Divalent Nickel, Cobalt and Iron Complexes of an Amide‐Appended N 2 S 2 Ligand: Synthesis, Characterization and Reactivity with Hydroxide Anion

Divalent nickel, cobalt and iron complexes {[(bmppa)Ni(CH 3 CN)](ClO 4 ) 2 ( 1 ), [(bmppa)Co(CH 3 CN)](ClO 4 ) 2 ( 2 ), [(bmppa)Fe(CH 3 CN)](ClO 4 ) 2 ( 3 )} of an amide‐appended N 2 S 2 ‐donor ligand {bmppa = N , N ‐bis(2‐methylthio)ethyl‐ N ‐[(6‐pivaloylamido‐2‐pyridyl)methyl]amine} have been prepared and characterized using 1 H NMR, IR, UV/Vis, elemental analysis and magnetic moment measurements. The complexes 2 and 3 were also characterized by X‐ray crystallography. When treated with 1 equiv. of Me 4 NOH · 5H 2 O in methanol, 1 and 2 form deprotonated amide complexes {[(bmppa – )Ni]ClO 4 ( 4 ), [(bmppa – )Co]ClO 4 · H 2 O ( 5 )} which were isolated and characterized by 1 H NMR, IR, UV/Vis, elemental analysis and magnetic moment measurements. Treatment of the Fe II complex 3 with 1 equiv. of Me 4 NOH · 5H 2 O in methanol produced the free bmppa chelate ligand and a precipitate of an unidentified iron species. Heating of 5 at 50 °C in methanol for 5 d resulted in a ca. 50 % yield of amide methanolysis products and a small amount of products resulting from oxidative N ‐dealkylation of the bmppa ligand. It has been previously shown that a zinc analog of 5 undergoes quantitative amide methanolysis under milder conditions. Complex 4 does not undergo amide cleavage upon heating at 50 °C in methanol for 5 d. A rationale for the metal‐dependent amide methanolysis reactivity of these complexes is proposed on the basis of structural differences in the “parent” protonated complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)