New chiral organosulfur donors related to bis(ethylenedithio)tetrathiafulvalene

Abstract

Abstract. Six new enantiopure chiral organosulfur donors, with structures related to BEDT-TTF, have been synthesised for use in the preparation of organic metals, starting either by double nucleophilic substitutions on the bis-mesylate of 2R,4R-pentane-2,4-diol or by a cycloaddition with subsequent elimination of acetic acid on the enol acetate of (+)-nopinone. Crystal structures of some of their radical cation triiodides salts and TCNQ complexes are reported. 2 IntroductionThe radical cation salts and charge transfer molecular complexes of TTF 1 and BEDT-TTF 2 show a wide range of electrical behaviour, and have found use in a range of systems including metallic systems, semiconductors and low-temperature superconductors. Here we report the synthesis of a group of novel chiral organosulfur donors, 11-16, in which chirality is provided by one or more hydrocarbon groupings. The structures of products from initial experiments to form charge transfer complexes are also described. 4 Discussion Synthesis of 11 and 12Electrocrystallisation of the enantiopure donor (S,S,S,S)-tetramethylBEDT-TTF 5 has given a series of radical cation salts, but their crystal structures were pseudocentrosymmetric, with the methyl groups adopting equatorial orientations. 6 However, we reasoned that insertion of a methylene group between each pair of stereogenic centres to give 11 would provide a more promising system. The outer seven-membered rings of donor 11 would be expected to adopt chair conformations and give two possible molecular conformations, A and B (Fig. 1), in analogy with the structures of 17-19. 17 The trans orientation of the methyl groups on the propylene bridge would force one into an axial position and the other into an equatorial position.Molecules in conformation B could be envisaged to stack in a helix. The synthesis of donor 11 started with the cyclisation of the dithiolate 20, prepared in three steps from carbon disulfide, 18 with the bis-mesylate of R,R-pentane-5 2,4-diol (Scheme 1). The first mesylate group is substituted by reaction in methanol at room temperature, but it was necessary to replace the methanol with THF and heat to reflux to complete the cyclisation to give the thione 21 in 45% yield. The thione was converted to oxo compound 22 using mercuric acetate in quantitative yield, and this was then homocoupled in refluxing trimethyl phosphite over 24 hours to give 11 in 75% yield. Cross-coupling, under similar conditions, of oxo compound 22 with a three-fold excess of the unsubstituted thione 23 yielded the cross-coupled donor 12 in 22% yield after chromatography. The low yield of 12 is a consequence of the faster homocoupling of thione 23 to give BEDT-TTF. Scheme 1The molecular structures of donors 11 and 12 were determined by X-ray crystallography. For both donors the seven-membered rings adopt chair conformations with one methyl group in an axial position and one in an equatorial position. For the homocoupled donor 11 (Fig. 2) the structure of the organosulfur system deviates very strongly from plana...

Chiral, radical, gold bis(dithiolene) complexes

“…29 Accordingly, reaction of 4 with NaOMe in MeOH followed by successive additions of KAuCl 4 and Bu 4 NBr afforded the anionic complex [Au(pdt) 2 ] À , as Bu 4 N + salt (1), as dark green crystals with 51% yield from 4. 29 Accordingly, reaction of 4 with NaOMe in MeOH followed by successive additions of KAuCl 4 and Bu 4 NBr afforded the anionic complex [Au(pdt) 2 ] À , as Bu 4 N + salt (1), as dark green crystals with 51% yield from 4.…”

“…30 As shown in Fig. 6 itself is prepared from (2S,4S)-pentane-2,4-diyl dimethanesulfonate, as described by Wallis et al 29 The anionic gold complex 2 crystallizes in the monoclinic system, chiral Table 1. 31 The chiral 1,3-dimethylpropylene analog [Au(dmpdt) 2 ] À (2) was obtained from the corresponding dithiocarbonate 6 by a similar procedure.…”

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

“…3-5, 13,14 or external to the donor system as in 6-7 15, 16 as well as donors fused to a chiral pinene system e.g. 8 17 or incorporating a stereogenic axis from a 1-,1'-binaphthyl system. 18 Examples of the latter have been investigated as redox sensitive chiroptical switches.…”

Chiral metal down to 4.2 K - a BDH-TTP radical-cation salt with spiroboronate anion B(2-chloromandelate)2−

“…9 The most successful method for producing chiral radicalcation salts has been by means of enantiopure donors based on EDT-TTF 10 or BEDT-TTF. 11 Whilst still difficult to obtain highly crystalline materials, the donor tetramethyl-BEDT-TTF has produced several enantiopure salts. 12 As an alternative to BEDT-TTF, we have utilised the donor 2,5-bis(1,3-dithiolan-2ylidene)-1,3,4,6-tetrathiapentalene (BDH-TTP) which has a tendency to form a k-type packing arrangement and show metallic behaviour.…”