Jump to main content
Jump to site search

Issue 43, 2014
Previous Article Next Article

Addition of C–C and C–H bonds by pincer-iridium complexes: a combined experimental and computational study

Author affiliations

Abstract

We report that pincer-ligated iridium complexes undergo oxidative addition of the strained C–C bond of biphenylene. The sterically crowded species (tBuPCP)Ir (RPCP = κ3-1,3-C6H3(CH2PR2)2) initially reacts with biphenylene to selectively add the C(1)–H bond, to give a relatively stable aryl hydride complex. Upon heating at 125 °C for 24 h, full conversion to the C–C addition product, (tBuPCP)Ir(2,2′-biphenyl), is observed. The much less crowded (iPrPCP)Ir undergoes relatively rapid C–C addition at room temperature. The large difference in the apparent barriers to C–C addition is notable in view of the fact that the addition products are not particularly crowded, since the planar biphenyl unit adopts an orientation perpendicular to the plane of the RPCP ligands. Based on DFT calculations the large difference in the barriers to C–C addition can be explained in terms of a “tilted” transition state. In the transition state the biphenylene cyclobutadiene core is calculated to be strongly tilted (ca. 50°–60°) relative to its orientation in the product in the plane perpendicular to that of the PCP ligand; this tilt results in very short, unfavorable, non-bonding contacts with the t-butyl groups in the case of the tBuPCP ligand. The conclusions of the biphenylene studies are applied to interpret computational results for cleavage of the unstrained C–C bond of biphenyl by (RPCP)Ir.

Graphical abstract: Addition of C–C and C–H bonds by pincer-iridium complexes: a combined experimental and computational study

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 06 Jul 2014, accepted on 12 Sep 2014 and first published on 12 Sep 2014


Article type: Paper
DOI: 10.1039/C4DT02043J
Citation: Dalton Trans., 2014,43, 16354-16365
  •   Request permissions

    Addition of C–C and C–H bonds by pincer-iridium complexes: a combined experimental and computational study

    D. A. Laviska, C. Guan, T. J. Emge, M. Wilklow-Marnell, W. W. Brennessel, W. D. Jones, K. Krogh-Jespersen and A. S. Goldman, Dalton Trans., 2014, 43, 16354
    DOI: 10.1039/C4DT02043J

Search articles by author