Stoichiometric and catalytic C-Cl activation of Aryl Chlorides using an NHC-stabilized nickel(0) complex

Ni₂(ⁱPr₂Im)₄(COD)] 1 catalyzes the Suzuki-Miyaura-type cross coupling reaction of chlorobenzene and phenylboronic acid efficiently. Compound 1 compares well with other nickel catalyst reported so far with the advantage that no further excess of ligand such as PPh₃ has to be added. Oxidative addition of different aryl chlorides to complex 1 is highly selective for a broad range of substrates, ranging from activated to deactivated aryl chlorides. The stoichiometric reaction of 1 with aryl chlorides (ArCl) afforded complexes of the type trans-Ni(ⁱPr₂Im)₂(Cl)(Ar)] (for Ar = Ph 2, 4-Me(O)CC₆H₄3, 4-H(O)CC₆H₄4, 4-MeOC₆H₄5, 4-H₂NC₆H₄6, 4-F₃CC₆H₄7, 4-ClC₆H₄8, 3-ClC₆H₄9, 2-ClC₅NH₃10 4-FC₆H₄11). All resulting nickel(II) complexes have been fully characterized, in most cases including X-ray diffraction. In contrast to the work described by Matsubara and coworkers just recently on the sterically slightly more demanding Ni(Dip₂Im)₂] system, we have found for the Ni(ⁱPr₂Im)₂] complexes no indication for the formation of three coordinated nickel(I) complexes.