Nickel(ii) complexes with amide ligands: oxidative dehydrogenation of the amines in a tetradentate diamide–diamine ligand
作者:Colin L. Weeks、Peter Turner、Ronald R. Fenton、Peter A. Lay
DOI:10.1039/b107378h
日期:——
Four complexes were prepared by the reaction of Ni(II) with three pyrrolidine based diamideâdiamine ligands. The two amine groups in the ligand N,Nâ²-bis(S-prolyl)-1,2-ethanediamine (S,S-bprolenH2) were oxidatively dehydrogenated during the preparation of the Ni(II) complex in air. The reaction involved O2 to yield a complex of a tetradentate ligand with 1-pyrroline terminal groups. The Ni(II) complex with S,S-bprolenH2 was synthesised under oxygen-free conditions, and the Ni(II) complexes with the analogous ligands N,Nâ²-bis(S-prolyl)-R,R-1,2-cyclohexanediamine (R,R-(S,S)-bprolchxnH2) and N,Nâ²-bis(S-prolyl)-1,2-benzenediamine (S,S-bprolbenH2) were prepared in air. The complexes
were characterised by X-ray crystallography, 1H and 13C NMR spectroscopy and IR spectroscopy. The Ni(III/II) reduction potentials of complexes with pyridyl and pyrrolidine based tetradentate diamide ligands were measured by cyclic voltammetry to assess the stability of the Ni(III) oxidation state, but did not show any correlation with the ease of ligand oxidation.
通过Ni(II)与三种以吡咯烷为基础的二胺–二酰胺配体的反应,制备了四个配合物。在配体N,N'-双(S-丙氨基)-1,2-乙二胺(S,S-bprolenH2)的制备过程中,两个胺基在空气中被氧化脱氢。该反应涉及O2,生成一种具有1-吡咯啉末端基团的四齿配体的配合物。在无氧条件下合成了与S,S-bprolenH2的Ni(II)配合物,而与类似配体N,N'-双(S-丙氨基)-R,R-1,2-环己烷二胺(R,R-(S,S)-bprolchxnH2)及N,N'-双(S-丙氨基)-1,2-苯二胺(S,S-bprolbenH2)的Ni(II)配合物则是在空气中制备的。这些配合物通过X射线晶体学、1H和13C NMR光谱以及红外光谱进行表征。采用循环伏安法测定了与以吡啶和吡咯烷为基础的四齿二酰胺配体的配合物的Ni(III/II)还原电位,以评估Ni(III)氧化态的稳定性,但未表现出与配体氧化难易程度的相关性。