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Spectroscopic characterization of the oxo-transfer reaction from a bis(µ-oxo)dicopper(III) complex to triphenylphosphine

Pavlova, Svetlana V. and Chen, Kelvin H.-C. and Chan, Sunney I. (2004) Spectroscopic characterization of the oxo-transfer reaction from a bis(µ-oxo)dicopper(III) complex to triphenylphosphine. Dalton Transactions, 2004 (20). pp. 3261-3272. ISSN 1477-9226. http://resolver.caltech.edu/CaltechAUTHORS:PAVdt04

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Abstract

The oxygen-atom transfer reaction from the bis(µ-oxo)dicopper(III) complex [CuIII2(µ-O)2(L)2]2+1, where L =N,N,N,N -tetraethylethylenediamine, to PPh3 has been studied by UV-vis, EPR, 1H NMR and Cu K-edge X-ray absorption spectroscopy in parallel at low temperatures (193 K) and above. Under aerobic conditions (excess dioxygen), 1 reacted with PPh3, giving OPPh3 and a diamagnetic species that has been assigned to an oxo-bridged dicopper(II) complex on the basis of EPR and Cu K-edge X-ray absorption spectroscopic data. Isotope-labeling experiments (18O2) established that the oxygen atom incorporated into the triphenylphosphine oxide came from both complex 1 and exogenous dioxygen. Detailed kinetic studies revealed that the process is a third-order reaction; the rate law is first order in both complex 1 and triphenylphosphine, as well as in dioxygen. At temperatures above 233 K, reaction of 1 with PPh3 was accompanied by ligand degradation, leading to oxidative N-dealkylation of one of the ethyl groups. By contrast, when the reaction was performed in the absence of excess dioxygen, negligible substrate (PPh3) oxidation was observed. Instead, highly symmetrical copper complexes with a characteristic isotropic EPR signal at g= 2.11 were formed. These results are discussed in terms of parallel reaction channels that are activated under various conditions of temperature and dioxygen.


Item Type:Article
Additional Information:© Royal Society of Chemistry 2004. Received 4th May 2004, Accepted 17th August 2004. First published on the web 31st August 2004. This work was supported by Academia Sinica and by grants from the National Science Council (NSC 90-2113-M-001-006, 90-2113-M-001-080 and 91-2113-M-006-006). We are grateful to Dr Jyh-Fu Lee of the Research Division of the National Synchrotron Radiation Research Center (NSRRC), Hsinchu, Taiwan for his kind assistance in the X-ray absorption measurements. We thank Mr Yuh-Sheng Wen for solving the X-ray structure of [CuII2(µ-OH)2(L)2](ClO4)2. We also thank Prof. J.F. Biellmann for helpful discussions. Crystal data. C20H50Cl2Cu2N4O10, M = 704.62, monoclinic, space group P21/c (no. 14), a = 7.6177(10), b = 17.850(3), c = 13.9471(17) , = 122.147(12)°, U = 1605.7(4) 3, T = 298(2) K, Z = 2, µ(Mo-K) = 1.542 mm–1, 3036 reflection measured, 2814 unique (Rint = 0.0220) which were used in all calculations. The final wR(F2) was 0.1084 (all data). CCDC reference number 245728. See http://www.rsc.org/suppdata/dt/b4/b406692h/ for crystallographic data in CIF or other electronic format.
Record Number:CaltechAUTHORS:PAVdt04
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:PAVdt04
Alternative URL:http://dx.doi.org/10.1039/B406692H
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ID Code:7090
Collection:CaltechAUTHORS
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Deposited On:08 Jan 2007
Last Modified:29 Aug 2014 15:21

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