Double Cyclometalation: Implications for C—H Oxidative Addition with PCP Pincer Compounds of Iridium
2004; American Chemical Society; Linguagem: Inglês
10.1021/bk-2004-0885.ch014
ISSN1947-5918
AutoresHani A. Y. Mohammad, Jost C. Grimm, Klaus Eichele, Hans‐Georg Mack, Bernd Speiser, Filip Novák, William C. Kaska, Hermann A. Mayer,
Tópico(s)Coordination Chemistry and Organometallics
ResumoTreatment of 4-X-C6H3-2,6-(CH2P'Bu2)2 (X = H (1), NO2 (2), MeO (3)) with IrCl3 nH2O in 2-propanol/water generates the corresponding cyclometalated pincer chlorohydrido iridium complexes (1a - 3a). In the case of 3, a second intramolecular oxidative addition reaction of one of the t-butyl C-H bonds to the Ir(III) center, followed by the reductive elimination of H2, gives the novel doubly metalated compound 3b, which is stable to air and water. Comparative electrochemical studies of 1a and 3a establish an equilibrium between the pincer chlorohydrido compound and the doubly metalated complexes 1b, 3b and H2. A square scheme can be used to describe the relationship between the redox couples and solution equilibria. Interestingly the oxidation product 1b+ undergoes a faster follow-up reaction as 3b+. The unusual stability of the doubly metalated complex was supported by DFT calculations at different levels of theory on model compounds.
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