Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan.
J Am Chem Soc. 2011 Nov 9;133(44):17901-11. doi: 10.1021/ja207572z. Epub 2011 Oct 13.
Ruthenium(II)-acetonitrile complexes having η(3)-tris(2-pyridylmethyl)amine (TPA) with an uncoordinated pyridine ring and diimine such as 2,2'-bipyridine (bpy) and 2,2'-bipyrimidine (bpm), Ru(II)(η(3)-TPA)(diimine)(CH(3)CN), reacted with m-chloroperbenzoic acid to afford corresponding Ru(II)-acetonitrile complexes having an uncoordinated pyridine-N-oxide arm, Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN), with retention of the coordination environment. Photoirradiation of the acetonitrile complexes having diimine and the η(3)-TPA with the uncoordinated pyridine-N-oxide arm afforded a mixture of Ru(II)(TPA)(diimine), intermediate-spin (S = 1) Ru(IV)-oxo complex with uncoordinated pyridine arm, and intermediate-spin Ru(IV)-oxo complex with uncoordinated pyridine-N-oxide arm. A Ru(II) complex bearing an oxygen-bound pyridine-N-oxide as a ligand and bpm as a diimine ligand was also obtained, and its crystal structure was determined by X-ray crystallography. Femtosecond laser flash photolysis of the isolated O-coordinated Ru(II)-pyridine-N-oxide complex has been investigated to reveal the photodynamics. The Ru(IV)-oxo complex with an uncoordinated pyridine moiety was alternatively prepared by reaction of the corresponding acetonitrile complex with 2,6-dichloropyridine-N-oxide (Cl(2)py-O) to identify the Ru(IV)-oxo species. The formation of Ru(IV)-oxo complexes was concluded to proceed via intermolecular oxygen atom transfer from the uncoordinated pyridine-N-oxide to a Ru(II) center on the basis of the results of the reaction with Cl(2)py-O and the concentration dependence of the consumption of the starting Ru(II) complexes having the uncoordinated pyridine-N-oxide moiety. Oxygenation reactions of organic substrates by Ru(II)(η(3)-TPA-O)(diimine)(CH(3)CN) were examined under irradiation (at 420 ± 5 nm) and showed selective allylic oxygenation of cyclohexene to give cyclohexen-1-ol and cyclohexen-1-one and cumene oxygenation to afford cumyl alcohol and acetophenone.
具有未配位吡啶环的η(3)-三(2-吡啶甲基)胺(TPA)和二亚胺如 2,2'-联吡啶(bpy)和 2,2'-联嘧啶(bpm)的钌(II)-乙腈配合物，Ru(II)(η(3)-TPA)(二亚胺)(CH(3)CN)，与间氯过苯甲酸反应得到具有未配位吡啶-N-氧化物臂的相应 Ru(II)-乙腈配合物，Ru(II)(η(3)-TPA-O)(二亚胺)(CH(3)CN)，保留配位环境。具有二亚胺和具有未配位吡啶-N-氧化物臂的η(3)-TPA 的乙腈配合物的光照射产生Ru(II)(TPA)(二亚胺)、具有未配位吡啶臂的中间自旋(S = 1)Ru(IV)-氧合配合物和具有未配位吡啶-N-氧化物臂的中间自旋 Ru(IV)-氧合配合物的混合物。还获得了一种带有配位氧的吡啶-N-氧化物作为配体和 bpm 作为二亚胺配体的 Ru(II)配合物，并通过 X 射线晶体学确定了其晶体结构。通过飞秒激光闪光光解分离的 O 配位 Ru(II)-吡啶-N-氧化物配合物，研究了光动力学。通过与 2,6-二氯吡啶-N-氧化物(Cl(2)py-O)反应，将相应的乙腈配合物制备得到具有未配位吡啶部分的 Ru(IV)-氧合配合物，以鉴定 Ru(IV)-氧合物种。根据与 Cl(2)py-O 的反应结果和起始 Ru(II)配合物(具有未配位吡啶-N-氧化物部分)消耗的浓度依赖性，得出 Ru(IV)-氧合配合物的形成是通过未配位吡啶-N-氧化物与 Ru(II)中心之间的分子间氧原子转移进行的结论。在光照下(在 420 ± 5nm 处)检查Ru(II)(η(3)-TPA-O)(二亚胺)(CH(3)CN)对有机底物的氧化反应，显示环己烯的选择性烯丙基氧化生成环己烯-1-醇和环己烯-1-酮以及cumene 的氧化生成cumyl alcohol 和 acetophenone。
