Murthy N N, Mahroof-Tahir M, Karlin K D
Departments of Chemistry, Johns Hopkins University, Charles and 34th Streets, Baltimore, Maryland 21218, USA.
Inorg Chem. 2001 Feb 12;40(4):628-35. doi: 10.1021/ic000792y.
The design, synthesis, and characterization of binuclear copper(I) complexes and investigations of their dioxygen reactivities are of interest in understanding fundamental aspects of copper/O2 reactivity and in modeling copper enzyme active-site chemistry. In the latter regard, unsymmetrical binuclear systems are of interest. Here, we describe the chemistry of new unsymmetrical binuclear copper complexes, starting with the binucleating ligand UN2-H, possessing a m-xylyl moiety linking a bis[2-(2-pyridyl)ethyl]amine (PY2) tridentate chelator and a 2-[2-(methylamino)ethyl]pyridine bidentate group. Dicopper(I) complexes of UN2-H, [Cu2(UN2-H)]2+ (1), as PF6- and ClO4- salts, are synthesized. These react with O2 (Cu:O2 = 2:1, manometry) resulting in the hydroxylation of the xylyl moiety, producing the phenoxohydroxodicopper(II) complex [Cu2(UN2-O-)(OH-)(CH3CN)]2+ (2). Compound 2(PF6)2 is characterized by X-ray crystallography, which reveals features similar to those of a structure described previously (Karlin, K. D.; et al. J. Am. Chem. Soc. 1984, 106, 2121-2128) for a symmetrical binucleating analogue having two tridentate PY2 moieties; here a CH3CN ligand replaces one pyridylethyl arm. Isotope labeling from a reaction of 1 using 18O2 shows that the ligand UN2-OH, extracted from 2, possesses an 18O-labeled phenol oxygen atom. Thus, the transformation 1 + O2-->2 represents a monooxygenase model system. [CuI2(UN2-OH)(CH3CN)]2+ (3), a new binuclear dicopper(I) complex with an unsymmetrical coordination environment is generated either by reduction of 2 with diphenylhydrazine or in reactions of cuprous salts with UN2-OH. Complex 3 reacts with O2 at -80 degrees C, producing the (mu-1,1-hydroperoxo)dicopper(II) complex [CuII2(UN2-O-)(OOH-)]2+ (4) (lambda max 390 nm (epsilon 4200 M-1 cm-1), formulated on the basis of the stoichiometry of O2 uptake by 3 (Cu:O2 = 2:1, manometry), its reaction with PPh3 giving O=PPh3 (85%), and comparison to previously studied close analogues. Discussions include the relevance and comparison to other copper bioinorganic chemistry.
双核铜（I）配合物的设计、合成与表征及其对二氧反应性的研究，对于理解铜/氧气反应性的基本方面以及模拟铜酶活性位点化学具有重要意义。在后一方面，不对称双核体系备受关注。在此，我们描述了新型不对称双核铜配合物的化学性质，从双核配体UN2-H开始，它具有一个间二甲苯基部分，连接着双[2-(2-吡啶基)乙基]胺（PY2）三齿螯合剂和2-[2-(甲氨基)乙基]吡啶双齿基团。合成了UN2-H的二铜（I）配合物[Cu2(UN2-H)]2+（1）的PF6-和ClO4-盐。这些配合物与O2（铜：O2 = 2:1，压力测量法）反应，导致间二甲苯基部分发生羟基化，生成苯氧基羟基二铜（II）配合物[Cu2(UN2-O-)(OH-)(CH3CN)]2+（2）。通过X射线晶体学对化合物2(PF6)2进行了表征，结果显示其结构特征与先前描述的具有两个三齿PY2部分的对称双核类似物的结构相似（卡林，K.D.等人，《美国化学会志》，1984年，106卷，2121 - 2128页）；在此，一个CH3CN配体取代了一个吡啶基乙基臂。使用18O2对1进行反应的同位素标记表明，从2中提取的配体UN2-OH含有一个18O标记的酚氧原子。因此，转化1 + O2→2代表了一个单加氧酶模型体系。[CuI2(UN2-OH)(CH3CN)]2+（3）是一种具有不对称配位环境的新型双核二铜（I）配合物，它可以通过用二苯肼还原2或者在亚铜盐与UN2-OH的反应中生成。配合物3在-80℃下与O2反应，生成（μ-1,1-氢过氧）二铜（II）配合物[CuII2(UN2-O-)(OOH-)]2+（4）（最大吸收波长390nm（ε4200 M-1 cm-1），根据3对O2的吸收化学计量比（铜：O2 = 2:1，压力测量法）、其与PPh3反应生成O=PPh3（85%）以及与先前研究的类似物进行比较来确定其结构）。讨论内容包括与其他铜生物无机化学的相关性及比较。
