Nickel(II) acetylacetonate Ni(CH3COCHCOCH3)2, is obtained as emerald green crystals by dehydration of the dihydrate at 50°C in vacuum; it has an unusual trimeric structure in the solid state. The dihydrate Ni(CH3COCH3)2.2H2O is prepared by the addition of acetylacetone to solutions of nickel(II) salts in the presence of a weak base such as sodium acetate. Nickel(II) acetylacetonate is soluble in organic solvents and finds use in the synthesis of organometallic compounds such as nickelocene and bis(cyclooctadiene) nickel. It is also industrially important as a catalyst component in the oligomerization of alkenes and in the conversion of acetylene to cyclooctatetraene.
용도
Nickel(II) acetylacetonate is usefully soluble in organic solvents and is therefore used in
the Grignard synthesis of nickelocene from cyclopentadienyl magnesium halides. More
ionic nickel(II) salts such as the thiocyanate can be reacted with potassium cyclopentadienide
in liquid ammonia.
제조 방법
Nickel(II) acetylacetonate is isolated as the dihydrate Ni(acac)2·2H2O from aqueous
solutions of nickel(II) salts in the presence of acetylacetone and a weak base such as sodium
acetate; it is readily dehydrated to the green anhydrous compound at 50° in vacuo.
From ammoniacal solutions of nickel(II) salts the diammoniate Ni(acac)2·2NH3 precipitates;
this also readily evolves the two extra ligands to give the green acetylacetonate.
Safety Profile
Confirmed human carcinogen. Poison by intraperitoneal route. When heated to decomposition it emits acrid smoke and irritating fumes.
Purification Methods
Wash the green solid with H2O, dry it in a vacuum desiccator and recrystallise it from MeOH. [Charles & Pawlikowski J Phys Chem 62 440 1958.] The complex can be conveniently dehydrated by azeotropic distillation with toluene, and the crystals may be isolated by concentrating the toluene solution. [Wilkinson et al. J Am Chem Soc 76 1970 1954, Beilstein 1 IV 3677.]
