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1,4-bis(phosphine)-2,5-difluoro-3,6-dihydroxybenzenes and their P-oxides: Syntheses, structures, ligating and electronic properties

Authors:
Pignotti, L. R.
Kongprakaiwoot, N.
Brennessel, W. W.
Baltrusaitis, J.
Luck, R. L.
Urnezius, E.
Published by: Journal of Organometallic Chemistry
Date: 10 2008
Volume, Number, Pages: 693 20 3263-3272

Accession Number: ISI:000259148800008

Abstract:

Reactions of 1,4-difluoro-2,5-dimethoxybenzene with LDA (1: 2) at low temperatures generated organodilithio intermediates; quenching the reaction mixtures with chlorophosphines ClPR2 produced 1,4bis(phosphino)-2,5-difluoro-3,6-dimethoxybenzenes 1a (R = Ph) and 1b (R = iPr). Demethylation of 1a-b was accomplished by BBr3, yielding bis(phosphino) hydroquinones 2a-b. Treating 2a-b with excess hydrogen peroxide produced bis(phosphinyl) hydroquinones 3a-b. The binucleating properties of 2a were established by the formation of a bimetallic nickel complex upon reaction with Ph2Ni(PMe3)(2). Electrochemical activity of hydroquinones 2a-b and 3a-b was examined by cyclic voltammetry. In addition, compounds 2a, 3a and 3b were obtained in crystalline form and characterized by single-crystal X-ray diffraction. The influence of the fluorine substituents on the composition of the frontier orbitals of 2a and 3a was examined by computational methods. (C) 2008 Elsevier B. V. All rights reserved.