A bis(μ-oxo)dicopper(III) complex with aromatic nitrogen donors:: Structural characterization and reversible conversion between copper(I) and bis(μ-oxo)dicopper(III) species
A bis(μ-oxo)dicopper(III) complex with aromatic nitrogen donors:: Structural characterization and reversible conversion between copper(I) and bis(μ-oxo)dicopper(III) species
复制标题
DOI：
10.1021/ja992680f
复制
发表时间：
2000-03-08
影响因子：
15
通讯作者：
Kitagawa, T
中科院分区：
文献类型：
--
作者：
Hayashi, H;Fujinami, S;Kitagawa, T
（μ-π ι 2）的变换：托尔曼等人报道了带有空间体积庞大的三齿N，N '，N''-三取代tacn 2的η2-过氧化）二铜（II）配合物，形成四方锥形双（μ-氧代）二铜（III）配合物。3在某些情况下，他们观察到双（μ-氧代）二铜（III）配合物的单加氧酶活性以配位配体为底物。Stack等人还制备了具有全烷基化-1，2-环己烷二胺配体的不同类型的正方形平面双（μ-氧代）二铜（III）配合物。4最近，已经报道了与含有两个吡啶基侧臂的三齿配体的双（μ-氧代）-二铜（III）配合物5和与含有吡啶基的二齿配体的双（μ-氧代）二铜（III）配合物的部分形成。6然而，没有晶体学表征的具有芳族氮供体的双（μ-氧代）-二铜（III）配合物。因此，重要的是探索供体原子的性质和支持配体的立体化学如何影响双（μ-氧代）二铜（III）配合物的形成、结构和反应性。Karlin等人已经证明，具有四齿三足tpa配体[Cu（tpa）（NCCH 3）]+的铜（I）络合物与O2反应形成反式-（μ-1，2-过氧）二铜（II）配合物（[Cu 2（O2）-（tpa）2] 2+），具有三角双锥结构（λmax（λ，M-1 cm-1））= 440 nm（4000）、525 nm（11500）和590 nm（7600））。7以前我们发现[Cu（Me-tpa）]+在丙酮中在-70 ℃下产生反式-（μ-1，2-peroxo）dicopper（II）物种，而[Cu（Me 2-tpa）]+（1a）与O2（Cu：O2）2：1）在丙酮中在-70 ℃下不形成反式-（μ-1，2-过氧）二铜（II）物质，但产生棕色物质（1b，λmax（μ，M-1 cm-1））378 nm（μ 22 000，0.1 mM），494 nm（330，10 mM））。8因此，在tpa配体中引入两个6-甲基吡啶基阻止了在三角双锥结构中形成反式-（μ-1，2-过氧）二铜（II）物种，这可能是由于两个6-甲基吡啶基的空间要求。然而，由于1b的光谱特征与（μ-η2：η2-过氧）二铜（II）9和双（μ-氧代）二铜（III）配合物的光谱特征有些不同，因此很难从其电子光谱推测1b的结构。本文报道了一种棕色双（μ-氧代）二铜（III）配合物[Cu 2（O）2（Me 2-tpa）2]（PF 6）2·2（CH 3）2CO（1b）的晶体结构以及1a和1b之间的可逆转化。配合物1a具有三角锥结构，在三角平面上具有三个吡啶基，在顶点具有叔胺。1a与O2在丙酮/MeOH（10：1）中在-78 ℃下反应，得到棕色溶液，从该溶液中得到适合于X射线晶体学的棕色晶体。图1显示了1b的络合阳离子的晶体结构，它由中心对称的Cu 2（μ-O）2核和Me 2-tpa氮组成。每个铜离子具有正方形平面结构，其由N2 O2供体组和两个6-甲基-2-吡啶甲基侧臂组成，所述侧臂在轴向位置（2.48（1）和2.55（1）π）与每个铜离子弱相互作用。平均铜（1.803）和Cu Cu*（2.758（4））距离远小于bis-（μ-hydroxo）dicopper（II）complex，[Cu2（OH）2（Me2-tpa）2]（ClO4）2（1c）10（分别为1.942 μ mol/L和2.9368（9）μ mol/L），与双（μ-氧代）二铜（III）配合物[Cu 2（O）2（Bn 3-tacn）2] 2+（3; 1.806和2.794 μ m）3a，c和[Cu 2（O）2（LME）2] 2+（4; 1.806和2.743 μ m）。4在-80 ℃下用488.0 nm激光激发在丙酮（10 mM）中测量的1b的共振拉曼光谱显示出在590 cm-1处有16 O2的同位素敏感带（18 O2为564 cm-1），如图2所示（插图...
Transformation of (μ-η2: η2-peroxo) dicopper (II) complexes bearing sterically bulky tridentate N, N′, N′′-trisubstituted tacn2 to square pyramidal bis (μ-oxo) dicopper (III) complexes has been reported by Tolman et al. 3 In certain instances, they have observed a monooxygenase activity of the bis (μ-oxo) dicopper (III) complexes for the coordinated ligand as substrate. A different type of square planar bis (μ-oxo) dicopper (III) complexes having peralkylated-1, 2-cyclohexanediamine ligands have been also prepared by Stack et al. 4 Very recently, partial formation of a bis (μ-oxo)-dicopper (III) complex with a tridentate ligand containing two pyridyl sidearms5 and a bis (μ-oxo) dicopper (III) complex with a bidentate ligand containing a pyridyl group have been reported. 6 However, there is no crystallographically characterized bis (μ-oxo)-dicopper (III) complex having aromatic nitrogen donors. Thus, it is important to explore how the nature of the donor atoms and the stereochemistry of supporting ligands influence the formation, structure, and reactivity of bis (μ-oxo) dicopper (III) complexes. Karlin et al. have demonstrated that a copper (I) complex having a tetradentate tripodal tpa ligand,[Cu (tpa)(NCCH3)]+, reacts with O2 to form a trans-(μ-1, 2-peroxo) dicopper (II) complex ([Cu2 (O2)-(tpa) 2] 2+) in a trigonal bipyramidal structure (λmax (ϵ, M-1 cm-1))∼ 440 nm (4000), 525 nm (11500), and∼ 590 nm (7600)). 7 Previously we found that [Cu (Me-tpa)]+ in acetone at-70 C generates a trans-(μ-1, 2-peroxo) dicopper (II) species, whereas the reaction of [Cu (Me2-tpa)]+(1a) with O2 (Cu: O2) 2: 1) in acetone at-70 C does not form a trans-(μ-1, 2-peroxo) dicopper (II) species, but produces a brown species (1b, λmax (ϵ, M-1 cm-1))378 nm (∼ 22 000, 0.1 mM), 494 nm (330, 10 mM)). 8 Thus, introduction of two 6-methylpyridyl groups into the tpa ligand prevents the formation of trans-(μ-1, 2-peroxo) dicopper (II) species in a trigonal bipyramidal structure, probably due to a steric requirement of two 6-methylpyridyl groups. However, it is difficult to presume the structure of 1b from its electronic spectrum, since the spectral feature of 1b is somewhat different from those of (μ-η2: η2-peroxo) dicopper (II) 9 and bis (μ-oxo) dicopper-(III) complexes. 3, 4 Herein, we report a crystal structure of a brown bis (μ-oxo) dicopper (III) complex,[Cu2 (O) 2 (Me2-tpa) 2](PF6) 2 ‚2 (CH3) 2CO (1b) and reversible conversion between 1a and 1b. Complex 1a has a trigonal pyramidal structure with three pyridyl groups in the trigonal plane and tertiary amine in the apex. 10 Reaction of 1a with O2 in acetone/MeOH (10: 1) at-78 C gave a brown solution, from which brown crystals suitable for X-ray crystallography were obtained. 11 Figure 1 shows a crystal structure of the complex cation of 1b which consists of a centrosymmetric Cu2 (μ-O) 2 core with the Me2-tpa nitrogens. Each copper ion has a square planar structure composed of a N2O2 donor set with two 6-methyl-2-pyridylmethyl sidearms which interact weakly with each copper ion in the axial positions (2.48 (1) and 2.55 (1) Å). The average Cu-O (1.803 Å) and Cu ‚‚‚Cu*(2.758 (4) Å) distances are substantially shorter than those of bis-(μ-hydroxo) dicopper (II) complex,[Cu2 (OH) 2 (Me2-tpa) 2](ClO4) 2 (1c) 10 (1.942 Å and 2.9368 (9) Å, respectively), and are comparable to those of bis (μ-oxo) dicopper (III) complexes,[Cu2 (O) 2 (Bn3-tacn) 2] 2+(3; 1.806 and 2.794 Å) 3a, c and [Cu2 (O) 2 (LME) 2] 2+(4; 1.806 and 2.743 Å). 4 The resonance Raman spectrum of 1b measured in acetone (∼ 10 mM) at-80 C with 488.0 nm laser excitation showed an isotope-sensitive band at 590 cm-1 with 16O2 (564 cm-1 with 18O2) shown in Figure 2 (inset …