1.1- Dithiolates, reaction chemistry

The synthesis of a large number of alkyl-sulfonyl 1,1-dithiolate ligands has been reported by the reaction between RS02CH2R and CS2 in DMSO in the presence of NaH as a base (399). The coordination chemistry of these new ligands, RS02 R C CS2", to the knowledge of the present author, has not been explored. 

To further exemplify this methodology, let us take a typical example of the application of a template reaction as seen in the synthesis of a mixed N2S2 donor macrocyclic ligand 6.11. This compound is of interest to the co-ordination chemist as it possesses a potentially square-planar array of soft (sulfur) and harder (nitrogen) donor atoms. What sort of co-ordination chemistry is it likely to exhibit Will the hard or the soft characteristics dominate The most obvious route for the synthesis of 6.11 would involve the reaction of the dithiol 6.10 with l,2-bis(bromomethyl)benzene (Fig. 6-7). 

These reactions form one of the most intensively studied areas of dithiole chemistry. 

The long lifetimes of CT excited states of the Pt(diimine)(dithiolate) complexes allow for bimolecular photochemistry, often involving oxidation of the complex. The earliest report of photoreactivity of these complexes dealt with the photooxidation of Pt(bpy)(tdt) (20) following excitation at 577 nm in chloroform (118). The reaction proceeds with a quantum yield of < ) = 0.03 and was attributed to ET to the halocarbon solvent (Eq. 8) similar to the CTTS photooxidation chemistry of the platinum bis(dithiolate) dianions described above. 

With respect to reactivity and synthetic aspects, various specific transition metal-mediated syntheses of new 1,2-dithioles and reactions, thereof, have been reported. Novel metal complexes have been isolated in a number of cases and they provide insight into new chemistry of 1,2-dithioles. 

As an extension of this chemistry, the [3+2] cycloaddition reaction of new atropisomeric 4-dialkylamino-5-chloro-l,2-dithiole-3-thiones 130 and DMAD or its diethyl analogue has been utilized to give thioacid chlorides 131 (Scheme 13) <20030L929>. These have been converted into thioamides 132 with 2 equiv of pyrrolidine (or morpholine) by substitution of the 5-chloro substituent and phthalimide ring opening. Similar reactivity toward 1 or 2 equiv of pyrrolidine was noted for 130, which was obtained according to the general method described. 

The chemistry of the l,3-dithiole-2,4,5-trithione oligomer system 374 derived from monomers 375 and 376 (Scheme 49) has been the subject of a review <2006CHE423>. This system easily depolymerized (heat or UV irradiation at 253 nm) and was effective in Diels-Alder-type cycloadditions. Reactions with unsaturated compounds constituted an efficient method for synthesis of functionalized l,3-dithiole-2-thiones containing substituted 1,4-dithiin rings and are examples of reactivity of thione or sulfenyl substituents (stmctures 374-376) attached to the 1,3-dithiole ring carbon atom. 

Monocyclic and some bicyclic l,2-dithiole-3-thiones are known that readily undergo 1,3-dipolar cycloaddition reactions to give cyclic 1,3-dithiole and spiro[l,3]dithiole systems. Due to a great variety of applications, the chemistry of this class of compounds still remains a subject of active research. 

On the other hand, the coordination chemistry of l,l -ferrocenylene dithiolate ligands (fcS2) and their heavier analogs (fcE2, E = Se, Te) has been the subject of numerous investigations. The reactions of l,l -dimercaptoferrocene, fc(SH)2, with monochloro complexes of the type CpM(NO)2Cl (M = Cr, Mo, W) and CpW (CO)3Cl in the presence of triethylamine (NEt3) proceed stepwise to give first the monothiol-thiolato and then the bis(thiolato) complexes, e.g.. Scheme 5-38 [236]. 

The reaction of l,2-dithiole-3-thiones with chloramine-T results in formation of analogous nitrogen compounds (e.g., 160), which may lose the exocyclic sulfur atom to form 161.220 Other N-chloroamines have been used.22 1,222 The chemistry of these imines has been studied.223 230... 

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