Dithiolene metal complexes synthesis

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]. 

The reactions of electrophilic alkynes, such as DMAD (dimethyl acetylene-dicarboxylate), with metal per- and poly-chalcogenido complexes have been exploited for the synthesis of homoleptic and heteroleptic 1,2-dithiolene,... 

Synthesis. The first known thiophene-based metal dithiolenes were reported by Gol dfarb and Kalik in 1968." These consisted of the nickel and copper complexes of 2,3-thiophenedithiolate produced from ethyl 3-thienyl sulfide as shown in Scheme 1. Both complexes were reported as black, high melting solids and were thought to be the neutral bis(2,3-thiophenedithiolate) species. 

In the synthesis of the parent dithiolenes, the reaction of the disodium salt of ethylene-cts-dithiolate with metal salts is the only useful method.15 For the preparation of substituted dithiolenes the use of substituted ethylenedithiolates is the most efficient choice. In the synthesis of 1,2-dicyanoethylene-l,2-dithiolato ( mnt ) complexes, it is the only available method.16... 

This chapter discusses the synthesis of transition metal dithiolene complexes and is current to late 2002. Dithiolene chemistry has been reviewed several times previously, but this is the first review dedicated to synthetic aspects. Emphasis is placed on more contemporary methods, and the reader should consult the older reviews, especially those by Mueller-Westerhoff et al. (8) and McCleverty (9) for discussions of earlier literature. An effort was made to be comprehensive with respect to methods and the range of complexes examined, but the chemistry of metal dithiolenes is so vast that it is not practical to be exhaustive. 

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