Dithiocarbonate complexes

Rate constants for the substitution reactions of square-planar dithio-phosphates and dithiocarbonate complexes of Ni(II), Pd(II), and Pt(II), with ethylenediamine and cyanide ion as nucleophiles, have been measured in methanol. The results were compared with those obtained in previous investigations, and interpreted in terms of the stabilities of 5-coordinate species that are formed prior to substitution (377). 

Adewuyi and Carmichael (73) observed the reaction of CS2 with OH- to form a dithiocarbonate complex as the rate-determining step for the overall reaction 74 above. The formation of sulfate was found to be dependent on the rate of hydrolysis and to be preceded by long induction periods. As shown in Figure 3, the formation rate of sulfate was also found to be pH dependent and to increase exponentially with time. 

The syntheses of the metal-benzenethiolate complexes are accomplished by a ligand substitution reaction between the appropriate O-ethyl dithiocarbonate complexes and potassium benzenethiolate, KSPh. In the original report on the syntheses of the [M(SPh)4]2 complexes,1 the bis(3,4-dimercapto-cyclobutane-1,2-dione) [dithiosquaric acid] metal complexes were used in the ligand substitution reactions. The rather involved synthesis of the dithiosquarate ligand,2 using expensive starting materials, prompted us to develop new synthetic procedures which utilize the readily available, inexpensive O-ethyl dithiocarbonate complexes.3... 

The effect of solvation on the Mossbauer parameters was investigated for iron(III)-dithiocarbonate complexes by De Vries et al [De 71]. They compared the Mossbauer parameters of mixed complexes of the composition Fe(dtc)2X (where X = C1 , SCN") in the solid state and in frozen solutions prepared with various solvents. These complexes are known to contain iron with a coordination number of... 

Danielsson L-Q, Magnusson B, Westerlund S, and Zhang V (1982) Trace metal determinations in estuarine waters by electrothermal atomic absorption spectrometry after extraction of dithiocarbonate complexes into freon. Ana-lytica Chimica Acta 144 183-188. 

The reaction of dithiocarbonate complexes of ruthenium 52 with carbon disulfide affords trithiocarbonate complexes 53. The reaction proceeds via addition across the ruthenium-sulfur bond with generation of 54 and carbonyl sulfide4. ... 

The (triphos)Ni0 template reacts with ethyl cyanoformate to give (220).648 The MO description and reactivity of the CS2 complex (221) has been studied in some detail.649 Treatment with 02 gives the dithiocarbonate compound (221a),650 while bubbling of C02 through a solution of (221) yields the carbonato complex (221b).651 In both cases, one of the phosphine arms has been oxidized and is found dangling. 

Substituted dithioformate anions as ligands R C(S)S are usually called dithiocarbamates (R = R2N), alkyl and aryl dithiocarbonates or xanthates (R = RO), alkyl and aryl trithiocar-bonates or thioxanthates (R = RS). Dithioacid anions (R = alkyl, aryl) have been rarely used as ligands of nickel(II) because of their instability. Structural properties of selected nickel(II) complexes with substituted dithioformate, dithiolene and related ligands are shown in Table 90. 

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... 

O-Allyl-5-alkyl dithiocarbonates react with Pd° catalysts to provide a ir-allyl complex with a thiocar-bonate serving as counterion. Under the reaction conditions the carbonate expels free methyl meicaptide, generating COS. Attack of the mercaptide was shown to occur exclusively via ligand addition (equation 195).221... 

A powerful route to dithiolene complexes employs alkenedithiolate dianions generated by the hydrolysis of cyclic unsaturated dithiocarbonates, which are formally called l,3-dithiole-2-ones. Representative of the many examples (60), the base hydrolysis route has been used to prepare the ferrocene-substituted dithiolene Ni[S2C2H(C5H4)FeCp]2 (61), the sulfur-rich dithiolene [Ni(S2C2S2-C2H4)2F (62), the cyano(dithiolenes) fra s- Ni[S2C2H(CN)]2 (n = 1, 2) (63), 2,3-thiophenedithiolates [Au(S2C,H2S)21 (64), and the tris(styryldithiolate)... 

Figure 8. Synthetic routes to alkene dithiocarbonates (dithioles) and their conversion to dithiolene complexes.

The conversion of the dithiocarbonates into alkenedithiolates involves base hydrolysis, which is usually effected with sodium alkoxides in alcohol. With the dianion in hand, the synthesis of complexes follows the usual course, as described above. Obviously, oxophilic metal centers, for example, Ti(IV) and Nb(V) (62), are incompatible with the usual alcohol solutions of in situ generated alkenedithiolates. In such cases, the anhydrous salts Na2S2C2R2 are employed in nonhydroxylic solvents, although after complex formation protic solvents are typically employed for cation exchange. 

A versatile route to RS-substituted dithiolenes entails S-alkylation of the trithiocarbonate dmit2 (see Section II.C.l), which provides an efficient means to introduction of diverse functionality to the dithiolene backbone. Subsequent to S-alkylation, the resulting S=CS2C2(SR)2 is converted to the dithiocarbonate 0=CS2C2(SR)2 with Hg(OAc)2 in acetic acid (63, 83, 84). Such dithiocarbo-nates are more easily hydrolyzed than the trithiocarbonates (72, 85). This approach has been used for the synthesis of Ni[S2C2(S(CH2) Me)2]2 (n = 2-11) (86) and related complexes with pendant alkene substituents (Eq. 8) (87). 

This method has found particular use in the preparation of pyridine-substituted dithiolene complexes, which exhibit pH sensitive luminescence properties (263). The a-halocarbonyl starting materials could include related precursors used in the synthesis of unsaturated dithiocarbonates described in Section II.C. 

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