Facile Syntheses of Thiophene-Substituted 1,4-Diazabutadiene (Alpha-Diimine) Ligands and their Conversion to Phosphenium Triiodide Salts
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Four novel N-aryl-2-thienyl substituted 1,4-diazabutadiene (alpha-diimine) ligands 5-8 have been prepared by cyanide ion-catalyzed intermolecular coupling of the appropriate aromatic aldimines. A ligand featuring a phenyl spacer moiety between a thiophene carbon atom and each imino nitrogen atom (12) has been prepared by a similar synthetic route. Ligands 5-8 and 12 were characterized on the basis of (1)H and (13)C NMR, IR and MS-CI spectroscopy. Upon treatment with PI(3) in CH(2)Cl(2) solution, ligands 5-8 undergo redox reactions to furnish the triiodide salts of the corresponding phosphenium cations 13-16 which were characterized by (1)H, (13)C and (31)P NMR, and MS-CI spectroscopy. The phosphenium triiodide salt 15, and ligands 5-7 and 12 were also structurally authenticated.