Synthesis and reactivity of a (μ-1,1-hydroperoxo)(μ-hydroxo)dicopper(II) complex:: Ligand hydroxylation by a bridging hydroperoxo ligand
Synthesis and reactivity of a (μ-1,1-hydroperoxo)(μ-hydroxo)dicopper(II) complex:: Ligand hydroxylation by a bridging hydroperoxo ligand
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DOI：
10.1021/ja047437h
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发表时间：
2005-04-13
影响因子：
15
通讯作者：
Kitagawa, T
中科院分区：
文献类型：
--
作者：
Itoh, K;Hayashi, H;Kitagawa, T
合成了一种新的含咪唑基的四齿三足配体（L3），其中L3为三（1-甲基-2-苯基-4-咪唑亚甲基）胺。双（μ-羟基）二铜（II）配合物[Cu-2（L3）（2）（OH）（2）]（2+）（1）与H2 O2在乙腈中在-40 ℃下反应生成（μ-1，1-氢过氧）二铜（II）配合物[Cu-2（L3）（2）（OOH）（OH）]（2+）（2），其通过包括X射线晶体学的各种物理化学测量表征。2的晶体结构显示，配合物阳离子具有Cu-2（mu-1，1-OOH）（mu-OH）核，并且每个铜具有正方形金字塔结构，该正方形金字塔结构具有N3 O2供体组，在顶点中具有叔胺氮的弱连接。因此，2中L3的一个侧臂不受配位，这在Cu-2（mu-1，1-OOH）（mu-OH）核心周围产生疏水空腔。疏水腔通过一侧中的氢过氧化物和未配位的侧臂的咪唑氮与另一侧中的氢氧化物和未配位的侧臂的咪唑氮之间的氢键来保持。与1相比，2中的疏水空腔显著抑制H/D和O-16/O-18交换反应，并稳定Cu-2（mu-1，1-OOH）（mu-OH）核心以防止分解。在0 ℃下，2在乙腈中的分解主要通过过氧化氢配体的反硝化和2被过氧化氢配体还原为[Cu（L3）]（+）进行。相比之下，在60 ° C下2的固体样品的分解得到具有羟基化配体[Cu-2（L3）（L3-OH）（OH）（2）]（2+）（2-（L3-OH））作为主要产物的络合物，其中L3-OH是其中侧臂的亚甲基之一被羟基化的氧化配体。ESI-TOF/MS测量显示配合物2-（L3-OH）在乙腈中在-40 ° C下是稳定的，而在室温下加热2-（L3-OH）导致从L3-OH的N-脱烷基化，得到N-脱烷基化配体，双（1-甲基-2-苯基-4-咪唑基甲基）胺（L2），基于2，和1-甲基-2-苯基-4-甲酰基咪唑（PhimCHO）的同位素标记实验证实，L3-OH和Phim-CHO中的氧原子均来自OOH。这种脂肪族羟基化进行的2是在显着的对比，芳烃羟基化报道的一些（mu-1，1-氢过氧）二铜（II）配合物与二甲苯基接头。
A new tetradentate tripodal ligand (L3) containing sterically bulky imidazolyl groups was synthesized, where L3 is tris(1-methyl-2-phenyl-4-imidazolylmethyl)amine. Reaction of a bis(mu-hydroxo)dicopper(II) complex, [Cu-2(L3)(2)(OH)(2)](2+) (1), with H2O2 in acetonitrile at -40 degrees C generated a (mu-1,1-hydroperoxo)dicopper(II) complex [Cu-2(L3)(2)(OOH)(OH)](2+) (2), which was characterized by various physicochemical measurements including X-ray crystallography. The crystal structure of 2 revealed that the complex cation has a Cu-2(mu-1, 1-OOH)(mu-OH) core and each copper has a square pyramidal structure having an N3O2 donor set with a weak ligation of a tertiary amine nitrogen in the apex. Consequently, one pendant arm of L3 in 2 is free from coordination, which produces a hydrophobic cavity around the Cu-2(mu-1,1-OOH)(mu-OH) core. The hydrophobic cavity is preserved by hydrogen bondings between the hydroperoxide and the imidazole nitrogen of an uncoordinated pendant arm in one side and the hydroxide and the imidazole nitrogen of an uncoordinated pendant arm in the other side. The hydrophobic cavity significantly suppresses the H/D and O-16/O-18 exchange reactions in 2 compared to that in 1 and stabilizes the Cu-2(mu-1, 1-OOH)(mu-OH) core against decomposition. Decomposition of 2 in acetonitrile at 0 degrees C proceeded mainly via disproportionation of the hydroperoxo ligand and reduction of 2 to [Cu(L3)](+) by hydroperoxo ligand. In contrast, decomposition of a solid sample of 2 at 60 degrees C gave a complex having a hydroxylated ligand [Cu-2(L3)(L3-OH)(OH)(2)](2+) (2-(L3-OH)) as a main product, where L3-OH is an oxidized ligand in which one of the methylene groups of the pendant arms is hydroxylated. ESI-TOF/MS measurement showed that complex 2-(L3-OH) is stable in acetonitrile at -40 degrees C, whereas warming 2-(L3-OH) at room temperature resulted in the N-dealkylation from L3-OH to give an N-dealkylated ligand, bis(1-methyl-2-phenyl-4-imidazolylmethyl)amine (L2) in similar to 80% yield based on 2, and 1-methyl-2-phenyl-4-formylimidazole (PhimCHO) Isotope labeling experiments confirmed that the oxygen atom in both L3-OH and Phim-CHO come from OOH. This aliphatic hydroxylation performed by 2 is in marked contrast to the arene hydroxylation reported for some (mu-1,1-hydroperoxo)dicopper(II) complexes with a xylyl linker.