Issue 3, 2007

Molecular and electronic structure of square planar complexes [PdII(tbpy)(L IPN,O)]0, [PdII(tbpy)(L ISQN,O)](PF6), and [PdII(tbpy)(L IBQN,O)](PF6)(BF4)·2CH2Cl2: an o-iminophenolato based ligand centered, three-membered redox series

Abstract

Three PdII complexes which are members of the same electron-transfer series have been synthesized. Refluxing of the reaction mixture containing equimolar amounts of PdCl2, 2-(2-trifluoromethyl)anilino-4,6-di-tert-butylphenol (H2LN,O), 4,4′-di-tert-butyl-2,2′-dipyridyl (tbpy), and 3 equiv of triethylamine in MeOH under an argon atmosphere followed by exposure to air and addition of KPF6 after cooling to room temperature yields reddish brown crystals of paramagnetic (S = 1/2) [Pd(LISQN,O)(tbpy)](PF6) (2). Reaction of 2 with one equiv of [CoCp2] in dry and degassed CH2Cl2 using anaerobic conditions gives diamagnetic [Pd(LIPN,O)(tbpy)] (1), which is the one-electron reduced form of 2. One-electron oxidation of 2 in CH2Cl2 under argon with one equiv of NOBF4 affords diamagnetic [Pd(LIBQN,O)(tbpy)](PF6)(BF4)·2CH2Cl2 (3). Complexes 1, 2, and 3 constitute three members of the same electron-transfer series. They are ideally suited to distinctly distinguish the geometrical and spectroscopic features of the N,O-coordinated, closed-shell, diamagnetic o-iminophenolate (LIPN,O)2−, the corresponding open-shell π-radical o-iminobenzosemiquinonate (LISQN,O)1−˙ (Srad = 1/2), and the closed-shell o-iminobenzoquinone (LIBQN,O)0 forms. All complexes were characterized by X-ray crystallography (100 K), cyclic voltammetry, EPR, and UV-vis spectroscopy. Complex 2 exhibits three reversible electron transfer waves in the cyclic voltammogram. Structural characterization of complex 3 reveals an interesting strong ion pairing between the BF4 anion and the complex dication with a short C–F distance of 2.7 Å.

Graphical abstract: Molecular and electronic structure of square planar complexes [PdII(tbpy)(LIPN,O)]0, [PdII(tbpy)(LISQN,O)](PF6), and [PdII(tbpy)(LIBQN,O)](PF6)(BF4)·2CH2Cl2: an o-iminophenolato based ligand centered, three-membered redox series

Supplementary files

Article information

Article type
Paper
Submitted
10 Oct 2006
Accepted
09 Nov 2006
First published
28 Nov 2006

Dalton Trans., 2007, 373-378

Molecular and electronic structure of square planar complexes [PdII(tbpy)(LIPN,O)]0, [PdII(tbpy)(LISQN,O)](PF6), and [PdII(tbpy)(LIBQN,O)](PF6)(BF4)·2CH2Cl2: an o-iminophenolato based ligand centered, three-membered redox series

S. Kokatam, P. Chaudhuri, T. Weyhermüller and K. Wieghardt, Dalton Trans., 2007, 373 DOI: 10.1039/B614745C

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