ZUSCHRIFTEN Angew. Chem. 2002, 114, Nr. 12 ¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044-8249/02/11412-2239 $ 20.00+.50/0 2239 Dioxygen Activation by a Mononuclear Ir II ± Ethene Complex Bas de Bruin,* Theo P.J. Peters, Simone Thewissen, Arno N. J. Blok, Jos B. M. Wilting, Rene ¬ de Gelder, Jan M. M. Smits, and Anton W. Gal* In an attempt to gain a mechanistic insight into the rhodium- and iridium-catalyzed oxygenation of olefins, we have recently investigated stoichiometric oxygenation of N ligand Rh I ± and Ir I ±olefin complexes by O 2 (olefin  ethene, propene, 1,5-cyclooctadiene). [1, 2] The reactivity of Rh I ± and Ir I ±ethene fragments towards dioxygen varied between ethene displacement (Figure 1a), formation of mixed O 2 ± ethene complexes (Figure 1b), C O bond making (giving a 3-metalla( iii )-1,2-dioxolane; Fig- ure 1c), and combined C  O bond making and O  O bond breaking (giving a 2-metalla( iii )oxetane; Figure 1d) The outcome of the oxygenation reaction varies with the N ligand and the central metal. Figure 1. Oxygenation products from the reaction of [(N ligand)M I (olefin)]  (M  Rh/Ir) complexes with O 2 . Recently, we described the oxygenation of the iridium( i )± ethene complex [(k 4 -Me 3 -tpa)Ir I (C 2 H 4 )]  (1; Me 3 -tpa  N,N,N-tri((6-methyl-2-pyridyl)methyl)amine) by O 2 to the peroxo±ethene complex [(k 3 -Me 3 -tpa)Ir III (C 2 H 4 )(O 2 )]  (Fig- ure 1b) and unidentified paramagnetic species. [2] We now report the one-electron oxidation of the Ir I ± ethene complex 1 to the unprecedented Ir II ±ethene complex [(k 4 -Me 3 - tpa)Ir II (C 2 H 4 )] 2 (2 ; see Scheme 1), and the reactivity of 2 towards O 2 . Treatment of 1-PF 6 with ferrocinium hexafluorophoshate ([Fc]PF 6 ) in CH 2 Cl 2 resulted in precipitation of 2-(PF 6 ) 2 as a brown powder. Thus, one-electron oxidation of Ir I ±ethene complex 1 with Fc  results in the clean formation of the stable Ir II ± ethene complex 2 (Scheme 1). 1998, 2249±2250; e) J. Renaud, C.-D. Graf, L. Oberer, Angew. Chem. 2000, 112, 3231±3234; Angew. Chem. Int. Ed. 2000, 39, 3101±3104, and references therein. [5] S.-H. Kim, W. J. Zuercher, N. B. Bowden, R. H. Grubbs, J. Org. Chem. 1996, 61, 1073±1081. [6] E. M. Codesido, L. Castedo, J. R. Granja, Org. Lett. 2001, 3, 1483 ± 1486. [7] F.-D. Boyer, I. Hanna, L. Ricard, Org. Lett. 2001, 3, 3095±3098. [8] For pioneering work with platinum complexes, see: a) B. M. Trost, V. K. Chang, Synthesis 1993, 824±832; b) J. Blum, H. Beer-Kraft, Y. Badrieh, J. Org. Chem. 1995, 60, 5567 ± 5569; see also: c) B. M. Trost, G. A. Doherty, J. Am. Chem. Soc. 2000, 122, 3801±3810. [9] a) N. Chatani, N. Furukawa, H. Sakurai, S. Murai, Organometallics 1996, 15, 901 ± 903; b) A. F¸rstner, H. Szillat, B. Gabor, R. Mynott, J. Am. Chem. Soc. 1998, 120, 8305 ± 8314; c) A. F¸rstner, H. Szillat, F. Stelzer, J. Am. Chem. Soc. 2000, 122, 6785 ± 6786; d) A. F¸rstner, F. Stelzer, H. Szillat, J. Am. Chem. Soc. 2001, 123,11863±11869. [10] For studies on a linear dienyne system, see: N. Chatani, K. Kataoka, S. Murai, N. Furukawa, Y. Seki, J. Am. Chem. Soc. 1998, 120,9104±9105. [11] For reactions with external trapping, see: a) M. Me ¬ndez, M. P. Mun ƒoz, A. M. Echavarren, J. Am. Chem. Soc. 2000, 122,11549±11550;b)M. Me ¬ndez, M. P. Mun ƒoz, C. Nevado, D. J. Ca ¬rdenas, A. M. Echavarren, J. Am. Chem. Soc. 2001, 123,10511±10520. [12] CCDC-172245 contains the supplementary crystallographic data for compund 3e. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ, UK; fax: ( 44)1223-336-033; or deposit@ccdc.cam.ac.uk). [13] For a related formation of a tetracyclic derivative with two cyclo- propyl rings from a linear dienyne precursor, see ref. [10]. [14] For further mechanistic data, see: a) N. Chatani, H. Inoue, T. Ikeda, S. Murai, J. Org. Chem. 2000, 65, 4913 ± 4918; b) S. Oi, I. Tsukamoto, S. Miyano, Y. Inoue, Organometallics 2001, 20, 3704±3709. [15] The stereochemical assignment was deduced from NOESY studies. [16] M. H. Chisholm, H. C. Clark, Acc. Chem. Res. 1973, 6, 202±209. [17] For such an intermediate with Ru II complexes, see: D. Pilette, S. Moreau,H. Le Bozec,P. H. Dixneuf, J. F. Corrigan, A. J. Carty, Chem. Commun. 1994, 409±410. [18] G. Mehta, V. Singh, Chem. Rev. 1999, 99, 881±930. [19] a) A. Padwa, K. E. Krumpe, Tetrahedron 1992, 48, 5385 ± 5453; b) T. Ye, A. McKervey, Chem. Rev. 1994, 94, 1091 ± 1160; c) M. P. Doyle in Comprehensive Organometallic Chemistry , Vol. 12 (Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson, L. Hegedus), Pergamon, Oxford, 1995, pp.387±420. [20] a) H.-U. Rei˚ig in The Chemistry of the Cyclopropyl Group (Eds.: S. Patai, Z. Rappoport), Wiley, Chichester, 1987 , pp. 375±443; b) J. Sala¸n in The Chemistry of the Cyclopropyl Group (Eds.: S. Patai, Z. Rappoport), Wiley, Chichester, 1987 , pp. 809±878. [21] The structural±functional assembly present in adducts 3 is partially incorporated in tricyclic DNA derivatives: R. Steffens, C. J. Leumann, J. Am. Chem. Soc. 1999, 121, 3249±3255. [*] Dr. B. de Bruin, Prof. Dr. A. W. Gal, T. P. J. Peters, S. Thewissen, A. N. J. Blok, J. B. M. Wilting, R. de Gelder, J. M. M. Smits Department of Inorganic Chemistry University of Nijmegen Toernooiveld 1, 6525 ED Nijmegen (The Netherlands) Fax: ( 31)24-355-3450 E-mail: bdebruin@sci.kun.nl, gal@sci.kun.nl Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author.