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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 12
BKCSDE 17(12)
December 20, 1996 

Cis-Trans Isomerization of Dimeric [Me2Al(μ-NHtBu)]2
Joon T. Park*, Weon Tae Oh, Younsoo Kim
The trans (2a)-cis (2b) isomerization of [Me2Al(μ -NHtBu)]2 (2) has been studied by 1H NMR spectroscopy. The equilibrium has been observed to follow reversible first order kinetics with Δ H0=2.22±0.07 kJmol-1 and ΔS0=2.85±0.07 JK-1mol-1. The activation parameters for the conversion 2a→2b are ΔH1=49.7±2.3 kJmol-1 and ΔS1=-126.3±0.2 JK-1mo1-1 and for the reverse reaction 2b→2a are ΔH-1=47.5±2.3 kJmol-1 and Δ S-1=-129.1±0.5 JK-1mol-1. The isomerization is markedly accelerated in the presence of Lewis bases. A crossover experiment indicates that the isomer interconversion is a unimolecular process. The large negative entropies of activation suggest either the existence of a sterically congested intermediate or the participation of solvent in the isomerization process.
1147 - 1149
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