Trifunctional Metal Ion-Catalyzed Solvolysis: Cu(II)-Promoted Methanolysis of N,N-bis(2-picolyl) Benzamides Involves Unusual Lewis Acid Activation of Substrate, Delivery of Coordinated Nucleophile, Powerful Assistance of the Leaving Group Departure

The methanolyses of Cu(II) complexes of a series of N,N-bis(2-picolyl) benzamides (4a–g) bearing substituents X on the aromatic ring were studied under sspH-controlled conditions at 25 °C. The active form of the complexes at neutral sspH has a stoichiometry of 4:Cu(II):(−OCH3)(HOCH3) and decomposes unimolecularly with a rate constant kx. A Hammett plot of log(kx) vs σx values has a ρx of 0.80 ± 0.05. Solvent deuterium kinetic isotope effects of 1.12 and 1.20 were determined for decomposition of the 4-nitro and 4-methoxy derivatives, 4b:Cu(II):(−OCH3)(HOCH3) and 4g:Cu(II):(−OCH3)(HOCH3), in the plateau region of the sspH/log(kx) profiles in both CH3OH and CH3OD. Activation parameters for decomposition of these complexes are ΔH⧧ = 19.1 and 21.3 kcal mol–1 respectively and ΔS⧧ = −5.1 and −2 cal K–1 mol–1. Density functional theory (DFT) calculations for the reactions of the Cu(II):(−OCH3)(HOCH3) complexes of 4a,b and g (4a, X = 3,5-dinitro) were conducted to probe the relative transition state energies and g...