Metal(II) Complexes of the Carbonylnitronate Ligands O2NCHC(O)R- (R = Ph, OMe or OEt) and X-ray Structure of (DMANH)[Ni(O2CHC(O)Ph)3] (DMANH = 1,8-bis(dimethylamino)naphthalene)

New coordination compounds involving carbonylnitronate ligands O2NCHC(O)R- (R = Ph, OMe or Oft) are prepared by a synthetic procedure based on the reaction of a nickel(II) or palladium(II) salt with benzoylnitromethane or alkyl nitroacetate in the presence of a deprotonating agent. The use of the proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) in tetrahydrofuran affords, in high yields, the anionic complexes (DMANH)[Ni(O2NCHC(O)R)(3)] as brilliant green solids. The benzoylnitronate complex (R = Ph) crystallises in a monoclinic unit cell [space group P2(1)/n, a = 13.061(2), b = 16.415(2), c = 17.827(2) Angstrom, beta = 102.7(2)degrees], which contains four octahedral anionic nickel complexes each close to a big DMANH (+) cation. One nitronate ligand is easily replaced by two molecules of ethanol to give the neutral complexes [Ni(O2NCHC(O)R)(2)(EtOH)(2)]. The nickel is O,O'-coordinated to the ligand through one carbonyl and one nitro oxygen atom. A different coordination mode, in which only the nitro group is bonded to the metal, is, however, observed in the palladium complexes [PdCl(O2NCHC(O)R)](2) (R = OMe, Oft).