Monoanionic bis(carbene) pincer complexes featuring cobalt() oxidation states

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 ( Ar CCC, 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(SiMe 3 ) 2 ) 2 (py) 2 , an equivalent of exogenous base, and trityl chloride to form the ( DIPP CCC)CoCl 2 py complex. This species could be reduced to the Co( ii ) and Co( i )-N 2 molecules with the appropriate equivalents of reductant. Subsequent generation of ( Mes CCC)Co I-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. 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 ( Ar CCC, Ar = 2,6-diispropylphenyl or mesityl) are reported.