a, 2b and 2c, respectively, with salicylaldehyde. When these chiral acyclic tellurated Schiff base ligands reacted with Na2PdCl4 in a 1 : 1 molar ratio, they afforded the corresponding orange-red asymmetric complexes [Pd(L1–3)Cl] (1–3). All these compounds were characterized by elemental analysis, polarimetry, and 1H, 13C{1H} NMR and FT-IR spectroscopies. The absolute structures of the complexes 1 and 2 were determined by single crystal X-ray diffraction, and the complexes 1 and 2 crystallized in the hexagonal and orthorhombic crystal systems with the space groups P65 and P212121, respectively. The characterisation data showed that the ligands coordinated in the deprotonated tridentate (Te, N, O) mode and acquired a square planar geometry around the central palladium(II) ion along with a monodentate chloro (Cl) in 1–3. The Pd–Te, Pd–Cl, Pd–O and Pd–N bond lengths found were 2.5008(9), 2.3286(19), 2.037(6) and 2.009(6) Å, respectively, in 1 and 2.497(2)/2.506(3), 2.293(6)/2.326(6), 2.035(15)/2.030(2) and 1.949(17)/2.010(2) Å, respectively, in 2. There was intermolecular CH⋯Cl [2.81–2.96 Å] and CH⋯O [2.40–2.64 Å] hydrogen bonding in 1 and 2, which resulted in supramolecular structures. The Te⋯Cl [3.309–3.710 Å] secondary interactions resulted in the helical structure of 1 and dimeric structure of 2 with a short Pd⋯Pd [3.500(1) Å] distance. The Flack parameters (x) of 1 [0.02(3)] and 2 [0.024(12)] confirmed their absolute configurations.

Graphical abstract: Synthesis, characterization and determination of absolute structures of palladium complexes of novel chiral acyclic tellurated Schiff base ligands
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