A Diazabutadiene stabilized Nickel(0) Cyclooctadiene Complex: Synthesis, Characterization and the Reaction with Diphenylacetylene

The reaction of [Ni(COD) 2 ] with one equivalent of DAB Mes (DAB Mes = (2,4,6‐Me 3 C 6 H 2 )N=C(Me)‐C(Me)=N(2,4,6‐Me 3 C 6 H 2 )) affords a mixture of the compound [Ni(DAB Mes ) 2 ] ( 2 ) and starting material [Ni(COD) 2 ]. The crystallographically characterized, diamagnetic complex 2 can be obtained in a stoichiometric reaction of [Ni(COD) 2 ] and two equivalents of DAB Mes . This reaction can be accelerated by addition of 1‐chloro‐fluorobenzene or methyl iodide. In the presence of 1‐chloro‐fluorobenzene, [Ni(DAB Mes )(COD)] ( 3 ) is available via reaction of [Ni(COD) 2 ] and one equivalent of DAB Mes . The crystallographically characterized complex 3 reacts with diphenylacetylene to afford [Ni(DAB Mes )(Ph‐C≡C‐Ph)] ( 4 ). A long‐wavelength absorption band in the UV‐Vis spectrum of this compound has to be assigned to a mixed MLCT/LL′CT transition, as quantum chemical calculations reveal.