Heterometallic Derivatives of the Unsaturated Methyl-Bridged Complex [Mo<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>(μ-CH<sub>3</sub>)(μ-PCy<sub>2</sub>)(CO)<sub>2</sub>]. Photochemical Generation of Methylidyne-Bridged Clusters
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The photochemical reactions of the methyl-bridged complex [Mo2Cp2(μ-CH3)(μ-PCy2)(CO)2] (1) (Cp = η5-C5H5) with the carbonyl complexes [M(CO)6] (M = Cr, Mo, W) and [MnCp′(CO)3] (Cp′ = η5-C5H4CH3) give the corresponding electron-precise methylidyne-bridged derivatives [MMo2Cp2(μ3-CH)(μ-PCy2)(CO)7] (Mo−Mo = 2.9340(13) Å for M = W) and [MnMo2Cp2Cp′(μ3-CH)(μ-PCy2)(CO)4] (Mo−Mo = 2.9678(6) Å) in good yields. Under similar conditions, the reaction of 1 with [Ru3(CO)12] gives the 46-electron methylidyne-bridged cluster [Mo2RuCp2(μ3-CH)(μ-PCy2)(CO)5] (Mo−Mo = 2.6824(7) Å), along with a small amount of the methoxy-bridged analogue [Mo2RuCp2(μ3-OCH3)(μ-PCy2)(CO)5]. A related iron species [FeMo2Cp2(μ3-OCH3)(μ-PCy2)(CO)5] (Mo−Mo = 2.667(1) Å) can be prepared in moderate yield from the reaction of the 30-electron methyl complex [Mo2Cp2(μ-κ1:η2-CH3)(μ-PCy2)(μ-CO)] and [Fe2(CO)9]. Compound 1 reacts with [Fe2(CO)9] at room temperature to give the acetyl-bridged cluster [FeMo2Cp2{μ3-κ1:η2:κ1-C(O)CH3}(μ-PCy2)(CO)5] (Mo−Mo = 2.8474(5) Å) in high yield, which undergoes full cleavage of the acetyl C−O bond under thermal or photolytic activation to give the oxoethylidyne derivative [FeMo2Cp2(μ3-CCH3)(μ-PCy2)(O)(CO)4] (Mo−Mo = 2.8469(4) Å). Under photochemical conditions, however, compound 1 reacts with [Fe2(CO)9] to give the methylidyne-bridged compound [Fe2Mo2Cp2(μ4-CH)(μ-PCy2)(CO)8] (Mo−Mo = 2.8351(7) Å) as major species. This 60-electron cluster displays a butterfly Mo2Fe2 core with no agostic interactions of the methylidyne ligand.
