Studies on Mixed Chelates. XVII. Crystal Structure and Spectral Properties of Mixed Nickel(II) Nitrate Complexes Containing 1,2-Dipiperidinoethane and β-Diketonate Ligands

Abstract Several new mixed nickel(II) nitrate complexes with 1,2-dipiperidinoethane (dipe) and β-diketonate ions (dike), [Ni(NO3)(dike)(dipe)], have been obtained and characterized. The crystal structure of one of them, [Ni(NO3)(acac)(dipe)], was determined by X-ray crystallography. The crystal is monoclinic with the space group Cc, Z=4, a=9.0517(4), b=21.932(1), c=9.8814(6) Å, β=88.151°. Block-diagonal least-squares refinements have led to a final R value of 0.036 for 2471 reflections. It was confirmed that the nitrate ion in the octahedral complex acts as a bidentate ligand and that the conformation of the piperidine ring in dipe is a chair form. The spectral behaviors of these complexes in various organic solvents are discussed in comparison with those of similar complexes with other N,N′-alkylated ethylenediamine ligands (diam). It was concluded that, in a solvent with low polarity, the complexes are dissolved unchanged; in a more polar solvent, however, dissociation of NO3− takes place, producing solvated or unsolvated cationic species ([Ni(dike)(diam)(Solvent)2]+ (Oh) or [Ni(dike)(diam)]+ (Square Planar)) according to the donor and acceptor properties of the solvent.