Nickel complexes with heterobutadiene ligands

The reactions of 4,4-bis(trifluoromethyl)-substituted hetero-1,3-dienes with Ni(cod)₂ and Ni(PMe₃)₂(cod) afford stable coordination compounds containing a trigonal planar Ni(0) center. The substitution of co-ligands by tert-butylisonitrile leads to five-membered nickelacycles by an unprecedented oxidative [4+1] cycloaddition of the hetero-1,3-diene to Ni(0) under formation of new Ni-C and Ni-O or Ni-N bonds. The nature of the resulting nickelacycloheteropentene derivatives decisively depends on the electronic and steric nature of the hetero-1,3-dienes. All compounds have been characterized by NMR, IR, or mass spectroscopy. X-ray crystal structure determinations are reported for four typical examples.