COPPER(I) DIOXYGEN REACTIVITY OF MONONUCLEAR COMPLEXES WITH PYRIDYL AND QUINOLYL TRIPODAL TETRADENTATE LIGANDS - REVERSIBLE FORMATION OF CUO2 = 1/1 AND 2/1 ADDUCTS-猫眼课题宝

DOI：

10.1021/ic00087a036

发表时间：

1994-04-27

期刊：

INORGANIC CHEMISTRY

影响因子：

4.6

通讯作者：

中科院分区：

化学2区

文献类型：

--

作者：

WEI, N;MURTHY, NN;KARLIN, KD

研究了一系列三脚架四齿配体与含吡啶和/或喹啉基团的铜(I)配合物与氧气(O2)的反应。配基变化允许测试配基供体能力和空间因子的影响。研究了铜-氧配合物的稳定性、形成1：1Cu2-O2和/或2：1Cu2-O2加合物的选择性、铜(N)-O2(n=1，2)、光谱性质和反应特性，其配体为：L=三(2-吡啶甲基)胺(bis(2-pyridylmethyl)(2-quinolylmethyl)amine(BPQA)，bis(2-quinolylmethyl)(2-pyridylmethyl)amine(BQPA)，)和三(2-喹啉甲基)胺(TMQA)。具有反式-(Mu-1，2-过氧基)双铜(II)结构的2：1加合物[{(TMPA)Cu}2(O2)]2+(1c)先前已被证明由O2与铜(I)络合物[(TMPA)-Cu(RCN)]+(1a)(R=Me，Et)(Tyklar，Z.；等)相互作用可逆地形成。J.Am化学。SoC。1993、115、2677)。相应的铜(I)配合物[(BPQA)Cu]+(2a)、[(BQPA)Cu]+(3a)和[(TMQA)Cu]+(4a)已被合成为PF6-或ClO4-盐。它们缺乏作为孤立固体的RCN腈配体，但2a-4a似乎与MeCN或EtCN溶液中的腈配位。测定了4a的X-射线结构(三斜空间群P1BAR，a=13.130(2)，b=16.570(2)，c=12.956(2)埃，α=111.44(1)，β=98.49(1)，γ=84.46(1)度；V=2592.1(6)埃~3；Z=2)，它与烷胺和三个喹啉N-给体呈假四面体配位。铜(I)配合物2a和3a与三苯基膦反应生成加合物[Lcu(PPh3)]+(2d，3d)。3d(单斜空间群C2/c；a=16.341(4)，b=19.017(6)，c=26.860(7)埃；β=8044(2)度，V=8044(4)埃~3；Z=8)的X-射线结构表明，BQPA配体的一个喹啉基臂是非配位的，与铜(I)离子悬垂，形成扭曲的四面体配位，包括N(吡啶)，N(喹啉)，N(烷基氨基)和P-铜配位。对1a-4a和[(Tmpa‘)Cu(CH3CN)]+(1a’；Tmpa‘在Tmpa的一个吡啶环的5位上带有-C(O)Me酯基团)的循环伏安测试表明，这些配体的变化对铜(II)/铜(I)的氧化还原电位有很大的影响。E_(1/2)值范围较大，1a-4a为-0.61~-0.24V，而二甲基甲酰胺为Ag/AgNO_3；1a‘的值为-0.56V。在乙腈溶剂中，BPQA络合物2a在-80℃与O2快速反应，生成深紫色的稳定溶液加合物[{(BpqA)Cu}2(O2)]2+(2c)，由测压吸氧测量(Cu：O2=2：1)和UV-Vis光谱证实，其波长(Max)=(epsilon=10 500 M-1 cm-1)，约440(sh，epsilon=2000 M-1 cm-1)，约600 nm(sh，epsilon=2000 M-1 cm-1)。Epsilon=7600M-1 cm-1)。化学反应活性与LC相似；与PPh3反应2d，放出O2，而暴露在H+中，通过碘滴定，生成过氧化氢的产率为94%。含有BQPA的络合物3a反应生成深棕色加合物[(BQPA)Cu(O2)]+(3b)，在-80℃下在EtCN中稳定。测压(Cu：O2=1：1)和波长(Max)=378 nm(epsilon=8200M-1 cm-1)的UV-Vis特征表明其为1：1加合物，形式为铜(II)-超氧化物物种。3b与PPh3和H+反应生成类似于2c的产物，可分离出膦加合物3d。3b与TMPA反应产生配体交换反应，生成过氧基团1c，随后在-80℃下进行UV-Vis光谱。O2与3a的结合生成1：1加合物3b是可逆的，如循环实验所证明的，即通过应用真空交替和重复地从3b中去除O2，然后3a再给氧；这个过程是用分光光度法监测的。空间因素被认为在铜-O2络合物3b的这种独特的稳定中是重要的。对于更大的TMQA配体络合物4a，没有观察到与O2的反应。列举了1：1加合物3b中铜结合的O2配体的可能结构。从电子(即氧化还原)特征和空间效应以及最近对1a-3a中O2-结合的完整动力学-热力学特征(Karlin，K.D.；等人)出发，研究了1a-4a和1a‘中观察到的氧结合特征和变化。J.Am化学。SoC。1993、115、9506)。空间效应而不是电子效应似乎是决定O2-反应化学的主要因素。文中还提到了2：1和1：1的铜：氧加合化学的生物学意义。

Copper(I) complexes possessing a series of related tripodal tetradentate ligands with pyridyl- and/or quinolyl-containing groups have been investigated in reactions with dioxygen (O2). The ligand variations allow for the testing of effects of ligand donor ability and steric factors. Copper-dioxygen complex stabilities, preference for formation of 1:1 Cu-O2 and/or 2:1 Cu2-O2 adducts, Cu(n)-O2 (n = 1, 2), spectroscopic properties, and reactivity characteristics have been investigated, The ligands are L = tris(2-pyridylmethyl)amine (TMPA), bis(2-pyridylmethyl)(2-quinolylmethyl)amine(BPQA), bis(2-quinolylmethyl)(2-pyridylmethyl)amine(BQPA), and tris(2-quinolylmethyl)-amine (TMQA). The 2:1 adduct [{(TMPA)CU}2(O2)]2+ (1c), with a trans-(mu-1,2-peroxo)dicopper(II) structure, has previously been shown to form reversibly from the interaction of O2 with the copper(I) complex [(TMPA)-Cu(RCN)]+ (1a) (R = Me, Et) (Tyklar, Z.; et al. J. Am. Chem. Soc. 1993,115, 2677). The corresponding Cu(I) complexes [(BPQA)Cu]+ (2a), [(BQPA)Cu]+ (3a), and [(TMQA)Cu]+ (4a) have been synthesized as either PF6- or ClO4- salts. They lack an RCN nitrile ligand as isolated solids, but 2a-4a appear to coordinate nitriles in MeCN or EtCN solutions. The X-ray structure of 4a has been determined (triclinic space group P1BAR, a = 13.130 (2), b = 16.570 (2), c = 12.956 (2) angstrom, alpha = 111.44 (1) beta = 98.49 (1), gamma = 84.46 (1)degrees; V = 2592.1 (6) angstrom3; Z = 2), and it exhibits a pseudotetrahedral coordination to the alkylamine and three quinolyl N-donors. Copper(I) complexes 2a and 3a react with triphenylphosphine to form adducts [LCu(PPh3)]+ (2d, 3d). The X-ray structure of 3d (monoclinic space group C2/c; a = 16.341 (4), b = 19.017 (6), c = 26.860 (7) angstrom; beta = 105.48 (2)degrees, V = 8044 (4) angstrom3; Z = 8) indicates that one of the quinolyl arms of the BQPA ligand is uncoordinated and dangles away from the Cu(I) ion, leaving a distorted tetrahedral coordination, comprising N(pyridyl), N(quinolyl), N(alkylamino), and P copper ligation. Cyclic voltammetric measurements carried out on 1a-4a plus [(TMPA')Cu(CH3CN)]+ (1a'; TMPA' possesses a -C(O)Me ester group attached to the 5-position of one pyridyl ring of TMPA) show that the Cu(II)/Cu(I) redox potentials can be greatly influenced by these ligand variations. E1/2 values span a large range, from -0.61 to -0.24 V for 1a-4a, versus Ag/AgNO3 in dimethylformamide; the value for 1a' is -0.56 V. The BPQA complex 2a reacts rapidly with O2 at -80-degrees-C in EtCN solvent to give an intensely purple stable solution adduct [{(BPQA)Cu}2(O2)]2+ (2c), as evidenced by manometric O2-uptake measurements (CU:O2 = 2:1) and the UV-vis spectrum, which closely resembles that of 1c, with lambda(max) = 535 (epsilon = 10 500 M-1 cm-1), ca. 440 (sh, epsilon = 2000 M-1 cm-1), and ca. 600 nm (sh, epsilon = 7600 M-1 cm-1). The chemical reactivity parallels that of lc; reaction with PPh3 gives 2d with evolution of O2, while exposure to H+ produces hydrogen peroxide in 94% yield, as determined by iodometric titration. The BQPA-containing complex 3a reacts to form a dark brown adduct [(BQPA)Cu(O2)]+ (3b), which is stable at -80-degrees-C in EtCN. Manometry (Cu:O2 = 1:1) and the drastically different UV-vis characteristics with lambda(max) = 378 nm (epsilon = 8200 M-1 cm-1) attest to its formulation as a 1:1 adduct, formally a Cu(II)-superoxide species.Reactions of 3b with PPh3 and H+ proceed with formation of products analogous to those found with 2c, and phosphine adduct 3d could be isolated. Reaction of 3b with the TMPA results in a ligand-exchange reaction, with production of peroxo species 1c, as followed by UV-vis spectroscopy at -80-degrees-C. The binding of O2 to 3a to give 1:1 adduct 3b is reversible, as demonstrated by cycling experiments, i.e., the alternate and repetitive removal of O2 from 3b by application of a vacuum, followed by reoxygenation of 3a; this process was monitored spectrophotometrically. Steric factors are seen to be important in this unique stabilization of the Cu-O2 complex 3b. With the even more bulky TMQA ligand complex 4a, no reaction with O2 is observed. Possible structures of the Cu-bound O2 ligand in 1:1 adduct 3b are enumerated. Dioxygen binding characteristics and variations observed for 1a-4a and 1a' are examined in terms of electronic (i.e. redox) characteristics and steric effects and in light of recent complete kinetic-thermodynamic characterization of the O2-binding in 1a-3a (Karlin, K. D.; et al. J. Am. Chem. Soc. 1993, 115, 9506). Steric and not electronic effects appear to predominate in determining the O2-reaction chemistry. The biological relevance of 2:1 and 1:1 Cu:O2 adduct chemistry is also mentioned.