Ruthenium(III) acetylacetonate

Ruthenium(III) acetylacetonate
IUPAC name

Tris(acetylacetonato)Ruthenium (III)
Other names

Ru(acac)3; Ruthenium (III) 2,4-Pentanedionate; Ruthenium (III) acetylacetonato, 2,4-pentanedione ruthenium (III)
Identifiers
CAS number 14284-93-6 Y
Properties
Molecular formula (C5H7O2)3Ru
Appearance Dark Violet Solid
Density 1.54 g/cm3[1]
Melting point

260 °C
Solubility in water insoluble in water
Solubility soluble in most organic solvents
Hazards
R-phrases R36, R37, R38
S-phrases S26, S36
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Ruthenium(III) acetylacetonate is a coordination complex with the formula Ru(acac)3, where acac is acetylacetonate. This compound exists as a dark violet solid that is soluble in most organic solvents. It is an example of a homoleptic trisacetylacetonato complex, that is a complex that only has acac ligands.[2]

Preparation

First described in 1914, tris(acetylacetonato)ruthenium (III) was first prepared by the reaction of ruthenium(III) chloride and acetylacetone in the presence of potassium bicarbonate.[3] Since then, alternative synthetic routes have been examined, but the original procedure remains useful with minor variations:[4]

RuCl3•3H2O + MeCOCH2COMe → Ru(acac)3 + 3 HCl + 3 H2O

Structure and properties

This compound has idealized D3 symmetry. Six oxygen atoms surround the central ruthenium atom in an octahedral arrangement. The average Ru-O bond length in Ru(acac)3 is 2.00 Å.[1] The complex is low spin with five d-electrons. Because Ru(acac)3 is low spin, there is one unpaired d electron, causing this compound to be paramagnetic. Ru(acac)3 has a magnetic susceptibility, χM, of 3.032×10−6 cm3/mol with an effective magnetic moment, μeff, of 1.66 μB.[5] As a solution in DMF, the compound oxidizes at 0.593 and reduces at -1.223 V vs the ferrocene/ferrocenium couple.[6]

Reduction of Ru(acac)3 in the presence of alkenes affords the related diolefin complexes. Typically, such reactions are conducted with zinc amalgam in moist tetrahydrofuran:[7]

2 Ru(acac)3 + 4 alkene + Zn → 2 Ru(acac)2(alkene)2 + Zn(acac)2

The resulting compounds are rare examples of metal-alkene complexes that reversibly sustain oxidation:

Ru(acac)2(alkene)2 \overrightarrow{\leftarrow} [Ru(acac)2(alkene)2]+ + e-

References

  1. ^ a b Chao, G.; Sime, R. L.; Sime, R. J. (1973). "Crystal and molecular structure of tris(acetylacetonato)ruthenium(III)". Acta Crystallographica B 29 (12): 2845. doi:10.1107/S0567740873007636. 
  2. ^ R.C. Mehrotra, R. Bohra, and D.P. Gaur "Metal β-Diketonates and Allied Derivatives", 1st ed.; Academic Press inc.: New York, 1978. ISBN 0124881505.
  3. ^ Barbieri, G. A. (1914). "Systematic chemical investigations: ruthenium, rhodium, palladium". Atti accad, Lincei 23 (1): 334–40. 
  4. ^ Gupta, A. (2000). "Improved synthesis and reactivity of tris(acetylacetonato)ruthenium(III)". Indian journal of chemistry. Section A, Inorganic, bio-inorganic, physical, theoretical & analytical chemistry 39A (4): 457. ISSN 0376-4710. 
  5. ^ Grobelny, R. (1966). "The absorption spectra and magnetic properties of the chelated compounds of Ru(III) with β-diketones". Journal of inorganic and nuclear chemistry 28 (11): 2715. doi:10.1016/0022-1902(66)80398-6. 
  6. ^ Paul Sharpe, N. George Alameddin, David E. Richardson (1994). "Alkyl Substituent Effects in the Redox Thermochemistry of Coordination Compounds: Oxidation and Reduction Energetics for Ruthenium Tris(β-diketonate) Complexes in Solution and the Gas Phase". Journal of the American Chemical Society 116 (24): 11098–11108. doi:10.1021/ja00103a027. 
  7. ^ Bennett, M. A.; Byrnes, Matthew J.; Kováčik, Ivan (2004). "The fragment bis(acetylacetonato)ruthenium: a meeting-point of coordination and organometallic chemistry". Journal of Organometallic Chemistry 689 (24): 4463. doi:10.1016/j.jorganchem.2004.07.027.