8865
. I . Ani. Chem. SOC.1995. 117, 8865-8866
A New Intermediate in Copper Dioxygen Chemistry: Breaking the 0-0 Bond To Form a ( C U , ( ~ - O ) ~Core }~'
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Samiran Mahapatra, Jason A. Halfen. Elizabeth C. Wilkinson, Gaofeng Pan, Christopher J. Cramer, Lawrence Que, Jr..* and William B. Tolman* Deporrnienr of Chemisrv and Superconipufer lnsrirure Uniuersin, of Minnesota. 207 Pleosonr Srreer SE Minneapolis. Minnesorn 55455
160*-'80,
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Received May 8. 1995
The significance of the binding and activation of dioxygen by copper ions in biological and catalytic systems has stimulated extensive research oriented toward uncovering the fundamental chemistry invo1ved.l A key prerequisite for understanding the course of substrate oxidations promoted by copper ions is identification of the initial product of the reaction of Cu(1) with 02. The recent definitive characterization of dicopper(l1) peroxo? and monocopper(l1) superoxo' complexes has provided important insights into the initial stages of dioxygen binding and activation, hut much remains to he learned about the order and nature of subsequent 0-0 bond cleavage and substrate oxidation events. Herein we report the isolation, spectroscopic and theoretical characterization, and C-H bond activation chemistry of a new species derived from the reaction of a Cu(I) complex with dioxygen. The proposed {Cu?&-O)z}'+ core of this molecule is unprecedented in copper chemistry' and may be viewed as a possible intermediate in oxidation reactions catalyzed by multicopper enzymes and small-molecule catalysts. We recently reported that addition of 0 2 to [(i-Pr,TACN)Cu(CH>CN)]OiSCF>in C H G at -80 "C reversibly afforded a Ol-~?:'l?-peroxo)dicopper(II)complex (1, Scheme I ) that was formulated on the basis of a low vu-o in its resonance Raman spectrum [722 cm-I; A V ( ' ~ O ?= ) 42 cm-l), EPR silence, and diagnostic UV-vis features [A,,,,,y = 365 ( F I I 000 M-l cm-I), 510 (1000) nm] (Figure l).2c,s When the same reaction was performed using [(Bn?TACN)Cu(CH?CN)]X (X = CIOa- or SbFa-) as starting material." rapid uptake of 1 O? per 2.2(2) Cu(l) ions (by manometry, average of five runs) and formation of an orange-brown species 2 (Scheme I ) with spectroscopic features clearly distinct from those exhibited by 1 were observed [Figure 1, A,,,,&, = 318 (t 6000 M-I cm-0, 430 (7000)nm]. Like 1, however, 2 decomposed upon warming to afford a bluegreen solution. from which a bis&-hydroxo)dicopper(II) comAurhors to whom correspondence should he addressed. I I)la1 Kitajima. N.: Moro~oka.Y . Cizrrn. R I I , . 1994.91. 737-757. i b ) Karlin. K. D.: TyeklAr. Z.: Zuherbuhler. A. D. In B i o i w r y m k Cm~l).~i.s: Reediik. 1.. Ed.: Marcel Dekker. Inc.: New York. 1993: 00 261-315. icl
F.: Root. D. E.: Brown. C. A. Ciier,!. Rev. 1994.Y4.827-USh. iel Solomon. E. I . : Bnldwin. M. J.: Lowery. M. D. CArn,. Rev. 1992.YZ. 521-542. 121 i a l Kirajima. N.: Fujisawa. K.: Fujimoto. C.: Moro-okn. Y . : Hashimotu. S.: Kitagnwa. T.: Toriumi. K.: Tatsumi. K.: Nakamura. A. 1. Am. Cbrrri. S r r 1992.114. 1277-lZYl. ihlTyekl5r.Z.: Jacobson. R. R.: Wei. N.: Munh?. N. N.:Zohiera. J.: Karlin. K. D. J. A m Clion. .So
