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Reaction of Phosphites with the Electrophilic Allenyl Complex [Fe2(CO)6(μ-PPh2){μ-η12-(H)CαCβCγH2}]:  Stepwise Transformation of a μ-η12-Allenyl into a μ-η12-Acetylide vs Phosphite Activation

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journal contribution
posted on 30.09.1997, 00:00 by Simon Doherty, Mark R. J. Elsegood, William Clegg, Mark F. Ward, Mark Waugh
Nucleophilic addition of P(OR)3 (R = Me, Et) to the electrophilic allenyl ligand in [Fe2(CO)6(μ-PPh2){μ-η12-(H)CαCβCγH2}] (1) affords the β,γ-unsaturated phosphonate-bridged complexes [Fe2(CO)6(μ-PPh2)(μ-η12-(CH3)CCH{PO(OR)2})], which we suggest result either from an Arbuzov-type dealkylation or a direct nucleophilic attack of water on the phosphorus atom of a zwitterionic phosphonium intermediate. In contrast, in the presence of PhC⋮CLi, which acts to remove extraneous water from the reaction mixture, P−Cα bond formation followed by a 1,3-hydrogen migration gives [Fe2(CO)6(μ-PPh2)(μ-η11-(CH3)CC{P(OR)3})] as the dominant product.