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Quantitative Determination of the Regioselectivity of Nucleophilic Addition to η3-Propargyl Rhenium Complexes and Direct Observation of an Equilibrium between η3-Propargyl Rhenium Complexes and Rhenacyclobutenes.
2009 (English)In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 28, no 1, 123-131 p.Article in journal (Refereed) Published
Abstract [en]

PMe3 adds selectively to the central C of the η3-propargyl complex [C5Me5(CO)2Re(η3-CH2C≡CCMe3)][BF4] (1-t-Bu) to form the metallacyclobutene [C5Me5(CO)2Re(CH2C(PMe3):CCMe3)][BF4] (7). The rate of rearrangement of the metallacyclobutene 7 to η2-alkyne complex [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)][BF4] (8) is independent of phosphine concn., consistent with a dissociative mechanism proceeding via η3-propargyl complex 1-t-Bu. The rate of this rearrangement is 480 times slower than the rate of exchange of PMe3 with the labeled metallacyclobutene 7-d9. This rate ratio provides an indirect measurement of the regioselectivity for addn. of PMe3 to the central C of η3-propargyl complex 1-t-Bu to give 7 compared to addn. to a terminal C to give 8. The addn. of PPh3 to 1-t-Bu gives the metallacyclobutene [C5Me5(CO)2Re(CH2C(PPh3):CCMe3)][BF4] (11). Low-temp. 1H NMR spectra provide evidence for an equil. between metallacyclobutene 11 and η3-propargyl complex 1-t-Bu (Keq ≈ 44 M-1 at -46° and ΔG°(0°) = -1.2 ± 0.2 kcal mol-1). The crystal and mol. structures of [C5Me5(CO)2Re[η2-(Ar2PCH2CH2PPh2)CH2C≡CCMe3]][BF4]·2CH2Cl2 (Ar = 3,5-(CF3)2C6H3) and [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)]Cl·H2O were detd. by x-ray crystallog. [on SciFinder(R)]

Place, publisher, year, edition, pages
2009. Vol. 28, no 1, 123-131 p.
Keyword [en]
rhenium cyclopentadienyl carbonyl propargyl complex nucleophilic addn phosphine regioselectivity, crystal structure rhenium cyclopentadienyl carbonyl alkynylphosphonioethylphosphine alkynylphosphonium complex, mol structure rhenium cyclopentadienyl carbonyl alkynylphosphonioethylphosphine alkynylphosphonium complex, kinetics phosphine nucleophilic addn rhenium propargyl complex, exchange rearrangement kinetics thermodn phosphoniorhenacyclobutene
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-174513DOI: 10.1021/om800739jOAI: oai:DiVA.org:uu-174513DiVA: diva2:527606
Note
CAPLUS AN 2008:1418835(Journal)Available from: 2012-05-21 Created: 2012-05-21 Last updated: 2017-12-07

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Samec, Joseph S. M.

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