Tetrathiafulvalene TTF -Derived Dithiolenes

Because of the close structural and preparative connections between the TTFs and dithiolene chemistry, it is only natural that extended dithiolenes have been developed with a TTF-like core. These complexes are generally prepared via the corresponding TTF-based di- or tetrathiolates. 

The synthesis of this hybrid TTF-dithiolene illustrates the use of the cyanoethyl group to protect the sulfur atoms of the dithiolene (81, 136, 137). The trimethylene-capped tetrathiafulvalenetetrathiolate forms a molecular 

A rare example of a unidentate dithiolene is Ru(k 1 - m n t) (CO )2( terpy) (terpy is 2,2,6,2 -terpyridine), prepared from the corresponding [RuCl(CO)2(terpy)]+ (156). The stability of this complex reflects the relatively low nucleophilicity of mnt2-. 

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The mesogenic nickel dithiolenes were found to have reduction potentials (against calomel) of +0.06V and 0.76 V and as such were expected to form charge-transfer complexes with the mesomorphic, substituted tetrathiafulvalene (TTF) derivatives (Figure 89), which had oxidation potentials (also against calomel) of +0.43 V and +0.88 V. 

To obtain ethylenedithiols, the main options described in Scheme 1 are available. Vicinal dithio-ethers, which can be prepared from cis-dichloro- or dibromo-alkenes or from alkenes through a stepwise synthesis, can be cleaved to produce dithiols (Route A). Ethylenedithiocarbonates can be prepared by several well-established procedures and by some less general ones as well. The ethylenedithiocarbonates are central intermediates for many dithiolene syntheses and for syntheses of derivatives of the electron donor tetrathiafulvalene (TTF), which has been intensively investigated in the past decade. This has widened the synthetic possibilities for ethylenedithio-carbonates. Their cleavage by alkali metal hydroxides or alkoxides produces salts of ethylenedithiolates (Route B). As an alternate route, their photolysis with loss of CO and generation of a dithioketone has been explored. ... 

The precursor dithiocarbonates were also used to prepare mesomorphic derivatives of TTF (tetrathiafulvalene), a strong electron donor compound used in the formation of highly conductive charge transfer complexes. Attempts to prepare CT complexes between the mesomorphic dithiolenes as acceptors and these mesomorphic TTF donors showed that the electron acceptor strength of this type of dithiolene does not suffice to form strong donor-acceptor complexes mixtures of the two components form mixed crystals without any visible degree of charge transfer.208... 

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