The Pt(II) complexes of 2N1O-donor ligands containing a pendent indole, 3-[N-2-pyridylmethyl-N-2-hydroxy-3,5-di(tert-butyl) benzylamino] ethylindole (Htbu-iepp), and 1-methyl-3-[N-2-pyridylmethyl-N-2-hydroxy-3,5-di(tert-butyl) benzylamino] ethylindole (Htbu-miepp) (H denotes an ionizable hydrogen), were synthesized, and the structure of [Pt(tbu-iepp) Cl] (1) was determined by X-ray analysis. Complex 1 prepared in CH3CN was revealed to have the C2 atom of the indole ring bound to Pt(II) with the Pt(II)-C2 distance of 1.981(3) angstrom. On the other hand, [Pt(tbu-miepp) Cl] (2) was concluded to have a phenolate coordination instead of the C2 atom of the indole ring by H-1 NMR spectra. Reaction of 1 with 1 equiv. of Ce(IV) in DMF gave the corresponding one-electron oxidized species, which exhibited an ESR signal at g = 2.004 and an absorption peak at 567 nm, indicating the formation of the Pt(II)-indole-pi-cation radical species. The half-life, t(1/2), of the radical species at -60 degrees C was calculated to be 43 s (k(obs) = 1.6 x 10(-2) s(-1)). (C) 2008 Elsevier B. V. All rights reserved.
Reactivity of the Indole Ring in Palladium(II) Complexes of 2N1O-Donor Ligands: Cyclopalladation and π-Cation Radical Formation
thylindole (Hp-iepp) (H denotes a dissociable proton), were synthesized, and the structures of [Pd(tbu-iepp)Cl] (1a), [Pd(tbu-iepp-c)Cl] (1b), [Pd(tbu-miepp)Cl] (3), and [Pd(p-iepp-c)Cl] (4) (tbu-iepp-c and p-iepp-c denote tbu-iepp and p-iepp bound to Pd(II) through a carbon atom, respectively) were determined by X-ray analysis. Complexes 1a prepared in CH(2)Cl(2)/CH(3)CN and 3 prepared in CH(3)CN