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Coordinated Hydrazone Ligands as Nucleophiles:  Reactions of Fe(papy)2

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journal contribution
posted on 27.12.2004, 00:00 by Aaron Wood, Wasim Aris, David J. R. Brook
The diamagnetic iron(II) complexes of the hydrazone ligand pyridinecarboxaldehyde-2‘-pyridylhydrazone (papyH) have been characterized by NMR, IR, UV−vis, and electrochemistry. The dication Fe(papyH)22+ undergoes reversible one-electron oxidation at 0.66 V vs internal ferrocene and shows a strong metal−ligand charge-transfer band in the visible region at 524 nm. Deprotonation with NaOH gives diamagnetic, neutral Fe(papy)2 with an oxidation potential of −0.25 V vs internal ferrocene and a charge-transfer band at 603 nm. Fe(papy)2 reacts with active alkylating agents to give dialkyl complexes Fe(papyR)22+ with spectroscopic properties similar to those of Fe(papyH)22+. Monitoring the alkylation by UV−vis reveals the intermediacy of a monoalkylated species.