Toggle Main Menu Toggle Search

Open Access padlockePrints

Regioselective Addition of tert-BuNC to the α Carbon Atom of the Allenyl Ligand in [Fe2(CO)6(μ-PPh2){μ-η1:η2α,β-(H)CαCβCγH2}]: Formation of [Fe2(CO)6(μ-PPh2){μ-η1:η1-(tert-BuNC)CCCH3}] and [Fe2(CO)6(μ-PPh2)(μ-η1:η2-{tert-BuNHC(O)CH2}CCH2)] via Competitive 1,3-Hydrogen Migration and Hydrolysis of the Reactive Allene-Bridged Intermediate [Fe2(CO)6(μ-PPh2){μ-η1:η1-(tert-BuNC)HCCCH2}]

Lookup NU author(s): Dr Simon DohertyORCiD, Mark Waugh, Thomas Scanlan, Emeritus Professor Bill CleggORCiD, Dr Mark Elsegood


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Addition of tert-BuN≡C to the σ-η-allenyl complex [Fe2(CO)6(μ-PPh2){μ-η 1:ηα,β2-(H)-Cα=Cβ=CγH 2}] results in nucleophilic addition to Cα to give the μ-η1:η1-∥-alkyne [Fe2(CO)6-(μ-PPh2){μ-η 1:η1-(tert-BuN≡C)C=CCH3}] (2) and the β,γ-unsaturated amide [Fe2(CO)6(6(μ-PPh 2)(μ-η1:η2-{tert-BuNHC(O)CH 2}C=CH2)] (3). Compounds 2 and 3 are proposed to form via initial nucleophilic attack at Cα to give [Fe2(CO)6(μ-PPh2){μ-η 1:η1-(tert-BuNC)-HC=C=CH2}], an unstable zwitterionic allene-bridged intermediate which subsequently undergoes either a 1,3-hydrogen migration to give 2 or hydrolysis by extraneous water to give the β,γ-unsaturated amide 3. An alternative pathway involving initial nucleophilic attack at Cβ to give the metallacyclopentene intermediate [Fe2(CO)6(μ-PPh2){μ-η 1:η1-HC=C(tert-BuNC)CH2}], followed by 1,3-hydrogen migration and Cβ to Cα tert-BuN≡C migration has been considered. Isotope labeling experiments using [Fe2(CO)6(μ-PPh2){μ-η 1:ηα,β2-(D)-Cα=Cβ=CγH 2}] (1-d1) are consistent with a large primary kinetic isotope effect for the transfer of hydrogen between Cα and Cγ. Addition of excess isopropylamine to a hexane solution of 2 gave the amidinium-substituted μ-η1:η1-parallel alkyne derivative [Fe2(CO)6(μ-PPh2){μ-η 1:η1-C(tert-BuHNC)(NHPri)C=CCH 3}] (4), in near quantitative yield via addition of N-H across the C-N multiple bond. Chloroform solutions of 3 smoothly decarbonylate over several days to afford [Fe2(CO)5(μ-PPh2)(μ-η 1(C):η1(O):η2(C)-{tert-BuNHC(O)CH 2}C=CH2)] (5), which contains a five-membered metallacycle by virtue of coordination of the amide carbonyl oxygen atom. The single-crystal X-ray structures of 2, 4, and 5 are reported.

Publication metadata

Author(s): Doherty S, Hogarth G, Waugh M, Scanlan TH, Clegg W, Elsegood MRJ

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 1999

Volume: 18

Issue: 16

Pages: 3178-3186

Print publication date: 02/08/1999

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society


DOI: 10.1021/om9901630


Altmetrics provided by Altmetric