Synthesis,Characterization, and Reaction Studies of Pd(II) Tripeptide Complexes |
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Authors: | Lindsey J. Monger Dmitrii Razinkov Ragnar Bjornsson Sigridur G. Suman |
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Affiliation: | 1.Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland; (L.J.M.); (D.R.);2.Max Planck Institute Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany; |
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Abstract: | The aqueous synthesis of Pd(II) complexes with alkylated tripeptides led to the hydrolysis of the peptides at low pH values and mixtures of complexed peptides were formed. A non-aqueous synthetic route allowed the formation and isolation of single products and their characterization. Pd(II) complexes with α-Asp(OR)AlaGly(OR), β-Asp(OR)AlaGly(OR), and TrpAlaGly(OR) (R = H or alkyl) as tri and tetradentate chelates were characterized. The tridentate coordination mode was accompanied by a fourth monodentate ligand that was shown to participate in both ligand exchange reactions and a direct removal to form the tetradentate coordination mode. The tetradentate coordination revealed a rare a hemi labile carbonyl goup coordination mode to Pd(II). Reactivity with small molecules such as ethylene, acids, formate, and episulfide was investigated. Under acidic conditions and in the presence of ethylene; acetaldehyde was formed. The Pd(II) is a soft Lewis acid and thiophilic and the complexes abstract sulfur from episulfide at apparent modest catalytic rates. The complexes adopt a square planar geometry according to a spectroscopic analysis and DFT calculations that were employed to evaluate the most energetically favorable coordination geometry and compared with the observed infrared and NMR data. |
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Keywords: | Pd(II), tripeptide, AspAlaGly, β -AspAlaGly, TrpAlaGly, DFT |
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