Nickel complexes with heterobutadiene ligands

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