Divalent Nickel, Cobalt and Iron Complexes of an Amide-Appended N2S2 Ligand: Synthesis, Characterization and Reactivity with Hydroxide Anion
✍ Scribed by Gajendrasingh K. Ingle; Magdalena M. Makowska-Grzyka; Atta M. Arif; Lisa M. Berreau
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 228 KB
- Volume
- 2007
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
Divalent nickel, cobalt and iron complexes {(bmppa)Ni(CH~3~CN)~2~ (1), (bmppa)Co(CH~3~CN)~2~ (2), (bmppa)Fe(CH~3~CN)~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)