Jump to main content
Jump to site search

Issue 4, 2008
Previous Article Next Article

Prototropic rearrangements in cycloheptatrienyl PCP pincer iridium complexes

Author affiliations


When the cycloheptatriene iridium(III) pincer complex (PCP)Ir(CO)(H)(Cl) (3) (PCP = 2,7-(CH2PtBu2)2C7H5) is treated with the bases NaH, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP) under various conditions different products are obtained. At elevated temperatures and with DBU or LiTMP as a base the transdihydride (PCP′)Ir(CO)(H)2 (PCP′ = 2-(CHPtBu2)-7-(CH2PtBu2)C7H4) (5) is formed where the π-system extends into one of the phosphine bridges. This compound loses H2 to give the square-planar iridium(I) carbonyl complex 7 (PCP′IrCO). The dihydride 5 can also rearrange to the new isomeric iridium(I) carbonyl 6 (PCP″IrCO, PCP″ = 2,7-(CH2PtBu2)2C7H5). Thus the two hydrides have moved into the ligand backbone creating a methylene group in the 3-position of the cycloheptatriene ring. Alternatively, 6 is formed by a rearrangement from 6a which differs from 6 by having the methylene group in the 4-position of the cycloheptatriene ring. The iridium(I) carbonyl 6a in turn is made from 3 by treatment with DBU at room temperature. Interestingly, when compound 3 is heated to reflux in THF the hydrogen bound at the metal carbon is shifted to a carbon atom in the cycloheptatriene ring generating a ring methylene group (3a). From this complex HCl is eliminated upon chromatography forming 6 as the final product. Quantum chemical calculations at various levels of theory illustrate the relative energetic stabilities of all iridium complexes.

Graphical abstract: Prototropic rearrangements in cycloheptatrienyl PCP pincer iridium complexes

Back to tab navigation

Supplementary files

Publication details

The article was received on 17 Aug 2007, accepted on 25 Oct 2007 and first published on 09 Nov 2007

Article type: Paper
DOI: 10.1039/B712712J
Citation: Dalton Trans., 2008,0, 527-532
  •   Request permissions

    Prototropic rearrangements in cycloheptatrienyl PCP pincer iridium complexes

    A. M. Winter, K. Eichele, H. Mack, W. C. Kaska and H. A. Mayer, Dalton Trans., 2008, 0, 527
    DOI: 10.1039/B712712J

Search articles by author