Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland.
Max Planck Institute Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.
Molecules. 2021 Aug 26;26(17):5169. doi: 10.3390/molecules26175169.
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.
具有烷基化三肽的 Pd(II) 配合物的水相合成导致在低 pH 值下肽的水解，并形成复合肽的混合物。非水合成路线允许形成和分离单一产物及其特性。α-Asp(OR)AlaGly(OR)、β-Asp(OR)AlaGly(OR) 和 TrpAlaGly(OR) (R = H 或烷基) 的 Pd(II) 配合物被表征为三齿和四齿螯合物。三齿配位模式伴随着第四个单价配体，该配体被证明参与配体交换反应和直接去除以形成四齿配位模式。四齿配位揭示了 Pd(II) 罕见的半不稳定羰基配位模式。研究了与小分子如乙烯、酸、甲酸盐和环硫醚的反应性。在酸性条件下并存在乙烯的情况下;形成乙醛。Pd(II) 是软路易斯酸和亲硫性的，配合物从环硫醚中提取硫，表观催化速率适中。根据光谱分析和 DFT 计算采用正方形平面几何形状，用于评估最具能量有利的配位几何形状，并与观察到的红外和 NMR 数据进行比较。
