Intermolecular Methyl Group Exchange and Reversible P鈥揗e Bond Cleavage at Cobalt(III) Dimethyl Halide Species

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• 作者：Hongwei Xu ; Paul G. Williard ; Wesley H. Bernskoetter
• 刊名：Organometallics
• 出版年：2013
• 出版时间：February 11, 2013
• 年：2013
• 卷：32
• 期：3
• 页码：798-806
• 全文大小：439K
• 年卷期：v.32,no.3(February 11, 2013)
• ISSN：1520-6041

文摘

The cobalt(III) dimethyl halide complexes cis,mer-(PMe₃)₃Co(CH₃)₂X (X = Cl, I) were found to undergo a degenerate cobalt-to-cobalt transfer of the methyl ligands during isotopic labeling experiments. Extensive mechanistic studies exclude radical, methyl iodide elimination, and disproportionation/comproportionation pathways for exchange of the methyl groups between metals. A related cobalt(III) dimethyl complex supported by the tridentate phosphine ligand MeP(CH₂CH₂PMe₂)₂ showed dramatically slower methyl ligand transfer, indicative of a mechanism for intermetallic exchange with a requisite phosphine dissociation. Crossover experiments between cobalt(III) dimethyl halide complexes supported by PMe₃ and MeP(CH₂CH₂PMe₂)₂ are consistent with a dicobalt transition structure in which only one cobalt center requires phosphine dissociation prior to methyl transfer. An additional methyl group scrambling process between cis,mer-(PMe₃)₃Co(CH₃)₂I and free PMe₃ was also identified during the investigation and originates from reversible P鈥揅H₃ bond cleavage.