Tridentate Copper Ligand Influences on Heme-Peroxo-Copper Formation and Properties: Reduced, Superoxo, and -Peroxo Iron/Copper Complex
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- 作者：Eunsuk Kim ; Matthew E. Helton ; Shen Lu ; Pierre Moë ; nne-Loccoz ; Christopher D. Incarvito ; Arnold L. Rheingold ; Susan Kaderli ; Andreas D. Zuberbü ; hler ; and Kenneth D. Karlin
- 刊名：Inorganic Chemistry
- 出版年：2005
- 出版时间：October 3, 2005
- 年：2005
- 卷：44
- 期：20
- 页码：7014 - 7029
- 全文大小：396K
- 年卷期：v.44,no.20(October 3, 2005)
- ISSN：1520-510X
文摘
In cytochrome c oxidase synthetic modeling studies, we recently reported a new 
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2:2-peroxo binding mode inthe heteronuclear heme/copper complex [(2L)FeIII-(O22-)-CuII]+ (6) which is effected by tridentate copper chelation(J. Am. Chem. Soc. 2004, 126, 12716). To establish fundamental coordination and O2-reactivity chemistry, wehave studied and describe here (i) the structure and dioxygen reactivity of the copper-free compound (2L)FeII (1),(ii) detailed spectroscopic properties of 6 in comparisons with those of known -2:1 heme-peroxo-coppercomplexes, (iii) formation of 6 from the reactions of [(2L)FeIICuI]+ (3) and dioxygen by stopped-flow kinetics, and(iv) reactivities of 6 with CO and PPh3. In the absence of copper, 1 serves as a myoglobin model compoundpossessing a pyridine-bound five-coordinate iron(II)-porphyrinate which undergoes reversible dioxygen binding.Oxygenation of 3 below -60 
C generates the heme-peroxo-copper complex 6 with strong antiferromagneticcoupling between high-spin iron(III) and copper(II) to yield an S = 2 spin system. Stopped-flow kinetics in CH2Cl2/6% EtCN show that dioxygen reacts with iron(II) first to form a heme-superoxide moiety, [(EtCN)(2L)FeIII-(O2-)···CuI(EtCN)]+ (5), which further reacts with CuI to generate 6. Compared to those properties of a known-2:1-heme-peroxo-copper complex, 6 has a significantly diminished resonance Raman 
(O-O) stretchingfrequency at 747 cm-1 and distinctive visible absorptions at 485, 541, and 572 nm, all of which seem to becharacteristics of a -2:2-heme-peroxo-copper system. Addition of CO or PPh3 to 6 yields a bis-CO adduct of3 or a PPh3 adduct of 5, the latter with a remaining FeIII-(O2-) moiety.
-2:2-peroxo binding mode inthe heteronuclear heme/copper complex [(2L)FeIII-(O22-)-CuII]+ (6) which is effected by tridentate copper chelation(J. Am. Chem. Soc. 2004, 126, 12716). To establish fundamental coordination and O2-reactivity chemistry, wehave studied and describe here (i) the structure and dioxygen reactivity of the copper-free compound (2L)FeII (1),(ii) detailed spectroscopic properties of 6 in comparisons with those of known -2:1 heme-peroxo-coppercomplexes, (iii) formation of 6 from the reactions of [(2L)FeIICuI]+ (3) and dioxygen by stopped-flow kinetics, and(iv) reactivities of 6 with CO and PPh3. In the absence of copper, 1 serves as a myoglobin model compoundpossessing a pyridine-bound five-coordinate iron(II)-porphyrinate which undergoes reversible dioxygen binding.Oxygenation of 3 below -60 C generates the heme-peroxo-copper complex 6 with strong antiferromagneticcoupling between high-spin iron(III) and copper(II) to yield an S = 2 spin system. Stopped-flow kinetics in CH2Cl2/6% EtCN show that dioxygen reacts with iron(II) first to form a heme-superoxide moiety, [(EtCN)(2L)FeIII-(O2-)···CuI(EtCN)]+ (5), which further reacts with CuI to generate 6. Compared to those properties of a known-2:1-heme-peroxo-copper complex, 6 has a significantly diminished resonance Raman (O-O) stretchingfrequency at 747 cm-1 and distinctive visible absorptions at 485, 541, and 572 nm, all of which seem to becharacteristics of a -2:2-heme-peroxo-copper system. Addition of CO or PPh3 to 6 yields a bis-CO adduct of3 or a PPh3 adduct of 5, the latter with a remaining FeIII-(O2-) moiety.