Molybdenum(II) acetate is a coordination compound with the formula Mo<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub>. 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.
Like several other transition metal carboxylate complexes, Mo<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub> adopts a Chinese lantern structure. Each Mo(II) center in Mo<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub> has four d valence electrons. These eight d-electrons form one ÃÂ, two àbonds, and one ô bond, creating a bonding electron configuration of ÃÂ<sup>2</sup>ÃÂ<sup>4</sup>ô<sup>2</sup>. Each of these bonds are formed by the overlapping of pairs of d orbitals. 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 à, and the Mo-Mo distance between the two metal centers is 2.0934 à.
Mo<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub> is prepared by treating molybdenum hexacarbonyl (Mo(CO)<sub>6</sub>) with acetic acid. The process strips CO ligands from the hexacarbonyl and results in the oxidation of Mo(0) to Mo(II).
Trinuclear clusters are byproducts.
The reaction of HO<sub>2</sub>CCH<sub>3</sub> and Mo(CO)<sub>6</sub> 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(O<sub>2</sub>CCH<sub>3</sub>)<sub>2</sub> was tetrahedral. This perspective changed with Mason's characterization.
Mo<sub>2</sub>(O<sub>2</sub>CCH<sub>3</sub>)<sub>4</sub> is generally used as an intermediate compound in a process to form other quadruply bonded molybdenum compounds. The acetate ligands can be replaced to give new compounds such as [Mo<sub>2</sub>Cl<sub>8</sub>]<sup>4âÂÂ</sup> and Mo<sub>2</sub>Cl<sub>4</sub>[P(C<sub>4</sub>H<sub>9</sub>)<sub>3</sub>]<sub>4</sub>.