1234673-05-2Relevant articles and documents
Monoanionic bis(carbene) pincer complexes featuring cobalt(I-III) oxidation states
Ibrahim, Abdulrahman D.,Tokmic, Kenan,Brennan, Marshall R.,Kim, Dongyoung,Matson, Ellen M.,Nilges, Mark J.,Bertke, Jeffery A.,Fout, Alison R.
, p. 9805 - 9811 (2016)
The synthesis and characterization of a series of cobalt complexes featuring a pincer bis(carbene) ligand of the meta-phenylene-bridged bis-N-heterocyclic carbene (ArCCC, Ar = 2,6-diispropylphenyl or mesityl) are reported. Cleavage of the aryl C-H bond of the ligand was achieved in a one-pot metalation procedure using Co(N(SiMe3)2)2(py)2, an equivalent of exogenous base, and trityl chloride to form the (DIPPCCC)CoCl2py complex. This species could be reduced to the Co(ii) and Co(i)-N2 molecules with the appropriate equivalents of reductant. Subsequent generation of (MesCCC)CoI-III derivatives with the mesityl ligand proceeded in good yields. A suite of characterization techniques and the interconversion between all three oxidation states of the cobalt complexes is described.
Lowering the barrier to C?H activation at IRIII through pincer ligand design
Chu, Wan-Yi,Goldberg, Karen I.,Rubashkin, Sophie B.
, p. 1296 - 1302 (2021)
Selective C?H activation of benzene and n-octane under mild conditions by a pincer IrIII carboxylate complex, (CCCMesityl)Ir(OAc)2(OH2) (1a), is described. A kinetic study of benzene activation was undertaken, and the resulting Eyring analysis informed the design of a tButylCCCMethyl-ligated IrIII carboxylate, which exhibited a ΔG? value for the reaction lower than that observed for 1a. Elimination of the aquo ligand was found to further lower the ΔG? value of benzene activation, enabling C?H activation by IrIII at temperatures as low as 30 °C.
Iridium complexes of CCC-pincer N-heterocyclic carbene ligands: Synthesis and catalytic C-H functionalization
Chianese, Anthony R.,Mo, Allen,Lampland, Nicole L.,Swartz, Raymond L.,Bremer, Paul T.
scheme or table, p. 3019 - 3026 (2010/10/03)
A series of four meta-phenylene-bridged bis-benzimidazolium chlorides were synthesized as precursors to rigid, monoanionic, CCC-pincer N-heterocyclic carbene ligands. For ligands with mesityl, 3,5-xylyl, or 3,5-di-tert-butylphenyl side groups, reaction with [Ir(1,5-cyclooctadiene)Cl]2 in acetonitrile with either excess triethylamine or stoichiometric cesium fluoride as base gave neutral, iridium(III) pincer complexes of the formula Ir(CCC)HCl(MeCN), which were purified by chromatography on silica gel. Metalation failed under these conditions for a 2,6-diisopropylphenyl-substituted derivative. In combination with NaOtBu, these complexes form active catalysts for the acceptorless dehydrogenation of cyclooctane and for arene C-H borylation in neat arene solvent.
