The kinetics of methanolysis of the title compound (3) were studied in the presence of Cu2+, introduced as Cu(OTf)2, in the presence of 0.5–1.0 eq. of methoxide and in the presence of 1.0 eq. of a ligand such as bipyridyl (5), phenanthroline (6) or 1,5,9-triazacyclododecane (4). In all cases the active species involve Cu2+(−OCH3). In the case of added strong-binding ligands 5 or 6, a plot of the observed rate constant for methanolysis of 3vs. [Cu2+]total gives a curved line modelled by a process having a [Cu2+]1/2 dependence consistent with an active monomeric species in equilibrium with an inactive dimer i.e.
{LCu2+(−OCH3)}2
⇆ 2
LCu2+(−OCH3). In the case of the added strong binding ligand 4, the plot of the observed rate constant for methanolysis of 3vs.
[Cu2+]total gives a straight line consistent with the catalytically active species being 4Cu2+(OCH3) which shows no propensity to form inactive dimers. Turnover experiments where the [3] > [Cu2+]total indicate that the systems are truly catalytic. In the optimum case a catalytic system comprising 1 mM of the complex 4Cu2+(−OCH3) catalyzes the methanolysis of 3 with a t1/2 of ∼58 s accounting for a 1.7 × 109-fold acceleration relative to the background reaction at near neutral sspH (8.75).
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