Other Dithio Ligands

Like metal chelates of some other dithio ligands, e.g. maleonitrile dithiolate, dithio-/J-diketonato complexes undergo reversible redox reactions in non-aqueous solvents. The square-planar complexes [ML2] (M = Co, Ni, Pd and Pt) exhibit two consecutive one-electron reductions as shown in equation (5).252,253... 

In nickel and palladium dithiobenzoato complexes, four-membered chelate rings are formed (366), whereas, in the corresponding phenyl-dithio acetates [M2(S2CCH2Ph)4], the dithio ligands act as bridging groups between the two metal atoms, with the formation of binuclear units (367). The molecular structure of the latter compounds shows that each metal atom is coordinated to four sulfur atoms and to the other metal atoms in a square-pyramidal geometry. Other evidence for... 

A variety of other reactions of carbon disulfide with nucleophiles are presented in a review (252). In the last 10 years a number of new 1,1-dithio ligands have been synthesized, and the chemistry of others has been explored in detail. 

The other reaction that has been explored with the Cu8(r-Bu2DED)J cluster is the sulfur addition to the coordinated 1,1-dithio ligands, which proceeds according to Eq. 51 ... 

Eventually we formed carbonyls in the liquid phase by redox disproportionation of nickel and cobalt derivatives of organic thioacids. In the reaction between nickel(II) dithiobenzoate and carbon monoxide in the presence of HS ion we assumed the formation of a sulfur-bridged nickel(IV) complex (VII, 32). More recent investigations (84), however, have shown that half the nickel appears as a monomeric nickel(II) complex of the same empirical formulation, formed by insertion of a sulfur atom in the dithio ligand, the other half of the nickel being reduced to nickel(O) by the sulfide. 

On the other hand, 4-nitrobenzenethiol gives [IrCl2(SC6H4N02)-(APh3)2]2- In view of the paucity of Ir-dithio ligand compounds, the reported... 

A ligand field model has been used for the interpretation of the magnetic behavior of the Mo(R2Dtc)4 complexes (485). Extended Hiickel calculations compare the electron-donating characteristics of the dithiocarbamate ligand to other 1,1-dithio chelates. This calculation concluded that (1) there is more metal character in the lowest unoccupied MO in the dithiocarbamate complexes, and (2) there is more ligand character in the lowest unoccupied MO in the dithioacid complexes (485). This seems to be in agreement with the electronic spectra. 

Compared to other 1,1-dithiolates, the R2DED ligands are quite unique in their properties. These ligands appear to be more effective than the dithio-carbamate ligands in stabilizing metal ions in high formal oxidation states and are characterized by a conjugated n system (Fig. 54). 

T2 >47 2(P) transitions at 15, 300, and 22,000 cm-1. The energy of the 4A2 - 4T2 transition, which is a direct measure of 10Dq, when compared to that of other Cr(lll) 1,1-dithio complexes, places the R2DEI) ligand between j -MNT and R2Dtc in the spectrochemical series. 

However, on the basis of N-benzoylthiourea 540, not only chelating complexes of type 541 can be synthesized, but also molecular compounds as shown by 542 [938]. In the case of compound 542 (M = Pt) being formed, 540 takes part as a monoden-tate S-donor ligand. In this respect it has to be noted that other 0,S-containing ligands can participate only as S-donors. In particular, dithio-oxalic acid 543 is assumed to belong to this group complexes of type 544 have been obtained on its basis [1, vol.2] ... 

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