Zakrzewska Joanna, Uznanski Pawel
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland.
Dalton Trans. 2021 May 25;50(20):6933-6948. doi: 10.1039/d1dt00638j.
The synthesis and characterization of the adducts of n-alkyl amine and palladium n-alkyl carboxylate, [Pd(R2NH2)2(R1COO)2] (R1 = 1, 7, and 11; R2 = 8, 12, and 16), as precursors for the synthesis of palladium nanoparticles (PdNPs) was carried out via differential scanning calorimetry, FT-IR, Raman and UV-Vis spectroscopy, NMR spectroscopy (1H, 13C pulsed field gradient spin-echo (PGSE), and 13C CP-MAS), and powder X-ray diffraction. Pd n-alkyl carboxylates were obtained by a ligand exchange reaction from palladium acetate and the appropriate aliphatic carboxylic acid. It is proposed that carboxyl moieties in the presence of amine ligands are bound to palladium ions via monodentate bonding as opposed to bridging bidentate coordination of pure palladium carboxylate which exists in the form of polymer aggregates. All the studied palladium carboxylate/amine complexes form bilayer lamellar structures and exhibit first-order melting transitions. The evidence presented in this study shows that the phase behavior of bivalent metal carboxylates is mainly controlled by the type of coordination of carboxylate head groups. For n-alkyl carboxylates, linear chain type aggregates replace the trimeric units of Pd acetate. In solution, in the presence of amine, palladium salt aggregates disintegrate and the Pd complex is isolated and stabilized by amine molecules. Using bis(amine) palladium carboxylate adducts as precursors, palladium nanoparticles were fabricated. During high temperature thermolysis, the bis(amine) Pd carboxylate complex decomposes to form small sized Pd nanoparticles. Combining NMR techniques with FTIR spectroscopy, it was possible to follow an original stabilization mechanism. PdNPs are stabilized by weakly interacting long chain aliphatic amide and carboxylic acid derived from the palladium precursor.
作为合成钯纳米颗粒（PdNPs）的前体，对正烷基胺与钯正烷基羧酸盐的加合物[Pd(R2NH2)2(R1COO)2]（R1 = 1、7和11；R2 = 8、12和16）进行了合成与表征，采用了差示扫描量热法、傅里叶变换红外光谱、拉曼光谱和紫外-可见光谱、核磁共振光谱（1H、13C脉冲场梯度自旋回波（PGSE）和13C交叉极化魔角旋转（CP-MAS））以及粉末X射线衍射。钯正烷基羧酸盐通过乙酸钯与适当的脂肪族羧酸进行配体交换反应制得。有人提出，在胺配体存在下，羧基部分通过单齿键与钯离子结合，这与纯钯羧酸盐以聚合物聚集体形式存在的桥连双齿配位不同。所有研究的钯羧酸盐/胺配合物均形成双层层状结构，并表现出一级熔融转变。本研究提供的证据表明，二价金属羧酸盐的相行为主要受羧酸盐头基的配位类型控制。对于正烷基羧酸盐，线性链状聚集体取代了乙酸钯的三聚体单元。在溶液中，在胺存在下，钯盐聚集体分解，钯配合物被胺分子分离并稳定。以双（胺）钯羧酸盐加合物为前体，制备了钯纳米颗粒。在高温热解过程中，双（胺）钯羧酸盐配合物分解形成小尺寸的钯纳米颗粒。将核磁共振技术与傅里叶变换红外光谱相结合，可以追踪一种原始的稳定机制。钯纳米颗粒通过与钯前体衍生的弱相互作用长链脂肪族酰胺和羧酸而稳定。
