TTF-dithiolate ligands

High conductivity for transition metal complexes of TTF-dithiolate ligands have long been known, due to the mixing of n-d orbitals resulting in a small HOMO-LUMO gap [80]. At present, 17 is the most reliable metal in this category (ctrt = 4 X 10 S cmT, metallic down to 0.6 K) based on its purity, temperature dependencies of resistivity and magnetic susceptibility, and de Haas-van Alphen (dHvA) oscillations [48, 75]. 

Kobayashi A, Fujiwara E, Kobayashi H (2004) Single-component molecular metals with extended-TTF dithiolate ligands. Chem Rev 104 5243-5264... 

Single-component molecular metals with extended-TTF dithiolate ligands 04CRV5243. 

Figure 4.17 Structural formulas of extended-TTF-dithiolate ligands...

A close structural relationship with I IF derivatives, especially BEDT-TTF, is exhibited by dddt metal complexes [dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate (63)]. The most interesting feature of this dithiolene ligand is the ability of its metal complexes to form not only anionic salts like dmit, but also cationic salts like TTF derivatives [89], to afford non-stoichiometric IR salts of type [M(dddt)2]mX . Thus the cyclic voltam-mogram of [Bu4N][Ni(dddt)2], after its initial oxidation, exhibits the reduction of neutral [Ni(ddt)2]° to anion [Ni(ddt)2]" at 0 V, and its further reduction to the dianion [Ni(dddt)2]2 , as well as the oxidation of [Ni(dddt)2]° to the cation [Ni(dddt)2] + at 0.8 V (MeCN versus Ag/Ag/Cl). The feasible synthesis of conducting donor-acceptor complexes involving dddt metal derivatives as donors and dmit metal derivatives as acceptors has also been demonstrated [90]. 

Dimercapto-l,3-dithiole-2-thione (dmit, 46) and 4,5-dihydro-l,4-dithiin-2,3-dithiolate (dddt, 47) ligands can be reacted with transition metal ions to give M(dmit)2 and M(dddt)2 complexes (M = Pt, Pd, Ni, and Au) [91]. The M(dmit)2 and M(dddt)2 anions, like BEDT-TTF, have numerous peripheral sulfur atoms and are planar. Additionally, they have variable redox potentials that can be adjusted through the metal that is selected. 

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