Reactions of the Carbyne-Bridged Radical Complex [Mo2(η5‑C5H5)2(μ-CPh)(μ-PCy2)(μ-CO)]+ with Bidentate Ligands Having E–H Bonds (E = O, S, N)
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The benzylidyne complex [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-CO)] (1) reacted with either 2-aminothiophenol or 2-hydroxythiophenol in the presence of 1 equiv of [FeCp2]BF4 to give selectively the corresponding thiolate-bridged derivatives [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-S:S,N-SC6H4NH2)(CO)]BF4 and [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-S:S,O-SC6H4OH)(CO)]BF4 (Cp = η5-C5H5). The latter complex was readily deprotonated by 1,8-diazabicycloundec-7-ene (DBU) to give the phenolate derivative [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-S:S,O-SC6H4O)(CO)] (Mo–Mo = 2.7837(8) Å), with retention of the overall stereochemistry. In contrast, the redox-induced reaction of 1 with 2-aminophenol gave the chelate derivative [Mo2Cp2(μ-CPh)(μ-PCy2)(O,N-OC6H4NH2)(CO)]BF4, whereas the reaction with catechol yielded the O-bound catecholate derivative [Mo2Cp2(μ-CPh)(μ-PCy2)(O-OC6H4OH)(CO)]BF4, an unstable complex that was deprotonated with DBU to give the more stable catechodiolate derivative [Mo2Cp2(μ-CPh)(μ-PCy2)(O,O′-O2C6H4)(CO)], displaying a chelate ligand (Mo–Mo = 2.7850(5) Å). The redox-induced reaction of 1 with benzoic acid still took a different pathway, to eventually yield the benzoate-bridged derivative [Mo2Cp2(μ-CPh)(μ-O:O′-O2CPh)(μ-PCy2)]BF4 (Mo–Mo = 2.577(1) Å). The formation and structures of all the above products could be satisfactorily explained by assuming different elemental steps starting from the radical [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-CO)]+ that follows from the one-electron oxidation of the neutral benzylidyne complex 1.
