The first “Kuhn verdazyl” ligand and comparative studies of its PdCl2 complex with analogous 6-oxoverdazyl ligands
作者:Cooper W. Johnston、Stephen D. J. McKinnon、Brian O. Patrick、Robin G. Hicks
DOI:10.1039/c3dt52191e
日期:——
The synthesis and characterization of two new N,Nâ²-diarylverdazyl radical ligands and their corresponding PdCl2 complexes are described. One of the two radicals is of the âKuhn verdazylâ structure type and was made by adaptation of standard synthetic procedures for this class of verdazyl. The N,Nâ²-diphenyl-6-oxoverdazyl was prepared by hydrolysis of a related tetrazane; the resulting N,Nâ²-diphenylcarbohydrazide was condensed with pyridinecarboxaldehyde and then oxidized to the verdazyl according to standard protocols. Square planar PdCl2 complexes of both verdazyls were prepared by reactions of the radicals with PdCl2 in acetonitrile solution. The structural, spectroscopic, and electrochemical properties of the new verdazyl ligands and their Pd complexes are reported; generally the distinct ligand-centred properties associated with each verdazyl type carry over into the properties of the complexes. The electrochemical studies reveal ligand-centred oxidation and reduction processes; despite the minimal extent of spin delocalization onto Pd in the metal complexes, large shifts in oxidation and reduction potentials (relative to those of the free verdazyl ligands) are discussed.
本文介绍了两种新型 N,Nâ²-二羰基verdazyl自由基配体及其相应 PdCl2 复合物的合成和特性。这两种自由基中的一种属于 "库恩"(Kuhn)verdazylâ结构类型,是通过对这类verdazyl的标准合成程序进行调整而制成的。N,N²-二苯基-6-氧代overdazyl是通过水解相关的四氮烷制备的;生成的N,N²-二苯基甲酰肼与吡啶甲醛缩合,然后按照标准程序氧化成verdazyl。在乙腈溶液中,通过自由基与氯化钯的反应,制备了这两种verdazyls的方形平面氯化钯配合物。报告介绍了新吠陀配体及其钯配合物的结构、光谱和电化学性质;一般来说,与每种吠陀类型相关的以配体为中心的独特性质会延续到配合物的性质中。电化学研究揭示了以配体为中心的氧化和还原过程;尽管金属配合物中钯上的自旋析出程度很小,但讨论了氧化和还原电位的巨大变化(相对于游离羰基配体的电位)。