Characterization of the structure and reactivity of monocopper-oxygen complexes supported by β-diketiminate and anilido-imine ligands
Characterization of the structure and reactivity of monocopper-oxygen complexes supported by β-diketiminate and anilido-imine ligands
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DOI：
10.1002/jcc.20502
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发表时间：
2006-12-01
影响因子：
3
通讯作者：
Cramer, Christopher J.
中科院分区：
文献类型：
--
作者：
Gherman, Benjamin F.;Tolman, William B.;Cramer, Christopher J.
最近有报道称，β -二酮酸盐和苯胺-亚胺配体支持的铜氧配合物（Aboelella et al., J Am Chem Soc 2004, 126, 16896; Reynolds et al., Inorg Chem 2005, 44, 6989）是多巴胺β -单加氧酶（D β M）和肽基甘氨酸α -羟化单加氧酶（PHM）的潜在仿生模型。然而，与酶系统相比，这些复合物不能表现出C-H羟基化活性（Reynolds et al., Chem comm2005, 2014）。1:1 Cu- o -2模型加合物和相关物质(Cu(III)-氢过氧化物、Cu（III)-氧和Cu(III)-氢氧化物）的量子化学表征表明，1:1 Cu- o -2模型加合物对底物无反应性，因为在氢原子抽离时形成的O-H键很弱。这反过来又归因于1:1加合物具有低还原电位和碱度。另一方面，Cu(III)-氧介于Cu(III)-氧和Cu(II)-氧之间，对底物的反应性要强得多。基于这些结果，提出了新的D β M和PHM仿生配体的设计策略：新配体应使电子富集较少，以有利于1:1 Cu-O-2加合物的端对双氧配位。对不同铜氧配合物作为羟基化剂的相对反应活性进行比较，支持了Cu(II)-超氧化物作为D β M和PHM中底物羟基化的中间体，并表明Cu(III)-氧中间体也能参与这一过程。(C) 2006 Wiley期刊有限公司
Copper-oxygen complexes supported by beta-diketiminate and anilido-imine ligands have recently been reported (Aboelella et al., J Am Chem Soc 2004, 126, 16896; Reynolds et al., Inorg Chem 2005, 44, 6989) as potential biomimetic models for dopamine beta-monooxygenase (D beta M) and peptidylglycine alpha-hydroxylating monooxygenase (PHM). However, in contrast to the enzymatic systems, these complexes fail to exhibit C-H hydroxylation activity (Reynolds et al., Chem Commun 2005, 2014). Quantum chemical characterization of the 1:1 Cu-O-2 model adducts and related species (Cu(III)-hydroperoxide, Cu(III)-oxo, and Cu(III)-hydroxide) indicates that the 1:1 Cu-O-2 adducts are unreactive toward substrates because of the weakness of the O-H bond that would be formed upon hydrogen-atom abstraction. This in turn is ascribed to the 1:1 adducts having both low reduction potentials and basicities. Cu(III)-oxo species on the other hand, determined to be intermediate between Cu(III)-oxo and Cu(II)-oxyl in character, are shown to be far more reactive toward substrates. Based on these results, design strategies for new D beta M and PHM biomimetic ligands are proposed: new ligands should be made less electron rich so as to favor end-on dioxygen coordination in the 1:1 Cu-O-2 adducts. Comparison of the relative reactivities of the various copper-oxygen complexes as hydroxylating agents provides support for a Cu(II)-superoxide species as the intermediate responsible for substrate hydroxylation in D beta M and PHM, and suggests that a Cu(III)-oxo intermediate would be competent in this process as well. (C) 2006 Wiley Periodicals, Inc.