Nickel(II) acetylacetonate
2(H2O)2.png) |
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| Names | |
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| Other names
Ni(acac)2, nickel acac
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| Identifiers | |
| ECHA InfoCard | 100.019.887 |
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PubChem CID
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| Properties | |
| C10H14NiO4 or C30H42Ni3O12 (trimer) | |
| Molar mass | 256.91 g/mol |
| Appearance | dark green |
| Density | 1.455 g/cm3 |
| Melting point | 229.5 °C (445.1 °F; 502.6 K) (decomposes) |
| Boiling point | decomposes |
| H2O | |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
Nickel(II) acetylacetonate is a coordination complex with the formula [Ni(acac)2]3, where acac is the anion C5H7O2− derived from deprotonation of acetylacetone, . It is a dark green paramagnetic solid that is soluble in organic solvents such as toluene. It reacts with water to give the blue-green diaquo complex Ni(acac)2(H2O)2.
Anhydrous nickel(II) acetylacetonate exists as molecules of Ni3(acac)6. This structure is not cyclic; the three nickel atoms are approximately collinear and each pair of them is bridged by two μ2 oxygen atoms. Each nickel atom has tetragonally distorted octahedral geometry, caused by the difference in the length of the Ni-O bonds between the bridging and non-bridging oxygens. Ni3(acac)6 molecules are almost centrosymmetric, despite the non-centrosymmetric point group of the cis-Ni(acac)2 "monomers," which is uncommon. The trimeric structure allows all nickel centers to achieve an octahedral coordination. The trimer is only formed if intramolecular sharing of oxygen centers between pairs of nickel centers occurs.
When bound to bulkier analogues of acetylacetonate ligand, steric hindrance favors formation of the mononickel derivatives. This behavior is observed for the derivative of 3-methylacetylacetonate.
As in the anhydrous form, the Ni(II) centres occupy octahedral coordination sites. The coordination sphere is provided by two bidentate acetylacetonate (acac) ligands and two aquo ligands. Ni(acac)2(H2O)2 exists as cis and trans isomers. The trans isomer is preferred over the cis isomer (which was only found when pyridine N-oxide was used as the solvent). In the trans isomer, the X group occupies the axial position, forming Ni-O bonds in ethanol solvents. These axial bonds are greater in length (2.1000Å) than the equatorial Ni-O bonds (2.0085 Å and 1.9961Å).
Bis(2,4-pentanedionato)nickel(II) is prepared by treating nickel nitrate with acetylacetone in the presence of base. The product is the blue-green diaquo complex Ni(CH3COCHCOCH3)2(H2O)2.
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