Nickel(II) bis(acetylacetonate)

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Nickel(II) bis(acetylacetonate)
ACACNI01.png
Nickel(II) acetylacetonate.jpg
Names
Other names
Ni(acac)2, nickel acac
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.019.887 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 221-875-7
PubChem CID
UNII
  • InChI=1S/2C5H8O2.Ni/c2*1-4(6)3-5(2)7;/h2*3,6H,1-2H3;/b2*4-3-;
    Key: SHWZFQPXYGHRKT-FDGPNNRMSA-N
  • C/C(=C/C(=O)C)/O.C/C(=C/C(=O)C)/O.[Ni]
Properties
C30H42Ni3O12
Molar mass 770.734 g·mol−1
Appearancedark green
Density 1.455 g/cm3
Melting point 229.5 °C (445.1 °F; 502.6 K) (decomposes)
H2O
Hazards
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Danger
H302, H317, H334, H350
P201, P202, P261, P264, P270, P272, P280, P281, P285, P301+P312, P302+P352, P304+P341, P308+P313, P321, P330, P333+P313, P342+P311, P363, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Nickel(II) bis(acetylacetonate) is a coordination complex with the formula [Ni(acac)2]3, where acac is the anion C5H7O−2 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. [1]

Contents

Structure and properties

Anhydrous nickel(II) acetylacetonate exists as molecules of Ni3(acac)6. 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. [2] Ni3(acac)6 molecules are almost centrosymmetric, despite the non-centrosymmetric point group of the cis-Ni(acac)2 "monomers," which is uncommon. [3] 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. The anhydrous complex has interesting magnetic properties. Down to about 80  K it exhibits normal paramagnetism with an effective magnetic moment of 3.2  μB, close to the spin-only moment expected of a d8 ion with two unpaired electrons. The effective moment rises to 4.1 μB at 4.3 K, due to ferromagnetic exchange interactions involving all three nickel ions. [4]

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. [5]

Dihydrate

Structure of Ni(acac)2(H2O)2. Ni(acac)2(H2O)2.png
Structure of Ni(acac)2(H2O)2.

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. [6] Trans isomers are also observed for Ni(acac)2(pyridine-N-oxide)2. [7] In the trans isomers, the axial Ni–O bonds are greater in length (210.00 pm) than the equatorial Ni–O bonds (200.85 pm and 199.61 pm). [8]

Trans and cis isomers of [Ni(acac)2X2] where X is a coordinating molecule Ni(acac)2.png
Trans and cis isomers of [Ni(acac)2X2] where X is a coordinating molecule

Synthesis

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. [9]

Ni(NO3)2 + 2 CH3COCH2COCH3 + 2 H2O + 2 NaOH → Ni(CH3COCHCOCH3)2(H2O)2 + 2 NaNO3

This complex can be dehydrated using a Dean–Stark trap by azeotropic distillation: [9]

3 Ni(CH3COCHCOCH3)2(H2O)2 → [Ni(CH3COCHCOCH3)2]3 + 6 H2O

Upon heating Ni(acac)2(H2O)2 at 170–210 °C under reduced pressure (0.2–0.4 mmHg, 27–53 Pa), the anhydrous form sublimes and water is removed. [3]

Reactions

The anhydrous complex reacts with a range of Lewis bases to give monomeric adducts. [10] Illustrative is the reaction with tetramethylethylenediamine (tmeda): [11]

[Ni(CH3COCHCOCH3)2]3 + 3 tmeda → 3 Ni(CH3COCHCOCH3)2(tmeda)

Ni(acac)2(H2O)2 reacts quickly in high yield at a methine positions, producing diamides from isocyanates. Related reactions occur with diethyl azodicarboxylate and dimethyl acetylenedicarboxylate:

Ni(acac)2(H2O)2 + 2 PhNCO → Ni(O2C5Me2CONHPh)2 + 2 H2O

Applications

The anhydrous complex is the precursor to nickel-based catalysts such as nickel bis(cyclooctadiene) and tetramethylethylenediamine(dimethyl)nickel(II). [12] [11]

[Ni(acac)2]3 is a precursor for the deposition of a thin film of NiO on conductive glass substrates using sol-gel techniques. [10]

Use of "Ni(acac)2" as the precatalyst. Ni(acac) scheme.tif
Use of "Ni(acac)2" as the precatalyst.

See also

Related Research Articles

<span class="mw-page-title-main">Nickel(II) chloride</span> Chemical compound

Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemical synthesis. The nickel chlorides are deliquescent, absorbing moisture from the air to form a solution. Nickel salts have been shown to be carcinogenic to the lungs and nasal passages in cases of long-term inhalation exposure.

1,5-Cyclooctadiene is a cyclic hydrocarbon with the chemical formula C8H12, specifically [−(CH2)2−CH=CH−]2.

<span class="mw-page-title-main">Tetramethylethylenediamine</span> Chemical compound

Tetramethylethylenediamine (TMEDA or TEMED) is a chemical compound with the formula (CH3)2NCH2CH2N(CH3)2. This species is derived from ethylenediamine by replacement of the four amine hydrogens with four methyl groups. It is a colorless liquid, although old samples often appear yellow. Its odor is similar to that of rotting fish.

<span class="mw-page-title-main">Organonickel chemistry</span> Branch of organometallic chemistry

Organonickel chemistry is a branch of organometallic chemistry that deals with organic compounds featuring nickel-carbon bonds. They are used as a catalyst, as a building block in organic chemistry and in chemical vapor deposition. Organonickel compounds are also short-lived intermediates in organic reactions. The first organonickel compound was nickel tetracarbonyl Ni(CO)4, reported in 1890 and quickly applied in the Mond process for nickel purification. Organonickel complexes are prominent in numerous industrial processes including carbonylations, hydrocyanation, and the Shell higher olefin process.

<span class="mw-page-title-main">Bis(cyclooctadiene)nickel(0)</span> Chemical compound

Bis(cyclooctadiene)nickel(0) is the organonickel compound with the formula Ni(C8H12)2, also written Ni(cod)2. It is a diamagnetic coordination complex featuring tetrahedral nickel(0) bound to the alkene groups in two 1,5-cyclooctadiene ligands. This highly air-sensitive yellow solid is a common source of Ni(0) in chemical synthesis.

Spin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt high-spin and low-spin configurations. The ambiguity only applies to first row metals, because second- and third-row metals are invariably low-spin. These configurations can be understood through the two major models used to describe coordination complexes; crystal field theory and ligand field theory.

<span class="mw-page-title-main">Ruthenium(III) acetylacetonate</span> Chemical compound

Ruthenium(III) acetylacetonate is a coordination complex with the formula Ru(O2C5H7)3. O2C5H7− is the ligand called acetylacetonate. This compound exists as a dark violet solid that is soluble in most organic solvents. It is used as a precursor to other compounds of ruthenium.

<span class="mw-page-title-main">Tris(acetylacetonato)iron(III)</span> Chemical compound

Tris(acetylacetonato) iron(III), often abbreviated Fe(acac)3, is a ferric coordination complex featuring acetylacetonate (acac) ligands, making it one of a family of metal acetylacetonates. It is a red air-stable solid that dissolves in nonpolar organic solvents.

Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion (CH
3COCHCOCH−
3) and metal ions, usually transition metals. The bidentate ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl (RCOCHCOR′−). Many such complexes are soluble in organic solvents, in contrast to the related metal halides. Because of these properties, acac complexes are sometimes used as catalyst precursors and reagents. Applications include their use as NMR "shift reagents" and as catalysts for organic synthesis, and precursors to industrial hydroformylation catalysts. C
5H
7O−
2 in some cases also binds to metals through the central carbon atom; this bonding mode is more common for the third-row transition metals such as platinum(II) and iridium(III).

<span class="mw-page-title-main">Vanadyl acetylacetonate</span> Chemical compound

Vanadyl acetylacetonate is the chemical compound with the formula VO(acac)2, where acac– is the conjugate base of acetylacetone. It is a blue-green solid that dissolves in polar organic solvents. The coordination complex consists of the vanadyl group, VO2+, bound to two acac– ligands via the two oxygen atoms on each. Like other charge-neutral acetylacetonate complexes, it is not soluble in water.

<span class="mw-page-title-main">Aluminium acetylacetonate</span> Chemical compound

Aluminium acetylacetonate, also referred to as Al(acac)3, is a coordination complex with formula Al(C5H7O2)3. This aluminium complex with three acetylacetone ligands is used in research on Al-containing materials. The molecule has D3 symmetry, being isomorphous with other octahedral tris(acetylacetonate)s.

<span class="mw-page-title-main">Iridium acetylacetonate</span> Chemical compound

Iridium acetylacetonate is the iridium coordination complex with the formula Ir(O2C5H7)3, which is sometimes known as Ir(acac)3. The molecule has D3-symmetry. It is a yellow-orange solid that is soluble in organic solvents.

Nickel compounds are chemical compounds containing the element nickel which is a member of the group 10 of the periodic table. Most compounds in the group have an oxidation state of +2. Nickel is classified as a transition metal with nickel(II) having much chemical behaviour in common with iron(II) and cobalt(II). Many salts of nickel(II) are isomorphous with salts of magnesium due to the ionic radii of the cations being almost the same. Nickel forms many coordination complexes. Nickel tetracarbonyl was the first pure metal carbonyl produced, and is unusual in its volatility. Metalloproteins containing nickel are found in biological systems.

<span class="mw-page-title-main">Rhodium acetylacetonate</span> Chemical compound

Rhodium acetylacetonate is the coordination complex with the formula Rh(C5H7O2)3, which is sometimes known as Rh(acac)3. The molecule has D3-symmetry. It is a yellow-orange solid that is soluble in organic solvents.

<span class="mw-page-title-main">Titanium bis(acetylacetonate)dichloride</span> Chemical compound

Titanium bis(acetylacetonate)dichloride is the coordination complex with the formula Ti(C5H7O2)2Cl2. It is a common acetylacetonate complex of titanium. It is a red-orange solid that hydrolyzes slowly in air.

<span class="mw-page-title-main">Tris(acetylacetonato)cobalt(III)</span> Chemical compound

Tris(acetylacetonato)cobalt(III) is the coordination complex with the formula Co(C5H7O2)3. Often abbreviated Co(acac)3, it is a green, diamagnetic solid that is soluble in organic solvents, but not in water. Owing to its solubility in organic solvents, tris(acetylacetonato)cobalt(III) is used to produce homogeneous catalysts by reduction.

<span class="mw-page-title-main">Transition metal pyridine complexes</span>

Transition metal pyridine complexes encompass many coordination complexes that contain pyridine as a ligand. Most examples are mixed-ligand complexes. Many variants of pyridine are also known to coordinate to metal ions, such as the methylpyridines, quinolines, and more complex rings.

<span class="mw-page-title-main">Tris(acetylacetonato)titanium(III)</span> Chemical compound

Tris(acetylacetonato)titanium(III), often abbreviated Ti(acac)3, is a coordination complex of titanium(III) featuring acetylacetonate (acac) ligands, making it one of a family of metal acetylacetonates. It is a blue air-sensitive solid that dissolves in nonpolar organic solvents. The compound is prepared by treating titanium trichloride with acetylacetone in the presence of base. Being paramagnetic, it gives a contact-shifted proton NMR signal at 60 ppm upfield of TMS assigned to the methyl group.

<span class="mw-page-title-main">Tetramethylethylenediamine(dimethyl)nickel(II)</span> Chemical compound

Tetramethylethylenediamine(dimethyl)nickel(II) is the organonickel complex with the formula (Me2NCH2CH2NMe2)NiMe2 (Me = CH3). This yellow-brown, air-sensitive compound is popular precursor to diverse organonickel complexes. It is prepared from the tmeda adduct of nickel(II) acetylacetonate by reaction with methyl lithium.

<span class="mw-page-title-main">Praseodymium acetylacetonate</span> Chemical compound

Praseodymium acetylacetonate is a coordination complex with the formula Pr(C3H7O2)3. This purported anhydrous acetylacetonate complex is widely discussed but only the dihydrate Pr(C3H7O2)3(H2O)2 has been characterized by X-ray crystallography.

References

  1. ↑ R. C. Mehrotra; R. Bohra; D. P. Gaur (1978). Metal β-Diketones and Allied Derivatives. Academic Press. ISBN   0124881505.
  2. ↑ G. J. Bullen, R. Mason & P. Pauling (1961). "Octahedral Co-ordination of Nickel in Nickel(II) Bisacetylacetone". Nature . 189 (4761): 291–292. doi:10.1038/189291a0. S2CID   37394858.
  3. 1 2 G. J. Bullen, R. Mason & P. Pauling. (1965). "The crystal and Molecular Structure of Bis(acetylacetonato)nickel (II)". Inorganic Chemistry . 4 (4): 456–462. doi:10.1021/ic50026a005.
  4. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1157. ISBN   978-0-08-037941-8.
  5. ↑ 1. A. Döhring, R. Goddard, P. W. Jolly, C. Krüger, V. R. Polyakov, "Monomer-Trimer Isomerism in 3-Substituted Pentane-2,4-dione Derivatives of Nickel(II)", Inorg. Chemistry 1997, 36, 177–183. doi : 10.1021/ic960441c
  6. ↑ M. Kudrat-e-Zahan, Y. Nishida & H. Sakiyama (2010). "Identification of cis/trans isomers of bis(acetylacetonato)nickel(II) complexes in solution based on electronic spectra". Inorganica Chimica Acta . 363: 168–172. doi:10.1016/j.ica.2009.09.011.
  7. ↑ B. N. Figgis; M. A. Hitchman (2000). "Ligand Field Theory and its Application".{{cite journal}}: Cite journal requires |journal= (help)
  8. ↑ O. Metin, L. T. Yildirim & S. Ozkar (2007). "Synthesis, characterization and crystal structure of bis(acetylacetonato)dimethanolnickel(II)". Inorganic Chemistry . 10 (9): 1121–1123. doi:10.1016/j.inoche.2007.06.011.
  9. 1 2 Wielandt, J. W.; Ruckerbauer, D. (2010). Bis(1,5-cyclooctadiene)nickel(0). Inorganic Syntheses. Vol. 35. p. 120. doi:10.1002/9780470651568.ch6.
  10. 1 2 Paul A. Williams; Anthony C. Jones; Jamie F. Bickley; Alexander Steiner; Hywel O. Davies; Timothy J. Leedham; Susan A. Impey; Joanne Garcia; Stephen Allen; Aline Rougier; Alexandra Blyr (2001). "Synthesis and Crystal Structures of Dimethylaminoethanol Adducts of Ni(II) Acetate and Ni(II) Acetylacetonate. Precursors for the Sol–Gel Deposition of Electrochromic Nickel Oxide Thin Films". Journal of Materials Chemistry . 11 (9): 2329–2334. doi:10.1039/b103288g.
  11. 1 2 Kaschube, Wilfried; Pörschke, Klaus R.; Wilke, Günther (1988). "Tmeda-Nickel-Komplexe". Journal of Organometallic Chemistry. 355 (1–3): 525–532. doi:10.1016/0022-328X(88)89050-8.
  12. ↑ Göttker-Schnetmann, Inigo; Mecking, Stefan (2020). "A Practical Synthesis of (tmeda)Ni(CH3)2, Isotopically Labeled (tmeda)Ni(13CH3)2, and Neutral Chelated-Nickel Methyl Complexes". Organometallics. 39 (18): 3433–3440. doi:10.1021/acs.organomet.0c00500. S2CID   224930545.
  13. ↑ Shrestha, Ruja; Dorn, Stephanie C. M.; Weix, Daniel J. (2013-01-16). "Nickel-Catalyzed Reductive Conjugate Addition to Enones via Allylnickel Intermediates". Journal of the American Chemical Society. 135 (2): 751–762. doi:10.1021/ja309176h. PMC   3547151 . PMID   23270480.
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