Several new palladium(II) complexes containing acetoxime as a unidentate ligand were synthesized from cis-[Pd(en)(solv)2]2+1a and cis-[Pd(dtod)(solv)2]2+1b, in which the displaceable ligand solv is water or acetone, en is ethane-1,2-diamine, and dtod is 3,6-dithia-1,8-octanediol. The acetoxime complexes are characterized by UV-visible spectrophotometry and 1H and 13C NMR spectroscopy in solution. Acetoxime in the mono-oxime complexes cis-[Pd(en)N(OH)C(CH3)2}(solv)]2+2a and cis-[Pd(dtod)N(OH)C(CH3)2}(solv)]2+2b undergoes hydrolysis to acetone and hydroxylamine. The proposed mechanism involves internal attack of a PdII-bound hydroxo ligand at the coordinated acetoxime. This palladium(II)-catalysed hydrolysis is at least 104 times faster than hydrolysis in the absence of a catalyst. The rate enhancement arises from polarization of acetoxime upon coordination to palladium(II), the availability of the nucleophilic hydroxo ligand, and close proximity of these two species. The complex [Pd(dien)N(OH)C(CH3)2}]2+, which contains the tridentate diethylenetriamine ligand, is almost unreactive toward hydrolysis because it lacks a PdII-bound aqua or hydroxo ligand, so that the reaction occurs via the less-favorable external attack of solvent water. Acetoxime in the bis-acetoxime complex cis-[Pd(dtod)N(OH)C(CH3)2}2]2+3b hydrolyses very slowly because this complex also lacks aqua or hydroxo ligands. Therefore, this complex was crystallized and its structure determined by X-ray crystallography.
由顺式-[Pd(en)(solv)2]2+1a 和顺式-[Pd(dtod)(solv)2]2+1b 合成了几种新的含乙酰
肟配体的
钯(II)配合物,其中可置换
配体 solv 为
水或
丙酮,en 为
乙烷-1,2-二胺,dtod 为
3,6-二硫杂-1,8-辛二醇。乙酮
肟复合物通过紫外-可见分光光度法以及溶液中的 1H 和 13C NMR 光谱法进行表征。单
肟复合物顺式-[Pd(en)N(OH)C(
CH3)2}(solv)]2+2a 和顺式-[Pd(dtod)N(OH)C( )2}(solv)]2+2b 中的乙酮
肟会
水解为
丙酮和
羟胺。所提出的机理涉及配位乙酮
肟中与
钯(II)结合的羟基
配体的内部攻击。这种
钯(II)催化的
水解作用比没有催化剂时的
水解作用至少快 104 倍。速度的提高源于乙酰
肟与
钯(II)配位后的极化、亲核羟
配体的存在以及这两种物质的接近。复合物[Pd(dien)N(OH)C( )2}]2+含有三叉式
二乙烯三胺配体,由于缺乏与
钯(II)结合的
水基或羟基
配体,几乎不发生
水解反应,因此反应是通过较不利的溶剂
水的外部侵蚀进行的。
双乙酮肟复合物 cis-[Pd(dtod)N(OH)C( )2}2]2+3b中的乙酮
肟水解非常缓慢,因为该复合物也缺乏
水或羟
配体。因此,我们对该复合物进行了结晶,并通过 X 射线晶体学确定了其结构。