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

Difluorinated p-diphosphino-1,4-benzenediols 2,5-F2-3,6-(R2P)2C6(OH)2-1,4 (2a,b; R = Ph, iPr), their nickel chelate P,O-complexes, and P,P'-dioxides (3a,b; R = Ph, iPr) were prepd. and characterized. Reactions of 1,4-difluoro-2,5-dimethoxybenzene with LDA (1:2) at low temps. generated organodilithio intermediates; quenching the reaction mixts. with chlorophosphines ClPR2 produced 1,4-(R2P)2-2,5-difluoro-3,6-dimethoxybenzenes (1a,b; R = Ph, 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. Electrochem. activity of hydroquinones 2a-b and 3a-b was examd. by cyclic voltammetry. In addn., compds. 2a, 3a and 3b were obtained in cryst. form and characterized by single-crystal x-ray diffraction. The influence of the fluorine substituents on the compn. of the frontier orbitals of 2a and 3a was examd. by computational methods. [on SciFinder(R)]