Electronic interactions in gold(I) complexes of 2,5-diferrocenyl-1-phenyl-1H-phosphole

The synthesis of gold(I) complexes of 2,5-diferrocenyl-1-phenyl-1H-phosphole (1) is presented. Chloro(2,5-diferrocenyl-1-phenyl-1H-phosphole) gold (3) has successfully been prepared by the reaction of 1 with AuCl(SMe2) (2). Treatment of 2 with arylethyne (aryl = ferrocenyl, phenyl) using catalytical amounts of [CuI] and 1 equiv. of 1 gave arylethynyl-(2,5-diferrocenyl-1-phenyl-1H-phosphole)gold 4a and 4b (aryl: a = ferrocenyl; b = phenyl). Compound [mu-(1,4-phenylenedi-2,1-ethynediyl)]bis(2,5-diferrocenyl-1-phenyl-1H-phosphole)digold (5) could be synthesized by a similar procedure using 0.5 equiv. of 1,4-diethynylbenzene. The electrochemical properties of 3, 4a, b and 5 were investigated by cyclic and square wave voltammetry. In 3, 4a and 4b each ferrocenyl unit shows one reversible redox event with redox separations of the ferrocenyl moieties in 2,5 position of approximately 260 mV. In 5 two redox events for the four ferrocenyl groups were observed. Spectroelectrochemical measurements of 3, 4a and 4b reveal IVCT absorptions with intensities of 1100-1300 L mol(-1) cm(-1) and a full-width-at-half-height of approximate to 3650 cm(-1). In 5 two mixed-valent units are present per molecule and therefore, the intensity of the IVCT band is increased to 2700 L mol(-1) cm(-1). Compounds 3, 4a, b and 5 can be classified as moderately coupled class II systems according to Robin and Day. The complexation of the gold(I) fragment by the phosphorus atom leads to a decreased metal-metal interaction when compared to 1. (C) 2015 Elsevier B.V. All rights reserved.