Single and Double C–H Activation of Biphenyl or Phenanthrene. An Example of C–H Addition to Ir(III) More Facile than Addition to Ir(I)

Abstract

Experimental: General methods and CompoundsGeneral Experimental Methods. All reactions, recrystallizations, and routine manipulations were performed at ambient temperature under argon atmosphere using an argon--filled glove box or by using standard Schlenk techniques. Reagent grade solvents were distilled from sodium/potassium alloy and degassed with argon. Norbornene was purified by sublimation. All deuterated NMR solvents were dried, vacuum--transferred, and stored in an argon--filled glovebox. 1 H and 31 P{ 1 H} NMR spectra were obtained on 400--MHz or 500 MHz Varian spectrometers. 1 H NMR chemical shifts are reported in ppm downfield from tetramethylsilane and were referenced to residual protiated ( 1 H) or deuterated solvent. 31 P{ 1 H} NMR chemical shifts are reported in ppm and were referenced to 85% H3PO4 or a capillary tube containing the external standard Me3P in mesitylene--d12 solvent (δ --62.0 ppm). The compounds tBu4 PCPIrH2 and iPr4 PCPIr(C2H4) were prepared as described in the literature. 14--18 ( tBu4 PCP)Ir(H)(C14H9) (1) tBu4 PCPIrH2 (5.9 mg, 0.010 mmol) was dissolved in 0.5 mL of mesitylene--d12 in a J--Young NMR tube at room temperature, and 2 equivalents of norbornene were added from a stock solution in p--xylene. Phenanthrene (1.1 eq; 0.011 mmol) was added to the resulting solution; after stirring for one minute, the dark red--orange solution turned bright orange. NMR spectra indicate the presence of multiple isomers/rotamers resulting from C--H oxidative addition. 31

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

“…Complex 3 has been independently generated by the reaction of ( tBu PCP)Ir(NBE) with biphenyl (eqn (2)) and was crystallographically characterized (Fig. 3); 38,39 in reaction (1) it may be viewed as the product of C-H elimination followed by C-C addition.…”

Synthesis and Structural Dynamics of Five-Coordinate Rh(III) and Ir(III) PNP and PONOP Pincer Complexes

“…As further precedent, five-coordinate iridium(III) 2,2′-biphenyl complexes of neutral PCP complexes ( C , D ) have previously been reported by Krogh-Jespersen, Goldman, and co-workers. 10,11…”

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

“…The effect of the geometry of the product on the chemoselectivity of C-H/C-F activation reactions in partially fluorinated substrates has been investigated by DFT(B3LYP) calculations for cobalt complexes formed by cyclometalation of Co III with fluorinated phenylimines. Reactions of fluorinated benzophenones with CoMe(PMe 3 ) 4 (Adapted with permission from ref 225; Copyright 2008 Royal Society of Chemistry)The cyclometalation of fluorinated biphenyls and fluorinated anisoles at iridium pincer complexes was discussed in Section 4.2.2.4 190,191. Kinetic and thermodynamic conditions have an impact on the chemoselectivity of the product in cyclometalation reactions at IrIII .…”