Molybdenum(II) acetate

Molybdenum(II) acetate is a coordination compound with the formula Mo2(O2CCH3)4. It is a yellow, diamagnetic, air-stable solid that is slightly soluble in organic solvents. Molybdenum(II) acetate is an iconic example of a compound with a metal-metal quadruple bond.[1]

Molybdenum(II) acetate
Names
Other names
Dimolybdenum tetraacetate,
tetra (aceto) dimolybdenum,
Molybdenum(II) acetate dimer
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.034.611
EC Number
  • 238-089-5
Properties
C8H12Mo2O8
Molar mass 428.1010 g/mol
Appearance Yellow solids
Boiling point decomposes
not soluble
Hazards
Safety data sheet External MSDS
R-phrases (outdated) 20/21/22, 36/37/38
S-phrases (outdated) 7/9, 22, 24/25, 29/35, 42, 43, 64
Related compounds
Related compounds
 Copper(II) acetate
Chromium(II) acetate
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

Structure and bonding

It adopts the same Chinese lantern structure as related acetate dimers such as rhodium(II) acetate, copper(II) acetate, and chromium(II) acetate.[2] Each Mo(II) center in Mo2(O2CCH3)4 has four d valence electrons. These eight d-electrons form one σ, two π bonds, and one δ bond, creating a bonding electron configuration of σ2π4δ2. Each of these bonds are formed by the overlapping of pairs of d orbitals.[3] The four acetate groups bridge the two metal centers. The Mo-O bond between each Mo(II) center and O atom from acetate has a distance of 2.119 Å, and the Mo-Mo distance between the two metal centers is 2.0934 Å.

Preparation

Mo2(O2CCH3)4is prepared by treating molybdenum hexacarbonyl (Mo(CO)6) with acetic acid. The process strips CO ligands from the hexacarbonyl and results in the oxidation of Mo(0) to Mo(II).[4][5]

2 Mo(CO)6 + 4 HO2CCH3 → Mo2(O2CCH3)4 + 12 CO + 2 H2

Trinuclear clusters are byproducts.[6]

The reaction of HO2CCH3 and Mo(CO)6 was first investigated by Bannister et al. in 1960. At the time, quadruple metal-metal bonds had not yet been discovered, so these authors proposed that Mo(O2CCH3)2 was tetrahedral.[7][8] This perspective changed with Mason's characterization.[9]

Applications

Mo2(O2CCH3)4 is generally used as an intermediate compound in a process to form other quadruply bonded molybdenum compounds.[1] The acetate ligands can be replaced to give new compounds such as [Mo2Cl8]4− and Mo2Cl4[P(C4H9)3]4.[1][10][11]

References
  1. Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., "Synthesis and Technique in Inorganic Chemistry third edition", University Science Books: Mill Valley, CA, 1999, ISBN 0-935702-48-2
  2. Cotton, F. A.; Hillard, E.A.; Murillo, C. A.; Zhou, H.-C. "After 155 Years, A Crystalline Chromium Carboxylate with a Supershort Cr-Cr Bond" J. Am. Chem. Soc., 2000, 122, 416-417. doi:10.1021/ja993755i.
  3. Blaudeau, J. P.; Pitzer, R. M. “ Ab Initio Studies of Ligand Effects on the Metal-Metal Bond in Dimolybdenum Complexes” J.Phys. Chem. 1994, vol. 98, pp. 4575-4579.
  4. Brignole, A.G.; Cotton, F.A., “Rhenium and Molybdenum compounds containing quadruple compounds” Inorg. Synth. 1972, volume 13, pp. 81-89. doi:10.1002/9780470132449.ch15
  5. Pence, L. E.; Weisgerber, A. M.; Maounis, F.A.; “Synthesis of Molybdenum-Molybdenum Quadruple Bonds” J. Chem. Educ., 1999, vol. 76, 404-405.
  6. Bino,A.; Cotton, F.A.; Dori, A.; J. Am. Chem. Soc. 1981, vol. 103, pp. 243-244. “A Aqueous New Chemistry of Organometallic, Trinuclear Cluster Compounds of Molybdenum”.
  7. Bannister, E.; Wikinson, G. “Molybdenum(II) carboxylates” Chem. Ind. 1960, 319.
  8. Stephenson, T.A.; Bannister, E.; Wilkinson, G. “Molybdenum(II) Carboxylates” J. Chem. Soc., 1964, pp. 2538. doi:10.1039/JR9640002538
  9. D. Lawton, R. Mason "The Molecular Structure of Molybdenum(II) Acetate"J. Am. Chem. Soc. 1965, vol 87, pp 921–922. doi:10.1021/ja01082a046
  10. Tsai, Y.C.; Chen H.Z.; Chang, C.C.; Yu, J.K.; Lee, G.H.; Wang, Y.; Kuo, T.S. “Journey from Mo-Mo Quadruple Bonds to Quintuple Bonds” J. Am. Chem. Soc.,2009, 131, 12534-12535. doi:10.1021/ja905035f
  11. Handa, M.; Mikuriya, M.; Kotera, T.; Yamada, K.; Nakso, T.; Matsumoto, H.; Kasuga, K. “Linear Chain Compounds of Molybdenum(II) Acetate Linked by Pyazine, 4,4’-Bipyridine,and 1,4- Diazabicyclo[2.2.2]octane” Bull. Chem. Soc. Jpn., 1995,68, 2567-2572.
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