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Science 10 October 2003:
Vol. 302. no. 5643, pp. 259 - 262
DOI: 10.1126/science.1089145
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Reports

Phosphadioxirane: A Peroxide from an Ortho-Substituted Arylphosphine and Singlet Dioxygen

David G. Ho,* Ruomei Gao,* Jeff Celaje, Ha-Yong Chung, Matthias Selke{dagger}

We prepared the primary adduct for the reaction of singlet dioxygen (1O2) with an arylphosphine by using the sterically hindered arylphosphine tris(o-methoxyphenyl)phosphine. The resulting phosphadioxirane has a dioxygen molecule triangularly bound to the phosphorus atom. Olefin trapping experiments show that the phosphadioxirane can undergo nonradical oxygen atom–transfer reactions. Under protic conditions, two different intermediates are formed during the reaction of singlet dioxygen with tris(o-methoxyphenyl)phosphine, namely, the corresponding hydroperoxy arylphosphine and a hydroxy phosphorane. Experiments with other arylphosphines possessing different electronic and steric properties demonstrate that the relative stability of the tris(o-methoxyphenyl)phosphadioxirane is due to both steric and electronic effects.

Department of Chemistry and Biochemistry, California State University, Los Angeles, Los Angeles, CA 90032, USA.



Note added in proof: Our kinetic data are also consistent with slow unimolecular conversion of the phosphadioxirane to a triplet phosphine oxide–oxygen complex followed by rapid reaction with phosphadioxirane leading to formation of phosphine oxide and triplet dioxygen. At present we do not have any experimental evidence for the formation of the triplet intermediate species (20).

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: mselke{at}calstatela.edu

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